mirror of
https://git.zx2c4.com/wireguard-go
synced 2024-11-15 01:05:15 +01:00
431 lines
9.4 KiB
Go
431 lines
9.4 KiB
Go
/* SPDX-License-Identifier: MIT
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*
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* Copyright (C) 2017-2021 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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"net"
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"os"
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"sync"
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"syscall"
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"unsafe"
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"golang.org/x/sys/unix"
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)
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const (
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_TUNSIFHEAD = 0x80047460
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_TUNSIFMODE = 0x8004745e
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_TUNGIFNAME = 0x4020745d
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_TUNSIFPID = 0x2000745f
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_SIOCGIFINFO_IN6 = 0xc048696c
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_SIOCSIFINFO_IN6 = 0xc048696d
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_ND6_IFF_AUTO_LINKLOCAL = 0x20
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_ND6_IFF_NO_DAD = 0x100
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)
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// Iface requests with just the name
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type ifreqName struct {
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Name [unix.IFNAMSIZ]byte
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_ [16]byte
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}
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// Iface requests with a pointer
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type ifreqPtr struct {
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Name [unix.IFNAMSIZ]byte
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Data uintptr
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_ [16 - unsafe.Sizeof(uintptr(0))]byte
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}
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// Iface requests with MTU
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type ifreqMtu struct {
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Name [unix.IFNAMSIZ]byte
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MTU uint32
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_ [12]byte
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}
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// ND6 flag manipulation
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type nd6Req struct {
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Name [unix.IFNAMSIZ]byte
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Linkmtu uint32
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Maxmtu uint32
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Basereachable uint32
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Reachable uint32
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Retrans uint32
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Flags uint32
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Recalctm int
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Chlim uint8
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Initialized uint8
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Randomseed0 [8]byte
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Randomseed1 [8]byte
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Randomid [8]byte
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}
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type NativeTun struct {
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name string
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tunFile *os.File
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events chan Event
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errors chan error
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routeSocket int
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closeOnce sync.Once
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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 errors.Is(err, 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 <- EventUp
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}
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if up != statusUp && !up {
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tun.events <- EventDown
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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 <- EventMTUUpdate
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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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var ifreq ifreqName
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_, _, err := unix.Syscall(unix.SYS_IOCTL, fd, _TUNGIFNAME, uintptr(unsafe.Pointer(&ifreq)))
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if err != 0 {
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return "", err
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}
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return unix.ByteSliceToString(ifreq.Name[:]), 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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fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, 0)
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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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var ifr [32]byte
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copy(ifr[:], name)
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_, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(unix.SIOCIFDESTROY), uintptr(unsafe.Pointer(&ifr[0])))
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if errno != 0 {
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return fmt.Errorf("failed to destroy interface %s: %w", name, errno)
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}
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return nil
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}
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func CreateTUN(name string, mtu int) (Device, 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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tun := NativeTun{tunFile: tunFile}
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var assignedName string
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tun.operateOnFd(func(fd uintptr) {
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assignedName, err = tunName(fd)
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})
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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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var errno syscall.Errno
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tun.operateOnFd(func(fd uintptr) {
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_, _, errno = unix.Syscall(unix.SYS_IOCTL, fd, _TUNSIFHEAD, uintptr(unsafe.Pointer(&ifheadmode)))
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})
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if errno != 0 {
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tunFile.Close()
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tunDestroy(assignedName)
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return nil, fmt.Errorf("unable to put into IFHEAD mode: %w", errno)
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}
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// Get out of PTP mode.
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ifflags := syscall.IFF_BROADCAST | syscall.IFF_MULTICAST
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tun.operateOnFd(func(fd uintptr) {
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_, _, errno = unix.Syscall(unix.SYS_IOCTL, fd, uintptr(_TUNSIFMODE), uintptr(unsafe.Pointer(&ifflags)))
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})
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if errno != 0 {
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tunFile.Close()
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tunDestroy(assignedName)
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return nil, fmt.Errorf("unable to put into IFF_BROADCAST mode: %w", errno)
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}
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// Disable link-local v6, not just because WireGuard doesn't do that anyway, but
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// also because there are serious races with attaching and detaching LLv6 addresses
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// in relation to interface lifetime within the FreeBSD kernel.
