Disable extended CONNECT by default

http2/http2.go

@@ -33,11 +33,19 @@ import (
 )
 
 var (
-	VerboseLogs                    bool
-	logFrameWrites                 bool
-	logFrameReads                  bool
-	inTests                        bool
-	disableExtendedConnectProtocol bool
+	VerboseLogs    bool
+	logFrameWrites bool
+	logFrameReads  bool
+	inTests        bool
+
+	// Enabling extended CONNECT by causes browsers to attempt to use
+	// WebSockets-over-HTTP/2. This results in problems when the server's websocket
+	// package doesn't support extended CONNECT.
+	//
+	// Disable extended CONNECT by default for now.
+	//
+	// Issue #71128.
+	disableExtendedConnectProtocol = true
 )
 
 func init() {
@@ -50,8 +58,8 @@ func init() {
 		logFrameWrites = true
 		logFrameReads = true
 	}
-	if strings.Contains(e, "http2xconnect=0") {
-		disableExtendedConnectProtocol = true
+	if strings.Contains(e, "http2xconnect=1") {
+		disableExtendedConnectProtocol = false
 	}
 }
 

http2/server.go

@@ -1993,6 +1993,11 @@ func (sc *serverConn) newWriterAndRequest(st *stream, f *MetaHeadersFrame) (*res
 		protocol:  f.PseudoValue("protocol"),
 	}
 
+	// extended connect is disabled, so we should not see :protocol
+	if disableExtendedConnectProtocol && rp.protocol != "" {
+		return nil, nil, streamError(f.StreamID, ErrCodeProtocol)
+	}
+
 	isConnect := rp.method == "CONNECT"
 	if isConnect {
 		if rp.protocol == "" && (rp.path != "" || rp.scheme != "" || rp.authority == "") {

http2/server_extended_connect_test.go

@@ -0,0 +1,64 @@
+package http2
+
+import (
+	"os"
+	"os/exec"
+	"testing"
+	"time"
+
+	http "github.com/bogdanfinn/fhttp"
+)
+
+// Extended CONNECT is off unless GODEBUG=http2xconnect=1 at startup
+// (golang/go#71128). GODEBUG is read at init, so each setting runs in a new
+// process.
+func TestServerExtendedConnect(t *testing.T) {
+	if want := os.Getenv("FHTTP_TEST_XCONNECT"); want != "" {
+		testServerExtendedConnect(t, want == "on")
+		return
+	}
+	for _, tt := range []struct{ godebug, want string }{
+		{"", "off"},
+		{"http2xconnect=0", "off"},
+		{"http2xconnect=1", "on"},
+	} {
+		cmd := exec.Command(os.Args[0], "-test.run=^TestServerExtendedConnect$")
+		cmd.Env = append(os.Environ(), "FHTTP_TEST_XCONNECT="+tt.want, "GODEBUG="+tt.godebug)
+		if out, err := cmd.CombinedOutput(); err != nil {
+			t.Errorf("GODEBUG=%q: %v\n%s", tt.godebug, err, out)
+		}
+	}
+}
+
+// testServerExtendedConnect checks that the server advertises extended CONNECT
+// and accepts requests with :protocol exactly when it is enabled.
+func testServerExtendedConnect(t *testing.T, enabled bool) {
+	gotProtocol := make(chan string, 1)
+	st := newServerTester(t, func(w http.ResponseWriter, r *http.Request) {
+		gotProtocol <- r.Header.Get(":protocol")
+	})
+	defer st.Close()
+
+	advertised := false
+	st.greetAndCheckSettings(func(s Setting) error {
+		advertised = advertised || s.ID == SettingEnableConnectProtocol && s.Val == 1
+		return nil
+	})
+	if advertised != enabled {
+		t.Fatalf("SETTINGS_ENABLE_CONNECT_PROTOCOL advertised = %v, want %v", advertised, enabled)
+	}
+
+	st.bodylessReq1(":method", "CONNECT", ":protocol", "websocket")
+	if !enabled {
+		st.wantRSTStream(1, ErrCodeProtocol)
+		return
+	}
+	select {
+	case p := <-gotProtocol:
+		if p != "websocket" {
+			t.Fatalf(":protocol = %q, want %q", p, "websocket")
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("handler was not called for an extended CONNECT request")
+	}
+}