validate_client()
{
	local mac_address="$1"
	local serial
	local mtime

	if [[ -z ${mac_address} ]]
	then
		eecho "Error: No mac_address given"
		return 1
	fi

	# first check if mac is registered
	serial=$(mysqldo "select serial from client_serials where mac='${mac_address}'")

	if [[ -z ${serial} ]]
	then
			mtime=$(date +%s)

			# request a new serial; one command now (cause must be done in the same session)
			serial=$(mysqldo "insert into client_serials (mtime, mac) values('${mtime}','${mac_address}'); select last_insert_id();")
	fi

	echo "serial='${serial}'"
}

register_client()
{
	local control_server_ip
	local iface_ip
	local iface
	local mac_address

	control_server_ip=$(dns_to_ip ${MCORE_CONTROL_SERVER})
	iface_ip=$(iface_for_remote_addr ${control_server_ip})
	iface=$(iface_for_ip ${iface_ip})
	mac_address=$(mac_for_iface ${iface})

	echo "DEBUG: MCORE_CONTROL_SERVER='${MCORE_CONTROL_SERVER}'"
	echo "DEBUG: iface_ip='${iface_ip}'"
	echo "DEBUG: iface='${iface}'"
	echo "DEBUG: mac_address='${mac_address}'"

	echo "register '${mac_address}'"
}