i'm pretty sure i recall reading somewhere that the INPUT vs. FORWARD decision is solely based on IP, not interface. so even though conceptually it seems as though the packet would be "forwarded" from eth1 to eth0, it's still just an INPUT packet, as it is destined for a local IP (172.16.12.130)... the "IN=" in a log entry should still show eth1, i think...
You are pretty right about that one. If packet is to be delivered to the local process, it will end up in INPUT chain. Decision is not made based upon interfaces or addresses, it is purely made based on whether or not packet will be delivered to local process, or forwarded to another (or same) interface. This is because all the packets from all interfaces first go to the PREROUTING chain of nat table, after that routing decisions are made, and after that if packet is to be "routed" to local process it goes to INPUT chain of filter table, otherwise it goes to FORWARD chain of filter table and than to POSTROUTING chain of nat table and to the physical interface. So, once packet ends up in FORWARD chain, kernel has already made decision through which interface it will be sent out, and there is no way back.
Jim Cliver has a nice diagram showing all this (one image is worth thousands of words):
http://www.aptalaska.net/~jclive/IPTablesFlowChart.pdf
-- Aleksandar Milivojevic <amilivojevic@xxxxxx> Pollard Banknote Limited Systems Administrator 1499 Buffalo Place Tel: (204) 474-2323 ext 276 Winnipeg, MB R3T 1L7
