Hi, i've seen in several scripts the following configuration for

iptables criteria -j ACCEPT
iptables the_same_criteria_as_above -j RETURN

for instance:

iptables -A INPUT -p tcp -m tcp --dport 100 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 100 -j RETURN

The last rule will be never matched, since all tcp incoming
connections with a destination port equal to 100 will be accepted, and
thus this connection will be testing for the next chain. The last line
is useless. So, what's the utility of this configuration?.