From dcb20e2824f36790fe2504022054b94fa405dc41 Mon Sep 17 00:00:00 2001
From: wwqgtxx <wwqgtxx@gmail.com>
Date: Wed, 16 Apr 2025 08:47:44 +0800
Subject: [PATCH] fix: websocket server upgrade in golang1.20

---
 transport/vmess/websocket.go       | 2 +-
 transport/vmess/websocket_go120.go | 7 +++++++
 transport/vmess/websocket_go121.go | 5 +++++
 3 files changed, 13 insertions(+), 1 deletion(-)
 create mode 100644 transport/vmess/websocket_go120.go
 create mode 100644 transport/vmess/websocket_go121.go

diff --git a/transport/vmess/websocket.go b/transport/vmess/websocket.go
index 772c6fef..31f09aac 100644
--- a/transport/vmess/websocket.go
+++ b/transport/vmess/websocket.go
@@ -555,7 +555,7 @@ func StreamUpgradedWebsocketConn(w http.ResponseWriter, r *http.Request) (net.Co
 		w.Header().Set("Sec-Websocket-Accept", getSecAccept(r.Header.Get("Sec-WebSocket-Key")))
 	}
 	w.WriteHeader(http.StatusSwitchingProtocols)
-	if flusher, isFlusher := w.(interface{ FlushError() error }); isFlusher {
+	if flusher, isFlusher := w.(interface{ FlushError() error }); isFlusher && writeHeaderShouldFlush {
 		err = flusher.FlushError()
 		if err != nil {
 			return nil, fmt.Errorf("flush response: %w", err)
diff --git a/transport/vmess/websocket_go120.go b/transport/vmess/websocket_go120.go
new file mode 100644
index 00000000..0b9ff5e3
--- /dev/null
+++ b/transport/vmess/websocket_go120.go
@@ -0,0 +1,7 @@
+//go:build !go1.21
+
+package vmess
+
+// Golang1.20's net.http Flush will mistakenly call w.WriteHeader(StatusOK) internally after w.WriteHeader(http.StatusSwitchingProtocols)
+// https://github.com/golang/go/issues/59564
+const writeHeaderShouldFlush = false
diff --git a/transport/vmess/websocket_go121.go b/transport/vmess/websocket_go121.go
new file mode 100644
index 00000000..9419cd50
--- /dev/null
+++ b/transport/vmess/websocket_go121.go
@@ -0,0 +1,5 @@
+//go:build go1.21
+
+package vmess
+
+const writeHeaderShouldFlush = true