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confd6, err := unix.Socket(unix.AF_INET6, unix.SOCK_DGRAM, 0)
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if err != nil {
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tunFile.Close()
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tunDestroy(assignedName)
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return nil, err
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}
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defer unix.Close(confd6)
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var ndireq nd6Req
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copy(ndireq.Name[:], assignedName)
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_, _, errno = unix.Syscall(unix.SYS_IOCTL, uintptr(confd6), uintptr(_SIOCGIFINFO_IN6), uintptr(unsafe.Pointer(&ndireq)))
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if errno != 0 {
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tunFile.Close()
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tunDestroy(assignedName)
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return nil, fmt.Errorf("unable to get nd6 flags for %s: %w", assignedName, errno)
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}
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ndireq.Flags = ndireq.Flags &^ _ND6_IFF_AUTO_LINKLOCAL
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ndireq.Flags = ndireq.Flags | _ND6_IFF_NO_DAD
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_, _, errno = unix.Syscall(unix.SYS_IOCTL, uintptr(confd6), uintptr(_SIOCSIFINFO_IN6), uintptr(unsafe.Pointer(&ndireq)))
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if errno != 0 {
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tunFile.Close()
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tunDestroy(assignedName)
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return nil, fmt.Errorf("unable to set nd6 flags for %s: %w", assignedName, errno)
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}
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if name != "" {
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confd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, 0)
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if err != nil {
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tunFile.Close()
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tunDestroy(assignedName)
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return nil, err
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}
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defer unix.Close(confd)
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var newnp [unix.IFNAMSIZ]byte
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copy(newnp[:], name)
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var ifr ifreqPtr
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copy(ifr.Name[:], assignedName)
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ifr.Data = uintptr(unsafe.Pointer(&newnp[0]))
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_, _, errno = unix.Syscall(unix.SYS_IOCTL, uintptr(confd), uintptr(unix.SIOCSIFNAME), uintptr(unsafe.Pointer(&ifr)))
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if errno != 0 {
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tunFile.Close()
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tunDestroy(assignedName)
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return nil, fmt.Errorf("Failed to rename %s to %s: %w", assignedName, name, errno)
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}
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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) (Device, error) {
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tun := &NativeTun{
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tunFile: file,
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events: make(chan Event, 10),
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errors: make(chan error, 1),
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}
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var errno syscall.Errno
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tun.operateOnFd(func(fd uintptr) {
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_, _, errno = unix.Syscall(unix.SYS_IOCTL, fd, _TUNSIFPID, uintptr(0))
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})
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if errno != 0 {
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tun.tunFile.Close()
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return nil, fmt.Errorf("unable to become controlling TUN process: %w", errno)
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}
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name, err := tun.Name()
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if err != nil {
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tun.tunFile.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.tunFile.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.tunFile.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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var name string
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var err error
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tun.operateOnFd(func(fd uintptr) {
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name, err = tunName(fd)
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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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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.tunFile
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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) 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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buff := buff[offset-4:]
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n, err := tun.tunFile.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) Write(buf []byte, offset int) (int, error) {
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if offset < 4 {
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return 0, io.ErrShortBuffer
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}
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buf = buf[offset-4:]
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if len(buf) < 5 {
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return 0, io.ErrShortBuffer
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}
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buf[0] = 0x00
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buf[1] = 0x00
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buf[2] = 0x00
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switch buf[4] >> 4 {
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case 4:
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buf[3] = unix.AF_INET
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case 6:
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buf[3] = unix.AF_INET6
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default:
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return 0, unix.EAFNOSUPPORT
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}
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return tun.tunFile.Write(buf)
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}
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func (tun *NativeTun) Flush() error {
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// TODO: can flushing be implemented by buffering and using sendmmsg?
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return nil
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}
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func (tun *NativeTun) Close() error {
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var err1, err2, err3 error
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tun.closeOnce.Do(func() {
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err1 = tun.tunFile.Close()
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err2 = 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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err3 = 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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})
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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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return err3
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}
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func (tun *NativeTun) setMTU(n int) error {
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fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, 0)
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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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var ifr ifreqMtu
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copy(ifr.Name[:], tun.name)
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ifr.MTU = uint32(n)
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_, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(unix.SIOCSIFMTU), uintptr(unsafe.Pointer(&ifr)))
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if errno != 0 {
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return fmt.Errorf("failed to set MTU on %s: %w", tun.name, 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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fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, 0)
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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 ifreqMtu
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copy(ifr.Name[:], tun.name)
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_, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), uintptr(unix.SIOCGIFMTU), uintptr(unsafe.Pointer(&ifr)))
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if errno != 0 {
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return 0, fmt.Errorf("failed to get MTU on %s: %w", tun.name, errno)
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}
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return int(*(*int32)(unsafe.Pointer(&ifr.MTU))), nil
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}
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