Start no prefix flush after the stop deadline (closes #188)

When a write ran past the stop deadline, a full batch's wake-up or a tick
could wait beside Stop's context. The flush goroutine's select picked one of
them at random, so about half the time it wrote that batch after the
deadline. That was the intermittent failure of
TestPrefixHandlerSkipsItsLastWriteAfterTheStopDeadline. The flush goroutine
now takes a waiting stop first. A new test hands over a full batch while a
write is held; it fails about half its runs on the old code.

TestPrefixHandlerSkipsItsLastWriteAfterTheStopDeadline and
TestPrefixHandlerStopLogsTheTableChangesLeftUnwritten also failed when the
flush timer fired between two of their steps. Both now give the handler a
timer interval longer than the test.

Model: opus-5-5

Dockerfile

@@ -139,8 +139,13 @@ EXPOSE 8080
 
 COPY ./entrypoint.sh /entrypoint.sh
 
-# Health check using the health endpoint, on the port PORT names
+# Health check using the health endpoint, on the port PORT names. During the
-HEALTHCHECK --interval=30s --timeout=5s --start-period=10s --retries=3 \
+# start period, Docker 25 and later checks every 5 seconds, and the first pass
+# makes the container healthy. After it, Docker checks every 30 seconds. The
+# start period covers the 60 seconds after which upaas reads the health
+# (README "Running under upaas"). Startup reads the routing table first,
+# which takes about 25 seconds when the table is full.
+HEALTHCHECK --interval=30s --timeout=5s --start-period=60s --retries=3 \
     CMD curl -sf "http://localhost:${PORT:-8080}/.well-known/healthcheck.json" || exit 1
 
 ENTRYPOINT ["/bin/bash", "/entrypoint.sh" ]

Makefile

@@ -52,7 +52,6 @@ clean:
 run: build
 	DEBUG=routewatch ./bin/routewatch 2>&1 | tee log.txt
 
+# Rebuild the AS list built into RouteWatch from as.csv (needs the network).
 asupdate:
-	@echo "Updating AS info data..."
+	@script/asupdate
-	@go run cmd/asinfo-gen/main.go | gzip > pkg/asinfo/asdata.json.gz.tmp && \
-		mv pkg/asinfo/asdata.json.gz.tmp pkg/asinfo/asdata.json.gz

README.md

@@ -1,9 +1,11 @@
 # RouteWatch
 
 RouteWatch is an MIT-licensed Go daemon by @sneak that monitors the BGP routing
-table in real time: it streams BGP UPDATE messages from the RIPE RIS Live
+table in real time. It works like this:
-service, maintains a live routing table in SQLite, and provides HTTP APIs for
+
-querying routing information.
+- It streams BGP UPDATE messages from the RIPE RIS Live service.
+- It keeps a live routing table in SQLite.
+- It serves web pages and a JSON API for looking routes up.
 
 ## Rationale
 
@@ -27,6 +29,8 @@ route the feed has withdrawn.
 - Maintains live IPv4 and IPv6 routing tables
 - Tracks AS peering relationships
 - HTTP API for IP-to-AS lookups, prefix details, and AS information
+- IP lookups report the public blocklists an address is on, from copies kept in
+  memory and on disk
 - Automatic reconnection with exponential backoff
 - Batched database writes for high performance
 - Backpressure handling to prevent memory exhaustion
@@ -57,7 +61,8 @@ Every route answers `HEAD` as it answers `GET`, without the body.
 ### Web Interface
 
 - `GET /` - Home page (HTML): headline figures, lookups by AS number and by IP
-  address, and a search of AS names
+  address, and a search of AS names. A card shows the `curl` command that looks
+  up the visitor's own address at `/ip/{addr}`, and that command's live answer.
 - `GET /status` - HTML status dashboard, which reads `/api/v1/stats`
 - `GET /status.json` - JSON statistics: feed, memory, database and route figures
 - `GET /.well-known/healthcheck.json` - Health check (JSON): 200 when the
@@ -84,18 +89,26 @@ Every route answers `HEAD` as it answers `GET`, without the body.
   collector, stream and handler queue statistics. `stream.route_churn_per_min`
   is the number of prefix announcements and withdrawals, from all peers, in the
   last full clock minute.
-- `GET /api/v1/ip/{ip}` - Looks up each address: its most specific live route
+- `GET /api/v1/ip/{ip}` - Looks up each address. `{ip}` is an IP address, a host
-  (`netblock`), that route's origin AS with its WHOIS details, and the address's
+  name, or a comma-separated list of at most 10 of these. `results` has one
-  PTR names. `{ip}` is an IP address, a host name, or a comma-separated list of
+  entry for each address, with:
-  at most 10 of these. Of the addresses a host name resolves to, only public
+    - `ip` and `ptr`: the address and its PTR names
-  ones are looked up: a name with none, such as one that resolves to a private
+    - `netblock` and the fields beside it: the address's most specific live
-  address, is reported as `host name has no public address`, without its
+      route, and that route's origin AS with its WHOIS details
-  addresses. `results` has one entry per address with a live route and `errors`
+    - `blocklists`: the public blocklists the address is on (see Blocklists)
-  one per address or name that failed. The answer is 400 when `{ip}` lists more
+
-  than 10, when it comes to more than 10 addresses once its names are resolved,
+    An address with no live route has a result without the route and AS fields.
-  or when nothing in it is an IP address or a host name with a public address;
+    Of the addresses a host name resolves to, only public ones are looked up. A
-  and 404 when none of the addresses has a live route. A PTR lookup gets 2
+    name with none, such as one that resolves to a private address, is reported
-  seconds; an address whose lookup takes longer is answered without PTR names.
+    as `host name has no public address`, without its addresses. `errors` has
+    one entry for each host name that failed. The answer is 400 when:
+    - `{ip}` lists more than 10
+    - `{ip}` comes to more than 10 addresses once its names are resolved
+    - nothing in `{ip}` is an IP address or a host name with a public address
+
+    A PTR lookup gets 2 seconds. An address whose lookup takes longer is
+    answered without PTR names.
+
 - `GET /api/v1/as/{asn}` - The AS and the prefixes it originates, IPv4 and IPv6
   apart, each with when its newest route was updated. When the database has no
   record of the AS, its handle and description come from the AS list built into
@@ -110,9 +123,10 @@ Every route answers `HEAD` as it answers `GET`, without the body.
       `handle` and `description`
 
     The search reads the AS list built into RouteWatch, not the database. The
-    list comes from [ipverse/asn-info](https://github.com/ipverse/asn-info). A
+    list comes from
-    match can therefore be an AS that the database has no record of. A `q` that
+    [ipverse/as-metadata](https://github.com/ipverse/as-metadata). A match can
-    is missing, empty or only spaces answers 400.
+    therefore be an AS that the database has no record of. A `q` that is
+    missing, empty or only spaces answers 400.
 
 A JSON answer is `{"status": "ok", "data": ...}`, or for an error
 `{"status": "error", "error": {"msg": ..., "code": ...}}`, and carries an
@@ -148,6 +162,66 @@ in a prefix's `origins`) means the route has no known origin: its AS path ends
 in an AS set of several members, any of which may have originated it. The pages
 show such a route as having no known origin.
 
