arp golang

The package implements a user level arp table management in golang that monitor the local network for ARP changes and provide notifications when a MAC switch between online and offline.

Force IP address change (IP spoofing)

The most useful function is to force an IP address change by claiming the IP of a target MAC. It achieves this by persistently claiming the IP address using ARP request/reply and activelly hunting the target MAC until it gives up its IP. This is very effective against mobile devices using DHCP however it does not work when client is using static address.

The package uses low level arp packets to enable:

• network discovery by polling 254 addresses
• notification when a MAC switch between online and offline
• forced IP address change

See the arplistener example for how to use it.

Limitations

• Tested on linux (Raspberry PI arm). Should work on Windows with tiny changes.
• IPv4 only

Getting started

	$ go get github.com/irai/arp
	$ cd $GOPATH/src/github.com/irai/arp/arplistener
	$ go install
	$ sudo $GOPATH/bin/arplistener -i eth0

Create your own listener in a goroutine

Simply create a new handler and run ListenAndServe in a goroutine. The goroutine will listen for ARP changes and generate a notification each time a mac changes between online/offline.

	HomeRouterIP := net.ParseIP("192.168.0.1").To4()
	HomeLAN := net.IPNet{IP: net.ParseIP("192.168.0.0").To4(), Mask: net.CIDRMask(25, 32)}

	c, err := arp.NewHandler(NIC, HostMAC, HostIP, HomeRouterIP, HomeLAN)
	if err != nil {
		log.Fatal("error ", err)
	}

	go c.ListenAndServe(time.Second * 30 * 5)

	c.printTable()

Listen to changes to mac table

    arpChannel := make(chan arp.MACEntry, 16)
	c.AddNotificationChannel(arpChannel)

	go arpNotification(arpChannel)

func arpNotification(arpChannel chan arp.MACEntry) {
	for {
		select {
		case MACEntry := <-arpChannel:
			log.Warnf("notification got ARP MACEntry for %s", MACEntry.MAC)

		}
	}
}

To force an IP change simply invoke ForceIPChange with the current mac and ip value.

	MACEntry := c.findByMAC("xx:xx:xx:xx:xx:xx")
	c.ForceIPChange(MACEntry.MAC, MACEntry.IP)