Reduce the chance of china firewall blocking

cmd/shadowsocks-local/local.go

@@ -77,7 +77,7 @@ func handShake(conn net.Conn) (err error) {
 	return
 }
 
-func getRequest(conn net.Conn) (rawaddr []byte, host string, err error) {
+func getRequest(conn net.Conn) (header []byte, host string, err error) {
 	const (
 		idVer   = 0
 		idCmd   = 1
@@ -94,8 +94,11 @@ func getRequest(conn net.Conn) (rawaddr []byte, host string, err error) {
 		lenIPv6   = 3 + 1 + net.IPv6len + 2 // 3(ver+cmd+rsv) + 1addrType + ipv6 + 2port
 		lenDmBase = 3 + 1 + 1 + 2           // 3 + 1addrType + 1addrLen + 2port, plus addrLen
 	)
-	// refer to getRequest in server.go for why set buffer size to 263
-	buf := make([]byte, 263)
+
+	// buf size should at least have the same size with the largest possible
+	// request size (when addrType is 3, domain name has at most 256 bytes)
+	// 1(addrType) + 1(lenByte) + 255(max length address) + 2(port) + 10(hmac-sha1) + [1~128](random length data buffer)
+	buf := make([]byte, 270+rand.Int()%128)
 	var n int
 	ss.SetReadTimeout(conn)
 	// read till we get possible domain length field
@@ -136,8 +139,6 @@ func getRequest(conn net.Conn) (rawaddr []byte, host string, err error) {
 		return
 	}
 
-	rawaddr = buf[idType:reqLen]
-
 	if debug {
 		switch buf[idType] {
 		case typeIPv4:
@@ -151,6 +152,21 @@ func getRequest(conn net.Conn) (rawaddr []byte, host string, err error) {
 		host = net.JoinHostPort(host, strconv.Itoa(int(port)))
 	}
 
+	// Sending connection established message immediately to client.
+	// This some round trip time for creating socks connection with the client.
+	// But if connection failed, the client will get connection reset error.
+	_, err = conn.Write([]byte{0x05, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x08, 0x43})
+	if err != nil {
+		debug.Println("send connection confirmation:", err)
+		return
+	}
+
+	// read until the client sends at least 1 byte of data
+	if n, err = io.ReadAtLeast(conn, buf[reqLen:], 1); err != nil {
+		return
+	}
+
+	header = buf[idType : reqLen+n]
 	return
 }
 
@@ -235,9 +251,9 @@ func parseServerConfig(config *ss.Config) {
 	return
 }
 
-func connectToServer(serverId int, rawaddr []byte, addr string) (remote *ss.Conn, err error) {
+func connectToServer(serverId int, header []byte, addr string) (remote *ss.Conn, err error) {
 	se := servers.srvCipher[serverId]
-	remote, err = ss.DialWithRawAddr(rawaddr, se.server, se.cipher.Copy())
+	remote, err = ss.DiaAndWriteData(header, se.server, se.cipher.Copy())
 	if err != nil {
 		log.Println("error connecting to shadowsocks server:", err)
 		const maxFailCnt = 30
@@ -255,7 +271,7 @@ func connectToServer(serverId int, rawaddr []byte, addr string) (remote *ss.Conn
 // connection failure, try the next server. A failed server will be tried with
 // some probability according to its fail count, so we can discover recovered
 // servers.
-func createServerConn(rawaddr []byte, addr string) (remote *ss.Conn, err error) {
+func createServerConn(header []byte, addr string) (remote *ss.Conn, err error) {
 	const baseFailCnt = 20
 	n := len(servers.srvCipher)
 	skipped := make([]int, 0)
@@ -265,14 +281,14 @@ func createServerConn(rawaddr []byte, addr string) (remote *ss.Conn, err error)
 			skipped = append(skipped, i)
 			continue
 		}
-		remote, err = connectToServer(i, rawaddr, addr)
+		remote, err = connectToServer(i, header, addr)
 		if err == nil {
 			return
 		}
 	}
 	// last resort, try skipped servers, not likely to succeed
 	for _, i := range skipped {
-		remote, err = connectToServer(i, rawaddr, addr)
+		remote, err = connectToServer(i, header, addr)
 		if err == nil {
 			return
 		}
@@ -296,21 +312,13 @@ func handleConnection(conn net.Conn) {
 		log.Println("socks handshake:", err)
 		return
 	}
-	rawaddr, addr, err := getRequest(conn)
+	header, addr, err := getRequest(conn)
 	if err != nil {
 		log.Println("error getting request:", err)
 		return
 	}
-	// Sending connection established message immediately to client.
-	// This some round trip time for creating socks connection with the client.
-	// But if connection failed, the client will get connection reset error.
-	_, err = conn.Write([]byte{0x05, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x08, 0x43})
-	if err != nil {
-		debug.Println("send connection confirmation:", err)
-		return
-	}
 
-	remote, err := createServerConn(rawaddr, addr)
+	remote, err := createServerConn(header, addr)
 	if err != nil {
 		if len(servers.srvCipher) > 1 {
 			log.Println("Failed connect to all available shadowsocks server")

shadowsocks/conn.go

@@ -9,7 +9,7 @@ import (
 )
 
 const (
-	AddrMask        byte = 0xf
+	AddrMask byte = 0xf
 )
 
 type Conn struct {
@@ -69,6 +69,22 @@ func DialWithRawAddr(rawaddr []byte, server string, cipher *Cipher) (c *Conn, er
 	return
 }
 
+// DiaAndWriteData is intended for use by users implementing a local socks proxy.
+// rawaddr shoud contain part of the data in socks request and forwarding data,
+// starting from the ATYP field. (Refer to rfc1928 for more information.)
+func DiaAndWriteData(data []byte, server string, cipher *Cipher) (c *Conn, err error) {
+	conn, err := net.Dial("tcp", server)
+	if err != nil {
+		return
+	}
+	c = NewConn(conn, cipher)
+	if _, err = c.Write(data); err != nil {
+		c.Close()
+		return nil, err
+	}
+	return
+}
+
 // Dial: addr should be in the form of host:port
 func Dial(addr, server string, cipher *Cipher) (c *Conn, err error) {
 	ra, err := RawAddr(addr)