#!/bin/bash
#allow a dyndns name

HOSTNAME=HOST_NAME_HERE
LOGFILE=LOGFILE_NAME_HERE
PORT=22

Current_IP=$(dig +short $HOSTNAME)

if [ ! -f $LOGFILE ] ; then
  ufw allow from $Current_IP proto tcp to any port $PORT
  echo $Current_IP > $LOGFILE
else

  Old_IP=$(cat $LOGFILE)

  if [ "$Current_IP" = "$Old_IP" ] ; then
    echo IP address has not changed
  else
    ufw delete allow from $Old_IP proto tcp to any port $PORT
    ufw allow from $Current_IP proto tcp to any port $PORT
    echo $Current_IP > $LOGFILE
    echo ufw have been updated
  fi
fi