summaryrefslogtreecommitdiffhomepage
path: root/tun/tun_linux.go
diff options
context:
space:
mode:
Diffstat (limited to 'tun/tun_linux.go')
-rw-r--r--tun/tun_linux.go468
1 files changed, 468 insertions, 0 deletions
diff --git a/tun/tun_linux.go b/tun/tun_linux.go
new file mode 100644
index 0000000..acfb942
--- /dev/null
+++ b/tun/tun_linux.go
@@ -0,0 +1,468 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ * Copyright (C) 2017-2018 Mathias N. Hall-Andersen <mathias@hall-andersen.dk>.
+ */
+
+/* Copyright 2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. */
+
+package tun
+
+/* Implementation of the TUN device interface for linux
+ */
+
+import (
+ "../rwcancel"
+ "bytes"
+ "errors"
+ "fmt"
+ "golang.org/x/net/ipv6"
+ "golang.org/x/sys/unix"
+ "net"
+ "os"
+ "strconv"
+ "sync"
+ "time"
+ "unsafe"
+)
+
+const (
+ cloneDevicePath = "/dev/net/tun"
+ ifReqSize = unix.IFNAMSIZ + 64
+)
+
+type nativeTun struct {
+ fd *os.File
+ fdCancel *rwcancel.RWCancel
+ index int32 // if index
+ name string // name of interface
+ errors chan error // async error handling
+ events chan TUNEvent // device related events
+ nopi bool // the device was pased IFF_NO_PI
+ netlinkSock int
+ netlinkCancel *rwcancel.RWCancel
+ hackListenerClosed sync.Mutex
+ statusListenersShutdown chan struct{}
+}
+
+func (tun *nativeTun) File() *os.File {
+ return tun.fd
+}
+
+func (tun *nativeTun) routineHackListener() {
+ defer tun.hackListenerClosed.Unlock()
+ /* This is needed for the detection to work across network namespaces
+ * If you are reading this and know a better method, please get in touch.
+ */
+ fd := int(tun.fd.Fd())
+ for {
+ _, err := unix.Write(fd, nil)
+ switch err {
+ case unix.EINVAL:
+ tun.events <- TUNEventUp
+ case unix.EIO:
+ tun.events <- TUNEventDown
+ default:
+ return
+ }
+ select {
+ case <-time.After(time.Second):
+ case <-tun.statusListenersShutdown:
+ return
+ }
+ }
+}
+
+func createNetlinkSocket() (int, error) {
+ sock, err := unix.Socket(unix.AF_NETLINK, unix.SOCK_RAW, unix.NETLINK_ROUTE)
+ if err != nil {
+ return -1, err
+ }
+ saddr := &unix.SockaddrNetlink{
+ Family: unix.AF_NETLINK,
+ Groups: uint32((1 << (unix.RTNLGRP_LINK - 1)) | (1 << (unix.RTNLGRP_IPV4_IFADDR - 1)) | (1 << (unix.RTNLGRP_IPV6_IFADDR - 1))),
+ }
+ err = unix.Bind(sock, saddr)
+ if err != nil {
+ return -1, err
+ }
+ return sock, nil
+}
+
+func (tun *nativeTun) routineNetlinkListener() {
+ defer func() {
+ unix.Close(tun.netlinkSock)
+ tun.hackListenerClosed.Lock()
+ close(tun.events)
+ }()
+
+ for msg := make([]byte, 1<<16); ; {
+
+ var err error
+ var msgn int
+ for {
+ msgn, _, _, _, err = unix.Recvmsg(tun.netlinkSock, msg[:], nil, 0)
+ if err == nil || !rwcancel.ErrorIsEAGAIN(err) {
+ break
+ }
+ if !tun.netlinkCancel.ReadyRead() {
+ tun.errors <- fmt.Errorf("netlink socket closed: %s", err.Error())
+ return
+ }
+ }
+ if err != nil {
+ tun.errors <- fmt.Errorf("failed to receive netlink message: %s", err.Error())
+ return
+ }
+
+ select {
+ case <-tun.statusListenersShutdown:
+ return
+ default:
+ }
+
