add dns handler

pkg/handler/tap/conn.go

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

pkg/handler/tap/handler.go

@@ -2,6 +2,7 @@ package tap
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"io"
 	"net"
@@ -122,7 +123,12 @@ func (h *tapHandler) handleLoop(ctx context.Context, conn net.Conn, addr net.Add
 				if err != nil {
 					return err
 				}
-				pc = &packetConn{cc}
+
+				var ok bool
+				pc, ok = cc.(net.PacketConn)
+				if !ok {
+					return errors.New("invalid connection")
+				}
 			} else {
 				if h.md.tcpMode {
 					if addr != nil {