internal/proxy/request.go

@@ -789,9 +789,19 @@ func (rq *request) responseTimedOut() {
 	}
 }
 
-// responseReceived is called once the app has sent its whole answer.
+// responseReceived is called once the app has sent its whole answer. An
+// app may answer before the client has sent its whole body, as with a 404
+// it sends without reading it. The timeouts then run on: until the
+// transport's read of the body returns, Go's server cannot send the
+// answer, and SWWAF_CLIENT_REQUEST_TIMEOUT is what ends that read for a
+// client that stops sending.
 func (rq *request) responseReceived() {
 	rq.complete = true
+
+	if rq.body != nil && !rq.body.received.Load() {
+		return
+	}
+
 	rq.stopTimers()
 }
 

internal/proxy/timeouts_test.go

@@ -194,6 +194,28 @@ func sendLargeBody(t *testing.T, addr string) net.Conn {
 	return conn
 }
 
+func TestClientStopsSendingAfterTheAppHasAnswered(t *testing.T) {
+	t.Parallel()
+
+	// The app answers at once without reading the body, as an app does
+	// for a path it does not serve.
+	app := startApp(t, http.NotFound)
+	addr, out := startProxy(t, app.URL, map[string]string{
+		clientRequestTimeout: shortTimeoutSetting,
+		metricsToken:         token,
+	})
+
+	start := time.Now()
+	got := readResponse(t, sendPartOfBody(t, addr))
+	wantTimedOut(t, start)
+
+	// The app's answer came before the time ran out, so the client is
+	// sent that answer, not smallwebwaf's 408.
+	wantStatus(t, got, http.StatusNotFound)
+	wantLine(t, out.requestLine(t), http.StatusNotFound, requestlog.ActionTimedOut)
+	wantLimitHits(t, addr, clientRequestTimeout, 1)
+}
+
 func TestAppTooSlowToAnswer(t *testing.T) {
 	t.Parallel()