#!/bin/sh
#
# DynDNS script for automating update of entries
#
# http://www.baszerr.eu/doku.php/prjs/dyndns_update
#

# configuration
USER="abc"
PASS="def"
DOMAIN="$USER.dyndns.org"

# metchod of getting current IP; this one's valid for OpenWRT/Backfire
#IP="`ifconfig  eth0.1 | grep addr: | sed 's#^ *inet addr:##' | sed 's# .*##'`"

# this workd in general case - IP is obtained via dyndns' page
IP="`wget -q -O - http://checkip.dyndns.com | sed 's%.*ddress: \([0-9\.]\+\).*%\1%'`"
if echo "$IP" | grep -q "[^0-9\.]"
then
  echo "$0: cannot obtain IP address (got: $IP)" >&2
  exit 2
fi

# get last set IP
LAST_IP_FILE="$HOME/.dyndns_last_ip"
touch "$LAST_IP_FILE"
LAST_IP="`cat "$LAST_IP_FILE"`"

# skip if not changed and not forced
[ "$1" != "-f" ] && [ "$LAST_IP" = "$IP" ] && exit 0

# update on change
wget -O /dev/null "http://$USER:$PASS@members.dyndns.org/nic/update?hostname=$DOMAIN&myip=$IP&wildcard=NOCHG&mx=NOCHG&backmx=NOCHG" || exit $?
echo "$IP" > "$LAST_IP_FILE"
exit $?