[ofa-general] opensm: Unsupported attribute = 0xFF02

[Sean Hefty]

> As mentioned in the past, client reregistration is a rather large
> hammer. There have been discussions on utilizing this mechanism in more
> scenarios (which FWIW is not a good thing IMO). This approach (and it is
> optional) pushes the burden back on the end nodes rather than the SM.
> Scalability is certainly an issue with it. It was begrudgingly put into
> the spec. It was intended only as a stopgap measure.
> 
> There was informative text put into the spec alluding to the
> "appropriate" use of this option:
> 
> "A reason for the SM doing this might be that the SM suffered a failure
> and as a result lost its own records of such subscriptions."
> This is referring to a single SM (although that is not the recommended
> deployment topology) crashing and being restarted.
> 
> IMO a civil SM would not rely on this mechanism.

There's still the problem that the ULPs on the end-node do not know when 
or if the data is lost.  IMO, making client reregistration mandatory 
would have been a better solution, allowing ULPs to only re-register on 
that event.  As it stands now, ULPs automatically reregister on SM LID 
changes, port events, etc..  In order to avoid ULP re-registration, SM 
failover has to bring along the LID.

An alternate solution could have let an SM learn what it needed from the 
end nodes through queries...

- Sean