iptables_update.sh

#!/bin/bash
function valid_ip()
{
    local  ip=$1
    local  stat=1

    if [[ $ip =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
        OIFS=$IFS
        IFS='.'
        ip=($ip)
        IFS=$OIFS
        [[ ${ip[0]} -le 255 && ${ip[1]} -le 255 \
            && ${ip[2]} -le 255 && ${ip[3]} -le 255 ]]
        stat=$?
    fi
    return $stat
}

HOSTNAME=YOUR.DNS.NAME.HERE
if [[ $EUID -ne 0 ]]; then
   echo "This script must be run as root"
   exit 1
fi

new_ip=$(host $HOSTNAME | head -n1 | cut -f4 -d ' ')
old_ip=$(/usr/sbin/ufw status | grep $HOSTNAME | head -n1 | tr -s ' ' | cut -f3 -d ' ')

if ! valid_ip $new_ip;
then
   exit 1
fi


if [ "$new_ip" = "$old_ip" ] ; then
    exit 0
else
    if [ -n "$old_ip" ] ; then
        /usr/sbin/ufw delete allow from $old_ip to any port 22,6556 proto tcp
    fi
    /usr/sbin/ufw allow from $new_ip to any port 22,6556 proto tcp comment $HOSTNAME
    echo "Se ha modificado iptables por cambio de ip $new_ip"
    exit 0
fi