Add asn= and prefix= tags from a routewatch instance (closes #204)

SWW_ROUTEWATCH_URL names the instance. The new heuristic routewatch_tags
asks it in the background about each client and tags the request. Answers
are kept in memory for an hour. A request without tags gives the reason in
routewatch_tags_missing, and it is never delayed or refused.

Model: opus-5-5

README.md

@@ -265,6 +265,7 @@ Every setting the code reads, with its default:
 | `SWW_TAG_LISTS`                          | empty                                                                          | Address lists that each add a tag to their clients' requests, as `name=URL` pairs, such as `torexit=https://example.com/tor.txt`.                                                                                                                               |
 | `SWW_TAG_DENY`                           | empty                                                                          | Tags whose requests are refused, such as `torexit,country=CN`.                                                                                                                                                                                                  |
 | `SWW_TAG_LIMIT_PERCENT`                  | empty                                                                          | Tags whose clients get a percentage, from 1 to 99, of every request and byte limit, such as `vpn:50,asn=14061:25`; the lowest applies.                                                                                                                          |
+| `SWW_ROUTEWATCH_URL`                     | unset                                                                          | The URL of a routewatch instance, which gives each client's `asn=` and `prefix=` tags. Unset, nothing asks routewatch.                                                                                                                                          |
 | `SWW_ASN_BYTES_PERCENT`                  | empty                                                                          | A percentage of the byte limits alone for the AS numbers listed, in place of their `asn=` tag's percentage.                                                                                                                                                     |
 | `SWW_COUNTRY_BYTES_PERCENT`              | empty                                                                          | A percentage of the byte limits alone for the countries listed, in place of their `country=` tag's percentage.                                                                                                                                                  |
 | `SWW_UNKNOWN_LIMIT_PERCENT`              | `100`                                                                          | The percentage of every limit a client without a country gets.                                                                                                                                                                                                  |
@@ -567,7 +568,9 @@ the `tags` field of its log line:
   or `vpn=mullvad`;
 - `crowdsec`, `dnsbl=<zone>` and `abuseipdb`, when that reputation source lists
   the client;
-- `exploitsignature`, when a rule file or the Core Rule Set matched the request.
+- `exploitsignature`, when a rule file or the Core Rule Set matched the request;
+- `asn=<number>` and `prefix=<netblock>`, from a routewatch instance, while
+  `SWW_ROUTEWATCH_URL` is set.
 
 `SWW_TAG_DENY` refuses requests by tag, and `SWW_TAG_LIMIT_PERCENT` lowers a
 client's limits by tag. See "Request tags" in [`SPEC.md`](SPEC.md).
@@ -630,8 +633,8 @@ is set aside as `<name>.bad`, and never stops the running process (see
 - `internal/discriminator`: `discriminator`'s server, which runs the checks and
   answers its own endpoints.
 - `internal/ratelimit`, `internal/bans`, `internal/rules`, `internal/waf`,
-  `internal/lookup`, `internal/reputation`, `internal/anomaly` and
-  `internal/alerts`: one check or source each.
+  `internal/lookup`, `internal/reputation`, `internal/routewatch`,
+  `internal/anomaly` and `internal/alerts`: one check or source each.
 - `internal/state`, `internal/requestlog`, `internal/remotelog` and
   `internal/metrics`: the state files, the log lines, the syslog sender and the
   metrics.

SPEC.md

@@ -87,6 +87,8 @@ to them.
       database.
     - `internal/reputation`: fetches the lists, asks the DNS blocklists and
       AbuseIPDB in the background, and keeps their answers.
+    - `internal/routewatch`: asks a routewatch instance about clients in the
+      background, and keeps its answers.
     - `internal/anomaly`: the anomaly counters and their alerts.
     - `internal/alerts`: holds back repeats and alerts past the hourly limit,
       and sends the rest to the webhook, Slack and ntfy, each from a queue of
@@ -144,7 +146,9 @@ request log's `heuristic` field gives that name. `refusal_limit` and
       around its address, a /64 by default, since one abuser usually controls a
       whole /64. A client is therefore one IPv4 address or one IPv6 group.
 3. The tag lists (`tag_lists`; see "Request tags"). Each list that holds the
-   client adds its tag. A client in `SWW_ALLOW_NETS` gets no tag.
+   client adds its tag. Next, `routewatch_tags` adds the client's `asn=` and
+   `prefix=` tags while `SWW_ROUTEWATCH_URL` is set. A client in
+   `SWW_ALLOW_NETS` gets no tag.
 4. The static lists. A client in `SWW_ALLOW_NETS` skips steps 5 to 15, the byte
    limits and the error burst. A client in `SWW_DENY_NETS` is refused
    (`deny_nets`); a client in both lists is let through.
@@ -554,6 +558,21 @@ Each tag and where it comes from:
 - `exploitsignature`, when a rule file or the Core Rule Set matched the request.
   For the Core Rule Set a match is a score at or over
   `SWW_WAF_ANOMALY_THRESHOLD`.
+- `asn=<number>` and `prefix=<netblock>` from a routewatch instance
+  (`routewatch_tags`), while `SWW_ROUTEWATCH_URL` is set:
+    - The tag `prefix=` holds the netblock the client's address is announced in,
+      such as `prefix=192.0.2.0/24`.
+    - An `asn=` tag has the same spelling as the lookup's. When routewatch and
+      the lookup give the same AS number, a request has one `asn=` tag. When
+      they differ, it has both.
+    - They are added before `deny_nets`, so the log line of a request it refused
+      has them.
+    - `discriminator` asks routewatch in the background and never waits for it.
+      An answer is kept for 1 hour, in memory only.
+    - After a query fails, routewatch is not asked for 1 minute.
+    - A request without these tags gives the reason in the log field
+      `routewatch_tags_missing` (see
+      [`docs/request-log.md`](docs/request-log.md)).
 
 A client in `SWW_ALLOW_NETS` skips the checks and gets no tag. Every tag is in
 lower case, except a country code, which is in capitals. `SWW_TAG_DENY` and
@@ -571,7 +590,9 @@ Two settings act on tags:
 
 The tag settings are empty by default, for the same reason as the country list.
 The lookup waits for GeoJS when either names an `asn=` or `country=` tag. A
-setting that names one stops the start while `SWW_LOOKUP_SOURCE` is `off`.
+setting that names one stops the start while `SWW_LOOKUP_SOURCE` is `off`. The
+exception is an `asn=` tag while `SWW_ROUTEWATCH_URL` is set, since routewatch
+gives that tag.
 
