From 47406ce4ce69e0b1df29e6caa7afdda6c2edd4c4 Mon Sep 17 00:00:00 2001
From: nadoo <287492+nadoo@users.noreply.github.com>
Date: Tue, 12 Mar 2019 23:32:23 +0800
Subject: [PATCH] udptun: fixed a bug in nat mapping. #91

---
 README.md              |  2 +-
 conf.go                |  2 +-
 dns/cache.go           | 12 ++++++------
 dns/client.go          | 22 ++++++++++-----------
 dns/message.go         | 44 +++++++++++++++++++++---------------------
 dns/server.go          | 12 ++++++------
 go.mod                 |  8 ++++----
 go.sum                 | 19 ++++++++++++++++++
 proxy/udptun/udptun.go | 28 +++++++++++++--------------
 9 files changed, 84 insertions(+), 65 deletions(-)

diff --git a/README.md b/README.md
index 55f5dad..a79a3c6 100644
--- a/README.md
+++ b/README.md
@@ -175,7 +175,7 @@ Available Schemes:
 
 Available schemes for different modes:
   listen: mixed ss socks5 http redir redir6 tcptun udptun uottun tls unix kcp
-  forward: ss socks5 http ssr vmess tls ws unix kcp simple-bfs
+  forward: reject ss socks5 http ssr vmess tls ws unix kcp simple-bfs
 
 SS scheme:
   ss://method:pass@host:port
diff --git a/conf.go b/conf.go
index abc9d4b..c2d7a32 100644
--- a/conf.go
+++ b/conf.go
@@ -128,7 +128,7 @@ func usage() {
 
 	fmt.Fprintf(os.Stderr, "Available schemes for different modes:\n")
 	fmt.Fprintf(os.Stderr, "  listen: mixed ss socks5 http redir redir6 tcptun udptun uottun tls unix kcp\n")
-	fmt.Fprintf(os.Stderr, "  forward: ss socks5 http ssr vmess tls ws unix kcp simple-bfs\n")
+	fmt.Fprintf(os.Stderr, "  forward: reject ss socks5 http ssr vmess tls ws unix kcp simple-bfs\n")
 	fmt.Fprintf(os.Stderr, "\n")
 
 	fmt.Fprintf(os.Stderr, "SS scheme:\n")
diff --git a/dns/cache.go b/dns/cache.go
index e3d7b0f..80e6e9e 100644
--- a/dns/cache.go
+++ b/dns/cache.go
@@ -5,7 +5,7 @@ import (
 	"time"
 )
 
-// LongTTL is 50 years duration in seconds, used for none-expired items
+// LongTTL is 50 years duration in seconds, used for none-expired items.
 const LongTTL = 50 * 365 * 24 * 3600
 
 type item struct {
@@ -13,13 +13,13 @@ type item struct {
 	expire time.Time
 }
 
-// Cache is the struct of cache
+// Cache is the struct of cache.
 type Cache struct {
 	m map[string]*item
 	l sync.RWMutex
 }
 
-// NewCache returns a new cache
+// NewCache returns a new cache.
 func NewCache() (c *Cache) {
 	c = &Cache{m: make(map[string]*item)}
 	go func() {
@@ -36,12 +36,12 @@ func NewCache() (c *Cache) {
 	return
 }
 
-// Len returns the length of cache
+// Len returns the length of cache.
 func (c *Cache) Len() int {
 	return len(c.m)
 }
 
-// Put an item into cache, invalid after ttl seconds
+// Put an item into cache, invalid after ttl seconds.
 func (c *Cache) Put(k string, v []byte, ttl int) {
 	if len(v) != 0 {
 		c.l.Lock()
@@ -55,7 +55,7 @@ func (c *Cache) Put(k string, v []byte, ttl int) {
 	}
 }
 
