661 lines
16 KiB
Go
661 lines
16 KiB
Go
/* SPDX-License-Identifier: MIT
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*
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* Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
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*/
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package tun
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/* Implementation of the TUN device interface for linux
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*/
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import (
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"errors"
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"fmt"
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"os"
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"sync"
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"syscall"
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"time"
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"unsafe"
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"golang.org/x/sys/unix"
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"gitea.hbanafa.com/hesham/wireguard-go/conn"
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"gitea.hbanafa.com/hesham/wireguard-go/rwcancel"
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)
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const (
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cloneDevicePath = "/dev/net/tun"
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ifReqSize = unix.IFNAMSIZ + 64
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)
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type NativeTun struct {
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tunFile *os.File
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index int32 // if index
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errors chan error // async error handling
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events chan Event // device related events
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netlinkSock int
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netlinkCancel *rwcancel.RWCancel
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hackListenerClosed sync.Mutex
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statusListenersShutdown chan struct{}
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batchSize int
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vnetHdr bool
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udpGSO bool
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closeOnce sync.Once
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nameOnce sync.Once // guards calling initNameCache, which sets following fields
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nameCache string // name of interface
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nameErr error
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readOpMu sync.Mutex // readOpMu guards readBuff
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readBuff [virtioNetHdrLen + 65535]byte // if vnetHdr every read() is prefixed by virtioNetHdr
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writeOpMu sync.Mutex // writeOpMu guards toWrite, tcpGROTable
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toWrite []int
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tcpGROTable *tcpGROTable
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udpGROTable *udpGROTable
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}
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func (tun *NativeTun) File() *os.File {
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return tun.tunFile
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}
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func (tun *NativeTun) routineHackListener() {
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defer tun.hackListenerClosed.Unlock()
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/* This is needed for the detection to work across network namespaces
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* If you are reading this and know a better method, please get in touch.
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*/
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last := 0
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const (
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up = 1
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down = 2
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)
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for {
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sysconn, err := tun.tunFile.SyscallConn()
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if err != nil {
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return
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}
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err2 := sysconn.Control(func(fd uintptr) {
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_, err = unix.Write(int(fd), nil)
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})
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if err2 != nil {
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return
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}
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switch err {
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case unix.EINVAL:
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if last != up {
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// If the tunnel is up, it reports that write() is
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// allowed but we provided invalid data.
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tun.events <- EventUp
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last = up
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}
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case unix.EIO:
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if last != down {
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// If the tunnel is down, it reports that no I/O
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// is possible, without checking our provided data.
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tun.events <- EventDown
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last = down
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}
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default:
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return
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}
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select {
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case <-time.After(time.Second):
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// nothing
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case <-tun.statusListenersShutdown:
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return
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}
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}
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}
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func createNetlinkSocket() (int, error) {
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sock, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW|unix.SOCK_CLOEXEC, unix.NETLINK_ROUTE)
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if err != nil {
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return -1, err
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}
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saddr := &unix.SockaddrNetlink{
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Family: unix.AF_NETLINK,
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Groups: unix.RTMGRP_LINK | unix.RTMGRP_IPV4_IFADDR | unix.RTMGRP_IPV6_IFADDR,
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}
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err = unix.Bind(sock, saddr)
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if err != nil {
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return -1, err
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}
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return sock, nil
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}
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func (tun *NativeTun) routineNetlinkListener() {
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defer func() {
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unix.Close(tun.netlinkSock)
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tun.hackListenerClosed.Lock()
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close(tun.events)
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tun.netlinkCancel.Close()
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}()
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for msg := make([]byte, 1<<16); ; {
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var err error
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var msgn int
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for {
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msgn, _, _, _, err = unix.Recvmsg(tun.netlinkSock, msg[:], nil, 0)
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if err == nil || !rwcancel.RetryAfterError(err) {
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break
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}
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if !tun.netlinkCancel.ReadyRead() {
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tun.errors <- fmt.Errorf("netlink socket closed: %w", err)
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return
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}
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}
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if err != nil {
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tun.errors <- fmt.Errorf("failed to receive netlink message: %w", err)
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return
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}
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select {
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case <-tun.statusListenersShutdown:
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return
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default:
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}
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wasEverUp := false
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for remain := msg[:msgn]; len(remain) >= unix.SizeofNlMsghdr; {
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hdr := *(*unix.NlMsghdr)(unsafe.Pointer(&remain[0]))
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if int(hdr.Len) > len(remain) {
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break
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}
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switch hdr.Type {
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case unix.NLMSG_DONE:
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remain = []byte{}
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case unix.RTM_NEWLINK:
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info := *(*unix.IfInfomsg)(unsafe.Pointer(&remain[unix.SizeofNlMsghdr]))
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remain = remain[hdr.Len:]
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if info.Index != tun.index {
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// not our interface
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continue
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}
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if info.Flags&unix.IFF_RUNNING != 0 {
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tun.events <- EventUp
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wasEverUp = true
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}
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if info.Flags&unix.IFF_RUNNING == 0 {
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// Don't emit EventDown before we've ever emitted EventUp.
