wireguard-go/tun_freebsd.go

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/* SPDX-License-Identifier: GPL-2.0
*
* Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
*/
package main
import (
"./rwcancel"
"bytes"
"errors"
"fmt"
"golang.org/x/net/ipv6"
"golang.org/x/sys/unix"
"net"
"os"
"unsafe"
)
// _TUNSIFHEAD, value derived from sys/net/{if_tun,ioccom}.h
// const _TUNSIFHEAD = ((0x80000000) | (((4) & ((1 << 13) - 1) ) << 16) | (uint32(byte('t')) << 8) | (96))
const _TUNSIFHEAD = 0x80047460
const _TUNSIFMODE = 0x8004745e
const _TUNSIFPID = 0x2000745f
// Iface status string max len
const _IFSTATMAX = 800
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const SIZEOF_UINTPTR = 4 << (^uintptr(0) >> 32 & 1)
// structure for iface requests with a pointer
type ifreq_ptr struct {
Name [unix.IFNAMSIZ]byte
Data uintptr
Pad0 [24 - SIZEOF_UINTPTR]byte
}
// Structure for iface mtu get/set ioctls
type ifreq_mtu struct {
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Name [unix.IFNAMSIZ]byte
MTU uint32
Pad0 [12]byte
}
// Structure for interface status request ioctl
type ifstat struct {
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IfsName [unix.IFNAMSIZ]byte
Ascii [_IFSTATMAX]byte
}
type NativeTun struct {
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name string
fd *os.File
rwcancel *rwcancel.RWCancel
events chan TUNEvent
errors chan error
routeSocket int
}
func (tun *NativeTun) RoutineRouteListener(tunIfindex int) {
var (
statusUp bool
statusMTU int
)
defer close(tun.events)
data := make([]byte, os.Getpagesize())
for {
n, err := unix.Read(tun.routeSocket, data)
if err != nil {
tun.errors <- err
return
}
if n < 14 {
continue
}
if data[3 /* type */] != unix.RTM_IFINFO {
continue
}
ifindex := int(*(*uint16)(unsafe.Pointer(&data[12 /* ifindex */])))
if ifindex != tunIfindex {
continue
}
iface, err := net.InterfaceByIndex(ifindex)
if err != nil {
tun.errors <- err
return
}
// Up / Down event
up := (iface.Flags & net.FlagUp) != 0
if up != statusUp && up {
tun.events <- TUNEventUp
}
if up != statusUp && !up {
tun.events <- TUNEventDown
}
statusUp = up
// MTU changes
if iface.MTU != statusMTU {
tun.events <- TUNEventMTUUpdate
}
statusMTU = iface.MTU
}
}
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func tunName(fd uintptr) (string, error) {
//Terrible hack to make up for freebsd not having a TUNGIFNAME
//First, make sure the tun pid matches this proc's pid
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(fd),
uintptr(_TUNSIFPID),
uintptr(0),
)
if errno != 0 {
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return "", fmt.Errorf("failed to set tun device PID: %s", errno.Error())
}
// Open iface control socket
confd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
return "", err
}
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defer unix.Close(confd)
procPid := os.Getpid()
//Try to find interface with matching PID
for i := 1; ; i++ {
iface, _ := net.InterfaceByIndex(i)
if err != nil || iface == nil {
break
}
// Structs for getting data in and out of SIOCGIFSTATUS ioctl
var ifstatus ifstat
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copy(ifstatus.IfsName[:], iface.Name)
// Make the syscall to get the status string
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(confd),
uintptr(unix.SIOCGIFSTATUS),
uintptr(unsafe.Pointer(&ifstatus)),
)
if errno != 0 {
continue
}
nullStr := ifstatus.Ascii[:]
i := bytes.IndexByte(nullStr, 0)
if i < 1 {
continue
}
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statStr := string(nullStr[:i])
var pidNum int = 0
// Finally get the owning PID
// Format string taken from sys/net/if_tun.c
_, err := fmt.Sscanf(statStr, "\tOpened by PID %d\n", &pidNum)
if err != nil {
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continue
}
if pidNum == procPid {
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return iface.Name, nil
}
}
return "", nil
}
// Destroy a named system interface
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func tunDestroy(name string) error {
// open control socket
var fd int
fd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
return err
}
defer unix.Close(fd)
// do ioctl call
var ifr [32]byte
copy(ifr[:], name)
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(fd),
uintptr(unix.SIOCIFDESTROY),
uintptr(unsafe.Pointer(&ifr[0])),
)
if errno != 0 {
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return fmt.Errorf("failed to destroy interface %s: %s", name, errno.Error())
}
return nil
}
func CreateTUN(name string) (TUNDevice, error) {
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if len(name) > unix.IFNAMSIZ-1 {
return nil, errors.New("interface name too long")
}
// See if interface already exists
iface, _ := net.InterfaceByName(name)
if iface != nil {
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return nil, fmt.Errorf("interface %s already exists", name)
}
tunfile, err := os.OpenFile("/dev/tun", unix.O_RDWR, 0)
if err != nil {
return nil, err
}
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tunfd := tunfile.Fd()
assignedName, err := tunName(tunfd)
if err != nil {
tunfile.Close()
return nil, err
}
// Enable ifhead mode, otherwise tun will complain if it gets a non-AF_INET packet
ifheadmode := 1
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(tunfd),
uintptr(_TUNSIFHEAD),
uintptr(unsafe.Pointer(&ifheadmode)),
)
if errno != 0 {
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return nil, fmt.Errorf("error %s", errno.Error())
