Here goes a very specific question about the insides of Shorewall and Iptables in general.

Shorewall supports configuration of "Stopped Policies" using the file routestopped, which defines the behaviour of the firewall when Shorewall is stopped. This works very well, but there is a parameter that we can configure in the options called "routeback" which according to the documentation enables the "traffic from a host back to itself". I'm trying to understand this option and a case where it could be applied but honestly i just don't see a use case for this option.

I've checked the Iptables rules before and after applying this option, and these 3 rules are additionally added when the option routeback is activated (for the 3 hosts i've configured):

-A FORWARD -s -d -i eth0 -o eth0 -c 0 0 
-A FORWARD -s -d -i eth0 -o eth0 -c 0 0 
-A FORWARD -s -d -i eth0 -o eth0 -c 0 0 

I'm not really an expert in Iptables, but i've read the documentation and it says that when the -j (ACTION) parameter is missing, Iptables doesn't do anything with the packet, it just adds the counters.

So this option is kind of useless in my opinion. Does anyone knows a use case for this option?


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