 ### Biased thresholds
 

docs/request-log.md

@@ -173,6 +173,12 @@ Every one of these lines has:
     - `abuseipdb`.
 - `tags`: the request's tags, sorted, left out when it has none. Each tag and
   where it comes from is under "Request tags" in [`SPEC.md`](../SPEC.md).
+- `routewatch_tags_missing`: why the request got no tags from routewatch,
+  present only while `SWW_ROUTEWATCH_URL` is set:
+    - `no_answer_yet`: routewatch has not answered about this client yet;
+    - `request_failed`: a query to routewatch failed within the last minute, and
+      the process log says why;
+    - `no_route`: routewatch knows no live route for the address.
 - `offence`: `limit`, for a request that broke a limit.
 - `ban_expires`: when the client's ban ends, for a request that made one or was
   refused under one: a time, or `permanent`.

docs/settings.md

@@ -145,8 +145,8 @@ cut off; the client is banned.
   the start while a setting that needs a lookup is set:
     - `SWW_EXCLUSIVELY_ALLOWED_COUNTRIES`;
     - `SWW_ADD_LOOKUP_HEADERS`;
-    - `SWW_TAG_DENY` or `SWW_TAG_LIMIT_PERCENT` naming an `asn=` or `country=`
-      tag;
+    - `SWW_TAG_DENY` or `SWW_TAG_LIMIT_PERCENT` naming a `country=` tag, or an
+      `asn=` tag while `SWW_ROUTEWATCH_URL` is unset;
     - the two byte percentage lists and `SWW_ASN_LIMIT_PERCENT_URL`;
     - `SWW_UNKNOWN_LIMIT_PERCENT` below `100`;
     - an anomaly threshold per AS number.
@@ -186,11 +186,20 @@ Every request gets tags from what `discriminator` knows of its client. See
   `exploitsignature`: a request gets that tag after the rate limits have counted
   it.
 
+- `SWW_ROUTEWATCH_URL` (default unset): the `http` or `https` URL of a
+  routewatch instance. [routewatch](https://git.eeqj.de/sneak/routewatch) is a
+  service that gives an address's announced netblock and origin AS.
+  `discriminator` asks it about each client, in the background, and adds the
+  tags `asn=<number>` and `prefix=<netblock>` from its answer. While it is
+  unset, nothing asks routewatch and no request gets a `prefix=` tag.
+
 `SWW_TAG_DENY` and `SWW_TAG_LIMIT_PERCENT` accept tags in either case. A tag
 that no request can get stops the start. A request can get only these:
 
 - a name in `SWW_TAG_LISTS`;
 - an `asn=` or `country=` tag;
+- a `prefix=` tag with a netblock, while `SWW_ROUTEWATCH_URL` is set. It matches
+  only that exact announced netblock, such as `prefix=192.0.2.0/24`;
 - a `dnsbl=` tag of a zone in `SWW_DNSBL_ZONES`, in lower case, with a key
   masked as the `reputation` field shows it;
 - `abuseipdb`, while `SWW_ABUSEIPDB_KEY` is set;

internal/config/config.go

@@ -12,6 +12,7 @@ import (
 	"errors"
 	"fmt"
 	"log/slog"
+	"maps"
 	"math"
 	"net"
 	"net/http"
@@ -106,6 +107,9 @@ type Config struct {
 	TagLists        []TagList
 	TagDeny         []string
 	TagLimitPercent map[string]int64
+	// RouteWatchURL is where the routewatch instance is that adds the asn=
+	// and prefix= tags, "" for none (SWW_ROUTEWATCH_URL).
+	RouteWatchURL string
 	// The biased thresholds. ASNBytesPercent and CountryBytesPercent give
 	// those they list a percentage of the byte limits in place of the one
 	// TagLimitPercent gives their asn= or country= tag
@@ -475,7 +479,9 @@ var (
 		"is not a tag, : and a percentage, such as vpn:50 or asn=14061:25")
 	errNotTagPercent = errors.New("is not a percentage from 1 to 99")
 	errNotASNTag     = errors.New("is not asn= and a number, such as asn=14061")
-	errExploitTag    = errors.New(
+	errNotPrefixTag  = errors.New(
+		"is not prefix= and a netblock, such as prefix=192.0.2.0/24")
+	errExploitTag = errors.New(
 		"cannot lower limits: the rate limits count a request before its " +
 			"rules are matched")
 	errCrowdSecTag = errors.New(
@@ -483,8 +489,9 @@ var (
 	errNoRequestGetsTag = errors.New(
 		"is a tag no request can get: it is not a name in SWW_TAG_LISTS, an " +
 			"asn= or country= tag, a dnsbl= tag of a zone in SWW_DNSBL_ZONES, " +
-			"abuseipdb with SWW_ABUSEIPDB_KEY set, or exploitsignature with " +
-			"rule files or the Core Rule Set on")
+			"a prefix= tag with SWW_ROUTEWATCH_URL set, abuseipdb with " +
+			"SWW_ABUSEIPDB_KEY set, or exploitsignature with rule files or the " +
+			"Core Rule Set on")
 )
 
 // FromEnvironment reads the settings with lookupEnv, normally
@@ -524,6 +531,7 @@ func FromEnvironment(
 		TagLists:             env.tagLists("SWW_TAG_LISTS"),
 		TagDeny:              env.tags("SWW_TAG_DENY"),
 		TagLimitPercent:      env.tagPercents("SWW_TAG_LIMIT_PERCENT"),
+		RouteWatchURL:        env.listURL("SWW_ROUTEWATCH_URL"),
 		ASNBytesPercent:      env.percents("SWW_ASN_BYTES_PERCENT", ParseASN),
 		CountryBytesPercent:  env.percents("SWW_COUNTRY_BYTES_PERCENT", parseCountry),
 		UnknownLimitPercent:  env.percent("SWW_UNKNOWN_LIMIT_PERCENT", "100"),
@@ -1064,14 +1072,21 @@ func (e *environment) checkCountriesAndLookups(cfg *Config) {
 		return
 	}
 
