#!/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 2.0

USERNAME=""
PASSWORD=""
HOSTNAME=""
USERAGENT="asuswrt-merlin No-IP Updater/2.0"
ASUSIP="$1" # passed to script, however, we have local ip so external providers to find ip is used
LOGFILE="/mnt/sda1/jffs/ddns.log" # 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 ####
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 $1 }')
    if [ "$RESPONSE_A" == "good" ]; then
            /sbin/ddns_custom_updated 1
            LOGLINE="(good) DNS hostname(s) successfully updated to $NEWIP."
    elif [ "$RESPONSE_A" == "nochg" ]; then
            /sbin/ddns_custom_updated 1
            LOGLINE="(nochg) IP address is current: $NEWIP; no update performed."
    elif [ "$RESPONSE_A" == "nohost" ]; then
            /sbin/ddns_custom_updated 0
            LOGLINE="(nohost) Hostname supplied does not exist under specified account. Revise config file."
    elif [ "$RESPONSE_A" == "badauth" ]; then
            /sbin/ddns_custom_updated 0
            LOGLINE="(badauth) Invalid username password combination."
    elif [ "$RESPONSE_A" == "badagent" ]; then
            /sbin/ddns_custom_updated 0
            LOGLINE="(badagent) Client disabled - No-IP is no longer allowing requests from this update script."
    elif [ "$RESPONSE_A" == "!donator" ]; then
            /sbin/ddns_custom_updated 0
            LOGLINE="(!donator) An update request was sent including a feature that is not available."
    elif [ "$RESPONSE_A" == "abuse" ]; then
            /sbin/ddns_custom_updated 0
            LOGLINE="(abuse) Username is blocked due to abuse."
    elif [ "$RESPONSE_A" == "911" ]; then
            /sbin/ddns_custom_updated 0
            LOGLINE="(911) A fatal error on our side such as a database outage. Retry the update in no sooner than 30 minutes."
    else
    /sbin/ddns_custom_updated 0
    LOGLINE="(error) Could not understand the response from No-IP. The DNS update server may be down."
    fi
}
Cronupdate(){
    if [ -n "$CUSTOM_UPDATE" ]; then
        if [[ -n "$(cru l | grep "CustomUpdateDDNS")" ]]; then
            /usr/sbin/cru a CustomUpdateDDNS "*/$CUSTOM_UPDATE * * * * /jffs/scripts/ddns-start"
            LOGLINE="(added to cron) CustomUpdateDDNS has been added to cron"
            echo "$LOGLINE"
            logger "CustomUpdateDDNS: $LOGLINE"
            if [ -n "$LOGFILE" ]; then
                echo "[$(date +'%Y-%m-%d %H:%M:%S')]: $LOGLINE" >> "$LOGFILE"
            fi
        fi
    else
        if [[ -z "$(cru l | grep "CustomUpdateDDNS")" ]]; then
            /usr/sbin/cru d "CustomUpdateDDNS"
            LOGLINE="(removed from cron) CustomUpdateDDNS has been removed from cron"
            logger "CustomUpdateDDNS: $LOGLINE"
            echo "$LOGLINE"
            if [ -n "$LOGFILE" ]; then
                echo "[$(date +'%Y-%m-%d %H:%M:%S')]: $LOGLINE" >> "$LOGFILE"
            fi
        fi
    fi
}

logger "CustomUpdateDDNS: Executing ddns-start script"

Cronupdate

logger "CustomUpdateDDNS: Reported asus router ip: $ASUSIP"
if [[ -n "$(echo "$ASUSIP" | grep -E '^(192\.168|10\.|172\.1[6789]\.|172\.2[0-9]\.|172\.3[01]\.)')" ]]; then
    # check if we have a local ip. If true, then look up external ip
    logger "CustomUpdateDDNS: Local ip detected"
    # look up external ip
    NEWIP=$(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
    logger "CustomUpdateDDNS: Found external ip: $NEWIP"
else
    logger "CustomUpdateDDNS: External ip detected"
    if [ -n "$LOGFILE" ]; then
        echo "[$(date +'%Y-%m-%d %H:%M:%S')]: External ip detected" >> "$LOGFILE"
    fi
fi
# load old ip from nvram
OLDIP=$(nvram get EXTERNALIP)

if [ "$NEWIP" == "$OLDIP" ]; 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
    LOGLINE="(nochange) External IP address is current: $NEWIP."
    /sbin/ddns_custom_updated 1
else
    UpdateIp
fi
if [ -n "$LOGFILE" ]; then
    # update logs
    logger "CustomUpdateDDNS: $LOGLINE"
    echo "[$(date +'%Y-%m-%d %H:%M:%S')]: $LOGLINE" >> "$LOGFILE"
fi
exit 0