Special packet inspecting bridging

[Mircea Ciocan]

                Hi all,

        I'd like to start a project involving a packet inspecting
Ethernet
bridge/firewall/traffic shaper that is protocol independent ( I mean no
ties to high level protocols like TCP/IP or IPX for ex.).
        What I want to do is get raw Ethernet packets from one
interface, pipe
it trough an user level program and then inject it in the other one, and
viceversa, of course ;).
        Please advise me of the means of doing this with minimum
overhead
possible, or if someone started a similar project please let me know.

                        Thank you,

                        Mircea C.