[openib-general] [Fwd: RE: IB mcast question]

[Steve Wise]

On Tue, 2006-08-15 at 13:55 -0700, Roland Dreier wrote:

>  > App 1:
>  > Creates QP with QKey=22
>  > Joins multicast group 1 with QKey=33
>  > 
>  > App 2:
>  > Creates QP with QKey=44
>  > Joins multicast group 1
>  > Sends to multicast group but with QKey=22
> 
> I think that last send is technically an IBA spec violation.
> 
>  - R.

You guys are confusing me.  "sends to multicast group but with
QKey=22"... Does that mean you posted a SEND with the remote_qkey=22?

According to the spec, C10-15 sez the qkey in the outgoing packet will
be the qkey from the QP context IF the high order bit of the qkey is
set.  If the high order bit is _not_ set, then the outgoing packet will
contain the qkey from the WR. (why? why?)

Now, in my experiment, my mcast qkey was 0xe00a0a0a and the qp qkeys
were zero. So when the sender posted a SEND with remote_qkey=0xe00a0a0a,
the interface placed the qkey from sender's qp, which was zero, in the
packet.  That's why it worked I guess...

Now my head hurts...