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tun.go
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tun.go
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// Copyright 2015 flannel authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ip
import (
"bytes"
"fmt"
"os"
"syscall"
"unsafe"
)
const (
tunDevice = "/dev/net/tun"
ifnameSize = 16
)
type ifreqFlags struct {
IfrnName [ifnameSize]byte
IfruFlags uint16
}
func ioctl(fd int, request, argp uintptr) error {
_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), request, argp)
if errno != 0 {
return fmt.Errorf("ioctl failed with '%s'", errno)
}
return nil
}
func fromZeroTerm(s []byte) string {
return string(bytes.TrimRight(s, "\000"))
}
func OpenTun(name string) (*os.File, string, error) {
tun, err := os.OpenFile(tunDevice, os.O_RDWR, 0)
if err != nil {
return nil, "", err
}
var ifr ifreqFlags
copy(ifr.IfrnName[:len(ifr.IfrnName)-1], []byte(name+"\000"))
ifr.IfruFlags = syscall.IFF_TUN | syscall.IFF_NO_PI
err = ioctl(int(tun.Fd()), syscall.TUNSETIFF, uintptr(unsafe.Pointer(&ifr)))
if err != nil {
return nil, "", err
}
ifname := fromZeroTerm(ifr.IfrnName[:ifnameSize])
return tun, ifname, nil
}