ns_ddns.sh

#!/bin/bash
## ns_ddns_1.0.1
## this script will check if OpenVPN is running and update the host's ip address with Namesilo if it is not

##List of domain names (separated with spaces).
##Subdomains are also supported, e.g., host.example.com, sub.host.example.com
DOMAINS=()
##APIKEY obtained from Namesilo:
APIKEY=""

## Do not edit lines below ##

##Saved history pubic IP from last check
IP_FILE="/var/tmp/MyPubIP"

##Time IP last updated or 'No IP change' log message output
IP_TIME="/var/tmp/MyIPTime"

##Temporary path for parsing DNS records from Namesilo
DOMAIN_XML_PATH="/var/tmp/"

##How often to output 'No IP change' log messages
NO_IP_CHANGE_TIME=86400

##Response from Namesilo
RESPONSE="/tmp/namesilo_response.xml"

## Check if OpenVPN is running
if [ "$(pidof openvpn)" ]; then
  logger -t IP.Check -- Update aborted. VPN connection detected.
else

  ##Choose randomly which OpenDNS resolver to use
  RESOLVER=resolver$(echo $((($RANDOM%4)+1))).opendns.com
  ##Get the current public IP using DNS
  CUR_IP="$(dig +short myip.opendns.com @$RESOLVER)"
  ODRC=$?

  ## Try google dns if opendns failed
  if [ $ODRC -ne 0 ]; then
     logger -t IP.Check -- IP Lookup at $RESOLVER failed!
     sleep 5
  ##Choose randomly which Google resolver to use
     RESOLVER=ns$(echo $((($RANDOM%4)+1))).google.com
  ##Get the current public IP 
     IPQUOTED=$(dig TXT +short o-o.myaddr.l.google.com @$RESOLVER)
     GORC=$?
  ## Exit if google failed
     if [ $GORC -ne 0 ]; then
       logger -t IP.Check -- IP Lookup at $RESOLVER failed!
       exit 1
     fi
     CUR_IP=$(echo $IPQUOTED | awk -F'"' '{ print $2}')
  fi

  ##Check file for previous IP address
  if [ -f $IP_FILE ]; then
    KNOWN_IP=$(cat $IP_FILE)
  else
    KNOWN_IP=
  fi


  ##See if the IP has changed
  if [ "$CUR_IP" != "$KNOWN_IP" ]; then
    echo $CUR_IP > $IP_FILE
    logger -t IP.Check -- Public IP changed to $CUR_IP from $RESOLVER

    ##Update DNS record in Namesilo:
    for FQDN in "${DOMAINS[@]}"
    do
      DOMAIN=$(echo $FQDN | grep -oP '[^.]+\.[^.]+$')
      HOST=$(echo $FQDN | sed 's/\.\?[^.]\+\.[^.]\+$//')
      HOST_WITH_DOT=$(echo $HOST | awk '{if($0!="") print $HOST"."; else print ""}')
      curl -s "https://www.namesilo.com/api/dnsListRecords?version=1&type=xml&key=$APIKEY&domain=$DOMAIN" > $DOMAIN_XML_PATH$DOMAIN.xml
      RECORD_ID=`xmllint --xpath "//namesilo/reply/resource_record/record_id[../host/text() = '$HOST_WITH_DOT$DOMAIN' ]" $DOMAIN_XML_PATH$DOMAIN.xml | grep -oP '(?<=<record_id>).*?(?=</record_id>)'`
      curl -s "https://www.namesilo.com/api/dnsUpdateRecord?version=1&type=xml&key=$APIKEY&domain=$DOMAIN&rrid=$RECORD_ID&rrhost=$HOST&rrvalue=$CUR_IP&rrttl=3600" > $RESPONSE
      RESPONSE_CODE=`xmllint --xpath "//namesilo/reply/code/text()"  $RESPONSE`
         case $RESPONSE_CODE in
         300)
           date "+%s" > $IP_TIME
           logger -t IP.Check -- Update success. $FQDN IP address is now $CUR_IP;;
         280)
           logger -t IP.Check -- Update aborted. $FQDN duplicate record found.;;
         *)
           ## put the old IP back, so that the update will be tried next time
           echo $KNOWN_IP > $IP_FILE
           logger -t IP.Check -- Update failure. DDNS response code was $RESPONSE_CODE!;;
      esac
    done

  else
    ## Only log all these events NO_IP_CHANGE_TIME after last update
    [ $(date "+%s") -gt $((($(cat $IP_TIME)+$NO_IP_CHANGE_TIME))) ] &&
      logger -t IP.Check -- Update unneded. $FQDN IP address unchanged from $RESOLVER &&
      date "+%s" > $IP_TIME
  fi

fi
exit 0