Merge branch 'master' into ip-forwarding

- Merges aleksej-paschenko's with HEAD
- Adds vfs2 support for ip_forward

10 files changed, 690 insertions, 0 deletions

diff --git a/pkg/sentry/devices/memdev/BUILD b/pkg/sentry/devices/memdev/BUILD
new file mode 100644
index 000000000..abe58f818
--- /dev/null
+++ b/pkg/sentry/devices/memdev/BUILD
@@ -0,0 +1,28 @@
+load("//tools:defs.bzl", "go_library")
+
+licenses(["notice"])
+
+go_library(
+    name = "memdev",
+    srcs = [
+        "full.go",
+        "memdev.go",
+        "null.go",
+        "random.go",
+        "zero.go",
+    ],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/context",
+        "//pkg/rand",
+        "//pkg/safemem",
+        "//pkg/sentry/fsimpl/devtmpfs",
+        "//pkg/sentry/memmap",
+        "//pkg/sentry/mm",
+        "//pkg/sentry/pgalloc",
+        "//pkg/sentry/vfs",
+        "//pkg/syserror",
+        "//pkg/usermem",
+    ],
+)
diff --git a/pkg/sentry/devices/memdev/full.go b/pkg/sentry/devices/memdev/full.go
new file mode 100644
index 000000000..511179e31
--- /dev/null
+++ b/pkg/sentry/devices/memdev/full.go
@@ -0,0 +1,76 @@
+// 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 memdev
+
+import (
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+const fullDevMinor = 7
+
+// fullDevice implements vfs.Device for /dev/full.
+type fullDevice struct{}
+
+// Open implements vfs.Device.Open.
+func (fullDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	fd := &fullFD{}
+	if err := fd.vfsfd.Init(fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
+		UseDentryMetadata: true,
+	}); err != nil {
+		return nil, err
+	}
+	return &fd.vfsfd, nil
+}
+
+// fullFD implements vfs.FileDescriptionImpl for /dev/full.
+type fullFD struct {
+	vfsfd vfs.FileDescription
+	vfs.FileDescriptionDefaultImpl
+	vfs.DentryMetadataFileDescriptionImpl
+	vfs.NoLockFD
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *fullFD) Release(context.Context) {
+	// noop
+}
+
+// PRead implements vfs.FileDescriptionImpl.PRead.
+func (fd *fullFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+	return dst.ZeroOut(ctx, dst.NumBytes())
+}
+
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *fullFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	return dst.ZeroOut(ctx, dst.NumBytes())
+}
+
+// PWrite implements vfs.FileDescriptionImpl.PWrite.
+func (fd *fullFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+	return 0, syserror.ENOSPC
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *fullFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+	return 0, syserror.ENOSPC
+}
+
+// Seek implements vfs.FileDescriptionImpl.Seek.
+func (fd *fullFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+	return 0, nil
+}
diff --git a/pkg/sentry/devices/memdev/memdev.go b/pkg/sentry/devices/memdev/memdev.go
new file mode 100644
index 000000000..5759900c4
--- /dev/null
+++ b/pkg/sentry/devices/memdev/memdev.go
@@ -0,0 +1,59 @@
+// 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 memdev implements "mem" character devices, as implemented in Linux
+// by drivers/char/mem.c and drivers/char/random.c.
+package memdev
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/devtmpfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+)
+
+// Register registers all devices implemented by this package in vfsObj.
+func Register(vfsObj *vfs.VirtualFilesystem) error {
+	for minor, dev := range map[uint32]vfs.Device{
+		nullDevMinor:    nullDevice{},
+		zeroDevMinor:    zeroDevice{},
+		fullDevMinor:    fullDevice{},
+		randomDevMinor:  randomDevice{},
+		urandomDevMinor: randomDevice{},
+	} {
+		if err := vfsObj.RegisterDevice(vfs.CharDevice, linux.MEM_MAJOR, minor, dev, &vfs.RegisterDeviceOptions{
+			GroupName: "mem",
+		}); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+// CreateDevtmpfsFiles creates device special files in dev representing all
+// devices implemented by this package.
+func CreateDevtmpfsFiles(ctx context.Context, dev *devtmpfs.Accessor) error {
+	for minor, name := range map[uint32]string{
+		nullDevMinor:    "null",
+		zeroDevMinor:    "zero",
+		fullDevMinor:    "full",
+		randomDevMinor:  "random",
+		urandomDevMinor: "urandom",
+	} {
+		if err := dev.CreateDeviceFile(ctx, name, vfs.CharDevice, linux.MEM_MAJOR, minor, 0666 /* mode */); err != nil {
+			return err
+		}
+	}
+	return nil
+}
diff --git a/pkg/sentry/devices/memdev/null.go b/pkg/sentry/devices/memdev/null.go
new file mode 100644
index 000000000..4918dbeeb
--- /dev/null
+++ b/pkg/sentry/devices/memdev/null.go
@@ -0,0 +1,77 @@
+// 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 memdev
+
+import (
+	"io"
+
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+const nullDevMinor = 3
+
+// nullDevice implements vfs.Device for /dev/null.