+ for remain := msg[:msgn]; len(remain) >= unix.SizeofNlMsghdr; {
+
+ hdr := *(*unix.NlMsghdr)(unsafe.Pointer(&remain[0]))
+
+ if int(hdr.Len) > len(remain) {
+ break
+ }
+
+ switch hdr.Type {
+ case unix.NLMSG_DONE:
+ remain = []byte{}
+
+ case unix.RTM_NEWLINK:
+ info := *(*unix.IfInfomsg)(unsafe.Pointer(&remain[unix.SizeofNlMsghdr]))
+ remain = remain[hdr.Len:]
+
+ if info.Index != tun.index {
+ // not our interface
+ continue
+ }
+
+ if info.Flags&unix.IFF_RUNNING != 0 {
+ tun.events <- TUNEventUp
+ }
+
+ if info.Flags&unix.IFF_RUNNING == 0 {
+ tun.events <- TUNEventDown
+ }
+
+ tun.events <- TUNEventMTUUpdate
+
+ default:
+ remain = remain[hdr.Len:]
+ }
+ }
+ }
+}
+
+func (tun *nativeTun) isUp() (bool, error) {
+ inter, err := net.InterfaceByName(tun.name)
+ return inter.Flags&net.FlagUp != 0, err
+}
+
+func getDummySock() (int, error) {
+ return unix.Socket(
+ unix.AF_INET,
+ unix.SOCK_DGRAM,
+ 0,
+ )
+}
+
+func getIFIndex(name string) (int32, error) {
+ fd, err := getDummySock()
+ if err != nil {
+ return 0, err
+ }
+
+ defer unix.Close(fd)
+
+ var ifr [ifReqSize]byte
+ copy(ifr[:], name)
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(fd),
+ uintptr(unix.SIOCGIFINDEX),
+ uintptr(unsafe.Pointer(&ifr[0])),
+ )
+
+ if errno != 0 {
+ return 0, errno
+ }
+
+ return *(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])), nil
+}
+
+func (tun *nativeTun) setMTU(n int) error {
+
+ // open datagram socket
+
+ 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 [ifReqSize]byte
+ copy(ifr[:], tun.name)
+ *(*uint32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = uint32(n)
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(fd),
+ uintptr(unix.SIOCSIFMTU),
+ uintptr(unsafe.Pointer(&ifr[0])),
+ )
+
+ if errno != 0 {
+ return errors.New("failed to set MTU of TUN device")
+ }
+
+ 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 [ifReqSize]byte
+ copy(ifr[:], tun.name)
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ uintptr(fd),
+ uintptr(unix.SIOCGIFMTU),
+ uintptr(unsafe.Pointer(&ifr[0])),
+ )
+ if errno != 0 {
+ return 0, errors.New("failed to get MTU of TUN device: " + strconv.FormatInt(int64(errno), 10))
+ }
+
+ return int(*(*int32)(unsafe.Pointer(&ifr[unix.IFNAMSIZ]))), nil
+}
+
+func (tun *nativeTun) Name() (string, error) {
+
+ var ifr [ifReqSize]byte
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ tun.fd.Fd(),
+ uintptr(unix.TUNGETIFF),
+ uintptr(unsafe.Pointer(&ifr[0])),
+ )
+ if errno != 0 {
+ return "", errors.New("failed to get name of TUN device: " + strconv.FormatInt(int64(errno), 10))
+ }
+ nullStr := ifr[:]
+ i := bytes.IndexByte(nullStr, 0)
+ if i != -1 {
+ nullStr = nullStr[:i]
+ }
+ tun.name = string(nullStr)
+ return tun.name, nil
+}
+
+func (tun *nativeTun) Write(buff []byte, offset int) (int, error) {
+
+ if tun.nopi {
+ buff = buff[offset:]
+ } else {
+ // reserve space for header
+
+ buff = buff[offset-4:]
+
+ // add packet information header
+
+ buff[0] = 0x00
+ buff[1] = 0x00
+
+ if buff[4]>>4 == ipv6.Version {
+ buff[2] = 0x86
