## Allow PPTP control connections from WAN
iptables -t nat -A prerouting_rule -i $WAN -p tcp --dport 1723 -j ACCEPT
iptables        -A input_rule      -i $WAN -p tcp --dport 1723 -j ACCEPT

## Allow GRE protocol (used by PPTP data stream)
iptables        -A output_rule             -p 47               -j ACCEPT
iptables        -A input_rule              -p 47               -j ACCEPT

### VPN Section
iptables        -A forwarding_rule -s 192.168.1.0/24 -d 192.168.1.0/24 -j ACCEPT
iptables        -A output_rule     -o ppp+ -s 192.168.1.0/24 -d 192.168.1.0/24 -j ACCEPT
iptables        -A input_rule      -i ppp+ -s 192.168.1.0/24 -d 192.168.1.0/24 -j ACCEPT

# allow VPN connections to get out WAN interface (to internet)
iptables        -A forwarding_rule -i ppp+ -o $WAN -j ACCEPT