+	// routewatch gives asn= tags too.
+	onlyLookupGives := func(tag string) bool {
+		return isLookupTag(tag) &&
+			(cfg.RouteWatchURL == "" || !strings.HasPrefix(tag, ASNTagPrefix))
+	}
+
 	for _, setting := range []struct {
 		name string
 		set  bool
 	}{
 		{"SWW_EXCLUSIVELY_ALLOWED_COUNTRIES", len(cfg.ExclusivelyAllowedCountries) > 0},
 		{"SWW_ADD_LOOKUP_HEADERS", cfg.AddLookupHeaders},
-		{"SWW_TAG_DENY", slices.ContainsFunc(cfg.TagDeny, isLookupTag)},
-		{"SWW_TAG_LIMIT_PERCENT", tagLimitNeedsLookups(cfg)},
+		{"SWW_TAG_DENY", slices.ContainsFunc(cfg.TagDeny, onlyLookupGives)},
+		{"SWW_TAG_LIMIT_PERCENT", slices.ContainsFunc(
+			slices.Collect(maps.Keys(cfg.TagLimitPercent)), onlyLookupGives)},
 		{"SWW_ASN_BYTES_PERCENT", len(cfg.ASNBytesPercent) > 0},
 		{"SWW_COUNTRY_BYTES_PERCENT", len(cfg.CountryBytesPercent) > 0},
 		{"SWW_UNKNOWN_LIMIT_PERCENT", cfg.UnknownLimitPercent < 100},
@@ -1171,6 +1186,10 @@ func requestCanGetTag(cfg *Config, tag string) bool {
 		return cfg.AbuseIPDBKey != ""
 	}
 
+	if strings.HasPrefix(tag, PrefixTagPrefix) {
+		return cfg.RouteWatchURL != ""
+	}
+
 	zone, isZoneTag := strings.CutPrefix(tag, DNSBLTagPrefix)
 
 	return isZoneTag && slices.ContainsFunc(cfg.DNSBLZones, func(each string) bool {
@@ -1179,7 +1198,7 @@ func requestCanGetTag(cfg *Config, tag string) bool {
 }
 
 // TagsNeedLookup reports whether SWW_TAG_DENY or SWW_TAG_LIMIT_PERCENT
-// names an asn= or country= tag, which only the lookup can give a request.
+// names an asn= or country= tag.
 func (c *Config) TagsNeedLookup() bool {
 	return slices.ContainsFunc(c.TagDeny, isLookupTag) || tagLimitNeedsLookups(c)
 }
@@ -1923,6 +1942,7 @@ const (
 	ASNTagPrefix     = "asn="
 	CountryTagPrefix = "country="
 	DNSBLTagPrefix   = "dnsbl="
+	PrefixTagPrefix  = "prefix="
 	AbuseIPDBTag     = "abuseipdb"
 	CrowdSecTag      = "crowdsec"
 	// ExploitSignatureTag is the tag of a request a rule file or the Core
@@ -1999,9 +2019,10 @@ func parseTags(value string) ([]string, error) {
 
 // parseTag reads a tag in either case, with spaces around it, and returns it
 // as a request carries it: in lower case, but for a country code, which is in
-// capitals, and an asn= tag's number without leading zeros. An asn= or
-// country= tag must name a number or a country, so that a mistyped one stops
-// the start instead of never matching.
+// capitals, an asn= tag's number without leading zeros, and a prefix= tag's
+// netblock as routewatch writes it. An asn=, country= or prefix= tag must name
+// a number, a country or a netblock, so that a mistyped one stops the start
+// instead of never matching.
 func parseTag(value string) (string, error) {
 	tag := strings.ToLower(strings.TrimSpace(value))
 
@@ -2023,6 +2044,15 @@ func parseTag(value string) (string, error) {
 		return CountryTagPrefix + country, nil
 	}
 
+	if text, isPrefix := strings.CutPrefix(tag, PrefixTagPrefix); isPrefix {
+		netblock, err := netip.ParsePrefix(text)
+		if err != nil || netblock != netblock.Masked() {
+			return "", fmt.Errorf("%q %w", value, errNotPrefixTag)
+		}
+
+		return PrefixTagPrefix + netblock.String(), nil
+	}
+
 	return tag, nil
 }
 

internal/config/config_test.go

@@ -61,6 +61,7 @@ const (
 	reputationAction     = "SWW_REPUTATION_ACTION"
 	reputationCacheTTL   = "SWW_REPUTATION_CACHE_TTL"
 	reputationTimeout    = "SWW_REPUTATION_TIMEOUT"
+	routeWatchURL        = "SWW_ROUTEWATCH_URL"
 	crowdSecURL          = "SWW_CROWDSEC_LAPI_URL"
 	crowdSecKey          = "SWW_CROWDSEC_LAPI_KEY"
 	banResponse          = "SWW_BAN_RESPONSE"
@@ -1403,6 +1404,54 @@ func TestTagSettingsAsSet(t *testing.T) {
 	}
 }
 
+func TestRouteWatchURLAndPrefixTags(t *testing.T) {
+	t.Parallel()
+
+	const rw = "https://routewatch.example"
+
+	if cfg := fromEnvironment(t, environment{}); cfg.RouteWatchURL != "" {
+		t.Errorf("default %s is %q, want unset", routeWatchURL, cfg.RouteWatchURL)
+	}
+
+	cfg := fromEnvironment(t, environment{
+		routeWatchURL: rw, tagDeny: "prefix=2001:DB8::/32",
+		tagLimitPercent: "prefix=192.0.2.0/24:50",
+	})
+	wantDeny := []string{"prefix=2001:db8::/32"}
+
+	if cfg.RouteWatchURL != rw || !slices.Equal(cfg.TagDeny, wantDeny) ||
+		cfg.TagLimitPercent["prefix=192.0.2.0/24"] != 50 {
+		t.Errorf("gave %q, %v, %v", cfg.RouteWatchURL, cfg.TagDeny, cfg.TagLimitPercent)
+	}
+
+	// routewatch gives asn= tags too, so an asn= tag needs no lookups while it is set.
+	fromEnvironment(t, environment{
+		lookupSource: off, routeWatchURL: rw, tagDeny: "asn=64496",
+	})
+
+	for _, stopped := range []struct {
+		env  environment
+		name string
+	}{
+		{environment{routeWatchURL: "ftp://routewatch.example"}, routeWatchURL},
+		{environment{routeWatchURL: "routewatch.example"}, routeWatchURL},
+		{environment{tagDeny: "prefix=192.0.2.0/24"}, tagDeny},
+		{environment{routeWatchURL: rw, tagDeny: "prefix=nowhere"}, tagDeny},
+		{environment{routeWatchURL: rw, tagDeny: "prefix=192.0.2.5/24"}, tagDeny},
+		{
+			environment{routeWatchURL: rw, tagLimitPercent: "prefix=192.0.2.0/33:50"},
+			tagLimitPercent,
+		},
+		{environment{lookupSource: off, routeWatchURL: rw, tagDeny: "country=DE"}, tagDeny},
+		{environment{lookupSource: off, tagDeny: "asn=64496"}, tagDeny},
+	} {
+		_, err := config.FromEnvironment(stopped.env.lookupEnv)
+		if err == nil || !strings.HasPrefix(err.Error(), stopped.name+": ") {
+			t.Errorf("%v gave the error %v, want one naming %s", stopped.env, err, stopped.name)
+		}
+	}
+}
+
 func TestTagThatNoRequestCanGetIsToldApartFromOneItCan(t *testing.T) {
 	t.Parallel()
 
