[openib-general] [PATCH] [CM] add private data comparison to match REQs with listens

[Caitlin Bestler]

openib-general-bounces at openib.org wrote:
> Sean Hefty wrote:
>> As an update: further testing revealed that there is an issue with
>> this implementation that is also found in the original code.  The
>> issue deals with how listen requests that rely on a data mask are
>> inserted and located in the red/black tree.  I'm trying to come up
>> with a fix for this. 
> 
> After researching into this, I'm coming to the conclusion
> that there does not exist an efficient way to sort/search for
> listens without adding some restrictions.
> 
> For example, a client listens on id1 with mask1.  A request
> is matched with the listen if its serviceid & mask1 = id1.
> If a second client listens on id2 with mask2, then a request
> must check against both requests for a match, or until a
> match is found.  There's no method that I can find that can
> be used to filter checks that works in a generic fashion,
> resulting in requests needing to walk a linear list of
> listens.  There are several potential fixes for this, with
> only a couple mentioned below.
> 
> One solution around this is to have the IB CM only listen on
> service IDs, and remove the mask parameter from the API.
> This requires SDP to change to only listen on ports that have a
> listener. 
> 
> Another alternative is to restrict the type of masks that are
> supported.  If masks are restricted to a series of most
> significant bits, then the existing algorithm can be used.
> For instance, we can support masks 0xFF00 and 0xFFF0, but not
> 0x00FF or 0xFF0F.  This restriction would work for both SDP and the
>   CMA. To be clear, the API could change from a mask to the number of
> bits to match. 
> 
> Matching on private data can either be done by clients, or
> restrictions can be placed on it as well.  For private data,
> I believe that a restriction that all listen requests on the
> same service ID use the same mask is sufficient.
> 
> Hopefully this makes sense to people.  Thoughts?
> 

Just listen on the Service ID / Port and let the ULP sort them
out by destination IP address.