diff --git a/gold/head/packet.go b/gold/head/packet.go
index ca4975d..2b89385 100644
--- a/gold/head/packet.go
+++ b/gold/head/packet.go
@@ -147,17 +147,19 @@ func (p *Packet) Marshal(src net.IP, teatype uint8, additional uint16, datasz ui
 	if hasmore {
 		offset |= 0x2000
 	}
+	p.Flags = PacketFlags(offset)
 
 	return helper.OpenWriterF(func(w *helper.Writer) {
 		w.WriteUInt32(p.idxdatsz)
 		w.WriteUInt16((uint16(p.TTL) << 8) | uint16(p.Proto))
 		w.WriteUInt16(p.SrcPort)
 		w.WriteUInt16(p.DstPort)
-		w.WriteUInt16(uint16(PacketFlags(offset)))
+		w.WriteUInt16(uint16(p.Flags))
 		w.Write(p.Src.To4())
 		w.Write(p.Dst.To4())
 		w.Write(p.Hash[:])
-		w.WriteUInt64(CalcCRC64(w.Bytes()))
+		p.crc64 = CalcCRC64(w.Bytes())
+		w.WriteUInt64(p.crc64)
 		w.Write(p.Body())
 	})
 }
@@ -213,6 +215,10 @@ func (p *Packet) Put() {
 	PutPacket(p)
 }
 
+func (p *Packet) CRC64() uint64 {
+	return p.crc64
+}
+
 // Body returns data
 func (p *Packet) Body() []byte {
 	return p.data[p.a:p.b]
@@ -256,3 +262,10 @@ func (p *Packet) Copy() *Packet {
 	newp.buffered = false
 	return newp
 }
+
+func (p *Packet) CopyWithBody() *Packet {
+	newp := p.Copy()
+	newp.data = helper.MakeBytes(len(p.data))
+	copy(newp.data, p.data)
+	return newp
+}
diff --git a/gold/link/listen.go b/gold/link/listen.go
index 8fb936b..b3c7351 100644
--- a/gold/link/listen.go
+++ b/gold/link/listen.go
@@ -21,6 +21,52 @@ import (
 