@@ -2503,6 +2552,7 @@ func TestLogsEachSettingWithItsValue(t *testing.T) {
 		reputationAction:     "limit:25",
 		reputationCacheTTL:   defaultReputationCacheTTL,
 		reputationTimeout:    "2s",
+		routeWatchURL:        "",
 		crowdSecURL:          "",
 		crowdSecKey:          "",
 		banResponse:          "403",

internal/discriminator/discriminator.go

@@ -123,6 +123,7 @@ func New(params Params) *Server {
 		Lists:      h.lists,
 		DNSBL:      h.dnsbl,
 		AbuseIPDB:  h.abuseIPDB,
+		RouteWatch: h.routeWatch,
 		Metrics:    h.metrics,
 	}
 }

internal/discriminator/heuristics.go

@@ -44,6 +44,7 @@ const (
 func beforeLookup() []heuristic {
 	return []heuristic{
 		tagLists{},
+		routeWatchTags{},
 		denyNets{},
 		activeBan{},
 	}

internal/discriminator/proxy.go

@@ -20,6 +20,7 @@ import (
 	"sneak.berlin/go/smallwebwaf/internal/metrics"
 	"sneak.berlin/go/smallwebwaf/internal/ratelimit"
 	"sneak.berlin/go/smallwebwaf/internal/reputation"
+	"sneak.berlin/go/smallwebwaf/internal/routewatch"
 	"sneak.berlin/go/smallwebwaf/internal/rules"
 	"sneak.berlin/go/smallwebwaf/internal/waf"
 )
@@ -85,7 +86,8 @@ type Params struct {
 // Server is the server discriminator runs, with the parts whose state the state
 // files keep, the lookup database, nil unless SWW_LOOKUP_SOURCE is file, the
 // lists fetched from URLs, which its Run fetches, the DNSBL zones' verdicts,
-// AbuseIPDB's scores and checks spent, and the metrics.
+// AbuseIPDB's scores and checks spent, and the metrics. RouteWatch, nil while
+// SWW_ROUTEWATCH_URL is unset, keeps its answers in memory only.
 type Server struct {
 	*http.Server
 
@@ -97,6 +99,7 @@ type Server struct {
 	Lists      *reputation.Lists
 	DNSBL      *reputation.DNSBL
 	AbuseIPDB  *reputation.AbuseIPDB
+	RouteWatch *routewatch.Client
 	Metrics    *metrics.Metrics
 }
 
@@ -152,6 +155,12 @@ func newHandler(params Params) *handler {
 		coreRuleSet: params.CoreRuleSet,
 		alerts:      params.Alerts,
 	}
+	if params.Config.RouteWatchURL != "" {
+		h.routeWatch = routewatch.New(routewatch.Params{
+			URL: params.Config.RouteWatchURL, Now: params.Now, ProcessLog: params.ProcessLog,
+		})
+	}
+
 	h.geojs = lookup.New(lookup.Params{
 		URL:     params.GeoJSURL,
 		Timeout: params.Config.LookupTimeout,
@@ -255,6 +264,7 @@ type handler struct {
 	lists       *reputation.Lists
 	dnsbl       *reputation.DNSBL
 	abuseIPDB   *reputation.AbuseIPDB
+	routeWatch  *routewatch.Client
 	rules       *rules.Files
 	coreRuleSet *waf.CoreRuleSet
 	alerts      *alerts.Queue

internal/discriminator/routewatchtags.go

@@ -0,0 +1,42 @@
+package discriminator
+
+// The heuristic routewatch_tags. It reads SWW_ROUTEWATCH_URL.
+
+import (
+	"context"
+	"strconv"
+	"time"
+
+	"sneak.berlin/go/smallwebwaf/internal/config"
+)
+
+// routeWatchTags adds to the request the tags asn=<number> and prefix=<netblock>
+// from what routewatch answered about the client. It refuses nothing, and the
+// request does not wait for routewatch. A request that gets no tags from it has
+// the reason in the log line's routewatch_tags_missing. While SWW_ROUTEWATCH_URL
+// is unset it does nothing. Answers are kept by client and asked for by the
+// request's address, and a route without an origin AS gives only the prefix= tag.
+type routeWatchTags struct{}
+
+func (routeWatchTags) name() string { return "routewatch_tags" }
+
+func (routeWatchTags) check(ctx context.Context, rq *request, _ time.Time) *verdict {
+	if rq.h.routeWatch == nil {
+		return nil
+	}
+
+	route, missing := rq.h.routeWatch.Route(ctx, rq.h.clientGroup(rq.client), rq.client)
+	if missing != "" {
+		rq.line.RouteWatchTagsMissing = string(missing)
+
+		return nil
+	}
+
+	rq.addTag(config.PrefixTagPrefix + route.Netblock.String())
+
+	if route.ASN != 0 {
+		rq.addTag(config.ASNTagPrefix + strconv.FormatUint(uint64(route.ASN), 10))
+	}
+
+	return nil
+}

