water

README

water

water is a native Go library for TUN/TAP interfaces.

water is designed to be simple and efficient. It

• wraps almost only syscalls and uses only Go standard types;
• exposes standard interfaces; plays well with standard packages like io, bufio, etc..
• does not handle memory management (allocating/destructing slice). It's up to user to decide whether/how to reuse buffers.

water/waterutil has some useful functions to interpret MAC frame headers and IP packet headers. It also contains some constants such as protocol numbers and ethernet frame types.

See https://github.com/songgao/packets for functions for parsing various packets.

Supported Platforms

• Linux
• Windows (experimental; APIs might change)
• macOS (point-to-point TUN only)

Installation

go get -u github.com/songgao/water
go get -u github.com/songgao/water/waterutil

Documentation

http://godoc.org/github.com/songgao/water

Example

TAP on Linux:

package main

import (
	"log"

	"github.com/songgao/packets/ethernet"
	"github.com/songgao/water"
)

func main() {
	config := water.Config{
		DeviceType: water.TAP,
	}
	config.Name = "O_O"

	ifce, err := water.New(config)
	if err != nil {
		log.Fatal(err)
	}
	var frame ethernet.Frame

	for {
		frame.Resize(1500)
		n, err := ifce.Read([]byte(frame))
		if err != nil {
			log.Fatal(err)
		}
		frame = frame[:n]
		log.Printf("Dst: %s\n", frame.Destination())
		log.Printf("Src: %s\n", frame.Source())
		log.Printf("Ethertype: % x\n", frame.Ethertype())
		log.Printf("Payload: % x\n", frame.Payload())
	}
}

This piece of code creates a TAP interface, and prints some header information for every frame. After pull up the main.go, you'll need to bring up the interface and assign an IP address. All of these need root permission.

sudo go run main.go

In a new terminal:

sudo ip addr add 10.1.0.10/24 dev O_O
sudo ip link set dev O_O up

Wait until the output main.go terminal, try sending some ICMP broadcast message:

ping -c1 -b 10.1.0.255

You'll see output containing the IPv4 ICMP frame:

2016/10/24 03:18:16 Dst: ff:ff:ff:ff:ff:ff
2016/10/24 03:18:16 Src: 72:3c:fc:29:1c:6f
2016/10/24 03:18:16 Ethertype: 08 00
2016/10/24 03:18:16 Payload: 45 00 00 54 00 00 40 00 40 01 25 9f 0a 01 00 0a 0a 01 00 ff 08 00 01 c1 08 49 00 01 78 7d 0d 58 00 00 00 00 a2 4c 07 00 00 00 00 00 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37

TUN on macOS

package main

import (
	"log"

	"github.com/songgao/water"
)

func main() {
	ifce, err := water.New(water.Config{
		DeviceType: water.TUN,
	})
	if err != nil {
		log.Fatal(err)
	}

	log.Printf("Interface Name: %s\n", ifce.Name())

	packet := make([]byte, 2000)
	for {
		n, err := ifce.Read(packet)
		if err != nil {
			log.Fatal(err)
		}
		log.Printf("Packet Received: % x\n", packet[:n])
	}
}

Run it!

$ sudo go run main.go

This is a point-to-point only interface. Use ifconfig to see its attributes. You need to bring it up and assign IP addresses (apparently replace utun2 if needed):

$ sudo ifconfig utun2 10.1.0.10 10.1.0.20 up

Now send some ICMP packets to the interface:

$ ping 10.1.0.20

You'd see the ICMP packets printed out:

2017/03/20 21:17:30 Interface Name: utun2
2017/03/20 21:17:40 Packet Received: 45 00 00 54 e9 1d 00 00 40 01 7d 6c 0a 01 00 0a 0a 01 00 14 08 00 ee 04 21 15 00 00 58 d0 a9 64 00 08 fb a5 08 09 0a 0b 0c 0d 0e 0f 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 30 31 32 33 34 35 36 37

Caveats

1. Only Point-to-Point user TUN devices are supported. TAP devices are not supported natively by macOS.
2. Custom interface names are not supported by macOS. Interface names are automatically generated serially, using the utun<#> naming convention.

TAP on Windows:

To use it with windows, you will need to install a tap driver, or OpenVPN client for windows.

It's compatible with the Linux code.

package main

import (
	"log"

	"github.com/songgao/packets/ethernet"
	"github.com/songgao/water"
)

func main() {
	ifce, err := water.New(water.Config{
		DeviceType: water.TAP,
	})
	if err != nil {
		log.Fatal(err)
	}
	var frame ethernet.Frame

	for {
		frame.Resize(1500)
		n, err := ifce.Read([]byte(frame))
		if err != nil {
			log.Fatal(err)
		}
		frame = frame[:n]
		log.Printf("Dst: %s\n", frame.Destination())
		log.Printf("Src: %s\n", frame.Source())
		log.Printf("Ethertype: % x\n", frame.Ethertype())
		log.Printf("Payload: % x\n", frame.Payload())
	}
}

Same as Linux version, but you don't need to bring up the device by hand, the only thing you need is to assign an IP address to it.

go run main.go

It will output a lot of lines because of some windows services and dhcp. You will need admin right to assign IP.

