[Fwd: Re: [openib-general] IPoIB Multicast]

[Hal Rosenstock]

On the first issue, I now understand why there are 2 joins for the
broadcast group.

ipoib_set_mcast_list causes the ipoib_restart_task to be run which stops
and starts the multicast thread. Doing this causes the first join to the
broadcast group to be cancelled (flushed) and even though it appears to
work on the IB wire, it is not completed in the host. The second join
for the broadcast group is completed without being cancelled. 

Not sure what (if anything) should be done about this.

-- Hal

-----Forwarded Message-----

From: Hal Rosenstock <halr at voltaire.com>
To: Roland Dreier <roland at topspin.com>
Cc: openib-general at openib.org
Subject: Re: [openib-general] IPoIB Multicast
Date: 06 Nov 2004 14:48:38 -0500

On Sat, 2004-11-06 at 14:27, Roland Dreier wrote:
>     Hal> 1. If you down the interface and bring it back up, the second
>     Hal> time up, there are 2 identical join requests for the
>     Hal> broadcast group rather than just 1. These 2 come out very
>     Hal> close to one another (217 usec apart). Is there some counting
>     Hal> issue that is causing this ?
> 
>     Hal> 2. When leaving an IP multicast group, there appears to be an
>     Hal> extra join to 0x16 (something like 224.0.0.22 which would be
>     Hal> for IGMP). Any ideas on this ?
> 
> If you or someone else doesn't debug these issues first, I'll take a
> look at the code.

I'll take a first crack and look at the code to see what I can
determine. 

On the second issue, I partially understand what is going on: IPmc group
changes need to be reported via IGMP so the IPmc router knows to prune
the multicast tree, but... I don't understand why it joins here (and not
earlier when a IPmc group is first joined by this node and second after
the join is successful, I do not see any IGMP packet come out of the
node (onto IB; maybe it is going out the ethernet instead).

-- Hal

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