dnsharper

Small DNS server to lookup local network IPs by their MAC addresses.

Build

dnsharper is written in Go so to build it you need go compiler.

% go build

Run

To map IP to MAC address, dnsharper performs an ARP scan permanently. It means that it's required root privilege to run it.

You also might need to know which network interface you want to be scanned using ifconfig.

% ifconfig
en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
	options=400<CHANNEL_IO>
	inet 192.168.0.167 netmask 0xffffff00 broadcast 192.168.0.255
	nd6 options=201<PERFORMNUD,DAD>
	media: autoselect
	status: active
...
% sudo dnsharper en0
INFO[0010] Added IP 192.168.0.1 at ed-71-bd-20-aa-be.dnsharper.local
INFO[0010] Added IP 192.168.0.165 at 9f-1c-49-3b-22-f1.dnsharper.local
INFO[0010] Added IP 192.168.0.140 at 64-21-e7-96-ad-1f.dnsharper.local
INFO[0010] Added IP 192.168.0.182 at f1-9b-ad-a2-4e-d4.dnsharper.local
...

Suppose some machine in your local network is accessible at 192.168.0.1 and has the hardware address ed:71:bd:20:aa:be. Then it might be resolved from a ed-71-bd-20-aa-be.dnsharper.local domain name.

Lets open nslookup in a parallel terminal and test:

% nslookup
> server 127.0.0.1
> set port=5333
> ed-71-bd-20-aa-be.dnsharper.local
Server:		127.0.0.1
Address:	127.0.0.1#5333

Non-authoritative answer:
Name:	ed-71-bd-20-aa-be.dnsharper.local
Address: 192.168.0.1

For more options see dnsharper --help.

Setup

MacOS

You can integrate dnsharper to MacOS as a resolver. Create a file named /etc/resolver/dnsharper:

domain dnsharper.local
nameserver 127.0.0.1
port 5333

Test it:

% ping ed-71-bd-20-aa-be.dnsharper.local
PING ed-71-bd-20-aa-be.dnsharper.local (192.168.0.1): 56 data bytes
64 bytes from 192.168.0.1: icmp_seq=0 ttl=64 time=1.274 ms
64 bytes from 192.168.0.1: icmp_seq=1 ttl=64 time=1.265 ms
64 bytes from 192.168.0.1: icmp_seq=2 ttl=64 time=2.380 ms

dnsmasq

Open /etc/dnsmasq.conf (or /usr/local/etc/dnsmasq.conf in MacOS) and add the line:

server=/.dnsharper.local/127.0.0.1#5333