ipt_set_udp

#!/bin/bash
# ipt-kit: ipt_set_udp
# Copyright (c) 2014, phiLLip maDDux II (foospidy)
# GNU GENERAL PUBLIC LICENSE
# https://github.com/foospidy/ipt-kit/blob/master/LICENSE#

whoami=`whoami`

if [ 'root' != $whoami ];
then
	echo manage_ports must be run as root, run this command again as root, or sudo manage_ports.
	exit;
fi

iptables=`which iptables`

if [ -z $iptables ];
then
	echo iptables not found, install iptables and try again.
	exit;
fi

usage ()
{
	echo "usage: ipt_set_tcp <source port> <destination port> [interface]"
}

if [ -z $1 ];
then
	usage
	exit;
fi

if [ -z $2 ];
then
	usage
	exit;
fi

if [ -z $3 ];
then
	interface=eth0
else
	interface=$3
fi

if [[ ! $1 =~ ^[0-9]+$ ]];
then
	usage
	exit;
fi

if [[ ! $2 =~ ^[0-9]+$ ]];
then
	usage
	exit;
fi

if (( $1 > 1024 ));
then
	echo "You only need to redirect low ports, $1 is not a low port."
	exit;
fi

echo
echo

iptables -t nat -A PREROUTING -i $interface -p udp --dport $1 -j REDIRECT --to-port $2

iptables-save

iptables -t nat -L -n -v

echo