+## Blocklists
+
+The IP lookup reports which public blocklists list each address. Each result has
+a `blocklists` list with one entry for each list the address is on:
+
+- `name`: the list's name, from the lists below
+- `description`: what being on the list means
+- `updated`: when RouteWatch last downloaded the list, or last heard from its
+  publisher that its copy was current
+
+An address on no list has an empty `blocklists`. An address with no live route
+still has a result with its `blocklists`.
+
+The lists:
+
+- `dshield`: the 20 networks that DShield saw scan the most targets in the last
+  three days. From [DShield](https://isc.sans.edu/feeds_doc.html), downloaded
+  every hour.
+- `feodo_tracker`: botnet command-and-control servers. From abuse.ch
+  [Feodo Tracker](https://feodotracker.abuse.ch/blocklist/), downloaded every 15
+  minutes.
+- `firehol_abusers_30d`: addresses reported for comment, form or forum spam in
+  the last 30 days. From
+  [FireHOL](https://iplists.firehol.org/?ipset=firehol_abusers_30d), downloaded
+  every 5 hours.
+- `firehol_level3`: addresses reported for attacks, spyware or viruses in the
+  last 30 days. From
+  [FireHOL](https://iplists.firehol.org/?ipset=firehol_level3), downloaded every
+  3 hours.
+- `spamhaus_drop` and `spamhaus_dropv6`: IPv4 and IPv6 networks that Spamhaus
+  says spammers or cyber criminals have hijacked or lease. From
+  [Spamhaus DROP](https://www.spamhaus.org/blocklists/do-not-route-or-peer/),
+  downloaded once a day. Spamhaus merged its EDROP list into DROP.
+- `tor_exits`: Tor exit nodes, where traffic from the Tor network leaves. From
+  the [Tor Project](https://check.torproject.org/torbulkexitlist), downloaded
+  every hour.
+
+No list is downloaded more often than its publisher updates it or allows. Each
+can be downloaded whole without an account or a key.
+
+How RouteWatch keeps the lists:
+
+- It holds each list in memory, so a lookup makes no outside request.
+- It keeps a copy of each list in the `blocklists` directory of the state
+  directory (see Configuration). Each copy is a file named after its list.
+- Beside each copy, a file ending in `.validators` keeps the `Last-Modified` and
+  `ETag` the publisher sent with that copy.
+- At startup it loads each list from its copy. It downloads a list at once when
+  the copy is older than the list's interval, or when there is no copy.
+- A download sends the copy's `Last-Modified` as `If-Modified-Since` and its
+  `ETag` as `If-None-Match`. The publisher then sends the list only when it has
+  changed. Without either, the download asks for the whole list.
+- A download fails when it takes over a minute or its file is over 16 MiB.
+- When a download fails, or its file does not parse, RouteWatch keeps the
+  previous copy and logs the failure. It tries again one interval later.
+
+A successful IP lookup answer carries `Cache-Control` with a `max-age` of 15
+minutes, the shortest list interval. The answer for the caller's own address
+(`/ip/`) is `private`, and the others are `public`.
+
 ## Code Structure
 
 ```
@@ -157,9 +231,11 @@ routewatch/
 │   ├── asinfo-gen/         # Utility to generate AS info data
 │   └── streamdumper/       # Debug utility for raw stream output
 ├── internal/
+│   ├── blocklist/          # Public IP blocklists: downloads and lookups
 │   ├── routewatch/         # Core application logic
 │   ├── server/             # HTTP server and handlers
 │   ├── database/           # SQLite storage layer
+│   ├── routetable/         # The whole routing table in memory
 │   ├── streamer/           # RIPE RIS Live client
 │   ├── ristypes/           # BGP message data structures
 │   ├── logger/             # Structured logging wrapper
@@ -209,6 +285,8 @@ routewatch/
 
 2. **Initialization** (`internal/routewatch/app.go`)
     - Database created with SQLite schema (WAL mode, page caches as in "Memory")
+    - The routing table read from the database into memory, before the streamer
+      connects
     - Message handlers registered with the streamer
     - HTTP server started on configured port
 
@@ -235,7 +313,10 @@ routewatch/
       holds AS 0 anywhere, deletes all of a peer's routes when its BGP session
       goes down). Routes are kept per peer IP, so when one peer IP has sessions
       on two collectors, a session going down on one also removes the routes the
-      other still carries, until they are announced again.
+      other still carries, until they are announced again. It also applies each
+      update to the routing table in memory, and writes the table's changes to
+      the database every second. A write takes at most 20,000 changed prefix and
+      origin AS pairs, and the rest follow in the next writes.
     - **PeeringHandler**: Extracts AS peering relationships from AS paths
 
 5. **HTTP Request Flow**
@@ -323,7 +404,7 @@ client sent. For a request from any other address they use the address the
 request came from, whatever forwarding headers it carries. `X-Real-IP` and
 `True-Client-IP` are not read.
 
-State directory (database location):
+State directory (the database and the blocklist copies):
 
 - macOS: `~/Library/Application Support/berlin.sneak.app.routewatch/`
 - Linux: `/var/lib/berlin.sneak.app.routewatch/` when running as root, otherwise
@@ -419,7 +500,9 @@ What the [upaas](https://git.eeqj.de/sneak/upaas) app needs:
 - Health check: the image's `HEALTHCHECK` requests
   `/.well-known/healthcheck.json` on the container port. upaas reads the
   container's health 60 seconds after a deploy and fails the deploy unless it is
-  `healthy`.
+  `healthy`. For the first 60 seconds, Docker 25 and later runs the check every
+  5 seconds, and the first pass makes the container healthy. Startup first reads
+  the routing table, which takes about 25 seconds when the table is full.
 - Stop grace: the container needs 9 seconds between SIGTERM and SIGKILL. upaas
   gives 10 (`stopTimeoutSeconds` in its `internal/docker/client.go`), as
   `docker stop` does by default. The daemon allows 8 seconds for the handlers to
@@ -485,6 +568,11 @@ provide:
   or `go.sum`) and `go fmt` (writes), then `script/check`
 - `script/install-precommit` — install the git pre-commit hook that runs
   `script/precommit`
+- `script/asupdate` — rebuild the AS list built into RouteWatch,
+  `pkg/asinfo/asdata.json.gz`, from the `as.csv` file of
+  [ipverse/as-metadata](https://github.com/ipverse/as-metadata). It needs the
+  network. It runs `cmd/asinfo-gen`, which fails when it finds no AS. When
+  `cmd/asinfo-gen` fails, the old list stays and the script exits non-zero.
 
 Tests and the linter run only in Docker, as the `test` and `lint` phases of the
 `Dockerfile`; the image cannot be built unless both pass. Every `docker build`

TODO.md

@@ -33,6 +33,74 @@ tested.
 
 # Completed Steps
 
+- 2026-10-27: once the stop deadline has passed, the prefix handler starts no
+  flush. A batch that filled while a write ran past the deadline could still be
+  written after it (closes #188)
+- 2026-10-27: the prefix handler applies each update to the routing table in
+  memory, and writes the table's changes to the database every second. A write
+  takes at most 20,000 changed pairs, and the rest follow in the next writes. A
+  failed write is written again later. Startup reads the table before the
+  streamer connects. The pages still read the per-peer route tables (part of
+  #122)
+- 2026-10-27: the database keeps a copy of the whole routing table in a new
+  `routes` table, one row per prefix and origin AS. The peers' numbers are in a
+  new `route_peers` table. One function writes the pairs that changed in memory,
+  and another reads the whole table back into memory at startup. Nothing uses
+  them yet (part of #122)
+- 2026-10-27: a new package, `internal/routetable`, holds the whole routing
+  table in memory. For each prefix and origin AS it keeps the peers that carry
+  it, one bit per peer, and the two newest of their routes. Nothing uses it yet
+  (part of #122)
+- 2026-10-27: each result of the IP lookup lists the public blocklists the
+  address is on, in `blocklists`. The lists are DShield, Feodo Tracker, two
+  FireHOL lists, Spamhaus DROP and the Tor exit list. RouteWatch downloads each
+  list on its own schedule and answers from copies in memory. The copies are
+  also kept in the state directory's `blocklists` directory. IP lookup answers
+  carry `Cache-Control`. An address with no live route now has a result too,
+  without route fields, so the IP lookup no longer answers 404 (closes #158)
+- 2026-10-27: the home page has an IP information API card. It shows the `curl`
+  command that looks up the visitor's own address at `/ip/{addr}`, and that
+  command's live answer (closes #156)
+- 2026-10-27: on the AS page, a click on the heading of the IPv4 or the IPv6
+  prefix list folds or unfolds the list. Both lists start open (closes #155)
+- 2026-10-27: the AS page lists its IPv4 and its IPv6 prefixes by mask length,
+  shortest first, and prefixes of one mask length by address. They used to be
+  listed by address (closes #153)
+- 2026-10-27: on `/` and `/status`, a spinner beside the status turns one frame
+  each time the stats show more messages than the time before. A page that has
+  not seen more messages for three refreshes shows "stale" and the time since
+  then instead, in red (closes #152)
+- 2026-10-27: the WHOIS details of a Brazilian AS keep their accented letters.
+  LACNIC's answer for such an AS comes from NIC.br, Brazil's registry, with each
+  accented letter replaced. The details now come from NIC.br's own server,
+  `whois.registro.br`. When that query fails, the details from LACNIC's answer
+  are kept and a warning is logged. After NIC.br answers that RouteWatch is over
+  its query limit, RouteWatch stops asking NIC.br for an hour (closes #174)
+- 2026-10-27: `make asupdate` stops with an error when the download of `as.csv`
+  breaks off. The generator used to retry the failed read forever. A record that
+  does not parse is still logged and skipped (closes #177)
+- 2026-10-27: `make asupdate` runs the new `script/asupdate`. It replaces the AS
+  list built into RouteWatch only when the generator succeeds and finds at least
+  one AS. A failed download used to replace the list with an empty file. The
+  generator reads `as.csv` from `ipverse/as-metadata`, the source's new name
+  (closes #173)
+- 2026-10-27: the WHOIS details of an AS at RIPE, APNIC or AFRINIC come only
+  from its `aut-num` object and the organisation object it names. RIPE and APNIC
+  start their answer with the `as-block` object of the AS's block. Its dates
+  were stored as the AS's (closes #168)
+- 2026-10-27: AS names keep their accented letters. The AS list built into
+  RouteWatch is rebuilt from today's `as.csv`, which added a country code
+  column. That file no longer lists AS 0 or the documentation AS numbers. A
+  WHOIS answer that is not valid UTF-8 is decoded as Latin-1, which RIPE and
+  APNIC send, before it is parsed and stored (closes #165)
+- 2026-10-27: the Age column on the AS and prefix pages reads in words, such as
+  "5 minutes ago" or "2 weeks ago", instead of Go durations such as "360h0m0s
+  ago". An age under a minute reads in seconds, and one over a month in months
+  or years instead of a date (closes #163)
+- 2026-10-26: a write to a stored AS, peering or peer keeps the earlier of the
+  two first-seen times and the later of the two last-seen times. An old update
+  from a collector catching up on a backlog no longer moves last seen back
+  (closes #162)
 - 2026-10-26: the status page shows "Route Churn/min", the number of prefix
   announcements and withdrawals, from all peers, in the last full clock minute.
   `/api/v1/stats` reports it as `route_churn_per_min` in `stream`, which
@@ -194,4 +262,6 @@ tested.
 
 # Future Steps
 
-None open.
+- the rest of https://git.eeqj.de/sneak/routewatch/issues/122, one PR each: the
+  pages and the API reading from the routing table, then removing the per-peer
+  route tables

cmd/asinfo-gen/main.go

@@ -6,6 +6,7 @@ import (
 	"encoding/csv"
 	"encoding/json"
 	"errors"
+	"fmt"
 	"io"
 	"log"
 	"net/http"
@@ -14,7 +15,21 @@ import (
 	"strings"
 )
 
-const asCsvURL = "https://github.com/ipverse/asn-info/raw/refs/heads/master/as.csv"
+const asCsvURL = "https://github.com/ipverse/as-metadata/raw/refs/heads/master/as.csv"
+
+// The first columns of as.csv, the ones the generator reads. It reads past
+// the columns after them, such as the country code.
+const (
+	asnColumn         = "asn"
+	handleColumn      = "handle"
+	descriptionColumn = "description"
+	columnsRead       = 3
+)
+
+var (
+	errUnexpectedHeader = errors.New("unexpected CSV header")
+	errNoASes           = errors.New("no AS in the CSV")
+)
 
 // ASInfo represents information about an Autonomous System
 type ASInfo struct {
@@ -45,40 +60,66 @@ func main() {
 		log.Fatalf("Failed to fetch CSV: HTTP %d", resp.StatusCode)
 	}
 
-	// Parse CSV
+	asInfos, err := parseCSV(resp.Body)
-	reader := csv.NewReader(resp.Body)
+
+	// Closed here rather than deferred: log.Fatalf exits without running
+	// deferred calls.
+	_ = resp.Body.Close()
+
+	if err != nil {
+		log.Fatalf("Failed to parse CSV: %v", err)
+	}
+
+	log.Printf("Parsed %d AS records", len(asInfos))
+
+	// Convert to JSON and output to stdout
+	encoder := json.NewEncoder(os.Stdout)
+	encoder.SetIndent("", "\t")
+
+	err = encoder.Encode(asInfos)
+	if err != nil {
+		log.Fatalf("Failed to encode JSON: %v", err)
+	}
+}
+
+// parseCSV reads as.csv from r and returns its ASes, with the handle and the
+// description as the file spells them. A header whose first columns are not
+// the AS number, the handle and the description is an error. A record that
+// does not parse is logged and skipped. A read that fails, such as on a broken
+// download, is an error. A file left with no AS is an error.
+func parseCSV(r io.Reader) ([]ASInfo, error) {
+	reader := csv.NewReader(r)
 
-	// Read header
 	header, err := reader.Read()
 	if err != nil {
-		log.Fatalf("Failed to read CSV header: %v", err)
+		return nil, fmt.Errorf("read CSV header: %w", err)
 	}
 
-	if len(header) != 3 || header[0] != "asn" || header[1] != "handle" ||
+	if len(header) < columnsRead || header[0] != asnColumn ||
-		header[2] != "description" {
+		header[1] != handleColumn || header[2] != descriptionColumn {
-		log.Fatalf("Unexpected CSV header: %v", header)
+		return nil, fmt.Errorf("%w: %v", errUnexpectedHeader, header)
 	}
 
-	// Read all records
 	var asInfos []ASInfo
 
 	for {
+		// The reader returns an error for a record with a different number
+		// of fields than the header.
 		record, err := reader.Read()
 		if errors.Is(err, io.EOF) {
 			break
 		}
 
-		if err != nil {
+		if _, ok := errors.AsType[*csv.ParseError](err); ok {
 			log.Printf("Error reading CSV record: %v", err)
 
 			continue
 		}
 
-		const expectedFields = 3
+		// Any other error comes from the download, such as a broken
-		if len(record) != expectedFields {
+		// connection. Every later read returns it again.
-			log.Printf("Skipping invalid record: %v", record)
+		if err != nil {
-
+			return nil, fmt.Errorf("read CSV record: %w", err)
-			continue
 		}
 
 		asn, err := strconv.Atoi(record[0])
@@ -95,18 +136,9 @@ func main() {
 		})
 	}
 
-	// Closed here rather than deferred: log.Fatalf exits without running
+	if len(asInfos) == 0 {
-	// deferred calls.
+		return nil, errNoASes
-	_ = resp.Body.Close()
-
-	log.Printf("Parsed %d AS records", len(asInfos))
-
-	// Convert to JSON and output to stdout
-	encoder := json.NewEncoder(os.Stdout)
-	encoder.SetIndent("", "\t")
-
-	err = encoder.Encode(asInfos)
-	if err != nil {
-		log.Fatalf("Failed to encode JSON: %v", err)
 	}
+
+	return asInfos, nil
 }

cmd/asinfo-gen/main_test.go

@@ -0,0 +1,142 @@
+package main
+
+import (
+	"errors"
+	"io"
+	"slices"
+	"strings"
+	"testing"
+	"testing/iotest"
+	"time"
+)
+
+// parseTimeLimit is how long a test waits for parseCSV to return before it
+// fails.
+const parseTimeLimit = 2 * time.Second
+
+// TestParseCSVReadsTodaysLayout parses an as.csv with the country code column
+// that the source added after the description. It expects each AS with its
+// handle and description spelled exactly as in the file, accents included.
+func TestParseCSVReadsTodaysLayout(t *testing.T) {
+	t.Parallel()
+
+	const asCSV = `asn,handle,description,country-code
+1,LVLT-1,Level 3 Parent LLC,US
+1251,FUNDACAO-AMPARO-PESQUISA,FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO SÃO PAULO,BR
+`
+
+	got, err := parseCSV(strings.NewReader(asCSV))
+	if err != nil {
+		t.Fatalf("parseCSV: %v", err)
+	}
+
+	want := []ASInfo{
+		{ASN: 1, Handle: "LVLT-1", Description: "Level 3 Parent LLC"},
+		{
+			ASN:    1251,
+			Handle: "FUNDACAO-AMPARO-PESQUISA",
+			Description: "FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO " +
+				"SÃO PAULO",
+		},
+	}
+
+	if !slices.Equal(got, want) {
+		t.Errorf("parseCSV = %+v, want %+v", got, want)
+	}
+}
+
+// TestParseCSVRejectsAnotherHeader parses files whose first columns are not
+// the AS number, the handle and the description. It expects an error rather
+// than a list read from the wrong columns.
+func TestParseCSVRejectsAnotherHeader(t *testing.T) {
+	t.Parallel()
+
+	for _, asCSV := range []string{
+		"asn,handle\n1,LVLT-1\n",
+		"asn,description,handle\n1,Level 3 Parent LLC,LVLT-1\n",
+	} {
+		_, err := parseCSV(strings.NewReader(asCSV))
+		if err == nil {
+			t.Errorf("parseCSV(%q): no error", asCSV)
+		}
+	}
+}
+
+// TestParseCSVRejectsAFileWithNoASes parses files that hold no AS, one with
+// only the header and one whose only record has no valid AS number. It
+// expects errNoASes, so that make asupdate keeps the old list.
+func TestParseCSVRejectsAFileWithNoASes(t *testing.T) {
+	t.Parallel()
+
+	for _, asCSV := range []string{
+		"asn,handle,description,country-code\n",
+		"asn,handle,description,country-code\nAS1,LVLT-1,Level 3,US\n",
+	} {
+		_, err := parseCSV(strings.NewReader(asCSV))
+		if !errors.Is(err, errNoASes) {
+			t.Errorf("parseCSV(%q) = %v, want %v", asCSV, err, errNoASes)
+		}
+	}
+}
+
+// TestParseCSVSkipsARecordThatDoesNotParse parses an as.csv with a record
+// that has too few fields between two valid records. It expects both valid
+// ASes and no error, so that one bad record does not stop make asupdate.
+func TestParseCSVSkipsARecordThatDoesNotParse(t *testing.T) {
+	t.Parallel()
+
+	const asCSV = "asn,handle,description,country-code\n" +
+		"1,LVLT-1,Level 3 Parent LLC,US\n" +
+		"2,UDEL-DCN\n" +
+		"3,MIT-GATEWAYS,Massachusetts Institute of Technology,US\n"
+
+	got, err := parseCSV(strings.NewReader(asCSV))
+	if err != nil {
+		t.Fatalf("parseCSV: %v", err)
+	}
+
+	want := []ASInfo{
+		{ASN: 1, Handle: "LVLT-1", Description: "Level 3 Parent LLC"},
+		{
+			ASN:         3,
+			Handle:      "MIT-GATEWAYS",
+			Description: "Massachusetts Institute of Technology",
+		},
+	}
+
+	if !slices.Equal(got, want) {
+		t.Errorf("parseCSV = %+v, want %+v", got, want)
+	}
+}
+
+// TestParseCSVStopsWhenTheDownloadBreaksOff parses an as.csv whose download
+// breaks off after the first record. From then on every read fails, as on a
+// broken connection. It expects parseCSV to return that error, so that make
+// asupdate keeps the old list.
+func TestParseCSVStopsWhenTheDownloadBreaksOff(t *testing.T) {
+	t.Parallel()
+
+	const asCSV = "asn,handle,description,country-code\n" +
+		"1,LVLT-1,Level 3 Parent LLC,US\n"
+
+	download := io.MultiReader(
+		strings.NewReader(asCSV), iotest.ErrReader(io.ErrUnexpectedEOF))
+
+	// parseCSV runs on its own goroutine, so that a parseCSV that never
+	// returns fails the test instead of hanging it.
+	parsed := make(chan error, 1)
+
+	go func() {
+		_, err := parseCSV(download)
+		parsed <- err
+	}()
+
+	select {
+	case err := <-parsed:
+		if !errors.Is(err, io.ErrUnexpectedEOF) {
+			t.Errorf("parseCSV = %v, want %v", err, io.ErrUnexpectedEOF)
+		}
+	case <-time.After(parseTimeLimit):
+		t.Fatalf("parseCSV did not return within %v", parseTimeLimit)
+	}
+}

go.mod

@@ -3,13 +3,17 @@ module git.eeqj.de/sneak/routewatch
 go 1.27.1
 
 require (
+	github.com/bits-and-blooms/bitset v1.26.0
 	github.com/dustin/go-humanize v1.0.1
 	github.com/go-chi/chi/v5 v5.2.2
+	github.com/google/btree v1.1.3
 	github.com/google/uuid v1.6.0
 	github.com/mattn/go-sqlite3 v1.14.29
 	github.com/rcrowley/go-metrics v0.0.0-20250401214520-65e299d6c5c9
 	go.uber.org/fx v1.24.0
+	go4.org/netipx v0.0.0-20260823151212-3075585bcbeb
 	golang.org/x/term v0.33.0
+	golang.org/x/text v0.43.0
 )
 
 require (

go.sum

@@ -1,9 +1,13 @@
+github.com/bits-and-blooms/bitset v1.26.0 h1:WPvcPZbP1yuKofmjs2SYIFO1EjzIGhCP9ducElLsh5Q=
+github.com/bits-and-blooms/bitset v1.26.0/go.mod h1:7hO7Gc7Pp1vODcmWvKMRA9BNmbv6a/7QIWpPxHddWR8=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/dustin/go-humanize v1.0.1 h1:GzkhY7T5VNhEkwH0PVJgjz+fX1rhBrR7pRT3mDkpeCY=
 github.com/dustin/go-humanize v1.0.1/go.mod h1:Mu1zIs6XwVuF/gI1OepvI0qD18qycQx+mFykh5fBlto=
 github.com/go-chi/chi/v5 v5.2.2 h1:CMwsvRVTbXVytCk1Wd72Zy1LAsAh9GxMmSNWLHCG618=
 github.com/go-chi/chi/v5 v5.2.2/go.mod h1:L2yAIGWB3H+phAw1NxKwWM+7eUH/lU8pOMm5hHcoops=
+github.com/google/btree v1.1.3 h1:CVpQJjYgC4VbzxeGVHfvZrv1ctoYCAI8vbl07Fcxlyg=
+github.com/google/btree v1.1.3/go.mod h1:qOPhT0dTNdNzV6Z/lhRX0YXUafgPLFUh+gZMl761Gm4=
 github.com/google/uuid v1.6.0 h1:NIvaJDMOsjHA8n1jAhLSgzrAzy1Hgr+hNrb57e+94F0=
 github.com/google/uuid v1.6.0/go.mod h1:TIyPZe4MgqvfeYDBFedMoGGpEw/LqOeaOT+nhxU+yHo=
 github.com/mattn/go-sqlite3 v1.14.29 h1:1O6nRLJKvsi1H2Sj0Hzdfojwt8GiGKm+LOfLaBFaouQ=
@@ -24,9 +28,13 @@ go.uber.org/multierr v1.10.0 h1:S0h4aNzvfcFsC3dRF1jLoaov7oRaKqRGC/pUEJ2yvPQ=
 go.uber.org/multierr v1.10.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
 go.uber.org/zap v1.26.0 h1:sI7k6L95XOKS281NhVKOFCUNIvv9e0w4BF8N3u+tCRo=
 go.uber.org/zap v1.26.0/go.mod h1:dtElttAiwGvoJ/vj4IwHBS/gXsEu/pZ50mUIRWuG0so=
+go4.org/netipx v0.0.0-20260823151212-3075585bcbeb h1:XBM4hvfwGAttkkiTIFfeigdfcL1xIfdKXqFdgiHGtDs=
+go4.org/netipx v0.0.0-20260823151212-3075585bcbeb/go.mod h1:PLyyIXexvUFg3Owu6p/WfdlivPbZJsZdgWZlrGope/Y=
 golang.org/x/sys v0.34.0 h1:H5Y5sJ2L2JRdyv7ROF1he/lPdvFsd0mJHFw2ThKHxLA=
 golang.org/x/sys v0.34.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
 golang.org/x/term v0.33.0 h1:NuFncQrRcaRvVmgRkvM3j/F00gWIAlcmlB8ACEKmGIg=
 golang.org/x/term v0.33.0/go.mod h1:s18+ql9tYWp1IfpV9DmCtQDDSRBUjKaw9M1eAv5UeF0=
+golang.org/x/text v0.43.0 h1:1QivrlhwAsnMOcqgOdl9my7s9OyZl8O5/UGUTJVXoWc=
+golang.org/x/text v0.43.0/go.mod h1:hbSIYA/amXcRXTFSZqh8tWHEoqRvvbKPJ2uz/KU+a+s=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/blocklist/blocklist.go

@@ -0,0 +1,184 @@
+// Package blocklist downloads public IP blocklists on a schedule, keeps the
+// last good copy of each on disk and in memory, and answers which lists
+// contain an address.
+package blocklist
+
+import (
+	"context"
+	"log/slog"
+	"net/netip"
+	"sync"
+	"time"
+
+	"go4.org/netipx"
+)
+
+// Format is how a list's file is written.
+type Format int
+
+const (
+	// FormatLines has one address or network per line, such as 192.0.2.1 or
+	// 192.0.2.0/24. Lines that start with # are comments.
+	FormatLines Format = iota
+
+	// FormatSpamhausJSON has one JSON object per line, with a network in its
+	// cidr field. The last line holds the file's metadata and no network.
+	FormatSpamhausJSON
+
+	// FormatDShield has one network per line, as tab-separated fields that
+	// start with the network's first and last address. Lines that start
+	// with # are comments.
+	FormatDShield
+)
+
+// List is one public blocklist.
+type List struct {
+	// Name names the list in lookup answers, and names its copy on disk.
+	Name string
+
+	// Description says in one line what being on the list means.
+	Description string
+
+	// URL is where the publisher serves the whole list.
+	URL string
+
+	// Interval is how long a copy is used before the list is downloaded
+	// again.
+	Interval time.Duration
+
+	// Format is how the list's file is written.
+	Format Format
+}
+
+// Listing says that a list contains an address.
+type Listing struct {
+	Name        string `json:"name"`
+	Description string `json:"description"`
+
+	// Updated is when routewatch last downloaded the list, or last heard from
+	// its publisher that its copy was still current.
+	Updated time.Time `json:"updated"`
+}
+
+// listCopy is a list's last good copy in memory.
+type listCopy struct {
+	addresses *netipx.IPSet
+	updated   time.Time
+
+	// validators identify the version of the list this copy holds.
+	validators validators
+}
+
+// Params is what New needs.
+type Params struct {
+	// Dir is the directory that holds the copies on disk.
+	Dir string
+
+	// Lists are the lists to download and look addresses up in.
+	Lists []List
+
+	Logger *slog.Logger
+}
+
+// Blocklists keeps a copy of each list and answers which lists contain an
+// address. Start loads the copies from disk and starts downloading the lists.
+type Blocklists struct {
+	dir    string
+	lists  []List
+	logger *slog.Logger
+
+	// copies holds each list's last good copy, by list name. A list with no
+	// good copy yet has none.
+	mu     sync.RWMutex
+	copies map[string]listCopy
+
+	// stop ends the goroutine Start runs, and done is closed when it returns.
+	stop context.CancelFunc
+	done chan struct{}
+}
+
+// New returns a Blocklists with no copies. Start loads them.
+func New(params Params) *Blocklists {
+	return &Blocklists{
+		dir:    params.Dir,
+		lists:  params.Lists,
+		logger: params.Logger.With("component", "blocklists"),
+		copies: make(map[string]listCopy),
+		done:   make(chan struct{}),
+	}
+}
+
+// Lookup returns a Listing for each list whose copy contains addr, in the
+// order of the lists given to New. It makes no outside request. When no list
+// contains addr, it returns an empty list, not nil.
+func (b *Blocklists) Lookup(addr netip.Addr) []Listing {
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+
+	listings := []Listing{}
+
+	for _, list := range b.lists {
+		c, ok := b.copies[list.Name]
+		if ok && c.addresses.Contains(addr.Unmap()) {
+			listings = append(listings, Listing{
+				Name:        list.Name,
+				Description: list.Description,
+				Updated:     c.updated,
+			})
+		}
+	}
+
+	return listings
+}
+
+// ShortestInterval returns the shortest Interval of the lists. That is the
+// soonest a copy can change, and so how long a lookup answer stays current.
+func (b *Blocklists) ShortestInterval() time.Duration {
+	var shortest time.Duration
+
+	for i, list := range b.lists {
+		if i == 0 || list.Interval < shortest {
+			shortest = list.Interval
+		}
+	}
+
+	return shortest
+}
+
+// updated returns when the named list's copy was last downloaded or found
+// current, or the zero time when the list has no copy.
+func (b *Blocklists) updated(name string) time.Time {
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+
+	return b.copies[name].updated
+}
+
+// copyValidators returns the validators of the named list's copy. They are
+// empty when the list has no copy.
+func (b *Blocklists) copyValidators(name string) validators {
+	b.mu.RLock()
+	defer b.mu.RUnlock()
+
+	return b.copies[name].validators
+}
+
+// setCopy makes c the named list's copy.
+func (b *Blocklists) setCopy(name string, c listCopy) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	b.copies[name] = c
+}
+
+// setUpdated records that the named list's copy was found current at t.
+func (b *Blocklists) setUpdated(name string, t time.Time) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	c, ok := b.copies[name]
+	if ok {
+		c.updated = t
+		b.copies[name] = c
+	}
+}

internal/blocklist/blocklist_internal_test.go

@@ -0,0 +1,494 @@
+package blocklist
+
+import (
+	"context"
+	"errors"
+	"io"
+	"io/fs"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"net/netip"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+	"testing"
+	"time"
+)
+
+// The test list's name and description, the address its good version lists,
+// and the address a newer version lists instead.
+const (
+	testListName        = "test_list"
+	testListDescription = "On the test list"
+	listedAddr          = "192.0.2.1"
+	goodListBody        = "# A test list\n" + listedAddr + "\n"
+	newListedAddr       = "192.0.2.2"
+	newListBody         = "# A test list\n" + newListedAddr + "\n"
+)
+
+// testETag is the ETag a publisher sends with a version of the test list.
+const testETag = `"v1"`
+
+// maxWait is how long a test waits for the download goroutine.
+const maxWait = 10 * time.Second
+
+// publisher stands in for a list's publisher. It answers every request with
+// its status and body, and keeps the headers of each request. A 200 answer
+// carries lastModified and etag, when set, as Last-Modified and ETag. As
+// from a real publisher, a request whose If-None-Match or If-Modified-Since
+// matches them is answered "not modified".
+type publisher struct {
+	mu           sync.Mutex
+	status       int
+	body         string
+	lastModified time.Time
+	etag         string
+	headers      []http.Header
+}
+
+// newPublisher starts a publisher that answers 200 with body, and returns it
+// and its URL.
+func newPublisher(t *testing.T, body string) (*publisher, string) {
+	t.Helper()
+
+	p := &publisher{status: http.StatusOK, body: body}
+	srv := httptest.NewServer(p)
+	t.Cleanup(srv.Close)
+
+	return p, srv.URL
+}
+
+func (p *publisher) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	p.headers = append(p.headers, r.Header.Clone())
+
+	if p.status != http.StatusOK {
+		w.WriteHeader(p.status)
+		_, _ = io.WriteString(w, p.body)
+
+		return
+	}
+
+	if p.etag != "" {
+		w.Header().Set(etagHeader, p.etag)
+	}
+
+	// ServeContent sends Last-Modified unless lastModified is zero, and
+	// answers "not modified" when the request's conditions match.
+	http.ServeContent(w, r, testListName, p.lastModified,
+		strings.NewReader(p.body))
+}
+
+// answer makes the publisher answer later requests with status and body.
+func (p *publisher) answer(status int, body string) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	p.status, p.body = status, body
+}
+
+// publish makes the publisher answer later requests with a version of the
+// list: body, with lastModified and etag. A zero lastModified or an empty
+// etag is not sent.
+func (p *publisher) publish(body string, lastModified time.Time, etag string) {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	p.status, p.body = http.StatusOK, body
+	p.lastModified, p.etag = lastModified, etag
+}
+
+// requests returns the headers of the requests the publisher has had.
+func (p *publisher) requests() []http.Header {
+	p.mu.Lock()
+	defer p.mu.Unlock()
+
+	return append([]http.Header(nil), p.headers...)
+}
+
+// testList returns a list served at url, written in format.
+func testList(url string, format Format) List {
+	return List{
+		Name:        testListName,
+		Description: testListDescription,
+		URL:         url,
+		Interval:    time.Hour,
+		Format:      format,
+	}
+}
+
+func newTestBlocklists(dir string, list List) *Blocklists {
+	return New(Params{
+		Dir:    dir,
+		Lists:  []List{list},
+		Logger: slog.New(slog.DiscardHandler),
+	})
+}
+
+// lookup looks addr up in b.
+func lookup(t *testing.T, b *Blocklists, addr string) []Listing {
+	t.Helper()
+
+	return b.Lookup(netip.MustParseAddr(addr))
+}
+
+// TestLookupFindsListedAddresses downloads a list in each format and looks
+// up addresses on it, inside its networks, and off it, in IPv4 and IPv6.
+// A listed address has one listing that names the list; any other has an
+// empty list of listings.
+func TestLookupFindsListedAddresses(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		format   Format
+		body     string
+		listed   []string
+		unlisted []string
+	}{
+		{
+			name:     "single addresses",
+			format:   FormatLines,
+			body:     "# comment\n192.0.2.1\n\n2001:db8::1\n",
+			listed:   []string{"192.0.2.1", "::ffff:192.0.2.1", "2001:db8::1"},
+			unlisted: []string{"192.0.2.2", "2001:db8::2"},
+		},
+		{
+			name:     "networks",
+			format:   FormatLines,
+			body:     "# comment\n198.51.100.0/24\n2001:db8:1::/48\n",
+			listed:   []string{"198.51.100.0", "198.51.100.255", "2001:db8:1::5"},
+			unlisted: []string{"198.51.101.0", "2001:db8:2::1"},
+		},
+		{
+			name:   "Spamhaus networks",
+			format: FormatSpamhausJSON,
+			body: `{"cidr":"203.0.113.0/25","sblid":"SBL1","rir":"arin"}` + "\n" +
+				`{"cidr":"2001:db8:3::/48","sblid":"SBL2","rir":"ripencc"}` + "\n" +
+				`{"type":"metadata","timestamp":1793074442,"records":2}` + "\n",
+			listed:   []string{"203.0.113.1", "2001:db8:3::1"},
+			unlisted: []string{"203.0.113.200", "2001:db8:4::1"},
+		},
+		{
+			name:   "DShield networks",
+			format: FormatDShield,
+			body: "#   DShield.org Recommended Block List\n" +
+				"192.0.2.0\t192.0.2.255\t24\t327\tEXAMPLE\tUS\tNone\n",
+			listed:   []string{"192.0.2.0", "192.0.2.77"},
+			unlisted: []string{"192.0.3.1", "2001:db8::1"},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			_, url := newPublisher(t, tt.body)
+			b := newTestBlocklists(t.TempDir(), testList(url, tt.format))
+
+			err := b.download(t.Context(), b.lists[0])
+			if err != nil {
+				t.Fatalf("download: %v", err)
+			}
+
+			for _, addr := range tt.listed {
+				listings := lookup(t, b, addr)
+				if len(listings) != 1 || listings[0].Name != testListName ||
+					listings[0].Description != testListDescription ||
+					listings[0].Updated.IsZero() {
+					t.Errorf("%s: listings %+v, want one for %s", addr,
+						listings, testListName)
+				}
+			}
+
+			for _, addr := range tt.unlisted {
+				listings := lookup(t, b, addr)
+				if listings == nil || len(listings) != 0 {
+					t.Errorf("%s: listings %#v, want an empty list", addr, listings)
+				}
+			}
+		})
+	}
+}
+
+// TestFailedDownloadKeepsThePreviousCopy downloads a good version of a list,
+// then one that fails. The good copy stays in memory and on disk, and no
+// part of the failed download is left beside it.
+func TestFailedDownloadKeepsThePreviousCopy(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name   string
+		status int
+		body   string
+	}{
+		{"server error", http.StatusInternalServerError, "unavailable"},
+		{"not a list", http.StatusOK, "<!DOCTYPE html>\n<html></html>\n"},
+		{
+			"over the size limit", http.StatusOK,
+			strings.Repeat(listedAddr+"\n", maxDownloadSize/len(listedAddr)),
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			dir := t.TempDir()
+			p, url := newPublisher(t, goodListBody)
+			b := newTestBlocklists(dir, testList(url, FormatLines))
+
+			err := b.download(t.Context(), b.lists[0])
+			if err != nil {
+				t.Fatalf("first download: %v", err)
+			}
+
+			before := lookup(t, b, listedAddr)
+
+			p.answer(tt.status, tt.body)
+
+			err = b.download(t.Context(), b.lists[0])
+			if err == nil {
+				t.Fatal("second download returned no error")
+			}
+
+			after := lookup(t, b, listedAddr)
+			if len(after) != 1 || len(before) != 1 ||
+				!after[0].Updated.Equal(before[0].Updated) {
+				t.Errorf("listings %+v after the failure, want %+v", after, before)
+			}
+
+			copies := os.DirFS(dir)
+
+			onDisk, err := fs.ReadFile(copies, testListName)
+			if err != nil || string(onDisk) != goodListBody {
+				t.Errorf("copy on disk %q (%v), want %q", onDisk, err, goodListBody)
+			}
+
+			_, err = fs.Stat(copies, testListName+downloadSuffix)
+			if !errors.Is(err, fs.ErrNotExist) {
+				t.Errorf("the failed download's file is still there (%v)", err)
+			}
+		})
+	}
+}
+
+// TestRestartLoadsCopiesFromDisk downloads a list, then starts a new
+// Blocklists on the same directory, as a restart does. The new one answers
+// from the copy on disk at once, and does not download the list again while
+// the copy is younger than the list's interval.
+func TestRestartLoadsCopiesFromDisk(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+	p, url := newPublisher(t, goodListBody)
+	list := testList(url, FormatLines)
+
+	first := newTestBlocklists(dir, list)
+
+	err := first.download(t.Context(), list)
+	if err != nil {
+		t.Fatalf("download: %v", err)
+	}
+
+	downloaded := lookup(t, first, listedAddr)[0].Updated
+
+	second := newTestBlocklists(dir, list)
+	second.Start(t.Context())
+	second.Stop(t.Context())
+
+	listings := lookup(t, second, listedAddr)
+	if len(listings) != 1 ||
+		listings[0].Updated.Sub(downloaded).Abs() > time.Second {
+		t.Errorf("after the restart, listings %+v, want one updated at %s",
+			listings, downloaded)
+	}
+
+	if got := len(p.requests()); got != 1 {
+		t.Errorf("the publisher had %d requests, want 1", got)
+	}
+}
+
+// TestStartRefreshesAnOldCopy starts on a copy older than its list's
+// interval. The list is downloaded at once, with routewatch's User-Agent and
+// the Last-Modified and ETag the publisher sent with the copy, kept on disk.
+// The publisher answers that the copy is still current, so the copy is kept
+// and marked as updated now.
+func TestStartRefreshesAnOldCopy(t *testing.T) {
+	t.Parallel()
+
+	dir := t.TempDir()
+	p, url := newPublisher(t, goodListBody)
+	list := testList(url, FormatLines)
+
+	lastModified := time.Now().Add(-3 * list.Interval).UTC().Truncate(time.Second)
+	p.publish(goodListBody, lastModified, testETag)
+
+	err := newTestBlocklists(dir, list).download(t.Context(), list)
+	if err != nil {
+		t.Fatalf("download: %v", err)
+	}
+
+	old := time.Now().Add(-2 * list.Interval).UTC().Truncate(time.Second)
+
+	err = os.Chtimes(filepath.Join(dir, testListName), old, old)
+	if err != nil {
+		t.Fatalf("Chtimes: %v", err)
+	}
+
+	b := newTestBlocklists(dir, list)
+	b.Start(t.Context())
+
+	deadline := time.Now().Add(maxWait)
+	for !lookup(t, b, listedAddr)[0].Updated.After(old) {
+		if time.Now().After(deadline) {
+			t.Fatalf("the copy was not marked updated within %s", maxWait)
+		}
+
+		time.Sleep(time.Millisecond)
+	}
+
+	b.Stop(t.Context())
+
+	requests := p.requests()
+	last := requests[len(requests)-1]
+
+	want := lastModified.Format(http.TimeFormat)
+	if got := last.Get(ifModifiedSinceHeader); got != want {
+		t.Errorf("If-Modified-Since %q, want %q", got, want)
+	}
+
+	if got := last.Get(ifNoneMatchHeader); got != testETag {
+		t.Errorf("If-None-Match %q, want %q", got, testETag)
+	}
+
+	if got := last.Get(userAgentHeader); got != userAgent {
+		t.Errorf("User-Agent %q, want %q", got, userAgent)
+	}
+}
+
+// TestNewVersionOlderThanTheLastDownloadReplacesTheCopy downloads a list.
+// The publisher then puts out a new version whose Last-Modified is earlier
+// than that download, as when a cache in front of the publisher passes the
+// version on late. The next download sends the Last-Modified of the copy,
+// not the time of the download, so it gets the new version.
+func TestNewVersionOlderThanTheLastDownloadReplacesTheCopy(t *testing.T) {
+	t.Parallel()
+
+	p, url := newPublisher(t, goodListBody)
+	list := testList(url, FormatLines)
+	b := newTestBlocklists(t.TempDir(), list)
+
+	firstVersion := time.Now().Add(-2 * list.Interval).UTC().Truncate(time.Second)
+	p.publish(goodListBody, firstVersion, "")
+
+	err := b.download(t.Context(), list)
+	if err != nil {
+		t.Fatalf("first download: %v", err)
+	}
+
+	p.publish(newListBody, firstVersion.Add(list.Interval), "")
+
+	err = b.download(t.Context(), list)
+	if err != nil {
+		t.Fatalf("second download: %v", err)
+	}
+
+	if listings := lookup(t, b, newListedAddr); len(listings) != 1 {
+		t.Errorf("%s: listings %+v, want one from the new version",
+			newListedAddr, listings)
+	}
+
+	want := firstVersion.Format(http.TimeFormat)
+	if got := p.requests()[1].Get(ifModifiedSinceHeader); got != want {
+		t.Errorf("If-Modified-Since %q, want %q", got, want)
+	}
+}
+
+// TestDownloadWithoutLastModifiedOrETagSendsNoCondition downloads a list
+// twice from a publisher that sends neither Last-Modified nor ETag. Neither
+// request carries If-Modified-Since or If-None-Match, so the second download
+// gets the whole list again.
+func TestDownloadWithoutLastModifiedOrETagSendsNoCondition(t *testing.T) {
+	t.Parallel()
+
+	p, url := newPublisher(t, goodListBody)
+	list := testList(url, FormatLines)
+	b := newTestBlocklists(t.TempDir(), list)
+
+	err := b.download(t.Context(), list)
+	if err != nil {
+		t.Fatalf("first download: %v", err)
+	}
+
+	err = b.download(t.Context(), list)
+	if err != nil {
+		t.Fatalf("second download: %v", err)
+	}
+
+	for i, request := range p.requests() {
+		if request.Get(ifModifiedSinceHeader) != "" ||
+			request.Get(ifNoneMatchHeader) != "" {
+			t.Errorf("request %d has a condition: %v", i, request)
+		}
+	}
+}
+
+// TestStopCancelsADownloadInProgress stops while the publisher has not
+// answered. Stop cancels the download and returns once the download
+// goroutine has stopped.
+func TestStopCancelsADownloadInProgress(t *testing.T) {
+	t.Parallel()
+
+	arrived := make(chan struct{})
+
+	var once sync.Once
+
+	srv := httptest.NewServer(http.HandlerFunc(
+		func(_ http.ResponseWriter, r *http.Request) {
+			once.Do(func() { close(arrived) })
+			<-r.Context().Done()
+		}))
+	t.Cleanup(srv.Close)
+
+	b := newTestBlocklists(t.TempDir(), testList(srv.URL, FormatLines))
+	b.Start(t.Context())
+
+	select {
+	case <-arrived:
+	case <-time.After(maxWait):
+		t.Fatalf("no download began within %s", maxWait)
+	}
+
+	ctx, cancel := context.WithTimeout(t.Context(), maxWait)
+	defer cancel()
+
+	b.Stop(ctx)
+
+	select {
+	case <-b.done:
+	default:
+		t.Error("Stop returned before the download goroutine stopped")
+	}
+}
+
+// TestPublicListsAreComplete checks that every public list has what a
+// download and a lookup answer need, and a unique name.
+func TestPublicListsAreComplete(t *testing.T) {
+	t.Parallel()
+
+	names := make(map[string]bool)
+
+	for _, list := range Lists() {
+		if list.Name == "" || list.Description == "" || list.URL == "" ||
+			list.Interval <= 0 || names[list.Name] {
+			t.Errorf("list %+v is incomplete or has a name used before", list)
+		}
+
+		names[list.Name] = true
+	}
+}

internal/blocklist/download.go

@@ -0,0 +1,379 @@
+package blocklist
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"io/fs"
+	"net/http"
+	"os"
+	"slices"
+	"time"
+
+	"go4.org/netipx"
+)
+
+// Limits of one download.
+const (
+	// downloadTimeout is how long one download may take.
+	downloadTimeout = time.Minute
+
+	// maxDownloadSize is the size of the largest list file accepted, in
+	// bytes. The largest list, FireHOL abusers, is about 2.5 MiB.
+	maxDownloadSize = 16 << 20
+)
+
+// The request headers a download sets.
+const (
+	userAgentHeader       = "User-Agent"
+	ifModifiedSinceHeader = "If-Modified-Since"
+	ifNoneMatchHeader     = "If-None-Match"
+
+	// userAgent names routewatch to the publishers.
+	userAgent = "routewatch (+https://git.eeqj.de/sneak/routewatch)"
+)
+
