NTP_CONF=/etc/ntpsec/ntp.conf
NTP_DHCP_CONF_DIR=/run/ntpsec
NTP_DHCP_CONF=$NTP_DHCP_CONF_DIR/ntp.conf.dhcp


ntp_server_restart() {
	if [ -r /etc/default/ntpsec ]; then
	        . /etc/default/ntpsec
	fi

	if [ "$IGNORE_DHCP" != "yes" ]; then
		invoke-rc.d ntpsec try-restart
	fi
}


ntp_servers_setup_remove() {
	if [ ! -e "$NTP_DHCP_CONF" ]; then
		return
	fi
	rm -f "$NTP_DHCP_CONF"
	ntp_server_restart
}


ntp_servers_setup_add() {
	# dhclient provides the old servers in $old_ntp_servers, but NetworkManager
	# and networkd do not.  Get the old list from the configuration file, if
	# it is present.
	old_ntp_servers=""
	if [ -e "$NTP_DHCP_CONF" ]; then
		old_ntp_servers=$(awk '/^server / {print $2}' "$NTP_DHCP_CONF")
	fi

	# $new_ntp_servers comes from dhclient.
	# $DHCP4_NTP_SERVERS and $DHCP6_NTP_SERVERS come from NetworkManager.
	new_ntp_servers=$(
		for i in \
			$new_ntp_servers \
			$DHCP4_NTP_SERVERS $DHCP6_NTP_SERVERS \
			$(sed -n 's/NTP=//p' /run/systemd/netif/leases/* 2>/dev/null)
		do
			echo $i
		done)

	# NOTE: By this point, both $old_ntp_servers and $new_ntp_servers are
	# NOTE: newline-separated.
	if [ "$new_ntp_servers" = "$old_ntp_servers" ]; then
		return
	fi

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

	mkdir -p "$NTP_DHCP_CONF_DIR"
	tmp=$(mktemp "$NTP_DHCP_CONF.XXXXXX") || return
	chmod --reference="$NTP_CONF" "$tmp"
	chown --reference="$NTP_CONF" "$tmp"

	(
	  echo "# This file was copied from $NTP_CONF with the server options changed"
	  echo "# to reflect the information sent by the DHCP server.  Any changes made"
	  echo "# here will be lost at the next DHCP event.  Edit $NTP_CONF instead."
	  echo
	  echo "# NTP server entries received from DHCP server"
	  for server in $new_ntp_servers; do
		echo "server $server iburst"
	  done
	  echo
	  sed '/^[[:space:]]*\(server\|peer\|pool\|tos\)[[:space:]]/d' \
		"$NTP_CONF"
	) >> "$tmp"

	mv "$tmp" "$NTP_DHCP_CONF"

	ntp_server_restart
}


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