diff --git a/constant/constant.go b/constant/constant.go
deleted file mode 100644
index 66ab104..0000000
--- a/constant/constant.go
+++ /dev/null
@@ -1,2 +0,0 @@
-// Package constant provides global constants/variables of this project.
-package constant
diff --git a/common/adapter/metadata.go b/constant/metadata.go
similarity index 99%
rename from common/adapter/metadata.go
rename to constant/metadata.go
index cca8d8b..c0fe485 100755
--- a/common/adapter/metadata.go
+++ b/constant/metadata.go
@@ -1,4 +1,4 @@
-package adapter
+package constant
 
 import (
 	"bytes"
diff --git a/common/adapter/adapter.go b/core/adapter.go
old mode 100755
new mode 100644
similarity index 79%
rename from common/adapter/adapter.go
rename to core/adapter.go
index 4880cc5..98803bc
--- a/common/adapter/adapter.go
+++ b/core/adapter.go
@@ -1,12 +1,14 @@
-package adapter
+package core
 
 import (
 	"net"
+
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
 type TCPConn interface {
 	net.Conn
-	Metadata() *Metadata
+	ID() *stack.TransportEndpointID
 }
 
 type UDPPacket interface {
@@ -16,12 +18,12 @@ type UDPPacket interface {
 	// Drop call after packet is used, could release resources in this function.
 	Drop()
 
+	// ID returns the transport endpoint id of packet.
+	ID() *stack.TransportEndpointID
+
 	// LocalAddr returns the source IP/Port of packet.
 	LocalAddr() net.Addr
 
-	// Metadata returns the metadata of packet.
-	Metadata() *Metadata
-
 	// RemoteAddr returns the destination IP/Port of packet.
 	RemoteAddr() net.Addr
 
diff --git a/core/handler.go b/core/handler.go
new file mode 100755
index 0000000..8606df1
--- /dev/null
+++ b/core/handler.go
@@ -0,0 +1,6 @@
+package core
+
+type Handler interface {
+	Add(TCPConn)
+	AddPacket(UDPPacket)
+}
diff --git a/core/stack/handler.go b/core/stack/handler.go
deleted file mode 100755
index f4219c2..0000000
--- a/core/stack/handler.go
+++ /dev/null
@@ -1,10 +0,0 @@
-package stack
-
-import (
-	"github.com/xjasonlyu/tun2socks/common/adapter"
-)
-
-type Handler interface {
-	Add(adapter.TCPConn)
-	AddPacket(adapter.UDPPacket)
-}
diff --git a/core/stack/stack.go b/core/stack/stack.go
index 629c774..bafbf2f 100755
--- a/core/stack/stack.go
+++ b/core/stack/stack.go
@@ -2,6 +2,8 @@
 package stack
 
 import (
+	"github.com/xjasonlyu/tun2socks/core"
+
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
@@ -14,12 +16,12 @@ import (
 type Stack struct {
 	*stack.Stack
 
-	handler Handler
+	handler core.Handler
 	nicID   tcpip.NICID
 }
 
 // New allocates a new *Stack with given options.
-func New(ep stack.LinkEndpoint, handler Handler, opts ...Option) (*Stack, error) {
+func New(ep stack.LinkEndpoint, handler core.Handler, opts ...Option) (*Stack, error) {
 	s := &Stack{
 		Stack: stack.New(stack.Options{
 			NetworkProtocols: []stack.NetworkProtocolFactory{
diff --git a/core/stack/tcp.go b/core/stack/tcp.go
index d13b4c0..309ad01 100755
--- a/core/stack/tcp.go
+++ b/core/stack/tcp.go
@@ -5,10 +5,9 @@ import (
 	"net"
 	"time"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
-
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/adapters/gonet"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
 	"gvisor.dev/gvisor/pkg/tcpip/transport/tcp"
 	"gvisor.dev/gvisor/pkg/waiter"
 )
@@ -50,15 +49,8 @@ func withTCPHandler() Option {
 
 			conn := &tcpConn{
 				Conn: gonet.NewTCPConn(&wq, ep),
-				metadata: &adapter.Metadata{
-					Net:     adapter.TCP,
-					SrcIP:   net.IP(id.RemoteAddress),
-					SrcPort: id.RemotePort,
-					DstIP:   net.IP(id.LocalAddress),
-					DstPort: id.LocalPort,
-				},
+				id:   &id,
 			}
-
 			s.handler.Add(conn)
 		})
 		s.SetTransportProtocolHandler(tcp.ProtocolNumber, tcpForwarder.HandlePacket)
@@ -83,9 +75,9 @@ func setKeepalive(ep tcpip.Endpoint) error {
 
 type tcpConn struct {
 	net.Conn
-	metadata *adapter.Metadata
+	id *stack.TransportEndpointID
 }
 
