transparent proxy with squid-2.2S4 on freebsd v3.2R

I am unable to go past the ./configure step when the directive
transparent proxying is enabled. It gives the following error:

[...many lines...]
checking if IP-filter header files are installed ... no
WARNING: Cannot find necessary IP-filter header files
                Transparent proxy support WILL NOT be enabled
[...many lines...]

I have recompiled the kernel with
options IPFIREWALL
options IPFIREWALL_FORWARD
options IPFIREWALL_DEFAULT_TO_ACCEPT

I've read the http://www.squid-cache.org/Doc/FAQ/FAQ-17.html
and it says that FreeBSD v3.x distribution comes with the necessary
files. What am I missing here?

Thanks in advance!

Regards

----
Dan Larsson ( mailto:dan@junglenote.com )