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https://github.com/songgao/water

A simple TUN/TAP library written in native Go.
https://github.com/songgao/water

go networking tap tun

Last synced: 24 days ago
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A simple TUN/TAP library written in native Go.

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# water



`water` is a native Go library for [TUN/TAP](http://en.wikipedia.org/wiki/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](http://godoc.org/github.com/songgao/water)



## Example



### TAP on Linux:



```go

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.



```bash

sudo go run main.go

```



In a new terminal:



```bash

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:

```bash

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



```go

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!



```bash

$ 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):



```bash

$ sudo ifconfig utun2 10.1.0.10 10.1.0.20 up

```



Now send some ICMP packets to the interface:



```bash

$ 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](https://github.com/OpenVPN/tap-windows6), or [OpenVPN client](https://github.com/OpenVPN/openvpn) for windows.



It's compatible with the Linux code.



```go

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.



```dos

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):



```dos

# 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:



```dos

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:



```go

	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/](https://code.google.com/p/tuntap/)