-func (c *tcpConn) Metadata() *adapter.Metadata {
-	return c.metadata
+func (c *tcpConn) ID() *stack.TransportEndpointID {
+	return c.id
 }
diff --git a/core/stack/udp.go b/core/stack/udp.go
index 0324be6..fcdde60 100755
--- a/core/stack/udp.go
+++ b/core/stack/udp.go
@@ -4,8 +4,6 @@ import (
 	"fmt"
 	"net"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
-
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
@@ -39,18 +37,11 @@ func withUDPHandler() Option {
 
 			packet := &udpPacket{
 				s:        s,
-				id:       id,
+				id:       &id,
 				nicID:    pkt.NICID,
 				netHdr:   pkt.Network(),
 				netProto: pkt.NetworkProtocolNumber,
 				payload:  pkt.Data.ToView(),
-				metadata: &adapter.Metadata{
-					Net:     adapter.UDP,
-					SrcIP:   net.IP(id.RemoteAddress),
-					SrcPort: id.RemotePort,
-					DstIP:   net.IP(id.LocalAddress),
-					DstPort: id.LocalPort,
-				},
 			}
 
 			s.handler.AddPacket(packet)
@@ -63,12 +54,11 @@ func withUDPHandler() Option {
 
 type udpPacket struct {
 	s        *Stack
-	id       stack.TransportEndpointID
+	id       *stack.TransportEndpointID
 	nicID    tcpip.NICID
 	netHdr   header.Network
 	netProto tcpip.NetworkProtocolNumber
 	payload  []byte
-	metadata *adapter.Metadata
 }
 
 func (p *udpPacket) Data() []byte {
@@ -79,12 +69,12 @@ func (p *udpPacket) Drop() {
 	/* Release */
 }
 
-func (p *udpPacket) LocalAddr() net.Addr {
-	return &net.UDPAddr{IP: net.IP(p.id.LocalAddress), Port: int(p.id.LocalPort)}
+func (p *udpPacket) ID() *stack.TransportEndpointID {
+	return p.id
 }
 
-func (p *udpPacket) Metadata() *adapter.Metadata {
-	return p.metadata
+func (p *udpPacket) LocalAddr() net.Addr {
+	return &net.UDPAddr{IP: net.IP(p.id.LocalAddress), Port: int(p.id.LocalPort)}
 }
 
 func (p *udpPacket) RemoteAddr() net.Addr {
diff --git a/engine/tunnel.go b/engine/tunnel.go
index 5c4f21c..b0e223f 100644
--- a/engine/tunnel.go
+++ b/engine/tunnel.go
@@ -1,19 +1,18 @@
 package engine
 
 import (
-	"github.com/xjasonlyu/tun2socks/common/adapter"
-	"github.com/xjasonlyu/tun2socks/core/stack"
+	"github.com/xjasonlyu/tun2socks/core"
 	"github.com/xjasonlyu/tun2socks/tunnel"
 )
 
-var _ stack.Handler = (*fakeTunnel)(nil)
+var _ core.Handler = (*fakeTunnel)(nil)
 
 type fakeTunnel struct{}
 
-func (*fakeTunnel) Add(conn adapter.TCPConn) {
+func (*fakeTunnel) Add(conn core.TCPConn) {
 	tunnel.Add(conn)
 }
 
-func (*fakeTunnel) AddPacket(packet adapter.UDPPacket) {
+func (*fakeTunnel) AddPacket(packet core.UDPPacket) {
 	tunnel.AddPacket(packet)
 }
diff --git a/proxy/base.go b/proxy/base.go
index 2185404..4453acd 100755
--- a/proxy/base.go
+++ b/proxy/base.go
@@ -5,7 +5,7 @@ import (
 	"errors"
 	"net"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
+	M "github.com/xjasonlyu/tun2socks/constant"
 	"github.com/xjasonlyu/tun2socks/proxy/proto"
 )
 
