Can anybody help me with understanding how IPFW works

[Hongying Liu]

Hi,

I think the packets is checked by using rules in kernel.
I am reading the code of IPFW. but I still can't understand
how the rules are passed from userland to kernel.

I found sysctl is used to pass some info. but I don't think
rules also are passed by using sysctl because there may be too
many data.

I also found raw socket is used in the userland source code.
is raw socket is used to pass rules from userland to kernel?

Thanks 

Liu