Add Rules from Within the Kernel -- Where to Start?

Add Rules from Within the Kernel -- Where to Start?

[Yacin Nadji]

Howdy list!

I'm working on a research project where I'd like to be able to
create/update iptables entries from within kernel-space instead of the
usual route through user-space (with the client iptables). The idea is
to have a separate rule set that can only be altered by the kernel,
and not by the normal iptables client in user-space. I've looked
around the documentation, but the majority of it seems focused on
adding extensions that would operate in userland.

My question is, where should I look for this functionality in
netfilter/the kernel? I was originally planning on tracing the calls
up into the kernel through the client iptables to see what kernel
functions end up being called, but things got pretty muddy for me as
it passed through libiptc/tipc. Any suggestions on where to look to
achieve iptables-like functionality entirely within the kernel would
be much appreciated.

Thanks!

Yacin