@@ -28,10 +28,10 @@ func (b *Base) Proto() proto.Proto {
 	return b.proto
 }
 
-func (b *Base) DialContext(context.Context, *adapter.Metadata) (net.Conn, error) {
+func (b *Base) DialContext(context.Context, *M.Metadata) (net.Conn, error) {
 	return nil, errors.New("not supported")
 }
 
-func (b *Base) DialUDP(*adapter.Metadata) (net.PacketConn, error) {
+func (b *Base) DialUDP(*M.Metadata) (net.PacketConn, error) {
 	return nil, errors.New("not supported")
 }
diff --git a/proxy/direct.go b/proxy/direct.go
index 6880c1f..7899f9b 100755
--- a/proxy/direct.go
+++ b/proxy/direct.go
@@ -4,8 +4,8 @@ import (
 	"context"
 	"net"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
 	"github.com/xjasonlyu/tun2socks/component/dialer"
+	M "github.com/xjasonlyu/tun2socks/constant"
 	"github.com/xjasonlyu/tun2socks/proxy/proto"
 )
 
@@ -23,7 +23,7 @@ func NewDirect() *Direct {
 	}
 }
 
-func (d *Direct) DialContext(ctx context.Context, metadata *adapter.Metadata) (net.Conn, error) {
+func (d *Direct) DialContext(ctx context.Context, metadata *M.Metadata) (net.Conn, error) {
 	c, err := dialer.DialContext(ctx, "tcp", metadata.DestinationAddress())
 	if err != nil {
 		return nil, err
@@ -32,7 +32,7 @@ func (d *Direct) DialContext(ctx context.Context, metadata *adapter.Metadata) (n
 	return c, nil
 }
 
-func (d *Direct) DialUDP(_ *adapter.Metadata) (net.PacketConn, error) {
+func (d *Direct) DialUDP(*M.Metadata) (net.PacketConn, error) {
 	pc, err := dialer.ListenPacket("udp", "")
 	if err != nil {
 		return nil, err
@@ -45,7 +45,7 @@ type directPacketConn struct {
 }
 
 func (pc *directPacketConn) WriteTo(b []byte, addr net.Addr) (int, error) {
-	if m, ok := addr.(*adapter.Metadata); ok && m.DstIP != nil {
+	if m, ok := addr.(*M.Metadata); ok && m.DstIP != nil {
 		return pc.PacketConn.WriteTo(b, m.UDPAddr())
 	}
 
diff --git a/proxy/proxy.go b/proxy/proxy.go
index df36883..3b0cdbd 100755
--- a/proxy/proxy.go
+++ b/proxy/proxy.go
@@ -6,7 +6,7 @@ import (
 	"net"
 	"time"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
+	M "github.com/xjasonlyu/tun2socks/constant"
 	"github.com/xjasonlyu/tun2socks/proxy/proto"
 )
 
@@ -19,8 +19,8 @@ var (
 )
 
 type Dialer interface {
-	DialContext(context.Context, *adapter.Metadata) (net.Conn, error)
-	DialUDP(*adapter.Metadata) (net.PacketConn, error)
+	DialContext(context.Context, *M.Metadata) (net.Conn, error)
+	DialUDP(*M.Metadata) (net.PacketConn, error)
 }
 
 type Proxy interface {
@@ -35,18 +35,18 @@ func SetDialer(d Dialer) {
 }
 
 // Dial uses default Dialer to dial TCP.
-func Dial(metadata *adapter.Metadata) (net.Conn, error) {
+func Dial(metadata *M.Metadata) (net.Conn, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), tcpConnectTimeout)
 	defer cancel()
 	return _defaultDialer.DialContext(ctx, metadata)
 }
 
 // DialContext uses default Dialer to dial TCP with context.
-func DialContext(ctx context.Context, metadata *adapter.Metadata) (net.Conn, error) {
+func DialContext(ctx context.Context, metadata *M.Metadata) (net.Conn, error) {
 	return _defaultDialer.DialContext(ctx, metadata)
 }
 