-// Get an item from cache
+// Get an item from cache.
 func (c *Cache) Get(k string) (v []byte) {
 	c.l.RLock()
 	if it, ok := c.m[k]; ok {
diff --git a/dns/client.go b/dns/client.go
index 71259aa..b7c1b4e 100644
--- a/dns/client.go
+++ b/dns/client.go
@@ -13,10 +13,10 @@ import (
 	"github.com/nadoo/glider/proxy"
 )
 
-// HandleFunc function handles the dns TypeA or TypeAAAA answer
+// HandleFunc function handles the dns TypeA or TypeAAAA answer.
 type HandleFunc func(Domain, ip string) error
 
-// Config for dns
+// Config for dns.
 type Config struct {
 	Servers   []string
 	Timeout   int
@@ -26,7 +26,7 @@ type Config struct {
 	AlwaysTCP bool
 }
 
-// Client is a dns client struct
+// Client is a dns client struct.
 type Client struct {
 	dialer      proxy.Dialer
 	cache       *Cache
@@ -36,7 +36,7 @@ type Client struct {
 	handlers    []HandleFunc
 }
 
-// NewClient returns a new dns client
+// NewClient returns a new dns client.
 func NewClient(dialer proxy.Dialer, config *Config) (*Client, error) {
 	c := &Client{
 		dialer:      dialer,
@@ -54,7 +54,7 @@ func NewClient(dialer proxy.Dialer, config *Config) (*Client, error) {
 	return c, nil
 }
 
-// Exchange handles request msg and returns response msg
+// Exchange handles request message and returns response message.
 // reqBytes = reqLen + reqMsg
 func (c *Client) Exchange(reqBytes []byte, clientAddr string, preferTCP bool) ([]byte, error) {
 	req, err := UnmarshalMessage(reqBytes[2:])
@@ -122,7 +122,7 @@ func (c *Client) Exchange(reqBytes []byte, clientAddr string, preferTCP bool) ([
 	return respBytes, nil
 }
 
-// exchange choose a upstream dns server based on qname, communicate with it on the network
+// exchange choose a upstream dns server based on qname, communicate with it on the network.
 func (c *Client) exchange(qname string, reqBytes []byte, preferTCP bool) (server, network string, respBytes []byte, err error) {
 	// use tcp to connect upstream server default
 	network = "tcp"
@@ -170,7 +170,7 @@ func (c *Client) exchange(qname string, reqBytes []byte, preferTCP bool) (server
 	return server, network, respBytes, err
 }
 
-// exchangeTCP exchange with server over tcp
+// exchangeTCP exchange with server over tcp.
 func (c *Client) exchangeTCP(rc net.Conn, reqBytes []byte) ([]byte, error) {
 	if _, err := rc.Write(reqBytes); err != nil {
 		log.F("[dns] failed to write req message: %v", err)
@@ -195,7 +195,7 @@ func (c *Client) exchangeTCP(rc net.Conn, reqBytes []byte) ([]byte, error) {
 	return respBytes, nil
 }
 
-// exchangeUDP exchange with server over udp
+// exchangeUDP exchange with server over udp.
 func (c *Client) exchangeUDP(rc net.Conn, reqBytes []byte) ([]byte, error) {
 	if _, err := rc.Write(reqBytes[2:]); err != nil {
 		log.F("[dns] failed to write req message: %v", err)
@@ -212,7 +212,7 @@ func (c *Client) exchangeUDP(rc net.Conn, reqBytes []byte) ([]byte, error) {
 	return reqBytes[:2+n], nil
 }
 
-// SetServers sets upstream dns servers for the given domain
+// SetServers sets upstream dns servers for the given domain.
 func (c *Client) SetServers(domain string, servers ...string) {
 	c.upServerMap[domain] = append(c.upServerMap[domain], servers...)
 }
@@ -232,7 +232,7 @@ func (c *Client) GetServers(domain string) []string {
 	return c.upServers
 }
 