+// The response headers that identify the version of a list a publisher sent.
+const (
+	lastModifiedHeader = "Last-Modified"
+	etagHeader         = "ETag"
+)
+
+const (
+	// downloadSuffix ends the name of the file a download is written to,
+	// beside the list's copy, until it has parsed.
+	downloadSuffix = ".download"
+
+	// validatorsSuffix ends the name of the file beside a list's copy that
+	// keeps the copy's validators.
+	validatorsSuffix = ".validators"
+
+	// dirPermissions are those of the directory that holds the copies.
+	dirPermissions = 0o750
+
+	// validatorsPermissions are those of the file that keeps a copy's
+	// validators.
+	validatorsPermissions = 0o600
+)
+
+// validators are the Last-Modified and ETag headers a publisher sent with a
+// version of a list. A download sends them back, as If-Modified-Since and
+// If-None-Match, so that the publisher sends the list only when it has
+// changed. They are kept as the publisher wrote them.
+//
+//nolint:tagliatelle // snake_case keys, as the Go style guide asks
+type validators struct {
+	LastModified string `json:"last_modified,omitempty"`
+	ETag         string `json:"etag,omitempty"`
+}
+
+var (
+	errUnexpectedStatus = errors.New("unexpected HTTP status")
+	errTooLarge         = errors.New("list is over the size limit")
+)
+
+// Start loads each list's copy from disk. It then starts the goroutine that
+// downloads each list once its copy is older than its Interval, and a list
+// with no copy at once. The goroutine runs until Stop: the end of ctx does
+// not stop it.
+func (b *Blocklists) Start(ctx context.Context) {
+	err := os.MkdirAll(b.dir, dirPermissions)
+	if err != nil {
+		b.logger.Error("Failed to create the blocklists directory",
+			"dir", b.dir, "error", err)
+	}
+
+	nextDownload := make([]time.Time, len(b.lists))
+
+	for i, list := range b.lists {
+		loadErr := b.loadCopy(list)
+		if loadErr != nil && !errors.Is(loadErr, fs.ErrNotExist) {
+			b.logger.Error("Failed to load a blocklist copy",
+				"list", list.Name, "error", loadErr)
+		}
+
+		// A list with no copy has the zero time, so it is due at once.
+		nextDownload[i] = b.updated(list.Name).Add(list.Interval)
+	}
+
+	ctx, b.stop = context.WithCancel(context.WithoutCancel(ctx))
+
+	go func() {
+		b.run(ctx, nextDownload)
+	}()
+
+	b.logger.Info("Blocklist downloads started", "dir", b.dir)
+}
+
+// Stop stops the downloads, cancelling one in progress, and waits until the
+// goroutine has returned or ctx ends. The copies in memory stay, so Lookup
+// still answers.
+func (b *Blocklists) Stop(ctx context.Context) {
+	b.stop()
+
+	select {
+	case <-b.done:
+		b.logger.Info("Blocklist downloads stopped")
+	case <-ctx.Done():
+		b.logger.Warn("Stop deadline passed before the blocklist downloads " +
+			"stopped")
+	}
+}
+
+// run downloads each list when nextDownload says, until ctx ends. After each
+// try, whether it worked or not, the list's next download is an Interval
+// later.
+func (b *Blocklists) run(ctx context.Context, nextDownload []time.Time) {
+	defer close(b.done)
+
+	if len(nextDownload) == 0 {
+		return
+	}
+
+	for {
+		soonest := slices.MinFunc(nextDownload, time.Time.Compare)
+		timer := time.NewTimer(time.Until(soonest))
+
+		select {
+		case <-ctx.Done():
+			timer.Stop()
+
+			return
+		case <-timer.C:
+		}
+
+		for i, list := range b.lists {
+			if time.Now().Before(nextDownload[i]) {
+				continue
+			}
+
+			err := b.download(ctx, list)
+			if ctx.Err() != nil {
+				return
+			}
+
+			if err != nil {
+				b.logger.Error("Blocklist download failed; keeping the "+
+					"previous copy", "list", list.Name, "error", err)
+			}
+
+			nextDownload[i] = time.Now().Add(list.Interval)
+		}
+	}
+}
+
+// download asks the publisher for list, sending the validators of the list's
+// copy when it has them. A new version that parses becomes the list's copy,
+// on disk and in memory. An answer that the copy is still current marks the
+// copy as updated now. Anything else leaves the copy as it is and returns an
+// error.
+func (b *Blocklists) download(ctx context.Context, list List) error {
+	ctx, cancel := context.WithTimeout(ctx, downloadTimeout)
+	defer cancel()
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, list.URL, nil)
+	if err != nil {
+		return err
+	}
+
+	req.Header.Set(userAgentHeader, userAgent)
+
+	held := b.copyValidators(list.Name)
+	if held.LastModified != "" {
+		req.Header.Set(ifModifiedSinceHeader, held.LastModified)
+	}
+
+	if held.ETag != "" {
+		req.Header.Set(ifNoneMatchHeader, held.ETag)
+	}
+
+	resp, err := http.DefaultClient.Do(req)
+	if err != nil {
+		return err
+	}
+
+	defer func() { _ = resp.Body.Close() }()
+
+	switch resp.StatusCode {
+	case http.StatusOK:
+		return b.replaceCopy(list, resp.Body, validators{
+			LastModified: resp.Header.Get(lastModifiedHeader),
+			ETag:         resp.Header.Get(etagHeader),
+		})
+	case http.StatusNotModified:
+		return b.markCurrent(list)
+	default:
+		return fmt.Errorf("%w: %s", errUnexpectedStatus, resp.Status)
+	}
+}
+
+// replaceCopy writes a new version of list, read from body, beside the list's
+// copy. Only when it parses does it replace the copy, on disk and in memory.
+// sent are the validators the publisher sent with the new version.
+func (b *Blocklists) replaceCopy(list List, body io.Reader, sent validators) error {
+	root, err := os.OpenRoot(b.dir)
+	if err != nil {
+		return err
+	}
+
+	defer func() { _ = root.Close() }()
+
+	downloadName := list.Name + downloadSuffix
+
+	addresses, err := writeAndParse(root, downloadName, body, list.Format)
+	if err != nil {
+		_ = root.Remove(downloadName)
+
+		return err
+	}
+
+	// The old copy's validators are removed before the copy is replaced, so
+	// that they are never kept with the new copy.
+	err = root.Remove(list.Name + validatorsSuffix)
+	if err != nil && !errors.Is(err, fs.ErrNotExist) {
+		return err
+	}
+
+	err = root.Rename(downloadName, list.Name)
+	if err != nil {
+		return err
+	}
+
+	b.setCopy(list.Name, listCopy{
+		addresses: addresses, updated: time.Now().UTC(), validators: sent,
+	})
+	b.logger.Info("Downloaded a new version of a blocklist", "list", list.Name)
+
+	// Without this file, the first download after a restart asks for the
+	// whole list.
+	err = writeValidators(root, list.Name, sent)
+	if err != nil {
+		b.logger.Error("Failed to keep the validators of a blocklist copy",
+			"list", list.Name, "error", err)
+	}
+
+	return nil
+}
+
+// writeAndParse writes body to the file name in root, up to maxDownloadSize
+// bytes, and parses the file as format.
+func writeAndParse(
+	root *os.Root, name string, body io.Reader, format Format,
+) (*netipx.IPSet, error) {
+	f, err := root.Create(name)
+	if err != nil {
+		return nil, err
+	}
+
+	defer func() { _ = f.Close() }()
+
+	written, err := io.Copy(f, io.LimitReader(body, maxDownloadSize+1))
+	if err != nil {
+		return nil, err
+	}
+
+	if written > maxDownloadSize {
+		return nil, errTooLarge
+	}
+
+	_, err = f.Seek(0, io.SeekStart)
+	if err != nil {
+		return nil, err
+	}
+
+	return parse(f, format)
+}
+
+// markCurrent records that the publisher says the list's copy is still
+// current: the copy, on disk and in memory, is marked as updated now.
+func (b *Blocklists) markCurrent(list List) error {
+	root, err := os.OpenRoot(b.dir)
+	if err != nil {
+		return err
+	}
+
+	defer func() { _ = root.Close() }()
+
+	now := time.Now().UTC()
+
+	err = root.Chtimes(list.Name, now, now)
+	if err != nil {
+		return err
+	}
+
+	b.setUpdated(list.Name, now)
+	b.logger.Debug("Blocklist copy is still current", "list", list.Name)
+
+	return nil
+}
+
+// loadCopy makes the list's copy on disk, with the validators kept beside it,
+// its copy in memory. The file's modification time is when the copy was
+// updated.
+func (b *Blocklists) loadCopy(list List) error {
+	root, err := os.OpenRoot(b.dir)
+	if err != nil {
+		return err
+	}
+
+	defer func() { _ = root.Close() }()
+
+	f, err := root.Open(list.Name)
+	if err != nil {
+		return err
+	}
+
+	defer func() { _ = f.Close() }()
+
+	info, err := f.Stat()
+	if err != nil {
+		return err
+	}
+
+	addresses, err := parse(f, list.Format)
+	if err != nil {
+		return err
+	}
+
+	held, err := readValidators(root, list.Name)
+	if err != nil {
+		return err
+	}
+
+	b.setCopy(list.Name, listCopy{
+		addresses: addresses, updated: info.ModTime().UTC(), validators: held,
+	})
+
+	return nil
+}
+
+// writeValidators keeps held in the file beside the named list's copy.
+func writeValidators(root *os.Root, name string, held validators) error {
+	data, err := json.Marshal(held)
+	if err != nil {
+		return err
+	}
+
+	return root.WriteFile(name+validatorsSuffix, data, validatorsPermissions)
+}
+
+// readValidators returns the validators kept beside the named list's copy.
+// They are empty when there is no such file.
+func readValidators(root *os.Root, name string) (validators, error) {
+	var held validators
+
+	data, err := root.ReadFile(name + validatorsSuffix)
+	if errors.Is(err, fs.ErrNotExist) {
+		return held, nil
+	}
+
+	if err != nil {
+		return held, err
+	}
+
+	err = json.Unmarshal(data, &held)
+
+	return held, err
+}

internal/blocklist/lists.go

@@ -0,0 +1,93 @@
+package blocklist
+
+import "time"
+
+// How often each list is downloaded. No list is downloaded more often than
+// its publisher updates it or allows.
+const (
+	// DShield asks that its feeds be downloaded at most once an hour:
+	// https://isc.sans.edu/feeds_doc.html
+	dshieldInterval = time.Hour
+
+	// abuse.ch makes the list every 5 minutes and recommends a download at
+	// least every 15: https://feodotracker.abuse.ch/blocklist/
+	feodoTrackerInterval = 15 * time.Minute
+
+	// FireHOL's page for each list gives how often the list changes on
+	// average: about every 5 hours for abusers and every 3 hours for level
+	// 3. FireHOL sets no download limit.
+	// https://iplists.firehol.org/?ipset=firehol_abusers_30d
+	// https://iplists.firehol.org/?ipset=firehol_level3
+	fireHOLAbusersInterval = 5 * time.Hour
+	fireHOLLevel3Interval  = 3 * time.Hour
+
+	// Spamhaus asks that DROP be downloaded at most once a day:
+	// https://www.spamhaus.org/blocklists/do-not-route-or-peer/
+	spamhausDROPInterval = 24 * time.Hour
+
+	// Tor publishes a new exit list every hour and sets no download limit:
+	// https://collector.torproject.org/recent/exit-lists/
+	torExitsInterval = time.Hour
+)
+
+// Lists returns the public blocklists routewatch downloads. Each can be
+// downloaded whole without an account or a key. Spamhaus merged its EDROP
+// list into DROP, so DROP covers both.
+func Lists() []List {
+	return []List{
+		{
+			Name: "dshield",
+			Description: "In one of the 20 networks that DShield saw scan " +
+				"the most targets in the last three days",
+			URL:      "https://feeds.dshield.org/block.txt",
+			Interval: dshieldInterval,
+			Format:   FormatDShield,
+		},
+		{
+			Name:        "feodo_tracker",
+			Description: "A botnet command-and-control server",
+			URL:         "https://feodotracker.abuse.ch/downloads/ipblocklist.txt",
+			Interval:    feodoTrackerInterval,
+			Format:      FormatLines,
+		},
+		{
+			Name: "firehol_abusers_30d",
+			Description: "Reported for comment, form or forum spam in the " +
+				"last 30 days",
+			URL:      "https://iplists.firehol.org/files/firehol_abusers_30d.netset",
+			Interval: fireHOLAbusersInterval,
+			Format:   FormatLines,
+		},
+		{
+			Name: "firehol_level3",
+			Description: "Reported for attacks, spyware or viruses in the " +
+				"last 30 days",
+			URL:      "https://iplists.firehol.org/files/firehol_level3.netset",
+			Interval: fireHOLLevel3Interval,
+			Format:   FormatLines,
+		},
+		{
+			Name: "spamhaus_drop",
+			Description: "In an IPv4 network that Spamhaus says spammers " +
+				"or cyber criminals have hijacked or lease",
+			URL:      "https://www.spamhaus.org/drop/drop_v4.json",
+			Interval: spamhausDROPInterval,
+			Format:   FormatSpamhausJSON,
+		},
+		{
+			Name: "spamhaus_dropv6",
+			Description: "In an IPv6 network that Spamhaus says spammers " +
+				"or cyber criminals have hijacked or lease",
+			URL:      "https://www.spamhaus.org/drop/drop_v6.json",
+			Interval: spamhausDROPInterval,
+			Format:   FormatSpamhausJSON,
+		},
+		{
+			Name:        "tor_exits",
+			Description: "A Tor exit node, where traffic from the Tor network leaves",
+			URL:         "https://check.torproject.org/torbulkexitlist",
+			Interval:    torExitsInterval,
+			Format:      FormatLines,
+		},
+	}
+}

internal/blocklist/parse.go

@@ -0,0 +1,158 @@
+package blocklist
+
+import (
+	"bufio"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"net/netip"
+	"strings"
+
+	"go4.org/netipx"
+)
+
+const (
+	// commentPrefix starts a comment line in a list file.
+	commentPrefix = "#"
+
+	// networkSeparator separates the address and the mask length of a
+	// network, as in 192.0.2.0/24.
+	networkSeparator = "/"
+
+	// dshieldFieldSeparator separates the fields of a DShield line.
+	dshieldFieldSeparator = "\t"
+
+	// spamhausMetadataType is the type of the line that ends a Spamhaus
+	// file. That line holds the file's metadata and no network.
+	spamhausMetadataType = "metadata"
+)
+
+var (
+	errUnknownFormat = errors.New("unknown list format")
+	errNoNetwork     = errors.New("no network on the line")
+	errBadRange      = errors.New("first and last address make no range")
+)
+
+// parse reads a list file written in format and returns the addresses it
+// holds. A line it cannot read fails the whole file, so a file that is not
+// the list, such as an error page, never replaces a good copy.
+func parse(r io.Reader, format Format) (*netipx.IPSet, error) {
+	var builder netipx.IPSetBuilder
+
+	scanner := bufio.NewScanner(r)
+
+	for lineNumber := 1; scanner.Scan(); lineNumber++ {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" || strings.HasPrefix(line, commentPrefix) {
+			continue
+		}
+
+		err := addLine(&builder, line, format)
+		if err != nil {
+			return nil, fmt.Errorf("line %d: %w", lineNumber, err)
+		}
+	}
+
+	err := scanner.Err()
+	if err != nil {
+		return nil, err
+	}
+
+	return builder.IPSet()
+}
+
+// addLine adds the address or network on one line of a list file to builder.
+func addLine(builder *netipx.IPSetBuilder, line string, format Format) error {
+	switch format {
+	case FormatLines:
+		return addAddressOrNetwork(builder, line)
+	case FormatSpamhausJSON:
+		return addSpamhausNetwork(builder, line)
+	case FormatDShield:
+		return addDShieldNetwork(builder, line)
+	default:
+		return errUnknownFormat
+	}
+}
+
+// addAddressOrNetwork adds an address, such as 192.0.2.1, or a network, such
+// as 192.0.2.0/24, to builder.
+func addAddressOrNetwork(builder *netipx.IPSetBuilder, text string) error {
+	if strings.Contains(text, networkSeparator) {
+		network, err := netip.ParsePrefix(text)
+		if err != nil {
+			return err
+		}
+
+		builder.AddPrefix(network)
+
+		return nil
+	}
+
+	addr, err := netip.ParseAddr(text)
+	if err != nil {
+		return err
+	}
+
+	builder.Add(addr)
+
+	return nil
+}
+
+// addSpamhausNetwork adds the network on a line of a Spamhaus file to
+// builder. The metadata line adds nothing.
+func addSpamhausNetwork(builder *netipx.IPSetBuilder, line string) error {
+	var entry struct {
+		CIDR string `json:"cidr"`
+		Type string `json:"type"`
+	}
+
+	err := json.Unmarshal([]byte(line), &entry)
+	if err != nil {
+		return err
+	}
+
+	if entry.Type == spamhausMetadataType {
+		return nil
+	}
+
+	network, err := netip.ParsePrefix(entry.CIDR)
+	if err != nil {
+		return err
+	}
+
+	builder.AddPrefix(network)
+
+	return nil
+}
+
+// addDShieldNetwork adds the network on a line of a DShield file to builder.
+// The line's first two fields are the network's first and last address.
+func addDShieldNetwork(builder *netipx.IPSetBuilder, line string) error {
+	firstField, rest, found := strings.Cut(line, dshieldFieldSeparator)
+	if !found {
+		return errNoNetwork
+	}
+
+	lastField, _, _ := strings.Cut(rest, dshieldFieldSeparator)
+
+	first, err := netip.ParseAddr(firstField)
+	if err != nil {
+		return err
+	}
+
+	last, err := netip.ParseAddr(lastField)
+	if err != nil {
+		return err
+	}
+
+	network := netipx.IPRangeFrom(first, last)
+	if !network.IsValid() {
+		return errBadRange
+	}
+
+	builder.AddRange(network)
+
+	return nil
+}

internal/database/database.go

@@ -945,6 +945,26 @@ func (d *Database) UpdatePrefixesBatch(prefixes map[string]time.Time) error {
 	return nil
 }
 
+// These statements update a stored AS, peering or peer. Each keeps the earlier
+// of the stored and the new first_seen, and the later of the stored and the new
+// last_seen. Some collectors send updates days old while they catch up on a
+// backlog. MIN and MAX compare the times as text, which is time order here: the
+// driver writes every time in one format, and every time is UTC.
+const (
+	updateASNSQL = `UPDATE asns
+		SET first_seen = MIN(first_seen, ?), last_seen = MAX(last_seen, ?)
+		WHERE asn = ?`
+
+	updatePeeringSQL = `UPDATE peerings
+		SET first_seen = MIN(first_seen, ?), last_seen = MAX(last_seen, ?)
+		WHERE as_a = ? AND as_b = ?`
+
+	updatePeerSQL = `UPDATE bgp_peers
+		SET peer_asn = ?, last_message_type = ?,
+		first_seen = MIN(first_seen, ?), last_seen = MAX(last_seen, ?)
+		WHERE peer_ip = ?`
+)
+
 // newASN returns a new ASN record first seen at seen.First and last seen at
 // seen.Last, with the handle and description from the AS info lookup when it
 // knows the number.
@@ -964,9 +984,8 @@ func newASN(number int, seen SeenTimes) ASN {
 	return asn
 }
 
-// upsertASN sets the last_seen time of ASN number to seen.Last with the given
+// upsertASN stores the seen times of ASN number with the given statements,
-// statements, inserting the ASN when it is new. It reports whether it inserted
+// inserting the ASN when it is new. It reports whether it inserted it.
-// it.
 func upsertASN(
 	ctx context.Context, selectStmt, updateStmt, insertStmt *sql.Stmt,
 	number int, seen SeenTimes,
@@ -979,8 +998,8 @@ func upsertASN(
 	err := selectStmt.QueryRowContext(ctx, number).Scan(&asn.ASN, &handle,
 		&description, &asn.FirstSeen, &asn.LastSeen)
 	if err == nil {
-		// ASN exists, update last_seen
+		// ASN exists, update its seen times
-		_, err = updateStmt.ExecContext(ctx, seen.Last, number)
+		_, err = updateStmt.ExecContext(ctx, seen.First, seen.Last, number)
 		if err != nil {
 			return false, fmt.Errorf("failed to update ASN %d: %w", number, err)
 		}
@@ -1030,8 +1049,7 @@ func (d *Database) GetOrCreateASNBatch(asns map[int]SeenTimes) error {
 	}
 	defer func() { _ = selectStmt.Close() }()
 
-	updateStmt, err := tx.PrepareContext(ctx,
+	updateStmt, err := tx.PrepareContext(ctx, updateASNSQL)
-		"UPDATE asns SET last_seen = ? WHERE asn = ?")
 	if err != nil {
 		return fmt.Errorf("failed to prepare update statement: %w", err)
 	}
@@ -1090,17 +1108,19 @@ func (d *Database) GetOrCreateASN(number int, timestamp time.Time) (*ASN, error)
 		"FROM asns WHERE asn = ?", number).
 		Scan(&asn.ASN, &handle, &description, &asn.FirstSeen, &asn.LastSeen)
 	if err == nil {
-		// ASN exists, update last_seen
+		// ASN exists, update its seen times
 		asn.Handle = handle.String
 		asn.Description = description.String
 
-		_, err = tx.Exec("UPDATE asns SET last_seen = ? WHERE asn = ?",
+		_, err = tx.Exec(updateASNSQL, timestamp, timestamp, number)
-			timestamp, number)
 		if err != nil {
 			return nil, err
 		}
 
-		asn.LastSeen = timestamp
+		// Return the seen times the update stored.
+		seen := SeenTimes{First: asn.FirstSeen, Last: asn.LastSeen}
+		seen.Add(timestamp)
+		asn.FirstSeen, asn.LastSeen = seen.First, seen.Last
 
 		err = tx.Commit()
 		if err != nil {
@@ -1259,9 +1279,7 @@ func (d *Database) RecordPeering(asA, asB int, seen SeenTimes) error {
 	}
 
 	if exists {
-		_, err = tx.Exec(
+		_, err = tx.Exec(updatePeeringSQL, seen.First, seen.Last, asA, asB)
-			"UPDATE peerings SET last_seen = ? WHERE as_a = ? AND as_b = ?",
-			seen.Last, asA, asB)
 	} else {
 		_, err = tx.Exec(`
 			INSERT INTO peerings (id, as_a, as_b, first_seen, last_seen)
@@ -1316,9 +1334,7 @@ func (d *Database) UpdatePeerBatch(peers map[string]PeerUpdate) error {
 	}
 	defer func() { _ = checkStmt.Close() }()
 
-	updateStmt, err := tx.PrepareContext(ctx,
+	updateStmt, err := tx.PrepareContext(ctx, updatePeerSQL)
-		"UPDATE bgp_peers SET peer_asn = ?, last_seen = ?, "+
-			"last_message_type = ? WHERE peer_ip = ?")
 	if err != nil {
 		return fmt.Errorf("failed to prepare update statement: %w", err)
 	}
@@ -1344,7 +1360,8 @@ func (d *Database) UpdatePeerBatch(peers map[string]PeerUpdate) error {
 
 		if exists {
 			_, err = updateStmt.ExecContext(ctx, update.PeerASN,
-				update.Seen.Last, update.MessageType, update.PeerIP)
+				update.MessageType, update.Seen.First, update.Seen.Last,
+				update.PeerIP)
 		} else {
 			_, err = insertStmt.ExecContext(ctx,
 				generateUUID().String(), update.PeerIP, update.PeerASN,
@@ -1393,11 +1410,8 @@ func (d *Database) UpdatePeer(
 	}
 
 	if exists {
-		_, err = tx.Exec(
+		_, err = tx.Exec(updatePeerSQL,
-			"UPDATE bgp_peers SET peer_asn = ?, last_seen = ?, "+
+			peerASN, messageType, timestamp, timestamp, peerIP)
-				"last_message_type = ? WHERE peer_ip = ?",
-			peerASN, timestamp, messageType, peerIP,
-		)
 	} else {
 		_, err = tx.Exec(
 			"INSERT INTO bgp_peers (id, peer_ip, peer_asn, first_seen, "+

internal/database/database_internal_test.go

@@ -20,6 +20,7 @@ import (
 
 	"git.eeqj.de/sneak/routewatch/internal/config"
 	"git.eeqj.de/sneak/routewatch/internal/logger"
+	"git.eeqj.de/sneak/routewatch/internal/ristypes"
 	"git.eeqj.de/sneak/routewatch/pkg/asinfo"
 	"github.com/mattn/go-sqlite3"
 )
@@ -1960,6 +1961,158 @@ func TestUpdatePeerBatchStoresTheEarliestAndLatestTimesOfANewPeer(
 	}
 }
 
+// backlogAge is how much older one write is than the other in the tests of
+// first_seen and last_seen, as when a collector catches up on a backlog.
+const backlogAge = 24 * time.Hour
+
+// batchSpan is how much earlier a batch's First is than its Last in the tests
+// of first_seen and last_seen.
+const batchSpan = time.Hour
+
+// TestWritesKeepEarliestFirstSeenAndLatestLastSeen writes a row of each of
+// asns, peerings and bgp_peers through each function that writes one, at a
+// newer time and at an older one. Each row takes the older write's First as
+// first_seen and the newer write's Last as last_seen. The test writes in both
+// orders, each in a database of its own. Newer then older is a collector
+// catching up on a backlog; older then newer is a feed that arrives in order.
+// Each function writes a row of its own. A batch write's First is batchSpan
+// before its Last, so the test catches the two swapped. A single-row write
+// takes one time.
+func TestWritesKeepEarliestFirstSeenAndLatestLastSeen(t *testing.T) {
+	t.Parallel()
+
+	const (
+		batchASN, singleASN = 64500, 64501
+		peerASN             = 64502
+		asnQuery            = "SELECT first_seen, last_seen FROM asns WHERE asn = ?"
+		peeringQuery        = "SELECT first_seen, last_seen FROM peerings " +
+			"WHERE as_a = ? AND as_b = ?"
+		peerQuery = "SELECT first_seen, last_seen FROM bgp_peers " +
+			"WHERE peer_ip = ?"
+	)
+
+	for name, olderFirst := range map[string]bool{
+		"newer then older": false,
+		"older then newer": true,
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			db, err := New(&config.Config{StateDir: t.TempDir()}, logger.New())
+			if err != nil {
+				t.Fatalf("failed to create database: %v", err)
+			}
+			defer func() { _ = db.Close() }()
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				return db.GetOrCreateASNBatch(map[int]SeenTimes{batchASN: seen})
+			}, batchSpan, asnQuery, batchASN)
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				_, err := db.GetOrCreateASN(singleASN, seen.Last)
+
+				return err
+			}, 0, asnQuery, singleASN)
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				return db.RecordPeering(batchASN, singleASN, seen)
+			}, batchSpan, peeringQuery, batchASN, singleASN)
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				return db.UpdatePeerBatch(map[string]PeerUpdate{
+					testV4PeerIP: {
+						PeerIP: testV4PeerIP, PeerASN: peerASN,
+						MessageType: ristypes.MessageTypeUpdate,
+						Seen:        seen,
+					},
+				})
+			}, batchSpan, peerQuery, testV4PeerIP)
+
+			checkSeenTimes(t, db, olderFirst, func(seen SeenTimes) error {
+				return db.UpdatePeer(testPeerIP, peerASN,
+					ristypes.MessageTypeUpdate, seen.Last)
+			}, 0, peerQuery, testPeerIP)
+		})
+	}
+}
+
+// checkSeenTimes calls write twice, each time with First span before Last: at
+// newer times and at times backlogAge older. It writes the older times first
+// when olderFirst is true. It checks that query, given args, reads the older
+// write's First as first_seen and the newer write's Last as last_seen.
+func checkSeenTimes(
+	t *testing.T, db *Database, olderFirst bool,
+	write func(seen SeenTimes) error,
+	span time.Duration, query string, args ...any,
+) {
+	t.Helper()
+
+	newerLast := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+	newer := SeenTimes{First: newerLast.Add(-span), Last: newerLast}
+	older := SeenTimes{
+		First: newer.First.Add(-backlogAge),
+		Last:  newer.Last.Add(-backlogAge),
+	}
+
+	writes := []SeenTimes{newer, older}
+	if olderFirst {
+		writes = []SeenTimes{older, newer}
+	}
+
+	for _, seen := range writes {
+		err := write(seen)
+		if err != nil {
+			t.Fatalf("writing first %s, last %s: %v", seen.First, seen.Last, err)
+		}
+	}
+
+	var firstSeen, lastSeen time.Time
+
+	err := db.db.QueryRowContext(t.Context(), query, args...).
+		Scan(&firstSeen, &lastSeen)
+	if err != nil {
+		t.Fatalf("reading the row: %v", err)
+	}
+
+	if !firstSeen.Equal(older.First) || !lastSeen.Equal(newer.Last) {
+		t.Errorf("first seen %s, last seen %s; want %s, %s",
+			firstSeen, lastSeen, older.First, newer.Last)
+	}
+}
+
+// TestGetOrCreateASNReturnsStoredSeenTimes stores an AS at a newer time, then
+// at an older one. The second call returns the times the row now holds: the
+// older first_seen and the newer last_seen.
+func TestGetOrCreateASNReturnsStoredSeenTimes(t *testing.T) {
+	t.Parallel()
+
+	db, err := New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("failed to create database: %v", err)
+	}
+	defer func() { _ = db.Close() }()
+
+	const asn = 64500
+
+	newer := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+	older := newer.Add(-backlogAge)
+
+	_, err = db.GetOrCreateASN(asn, newer)
+	if err != nil {
+		t.Fatalf("GetOrCreateASN at %s: %v", newer, err)
+	}
+
+	got, err := db.GetOrCreateASN(asn, older)
+	if err != nil {
+		t.Fatalf("GetOrCreateASN at %s: %v", older, err)
+	}
+
+	if !got.FirstSeen.Equal(older) || !got.LastSeen.Equal(newer) {
+		t.Errorf("first seen %s, last seen %s; want %s, %s",
+			got.FirstSeen, got.LastSeen, older, newer)
+	}
+}
+
 // TestUpsertLiveRouteBatchWritesInKeyOrder writes new routes of two peers out
 // of key order, the last one a second announcement of the first, and checks
 // that the rows were inserted in key order, peer then prefix (each new row's id

internal/database/interface.go

@@ -1,10 +1,14 @@
 // Package database provides SQLite storage for BGP routing data including ASNs,
-// prefixes, announcements, peerings, and live route tables.
+// prefixes, announcements, peerings, and live route tables. Its routes table
+// holds a copy of the whole routing table that internal/routetable keeps in
+// memory.
 package database
 
 import (
 	"context"
 	"time"
+
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
 )
 
 // Stats contains database statistics including counts for ASNs, prefixes,
@@ -67,6 +71,10 @@ type Store interface {
 	GetLiveRouteCounts() (ipv4Count, ipv6Count int, err error)
 	GetLiveRouteCountsContext(ctx context.Context) (ipv4Count, ipv6Count int, err error)
 
+	// Routing table operations: the database's copy of the table in memory
+	WriteRouteChanges(changes []routetable.Change, newPeers map[string]uint) error
+	ReadRouteTable(ctx context.Context) (*routetable.Table, error)
+
 	// IP lookup operations
 	GetIPInfo(ip string) (*IPInfo, error)
 	GetIPInfoContext(ctx context.Context, ip string) (*IPInfo, error)

internal/database/models.go

@@ -92,12 +92,11 @@ type PrefixDistribution struct {
 //
 //nolint:tagliatelle // field names are the existing JSON API
 type IPInfo struct {
-	IP         string   `json:"ip"`
+	IP         string `json:"ip"`
-	PTR        []string `json:"ptr,omitempty"`
+	Netblock   string `json:"netblock"`
-	Netblock   string   `json:"netblock"`
+	MaskLength int    `json:"mask_length"`
-	MaskLength int      `json:"mask_length"`
+	IPVersion  int    `json:"ip_version"`
-	IPVersion  int      `json:"ip_version"`
+	NumPeers   int    `json:"num_peers"`
-	NumPeers   int      `json:"num_peers"`
 	// AS information
 	ASN         int    `json:"asn"`
 	ASName      string `json:"as_name,omitempty"`
@@ -125,8 +124,8 @@ type LiveRouteDeletion struct {
 
 // SeenTimes is the earliest and the latest time one batch of updates saw an AS,
 // a peer or a peering. A row the batch adds is stored first seen at First and
-// last seen at Last; a row already stored keeps its first_seen and has its
+// last seen at Last. A row already stored takes First as its first_seen only
-// last_seen set to Last.
+// when First is earlier, and Last as its last_seen only when Last is later.
 type SeenTimes struct {
 	First time.Time
 	Last  time.Time

internal/database/routes.go

@@ -0,0 +1,339 @@
+package database
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/netip"
+	"time"
+
+	"github.com/bits-and-blooms/bitset"
+
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
+)
+
+// keptRoutesPerRow is how many kept routes a row of the routes table has
+// columns for: the newest and the older one.
+const keptRoutesPerRow = 2
+
+// errUnknownRoutePeer is returned for a peer that route_peers lacks: on a
+// write, the peer of a kept route; on a read, a peer number in a row.
+var errUnknownRoutePeer = errors.New("peer not in route_peers")
+
+// The statements of the routes and route_peers tables (schema.sql).
+const (
+	insertRoutePeerSQL = `INSERT INTO route_peers (number, address)
+		VALUES (?, ?)`
+	routePeerNumberSQL = `SELECT number FROM route_peers WHERE address = ?`
+	routePeersSQL      = `SELECT number, address FROM route_peers`
+
+	upsertRouteSQL = `INSERT INTO routes (prefix, origin_asn, peers,
+			newest_peer, newest_as_path, newest_time,
+			older_peer, older_as_path, older_time)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
+		ON CONFLICT (prefix, origin_asn) DO UPDATE SET peers = excluded.peers,
+			newest_peer = excluded.newest_peer,
+			newest_as_path = excluded.newest_as_path,
+			newest_time = excluded.newest_time,
+			older_peer = excluded.older_peer,
+			older_as_path = excluded.older_as_path,
+			older_time = excluded.older_time`
+	deleteRouteSQL = `DELETE FROM routes WHERE prefix = ? AND origin_asn = ?`
+	routesSQL      = `SELECT prefix, origin_asn, peers,
+		newest_peer, newest_as_path, newest_time,
+		older_peer, older_as_path, older_time FROM routes`
+)
+
+// WriteRouteChanges writes, in one transaction, what one call of the routing
+// table's TakeChanges returned. It stores each new peer with its number, writes
+// the row of each changed prefix and origin AS pair, and deletes the row of
+// each removed one. Route times are stored to the second, as the feed gives
+// them.
+//
+// When it fails, it writes nothing. The caller then writes these changes and
+// peers again, because later changes can name the peers it did not store.
+func (d *Database) WriteRouteChanges(
+	changes []routetable.Change, newPeers map[string]uint,
+) error {
+	if len(changes) == 0 && len(newPeers) == 0 {
+		return nil
+	}
+
+	d.lock("WriteRouteChanges")
+	defer d.unlock()
+
+	tx, err := d.beginTx()
+	if err != nil {
+		return fmt.Errorf("failed to begin transaction: %w", err)
+	}
+	defer d.rollback(tx)
+
+	ctx := context.Background()
+
+	// The new peers first, so that the rows can look up their numbers.
+	for address, number := range newPeers {
+		_, err := tx.ExecContext(ctx, insertRoutePeerSQL, number, address)
+		if err != nil {
+			return fmt.Errorf("failed to store peer %s: %w", address, err)
+		}
+	}
+
+	err = writeRouteRows(ctx, tx, changes)
+	if err != nil {
+		return err
+	}
+
+	err = tx.Commit()
+	if err != nil {
+		return fmt.Errorf("failed to commit transaction: %w", err)
+	}
+
+	return nil
+}
+
+// writeRouteRows upserts the row of each change in tx, or deletes it for a
+// removed pair.
+func writeRouteRows(
+	ctx context.Context, tx *loggingTx, changes []routetable.Change,
+) error {
+	upsert, err := tx.PrepareContext(ctx, upsertRouteSQL)
+	if err != nil {
+		return fmt.Errorf("failed to prepare route upsert: %w", err)
+	}
+	defer func() { _ = upsert.Close() }()
+
+	del, err := tx.PrepareContext(ctx, deleteRouteSQL)
+	if err != nil {
+		return fmt.Errorf("failed to prepare route delete: %w", err)
+	}
+	defer func() { _ = del.Close() }()
+
+	peerNumber, err := tx.PrepareContext(ctx, routePeerNumberSQL)
+	if err != nil {
+		return fmt.Errorf("failed to prepare peer number lookup: %w", err)
+	}
+	defer func() { _ = peerNumber.Close() }()
+
+	for _, change := range changes {
+		prefix := change.Prefix.String()
+
+		if change.Removed {
+			_, err := del.ExecContext(ctx, prefix, change.OriginASN)
+			if err != nil {
+				return fmt.Errorf("failed to delete route %s: %w", prefix, err)
+			}
+
+			continue
+		}
+
+		row, err := routeRow(ctx, peerNumber, change)
+		if err != nil {
+			return fmt.Errorf("failed to write route %s: %w", prefix, err)
+		}
+
+		_, err = upsert.ExecContext(ctx, row...)
+		if err != nil {
+			return fmt.Errorf("failed to write route %s: %w", prefix, err)
+		}
+	}
+
+	return nil
+}
+
+// routeRow returns the values of the routes row of change, in the order of
+// upsertRouteSQL. peerNumber looks up a peer's number by its address. The
+// table keeps at most keptRoutesPerRow routes of a pair.
+func routeRow(
+	ctx context.Context, peerNumber *sql.Stmt, change routetable.Change,
+) ([]any, error) {
+	peers, err := change.Peers.MarshalBinary()
+	if err != nil {
+		return nil, err
+	}
+
+	row := []any{change.Prefix.String(), change.OriginASN, peers}
+
+	for i := range keptRoutesPerRow {
+		if i >= len(change.Routes) {
+			row = append(row, nil, nil, nil)
+
+			continue
+		}
+
+		r := change.Routes[i]
+
+		var number uint
+
+		err := peerNumber.QueryRowContext(ctx, r.Peer).Scan(&number)
+		if errors.Is(err, sql.ErrNoRows) {
+			return nil, fmt.Errorf("%w: %s", errUnknownRoutePeer, r.Peer)
+		}
+
+		if err != nil {
+			return nil, err
+		}
+
+		path, err := json.Marshal(r.ASPath)
+		if err != nil {
+			return nil, err
+		}
+
+		row = append(row, number, string(path), r.Time.Unix())
+	}
+
+	return row, nil
+}
+
+// ReadRouteTable returns the routing table that the routes and route_peers
+// tables hold, as startup reads it. It reads the peers first, so that the
+// table keeps their numbers, then loads each row into the table as it reads
+// it. The two reads are separate, so nothing may write the tables meanwhile.
+// It fails on a row that names a peer number route_peers lacks.
+func (d *Database) ReadRouteTable(ctx context.Context) (*routetable.Table, error) {
+	peerNumbers, err := d.readRoutePeers(ctx)
+	if err != nil {
+		return nil, err
+	}
+
+	addresses := make(map[uint]string, len(peerNumbers))
+	numbers := new(bitset.BitSet)
+
+	for address, number := range peerNumbers {
+		addresses[number] = address
+		numbers.Set(number)
+	}
+
+	table := routetable.New(routetable.Params{PeerNumbers: peerNumbers})
+
+	rows, err := d.db.QueryContext(ctx, routesSQL)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read routes: %w", err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	for rows.Next() {
+		change, err := scanRouteRow(rows, addresses, numbers)
+		if err != nil {
+			return nil, err
+		}
+
+		table.Load(change)
+	}
+
+	err = rows.Err()
+	if err != nil {
+		return nil, fmt.Errorf("failed to read routes: %w", err)
+	}
+
+	return table, nil
+}
+
+// readRoutePeers returns the number of each peer in route_peers, by address.
+func (d *Database) readRoutePeers(ctx context.Context) (map[string]uint, error) {
+	rows, err := d.db.QueryContext(ctx, routePeersSQL)
+	if err != nil {
+		return nil, fmt.Errorf("failed to read route peers: %w", err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	peerNumbers := make(map[string]uint)
+
+	for rows.Next() {
+		var (
+			number  uint
+			address string
+		)
+
+		err := rows.Scan(&number, &address)
+		if err != nil {
+			return nil, fmt.Errorf("failed to read a route peer: %w", err)
+		}
+
+		peerNumbers[address] = number
+	}
+
+	err = rows.Err()
+	if err != nil {
+		return nil, fmt.Errorf("failed to read route peers: %w", err)
+	}
+
+	return peerNumbers, nil
+}
+
+// keptRouteColumns are the three columns of one kept route in a routes row.
+type keptRouteColumns struct {
+	peer   sql.Null[uint]
+	asPath sql.NullString
+	time   sql.NullInt64
+}
+
+// scanRouteRow returns the content of the routes row rows is at, with each kept
+// route's peer named by its address in addresses. It fails when the row names a
+// peer number that addresses lacks. numbers holds the numbers of addresses as a
+// set, against which a row's whole peer set is checked at once.
+func scanRouteRow(
+	rows *sql.Rows, addresses map[uint]string, numbers *bitset.BitSet,
+) (routetable.Change, error) {
+	var (
+		change routetable.Change
+		prefix string
+		peers  []byte
+		kept   [keptRoutesPerRow]keptRouteColumns
+	)
+
+	err := rows.Scan(&prefix, &change.OriginASN, &peers,
+		&kept[0].peer, &kept[0].asPath, &kept[0].time,
+		&kept[1].peer, &kept[1].asPath, &kept[1].time)
+	if err != nil {
+		return change, fmt.Errorf("failed to read a route: %w", err)
+	}
+
+	change.Prefix, err = netip.ParsePrefix(prefix)
+	if err != nil {
+		return change, fmt.Errorf("failed to read route %s: %w", prefix, err)
+	}
+
+	change.Peers = new(bitset.BitSet)
+
+	err = change.Peers.UnmarshalBinary(peers)
+	if err != nil {
+		return change, fmt.Errorf("failed to read the peers of route %s: %w",
+			prefix, err)
+	}
+
+	if !numbers.IsSuperSet(change.Peers) {
+		unknown, _ := change.Peers.Difference(numbers).NextSet(0)
+
+		return change, fmt.Errorf("%w: number %d in the peers of route %s",
+			errUnknownRoutePeer, unknown, prefix)
+	}
+
+	for _, columns := range kept {
+		if !columns.peer.Valid {
+			continue
+		}
+
+		address, known := addresses[columns.peer.V]
+		if !known {
+			return change, fmt.Errorf("%w: number %d in route %s",
+				errUnknownRoutePeer, columns.peer.V, prefix)
+		}
+
+		r := routetable.Route{
+			Peer: address,
+			Time: time.Unix(columns.time.Int64, 0).UTC(),
+		}
+
+		err := json.Unmarshal([]byte(columns.asPath.String), &r.ASPath)
+		if err != nil {
+			return change, fmt.Errorf("failed to read an AS path of route %s: %w",
+				prefix, err)
+		}
+
+		change.Routes = append(change.Routes, r)
+	}
+
+	return change, nil
+}

internal/database/routes_internal_test.go

@@ -0,0 +1,527 @@
+package database
+
+import (
+	"errors"
+	"fmt"
+	"math"
+	"math/rand/v2"
+	"net/netip"
+	"os"
+	"reflect"
+	"slices"
+	"testing"
+	"time"
+
+	"github.com/bits-and-blooms/bitset"
+
+	"git.eeqj.de/sneak/routewatch/internal/config"
+	"git.eeqj.de/sneak/routewatch/internal/logger"
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
+)
+
+// Peers, origin ASes and prefixes of the routes table tests.
+const (
+	peerA = "192.0.2.1"
+	peerB = "192.0.2.2"
+	peerC = "2001:db8::3"
+	peerD = "2001:db8::4"
+	peerE = "2001:db8::5"
+
+	asA = 64500
+	asB = 64501
+	// transitAS is the first AS of every test path, the peer's own.
+	transitAS = 64496
+
+	tablePrefixV4      = "10.1.2.0/24"
+	tablePrefixShortV4 = "10.9.0.0/16"
+	tablePrefixV6      = "2001:db8:1::/48"
+)
+
+// tableTime returns the time second seconds after the start of every routes
+// table test.
+func tableTime(second int) time.Time {
+	return time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC).
+		Add(time.Duration(second) * time.Second)
+}
+
+// announceTo has peer announce prefix with origin AS asn second seconds after
+// the start.
+func announceTo(
+	table *routetable.Table, prefix string, asn int, peer string, second int,
+) {
+	table.Announce(netip.MustParsePrefix(prefix), asn, routetable.Route{
+		Peer: peer, ASPath: []int{transitAS, asn}, Time: tableTime(second),
+	})
+}
+
+// newRoutesTestDatabase returns a new database in a temporary directory.
+func newRoutesTestDatabase(t *testing.T) *Database {
+	t.Helper()
+
+	db, err := New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("failed to create database: %v", err)
+	}
+
+	t.Cleanup(func() { _ = db.Close() })
+
+	return db
+}
+
+// writeTableChanges writes what table changed since the last call.
+func writeTableChanges(t *testing.T, db *Database, table *routetable.Table) {
+	t.Helper()
+
+	changes, newPeers := table.TakeChanges(math.MaxInt)
+
+	err := db.WriteRouteChanges(changes, newPeers)
+	if err != nil {
+		t.Fatalf("WriteRouteChanges: %v", err)
+	}
+}
+
+func TestReadRouteTableGivesBackWhatWasWritten(t *testing.T) {
+	t.Parallel()
+
+	db := newRoutesTestDatabase(t)
+	source := routetable.New(routetable.Params{})
+
+	// Two origins of one prefix: the routes of peerC and peerB are kept for
+	// asA, peerA keeps only its bit.
+	announceTo(source, tablePrefixV4, asA, peerA, 10)
+	announceTo(source, tablePrefixV4, asA, peerB, 20)
+	announceTo(source, tablePrefixV4, asA, peerC, 30)
+	announceTo(source, tablePrefixV4, asB, peerD, 40)
+	// Two routes with the same time.
+	announceTo(source, tablePrefixV6, asA, peerA, 50)
+	announceTo(source, tablePrefixV6, asA, peerC, 50)
+	// An origin whose kept routes were withdrawn while peerA carries it.
+	announceTo(source, tablePrefixShortV4, asB, peerA, 10)
+	announceTo(source, tablePrefixShortV4, asB, peerB, 20)
+	announceTo(source, tablePrefixShortV4, asB, peerC, 30)
+	source.Withdraw(netip.MustParsePrefix(tablePrefixShortV4), peerB)
+	source.Withdraw(netip.MustParsePrefix(tablePrefixShortV4), peerC)
+
+	writeTableChanges(t, db, source)
+	checkReadTable(t, db, source)
+
+	// A peer moves to another origin, one goes down and a new one comes.
+	announceTo(source, tablePrefixV4, asB, peerA, 60)
+	source.PeerDown(peerC)
+	announceTo(source, tablePrefixV6, asB, peerE, 70)
+
+	writeTableChanges(t, db, source)
+	checkReadTable(t, db, source)
+}
+
+func TestReadRouteTableGivesATableThatTakesLaterUpdates(t *testing.T) {
+	t.Parallel()
+
+	db := newRoutesTestDatabase(t)
+	source := routetable.New(routetable.Params{})
+
+	// peerA and peerB carry tablePrefixV4, peerB and peerC tablePrefixV6.
+	announceTo(source, tablePrefixV4, asA, peerA, 10)
+	announceTo(source, tablePrefixV4, asA, peerB, 20)
+	announceTo(source, tablePrefixV6, asA, peerB, 30)
+	announceTo(source, tablePrefixV6, asA, peerC, 40)
