reverseproxy: Use http1.1 upgrade for websocket for extended connect of http2 and http3 (#7305)

Co-authored-by: WeidiDeng <weidi_deng@icloud.com>

Author: tonyb486

modules/caddyhttp/reverseproxy/reverseproxy.go

@@ -409,12 +409,16 @@ func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request, next caddyht
 		return caddyhttp.Error(http.StatusInternalServerError,
 			fmt.Errorf("preparing request for upstream round-trip: %v", err))
 	}
-	// websocket over http2, assuming backend doesn't support this, the request will be modified to http1.1 upgrade
+
+	// websocket over http2 or http3 if extended connect is enabled, assuming backend doesn't support this, the request will be modified to http1.1 upgrade
+	// Both use the same upgrade mechanism: server advertizes extended connect support, and client sends the pseudo header :protocol in a CONNECT request
+	// The quic-go http3 implementation also puts :protocol in r.Proto for CONNECT requests (quic-go/http3/headers.go@70-72,185,203)
 	// TODO: once we can reliably detect backend support this, it can be removed for those backends
-	if r.ProtoMajor == 2 && r.Method == http.MethodConnect && r.Header.Get(":protocol") == "websocket" {
+	if (r.ProtoMajor == 2 && r.Method == http.MethodConnect && r.Header.Get(":protocol") == "websocket") ||
+		(r.ProtoMajor == 3 && r.Method == http.MethodConnect && r.Proto == "websocket") {
 		clonedReq.Header.Del(":protocol")
 		// keep the body for later use. http1.1 upgrade uses http.NoBody
-		caddyhttp.SetVar(clonedReq.Context(), "h2_websocket_body", clonedReq.Body)
+		caddyhttp.SetVar(clonedReq.Context(), "extended_connect_websocket_body", clonedReq.Body)
 		clonedReq.Body = http.NoBody
 		clonedReq.Method = http.MethodGet
 		clonedReq.Header.Set("Upgrade", "websocket")

modules/caddyhttp/reverseproxy/streaming.go

@@ -94,9 +94,9 @@ func (h *Handler) handleUpgradeResponse(logger *zap.Logger, wg *sync.WaitGroup,
 		conn io.ReadWriteCloser
 		brw  *bufio.ReadWriter
 	)
-	// websocket over http2, assuming backend doesn't support this, the request will be modified to http1.1 upgrade
+	// websocket over http2 or http3 if extended connect is enabled, assuming backend doesn't support this, the request will be modified to http1.1 upgrade
 	// TODO: once we can reliably detect backend support this, it can be removed for those backends
-	if body, ok := caddyhttp.GetVar(req.Context(), "h2_websocket_body").(io.ReadCloser); ok {
+	if body, ok := caddyhttp.GetVar(req.Context(), "extended_connect_websocket_body").(io.ReadCloser); ok {
 		req.Body = body
 		rw.Header().Del("Upgrade")
 		rw.Header().Del("Connection")