netdev - Re: [PATCH] bonding: fix to rejoin multicast groups immediately

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Message-ID: <20101005220436.GA19931@redhat.com>
Date:	Tue, 5 Oct 2010 19:04:36 -0300
From:	Flavio Leitner <fbl@...hat.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] bonding: fix to rejoin multicast groups immediately

On Tue, Oct 05, 2010 at 01:25:25PM -0700, David Miller wrote:
> From: Flavio Leitner <fbl@...hat.com>
> Date: Tue, 5 Oct 2010 11:34:30 -0300
> 
> > On Tue, Oct 05, 2010 at 12:13:38AM -0700, David Miller wrote:
> >> From: Flavio Leitner <fleitner@...hat.com>
> >> Date: Wed, 29 Sep 2010 04:12:07 -0300
> >> 
> >> > It should rejoin multicast groups immediately when
> >> > the failover happens to restore the multicast traffic.
> >> > 
> >> > Signed-off-by: Flavio Leitner <fleitner@...hat.com>
> >> 
> >> I suspect the IGMPv3 handling via a delayed action, as is currently
> >> implemented, is on purpose and is done so to follow the specification
> >> of the IGMPv3 RFCs.
> >> 
> >> Therefore you have to explain why your new behavior is so desirable
> >> and in particular why something as undesirable as violating the RFCs
> >> is therefore warranted.
> > 
> > That patch only changes the behavior for bonding during a link
> > failure, so if we have a bonding in active-backup or any other mode
> > with current-active-slave, the initialization will happen just fine
> > following IGMP specs.
> > 
> > However, neither the backup slave interface nor the backup switch
> > connected to backup slave knows about mcast. Thus when a link failure
> > happens, we shouldn't rely on timers to not stay out of the mcast
> > group losing traffic.
> > 
> > E.g. The V1 specs says that we shouldn't send any membership report
> > if it has been one in the last minute because that means the switch
> > is notified and the system will receive mcast traffic for that group. 
> > Therefore, if it sees one and a link failure happens right after that,
> > the backup slave will send another membership report only one minute
> > later. During this time the system loses traffic.
> 
> All of this valuable information belongs in the commit log message.
> 
> Please resubmit your patch with all of the necessary contextual
> information and reasoning explaining in the commit message.

Sure. I'll post replying to another thread so that the patch
can be applied in correct order.

thanks for reviewing it
-- 
Flavio
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