379 lines
7 KiB
Go
379 lines
7 KiB
Go
package main
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/* Implementation of the TUN device interface for linux
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*/
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import (
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"encoding/binary"
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"errors"
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"fmt"
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"golang.org/x/net/ipv6"
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"golang.org/x/sys/unix"
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"net"
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"os"
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"strings"
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"time"
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"unsafe"
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)
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const (
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cloneDevicePath = "/dev/net/tun"
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ifReqSize = unix.IFNAMSIZ + 64
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)
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type NativeTun struct {
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fd *os.File
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index int32 // if index
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name string // name of interface
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errors chan error // async error handling
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events chan TUNEvent // device related events
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nopi bool // the device was pased IFF_NO_PI
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}
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func toRTMGRP(sc uint) uint {
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return 1 << (sc - 1)
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}
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func (tun *NativeTun) bindRTMGRP() (int, error) {
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groups := toRTMGRP(unix.RTNLGRP_LINK)
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groups |= toRTMGRP(unix.RTNLGRP_IPV4_IFADDR)
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groups |= toRTMGRP(unix.RTNLGRP_IPV6_IFADDR)
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sock, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW, unix.NETLINK_ROUTE)
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if err != nil {
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return 0, err
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}
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saddr := &unix.SockaddrNetlink{
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Family: unix.AF_NETLINK,
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Pid: uint32(os.Getpid()),
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Groups: uint32(groups),
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}
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return sock, unix.Bind(sock, saddr)
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}
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func (tun *NativeTun) File() *os.File {
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return tun.fd
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}
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func (tun *NativeTun) RoutineHackListener() {
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/* This is needed for the detection to work across network namespaces
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* If you are reading this and know a better method, please get in touch.
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*/
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fd := int(tun.fd.Fd())
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for {
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_, err := unix.Write(fd, nil)
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switch err {
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case unix.EINVAL:
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tun.events <- TUNEventUp
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case unix.EIO:
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tun.events <- TUNEventDown
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default:
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}
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time.Sleep(time.Second / 10)
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}
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}
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func (tun *NativeTun) RoutineNetlinkListener() {
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sock, err := tun.bindRTMGRP()
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if err != nil {
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tun.errors <- errors.New("Failed to create netlink event listener")
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return
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}
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for msg := make([]byte, 1<<16); ; {
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msgn, _, _, _, err := unix.Recvmsg(sock, msg[:], nil, 0)
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if err != nil {
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tun.errors <- fmt.Errorf("Failed to receive netlink message: %s", err.Error())
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return
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}
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for remain := msg[:msgn]; len(remain) >= unix.SizeofNlMsghdr; {
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hdr := *(*unix.NlMsghdr)(unsafe.Pointer(&remain[0]))
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if int(hdr.Len) > len(remain) {
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break
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}
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switch hdr.Type {
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case unix.NLMSG_DONE:
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remain = []byte{}
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case unix.RTM_NEWLINK:
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info := *(*unix.IfInfomsg)(unsafe.Pointer(&remain[unix.SizeofNlMsghdr]))
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remain = remain[hdr.Len:]
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if info.Index != tun.index {
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// not our interface
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continue
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}
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if info.Flags&unix.IFF_RUNNING != 0 {
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tun.events <- TUNEventUp
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}
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if info.Flags&unix.IFF_RUNNING == 0 {
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tun.events <- TUNEventDown
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}
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tun.events <- TUNEventMTUUpdate
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default:
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remain = remain[hdr.Len:]
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}
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}
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}
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}
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func (tun *NativeTun) isUp() (bool, error) {
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inter, err := net.InterfaceByName(tun.name)
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return inter.Flags&net.FlagUp != 0, err
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}
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func (tun *NativeTun) Name() string {
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return tun.name
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}
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func getDummySock() (int, error) {
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return unix.Socket(
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unix.AF_INET,
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unix.SOCK_DGRAM,
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0,
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)
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}
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func getIFIndex(name string) (int32, error) {
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fd, err := getDummySock()
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if err != nil {
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return 0, err
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}
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defer unix.Close(fd)
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var ifr [ifReqSize]byte
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copy(ifr[:], name)
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_, _, errno := unix.Syscall(
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unix.SYS_IOCTL,
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uintptr(fd),
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uintptr(unix.SIOCGIFINDEX),
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uintptr(unsafe.Pointer(&ifr[0])),
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)
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if errno != 0 {
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return 0, errno
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}
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index := binary.LittleEndian.Uint32(ifr[unix.IFNAMSIZ:])
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return toInt32(index), nil
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}
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func (tun *NativeTun) setMTU(n int) error {
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// open datagram socket
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fd, err := unix.Socket(
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unix.AF_INET,
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unix.SOCK_DGRAM,
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0,
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)
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if err != nil {
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return err
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}
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defer unix.Close(fd)
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// do ioctl call
