[openib-general] multicast code/merge status

[Sean Hefty]

> sure, it can use the rdmacm qkey (0x1234567 etc) when it creates the QP 
> and later --if-- the user joins a multicast group modify the qp state 
> with the group qkey and report it in the cma event such that the 
> consumer of the rdmacm would set this into his IB UD TX WR

Changing the qkey would break its existing UD communication.

> Bottom line, Looking in the IB SPEC and IPoIB RFC i did not see 
> mentioning of privileged QKEY.

 From RFC 4391 (ipoib RFC), 4.1:

  2. Q_Key

           It is RECOMMENDED that a controlled Q_Key be used with the
           high-order bit set.  This is to prevent non-privileged
           software from fabricating and sending out bogus IP datagrams.

I don't know what qkey is actually assigned, however.

I have some path forward related tasks that I would like to complete before 
starting on this.  I hope to finish that before the end of this week.  I don't 
want to rush on the multicast support and miss something.  For the rdma cm, we 
may need to let the user set some options when joining a multicast group.  Maybe 
something like: join type (send-only or send-receive), group type (ipoib or rdma 
defined), etc.

I do plan on requesting that the core multicast changes to ib_sa and ib_ipoib be 
pulled into 2.6.21.

- Sean