375 lines
8.4 KiB
Go
375 lines
8.4 KiB
Go
/* SPDX-License-Identifier: MIT
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*
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* Copyright (C) 2018-2019 WireGuard LLC. All Rights Reserved.
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*/
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package tun
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import (
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"errors"
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"fmt"
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"io"
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"os"
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"sync"
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"time"
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"unsafe"
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"golang.org/x/sys/windows"
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"golang.zx2c4.com/wireguard/tun/wintun"
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)
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const (
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packetExchangeAlignment uint32 = 16 // Number of bytes packets are aligned to in exchange buffers
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packetSizeMax uint32 = 0xf000 - packetExchangeAlignment // Maximum packet size
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packetExchangeSize uint32 = 0x100000 // Exchange buffer size (defaults to 1MiB)
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retryRate = 4 // Number of retries per second to reopen device pipe
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retryTimeout = 30 // Number of seconds to tolerate adapter unavailable
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)
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type exchgBufRead struct {
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data [packetExchangeSize]byte
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offset uint32
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avail uint32
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}
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type exchgBufWrite struct {
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data [packetExchangeSize]byte
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offset uint32
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packetNum uint32
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}
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type NativeTun struct {
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wt *wintun.Wintun
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tunFileRead *os.File
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tunFileWrite *os.File
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tunLock sync.Mutex
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close bool
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rdBuff *exchgBufRead
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wrBuff *exchgBufWrite
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events chan TUNEvent
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errors chan error
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forcedMTU int
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}
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func packetAlign(size uint32) uint32 {
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return (size + (packetExchangeAlignment - 1)) &^ (packetExchangeAlignment - 1)
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}
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//
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// CreateTUN creates a Wintun adapter with the given name. Should a Wintun
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// adapter with the same name exist, it is reused.
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//
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func CreateTUN(ifname string) (TUNDevice, error) {
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var err error
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var wt *wintun.Wintun
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// Does an interface with this name already exist?
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wt, err = wintun.GetInterface(ifname, 0)
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if err == nil {
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// If so, we delete it, in case it has weird residual configuration.
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_, err = wt.DeleteInterface(0)
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if err != nil {
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return nil, fmt.Errorf("Unable to delete already existing Wintun interface: %v", err)
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}
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} else if err == windows.ERROR_ALREADY_EXISTS {
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return nil, fmt.Errorf("Foreign network interface with the same name exists")
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}
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wt, _, err = wintun.CreateInterface("WireGuard Tunnel Adapter", 0)
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if err != nil {
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return nil, fmt.Errorf("Unable to create Wintun interface: %v", err)
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}
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err = wt.SetInterfaceName(ifname)
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if err != nil {
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wt.DeleteInterface(0)
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return nil, fmt.Errorf("Unable to set name of Wintun interface: %v", err)
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}
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return &NativeTun{
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wt: wt,
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rdBuff: &exchgBufRead{},
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wrBuff: &exchgBufWrite{},
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events: make(chan TUNEvent, 10),
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errors: make(chan error, 1),
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forcedMTU: 1500,
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}, nil
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}
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func (tun *NativeTun) openTUN() error {
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retries := retryTimeout * retryRate
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if tun.close {
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return os.ErrClosed
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}
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var err error
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name := tun.wt.DataFileName()
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for tun.tunFileRead == nil {
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tun.tunFileRead, err = os.OpenFile(name, os.O_RDONLY, 0)
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if err != nil {
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if retries > 0 && !tun.close {
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time.Sleep(time.Second / retryRate)
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retries--
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continue
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}
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return err
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}
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}
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for tun.tunFileWrite == nil {
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tun.tunFileWrite, err = os.OpenFile(name, os.O_WRONLY, 0)
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if err != nil {
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if retries > 0 && !tun.close {
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time.Sleep(time.Second / retryRate)
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retries--
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continue
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}
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return err
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}
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}
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return nil
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}
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func (tun *NativeTun) closeTUN() (err error) {
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for tun.tunFileRead != nil {
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tun.tunLock.Lock()
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if tun.tunFileRead == nil {
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tun.tunLock.Unlock()
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break
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}
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t := tun.tunFileRead
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tun.tunFileRead = nil
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windows.CancelIoEx(windows.Handle(t.Fd()), nil)
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err = t.Close()
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tun.tunLock.Unlock()
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break
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}
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for tun.tunFileWrite != nil {
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tun.tunLock.Lock()
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if tun.tunFileWrite == nil {
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tun.tunLock.Unlock()
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break
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}
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t := tun.tunFileWrite
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tun.tunFileWrite = nil
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windows.CancelIoEx(windows.Handle(t.Fd()), nil)
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err2 := t.Close()
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tun.tunLock.Unlock()
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if err == nil {
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err = err2
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}
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break
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}
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return
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}
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func (tun *NativeTun) getTUN() (read *os.File, write *os.File, err error) {
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read, write = tun.tunFileRead, tun.tunFileWrite
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if read == nil || write == nil {
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read, write = nil, nil
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tun.tunLock.Lock()
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if tun.tunFileRead != nil && tun.tunFileWrite != nil {
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read, write = tun.tunFileRead, tun.tunFileWrite
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tun.tunLock.Unlock()
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return
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}
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err = tun.closeTUN()
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if err != nil {
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tun.tunLock.Unlock()
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return
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}
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err = tun.openTUN()
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if err == nil {
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read, write = tun.tunFileRead, tun.tunFileWrite
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}
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tun.tunLock.Unlock()
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return
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}
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return
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}
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func (tun *NativeTun) Name() (string, error) {
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return tun.wt.InterfaceName()
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}
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func (tun *NativeTun) File() *os.File {
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return nil
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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) Close() error {
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tun.close = true
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err1 := tun.closeTUN()
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if tun.events != nil {
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close(tun.events)
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}
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_, err2 := tun.wt.DeleteInterface(0)
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if err1 == nil {
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err1 = err2
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}
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return err1
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}
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func (tun *NativeTun) MTU() (int, error) {
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return tun.forcedMTU, nil
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}
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//TODO: This is a temporary hack. We really need to be monitoring the interface in real time and adapting to MTU changes.