In a new cmd (admin right):

# Replace with your device name, it can be achieved by ifce.Name().
netsh interface ip set address name="Ehternet 2" source=static addr=10.1.0.10 mask=255.255.255.0 gateway=none

The main.go terminal should be silenced after IP assignment, try sending some ICMP broadcast message:

ping 10.1.0.255

You'll see output containing the IPv4 ICMP frame same as the Linux version.

Specifying interface name

If you are going to use multiple TAP devices on the Windows, there is a way to specify an interface name to select the exact device that you need:

	ifce, err := water.New(water.Config{
		DeviceType: water.TAP,
		PlatformSpecificParams: water.PlatformSpecificParams{
			ComponentID:   "tap0901",
			InterfaceName: "Ethernet 3",
			Network:       "192.168.1.10/24",
		},
	})

TODO

• tuntaposx for TAP on Darwin

Alternatives

tuntap: https://code.google.com/p/tuntap/

Documentation

Overview

Package water is a simple TUN/TAP interface library that efficiently works with standard packages like io, bufio, etc.. Use waterutil with it to work with TUN/TAP packets/frames.

Index

• Constants
• type Config
• type DeviceType
• type Interface
  • func New(config Config) (ifce *Interface, err error)
  • func NewInterface(name string, file io.ReadWriteCloser, isTAP bool) *Interface
  • func (ifce *Interface) IsTAP() bool
  • func (ifce *Interface) IsTUN() bool
  • func (ifce *Interface) Name() string
  • func (ifce *Interface) SetTunNetwork(network string) error
• type PlatformSpecificParams

Constants

const (
	TUN
	TAP
)

TUN and TAP device types.

Types

type Config

type Config struct {
	// DeviceType specifies whether the device is a TUN or TAP interface. A
	// zero-value is treated as TUN.
	DeviceType DeviceType

	// PlatformSpecificParams defines parameters that differ on different
	// platforms. See comments for the type for more details.
	PlatformSpecificParams
}

Config defines parameters required to create a TUN/TAP interface. It's only used when the device is initialized. A zero-value Config is a valid configuration.

type DeviceType

type DeviceType int

DeviceType is the type for specifying device types.

type Interface

type Interface struct {
	io.ReadWriteCloser
	// contains filtered or unexported fields
}

Interface is a TUN/TAP interface.

MultiQueue(Linux kernel > 3.8): With MultiQueue enabled, user should hold multiple interfaces to send/receive packet in parallel. Kernel document about MultiQueue: https://www.kernel.org/doc/Documentation/networking/tuntap.txt

func New

func New(config Config) (ifce *Interface, err error)

New creates a new TUN/TAP interface using config.

func NewInterface

func NewInterface(name string, file io.ReadWriteCloser, isTAP bool) *Interface

func (*Interface) IsTAP

func (ifce *Interface) IsTAP() bool

IsTAP returns true if ifce is a TAP interface.

func (*Interface) IsTUN

func (ifce *Interface) IsTUN() bool

IsTUN returns true if ifce is a TUN interface.

func (*Interface) Name

func (ifce *Interface) Name() string

Name returns the interface name of ifce, e.g. tun0, tap1, tun0, etc..

func (*Interface) SetTunNetwork

func (ifce *Interface) SetTunNetwork(network string) error

Name returns the interface name of ifce, e.g. tun0, tap1, tun0, etc..

type PlatformSpecificParams

type PlatformSpecificParams struct {
	// ComponentID associates with the virtual adapter that exists in Windows.
	// This is usually configured when driver for the adapter is installed. A
	// zero-value of this field, i.e., an empty string, causes the interface to
	// use the default ComponentId. The default ComponentId is set to tap0901,
	// the one used by OpenVPN.
	ComponentID string
	// InterfaceName is a friendly name of the network adapter as set in Control Panel.
	// Of course, you may have multiple tap0901 adapters on the system, in which
	// case we need a friendlier way to identify them.
	InterfaceName string
	// Network is required when creating a TUN interface. The library will call
	// net.ParseCIDR() to parse this string into LocalIP, RemoteNetaddr,
	// RemoteNetmask. The underlying driver will need those to generate ARP
	// response to Windows kernel, to emulate an TUN interface.
	// Please note that it cannot perceive the IP changes caused by DHCP, user
	// configuration to the adapter and etc,. If IP changed, please reconfigure
	// the adapter using syscall, just like openDev().
	// For detail, please refer
	// https://github.com/OpenVPN/tap-windows6/blob/master/src/device.c#L431
	// and https://github.com/songgao/water/pull/13#issuecomment-270341777
	Network string
}

PlatformSpecificParams defines parameters in Config that are specific to Windows. A zero-value of such type is valid.