511 lines
10 KiB
Go
511 lines
10 KiB
Go
/* SPDX-License-Identifier: MIT
|
|
*
|
|
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
|
|
*/
|
|
|
|
package tun
|
|
|
|
/* Implementation of the TUN device interface for linux
|
|
*/
|
|
|
|
import (
|
|
"bytes"
|
|
"errors"
|
|
"fmt"
|
|
"os"
|
|
"sync"
|
|
"syscall"
|
|
"time"
|
|
"unsafe"
|
|
|
|
"golang.org/x/net/ipv6"
|
|
"golang.org/x/sys/unix"
|
|
|
|
"golang.zx2c4.com/wireguard/rwcancel"
|
|
)
|
|
|
|
const (
|
|
cloneDevicePath = "/dev/net/tun"
|
|
ifReqSize = unix.IFNAMSIZ + 64
|
|
)
|
|
|
|
type NativeTun struct {
|
|
tunFile *os.File
|
|
index int32 // if index
|
|
errors chan error // async error handling
|
|
events chan Event // device related events
|
|
nopi bool // the device was passed IFF_NO_PI
|
|
netlinkSock int
|
|
netlinkCancel *rwcancel.RWCancel
|
|
hackListenerClosed sync.Mutex
|
|
statusListenersShutdown chan struct{}
|
|
|
|
closeOnce sync.Once
|
|
|
|
nameOnce sync.Once // guards calling initNameCache, which sets following fields
|
|
nameCache string // name of interface
|
|
nameErr error
|
|
}
|
|
|
|
func (tun *NativeTun) File() *os.File {
|
|
return tun.tunFile
|
|
}
|
|
|
|
func (tun *NativeTun) routineHackListener() {
|
|
defer tun.hackListenerClosed.Unlock()
|
|
/* 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.
|
|
*/
|
|
last := 0
|
|
const (
|
|
up = 1
|
|
down = 2
|
|
)
|
|
for {
|
|
sysconn, err := tun.tunFile.SyscallConn()
|
|
if err != nil {
|
|
return
|
|
}
|
|
err2 := sysconn.Control(func(fd uintptr) {
|
|
_, err = unix.Write(int(fd), nil)
|
|
})
|
|
if err2 != nil {
|
|
return
|
|
}
|
|
switch err {
|
|
case unix.EINVAL:
|
|
if last != up {
|
|
// If the tunnel is up, it reports that write() is
|
|
// allowed but we provided invalid data.
|
|
tun.events <- EventUp
|
|
last = up
|
|
}
|
|
case unix.EIO:
|
|
if last != down {
|
|
// If the tunnel is down, it reports that no I/O
|
|
// is possible, without checking our provided data.
|
|
tun.events <- EventDown
|
|
last = down
|
|
}
|
|
default:
|
|
return
|
|
}
|
|
select {
|
|
case <-time.After(time.Second):
|
|
// nothing
|
|
case <-tun.statusListenersShutdown:
|
|
return
|
|
}
|
|
}
|
|
}
|
|
|
|
func createNetlinkSocket() (int, error) {
|
|
sock, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW, unix.NETLINK_ROUTE)
|
|
if err != nil {
|
|
return -1, err
|
|
}
|
|
saddr := &unix.SockaddrNetlink{
|
|
Family: unix.AF_NETLINK,
|
|
Groups: unix.RTMGRP_LINK | unix.RTMGRP_IPV4_IFADDR | unix.RTMGRP_IPV6_IFADDR,
|
|
}
|
|
err = unix.Bind(sock, saddr)
|
|
if err != nil {
|
|
return -1, err
|
|
}
|
|
return sock, nil
|
|
}
|
|
|
|
func (tun *NativeTun) routineNetlinkListener() {
|
|
defer func() {
|
|
unix.Close(tun.netlinkSock)
|
|
tun.hackListenerClosed.Lock()
|
|
close(tun.events)
|
|
tun.netlinkCancel.Close()
|
|
}()
|
|
|
|
for msg := make([]byte, 1<<16); ; {
|
|
var err error
|
|
var msgn int
|
|
for {
|
|
msgn, _, _, _, err = unix.Recvmsg(tun.netlinkSock, msg[:], nil, 0)
|
|
if err == nil || !rwcancel.RetryAfterError(err) {
|
|
break
|
|
}
|
|
if !tun.netlinkCancel.ReadyRead() {
|
|
tun.errors <- fmt.Errorf("netlink socket closed: %w", err)
|
|
return
|
|
}
|
|
}
|
|
if err != nil {
|
|
tun.errors <- fmt.Errorf("failed to receive netlink message: %w", err)
|
|
return
|
|
}
|
|
|
|
select {
|
|
case <-tun.statusListenersShutdown:
|
|
return
|
|
default:
|
|
}
|
|
|
|
wasEverUp := false
|
|
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:]
|
|
|
|
if info.Index != tun.index {
|
|
// not our interface
|
|
continue
|
|
}
|
|
|
|
if info.Flags&unix.IFF_RUNNING != 0 {
|
|
tun.events <- EventUp
|
|
wasEverUp = true
|
|
}
|
|
|
|
if info.Flags&unix.IFF_RUNNING == 0 {
|
|
// Don't emit EventDown before we've ever emitted EventUp.
