wireguard-go/tun/tun_freebsd.go
Jason A. Donenfeld 12ce53271b tun: freebsd: use broadcast mode instead of PPP mode
It makes the routing configuration simpler.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
2021-03-23 12:41:34 -06:00

585 lines
11 KiB
Go

/* SPDX-License-Identifier: MIT
*
* Copyright (C) 2017-2021 WireGuard LLC. All Rights Reserved.
*/
package tun
import (
"bytes"
"errors"
"fmt"
"net"
"os"
"sync"
"syscall"
"unsafe"
"golang.org/x/net/ipv6"
"golang.org/x/sys/unix"
)
// _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
_TUNSIFMODE = 0x8004745e
_TUNSIFPID = 0x2000745f
)
// TODO: move into x/sys/unix
const (
SIOCGIFINFO_IN6 = 0xc048696c
SIOCSIFINFO_IN6 = 0xc048696d
ND6_IFF_AUTO_LINKLOCAL = 0x20
ND6_IFF_NO_DAD = 0x100
)
// Iface status string max len
const _IFSTATMAX = 800
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 [16 - SIZEOF_UINTPTR]byte
}
// Structure for iface mtu get/set ioctls
type ifreq_mtu struct {
Name [unix.IFNAMSIZ]byte
MTU uint32
Pad0 [12]byte
}
// Structure for interface status request ioctl
type ifstat struct {
IfsName [unix.IFNAMSIZ]byte
Ascii [_IFSTATMAX]byte
}
// Structures for nd6 flag manipulation
type in6_ndireq struct {
Name [unix.IFNAMSIZ]byte
Linkmtu uint32
Maxmtu uint32
Basereachable uint32
Reachable uint32
Retrans uint32
Flags uint32
Recalctm int
Chlim uint8
Initialized uint8
Randomseed0 [8]byte
Randomseed1 [8]byte
Randomid [8]byte
}
type NativeTun struct {
name string
tunFile *os.File
events chan Event
errors chan error
routeSocket int
closeOnce sync.Once
}
func (tun *NativeTun) routineRouteListener(tunIfindex int) {
var (
statusUp bool
statusMTU int
)
defer close(tun.events)
data := make([]byte, os.Getpagesize())
for {
retry:
n, err := unix.Read(tun.routeSocket, data)
if err != nil {
if errno, ok := err.(syscall.Errno); ok && errno == syscall.EINTR {
goto retry
}
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 <- EventUp
}
if up != statusUp && !up {
tun.events <- EventDown
}
statusUp = up
// MTU changes
if iface.MTU != statusMTU {
tun.events <- EventMTUUpdate
}
statusMTU = iface.MTU
}
}
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 {
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
}
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
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
}
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 {
continue
}
if pidNum == procPid {
return iface.Name, nil
}
}
return "", nil
}
// Destroy a named system interface
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)
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 {
return fmt.Errorf("failed to destroy interface %s: %s", name, errno.Error())
}
return nil
}
func CreateTUN(name string, mtu int) (Device, error) {
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 {
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
}
tun := NativeTun{tunFile: tunFile}
var assignedName string
tun.operateOnFd(func(fd uintptr) {
assignedName, err = tunName(fd)
})
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
var errno syscall.Errno
tun.operateOnFd(func(fd uintptr) {
_, _, errno = unix.Syscall(
unix.SYS_IOCTL,
fd,
uintptr(_TUNSIFHEAD),
uintptr(unsafe.Pointer(&ifheadmode)),
)
})
if errno != 0 {
tunFile.Close()
tunDestroy(assignedName)
return nil, fmt.Errorf("Unable to put into IFHEAD mode: %w", errno)
}
// Get out of PPP mode.
ifflags := syscall.IFF_BROADCAST
tun.operateOnFd(func(fd uintptr) {
_, _, errno = unix.Syscall(
unix.SYS_IOCTL,
fd,
uintptr(_TUNSIFMODE),
uintptr(unsafe.Pointer(&ifflags)),
)
})
if errno != 0 {
tunFile.Close()
tunDestroy(assignedName)
return nil, fmt.Errorf("Unable to put into IFF_BROADCAST mode: %w", errno)
}
// Open control sockets
confd, err := unix.Socket(
unix.AF_INET,
unix.SOCK_DGRAM,
0,
)
if err != nil {
tunFile.Close()
tunDestroy(assignedName)
return nil, err
}
defer unix.Close(confd)
confd6, err := unix.Socket(
unix.AF_INET6,
unix.SOCK_DGRAM,
0,
)
if err != nil {
tunFile.Close()
tunDestroy(assignedName)
return nil, err
}
defer unix.Close(confd6)
// Disable link-local v6, not just because WireGuard doesn't do that anyway, but
// also because there are serious races with attaching and detaching LLv6 addresses
// in relation to interface lifetime within the FreeBSD kernel.