 // DialUDP uses default Dialer to dial UDP.
-func DialUDP(metadata *adapter.Metadata) (net.PacketConn, error) {
+func DialUDP(metadata *M.Metadata) (net.PacketConn, error) {
 	return _defaultDialer.DialUDP(metadata)
 }
diff --git a/proxy/shadowsocks.go b/proxy/shadowsocks.go
index d8de273..67987fb 100755
--- a/proxy/shadowsocks.go
+++ b/proxy/shadowsocks.go
@@ -6,10 +6,10 @@ import (
 	"fmt"
 	"net"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
 	"github.com/xjasonlyu/tun2socks/component/dialer"
 	obfs "github.com/xjasonlyu/tun2socks/component/simple-obfs"
 	"github.com/xjasonlyu/tun2socks/component/socks5"
+	M "github.com/xjasonlyu/tun2socks/constant"
 	"github.com/xjasonlyu/tun2socks/proxy/proto"
 
 	"github.com/Dreamacro/go-shadowsocks2/core"
@@ -43,7 +43,7 @@ func NewShadowsocks(addr, method, password, obfsMode, obfsHost string) (*Shadows
 	}, nil
 }
 
-func (ss *Shadowsocks) DialContext(ctx context.Context, metadata *adapter.Metadata) (c net.Conn, err error) {
+func (ss *Shadowsocks) DialContext(ctx context.Context, metadata *M.Metadata) (c net.Conn, err error) {
 	c, err = dialer.DialContext(ctx, "tcp", ss.Addr())
 	if err != nil {
 		return nil, fmt.Errorf("connect to %s: %w", ss.Addr(), err)
@@ -69,7 +69,7 @@ func (ss *Shadowsocks) DialContext(ctx context.Context, metadata *adapter.Metada
 	return
 }
 
-func (ss *Shadowsocks) DialUDP(_ *adapter.Metadata) (net.PacketConn, error) {
+func (ss *Shadowsocks) DialUDP(*M.Metadata) (net.PacketConn, error) {
 	pc, err := dialer.ListenPacket("udp", "")
 	if err != nil {
 		return nil, fmt.Errorf("listen packet: %w", err)
@@ -92,7 +92,7 @@ type ssPacketConn struct {
 
 func (pc *ssPacketConn) WriteTo(b []byte, addr net.Addr) (n int, err error) {
 	var packet []byte
-	if m, ok := addr.(*adapter.Metadata); ok {
+	if m, ok := addr.(*M.Metadata); ok {
 		packet, err = socks5.EncodeUDPPacket(m.SerializesSocksAddr(), b)
 	} else {
 		packet, err = socks5.EncodeUDPPacket(socks5.ParseAddrToSocksAddr(addr), b)
diff --git a/proxy/socks5.go b/proxy/socks5.go
index 7ccbbe6..a4eb879 100755
--- a/proxy/socks5.go
+++ b/proxy/socks5.go
@@ -7,9 +7,9 @@ import (
 	"io/ioutil"
 	"net"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
 	"github.com/xjasonlyu/tun2socks/component/dialer"
 	"github.com/xjasonlyu/tun2socks/component/socks5"
+	M "github.com/xjasonlyu/tun2socks/constant"
 	"github.com/xjasonlyu/tun2socks/proxy/proto"
 )
 
@@ -33,7 +33,7 @@ func NewSocks5(addr, user, pass string) (*Socks5, error) {
 	}, nil
 }
 
-func (ss *Socks5) DialContext(ctx context.Context, metadata *adapter.Metadata) (c net.Conn, err error) {
+func (ss *Socks5) DialContext(ctx context.Context, metadata *M.Metadata) (c net.Conn, err error) {
 	c, err = dialer.DialContext(ctx, "tcp", ss.Addr())
 	if err != nil {
 		return nil, fmt.Errorf("connect to %s: %w", ss.Addr(), err)
@@ -58,7 +58,7 @@ func (ss *Socks5) DialContext(ctx context.Context, metadata *adapter.Metadata) (
 	return
 }
 
-func (ss *Socks5) DialUDP(_ *adapter.Metadata) (_ net.PacketConn, err error) {
+func (ss *Socks5) DialUDP(*M.Metadata) (_ net.PacketConn, err error) {
 	ctx, cancel := context.WithTimeout(context.Background(), tcpConnectTimeout)
 	defer cancel()
 
