github.com/sagernet/gvisor@v0.0.0-20240428053021-e691de28565f/pkg/tcpip/link/tun/tun_unsafe.go (about)

     1  // Copyright 2018 The gVisor 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  //go:build linux
    16  // +build linux
    17  
    18  // Package tun contains methods to open TAP and TUN devices.
    19  package tun
    20  
    21  import (
    22  	"unsafe"
    23  
    24  	"golang.org/x/sys/unix"
    25  )
    26  
    27  // Open opens the specified TUN device, sets it to non-blocking mode, and
    28  // returns its file descriptor.
    29  func Open(name string) (int, error) {
    30  	return open(name, unix.IFF_TUN|unix.IFF_NO_PI)
    31  }
    32  
    33  // OpenTAP opens the specified TAP device, sets it to non-blocking mode, and
    34  // returns its file descriptor.
    35  func OpenTAP(name string) (int, error) {
    36  	return open(name, unix.IFF_TAP|unix.IFF_NO_PI)
    37  }
    38  
    39  func open(name string, flags uint16) (int, error) {
    40  	fd, err := unix.Open("/dev/net/tun", unix.O_RDWR, 0)
    41  	if err != nil {
    42  		return -1, err
    43  	}
    44  
    45  	var ifr struct {
    46  		name  [16]byte
    47  		flags uint16
    48  		_     [22]byte
    49  	}
    50  
    51  	copy(ifr.name[:], name)
    52  	ifr.flags = flags
    53  	_, _, errno := unix.Syscall(unix.SYS_IOCTL, uintptr(fd), unix.TUNSETIFF, uintptr(unsafe.Pointer(&ifr)))
    54  	if errno != 0 {
    55  		unix.Close(fd)
    56  		return -1, errno
    57  	}
    58  
    59  	if err = unix.SetNonblock(fd, true); err != nil {
    60  		unix.Close(fd)
    61  		return -1, err
    62  	}
    63  
    64  	return fd, nil
    65  }