Fix(socks5): fully udp associate support (#233)

proxy/socks/utils.go

@@ -0,0 +1,41 @@
+package socks
+
+import (
+	"bytes"
+	"net"
+
+	"github.com/Dreamacro/clash/component/socks5"
+)
+
+type fakeConn struct {
+	net.PacketConn
+	target     string
+	remoteAddr net.Addr
+	buffer     *bytes.Buffer
+}
+
+func newfakeConn(conn net.PacketConn, target string, remoteAddr net.Addr, buf []byte) *fakeConn {
+	buffer := bytes.NewBuffer(buf)
+	return &fakeConn{
+		PacketConn: conn,
+		target:     target,
+		buffer:     buffer,
+		remoteAddr: remoteAddr,
+	}
+}
+
+func (c *fakeConn) Read(b []byte) (n int, err error) {
+	return c.buffer.Read(b)
+}
+
+func (c *fakeConn) Write(b []byte) (n int, err error) {
+	packet, err := socks5.EncodeUDPPacket(c.target, b)
+	if err != nil {
+		return
+	}
+	return c.PacketConn.WriteTo(packet, c.remoteAddr)
+}
+
+func (c *fakeConn) RemoteAddr() net.Addr {
+	return c.remoteAddr
+}