nsupdate.info DDNS client

update.sh

#!/bin/bash

set -euo pipefail

DNS_REC=<your record>
SEC=<secret>
INTERVAL=1200 # in seconds
DNS_MASTER="$(dig SOA +short "${DNS_REC}")"

unchanged4() {
        local DNS_IP4 ASS_IP4

        DNS_IP4="$(dig    A +short "@${DNS_MASTER}" "${DNS_REC}")"
        ASS_IP4="$(curl -s https://ipv4.nsupdate.info/myip)"

        [ "${DNS_IP4}" == "${ASS_IP4}" ]
}

unchanged6() {
        local DNS_IP6 ASS_IP6

        DNS_IP6="$(dig AAAA +short "@${DNS_MASTER}" "${DNS_REC}")"
        ASS_IP6="$(curl -s https://ipv6.nsupdate.info/myip)"

        [ "${DNS_IP6}" == "${ASS_IP6}" ]
}

# Crawl nsupdate to update IP
update4(){
        echo "Updating IPv4 address"
        curl -s "https://${DNS_REC}:${SEC}@ipv4.nsupdate.info/nic/update"
}
update6(){
        echo "Updating IPv6 address"
        curl -s "https://${DNS_REC}:${SEC}@ipv6.nsupdate.info/nic/update"
}

while : ; do
        unchanged4 || update4
        unchanged6 || update6
        sleep "${INTERVAL}"
done