iptables -A FORWARD -j forwarding_rule
# allow
- iptables -A FORWARD -i br0 -o br0 -j ACCEPT
+ iptables -A FORWARD -i $LAN -o $LAN -j ACCEPT
[ -z "$WAN" ] || iptables -A FORWARD -i $LAN -o $WAN -j ACCEPT
# reject (what to do with anything not allowed earlier)