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tproxy: use nativeEndian instead of LittleEndian
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,207 @@ | ||
| // MIT License @LiamHaworth | ||
| // https://github.com/LiamHaworth/go-tproxy/blob/master/tproxy_udp.go | ||
| package tproxy | ||
|
|
||
| import ( | ||
| "bytes" | ||
| "encoding/binary" | ||
| "fmt" | ||
| "net" | ||
| "os" | ||
| "strconv" | ||
| "syscall" | ||
| "unsafe" | ||
| ) | ||
|
|
||
| var nativeEndian binary.ByteOrder | ||
|
|
||
| func init() { | ||
| buf := [2]byte{} | ||
| *(*uint16)(unsafe.Pointer(&buf[0])) = uint16(0xABCD) | ||
|
|
||
| switch buf { | ||
| case [2]byte{0xCD, 0xAB}: | ||
| nativeEndian = binary.LittleEndian | ||
| case [2]byte{0xAB, 0xCD}: | ||
| nativeEndian = binary.BigEndian | ||
| default: | ||
| panic("Could not determine native endianness.") | ||
| } | ||
| } | ||
|
|
||
| // ListenUDP will construct a new UDP listener | ||
| // socket with the Linux IP_TRANSPARENT option | ||
| // set on the underlying socket | ||
| func ListenUDP(network string, laddr *net.UDPAddr) (*net.UDPConn, error) { | ||
| listener, err := net.ListenUDP(network, laddr) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| fileDescriptorSource, err := listener.File() | ||
| if err != nil { | ||
| return nil, &net.OpError{Op: "listen", Net: network, Source: nil, Addr: laddr, Err: fmt.Errorf("get file descriptor: %s", err)} | ||
| } | ||
| defer fileDescriptorSource.Close() | ||
|
|
||
| fileDescriptor := int(fileDescriptorSource.Fd()) | ||
| if err = syscall.SetsockoptInt(fileDescriptor, syscall.SOL_IP, syscall.IP_TRANSPARENT, 1); err != nil { | ||
| return nil, &net.OpError{Op: "listen", Net: network, Source: nil, Addr: laddr, Err: fmt.Errorf("set socket option: IP_TRANSPARENT: %s", err)} | ||
| } | ||
|
|
||
| if err = syscall.SetsockoptInt(fileDescriptor, syscall.SOL_IP, syscall.IP_RECVORIGDSTADDR, 1); err != nil { | ||
| return nil, &net.OpError{Op: "listen", Net: network, Source: nil, Addr: laddr, Err: fmt.Errorf("set socket option: IP_RECVORIGDSTADDR: %s", err)} | ||
| } | ||
|
|
||
| return listener, nil | ||
| } | ||
|
|
||
| // 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), nativeEndian, 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 | ||
| } | ||
|
|
||
| // DialUDP connects to the remote address raddr on the network net, | ||
| // which must be "udp", "udp4", or "udp6". If laddr is not nil, it is | ||
| // used as the local address for the connection. | ||
| func DialUDP(network string, laddr *net.UDPAddr, raddr *net.UDPAddr) (*net.UDPConn, error) { | ||
| remoteSocketAddress, err := udpAddrToSocketAddr(raddr) | ||
| if err != nil { | ||
| return nil, &net.OpError{Op: "dial", Err: fmt.Errorf("build destination socket address: %s", err)} | ||
| } | ||
|
|
||
| localSocketAddress, err := udpAddrToSocketAddr(laddr) | ||
| if err != nil { | ||
| return nil, &net.OpError{Op: "dial", Err: fmt.Errorf("build local socket address: %s", err)} | ||
| } | ||
|
|
||
| fileDescriptor, err := syscall.Socket(udpAddrFamily(network, laddr, raddr), syscall.SOCK_DGRAM, 0) | ||
| if err != nil { | ||
| return nil, &net.OpError{Op: "dial", Err: fmt.Errorf("socket open: %s", err)} | ||
| } | ||
|
|
||
| if err = syscall.SetsockoptInt(fileDescriptor, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1); err != nil { | ||
| syscall.Close(fileDescriptor) | ||
| return nil, &net.OpError{Op: "dial", Err: fmt.Errorf("set socket option: SO_REUSEADDR: %s", err)} | ||
| } | ||
|
|
||
| if err = syscall.SetsockoptInt(fileDescriptor, syscall.SOL_IP, syscall.IP_TRANSPARENT, 1); err != nil { | ||
| syscall.Close(fileDescriptor) | ||
| return nil, &net.OpError{Op: "dial", Err: fmt.Errorf("set socket option: IP_TRANSPARENT: %s", err)} | ||
| } | ||
|
|
||
| if err = syscall.Bind(fileDescriptor, localSocketAddress); err != nil { | ||
| syscall.Close(fileDescriptor) | ||
| return nil, &net.OpError{Op: "dial", Err: fmt.Errorf("socket bind: %s", err)} | ||
| } | ||
|
|
||
| if err = syscall.Connect(fileDescriptor, remoteSocketAddress); err != nil { | ||
| syscall.Close(fileDescriptor) | ||
| return nil, &net.OpError{Op: "dial", Err: fmt.Errorf("socket connect: %s", err)} | ||
| } | ||
|
|
||
| fdFile := os.NewFile(uintptr(fileDescriptor), fmt.Sprintf("net-udp-dial-%s", raddr.String())) | ||
| defer fdFile.Close() | ||
|
|
||
| remoteConn, err := net.FileConn(fdFile) | ||
| if err != nil { | ||
| syscall.Close(fileDescriptor) | ||
| return nil, &net.OpError{Op: "dial", Err: fmt.Errorf("convert file descriptor to connection: %s", err)} | ||
| } | ||
|
|
||
| return remoteConn.(*net.UDPConn), nil | ||
| } | ||
|
|
||
| // udpAddToSockerAddr will convert a UDPAddr | ||
| // into a Sockaddr that may be used when | ||
| // connecting and binding sockets | ||
| func udpAddrToSocketAddr(addr *net.UDPAddr) (syscall.Sockaddr, error) { | ||
| switch { | ||
| case addr.IP.To4() != nil: | ||
| ip := [4]byte{} | ||
| copy(ip[:], addr.IP.To4()) | ||
|
|
||
| return &syscall.SockaddrInet4{Addr: ip, Port: addr.Port}, nil | ||
|
|
||
| default: | ||
| ip := [16]byte{} | ||
| copy(ip[:], addr.IP.To16()) | ||
|
|
||
| zoneID, err := strconv.ParseUint(addr.Zone, 10, 32) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| return &syscall.SockaddrInet6{Addr: ip, Port: addr.Port, ZoneId: uint32(zoneID)}, nil | ||
| } | ||
| } | ||
|
|
||
| // udpAddrFamily will attempt to work | ||
| // out the address family based on the | ||
| // network and UDP addresses | ||
| func udpAddrFamily(net string, laddr, raddr *net.UDPAddr) int { | ||
| switch net[len(net)-1] { | ||
| case '4': | ||
| return syscall.AF_INET | ||
| case '6': | ||
| return syscall.AF_INET6 | ||
| } | ||
|
|
||
| if (laddr == nil || laddr.IP.To4() != nil) && | ||
| (raddr == nil || laddr.IP.To4() != nil) { | ||
| return syscall.AF_INET | ||
| } | ||
| return syscall.AF_INET6 | ||
| } |