servewaf always answers rproxy well within its time limit (closes #182)

A question waits on GeoJS at most 800ms, the new default of
SWWAF_LOOKUP_TIMEOUT. In enforce mode it does not wait at all when it is
over the header limits, on a fetched blocklist with deny, on the CrowdSec
decision list, or over a whole rate limit. Not waiting never lowers a
client's limit. Just before the Core Rule Set, servewaf refuses more than
50 cookies or 100 header fields with 431.

Shared default changed: SWWAF_LOOKUP_TIMEOUT also applies to smallwebwaf
with no command.
Judgement call: SWWAF_REPUTATION_TIMEOUT stays 2s, since no request waits
on the DNS blocklists or AbuseIPDB.

Model: opus-5-5

internal/lookup/lookup.go

@@ -179,7 +179,7 @@ func New(params Params) *GeoJS {
 // own address for IPv4, and an address in the same place for an IPv6
 // netblock.
 func (g *GeoJS) LookUp(ctx context.Context, client netip.Prefix) Answer {
-	answer, asked := g.answerOrWait(ctx, client)
+	answer, asked := g.answerOrWait(ctx, client, g.wait)
 	if asked == nil {
 		return answer
 	}
@@ -209,6 +209,14 @@ func (g *GeoJS) LookUp(ctx context.Context, client netip.Prefix) Answer {
 	return answer
 }
 
+// LookUpWithoutWaiting is LookUp for a request that does not need the answer,
+// whatever Wait says: it returns the zero Answer at once when none is kept.
+func (g *GeoJS) LookUpWithoutWaiting(ctx context.Context, client netip.Prefix) Answer {
+	answer, _ := g.answerOrWait(ctx, client, false)
+
+	return answer
+}
+
 // Kept returns client's answer, if one is kept, without asking GeoJS.
 func (g *GeoJS) Kept(client netip.Prefix) (Answer, bool) {
 	g.mu.Lock()
@@ -263,9 +271,9 @@ func (g *GeoJS) Load(answers []Answer) {
 // answerOrWait returns client's kept answer if it has one. Otherwise it
 // puts the client among those waiting if there is room, has GeoJS asked
 // about them if it can be, and returns what to wait on for the answer, or
-// nil when there is nothing to wait for.
+// nil when there is nothing to wait for or mustWait is false.
 func (g *GeoJS) answerOrWait(
-	ctx context.Context, client netip.Prefix,
+	ctx context.Context, client netip.Prefix, mustWait bool,
 ) (Answer, <-chan struct{}) {
 	g.mu.Lock()
 	defer g.mu.Unlock()
@@ -283,7 +291,7 @@ func (g *GeoJS) answerOrWait(
 
 	g.ask(ctx)
 
-	if !g.wait {
+	if !mustWait {
 		return Answer{}, nil // the answer is not needed before the request goes on
 	}
 

internal/lookup/lookup_test.go

@@ -72,6 +72,39 @@ func TestKeptAnswerIsUsedFor7DaysThenAskedAgain(t *testing.T) {
 	})
 }
 
+func TestLookUpWithoutWaitingAsksGeoJSAndGoesOnAtOnce(t *testing.T) {
+	t.Parallel()
+
+	synctest.Test(t, func(t *testing.T) {
+		geojs, clock, g := start()
+		client := netip.MustParsePrefix("203.0.113.9/32")
+
+		// Wait is set, and GeoJS does not answer.
+		geojs.set(hanging)
+
+		began := time.Now()
+		answer := g.LookUpWithoutWaiting(t.Context(), client)
+
+		if waited := time.Since(began); waited != 0 || answer != (lookup.Answer{}) {
+			t.Errorf("got %+v after %s, want no answer at once", answer, waited)
+		}
+
+		waitForRequests(t, geojs, 1)
+		wantAsked(t, geojs, 0, "203.0.113.9")
+
+		// That request is abandoned, and has failed once this returns. GeoJS
+		// answers when it is asked again, and the answer is kept.
+		time.Sleep(timeout)
+		synctest.Wait()
+		geojs.set(answering)
+		waitForCountry(t, g, clock, client, germany)
+
+		if got := g.LookUpWithoutWaiting(t.Context(), client).Country; got != germany {
+			t.Errorf("the kept answer gives the country %q, want %q", got, germany)
+		}
+	})
+}
+
 func TestNewClientWaitsAtMostOneSecondThenCountsAsNotFound(t *testing.T) {
 	t.Parallel()
 
@@ -123,8 +156,8 @@ func TestRequestWaitsAsLongAsTheTimeoutSaysAndGeoJSIsAbandonedAfterIt(t *testing
 	t.Parallel()
 
 	synctest.Test(t, func(t *testing.T) {
-		// A timeout longer than the default second, and a GeoJS that does
-		// not answer.
+		// A timeout longer than the default, and a GeoJS that does not
+		// answer.
 		const longerTimeout = 3 * time.Second
 
 		m := metrics.New(1, "app")