trixie/roles/ddnsupdate/files/ddns-update

#!/bin/bash
set -eu

. /etc/ddns-update/ddns-update.conf

DDHOST="https://www.ddnss.de/upd.php"

if ! DNSRESULT="$(host $DDNSNAME)" ; then
    echo "Could not resolve IP address for '$DDNSNAME', no update."
    exit 0
fi

DNSIP4="$(echo "$DNSRESULT" | grep -m 1 -oE '[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}$' || true )"
DNSIP6="$(echo "$DNSRESULT" | grep -m 1 -oE '[0-9a-f]{1,4}:.+:[0-9a-f]{1,4}' || true )"

REALIP4="$(wget -q -O - https://ip4.ddnss.de/meineip.php | \
               grep -m 1 -oE '[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}.[0-9]{1,3}' || true )"
REALIP6="$(wget -q -O - https://ip6.ddnss.de/meineip.php | \
                grep -m 1 -oE '[0-9a-f]{1,4}:.+:[0-9a-f]{1,4}' || true )"

if [ -z "$REALIP4" -a -z "$REALIP6" ] ; then
    echo "Could not detect real IP addresses, exiting."
    exit 0
fi

echo "Current DNS: IPv4=$DNSIP4, IPv6=$DNSIP6."
echo "Detected:    IPv4=$REALIP4, IPv6=$REALIP6."

if [ "$REALIP4" == "$DNSIP4" -a "$REALIP6" == "$DNSIP6" ] ; then
    echo "IP address unchanged, no update."
else
    echo "IP address changed: $DNSIP4 → ${REALIP4}, $DNSIP6 → ${REALIP6}, updating ddns."
    wget -q -O - $DDHOST'?key='$KEYAUTH'&host='$DDNSNAME'&ip='$REALIP4'&ip6='$REALIP6 \
        | grep -oE "Updated .+ hostname." || echo "Update not confirmed, it might have failed."
fi