internal/discriminator/routewatchtags_test.go

@@ -0,0 +1,245 @@
+package discriminator_test
+
+import (
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"net/netip"
+	"strings"
+	"testing"
+	"time"
+
+	"sneak.berlin/go/smallwebwaf/internal/discriminator"
+	"sneak.berlin/go/smallwebwaf/internal/requestlog"
+)
+
+// routeWatchURL is SWW_ROUTEWATCH_URL, and tagsMissing the log line's field
+// that says why a request got no tags from routewatch.
+const (
+	routeWatchURL = "SWW_ROUTEWATCH_URL"
+	tagsMissing   = "routewatch_tags_missing"
+	fromV6        = "2001:db8:1::5"
+	prefixV6      = "2001:db8::/32"
+	prefixDE      = "203.0.113.0/24"
+	prefixKP      = "198.51.100.0/24"
+)
+
+// standInRoute is what the stand-in for routewatch answers about an address.
+type standInRoute struct {
+	Netblock string `json:"netblock"`
+	ASN      int    `json:"asn"`
+}
+
+// startRouteWatch starts a stand-in for routewatch's IP info API that knows the
+// routes given by address, and returns its URL.
+func startRouteWatch(t *testing.T, routes map[string]standInRoute) string {
+	t.Helper()
+
+	server := httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			address := strings.TrimPrefix(r.URL.Path, "/api/v1/ip/")
+
+			result := map[string]any{"ip": address}
+			if route, known := routes[address]; known {
+				result["netblock"], result["asn"] = route.Netblock, route.ASN
+			}
+
+			_ = json.NewEncoder(w).Encode(map[string]any{
+				"status": "ok",
+				"data":   map[string]any{"results": []any{result}},
+			})
+		}))
+	t.Cleanup(server.Close)
+
+	return server.URL
+}
+
+// waitForRouteWatch waits until routewatch's answer about from, in the client
+// group of the given length, is kept, so that the next request gets its tags.
+func waitForRouteWatch(
+	t *testing.T, server *discriminator.Server, from string, bits int,
+) {
+	t.Helper()
+
+	addr := netip.MustParseAddr(from)
+	client := netip.PrefixFrom(addr, bits).Masked()
+	deadline := time.Now().Add(5 * time.Second)
+
+	for {
+		_, missing := server.RouteWatch.Route(context.Background(), client, addr)
+		if missing == "" {
+			return
+		}
+
+		if time.Now().After(deadline) {
+			t.Fatalf("routewatch's answer about %s not kept: %q", from, missing)
+		}
+
+		time.Sleep(time.Millisecond)
+	}
+}
+
+func wantTagsMissing(t *testing.T, line logLine, want string) {
+	t.Helper()
+
+	got, _ := line.fields[tagsMissing].(string)
+	if got != want {
+		t.Errorf("log line has %s %q, want %q", tagsMissing, got, want)
+	}
+}
+
+func TestRouteWatchTagsAreOnTheLogLineWithTheLookupsTags(t *testing.T) {
+	t.Parallel()
+
+	url := startRouteWatch(t, map[string]standInRoute{fromDE: {prefixDE, 64496}})
+	s, server, _ := startWithLookups(t, map[string]string{routeWatchURL: url})
+
+	waitForRouteWatch(t, server, fromDE, 32)
+
+	line := s.get(fromDE, http.StatusOK, requestlog.ActionForward)
+	wantTags(t, line, "asn=64496", "country=DE", "prefix="+prefixDE)
+	wantTagsMissing(t, line, "")
+}
+
+func TestRouteWatchTagsAreOnALineDenyNetsRefused(t *testing.T) {
+	t.Parallel()
+
+	url := startRouteWatch(t, map[string]standInRoute{fromKP: {prefixKP, 64511}})
+	s, _, server := startWithClock(t, "", map[string]string{
+		lookupSource: off, routeWatchURL: url, denyNets: fromKP,
+	})
+
+	waitForRouteWatch(t, server, fromKP, 32)
+
+	line := s.get(fromKP, http.StatusForbidden, requestlog.ActionDenied)
+	wantHeuristic(t, line, "deny_nets", `{"netblock": "`+fromKP+`/32"}`)
+	wantTags(t, line, "asn=64511", "prefix="+prefixKP)
+}
+
+func TestRouteWithoutAnOriginASGivesOnlyThePrefixTag(t *testing.T) {
+	t.Parallel()
+
+	url := startRouteWatch(t, map[string]standInRoute{fromDE: {prefixDE, 0}})
+	s, _, server := startWithClock(t, "", map[string]string{
+		lookupSource: off, routeWatchURL: url,
+	})
+
+	waitForRouteWatch(t, server, fromDE, 32)
+
+	wantTags(t, s.get(fromDE, http.StatusOK, requestlog.ActionForward),
+		"prefix="+prefixDE)
+}
+
+func TestUnsetRouteWatchChangesNothing(t *testing.T) {
+	t.Parallel()
+
+	s, _, server := startWithClock(t, "", map[string]string{lookupSource: off})
+
+	if server.RouteWatch != nil {
+		t.Error("RouteWatch is set while SWW_ROUTEWATCH_URL is unset")
+	}
+
+	line := s.get(fromDE, http.StatusOK, requestlog.ActionForward)
+	if _, present := line.fields[tagsMissing]; present {
+		t.Errorf("log line has %s", tagsMissing)
+	}
+
+	if _, present := line.fields["tags"]; present {
+		t.Errorf("log line has tags %v", line.fields["tags"])
+	}
+}
+
+func TestUnreachableRouteWatchLetsTheRequestThroughAndSaysWhy(t *testing.T) {
+	t.Parallel()
+
+	// A stand-in that is closed at once, so that the port refuses connections.
+	dead := httptest.NewServer(http.NotFoundHandler())
+	url := dead.URL
+
+	dead.Close()
+
+	s, _, _ := startWithClock(t, "", map[string]string{
+		lookupSource: off, routeWatchURL: url,
+	})
+
+	wantTagsMissing(t, s.get(fromDE, http.StatusOK, requestlog.ActionForward),
+		"no_answer_yet")
+
+	deadline := time.Now().Add(5 * time.Second)
+
+	for {
+		line := s.get(fromDE, http.StatusOK, requestlog.ActionForward)
+
+		missing, _ := line.fields[tagsMissing].(string)
+		if missing == "request_failed" {
+			return
+		}
+
+		if time.Now().After(deadline) {
+			t.Fatalf("still %q, want request_failed", missing)
+		}
+
+		time.Sleep(time.Millisecond)
+	}
+}
+
+func TestAddressWithoutARouteHasNoTagsAndTheLineSaysSo(t *testing.T) {
+	t.Parallel()
+
+	s, _, _ := startWithClock(t, "", map[string]string{
+		lookupSource: off, routeWatchURL: startRouteWatch(t, nil),
+	})
+
+	deadline := time.Now().Add(5 * time.Second)
+
+	for {
+		line := s.get(fromDE, http.StatusOK, requestlog.ActionForward)
+
+		missing, _ := line.fields[tagsMissing].(string)
+		if missing == "no_route" {
+			return
+		}
+
+		if time.Now().After(deadline) {
+			t.Fatalf("still %q, want no_route", missing)
+		}
+
+		time.Sleep(time.Millisecond)
+	}
+}
+
+func TestTagDenyRefusesOnARouteWatchPrefix(t *testing.T) {
+	t.Parallel()
+
+	url := startRouteWatch(t, map[string]standInRoute{
+		fromDE: {prefixDE, 64496}, fromKP: {prefixKP, 64511},
+	})
+	s, _, server := startWithClock(t, "", map[string]string{
+		lookupSource: off, routeWatchURL: url, tagDeny: "prefix=" + prefixKP,
+	})
+
+	waitForRouteWatch(t, server, fromKP, 32)
+	waitForRouteWatch(t, server, fromDE, 32)
+
+	wantHeuristic(t, s.get(fromKP, http.StatusForbidden, requestlog.ActionDenied),
+		"tag_deny", `{"tag": "prefix=`+prefixKP+`"}`)
+	s.get(fromDE, http.StatusOK, requestlog.ActionForward)
+}
+
+func TestTagLimitPercentWorksWithAnIPv6Prefix(t *testing.T) {
+	t.Parallel()
+
+	url := startRouteWatch(t, map[string]standInRoute{fromV6: {prefixV6, 64496}})
+	s, _, server := startWithClock(t, "", map[string]string{
+		lookupSource: off, routeWatchURL: url, rateLimitPerMinute: "2",
+		tagLimitPercent: "prefix=" + prefixV6 + ":50",
+	})
+
+	waitForRouteWatch(t, server, fromV6, 64)
+
+	// Half of two is one: the second request breaks the limit.
+	line := s.get(fromV6, http.StatusOK, requestlog.ActionForward)
+	wantTags(t, line, "asn=64496", "prefix="+prefixV6)
+	s.get(fromV6, http.StatusForbidden, requestlog.ActionRateLimited)
+}

