do-dyndns

#!/bin/bash
if [ ! -z "$1" ]
then
  DOMAIN=`echo $1 | cut -d "." -f 2-9`
  if [ ! -z "$DOMAIN" ]
  then
    DO_DYNDNS_DOMAIN=$DOMAIN
  fi
  HOST=`echo $1 | cut -d "." -f 1`
  NOPUBLIC=1
else
  HOST=$HOSTNAME
fi

if [ ! -z "$2" ]
then
  LOCAL_IP="$2"
else
  LOCAL_IP="0"
fi

TTL=300
echo $0 "-------------------- Setting IP for $HOST.$DO_DYNDNS_DOMAIN"
########################################
# GIVE SOME HELP
########################################

help_message () {
  echo $basename
cat <<EOF
Create or update DNS record for hostname using a Digital Ocean's API.
Requires '$DO_DYNDNS_DOMAIN' and '$DO_API_KEY' to be defined.

DO_DYNDNS_DOMAIN should be a registered domain managed by Digital Ocean.

DO_API_KEY should be a Digital Ocean API key for the account that manages DO_DYNDNS_DOMAIN.

To install this script with your DO_API_KEY into /etc/$BASENAME/$BASENAME and put a symlink
in /etc/NetworkdManager/dispatch.d so that it is run when a network state changes, use:

    $basename --install

EOF

  }

########################################
# DO WE HAVE A KEY?
########################################
if [ -z "$DO_API_KEY" ]
then
   echo DO_API_KEY is empty or not defined
   echo
   echo
   help_message
   exit
fi

########################################
# DO WE HAVE A DOMAIN?
########################################
if [ -z "$DO_DYNDNS_DOMAIN" ]
then
   echo DO_DYNDNS_DOMAIN is empty or not defined
   echo
   echo
   help_message
   exit
fi

########################################
# DO WE HAVE doctl
########################################
if ! ( which doctl 2>&1 > /dev/null )
then
    echo Installing jq . . .
    sudo snap install --classic doctl
fi

########################################
#               GET THE IP             #
########################################
if [ $LOCAL_IP == "0" ]
then
  IFACE=`ip r get 8.8.8.8 |head -1 |cut -d " " -f 5`
  LOCAL_IP=`ip -4 a show $IFACE|grep inet|cut -d " " -f 6|cut -d '/' -f 1`
  FIREWALL=`dig +short myip.opendns.com @resolver1.opendns.com`
else
  LOCAL_IP="$2"
  FIREWALL=$LOCAL_IP
fi

echo "I $IFACE, IP $LOCAL_IP, FW: $FIREWALL. $0 -- $1"


########################################
# Is old-style if-up installed?
########################################

if [ -e /etc/network/if-up.d/do-dyndns ]
then
   INSTALL="YES"
   sudo rm /etc/network/if-up.d/do-dyndns
fi

########################################
# SHOULD WE INSTALL?
########################################
if [ "$#" == 1 ] || [ "$INSTALL" == "YES" ]
then
    BASENAME=`basename $0`
    if [ "$1" == "--install" ] || [ "$INSTALL" == "YES" ]
    then
	echo Installing $BASENAME to /etc/NetworkManager/dispatcher.d/
	sudo mkdir -p /etc/$BASENAME
	sudo chmod 700 /etc/$BASENAME
	echo "#!/usr/bin/env bash" | sudo tee /etc/$BASENAME/$BASENAME
	echo "export DO_API_KEY=$DO_API_KEY" | sudo tee -a /etc/$BASENAME/$BASENAME
	echo "export DO_DYNDNS_DOMAIN=$DO_DYNDNS_DOMAIN" | sudo tee -a /etc/$BASENAME/$BASENAME
	echo `realpath $0` | sudo tee -a /etc/$BASENAME/$BASENAME
	sudo chmod -R 600 /etc/$BASENAME
	sudo chmod 700 /etc/$BASENAME/$BASENAME
	sudo ln -sf /etc/$BASENAME/$BASENAME /etc/NetworkManager/dispatcher.d
	sudo /etc/$BASENAME/$BASENAME
	exit
    else
	echo ----------------------------------------
	echo Use \"$0 --install\" to install
	help_message
	echo ----------------------------------------
    fi
fi

########################################
# Get existing hostname
########################################
get_host_record() {

  echo DELETING DOMAIN RECORDS FOR $HOST.$DO_DYNDNS_DOMAIN >&2

  for x in `doctl -t $DO_API_KEY  compute domain records list $DO_DYNDNS_DOMAIN |grep $HOST|col1`
  do
    doctl  -t $DO_API_KEY compute domain records delete $DO_DYNDNS_DOMAIN $x --force
  done

  echo ""
}

########################################
# Define the function that does the work
########################################

set_hostname() {
  HOST=$1
  DO_DYNDNS_DOMAIN=$2
  IP=$3
  echo set_hostname: $HOST $DO_DYNDNS_DOMAIN $IP >&2
  # Get hostid if host exists

  CURRENT_IP=`dig +short $HOST.$DO_DYNDNS_DOMAIN @ns1.digitalocean.com`
  if [ "$IP" == "$CURRENT_IP" ]
  then
      echo "IP has not changed."
      return
  fi

  HOSTID=$(get_host_record)

  echo HOSTID: "$HOSTID" >&2

  if [ -n "$HOSTID" ]
  then
      echo Updating $HOSTID >&2
      curl -s -X PUT -H "Content-Type: application/json" -H "Authorization: Bearer $DO_API_KEY" -d "{\"data\":\"$IP\",\"ttl\":$TTL}" "https://api.digitalocean.com/v2/domains/$DO_DYNDNS_DOMAIN/records/$HOSTID"
      echo
  else
    echo Creating $HOST >&2
    curl -s -X POST -H "Content-Type: application/json" -H "Authorization: Bearer $DO_API_KEY" -d "{\"type\":\"A\",\"name\":\"$HOST\",\"data\":\"$IP\",\"priority\":null,\"port\":null,\"ttl\":$TTL,\"weight\":null}" "https://api.digitalocean.com/v2/domains/$DO_DYNDNS_DOMAIN/records"
    echo
  fi
  echo "$HOST.$DO_DYNDNS_DOMAIN ($IP) --> `dig +short $HOST.$DO_DYNDNS_DOMAIN @ns1.digitalocean.com`"
}

########################################
# Get on with the show
########################################

set_hostname $HOST $DO_DYNDNS_DOMAIN $LOCAL_IP
if [ -z $NOPUBLIC ]
then
   set_hostname "$HOST-public" $DO_DYNDNS_DOMAIN $FIREWALL
fi
echo $0 "-------------------- Setting IP for $HOST.$DO_DYNDNS_DOMAIN DONE"