easy to use but powerful iptables stateful firewall (docs)

 FireHOL generates generic firewalls with an extremely simple but powerful
 configuration language based on bash, enabling you to design any kind of
 local or routing stateful packet filtering firewall with ease.
 .
 FireHOL is the firewall counterpart of the FireQOS traffic shaper;
 both FireHOL and FireQOS support IPv4 and IPv6.
 .
 This package contains documentation and examples.