udptun: use routine to handle upstream connection

README.md

@@ -2,8 +2,6 @@
 
 [![Build Status](https://img.shields.io/travis/nadoo/glider.svg?style=flat-square)](https://travis-ci.org/nadoo/glider)
 [![Go Report Card](https://goreportcard.com/badge/github.com/nadoo/glider?style=flat-square)](https://goreportcard.com/report/github.com/nadoo/glider)
-[![Go Version](https://img.shields.io/badge/go-1.9%2B-brightgreen.svg?style=flat-square)](https://golang.org/dl/)
-[![License](https://img.shields.io/badge/license-GPL3.0-blue.svg?style=flat-square)](https://github.com/nadoo/glider/blob/master/LICENSE)
 [![GitHub tag](https://img.shields.io/github/tag/nadoo/glider.svg?style=flat-square)](https://github.com/nadoo/glider/releases)
 [![GitHub release](https://img.shields.io/github/release/nadoo/glider.svg?style=flat-square)](https://github.com/nadoo/glider/releases)
 
@@ -61,7 +59,7 @@ TODO:
 Binary: 
 - [https://github.com/nadoo/glider/releases](https://github.com/nadoo/glider/releases)
 
-Go Get (requires **Go 1.9 or newer**):
+Go Get (requires **Go 1.9+** ):
 ```bash
 go get -u github.com/nadoo/glider
 ```

tproxy.go

@@ -1,10 +1,18 @@
 // +build linux
 
+// ref: https://www.kernel.org/doc/Documentation/networking/tproxy.txt
+// @LiamHaworth: https://github.com/LiamHaworth/go-tproxy/blob/master/tproxy_udp.go
+
 package main
 
 import (
+	"bytes"
+	"encoding/binary"
+	"fmt"
 	"net"
+	"strconv"
 	"syscall"
+	"unsafe"
 )
 
 // TProxy struct
@@ -42,13 +50,13 @@ func (s *TProxy) ListenAndServeUDP() {
 		return
 	}
 
-	listener, err := net.ListenUDP("udp", laddr)
+	lc, err := net.ListenUDP("udp", laddr)
 	if err != nil {
 		logf("proxy-tproxy failed to listen on %s: %v", s.addr, err)
 		return
 	}
 
-	fd, err := listener.File()
+	fd, err := lc.File()
 	if err != nil {
 		logf("proxy-tproxy failed to get file descriptor: %v", err)
 		return
@@ -68,4 +76,78 @@ func (s *TProxy) ListenAndServeUDP() {
 		return
 	}
 
+	for {
+
+		buf := make([]byte, 1024)
+		_, srcAddr, dstAddr, err := ReadFromUDP(lc, buf)
+		if err != nil {
+			if netErr, ok := err.(net.Error); ok && netErr.Temporary() {
+				logf("proxy-tproxy Temporary error while reading data: %s", netErr)
+			}
+
+			logf("proxy-tproxy Unrecoverable error while reading data: %s", err)
+			return
+		}
+
+		logf("proxy-tproxy Accepting UDP connection from %s with destination of %s", srcAddr.String(), dstAddr.String())
+
+	}
+
+}
+
+// ReadFromUDP reads a UDP packet from c, copying the payload into b.
+// It returns the number of bytes copied into b and the return address
+// that was on the packet.
+//
+// Out-of-band data is also read in so that the original destination
+// address can be identified and parsed.
+func ReadFromUDP(conn *net.UDPConn, b []byte) (int, *net.UDPAddr, *net.UDPAddr, error) {
+	oob := make([]byte, 1024)
+	n, oobn, _, addr, err := conn.ReadMsgUDP(b, oob)
+	if err != nil {
+		return 0, nil, nil, err
+	}
+
+	msgs, err := syscall.ParseSocketControlMessage(oob[:oobn])
+	if err != nil {
+		return 0, nil, nil, fmt.Errorf("parsing socket control message: %s", err)
+	}
+
+	var originalDst *net.UDPAddr
+	for _, msg := range msgs {
+		if msg.Header.Level == syscall.SOL_IP && msg.Header.Type == syscall.IP_RECVORIGDSTADDR {
+			originalDstRaw := &syscall.RawSockaddrInet4{}
+			if err = binary.Read(bytes.NewReader(msg.Data), binary.LittleEndian, originalDstRaw); err != nil {
+				return 0, nil, nil, fmt.Errorf("reading original destination address: %s", err)
+			}
+
+			switch originalDstRaw.Family {
+			case syscall.AF_INET:
+				pp := (*syscall.RawSockaddrInet4)(unsafe.Pointer(originalDstRaw))
+				p := (*[2]byte)(unsafe.Pointer(&pp.Port))
+				originalDst = &net.UDPAddr{
+					IP:   net.IPv4(pp.Addr[0], pp.Addr[1], pp.Addr[2], pp.Addr[3]),
+					Port: int(p[0])<<8 + int(p[1]),
+				}
+
+			case syscall.AF_INET6:
+				pp := (*syscall.RawSockaddrInet6)(unsafe.Pointer(originalDstRaw))
+				p := (*[2]byte)(unsafe.Pointer(&pp.Port))
+				originalDst = &net.UDPAddr{
+					IP:   net.IP(pp.Addr[:]),
+					Port: int(p[0])<<8 + int(p[1]),
+					Zone: strconv.Itoa(int(pp.Scope_id)),
+				}
+
+			default:
+				return 0, nil, nil, fmt.Errorf("original destination is an unsupported network family")
+			}
+		}
+	}
+
+	if originalDst == nil {
+		return 0, nil, nil, fmt.Errorf("unable to obtain original destination: %s", err)
+	}
+
+	return n, addr, originalDst, nil
 }

uottun.go

@@ -45,11 +45,12 @@ func (s *UoTTun) ListenAndServe() {
 			continue
 		}
 
+		go func() {
 			// NOTE: acturally udp over tcp
 			rc, err := s.sDialer.Dial("udp", s.raddr)
 			if err != nil {
 				logf("failed to connect to server %v: %v", s.raddr, err)
-			continue
+				return
 			}
 
 			rc.Write(buf[:n])
@@ -64,5 +65,6 @@ func (s *UoTTun) ListenAndServe() {
 			c.WriteTo(resp, clientAddr)
 
 			logf("proxy-uottun %s <-> %s", clientAddr, s.raddr)
+		}()
 	}
 }