[openib-general] Re: rdma_cm.h: comment nits.

[Tom Tucker]

On Thu, 2006-05-11 at 10:56 +0300, Michael S. Tsirkin wrote:
> Quoting r. Tom Tucker <tom at opengridcomputing.com>:
> > Subject: RE: rdma_cm.h: comment nits.
> > 
> > On Wed, 2006-05-10 at 14:20 -0700, Caitlin Bestler wrote:
> > > Tom Tucker wrote:
> > > 
> > > > 
> > > > So... all that said, I could in fact support rdma_reject on
> > > > an active side connection. But this would effectively reduce
> > > > to a QP --> ERROR and I doubt this matches the semantics
> > > > you're looking for.
> > > > 
> > > > 
> > > 
> > > And you could send an RST. 
> > 
> > Yep, in fact that's what many RNIC's do when you move the QP to ERROR
> > instead of CLOSING. 
> > 
> > > There's just no way to send any user
> > > supplied private data. It's not just unreliable, it's guaranteed
> > > not to arrive. It's still a long way from the truly desired
> > > semantics, but the wire protocol just doesn't carry that info.
> > > 
> > 
> > Yeah, I think you're correct -- it would be a bogus "emulation".
> 
> I don't think any real ULP passes private data inside the Reject.

> 
> Private data in response (SYN/ACK) is clearly portable, is it not?

For iWARP the data is actually exchanged after TCP connection
establishment as part of MPA negotiation. But yes, private data exchange
is supported during connection establishment. It can be provided on the
active side (rdma_connect) and on the passive side (rdma_accept,
rdma_reject). What is not currently supported is calling rdma_connect
and then rdma_reject (presumably to cancel the connect request after
receiving the remote peers private data). The supported behavior for
iWARP on the active side would be to call rdma_disconnect if you didn't
like the private data provided.


>