if you compile 1.3.96 with firewalling enabled, when firewall.c
includes skbuff.h it complains about tons of things, the first one
being that __u32 is undefined.
what i did to fix it was add the following statement to
linux/skbuff.h at the appropriate place:
#include <asm/types.h>
if necessary, i can send a patch, but it's probably not necessary
for something this trivial :-)
mark