Take Brazilian AS details from NIC.br's WHOIS server (closes #174)

LACNIC's answer for an AS that NIC.br registers is NIC.br's answer with
each accented letter replaced by U+FFFD, so a name such as AS52751's
cannot be recovered from it. When LACNIC's answer carries NIC.br's
copyright notice, the client now also asks whois.registro.br for the AS
and takes the fields from that answer, which is Latin-1 and decoded as
before. When that query fails, when the answer has no fields, or when
NIC.br says the client is over its query limit, LACNIC's fields are kept
and a warning is logged. After an over-limit answer the client skips
NIC.br for an hour. The tests use recorded answers for AS52751.

Model: opus-5-5

TODO.md

@@ -37,7 +37,8 @@ tested.
   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 (closes #174)
+  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)

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(),
-		logger:          logger.With("component", "asn_fetcher"),
+		whoisClient:     whois.NewClient(logger),
+		logger:          logger,
 		immediateQueue:  make(chan int, immediateQueueSize),
 		stopCh:          make(chan struct{}),
 		done:            make(chan struct{}),

internal/whois/whois.go

@@ -7,9 +7,11 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"log/slog"
 	"net"
 	"regexp"
 	"strings"
+	"sync"
 	"time"
 	"unicode/utf8"
 
@@ -68,6 +70,13 @@ const nicbrHeader = "% Copyright (c) Nic.br"
 // 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"
@@ -140,18 +149,36 @@ 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.
-func NewClient() *Client {
+// NewClient creates a new WHOIS client that logs to logger.
+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. When LACNIC's answer is NIC.br's, it
-// returns what NIC.br's own server says instead, unless that query fails.
+// returns what NIC.br's own server says instead, unless that query fails or
+// is skipped, as askNICbr says.
 //
 // 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
@@ -209,19 +236,51 @@ func (c *Client) LookupASN(ctx context.Context, asn int) (*ASNInfo, error) {
 // 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,
-// 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.
+// 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 {
-	answer, err := c.query(ctx, whoisServerNICbr, asQuery)
-	if err != nil || strings.Contains(answer, nicbrLimitReached) {
+	asn := lacnicInfo.ASN
+
+	c.mu.Lock()
+	skipping := c.Now().Before(c.nicbrSkipUntil)
+	c.mu.Unlock()
+
+	if skipping {
 		return lacnicInfo
 	}
 
-	info := c.parseResponse(lacnicInfo.ASN, RIRLACNIC, answer)
+	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
 	}
 

internal/whois/whois_test.go

@@ -2,9 +2,12 @@ package whois_test
 
 import (
 	"bufio"
+	"bytes"
 	"context"
+	"encoding/json"
 	"errors"
 	"io"
+	"log/slog"
 	"maps"
 	"net"
 	"slices"
@@ -277,7 +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)
@@ -335,7 +338,7 @@ func TestLookupASNReadsTheRIRAnswer(t *testing.T) {
 func TestLookupASNReadsOnlyTheASAndItsOrganisation(t *testing.T) {
 	t.Parallel()
 
-	client := whois.NewClient()
+	client := whois.NewClient(slog.New(slog.DiscardHandler))
 	client.DialContext = fakeServers(t, map[string]string{
 		apnicIANAQuery: "refer:        whois.apnic.net\n",
 		apnicQuery:     apnicRecord,
@@ -539,6 +542,30 @@ 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(
@@ -546,23 +573,12 @@ func lookUpBrazilianAS(
 ) (*whois.ASNInfo, bool, error) {
 	t.Helper()
 
-	dial := fakeServers(t, answers)
-	askedNICbr := false
-
-	client := whois.NewClient()
-	client.DialContext = func(
-		ctx context.Context, network, address string,
-	) (net.Conn, error) {
-		if address == nicbrServer {
-			askedNICbr = true
-		}
-
-		return dial(ctx, network, address)
-	}
+	nicbrAsks := 0
+	client := newNICbrClient(t, answers, io.Discard, &nicbrAsks)
 
 	info, err := client.LookupASN(t.Context(), brazilASN)
 
-	return info, askedNICbr, err
+	return info, nicbrAsks > 0, err
 }
 
 // TestLookupASNTakesABrazilianASFromNICbr looks up an AS that NIC.br
@@ -599,17 +615,58 @@ func TestLookupASNTakesABrazilianASFromNICbr(t *testing.T) {
 	}
 }
 
+// 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.
+// 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, nicbrAnswer := range map[string]map[string]string{
-		"connection refused":   {},
-		"no answer":            {brazilNICbrQuery: ""},
-		"over the query limit": {brazilNICbrQuery: nicbrOverLimit},
+	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()
@@ -618,14 +675,19 @@ func TestLookupASNKeepsLACNICsAnswerWhenNICbrFails(t *testing.T) {
 				brazilIANAQuery:   lacnicReferral,
 				brazilLACNICQuery: lacnicBrazilRecord,
 			}
-			maps.Copy(answers, nicbrAnswer)
+			maps.Copy(answers, test.nicbrAnswer)
 
-			info, askedNICbr, err := lookUpBrazilianAS(t, answers)
+			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 !askedNICbr {
+			if nicbrAsks == 0 {
 				t.Error("LookupASN did not ask NIC.br's server")
 			}
 
@@ -633,10 +695,73 @@ func TestLookupASNKeepsLACNICsAnswerWhenNICbrFails(t *testing.T) {
 				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.