NTPDATE_CONF=/etc/default/ntpsec-ntpdate
NTPDATE_DHCP_CONF_DIR=/run/ntpsec
NTPDATE_DHCP_CONF=$NTPDATE_DHCP_CONF_DIR/ntpdate.dhcp


ntp_servers_setup_remove() {
	rm -f $NTPDATE_DHCP_CONF
}


ntp_servers_setup_add() {
	# dhclient provides the old servers in $old_ntp_servers, but NetworkManager
	# and networkd do not.  Get the old list from the configuration file, if
	# it is present.
	old_ntp_servers=""
	if [ -e "$NTPDATE_DHCP_CONF" ]; then
		. "$NTPDATE_DHCP_CONF"
		old_ntp_servers="$NTPSERVERS"
	fi

	# $new_ntp_servers comes from dhclient.
	# $DHCP4_NTP_SERVERS and $DHCP6_NTP_SERVERS come from NetworkManager.
	# NOTE: $old_ntp_servers is space-separated, and in this loop, the
	# NOTE: the newlines are changed to spaces for $new_ntp_servers.
	new_ntp_servers=$(
		for i in \
			$new_ntp_servers \
			$DHCP4_NTP_SERVERS $DHCP6_NTP_SERVERS
		do
			echo $i
		done | tr "\n" " " | sed "s| $||")

	if [ "$new_ntp_servers" = "$old_ntp_servers" ]; then
		return
	fi

	if [ -z "$new_ntp_servers" ]; then
		ntp_servers_setup_remove
		return
	fi

	mkdir -p "$NTPDATE_DHCP_CONF_DIR"
	tmp=$(mktemp "$NTPDATE_DHCP_CONF.XXXXXX") || return
	chmod --reference="$NTPDATE_CONF" "$tmp"
	chown --reference="$NTPDATE_CONF" "$tmp"

	(
	  echo "# NTP server entries received from DHCP server"
	  echo "NTPSERVERS='$new_ntp_servers'"
	) >> "$tmp"

	mv "$tmp" "$NTPDATE_DHCP_CONF"
}


ntp_servers_setup() {
	case $reason in
		BOUND|RENEW|REBIND|REBOOT)
			ntp_servers_setup_add
			;;
		EXPIRE|FAIL|RELEASE|STOP)
			ntp_servers_setup_remove
			;;
	esac
}


ntp_servers_setup