[openib-general] Extending umad for RMPP support

[Hal Rosenstock]

Hi Roland,

I am looking at adding RMPP support into umad (so OpenSM can support SA
GetTableResp for real).

Currently, the 256 byte MAD is the first field in the ib_user_mad
structure. In order to support variable length MADs (for RMPP), I would
propose moving this to the end of the struct and supporting a variable
size. (Obviously, there are a number of other associated changes with
doing this in the code). Just wanted to double check this with you to
make sure this approach is acceptable before investing time in doing it.

Of course, the ABI version will be bumped and rmpp_version will be added
as a field to the ib_user_mad_reg_req structure.

Thanks.

-- Hal