511 lines
9.1 KiB
Go
511 lines
9.1 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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*/
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package tun
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import (
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"bytes"
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"errors"
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"fmt"
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"git.zx2c4.com/wireguard-go/rwcancel"
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"golang.org/x/net/ipv6"
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"golang.org/x/sys/unix"
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"net"
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"os"
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"syscall"
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"unsafe"
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)
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// _TUNSIFHEAD, value derived from sys/net/{if_tun,ioccom}.h
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// const _TUNSIFHEAD = ((0x80000000) | (((4) & ((1 << 13) - 1) ) << 16) | (uint32(byte('t')) << 8) | (96))
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const _TUNSIFHEAD = 0x80047460
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const _TUNSIFMODE = 0x8004745e
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const _TUNSIFPID = 0x2000745f
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// Iface status string max len
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const _IFSTATMAX = 800
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const SIZEOF_UINTPTR = 4 << (^uintptr(0) >> 32 & 1)
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// structure for iface requests with a pointer
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type ifreq_ptr struct {
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Name [unix.IFNAMSIZ]byte
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Data uintptr
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Pad0 [24 - SIZEOF_UINTPTR]byte
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}
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// Structure for iface mtu get/set ioctls
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type ifreq_mtu struct {
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Name [unix.IFNAMSIZ]byte
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MTU uint32
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Pad0 [12]byte
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}
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// Structure for interface status request ioctl
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type ifstat struct {
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IfsName [unix.IFNAMSIZ]byte
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Ascii [_IFSTATMAX]byte
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}
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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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events chan TUNEvent
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errors chan error
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routeSocket int
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}
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func (tun *nativeTun) routineRouteListener(tunIfindex int) {
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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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defer close(tun.events)
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data := make([]byte, os.Getpagesize())
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for {
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retry:
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n, err := unix.Read(tun.routeSocket, data)
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if err != nil {
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if errno, ok := err.(syscall.Errno); ok && errno == syscall.EINTR {
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goto retry
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}
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tun.errors <- err
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return
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}
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if n < 14 {
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continue
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}
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if data[3 /* type */] != unix.RTM_IFINFO {
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continue
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}
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ifindex := int(*(*uint16)(unsafe.Pointer(&data[12 /* ifindex */])))
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if ifindex != tunIfindex {
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continue
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}
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iface, err := net.InterfaceByIndex(ifindex)
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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 := (iface.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 iface.MTU != statusMTU {
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tun.events <- TUNEventMTUUpdate
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}
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statusMTU = iface.MTU
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}
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}
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func tunName(fd uintptr) (string, error) {
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//Terrible hack to make up for freebsd not having a TUNGIFNAME
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//First, make sure the tun pid matches this proc's pid
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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(_TUNSIFPID),
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uintptr(0),
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)
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if errno != 0 {
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return "", fmt.Errorf("failed to set tun device PID: %s", errno.Error())
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}
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// Open iface control socket
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confd, 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(confd)
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procPid := os.Getpid()
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//Try to find interface with matching PID
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for i := 1; ; i++ {
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iface, _ := net.InterfaceByIndex(i)
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if err != nil || iface == nil {
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break
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}
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// Structs for getting data in and out of SIOCGIFSTATUS ioctl
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var ifstatus ifstat
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copy(ifstatus.IfsName[:], iface.Name)
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// Make the syscall to get the status string
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_, _, errno := unix.Syscall(
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unix.SYS_IOCTL,
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uintptr(confd),
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uintptr(unix.SIOCGIFSTATUS),
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uintptr(unsafe.Pointer(&ifstatus)),
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)
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if errno != 0 {
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continue
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}
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nullStr := ifstatus.Ascii[:]
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i := bytes.IndexByte(nullStr, 0)
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if i < 1 {
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continue
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}
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statStr := string(nullStr[:i])
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var pidNum int = 0
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// Finally get the owning PID
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// Format string taken from sys/net/if_tun.c
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_, err := fmt.Sscanf(statStr, "\tOpened by PID %d\n", &pidNum)
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if err != nil {
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continue
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}
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if pidNum == procPid {
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return iface.Name, nil
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}
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}
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return "", nil
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}
