ddwrt-wanip-notify-331321.sh

#!/bin/sh
# version: 1.0.0, 21-jan-2022, by eibgrad
# href: https://tinyurl.com/3w4mfv8b

SCRIPTS_DIR='/jffs/etc/config'
SCRIPT="$SCRIPTS_DIR/ddwrt-wanip-notify.startup"

mkdir -p $SCRIPTS_DIR

cat << 'EOF' > $SCRIPT
#!/bin/sh
DEBUG=; set -x # comment/uncomment to disable/enable debug mode
(
# ------------------------------ BEGIN OPTIONS ------------------------------- #

# how often to check (in secs) for a change in wan ip
INTERVAL=300

# smtp options
USER='sender@gmail.com'
PASS='XXXXXXXX'
FROM_NAME='sender@gmail.com'
TO='recipient@gmail.com'
TO_NAME='recipient@gmail.com'
SERVER='smtps://smtp.gmail.com:465'
SUBJECT='WAN IP has changed!'

# ------------------------------- END OPTIONS -------------------------------- #

# ---------------------- DO NOT CHANGE BELOW THIS LINE ----------------------- #

MESSAGE="/tmp/tmp.$$.message"

format_message() {
cat << EOM > $MESSAGE
From: "$FROM_NAME" <$USER>
To: "$TO_NAME" <$TO>
Subject: $SUBJECT

Current  WAN IP: $curr_wan_ip
Previous WAN IP: $prev_wan_ip
EOM
}

send_message() {
    format_message

    curl --ssl-reqd \
         --url "$SERVER" \
         --user "$USER:$PASS" \
         --mail-from "$USER" \
         --mail-rcpt "$TO" \
         --upload-file "$MESSAGE" \
         $([ ${DEBUG+x} ] || echo '--silent')
}

prev_wan_ip='N/A'

# wait for *reliable* internet connection
until ping -qc1 -W3 8.8.8.8 &>/dev/null; do sleep 10; done

while :; do
    curr_wan_ip="$(nvram get wan_ipaddr)"

    # send notification if wan ip changes
    if [ "$curr_wan_ip" != "$prev_wan_ip" ]; then
        echo "info: wan ip changed to $curr_wan_ip"

        if send_message; then
            echo "info: notification sent to $TO"
        else
            echo "error: failed to send notification ($?)"
        fi

        prev_wan_ip="$curr_wan_ip"
    fi

    sleep $INTERVAL
done

) 2>&1 | logger $([ ${DEBUG+x} ] && echo '-p user.debug') \
    -t $(echo $(basename $0) | grep -Eo '^.{0,23}')[$$] &
EOF
chmod +x $SCRIPT
echo "installed: $SCRIPT"