@@ -132,7 +132,7 @@ type socksPacketConn struct {
 
 func (pc *socksPacketConn) WriteTo(b []byte, addr net.Addr) (n int, err error) {
 	var packet []byte
-	if m, ok := addr.(*adapter.Metadata); ok {
+	if m, ok := addr.(*M.Metadata); ok {
 		packet, err = socks5.EncodeUDPPacket(m.SerializesSocksAddr(), b)
 	} else {
 		packet, err = socks5.EncodeUDPPacket(socks5.ParseAddrToSocksAddr(addr), b)
diff --git a/tunnel/statistic/tracker.go b/tunnel/statistic/tracker.go
index 5315993..f5a4155 100755
--- a/tunnel/statistic/tracker.go
+++ b/tunnel/statistic/tracker.go
@@ -4,7 +4,7 @@ import (
 	"net"
 	"time"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
+	M "github.com/xjasonlyu/tun2socks/constant"
 
 	"github.com/gofrs/uuid"
 	"go.uber.org/atomic"
@@ -16,11 +16,11 @@ type tracker interface {
 }
 
 type trackerInfo struct {
-	Start         time.Time         `json:"start"`
-	UUID          uuid.UUID         `json:"id"`
-	Metadata      *adapter.Metadata `json:"metadata"`
-	UploadTotal   *atomic.Int64     `json:"upload"`
-	DownloadTotal *atomic.Int64     `json:"download"`
+	Start         time.Time     `json:"start"`
+	UUID          uuid.UUID     `json:"id"`
+	Metadata      *M.Metadata   `json:"metadata"`
+	UploadTotal   *atomic.Int64 `json:"upload"`
+	DownloadTotal *atomic.Int64 `json:"download"`
 }
 
 type tcpTracker struct {
@@ -30,7 +30,7 @@ type tcpTracker struct {
 	manager *Manager
 }
 
-func NewTCPTracker(conn net.Conn, metadata *adapter.Metadata, manager *Manager) *tcpTracker {
+func NewTCPTracker(conn net.Conn, metadata *M.Metadata, manager *Manager) *tcpTracker {
 	id, _ := uuid.NewV4()
 
 	tt := &tcpTracker{
@@ -81,7 +81,7 @@ type udpTracker struct {
 	manager *Manager
 }
 
-func NewUDPTracker(conn net.PacketConn, metadata *adapter.Metadata, manager *Manager) *udpTracker {
+func NewUDPTracker(conn net.PacketConn, metadata *M.Metadata, manager *Manager) *udpTracker {
 	id, _ := uuid.NewV4()
 
 	ut := &udpTracker{
diff --git a/tunnel/tcp.go b/tunnel/tcp.go
index 5d8f04b..80e9499 100755
--- a/tunnel/tcp.go
+++ b/tunnel/tcp.go
@@ -7,8 +7,9 @@ import (
 	"sync"
 	"time"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
 	"github.com/xjasonlyu/tun2socks/common/pool"
+	M "github.com/xjasonlyu/tun2socks/constant"
+	"github.com/xjasonlyu/tun2socks/core"
 	"github.com/xjasonlyu/tun2socks/log"
 	"github.com/xjasonlyu/tun2socks/proxy"
 	"github.com/xjasonlyu/tun2socks/tunnel/statistic"
@@ -18,14 +19,21 @@ const (
 	tcpWaitTimeout = 5 * time.Second
 )
 
-func newTCPTracker(conn net.Conn, metadata *adapter.Metadata) net.Conn {
+func newTCPTracker(conn net.Conn, metadata *M.Metadata) net.Conn {
 	return statistic.NewTCPTracker(conn, metadata, statistic.DefaultManager)
 }
 
-func handleTCP(localConn adapter.TCPConn) {
+func handleTCP(localConn core.TCPConn) {
 	defer localConn.Close()
 
-	metadata := localConn.Metadata()
+	id := localConn.ID()
+	metadata := &M.Metadata{
+		Net:     M.TCP,
+		SrcIP:   net.IP(id.RemoteAddress),
+		SrcPort: id.RemotePort,
+		DstIP:   net.IP(id.LocalAddress),
+		DstPort: id.LocalPort,
+	}
 	if !metadata.Valid() {
 		log.Warnf("[Metadata] not valid: %#v", metadata)
 		return
diff --git a/tunnel/tunnel.go b/tunnel/tunnel.go
index 0ec5acd..55d7d7b 100755
--- a/tunnel/tunnel.go
+++ b/tunnel/tunnel.go
@@ -3,7 +3,7 @@ package tunnel
 import (
 	"runtime"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
+	"github.com/xjasonlyu/tun2socks/core"
 	"github.com/xjasonlyu/tun2socks/log"
 )
 