+type nullDevice struct{}
+
+// Open implements vfs.Device.Open.
+func (nullDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	fd := &nullFD{}
+	if err := fd.vfsfd.Init(fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
+		UseDentryMetadata: true,
+	}); err != nil {
+		return nil, err
+	}
+	return &fd.vfsfd, nil
+}
+
+// nullFD implements vfs.FileDescriptionImpl for /dev/null.
+type nullFD struct {
+	vfsfd vfs.FileDescription
+	vfs.FileDescriptionDefaultImpl
+	vfs.DentryMetadataFileDescriptionImpl
+	vfs.NoLockFD
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *nullFD) Release(context.Context) {
+	// noop
+}
+
+// PRead implements vfs.FileDescriptionImpl.PRead.
+func (fd *nullFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+	return 0, io.EOF
+}
+
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *nullFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	return 0, io.EOF
+}
+
+// PWrite implements vfs.FileDescriptionImpl.PWrite.
+func (fd *nullFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+	return src.NumBytes(), nil
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *nullFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+	return src.NumBytes(), nil
+}
+
+// Seek implements vfs.FileDescriptionImpl.Seek.
+func (fd *nullFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+	return 0, nil
+}
diff --git a/pkg/sentry/devices/memdev/random.go b/pkg/sentry/devices/memdev/random.go
new file mode 100644
index 000000000..5e7fe0280
--- /dev/null
+++ b/pkg/sentry/devices/memdev/random.go
@@ -0,0 +1,93 @@
+// 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 memdev
+
+import (
+	"sync/atomic"
+
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/rand"
+	"gvisor.dev/gvisor/pkg/safemem"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+const (
+	randomDevMinor  = 8
+	urandomDevMinor = 9
+)
+
+// randomDevice implements vfs.Device for /dev/random and /dev/urandom.
+type randomDevice struct{}
+
+// Open implements vfs.Device.Open.
+func (randomDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	fd := &randomFD{}
+	if err := fd.vfsfd.Init(fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
+		UseDentryMetadata: true,
+	}); err != nil {
+		return nil, err
+	}
+	return &fd.vfsfd, nil
+}
+
+// randomFD implements vfs.FileDescriptionImpl for /dev/random.
+type randomFD struct {
+	vfsfd vfs.FileDescription
+	vfs.FileDescriptionDefaultImpl
+	vfs.DentryMetadataFileDescriptionImpl
+	vfs.NoLockFD
+
+	// off is the "file offset". off is accessed using atomic memory
+	// operations.
+	off int64
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *randomFD) Release(context.Context) {
+	// noop
+}
+
+// PRead implements vfs.FileDescriptionImpl.PRead.
+func (fd *randomFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+	return dst.CopyOutFrom(ctx, safemem.FromIOReader{rand.Reader})
+}
+
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *randomFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	n, err := dst.CopyOutFrom(ctx, safemem.FromIOReader{rand.Reader})
+	atomic.AddInt64(&fd.off, n)
+	return n, err
+}
+
+// PWrite implements vfs.FileDescriptionImpl.PWrite.
+func (fd *randomFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+	// In Linux, this mixes the written bytes into the entropy pool; we just
+	// throw them away.
+	return src.NumBytes(), nil
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *randomFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+	atomic.AddInt64(&fd.off, src.NumBytes())
+	return src.NumBytes(), nil
+}
+
+// Seek implements vfs.FileDescriptionImpl.Seek.
+func (fd *randomFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+	// Linux: drivers/char/random.c:random_fops.llseek == urandom_fops.llseek
+	// == noop_llseek
+	return atomic.LoadInt64(&fd.off), nil
+}
diff --git a/pkg/sentry/devices/memdev/zero.go b/pkg/sentry/devices/memdev/zero.go
new file mode 100644
index 000000000..2e631a252
--- /dev/null
+++ b/pkg/sentry/devices/memdev/zero.go
@@ -0,0 +1,89 @@
+// 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 memdev
+
+import (
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/memmap"
+	"gvisor.dev/gvisor/pkg/sentry/mm"
+	"gvisor.dev/gvisor/pkg/sentry/pgalloc"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/usermem"
+)
+
+const zeroDevMinor = 5
+
+// zeroDevice implements vfs.Device for /dev/zero.
+type zeroDevice struct{}
+
+// Open implements vfs.Device.Open.
+func (zeroDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	fd := &zeroFD{}
+	if err := fd.vfsfd.Init(fd, opts.Flags, mnt, vfsd, &vfs.FileDescriptionOptions{
+		UseDentryMetadata: true,
+	}); err != nil {
+		return nil, err
+	}
+	return &fd.vfsfd, nil
+}
+
+// zeroFD implements vfs.FileDescriptionImpl for /dev/zero.
+type zeroFD struct {
+	vfsfd vfs.FileDescription
+	vfs.FileDescriptionDefaultImpl
+	vfs.DentryMetadataFileDescriptionImpl
+	vfs.NoLockFD
+}
+
+// Release implements vfs.FileDescriptionImpl.Release.
+func (fd *zeroFD) Release(context.Context) {
+	// noop
+}
+
+// PRead implements vfs.FileDescriptionImpl.PRead.
