[openib-general] Problem is routing CM REQ

[Hal Rosenstock]

On Thu, 2007-02-08 at 23:37, Jason Gunthorpe wrote:
> On Thu, Feb 08, 2007 at 03:43:24PM -0800, Sean Hefty wrote:
> > > Looking at the problem more, I think that the issue extends to the remote port 
> > > LID as well.  My expectation with a local path record query is that the SLID is 
> > > the local port, and the DLID is the local router.  This should be sufficient for 
> > > one-way UD traffic, but for connected traffic we still need to discover the 
> > > remote router and remote port LIDs.
> > 
> > Given a path record query for:
> > 
> > SGID - local
> > DGID - remote
> > 
> > What would be the SLID and DLID?
> > 
> > And if the query is reversed, such that:
> > 
> > SGID - remote
> > DGID - local
> > 
> > Are the SLID/DLID values simply reversed?
> 
> I have a follow up question to this.. With CM how is the SL for each
> side determined? I'm looking through the code here and it looks like
> the SL of the active side is passed in the REQ to the passive side (ie
> both sides are the same) But cma_query_ib_route does not set the
> reversible bit when it asks for the path. If you don't set the
> reversible bit isn't it necessary to make a 2nd path query to get the
> reverse path's SL? [Path responses without the reversible bit set
> are actually simplex paths and reversing them probably will run into
> SL2VL mapping tables that cause the packets to be dropped ie o7-8]
> 
> Infact, to get an optimal path aren't 3 path records required:
> 1) A reversible path from active to passive from the CM GMPs
>   (required by C12-5.1.3)
> 2) An optimal non-reversible path from active to passive
> 3) An optimal non-reversible path from passive to active

What you are saying seems correct to me although I am not sure about
reversibility in the intersubnet case.

It may be that the non reversible paths supplied (in a single subnet)
happen to also be reversible so this all works.

-- Hal

> Jason
> 
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