add ssu connector

pkg/dialer/udp/conn.go

@@ -0,0 +1,17 @@
+package udp
+
+import "net"
+
+type conn struct {
+	*net.UDPConn
+}
+
+func (c *conn) WriteTo(b []byte, addr net.Addr) (int, error) {
+	return c.UDPConn.Write(b)
+}
+
+func (c *conn) ReadFrom(b []byte) (n int, addr net.Addr, err error) {
+	n, err = c.UDPConn.Read(b)
+	addr = c.RemoteAddr()
+	return
+}