Logging all packets going past an interface when masquerading

Logging all packets going past an interface when masquerading

[David Cannings]

Hi,

I've created a chain called COUNTER with rules that have no target.  It's 
purpose is to simply count packets as they go past interfaces.  The rules 
in it are created like so:

iptables -A COUNTER -i eth0

I send all packets from the chains INPUT and OUTPUT to this chain and the 
counters increment as desired.  This works absolutely fine.  However, the 
machine I am running this on is using masquerading.  If I also link to 
the COUNTER chain from FORWARD, like..

iptables -I FORWARD -j COUNTER

.. it appears that masqueraded packets are also accounted for.  Is this 
the case though?  By the looks of some crude tests, it seems that the 
packet counts/bytes are correct but I'd just like some confirmation that 
this is the case and I don't have to also use the PREROUTING/POSTROUTING 
in order to count packets coming from the LAN (eth0) and going out across 
my ATM link.

Thanks,

David
david [at] edeca [dot] net