High Availability Tunnel

HATunnel is small application that establishes network tunnel with packet-level redundancy.
It is designed to allow working on very unreliable wireless connections, with a lot of dropped packets.
HATunnel is sending each packet multiple times to make correct delivery more probable.
Simple math says that if you have network connection that drops 20% of packets (quite unusable without hatunnel):

• just one duplication of each packet will give you line with only 4% of lost packets - with 1/2 of available bandwidth
• tripling each packet will give you 0.8% of lost packets which is completely OK for browsing web, ssh and other simple services

Of course real world is not so simple. In reality by sending more packets you can crowd the air - making packet loss higher. Surprisingly my own tests achieved much better results than simple theory :) That may be caused by (configurable) time-dispersion of duplicate sending in hatunel and specific nature of wireless packet losing.

To use hatunel you need kernel with TUN support. You also need working pthreads library.

compilation:
gcc hatun.c -lpthread -lrt -o hatunel

usage:
./hatunel listenaddress listenport remoteaddress remoteport numberof_duplicates timedispersion

NOTICE:
hatunel is used by nobody currently so it’s not finished. It’s basically one big memory leak. If you are using it - please tell me - I’ll make it better.