ipchains script (Score 1)

Here's a script that I use...
sccomp is the computer that you're playing starcraft on
gwcomp is the linux computer
gwcompex is the internet IP of your linux computer

You must have ipportfw support compiled in your kernel, or loaded as a module for this to work, and you might need to grab ipmasqadm from somewhere....
#!/bin/sh
sccomp=192.168.0.2
gwcomp=192.168.0.1
gwcompex=216.102.231.2
ipmasqadm portfw -a -P tcp -L $sccomp 6112 -R $gwcomp 6112
ipmasqadm portfw -a -P tcp -L $gwcompex 6112 -R $gwcomp 6112
ipmasqadm portfw -a -P udp -L $sccomp 6112 -R $gwcomp 6112
ipmasqadm portfw -a -P udp -L $gwcompex 6112 -R $gwcomp 6112