dnsupdate.sh

#!/bin/bash

# curl -s = silent mode
# if [ -z "$OLDIPv4" ] = true if $OLDIPv4 (a string) is null -> https://stackoverflow.com/a/18096739/11458487
# Configuration ################################################################
USERNAME=""         				# Your username at INWX
PASSWORD=""     				# Your password at INWX
DNSIDsv4=("1" "2")       	   		# The ID of the A record
DNSIDsv6=()          				# The ID of the AAAA record
SILENT=false        				# Should the script write a logfile? (true | false)
UPDATEURLv4=""					# Your prefered host to get the IPv4 from
UPDATEURLv6=""					# Your prefered host to get the IPv6 from
################################################################################

DNSIDS=("${DNSIDsv4[@]}" "${DNSIDsv6[@]}")	# Concat the two arrays
APIHOST="https://api.domrobot.com/xmlrpc/" 	# API URL from inwx.de

# Define functions #############################################################
function log() {
	# Only log if $SILENT is false
	$SILENT || echo "$(date) | $1" >> update.log
}

function get_v4_ip() {
	if [ ! -z "$UPDATEURLv4" ]
	then
		log "Host defined, get IP from $UPDATEURLv4"
		# get this from https://unix.stackexchange.com/a/20793
		echo $(host $UPDATEURLv4 | awk '/has address/ { print $4 ; exit }')
		return 0
	fi
	
	if [ ! -e v4.pool ]
	then
		log "No IPv4 pool (v4.pool file) found. Using https://ip4.ident.me/"
		echo $(curl -s "https://v4.ident.me")
		return 0
	fi

	V4_POOL=$(cat v4.pool)
	for V4_API in $V4_POOL; do
		MAYBE_V4_ADDR=$(curl -s "$V4_API")
		if [[ $MAYBE_V4_ADDR =~ ^[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+$ ]]; then
			echo "$MAYBE_V4_ADDR"
			return 0
		fi
	done
	return 1
}

function get_v6_ip() {
	if [ ! -z "$UPDATEURLv6" ]
	then
		log "Host defined, get IP from $UPDATEURLv6"
		# get this from https://unix.stackexchange.com/a/20793
		echo $(host $UPDATEURLv6 | awk '/has address/ { print $4 ; exit }')
		return 0
	fi

	if ! [ -e v6.pool ]
	then
		log "No IPv6 pool (v6.pool file) found. Using https://ip6.ident.me/"
		echo $(curl -s "https://v6.ident.me/")
		return 0
	fi

	V6_POOL=$(cat v6.pool)
	for V6_API in $V6_POOL; do
		MAYBE_V6_ADDR=$(curl -s "$V6_API")
		if [[ $MAYBE_V6_ADDR == *":"* ]]; then
			echo "$MAYBE_V6_ADDR"
			return 0
		fi
	done
	return 1
}

# Usage example: change_ip "IPv4" $DNSID $OLDIPv4 $NEWIPv4
function change_ip() {
	IPCAT=$1
	DNSID=$2
	OLDIP=$3
	NEWIP=$4
	if [ ! "$OLDIP" == "$NEWIP" ]; then
		log "Updating $IPCAT to $NEWIP"
		DATA=$(cat update.api | sed "s/%PASSWD%/$PASSWORD/g;s/%USER%/$USERNAME/g;s/%DNSID%/$DNSID/g;s/%NEWIP%/$NEWIP/g")
		RET=$(curl  -s -X POST -d "$DATA" "$APIHOST" --header "Content-Type:text/xml")

		if ! grep -q "Command completed successfully" <<< "$RET"; then
			log "Something went wrong updating the $IPCAT address. Check the configuration and make sure you're not using Two-Factor-Authentication."
			exit 1
		fi
		log "Updated $IPCAT: $OLDIP --> $NEWIP"
	else
		log "$IPCAT: No changes"
	fi
	return 0
}

# Usage example: write_ip_to_file "old.ipv4" $OLDIPv4 $NEWIPv4
function write_ip_to_file() {
	FILENAME=$1
	OLDIP=$2
	NEWIP=$3
	if [ ! -z "$NEWIP" ]
	then
		if [ $OLDIP != $NEWIP ]
		then
			echo $NEWIP > $FILENAME
			log "IP: $NEWIP in $FILENAME written"
		else
			log "IP: $NEWIP already in $FILENAME"
		fi
	fi
	return 0
}
################################################################################
# Do the update if needed ######################################################
# check if the IPv4/6 array exists, then create old.ipv4/6 if not available and get new IPs
log "##################BEGINN OF UPDATE#################"
if [ ${#DNSIDsv4[@]} -ne 0 ]
then
	if ! [ -e old.ipv4 ]
	then
		echo "empty" > old.ipv4
	fi
	OLDIPv4=$(cat old.ipv4)
	NEWIPv4=$(get_v4_ip)
	if [[ $? == 1 ]] || [ -z "$NEWIPv4" ]; then
		echo $NEWIPv4
		log "Could not get a valid IPv4 address from the pool or URL. Is the connection up?"
		exit 1
	fi
fi
if [ ${#DNSIDsv6[@]} -ne 0 ]
then
	if ! [ -e old.ipv6 ]
	then
		echo "empty" > old.ipv6
	fi
	OLDIPv6=$(cat old.ipv6)
	NEWIPv6=$(get_v6_ip)
	if [[ $? == 1 ]] || [ -z "$NEWIPv6" ]; then
		log "Could not get a valid IPv6 address from the pool or URL. Is the connection up?"
		exit 1
	fi
fi

for DNSID in ${DNSIDS[@]}; do
	# checking if the entry is v4 or not, see https://stackoverflow.com/a/15394738/11458487
	if [[ " ${DNSIDsv4[@]} " =~ " ${DNSID} " ]]; then
		ISIPv4=true
		log "Entry $DNSID, IPv4 starts"
	else
		ISIPv4=false
		log "Entry $DNSID, IPv6 starts"
	fi

	if [[ "$ISIPv4" = true ]]; then
		# update the A-record
		change_ip "IPv4" $DNSID $OLDIPv4 $NEWIPv4
	else
		log "Skipping IPv4: No DNS record ID set"
	fi

	if [[ "$ISIPv4" = false ]]; then
		# update the AAAA-record
		change_ip "IPv6" $DNSID $OLDIPv6 $NEWIPv6
	else
		log "Skipping IPv6: No DNS record ID set"
	fi
	
	log "Entry $DNSID finished"
	log "###################################################"
done

# save new IPs in old file (only if they are different), these are now the old IPs
write_ip_to_file "old.ipv4" $OLDIPv4 $NEWIPv4
write_ip_to_file "old.ipv6" $OLDIPv6 $NEWIPv6

log "###################END OF UPDATE###################"
log "###################################################"
################################################################################