-// AddHandler adds a custom handler to handle the resolved result (A and AAAA)
+// AddHandler adds a custom handler to handle the resolved result (A and AAAA).
 func (c *Client) AddHandler(h HandleFunc) {
 	c.handlers = append(c.handlers, h)
 }
@@ -258,7 +258,7 @@ func (c *Client) AddRecord(record string) error {
 	return nil
 }
 
-// GenResponse generates a dns response message for the given domani an ip address
+// GenResponse generates a dns response message for the given domain and ip address.
 func (c *Client) GenResponse(domain string, ip string) (*Message, error) {
 	ipb := net.ParseIP(ip)
 	if ipb == nil {
diff --git a/dns/message.go b/dns/message.go
index 1a57ebb..efc0f23 100644
--- a/dns/message.go
+++ b/dns/message.go
@@ -16,7 +16,7 @@ import (
 // the header.
 const UDPMaxLen = 512
 
-// HeaderLen is the length of dns msg header
+// HeaderLen is the length of dns msg header.
 const HeaderLen = 12
 
 // Message types
@@ -25,7 +25,7 @@ const (
 	Response = 1
 )
 
-// QType .
+// Query types
 const (
 	QTypeA    uint16 = 1  //ipv4
 	QTypeAAAA uint16 = 28 ///ipv6
@@ -62,7 +62,7 @@ type Message struct {
 	unMarshaled []byte
 }
 
-// NewMessage returns a new message
+// NewMessage returns a new message.
 func NewMessage(id uint16, msgType int) *Message {
 	if id == 0 {
 		id = uint16(rand.Uint32())
@@ -74,20 +74,20 @@ func NewMessage(id uint16, msgType int) *Message {
 	return m
 }
 
-// SetQuestion sets a question to dns message,
+// SetQuestion sets a question to dns message.
 func (m *Message) SetQuestion(q *Question) error {
 	m.Question = q
 	m.Header.SetQdcount(1)
 	return nil
 }
 
-// AddAnswer adds an answer to dns message
+// AddAnswer adds an answer to dns message.
 func (m *Message) AddAnswer(rr *RR) error {
 	m.Answers = append(m.Answers, rr)
 	return nil
 }
 
-// Marshal marshals message struct to []byte
+// Marshal marshals message struct to []byte.
 func (m *Message) Marshal() ([]byte, error) {
 	var buf bytes.Buffer
 
@@ -117,7 +117,7 @@ func (m *Message) Marshal() ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
-// UnmarshalMessage unmarshals []bytes to Message
+// UnmarshalMessage unmarshals []bytes to Message.
 func UnmarshalMessage(b []byte) (*Message, error) {
 	if len(b) < HeaderLen {
 		return nil, errors.New("UnmarshalMessage: not enough data")
@@ -183,22 +183,22 @@ type Header struct {
 	ARCOUNT uint16
 }
 
-// SetMsgType .
+// SetMsgType sets the message type.
 func (h *Header) SetMsgType(qr int) {
 	h.Bits |= uint16(qr) << 15
 }
 
-// SetTC .
+// SetTC sets the tc flag.
 func (h *Header) SetTC(tc int) {
 	h.Bits |= uint16(tc) << 9
 }
 
-// SetQdcount sets query count, most dns servers only support 1 query per request
+// SetQdcount sets query count, most dns servers only support 1 query per request.
 func (h *Header) SetQdcount(qdcount int) {
 	h.QDCOUNT = uint16(qdcount)
 }
 
-// SetAncount sets answers count
+// SetAncount sets answers count.
 func (h *Header) SetAncount(ancount int) {
 	h.ANCOUNT = uint16(ancount)
 }
@@ -208,14 +208,14 @@ func (h *Header) setFlag(QR uint16, Opcode uint16, AA uint16,
 	h.Bits = QR<<15 + Opcode<<11 + AA<<10 + TC<<9 + RD<<8 + RA<<7 + RCODE
 }
 
-// Marshal marshals header struct to []byte
+// Marshal marshals header struct to []byte.
 func (h *Header) Marshal() ([]byte, error) {
 	var buf bytes.Buffer
 	err := binary.Write(&buf, binary.BigEndian, h)
 	return buf.Bytes(), err
 }
 
