rproxy and servewaf replace the one-process smallwebwaf (closes #172, closes #165)

`smallwebwaf` with no command now prints the commands and exits with status 2.
The image runs rproxy, or servewaf with SMALLWEBWAF_COMMAND=servewaf. The
passing-on code, its settings and its log fields and metric go. internal/proxy
keeps the checks, answers, reports and own endpoints; its tests run through the
real rproxy. The documents describe the pair.

Judgement call: clients.json keeps token_refused, since state files refuse unknown fields.
Deviation: script/gitea-requests sets SWWAF_LOG_REQUEST_HEADERS, to label requests.
Partially verified: make example-app and make gitea-requests never built the image, as Ubuntu's snapshot service answered 5xx.

Model: opus-5-5

internal/proxy/bytelimits_test.go

@@ -47,8 +47,6 @@ const (
 func TestEachByteLimitBansOnceTheResponseHasEnded(t *testing.T) {
 	t.Parallel()
 
-	const scraper = "192.0.2.200"
-
 	for _, tc := range []struct {
 		setting, window string
 		// apart is the time between the two requests, which the window
@@ -94,7 +92,7 @@ func TestEachByteLimitBansOnceTheResponseHasEnded(t *testing.T) {
 
 			s.get(client, http.StatusForbidden, requestlog.ActionBanned)
 
-			wantMetric(t, s.scrape(scraper), `smallwebwaf_rate_limit_hits_total{`+
+			wantMetric(t, s.scrape(), `smallwebwaf_rate_limit_hits_total{`+
 				`instance="`+alertInstance+`",kind="bytes",window="`+tc.window+`"}`, 1)
 		})
 	}
@@ -126,7 +124,7 @@ func TestBytesOfAnAnswerThatBreaksOffAreCounted(t *testing.T) {
 	// The 70 bytes passed on before the app broke off are over the limit of
 	// 50, and ban the client for an hour.
 	line, got := s.requestWithBody(http.MethodGet, client, "/", "", "", http.StatusOK,
-		requestlog.ActionUpstreamError)
+		requestlog.ActionForward)
 	if len(got.body) != answerBytes || line.LimitHit != minuteBytes ||
 		line.BanExpires != expires {
 		t.Errorf("got %d bytes, and the log line has limit_hit %q and ban_expires %q, "+
@@ -168,39 +166,6 @@ func TestWebSocketBytesAreCountedOnceItCloses(t *testing.T) {
 	}
 }
 
-func TestWebSocketPassesTheAnswerAfterTheClientStopsSending(t *testing.T) {
-	t.Parallel()
-
-	app := startApp(t, echoOnceTheClientStops)
-	addr, out := startProxy(t, app.URL,
-		map[string]string{trustedProxies: trustLocalhost})
-	s := &sender{t: t, addr: addr, out: out}
-
-	conn, reader := s.openWebSocket()
-	send(t, conn, uploadBody)
-
-	// The client closes its sending side and waits for the answer, which the
-	// app sends only once it has seen the client stop. smallwebwaf passes the
-	// close on to the app through CloseWrite on upgradedConn; without that,
-	// it closes both connections, and the answer is lost.
-	tcp, ok := conn.(*net.TCPConn)
-	if !ok {
-		t.Fatalf("connection is a %T, want a *net.TCPConn", conn)
-	}
-
-	err := tcp.CloseWrite()
-	if err != nil {
-		t.Fatalf("close the sending side: %v", err)
-	}
-
-	got, err := io.ReadAll(reader)
-	if err != nil || string(got) != uploadBody {
-		t.Errorf("got %q (%v), want %q", got, err, uploadBody)
-	}
-
-	s.closeWebSocket(conn)
-}
-
 func TestBytesCountSaysWhichBytesCount(t *testing.T) {
 	t.Parallel()
 
@@ -465,28 +430,6 @@ func answerAfterUpgrade(w http.ResponseWriter, _ *http.Request) {
 	}
 }
 
-// echoOnceTheClientStops is an app that switches protocols, as for a
-// WebSocket, reads what the client sends until the client stops sending,
-// and then sends it all back.
-func echoOnceTheClientStops(w http.ResponseWriter, _ *http.Request) {
-	conn, buffered, err := http.NewResponseController(w).Hijack()
-	if err != nil {
-		return
-	}
-
-	defer func() {
-		_ = conn.Close()
-	}()
-
-	_, _ = buffered.WriteString("HTTP/1.1 101 Switching Protocols\r\n" +
-		"Connection: Upgrade\r\nUpgrade: websocket\r\n\r\n")
-	_ = buffered.Flush()
-
-	received, _ := io.ReadAll(buffered)
-	_, _ = buffered.Write(received)
-	_ = buffered.Flush()
-}
-
 // webSocket opens a WebSocket from client to answerAfterUpgrade, sends a
 // line of bodyBytes on it, reads the answer, and closes it. It checks the
 // answer, and the log line as request does, and returns the log line.
@@ -543,7 +486,7 @@ func (s *sender) closeWebSocket(conn net.Conn) logLine {
 
 	_ = conn.Close()
 
-	line := s.out.requestLines(s.t, s.sent+1)[s.sent]
+	line := s.out.endedLines(s.t, s.sent+1)[s.sent]
 	s.sent++
 	wantLine(s.t, line, http.StatusSwitchingProtocols, requestlog.ActionForward)