[openib-general] [PATCH] [RFC] dapltest change for iwarp

[James Lentini]

On Fri, 28 Apr 2006, Steve Wise wrote:

> On Fri, 2006-04-28 at 11:32 -0700, Sean Hefty wrote:
> > Steve Wise wrote:
> > > This patch changes the dapltest transaction test to force the client
> > > side (the side that dat_ep_connect()) to send the first RDMA message.
> > > This ensures that the IWARP MPA protocol requirements are met.
> > > 
> > > I'm presenting this for discussion and possible inclusion in the
> > > trunk.  
> > > 
> > > A transport independent application should be designed to work over all
> > > transports and should therefore utilize the only the common features.
> > > This implies that the application should always initiate RDMA exchanges
> > > starting with the client, to avoid MPA problems.
> > 
> > What if someone comes up with an RDMA transport that requires the server side to 
> > send the first message?
> > 
> 
> We shoot them. ;-)
> 
> Seriously... Good point.
> 
> The Chelsio RNIC has this issue.  If the server sends the first FPDU
> _before_ the client driver has moved the connection/qp into RDMA mode,
> then the data is placed as streaming data and the connection must be
> terminated (dapltest 6 exposes this intermittently).  Ammasso doesn't
> have this issue, but other RNIC's probably will.  

I'm confused. Is this an iWARP requirement or a Chelsio requirement? 
It sounds like iWARP supports data transfers being initiated by the 
server but the Chelsio implementation does not.

> One thing I'm experimenting with is to delay the ESTABLISHED event on
> the server side until the first FPDU is received.  However, we still
> probably need a way for an application to know whether the client has to
> send first (or the server as you pointed out).
> 
> I believe rnic-pi has an attribute that indicated this behavior...
>
> Steve.