water

water is a native Go library for TUN/TAP interfaces. It's designed to be simple and scalable. water wraps almost only syscalls and uses only Go standard types, so it plays well with standard packages like io, bufio, etc.

water/waterutil has some useful functions to interpret MAC farme headers and IP packet headers.

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/waterutil

Example

package main

import (
	"github.com/songgao/water"
	"github.com/songgao/water/waterutil"
	"fmt"
)

const BUFFERSIZE = 1522

func main() {
	ifce, err := water.NewTAP("")
	fmt.Printf("%v, %v\n\n", err, ifce)
	buffer := make([]byte, BUFFERSIZE)
	for {
		_, err = ifce.Read(buffer)
		if err != nil {
			break
		}
		ethertype := waterutil.MACEthertype(buffer)
		if ethertype == waterutil.IPv4 {
			packet := waterutil.MACPayload(buffer)
			if waterutil.IsIPv4(packet) {
				fmt.Printf("Source:      %v [%v]\n", waterutil.MACSource(buffer), waterutil.IPv4Source(packet))
				fmt.Printf("Destination: %v [%v]\n", waterutil.MACDestination(buffer), waterutil.IPv4Destination(packet))
				fmt.Printf("Protocol:    %v\n\n", waterutil.IPv4Protocol(packet))
			}
		}
	}
}

This piece of code creates a TAP interface, and prints some header information for every IPv4 packet. After pull up the main.go, you'll need to bring up the interface and assign IP address. All of these need root permission.

sudo go run main.go

sudo ip link set dev tap0 up
sudo ip addr add 10.0.0.1/24 dev tap0

Now, try sending some ICMP broadcast message:

ping -b 10.0.0.255

You'll see the main.go print something like:

<nil>, &{true 0xf84003f058 tap0}

Source:      42:35:da:af:2b:00 [10.10.10.1]
Destination: ff:ff:ff:ff:ff:ff [10.10.10.255]
Protocol:    1

Source:      42:35:da:af:2b:00 [10.10.10.1]
Destination: ff:ff:ff:ff:ff:ff [10.10.10.255]
Protocol:    1

Source:      42:35:da:af:2b:00 [10.10.10.1]
Destination: ff:ff:ff:ff:ff:ff [10.10.10.255]
Protocol:    1