-// UnmarshalHeader unmarshals []bytes to Header
+// UnmarshalHeader unmarshals []bytes to Header.
 func UnmarshalHeader(b []byte, h *Header) error {
 	if h == nil {
 		return errors.New("unmarshal header must not be nil")
@@ -258,7 +258,7 @@ type Question struct {
 	QCLASS uint16
 }
 
-// NewQuestion returns a new dns question
+// NewQuestion returns a new dns question.
 func NewQuestion(qtype uint16, domain string) *Question {
 	return &Question{
 		QNAME:  domain,
@@ -267,7 +267,7 @@ func NewQuestion(qtype uint16, domain string) *Question {
 	}
 }
 
-// Marshal marshals Question struct to []byte
+// Marshal marshals Question struct to []byte.
 func (q *Question) Marshal() ([]byte, error) {
 	var buf bytes.Buffer
 
@@ -278,7 +278,7 @@ func (q *Question) Marshal() ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
-// UnmarshalQuestion unmarshals []bytes to Question
+// UnmarshalQuestion unmarshals []bytes to Question.
 func (m *Message) UnmarshalQuestion(b []byte, q *Question) (n int, err error) {
 	if q == nil {
 		return 0, errors.New("unmarshal question must not be nil")
@@ -339,13 +339,13 @@ type RR struct {
 	IP string
 }
 
-// NewRR returns a new dns rr
+// NewRR returns a new dns rr.
 func NewRR() *RR {
 	rr := &RR{}
 	return rr
 }
 
-// Marshal marshals RR struct to []byte
+// Marshal marshals RR struct to []byte.
 func (rr *RR) Marshal() ([]byte, error) {
 	var buf bytes.Buffer
 
@@ -359,7 +359,7 @@ func (rr *RR) Marshal() ([]byte, error) {
 	return buf.Bytes(), nil
 }
 
-// UnmarshalRR unmarshals []bytes to RR
+// UnmarshalRR unmarshals []bytes to RR.
 func (m *Message) UnmarshalRR(start int, rr *RR) (n int, err error) {
 	if rr == nil {
 		return 0, errors.New("unmarshal rr must not be nil")
@@ -399,7 +399,7 @@ func (m *Message) UnmarshalRR(start int, rr *RR) (n int, err error) {
 	return n, nil
 }
 
-// MarshalDomain marshals domain string struct to []byte
+// MarshalDomain marshals domain string struct to []byte.
 func MarshalDomain(domain string) []byte {
 	var buf bytes.Buffer
 
@@ -412,7 +412,7 @@ func MarshalDomain(domain string) []byte {
 	return buf.Bytes()
 }
 
-// UnmarshalDomain gets domain from bytes
+// UnmarshalDomain gets domain from bytes.
 func (m *Message) UnmarshalDomain(b []byte) (string, int, error) {
 	var idx, size int
 	var labels = []string{}
@@ -457,7 +457,7 @@ func (m *Message) UnmarshalDomain(b []byte) (string, int, error) {
 	return domain, idx, nil
 }
 
-// UnmarshalDomainPoint gets domain from offset point
+// UnmarshalDomainPoint gets domain from offset point.
 func (m *Message) UnmarshalDomainPoint(offset int) (string, error) {
 	if offset > len(m.unMarshaled) {
 		return "", errors.New("UnmarshalDomainPoint: offset larger than msg length")
diff --git a/dns/server.go b/dns/server.go
index 2adbb80..ffddc39 100644
--- a/dns/server.go
+++ b/dns/server.go
@@ -14,14 +14,14 @@ import (
 // conn timeout, seconds
 const timeout = 30
 
-// Server is a dns server struct
+// Server is a dns server struct.
 type Server struct {
 	addr string
 	// Client is used to communicate with upstream dns servers
 	*Client
 }
 