+ buff[3] = 0xdd
+ } else {
+ buff[2] = 0x08
+ buff[3] = 0x00
+ }
+ }
+
+ // write
+
+ return tun.fd.Write(buff)
+}
+
+func (tun *nativeTun) doRead(buff []byte, offset int) (int, error) {
+ select {
+ case err := <-tun.errors:
+ return 0, err
+ default:
+ if tun.nopi {
+ return tun.fd.Read(buff[offset:])
+ } else {
+ 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.fdCancel.ReadyRead() {
+ return 0, errors.New("tun device closed")
+ }
+ }
+}
+
+func (tun *nativeTun) Events() chan TUNEvent {
+ return tun.events
+}
+
+func (tun *nativeTun) Close() error {
+ var err1 error
+ if tun.statusListenersShutdown != nil {
+ close(tun.statusListenersShutdown)
+ if tun.netlinkCancel != nil {
+ err1 = tun.netlinkCancel.Cancel()
+ }
+ } else if tun.events != nil {
+ close(tun.events)
+ }
+ err2 := tun.fd.Close()
+ err3 := tun.fdCancel.Cancel()
+
+ if err1 != nil {
+ return err1
+ }
+ if err2 != nil {
+ return err2
+ }
+ return err3
+}
+
+func CreateTUN(name string, mtu int) (TUNDevice, error) {
+
+ // open clone device
+
+ // HACK: we open it as a raw Fd first, so that f.nonblock=false
+ // when we make it into a file object.
+ nfd, err := unix.Open(cloneDevicePath, os.O_RDWR, 0)
+ if err != nil {
+ return nil, err
+ }
+
+ err = unix.SetNonblock(nfd, true)
+ if err != nil {
+ return nil, err
+ }
+
+ fd := os.NewFile(uintptr(nfd), cloneDevicePath)
+ if err != nil {
+ return nil, err
+ }
+
+ // create new device
+
+ var ifr [ifReqSize]byte
+ var flags uint16 = unix.IFF_TUN // | unix.IFF_NO_PI (disabled for TUN status hack)
+ nameBytes := []byte(name)
+ if len(nameBytes) >= unix.IFNAMSIZ {
+ return nil, errors.New("interface name too long")
+ }
+ copy(ifr[:], nameBytes)
+ *(*uint16)(unsafe.Pointer(&ifr[unix.IFNAMSIZ])) = flags
+
+ _, _, errno := unix.Syscall(
+ unix.SYS_IOCTL,
+ fd.Fd(),
+ uintptr(unix.TUNSETIFF),
+ uintptr(unsafe.Pointer(&ifr[0])),
+ )
+ if errno != 0 {
+ return nil, errno
+ }
+
+ return CreateTUNFromFile(fd, mtu)
+}
+
+func CreateTUNFromFile(file *os.File, mtu int) (TUNDevice, error) {
+ tun := &nativeTun{
+ fd: file,
+ events: make(chan TUNEvent, 5),
+ errors: make(chan error, 5),
+ statusListenersShutdown: make(chan struct{}),
+ nopi: false,
+ }
+ var err error
+
+ tun.fdCancel, err = rwcancel.NewRWCancel(int(file.Fd()))
+ if err != nil {
+ tun.fd.Close()
+ return nil, err
+ }
+
+ _, err = tun.Name()
+ if err != nil {
+ tun.fd.Close()
+ return nil, err
+ }
+
+ // start event listener
+
+ tun.index, err = getIFIndex(tun.name)
+ if err != nil {
+ return nil, err
+ }
+
+ tun.netlinkSock, err = createNetlinkSocket()
+ if err != nil {
+ tun.fd.Close()
+ return nil, err
+ }
+ tun.netlinkCancel, err = rwcancel.NewRWCancel(tun.netlinkSock)
+ if err != nil {
+ tun.fd.Close()
+ return nil, err
+ }
+
+ tun.hackListenerClosed.Lock()
+ go tun.routineNetlinkListener()
+ go tun.routineHackListener() // cross namespace
+
+ err = tun.setMTU(mtu)
+ if err != nil {
+ tun.Close()
+ return nil, err
+ }
+
+ return tun, nil
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-01 07:28:01 +0000