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

[Sean Hefty]

> Basically, if IB routers are used, and the IPoIB feature of *not*
> spanning a subnet is used (for scalabililty?) then you need an
> alternate way to specify addresses to rdma cm.

This was the case I was thinking of.  Without global IB name service resolution, 
how do you get the GID of the remote system?

> I agree that special casing some IPv6 addresses is a bad idea. It
> needs to be integrated correctly with NET and the routing table/etc

I haven't given this more than a few minutes of thought, but I was thinking more 
along the lines of a port having an assigned GID that's the same as an assigned 
IPv6 address.  (Is there some reason this wouldn't work?)  IP name service 
resolution would map the name to the IPv6 address.  The mapping from the IPv6 
address to a GID would then be straightforward, as opposed to using a mapping 
using ARP.

If name service resolution gives me an IPv6 address that's off of the local 
subnet, but the ARP response gives me an address that's on the local subnet, 
then I think we can assume that ARP was unsuccessful is resolving the address to 
the remote GID.  (I.e. the GID should be for a router.)  If this is true, then 
we need some other way to acquire the DGID.

- Sean