[openib-general] [PATCH 1/2] rdma_cm: add support to join IPOIB multicast groups

[Or Gerlitz]

On 1/24/07, Sean Hefty <mshefty at ichips.intel.com> wrote:
> > The peer IPoIB would send an ARP and then would assume it can send its
> > packets to the QP number provided in the arp reply, so it would be
> > talking not with the rdma cm consumer but rather with the underlying
> > IPoIB in this node.
>
> Okay - so you want to change the QPN from that given in the ARP?  I missed that
> you wanted this, and I think I understand better what you're trying to do.

we don't want to use the QPN from the arp reply but rather the sidr
exchange etc as it is implemented in the rdma cm.


> > no! it is broken since the PS_IPOIB ID/QP that joined/attached the
> > multicast group is now using the ipoib broadcast qkey where the PS_UDP
> > ID/QP is using the RDMA_UDP_QKEY
>
> I'm only trying to support communication within the same port space, not between
> them.  Unicast is supported between different RDMA_PS_IPOIB QPs.

working only within a port space makes sense. However, your patch does
not allow for PS_IPOIB IDs  to do unicast since some places in the cma
kernel code only care for PS_UDP where they should care for PS_UDP OR
PS_IPOIB as i did in my patch...

> The question
> is how to obtain the IB unicast address (i.e. QPN, etc.) for RDMA_PS_IPOIB.  My
> assumption was that this capability wasn't needed, but you're saying that it is.
> I will update the patches.

thanks, and again its fine to obtain the IB unicast address for
PS_IPOIB IDs using the sidr exchange, you don't need to worry on the
ARP result. Only make sure that PS_IPOIB uses the ipoib broadcast
group qkey and also to what i mention above (code branching on PS_UDP
where it should do so on PS_UDP or PS_IPOIB).

thanks!

Or.