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wireguard-go/tun/tun_darwin.go

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/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
*/
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package tun
import (
"fmt"
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"io/ioutil"
"net"
"os"
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"syscall"
"time"
"unsafe"
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"golang.org/x/net/ipv6"
"golang.org/x/sys/unix"
)
const utunControlName = "com.apple.net.utun_control"
type NativeTun struct {
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name string
tunFile *os.File
events chan Event
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errors chan error
routeSocket int
}
func retryInterfaceByIndex(index int) (iface *net.Interface, err error) {
for i := 0; i < 20; i++ {
iface, err = net.InterfaceByIndex(index)
if err != nil {
if opErr, ok := err.(*net.OpError); ok {
if syscallErr, ok := opErr.Err.(*os.SyscallError); ok && syscallErr.Err == syscall.ENOMEM {
time.Sleep(time.Duration(i) * time.Second / 3)
continue
}
}
}
return iface, err
}
return nil, err
}
func (tun *NativeTun) routineRouteListener(tunIfindex int) {
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var (
statusUp bool
statusMTU int
)
defer close(tun.events)
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data := make([]byte, os.Getpagesize())
for {
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retry:
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n, err := unix.Read(tun.routeSocket, data)
if err != nil {
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if errno, ok := err.(syscall.Errno); ok && errno == syscall.EINTR {
goto retry
}
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tun.errors <- err
return
}
if n < 14 {
continue
}
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if data[3 /* type */] != unix.RTM_IFINFO {
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continue
}
ifindex := int(*(*uint16)(unsafe.Pointer(&data[12 /* ifindex */])))
if ifindex != tunIfindex {
continue
}
iface, err := retryInterfaceByIndex(ifindex)
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if err != nil {
tun.errors <- err
return
}
// Up / Down event
up := (iface.Flags & net.FlagUp) != 0
if up != statusUp && up {
tun.events <- EventUp
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}
if up != statusUp && !up {
tun.events <- EventDown
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}
statusUp = up
// MTU changes
if iface.MTU != statusMTU {
tun.events <- EventMTUUpdate
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}
statusMTU = iface.MTU
}
}
func CreateTUN(name string, mtu int) (Device, error) {
ifIndex := -1
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if name != "utun" {
_, err := fmt.Sscanf(name, "utun%d", &ifIndex)
if err != nil || ifIndex < 0 {
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return nil, fmt.Errorf("Interface name must be utun[0-9]*")
}
}
fd, err := unix.Socket(unix.AF_SYSTEM, unix.SOCK_DGRAM, 2)
if err != nil {
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return nil, err
}
ctlInfo := &unix.CtlInfo{}
copy(ctlInfo.Name[:], []byte(utunControlName))
err = unix.IoctlCtlInfo(fd, ctlInfo)
if err != nil {
return nil, fmt.Errorf("IoctlGetCtlInfo: %w", err)
}
sc := &unix.SockaddrCtl{
ID: ctlInfo.Id,
Unit: uint32(ifIndex) + 1,
}
err = unix.Connect(fd, sc)
if err != nil {
return nil, err
}
err = syscall.SetNonblock(fd, true)
if err != nil {
return nil, err
}
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tun, err := CreateTUNFromFile(os.NewFile(uintptr(fd), ""), mtu)
if err == nil && name == "utun" {
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fname := os.Getenv("WG_TUN_NAME_FILE")
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if fname != "" {
ioutil.WriteFile(fname, []byte(tun.(*NativeTun).name+"\n"), 0400)
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}
}
return tun, err
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}
func CreateTUNFromFile(file *os.File, mtu int) (Device, error) {
tun := &NativeTun{
tunFile: file,
events: make(chan Event, 10),
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errors: make(chan error, 5),
}
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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
}()
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if err != nil {
tun.tunFile.Close()
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return nil, err
}
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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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if mtu > 0 {
err = tun.setMTU(mtu)
if err != nil {
tun.Close()
return nil, err
}
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}
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return tun, nil
}
func (tun *NativeTun) Name() (string, error) {
var err error
tun.operateOnFd(func(fd uintptr) {
tun.name, err = unix.GetsockoptString(
int(fd),
2, /* #define SYSPROTO_CONTROL 2 */
2, /* #define UTUN_OPT_IFNAME 2 */
)
})
if err != nil {
return "", fmt.Errorf("GetSockoptString: %w", err)
}
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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:
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return 0, err
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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
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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
buff[2] = 0x00
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if buff[4]>>4 == ipv6.Version {
buff[3] = unix.AF_INET6
} else {
buff[3] = unix.AF_INET
}
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// write
return tun.tunFile.Write(buff)
}
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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 err2 error
err1 := tun.tunFile.Close()
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if tun.routeSocket != -1 {
unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
err2 = unix.Close(tun.routeSocket)
} else if tun.events != nil {
close(tun.events)
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}
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if err1 != nil {
return err1
}
return err2
}
func (tun *NativeTun) setMTU(n int) error {
fd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
return err
}
defer unix.Close(fd)
var ifr unix.IfreqMTU
copy(ifr.Name[:], tun.name)
ifr.MTU = int32(n)
err = unix.IoctlSetIfreqMTU(fd, &ifr)
if err != nil {
return fmt.Errorf("failed to set MTU on %s: %w", tun.name, err)
}
return nil
}
func (tun *NativeTun) MTU() (int, error) {
fd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
return 0, err
}
defer unix.Close(fd)
ifr, err := unix.IoctlGetIfreqMTU(fd, tun.name)
if err != nil {
return 0, fmt.Errorf("failed to get MTU on %s: %w", tun.name, err)
}
return int(ifr.MTU), nil
}