jamesbarlow/icmptunnel ? reverse-engineered prompt

Build me a small C command line tool that can tunnel IP traffic over ICMP echo request and reply packets, so I can use it to get through networks where ping still works.

I want it to run in a client mode and a server mode, create a TUN interface, and move packets between that interface and ICMP packets over the network. It should be reliable enough to work through stateful firewalls and NAT, not just a toy proof of concept. Please include a simple Makefile, a clear README with quick start instructions, and a help screen with the basic options.

It should be easy to set up on two Linux machines, where the server listens and the client connects to it, then I can assign IPs to the tunnel and use it for SSH or as a SOCKS proxy through SSH. If you need to, look up current docs online for TUN and ICMP handling details.