[relay-server] Use X-Real-IP in case of reverse proxy (#2848)

* Use X-Real-IP in case of reverse proxy

* Use sprintf

relay/server/listener/ws/listener.go

@@ -63,13 +63,14 @@ func (l *Listener) Shutdown(ctx context.Context) error {
 }
 
 func (l *Listener) onAccept(w http.ResponseWriter, r *http.Request) {
+	connRemoteAddr := remoteAddr(r)
 	wsConn, err := websocket.Accept(w, r, nil)
 	if err != nil {
-		log.Errorf("failed to accept ws connection from %s: %s", r.RemoteAddr, err)
+		log.Errorf("failed to accept ws connection from %s: %s", connRemoteAddr, err)
 		return
 	}
 
-	rAddr, err := net.ResolveTCPAddr("tcp", r.RemoteAddr)
+	rAddr, err := net.ResolveTCPAddr("tcp", connRemoteAddr)
 	if err != nil {
 		err = wsConn.Close(websocket.StatusInternalError, "internal error")
 		if err != nil {
@@ -90,3 +91,10 @@ func (l *Listener) onAccept(w http.ResponseWriter, r *http.Request) {
 	conn := NewConn(wsConn, lAddr, rAddr)
 	l.acceptFn(conn)
 }
+
+func remoteAddr(r *http.Request) string {
+	if r.Header.Get("X-Real-Ip") == "" || r.Header.Get("X-Real-Port") == "" {
+		return r.RemoteAddr
+	}
+	return fmt.Sprintf("%s:%s", r.Header.Get("X-Real-Ip"), r.Header.Get("X-Real-Port"))
+}