Enable OPTIONS and CloudEvent Webhook headers

pkg/broker/filter/filter_handler.go

@@ -105,6 +105,7 @@ func (h *Handler) Start(ctx context.Context) error {
 // 5. send event to trigger's subscriber
 // 6. write the response
 func (h *Handler) ServeHTTP(writer http.ResponseWriter, request *http.Request) {
+	writer.Header().Set("Allow", "POST")
 
 	if request.Method != http.MethodPost {
 		writer.WriteHeader(http.StatusMethodNotAllowed)

pkg/broker/ingress/ingress_handler.go

@@ -101,7 +101,14 @@ func (h *Handler) Start(ctx context.Context) error {
 }
 
 func (h *Handler) ServeHTTP(writer http.ResponseWriter, request *http.Request) {
+	writer.Header().Set("Allow", "POST, OPTIONS")
 	// validate request method
+	if request.Method == http.MethodOptions {
+		writer.Header().Set("WebHook-Allowed-Origin", "*") // Accept from any Origin:
+		writer.Header().Set("WebHook-Allowed-Rate", "*")   // Unlimited requests/minute
+		writer.WriteHeader(http.StatusOK)
+		return
+	}
 	if request.Method != http.MethodPost {
 		h.Logger.Warn("unexpected request method", zap.String("method", request.Method))
 		writer.WriteHeader(http.StatusMethodNotAllowed)

pkg/broker/ingress/ingress_handler_test.go

@@ -104,20 +104,29 @@ func TestHandler_ServeHTTP(t *testing.T) {
 			defaulter:  broker.TTLDefaulter(logger, 100),
 		},
 		{
-			name:       "invalid method OPTIONS",
-			method:     nethttp.MethodOptions,
-			uri:        "/ns/name",
-			body:       getValidEvent(),
-			statusCode: nethttp.StatusMethodNotAllowed,
+			name:   "valid method OPTIONS",
+			method: nethttp.MethodOptions,
+			uri:    "/ns/name",
+			body:   strings.NewReader(""),
+			expectedHeaders: nethttp.Header{
+				"Allow":                  []string{"PUT, OPTIONS"},
+				"WebHook-Allowed-Origin": []string{"*"},
+				"WebHook-Allowed-Rate":   []string{"*"},
+				"Content-Length":         []string{"0"},
+			},
+			statusCode: nethttp.StatusOK,
 			handler:    handler(),
 			reporter:   &mockReporter{},
 			defaulter:  broker.TTLDefaulter(logger, 100),
 		},
 		{
-			name:       "valid (happy path)",
-			method:     nethttp.MethodPost,
-			uri:        "/ns/name",
-			body:       getValidEvent(),
+			name:   "valid (happy path POST)",
+			method: nethttp.MethodPost,
+			uri:    "/ns/name",
+			body:   getValidEvent(),
+			expectedHeaders: nethttp.Header{
+				"Allow": []string{"PUT, OPTIONS"},
+			},
 			statusCode: senderResponseStatusCode,
 			handler:    handler(),
 			reporter:   &mockReporter{StatusCode: senderResponseStatusCode, EventDispatchTimeReported: true},

pkg/channel/message_receiver.go

@@ -136,6 +136,13 @@ func (r *MessageReceiver) Start(ctx context.Context) error {
 }
 
 func (r *MessageReceiver) ServeHTTP(response nethttp.ResponseWriter, request *nethttp.Request) {
+	response.Header().Set("Allow", "POST, OPTIONS")
+	if request.Method == nethttp.MethodOptions {
+		response.Header().Set("WebHook-Allowed-Origin", "*") // Accept from any Origin:
+		response.Header().Set("WebHook-Allowed-Rate", "*")   // Unlimited requests/minute
+		response.WriteHeader(nethttp.StatusOK)
+		return
+	}
 	if request.Method != nethttp.MethodPost {
 		response.WriteHeader(nethttp.StatusMethodNotAllowed)
 		return