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// Destroy a named system interface
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func tunDestroy(name string) error {
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// open control 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[:], 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.SIOCIFDESTROY),
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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 destroy interface %s: %s", name, errno.Error())
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}
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return nil
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}
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func CreateTUN(name string, mtu int) (TUNDevice, error) {
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if len(name) > unix.IFNAMSIZ-1 {
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return nil, errors.New("interface name too long")
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}
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// See if interface already exists
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iface, _ := net.InterfaceByName(name)
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if iface != nil {
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return nil, fmt.Errorf("interface %s already exists", name)
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}
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tunfile, err := os.OpenFile("/dev/tun", unix.O_RDWR, 0)
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if err != nil {
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return nil, err
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}
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tunfd := tunfile.Fd()
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assignedName, err := tunName(tunfd)
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if err != nil {
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tunfile.Close()
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return nil, err
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}
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// Enable ifhead mode, otherwise tun will complain if it gets a non-AF_INET packet
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ifheadmode := 1
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_, _, errno := unix.Syscall(
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unix.SYS_IOCTL,
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uintptr(tunfd),
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uintptr(_TUNSIFHEAD),
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uintptr(unsafe.Pointer(&ifheadmode)),
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)
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if errno != 0 {
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return nil, fmt.Errorf("error %s", errno.Error())
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}
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// Rename tun interface
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// Open control socket
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confd, 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 nil, err
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}
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defer unix.Close(confd)
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// set up struct for iface rename
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var newnp [unix.IFNAMSIZ]byte
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copy(newnp[:], name)
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var ifr ifreq_ptr
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copy(ifr.Name[:], assignedName)
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ifr.Data = uintptr(unsafe.Pointer(&newnp[0]))
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//do actual ioctl to rename iface
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_, _, errno = unix.Syscall(
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unix.SYS_IOCTL,
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uintptr(confd),
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uintptr(unix.SIOCSIFNAME),
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uintptr(unsafe.Pointer(&ifr)),
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)
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if errno != 0 {
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tunfile.Close()
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tunDestroy(name)
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return nil, fmt.Errorf("failed to rename %s to %s: %s", assignedName, name, errno.Error())
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}
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return CreateTUNFromFile(tunfile, mtu)
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}
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func CreateTUNFromFile(file *os.File, mtu int) (TUNDevice, error) {
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tun := &nativeTun{
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fd: file,
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events: make(chan TUNEvent, 10),
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errors: make(chan error, 1),
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}
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name, 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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tunIfindex, err := func() (int, error) {
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iface, err := net.InterfaceByName(name)
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if err != nil {
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return -1, err
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}
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return iface.Index, nil
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}()
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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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tun.routeSocket, err = unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
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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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go tun.routineRouteListener(tunIfindex)
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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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}
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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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name, err := tunName(tun.fd.Fd())
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if err != nil {
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return "", err
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}
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tun.name = name
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return 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.RetryAfterError(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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var err4 error
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err1 := tun.rwcancel.Cancel()
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err2 := tun.fd.Close()
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err3 := tunDestroy(tun.name)
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if tun.routeSocket != -1 {
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unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
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err4 = unix.Close(tun.routeSocket)
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tun.routeSocket = -1
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} else if tun.events != nil {
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close(tun.events)
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}
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if err1 != nil {
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return err1
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}
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if err2 != nil {
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return err2
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}
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if err3 != nil {
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return err3
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}
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return err4
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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 ifreq_mtu
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copy(ifr.Name[:], tun.name)
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ifr.MTU = 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)),
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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 ifreq_mtu
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copy(ifr.Name[:], 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)),
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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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return int(*(*int32)(unsafe.Pointer(&ifr.MTU))), nil
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}
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