-// NewServer returns a new dns server
+// NewServer returns a new dns server.
 func NewServer(addr string, dialer proxy.Dialer, config *Config) (*Server, error) {
 	c, err := NewClient(dialer, config)
 	s := &Server{
@@ -32,7 +32,7 @@ func NewServer(addr string, dialer proxy.Dialer, config *Config) (*Server, error
 	return s, err
 }
 
-// Start starts the dns forwarding server
+// Start starts the dns forwarding server.
 // We use WaitGroup here to ensure both udp and tcp serer are completly running,
 // so we can start any other services later, since they may rely on dns service.
 func (s *Server) Start() {
@@ -43,7 +43,7 @@ func (s *Server) Start() {
 	wg.Wait()
 }
 
-// ListenAndServeUDP .
+// ListenAndServeUDP listen and serves on udp port.
 func (s *Server) ListenAndServeUDP(wg *sync.WaitGroup) {
 	c, err := net.ListenPacket("udp", s.addr)
 	wg.Done()
@@ -88,7 +88,7 @@ func (s *Server) ListenAndServeUDP(wg *sync.WaitGroup) {
 
 }
 
-// ListenAndServeTCP .
+// ListenAndServeTCP listen and serves on tcp port.
 func (s *Server) ListenAndServeTCP(wg *sync.WaitGroup) {
 	l, err := net.Listen("tcp", s.addr)
 	wg.Done()
@@ -110,7 +110,7 @@ func (s *Server) ListenAndServeTCP(wg *sync.WaitGroup) {
 	}
 }
 
-// ServeTCP .
+// ServeTCP serves a tcp connection.
 func (s *Server) ServeTCP(c net.Conn) {
 	defer c.Close()
 
diff --git a/go.mod b/go.mod
index a0054e7..d5f321d 100644
--- a/go.mod
+++ b/go.mod
@@ -10,7 +10,7 @@ require (
 	github.com/dgryski/go-rc2 v0.0.0-20150621095337-8a9021637152 // indirect
 	github.com/ebfe/rc2 v0.0.0-20131011165748-24b9757f5521 // indirect
 	github.com/klauspost/cpuid v1.2.0 // indirect
-	github.com/klauspost/reedsolomon v1.9.0 // indirect
+	github.com/klauspost/reedsolomon v1.9.1 // indirect
 	github.com/nadoo/conflag v0.2.0
 	github.com/nadoo/go-shadowsocks2 v0.1.0
 	github.com/pkg/errors v0.8.1 // indirect
@@ -19,9 +19,9 @@ require (
 	github.com/templexxx/xor v0.0.0-20181023030647-4e92f724b73b // indirect
 	github.com/tjfoc/gmsm v1.0.1 // indirect
 	github.com/xtaci/kcp-go v5.0.7+incompatible
-	golang.org/x/crypto v0.0.0-20190228161510-8dd112bcdc25
-	golang.org/x/net v0.0.0-20190301231341-16b79f2e4e95 // indirect
-	golang.org/x/sys v0.0.0-20190306220723-b294cbcfc56d // indirect
+	golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2
+	golang.org/x/net v0.0.0-20190311183353-d8887717615a // indirect
+	golang.org/x/sys v0.0.0-20190312061237-fead79001313 // indirect
 )
 
