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// Copyright 2016 The Netstack Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package tun contains methods to open TAP and TUN devices.
package tun
import (
"syscall"
"unsafe"
)
// Open opens the specified TUN device, sets it to non-blocking mode, and
// returns its file descriptor.
func Open(name string) (int, error) {
return open(name, syscall.IFF_TUN|syscall.IFF_NO_PI)
}
// OpenTAP opens the specified TAP device, sets it to non-blocking mode, and
// returns its file descriptor.
func OpenTAP(name string) (int, error) {
return open(name, syscall.IFF_TAP|syscall.IFF_NO_PI)
}
func open(name string, flags uint16) (int, error) {
fd, err := syscall.Open("/dev/net/tun", syscall.O_RDWR, 0)
if err != nil {
return -1, err
}
var ifr struct {
name [16]byte
flags uint16
_ [22]byte
}
copy(ifr.name[:], name)
ifr.flags = flags
_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, uintptr(fd), syscall.TUNSETIFF, uintptr(unsafe.Pointer(&ifr)))
if errno != 0 {
syscall.Close(fd)
return -1, errno
}
if err = syscall.SetNonblock(fd, true); err != nil {
syscall.Close(fd)
return -1, err
}
return fd, nil
}
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