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 how to deal with buffers; whether to use GC.

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

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 [10.0.0.1]
Destination: ff:ff:ff:ff:ff:ff [10.0.0.255]
Protocol:    1

Source:      42:35:da:af:2b:00 [10.0.0.1]
Destination: ff:ff:ff:ff:ff:ff [10.0.0.255]
Protocol:    1

Source:      42:35:da:af:2b:00 [10.0.0.1]
Destination: ff:ff:ff:ff:ff:ff [10.0.0.255]
Protocol:    1

TODO

• IPv6 Support in waterutil
• Darwin(Mac) Support

LICENSE

GNU LESSER GENERAL PUBLIC LICENSE Version 3

Alternatives

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