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// This avoids a startup race with HackListener, which
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// might detect Up before we have finished reporting Down.
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if wasEverUp {
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tun.events <- EventDown
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}
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}
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tun.events <- EventMTUUpdate
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default:
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remain = remain[hdr.Len:]
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}
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}
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}
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}
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func getIFIndex(name string) (int32, error) {
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fd, err := unix.Socket(
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unix.AF_INET,
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unix.SOCK_DGRAM|unix.SOCK_CLOEXEC,
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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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var ifr [ifReqSize]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.SIOCGIFINDEX),
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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, errno
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}
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return *(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])), nil
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}
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func (tun *NativeTun) setMTU(n int) error {
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name, err := tun.Name()
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if err != nil {
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return err
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}
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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|unix.SOCK_CLOEXEC,
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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 [ifReqSize]byte
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copy(ifr[:], name)
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*(*uint32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = 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 of TUN device: %w", errno)
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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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name, err := tun.Name()
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if err != nil {
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return 0, err
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}
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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|unix.SOCK_CLOEXEC,
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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 [ifReqSize]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.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 of TUN device: %w", errno)
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}
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return int(*(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ]))), nil
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}
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func (tun *NativeTun) Name() (string, error) {
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tun.nameOnce.Do(tun.initNameCache)
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return tun.nameCache, tun.nameErr
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}
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func (tun *NativeTun) initNameCache() {
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tun.nameCache, tun.nameErr = tun.nameSlow()
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}
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func (tun *NativeTun) nameSlow() (string, error) {
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sysconn, err := tun.tunFile.SyscallConn()
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if err != nil {
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return "", err
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}
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var ifr [ifReqSize]byte
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var errno syscall.Errno
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err = sysconn.Control(func(fd uintptr) {
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_, _, errno = unix.Syscall(
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unix.SYS_IOCTL,
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fd,
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uintptr(unix.TUNGETIFF),
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uintptr(unsafe.Pointer(&ifr[0])),
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)
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})
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if err != nil {
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return "", fmt.Errorf("failed to get name of TUN device: %w", err)
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}
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if errno != 0 {
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return "", fmt.Errorf("failed to get name of TUN device: %w", errno)
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}
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return unix.ByteSliceToString(ifr[:]), nil
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}
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func (tun *NativeTun) Write(bufs [][]byte, offset int) (int, error) {
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tun.writeOpMu.Lock()
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defer func() {
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tun.tcpGROTable.reset()
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tun.udpGROTable.reset()
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tun.writeOpMu.Unlock()
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}()
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var (
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errs error
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total int
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)
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tun.toWrite = tun.toWrite[:0]
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if tun.vnetHdr {
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err := handleGRO(bufs, offset, tun.tcpGROTable, tun.udpGROTable, tun.udpGSO, &tun.toWrite)
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if err != nil {
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return 0, err
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}
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offset -= virtioNetHdrLen
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} else {
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for i := range bufs {
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tun.toWrite = append(tun.toWrite, i)
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}
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}
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for _, bufsI := range tun.toWrite {
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n, err := tun.tunFile.Write(bufs[bufsI][offset:])
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if errors.Is(err, syscall.EBADFD) {
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return total, os.ErrClosed
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}
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if err != nil {
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errs = errors.Join(errs, err)
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} else {
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total += n
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}
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}
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return total, errs
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}
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// handleVirtioRead splits in into bufs, leaving offset bytes at the front of
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// each buffer. It mutates sizes to reflect the size of each element of bufs,
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// and returns the number of packets read.
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func handleVirtioRead(in []byte, bufs [][]byte, sizes []int, offset int) (int, error) {
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var hdr virtioNetHdr
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err := hdr.decode(in)
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if err != nil {
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return 0, err
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}
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in = in[virtioNetHdrLen:]
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if hdr.gsoType == unix.VIRTIO_NET_HDR_GSO_NONE {
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if hdr.flags&unix.VIRTIO_NET_HDR_F_NEEDS_CSUM != 0 {
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// This means CHECKSUM_PARTIAL in skb context. We are responsible
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// for computing the checksum starting at hdr.csumStart and placing
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// at hdr.csumOffset.