 // Replace dependency modules with local developing copy
diff --git a/go.sum b/go.sum
index e618779..aa60bf7 100644
--- a/go.sum
+++ b/go.sum
@@ -14,6 +14,8 @@ github.com/klauspost/cpuid v1.2.0 h1:NMpwD2G9JSFOE1/TJjGSo5zG7Yb2bTe7eq1jH+irmeE
 github.com/klauspost/cpuid v1.2.0/go.mod h1:Pj4uuM528wm8OyEC2QMXAi2YiTZ96dNQPGgoMS4s3ek=
 github.com/klauspost/reedsolomon v1.9.0 h1:usyTY5K7D2B6WOHn2jmpB7ky8Qom96mShZmmq3OW4JU=
 github.com/klauspost/reedsolomon v1.9.0/go.mod h1:CwCi+NUr9pqSVktrkN+Ondf06rkhYZ/pcNv7fu+8Un4=
+github.com/klauspost/reedsolomon v1.9.1 h1:kYrT1MlR4JH6PqOpC+okdb9CDTcwEC/BqpzK4WFyXL8=
+github.com/klauspost/reedsolomon v1.9.1/go.mod h1:CwCi+NUr9pqSVktrkN+Ondf06rkhYZ/pcNv7fu+8Un4=
 github.com/nadoo/conflag v0.1.0 h1:m9xSrL0UILGXPCZW66mhW57V2D2IraVpWLNIr2Op8X8=
 github.com/nadoo/conflag v0.1.0/go.mod h1:C3xchp3tIA3J2haACChSHFrlih7w00f31DXfjVUQa+0=
 github.com/nadoo/conflag v0.2.0 h1:xao13tYqfD+5bjQ1A/jT2kBL8tUcVpFhq3seuN5kpeM=
@@ -34,8 +36,16 @@ github.com/xtaci/kcp-go v5.0.7+incompatible h1:zs9tc8XRID0m+aetu3qPWZFyRt2UIMqbX
 github.com/xtaci/kcp-go v5.0.7+incompatible/go.mod h1:bN6vIwHQbfHaHtFpEssmWsN45a+AZwO7eyRCmEIbtvE=
 golang.org/x/crypto v0.0.0-20190228161510-8dd112bcdc25 h1:jsG6UpNLt9iAsb0S2AGW28DveNzzgmbXR+ENoPjUeIU=
 golang.org/x/crypto v0.0.0-20190228161510-8dd112bcdc25/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2 h1:VklqNMn3ovrHsnt90PveolxSbWFaJdECFbxSq0Mqo2M=
+golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/net v0.0.0-20190301231341-16b79f2e4e95 h1:fY7Dsw114eJN4boqzVSbpVHO6rTdhq6/GnXeu+PKnzU=
 golang.org/x/net v0.0.0-20190301231341-16b79f2e4e95/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.0.0-20190310074541-c10a0554eabf h1:J7RqX9u0J9ZB37CGaFc2VC+QZZT6E6jnDbrboEFVo0U=
+golang.org/x/net v0.0.0-20190310074541-c10a0554eabf/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.0.0-20190311031020-56fb01167e7d h1:vQJbQvu6+H699vOmHa20TEBI9nEqroRbMtf/9biIE3A=
+golang.org/x/net v0.0.0-20190311031020-56fb01167e7d/go.mod h1:mL1N/T3taQHkDXs73rZJwtUhF3w3ftmwwsq0BUmARs4=
+golang.org/x/net v0.0.0-20190311183353-d8887717615a h1:oWX7TPOiFAMXLq8o0ikBYfCJVlRHBcsciT5bXOrH628=
+golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190302025703-b6889370fb10 h1:xQJI9OEiErEQ++DoXOHqEpzsGMrAv2Q2jyCpi7DmfpQ=
 golang.org/x/sys v0.0.0-20190302025703-b6889370fb10/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
@@ -51,3 +61,12 @@ golang.org/x/sys v0.0.0-20190306155319-3e9a981b8ddb h1:xIUJ1YHSR/6NhHkg597Yw0jPK
 golang.org/x/sys v0.0.0-20190306155319-3e9a981b8ddb/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190306220723-b294cbcfc56d h1:4Ew1XHJYjwX6RiE8SgSymqS1zCRQyGpcAnVfbpEuXfE=
 golang.org/x/sys v0.0.0-20190306220723-b294cbcfc56d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190308023053-584f3b12f43e h1:K7CV15oJ823+HLXQ+M7MSMrUg8LjfqY7O3naO+8Pp/I=
+golang.org/x/sys v0.0.0-20190308023053-584f3b12f43e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190310054646-10058d7d4faa h1:lqti/xP+yD/6zH5TqEwx2MilNIJY5Vbc6Qr8J3qyPIQ=
+golang.org/x/sys v0.0.0-20190310054646-10058d7d4faa/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190311152110-c8c8c57fd1e1 h1:FQNj2xvjQ1lgFyzbSybGZr792Y8Dy95D7uuqnZAzNaA=
+golang.org/x/sys v0.0.0-20190311152110-c8c8c57fd1e1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190312061237-fead79001313 h1:pczuHS43Cp2ktBEEmLwScxgjWsBSzdaQiKzUyf3DTTc=
+golang.org/x/sys v0.0.0-20190312061237-fead79001313/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
diff --git a/proxy/udptun/udptun.go b/proxy/udptun/udptun.go
index 4d43045..31976a1 100644
--- a/proxy/udptun/udptun.go
+++ b/proxy/udptun/udptun.go
@@ -12,23 +12,23 @@ import (
 	"github.com/nadoo/glider/proxy"
 )
 
