wireguard-go/tun/tun_openbsd.go

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/* SPDX-License-Identifier: MIT
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*
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
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*/
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package tun
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import (
"errors"
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"fmt"
"net"
"os"
"sync"
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"syscall"
"unsafe"
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"golang.org/x/net/ipv6"
"golang.org/x/sys/unix"
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)
// Structure for iface mtu get/set ioctls
type ifreq_mtu struct {
Name [unix.IFNAMSIZ]byte
MTU uint32
Pad0 [12]byte
}
const _TUNSIFMODE = 0x8004745d
type NativeTun struct {
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name string
tunFile *os.File
events chan Event
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errors chan error
routeSocket int
closeOnce sync.Once
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}
func (tun *NativeTun) routineRouteListener(tunIfindex int) {
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var (
statusUp bool
statusMTU int
)
defer close(tun.events)
check := func() bool {
iface, err := net.InterfaceByIndex(tunIfindex)
if err != nil {
tun.errors <- err
return true
}
// Up / Down event
up := (iface.Flags & net.FlagUp) != 0
if up != statusUp && up {
tun.events <- EventUp
}
if up != statusUp && !up {
tun.events <- EventDown
}
statusUp = up
// MTU changes
if iface.MTU != statusMTU {
tun.events <- EventMTUUpdate
}
statusMTU = iface.MTU
return false
}
if check() {
return
}
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data := make([]byte, os.Getpagesize())
for {
n, err := unix.Read(tun.routeSocket, data)
if err != nil {
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if errno, ok := err.(syscall.Errno); ok && errno == syscall.EINTR {
continue
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}
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tun.errors <- err
return
}
if n < 8 {
continue
}
if data[3 /* type */] != unix.RTM_IFINFO {
continue
}
ifindex := int(*(*uint16)(unsafe.Pointer(&data[6 /* ifindex */])))
if ifindex != tunIfindex {
continue
}
if check() {
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return
}
}
}
func CreateTUN(name string, mtu int) (Device, error) {
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ifIndex := -1
if name != "tun" {
_, err := fmt.Sscanf(name, "tun%d", &ifIndex)
if err != nil || ifIndex < 0 {
return nil, fmt.Errorf("Interface name must be tun[0-9]*")
}
}
var tunfile *os.File
var err error
if ifIndex != -1 {
tunfile, err = os.OpenFile(fmt.Sprintf("/dev/tun%d", ifIndex), unix.O_RDWR, 0)
} else {
for ifIndex = 0; ifIndex < 256; ifIndex++ {
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tunfile, err = os.OpenFile(fmt.Sprintf("/dev/tun%d", ifIndex), unix.O_RDWR, 0)
if err == nil || !errors.Is(err, syscall.EBUSY) {
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break
}
}
}
if err != nil {
return nil, err
}
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tun, err := CreateTUNFromFile(tunfile, mtu)
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if err == nil && name == "tun" {
fname := os.Getenv("WG_TUN_NAME_FILE")
if fname != "" {
os.WriteFile(fname, []byte(tun.(*NativeTun).name+"\n"), 0400)
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}
}
return tun, err
}
func CreateTUNFromFile(file *os.File, mtu int) (Device, error) {
tun := &NativeTun{
tunFile: file,
events: make(chan Event, 10),
errors: make(chan error, 1),
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}
name, err := tun.Name()
if err != nil {
tun.tunFile.Close()
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return nil, err
}
tunIfindex, err := func() (int, error) {
iface, err := net.InterfaceByName(name)
if err != nil {
return -1, err
}
return iface.Index, nil
}()
if err != nil {
tun.tunFile.Close()
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return nil, err
}
tun.routeSocket, err = unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
if err != nil {
tun.tunFile.Close()
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return nil, err
}
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go tun.routineRouteListener(tunIfindex)
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currentMTU, err := tun.MTU()
if err != nil || currentMTU != mtu {
err = tun.setMTU(mtu)
if err != nil {
tun.Close()
return nil, err
}
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}
return tun, nil
}
func (tun *NativeTun) Name() (string, error) {
gostat, err := tun.tunFile.Stat()
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if err != nil {
tun.name = ""
return "", err
}
stat := gostat.Sys().(*syscall.Stat_t)
tun.name = fmt.Sprintf("tun%d", stat.Rdev%256)
return tun.name, nil
}
func (tun *NativeTun) File() *os.File {
return tun.tunFile
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}
func (tun *NativeTun) Events() chan Event {
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return tun.events
}
func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
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select {
case err := <-tun.errors:
return 0, err
default:
buff := buff[offset-4:]
n, err := tun.tunFile.Read(buff[:])
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if n < 4 {
return 0, err
}
return n - 4, err
}
}
func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
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// reserve space for header
buff = buff[offset-4:]
// add packet information header
buff[0] = 0x00
buff[1] = 0x00
buff[2] = 0x00
if buff[4]>>4 == ipv6.Version {
buff[3] = unix.AF_INET6
} else {
buff[3] = unix.AF_INET
}
// write
return tun.tunFile.Write(buff)
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}
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func (tun *NativeTun) Flush() error {
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// TODO: can flushing be implemented by buffering and using sendmmsg?
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return nil
}
func (tun *NativeTun) Close() error {
var err1, err2 error
tun.closeOnce.Do(func() {
err1 = tun.tunFile.Close()
if tun.routeSocket != -1 {
unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
err2 = unix.Close(tun.routeSocket)
tun.routeSocket = -1
} else if tun.events != nil {
close(tun.events)
}
})
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if err1 != nil {
return err1
}
return err2
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}
func (tun *NativeTun) setMTU(n int) error {
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// open datagram socket
var fd int
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 ifreq_mtu
copy(ifr.Name[:], tun.name)
ifr.MTU = uint32(n)
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(fd),
uintptr(unix.SIOCSIFMTU),
uintptr(unsafe.Pointer(&ifr)),
)
if errno != 0 {
return fmt.Errorf("failed to set MTU on %s", tun.name)
}
return nil
}
func (tun *NativeTun) MTU() (int, error) {
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// 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 ifreq_mtu
copy(ifr.Name[:], tun.name)
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(fd),
uintptr(unix.SIOCGIFMTU),
uintptr(unsafe.Pointer(&ifr)),
)
if errno != 0 {
return 0, fmt.Errorf("failed to get MTU on %s", tun.name)
}
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return int(*(*int32)(unsafe.Pointer(&ifr.MTU))), nil
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}