travelling the tables and chains...

[Guido Lorenzutti]

Hi people, i would like to clean up my firewall script by creating new 
chains in the filter table. Like this:

iptables -N FORWARD_WAN_TO_LAN

Then, call the traffic in the FORWARD chain:

iptables -A FORWARD -i $WAN -o $LAN -j FORWARD_WAN_TO_LAN

Now how can i discriminate the DNATed packets from that rule? It's OK if 
i MARK them in the PREROUTING chain and create a rule BEFORE in the 
FORWARD chain to check if the packet im MARKed then -j DNATED_WAN_TO_LAN?

Any better ideas?