[openib-general] RDMA connection and address translation API

[Caitlin Bestler]

The data required when doing a qp-modify-to-rts is inherently
transport specific. IB requires a set of data obtained from the
IB CM protocol (or the equivalent data through application specific
black magic), while iWARP requires a handle for a TCP connection
(assumed to be a socket, but not explicitly required to be so).

The problem is that when the RDMAC specified the iWARP modify qp
to RTS behaviour they did not forsee the non-technical barriers
to simply using a socket handle to specify transfer of ownership
of a TCP connection from one stack to another.
 

> -----Original Message-----
> From: openib-general-bounces at openib.org 
> [mailto:openib-general-bounces at openib.org] On Behalf Of James Lentini
> Sent: Thursday, August 25, 2005 7:54 AM
> To: Roland Dreier
> Cc: openib-general at openib.org
> Subject: Re: [openib-general] RDMA connection and address 
> translation API
> 
> 
> 
> On Wed, 24 Aug 2005, Roland Dreier wrote:
> 
> >     Sean> Is the idea that the user calls connect() and 
> then receives
> >     Sean> a single callback indicating that the connection has been
> >     Sean> established?  If so, then the user may need to 
> modify the QP
> >     Sean> to the INIT state, which would require some knowledge
> >     Sean> already of the path.  We would also need to be clear on
> >     Sean> whether the QP is expected to be in the INIT state before
> >     Sean> connect is called, or if it could be in any 
> arbitrary state.
> >     Sean> The other alternative is to provide multiple callbacks
> >     Sean> during connection establishment.
> > 
> > To me it makes sense for the generic CM API to be defined 
> so that an 
> > IB QP must be in the INIT state before being passed to connect().
> 
> Will the ib_modify_qp() function be made transport neutral? I 
> see some fields in the ib_qp_attr structure that are IB specific.
> 
> I think the RDMA connection API should perform all the QP 
> state transitions for the ULP. How about a new call to create 
> the QP and perform all QP state transitions necessary for the 
> posting receive work requests?
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