This shell script is an update client for dtdns.com. The client update the dynamic ip for a given host

README.md

Description

dtdnsbash is an update client (https://www.dtdns.com/dtsite/updateclients) which updates your dynamic ip on https://www.dtdns.com/ to a given hostname.

Requirements

Base

• bash
• grep
• awk

Network

• ifconfig
• nslookup
• openbsd-netcat

Usage

The best way to use dtdnsbash is to start the script in a screen session. Simply install screen and execute the following.

> screen -S dtdns

> bash dtdnsbash.sh <interface> <hostname> <update.intervall.in.seconds>

As an example when your external interface is eth0 and your hostname is blabla.blabla.com and your dynamic ip will change every hour you can use this command > bash dtdnsbash.sh eth0 blabla.blabla.com 3600

After start you have to type your password and the update will update every hour. To bring the process in background you can hit

> screen CTRL+a d

When you login again on your server you can re-attach your screen session with

> screen -r dtdns

dtdnsbash.sh

 #!/bin/bash

function assertArgs {
  EXPECTED_ARGS=3
  if [ $# -ne $EXPECTED_ARGS ]
  then
    echo "Usage: `basename $0` <interface> <host.name> <dns.update.interval>" 
    exit 1
  fi
}

function readPassword {
  read -se password
  echo $password
}

function getIpFromInterface {
  echo `ifconfig "${1}" | grep  'inet '| awk '{print $2}'`
}

function parseIp {
  echo `echo "${1}." | grep -E '([0-9]{1,3}\.){4}'`
}

function assertIp {
  if [ ! "$1" ]
  then
    echo $2
    exit 1
  fi
}

function lookupIpFromNet {
  echo `nslookup "${1}" NS1.DTDNS.COM | grep "${1}" -A1 | grep 'Address' | awk '{print $2}'`
}

function updateDnsEntry {
  echo -e "\n
GET /api/autodns.cfm?id=${1}&pw=${2}&client=dtdnsbash&ip=${3}
HTTP/1.1
Host: www.dtdns.com
User-Agent: bash

" | nc www.dtdns.com 80
  echo "Done."
}


assertArgs $@
INTERFACE=$1
HOST_NAME=$2
DNS_UPDATE_INTERVAL=$3

echo -n "Please enter dtdns.com account password: "
DTDNS_PASSWORD=$(readPassword)

for (( ; ; ))
do

  echo `date`
  CURRENT_IP=`getIpFromInterface $INTERFACE`
  echo "Lookup IP on interface ${INTERFACE}: ${CURRENT_IP}"
  VALID_IP=`parseIp $CURRENT_IP`
  assertIp "${VALID_IP}" "Invalid IP ${CURRENT_IP} on interface ${INTERFACE}"

  LAST_IP=`lookupIpFromNet $HOST_NAME`
  echo "Lookup IP for hostname ${HOST_NAME}: ${LAST_IP}"
  VALID_LAST_IP=`parseIp $LAST_IP`
  assertIp "${VALID_LAST_IP}" "Invalid IP ${LAST_IP} for host ${HOST_NAME}"

  if [ $CURRENT_IP == $LAST_IP ]
  then
    echo "Your current IP ${CURRENT_IP} still points to ${HOST_NAME}. No dns update necessary."
  else
    echo "Your IP ${CURRENT_IP} does not point to ${HOST_NAME}/${LAST_IP}. Trigger a dns update."
    updateDnsEntry $HOST_NAME $DTDNS_PASSWORD $CURRENT_IP
  fi

  sleep $DNS_UPDATE_INTERVAL

done