[openib-general] gen2 dev branch

[Roland Dreier]

I snipped a lot of stuff that I agree with.  I just want to comment on one item:

> * A useful feature would be matching responses with requests, with automatic retries.

On general principles I'm leery of automatic retries (experience has
shown that error handling should be moved up to the highest level
possible).

In particular for IB, we have found that exponential backoff is useful
for preventing livelock in large fabrics (if a lot of clients are
sending requests to a single server and the clients don't back off,
the system may get stuck in a state where the server is spending all
its time responding to requests that the client has already timed
out).

 - Roland