root@link:~# cat /etc/firewall.user
#!/bin/sh
. /etc/functions.sh

WAN=$(nvram get wan_ifname)
LAN=$(nvram get lan_ifname)

iptables -F input_rule
iptables -F output_rule
iptables -F forwarding_rule
iptables -t nat -F prerouting_rule
iptables -t nat -F postrouting_rule

### BIG FAT DISCLAIMER
### The "-i $WAN" literally means packets that came in over the $WAN interface;
### this WILL NOT MATCH packets sent from the LAN to the WAN address.

### Allow SSH on the WAN interface
# iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 22 -j ACCEPT
# iptables        -A input_rule      -i $WAN -p tcp --dport 22 -j ACCEPT

### Port forwarding
iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 80 -j DNAT --to 192.168.10.3
iptables        -A forwarding_rule -i $WAN -p tcp --dport 80 -d 192.168.10.3 -j ACCEPT
iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 8080 -j DNAT --to 192.168.10.3
iptables        -A forwarding_rule -i $WAN -p tcp --dport 8080 -d 192.168.10.3 -j ACCEPT