lib/connections, vendor: Change KCP mux to SMUX

Closes #4032

vendor/github.com/xtaci/kcp-go/emitter.go

@@ -7,17 +7,17 @@ import (
 
 var defaultEmitter Emitter
 
-const emitQueue = 8192
-
 func init() {
 	defaultEmitter.init()
 }
 
 type (
+	// packet emit request
 	emitPacket struct {
-		conn    net.PacketConn
-		to      net.Addr
-		data    []byte
+		conn net.PacketConn
+		to   net.Addr
+		data []byte
+		// mark this packet should recycle to global xmitBuf
 		recycle bool
 	}
 
@@ -28,7 +28,7 @@ type (
 )
 
 func (e *Emitter) init() {
-	e.ch = make(chan emitPacket, emitQueue)
+	e.ch = make(chan emitPacket)
 	go e.emitTask()
 }
 
@@ -36,7 +36,7 @@ func (e *Emitter) init() {
 func (e *Emitter) emitTask() {
 	for p := range e.ch {
 		if n, err := p.conn.WriteTo(p.data, p.to); err == nil {
-			atomic.AddUint64(&DefaultSnmp.OutSegs, 1)
+			atomic.AddUint64(&DefaultSnmp.OutPkts, 1)
 			atomic.AddUint64(&DefaultSnmp.OutBytes, uint64(n))
 		}
 		if p.recycle {