pkg/channel/message_receiver_test.go

@@ -53,6 +53,7 @@ func TestMessageReceiver_ServeHTTP(t *testing.T) {
 		additionalHeaders nethttp.Header
 		expected          int
 		receiverFunc      UnbufferedMessageReceiverFunc
+		responseValidator func(r httptest.ResponseRecorder) error
 	}{
 		"non '/' path": {
 			path:     "/something",
@@ -121,6 +122,22 @@ func TestMessageReceiver_ServeHTTP(t *testing.T) {
 			},
 			expected: nethttp.StatusAccepted,
 		},
+		"OPTIONS okay": {
+			method:   nethttp.MethodOptions,
+			host:     "test-name.test-namespace.svc." + network.GetClusterDomainName(),
+			expected: nethttp.StatusOK,
+			responseValidator: func(res httptest.ResponseRecorder) error {
+				expectedHeaders := nethttp.Header{
+					"Allow":                  []string{"POST, OPTIONS"},
+					"Webhook-Allowed-Origin": []string{"*"},
+					"Webhook-Allowed-Rate":   []string{"*"},
+				}
+				if diff := cmp.Diff(expectedHeaders, res.Header()); diff != "" {
+					return fmt.Errorf("test receiver func -- bad OPTION headers (-want, +got): %s", diff)
+				}
+				return nil
+			},
+		},
 	}
 	reporter := NewStatsReporter("testcontainer", "testpod")
 	for n, tc := range testCases {
@@ -172,6 +189,11 @@ func TestMessageReceiver_ServeHTTP(t *testing.T) {
 			if res.Code != tc.expected {
 				t.Fatalf("Unexpected status code. Expected %v. Actual %v", tc.expected, res.Code)
 			}
+			if tc.responseValidator != nil {
+				if err := tc.responseValidator(res); err != nil {
+					t.Errorf("Incorrect response: %v", err)
+				}
+			}
 		})
 	}
 }

test/conformance/helpers/broker_data_plane_test_helper.go

@@ -84,7 +84,7 @@ func BrokerDataPlaneNamespaceSetupOption(ctx context.Context, namespace string)
 //Supports structured or Binary mode
 //Respond with 2xx on good CE
 //Respond with 400 on bad CE
-//Reject non-POST requests to publish URI
+//Reject non-POST, non-OPTIONS requests to publish URI (beyond spec?!)
 func BrokerIngressDataPlaneTestHelper(
 	ctx context.Context,
 	t *testing.T,
@@ -108,6 +108,22 @@ func BrokerIngressDataPlaneTestHelper(
 			resources.WithSubscriberServiceRefForTrigger(loggerName),
 		)
 
+		st.Run("Ingress supports OPTIONS", func(t *testing.T) {
+			// TODO(evana): check "Allow" header and other options.
+			// This may be simpler if the setup requires a local HTTP proxy which can reach into the cluster.
+			method := sender.WithMethod("OPTIONS")
+			responseSink := "http://" + client.GetServiceHost(loggerName)
+			responseForward := sender.WithResponseSink(responseSink)
+			senderName := "options-test-sender"
+			client.SendRequestToAddressable(ctx, senderName, broker.Name, testlib.BrokerTypeMeta, map[string]string{}, "", method, responseForward)
+			client.WaitForResourceReadyOrFail(senderName, &podMeta)
+			eventTracker.AssertAtLeast(1, recordevents.MatchEvent(cetest.AllOf(
+				cetest.AnyOf(
+					sender.MatchStatusCode(200), sender.MatchStatusCode(405)),
+				cetest.HasSource("https://knative.dev/eventing/test/event-sender"),
+			)))
+		})
+
 		client.WaitForResourceReadyOrFail(trigger.Name, testlib.TriggerTypeMeta)
 		st.Run("Ingress Supports CE0.3", func(t *testing.T) {
 			eventID := "CE0.3"