#!/bin/bash
while getopts a: opt; do
  case $opt in
    a)
      ADDRESS="$OPTARG"
      ;;
    \?)
      echo "Invalid option -$OPTARG. usage: test -a [ipaddress]." 
      exit 1
      ;;
    :)
      echo "Option -$OPTARG" 
      exit 1
      ;;
  esac
done
if [ -z "$ADDRESS" ]; then 
  echo "usage: test -a [ipaddress]"
  exit 1; 
fi

#setup the new eth1
cat ./interface >> /etc/network/interfaces
ifup eth1

#clear the tables
iptables -F
iptables -t nat -F POSTROUTING
iptables -t nat -F PREROUTING

#Enable forwarding
iptables -A FORWARD -o eth0 -i eth1 -s 192.168.1.0/24 -m conntrack --ctstate NEW -j ACCEPT
iptables -A FORWARD -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT

#Enable outgoing NAT (MAQUERADE is for dyanmic IPs but I want this script to work for anyone
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

iptables -t nat -A PREROUTING -i eth0 -p tcp -d $ADDRESS --sport 1024:65535 --dport 3389 -j DNAT --to-destination 192.168.1.2
iptables -t nat -A PREROUTING -i eth0 -p tcp -d $ADDRESS --sport 1024:65535 --dport 3390 -j DNAT --to-destination 192.168.1.3:3389
iptables -t nat -A PREROUTING -i eth0 -p tcp -d $ADDRESS --sport 1024:65535 --dport 3391 -j DNAT --to-destination 192.168.1.4:3389
iptables -t nat -A PREROUTING -i eth0 -p tcp -d $ADDRESS --sport 1024:65535 --dport 3392 -j DNAT --to-destination 192.168.1.5:3389
iptables -t nat -A PREROUTING -i eth0 -p tcp -d $ADDRESS --sport 1024:65535 --dport 3393 -j DNAT --to-destination 192.168.1.6:3389
iptables -t nat -A PREROUTING -i eth0 -p tcp -d $ADDRESS --sport 1024:65535 --dport 3394 -j DNAT --to-destination 192.168.1.7:3389
iptables -t nat -A PREROUTING -i eth0 -p tcp -d $ADDRESS --sport 1024:65535 --dport 3395 -j DNAT --to-destination 192.168.1.8:3389

#Save the configuration
iptables-save > /etc/iptables.sav

#enable forwarding now
echo 1 > /proc/sys/net/ipv4/ip_forward

#enable forwarding when rebooted
sed -i 's/#net.ipv4.ip_forward=1/net.ipv4.ip_forward=1/g' /etc/sysctl.conf
sed -i 's@# By default this script does nothing.@iptables-restore < /etc/iptables.sav@g' /etc/rc.local