[openib-general] ib_gid_is_link_local

[Jason Gunthorpe]

On Thu, Jan 04, 2007 at 07:04:19AM -0500, Hal Rosenstock wrote:

> > I think it depends how you code it.. In IP-like terms you have two
> > processes going on here, a route lookup and a 'neighbour lookup' (GID
> > to LID/etc conversion) for the link address.
> > 
> > An non-existing link local GID should pass the routing lookup, but fail the
> > neighbour lookup since there is no LID.
> > 
> > So typically you'd do the routing lookup and end up with an on-link
> > GID. Then you'd do the neighbour lookup and get a link address (IB path).
> 
> I think you are talking here about the end node and router function
> rather than SM/SA, right ?

The way I was hoping to start out is by putting this in the SA and the
routers, not in the end nodes.

> And in terms of IB path lookup, is the path just local with a
> destination of the neighbor (router) or global to the end point ?

With this kind of model the IB path lookup would return a LID/SL/etc
so it is a local path but might terminate on a router and might
require a GRH so it can be forwarded.

> > As an initial start I'd like to see support for an entry like this:
> > 
> > default via fe80::17:77ff:feff:5
> > 
> > Where fe80::17:77ff:feff:5 is the GID of a router. A full table for a
> > routing environment might look like:
> >  
> > fe80::/64 onlink
> > fe80::/10 unreachable ; IBA requires link local scope addresses never
> >                       ; to be routed
> > ff00::/8 onlink       ; Multicast is 'on link'
> 
> Why is all multicast scoped onlink ? I guess this is a starting point
> but not what IPoIB needs to run across IB subnets.

I'm thinking to start it would be OK to just force routers to be
subscribed to all MLIDs until we have a better idea how this needs to
work. This would work for IPoIB and is why I put it as onlink.

If the SM is doing the inter-subnet spanning tree then it probably
needs more routing entries.. If it is staying out of the picture then
this is probably enough.

Jason