Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

2 files changed, 62 insertions, 0 deletions

diff --git a/pkg/tcpip/link/tun/BUILD b/pkg/tcpip/link/tun/BUILD
new file mode 100644
index 000000000..d627f00f1
--- /dev/null
+++ b/pkg/tcpip/link/tun/BUILD
@@ -0,0 +1,12 @@
+package(licenses = ["notice"])  # BSD
+
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+go_library(
+    name = "tun",
+    srcs = ["tun_unsafe.go"],
+    importpath = "gvisor.googlesource.com/gvisor/pkg/tcpip/link/tun",
+    visibility = [
+        "//visibility:public",
+    ],
+)
diff --git a/pkg/tcpip/link/tun/tun_unsafe.go b/pkg/tcpip/link/tun/tun_unsafe.go
new file mode 100644
index 000000000..5b6c9b4ab
--- /dev/null
+++ b/pkg/tcpip/link/tun/tun_unsafe.go
@@ -0,0 +1,50 @@
+// 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
+
+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
+}