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func (tun *NativeTun) ForceMTU(mtu int) {
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tun.forcedMTU = mtu
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}
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func (tun *NativeTun) Read(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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}
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retries := 1000
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for {
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if tun.rdBuff.offset+packetExchangeAlignment <= tun.rdBuff.avail {
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// Get packet from the exchange buffer.
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packet := tun.rdBuff.data[tun.rdBuff.offset:]
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size := *(*uint32)(unsafe.Pointer(&packet[0]))
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pSize := packetAlign(packetExchangeAlignment + size)
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if packetSizeMax < size || tun.rdBuff.avail < tun.rdBuff.offset+pSize {
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// Invalid packet size.
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tun.rdBuff.avail = 0
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continue
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}
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packet = packet[packetExchangeAlignment : packetExchangeAlignment+size]
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// Copy data.
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copy(buff[offset:], packet)
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tun.rdBuff.offset += pSize
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return int(size), nil
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}
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// Get TUN data pipe.
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file, _, err := tun.getTUN()
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if err != nil {
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return 0, err
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}
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n, err := file.Read(tun.rdBuff.data[:])
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if err != nil {
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tun.rdBuff.offset = 0
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tun.rdBuff.avail = 0
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pe, ok := err.(*os.PathError)
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if tun.close {
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return 0, os.ErrClosed
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}
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if retries > 0 && ok && (pe.Err == windows.ERROR_HANDLE_EOF || pe.Err == windows.ERROR_OPERATION_ABORTED) {
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retries--
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tun.closeTUN()
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time.Sleep(time.Millisecond * 2)
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continue
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}
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return 0, err
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}
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if n == 0 {
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if retries == 0 {
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return 0, io.ErrShortBuffer
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}
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retries--
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continue
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}
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tun.rdBuff.offset = 0
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tun.rdBuff.avail = uint32(n)
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}
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}
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// Note: flush() and putTunPacket() assume the caller comes only from a single thread; there's no locking.
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func (tun *NativeTun) Flush() error {
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if tun.wrBuff.offset == 0 {
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return nil
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}
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defer func() {
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tun.wrBuff.packetNum = 0
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tun.wrBuff.offset = 0
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}()
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retries := 1000
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for {
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// Get TUN data pipe.
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_, file, err := tun.getTUN()
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if err != nil {
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return err
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}
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for {
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_, err = file.Write(tun.wrBuff.data[:tun.wrBuff.offset])
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if err != nil {
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pe, ok := err.(*os.PathError)
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if tun.close {
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return os.ErrClosed
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}
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if retries > 0 && ok && pe.Err == windows.ERROR_OPERATION_ABORTED { // Adapter is paused or in low-power state.
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retries--
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time.Sleep(time.Millisecond * 2)
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continue
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}
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if retries > 0 && ok && pe.Err == windows.ERROR_HANDLE_EOF { // Adapter is going down.
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retries--
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tun.closeTUN()
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time.Sleep(time.Millisecond * 2)
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break
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}
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return err
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}
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return nil
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}
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}
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}
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func (tun *NativeTun) putTunPacket(buff []byte) error {
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size := uint32(len(buff))
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if size == 0 {
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return errors.New("Empty packet")
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}
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if size > packetSizeMax {
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return errors.New("Packet too big")
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}
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pSize := packetAlign(packetExchangeAlignment + size)
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if tun.wrBuff.offset+pSize >= packetExchangeSize {
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// Exchange buffer is full -> flush first.
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err := tun.Flush()
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if err != nil {
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return err
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}
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}
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// Write packet to the exchange buffer.
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packet := tun.wrBuff.data[tun.wrBuff.offset : tun.wrBuff.offset+pSize]
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*(*uint32)(unsafe.Pointer(&packet[0])) = size
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packet = packet[packetExchangeAlignment : packetExchangeAlignment+size]
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copy(packet, buff)
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tun.wrBuff.packetNum++
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tun.wrBuff.offset += pSize
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return nil
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}
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func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
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err := tun.putTunPacket(buff[offset:])
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if err != nil {
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return 0, err
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}
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return len(buff) - offset, nil
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}
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//
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// LUID returns Windows adapter instance ID.
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//
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func (tun *NativeTun) LUID() uint64 {
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return tun.wt.LUID()
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}
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