github.com/stackdocker/rkt@v0.10.1-0.20151109095037-1aa827478248/networking/tuntap/tuntap.go (about)

     1  // Copyright 2015 The rkt Authors
     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 tuntap
    16  
    17  import (
    18  	"bytes"
    19  	"fmt"
    20  	"os"
    21  	"syscall"
    22  	"unsafe"
    23  )
    24  
    25  const (
    26  	Tun = 0x1
    27  	Tap = 0x2
    28  
    29  	NoPi     = 0x1000
    30  	OneQueue = 0x2000
    31  	VnetHdr  = 0x4000
    32  	TunExcl  = 0x8000
    33  )
    34  
    35  type ifReq struct {
    36  	Name  [0x10]byte
    37  	Flags uint16
    38  	pad   [0x28 - 0x12]byte
    39  }
    40  
    41  type Interface struct {
    42  	name string
    43  	file *os.File
    44  }
    45  
    46  func Open(ifName string, kind uint16) (*Interface, error) {
    47  	if ifName == "" {
    48  		ifName = "tap%d"
    49  	}
    50  	file, err := os.OpenFile("/dev/net/tun", os.O_RDWR, 0)
    51  	if err != nil {
    52  		return nil, err
    53  	}
    54  
    55  	var req ifReq
    56  	copy(req.Name[:15], ifName)
    57  	req.Flags = kind | NoPi | VnetHdr
    58  
    59  	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, file.Fd(), uintptr(syscall.TUNSETIFF), uintptr(unsafe.Pointer(&req)))
    60  	if errno != 0 {
    61  		file.Close()
    62  		return nil, fmt.Errorf("ioctl failed (TUNSETIFF): %v", errno)
    63  	}
    64  
    65  	return &Interface{
    66  		name: string(req.Name[:bytes.IndexByte(req.Name[:], 0)]),
    67  		file: file,
    68  	}, nil
    69  }
    70  
    71  func (iface *Interface) Close() error {
    72  	return iface.file.Close()
    73  }
    74  
    75  func operateOnIface(name string, kind uint16, persistency uintptr) (string, error) {
    76  	iface, err := Open(name, kind)
    77  	if err != nil {
    78  		return "", err
    79  	}
    80  
    81  	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, iface.file.Fd(), uintptr(syscall.TUNSETPERSIST), persistency)
    82  	err = iface.Close()
    83  	if err != nil {
    84  		return "", fmt.Errorf("iface close error : %v", err)
    85  	}
    86  
    87  	if errno != 0 {
    88  		return "", fmt.Errorf("ioctl failed (TUNSETPERSIST): %v", errno)
    89  	}
    90  
    91  	return iface.name, nil
    92  }
    93  
    94  func CreatePersistentIface(nameTemplate string, kind uint16) (string, error) {
    95  	return operateOnIface(nameTemplate, kind, 1)
    96  }
    97  
    98  func RemovePersistentIface(name string, kind uint16) error {
    99  	_, err := operateOnIface(name, kind, 0)
   100  	return err
   101  }