#!/bin/sh
# Custom DDNS (dynamic DNS) for the no-ip.com service for asuswrt-merlin
# The scripts works in a double NAT setup and single NAT setup, and will automatically detect the configuration
VERSION="2.4"
USERNAME=""
PASSWORD=""
HOSTNAME=""
USERAGENT="asuswrt-merlin No-IP Updater/$version"
ASUSIP="$(nvram get wan0_ipaddr)" # $1 could have been used, but doesn't work in cron mode, so we get the the reported wan_ipaddr from nvram instead. (dual wan uses wan_ipaddr_x, not supported)
LOGFILE="" # leave empty if not used
CUSTOM_UPDATE="" # use cron to check for new ip every X minute. Leave empty if you're using the default from merlin (24 hours). Any previous, or if used, setting will be removed if left empty.
## CODE BELOW ####
LogMe(){
	if [[ -n "$LOGFILE" ]]; then
		echo "[$(date +'%Y-%m-%d %H:%M:%S')]: $1" >> "$LOGFILE"
	fi
	logger "$1"
}
UpdateMerlin(){
	/sbin/ddns_custom_updated "$1"
}
UpdateIp(){
	# update ip
	nvram set EXTERNALIP="$NEWIP"
	URL="https://$USERNAME:$PASSWORD@dynupdate.no-ip.com/nic/update?hostname=$HOSTNAME&myip=$NEWIP"
	RESPONSE=$(curl -s -k --user-agent "$USERAGENT" "$URL")
	RESPONSE_A=$(echo $RESPONSE | awk '{ print $1 }')
	case "$RESPONSE_A" in
		"good")	UpdateMerlin 1; LogMe "CustomUpdateDDNS: (good) DNS hostname(s) successfully updated to $NEWIP."
		;;
		"nochg") UpdateMerlin 1; LogMe "CustomUpdateDDNS: (nochg) IP address is current: $NEWIP; no update performed."
		;;
		"nohost") UpdateMerlin 0; LogMe "CustomUpdateDDNS: (nohost) Hostname supplied does not exist under specified account. Revise config file."
		;;
		"badauth") UpdateMerlin 0; LogMe "CustomUpdateDDNS: (badauth) Invalid username password combination."
		;;
		"badagent")	UpdateMerlin 0;	LogMe "CustomUpdateDDNS: (badagent) Client disabled - No-IP is no longer allowing requests from this update script."
		;;
		"!donator")	UpdateMerlin 0;	LogMe "CustomUpdateDDNS: (!donator) An update request was sent including a feature that is not available."
		;;
		"abuse") UpdateMerlin 0; LogMe "CustomUpdateDDNS: (abuse) Username is blocked due to abuse."
		;;
		"911") UpdateMerlin 0; LogMe "CustomUpdateDDNS: (911) A fatal error on our side such as a database outage. Retry the update in no sooner than 30 minutes."
		;;
		"*") UpdateMerlin 0; LogMe "CustomUpdateDDNS: (error) Could not understand the response from No-IP. The DNS update server may be down."
		;;
	esac
}
CronUpdate(){
	if [[ -n "$CUSTOM_UPDATE" ]]; then
		if [[ -z "$(cru l | grep "CustomUpdateDDNS")" ]]; then
			/usr/sbin/cru a CustomUpdateDDNS "*/$CUSTOM_UPDATE * * * * /jffs/scripts/ddns-start"
			LogMe "CustomUpdateDDNS has been added to cron (x $CUSTOM_UPDATE mins)"
		fi
	else
		if [[ -n "$(cru l | grep "CustomUpdateDDNS")" ]]; then
			/usr/sbin/cru d "CustomUpdateDDNS"
			LogMe "CustomUpdateDDNS has been removed from cron"
		fi
	fi
}

LogMe "CustomUpdateDDNS: Starting custom DDNS updater v$VERSION"

if [[ -z "$ASUSIP" ]]; then
	LogMe "(error) Router has no ip or no network configuration"
	exit 1
fi

CronUpdate

LogMe "CustomUpdateDDNS: Reported asus router ip: $ASUSIP"

if [[ -n "$(echo "$ASUSIP" | grep -E '^(10\.|100\.(6[4-9]|7[0-9]|8[0-9]|9[0-9]|1[0-2][0-9])\.|172\.(1[6789]|2[0-9]|3[01])\.|192\.0\.0\.|192\.168|198\.1[89])')" ]]; then
	# check if we have a local ip. If true, then look up external ip
	LogMe "CustomUpdateDDNS: Local ip detected"
	# look up external ip
	NEWIP=$(curl -s http://ipv4.myip.dk/api/info/IPv4Address | cut -d "\"" -f2)
	# backup ipcheck if first one fails
	if [[ -z "$NEWIP" ]]; then
		NEWIP=$(curl -s http://icanhazip.com/)
	fi
	LogMe "CustomUpdateDDNS: Found external ip: $NEWIP"
else
	NEWIP="$ASUSIP"
	LogMe "CustomUpdateDDNS: External ip detected"
fi

# compare found ip with stored ip. If nothing is stored, assume an update is needed

if [[ "$NEWIP" == "$(nvram get EXTERNALIP)" ]]; then
	# ip has not changed there's no need to hammer the ddns provider, so compare it to the previosuly found ip and save in ram
	LogMe "CustomUpdateDDNS: (nochange) External IP address is current: $NEWIP"
	LogMe "CustomUpdateDDNS: Update not needed"
	/sbin/ddns_custom_updated 1
else
	UpdateIp
fi
LogMe "CustomUpdateDDNS: DDNS update complete"
exit 0