+
+	writeTableChanges(t, db, source)
+	read := checkReadTable(t, db, source)
+
+	// The same updates to both tables: a loaded peer withdraws a prefix,
+	// another one goes down, and a new peer comes.
+	for _, table := range []*routetable.Table{source, read} {
+		table.Withdraw(netip.MustParsePrefix(tablePrefixV4), peerA)
+		table.PeerDown(peerB)
+		announceTo(table, tablePrefixShortV4, asB, peerD, 50)
+	}
+
+	checkSameReads(t, read, source)
+}
+
+func TestReadRouteTableFailsOnAPeerWithoutANumber(t *testing.T) {
+	t.Parallel()
+
+	db := newRoutesTestDatabase(t)
+	table := routetable.New(routetable.Params{})
+
+	// Only the routes of peerB and peerC are kept, so only the peer set names
+	// peerA.
+	announceTo(table, tablePrefixV4, asA, peerA, 10)
+	announceTo(table, tablePrefixV4, asA, peerB, 20)
+	announceTo(table, tablePrefixV4, asA, peerC, 30)
+	writeTableChanges(t, db, table)
+
+	_, err := db.db.ExecContext(t.Context(),
+		"DELETE FROM route_peers WHERE address = ?", peerA)
+	if err != nil {
+		t.Fatalf("deleting a route peer: %v", err)
+	}
+
+	_, err = db.ReadRouteTable(t.Context())
+	if !errors.Is(err, errUnknownRoutePeer) {
+		t.Fatalf("ReadRouteTable = %v, want %v", err, errUnknownRoutePeer)
+	}
+}
+
+// checkReadTable checks that the table ReadRouteTable reads answers every read
+// as want does, and that reading it recorded no change. It returns that table.
+func checkReadTable(
+	t *testing.T, db *Database, want *routetable.Table,
+) *routetable.Table {
+	t.Helper()
+
+	got, err := db.ReadRouteTable(t.Context())
+	if err != nil {
+		t.Fatalf("ReadRouteTable: %v", err)
+	}
+
+	checkSameReads(t, got, want)
+
+	changes, newPeers := got.TakeChanges(math.MaxInt)
+	if len(changes) != 0 || len(newPeers) != 0 {
+		t.Errorf("the read recorded changes %+v and new peers %v, want none",
+			changes, newPeers)
+	}
+
+	return got
+}
+
+// checkSameReads checks that got answers every read as want does, for the
+// prefixes and the origin ASes the tests use.
+func checkSameReads(t *testing.T, got, want *routetable.Table) {
+	t.Helper()
+
+	if !reflect.DeepEqual(got.Counts(), want.Counts()) {
+		t.Errorf("Counts() = %+v, want %+v", got.Counts(), want.Counts())
+	}
+
+	for _, text := range []string{
+		tablePrefixV4, tablePrefixShortV4, tablePrefixV6,
+	} {
+		prefix := netip.MustParsePrefix(text)
+
+		if !reflect.DeepEqual(got.Origins(prefix), want.Origins(prefix)) {
+			t.Errorf("Origins(%s) = %+v, want %+v",
+				prefix, got.Origins(prefix), want.Origins(prefix))
+		}
+
+		gotSummary, gotFound := got.Lookup(prefix.Addr())
+		wantSummary, wantFound := want.Lookup(prefix.Addr())
+
+		if gotFound != wantFound || !reflect.DeepEqual(gotSummary, wantSummary) {
+			t.Errorf("Lookup(%s) = %+v, %v; want %+v, %v", prefix.Addr(),
+				gotSummary, gotFound, wantSummary, wantFound)
+		}
+
+		ipVersion := ipVersionV6
+		if prefix.Addr().Is4() {
+			ipVersion = ipVersionV4
+		}
+
+		gotSample := sortedSample(got, ipVersion, prefix.Bits())
+		wantSample := sortedSample(want, ipVersion, prefix.Bits())
+
+		if !reflect.DeepEqual(gotSample, wantSample) {
+			t.Errorf("SamplePrefixes(%d, %d) = %+v, want %+v",
+				ipVersion, prefix.Bits(), gotSample, wantSample)
+		}
+	}
+
+	for _, asn := range []int{asA, asB} {
+		if !reflect.DeepEqual(got.OriginatedPrefixes(asn),
+			want.OriginatedPrefixes(asn)) {
+			t.Errorf("OriginatedPrefixes(%d) = %+v, want %+v", asn,
+				got.OriginatedPrefixes(asn), want.OriginatedPrefixes(asn))
+		}
+	}
+}
+
+// sortedSample returns every prefix of the IP version and mask length in
+// table, in prefix order.
+func sortedSample(
+	table *routetable.Table, ipVersion, maskLength int,
+) []routetable.PrefixSummary {
+	// More than the tests have of any mask length.
+	const all = 100
+
+	sample := table.SamplePrefixes(ipVersion, maskLength, all)
+	slices.SortFunc(sample, func(a, b routetable.PrefixSummary) int {
+		return a.Prefix.Compare(b.Prefix)
+	})
+
+	return sample
+}
+
+func TestWriteRouteChangesDeletesTheRowOfARemovedPair(t *testing.T) {
+	t.Parallel()
+
+	db := newRoutesTestDatabase(t)
+	table := routetable.New(routetable.Params{})
+
+	announceTo(table, tablePrefixV4, asA, peerA, 10)
+	announceTo(table, tablePrefixV4, asB, peerB, 20)
+	writeTableChanges(t, db, table)
+
+	// The prefix's only peer with asA withdraws it.
+	table.Withdraw(netip.MustParsePrefix(tablePrefixV4), peerA)
+	writeTableChanges(t, db, table)
+
+	var origins []int
+
+	rows, err := db.db.QueryContext(t.Context(),
+		"SELECT origin_asn FROM routes WHERE prefix = ?", tablePrefixV4)
+	if err != nil {
+		t.Fatalf("reading the routes: %v", err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	for rows.Next() {
+		var origin int
+
+		err := rows.Scan(&origin)
+		if err != nil {
+			t.Fatalf("reading a route: %v", err)
+		}
+
+		origins = append(origins, origin)
+	}
+
+	err = rows.Err()
+	if err != nil {
+		t.Fatalf("reading the routes: %v", err)
+	}
+
+	if !slices.Equal(origins, []int{asB}) {
+		t.Errorf("rows of %s have origins %v, want only %d",
+			tablePrefixV4, origins, asB)
+	}
+}
+
+// routePeer is one row of route_peers.
+type routePeer struct {
+	number  uint
+	address string
+}
+
+// readRoutePeerRows returns the rows of route_peers in number order.
+func readRoutePeerRows(t *testing.T, db *Database) []routePeer {
+	t.Helper()
+
+	rows, err := db.db.QueryContext(t.Context(),
+		"SELECT number, address FROM route_peers ORDER BY number")
+	if err != nil {
+		t.Fatalf("reading the route peers: %v", err)
+	}
+	defer func() { _ = rows.Close() }()
+
+	var peers []routePeer
+
+	for rows.Next() {
+		var peer routePeer
+
+		err := rows.Scan(&peer.number, &peer.address)
+		if err != nil {
+			t.Fatalf("reading a route peer: %v", err)
+		}
+
+		peers = append(peers, peer)
+	}
+
+	err = rows.Err()
+	if err != nil {
+		t.Fatalf("reading the route peers: %v", err)
+	}
+
+	return peers
+}
+
+func TestWriteRouteChangesStoresNewPeers(t *testing.T) {
+	t.Parallel()
+
+	db := newRoutesTestDatabase(t)
+	table := routetable.New(routetable.Params{})
+
+	announceTo(table, tablePrefixV4, asA, peerA, 10)
+	announceTo(table, tablePrefixV6, asA, peerC, 20)
+	writeTableChanges(t, db, table)
+
+	// peerA is stored already; peerB is new.
+	announceTo(table, tablePrefixV4, asA, peerA, 30)
+	announceTo(table, tablePrefixV4, asA, peerB, 40)
+	writeTableChanges(t, db, table)
+
+	want := []routePeer{{0, peerA}, {1, peerC}, {2, peerB}}
+
+	got := readRoutePeerRows(t, db)
+	if !slices.Equal(got, want) {
+		t.Errorf("route_peers = %+v, want %+v", got, want)
+	}
+}
+
+func TestWriteRouteChangesWritesNothingWhenItFails(t *testing.T) {
+	t.Parallel()
+
+	db := newRoutesTestDatabase(t)
+	table := routetable.New(routetable.Params{})
+
+	announceTo(table, tablePrefixV4, asA, peerA, 10)
+	announceTo(table, tablePrefixV6, asA, peerB, 20)
+
+	// peerB's number is missing, so its kept route cannot be written.
+	changes, newPeers := table.TakeChanges(math.MaxInt)
+	delete(newPeers, peerB)
+
+	err := db.WriteRouteChanges(changes, newPeers)
+	if !errors.Is(err, errUnknownRoutePeer) {
+		t.Fatalf("WriteRouteChanges = %v, want %v", err, errUnknownRoutePeer)
+	}
+
+	peers := readRoutePeerRows(t, db)
+	if len(peers) != 0 {
+		t.Errorf("route_peers = %+v after the failed write, want none", peers)
+	}
+
+	var routes int
+
+	err = db.db.QueryRowContext(t.Context(),
+		"SELECT COUNT(*) FROM routes").Scan(&routes)
+	if err != nil {
+		t.Fatalf("counting the routes: %v", err)
+	}
+
+	if routes != 0 {
+		t.Errorf("routes holds %d rows after the failed write, want none", routes)
+	}
+}
+
+// Parameters for BenchmarkReadRouteTable.
+const (
+	// benchTablePairs is how many prefix and origin AS pairs the table holds:
+	// one origin AS for each prefix. Every benchTableV6Every-th prefix is an
+	// IPv6 /48, the others IPv4 /24s.
+	benchTablePairs   = 200000
+	benchTableV6Every = 5
+	// benchTablePeers is how many peers there are, about as many as RIS has.
+	// benchTablePeersPerPair is how many of them, picked at random, carry each
+	// pair: RIS's 460 million routes over 1.4 million pairs.
+	benchTablePeers        = 1400
+	benchTablePeersPerPair = 330
+	// benchTableBatch is how many changes each write holds.
+	benchTableBatch = 10000
+)
+
+// BenchmarkReadRouteTable times the read of a routing table of 200,000 prefix
+// and origin AS pairs, each carried by 330 of 1,400 peers and keeping two
+// routes. It writes that table first. It reports the bytes of the database
+// file per pair. It is run by hand, not by make test, for example in the test
+// image:
+//
+//	go test -run '^$' -bench ReadRouteTable -benchtime 5x ./internal/database/
+func BenchmarkReadRouteTable(b *testing.B) {
+	db, err := New(&config.Config{StateDir: b.TempDir()}, logger.New())
+	if err != nil {
+		b.Fatalf("failed to create database: %v", err)
+	}
+	defer func() { _ = db.Close() }()
+
+	//nolint:gosec // The benchmark needs the same table every run.
+	rng := rand.New(rand.NewPCG(1, 2))
+
+	newPeers := make(map[string]uint, benchTablePeers)
+	for number := range uint(benchTablePeers) {
+		newPeers[benchPeerAddress(number)] = number
+	}
+
+	for first := 0; first < benchTablePairs; first += benchTableBatch {
+		changes := make([]routetable.Change, 0, benchTableBatch)
+		for pair := first; pair < first+benchTableBatch; pair++ {
+			changes = append(changes, benchTableChange(rng, pair))
+		}
+
+		err := db.WriteRouteChanges(changes, newPeers)
+		if err != nil {
+			b.Fatalf("WriteRouteChanges: %v", err)
+		}
+
+		newPeers = nil
+	}
+
+	// The WAL is copied into the database file, whose size is reported.
+	err = db.Checkpoint(b.Context())
+	if err != nil {
+		b.Fatalf("Checkpoint: %v", err)
+	}
+
+	file, err := os.Stat(db.path)
+	if err != nil {
+		b.Fatalf("reading the database file's size: %v", err)
+	}
+
+	for b.Loop() {
+		table, err := db.ReadRouteTable(b.Context())
+		if err != nil {
+			b.Fatalf("ReadRouteTable: %v", err)
+		}
+
+		counts := table.Counts()
+		if counts.IPv4Prefixes+counts.IPv6Prefixes != benchTablePairs {
+			b.Fatalf("read %d prefixes, want %d",
+				counts.IPv4Prefixes+counts.IPv6Prefixes, benchTablePairs)
+		}
+	}
+
+	// After the loop: b.Loop drops the metrics reported before it starts.
+	b.ReportMetric(float64(file.Size())/benchTablePairs, "file-bytes/pair")
+}
+
+// benchPeerAddress returns the address of the peer numbered number.
+func benchPeerAddress(number uint) string {
+	const addressesPerBlock = 256
+
+	return fmt.Sprintf("198.18.%d.%d",
+		number/addressesPerBlock, number%addressesPerBlock)
+}
+
+// benchTableChange returns the content of the pair numbered pair: its prefix,
+// its origin AS, benchTablePeersPerPair peers picked at random, and the routes
+// of two of them, each with an AS path of four ASes.
+func benchTableChange(rng *rand.Rand, pair int) routetable.Change {
+	const (
+		firstOrigin  = 64500
+		transitASes  = 50000
+		olderSeconds = 10
+	)
+
+	text := fmt.Sprintf("%d.%d.%d.0/24", 1+pair>>16, (pair>>8)%256, pair%256)
+	if pair%benchTableV6Every == 0 {
+		text = fmt.Sprintf("2001:%x:%x::/48", pair>>16, pair%65536)
+	}
+
+	prefix := netip.MustParsePrefix(text)
+	origin := firstOrigin + pair%transitASes
+	peers := bitset.New(benchTablePeers)
+
+	for peers.Count() < benchTablePeersPerPair {
+		peers.Set(rng.UintN(benchTablePeers))
+	}
+
+	change := routetable.Change{Prefix: prefix, OriginASN: origin, Peers: peers}
+
+	// The routes of the first two peers, newest first.
+	for i, number := range slices.Collect(peers.EachSet())[:keptRoutesPerRow] {
+		change.Routes = append(change.Routes, routetable.Route{
+			Peer: benchPeerAddress(number),
+			ASPath: []int{
+				firstOrigin + rng.IntN(transitASes),
+				firstOrigin + rng.IntN(transitASes),
+				firstOrigin + rng.IntN(transitASes),
+				origin,
+			},
+			Time: tableTime(pair - i*olderSeconds),
+		})
+	}
+
+	return change
+}

internal/database/schema.sql

@@ -146,4 +146,33 @@ CREATE INDEX IF NOT EXISTS idx_live_routes_v6_origin_prefix ON live_routes_v6(or
 -- last_updated: the oldest and newest route times in /api/v1/stats and
 -- /status.json.
 CREATE INDEX IF NOT EXISTS idx_live_routes_v4_last_updated ON live_routes_v4(last_updated);
-CREATE INDEX IF NOT EXISTS idx_live_routes_v6_last_updated ON live_routes_v6(last_updated);
+CREATE INDEX IF NOT EXISTS idx_live_routes_v6_last_updated ON live_routes_v6(last_updated);
+
+-- The whole routing table, as internal/routetable keeps it in memory: one row
+-- for each prefix and origin AS that some peer carries. Startup reads every
+-- row, and the rows of the pairs that change are written back.
+CREATE TABLE IF NOT EXISTS routes (
+	prefix TEXT NOT NULL, -- in the text form Go's net/netip prints
+	origin_asn INTEGER NOT NULL,
+	-- The peers whose current route to the prefix has this origin AS: a set
+	-- of their numbers in route_peers, as the bitset package's MarshalBinary
+	-- writes it.
+	peers BLOB NOT NULL,
+	-- The newest of those routes and the one before it, the two kept in full.
+	-- Each has its peer's number in route_peers, its AS path as a JSON array,
+	-- and its time in seconds since 1970, UTC. A route that is not kept has
+	-- NULL in its three columns.
+	newest_peer INTEGER,
+	newest_as_path TEXT,
+	newest_time INTEGER,
+	older_peer INTEGER,
+	older_as_path TEXT,
+	older_time INTEGER,
+	PRIMARY KEY (prefix, origin_asn)
+) WITHOUT ROWID;
+
+-- The peers of the routes table, each with the number it has there.
+CREATE TABLE IF NOT EXISTS route_peers (
+	number INTEGER PRIMARY KEY,
+	address TEXT NOT NULL UNIQUE
+);

internal/routetable/benchmark_test.go

@@ -0,0 +1,155 @@
+package routetable_test
+
+import (
+	"fmt"
+	"math"
+	"math/rand/v2"
+	"net/netip"
+	"runtime"
+	"testing"
+	"time"
+
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
+)
+
+// Parameters for BenchmarkApplyMixedBatch.
+const (
+	// benchPeers is how many peers there are, about as many as RIS has.
+	benchPeers = 1400
+	// benchPrefixes is how many IPv4 /24 prefixes the table holds, and
+	// benchPeersPerPrefix how many peers, picked at random, carry each.
+	benchPrefixes       = 100000
+	benchPeersPerPrefix = 20
+	// benchBatchSize is how many updates the timed batch holds, as many as
+	// the prefix handler's largest batch (prefixBatchMaxSize in
+	// internal/routewatch).
+	benchBatchSize = 250000
+	// In the timed batch every benchWithdrawalEvery-th update is a
+	// withdrawal, and every benchNewOriginEvery-th announcement has an
+	// origin AS other than the prefix's.
+	benchWithdrawalEvery = 5
+	benchNewOriginEvery  = 7
+	// benchOrigins is how many origin ASes the prefixes are spread over,
+	// from benchFirstASN on: 20 prefixes each, about as many as an origin AS
+	// has on average in the full table.
+	benchOrigins  = 5000
+	benchFirstASN = 64500
+	// benchUpdatesPerSecond is how many updates share one time.
+	benchUpdatesPerSecond = 1000
+	benchMaskLength       = 24
+)
+
+// benchUpdate is one update of the benchmark.
+type benchUpdate struct {
+	prefix   netip.Prefix
+	origin   int
+	route    routetable.Route
+	withdraw bool
+}
+
+// BenchmarkApplyMixedBatch times one batch of 250,000 updates of routes picked
+// at random: announcements, withdrawals and announcements with a new origin AS.
+// The table it applies them to holds 100,000 IPv4 prefixes from 5,000 origin
+// ASes, each carried by 20 of 1,400 peers. It reports the heap bytes that table
+// takes per prefix and origin AS pair. It is run by hand, not by make test, for
+// example in the test image:
+//
+//	go test -run '^$' -bench MixedBatch -benchtime 10x ./internal/routetable/
+func BenchmarkApplyMixedBatch(b *testing.B) {
+	//nolint:gosec // The benchmark needs the same updates every run.
+	rng := rand.New(rand.NewPCG(1, 2))
+	peers := make([]string, benchPeers)
+
+	for i := range peers {
+		peers[i] = fmt.Sprintf("198.18.%d.%d", i/256, i%256)
+	}
+
+	before := heapBytes()
+	table := routetable.New(routetable.Params{})
+	updates := 0
+
+	for prefix := range benchPrefixes {
+		for range benchPeersPerPrefix {
+			peer := peers[rng.IntN(benchPeers)]
+			apply(table, benchAnnouncement(rng, prefix, peer, updates, false))
+			updates++
+		}
+	}
+
+	// The record of changes is handed over every second while routewatch
+	// runs, so it is not part of the table's size.
+	table.TakeChanges(math.MaxInt)
+
+	bytesPerPair := float64(heapBytes()-before) / benchPrefixes
+
+	batch := make([]benchUpdate, 0, benchBatchSize)
+	for i := range benchBatchSize {
+		update := benchAnnouncement(rng, rng.IntN(benchPrefixes),
+			peers[rng.IntN(benchPeers)], updates+i, i%benchNewOriginEvery == 0)
+		update.withdraw = i%benchWithdrawalEvery == 0
+		batch = append(batch, update)
+	}
+
+	for b.Loop() {
+		for _, update := range batch {
+			apply(table, update)
+		}
+	}
+
+	// After the loop: b.Loop drops the metrics reported before it starts.
+	b.ReportMetric(bytesPerPair, "bytes/pair")
+}
+
+// benchAnnouncement returns the announcement of the prefix numbered prefix, a
+// /24 from 1.0.0.0/24 on, by peer. It is the updates-th update of the
+// benchmark, and its AS path holds four ASes from the peer's AS to the origin
+// AS. newOrigin gives it an origin AS other than the prefix's.
+func benchAnnouncement(
+	rng *rand.Rand, prefix int, peer string, updates int, newOrigin bool,
+) benchUpdate {
+	origin := benchFirstASN + prefix%benchOrigins
+	if newOrigin {
+		origin += benchOrigins
+	}
+
+	start := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
+
+	return benchUpdate{
+		prefix: netip.MustParsePrefix(fmt.Sprintf("%d.%d.%d.0/%d",
+			1+prefix>>16, (prefix>>8)%256, prefix%256, benchMaskLength)),
+		origin: origin,
+		route: routetable.Route{
+			Peer: peer,
+			ASPath: []int{
+				benchFirstASN + rng.IntN(benchOrigins),
+				benchFirstASN + rng.IntN(benchOrigins),
+				benchFirstASN + rng.IntN(benchOrigins),
+				origin,
+			},
+			Time: start.Add(time.Duration(updates/benchUpdatesPerSecond) *
+				time.Second),
+		},
+	}
+}
+
+// apply applies update to table.
+func apply(table *routetable.Table, update benchUpdate) {
+	if update.withdraw {
+		table.Withdraw(update.prefix, update.route.Peer)
+
+		return
+	}
+
+	table.Announce(update.prefix, update.origin, update.route)
+}
+
+// heapBytes returns the bytes of the live heap objects, after a collection.
+func heapBytes() uint64 {
+	runtime.GC()
+
+	var stats runtime.MemStats
+
+	runtime.ReadMemStats(&stats)
+
+	return stats.HeapAlloc
+}

internal/routetable/reads.go

@@ -0,0 +1,233 @@
+package routetable
+
+import (
+	"net/netip"
+	"slices"
+	"time"
+
+	"github.com/bits-and-blooms/bitset"
+)
+
+// PrefixSummary is what the table answers about one prefix.
+type PrefixSummary struct {
+	Prefix netip.Prefix
+	// OriginASN is the origin AS that the most peers carry the prefix with.
+	// When several have as many peers, it is the lowest AS number.
+	OriginASN int
+	// Peers is how many peers carry the prefix.
+	Peers int
+	// Newest is the time of the newest kept route of the prefix, or nil when
+	// it keeps none.
+	Newest *time.Time
+}
+
+// OriginatedPrefix is one prefix an AS originates.
+type OriginatedPrefix struct {
+	Prefix netip.Prefix
+	// Newest is the time of the newest kept route of the prefix with that
+	// origin AS, or nil when it keeps none.
+	Newest *time.Time
+}
+
+// Counts are the table's figures for the stats.
+type Counts struct {
+	// Pairs counts the prefix and origin AS pairs that some peer carries.
+	Pairs int
+	// Peers counts the peers that have a number: those given in
+	// Params.PeerNumbers and those numbered since.
+	Peers        int
+	IPv4Prefixes int
+	IPv6Prefixes int
+	// IPv4PrefixesByLength[n] and IPv6PrefixesByLength[n] are how many
+	// prefixes of mask length n some peer carries.
+	IPv4PrefixesByLength []int
+	IPv6PrefixesByLength []int
+	// IPv4Routes and IPv6Routes count peer and prefix pairs: each peer that
+	// carries a prefix counts once for it.
+	IPv4Routes int
+	IPv6Routes int
+	// OriginsWithoutKeptRoute counts the prefix and origin AS pairs that peers
+	// carry but whose kept routes were all withdrawn.
+	OriginsWithoutKeptRoute int
+	// OldestKeptRoute and NewestKeptRoute are the times of the oldest and the
+	// newest kept routes, or nil when the table keeps none.
+	OldestKeptRoute *time.Time
+	NewestKeptRoute *time.Time
+}
+
+// Lookup returns the most specific prefix that holds addr and that some peer
+// carries. It ignores prefixes shorter than /8 for IPv4 and /16 for IPv6. It
+// makes one map lookup per mask length, and reports false when no prefix
+// holds addr.
+func (t *Table) Lookup(addr netip.Addr) (PrefixSummary, bool) {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+
+	// An IPv4 address written in IPv6 form (::ffff:192.0.2.1) is looked up as
+	// IPv4.
+	addr = addr.Unmap()
+	f := t.familyOf(addr)
+
+	for bits := addr.BitLen(); bits >= f.minLookupLength; bits-- {
+		prefix := netip.PrefixFrom(addr, bits).Masked()
+
+		origins, found := f.byLength[bits][prefix]
+		if found {
+			return summarize(prefix, origins), true
+		}
+	}
+
+	return PrefixSummary{}, false
+}
+
+// OriginatedPrefixes returns the prefixes AS asn originates, in prefix order.
+func (t *Table) OriginatedPrefixes(asn int) []OriginatedPrefix {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+
+	prefixes := make([]OriginatedPrefix, 0, len(t.byOrigin[asn]))
+	for prefix, o := range t.byOrigin[asn] {
+		prefixes = append(prefixes,
+			OriginatedPrefix{Prefix: prefix, Newest: o.newestTime()})
+	}
+
+	slices.SortFunc(prefixes, func(a, b OriginatedPrefix) int {
+		return a.Prefix.Compare(b.Prefix)
+	})
+
+	return prefixes
+}
+
+// Origins returns each origin AS of prefix, in AS number order, with its peers
+// and its kept routes. It returns nil when no peer carries the prefix.
+func (t *Table) Origins(prefix netip.Prefix) []Origin {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+
+	if !prefix.IsValid() {
+		return nil
+	}
+
+	var origins []Origin
+
+	for _, o := range t.origins(prefix.Masked()) {
+		origins = append(origins, Origin{
+			ASN:    o.asn,
+			Peers:  t.addresses(&o.peers),
+			Routes: t.exportRoutes(o.routes),
+		})
+	}
+
+	return origins
+}
+
+// SamplePrefixes returns up to limit of the prefixes of IP version ipVersion
+// (4 or 6) and mask length maskLength. It reads only the prefixes it returns.
+// Go starts each walk over a map at a random place, so each call returns
+// another sample.
+func (t *Table) SamplePrefixes(ipVersion, maskLength, limit int) []PrefixSummary {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+
+	var f *family
+
+	switch ipVersion {
+	case ipVersion4:
+		f = &t.ipv4
+	case ipVersion6:
+		f = &t.ipv6
+	default:
+		return nil
+	}
+
+	if maskLength < 0 || maskLength >= len(f.byLength) || limit <= 0 {
+		return nil
+	}
+
+	prefixes := f.byLength[maskLength]
+	sample := make([]PrefixSummary, 0, min(limit, len(prefixes)))
+
+	for prefix, origins := range prefixes {
+		if len(sample) == limit {
+			break
+		}
+
+		sample = append(sample, summarize(prefix, origins))
+	}
+
+	return sample
+}
+
+// Counts returns the table's figures for the stats. The writes keep them up to
+// date, so this reads no prefix.
+func (t *Table) Counts() Counts {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+
+	counts := Counts{
+		Peers:                   len(t.peerNumbers),
+		IPv4PrefixesByLength:    t.ipv4.prefixesByLength(),
+		IPv6PrefixesByLength:    t.ipv6.prefixesByLength(),
+		IPv4Routes:              t.ipv4.routes,
+		IPv6Routes:              t.ipv6.routes,
+		OriginsWithoutKeptRoute: t.originsWithoutKeptRoute,
+	}
+
+	for _, n := range counts.IPv4PrefixesByLength {
+		counts.IPv4Prefixes += n
+	}
+
+	for _, n := range counts.IPv6PrefixesByLength {
+		counts.IPv6Prefixes += n
+	}
+
+	for _, prefixes := range t.byOrigin {
+		counts.Pairs += len(prefixes)
+	}
+
+	oldest, found := t.keptTimes.Min()
+	if found {
+		counts.OldestKeptRoute = &oldest.time
+	}
+
+	newest, found := t.keptTimes.Max()
+	if found {
+		counts.NewestKeptRoute = &newest.time
+	}
+
+	return counts
+}
+
+// addresses returns the addresses of the peers in peers, in number order.
+func (t *Table) addresses(peers *bitset.BitSet) []string {
+	addresses := make([]string, 0, peers.Count())
+	for number := range peers.EachSet() {
+		addresses = append(addresses, t.peerAddresses[number])
+	}
+
+	return addresses
+}
+
+// summarize returns the summary of prefix, whose origins are in AS number
+// order.
+func summarize(prefix netip.Prefix, origins []*origin) PrefixSummary {
+	summary := PrefixSummary{Prefix: prefix}
+	mostPeers := 0
+
+	for _, o := range origins {
+		peers := int(o.peers.Count())
+		summary.Peers += peers
+
+		if peers > mostPeers {
+			mostPeers = peers
+			summary.OriginASN = o.asn
+		}
+
+		newest := o.newestTime()
+		if newest != nil && (summary.Newest == nil || newest.After(*summary.Newest)) {
+			summary.Newest = newest
+		}
+	}
+
+	return summary
+}

internal/routetable/reads_test.go

@@ -0,0 +1,265 @@
+package routetable_test
+
+import (
+	"net/netip"
+	"reflect"
+	"testing"
+
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
+)
+
+// announceAll has each listed peer announce prefix with origin AS asn, the
+// peer at index i i*10 seconds after start.
+func announceAll(
+	table *routetable.Table, prefix string, asn, start int, peers ...string,
+) {
+	const secondsBetweenPeers = 10
+
+	for i, peer := range peers {
+		table.Announce(netip.MustParsePrefix(prefix), asn,
+			routeOf(peer, asn, start+i*secondsBetweenPeers))
+	}
+}
+
+func TestLookup(t *testing.T) {
+	t.Parallel()
+
+	table := routetable.New(routetable.Params{})
+	announceAll(table, "10.0.0.0/8", asA, 10, peerA)
+	// Three peers with two origins: asB has more of them.
+	announceAll(table, "10.1.0.0/16", asA, 10, peerA)
+	announceAll(table, "10.1.0.0/16", asB, 20, peerB, peerC)
+	// Two origins with one peer each: the lower AS number wins.
+	announceAll(table, prefixV4, asB, 20, peerB)
+	announceAll(table, prefixV4, asA, 10, peerA)
+	// An origin whose kept routes were withdrawn: no newest time.
+	announceAll(table, "10.9.0.0/16", asA, 10, peerA, peerB, peerC)
+	table.Withdraw(netip.MustParsePrefix("10.9.0.0/16"), peerB)
+	table.Withdraw(netip.MustParsePrefix("10.9.0.0/16"), peerC)
+	announceAll(table, "2001:db8::/32", asA, 10, peerA)
+	announceAll(table, prefixV6, asB, 20, peerB)
+	announceAll(table, "3000::/16", asA, 10, peerA)
+	// Shorter than the lookup uses.
+	announceAll(table, "192.0.0.0/7", asA, 10, peerA)
+	announceAll(table, "2000::/15", asA, 10, peerA)
+
+	tests := []struct {
+		addr string
+		// want is the summary's prefix, or empty when none is found.
+		want      string
+		originASN int
+		peers     int
+		newest    int // in seconds after the start; 0 for none
+	}{
+		{"10.1.2.3", prefixV4, asA, 2, 20},
+		{"::ffff:10.1.2.3", prefixV4, asA, 2, 20},
+		{"10.1.3.4", "10.1.0.0/16", asB, 3, 30},
+		{"10.2.0.1", "10.0.0.0/8", asA, 1, 10},
+		{"10.9.0.1", "10.9.0.0/16", asA, 1, 0},
+		{"192.0.2.1", "", 0, 0, 0},
+		{"2001:db8:1::5", prefixV6, asB, 1, 20},
+		{"2001:db8:2::1", "2001:db8::/32", asA, 1, 10},
+		{"3000::1", "3000::/16", asA, 1, 10},
+		{"2001:db9::1", "", 0, 0, 0},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.addr, func(t *testing.T) {
+			t.Parallel()
+
+			got, found := table.Lookup(netip.MustParseAddr(tc.addr))
+			if tc.want == "" {
+				if found {
+					t.Errorf("Lookup(%s) = %+v, want none", tc.addr, got)
+				}
+
+				return
+			}
+
+			want := routetable.PrefixSummary{
+				Prefix:    netip.MustParsePrefix(tc.want),
+				OriginASN: tc.originASN,
+				Peers:     tc.peers,
+			}
+			if tc.newest != 0 {
+				want.Newest = timeAt(tc.newest)
+			}
+
+			if !found || !reflect.DeepEqual(got, want) {
+				t.Errorf("Lookup(%s) = %+v, %v; want %+v", tc.addr, got, found, want)
+			}
+		})
+	}
+}
+
+func TestOriginatedPrefixes(t *testing.T) {
+	t.Parallel()
+
+	table := routetable.New(routetable.Params{})
+	announceAll(table, "2001:db8::/32", asA, 30, peerA)
+	announceAll(table, prefixV4, asA, 10, peerA)
+	// asB's newer route for the same prefix does not count for asA.
+	announceAll(table, prefixV4, asB, 40, peerB)
+	announceAll(table, "10.1.0.0/16", asA, 10, peerA, peerB)
+	announceAll(table, "10.9.0.0/16", asA, 10, peerA, peerB, peerC)
+	table.Withdraw(netip.MustParsePrefix("10.9.0.0/16"), peerB)
+	table.Withdraw(netip.MustParsePrefix("10.9.0.0/16"), peerC)
+
+	want := []routetable.OriginatedPrefix{
+		{Prefix: netip.MustParsePrefix("10.1.0.0/16"), Newest: timeAt(20)},
+		{Prefix: netip.MustParsePrefix(prefixV4), Newest: timeAt(10)},
+		{Prefix: netip.MustParsePrefix("10.9.0.0/16")},
+		{Prefix: netip.MustParsePrefix("2001:db8::/32"), Newest: timeAt(30)},
+	}
+
+	got := table.OriginatedPrefixes(asA)
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("OriginatedPrefixes(%d) = %+v, want %+v", asA, got, want)
+	}
+
+	got = table.OriginatedPrefixes(asC)
+	if len(got) != 0 {
+		t.Errorf("OriginatedPrefixes(%d) = %+v, want none", asC, got)
+	}
+}
+
+func TestSamplePrefixes(t *testing.T) {
+	t.Parallel()
+
+	table := routetable.New(routetable.Params{})
+
+	announced := []string{
+		"10.0.0.0/24", "10.0.1.0/24", "10.0.2.0/24", "10.0.3.0/24",
+		"10.0.4.0/24", "10.0.0.0/16",
+		"2001:db8::/48", "2001:db8:1::/48", "2001:db8:2::/48",
+	}
+	for _, prefix := range announced {
+		announceAll(table, prefix, asA, 10, peerA)
+	}
+
+	tests := []struct {
+		name                         string
+		ipVersion, maskLength, limit int
+		want                         int
+	}{
+		{"fewer than there are", 4, 24, 3, 3},
+		{"more than there are", 4, 24, 10, 5},
+		{"IPv6", 6, 48, 10, 3},
+		{"a mask length with none", 4, 20, 10, 0},
+		{"no such IP version", 5, 24, 10, 0},
+		{"a mask length too long", 4, 33, 10, 0},
+		{"a negative mask length", 4, -1, 10, 0},
+		{"a limit of zero", 4, 24, 0, 0},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			sample := table.SamplePrefixes(tc.ipVersion, tc.maskLength, tc.limit)
+			if len(sample) != tc.want {
+				t.Fatalf("SamplePrefixes(%d, %d, %d) returned %d prefixes, want %d",
+					tc.ipVersion, tc.maskLength, tc.limit, len(sample), tc.want)
+			}
+
+			seen := make(map[netip.Prefix]bool)
+
+			for _, got := range sample {
+				want := routetable.PrefixSummary{
+					Prefix: got.Prefix, OriginASN: asA, Peers: 1, Newest: timeAt(10),
+				}
+				if seen[got.Prefix] || got.Prefix.Bits() != tc.maskLength ||
+					!reflect.DeepEqual(got, want) {
+					t.Errorf("SamplePrefixes(%d, %d, %d) returned %+v",
+						tc.ipVersion, tc.maskLength, tc.limit, got)
+				}
+
+				seen[got.Prefix] = true
+			}
+		})
+	}
+}
+
+func TestCounts(t *testing.T) {
+	t.Parallel()
+
+	table := routetable.New(routetable.Params{})
+	checkCounts(t, table, routetable.Counts{
+		IPv4PrefixesByLength: byLength(ipv4Bits, nil),
+		IPv6PrefixesByLength: byLength(ipv6Bits, nil),
+	})
+
+	announceAll(table, prefixV4, asA, 10, peerA, peerB)
+	announceAll(table, "10.2.0.0/16", asA, 15, peerA)
+	announceAll(table, "2001:db8::/32", asA, 5, peerA)
+	announceAll(table, "2001:db8::/32", asA, 25, peerC)
+	checkCounts(t, table, routetable.Counts{
+		Pairs:                3,
+		Peers:                3,
+		IPv4Prefixes:         2,
+		IPv6Prefixes:         1,
+		IPv4PrefixesByLength: byLength(ipv4Bits, map[int]int{16: 1, 24: 1}),
+		IPv6PrefixesByLength: byLength(ipv6Bits, map[int]int{32: 1}),
+		IPv4Routes:           3,
+		IPv6Routes:           2,
+		OldestKeptRoute:      timeAt(5),
+		NewestKeptRoute:      timeAt(25),
+	})
+
+	// peerC's route drops peerA's from the kept ones, and peerA leaves the
+	// IPv6 prefix.
+	announceAll(table, prefixV4, asA, 30, peerC)
+	table.Withdraw(netip.MustParsePrefix("2001:db8::/32"), peerA)
+	checkCounts(t, table, routetable.Counts{
+		Pairs:                3,
+		Peers:                3,
+		IPv4Prefixes:         2,
+		IPv6Prefixes:         1,
+		IPv4PrefixesByLength: byLength(ipv4Bits, map[int]int{16: 1, 24: 1}),
+		IPv6PrefixesByLength: byLength(ipv6Bits, map[int]int{32: 1}),
+		IPv4Routes:           4,
+		IPv6Routes:           1,
+		OldestKeptRoute:      timeAt(15),
+		NewestKeptRoute:      timeAt(30),
+	})
+
+	// peerC was the last peer of the IPv6 prefix. It keeps its number.
+	table.PeerDown(peerC)
+	checkCounts(t, table, routetable.Counts{
+		Pairs:                2,
+		Peers:                3,
+		IPv4Prefixes:         2,
+		IPv4PrefixesByLength: byLength(ipv4Bits, map[int]int{16: 1, 24: 1}),
+		IPv6PrefixesByLength: byLength(ipv6Bits, nil),
+		IPv4Routes:           3,
+		OldestKeptRoute:      timeAt(15),
+		NewestKeptRoute:      timeAt(20),
+	})
+}
+
+// The address lengths of the two IP versions.
+const (
+	ipv4Bits = 32
+	ipv6Bits = 128
+)
+
+// byLength returns the prefix counts by mask length, for addresses of bits
+// bits, with counts[n] prefixes of mask length n and none of any other.
+func byLength(bits int, counts map[int]int) []int {
+	all := make([]int, bits+1)
+	for n, count := range counts {
+		all[n] = count
+	}
+
+	return all
+}
+
+// checkCounts checks that the table's counts are want.
+func checkCounts(t *testing.T, table *routetable.Table, want routetable.Counts) {
+	t.Helper()
+
+	got := table.Counts()
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Counts() = %+v, want %+v", got, want)
+	}
+}

internal/routetable/routetable.go

@@ -0,0 +1,677 @@
+// Package routetable holds the whole routing table in memory. For each prefix
+// and origin AS, it keeps the peers whose current route to the prefix has that
+// origin AS. It also keeps the two newest of those routes in full. It applies
+// announcements, withdrawals and peers' sessions going down. It answers the
+// route reads that the pages and the API need.
+package routetable
+
+import (
+	"cmp"
+	"maps"
+	"net/netip"
+	"slices"
+	"sync"
+	"time"
+
+	"github.com/bits-and-blooms/bitset"
+	"github.com/google/btree"
+)
+
+const (
+	// keptRoutesPerOrigin is how many routes of each prefix and origin AS are
+	// kept in full: the newest ones. Every other peer that carries the prefix
+	// with that origin AS keeps only its bit in the peer set.
+	keptRoutesPerOrigin = 2
+
+	// keptTimesDegree is the degree of the B-tree that holds the times of the
+	// kept routes in order: each of its nodes holds up to 63 times.
+	keptTimesDegree = 32
+
+	ipv4Bits = 32
+	ipv6Bits = 128
+
+	// The address lookup ignores prefixes shorter than these mask lengths. A
+	// default route or a route this short only says where a peer sends traffic
+	// it has no better route for; it does not say who holds the address.
+	minLookupMaskLengthV4 = 8
+	minLookupMaskLengthV6 = 16
+
+	// The IP versions SamplePrefixes takes.
+	ipVersion4 = 4
+	ipVersion6 = 6
+)
+
+// Route is one peer's route to one prefix. The next hop is the peer itself, so
+// it is not stored.
+type Route struct {
+	// Peer is the peer's address.
+	Peer   string
+	ASPath []int
+	// Time is when the peer announced the route.
+	Time time.Time
+}
+
+// Origin is one origin AS of a prefix: the peers whose current route to the
+// prefix has that origin AS, and the newest of those routes in full.
+type Origin struct {
+	// ASN is the origin AS. 0 means no known origin: the path ends in an AS
+	// set of several members.
+	ASN int
+	// Peers are the peers' addresses, in the order of their numbers: the
+	// order they were first seen in.
+	Peers []string
+	// Routes are the kept routes, newest first: at most two, and none when
+	// both were withdrawn while other peers still carry the prefix.
+	Routes []Route
+}
+
+// Change is the current content of one prefix and origin AS pair that changed:
+// what a database row for the pair holds.
+type Change struct {
+	Prefix    netip.Prefix
+	OriginASN int
+	// Removed says that no peer carries the prefix with this origin AS any
+	// more. Peers and Routes are then nil.
+	Removed bool
+	// Peers holds the number of each peer that carries the prefix with this
+	// origin AS.
+	Peers *bitset.BitSet
+	// Routes are the kept routes, newest first.
+	Routes []Route
+}
+
+// Params configures New.
+type Params struct {
+	// PeerNumbers holds the number each peer was given before, by address. A
+	// peer not in it gets the next number above all of them the first time it
+	// announces a route.
+	PeerNumbers map[string]uint
+}
+
+// Table is the routing table. Its methods are safe for concurrent use.
+type Table struct {
+	mu sync.RWMutex
+
+	ipv4 family
+	ipv6 family
+	// byOrigin holds, for each origin AS, the prefixes it originates.
+	byOrigin map[int]map[netip.Prefix]*origin
+
+	// peerNumbers and peerAddresses give each peer's number by its address
+	// and its address by its number. nextPeerNumber is the number the next
+	// new peer gets.
+	peerNumbers    map[string]uint
+	peerAddresses  map[uint]string
+	nextPeerNumber uint
+	// peerPrefixes[n] counts the prefixes the peer numbered n carries, for
+	// each n below nextPeerNumber. It is a slice, not a map, because Load
+	// counts once for every peer of every pair it loads: with a map, reading
+	// a full table at startup took several times as long.
+	peerPrefixes []int
+
+	// newPeers and changed are what TakeChanges hands over: the peers
+	// numbered since it last ran, and the prefix and origin AS pairs changed
+	// since it last took them.
+	newPeers map[string]uint
+	changed  map[pair]struct{}
+
+	// keptTimes counts the kept routes at each time, in time order, so its
+	// first and last items are the oldest and newest kept routes.
+	keptTimes *btree.BTreeG[keptTime]
+	// originsWithoutKeptRoute counts the origins that peers carry but that
+	// keep no route.
+	originsWithoutKeptRoute int
+}
+
+// New returns an empty table that numbers new peers on from
+// params.PeerNumbers.
+func New(params Params) *Table {
+	t := &Table{
+		ipv4:          newFamily(ipv4Bits, minLookupMaskLengthV4),
+		ipv6:          newFamily(ipv6Bits, minLookupMaskLengthV6),
+		byOrigin:      make(map[int]map[netip.Prefix]*origin),
+		peerNumbers:   make(map[string]uint, len(params.PeerNumbers)),
+		peerAddresses: make(map[uint]string, len(params.PeerNumbers)),
+		newPeers:      make(map[string]uint),
+		changed:       make(map[pair]struct{}),
+		keptTimes: btree.NewG(keptTimesDegree, func(a, b keptTime) bool {
+			return a.time.Before(b.time)
+		}),
+	}
+
+	for address, number := range params.PeerNumbers {
+		t.peerNumbers[address] = number
+		t.peerAddresses[number] = address
+		t.nextPeerNumber = max(t.nextPeerNumber, number+1)
+	}
+
+	t.peerPrefixes = make([]int, t.nextPeerNumber)
+
+	return t
+}
+
+// Announce applies an announcement: the peer's current route to prefix is now
+// r, with origin AS originASN. A peer that carried the prefix with another
+// origin AS leaves that origin's peer set, and its route there is dropped. r
+// is kept in full when it is one of the two newest routes of its prefix and
+// origin AS; otherwise only the peer's bit is.
+//
+// An announcement whose path is empty or holds AS 0 is a withdrawal, and the
+// caller passes it to Withdraw instead.
+func (t *Table) Announce(prefix netip.Prefix, originASN int, r Route) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	if !prefix.IsValid() {
+		return
+	}
+
+	prefix = prefix.Masked()
+	peer := t.numberPeer(r.Peer)
+
+	current := originWithPeer(t.origins(prefix), peer)
+	if current != nil && current.asn != originASN {
+		t.leave(prefix, current, peer)
+	}
+
+	t.join(prefix, t.findOrAddOrigin(prefix, originASN), route{
+		peer: peer,
+		path: slices.Clone(r.ASPath),
+		time: r.Time,
+	})
+}
+
+// Withdraw applies a withdrawal: the peer no longer carries prefix. It leaves
+// the prefix's peer set, and its kept route, if any, is dropped.
+func (t *Table) Withdraw(prefix netip.Prefix, peer string) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	number, known := t.peerNumbers[peer]
+	if !known || !prefix.IsValid() {
+		return
+	}
+
+	prefix = prefix.Masked()
+
+	o := originWithPeer(t.origins(prefix), number)
+	if o != nil {
+		t.leave(prefix, o, number)
+	}
+}
+
+// PeerDown applies a peer's session going down: the peer leaves every peer
+// set, and every route of it is dropped. When the peer carries any prefix, it
+// visits every prefix in the table.
+func (t *Table) PeerDown(peer string) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	number, known := t.peerNumbers[peer]
+	if !known || t.peerPrefixes[number] == 0 {
+		return
+	}
+
+	for _, f := range []*family{&t.ipv4, &t.ipv6} {
+		for _, prefixes := range f.byLength {
+			for prefix, origins := range prefixes {
+				o := originWithPeer(origins, number)
+				if o != nil {
+					t.leave(prefix, o, number)
+				}
+			}
+		}
+	}
+}
+
+// Load puts one prefix and origin AS pair that the database holds into the
+// table, as startup does with each row it reads. The change's peers join the
+// pair's peer set, and its routes are kept as an announcement's would be.
+// Unlike an update, Load records no change, so TakeChanges does not hand the
+// pair back to be written again. Loading a pair twice changes nothing.
+//
+// The caller makes sure that every peer change names, in its peer set or in
+// its routes, has a number in Params.PeerNumbers.
+func (t *Table) Load(change Change) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	// A removed pair has no peers, and a pair without peers is not in the
+	// table.
+	if change.Peers == nil || change.Peers.None() || !change.Prefix.IsValid() {
+		return
+	}
+
+	prefix := change.Prefix.Masked()
+	o := t.findOrAddOrigin(prefix, change.OriginASN)
+	wasWithoutKeptRoute := o.withoutKeptRoute()
+
+	// The peers not yet in the peer set join it in one union, which takes
+	// less time than setting their bits one at a time.
+	joining := change.Peers.Difference(&o.peers)
+	o.peers.InPlaceUnion(joining)
+	t.familyOf(prefix.Addr()).routes += int(joining.Count())
+
+	for peer := range joining.EachSet() {
+		t.peerPrefixes[peer]++
+	}
+
+	// Oldest first, as they were announced, so that two routes with the same
+	// time are kept in the order they had.
+	for _, r := range slices.Backward(change.Routes) {
+		peer := t.peerNumbers[r.Peer]
+
+		t.dropKeptRoute(o, peer)
+		t.keepIfNewest(o, route{
+			peer: peer,
+			path: slices.Clone(r.ASPath),
+			time: r.Time,
+		})
+	}
+
+	t.countOriginWithoutKeptRoute(o, wasWithoutKeptRoute)
+}
+
+// TakeChanges returns at most maxChanges of the prefix and origin AS pairs that
+// changed since they were last taken, in prefix order, each with its current
+// content. The other changed pairs wait for a later call. It also returns every
+// peer numbered since it last ran, by address, so a pair taken later names only
+// peers already returned. It then forgets what it returned.
+func (t *Table) TakeChanges(maxChanges int) ([]Change, map[string]uint) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	changes := make([]Change, 0, min(maxChanges, len(t.changed)))
+	for key := range t.changed {
+		if len(changes) == maxChanges {
+			break
+		}
+
