I would like to restrict outbound traffic to only localhost using iptables. I already have a default DROP policy on OUTPUT and a rule REJECTing all traffic. I need to add a rule above that in the OUTPUT chain.
I have seen a couple different examples for this type of rule, the most common being:
-A OUTPUT -o lo -j ACCEPT
-A OUTPUT -o lo -s 127.0.0.1 -d 127.0.0.1 -j ACCEPT
Is there any reason to use the latter rather than the former? Can packets on
lo have an address other than 127.0.0.1?