cloudflare dyndns

#!/bin/sh

# interface going down
if [ "${0#*ip-down.d/}" = "${0##*/}" ]; then
    exec killall -w "${0##*/}"
fi

[ "$PPP_IFACE" = 'pppoe-data' ] || exec logger -p daemon.info -t dyndns "Not applying DNS to iface '$PPP_IFACE'"

read domain </proc/sys/kernel/hostname

domain=$domain.example.com
email=
key=
zone=
api=https://api.cloudflare.com/client/v4/zones/$zone/dns_records

auth="-H X-Auth-Email:$email -H X-Auth-Key:$key"

updatedns() {
    ret=0
    if ! id=$(curl -s $auth $api |jq -er ".result[] | select(.name == \"$domain\") | .id"); then
        return 1
    fi
    uri="$api/$id"
    json=/tmp/dyndns-$$.json

    curl -sS -XPUT $uri $auth \
        -H 'Content-Type: application/json' \
        -d "{\"type\":\"A\", \"name\":\"$domain\", \"content\":\"$IPLOCAL\"}" >$json
    if jq -ec '.success == false' <$json >/dev/null; then
        logger -p daemon.warning -t dyndns "server returned '$(jq -c .errors <$json)'"
        ret=1
    fi
    rm -f $json
    return $ret
}

i=60
while [ $i -ge 0 ]; do
    updatedns && exec logger -p daemon.info -t dyndns "DNS for $domain set to $IPLOCAL"
    sleep 5
    logger -p daemon.notice -t dyndns "Retry setting DNS for $domain ($i more tries)"
    i=$((i - 1))
done &

exit 0