Packet traversal when tunneling

[Steffen Bloedt]

Hello all,

I am currently working on policy routing and tunneling and I discovered
a strange behavior. I am using iptables 1.2.1 with kernel 2.4.4 (with
FTOS patch). Under
 
http://www.knowplace.org/netfilter/ipt_flow_mirror.html

I found the a very good diagram about the packet traversal. This diagram
is not true when I am tunneling packets (ip tunnel ...). The packets go
the following way:

PREROUTING -> IN-ROUTE -> FORWARD -> Encapsulator -> OUTPUT -> OUT-Route

I think this is very strange. The packets go directly from the
FORWARD-chain to the encapsulator. Is the encapsulator a sort of local
process? The packets don't cross the POSTROUTING-chain!!! Why?

I discovered this behavior by dropping special packets in different
chains. Maybe I made a mistake. Is there a more complete diagram that
shows the packet traversal when tunneling packets?

TIA
	Steffen

-- 
Steffen Bloedt                       Ericsson Eurolab Deutschland GmbH
Steffen.Bloedt@eed.ericsson.se                          D-52072 Aachen