tun_openbsd.go raw
1 /* SPDX-License-Identifier: MIT
2 *
3 * Copyright (C) 2017-2025 WireGuard LLC. All Rights Reserved.
4 */
5
6 package tun
7
8 import (
9 "errors"
10 "fmt"
11 "io"
12 "net"
13 "os"
14 "sync"
15 "syscall"
16 "unsafe"
17
18 "golang.org/x/sys/unix"
19 )
20
21 // Structure for iface mtu get/set ioctls
22 type ifreq_mtu struct {
23 Name [unix.IFNAMSIZ]byte
24 MTU uint32
25 Pad0 [12]byte
26 }
27
28 const _TUNSIFMODE = 0x8004745d
29
30 type NativeTun struct {
31 name string
32 tunFile *os.File
33 events chan Event
34 errors chan error
35 routeSocket int
36 closeOnce sync.Once
37 }
38
39 func (tun *NativeTun) routineRouteListener(tunIfindex int) {
40 var (
41 statusUp bool
42 statusMTU int
43 )
44
45 defer close(tun.events)
46
47 check := func() bool {
48 iface, err := net.InterfaceByIndex(tunIfindex)
49 if err != nil {
50 tun.errors <- err
51 return true
52 }
53
54 // Up / Down event
55 up := (iface.Flags & net.FlagUp) != 0
56 if up != statusUp && up {
57 tun.events <- EventUp
58 }
59 if up != statusUp && !up {
60 tun.events <- EventDown
61 }
62 statusUp = up
63
64 // MTU changes
65 if iface.MTU != statusMTU {
66 tun.events <- EventMTUUpdate
67 }
68 statusMTU = iface.MTU
69 return false
70 }
71
72 if check() {
73 return
74 }
75
76 data := make([]byte, os.Getpagesize())
77 for {
78 n, err := unix.Read(tun.routeSocket, data)
79 if err != nil {
80 if errno, ok := err.(syscall.Errno); ok && errno == syscall.EINTR {
81 continue
82 }
83 tun.errors <- err
84 return
85 }
86
87 if n < 8 {
88 continue
89 }
90
91 if data[3 /* type */] != unix.RTM_IFINFO {
92 continue
93 }
94 ifindex := int(*(*uint16)(unsafe.Pointer(&data[6 /* ifindex */])))
95 if ifindex != tunIfindex {
96 continue
97 }
98 if check() {
99 return
100 }
101 }
102 }
103
104 func CreateTUN(name string, mtu int) (Device, error) {
105 ifIndex := -1
106 if name != "tun" {
107 _, err := fmt.Sscanf(name, "tun%d", &ifIndex)
108 if err != nil || ifIndex < 0 {
109 return nil, fmt.Errorf("Interface name must be tun[0-9]*")
110 }
111 }
112
113 var tunfile *os.File
114 var err error
115
116 if ifIndex != -1 {
117 tunfile, err = os.OpenFile(fmt.Sprintf("/dev/tun%d", ifIndex), unix.O_RDWR|unix.O_CLOEXEC, 0)
118 } else {
119 for ifIndex = 0; ifIndex < 256; ifIndex++ {
120 tunfile, err = os.OpenFile(fmt.Sprintf("/dev/tun%d", ifIndex), unix.O_RDWR|unix.O_CLOEXEC, 0)
121 if err == nil || !errors.Is(err, syscall.EBUSY) {
122 break
123 }
124 }
125 }
126
127 if err != nil {
128 return nil, err
129 }
130
131 tun, err := CreateTUNFromFile(tunfile, mtu)
132
133 if err == nil && name == "tun" {
134 fname := os.Getenv("WG_TUN_NAME_FILE")
135 if fname != "" {
136 os.WriteFile(fname, []byte(tun.(*NativeTun).name+"\n"), 0o400)
137 }
138 }
139
140 return tun, err
141 }
142
143 func CreateTUNFromFile(file *os.File, mtu int) (Device, error) {
144 tun := &NativeTun{
145 tunFile: file,
146 events: make(chan Event, 10),
147 errors: make(chan error, 1),
148 }
149
150 name, err := tun.Name()
151 if err != nil {
152 tun.tunFile.Close()
153 return nil, err
154 }
155
156 tunIfindex, err := func() (int, error) {
157 iface, err := net.InterfaceByName(name)
158 if err != nil {
159 return -1, err
160 }
161 return iface.Index, nil
162 }()
163 if err != nil {
164 tun.tunFile.Close()
165 return nil, err
166 }
167
168 tun.routeSocket, err = unix.Socket(unix.AF_ROUTE, unix.SOCK_RAW|unix.SOCK_CLOEXEC, unix.AF_UNSPEC)
