Rename internal/proxy to internal/servewaf (closes #173)

The package passes nothing on since the one-process mode went: it answers rproxy's questions, takes its reports and answers servewaf's own endpoints. It is now named after the command it serves, with `git mv`, and its constructor is `servewaf.New`. `SPEC.md` and the other documents follow. No change of behaviour.

Model: opus-5-5

internal/servewaf/lookup.go

@@ -0,0 +1,78 @@
+package servewaf
+
+import (
+	"context"
+	"net/http"
+	"net/netip"
+	"time"
+
+	"sneak.berlin/go/smallwebwaf/internal/lookup"
+)
+
+// The headers in which an answer of allow gives rproxy the client's AS number
+// and country, for the app, while SWWAF_ADD_LOOKUP_HEADERS is set. Go writes
+// every header name in this form, as it sends it and as it receives it, so
+// X-Client-ASN arrives as X-Client-Asn; header names are not case-sensitive.
+const (
+	asnHeader     = "X-Client-Asn"
+	countryHeader = "X-Client-Country"
+)
+
+// lookUp looks up the client's AS number and country, in the lookup
+// database or through GeoJS, and notes them for the log line, unless
+// SWWAF_LOOKUP_SOURCE is off or the client is on a private, loopback or
+// link-local address, which no lookup can place. The lookup database
+// answers at once. With GeoJS, while a setting needs the answer, such as a
+// country list or a biased threshold, a new client's request waits for it,
+// unless refusedWhateverTheAnswer reports true. ctx is the request's own
+// context.
+func (rq *request) lookUp(ctx context.Context, now time.Time) {
+	if rq.h.config.LookupSource == "off" || !canBePlaced(rq.client) {
+		return
+	}
+
+	client := rq.h.clientGroup(rq.client)
+
+	switch {
+	case rq.h.config.LookupSource == "file":
+		rq.lookupAnswer = rq.h.lookupFile.LookUp(client)
+	case rq.refusedWhateverTheAnswer(now):
+		rq.lookupAnswer = rq.h.geojs.LookUpWithoutWaiting(ctx, client)
+		rq.skippedLookupWait = rq.lookupAnswer.Answered.IsZero()
+	default:
+		rq.lookupAnswer = rq.h.geojs.LookUp(ctx, client)
+	}
+
+	rq.lookedUp = true
+	rq.line.ASN = rq.lookupAnswer.ASN
+	rq.line.ASName = rq.lookupAnswer.ASName
+	rq.line.Country = rq.lookupAnswer.Country
+}
+
+// addLookup adds answer, an answer about a client from the lookup
+// database or GeoJS, to the client's history, and to the notes of the bans
+// on its netblock that have no AS number, AS name or country yet.
+func (h *handler) addLookup(answer lookup.Answer) {
+	h.limiter.AddLookup(answer.Client, answer.Answered,
+		answer.ASN, answer.ASName, answer.Country)
+	h.ledger.AddLookup(h.netblock(answer.Client.Addr()),
+		answer.ASN, answer.ASName, answer.Country)
+}
+
+// setLookupHeaders sets the headers that give the client's AS number and
+// country, leaving out one that is unknown.
+func setLookupHeaders(header http.Header, asn, country string) {
+	if asn != "" {
+		header.Set(asnHeader, asn)
+	}
+
+	if country != "" {
+		header.Set(countryHeader, country)
+	}
+}
+
+// canBePlaced reports whether a lookup can place addr: private, loopback
+// and link-local addresses have no AS number or country.
+func canBePlaced(addr netip.Addr) bool {
+	return !addr.IsPrivate() && !addr.IsLoopback() && !addr.IsLinkLocalUnicast()
+}