-// UDPTun struct
+// UDPTun is a base udptun struct.
 type UDPTun struct {
 	dialer proxy.Dialer
 	addr   string
-
-	raddr string
+	taddr  string       // tunnel addr
+	uaddr  *net.UDPAddr // tunnel addr
 }
 
 func init() {
 	proxy.RegisterServer("udptun", NewUDPTunServer)
 }
 
-// NewUDPTun returns a UDPTun proxy
+// NewUDPTun returns a UDPTun proxy.
 func NewUDPTun(s string, dialer proxy.Dialer) (*UDPTun, error) {
 	u, err := url.Parse(s)
 	if err != nil {
-		log.F("parse err: %s", err)
+		log.F("[udptun] parse err: %s", err)
 		return nil, err
 	}
 
@@ -38,18 +38,19 @@ func NewUDPTun(s string, dialer proxy.Dialer) (*UDPTun, error) {
 	p := &UDPTun{
 		dialer: dialer,
 		addr:   d[0],
-		raddr:  d[1],
+		taddr:  d[1],
 	}
 
-	return p, nil
+	p.uaddr, err = net.ResolveUDPAddr("udp", p.taddr)
+	return p, err
 }
 
-// NewUDPTunServer returns a udp tunnel server
+// NewUDPTunServer returns a udp tunnel server.
 func NewUDPTunServer(s string, dialer proxy.Dialer) (proxy.Server, error) {
 	return NewUDPTun(s, dialer)
 }
 
-// ListenAndServe .
+// ListenAndServe listen and serves on the given address.
 func (s *UDPTun) ListenAndServe() {
 	c, err := net.ListenPacket("udp", s.addr)
 	if err != nil {
@@ -71,12 +72,11 @@ func (s *UDPTun) ListenAndServe() {
 		}
 
 		var pc net.PacketConn
-		var writeAddr net.Addr
 
 		v, ok := nm.Load(raddr.String())
 		if !ok && v == nil {
 
-			pc, writeAddr, err = s.dialer.DialUDP("udp", s.raddr)
+			pc, _, err = s.dialer.DialUDP("udp", s.taddr)
 			if err != nil {
 				log.F("[udptun] remote dial error: %v", err)
 				continue
@@ -94,18 +94,18 @@ func (s *UDPTun) ListenAndServe() {
 			pc = v.(net.PacketConn)
 		}
 
-		_, err = pc.WriteTo(buf[:n], writeAddr)
+		_, err = pc.WriteTo(buf[:n], s.uaddr)
 		if err != nil {
 			log.F("[udptun] remote write error: %v", err)
 			continue
 		}
 
-		log.F("[udptun] %s <-> %s", raddr, s.raddr)
+		log.F("[udptun] %s <-> %s", raddr, s.taddr)
 
 	}
 }
 
-// Serve .
+// Serve serves a net.Conn, can not be called directly.
 func (s *UDPTun) Serve(c net.Conn) {
 	log.F("[udptun] func Serve: can not be called directly")
 }