Adapt new shadowsocks library.

1. Modify ss/ssu handler and connector
2. Add users to metadata of ss and ssu handler

internal/util/ss/conn.go

@@ -1,11 +1,14 @@
 package ss
 
 import (
-	"bytes"
+	"errors"
 	"net"
+	"net/netip"
+	"sync"
 
 	"github.com/go-gost/core/common/bufpool"
-	"github.com/go-gost/gosocks5"
+	"github.com/go-gost/go-shadowsocks2/core"
+	"github.com/go-gost/go-shadowsocks2/socks"
 )
 
 const (
@@ -17,14 +20,19 @@ var (
 	_ net.Conn       = (*UDPConn)(nil)
 )
 
+// This wrapped connection has different behavior than ordinary connection:
+// 1. ReadFrom will return target addr of shadowsocks instead of remote addr
 type UDPConn struct {
+	client     *core.UDPClient
+	server     *core.UDPServer
+	sessionMap *sync.Map
 	net.PacketConn
 	raddr      net.Addr
 	taddr      net.Addr
 	bufferSize int
 }
 
-func UDPClientConn(c net.PacketConn, remoteAddr, targetAddr net.Addr, bufferSize int) *UDPConn {
+func UDPClientConn(c net.PacketConn, remoteAddr, targetAddr net.Addr, bufferSize int, client *core.UDPClient, sessionMap *sync.Map) *UDPConn {
 	if bufferSize <= 0 {
 		bufferSize = defaultBufferSize
 	}
@@ -34,18 +42,8 @@ func UDPClientConn(c net.PacketConn, remoteAddr, targetAddr net.Addr, bufferSize
 		raddr:      remoteAddr,
 		taddr:      targetAddr,
 		bufferSize: bufferSize,
-	}
-}
-
-func UDPServerConn(c net.PacketConn, remoteAddr net.Addr, bufferSize int) *UDPConn {
-	if bufferSize <= 0 {
-		bufferSize = defaultBufferSize
-	}
-
-	return &UDPConn{
-		PacketConn: c,
-		raddr:      remoteAddr,
-		bufferSize: bufferSize,
+		client:     client,
+		sessionMap: sessionMap,
 	}
 }
 
@@ -53,19 +51,34 @@ func (c *UDPConn) ReadFrom(b []byte) (n int, addr net.Addr, err error) {
 	buf := bufpool.Get(c.bufferSize)
 	defer bufpool.Put(buf)
 
+	clientAddr, err := netip.ParseAddrPort(c.LocalAddr().String())
+	if err != nil {
+		return
+	}
+
 	n, _, err = c.PacketConn.ReadFrom(buf)
 	if err != nil {
 		return
 	}
 
-	saddr := gosocks5.Addr{}
-	addrLen, err := saddr.ReadFrom(bytes.NewReader(buf[:n]))
-	if err != nil {
-		return
+	var payload []byte
+	var session core.UDPSession
+	if c.client != nil {
+		s, ok := c.sessionMap.Load(core.SessionHashFromAddrPort(clientAddr))
+		if !ok {
+			return 0, nil, errors.New("udp session cannot find")
+		}
+		session = s.(core.UDPSession)
+		payload, err = c.client.Outbound(buf[:n], session)
+		if err != nil {
+			return
+		}
+	} else {
+		return 0, nil, errors.New("UDPConn must be client ")
 	}
 
-	n = copy(b, buf[addrLen:n])
-	addr, err = net.ResolveUDPAddr("udp", saddr.String())
+	n = copy(b, payload)
+	addr, err = net.ResolveUDPAddr("udp", session.Target().String())
 
 	return
 }
@@ -76,22 +89,26 @@ func (c *UDPConn) Read(b []byte) (n int, err error) {
 }
 
 func (c *UDPConn) WriteTo(b []byte, addr net.Addr) (n int, err error) {
-	socksAddr := gosocks5.Addr{}
-	if err = socksAddr.ParseFrom(addr.String()); err != nil {
-		return
-	}
-
-	buf := bufpool.Get(c.bufferSize)
-	defer bufpool.Put(buf)
-
-	addrLen, err := socksAddr.Encode(buf)
+	target := socks.ParseAddr(c.taddr.String())
+	clientAddr, err := netip.ParseAddrPort(c.LocalAddr().String())
 	if err != nil {
 		return
 	}
 
-	n = copy(buf[addrLen:], b)
-	_, err = c.PacketConn.WriteTo(buf[:addrLen+n], c.raddr)
+	var session core.UDPSession
+	var encrypted []byte
+	if c.client != nil {
+		session, encrypted, err = c.client.Inbound(b, clientAddr, target)
+		if err != nil {
+			return
+		}
+		c.sessionMap.Store(session.Hash(), session)
+	} else {
+		return 0, errors.New("UDPConn must be client")
+	}
 
+	_, err = c.PacketConn.WriteTo(encrypted, c.raddr)
+	n = len(b)
 	return
 }