Linux device drivers

[Doug Winterburn]

I'm playing around with the snull network driver from the O'Reilly
"Linux Device Drivers" book.  I'm working on RH 6.2, and had to hack
slightly on the driver.  It appears to work - except it doesn't respond
to pings and I can't make connections (telnet) through it.  tcpdump
shows the receiving interface (eth2) getting the data from the sending
interface (eth1) with proper ip headers.

The original was based on the 2.1 kernel and of course, RH6.2 is 2.2. 
Anyone played with this or know what I might look at next?

Thanks,

-Doug Winterburn