update error detect

proxy/udp.go

@@ -43,7 +43,7 @@ func (h *udpHandler) fetchUDPInput(conn core.UDPConn, input net.PacketConn, addr
 		input.SetDeadline(time.Now().Add(h.timeout))
 		n, _, err := input.ReadFrom(buf)
 		if err != nil {
-			if netErr, ok := err.(net.Error); !ok || !netErr.Timeout() {
+			if !isTimeout(err) && !isClosed(err) {
 				log.Warnf("failed to read UDP data from remote: %v", err)
 			}
 			return

proxy/utils.go

@@ -5,11 +5,25 @@ import (
 	"io"
 	"io/ioutil"
 	"net"
+	"strings"
 	"time"
 
 	"github.com/xjasonlyu/tun2socks/proxy/socks"
 )
 
+// Error
+func isTimeout(err error) bool {
+	if netErr, ok := err.(net.Error); ok {
+		return netErr.Timeout()
+	}
+	return false
+}
+
+func isClosed(err error) bool {
+	want := "use of closed network connection"
+	return strings.Contains(err.Error(), want)
+}
+
 // UDP util
 type udpElement struct {
 	remoteAddr net.Addr