+		changes = append(changes, t.currentContent(key))
+		delete(t.changed, key)
+	}
+
+	// A map keeps the memory of its largest size, so an emptied one is
+	// replaced.
+	if len(t.changed) == 0 {
+		t.changed = make(map[pair]struct{})
+	}
+
+	slices.SortFunc(changes, func(a, b Change) int {
+		return cmp.Or(a.Prefix.Compare(b.Prefix),
+			cmp.Compare(a.OriginASN, b.OriginASN))
+	})
+
+	newPeers := t.newPeers
+	t.newPeers = make(map[string]uint)
+
+	return changes, newPeers
+}
+
+// PutBackChanges records again what one TakeChanges call returned, for a
+// caller that could not write it. The next TakeChanges returns those peers
+// again, and those pairs wait to be taken again like any changed pair. Each is
+// then taken with its content at that time, so a later change of a pair
+// replaces the earlier.
+func (t *Table) PutBackChanges(changes []Change, newPeers map[string]uint) {
+	t.mu.Lock()
+	defer t.mu.Unlock()
+
+	for _, change := range changes {
+		t.changed[pair{prefix: change.Prefix, asn: change.OriginASN}] = struct{}{}
+	}
+
+	maps.Copy(t.newPeers, newPeers)
+}
+
+// ChangeCount returns how many changed prefix and origin AS pairs wait for
+// TakeChanges.
+func (t *Table) ChangeCount() int {
+	t.mu.RLock()
+	defer t.mu.RUnlock()
+
+	return len(t.changed)
+}
+
+// numberPeer returns the peer's number, and gives it the next one the first
+// time the table sees it.
+func (t *Table) numberPeer(address string) uint {
+	number, known := t.peerNumbers[address]
+	if known {
+		return number
+	}
+
+	number = t.nextPeerNumber
+	t.nextPeerNumber++
+	t.peerNumbers[address] = number
+	t.peerAddresses[number] = address
+	t.peerPrefixes = append(t.peerPrefixes, 0)
+	t.newPeers[address] = number
+
+	return number
+}
+
+// familyOf returns the part of the table for addr's IP version.
+func (t *Table) familyOf(addr netip.Addr) *family {
+	if addr.Is4() {
+		return &t.ipv4
+	}
+
+	return &t.ipv6
+}
+
+// prefixesOfLength returns the prefixes of the IP version and the mask length
+// of prefix, a valid masked prefix.
+func (t *Table) prefixesOfLength(prefix netip.Prefix) map[netip.Prefix][]*origin {
+	return t.familyOf(prefix.Addr()).byLength[prefix.Bits()]
+}
+
+// origins returns the origins of prefix, a valid masked prefix.
+func (t *Table) origins(prefix netip.Prefix) []*origin {
+	return t.prefixesOfLength(prefix)[prefix]
+}
+
+// findOrAddOrigin returns the origin of prefix with AS asn, added with no
+// peers when the prefix has none with that AS.
+func (t *Table) findOrAddOrigin(prefix netip.Prefix, asn int) *origin {
+	prefixes := t.prefixesOfLength(prefix)
+	origins := prefixes[prefix]
+
+	i, found := slices.BinarySearchFunc(origins, asn,
+		func(o *origin, asn int) int { return cmp.Compare(o.asn, asn) })
+	if found {
+		return origins[i]
+	}
+
+	o := &origin{asn: asn}
+	prefixes[prefix] = slices.Insert(origins, i, o)
+
+	if t.byOrigin[asn] == nil {
+		t.byOrigin[asn] = make(map[netip.Prefix]*origin)
+	}
+
+	t.byOrigin[asn][prefix] = o
+
+	return o
+}
+
+// removeOrigin removes o, which no peer carries any more, from prefix, and the
+// prefix from the table when it has no origin left.
+func (t *Table) removeOrigin(prefix netip.Prefix, o *origin) {
+	prefixes := t.prefixesOfLength(prefix)
+
+	origins := slices.DeleteFunc(prefixes[prefix],
+		func(other *origin) bool { return other == o })
+	if len(origins) == 0 {
+		delete(prefixes, prefix)
+	} else {
+		prefixes[prefix] = origins
+	}
+
+	delete(t.byOrigin[o.asn], prefix)
+
+	if len(t.byOrigin[o.asn]) == 0 {
+		delete(t.byOrigin, o.asn)
+	}
+}
+
+// join puts the peer of r in the peer set of o, an origin of prefix, and keeps
+// r in full when it is one of the two newest routes of o. The peer's earlier
+// route, if o keeps one, is replaced: it is no longer the peer's current route.
+// The pair is recorded as changed only when its peer set or kept routes change.
+func (t *Table) join(prefix netip.Prefix, o *origin, r route) {
+	if slices.ContainsFunc(o.routes, r.equal) {
+		// The peer announced its kept route again.
+		return
+	}
+
+	wasWithoutKeptRoute := o.withoutKeptRoute()
+
+	joined := !o.peers.Test(r.peer)
+	if joined {
+		o.peers.Set(r.peer)
+
+		t.familyOf(prefix.Addr()).routes++
+		t.peerPrefixes[r.peer]++
+	}
+
+	dropped := t.dropKeptRoute(o, r.peer)
+	kept := t.keepIfNewest(o, r)
+
+	if joined || dropped || kept {
+		t.recordChange(prefix, o, wasWithoutKeptRoute)
+	}
+}
+
+// leave takes peer out of the peer set of o, an origin of prefix, and drops
+// its kept route, if any.
+func (t *Table) leave(prefix netip.Prefix, o *origin, peer uint) {
+	wasWithoutKeptRoute := o.withoutKeptRoute()
+
+	o.peers.Clear(peer)
+	t.dropKeptRoute(o, peer)
+
+	t.familyOf(prefix.Addr()).routes--
+	t.peerPrefixes[peer]--
+
+	t.recordChange(prefix, o, wasWithoutKeptRoute)
+}
+
+// keepIfNewest keeps r in o unless both kept routes of o are newer, and says
+// whether it kept r. When o already keeps two routes, the older one is
+// dropped, and its peer keeps only its bit.
+func (t *Table) keepIfNewest(o *origin, r route) bool {
+	// The kept routes stay newest first: r goes before the first one that is
+	// not newer than it.
+	i := 0
+	for i < len(o.routes) && o.routes[i].time.After(r.time) {
+		i++
+	}
+
+	if i == keptRoutesPerOrigin {
+		return false
+	}
+
+	if len(o.routes) == keptRoutesPerOrigin {
+		t.dropKeptRoute(o, o.routes[keptRoutesPerOrigin-1].peer)
+	}
+
+	o.routes = slices.Insert(o.routes, i, r)
+	t.countKeptTime(r.time, 1)
+
+	return true
+}
+
+// dropKeptRoute drops the peer's route from the kept routes of o, if o keeps
+// one, and says whether it did.
+func (t *Table) dropKeptRoute(o *origin, peer uint) bool {
+	i := slices.IndexFunc(o.routes, func(r route) bool { return r.peer == peer })
+	if i < 0 {
+		return false
+	}
+
+	t.countKeptTime(o.routes[i].time, -1)
+	o.routes = slices.Delete(o.routes, i, i+1)
+
+	return true
+}
+
+// recordChange records that the pair of prefix and the AS of o changed, and
+// brings the count of origins without a kept route up to date.
+// wasWithoutKeptRoute says whether o was such an origin before the change. An
+// origin that no peer carries any more is removed.
+func (t *Table) recordChange(
+	prefix netip.Prefix, o *origin, wasWithoutKeptRoute bool,
+) {
+	t.changed[pair{prefix: prefix, asn: o.asn}] = struct{}{}
+
+	t.countOriginWithoutKeptRoute(o, wasWithoutKeptRoute)
+
+	if o.peers.None() {
+		t.removeOrigin(prefix, o)
+	}
+}
+
+// countOriginWithoutKeptRoute brings the count of origins without a kept route
+// up to date after a change to o. wasWithoutKeptRoute says whether o was such
+// an origin before the change.
+func (t *Table) countOriginWithoutKeptRoute(o *origin, wasWithoutKeptRoute bool) {
+	if wasWithoutKeptRoute {
+		t.originsWithoutKeptRoute--
+	}
+
+	if o.withoutKeptRoute() {
+		t.originsWithoutKeptRoute++
+	}
+}
+
+// countKeptTime adds delta to the number of kept routes with time at.
+func (t *Table) countKeptTime(at time.Time, delta int) {
+	count, _ := t.keptTimes.Get(keptTime{time: at})
+	count.time = at
+	count.routes += delta
+
+	if count.routes == 0 {
+		t.keptTimes.Delete(count)
+
+		return
+	}
+
+	t.keptTimes.ReplaceOrInsert(count)
+}
+
+// currentContent returns what the table holds for the pair now.
+func (t *Table) currentContent(key pair) Change {
+	o := t.byOrigin[key.asn][key.prefix]
+	if o == nil {
+		return Change{Prefix: key.prefix, OriginASN: key.asn, Removed: true}
+	}
+
+	return Change{
+		Prefix:    key.prefix,
+		OriginASN: key.asn,
+		Peers:     o.peers.Clone(),
+		Routes:    t.exportRoutes(o.routes),
+	}
+}
+
+// exportRoutes returns copies of routes that name each peer by its address, or
+// nil when there are none.
+func (t *Table) exportRoutes(routes []route) []Route {
+	if len(routes) == 0 {
+		return nil
+	}
+
+	exported := make([]Route, 0, len(routes))
+	for _, r := range routes {
+		exported = append(exported, Route{
+			Peer:   t.peerAddresses[r.peer],
+			ASPath: slices.Clone(r.path),
+			Time:   r.time,
+		})
+	}
+
+	return exported
+}
+
+// family is the part of the table for one IP version.
+type family struct {
+	// byLength[n] holds the prefixes of mask length n that some peer carries,
+	// each with its origins in AS number order.
+	byLength []map[netip.Prefix][]*origin
+	// minLookupLength is the shortest mask length the address lookup uses.
+	minLookupLength int
+	// routes counts the peer and prefix pairs: each peer that carries a
+	// prefix counts once for it.
+	routes int
+}
+
+// newFamily returns an empty family for addresses of bits bits.
+func newFamily(bits, minLookupLength int) family {
+	f := family{
+		byLength:        make([]map[netip.Prefix][]*origin, bits+1),
+		minLookupLength: minLookupLength,
+	}
+
+	for n := range f.byLength {
+		f.byLength[n] = make(map[netip.Prefix][]*origin)
+	}
+
+	return f
+}
+
+// prefixesByLength returns how many prefixes of each mask length f holds.
+func (f *family) prefixesByLength() []int {
+	counts := make([]int, len(f.byLength))
+	for n, prefixes := range f.byLength {
+		counts[n] = len(prefixes)
+	}
+
+	return counts
+}
+
+// origin is what the table holds for one prefix and origin AS.
+type origin struct {
+	asn int
+	// peers holds the number of each peer whose current route to the prefix
+	// has this origin AS.
+	peers bitset.BitSet
+	// routes are the newest of those routes, newest first, at most
+	// keptRoutesPerOrigin.
+	routes []route
+}
+
+// withoutKeptRoute says whether peers carry o but o keeps no route.
+func (o *origin) withoutKeptRoute() bool {
+	return o.peers.Any() && len(o.routes) == 0
+}
+
+// newestTime returns the time of the newest kept route of o, or nil when o
+// keeps none.
+func (o *origin) newestTime() *time.Time {
+	if len(o.routes) == 0 {
+		return nil
+	}
+
+	newest := o.routes[0].time
+
+	return &newest
+}
+
+// originWithPeer returns the origin whose peer set holds peer, or nil when
+// none does. A peer carries a prefix with one origin AS at most.
+func originWithPeer(origins []*origin, peer uint) *origin {
+	for _, o := range origins {
+		if o.peers.Test(peer) {
+			return o
+		}
+	}
+
+	return nil
+}
+
+// route is a kept route. peer is the peer's number.
+type route struct {
+	peer uint
+	path []int
+	time time.Time
+}
+
+// equal says whether r and other are the same peer's route with the same path
+// and time.
+func (r route) equal(other route) bool {
+	return r.peer == other.peer && r.time.Equal(other.time) &&
+		slices.Equal(r.path, other.path)
+}
+
+// pair names one prefix and origin AS.
+type pair struct {
+	prefix netip.Prefix
+	asn    int
+}
+
+// keptTime counts the kept routes with one time.
+type keptTime struct {
+	time   time.Time
+	routes int
+}

internal/routetable/routetable_test.go

@@ -0,0 +1,667 @@
+package routetable_test
+
+import (
+	"math"
+	"net/netip"
+	"reflect"
+	"slices"
+	"sync"
+	"testing"
+	"time"
+
+	"github.com/bits-and-blooms/bitset"
+
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
+)
+
+const (
+	peerA = "192.0.2.1"
+	peerB = "192.0.2.2"
+	peerC = "2001:db8::3"
+	peerD = "2001:db8::4"
+
+	asA = 64500
+	asB = 64501
+	asC = 64502
+	// transitAS is the first AS of every test path, the peer's own.
+	transitAS = 64496
+
+	prefixV4 = "10.1.2.0/24"
+	prefixV6 = "2001:db8:1::/48"
+)
+
+// at returns the time second seconds after the start of every test.
+func at(second int) time.Time {
+	return time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC).
+		Add(time.Duration(second) * time.Second)
+}
+
+// timeAt returns at(second) for a field that may be nil.
+func timeAt(second int) *time.Time {
+	t := at(second)
+
+	return &t
+}
+
+// routeOf returns the route peer announces with origin AS asn second seconds
+// after the start.
+func routeOf(peer string, asn, second int) routetable.Route {
+	return routetable.Route{
+		Peer: peer, ASPath: []int{transitAS, asn}, Time: at(second),
+	}
+}
+
+// step is one update a test applies to a table for one prefix.
+type step func(table *routetable.Table, prefix netip.Prefix)
+
+// announce is the step of peer announcing prefix with origin AS asn second
+// seconds after the start.
+func announce(peer string, asn, second int) step {
+	return func(table *routetable.Table, prefix netip.Prefix) {
+		table.Announce(prefix, asn, routeOf(peer, asn, second))
+	}
+}
+
+// withdraw is the step of peer withdrawing prefix.
+func withdraw(peer string) step {
+	return func(table *routetable.Table, prefix netip.Prefix) {
+		table.Withdraw(prefix, peer)
+	}
+}
+
+// peerDown is the step of peer's session going down.
+func peerDown(peer string) step {
+	return func(table *routetable.Table, _ netip.Prefix) {
+		table.PeerDown(peer)
+	}
+}
+
+// rule is one case of the rule that decides what the table holds for a prefix:
+// the steps applied to an empty table, and the prefix's origins after them.
+// The peers are numbered in the order they first announce, which is the order
+// Origin.Peers lists them in.
+type rule struct {
+	name  string
+	steps []step
+	want  []routetable.Origin
+}
+
+// checkRules runs each case for an IPv4 and an IPv6 prefix.
+func checkRules(t *testing.T, rules []rule) {
+	t.Helper()
+
+	for _, tc := range rules {
+		for _, text := range []string{prefixV4, prefixV6} {
+			t.Run(tc.name+" "+text, func(t *testing.T) {
+				t.Parallel()
+
+				prefix := netip.MustParsePrefix(text)
+				table := routetable.New(routetable.Params{})
+
+				for _, apply := range tc.steps {
+					apply(table, prefix)
+				}
+
+				got := table.Origins(prefix)
+				if !reflect.DeepEqual(got, tc.want) {
+					t.Errorf("Origins(%s) = %+v, want %+v", prefix, got, tc.want)
+				}
+			})
+		}
+	}
+}
+
+func TestAnnouncementsKeepTheTwoNewestRoutes(t *testing.T) {
+	t.Parallel()
+
+	checkRules(t, []rule{
+		{
+			name:  "an announcement is kept",
+			steps: []step{announce(peerA, asA, 10)},
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerA},
+				Routes: []routetable.Route{routeOf(peerA, asA, 10)}}},
+		},
+		{
+			name: "a lagging peer's older route is not kept",
+			steps: []step{announce(peerA, asA, 20), announce(peerB, asA, 30),
+				announce(peerC, asA, 10)},
+			want: []routetable.Origin{{ASN: asA,
+				Peers: []string{peerA, peerB, peerC}, Routes: []routetable.Route{
+					routeOf(peerB, asA, 30), routeOf(peerA, asA, 20),
+				}}},
+		},
+		{
+			name: "a third newer route drops the older kept one, whose peer " +
+				"keeps its bit",
+			steps: []step{announce(peerA, asA, 10), announce(peerB, asA, 20),
+				announce(peerC, asA, 30)},
+			want: []routetable.Origin{{ASN: asA,
+				Peers: []string{peerA, peerB, peerC}, Routes: []routetable.Route{
+					routeOf(peerC, asA, 30), routeOf(peerB, asA, 20),
+				}}},
+		},
+		{
+			name: "a route as old as the older kept one replaces it",
+			steps: []step{announce(peerA, asA, 10), announce(peerB, asA, 20),
+				announce(peerC, asA, 10)},
+			want: []routetable.Origin{{ASN: asA,
+				Peers: []string{peerA, peerB, peerC}, Routes: []routetable.Route{
+					routeOf(peerB, asA, 20), routeOf(peerC, asA, 10),
+				}}},
+		},
+		{
+			name: "a peer's new route replaces its kept one",
+			steps: []step{announce(peerA, asA, 10), announce(peerB, asA, 20),
+				announce(peerA, asA, 30)},
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerA, peerB},
+				Routes: []routetable.Route{
+					routeOf(peerA, asA, 30), routeOf(peerB, asA, 20),
+				}}},
+		},
+		{
+			name: "a peer's new route replaces its kept one even when older",
+			steps: []step{announce(peerA, asA, 10), announce(peerB, asA, 20),
+				announce(peerB, asA, 5)},
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerA, peerB},
+				Routes: []routetable.Route{
+					routeOf(peerA, asA, 10), routeOf(peerB, asA, 5),
+				}}},
+		},
+	})
+}
+
+func TestAPeerCarriesAPrefixWithOneOrigin(t *testing.T) {
+	t.Parallel()
+
+	checkRules(t, []rule{
+		{
+			name: "a peer moving to a new origin leaves the old one",
+			steps: []step{announce(peerA, asA, 10), announce(peerB, asA, 20),
+				announce(peerA, asB, 30)},
+			want: []routetable.Origin{
+				{ASN: asA, Peers: []string{peerB},
+					Routes: []routetable.Route{routeOf(peerB, asA, 20)}},
+				{ASN: asB, Peers: []string{peerA},
+					Routes: []routetable.Route{routeOf(peerA, asB, 30)}},
+			},
+		},
+		{
+			name: "a peer whose route is not kept moves to a new origin",
+			steps: []step{announce(peerA, asA, 10), announce(peerB, asA, 20),
+				announce(peerC, asA, 30), announce(peerA, asB, 40)},
+			want: []routetable.Origin{
+				{ASN: asA, Peers: []string{peerB, peerC},
+					Routes: []routetable.Route{
+						routeOf(peerC, asA, 30), routeOf(peerB, asA, 20),
+					}},
+				{ASN: asB, Peers: []string{peerA},
+					Routes: []routetable.Route{routeOf(peerA, asB, 40)}},
+			},
+		},
+		{
+			name: "origins are listed in AS number order",
+			steps: []step{announce(peerA, asC, 10), announce(peerB, asA, 20),
+				announce(peerC, asB, 30)},
+			want: []routetable.Origin{
+				{ASN: asA, Peers: []string{peerB},
+					Routes: []routetable.Route{routeOf(peerB, asA, 20)}},
+				{ASN: asB, Peers: []string{peerC},
+					Routes: []routetable.Route{routeOf(peerC, asB, 30)}},
+				{ASN: asC, Peers: []string{peerA},
+					Routes: []routetable.Route{routeOf(peerA, asC, 10)}},
+			},
+		},
+	})
+}
+
+func TestWithdrawalsAndPeerDowns(t *testing.T) {
+	t.Parallel()
+
+	// threePeers is peerA, peerB and peerC announcing in turn; the routes of
+	// peerC and peerB are kept.
+	threePeers := []step{announce(peerA, asA, 10), announce(peerB, asA, 20),
+		announce(peerC, asA, 30)}
+
+	checkRules(t, []rule{
+		{
+			name:  "a withdrawal drops the peer's kept route",
+			steps: append(slices.Clone(threePeers), withdraw(peerC)),
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerA, peerB},
+				Routes: []routetable.Route{routeOf(peerB, asA, 20)}}},
+		},
+		{
+			name:  "a withdrawal of a route that is not kept leaves the kept ones",
+			steps: append(slices.Clone(threePeers), withdraw(peerA)),
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerB, peerC},
+				Routes: []routetable.Route{
+					routeOf(peerC, asA, 30), routeOf(peerB, asA, 20),
+				}}},
+		},
+		{
+			name: "an origin whose kept routes are withdrawn keeps its other " +
+				"peers",
+			steps: append(slices.Clone(threePeers), withdraw(peerB),
+				withdraw(peerC)),
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerA}}},
+		},
+		{
+			name: "an origin without kept routes keeps the next update",
+			steps: append(slices.Clone(threePeers), withdraw(peerB),
+				withdraw(peerC), announce(peerA, asA, 5)),
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerA},
+				Routes: []routetable.Route{routeOf(peerA, asA, 5)}}},
+		},
+		{
+			name: "an origin no peer carries is removed",
+			steps: []step{announce(peerA, asA, 10), announce(peerB, asB, 20),
+				withdraw(peerA)},
+			want: []routetable.Origin{{ASN: asB, Peers: []string{peerB},
+				Routes: []routetable.Route{routeOf(peerB, asB, 20)}}},
+		},
+		{
+			name:  "a prefix no peer carries is removed",
+			steps: []step{announce(peerA, asA, 10), withdraw(peerA)},
+			want:  nil,
+		},
+		{
+			name:  "a withdrawal from a peer that does not carry it changes nothing",
+			steps: []step{announce(peerA, asA, 10), withdraw(peerB)},
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerA},
+				Routes: []routetable.Route{routeOf(peerA, asA, 10)}}},
+		},
+		{
+			name: "a peer going down leaves the prefix",
+			steps: []step{announce(peerA, asA, 10), announce(peerB, asA, 20),
+				peerDown(peerB)},
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerA},
+				Routes: []routetable.Route{routeOf(peerA, asA, 10)}}},
+		},
+		{
+			name: "a peer going down after it withdrew changes nothing",
+			steps: []step{announce(peerA, asA, 10), announce(peerB, asA, 20),
+				withdraw(peerB), peerDown(peerB)},
+			want: []routetable.Origin{{ASN: asA, Peers: []string{peerA},
+				Routes: []routetable.Route{routeOf(peerA, asA, 10)}}},
+		},
+	})
+}
+
+func TestPeerDownLeavesEveryPrefix(t *testing.T) {
+	t.Parallel()
+
+	table := routetable.New(routetable.Params{})
+	prefixes := []netip.Prefix{
+		netip.MustParsePrefix(prefixV4),
+		netip.MustParsePrefix("10.2.0.0/16"),
+		netip.MustParsePrefix(prefixV6),
+	}
+
+	// peerA carries every prefix with origin asA, peerB the first one with
+	// origin asB.
+	for _, prefix := range prefixes {
+		table.Announce(prefix, asA, routeOf(peerA, asA, 10))
+	}
+
+	table.Announce(prefixes[0], asB, routeOf(peerB, asB, 20))
+	table.PeerDown(peerA)
+
+	want := []routetable.Origin{{ASN: asB, Peers: []string{peerB},
+		Routes: []routetable.Route{routeOf(peerB, asB, 20)}}}
+
+	got := table.Origins(prefixes[0])
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("Origins(%s) = %+v, want %+v", prefixes[0], got, want)
+	}
+
+	for _, prefix := range prefixes[1:] {
+		got := table.Origins(prefix)
+		if got != nil {
+			t.Errorf("Origins(%s) = %+v after the only peer went down, want nil",
+				prefix, got)
+		}
+	}
+
+	counts := table.Counts()
+	if counts.IPv4Prefixes != 1 || counts.IPv6Prefixes != 0 ||
+		counts.IPv4Routes != 1 || counts.IPv6Routes != 0 {
+		t.Errorf("Counts() = %+v, want one IPv4 prefix and route", counts)
+	}
+
+	if len(table.OriginatedPrefixes(asA)) != 0 {
+		t.Errorf("OriginatedPrefixes(%d) = %+v, want none",
+			asA, table.OriginatedPrefixes(asA))
+	}
+}
+
+func TestCountsOriginsWithoutKeptRoute(t *testing.T) {
+	t.Parallel()
+
+	prefix := netip.MustParsePrefix(prefixV4)
+	table := routetable.New(routetable.Params{})
+
+	steps := []struct {
+		apply step
+		want  int
+	}{
+		{announce(peerA, asA, 10), 0},
+		{announce(peerB, asA, 20), 0},
+		{announce(peerC, asA, 30), 0},
+		{withdraw(peerC), 0},
+		{withdraw(peerB), 1},
+		// An update from the last peer is kept.
+		{announce(peerA, asA, 40), 0},
+		{withdraw(peerA), 0},
+		// Once more without kept routes, then without peers: the origin
+		// is removed.
+		{announce(peerA, asA, 10), 0},
+		{announce(peerB, asA, 20), 0},
+		{announce(peerC, asA, 30), 0},
+		{withdraw(peerB), 0},
+		{withdraw(peerC), 1},
+		{peerDown(peerA), 0},
+	}
+
+	for i, s := range steps {
+		s.apply(table, prefix)
+
+		got := table.Counts().OriginsWithoutKeptRoute
+		if got != s.want {
+			t.Errorf("after step %d, OriginsWithoutKeptRoute = %d, want %d",
+				i, got, s.want)
+		}
+	}
+}
+
+// change is a routetable.Change with its peer set as a list of peer numbers.
+type change struct {
+	Prefix    string
+	OriginASN int
+	Removed   bool
+	Peers     []uint
+	Routes    []routetable.Route
+}
+
+// peerNumbers returns the numbers in set, or nil for a nil set.
+func peerNumbers(set *bitset.BitSet) []uint {
+	if set == nil {
+		return nil
+	}
+
+	return slices.Collect(set.EachSet())
+}
+
+func TestTakeChanges(t *testing.T) {
+	t.Parallel()
+
+	// peerA was numbered 5 before; the next new peer is 6.
+	table := routetable.New(routetable.Params{
+		PeerNumbers: map[string]uint{peerA: 5},
+	})
+	v4 := netip.MustParsePrefix(prefixV4)
+	v6 := netip.MustParsePrefix(prefixV6)
+
+	table.Announce(v6, asA, routeOf(peerA, asA, 10))
+	table.Announce(v4, asA, routeOf(peerA, asA, 10))
+	table.Announce(v4, asA, routeOf(peerB, asA, 20))
+
+	checkChanges(t, table, []change{
+		{Prefix: prefixV4, OriginASN: asA, Peers: []uint{5, 6},
+			Routes: []routetable.Route{
+				routeOf(peerB, asA, 20), routeOf(peerA, asA, 10),
+			}},
+		{Prefix: prefixV6, OriginASN: asA, Peers: []uint{5},
+			Routes: []routetable.Route{routeOf(peerA, asA, 10)}},
+	}, map[string]uint{peerB: 6})
+
+	// TakeChanges cleared the record.
+	checkChanges(t, table, []change{}, map[string]uint{})
+
+	// peerB moves to asB; peerA withdraws, which removes the pair of v4 and
+	// asA.
+	table.Announce(v4, asB, routeOf(peerB, asB, 30))
+	table.Withdraw(v4, peerA)
+
+	checkChanges(t, table, []change{
+		{Prefix: prefixV4, OriginASN: asA, Removed: true},
+		{Prefix: prefixV4, OriginASN: asB, Peers: []uint{6},
+			Routes: []routetable.Route{routeOf(peerB, asB, 30)}},
+	}, map[string]uint{})
+}
+
+func TestTakeChangesHoldsOnlyPairsThatChanged(t *testing.T) {
+	t.Parallel()
+
+	table := routetable.New(routetable.Params{})
+	v4 := netip.MustParsePrefix(prefixV4)
+	v6 := netip.MustParsePrefix(prefixV6)
+
+	// peerA, peerB and peerC are numbered 0, 1 and 2. The routes of peerC and
+	// peerB to v4 are kept; peerA keeps only its bit.
+	announceAll(table, prefixV4, asA, 10, peerA, peerB, peerC)
+	table.Announce(v6, asA, routeOf(peerB, asA, 10))
+	table.TakeChanges(math.MaxInt)
+
+	// peerA announces again, with a time older than both kept routes.
+	table.Announce(v4, asA, routeOf(peerA, asA, 15))
+	checkChanges(t, table, []change{}, map[string]uint{})
+
+	// peerC announces its kept route again.
+	table.Announce(v4, asA, routeOf(peerC, asA, 30))
+	checkChanges(t, table, []change{}, map[string]uint{})
+
+	// peerC announces the same path with a newer time, so its kept route
+	// changes.
+	table.Announce(v4, asA, routeOf(peerC, asA, 40))
+	checkChanges(t, table, []change{
+		{Prefix: prefixV4, OriginASN: asA, Peers: []uint{0, 1, 2},
+			Routes: []routetable.Route{
+				routeOf(peerC, asA, 40), routeOf(peerB, asA, 20),
+			}},
+	}, map[string]uint{})
+
+	// peerA withdraws v6, which it does not carry.
+	table.Withdraw(v6, peerA)
+	checkChanges(t, table, []change{}, map[string]uint{})
+
+	// peerA going down changes v4, the one prefix it carries.
+	table.PeerDown(peerA)
+	checkChanges(t, table, []change{
+		{Prefix: prefixV4, OriginASN: asA, Peers: []uint{1, 2},
+			Routes: []routetable.Route{
+				routeOf(peerC, asA, 40), routeOf(peerB, asA, 20),
+			}},
+	}, map[string]uint{})
+
+	// peerA, which carries nothing now, goes down again.
+	table.PeerDown(peerA)
+	checkChanges(t, table, []change{}, map[string]uint{})
+}
+
+// TestTakeChangesTakesAtMostMaxChanges changes three prefix and origin AS
+// pairs, then takes the changes two at a time. The first call must return two
+// pairs and both new peers, and the second the third pair and no peer.
+func TestTakeChangesTakesAtMostMaxChanges(t *testing.T) {
+	t.Parallel()
+
+	const maxChanges = 2
+
+	table := routetable.New(routetable.Params{})
+	v4 := netip.MustParsePrefix(prefixV4)
+	v6 := netip.MustParsePrefix(prefixV6)
+
+	table.Announce(v4, asA, routeOf(peerA, asA, 10))
+	table.Announce(v4, asB, routeOf(peerB, asB, 10))
+	table.Announce(v6, asA, routeOf(peerA, asA, 10))
+
+	first, firstPeers := table.TakeChanges(maxChanges)
+	second, secondPeers := table.TakeChanges(maxChanges)
+
+	if len(first) != maxChanges || len(second) != 1 {
+		t.Fatalf("TakeChanges(%d) returned %d and then %d pairs, want %d and 1",
+			maxChanges, len(first), len(second), maxChanges)
+	}
+
+	wantPeers := map[string]uint{peerA: 0, peerB: 1}
+	if !reflect.DeepEqual(firstPeers, wantPeers) || len(secondPeers) != 0 {
+		t.Errorf("TakeChanges(%d) returned the new peers %v and then %v, "+
+			"want %v and none", maxChanges, firstPeers, secondPeers, wantPeers)
+	}
+
+	for _, c := range first {
+		if c.Prefix == second[0].Prefix && c.OriginASN == second[0].OriginASN {
+			t.Errorf("both calls returned %s with AS%d", c.Prefix, c.OriginASN)
+		}
+	}
+}
+
+// TestPutBackChanges takes a table's changes and puts them back, as a caller
+// does whose write failed. The next TakeChanges must return them again, with
+// each pair's content then, and with the changes since.
+func TestPutBackChanges(t *testing.T) {
+	t.Parallel()
+
+	table := routetable.New(routetable.Params{})
+	v4 := netip.MustParsePrefix(prefixV4)
+	v6 := netip.MustParsePrefix(prefixV6)
+
+	table.Announce(v4, asA, routeOf(peerA, asA, 10))
+	table.Announce(v6, asA, routeOf(peerA, asA, 10))
+	table.PutBackChanges(table.TakeChanges(math.MaxInt))
+
+	if got := table.ChangeCount(); got != 2 {
+		t.Errorf("ChangeCount() = %d after the changes were put back, want 2",
+			got)
+	}
+
+	// peerA withdraws v4, so v4's earlier content must not come back; peerB
+	// announces v6, and is a new peer as well.
+	table.Withdraw(v4, peerA)
+	table.Announce(v6, asA, routeOf(peerB, asA, 20))
+
+	checkChanges(t, table, []change{
+		{Prefix: prefixV4, OriginASN: asA, Removed: true},
+		{Prefix: prefixV6, OriginASN: asA, Peers: []uint{0, 1},
+			Routes: []routetable.Route{
+				routeOf(peerB, asA, 20), routeOf(peerA, asA, 10),
+			}},
+	}, map[string]uint{peerA: 0, peerB: 1})
+
+	if got := table.ChangeCount(); got != 0 {
+		t.Errorf("ChangeCount() = %d after TakeChanges, want 0", got)
+	}
+}
+
+func TestLoad(t *testing.T) {
+	t.Parallel()
+
+	const otherV4 = "10.9.0.0/16"
+
+	v4 := netip.MustParsePrefix(prefixV4)
+	v6 := netip.MustParsePrefix(prefixV6)
+	other := netip.MustParsePrefix(otherV4)
+
+	// The routes of peerC and peerB to v4 are kept; peerA keeps only its bit.
+	// The two routes to v6 have the same time. The routes of other were
+	// withdrawn while peerA still carries it.
+	source := routetable.New(routetable.Params{})
+	announceAll(source, prefixV4, asA, 10, peerA, peerB, peerC)
+	announceAll(source, prefixV4, asB, 40, peerD)
+	source.Announce(v6, asA, routeOf(peerA, asA, 50))
+	source.Announce(v6, asA, routeOf(peerC, asA, 50))
+	announceAll(source, otherV4, asB, 10, peerA, peerB, peerC)
+	source.Withdraw(other, peerB)
+	source.Withdraw(other, peerC)
+
+	changes, peers := source.TakeChanges(math.MaxInt)
+	loaded := routetable.New(routetable.Params{PeerNumbers: peers})
+
+	// Loading a pair twice changes nothing.
+	for range 2 {
+		for _, change := range changes {
+			loaded.Load(change)
+		}
+	}
+
+	for _, prefix := range []netip.Prefix{v4, v6, other} {
+		got, want := loaded.Origins(prefix), source.Origins(prefix)
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("Origins(%s) = %+v after the load, want %+v", prefix, got, want)
+		}
+	}
+
+	if !reflect.DeepEqual(loaded.Counts(), source.Counts()) {
+		t.Errorf("Counts() = %+v after the load, want %+v",
+			loaded.Counts(), source.Counts())
+	}
+
+	checkChanges(t, loaded, []change{}, map[string]uint{})
+}
+
+// TestConcurrentUse has goroutines update one table while others read it. The
+// race detector, which make test runs, fails it when a method uses the table
+// without its lock.
+func TestConcurrentUse(t *testing.T) {
+	t.Parallel()
+
+	const (
+		// rounds is how many times each goroutine calls its method.
+		rounds     = 1000
+		ipVersion  = 4
+		sampleSize = 10
+	)
+
+	table := routetable.New(routetable.Params{})
+	prefix := netip.MustParsePrefix(prefixV4)
+
+	uses := []func(round int){
+		func(round int) { table.Announce(prefix, asA, routeOf(peerA, asA, round)) },
+		func(round int) { table.Announce(prefix, asB, routeOf(peerB, asB, round)) },
+		func(int) { table.Withdraw(prefix, peerA) },
+		func(int) { table.PeerDown(peerB) },
+		func(int) { table.PutBackChanges(table.TakeChanges(math.MaxInt)) },
+		func(int) { table.ChangeCount() },
+		func(int) { table.Lookup(prefix.Addr()) },
+		func(int) { table.Origins(prefix) },
+		func(int) { table.OriginatedPrefixes(asA) },
+		func(int) { table.SamplePrefixes(ipVersion, prefix.Bits(), sampleSize) },
+		func(int) { table.Counts() },
+	}
+
+	var wg sync.WaitGroup
+	for _, use := range uses {
+		wg.Go(func() {
+			for round := range rounds {
+				use(round)
+			}
+		})
+	}
+
+	wg.Wait()
+}
+
+// checkChanges checks that TakeChanges, taking every change, returns want and
+// wantPeers.
+func checkChanges(
+	t *testing.T, table *routetable.Table, want []change,
+	wantPeers map[string]uint,
+) {
+	t.Helper()
+
+	changes, newPeers := table.TakeChanges(math.MaxInt)
+
+	got := make([]change, 0, len(changes))
+	for _, c := range changes {
+		got = append(got, change{
+			Prefix: c.Prefix.String(), OriginASN: c.OriginASN, Removed: c.Removed,
+			Peers: peerNumbers(c.Peers), Routes: c.Routes,
+		})
+	}
+
+	if !reflect.DeepEqual(got, want) {
+		t.Errorf("TakeChanges() changes = %+v, want %+v", got, want)
+	}
+
+	if !reflect.DeepEqual(newPeers, wantPeers) {
+		t.Errorf("TakeChanges() new peers = %v, want %v", newPeers, wantPeers)
+	}
+}

internal/routewatch/app.go

@@ -8,13 +8,17 @@ package routewatch
 import (
 	"context"
 	"errors"
+	"fmt"
+	"path/filepath"
 	"sync"
 	"time"
 
+	"git.eeqj.de/sneak/routewatch/internal/blocklist"
 	"git.eeqj.de/sneak/routewatch/internal/config"
 	"git.eeqj.de/sneak/routewatch/internal/database"
 	"git.eeqj.de/sneak/routewatch/internal/logger"
 	"git.eeqj.de/sneak/routewatch/internal/metrics"
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
 	"git.eeqj.de/sneak/routewatch/internal/server"
 	"git.eeqj.de/sneak/routewatch/internal/streamer"
 
@@ -52,8 +56,13 @@ type RouteWatch struct {
 	peeringHandler *PeeringHandler
 	asnFetcher     *ASNFetcher
 	dbMaintainer   *DBMaintainer
+	blocklists     *blocklist.Blocklists
 }
 
+// blocklistsDirName is the directory in the state directory that holds the
+// blocklist copies.
+const blocklistsDirName = "blocklists"
+
 // New creates a new RouteWatch instance
 func New(deps Dependencies) *RouteWatch {
 	rw := &RouteWatch{
@@ -85,6 +94,14 @@ func (rw *RouteWatch) Run(ctx context.Context) error {
 	// Register database handler to process BGP UPDATE messages
 	if rw.config.EnableBatchedDatabaseWrites {
 		rw.logger.Info("Using batched database handlers for improved performance")
+
+		// The routing table is read before the streamer connects, so that
+		// the prefix handler applies the feed's updates to all of it.
+		table, err := rw.readRouteTable(ctx)
+		if err != nil {
+			return err
+		}
+
 		// ASHandler maintains the asns table
 		rw.dbHandler = NewASHandler(rw.db, rw.logger)
 		rw.streamer.RegisterHandler(rw.dbHandler)
@@ -93,8 +110,9 @@ func (rw *RouteWatch) Run(ctx context.Context) error {
 		rw.peerHandler = NewPeerHandler(rw.db, rw.logger)
 		rw.streamer.RegisterHandler(rw.peerHandler)
 
-		// PrefixHandler maintains the prefixes and live_routes tables
+		// PrefixHandler maintains the prefixes and live_routes tables, and
-		rw.prefixHandler = NewPrefixHandler(rw.db, rw.logger)
+		// the routing table in memory and its copy in the routes table
+		rw.prefixHandler = NewPrefixHandler(rw.db, rw.logger, table)
 		rw.prefixHandler.SetMetricsTracker(rw.streamer.GetMetricsTracker())
 		rw.streamer.RegisterHandler(rw.prefixHandler)
 
@@ -122,6 +140,18 @@ func (rw *RouteWatch) Run(ctx context.Context) error {
 	rw.asnFetcher.Start(ctx)
 	rw.server.SetASNFetcher(rw.asnFetcher)
 
+	// Load the blocklist copies from disk and start downloading the lists.
+	// The HTTP handlers read the server's blocklists without a lock, so they
+	// are set before the handlers run.
+	blocklists := blocklist.New(blocklist.Params{
+		Dir:    filepath.Join(rw.config.StateDir, blocklistsDirName),
+		Lists:  blocklist.Lists(),
+		Logger: rw.logger.Logger,
+	})
+	blocklists.Start(ctx)
+	rw.blocklists = blocklists
+	rw.server.SetBlocklists(blocklists)
+
 	// Start HTTP server
 	err = rw.server.Start(ctx)
 	if err != nil {
@@ -139,11 +169,12 @@ func (rw *RouteWatch) Run(ctx context.Context) error {
 }
 
 // Shutdown stops all services in order: the streamer, the handlers, which
-// write what they hold, the WHOIS fetcher, the database maintainer and the
+// write what they hold, the WHOIS fetcher, the database maintainer, the
-// HTTP server, and last the database, which it checkpoints and closes. Each
+// blocklist downloads and the HTTP server, and last the database, which it
-// stage waits at most until ctx ends, so Shutdown returns soon after: a
+// checkpoints and closes. Each stage waits at most until ctx ends, so
-// handler logs what it could not write by then, and the HTTP server closes
+// Shutdown returns soon after: a handler logs what it could not write by
-// the connections of requests still running.
+// then, and the HTTP server closes the connections of requests still
+// running.
 func (rw *RouteWatch) Shutdown(ctx context.Context) {
 	rw.mu.Lock()
 	if rw.shutdown {
@@ -190,6 +221,10 @@ func (rw *RouteWatch) Shutdown(ctx context.Context) {
 		rw.dbMaintainer.Stop(ctx)
 	}
 
+	if rw.blocklists != nil {
+		rw.blocklists.Stop(ctx)
+	}
+
 	err := rw.server.Stop(ctx)
 	if err != nil {
 		rw.logger.Error("Stopped the HTTP server before every request finished",
@@ -230,6 +265,27 @@ func (rw *RouteWatch) closeDatabase(ctx context.Context) {
 	}
 }
 
+// readRouteTable reads the routing table from the database and logs how many
+// prefix and origin AS pairs and peers it holds and how long the read took.
+// ctx is fx's start context, which ends 15 seconds after the start. Reading a
+// full table can take longer, so the read does not stop with ctx.
+func (rw *RouteWatch) readRouteTable(
+	ctx context.Context,
+) (*routetable.Table, error) {
+	start := time.Now()
+
+	table, err := rw.db.ReadRouteTable(context.WithoutCancel(ctx))
+	if err != nil {
+		return nil, fmt.Errorf("failed to read the routing table: %w", err)
+	}
+
+	counts := table.Counts()
+	rw.logger.Info("Read the routing table", "pairs", counts.Pairs,
+		"peers", counts.Peers, "duration_ms", time.Since(start).Milliseconds())
+
+	return table, nil
+}
+
 // getModule provides all fx dependencies
 func getModule() []fx.Option {
 	return []fx.Option{

internal/routewatch/app_integration_internal_test.go

@@ -19,6 +19,7 @@ import (
 	"git.eeqj.de/sneak/routewatch/internal/logger"
 	"git.eeqj.de/sneak/routewatch/internal/metrics"
 	"git.eeqj.de/sneak/routewatch/internal/ristypes"
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
 	"git.eeqj.de/sneak/routewatch/internal/server"
 	"git.eeqj.de/sneak/routewatch/internal/streamer"
 )
@@ -39,6 +40,9 @@ type mockStore struct {
 	Prefixes map[string]*database.Prefix
 	Peerings map[string]bool // key is "from_to"
 	Routes   map[string]bool // key is "prefix_origin_peer"
+	// TablePrefixes holds the prefixes that the written changes of the
+	// routing table leave some peer carrying.
+	TablePrefixes map[string]bool
 
 	// Track IP versions
 	IPv4Prefixes int
@@ -48,10 +52,11 @@ type mockStore struct {
 // newMockStore creates a new mock store
 func newMockStore() *mockStore {
 	return &mockStore{
-		ASNs:     make(map[int]*database.ASN),
+		ASNs:          make(map[int]*database.ASN),
-		Prefixes: make(map[string]*database.Prefix),
+		Prefixes:      make(map[string]*database.Prefix),
-		Peerings: make(map[string]bool),
+		Peerings:      make(map[string]bool),
-		Routes:   make(map[string]bool),
+		Routes:        make(map[string]bool),
+		TablePrefixes: make(map[string]bool),
 	}
 }
 
@@ -395,6 +400,30 @@ func (m *mockStore) DeleteLiveRoutesOfPeer(_ string) (int, error) {
 	return 0, nil
 }
 
+// WriteRouteChanges records the prefixes the changes leave some peer carrying,
+// whatever their origin AS.
+func (m *mockStore) WriteRouteChanges(
+	changes []routetable.Change, _ map[string]uint,
+) error {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+
+	for _, change := range changes {
+		if change.Removed {
+			delete(m.TablePrefixes, change.Prefix.String())
+		} else {
+			m.TablePrefixes[change.Prefix.String()] = true
+		}
+	}
+
+	return nil
+}
+
+// ReadRouteTable returns an empty routing table.
+func (m *mockStore) ReadRouteTable(_ context.Context) (*routetable.Table, error) {
+	return routetable.New(routetable.Params{}), nil
+}
+
 // GetOrCreateASNBatch mock implementation
 func (m *mockStore) GetOrCreateASNBatch(asns map[int]database.SeenTimes) error {
 	m.mu.Lock()
@@ -466,9 +495,9 @@ func TestRouteWatchLiveFeed(t *testing.T) {
 	// Create streamer
 	s := streamer.New(logger, metricsTracker)
 
-	// Create test config with empty state dir (no snapshot loading)
+	// The state directory holds the blocklist copies Run downloads.
 	cfg := &config.Config{
-		StateDir:                    "",
+		StateDir:                    t.TempDir(),
 		MaxRuntime:                  5 * time.Second,
 		EnableBatchedDatabaseWrites: true,
 	}
@@ -566,7 +595,8 @@ func announcementFeed(prefixes []string) string {
 // handler's worker waits on the first one until the server sees the streamer
 // close the connection, which only Shutdown does, so all three are still in
 // the streamer when Shutdown starts. Each prefix must be in the database when
-// Shutdown returns.
+// Shutdown returns, both in the prefix tables and in the routing table's
+// writes.
 func TestShutdownWritesTheUpdatesQueuedInTheStreamer(t *testing.T) {
 	t.Parallel()
 
@@ -600,7 +630,7 @@ func TestShutdownWritesTheUpdatesQueuedInTheStreamer(t *testing.T) {
 		Logger:   log,
 		Config:   cfg,
 	})
-	rw.prefixHandler = NewPrefixHandler(store, log)
+	rw.prefixHandler = NewPrefixHandler(store, log, routetable.New(routetable.Params{}))
 	s.RegisterHandler(gatedPrefixHandler{
 		PrefixHandler: rw.prefixHandler, release: release,
 	})
@@ -640,9 +670,11 @@ func TestShutdownWritesTheUpdatesQueuedInTheStreamer(t *testing.T) {
 	defer store.mu.Unlock()
 
 	for _, prefix := range prefixes {
-		if _, ok := store.Prefixes[prefix]; !ok {
+		_, inPrefixTables := store.Prefixes[prefix]
-			t.Errorf("%s was queued in the streamer when Shutdown started "+
+		if !inPrefixTables || !store.TablePrefixes[prefix] {
-				"but is not in the database", prefix)
+			t.Errorf("%s was queued in the streamer when Shutdown started; "+
+				"written to the prefix tables %t, in the routing table's "+
+				"writes %t", prefix, inPrefixTables, store.TablePrefixes[prefix])
 		}
 	}
 }

internal/routewatch/asnfetcher.go

@@ -68,10 +68,12 @@ type ASNFetcher struct {
 
 // NewASNFetcher creates a new ASN fetcher.
 func NewASNFetcher(db database.Store, logger *slog.Logger) *ASNFetcher {
+	logger = logger.With("component", "asn_fetcher")
+
 	return &ASNFetcher{
 		db:              db,
-		whoisClient:     whois.NewClient(),
+		whoisClient:     whois.NewClient(logger),
-		logger:          logger.With("component", "asn_fetcher"),
+		logger:          logger,
 		immediateQueue:  make(chan int, immediateQueueSize),
 		stopCh:          make(chan struct{}),
 		done:            make(chan struct{}),

internal/routewatch/batchwrite_internal_test.go

@@ -13,6 +13,7 @@ import (
 	"git.eeqj.de/sneak/routewatch/internal/database"
 	"git.eeqj.de/sneak/routewatch/internal/logger"
 	"git.eeqj.de/sneak/routewatch/internal/ristypes"
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
 )
 
 const (
@@ -119,10 +120,11 @@ func (s *blockingStore) releaseWrites() {
 //
 //nolint:tagliatelle // field names are the keys the handlers log
 type stopLog struct {
-	Msg       string `json:"msg"`
+	Msg          string `json:"msg"`
-	Updates   int    `json:"updates"`
+	Updates      int    `json:"updates"`
-	PeersDown int    `json:"peers_down"`
+	PeersDown    int    `json:"peers_down"`
-	Paths     int    `json:"paths"`
+	TableChanges int    `json:"table_changes"`
+	Paths        int    `json:"paths"`
 }
 
 // newErrorLogger returns a logger that writes only errors, as JSON lines, to
@@ -313,6 +315,11 @@ func stopWhileAWriteIsBlocked(
 	}
 }
 
+// TestPrefixHandlerSkipsItsLastWriteAfterTheStopDeadline also checks the
+// routing table's changes: the flush whose delete is held wrote those of the
+// fill, so Stop must log the one of the extra prefix as not written. The flush
