#!/bin/sh

EXTIF=eth0
INTIF=eth1
INTIF2=wlan0

# delete all existing rules
iptables -F
iptables -t nat -F
iptables -t mangle -F
iptables -X

# Always accept loopback traffic
iptables -A INPUT -i lo -j ACCEPT

# Allow established connections, and those not coming from the outside
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -m state --state NEW -i $INTIF -j ACCEPT
iptables -A INPUT -m state --state NEW -i $INTIF2 -j ACCEPT
iptables -A FORWARD -i $EXTIF -o $INTIF -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A FORWARD -i $EXTIF -o $INTIF2 -m state --state ESTABLISHED,RELATED -j ACCEPT

# Allow outgoing connections from the LAN side
iptables -A FORWARD -i $INTIF -o $EXTIF -j ACCEPT
iptables -A FORWARD -i $INTIF2 -o $EXTIF -j ACCEPT

# Connect LANs
iptables -A FORWARD -i $INTIF -o $INTIF2 -j ACCEPT
iptables -A FORWARD -i $INTIF2 -o $INTIF -j ACCEPT

# Masquerade
iptables -t nat -A POSTROUTING -o $EXTIF -j MASQUERADE

# Don't forward from the outside to the inside
iptables -A FORWARD -i $EXTIF -o $EXTIF -j REJECT
iptables -A FORWARD -i $EXTIF -o $INTIF -j REJECT # masked for ssh to LAN
iptables -A FORWARD -i $EXTIF -o $INTIF2 -j REJECT # masked for ssh to LAN

# MTU
iptables -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu

echo 1 > /proc/sys/net/ipv4/ip_forward

for f in /proc/sys/net/ipv4/conf/*/rp_filter ; do echo 1 > $f ; done