internal/requestlog/requestlog.go

@@ -182,6 +182,10 @@ type Line struct {
 	Reputation []string `json:"reputation,omitempty"`
 	// Tags are the request's tags, sorted.
 	Tags []string `json:"tags,omitempty"`
+	// RouteWatchTagsMissing, while SWW_ROUTEWATCH_URL is set, says why the
+	// request got no tags from routewatch: no_answer_yet, request_failed or
+	// no_route.
+	RouteWatchTagsMissing string `json:"routewatch_tags_missing,omitempty"`
 	// Offence is the offence the request was held as, OffenceLimit.
 	Offence string `json:"offence,omitempty"`
 	// BanExpires is when the ban the request made, or was refused under,

internal/routewatch/routewatch.go

@@ -0,0 +1,243 @@
+// Package routewatch asks a routewatch instance about client addresses, in the
+// background, and keeps its answers in memory. A routewatch instance knows, for
+// an address, the netblock it is announced in and the AS that originates it.
+package routewatch
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/netip"
+	"net/url"
+	"sync"
+	"time"
+
+	"github.com/hashicorp/golang-lru/v2/simplelru"
+)
+
+const (
+	// answerKept is how long an answer is used after it came.
+	answerKept = time.Hour
+	// failureKept is how long routewatch is not asked again after a query
+	// fails, so that a dead routewatch is not asked on every request.
+	failureKept = time.Minute
+	// queryTimeout is how long one query may take. routewatch answers only
+	// after a reverse DNS lookup it allows 2 seconds, so this is longer.
+	queryTimeout = 5 * time.Second
+	// maxAnswers is how many answers are kept. Past it, the one that came
+	// longest ago is dropped.
+	maxAnswers = 100000
+	// maxQueries is how many queries may be under way at once. Past it, a
+	// client is not asked about until its next request, so that a swarm of
+	// new addresses cannot fill the memory.
+	maxQueries = 100
+	// maxAnswerBytes is the most of an answer that is read.
+	maxAnswerBytes = 64 << 10
+)
+
+// Missing is why Route gives no route. The request log's field
+// routewatch_tags_missing gives these values.
+type Missing string
+
+const (
+	// NoAnswerYet is a client routewatch has not answered about yet.
+	NoAnswerYet Missing = "no_answer_yet"
+	// RequestFailed is no answer because a recent query failed.
+	RequestFailed Missing = "request_failed"
+	// NoRoute is routewatch knowing no live route for the address.
+	NoRoute Missing = "no_route"
+)
+
+var (
+	errStatus      = errors.New("routewatch answered")
+	errNoResult    = errors.New("the answer holds no result")
+	errNotNetblock = errors.New("the answer's netblock is not a netblock")
+)
+
+// Route is what routewatch knows of an address: the netblock it is announced
+// in, and the AS that originates it.
+type Route struct {
+	Netblock netip.Prefix
+	ASN      uint32
+}
+
+// Params are what New needs.
+type Params struct {
+	// URL is where routewatch is (SWW_ROUTEWATCH_URL).
+	URL string
+	// Now tells the time, normally time.Now in UTC.
+	Now func() time.Time
+	// ProcessLog receives the query that fails, and why.
+	ProcessLog *slog.Logger
+}
+
+// Client asks a routewatch instance about clients, in the background, and keeps
+// its answers. It is safe for concurrent use.
+type Client struct {
+	params     Params
+	httpClient *http.Client
+
+	mu sync.Mutex
+	// answers are by client. Each is added as it comes and never moved up,
+	// so that the one that came longest ago is the first dropped.
+	answers *simplelru.LRU[netip.Prefix, answer]
+	// asking are the clients whose query is under way.
+	asking map[netip.Prefix]bool
+	// retryAt is when routewatch may be asked again after a query failed.
+	retryAt time.Time
+}
+
+// answer is one kept answer: the route, or why there is none, and when it came.
+type answer struct {
+	route   Route
+	missing Missing
+	came    time.Time
+}
+
+// New returns a Client with no answer yet.
+func New(params Params) *Client {
+	answers, err := simplelru.NewLRU[netip.Prefix, answer](maxAnswers, nil)
+	if err != nil {
+		panic(err) // NewLRU fails only for a size below one
+	}
+
+	return &Client{
+		params:     params,
+		httpClient: &http.Client{},
+		answers:    answers,
+		asking:     map[netip.Prefix]bool{},
+	}
+}
+
+// Route returns what routewatch answered about client, an IPv4 address or an
+// IPv6 group, or why it has no route. It never waits for a query. A client
+// without an answer is asked about in the background, by addr, the address its
+// request came from, unless its query is under way, a query failed less than
+// failureKept ago, or maxQueries are under way. ctx is the context of the
+// client's request, and a query goes on after the request ends.
+func (c *Client) Route(
+	ctx context.Context, client netip.Prefix, addr netip.Addr,
+) (Route, Missing) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	now := c.params.Now()
+
+	kept, found := c.answers.Peek(client)
+	if found && now.Sub(kept.came) < answerKept {
+		return kept.route, kept.missing
+	}
+
+	if now.Before(c.retryAt) {
+		return Route{}, RequestFailed
+	}
+
+	if !c.asking[client] && len(c.asking) < maxQueries {
+		c.asking[client] = true
+
+		go c.ask(context.WithoutCancel(ctx), client, addr)
+	}
+
+	return Route{}, NoAnswerYet
+}
+
+// ask asks routewatch about addr, keeps the answer as client's, and notes the
+// query as no longer under way. A query that fails gives no answer, and
+// routewatch is not asked again for failureKept. Only the first failure of
+// those under way is logged.
+func (c *Client) ask(ctx context.Context, client netip.Prefix, addr netip.Addr) {
+	route, missing, err := c.query(ctx, addr)
+	now := c.params.Now()
+
+	c.mu.Lock()
+
+	delete(c.asking, client)
+
+	firstFailure := err != nil && !now.Before(c.retryAt)
+
+	if err == nil {
+		c.answers.Add(client, answer{route: route, missing: missing, came: now})
+	} else {
+		c.retryAt = now.Add(failureKept)
+	}
+
+	c.mu.Unlock()
+
+	if firstFailure {
+		c.params.ProcessLog.Warn("asking routewatch failed", "error", err.Error())
+	}
+}
+
+// query asks routewatch's IP info API about addr. An answer other than 200, one
+// that cannot be read, and none within queryTimeout, fail. A result with no
+// netblock is an address without a live route.
+func (c *Client) query(ctx context.Context, addr netip.Addr) (Route, Missing, error) {
+	ctx, cancel := context.WithTimeout(ctx, queryTimeout)
+	defer cancel()
+
+	endpoint, err := url.JoinPath(c.params.URL, "api/v1/ip", addr.String())
+	if err != nil {
+		return Route{}, "", fmt.Errorf("make the URL: %w", err)
+	}
+
+	req, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, http.NoBody)
+	if err != nil {
+		return Route{}, "", fmt.Errorf("make the request: %w", err)
+	}
+
+	req.Header.Set("Accept", "application/json")
+
+	res, err := c.httpClient.Do(req)
+	if err != nil {
+		// Do's error names the URL, which holds the client's address, which
+		// is not to be logged: only what went wrong is kept.
+		return Route{}, "", fmt.Errorf("ask routewatch: %w", errors.Unwrap(err))
+	}
+
+	defer func() {
+		_ = res.Body.Close()
+	}()
+
+	if res.StatusCode != http.StatusOK {
+		return Route{}, "", fmt.Errorf("%w %s", errStatus, res.Status)
+	}
+
+	return readAnswer(io.LimitReader(res.Body, maxAnswerBytes))
+}
+
+// readAnswer reads routewatch's answer about one address.
+func readAnswer(body io.Reader) (Route, Missing, error) {
+	var decoded struct {
+		Data struct {
+			Results []struct {
+				Netblock string `json:"netblock"`
+				ASN      uint32 `json:"asn"`
+			} `json:"results"`
+		} `json:"data"`
+	}
+
+	err := json.NewDecoder(body).Decode(&decoded)
+	if err != nil {
+		return Route{}, "", fmt.Errorf("read the answer: %w", err)
+	}
+
+	if len(decoded.Data.Results) == 0 {
+		return Route{}, "", errNoResult
+	}
+
+	result := decoded.Data.Results[0]
+	if result.Netblock == "" {
+		return Route{}, NoRoute, nil
+	}
+
+	netblock, err := netip.ParsePrefix(result.Netblock)
+	if err != nil {
+		return Route{}, "", fmt.Errorf("%w: %q", errNotNetblock, result.Netblock)
+	}
+
+	return Route{Netblock: netblock.Masked(), ASN: result.ASN}, "", nil
+}

