root@OpenWrt:~# 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" is used to match packets that come in via the $WAN interface.
## it WILL NOT MATCH packets sent from the $WAN ip address -- you won't be able
## to see the effects from within the LAN.
### Open port to WAN
## -- This allows port 22 to be answered by (dropbear on) the router
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
## -- This forwards port 8080 on the WAN to port 80 on 192.168.1.2
# iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 8080 -j DNAT --to 192.168.1.2:80
# iptables -A forwarding_rule -i $WAN -p tcp --dport 80 -d 192.168.1.2 -j ACCEPT
iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 993 -j DNAT --to-destination 192.168.0.2
iptables -A forwarding_rule -i $WAN -p tcp --dport 993 -d 192.168.0.2 -j ACCEPT
iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 60000:60021 -j DNAT --to-destination 192.168.0.10
iptables -A forwarding_rule -i $WAN -p tcp --dport 60000:60021 -d 192.168.0.10 -j ACCEPT
iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 60022 -j DNAT --to 192.168.0.10:22
iptables -A forwarding_rule -i $WAN -p tcp --dport 22 -d 192.168.0.10 -j ACCEPT
iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 60023:60999 -j DNAT --to-destination 192.168.0.10
iptables -A forwarding_rule -i $WAN -p tcp --dport 60023:60999 -d 192.168.0.10 -j ACCEPT
iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 5900 -j DNAT --to-destination 192.168.0.10
iptables -A forwarding_rule -i $WAN -p tcp --dport 5900 -d 192.168.0.10 -j ACCEPT
### DMZ
## -- Connections to ports not handled above will be forwarded to 192.168.1.2
# iptables -t nat -A prerouting_rule -i $WAN -j DNAT --to 192.168.1.2
# iptables -A forwarding_rule -i $WAN -d 192.168.1.2 -j ACCEPT
root@OpenWrt:~# cat /etc/init.d/S35firewall
#!/bin/sh
## Please make changes in /etc/firewall.user
. /etc/functions.sh
WAN="$(nvram get wan_ifname)"
WANDEV="$(nvram get wan_device)"
LAN="$(nvram get lan_ifname)"
WDS="$(nvram get wds0_ifname)"
## CLEAR TABLES
for T in filter nat; do
iptables -t $T -F
iptables -t $T -X
done
iptables -N input_rule
iptables -N output_rule
iptables -N forwarding_rule
iptables -t nat -N prerouting_rule
iptables -t nat -N postrouting_rule
iptables -N LAN_ACCEPT
[ -z "$WAN" ] || iptables -A LAN_ACCEPT -i "$WAN" -j RETURN
[ -z "$WANDEV" -o "$WANDEV" = "$WAN" ] || iptables -A LAN_ACCEPT -i "$WANDEV" -j RETURN
iptables -A LAN_ACCEPT -j ACCEPT
### INPUT
### (connections with the router as destination)
# base case
iptables -P INPUT DROP
iptables -A INPUT -m state --state INVALID -j REJECT
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -p tcp --tcp-flags SYN SYN --tcp-option \! 2 -j REJECT
#
# insert accept rule or to jump to new accept-check table here
#
iptables -A INPUT -j input_rule
# allow
iptables -A INPUT -j LAN_ACCEPT # allow from lan/wifi interfaces
iptables -A INPUT -p icmp -j ACCEPT # allow ICMP
iptables -A INPUT -p gre -j ACCEPT # allow GRE
# reject (what to do with anything not allowed earlier)
iptables -A INPUT -p tcp -j REJECT --reject-with tcp-reset
iptables -A INPUT -j REJECT --reject-with icmp-port-unreachable
### OUTPUT
### (connections with the router as source)
# base case
iptables -P OUTPUT DROP
iptables -A OUTPUT -m state --state INVALID -j REJECT
iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
#
# insert accept rule or to jump to new accept-check table here
#
iptables -A OUTPUT -j output_rule
# allow
iptables -A OUTPUT -j ACCEPT #allow everything out
# reject (what to do with anything not allowed earlier)
iptables -A OUTPUT -p tcp -j REJECT --reject-with tcp-reset
iptables -A OUTPUT -j REJECT --reject-with icmp-port-unreachable
### FORWARDING
### (connections routed through the router)
# base case
iptables -P FORWARD DROP
iptables -A FORWARD -m state --state INVALID -j REJECT
iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
#
# insert accept rule or to jump to new accept-check table here
#
iptables -A FORWARD -j forwarding_rule
# allow
iptables -A FORWARD -i $LAN -o $LAN -j ACCEPT
iptables -A FORWARD -i $WDS -o $LAN -j ACCEPT
iptables -A FORWARD -i $LAN -o $WDS -j ACCEPT
iptables -A FORWARD -i $LAN -o $WAN -j ACCEPT
# reject (what to do with anything not allowed earlier)
# uses the default -P REJECT
### MASQ
iptables -t nat -A PREROUTING -j prerouting_rule
iptables -t nat -A POSTROUTING -j postrouting_rule
iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE
## USER RULES
[ -f /etc/firewall.user ] && . /etc/firewall.user
[ -e /etc/config/firewall ] && {
awk -f /usr/lib/common.awk -f /usr/lib/firewall.awk /etc/config/firewall | ash
}