|
|
// This avoids a startup race with HackListener, which
|
|
// might detect Up before we have finished reporting Down.
|
|
if wasEverUp {
|
|
tun.events <- EventDown
|
|
}
|
|
}
|
|
|
|
tun.events <- EventMTUUpdate
|
|
|
|
default:
|
|
remain = remain[hdr.Len:]
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
func getIFIndex(name string) (int32, error) {
|
|
fd, err := unix.Socket(
|
|
unix.AF_INET,
|
|
unix.SOCK_DGRAM,
|
|
0,
|
|
)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
|
|
defer unix.Close(fd)
|
|
|
|
var ifr [ifReqSize]byte
|
|
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
|
|
}
|
|
|
|
return *(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])), nil
|
|
}
|
|
|
|
func (tun *NativeTun) setMTU(n int) error {
|
|
name, err := tun.Name()
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
// open datagram socket
|
|
fd, err := unix.Socket(
|
|
unix.AF_INET,
|
|
unix.SOCK_DGRAM,
|
|
0,
|
|
)
|
|
if err != nil {
|
|
return err
|
|
}
|
|
|
|
defer unix.Close(fd)
|
|
|
|
// do ioctl call
|
|
var ifr [ifReqSize]byte
|
|
copy(ifr[:], name)
|
|
*(*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 {
|
|
return fmt.Errorf("failed to set MTU of TUN device: %w", errno)
|
|
}
|
|
|
|
return nil
|
|
}
|
|
|
|
func (tun *NativeTun) MTU() (int, error) {
|
|
name, err := tun.Name()
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
|
|
// open datagram socket
|
|
fd, err := unix.Socket(
|
|
unix.AF_INET,
|
|
unix.SOCK_DGRAM,
|
|
0,
|
|
)
|
|
if err != nil {
|
|
return 0, err
|
|
}
|
|
|
|
defer unix.Close(fd)
|
|
|
|
// do ioctl call
|
|
|
|
var ifr [ifReqSize]byte
|
|
copy(ifr[:], name)
|
|
_, _, errno := unix.Syscall(
|
|
unix.SYS_IOCTL,
|
|
uintptr(fd),
|
|
uintptr(unix.SIOCGIFMTU),
|
|
uintptr(unsafe.Pointer(&ifr[0])),
|
|
)
|
|
if errno != 0 {
|
|
return 0, fmt.Errorf("failed to get MTU of TUN device: %w", errno)
|
|
}
|
|
|
|
return int(*(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ]))), nil
|
|
}
|
|
|
|
func (tun *NativeTun) Name() (string, error) {
|
|
tun.nameOnce.Do(tun.initNameCache)
|
|
return tun.nameCache, tun.nameErr
|
|
}
|
|
|
|
func (tun *NativeTun) initNameCache() {
|
|
tun.nameCache, tun.nameErr = tun.nameSlow()
|
|
}
|
|
|
|
func (tun *NativeTun) nameSlow() (string, error) {
|
|
sysconn, err := tun.tunFile.SyscallConn()
|
|
if err != nil {
|
|
return "", err
|
|
}
|
|
var ifr [ifReqSize]byte
|
|
var errno syscall.Errno
|
|
err = sysconn.Control(func(fd uintptr) {
|
|
_, _, errno = unix.Syscall(
|
|
unix.SYS_IOCTL,
|
|
fd,
|
|
uintptr(unix.TUNGETIFF),
|
|
uintptr(unsafe.Pointer(&ifr[0])),
|
|
)
|
|
})
|
|
if err != nil {
|
|
return "", fmt.Errorf("failed to get name of TUN device: %w", err)
|
|
}
|
|
if errno != 0 {
|
|
return "", fmt.Errorf("failed to get name of TUN device: %w", errno)
|
|
}
|
|
name := ifr[:]
|
|
if i := bytes.IndexByte(name, 0); i != -1 {
|
|
name = name[:i]
|
|
}
|
|
return string(name), nil
|
|
}
|
|
|
|
func (tun *NativeTun) Write(buf []byte, offset int) (int, error) {
|
|
if tun.nopi {
|
|
buf = buf[offset:]
|
|
} else {
|
|
// reserve space for header
|
|
buf = buf[offset-4:]
|
|
|
|
// add packet information header
|
|
buf[0] = 0x00
|
|
buf[1] = 0x00
|
|
if buf[4]>>4 == ipv6.Version {
|
|
buf[2] = 0x86
|
|
buf[3] = 0xdd
|
|
} else {
|
|
buf[2] = 0x08
|
|
buf[3] = 0x00
|
|
}
|
|
}
|
|
|
|
n, err := tun.tunFile.Write(buf)
|
|
if errors.Is(err, syscall.EBADFD) {
|
|
err = os.ErrClosed
|
|
}
|
|
return n, err
|
|
}
|
|
|
|
func (tun *NativeTun) Flush() error {
|
|
// TODO: can flushing be implemented by buffering and using sendmmsg?
