[ofa-general] [RFP] support for iWARP requirement - active connect side MUST send first FPDU

[Steve Wise]

Sean Hefty wrote:
>> That is what I've been trying to push.  Both MVAPICH2 and OMPI have 
>> been open to adjusting their transports to adhere to this requirement.
>>
>> I wouldn't mind implementing something to enforce this in the IWCM or 
>> the iWARP drivers IF there was a clean way to do it.  So far there 
>> hasn't been a clean way proposed.
> 
> Why can't either uDAPL or iW CM always do a send from the active to 
> passive side that gets stripped off?  From the active side, the first 
> send is always posted before any user sends, and if necessary, a user 
> send can be queued by software to avoid a QP/CQ overrun.  The completion 
> can simply be eaten by software.  On the passive side, you have a 
> similar process for receiving the data.
> 
> (Yes this adds wire protocol, which requires both sides to support it.)
> 
> - Sean

I said "clean way to do it". ;-)

Yes, this is the only "under the covers" solution I know of that will 
work with existing HW.   However, I don't think it can be done totally 
within the rdmacm or iwcm.  I think it involves providers "poll" 
function to deal with the send completion/error and the passive side 
recv completion/error.

Steve.