新增dnst隧道

internal/util/dns/conn.go

@@ -21,6 +21,7 @@ const (
 var (
 	ErrInvalidPacket = errors.New("dns: invalid packet")
 	ErrShortBuffer   = errors.New("dns: short buffer")
+	ErrUnsupported   = errors.New("dns: unsupported operation")
 )
 
 type options struct {
@@ -28,6 +29,11 @@ type options struct {
 	udpSize uint16
 }
 
+type setBuffer interface {
+	SetReadBuffer(int) error
+	SetWriteBuffer(int) error
+}
+
 // Option configures a DNS packet wrapper.
 type Option func(*options)
 
@@ -117,6 +123,20 @@ func (c *clientConn) WriteTo(b []byte, addr net.Addr) (n int, err error) {
 	return len(b), nil
 }
 
+func (c *clientConn) SetReadBuffer(n int) error {
+	if pc, ok := c.PacketConn.(setBuffer); ok {
+		return pc.SetReadBuffer(n)
+	}
+	return ErrUnsupported
+}
+
+func (c *clientConn) SetWriteBuffer(n int) error {
+	if pc, ok := c.PacketConn.(setBuffer); ok {
+		return pc.SetWriteBuffer(n)
+	}
+	return ErrUnsupported
+}
+
 type queryState struct {
 	id       uint16
 	question []mdns.Question
@@ -184,6 +204,20 @@ func (c *serverConn) WriteTo(b []byte, addr net.Addr) (n int, err error) {
 	return len(b), nil
 }
 
+func (c *serverConn) SetReadBuffer(n int) error {
+	if pc, ok := c.PacketConn.(setBuffer); ok {
+		return pc.SetReadBuffer(n)
+	}
+	return ErrUnsupported
+}
+
+func (c *serverConn) SetWriteBuffer(n int) error {
+	if pc, ok := c.PacketConn.(setBuffer); ok {
+		return pc.SetWriteBuffer(n)
+	}
+	return ErrUnsupported
+}
+
 func (c *serverConn) storeQuery(addr net.Addr, m *mdns.Msg) {
 	if addr == nil {
 		return