[ofa-general] [RFC] ipoib: multicast sender will leave the group when neighbour is cleaned

[Yosef Eitgin]

Roland Dreier wrote:
>  > The problem:
>  > A multicast sender joins the MGID as full member, but does not leave
>  > (as long as the interface is up). This causes an MGID leakage in the
>  > SM.
> 
> I think ipoib has used send-only joins for a while now.  But the problem
> of never cleaning up these memberships stands.

The problem worse because ipoib is not really using send-only joins, it
joins as full member. See ipoib_multicast.c/ipoib_mcast_sendonly_join():

	struct ib_sa_mcmember_rec rec = {
#if 0				/* Some SMs don't support send-only yet */
		.join_state = 4
#else
		.join_state = 1
#endif
	};


> 
> Thanks for looking at this -- it would be nice to deal with this.
> 
>  > An issue we found with this solution, is that it takes a while until the
>  > neighbour is cleaned, and it requires that the host will send some traffic
>  > (I supposed that unless we put more entries in the routing table, out neighbour
>  > will not be garbage collected).
> 
> Would it work to have a more naive approach, and just keep track of the
> last time each send-only membership was used, and set up a timer that
> runs, say every minute, and garbage collect send-only memberships that
> are more than 2 minutes old, or something like that?

I guess it would, and it will sure be simpler.

> 
>  - R.
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