+START=45
+start() {
+ include /lib/network
+ scan_interfaces
+
+ config_get WAN wan ifname
+ config_get WANDEV wan device
+ config_get LAN lan ifname
+
+ ## CLEAR TABLES
+ for T in filter nat; do
+ iptables -t $T -F
+ iptables -t $T -X
+ done
+
+ iptables -N input_rule
+ iptables -N input_wan
+ iptables -N output_rule
+ iptables -N forwarding_rule
+ iptables -N forwarding_wan
+
+ iptables -t nat -N prerouting_rule
+ iptables -t nat -N prerouting_wan
+ iptables -t nat -N postrouting_rule
+
+ iptables -N LAN_ACCEPT
+ [ -z "$WAN" ] || iptables -A LAN_ACCEPT -i "$WAN" -j RETURN
+ [ -z "$WANDEV" -o "$WANDEV" = "$WAN" ] || iptables -A LAN_ACCEPT -i "$WANDEV" -j RETURN
+ iptables -A LAN_ACCEPT -j ACCEPT
+
+ ### INPUT
+ ### (connections with the router as destination)
+
+ # base case
+ iptables -P INPUT DROP
+ iptables -A INPUT -m state --state INVALID -j DROP
+ iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
+ iptables -A INPUT -p tcp --tcp-flags SYN SYN --tcp-option \! 2 -j DROP
+
+ #
+ # insert accept rule or to jump to new accept-check table here
+ #
+ iptables -A INPUT -j input_rule
+ [ -z "$WAN" ] || iptables -A INPUT -i $WAN -j input_wan
+
+ # allow
+ iptables -A INPUT -j LAN_ACCEPT # allow from lan/wifi interfaces
+ iptables -A INPUT -p icmp -j ACCEPT # allow ICMP
+ iptables -A INPUT -p gre -j ACCEPT # allow GRE
+
+ # reject (what to do with anything not allowed earlier)
+ iptables -A INPUT -p tcp -j REJECT --reject-with tcp-reset
+ iptables -A INPUT -j REJECT --reject-with icmp-port-unreachable
+
+ ### OUTPUT
+ ### (connections with the router as source)
+
+ # base case
+ iptables -P OUTPUT DROP
+ iptables -A OUTPUT -m state --state INVALID -j DROP
+ iptables -A OUTPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
+
+ #
+ # insert accept rule or to jump to new accept-check table here
+ #
+ iptables -A OUTPUT -j output_rule
+
+ # allow
+ iptables -A OUTPUT -j ACCEPT #allow everything out
+
+ # reject (what to do with anything not allowed earlier)
+ iptables -A OUTPUT -p tcp -j REJECT --reject-with tcp-reset
+ iptables -A OUTPUT -j REJECT --reject-with icmp-port-unreachable
+
+ ### FORWARDING
+ ### (connections routed through the router)
+
+ # base case
+ iptables -P FORWARD DROP
+ iptables -A FORWARD -m state --state INVALID -j DROP
+ iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu
+ iptables -A FORWARD -m state --state RELATED,ESTABLISHED -j ACCEPT
+
+ #
+ # insert accept rule or to jump to new accept-check table here
+ #
+ iptables -A FORWARD -j forwarding_rule
+ [ -z "$WAN" ] || iptables -A FORWARD -i $WAN -j forwarding_wan
+
+ # allow
+ iptables -A FORWARD -i $LAN -o $LAN -j ACCEPT
+ [ -z "$WAN" ] || iptables -A FORWARD -i $LAN -o $WAN -j ACCEPT
+
+ # reject (what to do with anything not allowed earlier)
+ # uses the default -P DROP
+
+ ### MASQ
+ iptables -t nat -A PREROUTING -j prerouting_rule
+ [ -z "$WAN" ] || iptables -t nat -A PREROUTING -i "$WAN" -j prerouting_wan
+ iptables -t nat -A POSTROUTING -j postrouting_rule
+ [ -z "$WAN" ] || iptables -t nat -A POSTROUTING -o $WAN -j MASQUERADE
+
+ ## USER RULES
+ [ -f /etc/firewall.user ] && . /etc/firewall.user
+ [ -n "$WAN" -a -e /etc/config/firewall ] && {
+ export WAN
+ awk -f /usr/lib/common.awk -f /usr/lib/firewall.awk /etc/config/firewall | ash
+ }
+}