wireguard-go/tun/tun_linux.go

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/* SPDX-License-Identifier: MIT
*
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* Copyright (C) 2017-2019 WireGuard LLC. All Rights Reserved.
*/
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package tun
/* Implementation of the TUN device interface for linux
*/
import (
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"bytes"
"errors"
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"fmt"
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"golang.zx2c4.com/wireguard/rwcancel"
"golang.org/x/net/ipv6"
"golang.org/x/sys/unix"
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"net"
"os"
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"strconv"
"sync"
"time"
"unsafe"
)
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const (
cloneDevicePath = "/dev/net/tun"
ifReqSize = unix.IFNAMSIZ + 64
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)
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type nativeTun struct {
tunFile *os.File
fd uintptr
fdCancel *rwcancel.RWCancel
index int32 // if index
name string // name of interface
errors chan error // async error handling
events chan TUNEvent // device related events
nopi bool // the device was pased IFF_NO_PI
netlinkSock int
netlinkCancel *rwcancel.RWCancel
hackListenerClosed sync.Mutex
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statusListenersShutdown chan struct{}
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}
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func (tun *nativeTun) File() *os.File {
return tun.tunFile
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}
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func (tun *nativeTun) routineHackListener() {
defer tun.hackListenerClosed.Unlock()
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/* This is needed for the detection to work across network namespaces
* If you are reading this and know a better method, please get in touch.
*/
fd := int(tun.fd)
for {
_, err := unix.Write(fd, nil)
switch err {
case unix.EINVAL:
tun.events <- TUNEventUp
case unix.EIO:
tun.events <- TUNEventDown
default:
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return
}
select {
case <-time.After(time.Second):
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case <-tun.statusListenersShutdown:
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return
}
}
}
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func createNetlinkSocket() (int, error) {
sock, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW, unix.NETLINK_ROUTE)
if err != nil {
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return -1, err
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}
saddr := &unix.SockaddrNetlink{
Family: unix.AF_NETLINK,
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Groups: uint32((1 << (unix.RTNLGRP_LINK - 1)) | (1 << (unix.RTNLGRP_IPV4_IFADDR - 1)) | (1 << (unix.RTNLGRP_IPV6_IFADDR - 1))),
}
err = unix.Bind(sock, saddr)
if err != nil {
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return -1, err
}
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return sock, nil
}
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func (tun *nativeTun) routineNetlinkListener() {
defer func() {
unix.Close(tun.netlinkSock)
tun.hackListenerClosed.Lock()
close(tun.events)
}()
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for msg := make([]byte, 1<<16); ; {
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var err error
var msgn int
for {
msgn, _, _, _, err = unix.Recvmsg(tun.netlinkSock, msg[:], nil, 0)
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if err == nil || !rwcancel.RetryAfterError(err) {
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break
}
if !tun.netlinkCancel.ReadyRead() {
tun.errors <- fmt.Errorf("netlink socket closed: %s", err.Error())
return
}
}
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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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select {
case <-tun.statusListenersShutdown:
return
default:
}
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for remain := msg[:msgn]; len(remain) >= unix.SizeofNlMsghdr; {
hdr := *(*unix.NlMsghdr)(unsafe.Pointer(&remain[0]))
if int(hdr.Len) > len(remain) {
break
}
switch hdr.Type {
case unix.NLMSG_DONE:
remain = []byte{}
case unix.RTM_NEWLINK:
info := *(*unix.IfInfomsg)(unsafe.Pointer(&remain[unix.SizeofNlMsghdr]))
remain = remain[hdr.Len:]
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if info.Index != tun.index {
// not our interface
continue
}
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if info.Flags&unix.IFF_RUNNING != 0 {
tun.events <- TUNEventUp
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}
if info.Flags&unix.IFF_RUNNING == 0 {
tun.events <- TUNEventDown
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}
tun.events <- TUNEventMTUUpdate
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default:
remain = remain[hdr.Len:]
}
}
}
}
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func (tun *nativeTun) isUp() (bool, error) {
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inter, err := net.InterfaceByName(tun.name)
return inter.Flags&net.FlagUp != 0, err
}
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func getDummySock() (int, error) {
return unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
}
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func getIFIndex(name string) (int32, error) {
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fd, err := getDummySock()
if err != nil {
return 0, err
}
defer unix.Close(fd)
var ifr [ifReqSize]byte
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copy(ifr[:], name)
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(fd),
uintptr(unix.SIOCGIFINDEX),
uintptr(unsafe.Pointer(&ifr[0])),
)
if errno != 0 {
return 0, errno
}
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return *(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])), nil
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}
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func (tun *nativeTun) setMTU(n int) error {
// open datagram socket
fd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
return err
}
defer unix.Close(fd)
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// do ioctl call
var ifr [ifReqSize]byte
copy(ifr[:], tun.name)
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*(*uint32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = uint32(n)
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(fd),
uintptr(unix.SIOCSIFMTU),
uintptr(unsafe.Pointer(&ifr[0])),
)
if errno != 0 {
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return errors.New("failed to set MTU of TUN device")
}
return nil
}
