Questions regarding routing in the stack

[JC <bikkit@gmail.com>]

I was hoping someone could possibly shed some light into this or at
least point me to the right direction...

I am trying to develop a kernel module level solution for dynamic host
multihoming. This requires that I mangle packets from specific
applications running on the system right in the stack and basically
change the interface the packets are sent from (at least two
interfaces).

I understand that I need to register my mangling function with one of
the 5 netfilter hooks (the ROUTING one?), grab the interesting packets
and change..... something in the skbuff.

What really evades me is where/when does routing *exactly* happen. If
I know at which point it happens, I should tap right after it and
change the interface to the one I want. Or this whole idea could be
bad and I end up breaking something in the
packet and it gets dropped...

Of course, that needs to happen for both locally generated traffic and
incoming traffic, so that I link the incoming packets to the right
applications.

regards,
JC