[openib-general] RDMA connection and address translation API

[Fab Tillier]

> From: Roland Dreier [mailto:rolandd at cisco.com]
> Sent: Wednesday, August 24, 2005 11:03 AM
> 
>     Fab> Why can't the IPV field be ignored?  If a listen wants only
>     Fab> IPV4 addresses, it would specify a 16-byte compare buffer
>     Fab> with the first 12 bytes zero, the next 4 filled with the IPV4
>     Fab> address, and would set the offset to that of the hello
>     Fab> message's destination address (32).
> 
> Yes, you're right for SDP.  I guess if we're comfortable mandating
> that all protocols put their source and destination IPs in the private
> data for the IB case, then this works.  Of course it's somewhat
> awkward to pass this information into the transport-neutral CM API but
> I think this can be worked around.

I don't know if we need to mandate IP usage - it's up to the application.  Any
application that wants to have similar semantics to the way socket listens work
(especially when bound to one of multiple IP addresses on a port) the
application would have to define its private data to accommodate this.
 
At the IB level, the contents of the private data are still opaque, even to the
CM.  The CM would only expose the ability to have it perform an initial triage
of requests by doing binary comparisons over regions of private data.  It
doesn't know (or need to know) what the data represents - it only cares about
finding a match (or not).  The CM doesn't define any sort of policy here, and I
don't think it should.  It's just bytes to the CM, and it's doing a blind
comparison without interpreting the contents.

- Fab