Back off WHOIS lookups more slowly and stop asking for personal data (closes #159)

A failed lookup now makes the fetcher's wait 1.5 times as long, up to
one minute instead of five. A success still halves it.

RIPE counts the person and role objects an answer holds against a daily
limit per IP address, and refuses an address for good that passes it
too often. RIPE, APNIC and AFRINIC are now asked with --no-personal,
which leaves those objects out but keeps the organisation object.

An answer with RIPE's access-denied or limit-reached error line is now
reported as a refusal holding that line, not as an answer with no
fields.

Model: opus-5-5

internal/whois/whois.go

@@ -49,6 +49,31 @@ const (
 	RIRAFRNIC = "AFRINIC"
 )
 
+// noPersonalFlag keeps person and role objects out of an answer. The
+// organisation object stays in it. RIPE counts the person and role objects
+// it returns against a daily limit per IP address. Role objects for abuse
+// contacts do not count. RIPE refuses an address for good that passes the
+// limit too often:
+// https://docs.db.ripe.net/Types-of-Queries/Access-Control-for-Queries/
+//
+// RIPE documents the flag here:
+// https://docs.db.ripe.net/Types-of-Queries/Referenced-Objects-in-Query-Response/
+// APNIC and AFRINIC list it in their answers to the query "help". AFRINIC
+// sends readers to that answer for its full list of flags:
+// https://afrinic.net/whois-getting-started
+const noPersonalFlag = "--no-personal"
+
+// The error lines with which RIPE's database software refuses a query:
+// access denied to the client's IP address, and that address's limit
+// reached. APNIC and AFRINIC run the same software. The lines are listed
+// under "Access Errors" on this page, whose URL is split over two lines:
+// https://docs.db.ripe.net/Appendices/
+// Appendix-C--RIPE-Database-Query-Server-Response-Codes-and-Messages/
+const (
+	accessDeniedError = "%ERROR:201:"
+	accessLimitError  = "%ERROR:202:"
+)
+
 // Errors LookupASN returns when a WHOIS answer has nothing to store.
 var (
 	// ErrNoReferral is returned when IANA refers the AS to no RIR, as it
@@ -58,6 +83,7 @@ var (
 	errNoASBlock = errors.New("IANA answered with neither a referral " +
 		"nor an AS block")
 	errNoFields       = errors.New("RIR answered with no WHOIS fields")
+	errRefused        = errors.New("RIR refused the query")
 	errUnknownServer  = errors.New("IANA refers the AS to a server no RIR runs")
 	errAnswerTooLarge = errors.New("WHOIS answer reached the size cap")
 )
@@ -97,10 +123,10 @@ func NewClient() *Client {
 
 // 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
-// refers the AS to no RIR, and another error when a query fails, 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 RIR's answer carries
-// none of ASNInfo's fields, as a refusal of service does.
+// refers the AS to no RIR, and another error when a query 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 RIR's 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)
@@ -127,7 +153,7 @@ func (c *Client) LookupASN(ctx context.Context, asn int) (*ASNInfo, error) {
 	}
 
 	// Query the authoritative RIR
-	rirResp, err := c.query(ctx, whoisServer, query)
+	rirResp, err := c.queryRIR(ctx, whoisServer, rirQuery(rir, query))
 	if err != nil {
 		return nil, fmt.Errorf("RIR query failed: %w", err)
 	}
@@ -154,6 +180,39 @@ func (info *ASNInfo) isEmpty() bool {
 		info.RegDate == nil && info.LastMod == nil
 }
 
+// rirQuery returns the query sent to rir's server for asQuery, an AS
+// number such as "AS3333". RIPE, APNIC and AFRINIC are asked to keep person
+// and role objects out of the answer.
+func rirQuery(rir, asQuery string) string {
+	switch rir {
+	case RIRRIPE, RIRAPNIC, RIRAFRNIC:
+		return noPersonalFlag + " " + asQuery
+	default:
+		return asQuery
+	}
+}
+
+// queryRIR sends query to an RIR's server and returns the answer. An answer
+// holding an error line with which the server refuses the query is an
+// error, and the error holds that line.
+func (c *Client) queryRIR(
+	ctx context.Context, server, query string,
+) (string, error) {
+	answer, err := c.query(ctx, server, query)
+	if err != nil {
+		return "", err
+	}
+
+	for line := range strings.SplitSeq(answer, "\n") {
+		if strings.HasPrefix(line, accessDeniedError) ||
+			strings.HasPrefix(line, accessLimitError) {
+			return "", fmt.Errorf("%w: %s", errRefused, line)
+		}
+	}
+
+	return answer, nil
+}
+
 // query performs a raw WHOIS query to the specified server. An answer that
 // reaches maxAnswerSize is an error.
 func (c *Client) query(ctx context.Context, server, query string) (string, error) {