 const lstnbufgragsz = 65536
 
+type lstnq struct {
+	index int
+	addr  p2p.EndPoint
+	buf   []byte
+}
+
+type listenqueue chan lstnq
+
+func (q listenqueue) listen(m *Me, hasntfinished []sync.Mutex) {
+	recvtotlcnt := uint64(0)
+	recvloopcnt := uint16(0)
+	recvlooptime := time.Now().UnixMilli()
+	for lstn := range q {
+		recvtotlcnt += uint64(len(lstn.buf))
+		recvloopcnt++
+		if recvloopcnt%m.speedloop == 0 {
+			now := time.Now().UnixMilli()
+			logrus.Infof("[listen] queue recv avg speed: %.2f KB/s", float64(recvtotlcnt)/float64(now-recvlooptime))
+			recvtotlcnt = 0
+			recvlooptime = now
+		}
+		packet := m.wait(lstn.buf[:len(lstn.buf):lstnbufgragsz])
+		if packet == nil {
+			if lstn.index < 0 {
+				if config.ShowDebugLog {
+					logrus.Debugln("[listen] queue waiting")
+				}
+				helper.PutBytes(lstn.buf)
+				continue
+			}
+			if config.ShowDebugLog {
+				logrus.Debugln("[listen] queue waiting, unlock index", lstn.index)
+			}
+			hasntfinished[lstn.index].Unlock()
+			continue
+		}
+		if lstn.index >= 0 {
+			go m.dispatch(packet, lstn.addr, lstn.index, hasntfinished[lstn.index].Unlock)
+		} else {
+			go m.dispatch(packet, lstn.addr, lstn.index, func() {
+				helper.PutBytes(lstn.buf)
+			})
+		}
+	}
+}
+
 // 监听本机 endpoint
 func (m *Me) listen() (conn p2p.Conn, err error) {
 	conn, err = m.ep.Listen()
@@ -30,29 +76,40 @@ func (m *Me) listen() (conn p2p.Conn, err error) {
 	m.ep = conn.LocalAddr()
 	logrus.Infoln("[listen] at", m.ep)
 	go func() {
-		recvtotlcnt := uint64(0)
-		recvloopcnt := uint16(0)
-		recvlooptime := time.Now().UnixMilli()
-		n := runtime.NumCPU()
+		n := uint(runtime.NumCPU())
 		if n > 64 {
 			n = 64 // 只用最多 64 核
 		}
 		logrus.Infoln("[listen] use cpu num:", n)
-		listenbuff := make([]byte, lstnbufgragsz*n)
+		listenbuf := make([]byte, lstnbufgragsz*n)
 		hasntfinished := make([]sync.Mutex, n)
-		for i := 0; err == nil; i++ {
+		q := make(listenqueue, n)
+		defer close(q)
+		go q.listen(m, hasntfinished)
+		i := uint(0)
+		for {
+			usenewbuf := false
 			i %= n
 			for !hasntfinished[i].TryLock() {
 				i++
 				i %= n
-				if i == 0 { // looked up a full round
-					time.Sleep(time.Millisecond * 10)
+				if i == 0 { // looked up a full round, make a new buf
+					usenewbuf = true
+					if config.ShowDebugLog {
+						logrus.Debugln("[listen] use new buf")
+					}
+					break
 				}
 			}
-			if config.ShowDebugLog {
+			if config.ShowDebugLog && !usenewbuf {
 				logrus.Debugln("[listen] lock index", i)
 			}
-			lbf := listenbuff[i*lstnbufgragsz : (i+1)*lstnbufgragsz]
+			var lbf []byte
+			if usenewbuf {
+				lbf = helper.MakeBytes(lstnbufgragsz)
+			} else {
+				lbf = listenbuf[i*lstnbufgragsz : (i+1)*lstnbufgragsz]
+			}
 			n, addr, err := conn.ReadFromPeer(lbf)
 			if m.connections == nil || errors.Is(err, net.ErrClosed) {
 				logrus.Warnln("[listen] quit listening")
@@ -65,31 +122,24 @@ func (m *Me) listen() (conn p2p.Conn, err error) {
 					logrus.Errorln("[listen] reconnect udp err:", err)
 					return
 				}
-				if config.ShowDebugLog {
-					logrus.Debugln("[listen] unlock index", i)
+				if !usenewbuf {
+					if config.ShowDebugLog {
+						logrus.Debugln("[listen] unlock index", i)
+					}
+					hasntfinished[i].Unlock()
+					i--
 				}
-				hasntfinished[i].Unlock()
-				i--
 				continue
 			}
-			recvtotlcnt += uint64(n)
-			recvloopcnt++
-			if recvloopcnt%m.speedloop == 0 {
-				now := time.Now().UnixMilli()
-				logrus.Infof("[listen] recv avg speed: %.2f KB/s", float64(recvtotlcnt)/float64(now-recvlooptime))
-				recvtotlcnt = 0
-				recvlooptime = now
+			lq := lstnq{
+				index: -1,
+				addr:  addr,
+				buf:   lbf[:n],
 			}
-			packet := m.wait(lbf[:n:lstnbufgragsz])
-			if packet == nil {
-				if config.ShowDebugLog {
-					logrus.Debugln("[listen] waiting, unlock index", i)
-				}
-				hasntfinished[i].Unlock()
-				i--
-				continue
+			if !usenewbuf {
+				lq.index = int(i)
 			}
-			go m.dispatch(packet, addr, i, hasntfinished[i].Unlock)
+			q <- lq
 		}
 	}()
 	return
@@ -193,7 +243,7 @@ func (m *Me) dispatch(packet *head.Packet, addr p2p.EndPoint, index int, finish
 			packet.Put()
 		case head.ProtoData:
 			if p.pipe != nil {
-				p.pipe <- packet
+				p.pipe <- packet.CopyWithBody()
 				if config.ShowDebugLog {
 					logrus.Debugln("[listen] @", index, "deliver to pipe of", p.peerip)
 				}
@@ -204,8 +254,8 @@ func (m *Me) dispatch(packet *head.Packet, addr p2p.EndPoint, index int, finish
 				} else if config.ShowDebugLog {
 					logrus.Debugln("[listen] @", index, "deliver", packet.BodyLen(), "bytes data to nic")
 				}
-				packet.Put()
 			}
+			packet.Put()
 		default:
 			logrus.Warnln("[listen] @", index, "recv unknown proto:", packet.Proto)
 			packet.Put()
diff --git a/gold/link/recv.go b/gold/link/recv.go
index 8f46196..90496b4 100644
--- a/gold/link/recv.go
+++ b/gold/link/recv.go
@@ -52,17 +52,17 @@ func (m *Me) wait(data []byte) *head.Packet {
 		}
 		return nil
 	}
+	m.recved.Set(crc, true)
 	if config.ShowDebugLog {
-		logrus.Debugln("[recv]", len(data), "bytes data with flag", hex.EncodeToString(data[11:12]), hex.EncodeToString(data[10:11]))
+		logrus.Debugln("[recv]", strconv.FormatUint(crc, 16), len(data), "bytes data with flag", hex.EncodeToString(data[11:12]), hex.EncodeToString(data[10:11]))
 	}
 	if flags.IsSingle() || flags.NoFrag() {
 		h := head.SelectPacket()
 		_, err := h.Unmarshal(data)
 		if err != nil {
-			logrus.Errorln("[recv] unmarshal err:", err)
+			logrus.Errorln("[recv]", strconv.FormatUint(crc, 16), "unmarshal err:", err)
 			return nil
 		}
-		m.recved.Set(crc, true)
 		return h
 	}
 