+func (fd *zeroFD) PRead(ctx context.Context, dst usermem.IOSequence, offset int64, opts vfs.ReadOptions) (int64, error) {
+	return dst.ZeroOut(ctx, dst.NumBytes())
+}
+
+// Read implements vfs.FileDescriptionImpl.Read.
+func (fd *zeroFD) Read(ctx context.Context, dst usermem.IOSequence, opts vfs.ReadOptions) (int64, error) {
+	return dst.ZeroOut(ctx, dst.NumBytes())
+}
+
+// PWrite implements vfs.FileDescriptionImpl.PWrite.
+func (fd *zeroFD) PWrite(ctx context.Context, src usermem.IOSequence, offset int64, opts vfs.WriteOptions) (int64, error) {
+	return src.NumBytes(), nil
+}
+
+// Write implements vfs.FileDescriptionImpl.Write.
+func (fd *zeroFD) Write(ctx context.Context, src usermem.IOSequence, opts vfs.WriteOptions) (int64, error) {
+	return src.NumBytes(), nil
+}
+
+// Seek implements vfs.FileDescriptionImpl.Seek.
+func (fd *zeroFD) Seek(ctx context.Context, offset int64, whence int32) (int64, error) {
+	return 0, nil
+}
+
+// ConfigureMMap implements vfs.FileDescriptionImpl.ConfigureMMap.
+func (fd *zeroFD) ConfigureMMap(ctx context.Context, opts *memmap.MMapOpts) error {
+	m, err := mm.NewSharedAnonMappable(opts.Length, pgalloc.MemoryFileProviderFromContext(ctx))
+	if err != nil {
+		return err
+	}
+	opts.MappingIdentity = m
+	opts.Mappable = m
+	return nil
+}
diff --git a/pkg/sentry/devices/ttydev/BUILD b/pkg/sentry/devices/ttydev/BUILD
new file mode 100644
index 000000000..b4b6ca38a
--- /dev/null
+++ b/pkg/sentry/devices/ttydev/BUILD
@@ -0,0 +1,16 @@
+load("//tools:defs.bzl", "go_library")
+
+licenses(["notice"])
+
+go_library(
+    name = "ttydev",
+    srcs = ["ttydev.go"],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/context",
+        "//pkg/sentry/fsimpl/devtmpfs",
+        "//pkg/sentry/vfs",
+        "//pkg/syserror",
+    ],
+)
diff --git a/pkg/sentry/devices/ttydev/ttydev.go b/pkg/sentry/devices/ttydev/ttydev.go
new file mode 100644
index 000000000..664e54498
--- /dev/null
+++ b/pkg/sentry/devices/ttydev/ttydev.go
@@ -0,0 +1,51 @@
+// 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 ttydev implements an unopenable vfs.Device for /dev/tty.
+package ttydev
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/devtmpfs"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+const (
+	// See drivers/tty/tty_io.c:tty_init().
+	ttyDevMinor     = 0
+	consoleDevMinor = 1
+)
+
+// ttyDevice implements vfs.Device for /dev/tty.
+type ttyDevice struct{}
+
+// Open implements vfs.Device.Open.
+func (ttyDevice) Open(ctx context.Context, mnt *vfs.Mount, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	return nil, syserror.EIO
+}
+
+// Register registers all devices implemented by this package in vfsObj.
+func Register(vfsObj *vfs.VirtualFilesystem) error {
+	return vfsObj.RegisterDevice(vfs.CharDevice, linux.TTYAUX_MAJOR, ttyDevMinor, ttyDevice{}, &vfs.RegisterDeviceOptions{
+		GroupName: "tty",
+	})
+}
+
+// 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, "tty", vfs.CharDevice, linux.TTYAUX_MAJOR, ttyDevMinor, 0666 /* mode */)
+}
diff --git a/pkg/sentry/devices/tundev/BUILD b/pkg/sentry/devices/tundev/BUILD
new file mode 100644
index 000000000..71c59287c
--- /dev/null
+++ b/pkg/sentry/devices/tundev/BUILD
@@ -0,0 +1,23 @@
+load("//tools:defs.bzl", "go_library")
+
+licenses(["notice"])
+
+go_library(
+    name = "tundev",
+    srcs = ["tundev.go"],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/context",
+        "//pkg/sentry/arch",
+        "//pkg/sentry/fsimpl/devtmpfs",
+        "//pkg/sentry/inet",
+        "//pkg/sentry/kernel",
+        "//pkg/sentry/socket/netstack",
+        "//pkg/sentry/vfs",
+        "//pkg/syserror",
+        "//pkg/tcpip/link/tun",
+        "//pkg/usermem",
+        "//pkg/waiter",
+    ],
+)
diff --git a/pkg/sentry/devices/tundev/tundev.go b/pkg/sentry/devices/tundev/tundev.go
new file mode 100644
index 000000000..a40625e19
--- /dev/null
+++ b/pkg/sentry/devices/tundev/tundev.go
@@ -0,0 +1,178 @@
+// 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(ctx context.Context) {
+	fd.device.Release(ctx)
+}
+
+// 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 */)
+}