169 if err != nil {
170 tun.tunFile.Close()
171 return nil, err
172 }
173
174 go tun.routineRouteListener(tunIfindex)
175
176 currentMTU, err := tun.MTU()
177 if err != nil || currentMTU != mtu {
178 err = tun.setMTU(mtu)
179 if err != nil {
180 tun.Close()
181 return nil, err
182 }
183 }
184
185 return tun, nil
186 }
187
188 func (tun *NativeTun) Name() (string, error) {
189 gostat, err := tun.tunFile.Stat()
190 if err != nil {
191 tun.name = ""
192 return "", err
193 }
194 stat := gostat.Sys().(*syscall.Stat_t)
195 tun.name = fmt.Sprintf("tun%d", stat.Rdev%256)
196 return tun.name, nil
197 }
198
199 func (tun *NativeTun) File() *os.File {
200 return tun.tunFile
201 }
202
203 func (tun *NativeTun) Events() <-chan Event {
204 return tun.events
205 }
206
207 func (tun *NativeTun) Read(bufs [][]byte, sizes []int, offset int) (int, error) {
208 select {
209 case err := <-tun.errors:
210 return 0, err
211 default:
212 buf := bufs[0][offset-4:]
213 n, err := tun.tunFile.Read(buf[:])
214 if n < 4 {
215 return 0, err
216 }
217 sizes[0] = n - 4
218 return 1, err
219 }
220 }
221
222 func (tun *NativeTun) Write(bufs [][]byte, offset int) (int, error) {
223 if offset < 4 {
224 return 0, io.ErrShortBuffer
225 }
226 for i, buf := range bufs {
227 buf = buf[offset-4:]
228 buf[0] = 0x00
229 buf[1] = 0x00
230 buf[2] = 0x00
231 switch buf[4] >> 4 {
232 case 4:
233 buf[3] = unix.AF_INET
234 case 6:
235 buf[3] = unix.AF_INET6
236 default:
237 return i, unix.EAFNOSUPPORT
238 }
239 if _, err := tun.tunFile.Write(buf); err != nil {
240 return i, err
241 }
242 }
243 return len(bufs), nil
244 }
245
246 func (tun *NativeTun) Close() error {
247 var err1, err2 error
248 tun.closeOnce.Do(func() {
249 err1 = tun.tunFile.Close()
250 if tun.routeSocket != -1 {
251 unix.Shutdown(tun.routeSocket, unix.SHUT_RDWR)
252 err2 = unix.Close(tun.routeSocket)
253 tun.routeSocket = -1
254 } else if tun.events != nil {
255 close(tun.events)
256 }
257 })
258 if err1 != nil {
259 return err1
260 }
261 return err2
262 }
263
264 func (tun *NativeTun) setMTU(n int) error {
265 // open datagram socket
266
267 var fd int
268
269 fd, err := unix.Socket(
270 unix.AF_INET,
271 unix.SOCK_DGRAM|unix.SOCK_CLOEXEC,
272 0,
273 )
274 if err != nil {
275 return err
276 }
277
278 defer unix.Close(fd)
279
280 // do ioctl call
281
282 var ifr ifreq_mtu
283 copy(ifr.Name[:], tun.name)
284 ifr.MTU = uint32(n)
285
286 _, _, errno := unix.Syscall(
287 unix.SYS_IOCTL,
288 uintptr(fd),
289 uintptr(unix.SIOCSIFMTU),
290 uintptr(unsafe.Pointer(&ifr)),
291 )
292
293 if errno != 0 {
294 return fmt.Errorf("failed to set MTU on %s", tun.name)
295 }
296
297 return nil
298 }
299
300 func (tun *NativeTun) MTU() (int, error) {
301 // open datagram socket
302
303 fd, err := unix.Socket(
304 unix.AF_INET,
305 unix.SOCK_DGRAM|unix.SOCK_CLOEXEC,
306 0,
307 )
308 if err != nil {
309 return 0, err
310 }
311
312 defer unix.Close(fd)
313
314 // do ioctl call
315 var ifr ifreq_mtu
316 copy(ifr.Name[:], tun.name)
317
318 _, _, errno := unix.Syscall(
319 unix.SYS_IOCTL,
320 uintptr(fd),
321 uintptr(unix.SIOCGIFMTU),
322 uintptr(unsafe.Pointer(&ifr)),
323 )
324 if errno != 0 {
325 return 0, fmt.Errorf("failed to get MTU on %s", tun.name)
326 }
327
328 return int(*(*int32)(unsafe.Pointer(&ifr.MTU))), nil
329 }
330
331 func (tun *NativeTun) BatchSize() int {
332 return 1
333 }
334