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err = gsoNoneChecksum(in, hdr.csumStart, hdr.csumOffset)
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if err != nil {
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return 0, err
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}
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}
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if len(in) > len(bufs[0][offset:]) {
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return 0, fmt.Errorf("read len %d overflows bufs element len %d", len(in), len(bufs[0][offset:]))
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}
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n := copy(bufs[0][offset:], in)
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sizes[0] = n
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return 1, nil
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}
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if hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV4 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV6 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
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return 0, fmt.Errorf("unsupported virtio GSO type: %d", hdr.gsoType)
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}
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ipVersion := in[0] >> 4
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switch ipVersion {
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case 4:
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if hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV4 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
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return 0, fmt.Errorf("ip header version: %d, GSO type: %d", ipVersion, hdr.gsoType)
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}
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case 6:
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if hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_TCPV6 && hdr.gsoType != unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
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return 0, fmt.Errorf("ip header version: %d, GSO type: %d", ipVersion, hdr.gsoType)
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}
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default:
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return 0, fmt.Errorf("invalid ip header version: %d", ipVersion)
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}
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// Don't trust hdr.hdrLen from the kernel as it can be equal to the length
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// of the entire first packet when the kernel is handling it as part of a
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// FORWARD path. Instead, parse the transport header length and add it onto
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// csumStart, which is synonymous for IP header length.
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if hdr.gsoType == unix.VIRTIO_NET_HDR_GSO_UDP_L4 {
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hdr.hdrLen = hdr.csumStart + 8
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} else {
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if len(in) <= int(hdr.csumStart+12) {
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return 0, errors.New("packet is too short")
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}
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tcpHLen := uint16(in[hdr.csumStart+12] >> 4 * 4)
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if tcpHLen < 20 || tcpHLen > 60 {
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// A TCP header must be between 20 and 60 bytes in length.
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return 0, fmt.Errorf("tcp header len is invalid: %d", tcpHLen)
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}
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hdr.hdrLen = hdr.csumStart + tcpHLen
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}
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if len(in) < int(hdr.hdrLen) {
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return 0, fmt.Errorf("length of packet (%d) < virtioNetHdr.hdrLen (%d)", len(in), hdr.hdrLen)
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}
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if hdr.hdrLen < hdr.csumStart {
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return 0, fmt.Errorf("virtioNetHdr.hdrLen (%d) < virtioNetHdr.csumStart (%d)", hdr.hdrLen, hdr.csumStart)
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}
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cSumAt := int(hdr.csumStart + hdr.csumOffset)
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if cSumAt+1 >= len(in) {
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return 0, fmt.Errorf("end of checksum offset (%d) exceeds packet length (%d)", cSumAt+1, len(in))
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}
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return gsoSplit(in, hdr, bufs, sizes, offset, ipVersion == 6)
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}
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func (tun *NativeTun) Read(bufs [][]byte, sizes []int, offset int) (int, error) {
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tun.readOpMu.Lock()
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defer tun.readOpMu.Unlock()
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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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readInto := bufs[0][offset:]
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if tun.vnetHdr {
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readInto = tun.readBuff[:]
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}
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n, err := tun.tunFile.Read(readInto)
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if errors.Is(err, syscall.EBADFD) {
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err = os.ErrClosed
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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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if tun.vnetHdr {
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return handleVirtioRead(readInto[:n], bufs, sizes, offset)
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} else {
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sizes[0] = n
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return 1, nil
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}
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}
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}
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func (tun *NativeTun) Events() <-chan Event {
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return tun.events
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}
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func (tun *NativeTun) Close() error {
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var err1, err2 error
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tun.closeOnce.Do(func() {
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if tun.statusListenersShutdown != nil {
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close(tun.statusListenersShutdown)
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if tun.netlinkCancel != nil {
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err1 = tun.netlinkCancel.Cancel()
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}
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} else if tun.events != nil {
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close(tun.events)
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}
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err2 = tun.tunFile.Close()
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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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return err2
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}
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|
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func (tun *NativeTun) BatchSize() int {
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return tun.batchSize
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}
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|
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const (
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// TODO: support TSO with ECN bits
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tunTCPOffloads = unix.TUN_F_CSUM | unix.TUN_F_TSO4 | unix.TUN_F_TSO6
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tunUDPOffloads = unix.TUN_F_USO4 | unix.TUN_F_USO6
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)
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|
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func (tun *NativeTun) initFromFlags(name string) error {
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sc, err := tun.tunFile.SyscallConn()
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if err != nil {
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return err
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}
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if e := sc.Control(func(fd uintptr) {
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var (
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ifr *unix.Ifreq
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)
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ifr, err = unix.NewIfreq(name)
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if err != nil {
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return
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}
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err = unix.IoctlIfreq(int(fd), unix.TUNGETIFF, ifr)
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if err != nil {
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return
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}
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got := ifr.Uint16()
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if got&unix.IFF_VNET_HDR != 0 {
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// tunTCPOffloads were added in Linux v2.6. We require their support
|
|
// if IFF_VNET_HDR is set.