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func (tun *nativeTun) MTU() (int, error) {
// open datagram socket
fd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
return 0, err
}
defer unix.Close(fd)
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// do ioctl call
var ifr [ifReqSize]byte
copy(ifr[:], tun.name)
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(fd),
uintptr(unix.SIOCGIFMTU),
uintptr(unsafe.Pointer(&ifr[0])),
)
if errno != 0 {
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return 0, errors.New("failed to get MTU of TUN device: " + strconv.FormatInt(int64(errno), 10))
}
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return int(*(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ]))), nil
}
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func (tun *nativeTun) Name() (string, error) {
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var ifr [ifReqSize]byte
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
tun.fd,
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uintptr(unix.TUNGETIFF),
uintptr(unsafe.Pointer(&ifr[0])),
)
if errno != 0 {
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return "", errors.New("failed to get name of TUN device: " + strconv.FormatInt(int64(errno), 10))
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}
nullStr := ifr[:]
i := bytes.IndexByte(nullStr, 0)
if i != -1 {
nullStr = nullStr[:i]
}
tun.name = string(nullStr)
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return tun.name, nil
}
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func (tun *nativeTun) Write(buff []byte, offset int) (int, error) {
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if tun.nopi {
buff = buff[offset:]
} else {
// 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
buff[1] = 0x00
if buff[4]>>4 == ipv6.Version {
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buff[2] = 0x86
buff[3] = 0xdd
} else {
buff[2] = 0x08
buff[3] = 0x00
}
}
// write
return tun.tunFile.Write(buff)
}
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func (tun *nativeTun) doRead(buff []byte, offset int) (int, error) {
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select {
case err := <-tun.errors:
return 0, err
default:
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if tun.nopi {
return tun.tunFile.Read(buff[offset:])
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} else {
buff := buff[offset-4:]
n, err := tun.tunFile.Read(buff[:])
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if n < 4 {
return 0, err
}
return n - 4, err
}
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}
}
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func (tun *nativeTun) Read(buff []byte, offset int) (int, error) {
for {
n, err := tun.doRead(buff, offset)
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if err == nil || !rwcancel.RetryAfterError(err) {
return n, err
}
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if !tun.fdCancel.ReadyRead() {
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return 0, errors.New("tun device closed")
}
}
}
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func (tun *nativeTun) Events() chan TUNEvent {
return tun.events
}
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func (tun *nativeTun) Close() error {
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var err1 error
if tun.statusListenersShutdown != nil {
close(tun.statusListenersShutdown)
if tun.netlinkCancel != nil {
err1 = tun.netlinkCancel.Cancel()
}
} else if tun.events != nil {
close(tun.events)
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}
err2 := tun.tunFile.Close()
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err3 := tun.fdCancel.Cancel()
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if err1 != nil {
return err1
}
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if err2 != nil {
return err2
}
return err3
}
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func CreateTUN(name string, mtu int) (TUNDevice, error) {
nfd, err := unix.Open(cloneDevicePath, os.O_RDWR, 0)
if err != nil {
return nil, err
}
fd := os.NewFile(uintptr(nfd), cloneDevicePath)
if err != nil {
return nil, err
}
// create new device
var ifr [ifReqSize]byte
var flags uint16 = unix.IFF_TUN // | unix.IFF_NO_PI (disabled for TUN status hack)
nameBytes := []byte(name)
if len(nameBytes) >= unix.IFNAMSIZ {
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return nil, errors.New("interface name too long")
}
copy(ifr[:], nameBytes)
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*(*uint16)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = flags
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
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fd.Fd(),
uintptr(unix.TUNSETIFF),
uintptr(unsafe.Pointer(&ifr[0])),
)
if errno != 0 {
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return nil, errno
}
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return CreateTUNFromFile(fd, mtu)
}
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func CreateTUNFromFile(file *os.File, mtu int) (TUNDevice, error) {
tun := &nativeTun{
tunFile: file,
fd: file.Fd(),
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events: make(chan TUNEvent, 5),
errors: make(chan error, 5),
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statusListenersShutdown: make(chan struct{}),
nopi: false,
}
var err error
tun.fdCancel, err = rwcancel.NewRWCancel(int(tun.fd))
if err != nil {
tun.tunFile.Close()
return nil, err
}
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_, err = tun.Name()
if err != nil {
tun.tunFile.Close()
return nil, err
}
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// start event listener
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tun.index, err = getIFIndex(tun.name)
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if err != nil {
return nil, err
}
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tun.netlinkSock, err = createNetlinkSocket()
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if err != nil {
tun.tunFile.Close()
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return nil, err
}
tun.netlinkCancel, err = rwcancel.NewRWCancel(tun.netlinkSock)
if err != nil {
tun.tunFile.Close()
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return nil, err
}
tun.hackListenerClosed.Lock()
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go tun.routineNetlinkListener()
go tun.routineHackListener() // cross namespace
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err = tun.setMTU(mtu)
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if err != nil {
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tun.Close()
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return nil, err
}
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return tun, nil
}