[e2e] IP puzzle implementation

[Wu-chang Feng]

For those who are interested, we've released a netfilter/iptables 
implementation of our IP layer puzzle system at...

  http://sourceforge.net/projects/ippuzzles

The code was used in evaluating the hint-based hash reversal scheme 
described in the paper below....

  Wu-chang Feng, Ed Kaiser, Wu-chi Feng, Antione Luu
  "The Design and Implementation of Network Puzzles"
  IEEE INFOCOM 2005.

Wu