@@ -15,8 +15,8 @@ const (
 )
 
 var (
-	tcpQueue      = make(chan adapter.TCPConn) /* unbuffered */
-	udpQueue      = make(chan adapter.UDPPacket, maxUDPQueueSize)
+	tcpQueue      = make(chan core.TCPConn) /* unbuffered */
+	udpQueue      = make(chan core.UDPPacket, maxUDPQueueSize)
 	numUDPWorkers = max(runtime.NumCPU(), 4 /* at least 4 workers */)
 )
 
@@ -25,12 +25,12 @@ func init() {
 }
 
 // Add adds tcpConn to tcpQueue.
-func Add(conn adapter.TCPConn) {
+func Add(conn core.TCPConn) {
 	tcpQueue <- conn
 }
 
 // AddPacket adds udpPacket to udpQueue.
-func AddPacket(packet adapter.UDPPacket) {
+func AddPacket(packet core.UDPPacket) {
 	select {
 	case udpQueue <- packet:
 	default:
diff --git a/tunnel/udp.go b/tunnel/udp.go
index 01d99a0..f54458b 100755
--- a/tunnel/udp.go
+++ b/tunnel/udp.go
@@ -7,9 +7,10 @@ import (
 	"strconv"
 	"time"
 
-	"github.com/xjasonlyu/tun2socks/common/adapter"
 	"github.com/xjasonlyu/tun2socks/common/pool"
 	"github.com/xjasonlyu/tun2socks/component/nat"
+	M "github.com/xjasonlyu/tun2socks/constant"
+	"github.com/xjasonlyu/tun2socks/core"
 	"github.com/xjasonlyu/tun2socks/log"
 	"github.com/xjasonlyu/tun2socks/proxy"
 	"github.com/xjasonlyu/tun2socks/tunnel/statistic"
@@ -25,18 +26,25 @@ var (
 	natTable = nat.NewTable()
 )
 
-func newUDPTracker(conn net.PacketConn, metadata *adapter.Metadata) net.PacketConn {
+func newUDPTracker(conn net.PacketConn, metadata *M.Metadata) net.PacketConn {
 	return statistic.NewUDPTracker(conn, metadata, statistic.DefaultManager)
 }
 
-func handleUDP(packet adapter.UDPPacket) {
-	metadata := packet.Metadata()
+func handleUDP(packet core.UDPPacket) {
+	id := packet.ID()
+	metadata := &M.Metadata{
+		Net:     M.UDP,
+		SrcIP:   net.IP(id.RemoteAddress),
+		SrcPort: id.RemotePort,
+		DstIP:   net.IP(id.LocalAddress),
+		DstPort: id.LocalPort,
+	}
 	if !metadata.Valid() {
 		log.Warnf("[Metadata] not valid: %#v", metadata)
 		return
 	}
 
-	generateNATKey := func(m *adapter.Metadata) string {
+	generateNATKey := func(m *M.Metadata) string {
 		return m.SourceAddress() /* Full Cone NAT Key */
 	}
 	key := generateNATKey(metadata)
@@ -101,7 +109,7 @@ func handleUDP(packet adapter.UDPPacket) {
 	}()
 }
 
-func handleUDPToRemote(packet adapter.UDPPacket, pc net.PacketConn, remote net.Addr, drop bool) {
+func handleUDPToRemote(packet core.UDPPacket, pc net.PacketConn, remote net.Addr, drop bool) {
 	defer func() {
 		if drop {
 			packet.Drop()
@@ -115,7 +123,7 @@ func handleUDPToRemote(packet adapter.UDPPacket, pc net.PacketConn, remote net.A
 	log.Infof("[UDP] %s --> %s", packet.RemoteAddr(), remote)
 }
 
-func handleUDPToLocal(packet adapter.UDPPacket, pc net.PacketConn, timeout time.Duration) {
+func handleUDPToLocal(packet core.UDPPacket, pc net.PacketConn, timeout time.Duration) {
 	buf := pool.Get(pool.MaxSegmentSize)
 	defer pool.Put(buf)