|
|
return nil
|
|
}
|
|
|
|
func (tun *NativeTun) Read(buf []byte, offset int) (n int, err error) {
|
|
select {
|
|
case err = <-tun.errors:
|
|
default:
|
|
if tun.nopi {
|
|
n, err = tun.tunFile.Read(buf[offset:])
|
|
} else {
|
|
buff := buf[offset-4:]
|
|
n, err = tun.tunFile.Read(buff[:])
|
|
if errors.Is(err, syscall.EBADFD) {
|
|
err = os.ErrClosed
|
|
}
|
|
if n < 4 {
|
|
n = 0
|
|
} else {
|
|
n -= 4
|
|
}
|
|
}
|
|
}
|
|
return
|
|
}
|
|
|
|
func (tun *NativeTun) Events() chan Event {
|
|
return tun.events
|
|
}
|
|
|
|
func (tun *NativeTun) Close() error {
|
|
var err1, err2 error
|
|
tun.closeOnce.Do(func() {
|
|
if tun.statusListenersShutdown != nil {
|
|
close(tun.statusListenersShutdown)
|
|
if tun.netlinkCancel != nil {
|
|
err1 = tun.netlinkCancel.Cancel()
|
|
}
|
|
} else if tun.events != nil {
|
|
close(tun.events)
|
|
}
|
|
err2 = tun.tunFile.Close()
|
|
})
|
|
if err1 != nil {
|
|
return err1
|
|
}
|
|
return err2
|
|
}
|
|
|
|
func CreateTUN(name string, mtu int) (Device, error) {
|
|
nfd, err := unix.Open(cloneDevicePath, os.O_RDWR, 0)
|
|
if err != nil {
|
|
if os.IsNotExist(err) {
|
|
return nil, fmt.Errorf("CreateTUN(%q) failed; %s does not exist", name, cloneDevicePath)
|
|
}
|
|
return nil, err
|
|
}
|
|
|
|
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 {
|
|
unix.Close(nfd)
|
|
return nil, fmt.Errorf("interface name too long: %w", unix.ENAMETOOLONG)
|
|
}
|
|
copy(ifr[:], nameBytes)
|
|
*(*uint16)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = flags
|
|
|
|
_, _, errno := unix.Syscall(
|
|
unix.SYS_IOCTL,
|
|
uintptr(nfd),
|
|
uintptr(unix.TUNSETIFF),
|
|
uintptr(unsafe.Pointer(&ifr[0])),
|
|
)
|
|
if errno != 0 {
|
|
unix.Close(nfd)
|
|
return nil, errno
|
|
}
|
|
|
|
err = unix.SetNonblock(nfd, true)
|
|
if err != nil {
|
|
unix.Close(nfd)
|
|
return nil, err
|
|
}
|
|
|
|
// Note that the above -- open,ioctl,nonblock -- must happen prior to handing it to netpoll as below this line.
|
|
|
|
fd := os.NewFile(uintptr(nfd), cloneDevicePath)
|
|
return CreateTUNFromFile(fd, mtu)
|
|
}
|
|
|
|
func CreateTUNFromFile(file *os.File, mtu int) (Device, error) {
|
|
tun := &NativeTun{
|
|
tunFile: file,
|
|
events: make(chan Event, 5),
|
|
errors: make(chan error, 5),
|
|
statusListenersShutdown: make(chan struct{}),
|
|
nopi: false,
|
|
}
|
|
|
|
name, err := tun.Name()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// start event listener
|
|
|
|
tun.index, err = getIFIndex(name)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
tun.netlinkSock, err = createNetlinkSocket()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
tun.netlinkCancel, err = rwcancel.NewRWCancel(tun.netlinkSock)
|
|
if err != nil {
|
|
unix.Close(tun.netlinkSock)
|
|
return nil, err
|
|
}
|
|
|
|
tun.hackListenerClosed.Lock()
|
|
go tun.routineNetlinkListener()
|
|
go tun.routineHackListener() // cross namespace
|
|
|
|
err = tun.setMTU(mtu)
|
|
if err != nil {
|
|
unix.Close(tun.netlinkSock)
|
|
return nil, err
|
|
}
|
|
|
|
return tun, nil
|
|
}
|
|
|
|
func CreateUnmonitoredTUNFromFD(fd int) (Device, string, error) {
|
|
err := unix.SetNonblock(fd, true)
|
|
if err != nil {
|
|
return nil, "", err
|
|
}
|
|
file := os.NewFile(uintptr(fd), "/dev/tun")
|
|
tun := &NativeTun{
|
|
tunFile: file,
|
|
events: make(chan Event, 5),
|
|
errors: make(chan error, 5),
|
|
nopi: true,
|
|
}
|
|
name, err := tun.Name()
|
|
if err != nil {
|
|
return nil, "", err
|
|
}
|
|
return tun, name, nil
|
|
}
|