netdev - Re: [PATCH] bonding: Don't allow mode change via sysfs with slaves present

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Date:	Tue, 15 Nov 2011 15:47:00 -0500
From:	Andy Gospodarek <andy@...yhouse.net>
To:	Nicolas de Pesloüan 
	<nicolas.2p.debian@...il.com>
Cc:	Andy Gospodarek <andy@...yhouse.net>,
	Veaceslav Falico <vfalico@...hat.com>, netdev@...r.kernel.org,
	Jay Vosburgh <fubar@...ibm.com>
Subject: Re: [PATCH] bonding: Don't allow mode change via sysfs with slaves
	present

On Tue, Nov 15, 2011 at 09:02:24PM +0100, Nicolas de Pesloüan wrote:
> Le 15/11/2011 20:35, Andy Gospodarek a écrit :
>> On Tue, Nov 15, 2011 at 08:24:29PM +0100, Nicolas de Pesloüan wrote:
>>> Le 15/11/2011 18:00, Andy Gospodarek a écrit :
>>>> On Tue, Nov 15, 2011 at 05:44:42PM +0100, Veaceslav Falico wrote:
>>>>> When changing mode via bonding's sysfs, the slaves are not initialized
>>>>> correctly. Forbid to change modes with slaves present to ensure that every
>>>>> slave is initialized correctly via bond_enslave().
>>>>>
>>>>> Signed-off-by: Veaceslav Falico<vfalico@...hat.com>
>>>>
>>>> Looks good.  This behavior forces someone who wants to change to mode to
>>>> go through steps that are almost as destructive as when module options
>>>> are used to configure the mode.  I do not see a problem with this.
>>>
>>> Except the fact that is enforce one more constraint on the exact order
>>> one should write into sysfs to setup a bonding interface. We already have
>>> many such constraints and probably don't need more.
>>>
>>> Currently, it is possible to enslave slaves before selecting the mode.
>>> The ifenslave-2.6 package from Debian currently enslave slaves before
>>> setting the mode and would break with this change.
>>>
>>
>> Our testing indicates that 802.3ad mode bonding will not work unless the
>> devices are enslaved after the mode is set.  Does this mean that no one
>> using Debian is using 802.2ad mode or are they just not reporting it?
>
> I don't know. Possibly, they setup the bonding by hand, instead of 
> relying on the bonding extensions of /etc/network/interfaces provided by 
> the ifenslave-2.6 package.
>
> Having a look at popularity for the package 
> (http://qa.debian.org/popcon.php?package=ifenslave-2.6), it is obviously 
> not the most popular one, but...
>

Nicolas,

I took a look at the ifenslave package for debian more closely and it
actually looks like devices are enslaved last, after mode is set.  Can
you please take a look at this package and confirm what I'm seeing in
the 'pre-up' script.

It appears to me that setup_master sets the mode and enslave_slaves is
called after and enslaves the devices:

# Option slaves deprecated, replaced by bond-slaves, but still supported
# for backward compatibility.
IF_BOND_SLAVES=${IF_BOND_SLAVES:-$IF_SLAVES}

if [ "$IF_BOND_MASTER" ] ; then
        BOND_MASTER="$IF_BOND_MASTER"
        BOND_SLAVES="$IFACE"
else
        if [ "$IF_BOND_SLAVES" ] ; then
                BOND_MASTER="$IFACE"
                BOND_SLAVES="$IF_BOND_SLAVES"
        fi
fi

# Exit if nothing to do...
[ -z "$BOND_MASTER$BOND_SLAVES" ] && exit

add_master
early_setup_master
setup_master
enslave_slaves
exit 0

-andy

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