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// Copyright 2020 The gVisor 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 tundev implements the /dev/net/tun device.
package tundev
import (
"gvisor.dev/gvisor/pkg/abi/linux"
"gvisor.dev/gvisor/pkg/context"
"gvisor.dev/gvisor/pkg/sentry/arch"
"gvisor.dev/gvisor/pkg/sentry/fsimpl/devtmpfs"
"gvisor.dev/gvisor/pkg/sentry/inet"
"gvisor.dev/gvisor/pkg/sentry/kernel"
"gvisor.dev/gvisor/pkg/sentry/socket/netstack"
"gvisor.dev/gvisor/pkg/sentry/vfs"
"gvisor.dev/gvisor/pkg/syserror"
"gvisor.dev/gvisor/pkg/tcpip/link/tun"
"gvisor.dev/gvisor/pkg/usermem"
"gvisor.dev/gvisor/pkg/waiter"
)
const (
netTunDevMajor = 10
netTunDevMinor = 200
)
// tunDevice implements vfs.Device for /dev/net/tun.
type tunDevice struct{}
// Open implements vfs.Device.Open.
func (tunDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
fd := &tunFD{}
if err := fd.vfsfd.Init(fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
UseDentryMetadata: true,
}); err != nil {
return nil, err
}
return &fd.vfsfd, nil
}
// tunFD implements vfs.FileDescriptionImpl for /dev/net/tun.
type tunFD struct {
vfsfd vfs.FileDescription
vfs.FileDescriptionDefaultImpl
vfs.DentryMetadataFileDescriptionImpl
vfs.NoLockFD
device tun.Device
}
// Ioctl implements vfs.FileDescriptionImpl.Ioctl.
func (fd *tunFD) Ioctl(ctx context.Context, uio usermem.IO, args arch.SyscallArguments) (uintptr, error) {
request := args[1].Uint()
data := args[2].Pointer()
switch request {
case linux.TUNSETIFF:
t := kernel.TaskFromContext(ctx)
if t == nil {
panic("Ioctl should be called from a task context")
}
if !t.HasCapability(linux.CAP_NET_ADMIN) {
return 0, syserror.EPERM
}
stack, ok := t.NetworkContext().(*netstack.Stack)
if !ok {
return 0, syserror.EINVAL
}
var req linux.IFReq
if _, err := usermem.CopyObjectIn(ctx, uio, data, &req, usermem.IOOpts{
AddressSpaceActive: true,
}); err != nil {
return 0, err
}
flags := usermem.ByteOrder.Uint16(req.Data[:])
return 0, fd.device.SetIff(stack.Stack, req.Name(), flags)
case linux.TUNGETIFF:
var req linux.IFReq
copy(req.IFName[:], fd.device.Name())
// Linux adds IFF_NOFILTER (the same value as IFF_NO_PI unfortunately) when
// there is no sk_filter. See __tun_chr_ioctl() in net/drivers/tun.c.
flags := fd.device.Flags() | linux.IFF_NOFILTER
usermem.ByteOrder.PutUint16(req.Data[:], flags)
_, err := usermem.CopyObjectOut(ctx, uio, data, &req, usermem.IOOpts{
AddressSpaceActive: true,
})
return 0, err
default:
return 0, syserror.ENOTTY
}
}
// Release implements vfs.FileDescriptionImpl.Release.
func (fd *tunFD) Release() {
fd.device.Release()
}
// PRead implements vfs.FileDescriptionImpl.PRead.
func (fd *tunFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
return fd.Read(ctx, dst, opts)
}
// Read implements vfs.FileDescriptionImpl.Read.
func (fd *tunFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
data, err := fd.device.Read()
if err != nil {
return 0, err
}
n, err := dst.CopyOut(ctx, data)
if n > 0 && n < len(data) {
// Not an error for partial copying. Packet truncated.
err = nil
}
return int64(n), err
}
// PWrite implements vfs.FileDescriptionImpl.PWrite.
func (fd *tunFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
return fd.Write(ctx, src, opts)
}
// Write implements vfs.FileDescriptionImpl.Write.
func (fd *tunFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
data := make([]byte, src.NumBytes())
if _, err := src.CopyIn(ctx, data); err != nil {
return 0, err
}
return fd.device.Write(data)
}
// Readiness implements watier.Waitable.Readiness.
func (fd *tunFD) Readiness(mask waiter.EventMask) waiter.EventMask {
return fd.device.Readiness(mask)
}
// EventRegister implements watier.Waitable.EventRegister.
func (fd *tunFD) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
fd.device.EventRegister(e, mask)
}
// EventUnregister implements watier.Waitable.EventUnregister.
func (fd *tunFD) EventUnregister(e *waiter.Entry) {
fd.device.EventUnregister(e)
}
// isNetTunSupported returns whether /dev/net/tun device is supported for s.
func isNetTunSupported(s inet.Stack) bool {
_, ok := s.(*netstack.Stack)
return ok
}
// Register registers all devices implemented by this package in vfsObj.
func Register(vfsObj *vfs.VirtualFilesystem) error {
return vfsObj.RegisterDevice(vfs.CharDevice, netTunDevMajor, netTunDevMinor, tunDevice{}, &vfs.RegisterDeviceOptions{})
}
// CreateDevtmpfsFiles creates device special files in dev representing all
// devices implemented by this package.
func CreateDevtmpfsFiles(ctx context.Context, dev *devtmpfs.Accessor) error {
return dev.CreateDeviceFile(ctx, "net/tun", vfs.CharDevice, netTunDevMajor, netTunDevMinor, 0666 /* mode */)
}
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