I've tried to patch the kernel in order to use the iptables -m layer7 classifier.

I followed the instructions from http://l7-filter.sourceforge.net/L7-HOWTO-Netfilter
1. download the kernel
2. apply the patch to the kernel
3. Compile + install the kernel
4. Boot with the new kernel
5. Download, patch and install iptables

Now when I try something like:

iptables -t mangle -A POSTROUTING -m layer7 --l7proto http -j MARK --set-mark 1
I get:
iptables v1.3.2: Couldn't load match `layer7':/usr/local/lib/iptables/libipt_layer7.so: cannot open shared object file: No such file or directory
I've searched on my system and there is no libipt_layer7.so file (or *layer7*).
What did I do wrong? The distro is slack 10.1

Thanks for your help.