[openib-general] [PATCH] IPOIB: Use a GRH when appropriate for unicast packets

[Jason Gunthorpe]

On Wed, Feb 07, 2007 at 12:24:08PM -0800, Sean Hefty wrote:
> >I didn't get too far on getting CMA to work. Beyond the bad HopLimit
> >feild I was seeing Hal pointed out a number of problems in IBA that
> >would prevent it from working as is :<
> 
> I've started thinking about what it would take to get the rdma cm to work 
> across a router.  I think the rdma cm may need to treat IPv6 addresses as a 
> GID for this to work across subnets, versus trying to map an ipoib IP 
> address to a GID based on ARP.

I don't think that is the main problem - though clearly the way things
are now (for better or worse) rdma cm requires the IPoIB subnet to
span all of the IB subnets.. The main problem with the protocol is in
the LID selection for routed paths on the passive side. It can't rely
on the active side to identify the lids if a router is involved.

One feature I've thought has been underused in IBA is the raw IPv6
packet feature. It would be nice to have a linux netdev interface to
be able to do IPv6 traffic using GID addressing. That would seem to me
to be the natural way to bolt native GID addressing into rdma
cm..

Jason