[openib-general] [RFC] [PATCH 2/7] ib_multicast 2.6.20: add ib_multicast module to track join requests from the same port

[Hal Rosenstock]

On Wed, 2006-10-11 at 12:24, Eitan Zahavi wrote:
> Sean Hefty wrote:
> > Michael S. Tsirkin wrote:
> >   
> >> Why is this even a good idea?
> >> If you are looking for reasons using mutlicast module in ipoib is good, I would
> >> say blocking unpriviledged userspace from joining IPoIB GID and snoopig on all
> >> mcast traffic sounds like a better idea.  BTW, Sean, I think this is something
> >> we need for the ucma multicast part to go in. I would imagine kernel components
> >> could set some kind of flag on mcast join to make them exclusive.
> >> API currently does not allow for that.
> >>     
> >
> > http://openib.org/pipermail/openib-general/2006-March/019147.html
> >
> > Why is it a bad idea?  The architecture allows this.  However, none of the 
> > proposed patches allows a userspace app to join an ipoib multicast group.  And 
> > an application that talks directly to the SA via MADs puts us no worse off than 
> > before.
> >
> >   
> This is incorrect. The SA can track requests from multiple different 
> QPs. It could actually also enforce using QP1 for the requests. But it 
> can not differentiate requests from same port different applications 
> comming on QP1...
> So if you did catch all QP1 traffic and refcount at that level you will 
> be 100% clean.

What about redirection ?

-- Hal

> 
> 
> >> And why the rush? Is the new module used at all yet?
> >> Let's see it get some use before switching a basic component over.
> >>     
> >
> > This module was added to svn in April.  The request was to begin the process for 
> > queuing it to 2.6.20, which is likely 2-3 more months out.  I hardly call that a 
> > rush.
> >
> >   
> >> Finally, the patch in question also seems to introduce more cleanups and
> >> such. It would be less controversial if it was just an API change.
> >>     
> >
> > The cleanups are part of the change.  Once ib_join_multicast() has been invoked, 
> > ib_free_multicast() must be called exactly once.  Proper state tracking for this 
> > is required.
> >
> > - Sean
> >
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