Ip Address resolution using Mac Address programatically

Question

I am writing a discovery program, written in C++ that will run on linux, to enable me to determine if certain devices are connected to the network. I have the Mac Address of the other devices and I need to resolve their Ip Addresses.

I have checked /proc/net/arp and the devices don't appear. I tried pinging the broadcast address and this doesn't reach the target and therefore the ARP cache is not updated. However, if I ping the ip address directly it is (but this is not an option).

Also, the devices can be configured with either static ips or can get them via dhcp.

Is there any way that I can determine the ip addresses given the Mac addresses?

Answer 1

Some years ago I'd have suggested to use RARP but it is not supported by Linux kernel any more. Unless there is already a solution I would suggest you the following home-made solution:

-You can use Packet sockets to implement your own Layer 2 protocol: instead of using IP as payload of the Ethernet frame you can select your own protocol code (for example: instead of 0x0800 for IP use 0xABAB, always a number greater than 1536)

-In each node you implement a simple server that use packet socket to read the frames with that protocol code or you could use pcap, as you prefer.

-Whenever you need the IP address of another node you send an Ethernet frame to that MAC address. The server will read the new frame and respond with another frame conveying its own IP address.

-If you choose this solution please remember the payload has to be at least 46 Bytes long, so you may need to use padding. Also you can use the TLV (type length value) format for your own protocol.

Read this:

http://en.wikipedia.org/wiki/Ethernet_frame

http://man7.org/linux/man-pages/man7/packet.7.html

I hope this helps.