|
|
err = unix.IoctlSetInt(int(fd), unix.TUNSETOFFLOAD, tunTCPOffloads)
|
|
if err != nil {
|
|
return
|
|
}
|
|
tun.vnetHdr = true
|
|
tun.batchSize = conn.IdealBatchSize
|
|
// tunUDPOffloads were added in Linux v6.2. We do not return an
|
|
// error if they are unsupported at runtime.
|
|
tun.udpGSO = unix.IoctlSetInt(int(fd), unix.TUNSETOFFLOAD, tunTCPOffloads|tunUDPOffloads) == nil
|
|
} else {
|
|
tun.batchSize = 1
|
|
}
|
|
}); e != nil {
|
|
return e
|
|
}
|
|
return err
|
|
}
|
|
|
|
// CreateTUN creates a Device with the provided name and MTU.
|
|
func CreateTUN(name string, mtu int) (Device, error) {
|
|
nfd, err := unix.Open(cloneDevicePath, unix.O_RDWR|unix.O_CLOEXEC, 0)
|
|
if err != nil {
|
|
if os.IsNotExist(err) {
|
|
return nil, fmt.Errorf("CreateTUN(%q) failed; %s does not exist", name, cloneDevicePath)
|
|
}
|
|
return nil, err
|
|
}
|
|
|
|
ifr, err := unix.NewIfreq(name)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
// IFF_VNET_HDR enables the "tun status hack" via routineHackListener()
|
|
// where a null write will return EINVAL indicating the TUN is up.
|
|
ifr.SetUint16(unix.IFF_TUN | unix.IFF_NO_PI | unix.IFF_VNET_HDR)
|
|
err = unix.IoctlIfreq(nfd, unix.TUNSETIFF, ifr)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
err = unix.SetNonblock(nfd, true)
|
|
if err != nil {
|
|
unix.Close(nfd)
|
|
return nil, err
|
|
}
|
|
|
|
// Note that the above -- open,ioctl,nonblock -- must happen prior to handing it to netpoll as below this line.
|
|
|
|
fd := os.NewFile(uintptr(nfd), cloneDevicePath)
|
|
return CreateTUNFromFile(fd, mtu)
|
|
}
|
|
|
|
// CreateTUNFromFile creates a Device from an os.File with the provided MTU.
|
|
func CreateTUNFromFile(file *os.File, mtu int) (Device, error) {
|
|
tun := &NativeTun{
|
|
tunFile: file,
|
|
events: make(chan Event, 5),
|
|
errors: make(chan error, 5),
|
|
statusListenersShutdown: make(chan struct{}),
|
|
tcpGROTable: newTCPGROTable(),
|
|
udpGROTable: newUDPGROTable(),
|
|
toWrite: make([]int, 0, conn.IdealBatchSize),
|
|
}
|
|
|
|
name, err := tun.Name()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
err = tun.initFromFlags(name)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
// start event listener
|
|
tun.index, err = getIFIndex(name)
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
|
|
tun.netlinkSock, err = createNetlinkSocket()
|
|
if err != nil {
|
|
return nil, err
|
|
}
|
|
tun.netlinkCancel, err = rwcancel.NewRWCancel(tun.netlinkSock)
|
|
if err != nil {
|
|
unix.Close(tun.netlinkSock)
|
|
return nil, err
|
|
}
|
|
|
|
tun.hackListenerClosed.Lock()
|
|
go tun.routineNetlinkListener()
|
|
go tun.routineHackListener() // cross namespace
|
|
|
|
err = tun.setMTU(mtu)
|
|
if err != nil {
|
|
unix.Close(tun.netlinkSock)
|
|
return nil, err
|
|
}
|
|
|
|
return tun, nil
|
|
}
|
|
|
|
// CreateUnmonitoredTUNFromFD creates a Device from the provided file
|
|
// descriptor.
|
|
func CreateUnmonitoredTUNFromFD(fd int) (Device, string, error) {
|
|
err := unix.SetNonblock(fd, true)
|
|
if err != nil {
|
|
return nil, "", err
|
|
}
|
|
file := os.NewFile(uintptr(fd), "/dev/tun")
|
|
tun := &NativeTun{
|
|
tunFile: file,
|
|
events: make(chan Event, 5),
|
|
errors: make(chan error, 5),
|
|
tcpGROTable: newTCPGROTable(),
|
|
udpGROTable: newUDPGROTable(),
|
|
toWrite: make([]int, 0, conn.IdealBatchSize),
|
|
}
|
|
name, err := tun.Name()
|
|
if err != nil {
|
|
return nil, "", err
|
|
}
|
|
err = tun.initFromFlags(name)
|
|
if err != nil {
|
|
return nil, "", err
|
|
}
|
|
return tun, name, err
|
|
}
|