+// timer must not fire. A flush it started before the fill would be the one
+// held, and it would not have written the fill's change.
 func TestPrefixHandlerSkipsItsLastWriteAfterTheStopDeadline(t *testing.T) {
 	t.Parallel()
 
@@ -321,7 +328,8 @@ func TestPrefixHandlerSkipsItsLastWriteAfterTheStopDeadline(t *testing.T) {
 	var logs bytes.Buffer
 
 	store := newBlockingStore()
-	h := NewPrefixHandler(store, newErrorLogger(&logs))
+	h := newPrefixHandler(store, newErrorLogger(&logs),
+		routetable.New(routetable.Params{}), longerThanAnyTest)
 	fill := slices.Repeat([]string{testV4Prefix}, prefixBatchSize)
 	// The peer's session goes down first, so the write held is the delete of
 	// its routes, and Stop must log that peer down too.
@@ -337,9 +345,76 @@ func TestPrefixHandlerSkipsItsLastWriteAfterTheStopDeadline(t *testing.T) {
 	}
 
 	logged := lastLogged(t, &logs)
-	if logged.Updates != prefixBatchSize+1 || logged.PeersDown != 1 {
+	if logged.Updates != prefixBatchSize+1 || logged.PeersDown != 1 ||
-		t.Errorf("Stop logged %d updates and %d peer downs not written, "+
+		logged.TableChanges != 1 {
-			"want %d and 1", logged.Updates, logged.PeersDown, prefixBatchSize+1)
+		t.Errorf("Stop logged %d updates, %d peer downs and %d table changes "+
+			"not written, want %d, 1 and 1", logged.Updates, logged.PeersDown,
+			logged.TableChanges, prefixBatchSize+1)
+	}
+}
+
+// TestPrefixHandlerSkipsAFullBatchAfterTheStopDeadline hands the prefix handler
+// a full batch while a write is held, so the batch's wake-up of the flush
+// goroutine waits. The stop deadline passes meanwhile. When the write ends, the
+// flush goroutine must stop instead of writing the batch.
+func TestPrefixHandlerSkipsAFullBatchAfterTheStopDeadline(t *testing.T) {
+	t.Parallel()
+
+	const extraPrefix = "198.51.100.0/24"
+
+	store := newBlockingStore()
+	h := NewPrefixHandler(store, logger.New(), routetable.New(routetable.Params{}))
+	fill := slices.Repeat([]string{testV4Prefix}, prefixBatchSize)
+	full := slices.Repeat([]string{extraPrefix}, prefixBatchSize)
+	stopWhileAWriteIsBlocked(t, store, h, h.done,
+		[]*ristypes.RISMessage{prefixAnnouncement(fill)},
+		prefixAnnouncement(full))
+
+	store.mu.Lock()
+	defer store.mu.Unlock()
+
+	if store.prefixes[extraPrefix] {
+		t.Errorf("%s was written after the stop deadline", extraPrefix)
+	}
+}
+
+// tableWriteBlockingStore is a blockingStore whose writes of the routing
+// table's changes also wait until the test calls releaseWrites.
+type tableWriteBlockingStore struct {
+	*blockingStore
+}
+
+func (s tableWriteBlockingStore) WriteRouteChanges(
+	changes []routetable.Change, newPeers map[string]uint,
+) error {
+	s.waitForRelease()
+
+	return s.mockStore.WriteRouteChanges(changes, newPeers)
+}
+
+// TestPrefixHandlerStopCountsTheTableChangesOfAWriteInProgress holds the write
+// of the routing table's changes that a full batch starts, then hands the
+// prefix handler one more prefix and stops it with a deadline that passes
+// meanwhile. Stop must log as not written both the change the held write took
+// and the one since.
+func TestPrefixHandlerStopCountsTheTableChangesOfAWriteInProgress(t *testing.T) {
+	t.Parallel()
+
+	const extraPrefix = "198.51.100.0/24"
+
+	var logs bytes.Buffer
+
+	blocking := newBlockingStore()
+	h := NewPrefixHandler(tableWriteBlockingStore{blockingStore: blocking},
+		newErrorLogger(&logs), routetable.New(routetable.Params{}))
+	fill := slices.Repeat([]string{testV4Prefix}, prefixBatchSize)
+	stopWhileAWriteIsBlocked(t, blocking, h, h.done,
+		[]*ristypes.RISMessage{prefixAnnouncement(fill)},
+		prefixAnnouncement([]string{extraPrefix}))
+
+	if logged := lastLogged(t, &logs); logged.TableChanges != 2 {
+		t.Errorf("Stop logged %d table changes not written, want 2",
+			logged.TableChanges)
 	}
 }
 
@@ -455,7 +530,7 @@ func TestPrefixHandlerHandlesMessagesWhileAWriteIsBlocked(t *testing.T) {
 	const extraPrefix = "198.51.100.0/24"
 
 	store := newBlockingStore()
-	h := NewPrefixHandler(store, logger.New())
+	h := NewPrefixHandler(store, logger.New(), routetable.New(routetable.Params{}))
 	fill := slices.Repeat([]string{testV4Prefix}, prefixBatchSize)
 	handleWhileAWriteIsBlocked(t, store, h,
 		[]*ristypes.RISMessage{prefixAnnouncement(fill)},
@@ -515,7 +590,7 @@ func TestPrefixHandlerWaitsAtTheMaximumBatchSize(t *testing.T) {
 	const extraPrefix = "198.51.100.0/24"
 
 	store := newBlockingStore()
-	h := NewPrefixHandler(store, logger.New())
+	h := NewPrefixHandler(store, logger.New(), routetable.New(routetable.Params{}))
 	fill := slices.Repeat([]string{testV4Prefix}, prefixBatchSize)
 	toMax := slices.Repeat([]string{testV4Prefix}, prefixBatchMaxSize)
 	handleAtMaxBatchSize(t, store, h,
@@ -592,7 +667,10 @@ func TestHandlersWakeTheFlushGoroutineWhenTheBatchIsFull(t *testing.T) {
 			name:      "prefix",
 			batchSize: prefixBatchSize,
 			handle: func(n int) chan struct{} {
-				h := &PrefixHandler{batchFullCh: make(chan struct{}, 1)}
+				h := &PrefixHandler{
+					batchFullCh: make(chan struct{}, 1),
+					table:       routetable.New(routetable.Params{}),
+				}
 				h.HandleMessage(prefixAnnouncement(
 					slices.Repeat([]string{testV4Prefix}, n)))
 

internal/routewatch/prefixhandler.go

@@ -13,6 +13,7 @@ import (
 	"git.eeqj.de/sneak/routewatch/internal/logger"
 	"git.eeqj.de/sneak/routewatch/internal/metrics"
 	"git.eeqj.de/sneak/routewatch/internal/ristypes"
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
 )
 
 const (
@@ -38,6 +39,16 @@ const (
 	// DO NOT reduce this timeout - larger batches are more efficient
 	prefixBatchTimeout = 1 * time.Second
 
+	// maxTableChangesPerWrite is the most changed prefix and origin AS pairs
+	// of the routing table that one flush writes; the rest wait for the next
+	// flushes. The change of one pair takes about 430 bytes of memory and 15
+	// microseconds to write. So a write holds about 9 MB and takes about a
+	// third of the one-second flush interval, which leaves the rest to the
+	// batch. The feed peaks at about 5,000 updates a second, each changing at
+	// most one pair. So the million pairs that a full-table peer's session
+	// going down changes are written in about a minute.
+	maxTableChangesPerWrite = 20000
+
 	// IP version constants
 	ipv4Version = 4
 	ipv6Version = 6
@@ -47,15 +58,19 @@ const (
 // database. Routes are added on announcement and deleted on withdrawal or on an
 // announcement whose AS path is empty or holds AS 0 anywhere, and all routes of
 // a peer are deleted when its BGP session goes down.
+//
+// It applies the same updates to the routing table in memory as it handles
+// them, and writes the table's changes to the database with each flush.
 type PrefixHandler struct {
 	db      database.Store
 	logger  *logger.Logger
 	metrics *metrics.Tracker
+	table   *routetable.Table
 
-	// Batching. mu guards batch, held, peersDown, writing and deleting only:
+	// Batching. mu guards batch, held, peersDown, writing, deleting and
-	// the flush goroutine takes them under mu and writes them after releasing
+	// writingTableChanges only: the flush goroutine takes them under mu and
-	// mu, so HandleMessage waits for a database write only while batch is at
+	// writes them after releasing mu, so HandleMessage waits for a database
-	// prefixBatchMaxSize.
+	// write only while batch is at prefixBatchMaxSize.
 	mu    sync.Mutex
 	batch []prefixUpdate
 	// held holds the updates that the peers whose route delete failed in the
@@ -74,6 +89,9 @@ type PrefixHandler struct {
 	// deleting is how many peers from peersDown the flush goroutine took and
 	// has not yet deleted the routes of.
 	deleting int
+	// writingTableChanges is how many changes the flush goroutine took from
+	// the routing table and has not finished writing.
+	writingTableChanges int
 	// batchTaken is signalled when the flush goroutine takes batch; its L is
 	// &mu.
 	batchTaken  sync.Cond
@@ -97,11 +115,36 @@ type prefixUpdate struct {
 	endsInSet bool
 }
 
-// NewPrefixHandler creates a new batched prefix tracking handler
+// announcesRoute says whether u gives the peer a route to the prefix: an
-func NewPrefixHandler(db database.Store, logger *logger.Logger) *PrefixHandler {
+// announcement whose path gives an origin, or ends in an AS set of several
+// members, which gives origin 0 (none). Any other update removes the peer's
+// route for the prefix: a withdrawal, or an announcement whose path is empty
+// or holds AS 0 anywhere (the decoder empties such a path). Such an
+// announcement replaces the peer's route, as any announcement does, with none
+// (RFC 7607 treats AS 0 in a path as a withdrawal).
+func (u prefixUpdate) announcesRoute() bool {
+	return u.messageType == "announcement" && (u.originASN > 0 || u.endsInSet)
+}
+
+// NewPrefixHandler creates a new batched prefix tracking handler, which applies
+// the updates to table, the routing table read from db at startup.
+func NewPrefixHandler(
+	db database.Store, logger *logger.Logger, table *routetable.Table,
+) *PrefixHandler {
+	return newPrefixHandler(db, logger, table, prefixBatchTimeout)
+}
+
+// newPrefixHandler is NewPrefixHandler with the flush timer's interval,
+// batchTimeout, in place of prefixBatchTimeout. A test that the timer must not
+// disturb gives an interval longer than the test runs.
+func newPrefixHandler(
+	db database.Store, logger *logger.Logger, table *routetable.Table,
+	batchTimeout time.Duration,
+) *PrefixHandler {
 	h := &PrefixHandler{
 		db:          db,
 		logger:      logger,
+		table:       table,
 		batch:       make([]prefixUpdate, 0, prefixBatchSize),
 		batchFullCh: make(chan struct{}, 1),
 		lastFlush:   time.Now(),
@@ -111,7 +154,7 @@ func NewPrefixHandler(db database.Store, logger *logger.Logger) *PrefixHandler {
 	h.batchTaken.L = &h.mu
 
 	// Start the flush timer goroutine
-	go h.flushLoop()
+	go h.flushLoop(batchTimeout)
 
 	return h
 }
@@ -165,18 +208,22 @@ func (h *PrefixHandler) HandleMessage(msg *ristypes.RISMessage) {
 		h.batchTaken.Wait()
 	}
 
-	// Withdrawals are queued before announcements, because the batch keeps
+	// Withdrawals are queued, and applied to the routing table, before
-	// each peer's last update for a prefix: a message that lists a prefix as
+	// announcements, because the batch keeps each peer's last update for a
-	// both withdrawn and announced keeps the route (RFC 4271 section 4.3).
+	// prefix: a message that lists a prefix as both withdrawn and announced
-	// A withdrawal names only the prefix and peer: the message's AS path, and
+	// keeps the route (RFC 4271 section 4.3). A withdrawal names only the
-	// so its origin AS, belongs to the announced prefixes.
+	// prefix and peer: the message's AS path, and so its origin AS, belongs
+	// to the announced prefixes.
 	for _, prefix := range msg.Withdrawals {
-		h.batch = append(h.batch, prefixUpdate{
+		update := prefixUpdate{
 			prefix:      canonicalPrefix(prefix),
 			peer:        msg.Peer,
 			messageType: "withdrawal",
 			timestamp:   timestamp,
-		})
+		}
+		h.batch = append(h.batch, update)
+		h.applyToTable(update)
+
 		// Record withdrawal in metrics
 		if h.metrics != nil {
 			h.metrics.RecordWithdrawal()
@@ -185,7 +232,7 @@ func (h *PrefixHandler) HandleMessage(msg *ristypes.RISMessage) {
 
 	for _, announcement := range msg.Announcements {
 		for _, prefix := range announcement.Prefixes {
-			h.batch = append(h.batch, prefixUpdate{
+			update := prefixUpdate{
 				prefix:      canonicalPrefix(prefix),
 				originASN:   originASN,
 				peer:        msg.Peer,
@@ -193,7 +240,10 @@ func (h *PrefixHandler) HandleMessage(msg *ristypes.RISMessage) {
 				timestamp:   timestamp,
 				path:        path,
 				endsInSet:   len(msg.Path.Set) > 0,
-			})
+			}
+			h.batch = append(h.batch, update)
+			h.applyToTable(update)
+
 			// Record announcement in metrics
 			if h.metrics != nil {
 				h.metrics.RecordAnnouncement()
@@ -212,12 +262,15 @@ func (h *PrefixHandler) HandleMessage(msg *ristypes.RISMessage) {
 	}
 }
 
-// Stop stops the flush goroutine, which writes the updates and peer downs the
+// Stop stops the flush goroutine, which makes one last flush before it returns,
-// handler holds before it returns, and waits for it until ctx ends. Once ctx
+// and waits for it until ctx ends. That flush writes the updates and peer downs
-// has ended the flush goroutine skips that last write, and a write still
+// the handler holds, and at most maxTableChangesPerWrite of the routing table's
-// running is lost when the process exits. A peer whose route delete fails in
+// changes. Once ctx has ended the flush goroutine skips that last flush, and a
-// the last write is not retried either. Stop logs how many updates are not
+// write still running is lost when the process exits. A peer whose route delete
-// written and how many peer downs have not had their routes deleted.
+// fails in the last flush is not retried either, nor is a failed write of the
+// table's changes. Stop logs how many updates are not written, how many peer
+// downs have not had their routes deleted, and how many of the table's changes
+// are not written.
 func (h *PrefixHandler) Stop(ctx context.Context) {
 	h.stopCh <- ctx
 
@@ -229,22 +282,24 @@ func (h *PrefixHandler) Stop(ctx context.Context) {
 	h.mu.Lock()
 	unwritten := h.writing + len(h.batch) + len(h.held)
 	peersDown := h.deleting + len(h.peersDown)
+	tableChanges := h.writingTableChanges + h.table.ChangeCount()
 	h.mu.Unlock()
 
-	if unwritten == 0 && peersDown == 0 {
+	if unwritten == 0 && peersDown == 0 && tableChanges == 0 {
 		return
 	}
 
 	if ctx.Err() != nil {
 		h.logger.Error("Stop deadline passed before the prefix handler wrote "+
-			"its updates", "updates", unwritten, "peers_down", peersDown)
+			"its updates", "updates", unwritten, "peers_down", peersDown,
+			"table_changes", tableChanges)
 
 		return
 	}
 
-	h.logger.Error("The prefix handler stopped without deleting the routes "+
+	h.logger.Error("The prefix handler stopped before it wrote everything",
-		"of peers whose session went down", "updates", unwritten,
+		"updates", unwritten, "peers_down", peersDown,
-		"peers_down", peersDown)
+		"table_changes", tableChanges)
 }
 
 // peerSessionDown notes that the peer's BGP session went down, so that the next
@@ -252,11 +307,14 @@ func (h *PrefixHandler) Stop(ctx context.Context) {
 // peer's updates still in the batch or held came before the down, which
 // replaces them, so they are dropped; updates the peer sends later stay in the
 // batch and are written after the delete. A peer already in peersDown is not
-// added again: one delete removes all of its routes.
+// added again: one delete removes all of its routes. In the routing table in
+// memory the down takes effect at once.
 func (h *PrefixHandler) peerSessionDown(peer string) {
 	h.mu.Lock()
 	defer h.mu.Unlock()
 
+	h.table.PeerDown(peer)
+
 	isPeers := func(update prefixUpdate) bool { return update.peer == peer }
 	h.batch = slices.DeleteFunc(h.batch, isPeers)
 	h.held = slices.DeleteFunc(h.held, isPeers)
@@ -267,17 +325,32 @@ func (h *PrefixHandler) peerSessionDown(peer string) {
 }
 
 // flushLoop runs in a goroutine, the only one that writes the batch: it
-// flushes when the batch is full, periodically, and once more on Stop.
+// flushes when the batch is full, every batchTimeout, and once more on Stop.
-func (h *PrefixHandler) flushLoop() {
+func (h *PrefixHandler) flushLoop(batchTimeout time.Duration) {
 	defer close(h.done)
 
-	ticker := time.NewTicker(prefixBatchTimeout)
+	ticker := time.NewTicker(batchTimeout)
 	defer ticker.Stop()
 
 	for {
+		// Stop goes first. A write can run past the stop deadline while a full
+		// batch's wake-up or a tick waits beside Stop's context. The select
+		// below picks one of them at random, but past the deadline no flush
+		// may start.
+		select {
+		case ctx := <-h.stopCh:
+			// Final flush, unless the stop deadline has passed
+			if ctx.Err() == nil {
+				h.flushBatch()
+			}
+
+			return
+		default:
+		}
+
 		select {
 		case <-ticker.C:
-			if time.Since(h.lastFlush) >= prefixBatchTimeout {
+			if time.Since(h.lastFlush) >= batchTimeout {
 				h.flushBatch()
 			}
 		case <-h.batchFullCh:
@@ -321,9 +394,11 @@ func (h *PrefixHandler) takeBatch() ([]prefixUpdate, []string) {
 	return batch, peersDown
 }
 
-// flushBatch takes the pending batch and writes it to the database, without
+// flushBatch writes the routing table's changes, then takes the pending batch
-// holding the mutex during the write.
+// and writes it to the database, without holding the mutex during the writes.
 func (h *PrefixHandler) flushBatch() {
+	h.writeTableChanges()
+
 	batch, peersDown := h.takeBatch()
 	if len(batch) == 0 && len(peersDown) == 0 {
 		return
@@ -370,15 +445,7 @@ func (h *PrefixHandler) flushBatch() {
 	)
 
 	for _, update := range lastUpdates {
-		// An announcement is stored when its path gives an origin, or when it
+		if update.announcesRoute() {
-		// ends in an AS set of several members: that route is stored with
-		// origin 0 (none). Any other update deletes the peer's route for the
-		// prefix: a withdrawal, or an announcement whose path is empty or
-		// holds AS 0 anywhere (the decoder empties such a path). Such an
-		// announcement replaces the peer's route, as any announcement does,
-		// with none (RFC 7607 treats AS 0 in a path as a withdrawal).
-		if update.messageType == "announcement" &&
-			(update.originASN > 0 || update.endsInSet) {
 			// Create live route for batch upsert
 			route := h.createLiveRoute(update)
 			if route != nil {
@@ -421,6 +488,59 @@ func (h *PrefixHandler) flushBatch() {
 	h.lastFlush = time.Now()
 }
 
+// applyToTable applies update to the routing table in memory: as an
+// announcement when it gives the peer a route, otherwise as a withdrawal. A
+// prefix that does not parse is left out; flushBatch logs it.
+func (h *PrefixHandler) applyToTable(update prefixUpdate) {
+	prefix, err := netip.ParsePrefix(update.prefix)
+	if err != nil {
+		return
+	}
+
+	if !update.announcesRoute() {
+		h.table.Withdraw(prefix, update.peer)
+
+		return
+	}
+
+	h.table.Announce(prefix, update.originASN, routetable.Route{
+		Peer:   update.peer,
+		ASPath: update.path,
+		Time:   update.timestamp,
+	})
+}
+
+// writeTableChanges writes at most maxTableChangesPerWrite changes of the
+// routing table in memory, and every peer the table numbered since the last
+// write.
+// When the write fails, they go back to the table, so that a later write writes
+// them again, each pair with its content then.
+func (h *PrefixHandler) writeTableChanges() {
+	h.mu.Lock()
+	changes, newPeers := h.table.TakeChanges(maxTableChangesPerWrite)
+	h.writingTableChanges = len(changes)
+	h.mu.Unlock()
+
+	if len(changes) == 0 && len(newPeers) == 0 {
+		return
+	}
+
+	err := h.db.WriteRouteChanges(changes, newPeers)
+
+	h.mu.Lock()
+	defer h.mu.Unlock()
+
+	h.writingTableChanges = 0
+
+	if err != nil {
+		h.logger.Error("Failed to write the routing table's changes; the next "+
+			"flush retries", "changes", len(changes), "new_peers", len(newPeers),
+			"error", err)
+
+		h.table.PutBackChanges(changes, newPeers)
+	}
+}
+
 // deleteLiveRoutesOfPeers deletes all live routes of each of peers, the peers
 // whose BGP session went down, and returns those whose delete failed. Most
 // downs come from peers that have no routes, so only a delete that removed

internal/routewatch/prefixhandler_internal_test.go

@@ -16,6 +16,7 @@ import (
 	"git.eeqj.de/sneak/routewatch/internal/database"
 	"git.eeqj.de/sneak/routewatch/internal/logger"
 	"git.eeqj.de/sneak/routewatch/internal/ristypes"
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
 )
 
 const testPeerIP = "2001:db8:ffff::1"
@@ -40,9 +41,7 @@ func TestPrefixHandlerStoresPrefixesTheIPLookupFinds(t *testing.T) {
 	t.Parallel()
 
 	db := newTestDatabase(t)
-
+	h := prefixHandlerWithoutTimer(db)
-	// Built without NewPrefixHandler's flush timer, so the test flushes itself.
-	h := &PrefixHandler{db: db, logger: logger.New()}
 
 	ts := time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)
 	h.HandleMessage(&ristypes.RISMessage{
@@ -462,8 +461,7 @@ func TestPrefixHandlerDoesNotStoreAPrefixThatDoesNotParse(t *testing.T) {
 		t.Fatalf("failed to create database: %v", err)
 	}
 
-	// Built without NewPrefixHandler's flush timer, so the test flushes itself.
+	h := prefixHandlerWithoutTimer(db)
-	h := &PrefixHandler{db: db, logger: logger.New()}
 
 	withdrawal := &ristypes.RISMessage{
 		Type:            ristypes.MessageTypeUpdate,
@@ -694,8 +692,7 @@ func TestPrefixHandlerHandlesADownWhileAFlushWrites(t *testing.T) {
 		release:      make(chan struct{}),
 	}
 
-	// Built without NewPrefixHandler's flush timer, so the test flushes itself.
+	h := prefixHandlerWithoutTimer(store)
-	h := &PrefixHandler{db: store, logger: logger.New()}
 	h.HandleMessage(peerAnnouncement(testPeerIP, beforeDown))
 
 	flushed := make(chan struct{})
@@ -832,10 +829,7 @@ func TestPrefixHandlerRetriesAFailedDeleteOfAPeersRoutes(t *testing.T) {
 
 			db := newTestDatabase(t)
 			store := &firstPeerDeleteFailsStore{Database: db}
-
+			h := prefixHandlerWithoutTimer(store)
-			// Built without NewPrefixHandler's flush timer, so the test
-			// flushes itself.
-			h := &PrefixHandler{db: store, logger: logger.New()}
 			store.whileFailing = func() {
 				for _, msg := range tt.whileFailing {
 					h.HandleMessage(msg)
@@ -897,11 +891,7 @@ func TestPrefixHandlerKeepsAtMostABatchOfUpdatesWhileADeleteKeepsFailing(
 	otherPeersPrefixes := []string{testV4Prefix, testV6Prefix, "2001:db8:2::/48"}
 
 	db := newTestDatabase(t)
-
+	h := prefixHandlerWithoutTimer(peerDeleteAlwaysFailsStore{Database: db})
-	// Built without NewPrefixHandler's flush timer, so the test flushes itself.
-	h := &PrefixHandler{
-		db: peerDeleteAlwaysFailsStore{Database: db}, logger: logger.New(),
-	}
 	h.HandleMessage(sessionDown())
 
 	// The peer announces a /32 for each address from 10.0.0.0 on, each
@@ -953,7 +943,7 @@ func TestPrefixHandlerStopLogsAFailedDeleteWithoutTheDeadline(t *testing.T) {
 	var logs bytes.Buffer
 
 	h := NewPrefixHandler(peerDeleteAlwaysFailsStore{Database: newTestDatabase(t)},
-		newErrorLogger(&logs))
+		newErrorLogger(&logs), routetable.New(routetable.Params{}))
 	h.HandleMessage(sessionDown())
 	h.HandleMessage(peerAnnouncement(testPeerIP, testV4Prefix))
 	h.Stop(t.Context())
@@ -979,7 +969,8 @@ func TestPrefixHandlerStopLogsNothingAfterADeleteThatSucceeds(t *testing.T) {
 
 	var logs bytes.Buffer
 
-	h := NewPrefixHandler(newTestDatabase(t), newErrorLogger(&logs))
+	h := NewPrefixHandler(newTestDatabase(t), newErrorLogger(&logs),
+		routetable.New(routetable.Params{}))
 	h.HandleMessage(sessionDown())
 	h.Stop(t.Context())
 
@@ -989,6 +980,22 @@ func TestPrefixHandlerStopLogsNothingAfterADeleteThatSucceeds(t *testing.T) {
 	}
 }
 
+// longerThanAnyTest is a flush timer interval that no test lasts. A test whose
+// prefix handler must flush only when its batch is full and on Stop gives it to
+// newPrefixHandler.
+const longerThanAnyTest = time.Hour
+
+// prefixHandlerWithoutTimer returns a prefix handler that writes to store and
+// applies the updates to an empty routing table. It is built without
+// NewPrefixHandler's flush goroutine, so the test flushes itself.
+func prefixHandlerWithoutTimer(store database.Store) *PrefixHandler {
+	return &PrefixHandler{
+		db:     store,
+		logger: logger.New(),
+		table:  routetable.New(routetable.Params{}),
+	}
+}
+
 // newTestDatabase opens a database in a new temporary directory. It is closed
 // when the test ends.
 func newTestDatabase(t *testing.T) *database.Database {
@@ -1012,9 +1019,7 @@ func handleBatches(
 	t.Helper()
 
 	db := newTestDatabase(t)
-
+	h := prefixHandlerWithoutTimer(db)
-	// Built without NewPrefixHandler's flush timer, so the test flushes itself.
-	h := &PrefixHandler{db: db, logger: logger.New()}
 
 	for _, batch := range batches {
 		for _, msg := range batch {

internal/routewatch/prefixhandler_table_internal_test.go

@@ -0,0 +1,534 @@
+package routewatch
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"log/slog"
+	"net/netip"
+	"reflect"
+	"slices"
+	"testing"
+	"time"
+
+	"git.eeqj.de/sneak/routewatch/internal/database"
+	"git.eeqj.de/sneak/routewatch/internal/logger"
+	"git.eeqj.de/sneak/routewatch/internal/ristypes"
+	"git.eeqj.de/sneak/routewatch/internal/routetable"
+)
+
+// More peers and prefixes for the tests of the routing table in memory.
+const (
+	secondPeerIP = "2001:db8:ffff::2"
+	thirdPeerIP  = "2001:db8:ffff::3"
+	fourthPeerIP = "192.0.2.4"
+	fifthPeerIP  = "192.0.2.5"
+
+	otherV4Prefix = "198.51.100.0/24"
+	setV4Prefix   = "203.0.113.0/24"
+
+	// firstManyPrefix is the first prefix announceManyPrefixes announces.
+	firstManyPrefix = "10.0.0.0/32"
+)
+
+// tableWriteTimeout is how long a test waits for the flush timer to write the
+// routing table's changes: a few ticks of it.
+const tableWriteTimeout = 5 * prefixBatchTimeout
+
+// tableCase is one test of the routing table in memory: the messages handed to
+// the prefix handler, and for each prefix the peers that carry it with each
+// origin AS after them.
+type tableCase struct {
+	name     string
+	messages []*ristypes.RISMessage
+	want     map[string]map[int][]string
+}
+
+// TestPrefixHandlerAppliesUpdatesToTheRoutingTable hands the prefix handler
+// announcements, withdrawals and a peer's session going down.
+func TestPrefixHandlerAppliesUpdatesToTheRoutingTable(t *testing.T) {
+	t.Parallel()
+
+	announceAndWithdraw := peerAnnouncement(testPeerIP, testV4Prefix)
+	announceAndWithdraw.Withdrawals = []string{testV4Prefix}
+
+	checkTableCases(t, []tableCase{
+		{
+			name:     "an announcement",
+			messages: []*ristypes.RISMessage{peerAnnouncement(testPeerIP, testV4Prefix)},
+			want:     map[string]map[int][]string{testV4Prefix: {testASNB: {testPeerIP}}},
+		},
+		{
+			name: "a withdrawal",
+			messages: []*ristypes.RISMessage{
+				peerAnnouncement(testPeerIP, testV4Prefix),
+				peerWithdrawal(testPeerIP, testV4Prefix),
+			},
+			want: map[string]map[int][]string{testV4Prefix: {}},
+		},
+		{
+			// RFC 4271 section 4.3: the announcement counts, not the withdrawal.
+			name:     "a message that announces and withdraws the prefix",
+			messages: []*ristypes.RISMessage{announceAndWithdraw},
+			want:     map[string]map[int][]string{testV4Prefix: {testASNB: {testPeerIP}}},
+		},
+		{
+			name: "a peer's session going down",
+			messages: []*ristypes.RISMessage{
+				peerAnnouncement(testPeerIP, testV4Prefix, testV6Prefix),
+				peerAnnouncement(secondPeerIP, testV4Prefix),
+				sessionDown(),
+			},
+			want: map[string]map[int][]string{
+				testV4Prefix: {testASNB: {secondPeerIP}},
+				testV6Prefix: {},
+			},
+		},
+	})
+}
+
+// TestPrefixHandlerAppliesAPathWithoutAnOriginToTheRoutingTable hands the
+// prefix handler announcements whose AS path gives no origin. One whose path
+// holds AS 0 removes the peer's route, as a withdrawal does; one whose path ends
+// in an AS set of several members is kept with origin 0.
+func TestPrefixHandlerAppliesAPathWithoutAnOriginToTheRoutingTable(t *testing.T) {
+	t.Parallel()
+
+	announceWithPath := func(path ristypes.ASPath) *ristypes.RISMessage {
+		msg := peerAnnouncement(testPeerIP, testV4Prefix)
+		msg.Path = path
+
+		return msg
+	}
+
+	checkTableCases(t, []tableCase{
+		{
+			name: "a path whose last AS is 0",
+			messages: []*ristypes.RISMessage{
+				peerAnnouncement(testPeerIP, testV4Prefix),
+				announceWithPath(ristypes.ASPath{Sequence: []int{testASNA, 0}}),
+			},
+			want: map[string]map[int][]string{testV4Prefix: {}},
+		},
+		{
+			name: "a path with AS 0 before its end",
+			messages: []*ristypes.RISMessage{
+				peerAnnouncement(testPeerIP, testV4Prefix),
+				announceWithPath(decodePath(t, testASNA, 0, testASNB)),
+			},
+			want: map[string]map[int][]string{testV4Prefix: {}},
+		},
+		{
+			name: "a path that ends in an AS set",
+			messages: []*ristypes.RISMessage{
+				announceWithPath(decodePath(t, testASNA, []int{testASNC, testASND})),
+			},
+			want: map[string]map[int][]string{testV4Prefix: {0: {testPeerIP}}},
+		},
+	})
+}
+
+// checkTableCases hands the messages of each case to a new prefix handler and
+// checks its routing table right after, with no flush.
+func checkTableCases(t *testing.T, tests []tableCase) {
+	t.Helper()
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+
+			h := prefixHandlerWithoutTimer(newMockStore())
+			for _, msg := range tt.messages {
+				h.HandleMessage(msg)
+			}
+
+			for prefix, want := range tt.want {
+				got := tableOrigins(h.table, prefix)
+				if !reflect.DeepEqual(got, want) {
+					t.Errorf("peers of %s by origin AS = %v, want %v",
+						prefix, got, want)
+				}
+			}
+		})
+	}
+}
+
+// tableWritesStore is a real database that hands each write of the routing
+// table's changes to written once it is made.
+type tableWritesStore struct {
+	*database.Database
+
+	written chan []routetable.Change
+}
+
+func (s tableWritesStore) WriteRouteChanges(
+	changes []routetable.Change, newPeers map[string]uint,
+) error {
+	err := s.Database.WriteRouteChanges(changes, newPeers)
+	s.written <- changes
+
+	return err
+}
+
+// TestPrefixHandlerWritesTheTableChangesEachSecond hands a running prefix
+// handler an announcement and then its withdrawal, each far short of a full
+// batch. The flush timer must write the change of each to the database.
+func TestPrefixHandlerWritesTheTableChangesEachSecond(t *testing.T) {
+	t.Parallel()
+
+	// The two writes the test waits for, and room for one more.
+	const writesBuffered = 3
+
+	store := tableWritesStore{
+		Database: newTestDatabase(t),
+		written:  make(chan []routetable.Change, writesBuffered),
+	}
+	h := NewPrefixHandler(store, logger.New(), routetable.New(routetable.Params{}))
+
+	defer h.Stop(t.Context())
+
+	prefix := netip.MustParsePrefix(testV4Prefix)
+
+	for _, step := range []struct {
+		msg         *ristypes.RISMessage
+		wantRemoved bool
+	}{
+		{msg: peerAnnouncement(testPeerIP, testV4Prefix)},
+		{msg: peerWithdrawal(testPeerIP, testV4Prefix), wantRemoved: true},
+	} {
+		h.HandleMessage(step.msg)
+
+		select {
+		case changes := <-store.written:
+			if len(changes) != 1 || changes[0].Prefix != prefix ||
+				changes[0].OriginASN != testASNB ||
+				changes[0].Removed != step.wantRemoved {
+				t.Fatalf("wrote %+v, want the pair of %s and AS%d with "+
+					"removed %t", changes, prefix, testASNB, step.wantRemoved)
+			}
+		case <-time.After(tableWriteTimeout):
+			t.Fatalf("the routing table's change was not written within %s",
+				tableWriteTimeout)
+		}
+	}
+}
+
+// errTestTableWrite is the error a test store's failing write of the routing
+// table's changes returns.
+var errTestTableWrite = errors.New("test: the write of the table's changes failed")
+
+// firstTableWriteFailsStore is a real database whose first write of the
+// routing table's changes fails, writing nothing. writes counts the writes
+// asked for.
+type firstTableWriteFailsStore struct {
+	*database.Database
+
+	writes int
+}
+
+func (s *firstTableWriteFailsStore) WriteRouteChanges(
+	changes []routetable.Change, newPeers map[string]uint,
+) error {
+	s.writes++
+	if s.writes == 1 {
+		return errTestTableWrite
+	}
+
+	return s.Database.WriteRouteChanges(changes, newPeers)
+}
+
+// TestPrefixHandlerWritesAFailedTableWriteAgain runs two flushes into a
+// database whose first write of the routing table's changes fails. Before the
+// first, two new peers announce a prefix each; before the second, one of them
+// announces its prefix again with another path to the same origin AS. The
+// second write must hold the changes and new peers of the first, with the later
+// path, so the database holds the table that is in memory.
+func TestPrefixHandlerWritesAFailedTableWriteAgain(t *testing.T) {
+	t.Parallel()
+
+	db := newTestDatabase(t)
+	store := &firstTableWriteFailsStore{Database: db}
+	h := prefixHandlerWithoutTimer(store)
+
+	first := peerAnnouncement(testPeerIP, testV4Prefix)
+	h.HandleMessage(first)
+	h.HandleMessage(peerAnnouncement(secondPeerIP, otherV4Prefix))
+	h.flushBatch()
+
+	laterPath := []int{testASNC, testASNB}
+	later := peerAnnouncement(testPeerIP, testV4Prefix)
+	later.Path = ristypes.ASPath{Sequence: laterPath}
+	later.ParsedTimestamp = first.ParsedTimestamp.Add(secondUpdateAfter)
+	h.HandleMessage(later)
+	h.flushBatch()
+
+	if store.writes != 2 {
+		t.Fatalf("the store was asked for %d writes of the table's changes, "+
+			"want 2", store.writes)
+	}
+
+	read, err := db.ReadRouteTable(t.Context())
+	if err != nil {
+		t.Fatalf("ReadRouteTable: %v", err)
+	}
+
+	checkSameTable(t, read, h.table, testV4Prefix, otherV4Prefix)
+
+	origins := read.Origins(netip.MustParsePrefix(testV4Prefix))
+	if len(origins) != 1 || len(origins[0].Routes) != 1 ||
+		!slices.Equal(origins[0].Routes[0].ASPath, laterPath) {
+		t.Errorf("Origins(%s) = %+v, want one route with the path %v",
+			testV4Prefix, origins, laterPath)
+	}
+}
+
+// tableWriteSizesStore is a real database that records how many changes and
+// how many new peers each write of the routing table's changes holds.
+type tableWriteSizesStore struct {
+	*database.Database
+
+	changes  []int
+	newPeers []int
+}
+
+func (s *tableWriteSizesStore) WriteRouteChanges(
+	changes []routetable.Change, newPeers map[string]uint,
+) error {
+	s.changes = append(s.changes, len(changes))
+	s.newPeers = append(s.newPeers, len(newPeers))
+
+	return s.Database.WriteRouteChanges(changes, newPeers)
+}
+
+// TestPrefixHandlerWritesManyTableChangesOverSeveralFlushes has one new peer
+// change one and a half times as many prefix and origin AS pairs as one write
+// takes, then flushes three times. The first write must hold as many pairs as
+// one write takes, and the peer. The second must hold the other pairs, and the
+// third flush must write nothing. The database must then hold the table in
+// memory.
+func TestPrefixHandlerWritesManyTableChangesOverSeveralFlushes(t *testing.T) {
+	t.Parallel()
+
+	const (
+		pairs   = maxTableChangesPerWrite * 3 / 2
+		flushes = 3
+	)
+
+	db := newTestDatabase(t)
+	store := &tableWriteSizesStore{Database: db}
+	h := prefixHandlerWithoutTimer(store)
+	announceManyPrefixes(h.table, pairs)
+
+	for range flushes {
+		h.flushBatch()
+	}
+
+	wantChanges := []int{maxTableChangesPerWrite, pairs - maxTableChangesPerWrite}
+	wantNewPeers := []int{1, 0}
+
+	if !slices.Equal(store.changes, wantChanges) ||
+		!slices.Equal(store.newPeers, wantNewPeers) {
+		t.Errorf("the writes held %v pairs and %v new peers, want %v and %v",
+			store.changes, store.newPeers, wantChanges, wantNewPeers)
+	}
+
+	read, err := db.ReadRouteTable(t.Context())
+	if err != nil {
+		t.Fatalf("ReadRouteTable: %v", err)
+	}
+
+	checkSameTable(t, read, h.table, firstManyPrefix)
+}
+
+// TestPrefixHandlerStopLogsTheTableChangesLeftUnwritten stops a prefix handler,
+// with no deadline, whose routing table holds more changed pairs than one write
+// takes. Its last flush writes one write's worth, so Stop must log the pairs
+// that no write took. The flush timer must not fire, or its writes could leave
+// no pairs for Stop to log.
+func TestPrefixHandlerStopLogsTheTableChangesLeftUnwritten(t *testing.T) {
+	t.Parallel()
+
+	const pairs = maxTableChangesPerWrite + 1
+
+	var logs bytes.Buffer
+
+	store := &tableWriteSizesStore{Database: newTestDatabase(t)}
+	table := routetable.New(routetable.Params{})
+	announceManyPrefixes(table, pairs)
+
+	h := newPrefixHandler(store, newErrorLogger(&logs), table, longerThanAnyTest)
+	h.Stop(t.Context())
+
+	written := 0
+	for _, n := range store.changes {
+		written += n
+	}
+
+	if logged := lastLogged(t, &logs); logged.TableChanges != pairs-written {
+		t.Errorf("Stop logged %d table changes not written, want %d",
+			logged.TableChanges, pairs-written)
+	}
+}
+
+// readLog holds what readRouteTable logs.
+//
+//nolint:tagliatelle // field names are the keys readRouteTable logs
+type readLog struct {
+	Msg        string `json:"msg"`
+	Pairs      int    `json:"pairs"`
+	Peers      int    `json:"peers"`
+	DurationMs *int64 `json:"duration_ms"`
+}
+
+// TestARestartReadsTheRoutingTableBack runs announcements, a withdrawal and a
+// peer's session going down through a prefix handler into a database, then
+// reads the table back as startup does. The table read must answer as the one
+// in memory, and the log must give its pairs and peers. A new handler on the
+// table read then takes later updates and writes them as it stops: the
+// database must then hold what the first table holds after the same updates.
+func TestARestartReadsTheRoutingTableBack(t *testing.T) {
+	t.Parallel()
+
+	prefixes := []string{testV4Prefix, testV6Prefix, otherV4Prefix, setV4Prefix}
+
+	db := newTestDatabase(t)
+	h := prefixHandlerWithoutTimer(db)
+
+	viaOtherOrigin := peerAnnouncement(thirdPeerIP, testV4Prefix)
+	viaOtherOrigin.Path = ristypes.ASPath{Sequence: []int{testASNA, testASNC}}
+	endsInSet := peerAnnouncement(secondPeerIP, setV4Prefix)
+	endsInSet.Path = decodePath(t, testASNA, []int{testASNC, testASND})
+
+	for _, msg := range []*ristypes.RISMessage{
+		peerAnnouncement(testPeerIP, testV4Prefix, testV6Prefix),
+		peerAnnouncement(secondPeerIP, testV4Prefix),
+		viaOtherOrigin,
+		endsInSet,
+		peerAnnouncement(thirdPeerIP, otherV4Prefix),
+		peerWithdrawal(thirdPeerIP, otherV4Prefix),
+		peerAnnouncement(fourthPeerIP, otherV4Prefix),
+		sessionDownOf(fourthPeerIP),
+	} {
+		h.HandleMessage(msg)
+	}
+
+	h.flushBatch()
+
+	var logs bytes.Buffer
+
+	rw := &RouteWatch{
+		db:     db,
+		logger: &logger.Logger{Logger: slog.New(slog.NewJSONHandler(&logs, nil))},
+	}
+
+	table, err := rw.readRouteTable(t.Context())
+	if err != nil {
+		t.Fatalf("readRouteTable: %v", err)
+	}
+
+	checkSameTable(t, table, h.table, prefixes...)
+
+	// testV4Prefix with two origin ASes, testV6Prefix and setV4Prefix; four
+	// peers, the last of which carries nothing.
+	const wantPairs, wantPeers = 4, 4
+
+	var logged readLog
+
+	err = json.Unmarshal(bytes.TrimSpace(logs.Bytes()), &logged)
+	if err != nil || logged.Pairs != wantPairs || logged.Peers != wantPeers ||
+		logged.DurationMs == nil {
+		t.Errorf("readRouteTable logged %q, want %d pairs, %d peers and the "+
+			"duration", logs.String(), wantPairs, wantPeers)
+	}
+
+	restarted := NewPrefixHandler(db, logger.New(), table)
+
+	for _, msg := range []*ristypes.RISMessage{
+		peerWithdrawal(testPeerIP, testV6Prefix),
+		sessionDownOf(secondPeerIP),
+		peerAnnouncement(fourthPeerIP, otherV4Prefix),
+		peerAnnouncement(fifthPeerIP, setV4Prefix),
+	} {
+		// The first handler only applies the updates to its table.
+		h.HandleMessage(msg)
+		restarted.HandleMessage(msg)
+	}
+
+	restarted.Stop(t.Context())
+
+	read, err := db.ReadRouteTable(t.Context())
+	if err != nil {
+		t.Fatalf("ReadRouteTable after the restart: %v", err)
+	}
+
+	checkSameTable(t, read, h.table, prefixes...)
+}
+
+// peerWithdrawal returns an UPDATE message in which peer withdraws prefixes.
+func peerWithdrawal(peer string, prefixes ...string) *ristypes.RISMessage {
+	return &ristypes.RISMessage{
+		Type:            ristypes.MessageTypeUpdate,
+		Peer:            peer,
+		ParsedTimestamp: time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC),
+		Withdrawals:     prefixes,
+	}
+}
+
+// announceManyPrefixes has testPeerIP announce n prefixes in table, with the
+// path of peerAnnouncement: the /32 of each address from firstManyPrefix on.
+func announceManyPrefixes(table *routetable.Table, n int) {
+	addr := netip.MustParsePrefix(firstManyPrefix).Addr()
+	route := routetable.Route{
+		Peer:   testPeerIP,
+		ASPath: []int{testASNA, testASNB},
+		Time:   time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC),
+	}
+
+	for range n {
+		table.Announce(netip.PrefixFrom(addr, addr.BitLen()), testASNB, route)
+		addr = addr.Next()
+	}
+}
+
+// sessionDownOf returns the STATE message that says the BGP session of peer
+// went down.
+func sessionDownOf(peer string) *ristypes.RISMessage {
+	return &ristypes.RISMessage{
+		Type:  ristypes.MessageTypeState,
+		Peer:  peer,
+		State: ristypes.StateDown,
+	}
+}
+
+// tableOrigins returns, for each origin AS of prefix in table, the peers that
+// carry the prefix with it.
+func tableOrigins(table *routetable.Table, prefix string) map[int][]string {
+	origins := make(map[int][]string)
+	for _, o := range table.Origins(netip.MustParsePrefix(prefix)) {
+		origins[o.ASN] = o.Peers
+	}
+
+	return origins
+}
+
+// checkSameTable checks that got answers as want does for each of prefixes, and
+// that the two tables have the same counts.
+func checkSameTable(
+	t *testing.T, got, want *routetable.Table, prefixes ...string,
+) {
+	t.Helper()
+
+	for _, text := range prefixes {
+		prefix := netip.MustParsePrefix(text)
+
+		gotOrigins, wantOrigins := got.Origins(prefix), want.Origins(prefix)
+		if !reflect.DeepEqual(gotOrigins, wantOrigins) {
+			t.Errorf("Origins(%s) = %+v, want %+v", text, gotOrigins, wantOrigins)
+		}
+	}
+
+	gotCounts, wantCounts := got.Counts(), want.Counts()
+	if !reflect.DeepEqual(gotCounts, wantCounts) {
+		t.Errorf("Counts() = %+v, want %+v", gotCounts, wantCounts)
+	}
+}

internal/server/handlers.go

@@ -1,7 +1,7 @@
 package server
 
 import (
-	"bytes"
+	"cmp"
 	"context"
 	"encoding/json"
 	"errors"
@@ -9,11 +9,13 @@ import (
 	"net/http"
 	"net/netip"
 	"runtime"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
 	"time"
 
+	"git.eeqj.de/sneak/routewatch/internal/blocklist"
 	"git.eeqj.de/sneak/routewatch/internal/database"
 	"git.eeqj.de/sneak/routewatch/internal/metrics"
 	"git.eeqj.de/sneak/routewatch/internal/ristypes"
@@ -44,6 +46,15 @@ const (
 	ptrLookupTimeout = 2 * time.Second
 )
 
+// The Cache-Control header of an IP lookup answer, such as
+// "public, max-age=900".
+const (
+	cacheControlHeader  = "Cache-Control"
+	cacheControlPublic  = "public"
+	cacheControlPrivate = "private"
+	cacheControlMaxAge  = ", max-age="
+)
+
 // Keys of the JSON envelope the handlers and middleware write, and the status
 // value of an error answer.
 const (
@@ -145,7 +156,10 @@ func (s *Server) handleIndex() http.HandlerFunc {
 
 		tmpl := templates.IndexTemplate()
 
-		err := tmpl.Execute(w, pageData{CSPNonce: cspNonce(r.Context())})
+		err := tmpl.Execute(w, indexPageData{
+			CSPNonce: cspNonce(r.Context()),
+			ClientIP: extractClientIP(r),
+		})
 		if err != nil {
 			s.logger.Error("Failed to render index template", "error", err)
 			http.Error(w, "Internal Server Error", http.StatusInternalServerError)
@@ -159,6 +173,15 @@ type pageData struct {
 	CSPNonce string
 }
 
+// indexPageData is what the home page is rendered with.
+type indexPageData struct {
+	// CSPNonce is the nonce the page's script and style blocks carry.
+	CSPNonce string
