yamux: change default MaxStreamWindowSize to 6MB (#3474)

server/service.go

@@ -461,6 +461,7 @@ func (svr *Service) HandleListener(l net.Listener) {
 				fmuxCfg := fmux.DefaultConfig()
 				fmuxCfg.KeepAliveInterval = time.Duration(svr.cfg.TCPMuxKeepaliveInterval) * time.Second
 				fmuxCfg.LogOutput = io.Discard
+				fmuxCfg.MaxStreamWindowSize = 6 * 1024 * 1024
 				session, err := fmux.Server(frpConn, fmuxCfg)
 				if err != nil {
 					log.Warn("Failed to create mux connection: %v", err)