@@ -75,35 +75,33 @@ func (m *Me) wait(data []byte) *head.Packet {
 	h := m.recving.Get(hsh)
 	if h != nil {
 		if config.ShowDebugLog {
-			logrus.Debugln("[recv] get another frag part of", strconv.FormatUint(hsh, 16))
+			logrus.Debugln("[recv]", strconv.FormatUint(crc, 16), "get another frag part of", strconv.FormatUint(hsh, 16))
 		}
 		ok, err := h.Unmarshal(data)
 		if err == nil {
 			if ok {
 				m.recving.Delete(hsh)
-				m.recved.Set(crc, true)
 				if config.ShowDebugLog {
-					logrus.Debugln("[recv] all parts of", strconv.FormatUint(hsh, 16), "has reached")
+					logrus.Debugln("[recv]", strconv.FormatUint(crc, 16), "all parts of", strconv.FormatUint(hsh, 16), "has reached")
 				}
 				return h
 			}
 		} else {
 			h.Put()
-			logrus.Errorln("[recv] unmarshal err:", err)
+			logrus.Errorln("[recv]", strconv.FormatUint(crc, 16), "unmarshal err:", err)
 		}
 		return nil
 	}
 	if config.ShowDebugLog {
-		logrus.Debugln("[recv] get new frag part of", strconv.FormatUint(hsh, 16))
+		logrus.Debugln("[recv]", strconv.FormatUint(crc, 16), "get new frag part of", strconv.FormatUint(hsh, 16))
 	}
 	h = head.SelectPacket()
 	_, err := h.Unmarshal(data)
 	if err != nil {
 		h.Put()
-		logrus.Errorln("[recv] unmarshal err:", err)
+		logrus.Errorln("[recv]", strconv.FormatUint(crc, 16), "unmarshal err:", err)
 		return nil
 	}
 	m.recving.Set(hsh, h)
-	m.recved.Set(crc, true)
 	return nil
 }
diff --git a/gold/link/send.go b/gold/link/send.go
index 8631112..1bcf61e 100644
--- a/gold/link/send.go
+++ b/gold/link/send.go
@@ -9,7 +9,6 @@ import (
 	"fmt"
 	"io"
 	"math/rand"
-	"time"
 
 	"github.com/klauspost/compress/zstd"
 	"github.com/sirupsen/logrus"
@@ -30,7 +29,8 @@ func (l *Link) WriteAndPut(p *head.Packet, istransfer bool) (n int, err error) {
 	teatype := l.randkeyidx()
 	sndcnt := uint16(l.incgetsndcnt())
 	var buf [4]byte
-	_, _ = crand.Read(buf[:])
+	_, _ = crand.Read(buf[:2])
+	binary.BigEndian.PutUint16(buf[2:4], sndcnt)
 	seq := binary.BigEndian.Uint32(buf[:])
 	mtu := l.mtu
 	if l.mturandomrange > 0 {
@@ -114,11 +114,7 @@ func (l *Link) write(p *head.Packet, teatype uint8, additional uint16, datasz ui
 		return 0, ErrTTL
 	}
 	if l.doublepacket {
-		cpp := p.Copy()
-		_ = time.AfterFunc(time.Millisecond*(10+time.Duration(rand.Intn(40))), func() {
-			defer cpp.Put()
-			_, _ = l.writeonce(cpp, teatype, additional, datasz, offset, istransfer, hasmore, seq)
-		})
+		_, _ = l.writeonce(p, teatype, additional, datasz, offset, istransfer, hasmore, seq)
 	}
 	return l.writeonce(p, teatype, additional, datasz, offset, istransfer, hasmore, seq)
 }
@@ -147,7 +143,7 @@ func (l *Link) writeonce(p *head.Packet, teatype uint8, additional uint16, datas
 		endl = "."
 	}
 	if config.ShowDebugLog {
-		logrus.Debugln("[send] write", len(d), "bytes data from ep", l.me.conn.LocalAddr(), "to", peerep, "offset:", fmt.Sprintf("%04x", offset))
+		logrus.Debugln("[send] write", len(d), "bytes data from ep", l.me.conn.LocalAddr(), "to", peerep, "offset", fmt.Sprintf("%04x", offset), "crc", fmt.Sprintf("%016x", p.CRC64()))
 		logrus.Debugln("[send] data bytes", hex.EncodeToString(d[:bound]), endl)
 	}
 	d = l.me.xorenc(d, seq)
diff --git a/upper/services/tunnel/tunnel_test.go b/upper/services/tunnel/tunnel_test.go
index e0396de..3801496 100644
--- a/upper/services/tunnel/tunnel_test.go
+++ b/upper/services/tunnel/tunnel_test.go
@@ -81,6 +81,7 @@ func testTunnel(t *testing.T, nw string, isplain bool, pshk *[32]byte, mtu uint1
 		MTU:            mtu,
 		MTURandomRange: mtu / 2,
 		UseZstd:        true,
+		DoublePacket:   true,
 	})
 	p.AddPeer(&link.PeerConfig{
 		PeerIP:         "192.168.1.2",