+	// ClientIP is the visitor's address, which the IP information API card
+	// looks up: the address /ip/ would look up for the same request.
+	ClientIP string
+}
+
 // writeJSONError writes a standardized JSON error response with the given
 // status code and error message.
 func (s *Server) writeJSONError(w http.ResponseWriter, statusCode int, message string) {
@@ -680,9 +703,24 @@ func (s *Server) handleIPLookup() http.HandlerFunc {
 
 // IPLookupResponse is the standard response for IP/hostname lookups.
 type IPLookupResponse struct {
-	Query   string             `json:"query"`
+	Query   string           `json:"query"`
-	Results []*database.IPInfo `json:"results"`
+	Results []IPLookupResult `json:"results"`
-	Errors  []string           `json:"errors,omitempty"`
+	Errors  []string         `json:"errors,omitempty"`
+}
+
+// IPLookupResult is the answer for one address: its PTR names, its live route
+// and that route's AS, and the blocklists that list it. IPInfo is nil when
+// the address has no live route, and the answer then has no route or AS
+// fields. IP hides the IPInfo field of the same name, so that an address with
+// no route has it too.
+type IPLookupResult struct {
+	*database.IPInfo
+
+	IP  string   `json:"ip"`
+	PTR []string `json:"ptr,omitempty"`
+
+	// Blocklists has one entry for each blocklist the address is on.
+	Blocklists []blocklist.Listing `json:"blocklists"`
 }
 
 // handleIPInfo returns a handler that provides comprehensive IP information.
@@ -691,7 +729,7 @@ type IPLookupResponse struct {
 // Always returns the same response structure with PTR records for each IP.
 func (s *Server) handleIPInfo() http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		target := lookupTarget(r)
+		target, ownAddress := lookupTarget(r)
 		if target == "" {
 			s.writeJSONError(w, http.StatusBadRequest, "Could not determine IP address")
 
@@ -699,7 +737,7 @@ func (s *Server) handleIPInfo() http.HandlerFunc {
 		}
 
 		ctx := r.Context()
-		response := IPLookupResponse{Query: target, Results: make([]*database.IPInfo, 0)}
+		response := IPLookupResponse{Query: target, Results: make([]IPLookupResult, 0)}
 
 		// Collect all IPs to look up
 		ipsToLookup, resolveErrors, err := s.resolveLookupTargets(ctx, target)
@@ -736,7 +774,10 @@ func (s *Server) handleIPInfo() http.HandlerFunc {
 			}
 
 			switch {
-			case errors.Is(err, database.ErrNoRoute), errors.Is(err, database.ErrInvalidIP):
+			case errors.Is(err, database.ErrNoRoute):
+				// The address still gets a result, without route fields.
+				ipInfo = nil
+			case errors.Is(err, database.ErrInvalidIP):
 				response.Errors = append(response.Errors, ip+": "+err.Error())
 
 				continue
@@ -755,13 +796,14 @@ func (s *Server) handleIPInfo() http.HandlerFunc {
 				return
 			}
 
-			if len(ptrs) > 0 {
+			response.Results = append(response.Results, IPLookupResult{
-				ipInfo.PTR = ptrs
+				IP:         ip,
-			}
+				PTR:        ptrs,
+				IPInfo:     ipInfo,
+				Blocklists: s.blocklistListings(ip),
+			})
 
-			response.Results = append(response.Results, ipInfo)
+			if ipInfo != nil && ipInfo.NeedsWHOISRefresh {
-
-			if ipInfo.NeedsWHOISRefresh {
 				refreshASNs[ipInfo.ASN] = true
 			}
 		}
@@ -769,10 +811,40 @@ func (s *Server) handleIPInfo() http.HandlerFunc {
 		// Queue WHOIS refresh for stale ASNs (non-blocking)
 		s.queueWHOISRefresh(refreshASNs)
 
-		s.writeIPLookupAnswer(w, response)
+		s.writeIPLookupAnswer(w, response, ownAddress)
 	}
 }
 
+// blocklistListings returns the blocklists that list ip. It returns an empty
+// list, never nil, so that an answer's blocklists is [] rather than null.
+func (s *Server) blocklistListings(ip string) []blocklist.Listing {
+	addr, err := netip.ParseAddr(ip)
+	if s.blocklists == nil || err != nil {
+		return []blocklist.Listing{}
+	}
+
+	return s.blocklists.Lookup(addr)
+}
+
+// setIPLookupCacheControl lets caches keep an IP lookup answer for the
+// shortest blocklist interval, the soonest a blocklist copy can change. The
+// answer about the caller's own address is private, so that a shared cache
+// does not give it to another caller. Without blocklists it sets nothing.
+func (s *Server) setIPLookupCacheControl(w http.ResponseWriter, ownAddress bool) {
+	if s.blocklists == nil {
+		return
+	}
+
+	visibility := cacheControlPublic
+	if ownAddress {
+		visibility = cacheControlPrivate
+	}
+
+	maxAgeSeconds := int(s.blocklists.ShortestInterval().Seconds())
+	w.Header().Set(cacheControlHeader,
+		visibility+cacheControlMaxAge+strconv.Itoa(maxAgeSeconds))
+}
+
 // noTargetsMessage returns the message of the 400 an IP lookup answers when
 // no address is left to look up, followed by the first of resolveErrors, which
 // says why, when there is one.
@@ -786,16 +858,12 @@ func noTargetsMessage(resolveErrors []string) string {
 	return message + ": " + resolveErrors[0]
 }
 
-// writeIPLookupAnswer sends response, or 404 with its first error when no
+// writeIPLookupAnswer sends response with its Cache-Control header.
-// address had a route.
+// ownAddress says the request asked about the caller's own address.
 func (s *Server) writeIPLookupAnswer(
-	w http.ResponseWriter, response IPLookupResponse,
+	w http.ResponseWriter, response IPLookupResponse, ownAddress bool,
 ) {
-	if len(response.Results) == 0 && len(response.Errors) > 0 {
+	s.setIPLookupCacheControl(w, ownAddress)
-		s.writeJSONError(w, http.StatusNotFound, "No routes found: "+response.Errors[0])
-
-		return
-	}
 
 	err := writeJSONSuccess(w, response)
 	if err != nil {
@@ -804,8 +872,9 @@ func (s *Server) writeIPLookupAnswer(
 }
 
 // lookupTarget returns what an IP lookup request asks for: the ip or addr URL
-// parameter, or else the client's own address.
+// parameter, or else the client's own address. The bool is true for the
-func lookupTarget(r *http.Request) string {
+// client's own address.
+func lookupTarget(r *http.Request) (string, bool) {
 	target := chi.URLParam(r, "ip")
 	if target == "" {
 		target = chi.URLParam(r, "addr")
@@ -813,10 +882,10 @@ func lookupTarget(r *http.Request) string {
 
 	if target == "" {
 		// Use client IP (RealIP middleware has already processed this)
-		target = extractClientIP(r)
+		return extractClientIP(r), true
 	}
 
-	return target
+	return target, false
 }
 
 // queueWHOISRefresh asks the WHOIS fetcher, when there is one, to refresh
@@ -1028,24 +1097,15 @@ func splitRoutesByIPVersion(
 	return ipv4Routes, ipv6Routes
 }
 
-// sortRoutesByNetwork sorts routes by network address, then by mask length.
+// sortRoutesByMaskLength sorts routes by mask length, shortest first, and
-func sortRoutesByNetwork(routes []database.LiveRoute) {
+// routes with the same mask length by network address.
-	sort.Slice(routes, func(i, j int) bool {
+func sortRoutesByMaskLength(routes []database.LiveRoute) {
-		// Parse the prefixes to compare network addresses
+	slices.SortFunc(routes, func(a, b database.LiveRoute) int {
-		ipI, netI, _ := net.ParseCIDR(routes[i].Prefix)
+		prefixA, _ := netip.ParsePrefix(a.Prefix)
-		ipJ, netJ, _ := net.ParseCIDR(routes[j].Prefix)
+		prefixB, _ := netip.ParsePrefix(b.Prefix)
 
-		// Compare by network address first
+		return cmp.Or(cmp.Compare(prefixA.Bits(), prefixB.Bits()),
-		cmp := bytes.Compare(ipI.To16(), ipJ.To16())
+			prefixA.Addr().Compare(prefixB.Addr()))
-		if cmp != 0 {
-			return cmp < 0
-		}
-
-		// If network addresses are equal, compare by mask length
-		onesI, _ := netI.Mask.Size()
-		onesJ, _ := netJ.Mask.Size()
-
-		return onesI < onesJ
 	})
 }
 
@@ -1212,9 +1272,8 @@ func (s *Server) handleASDetail() http.HandlerFunc {
 		// Group prefixes by IP version
 		ipv4Prefixes, ipv6Prefixes := splitRoutesByIPVersion(prefixes)
 
-		// Sort prefixes by network address
+		sortRoutesByMaskLength(ipv4Prefixes)
-		sortRoutesByNetwork(ipv4Prefixes)
+		sortRoutesByMaskLength(ipv6Prefixes)
-		sortRoutesByNetwork(ipv6Prefixes)
 
 		// Prepare template data
 		data := struct {

internal/server/handlers_internal_test.go

@@ -5,8 +5,10 @@ import (
 	"encoding/json"
 	"errors"
 	"html"
+	"net"
 	"net/http"
 	"net/http/httptest"
+	"net/netip"
 	"runtime"
 	"slices"
 	"strconv"
@@ -15,6 +17,7 @@ import (
 	"testing"
 	"time"
 
+	"git.eeqj.de/sneak/routewatch/internal/blocklist"
 	"git.eeqj.de/sneak/routewatch/internal/config"
 	"git.eeqj.de/sneak/routewatch/internal/database"
 	"git.eeqj.de/sneak/routewatch/internal/logger"
@@ -458,8 +461,8 @@ func TestPrefixDetailShowsOriginNames(t *testing.T) {
 // TestPagesSayOriginZeroIsNoKnownOrigin stores a route with origin 0, as the
 // prefix handler stores a route whose AS path ends in an AS set of several
 // members, and checks that the prefix page and the prefix length page say it
-// has no known origin, without a link to AS0 or the description of the
+// has no known origin, without a link to AS0
-// reserved AS 0 (https://git.eeqj.de/sneak/routewatch/issues/75).
+// (https://git.eeqj.de/sneak/routewatch/issues/75).
 func TestPagesSayOriginZeroIsNoKnownOrigin(t *testing.T) {
 	t.Parallel()
 
@@ -479,11 +482,6 @@ func TestPagesSayOriginZeroIsNoKnownOrigin(t *testing.T) {
 		t.Fatalf("UpsertLiveRouteBatch: %v", err)
 	}
 
-	reserved, ok := asinfo.Get(0)
-	if !ok {
-		t.Fatal("AS0 is not in the AS info data")
-	}
-
 	s := New(db, streamer.New(logger.New(), metrics.New()), logger.New(), &config.Config{})
 
 	for _, path := range []string{"/prefix/" + testPrefixV4, prefixLengthPagePath} {
@@ -505,9 +503,128 @@ func TestPagesSayOriginZeroIsNoKnownOrigin(t *testing.T) {
 		if strings.Contains(page, `href="/as/0"`) {
 			t.Errorf("%s links to AS0", path)
 		}
+	}
+}
 
-		if strings.Contains(page, html.EscapeString(reserved.Description)) {
+// TestIndexShowsTheClientAddress requests the home page and checks that it has
-			t.Errorf("%s shows AS0's description %q", path, reserved.Description)
+// the IP information API card, holding the address /ip/ would look up for the
+// same request: the TCP peer, or, when the peer is a trusted proxy, the client
+// the proxy names in X-Forwarded-For
+// (https://git.eeqj.de/sneak/routewatch/issues/156).
+func TestIndexShowsTheClientAddress(t *testing.T) {
+	t.Parallel()
+
+	const cardHeading = "<h2>IP Information API</h2>"
+
+	// Both requests carry an X-Forwarded-For naming forwardedClient; only a
+	// trusted proxy's is believed.
+	tests := []struct {
+		name           string
+		trustedProxies []netip.Prefix
+		peer           string
+		want           string
+	}{
+		{"direct request", nil, untrustedPeer, untrustedPeerAddr},
+		{
+			"request through a trusted proxy",
+			[]netip.Prefix{netip.MustParsePrefix(trustedProxyRange)},
+			trustedPeer, forwardedClient,
+		},
+	}
+
+	for _, tt := range tests {
+		// The home page reads nothing from the database, so the server has none.
+		s := New(nil, streamer.New(logger.New(), metrics.New()), logger.New(),
+			&config.Config{TrustedProxies: tt.trustedProxies})
+
+		req := httptest.NewRequestWithContext(t.Context(), http.MethodGet, "/", nil)
+		req.RemoteAddr = tt.peer
+		req.Header.Set("X-Forwarded-For", forwardedClient)
+
+		rec := httptest.NewRecorder()
+		s.router.ServeHTTP(rec, req)
+
+		if rec.Code != http.StatusOK {
+			t.Errorf("%s: status %d, want %d; body %s",
+				tt.name, rec.Code, http.StatusOK, rec.Body)
+
+			continue
+		}
+
+		page := rec.Body.String()
+
+		if !strings.Contains(page, cardHeading) {
+			t.Errorf("%s: the page has no IP information API card", tt.name)
+		}
+
+		want := `data-client-ip="` + tt.want + `"`
+		if !strings.Contains(page, want) {
+			t.Errorf("%s: the card does not hold %s", tt.name, want)
+		}
+	}
+}
+
+// TestPagesShowAgesInWords stores routes last updated about 5 minutes, 3 hours
+// and 15 days ago, and checks that the AS page and the prefix pages show each
+// age in words. Before the fix the ages read "5m0s ago", "3h0m0s ago" and
+// "360h0m0s ago" (https://git.eeqj.de/sneak/routewatch/issues/163).
+func TestPagesShowAgesInWords(t *testing.T) {
+	t.Parallel()
+
+	db, err := database.New(&config.Config{StateDir: t.TempDir()}, logger.New())
+	if err != nil {
+		t.Fatalf("database.New: %v", err)
+	}
+
+	t.Cleanup(func() { _ = db.Close() })
+
+	// Each age is well past a whole number of its unit, so the time the test
+	// takes to run does not change the words.
+	ages := []struct {
+		prefix string
+		age    time.Duration
+		want   string
+	}{
+		{testPrefixV4, 5*time.Minute + 30*time.Second, "5 minutes ago"},
+		{"198.51.100.0/24", 3*time.Hour + 30*time.Minute, "3 hours ago"},
+		{"203.0.113.0/24", 15 * 24 * time.Hour, "2 weeks ago"},
+	}
+
+	now := time.Now().UTC()
+	routes := make([]*database.LiveRoute, 0, len(ages))
+
+	for _, a := range ages {
+		routes = append(routes, &database.LiveRoute{
+			Prefix: a.prefix, MaskLength: 24, IPVersion: 4,
+			OriginASN: 64500, PeerIP: testPeerV4, ASPath: []int{64500},
+			NextHop: testPeerV4, LastUpdated: now.Add(-a.age),
+		})
+	}
+
+	err = db.UpsertLiveRouteBatch(routes)
+	if err != nil {
+		t.Fatalf("UpsertLiveRouteBatch: %v", err)
+	}
+
+	s := New(db, streamer.New(logger.New(), metrics.New()), logger.New(), &config.Config{})
+
+	for _, a := range ages {
+		cell := `<td class="age">` + a.want + `</td>`
+
+		for _, path := range []string{asPagePath, "/prefix/" + a.prefix} {
+			rec := httptest.NewRecorder()
+			s.router.ServeHTTP(rec, httptest.NewRequestWithContext(
+				t.Context(), http.MethodGet, path, nil))
+
+			if rec.Code != http.StatusOK {
+				t.Fatalf("%s: status %d, want %d; body %s",
+					path, rec.Code, http.StatusOK, rec.Body)
+			}
+
+			if !strings.Contains(rec.Body.String(), cell) {
+				t.Errorf("%s does not show the age of the route for %s as %q",
+					path, a.prefix, a.want)
+			}
 		}
 	}
 }
@@ -925,14 +1042,15 @@ func (failingIPLookupDB) GetIPInfoContext(
 // server's router with a store whose read of one address fails with the
 // driver's error. A lookup that asks for that address answers 500 with the
 // JSON error body, as the AS and prefix JSON routes do; an address with no
-// route still answers 404. Before the fix the failed read was reported as if
+// route answers 200. Before the fix the failed read was reported as if the
-// the address had no route: 404 for that address alone, and 200 beside a
+// address had no route: 404 for that address alone, and 200 beside a routed
-// routed address (https://git.eeqj.de/sneak/routewatch/issues/109).
+// address (https://git.eeqj.de/sneak/routewatch/issues/109).
 func TestIPLookupAnswers500WhenDatabaseReadFails(t *testing.T) {
 	t.Parallel()
 
 	s := New(failingIPLookupDB{}, streamer.New(logger.New(), metrics.New()),
 		logger.New(), &config.Config{})
+	s.resolver = &fakeResolver{}
 
 	tests := []struct {
 		path     string
@@ -948,7 +1066,7 @@ func TestIPLookupAnswers500WhenDatabaseReadFails(t *testing.T) {
 		},
 		{
 			path:     "/api/v1/ip/203.0.113.1",
-			wantCode: http.StatusNotFound,
+			wantCode: http.StatusOK,
 		},
 	}
 
@@ -962,7 +1080,9 @@ func TestIPLookupAnswers500WhenDatabaseReadFails(t *testing.T) {
 				tt.path, rec.Code, tt.wantCode, rec.Body)
 		}
 
-		checkJSONErrorCode(t, tt.path, rec, tt.wantCode)
+		if tt.wantCode != http.StatusOK {
+			checkJSONErrorCode(t, tt.path, rec, tt.wantCode)
+		}
 	}
 }
 
@@ -1050,10 +1170,10 @@ func TestIPLookupRefusesTooManyAddresses(t *testing.T) {
 	}{
 		{
 			strings.Join(addrs[:maxLookupTargets], ","),
-			http.StatusNotFound, maxLookupTargets, 0,
+			http.StatusOK, maxLookupTargets, 0,
 		},
 		{strings.Join(addrs, ","), http.StatusBadRequest, 0, 0},
-		{"most.test", http.StatusNotFound, maxLookupTargets, 1},
+		{"most.test", http.StatusOK, maxLookupTargets, 1},
 		{"too-many.test", http.StatusBadRequest, 0, 1},
 		{strings.Join(names, ","), http.StatusBadRequest, 0, 0},
 	}
@@ -1074,7 +1194,9 @@ func TestIPLookupRefusesTooManyAddresses(t *testing.T) {
 				tt.target, rec.Code, tt.wantCode, rec.Body)
 		}
 
-		checkJSONErrorCode(t, tt.target, rec, tt.wantCode)
+		if tt.wantCode != http.StatusOK {
+			checkJSONErrorCode(t, tt.target, rec, tt.wantCode)
+		}
 
 		got := db.lookups.Load()
 		if got != tt.wantLookups {
@@ -1131,6 +1253,191 @@ func TestIPLookupKeepsRouteWhenPTRLookupDoesNotAnswer(t *testing.T) {
 	}
 }
 
+// addrInTestPrefixV6 is an address in testPrefixV6, which
+// newServerWithTestRoutes stores a route for.
+const addrInTestPrefixV6 = "2001:db8::1"
+
+// testBlocklistInterval is fakeBlocklists' shortest interval.
+const testBlocklistInterval = 15 * time.Minute
+
+// ownAddressPath is the IP lookup of the caller's own address.
+const ownAddressPath = "/ip/"
+
+// listedUnroutedAddr is an address that fakeBlocklists lists, outside the
+// routes newServerWithTestRoutes stores.
+const listedUnroutedAddr = "203.0.113.1"
+
+// fakeBlocklists has one list, which lists addrInTestPrefixV4 and
+// listedUnroutedAddr and no other address.
+type fakeBlocklists struct{}
+
+func testListing() blocklist.Listing {
+	return blocklist.Listing{
+		Name:        "test_list",
+		Description: "On the test list",
+		Updated:     time.Date(2026, 10, 27, 4, 0, 0, 0, time.UTC),
+	}
+}
+
+func (fakeBlocklists) Lookup(addr netip.Addr) []blocklist.Listing {
+	if addr == netip.MustParseAddr(addrInTestPrefixV4) ||
+		addr == netip.MustParseAddr(listedUnroutedAddr) {
+		return []blocklist.Listing{testListing()}
+	}
+
+	return []blocklist.Listing{}
+}
+
+func (fakeBlocklists) ShortestInterval() time.Duration {
+	return testBlocklistInterval
+}
+
+// TestIPLookupReportsBlocklists looks up two routed addresses, one of them on
+// a blocklist. The listed address's result names the list, says what it means
+// and when it was updated. The other's result has an empty list.
+func TestIPLookupReportsBlocklists(t *testing.T) {
+	t.Parallel()
+
+	s := newServerWithTestRoutes(t)
+	s.resolver = &fakeResolver{}
+	s.SetBlocklists(fakeBlocklists{})
+
+	rec := httptest.NewRecorder()
+	s.router.ServeHTTP(rec, httptest.NewRequestWithContext(t.Context(),
+		http.MethodGet,
+		"/api/v1/ip/"+addrInTestPrefixV4+","+addrInTestPrefixV6, nil))
+
+	if rec.Code != http.StatusOK {
+		t.Fatalf("status %d, want %d; body %s", rec.Code, http.StatusOK, rec.Body)
+	}
+
+	var body struct {
+		Data IPLookupResponse `json:"data"`
+	}
+
+	err := json.Unmarshal(rec.Body.Bytes(), &body)
+	if err != nil {
+		t.Fatalf("decoding the answer %q: %v", rec.Body, err)
+	}
+
+	results := body.Data.Results
+	if len(results) != 2 {
+		t.Fatalf("answer %s, want two results", rec.Body)
+	}
+
+	want := testListing()
+
+	listed := results[0].Blocklists
+	if len(listed) != 1 || listed[0].Name != want.Name ||
+		listed[0].Description != want.Description ||
+		!listed[0].Updated.Equal(want.Updated) {
+		t.Errorf("%s: blocklists %+v, want [%+v]", results[0].IP, listed, want)
+	}
+
+	if !strings.Contains(rec.Body.String(), `"blocklists":[]`) {
+		t.Errorf("answer %s, want an empty blocklists list for %s",
+			rec.Body, addrInTestPrefixV6)
+	}
+}
+
+// TestIPLookupReportsBlocklistsOfAnAddressWithNoRoute looks up a listed
+// address that has no live route, alone and beside a routed address. Each
+// answer is 200 and has a result for the address, with its blocklists and no
+// route fields. Before the fix the lookup of that address alone answered
+// 404, and beside a routed address it was only named in errors, so its
+// blocklists were never reported.
+func TestIPLookupReportsBlocklistsOfAnAddressWithNoRoute(t *testing.T) {
+	t.Parallel()
+
+	s := newServerWithTestRoutes(t)
+	s.resolver = &fakeResolver{}
+	s.SetBlocklists(fakeBlocklists{})
+
+	for _, target := range []string{
+		listedUnroutedAddr,
+		addrInTestPrefixV4 + "," + listedUnroutedAddr,
+	} {
+		rec := httptest.NewRecorder()
+		s.router.ServeHTTP(rec, httptest.NewRequestWithContext(t.Context(),
+			http.MethodGet, "/api/v1/ip/"+target, nil))
+
+		var body struct {
+			Data IPLookupResponse `json:"data"`
+		}
+
+		err := json.Unmarshal(rec.Body.Bytes(), &body)
+		if rec.Code != http.StatusOK || err != nil {
+			t.Errorf("%s: status %d (%v), want %d; body %s",
+				target, rec.Code, err, http.StatusOK, rec.Body)
+
+			continue
+		}
+
+		i := slices.IndexFunc(body.Data.Results, func(r IPLookupResult) bool {
+			return r.IP == listedUnroutedAddr
+		})
+		if i < 0 || len(body.Data.Errors) != 0 {
+			t.Errorf("%s: answer %s, want a result for %s and no errors",
+				target, rec.Body, listedUnroutedAddr)
+
+			continue
+		}
+
+		result := body.Data.Results[i]
+		if result.IPInfo != nil {
+			t.Errorf("%s: result for %s has route fields %+v",
+				target, listedUnroutedAddr, result.IPInfo)
+		}
+
+		if len(result.Blocklists) != 1 ||
+			result.Blocklists[0].Name != testListing().Name {
+			t.Errorf("%s: blocklists %+v, want [%+v]",
+				target, result.Blocklists, testListing())
+		}
+	}
+}
+
+// TestIPLookupAnswersMayBeCached checks the Cache-Control header of the IP
+// lookup answers. Caches may keep them for the blocklists' shortest interval,
+// and only the caller's own browser may keep the answer about the caller's
+// own address.
+func TestIPLookupAnswersMayBeCached(t *testing.T) {
+	t.Parallel()
+
+	s := newServerWithTestRoutes(t)
+	s.resolver = &fakeResolver{}
+	s.SetBlocklists(fakeBlocklists{})
+
+	tests := []struct {
+		path string
+		want string
+	}{
+		{"/api/v1/ip/" + addrInTestPrefixV4, "public, max-age=900"},
+		{ownAddressPath + addrInTestPrefixV4, "public, max-age=900"},
+		{ownAddressPath, "private, max-age=900"},
+	}
+
+	for _, tt := range tests {
+		req := httptest.NewRequestWithContext(t.Context(), http.MethodGet,
+			tt.path, nil)
+		req.RemoteAddr = net.JoinHostPort(addrInTestPrefixV4, "1234")
+
+		rec := httptest.NewRecorder()
+		s.router.ServeHTTP(rec, req)
+
+		if rec.Code != http.StatusOK {
+			t.Errorf("%s: status %d, want %d; body %s",
+				tt.path, rec.Code, http.StatusOK, rec.Body)
+
+			continue
+		}
+
+		if got := rec.Header().Get(cacheControlHeader); got != tt.want {
+			t.Errorf("%s: Cache-Control %q, want %q", tt.path, got, tt.want)
+		}
+	}
+}
+
 // The host name TestIPLookupHidesPrivateAddresses resolves to a private
 // address, and that address.
 const (
@@ -1262,7 +1569,7 @@ func TestASSearchAnswersMatches(t *testing.T) {
 	}
 
 	cloudflare := asinfo.Info{
-		ASN: 13335, Handle: "CLOUDFLARENET", Description: "Cloudflare, Inc.",
+		ASN: 13335, Handle: "CLOUDFLARENET", Description: "Cloudflare Inc.",
 	}
 	if !slices.Contains(data.Results, cloudflare) {
 		t.Errorf("results %v do not hold %v", data.Results, cloudflare)
@@ -1335,8 +1642,9 @@ func TestASSearchShowsFirstMatchesAndTotal(t *testing.T) {
 // The AS numbers the AS detail tests ask for. storedASN originates the route
 // for testPrefixV4 and is in the database. routeOnlyASN originates the route
 // for testPrefixV6, but the database has no record of the AS itself, as when
-// a route is stored before its AS. builtInOnlyASN is in the AS list built into
+// a route is stored before its AS. Both are documentation AS numbers, which
-// asinfo but not in the database. unknownASN is in neither.
+// the AS list built into asinfo does not hold. builtInOnlyASN is in that list
+// but not in the database. unknownASN is in neither.
 const (
 	storedASN      = 64500
 	routeOnlyASN   = 64501
@@ -1352,14 +1660,12 @@ const firstSeenCard = `<div class="info-label">First Seen</div>`
 
 // newServerWithStoredAS returns newServerWithTestRoutes's server with storedASN
 // added to the database. It fails the test when the AS list built into asinfo
-// lacks routeOnlyASN or builtInOnlyASN, or holds unknownASN.
+// lacks builtInOnlyASN or holds unknownASN.
 func newServerWithStoredAS(t *testing.T) *Server {
 	t.Helper()
 
-	for _, asn := range []int{routeOnlyASN, builtInOnlyASN} {
+	if _, ok := asinfo.Get(builtInOnlyASN); !ok {
-		if _, ok := asinfo.Get(asn); !ok {
+		t.Fatalf("AS%d is not in the AS info data", builtInOnlyASN)
-			t.Fatalf("AS%d is not in the AS info data", asn)
-		}
 	}
 
 	if _, ok := asinfo.Get(unknownASN); ok {
@@ -1377,10 +1683,10 @@ func newServerWithStoredAS(t *testing.T) *Server {
 }
 
 // TestASDetailJSONAnswersBuiltInAS asks /api/v1/as/ for each of the ASes above.
-// All but unknownASN answer 200 with the handle and description from the
+// All but unknownASN answer 200 with the handle and description the built-in
-// built-in AS list and their prefixes, as lists even when empty. Only storedASN
+// AS list has for them, if any, and their prefixes, as lists even when empty.
-// has a first_seen time. unknownASN answers 404. Before the fix builtInOnlyASN
+// Only storedASN has a first_seen time. unknownASN answers 404. Before the fix
-// and routeOnlyASN answered 404 too
+// builtInOnlyASN and routeOnlyASN answered 404 too
 // (https://git.eeqj.de/sneak/routewatch/issues/151).
 func TestASDetailJSONAnswersBuiltInAS(t *testing.T) {
 	t.Parallel()
@@ -1434,13 +1740,13 @@ func TestASDetailJSONAnswersBuiltInAS(t *testing.T) {
 			continue
 		}
 
-		info, _ := asinfo.Get(tt.asn)
+		handle, description := asinfo.GetHandle(tt.asn), asinfo.GetDescription(tt.asn)
 		got := body.Data.ASN
 
-		if got.ASN != tt.asn || got.Handle != info.Handle ||
+		if got.ASN != tt.asn || got.Handle != handle ||
-			got.Description != info.Description {
+			got.Description != description {
 			t.Errorf("%s: AS %d %q %q, want %d %q %q", path, got.ASN,
-				got.Handle, got.Description, tt.asn, info.Handle, info.Description)
+				got.Handle, got.Description, tt.asn, handle, description)
 		}
 
 		if body.Data.IPv4Prefixes == nil || body.Data.IPv6Prefixes == nil {
@@ -1467,11 +1773,11 @@ func TestASDetailJSONAnswersBuiltInAS(t *testing.T) {
 }
 
 // TestASDetailPageShowsBuiltInAS asks /as/ for each of the ASes above. All but
-// unknownASN answer 200 with the handle and description from the built-in AS
+// unknownASN answer 200 with the handle and description the built-in AS list
-// list. storedASN and routeOnlyASN list their prefixes, and builtInOnlyASN says
+// has for them, if any. storedASN and routeOnlyASN list their prefixes, and
-// the AS announces none. Only storedASN shows a first-seen date, and no page
+// builtInOnlyASN says the AS announces none. Only storedASN shows a first-seen
-// shows a date that was never set. unknownASN answers 404. Before the fix
+// date, and no page shows a date that was never set. unknownASN answers 404.
-// builtInOnlyASN and routeOnlyASN answered 404 too
+// Before the fix builtInOnlyASN and routeOnlyASN answered 404 too
 // (https://git.eeqj.de/sneak/routewatch/issues/151).
 func TestASDetailPageShowsBuiltInAS(t *testing.T) {
 	t.Parallel()
@@ -1507,12 +1813,11 @@ func TestASDetailPageShowsBuiltInAS(t *testing.T) {
 			continue
 		}
 
-		info, _ := asinfo.Get(tt.asn)
 		page := rec.Body.String()
 
 		for _, want := range []string{
-			html.EscapeString(info.Handle),
+			html.EscapeString(asinfo.GetHandle(tt.asn)),
-			html.EscapeString(info.Description),
+			html.EscapeString(asinfo.GetDescription(tt.asn)),
 			tt.wantText,
 		} {
 			if !strings.Contains(page, want) {
@@ -1532,19 +1837,68 @@ func TestASDetailPageShowsBuiltInAS(t *testing.T) {
 	}
 }
 
+// TestSortRoutesByMaskLength expects the AS page's prefix lists in mask length
+// order, shortest first, and in address order within one mask length. Before
+// the fix they were in address order, so 10.1.0.0/16 came before 11.0.0.0/8
+// (https://git.eeqj.de/sneak/routewatch/issues/153).
+func TestSortRoutesByMaskLength(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name     string
+		prefixes []string
+		want     []string
+	}{
+		{
+			name: "IPv4",
+			prefixes: []string{
+				"100.64.1.0/24", "11.0.0.0/8", "10.1.0.0/16",
+				"20.0.1.0/24", "172.16.0.0/12", "9.0.0.0/8",
+			},
+			want: []string{
+				"9.0.0.0/8", "11.0.0.0/8", "172.16.0.0/12",
+				"10.1.0.0/16", "20.0.1.0/24", "100.64.1.0/24",
+			},
+		},
+		{
+			name: "IPv6",
+			prefixes: []string{
+				"2001:db8:1::/48", "2001:db8:8000::/33", "2001:db8:0:1::/64",
+				"2001:db8::/48", "2001:db8::/33",
+			},
+			want: []string{
+				"2001:db8::/33", "2001:db8:8000::/33", "2001:db8::/48",
+				"2001:db8:1::/48", "2001:db8:0:1::/64",
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		routes := make([]database.LiveRoute, 0, len(tt.prefixes))
+		for _, prefix := range tt.prefixes {
+			routes = append(routes, database.LiveRoute{Prefix: prefix})
+		}
+
+		sortRoutesByMaskLength(routes)
+
+		got := make([]string, 0, len(routes))
+		for _, route := range routes {
+			got = append(got, route.Prefix)
+		}
+
+		if !slices.Equal(got, tt.want) {
+			t.Errorf("%s: order %v, want %v", tt.name, got, tt.want)
+		}
+	}
+}
+
 // TestNoOriginHasNoASAnswers stores a route with no known origin, which has
 // origin AS 0 (https://git.eeqj.de/sneak/routewatch/issues/75). It expects
-// /as/0 and /api/v1/as/0 to answer 404. It expects a search for "iana" to leave
+// /as/0 and /api/v1/as/0 to answer 404.
-// AS 0 out of its results and its total, although the AS list built into
-// asinfo holds AS 0. That search has more matches than an answer holds, so it
-// still lists maxASSearchResults of them.
 func TestNoOriginHasNoASAnswers(t *testing.T) {
 	t.Parallel()
 
-	const (
+	const noOriginPrefix = "203.0.113.0/24"
-		noOriginPrefix = "203.0.113.0/24"
-		query          = "iana"
-	)
 
 	s := newServerWithTestRoutes(t)
 
@@ -1570,30 +1924,6 @@ func TestNoOriginHasNoASAnswers(t *testing.T) {
 				path, rec.Code, http.StatusNotFound, rec.Body)
 		}
 	}
-
-	first, total := asinfo.Search(query, 1)
-	if len(first) != 1 || first[0].ASN != ristypes.NoOrigin {
-		t.Fatalf("AS%d is not the first match for %q in the AS info data",
-			ristypes.NoOrigin, query)
-	}
-
-	data := searchAS(t, s, "q="+query)
-
-	for _, info := range data.Results {
-		if info.ASN == ristypes.NoOrigin {
-			t.Errorf("the search for %q lists AS%d", query, info.ASN)
-		}
-	}
-
-	if data.Total != total-1 {
-		t.Errorf("the search for %q has a total of %d, want %d",
-			query, data.Total, total-1)
-	}
-
-	if len(data.Results) != maxASSearchResults {
-		t.Errorf("the search for %q lists %d matches, want %d",
-			query, len(data.Results), maxASSearchResults)
-	}
 }
 
 // settledGoroutineCount lets transient goroutines finish, then reports the

internal/server/middleware_internal_test.go

@@ -11,11 +11,12 @@ import (
 )
 
 // The addresses the forwarding tests use: the client a proxy names in
-// X-Forwarded-For, a peer inside the trusted range of
+// X-Forwarded-For, the range of trusted proxies, a peer inside it, and a peer
-// TestRealIPMiddlewareTrustsOnlyConfiguredProxies, and a peer outside it,
+// outside it, which lies in testPrefixV4 so that an IP lookup of it finds a
-// which lies in testPrefixV4 so that an IP lookup of it finds a route.
+// route.
 const (
 	forwardedClient   = "203.0.113.9"
+	trustedProxyRange = "10.0.0.0/8"
 	trustedPeer       = "10.0.0.2:1234"
 	untrustedPeerAddr = "192.0.2.1"
 	untrustedPeer     = untrustedPeerAddr + ":1234"
@@ -189,7 +190,7 @@ func TestForwardedForFromUntrustedPeerIsIgnored(t *testing.T) {
 func TestRealIPMiddlewareTrustsOnlyConfiguredProxies(t *testing.T) {
 	t.Parallel()
 
-	trusted := []netip.Prefix{netip.MustParsePrefix("10.0.0.0/8")}
+	trusted := []netip.Prefix{netip.MustParsePrefix(trustedProxyRange)}
 
 	tests := []struct {
 		name         string

internal/server/server.go

@@ -15,6 +15,7 @@ import (
 	"strconv"
 	"time"
 
+	"git.eeqj.de/sneak/routewatch/internal/blocklist"
 	"git.eeqj.de/sneak/routewatch/internal/config"
 	"git.eeqj.de/sneak/routewatch/internal/database"
 	"git.eeqj.de/sneak/routewatch/internal/logger"
@@ -36,6 +37,13 @@ type ASNFetcher interface {
 	GetStats() ASNFetcherStats
 }
 
+// Blocklists tells which public blocklists list an address, from copies it
+// keeps in memory, as *blocklist.Blocklists does.
+type Blocklists interface {
+	Lookup(addr netip.Addr) []blocklist.Listing
+	ShortestInterval() time.Duration
+}
+
 // dnsResolver looks up the addresses of host names and the names of addresses
 // in DNS, as *net.Resolver does.
 type dnsResolver interface {
@@ -52,6 +60,7 @@ type Server struct {
 	port       int
 	srv        *http.Server
 	asnFetcher ASNFetcher
+	blocklists Blocklists
 
 	// trustedProxies are the reverse proxies whose X-Forwarded-For header
 	// RealIPMiddleware believes
@@ -148,3 +157,9 @@ func (s *Server) Stop(ctx context.Context) error {
 func (s *Server) SetASNFetcher(fetcher ASNFetcher) {
 	s.asnFetcher = fetcher
 }
+
+// SetBlocklists sets the blocklists the IP lookups report. Call it before
+// Start: the handlers read the blocklists without a lock.
+func (s *Server) SetBlocklists(blocklists Blocklists) {
+	s.blocklists = blocklists
+}

internal/templates/as_detail.html

@@ -126,6 +126,26 @@
             margin: 0;
             color: #2c3e50;
         }
+        /* A click on a prefix list's heading folds or unfolds the list. Not
+           every browser shows its own marker on a flex element, so the page
+           hides it and draws a triangle before the heading. The triangle
+           points down while the list is open. */
+        summary.prefix-header {
+            cursor: pointer;
+            list-style: none;
+        }
+        summary.prefix-header::-webkit-details-marker {
+            display: none;
+        }
+        summary.prefix-header h2::before {
+            content: "\25B8";
+            display: inline-block;
+            margin-right: 10px;
+            transition: transform 0.2s;
+        }
+        details[open] > summary.prefix-header h2::before {
+            transform: rotate(90deg);
+        }
         .prefix-count {
             background: #e74c3c;
             color: white;
@@ -242,11 +262,11 @@
         </div>
 
         {{if .IPv4Prefixes}}
-        <div class="prefix-section">
+        <details class="prefix-section" open>
-            <div class="prefix-header">
+            <summary class="prefix-header">
                 <h2>IPv4 Prefixes</h2>
                 <span class="prefix-count">{{.IPv4Count}}</span>
-            </div>
+            </summary>
             <table class="prefix-table">
                 <thead>
                     <tr>
@@ -267,15 +287,15 @@
                     {{end}}
                 </tbody>
             </table>
-        </div>
+        </details>
         {{end}}
 
         {{if .IPv6Prefixes}}
-        <div class="prefix-section">
+        <details class="prefix-section" open>
-            <div class="prefix-header">
+            <summary class="prefix-header">
                 <h2>IPv6 Prefixes</h2>
                 <span class="prefix-count">{{.IPv6Count}}</span>
-            </div>
+            </summary>
             <table class="prefix-table">
                 <thead>
                     <tr>
@@ -296,7 +316,7 @@
                     {{end}}
                 </tbody>
             </table>
-        </div>
+        </details>
         {{end}}
 
         {{if eq .TotalCount 0}}

internal/templates/index.html

@@ -107,9 +107,15 @@
         .stat-card.connected .stat-value {
             color: #27ae60;
         }
-        .stat-card.disconnected .stat-value {
+        .stat-card.disconnected .stat-value,
+        .stale {
             color: #e74c3c;
         }
+        /* The card has no room beside "Connected", so the spinner and "stale" go under it */
+        #freshness {
+            display: block;
+            font-size: 20px;
+        }
 
         /* Search section */
         .search-section {
@@ -233,7 +239,8 @@
             cursor: pointer;
             font-size: 12px;
         }
-        .ip-result pre {
+        .ip-result pre,
+        #ip-api pre {
             background: #2c3e50;
             color: #ecf0f1;
             padding: 16px;
@@ -245,18 +252,30 @@
             max-height: 400px;
             overflow-y: auto;
         }
-        .ip-result .error {
+        .ip-result .error,
+        #ip-api .error {
             background: #fee;
             color: #c00;
             padding: 12px;
             border-radius: 6px;
             font-size: 14px;
         }
-        .ip-result .loading {
+        .ip-result .loading,
+        #ip-api .loading {
             color: #7f8c8d;
             font-style: italic;
         }
 
+        /* IP information API card: the command, then its answer */
+        #ip-api p {
+            margin: 0;
+            color: #7f8c8d;
+            font-size: 14px;
+        }
+        #ip-api pre {
+            margin-top: 12px;
+        }
+
         /* Footer */
         .footer {
             margin-top: 40px;
@@ -297,7 +316,10 @@
     <main class="main-content">
         <div class="stats-grid">
             <div class="stat-card" id="status-card">
-                <div class="stat-value" id="stat-status">-</div>
+                <div class="stat-value">
+                    <span id="stat-status">-</span>
+                    <span id="freshness"></span>
+                </div>
                 <div class="stat-label">Status</div>
             </div>
             <div class="stat-card">
@@ -358,6 +380,13 @@
                 </div>
             </div>
         </div>
+
+        <div class="search-card" id="ip-api">
+            <h2>IP Information API</h2>
+            <p>The API answers what RouteWatch knows about an IP address, such as its AS number and country. <code>/ip/</code> with no address answers for the caller's own address.</p>
+            <pre id="ip-api-command" data-client-ip="{{.ClientIP}}"></pre>
+            <pre id="ip-api-answer" class="loading">Loading...</pre>
+        </div>
     </main>
 
     <footer class="footer">
@@ -369,6 +398,44 @@
     </footer>
 
     <script nonce="{{.CSPNonce}}">
+        // The stats are fetched every REFRESH_PERIOD_MS. Next to the status, a
+        // spinner turns one frame each time an answer counts more messages
+        // than the one before. After STALE_AFTER_REFRESHES refreshes without
+        // such an answer, the spinner gives way to "stale" and the time since.
+        const REFRESH_PERIOD_MS = 5000;
+        const STALE_AFTER_REFRESHES = 3;
+        const MS_PER_SECOND = 1000;
+        const SPINNER_FRAMES = ['⠋', '⠙', '⠹', '⠸', '⠼', '⠴', '⠦', '⠧', '⠇', '⠏'];
+        const SPINNER_COLOURS = ['#e74c3c', '#e67e22', '#f1c40f', '#27ae60', '#3498db', '#9b59b6'];
+
+        let spinnerFrame = 0;
+        let lastMessageCount = null;
+        let lastFreshAt = Date.now();
+
+        // Turn the spinner when the message count has risen since the last answer.
+        function noteMessageCount(count) {
+            if (lastMessageCount !== null && count > lastMessageCount) {
+                spinnerFrame = (spinnerFrame + 1) % SPINNER_FRAMES.length;
+                lastFreshAt = Date.now();
+            }
+            lastMessageCount = count;
+            showFreshness();
+        }
+
+        function showFreshness() {
+            const freshness = document.getElementById('freshness');
+            const sinceFreshMs = Date.now() - lastFreshAt;
+            const stale = sinceFreshMs >= STALE_AFTER_REFRESHES * REFRESH_PERIOD_MS;
+            freshness.classList.toggle('stale', stale);
+            if (stale) {
+                freshness.textContent = 'stale for ' + Math.floor(sinceFreshMs / MS_PER_SECOND) + 's';
+                freshness.style.color = '';
+                return;
+            }
+            freshness.textContent = SPINNER_FRAMES[spinnerFrame];
+            freshness.style.color = SPINNER_COLOURS[spinnerFrame % SPINNER_COLOURS.length];
+        }
+
         function formatNumber(num) {
             if (num >= 1000000) {
                 return (num / 1000000).toFixed(1) + 'M';
@@ -390,6 +457,7 @@
                     const statusEl = document.getElementById('stat-status');
                     statusEl.textContent = data.connected ? 'Connected' : 'Disconnected';
                     statusCard.className = 'stat-card ' + (data.connected ? 'connected' : 'disconnected');
+                    noteMessageCount(data.total_messages);
 
                     document.getElementById('stat-routes').textContent = formatNumber(data.live_routes);
                     document.getElementById('stat-asns').textContent = formatNumber(data.asns);
@@ -536,9 +604,33 @@
             document.getElementById('ip-input').value = '';
         });
 
-        // Initial load and refresh stats every 5 seconds
+        // IP information API card: show the curl command that asks /ip/ about
+        // the visitor's own address, then make that same request and show the
+        // JSON it answers, an error answer included. The answer holds outside
+        // data, so it is set with textContent, never innerHTML.
+        const ipAPICommand = document.getElementById('ip-api-command');
+        const ipAPIAnswer = document.getElementById('ip-api-answer');
+        const ipAPIURL = window.location.origin + '/ip/' + ipAPICommand.dataset.clientIp;
+
+        ipAPICommand.textContent = 'curl ' + ipAPIURL;
+
+        fetch(ipAPIURL)
+            .then(response => response.json())
+            .then(answer => {
+                ipAPIAnswer.className = '';
+                ipAPIAnswer.textContent = JSON.stringify(answer, null, 2);
+            })
+            .catch(error => {
+                ipAPIAnswer.className = 'error';
+                ipAPIAnswer.textContent = 'Error: ' + error.message;
+            });
+
+        // Initial load and refresh stats every REFRESH_PERIOD_MS. The freshness
+        // check runs every second on its own, so a request that never returns
+        // still turns the spinner into "stale".
         updateStats();
-        setInterval(updateStats, 5000);
+        setInterval(updateStats, REFRESH_PERIOD_MS);
+        setInterval(showFreshness, MS_PER_SECOND);
     </script>
 </body>
 </html>

internal/templates/status.html

@@ -126,7 +126,8 @@
         .connected {
             color: #22c55e;
         }
-        .disconnected {
+        .disconnected,
+        .stale {
             color: #ef4444;
         }
         .error {
@@ -180,7 +181,10 @@
             <h2>RouteWatch</h2>
             <div class="metric">
                 <span class="metric-label">Status</span>
-                <span class="metric-value" id="connected">-</span>
+                <span>
+                    <span class="metric-value" id="connected">-</span>
+                    <span class="metric-value" id="freshness"></span>
+                </span>
             </div>
             <div class="metric">
                 <span class="metric-label">Uptime</span>
@@ -386,6 +390,44 @@
     </div>
 
     <script nonce="{{.CSPNonce}}">
+        // The stats are fetched every REFRESH_PERIOD_MS. Next to the status, a
+        // spinner turns one frame each time an answer counts more messages
+        // than the one before. After STALE_AFTER_REFRESHES refreshes without
+        // such an answer, the spinner gives way to "stale" and the time since.
+        const REFRESH_PERIOD_MS = 2000;
+        const STALE_AFTER_REFRESHES = 3;
+        const MS_PER_SECOND = 1000;