internal/routewatch/routewatch_test.go

@@ -0,0 +1,333 @@
+package routewatch_test
+
+import (
+	"bytes"
+	"context"
+	"log/slog"
+	"net/http"
+	"net/http/httptest"
+	"net/netip"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+
+	"sneak.berlin/go/smallwebwaf/internal/routewatch"
+)
+
+const (
+	clientAddr   = "192.0.2.1"
+	routedAnswer = `{"status":"ok","data":{"results":[` +
+		`{"ip":"192.0.2.1","netblock":"192.0.2.0/24","asn":64496}]}}`
+	noRouteAnswer = `{"status":"ok","data":{"results":[{"ip":"192.0.2.1"}]}}`
+	// slowAnswer is longer than routewatch allows a reverse DNS lookup.
+	slowAnswer = 2500 * time.Millisecond
+	// waitLimit is longer than the Client allows a query.
+	waitLimit = 10 * time.Second
+)
+
+// clock is a time the tests move by hand.
+type clock struct {
+	mu  sync.Mutex
+	now time.Time
+}
+
+func (c *clock) Now() time.Time {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	return c.now
+}
+
+func (c *clock) advance(by time.Duration) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+
+	c.now = c.now.Add(by)
+}
+
+// fixture is a Client asking a stand-in for routewatch. queries counts what the
+// stand-in was asked, paths holds the last path it was asked for, and log holds
+// the process log.
+type fixture struct {
+	t       *testing.T
+	server  *httptest.Server
+	client  *routewatch.Client
+	clk     *clock
+	queries *atomic.Int32
+	path    *atomic.Value
+	log     *syncBuffer
+}
+
+// syncBuffer is a buffer the background queries can log to while a test reads it.
+type syncBuffer struct {
+	mu  sync.Mutex
+	buf bytes.Buffer
+}
+
+func (b *syncBuffer) Write(p []byte) (int, error) {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	return b.buf.Write(p)
+}
+
+func (b *syncBuffer) String() string {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	return b.buf.String()
+}
+
+func newFixture(t *testing.T, standIn http.HandlerFunc) *fixture {
+	t.Helper()
+
+	f := &fixture{
+		t:       t,
+		clk:     &clock{now: time.Date(2026, 11, 9, 0, 0, 0, 0, time.UTC)},
+		queries: &atomic.Int32{},
+		path:    &atomic.Value{},
+		log:     &syncBuffer{},
+	}
+
+	f.server = httptest.NewServer(http.HandlerFunc(
+		func(w http.ResponseWriter, r *http.Request) {
+			f.queries.Add(1)
+			f.path.Store(r.URL.Path)
+			standIn(w, r)
+		}))
+	t.Cleanup(f.server.Close)
+
+	f.client = routewatch.New(routewatch.Params{
+		URL: f.server.URL + "/", Now: f.clk.Now,
+		ProcessLog: slog.New(slog.NewTextHandler(f.log, nil)),
+	})
+
+	return f
+}
+
+func answering(body string) http.HandlerFunc {
+	return func(w http.ResponseWriter, _ *http.Request) {
+		_, _ = w.Write([]byte(body))
+	}
+}
+
+func (f *fixture) route() (routewatch.Route, routewatch.Missing) {
+	addr := netip.MustParseAddr(clientAddr)
+	client := netip.PrefixFrom(addr, addr.BitLen())
+
+	return f.client.Route(context.Background(), client, addr)
+}
+
+// waitFor asks until the answer is why, or, while why is "", until there is a
+// route, and returns the route.
+func (f *fixture) waitFor(why routewatch.Missing) routewatch.Route {
+	f.t.Helper()
+
+	deadline := time.Now().Add(waitLimit)
+
+	for {
+		route, missing := f.route()
+		if missing == why {
+			return route
+		}
+
+		if time.Now().After(deadline) {
+			f.t.Fatalf("still %q after %s, want %q", missing, waitLimit, why)
+		}
+
+		time.Sleep(time.Millisecond)
+	}
+}
+
+// wantFailureLoggedWithoutTheClient waits for the process log to name a failed
+// query, and checks that it does not name the client.
+func (f *fixture) wantFailureLoggedWithoutTheClient() {
+	f.t.Helper()
+
+	// The failure is noted before it is logged.
+	deadline := time.Now().Add(waitLimit)
+	for !strings.Contains(f.log.String(), "asking routewatch failed") {
+		if time.Now().After(deadline) {
+			f.t.Fatalf("process log %q names no failure", f.log.String())
+		}
+
+		time.Sleep(time.Millisecond)
+	}
+
+	if strings.Contains(f.log.String(), clientAddr) {
+		f.t.Errorf("process log %q names the client", f.log.String())
+	}
+}
+
