I've never did get this working, but there are some prehistoric drivers in the Linux kernel that support MacIP (?), which will allow you to route TCP/IP over AppleTalk networks. If you want to use it, expect to do some searching for online documentation, online source code, compiling the source code, and potentially patching the source code. (That, or I was going about things the wrong way.)
FWIW, this is either independent of or in conjunction with Netatalk. So don't expect installing Netatalk to solve the problem. Netatalk only provides AppleTalk file sharing and network printer support -- not TCP/IP tunneling.