http2/h2c: allow to disable http upgrade in h2c

http2/h2c/h2c.go

@@ -37,6 +37,20 @@ func init() {
 	}
 }
 
+// Option is used to specify the behavior for the h2c handler
+type Option = func(*option)
+
+type option struct {
+	disableUpgrade bool
+}
+
+// DisableH2CUpgrade disable the Upgrade mechanism mentioned in RFC7203 topic 6.7 by the h2c server.
+func DisableH2CUpgrade() Option {
+	return func(o *option) {
+		o.disableUpgrade = true
+	}
+}
+
 // h2cHandler is a Handler which implements h2c by hijacking the HTTP/1 traffic
 // that should be h2c traffic. There are two ways to begin a h2c connection
 // (RFC 7540 Section 3.2 and 3.4): (1) Starting with Prior Knowledge - this
@@ -48,6 +62,7 @@ func init() {
 type h2cHandler struct {
 	Handler http.Handler
 	s       *http2.Server
+	opt     option
 }
 
 // NewHandler returns an http.Handler that wraps h, intercepting any h2c
@@ -63,10 +78,16 @@ type h2cHandler struct {
 // The first request on an h2c connection is read entirely into memory before
 // the Handler is called. To limit the memory consumed by this request, wrap
 // the result of NewHandler in an http.MaxBytesHandler.
-func NewHandler(h http.Handler, s *http2.Server) http.Handler {
+func NewHandler(h http.Handler, s *http2.Server, opts ...Option) http.Handler {
+	var o option
+	for _, opt := range opts {
+		opt(&o)
+	}
+
 	return &h2cHandler{
 		Handler: h,
 		s:       s,
+		opt:     o,
 	}
 }
 
@@ -103,7 +124,7 @@ func (s h2cHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 	// Handle Upgrade to h2c (RFC 7540 Section 3.2)
-	if isH2CUpgrade(r.Header) {
+	if !s.opt.disableUpgrade && isH2CUpgrade(r.Header) {
 		conn, settings, err := h2cUpgrade(w, r)
 		if err != nil {
 			if http2VerboseLogs {

http2/h2c/h2c_test.go

@@ -169,3 +169,69 @@ func TestMaxBytesHandler(t *testing.T) {
 		t.Errorf("resp.StatusCode = %v, want %v", got, want)
 	}
 }
+
+func TestH2CProtocolSwitch(t *testing.T) {
+	const bodyLimit = 10
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+
+	})
+
+	h2s := &http2.Server{}
+	h1s := httptest.NewUnstartedServer(http.MaxBytesHandler(NewHandler(handler, h2s), bodyLimit))
+	h1s.Start()
+	defer h1s.Close()
+
+	req, err := http.NewRequest("POST", h1s.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	req.Header.Set("Http2-Settings", "")
+	req.Header.Set("Upgrade", "h2c")
+	req.Header.Set("Connection", "Upgrade, HTTP2-Settings")
+
+	resp, err := h1s.Client().Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	_, err = io.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got, want := resp.StatusCode, http.StatusSwitchingProtocols; got != want {
+		t.Errorf("resp.StatusCode = %v, want %v", got, want)
+	}
+}
+
+func TestDisableH2CUpgrade(t *testing.T) {
+	const bodyLimit = 10
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+
+	})
+
+	h2s := &http2.Server{}
+	h1s := httptest.NewUnstartedServer(http.MaxBytesHandler(NewHandler(handler, h2s, DisableH2CUpgrade()), bodyLimit))
+	h1s.Start()
+	defer h1s.Close()
+
+	req, err := http.NewRequest("POST", h1s.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	req.Header.Set("Http2-Settings", "")
+	req.Header.Set("Upgrade", "h2c")
+	req.Header.Set("Connection", "Upgrade, HTTP2-Settings")
+
+	resp, err := h1s.Client().Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	_, err = io.ReadAll(resp.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got, want := resp.StatusCode, http.StatusOK; got != want {
+		t.Errorf("resp.StatusCode = %v, want %v", got, want)
+	}
+}