+func TestRouteGivesRoutewatchsAnswerAndAsksByAddress(t *testing.T) {
+	t.Parallel()
+
+	f := newFixture(t, answering(routedAnswer))
+
+	if _, missing := f.route(); missing != routewatch.NoAnswerYet {
+		t.Errorf("before the answer: %q, want %q", missing, routewatch.NoAnswerYet)
+	}
+
+	route := f.waitFor("")
+
+	want := routewatch.Route{Netblock: netip.MustParsePrefix("192.0.2.0/24"), ASN: 64496}
+	if route != want {
+		t.Errorf("route %+v, want %+v", route, want)
+	}
+
+	if got := f.path.Load(); got != "/api/v1/ip/"+clientAddr {
+		t.Errorf("asked for path %v", got)
+	}
+}
+
+func TestAnswerAfterASlowReverseDNSLookupIsKept(t *testing.T) {
+	t.Parallel()
+
+	f := newFixture(t, func(w http.ResponseWriter, _ *http.Request) {
+		time.Sleep(slowAnswer)
+
+		_, _ = w.Write([]byte(routedAnswer))
+	})
+
+	f.route()
+
+	route := f.waitFor("")
+
+	want := routewatch.Route{Netblock: netip.MustParsePrefix("192.0.2.0/24"), ASN: 64496}
+	if route != want {
+		t.Errorf("route %+v, want %+v", route, want)
+	}
+}
+
+func TestAddressWithoutARouteIsKeptAsNoRoute(t *testing.T) {
+	t.Parallel()
+
+	f := newFixture(t, answering(noRouteAnswer))
+
+	f.route()
+	f.waitFor(routewatch.NoRoute)
+
+	if got := f.queries.Load(); got != 1 {
+		t.Errorf("%d queries, want 1", got)
+	}
+}
+
+func TestAnswerRoutewatchCannotBeTakenFromFails(t *testing.T) {
+	t.Parallel()
+
+	tests := map[string]http.HandlerFunc{
+		"500": func(w http.ResponseWriter, _ *http.Request) {
+			w.WriteHeader(http.StatusInternalServerError)
+		},
+		"not JSON":   answering("no"),
+		"no results": answering(`{"status":"ok","data":{"results":[]}}`),
+		"bad netblock": answering(
+			`{"status":"ok","data":{"results":[{"netblock":"nowhere","asn":1}]}}`),
+	}
+	for name, standIn := range tests {
+		t.Run(name, func(t *testing.T) {
+			t.Parallel()
+
+			f := newFixture(t, standIn)
+
+			f.route()
+			f.waitFor(routewatch.RequestFailed)
+			f.wantFailureLoggedWithoutTheClient()
+		})
+	}
+}
+
+func TestRefusedConnectionFailsTheQueryAndTheLogOmitsTheClient(t *testing.T) {
+	t.Parallel()
+
+	f := newFixture(t, answering(routedAnswer))
+
+	f.server.Close()
+
+	f.route()
+	f.waitFor(routewatch.RequestFailed)
+	f.wantFailureLoggedWithoutTheClient()
+}
+
+func TestFailureIsKeptForAMinuteSoRoutewatchIsNotAskedPerRequest(t *testing.T) {
+	t.Parallel()
+
+	f := newFixture(t, func(w http.ResponseWriter, _ *http.Request) {
+		w.WriteHeader(http.StatusInternalServerError)
+	})
+
+	f.route()
+	f.waitFor(routewatch.RequestFailed)
+	f.route()
+
+	if got := f.queries.Load(); got != 1 {
+		t.Errorf("%d queries while the failure is kept, want 1", got)
+	}
+
+	f.clk.advance(time.Minute)
+	f.route()
+
+	deadline := time.Now().Add(waitLimit)
+	for f.queries.Load() != 2 {
+		if time.Now().After(deadline) {
+			t.Fatalf("%d queries after the failure expired, want 2", f.queries.Load())
+		}
+
+		time.Sleep(time.Millisecond)
+	}
+}
+
+func TestHangingRoutewatchNeverDelaysAndFailsTheQuery(t *testing.T) {
+	t.Parallel()
+
+	f := newFixture(t, func(_ http.ResponseWriter, r *http.Request) {
+		<-r.Context().Done()
+	})
+
+	start := time.Now()
+
+	f.route()
+
+	if elapsed := time.Since(start); elapsed > time.Second {
+		t.Errorf("Route took %s while routewatch hangs", elapsed)
+	}
+
+	f.waitFor(routewatch.RequestFailed)
+	f.wantFailureLoggedWithoutTheClient()
+}
+
+func TestRepeatedRequestsMakeOneQueryAndTheAnswerExpires(t *testing.T) {
+	t.Parallel()
+
+	release := make(chan struct{})
+	f := newFixture(t, func(w http.ResponseWriter, _ *http.Request) {
+		<-release
+
+		_, _ = w.Write([]byte(routedAnswer))
+	})
+
+	for range 50 {
+		f.route()
+	}
+
+	close(release)
+	f.waitFor("")
+
+	for range 50 {
+		f.route()
+	}
+
+	if got := f.queries.Load(); got != 1 {
+		t.Errorf("%d queries for repeated requests, want 1", got)
+	}
+
+	f.clk.advance(time.Hour)
+	f.waitFor(routewatch.NoAnswerYet)
+	f.waitFor("")
+
+	if got := f.queries.Load(); got != 2 {
+		t.Errorf("%d queries after the answer expired, want 2", got)
+	}
+}