+        const SPINNER_FRAMES = ['⠋', '⠙', '⠹', '⠸', '⠼', '⠴', '⠦', '⠧', '⠇', '⠏'];
+        const SPINNER_COLOURS = ['#e74c3c', '#e67e22', '#f1c40f', '#27ae60', '#3498db', '#9b59b6'];
+
+        let spinnerFrame = 0;
+        let lastMessageCount = null;
+        let lastFreshAt = Date.now();
+
+        // Turn the spinner when the message count has risen since the last answer.
+        function noteMessageCount(count) {
+            if (lastMessageCount !== null && count > lastMessageCount) {
+                spinnerFrame = (spinnerFrame + 1) % SPINNER_FRAMES.length;
+                lastFreshAt = Date.now();
+            }
+            lastMessageCount = count;
+            showFreshness();
+        }
+
+        function showFreshness() {
+            const freshness = document.getElementById('freshness');
+            const sinceFreshMs = Date.now() - lastFreshAt;
+            const stale = sinceFreshMs >= STALE_AFTER_REFRESHES * REFRESH_PERIOD_MS;
+            freshness.classList.toggle('stale', stale);
+            if (stale) {
+                freshness.textContent = 'stale for ' + Math.floor(sinceFreshMs / MS_PER_SECOND) + 's';
+                freshness.style.color = '';
+                return;
+            }
+            freshness.textContent = SPINNER_FRAMES[spinnerFrame];
+            freshness.style.color = SPINNER_COLOURS[spinnerFrame % SPINNER_COLOURS.length];
+        }
+
         function formatBytes(bytes) {
             if (bytes === 0) return '0 B';
             const k = 1024;
@@ -569,7 +611,8 @@
                     const connectedEl = document.getElementById('connected');
                     connectedEl.textContent = data.connected ? 'Connected' : 'Disconnected';
                     connectedEl.className = 'metric-value ' + (data.connected ? 'connected' : 'disconnected');
-                    
+                    noteMessageCount(data.total_messages);
+
                     // Update all metrics
                     document.getElementById('uptime').textContent = data.uptime;
                     document.getElementById('go_version').textContent = data.go_version;
@@ -643,9 +686,12 @@
                 });
         }
         
-        // Update immediately and then every 2 seconds
+        // Update immediately and then every REFRESH_PERIOD_MS. The freshness
+        // check runs every second on its own, so a request that never returns
+        // still turns the spinner into "stale".
         updateStatus();
-        setInterval(updateStatus, 2000);
+        setInterval(updateStatus, REFRESH_PERIOD_MS);
+        setInterval(showFreshness, MS_PER_SECOND);
     </script>
     </main>
 

internal/templates/templates.go

@@ -7,9 +7,9 @@ import (
 	"net/url"
 	"strings"
 	"sync"
-	"time"
 
 	"git.eeqj.de/sneak/routewatch/internal/version"
+	"github.com/dustin/go-humanize"
 )
 
 //go:embed index.html
@@ -48,48 +48,7 @@ var (
 	once sync.Once
 )
 
-const (
+const cidrPartCount = 2 // A CIDR has two parts: prefix and length
-	hoursPerDay   = 24
-	daysPerMonth  = 30
-	cidrPartCount = 2 // A CIDR has two parts: prefix and length
-)
-
-// timeSince returns a human-readable duration since the given time
-func timeSince(t time.Time) string {
-	duration := time.Since(t)
-	if duration < time.Minute {
-		return "just now"
-	}
-
-	if duration < time.Hour {
-		minutes := int(duration.Minutes())
-		if minutes == 1 {
-			return "1 minute ago"
-		}
-
-		return duration.Truncate(time.Minute).String() + " ago"
-	}
-
-	if duration < hoursPerDay*time.Hour {
-		hours := int(duration.Hours())
-		if hours == 1 {
-			return "1 hour ago"
-		}
-
-		return duration.Truncate(time.Hour).String() + " ago"
-	}
-
-	days := int(duration.Hours() / hoursPerDay)
-	if days == 1 {
-		return "1 day ago"
-	}
-
-	if days < daysPerMonth {
-		return duration.Truncate(hoursPerDay*time.Hour).String() + " ago"
-	}
-
-	return t.Format("2006-01-02")
-}
 
 // prefixURL generates a URL path for a prefix in CIDR notation.
 // Takes a prefix like "192.168.1.0/24" and returns "/prefix/192.168.1.0/24"
@@ -113,7 +72,7 @@ func initTemplates() {
 
 	// Create common template functions
 	funcs := template.FuncMap{
-		"timeSince":       timeSince,
+		"timeSince":       humanize.Time,
 		"urlEncode":       url.QueryEscape,
 		"prefixURL":       prefixURL,
 		"appName":         func() string { return version.Name },

internal/templates/templates_test.go

@@ -6,9 +6,25 @@ import (
 	"strings"
 	"testing"
 
+	"git.eeqj.de/sneak/routewatch/internal/database"
 	"git.eeqj.de/sneak/routewatch/internal/templates"
 )
 
+// renderPage renders a page with the data every page needs, and the visitor's
+// address, which the home page also needs.
+func renderPage(t *testing.T, tmpl *template.Template) string {
+	t.Helper()
+
+	var page bytes.Buffer
+
+	err := tmpl.Execute(&page, struct{ CSPNonce, ClientIP string }{})
+	if err != nil {
+		t.Fatalf("rendering the page: %v", err)
+	}
+
+	return page.String()
+}
+
 // TestFooterLicense renders the home and status pages and expects each footer
 // to name the licence in LICENSE, MIT, and not WTFPL.
 func TestFooterLicense(t *testing.T) {
@@ -28,14 +44,7 @@ func TestFooterLicense(t *testing.T) {
 		t.Run(name, func(t *testing.T) {
 			t.Parallel()
 
-			var page bytes.Buffer
+			_, footer, found := strings.Cut(renderPage(t, tmpl), "<footer")
-
-			err := tmpl.Execute(&page, struct{ CSPNonce string }{})
-			if err != nil {
-				t.Fatalf("rendering the page: %v", err)
-			}
-
-			_, footer, found := strings.Cut(page.String(), "<footer")
 			if !found {
 				t.Fatal("the page has no footer")
 			}
@@ -52,3 +61,121 @@ func TestFooterLicense(t *testing.T) {
 		})
 	}
 }
+
+// TestFreshnessIndicator renders the home and status pages and expects each to
+// have, right after the status element, the element where the page's script
+// shows its spinner or "stale".
+func TestFreshnessIndicator(t *testing.T) {
+	t.Parallel()
+
+	pages := map[string]struct {
+		tmpl      *template.Template
+		status    string
+		indicator string
+	}{
+		"index": {
+			tmpl:      templates.IndexTemplate(),
+			status:    `<span id="stat-status">-</span>`,
+			indicator: `<span id="freshness"></span>`,
+		},
+		"status": {
+			tmpl:      templates.StatusTemplate(),
+			status:    `<span class="metric-value" id="connected">-</span>`,
+			indicator: `<span class="metric-value" id="freshness"></span>`,
+		},
+	}
+
+	for name, page := range pages {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			_, afterStatus, found := strings.Cut(renderPage(t, page.tmpl), page.status)
+			if !found {
+				t.Fatalf("the page has no status element %s", page.status)
+			}
+
+			if !strings.HasPrefix(strings.TrimSpace(afterStatus), page.indicator) {
+				t.Errorf("the status element is not followed by %s", page.indicator)
+			}
+		})
+	}
+}
+
+// TestASDetailPrefixListsFold renders the AS page with one IPv4 and one IPv6
+// prefix. It expects each prefix list inside its own <details> element that
+// starts open and whose <summary> holds the list's heading, so that a click on
+// the heading folds the list.
+func TestASDetailPrefixListsFold(t *testing.T) {
+	t.Parallel()
+
+	const (
+		asn      = 64500
+		prefixV4 = "192.0.2.0/24"
+		prefixV6 = "2001:db8::/32"
+	)
+
+	ipv4 := []database.LiveRoute{{Prefix: prefixV4}}
+	ipv6 := []database.LiveRoute{{Prefix: prefixV6}}
+
+	// The fields the AS page handler gives the template.
+	data := struct {
+		ASN          *database.ASN
+		IPv4Prefixes []database.LiveRoute
+		IPv6Prefixes []database.LiveRoute
+		TotalCount   int
+		IPv4Count    int
+		IPv6Count    int
+		Peers        []database.ASPeer
+		PeerCount    int
+		CSPNonce     string
+	}{
+		ASN:          &database.ASN{ASN: asn},
+		IPv4Prefixes: ipv4,
+		IPv6Prefixes: ipv6,
+		TotalCount:   len(ipv4) + len(ipv6),
+		IPv4Count:    len(ipv4),
+		IPv6Count:    len(ipv6),
+	}
+
+	var rendered bytes.Buffer
+
+	err := templates.ASDetailTemplate().Execute(&rendered, data)
+	if err != nil {
+		t.Fatalf("rendering the page: %v", err)
+	}
+
+	page := rendered.String()
+
+	lists := []struct{ heading, prefix string }{
+		{"IPv4 Prefixes", prefixV4},
+		{"IPv6 Prefixes", prefixV6},
+	}
+
+	for _, list := range lists {
+		before, _, found := strings.Cut(page, list.prefix)
+		if !found {
+			t.Fatalf("the page does not list %s", list.prefix)
+		}
+
+		// The list's section starts at the last <details before its prefix.
+		start := strings.LastIndex(before, "<details")
+		if start < 0 || strings.Contains(before[start:], "</details>") {
+			t.Errorf("%s: the list is not inside a <details> element", list.heading)
+
+			continue
+		}
+
+		tag, section, _ := strings.Cut(before[start:], ">")
+		if !strings.Contains(tag, " open") {
+			t.Errorf("%s: the <details> element does not start open: %s>",
+				list.heading, tag)
+		}
+
+		_, summary, _ := strings.Cut(section, "<summary")
+		summary, _, _ = strings.Cut(summary, "</summary>")
+
+		if !strings.Contains(summary, list.heading) {
+			t.Errorf("%s: the <summary> does not hold the heading", list.heading)
+		}
+	}
+}

internal/whois/whois.go

@@ -7,10 +7,15 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log/slog"
 	"net"
 	"regexp"
 	"strings"
+	"sync"
 	"time"
+	"unicode/utf8"
+
+	"golang.org/x/text/encoding/charmap"
 )
 
 // Timeout constants for WHOIS queries.
@@ -26,10 +31,18 @@ const maxAnswerSize = 1 << 20
 
 // Parsing constants.
 const (
-	keyValueParts       = 2 // Expected parts when splitting "key: value"
 	lacnicDateFormatLen = 8 // Length of YYYYMMDD date format
 )
 
+// The classes of the two objects that describe an AS in an answer from
+// RIPE, APNIC or AFRINIC, and the key of the aut-num object's line that
+// gives the ID of the AS's organisation object.
+const (
+	autNumClass       = "aut-num"
+	organisationClass = "organisation"
+	orgKey            = "org"
+)
+
 // WHOIS server addresses.
 const (
 	whoisServerIANA    = "whois.iana.org:43"
@@ -38,8 +51,32 @@ const (
 	whoisServerAPNIC   = "whois.apnic.net:43"
 	whoisServerLACNIC  = "whois.lacnic.net:43"
 	whoisServerAFRINIC = "whois.afrinic.net:43"
+
+	// NIC.br registers Brazil's ASes under LACNIC.
+	whoisServerNICbr = "whois.registro.br:43"
 )
 
+// nicbrHeader starts the copyright notice at the top of NIC.br's WHOIS
+// answers. LACNIC's answer for an AS that NIC.br registers is NIC.br's, and
+// carries the same notice:
+//
+//	% Copyright (c) Nic.br - Use of this data is governed by the Use and
+//	% Privacy Policy at https://registro.br/upp . Distribution,
+const nicbrHeader = "% Copyright (c) Nic.br"
+
+// nicbrLimitReached is in the line that marks NIC.br's reduced answer to a
+// client over its query limit. NIC.br publishes no limit. Its Use and
+// Privacy Policy, https://registro.br/upp, says only that it restricts
+// queries to stop the data being taken in bulk.
+const nicbrLimitReached = "Query rate limit exceeded"
+
+// NICbrSkipTime is how long the client stops asking NIC.br after NIC.br
+// answers that the client is over its query limit. NIC.br publishes
+// neither the limit nor how long it lasts. An hour outlasts a limit
+// counted per minute or per hour. The ASes looked up meanwhile get
+// NIC.br's fields when they are next refreshed.
+const NICbrSkipTime = time.Hour
+
 // RIR identifiers.
 const (
 	RIRARIN   = "ARIN"
@@ -112,21 +149,42 @@ type Client struct {
 	// host:port. NewClient sets a net.Dialer's; tests replace it to reach
 	// local servers instead.
 	DialContext func(ctx context.Context, network, address string) (net.Conn, error)
+
+	// Now returns the current time. NewClient sets time.Now; tests replace
+	// it to move the clock.
+	Now func() time.Time
+
+	logger *slog.Logger
+
+	// mu guards nicbrSkipUntil.
+	mu sync.Mutex
+
+	// nicbrSkipUntil is when the client next asks NIC.br, after NIC.br
+	// answered that the client is over its query limit.
+	nicbrSkipUntil time.Time
 }
 
-// NewClient creates a new WHOIS client.
+// NewClient creates a new WHOIS client that logs to logger.
-func NewClient() *Client {
+func NewClient(logger *slog.Logger) *Client {
 	dialer := &net.Dialer{Timeout: dialTimeout}
 
-	return &Client{DialContext: dialer.DialContext}
+	return &Client{
+		DialContext: dialer.DialContext,
+		Now:         time.Now,
+		logger:      logger,
+	}
 }
 
 // LookupASN asks IANA which RIR holds the given ASN, asks that RIR, and
-// returns what the RIR's answer says. It returns ErrNoReferral when IANA
+// returns what the RIR's answer says. When LACNIC's answer is NIC.br's, it
-// refers the AS to no RIR, and another error when a query fails, when the
+// returns what NIC.br's own server says instead, unless that query fails or
-// RIR refuses it, when IANA's answer has neither a referral nor the AS's
+// is skipped, as askNICbr says.
-// block, when IANA refers the AS to a server none of the five RIRs run, or
+//
-// when the RIR's answer carries none of ASNInfo's fields.
+// It returns ErrNoReferral when IANA refers the AS to no RIR, and another
+// error when the query to IANA or to the RIR fails, when the RIR refuses
+// it, when IANA's answer has neither a referral nor the AS's block, when
+// IANA refers the AS to a server none of the five RIRs run, or when the
+// answer carries none of ASNInfo's fields.
 func (c *Client) LookupASN(ctx context.Context, asn int) (*ASNInfo, error) {
 	// Query IANA first to find the authoritative RIR
 	query := fmt.Sprintf("AS%d", asn)
@@ -158,18 +216,77 @@ func (c *Client) LookupASN(ctx context.Context, asn int) (*ASNInfo, error) {
 		return nil, fmt.Errorf("RIR query failed: %w", err)
 	}
 
-	// The fields come from the RIR's answer alone: IANA's describes the
+	// The fields never come from IANA's answer, which describes the block
-	// block the AS is in.
+	// the AS is in.
 	info := c.parseResponse(asn, rir, rirResp)
+
+	if rir == RIRLACNIC && strings.Contains(rirResp, nicbrHeader) {
+		info = c.askNICbr(ctx, query, info)
+	}
+
 	if info.isEmpty() {
 		return nil, fmt.Errorf("%s from %s: %w", query, whoisServer, errNoFields)
 	}
 
-	info.RawResponse = ianaResp + "\n" + rirResp
+	info.RawResponse = ianaResp + "\n" + info.RawResponse
 
 	return info, nil
 }
 
+// askNICbr asks NIC.br's server about an AS whose answer from LACNIC is
+// NIC.br's, and returns what NIC.br's answer says. LACNIC replaces each
+// accented letter in such an answer with U+FFFD. NIC.br's own server keeps
+// them, in Latin-1.
+//
+// askNICbr returns lacnicInfo, what LACNIC's answer says, and logs a
+// warning when the query fails, when NIC.br sends the reduced answer for a
+// client over its limit, or when NIC.br's answer carries none of ASNInfo's
+// fields. After the reduced answer, it returns lacnicInfo without asking
+// NIC.br until NICbrSkipTime has passed.
+func (c *Client) askNICbr(
+	ctx context.Context, asQuery string, lacnicInfo *ASNInfo,
+) *ASNInfo {
+	asn := lacnicInfo.ASN
+
+	c.mu.Lock()
+	skipping := c.Now().Before(c.nicbrSkipUntil)
+	c.mu.Unlock()
+
+	if skipping {
+		return lacnicInfo
+	}
+
+	answer, err := c.query(ctx, whoisServerNICbr, asQuery)
+	if err != nil {
+		c.logger.Warn("NIC.br query failed, keeping LACNIC's fields",
+			"asn", asn, "error", err)
+
+		return lacnicInfo
+	}
+
+	if strings.Contains(answer, nicbrLimitReached) {
+		c.mu.Lock()
+		c.nicbrSkipUntil = c.Now().Add(NICbrSkipTime)
+		c.mu.Unlock()
+
+		c.logger.Warn("NIC.br answered that the client is over its query "+
+			"limit, keeping LACNIC's fields and skipping NIC.br",
+			"asn", asn, "skip_for", NICbrSkipTime)
+
+		return lacnicInfo
+	}
+
+	info := c.parseResponse(asn, RIRLACNIC, answer)
+	if info.isEmpty() {
+		c.logger.Warn("NIC.br answered with no WHOIS fields, "+
+			"keeping LACNIC's fields", "asn", asn)
+
+		return lacnicInfo
+	}
+
+	return info
+}
+
 // isEmpty reports whether info holds none of the fields a WHOIS answer
 // fills, as when the answer is only comment and error lines.
 func (info *ASNInfo) isEmpty() bool {
@@ -213,8 +330,8 @@ func (c *Client) queryRIR(
 	return answer, nil
 }
 
-// query performs a raw WHOIS query to the specified server. An answer that
+// query performs a raw WHOIS query to the specified server and returns the
-// reaches maxAnswerSize is an error.
+// answer in UTF-8. An answer that reaches maxAnswerSize is an error.
 func (c *Client) query(ctx context.Context, server, query string) (string, error) {
 	conn, err := c.DialContext(ctx, "tcp", server)
 	if err != nil {
@@ -261,7 +378,25 @@ func (c *Client) query(ctx context.Context, server, query string) (string, error
 		return "", fmt.Errorf("read response: %w", errAnswerTooLarge)
 	}
 
-	return sb.String(), nil
+	return toUTF8(sb.String())
+}
+
+// toUTF8 returns a WHOIS answer in UTF-8. An answer that is valid UTF-8 is
+// returned as it is. Any other answer is decoded as Latin-1, which RIPE,
+// APNIC and NIC.br send. LACNIC, ARIN and AFRINIC send UTF-8. RIPE's
+// database working group lists the five RIRs here:
+// https://www.ripe.net/ripe/mail/archives/db-wg/2024-May/008075.html
+func toUTF8(answer string) (string, error) {
+	if utf8.ValidString(answer) {
+		return answer, nil
+	}
+
+	decoded, err := charmap.ISO8859_1.NewDecoder().String(answer)
+	if err != nil {
+		return "", fmt.Errorf("decode Latin-1 answer: %w", err)
+	}
+
+	return decoded, nil
 }
 
 // parseIANAReferral extracts the RIR and WHOIS server from an IANA response.
@@ -297,7 +432,9 @@ func (c *Client) parseIANAReferral(response string) (string, string, error) {
 	return "", "", nil
 }
 
-// parseResponse extracts ASN information from a WHOIS response.
+// parseResponse extracts ASN information from a WHOIS response. Of an
+// answer from RIPE, APNIC or AFRINIC it reads only the lines asObjectLines
+// returns. Of an answer from ARIN or LACNIC it reads every line.
 func (c *Client) parseResponse(asn int, rir, response string) *ASNInfo {
 	info := &ASNInfo{
 		ASN:         asn,
@@ -306,26 +443,15 @@ func (c *Client) parseResponse(asn int, rir, response string) *ASNInfo {
 	}
 
 	lines := strings.Split(response, "\n")
+	if rir == RIRRIPE || rir == RIRAPNIC || rir == RIRAFRNIC {
+		lines = asObjectLines(lines)
+	}
 
 	var addressLines []string
 
 	for _, line := range lines {
-		line = strings.TrimSpace(line)
+		key, value, ok := splitField(line)
-		if line == "" || strings.HasPrefix(line, "%") ||
+		if !ok || value == "" {
-			strings.HasPrefix(line, "#") {
-			continue
-		}
-
-		// Split on first colon
-		parts := strings.SplitN(line, ":", keyValueParts)
-		if len(parts) != keyValueParts {
-			continue
-		}
-
-		key := strings.TrimSpace(strings.ToLower(parts[0]))
-		value := strings.TrimSpace(parts[1])
-
-		if value == "" {
 			continue
 		}
 
@@ -352,6 +478,72 @@ func (c *Client) parseResponse(asn int, rir, response string) *ASNInfo {
 	return info
 }
 
+// splitField splits a "key: value" line of a WHOIS answer into its key, in
+// lower case, and its value. The third result is false for a line that
+// holds no field: a blank line, a comment line or a line without a colon.
+func splitField(line string) (string, string, bool) {
+	line = strings.TrimSpace(line)
+	if strings.HasPrefix(line, "%") || strings.HasPrefix(line, "#") {
+		return "", "", false
+	}
+
+	key, value, ok := strings.Cut(line, ":")
+
+	return strings.ToLower(strings.TrimSpace(key)), strings.TrimSpace(value), ok
+}
+
+// asObjectLines returns the lines of the aut-num object in an answer from
+// RIPE, APNIC or AFRINIC, followed by the lines of the organisation object
+// whose ID the aut-num object gives on its "org:" line. The answer's other
+// objects are left out. RIPE and APNIC start their answer with the
+// as-block object of the block the AS is in, whose dates are not the AS's.
+//
+// These answers are in RPSL. A blank line ends an object. An object's first
+// line has the object's class as its key and the object's ID as its value,
+// as in "organisation: ORG-APNI1-AP".
+func asObjectLines(lines []string) []string {
+	var autNum []string
+
+	// The lines of each organisation object, by its ID.
+	organisations := make(map[string][]string)
+
+	// The class and ID of the object the line is in, "" between objects.
+	var class, id string
+
+	// The ID of the organisation object the aut-num object refers to.
+	var orgID string
+
+	for _, line := range lines {
+		if strings.TrimSpace(line) == "" {
+			class = ""
+
+			continue
+		}
+
+		key, value, ok := splitField(line)
+		if !ok {
+			continue
+		}
+
+		if class == "" {
+			class, id = key, value
+		}
+
+		switch class {
+		case autNumClass:
+			autNum = append(autNum, line)
+
+			if key == orgKey {
+				orgID = value
+			}
+		case organisationClass:
+			organisations[id] = append(organisations[id], line)
+		}
+	}
+
+	return append(autNum, organisations[orgID]...)
+}
+
 // setResponseField stores the value of one "key: value" line of a WHOIS
 // response in info, keeping the first value seen for each field.
 func (c *Client) setResponseField(info *ASNInfo, key, value string) {

internal/whois/whois_test.go

@@ -2,9 +2,13 @@ package whois_test
 
 import (
 	"bufio"
+	"bytes"
 	"context"
+	"encoding/json"
 	"errors"
 	"io"
+	"log/slog"
+	"maps"
 	"net"
 	"slices"
 	"strings"
@@ -12,6 +16,7 @@ import (
 	"syscall"
 	"testing"
 	"time"
+	"unicode/utf8"
 
 	"git.eeqj.de/sneak/routewatch/internal/whois"
 )
@@ -49,14 +54,30 @@ changed:      2002-09-01
 source:       IANA
 `
 
+// lacnicReferral is IANA's answer for an AS in a block it gave to LACNIC,
+// shortened to the referral.
+const lacnicReferral = "refer:        whois.lacnic.net\n"
+
 // ripeRecord is RIPE's answer for the AS when asked to leave out person and
-// role objects: the abuse address as a comment, the AS's object and the
+// role objects. It starts with the as-block object of the block the AS is
+// in. Then come the abuse address as a comment, the AS's object and the
 // organisation object it refers to.
 const ripeRecord = `% This is the RIPE Database query service.
 % The objects are in RPSL format.
 
 % Note: --no-personal means ALL personal data has been filtered from this output.
 
+% Information related to 'AS3209 - AS3353'
+
+as-block:       AS3209 - AS3353
+descr:          RIPE NCC ASN block
+remarks:        These AS Numbers are assigned to network operators
+remarks:        in the RIPE NCC service region.
+mnt-by:         RIPE-NCC-HM-MNT
+created:        2018-11-22T15:27:19Z
+last-modified:  2018-11-22T15:27:19Z
+source:         RIPE
+
 % Information related to 'AS3333'
 
 % Abuse contact for 'AS3333' is 'abuse@ripe.net'
@@ -118,6 +139,78 @@ country:        ZA
 address:        1 Example Road
 `
 
+// apnicServer is APNIC's WHOIS server, and apnicASN an AS that APNIC holds.
+const (
+	apnicServer = "whois.apnic.net:43"
+	apnicASN    = 4608
+)
+
+// The keys of the queries LookupASN sends for apnicASN: IANA's, then
+// APNIC's, which asks APNIC to leave out person and role objects.
+const (
+	apnicIANAQuery = ianaServer + " AS4608"
+	apnicQuery     = apnicServer + " --no-personal AS4608"
+)
+
+// apnicRecord is APNIC's answer for apnicASN when asked to leave out person
+// and role objects, shortened. It starts with the as-block object of the
+// block the AS is in. Then come the abuse address as a comment, the AS's
+// object, and the irt and organisation objects it refers to.
+const apnicRecord = `% [whois.apnic.net]
+% Whois data copyright terms    http://www.apnic.net/db/dbcopyright.html
+
+% Note: --no-personal means ALL personal data has been filtered from this output.
+
+% Information related to 'AS4608 - AS4865'
+
+as-block:       AS4608 - AS4865
+descr:          APNIC ASN block
+remarks:        These AS numbers are further assigned by APNIC
+remarks:        to APNIC members and end-users in the APNIC region
+mnt-by:         APNIC-HM
+mnt-lower:      APNIC-HM
+last-modified:  2019-05-20T03:52:26Z
+source:         APNIC
+
+% Information related to 'AS4608'
+
+% Abuse contact for 'AS4608' is 'abuse@apnic.net'
+
+aut-num:        AS4608
+as-name:        APNIC-SERVICES
+descr:          Asia Pacific Network Information Centre
+country:        AU
+org:            ORG-APNI1-AP
+admin-c:        AIC1-AP
+abuse-c:        AA1589-AP
+mnt-by:         APNIC-HM
+mnt-irt:        IRT-APNIC-IS-AP
+last-modified:  2026-08-26T00:40:00Z
+source:         APNIC
+
+irt:            IRT-APNIC-IS-AP
+address:        South Brisbane, Australia
+e-mail:         helpdesk@apnic.net
+abuse-mailbox:  abuse@apnic.net
+mnt-by:         MAINT-APNIC-IS-AP
+last-modified:  2025-11-18T00:27:08Z
+source:         APNIC
+
+organisation:   ORG-APNI1-AP
+org-name:       Asia Pacific Network Information Centre
+org-type:       LIR
+country:        AU
+address:        PO Box 3646
+address:        South Brisbane, QLD 4101,
+address:        Australia
+e-mail:         noc@apnic.net
+mnt-by:         APNIC-HM
+last-modified:  2026-08-24T12:58:43Z
+source:         APNIC
+
+% This query was served by the APNIC Whois Service version 1.88.48 (WHOIS-UK2)
+`
+
 // ianaPrivateUse is IANA's answer for a private-use AS: its block and no
 // referral.
 const ianaPrivateUse = `% IANA WHOIS server
@@ -187,7 +280,7 @@ func lookUp(
 ) (*whois.ASNInfo, error) {
 	t.Helper()
 
-	client := whois.NewClient()
+	client := whois.NewClient(slog.New(slog.DiscardHandler))
 	client.DialContext = fakeServers(t, answers)
 
 	return client.LookupASN(t.Context(), testASN)
@@ -197,7 +290,8 @@ func lookUp(
 // answers only a query that leaves out person and role objects, and its
 // answer to that still fills the AS's fields: the abuse address from the
 // comment line, and the organisation's name and country from its object.
-// The dates are the AS's: IANA's "changed:" line dates its block.
+// The dates are the AS's. IANA's "changed:" line dates the AS's block, and
+// so do the dates of the as-block object at the start of RIPE's answer.
 func TestLookupASNReadsTheRIRAnswer(t *testing.T) {
 	t.Parallel()
 
@@ -237,6 +331,46 @@ func TestLookupASNReadsTheRIRAnswer(t *testing.T) {
 	}
 }
 
+// TestLookupASNReadsOnlyTheASAndItsOrganisation looks up an AS at APNIC,
+// whose answer starts with the as-block object of the block the AS is in.
+// The last-modified date is the aut-num object's, not the block's. The
+// address is the organisation object's alone, without the irt object's.
+func TestLookupASNReadsOnlyTheASAndItsOrganisation(t *testing.T) {
+	t.Parallel()
+
+	client := whois.NewClient(slog.New(slog.DiscardHandler))
+	client.DialContext = fakeServers(t, map[string]string{
+		apnicIANAQuery: "refer:        whois.apnic.net\n",
+		apnicQuery:     apnicRecord,
+	})
+
+	info, err := client.LookupASN(t.Context(), apnicASN)
+	if err != nil {
+		t.Fatalf("LookupASN: %v", err)
+	}
+
+	wantLastMod := time.Date(2026, 8, 26, 0, 40, 0, 0, time.UTC)
+	if info.LastMod == nil || !info.LastMod.Equal(wantLastMod) {
+		t.Errorf("LookupASN last modified = %v, want %v",
+			info.LastMod, wantLastMod)
+	}
+
+	got := []string{
+		info.ASName, info.OrgID, info.OrgName, info.CountryCode,
+		info.Address, info.AbuseEmail,
+	}
+	want := []string{
+		"APNIC-SERVICES", "ORG-APNI1-AP",
+		"Asia Pacific Network Information Centre", "AU",
+		"PO Box 3646\nSouth Brisbane, QLD 4101,\nAustralia", "abuse@apnic.net",
+	}
+
+	if !slices.Equal(got, want) {
+		t.Errorf("LookupASN = AS name, org ID, org name, country, address, "+
+			"abuse address %q; want %q", got, want)
+	}
+}
+
 // TestLookupASNAsksAPNICAndAFRINICToLeaveOutPersonalData looks up an AS at
 // APNIC and at AFRINIC. Each answers only a query that leaves out person
 // and role objects, as RIPE does. That one answer still holds the
@@ -273,6 +407,361 @@ func TestLookupASNAsksAPNICAndAFRINICToLeaveOutPersonalData(t *testing.T) {
 	}
 }
 
+// The name of an organisation with accented letters, in Latin-1, one byte for
+// each letter, and in UTF-8.
+const (
+	latin1OrgName = "Fundaci\xf3n Ra\xedces de Espa\xf1a"
+	utf8OrgName   = "Fundación Raíces de España"
+)
+
+// TestLookupASNStoresAnswersInUTF8 looks up an AS at RIPE, which answers in
+// Latin-1, and at LACNIC, which answers in UTF-8. Both answers give the
+// organisation's name with its accented letters in UTF-8, in the parsed field
+// and in the stored answer. Before the fix the Latin-1 answer was kept as
+// received, which is not valid UTF-8.
+func TestLookupASNStoresAnswersInUTF8(t *testing.T) {
+	t.Parallel()
+
+	for name, answers := range map[string]map[string]string{
+		"RIPE in Latin-1": {
+			ianaQuery: ianaReferral,
+			ripeQuery: "aut-num:        AS3333\n" +
+				"org-name:       " + latin1OrgName + "\n",
+		},
+		"LACNIC in UTF-8": {
+			ianaQuery: lacnicReferral,
+			"whois.lacnic.net:43 " + asQuery: "aut-num:     AS3333\n" +
+				"owner:       " + utf8OrgName + "\n",
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			info, err := lookUp(t, answers)
+			if err != nil {
+				t.Fatalf("LookupASN: %v", err)
+			}
+
+			if info.OrgName != utf8OrgName {
+				t.Errorf("LookupASN org name = %q, want %q",
+					info.OrgName, utf8OrgName)
+			}
+
+			if !utf8.ValidString(info.RawResponse) ||
+				!strings.Contains(info.RawResponse, utf8OrgName) {
+				t.Errorf("LookupASN answer = %q, want UTF-8 holding %q",
+					info.RawResponse, utf8OrgName)
+			}
+		})
+	}
+}
+
+// lacnicServer is LACNIC's WHOIS server and nicbrServer NIC.br's, which
+// registers Brazil's ASes under LACNIC. brazilASN is one of those ASes.
+const (
+	lacnicServer = "whois.lacnic.net:43"
+	nicbrServer  = "whois.registro.br:43"
+	brazilASN    = 52751
+)
+
+// The keys of the queries LookupASN sends for brazilASN: IANA's, LACNIC's,
+// then NIC.br's.
+const (
+	brazilIANAQuery   = ianaServer + " AS52751"
+	brazilLACNICQuery = lacnicServer + " AS52751"
+	brazilNICbrQuery  = nicbrServer + " AS52751"
+)
+
+// The name of brazilASN's organisation in three forms: as LACNIC sends it,
+// with each accented letter replaced by U+FFFD; as NIC.br sends it, in
+// Latin-1; and in UTF-8.
+const (
+	lacnicBrazilOrgName = "Brasrede Telecomunica\U0000FFFD\U0000FFFDes LTDA"
+	nicbrBrazilOrgName  = "Brasrede Telecomunica\xe7\xf5es LTDA"
+	brazilOrgName       = "Brasrede Telecomunicações LTDA"
+)
+
+// nicbrCopyright is the copyright notice at the top of NIC.br's answers.
+const nicbrCopyright = "% Copyright (c) Nic.br - " +
+	"Use of this data is governed by the Use and\n" +
+	"% Privacy Policy at https://registro.br/upp . Distribution,\n" +
+	"% commercialization, reproduction, and use for advertising or similar\n" +
+	"% purposes are expressly prohibited.\n"
+
+// lacnicBrazilRecord is LACNIC's answer for brazilASN, recorded on
+// 2026-10-26. It is NIC.br's answer, which LACNIC passes on after a line
+// of its own and a space. It is shortened. The client's address is a
+// documentation address. The contact's name, the contact's object and the
+// footer are left out.
+const lacnicBrazilRecord = "% IP Client: 192.0.2.1\n" +
+	" " + nicbrCopyright + `% 2026-10-26T23:12:22-03:00 - 192.0.2.1
+
+aut-num:     AS52751
+owner:       ` + lacnicBrazilOrgName + `
+owner-c:     AVL217
+routing-c:   AVL217
+abuse-c:     AVL217
+created:     20120829
+changed:     20130306
+inetnum:     177.38.152.0/21
+inetnum:     2804:b34::/32
+inetnum:     191.243.4.0/22
+inetnum:     131.72.248.0/22
+inetnum:     138.94.228.0/22
+inetnum:     170.233.8.0/22
+inetnum:     170.246.4.0/22
+`
+
+// nicbrRecord is NIC.br's answer for brazilASN, in Latin-1, recorded on
+// 2026-10-26 and shortened as lacnicBrazilRecord is.
+const nicbrRecord = nicbrCopyright + `% 2026-10-26T23:14:41-03:00 - 192.0.2.1
+
+aut-num:     AS52751
+owner:       ` + nicbrBrazilOrgName + `
+owner-c:     AVL217
+routing-c:   AVL217
+abuse-c:     AVL217
+created:     20120829
+changed:     20130306
+inetnum:     177.38.152.0/21
+inetnum:     2804:b34::/32
+inetnum:     191.243.4.0/22
+inetnum:     131.72.248.0/22
+inetnum:     138.94.228.0/22
+inetnum:     170.233.8.0/22
+inetnum:     170.246.4.0/22
+`
+
+// nicbrOverLimit stands for NIC.br's answer for brazilASN to a client over
+// its query limit, and is not recorded. Such an answer leaves information
+// out, here the owner, and says so in its first line.
+const nicbrOverLimit = `% Query rate limit exceeded. Reduced information.
+
+aut-num:     AS52751
+created:     20120829
+changed:     20130306
+`
+
+// newNICbrClient returns a client whose fake servers send answers and
+// whose logger writes JSON lines to logs. It adds one to *nicbrAsks each
+// time it connects to NIC.br's server.
+func newNICbrClient(
+	t *testing.T, answers map[string]string, logs io.Writer, nicbrAsks *int,
+) *whois.Client {
+	t.Helper()
+
+	dial := fakeServers(t, answers)
+
+	client := whois.NewClient(slog.New(slog.NewJSONHandler(logs, nil)))
+	client.DialContext = func(
+		ctx context.Context, network, address string,
+	) (net.Conn, error) {
+		if address == nicbrServer {
+			*nicbrAsks++
+		}
+
+		return dial(ctx, network, address)
+	}
+
+	return client
+}
+
+// lookUpBrazilianAS looks brazilASN up with fake servers sending answers,
+// and reports whether the client connected to NIC.br's server.
+func lookUpBrazilianAS(
+	t *testing.T, answers map[string]string,
+) (*whois.ASNInfo, bool, error) {
+	t.Helper()
+
+	nicbrAsks := 0
+	client := newNICbrClient(t, answers, io.Discard, &nicbrAsks)
+
+	info, err := client.LookupASN(t.Context(), brazilASN)
+
+	return info, nicbrAsks > 0, err
+}
+
+// TestLookupASNTakesABrazilianASFromNICbr looks up an AS that NIC.br
+// registers. LACNIC's answer is NIC.br's with each accented letter replaced
+// by U+FFFD, so the client also asks NIC.br's server, which answers in
+// Latin-1. The organisation's name has its accented letters, in the parsed
+// field and in the stored answer.
+func TestLookupASNTakesABrazilianASFromNICbr(t *testing.T) {
+	t.Parallel()
+
+	info, _, err := lookUpBrazilianAS(t, map[string]string{
+		brazilIANAQuery:   lacnicReferral,
+		brazilLACNICQuery: lacnicBrazilRecord,
+		brazilNICbrQuery:  nicbrRecord,
+	})
+	if err != nil {
+		t.Fatalf("LookupASN: %v", err)
+	}
+
+	if info.OrgName != brazilOrgName || info.RIR != whois.RIRLACNIC {
+		t.Errorf("LookupASN org name, RIR = %q, %q; want %q, %q",
+			info.OrgName, info.RIR, brazilOrgName, whois.RIRLACNIC)
+	}
+
+	if !strings.Contains(info.RawResponse, brazilOrgName) {
+		t.Errorf("LookupASN answer = %q, want one holding %q",
+			info.RawResponse, brazilOrgName)
+	}
+
+	wantRegDate := time.Date(2012, 8, 29, 0, 0, 0, 0, time.UTC)
+	if info.RegDate == nil || !info.RegDate.Equal(wantRegDate) {
+		t.Errorf("LookupASN registered = %v, want %v",
+			info.RegDate, wantRegDate)
+	}
+}
+
+// TestLookupASNAsksNICbrOnlyForItsASes looks up an AS at LACNIC whose
+// answer does not carry NIC.br's copyright notice, as for an AS that LACNIC
+// registers itself. The client does not connect to NIC.br's server, which
+// would answer with a record, and keeps LACNIC's fields.
+func TestLookupASNAsksNICbrOnlyForItsASes(t *testing.T) {
+	t.Parallel()
+
+	info, askedNICbr, err := lookUpBrazilianAS(t, map[string]string{
+		brazilIANAQuery: lacnicReferral,
+		brazilLACNICQuery: "aut-num:     AS52751\n" +
+			"owner:       " + utf8OrgName + "\n",
+		brazilNICbrQuery: nicbrRecord,
+	})
+	if err != nil {
+		t.Fatalf("LookupASN: %v", err)
+	}
+
+	if askedNICbr {
+		t.Error("LookupASN asked NIC.br's server about an AS whose " +
+			"answer from LACNIC is not NIC.br's")
+	}
+
+	if info.OrgName != utf8OrgName {
+		t.Errorf("LookupASN org name = %q, want LACNIC's %q",
+			info.OrgName, utf8OrgName)
+	}
+}
+
+// TestLookupASNKeepsLACNICsAnswerWhenNICbrFails looks up an AS that NIC.br
+// registers when NIC.br's server refuses the connection, sends nothing, or
+// sends the reduced answer for a client over its query limit. The client
+// asks NIC.br, and the lookup still succeeds with LACNIC's fields. The
+// client logs one warning, which names the AS and the reason.
+func TestLookupASNKeepsLACNICsAnswerWhenNICbrFails(t *testing.T) {
+	t.Parallel()
+
+	for name, test := range map[string]struct {
+		nicbrAnswer map[string]string
+		reason      string
+	}{
+		"connection refused": {
+			nicbrAnswer: map[string]string{},
+			reason:      syscall.ECONNREFUSED.Error(),
+		},
+		"no answer": {
+			nicbrAnswer: map[string]string{brazilNICbrQuery: ""},
+			reason:      "no WHOIS fields",
+		},
+		"over the query limit": {
+			nicbrAnswer: map[string]string{brazilNICbrQuery: nicbrOverLimit},
+			reason:      "over its query limit",
+		},
+	} {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			answers := map[string]string{
+				brazilIANAQuery:   lacnicReferral,
+				brazilLACNICQuery: lacnicBrazilRecord,
+			}
+			maps.Copy(answers, test.nicbrAnswer)
+
+			var logs bytes.Buffer
+
+			nicbrAsks := 0
+			client := newNICbrClient(t, answers, &logs, &nicbrAsks)
+
+			info, err := client.LookupASN(t.Context(), brazilASN)
+			if err != nil {
+				t.Fatalf("LookupASN: %v", err)
+			}
+
+			if nicbrAsks == 0 {
+				t.Error("LookupASN did not ask NIC.br's server")
+			}
+
+			if info.OrgName != lacnicBrazilOrgName {
+				t.Errorf("LookupASN org name = %q, want LACNIC's %q",
+					info.OrgName, lacnicBrazilOrgName)
+			}
+
+			var logged struct {
+				Level string `json:"level"`
+				ASN   int    `json:"asn"`
+			}
+
+			err = json.Unmarshal(logs.Bytes(), &logged)
+			if err != nil {
+				t.Fatalf("want one log line, got %q: %v", logs.String(), err)
+			}
+
+			if logged.Level != slog.LevelWarn.String() ||
+				logged.ASN != brazilASN ||
+				!strings.Contains(logs.String(), test.reason) {
+				t.Errorf("logged %q, want a warning for AS%d holding %q",
+					logs.String(), brazilASN, test.reason)
+			}
+		})
+	}
+}
+
+// TestLookupASNSkipsNICbrAfterItsLimit looks up an AS that NIC.br
+// registers three times with one client, while NIC.br answers that the
+// client is over its query limit. The first lookup asks NIC.br. The
+// second, a second before NICbrSkipTime has passed, does not. The third,
+// once NICbrSkipTime has passed, asks again. Each keeps LACNIC's fields.
+func TestLookupASNSkipsNICbrAfterItsLimit(t *testing.T) {
+	t.Parallel()
+
+	nicbrAsks := 0
+	client := newNICbrClient(t, map[string]string{
+		brazilIANAQuery:   lacnicReferral,
+		brazilLACNICQuery: lacnicBrazilRecord,
+		brazilNICbrQuery:  nicbrOverLimit,
+	}, io.Discard, &nicbrAsks)
+
+	start := time.Date(2026, 10, 27, 0, 0, 0, 0, time.UTC)
+	now := start
+	client.Now = func() time.Time { return now }
+
+	for _, step := range []struct {
+		after    time.Duration
+		wantAsks int
+	}{
+		{after: 0, wantAsks: 1},
+		{after: whois.NICbrSkipTime - time.Second, wantAsks: 1},
+		{after: whois.NICbrSkipTime, wantAsks: 2},
+	} {
+		now = start.Add(step.after)
+
+		info, err := client.LookupASN(t.Context(), brazilASN)
+		if err != nil {
+			t.Fatalf("LookupASN after %v: %v", step.after, err)
+		}
+
+		if nicbrAsks != step.wantAsks {
+			t.Errorf("after %v NIC.br's server was asked %d times, want %d",
+				step.after, nicbrAsks, step.wantAsks)
+		}
+
+		if info.OrgName != lacnicBrazilOrgName {
+			t.Errorf("LookupASN after %v org name = %q, want LACNIC's %q",
+				step.after, info.OrgName, lacnicBrazilOrgName)
+		}
+	}
+}
+
 // TestLookupASNReportsARefusal looks up an AS IANA refers to RIPE when RIPE
 // refuses the query, with each of the error lines RIPE refuses with. The
 // error holds RIPE's line, so the log says why the lookup failed.

pkg/asinfo/asinfo_test.go

@@ -22,7 +22,7 @@ func TestGet(t *testing.T) {
 			name:     "AS1 Level 3",
 			asn:      1,
 			wantOK:   true,
-			wantDesc: "Level 3 Parent, LLC",
+			wantDesc: "Level 3 Parent LLC",
 		},
 		{
 			name:     "AS15169 Google",
@@ -36,10 +36,10 @@ func TestGet(t *testing.T) {
 			wantOK: false,
 		},
 		{
-			name:     "AS0 IANA Reserved",
+			name:     "AS1251 with accented letters",
-			asn:      0,
+			asn:      1251,
 			wantOK:   true,
-			wantDesc: "Internet Assigned Numbers Authority",
+			wantDesc: "FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO SÃO PAULO",
 		},
 	}
 
@@ -69,7 +69,7 @@ func TestGetDescription(t *testing.T) {
 		asn  int
 		want string
 	}{
-		{1, "Level 3 Parent, LLC"},
+		{1, "Level 3 Parent LLC"},
 		{999999999, ""},
 	}
 
@@ -92,8 +92,7 @@ func TestGetHandle(t *testing.T) {
 		asn  int
 		want string
 	}{
-		{1, "LVLT"},
+		{1, "LVLT-1"},
-		{0, "IANA-RSVD"},
 		{999999999, ""},
 	}
 
@@ -142,6 +141,11 @@ func TestSearch(t *testing.T) {
 			query:   "University",
 			wantMin: 10,
 		},
+		{
+			name:    "Search for São Paulo",
+			query:   "São Paulo",
+			wantMin: 1,
+		},
 		{
 			name:    "Non-existent org",
 			query:   "XYZABC123456",
@@ -189,13 +193,13 @@ func TestSearchEmptyQueryMatchesNothing(t *testing.T) {
 func TestSearchIgnoresCase(t *testing.T) {
 	t.Parallel()
 
-	const cloudflareASN = 13335 // handle CLOUDFLARENET, "Cloudflare, Inc."
+	const cloudflareASN = 13335 // handle CLOUDFLARENET, "Cloudflare Inc."
 
 	isCloudflare := func(info asinfo.Info) bool {
 		return info.ASN == cloudflareASN
 	}
 
-	for _, query := range []string{"cloudflarenet", "CLOUDFLARE, INC."} {
+	for _, query := range []string{"cloudflarenet", "CLOUDFLARE INC."} {
 		results, _ := asinfo.Search(query, asinfo.Total())
 		if !slices.ContainsFunc(results, isCloudflare) {
 			t.Errorf("Search(%q) did not find AS%d", query, cloudflareASN)

pkg/asinfo/doc.go

@@ -2,7 +2,7 @@
 Package asinfo provides information about Autonomous Systems (AS).
 
 The package embeds a comprehensive database of AS numbers, handles, and descriptions
-sourced from https://github.com/ipverse/asn-info. The data is embedded at compile
+sourced from https://github.com/ipverse/as-metadata. The data is embedded at compile
 time and provides fast, offline lookups.
 
 Basic usage:

pkg/asinfo/example_test.go

@@ -17,7 +17,7 @@ func ExampleGet() {
 func ExampleGetDescription() {
 	desc := asinfo.GetDescription(13335)
 	fmt.Println(desc)
-	// Output: Cloudflare, Inc.
+	// Output: Cloudflare Inc.
 }
 
 func ExampleSearch() {

script/asupdate

@@ -0,0 +1,34 @@
+#!/bin/sh
+# script/asupdate: rebuild the AS list built into RouteWatch from
+# as.csv with cmd/asinfo-gen, which fails when it finds no AS. The new
+# list replaces the old one only when the generator succeeds. Otherwise
+# the old list stays as it was and the script exits non-zero.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+AS_DATA="pkg/asinfo/asdata.json.gz"
+# Next to AS_DATA, so the final mv is a rename on one file system.
+AS_DATA_TMP="$AS_DATA.tmp"
+
+main() {
+    cd "$ROOT"
+
+    json="$(mktemp)"
+    trap 'rm -f "$json" "$AS_DATA_TMP"' EXIT
+    # A signal exits through the EXIT trap too.
+    trap 'exit 1' HUP INT TERM
+
+    echo "Updating AS info data..."
+    if ! go run ./cmd/asinfo-gen >"$json"; then
+        echo "asupdate: the generator failed; $AS_DATA is unchanged" >&2
+        exit 1
+    fi
+
+    # -n leaves the time out of the file, so an unchanged list gives the
+    # same bytes.
+    gzip -n -c <"$json" >"$AS_DATA_TMP"
+    mv "$AS_DATA_TMP" "$AS_DATA"
+}
+
+main "$@"