Re: IPoIB: Fix multicast packet drops before join is complete

[David Miller <davem@davemloft.net>]

From: Roland Dreier <rdreier@cisco.com>
Date: Tue, 09 Jun 2009 13:52:45 -0700

> 
>  > > Maybe we need a different approach but (since we are at the point of
>  > > talking about categorical fundamentally wrong statements) its
>  > > fundamentally wrong if the IPoIB layer works differently from a regular
>  > > Ethernet NIC. They should work in the same way.
>  > 
>  > This I agree on.  When a multicast group is joined, the IPoIB layer
>  > should block in some way until the subscription is fully available
>  > for use.
> 
> Not sure I understand.  What do you mean by block?  It is quite possible
> that a single multicast group is waiting to be joined, while other
> multicast groups and unicast traffic can be sent with no problem.  So
> stopping the whole device queue and blocking everything doesn't seem
> appropriate.

Block the process joining the multicast group, not the entire
interface.