detect original chain after jump?

[Richard Hector <rhector@paradise.net.nz>]

Hi,

Mostly, people seem to write their filter chains splitting first by
interface and/or address, then by protocol/port.

I'm experimenting with doing it the other way round: I want to process
all the ssh traffic in one chain, then all the smtp in another etc.

This means that early on, I have something like:

iptables -A INPUT -j protocol
iptables -A FORWARD -j protocol

iptables -A protocol -p tcp --dport 22 -j ssh

But then I get a bit stuck. I need to then do different things depending
on the source and destination - which includes whether this packet is
arriving locally or being forwarded. Therefore it would be useful to
know whether this packet started out in the INPUT or FORWARD chain - but
that info seems to have been lost with the jump.

Is there any way to regain that?

Many thanks,

Richard