var ndireq in6_ndireq
copy(ndireq.Name[:], assignedName)
_, _, errno = unix.Syscall(
unix.SYS_IOCTL,
uintptr(confd6),
uintptr(SIOCGIFINFO_IN6),
uintptr(unsafe.Pointer(&ndireq)),
)
if errno != 0 {
tunFile.Close()
tunDestroy(assignedName)
return nil, fmt.Errorf("Unable to get nd6 flags for %s: %w", assignedName, errno)
}
ndireq.Flags = ndireq.Flags &^ ND6_IFF_AUTO_LINKLOCAL
ndireq.Flags = ndireq.Flags | ND6_IFF_NO_DAD
_, _, errno = unix.Syscall(
unix.SYS_IOCTL,
uintptr(confd6),
uintptr(SIOCSIFINFO_IN6),
uintptr(unsafe.Pointer(&ndireq)),
)
if errno != 0 {
tunFile.Close()
tunDestroy(assignedName)
return nil, fmt.Errorf("Unable to set nd6 flags for %s: %w", assignedName, errno)
}
if name != "" {
// Rename the interface
var newnp [unix.IFNAMSIZ]byte
copy(newnp[:], name)
var ifr ifreq_ptr
copy(ifr.Name[:], assignedName)
ifr.Data = uintptr(unsafe.Pointer(&newnp[0]))
_, _, errno = unix.Syscall(
unix.SYS_IOCTL,
uintptr(confd),
uintptr(unix.SIOCSIFNAME),
uintptr(unsafe.Pointer(&ifr)),
)
if errno != 0 {
tunFile.Close()
tunDestroy(assignedName)
return nil, fmt.Errorf("Failed to rename %s to %s: %w", assignedName, name, errno)
}
}
return CreateTUNFromFile(tunFile, mtu)
}
func CreateTUNFromFile(file *os.File, mtu int) (Device, error) {
tun := &NativeTun{
tunFile: file,
events: make(chan Event, 10),
errors: make(chan error, 1),
}
name, err := tun.Name()
if err != nil {
tun.tunFile.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.tunFile.Close()
return nil, err
}
tun.routeSocket, err = unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW, unix.AF_UNSPEC)
if err != nil {
tun.tunFile.Close()
return nil, err
}
go tun.routineRouteListener(tunIfindex)
err = tun.setMTU(mtu)
if err != nil {
tun.Close()
return nil, err
}
return tun, nil
}
func (tun *NativeTun) Name() (string, error) {
var name string
var err error
tun.operateOnFd(func(fd uintptr) {
name, err = tunName(fd)
})
if err != nil {
return "", err
}
tun.name = name
return name, nil
}
func (tun *NativeTun) File() *os.File {
return tun.tunFile
}
func (tun *NativeTun) Events() chan Event {
return tun.events
}
func (tun *NativeTun) Read(buff []byte, offset int) (int, error) {
select {
case err := <-tun.errors:
return 0, err
default:
buff := buff[offset-4:]
n, err := tun.tunFile.Read(buff[:])
if n < 4 {
return 0, err
}
return n - 4, err
}
}
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.tunFile.Write(buff)
}
func (tun *NativeTun) Flush() error {
// TODO: can flushing be implemented by buffering and using sendmmsg?
return nil
}
func (tun *NativeTun) Close() error {
var err1, err2, err3 error
tun.closeOnce.Do(func() {
err1 = tun.tunFile.Close()
err2 = tunDestroy(tun.name)
if tun.routeSocket != -1 {
unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
err3 = 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
}
return err3
}
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 {
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 {
return 0, fmt.Errorf("failed to get MTU on %s", tun.name)
}
return int(*(*int32)(unsafe.Pointer(&ifr.MTU))), nil
}