Mason is a tool that interactively builds a firewall using Linux' ipfwadm or ipchains firewalling. You leave mason running on the firewall machine while you are making all the kinds of connections that you want the firewall to support . Mason gives you a list of firewall rules that exactly allow and block those connections.
One whose occupation is to build with stone or brick; also, one who prepares stone for building purposes.
To build stonework or brickwork about, under, in, over, etc.; to construct by masons; -- with a prepositional suffix; as, to mason up a well or terrace; to mason in a kettle or boiler.