Netfilter uses u_intXX_t types in it's headers shared with userspace. 
Some patch
added uXX types to a header, but iptables userspace doesn't know these 
types. This
breaks compilation with recent kernels. I know netfilter shouldn't use 
these types
in headers shared with userspace, but it currently does so in all files, 
so the
simple fix is to replace uXX by u_intXX_t.