}
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// Set TUN iface to broadcast mode. TUN inferfaces on freebsd come up in point to point by default
ifmodemode := unix.IFF_BROADCAST
_, _, errno = unix.Syscall(
unix.SYS_IOCTL,
uintptr(tunfd),
uintptr(_TUNSIFMODE),
uintptr(unsafe.Pointer(&ifmodemode)),
)
if errno != 0 {
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return nil, fmt.Errorf("error %s", errno.Error())
}
// Rename tun interface
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// Open control socket
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confd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
return nil, err
}
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defer unix.Close(confd)
// set up struct for iface rename
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var newnp [unix.IFNAMSIZ]byte
copy(newnp[:], name)
var ifr ifreq_ptr
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copy(ifr.Name[:], assignedName)
ifr.Data = uintptr(unsafe.Pointer(&newnp[0]))
//do actual ioctl to rename iface
_, _, errno = unix.Syscall(
unix.SYS_IOCTL,
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uintptr(confd),
uintptr(unix.SIOCSIFNAME),
uintptr(unsafe.Pointer(&ifr)),
)
if errno != 0 {
tunfile.Close()
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tunDestroy(name)
return nil, fmt.Errorf("failed to rename %s to %s: %s", assignedName, name, errno.Error())
}
tun, err := CreateTUNFromFile(tunfile)
if err != nil {
return nil, err
}
return tun, err
}
func CreateTUNFromFile(file *os.File) (TUNDevice, error) {
tun := &NativeTun{
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fd: file,
events: make(chan TUNEvent, 10),
errors: make(chan error, 1),
}
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name, err := tun.Name()
if err != nil {
tun.fd.Close()
return nil, err
}
tunIfindex, err := func() (int, error) {
iface, err := net.InterfaceByName(name)
if err != nil {
return -1, err
}
return iface.Index, nil
}()
if err != nil {
tun.fd.Close()
return nil, err
}
if err != nil {
tun.fd.Close()
return nil, err
}
tun.rwcancel, err = rwcancel.NewRWCancel(int(file.Fd()))
if err != nil {
tun.fd.Close()
return nil, err
}
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tun.routeSocket, err = unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
if err != nil {
tun.fd.Close()
return nil, err
}
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go tun.RoutineRouteListener(tunIfindex)
// set default MTU
err = tun.setMTU(DefaultMTU)
if err != nil {
tun.Close()
return nil, err
}
return tun, nil
}
func (tun *NativeTun) Name() (string, error) {
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name, err := tunName(tun.fd.Fd())
if err != nil {
return "", err
}
tun.name = name
return name, nil
}
func (tun *NativeTun) File() *os.File {
return tun.fd
}
func (tun *NativeTun) Events() chan TUNEvent {
return tun.events
}
func (tun *NativeTun) doRead(buff []byte, offset int) (int, error) {
select {
case err := <-tun.errors:
return 0, err
default:
buff := buff[offset-4:]
n, err := tun.fd.Read(buff[:])
if n < 4 {
return 0, err
}
return n - 4, err
}
}
func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
for {
n, err := tun.doRead(buff, offset)
if err == nil || !rwcancel.ErrorIsEAGAIN(err) {
return n, err
}
if !tun.rwcancel.ReadyRead() {
return 0, errors.New("tun device closed")
}
}
}
func (tun *NativeTun) Write(buff []byte, offset int) (int, error) {
// reserve space for header
buff = buff[offset-4:]
// add packet information header
buff[0] = 0x00
buff[1] = 0x00
buff[2] = 0x00
if buff[4]>>4 == ipv6.Version {
buff[3] = unix.AF_INET6
} else {
buff[3] = unix.AF_INET
}
// write
return tun.fd.Write(buff)
}
func (tun *NativeTun) Close() error {
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var err4 error
err1 := tun.rwcancel.Cancel()
err2 := tun.fd.Close()
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err3 := tunDestroy(tun.name)
if tun.routeSocket != -1 {
unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
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err4 = unix.Close(tun.routeSocket)
tun.routeSocket = -1
} else if tun.events != nil {
close(tun.events)
}
if err1 != nil {
return err1
}
if err2 != nil {
return err2
}
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if err3 != nil {
return err3
}
return err4
}
func (tun *NativeTun) setMTU(n int) error {
// open datagram socket
var fd int
fd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
return err
}
defer unix.Close(fd)
// do ioctl call
var ifr ifreq_mtu
copy(ifr.Name[:], tun.name)
ifr.MTU = uint32(n)
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(fd),
uintptr(unix.SIOCSIFMTU),
uintptr(unsafe.Pointer(&ifr)),
)
if errno != 0 {
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return fmt.Errorf("failed to set MTU on %s", tun.name)
}
return nil
}
func (tun *NativeTun) MTU() (int, error) {
// open datagram socket
fd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
return 0, err
}
defer unix.Close(fd)
// do ioctl call
var ifr ifreq_mtu
copy(ifr.Name[:], tun.name)
_, _, errno := unix.Syscall(
unix.SYS_IOCTL,
uintptr(fd),
uintptr(unix.SIOCGIFMTU),
uintptr(unsafe.Pointer(&ifr)),
)
if errno != 0 {
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return 0, fmt.Errorf("failed to get MTU on %s", tun.name)
}
// convert result to signed 32-bit int
mtu := ifr.MTU
if mtu >= (1 << 31) {
return int(mtu-(1<<31)) - (1 << 31), nil
}
return int(mtu), nil
}