356 lines
6.6 KiB
Go
356 lines
6.6 KiB
Go
/* SPDX-License-Identifier: GPL-2.0
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*
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* Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
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* Copyright (C) 2017-2018 Mathias N. Hall-Andersen <mathias@hall-andersen.dk>.
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*/
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package main
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import (
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"./rwcancel"
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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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"io/ioutil"
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"net"
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"os"
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"path/filepath"
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"time"
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"unsafe"
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)
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const utunControlName = "com.apple.net.utun_control"
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// _CTLIOCGINFO value derived from /usr/include/sys/{kern_control,ioccom}.h
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const _CTLIOCGINFO = (0x40000000 | 0x80000000) | ((100 & 0x1fff) << 16) | uint32(byte('N'))<<8 | 3
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// sockaddr_ctl specifeid in /usr/include/sys/kern_control.h
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type sockaddrCtl struct {
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scLen uint8
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scFamily uint8
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ssSysaddr uint16
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scID uint32
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scUnit uint32
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scReserved [5]uint32
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}
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// NativeTun is a hack to work around the first 4 bytes "packet
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// information" because there doesn't seem to be an IFF_NO_PI for darwin.
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type NativeTun struct {
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name string
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fd *os.File
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rwcancel *rwcancel.RWCancel
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mtu int
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events chan TUNEvent
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errors chan error
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statusListenersShutdown chan struct{}
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}
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var sockaddrCtlSize uintptr = 32
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func CreateTUN(name string) (TUNDevice, error) {
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ifIndex := -1
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if name != "utun" {
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fmt.Sscanf(name, "utun%d", &ifIndex)
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if ifIndex < 0 {
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return nil, fmt.Errorf("Interface name must be utun[0-9]*")
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}
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}
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fd, err := unix.Socket(unix.AF_SYSTEM, unix.SOCK_DGRAM, 2)
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if err != nil {
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return nil, err
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}
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var ctlInfo = &struct {
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ctlID uint32
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ctlName [96]byte
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}{}
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copy(ctlInfo.ctlName[:], []byte(utunControlName))
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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(_CTLIOCGINFO),
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uintptr(unsafe.Pointer(ctlInfo)),
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)
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if errno != 0 {
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return nil, fmt.Errorf("_CTLIOCGINFO: %v", errno)
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}
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sc := sockaddrCtl{
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scLen: uint8(sockaddrCtlSize),
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scFamily: unix.AF_SYSTEM,
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ssSysaddr: 2,
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scID: ctlInfo.ctlID,
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scUnit: uint32(ifIndex) + 1,
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}
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scPointer := unsafe.Pointer(&sc)
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_, _, errno = unix.RawSyscall(
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unix.SYS_CONNECT,
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uintptr(fd),
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uintptr(scPointer),
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uintptr(sockaddrCtlSize),
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)
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if errno != 0 {
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return nil, fmt.Errorf("SYS_CONNECT: %v", errno)
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}
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tun, err := CreateTUNFromFile(os.NewFile(uintptr(fd), ""))
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if err == nil && name == "utun" {
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fname := os.Getenv("WG_DARWIN_UTUN_NAME_FILE")
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if fname != "" {
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os.MkdirAll(filepath.Dir(fname), 0700)
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ioutil.WriteFile(fname, []byte(tun.(*NativeTun).name+"\n"), 0400)
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}
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}
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return tun, err
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}
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func CreateTUNFromFile(file *os.File) (TUNDevice, error) {
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tun := &NativeTun{
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fd: file,
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mtu: 1500,
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events: make(chan TUNEvent, 10),
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errors: make(chan error, 1),
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statusListenersShutdown: make(chan struct{}),
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}
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_, err := tun.Name()
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if err != nil {
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tun.fd.Close()
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return nil, err
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}
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tun.rwcancel, err = rwcancel.NewRWCancel(int(file.Fd()))
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if err != nil {
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tun.fd.Close()
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return nil, err
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}
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// TODO: Fix this very naive implementation
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go func(tun *NativeTun) {
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var (
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statusUp bool
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statusMTU int
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)
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for {
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intr, err := net.InterfaceByName(tun.name)
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if err != nil {
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tun.errors <- err
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return
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}
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// Up / Down event
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up := (intr.Flags & net.FlagUp) != 0
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if up != statusUp && up {
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tun.events <- TUNEventUp
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}
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if up != statusUp && !up {
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tun.events <- TUNEventDown
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}
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statusUp = up
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// MTU changes
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if intr.MTU != statusMTU {
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tun.events <- TUNEventMTUUpdate
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}
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statusMTU = intr.MTU
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select {
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case <-time.After(time.Second / 10):
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case <-tun.statusListenersShutdown:
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return
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}
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}
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}(tun)
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// set default MTU
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err = tun.setMTU(DefaultMTU)
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if err != nil {
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tun.Close()
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return nil, err
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}
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return tun, nil
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}
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func (tun *NativeTun) Name() (string, error) {
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var ifName struct {
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name [16]byte
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}
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ifNameSize := uintptr(16)
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_, _, errno := unix.Syscall6(
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unix.SYS_GETSOCKOPT,
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uintptr(tun.fd.Fd()),
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2, /* #define SYSPROTO_CONTROL 2 */
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2, /* #define UTUN_OPT_IFNAME 2 */
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uintptr(unsafe.Pointer(&ifName)),
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uintptr(unsafe.Pointer(&ifNameSize)), 0)
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if errno != 0 {
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return "", fmt.Errorf("SYS_GETSOCKOPT: %v", errno)
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}
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tun.name = string(ifName.name[:ifNameSize-1])
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return tun.name, nil
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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) Events() chan TUNEvent {
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return tun.events
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}
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func (tun *NativeTun) doRead(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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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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func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
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for {
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n, err := tun.doRead(buff, offset)
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if err == nil || !rwcancel.ErrorIsEAGAIN(err) {
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return n, err
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}
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if !tun.rwcancel.ReadyRead() {
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return 0, errors.New("tun device closed")
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}
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}
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}
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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
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buff[1] = 0x00
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buff[2] = 0x00
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if buff[4]>>4 == ipv6.Version {
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buff[3] = unix.AF_INET6
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} else {
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buff[3] = unix.AF_INET
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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) Close() error {
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close(tun.statusListenersShutdown)
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err1 := tun.rwcancel.Cancel()
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err2 := tun.fd.Close()
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close(tun.events)
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if err1 != nil {
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return err1
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}
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return err2
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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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var fd int
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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 [32]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 fmt.Errorf("Failed to set MTU on %s", tun.name)
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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 [64]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, fmt.Errorf("Failed to get MTU on %s", tun.name)
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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(val-(1<<31)) - (1 << 31), nil
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}
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return int(val), nil
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}
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