github.com/coreos/mantle@v0.13.0/platform/local/tap.go (about)

     1  // Copyright 2014-2015 CoreOS, Inc.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package local
    16  
    17  import (
    18  	"bytes"
    19  	"os"
    20  	"syscall"
    21  	"unsafe"
    22  
    23  	"github.com/vishvananda/netlink"
    24  )
    25  
    26  const (
    27  	tunDevice = "/dev/net/tun"
    28  )
    29  
    30  // Tun/Tap device that is compatible with the netlink library.
    31  type TunTap struct {
    32  	*netlink.LinkAttrs
    33  	*os.File
    34  }
    35  
    36  func (tt *TunTap) Attrs() *netlink.LinkAttrs {
    37  	return tt.LinkAttrs
    38  }
    39  
    40  func (tt *TunTap) Type() string {
    41  	return "tun"
    42  }
    43  
    44  type ifreqFlags struct {
    45  	IfrnName  [syscall.IFNAMSIZ]byte
    46  	IfruFlags uint16
    47  }
    48  
    49  func ioctl(fd, request, argp uintptr) error {
    50  	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, fd, request, argp)
    51  	if errno != 0 {
    52  		return errno
    53  	}
    54  	return nil
    55  }
    56  
    57  func fromZeroTerm(s []byte) string {
    58  	return string(bytes.TrimRight(s, "\000"))
    59  }
    60  
    61  func newTunTap(name string, flags uint16) (*TunTap, error) {
    62  	dev, err := os.OpenFile(tunDevice, os.O_RDWR, 0)
    63  	if err != nil {
    64  		return nil, err
    65  	}
    66  
    67  	var ifr ifreqFlags
    68  	copy(ifr.IfrnName[:len(ifr.IfrnName)-1], []byte(name+"\000"))
    69  	ifr.IfruFlags = flags | syscall.IFF_NO_PI
    70  
    71  	err = ioctl(dev.Fd(), syscall.TUNSETIFF, uintptr(unsafe.Pointer(&ifr)))
    72  	if err != nil {
    73  		return nil, err
    74  	}
    75  
    76  	ifname := fromZeroTerm(ifr.IfrnName[:len(ifr.IfrnName)-1])
    77  	iflink, err := netlink.LinkByName(ifname)
    78  	if err != nil {
    79  		dev.Close()
    80  		return nil, err
    81  	}
    82  
    83  	tt := TunTap{
    84  		File:      dev,
    85  		LinkAttrs: iflink.Attrs(),
    86  	}
    87  
    88  	return &tt, nil
    89  }
    90  
    91  func AddLinkTap(name string) (*TunTap, error) {
    92  	return newTunTap(name, syscall.IFF_TAP)
    93  }
    94  
    95  func AddLinkTun(name string) (*TunTap, error) {
    96  	return newTunTap(name, syscall.IFF_TUN)
    97  }