NAT traversal

Hi all,

I've been using the firewall/router from firestarter.sourceforge.net for
long time now and am still very happy about it. It is not a separate
firewall linux distro, but a program you can run on any running linux
machine, which I prefer.

Yet it has a few things I miss. My question is: does anybody know a firewall
program that is similar to firestarter but has:
NAT Traversal through uPnP. This way the linux machine will show as internet
gateway at the XP machines. This has the great advantage that people can
manage port forwarding from their own machine, which makes playing online
games and using messenger a lot easier.

Thanx in advance.

Daniel