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var ifr [ifReqSize]byte
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copy(ifr[:], tun.name)
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binary.LittleEndian.PutUint32(ifr[16:20], uint32(n))
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_, _, errno := unix.Syscall(
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unix.SYS_IOCTL,
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uintptr(fd),
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uintptr(unix.SIOCSIFMTU),
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uintptr(unsafe.Pointer(&ifr[0])),
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)
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if errno != 0 {
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return errors.New("Failed to set MTU of TUN device")
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}
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return nil
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}
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func (tun *NativeTun) MTU() (int, error) {
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// open datagram socket
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fd, err := unix.Socket(
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unix.AF_INET,
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unix.SOCK_DGRAM,
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0,
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)
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if err != nil {
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return 0, err
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}
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defer unix.Close(fd)
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// do ioctl call
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var ifr [ifReqSize]byte
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copy(ifr[:], tun.name)
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_, _, errno := unix.Syscall(
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unix.SYS_IOCTL,
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uintptr(fd),
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uintptr(unix.SIOCGIFMTU),
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uintptr(unsafe.Pointer(&ifr[0])),
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)
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if errno != 0 {
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return 0, errors.New("Failed to get MTU of TUN device")
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}
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// convert result to signed 32-bit int
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val := binary.LittleEndian.Uint32(ifr[16:20])
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if val >= (1 << 31) {
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return int(toInt32(val)), nil
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}
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return int(val), nil
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}
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func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
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if tun.nopi {
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buff = buff[offset:]
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} else {
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// reserve space for header
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buff = buff[offset-4:]
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// add packet information header
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buff[0] = 0x00
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buff[1] = 0x00
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if buff[4] == ipv6.Version<<4 {
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buff[2] = 0x86
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buff[3] = 0xdd
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} else {
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buff[2] = 0x08
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buff[3] = 0x00
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}
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}
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// write
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return tun.fd.Write(buff)
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}
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func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
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select {
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case err := <-tun.errors:
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return 0, err
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default:
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if tun.nopi {
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return tun.fd.Read(buff[offset:])
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} else {
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buff := buff[offset-4:]
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n, err := tun.fd.Read(buff[:])
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if n < 4 {
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return 0, err
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}
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return n - 4, err
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}
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}
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}
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func (tun *NativeTun) Events() chan TUNEvent {
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return tun.events
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}
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func (tun *NativeTun) Close() error {
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return tun.fd.Close()
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}
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func CreateTUNFromFile(name string, fd *os.File) (TUNDevice, error) {
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device := &NativeTun{
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fd: fd,
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name: name,
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events: make(chan TUNEvent, 5),
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errors: make(chan error, 5),
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nopi: false,
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}
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// start event listener
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var err error
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device.index, err = getIFIndex(device.name)
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if err != nil {
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return nil, err
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}
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go device.RoutineNetlinkListener()
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go device.RoutineHackListener() // cross namespace
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// set default MTU
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return device, device.setMTU(DefaultMTU)
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}
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func CreateTUN(name string) (TUNDevice, error) {
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// open clone device
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fd, err := os.OpenFile(cloneDevicePath, os.O_RDWR, 0)
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if err != nil {
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return nil, err
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}
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// create new device
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var ifr [ifReqSize]byte
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var flags uint16 = unix.IFF_TUN // | unix.IFF_NO_PI (disabled for TUN status hack)
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nameBytes := []byte(name)
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if len(nameBytes) >= unix.IFNAMSIZ {
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return nil, errors.New("Interface name too long")
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}
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copy(ifr[:], nameBytes)
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binary.LittleEndian.PutUint16(ifr[16:], flags)
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_, _, errno := unix.Syscall(
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unix.SYS_IOCTL,
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uintptr(fd.Fd()),
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uintptr(unix.TUNSETIFF),
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uintptr(unsafe.Pointer(&ifr[0])),
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)
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if errno != 0 {
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return nil, errno
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}
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// read (new) name of interface
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newName := string(ifr[:])
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newName = newName[:strings.Index(newName, "\000")]
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device := &NativeTun{
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fd: fd,
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name: newName,
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events: make(chan TUNEvent, 5),
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errors: make(chan error, 5),
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nopi: false,
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}
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// start event listener
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device.index, err = getIFIndex(device.name)
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if err != nil {
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return nil, err
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}
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go device.RoutineNetlinkListener()
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go device.RoutineHackListener() // cross namespace
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// set default MTU
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return device, device.setMTU(DefaultMTU)
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}
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