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.

NOTE: A new package packet has better arp spoofing support
This package is functional and useful for experimentation but all efforts going forward focus on packet which addresses many issues and in addition to arp spoofing it also support general packet mangling and dhcp4 and icmp6 spoofing.

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)}
	NIC := "eth0"
	HostMAC, _ := net.ParseMAC("xx:xx:xx:xx:xx:xx")
	HostIP := net.ParseIP("192.168.1.2").To4()

	c, err := arp.New(arp.Config{
		NIC:                     NIC,
		HostMAC:                 HostMAC,
		HostIP:                  HostIP,
		RouterIP:                HomeRouterIP,
		HomeLAN:                 HomeLAN,
		ProbeInterval:           time.Minute,
		FullNetworkScanInterval: 0,
	})
	if err != nil {
		log.Fatal("error ", err)
	}
	defer c.Close()

	go c.ListenAndServe(context.Background())

	c.printTable()

Listen to changes to mac table

New a message broker function

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

		}
	}
}

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

go arpNotification(arpChannel)

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)