netdev - Re: [PATCH] bonding: set device in RLB ARP packet handler

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Message-ID: <20100723195947.GA7123@w-gedwards.lhn.com>
Date:	Fri, 23 Jul 2010 13:59:47 -0600
From:	Greg Edwards <greg.edwards@...com>
To:	Andy Gospodarek <andy@...yhouse.net>
Cc:	Jay Vosburgh <fubar@...ibm.com>,
	"bonding-devel@...ts.sourceforge.net" 
	<bonding-devel@...ts.sourceforge.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] bonding: set device in RLB ARP packet handler

On Fri, Jul 23, 2010 at 07:34:56PM +0000, Andy Gospodarek wrote:
> On Thu, Jul 22, 2010 at 3:52 PM, Greg Edwards <greg.edwards@...com> wrote:
>> With commit 6146b1a4, the dev field in the RLB ARP packet handler was
>> set to NULL to wildcard and accommodate balancing VLANs on top of
>> bonds.
>>
>> This has the side-effect of the packet handler being called against
>> other, non RLB-enabled bonds, and a kernel oops results when it tries
>> to
>> dereference rx_hashtbl in rlb_update_entry_from_arp(), which won't be
>> set for those bonds, e.g. active-backup.
>>
>> With the __netif_receive_skb() changes from commit 1f3c8804, frames
>> received on VLANs correctly make their way to the bond's handler,
>> so we no longer need to wildcard the device.
>
> I see this problem as well, but I would propose to fix it another way to
> not alter the receive path so close to the release of 2.6.35 and to
> catch this for 802.3ad bonds as well.

Is the problem demonstrable with 802.3ad bonds?  bond_register_lacpdu()
sets pk_type->dev = bond->dev.

>> Signed-off-by: Greg Edwards <greg.edwards@...com>
>> ---
>> Jay,
>>
>> The oops can be reproduced by:
>>
>> modprobe bonding
>>
>> echo active-backup > /sys/class/net/bond0/bonding/mode
>> echo 100 > /sys/class/net/bond0/bonding/miimon
>> ifconfig bond0 xxx.xxx.xxx.xxx netmask xxx.xxx.xxx.xxx
>> echo +eth0 > /sys/class/net/bond0/bonding/slaves
>> echo +eth1 > /sys/class/net/bond0/bonding/slaves
>>
>> echo +bond1 > /sys/class/net/bonding_masters
>> echo balance-alb > /sys/class/net/bond1/bonding/mode
>> echo 100 > /sys/class/net/bond1/bonding/miimon
>> ifconfig bond1 xxx.xxx.xxx.xxx netmask xxx.xxx.xxx.xxx
>> echo +eth2 > /sys/class/net/bond1/bonding/slaves
>> echo +eth3 > /sys/class/net/bond1/bonding/slaves
>>
>> Pass some traffic on bond0.  Boom.
>>
>
> bonding: make sure mode-specific handlers handle appropriate frames
>
> This patch will exit out of rlb_arp_recv and bond_3ad_lacpdu_recv early
> if the bond receiving the frame isn't using that mode.

I had originally thought of doing something like this, but it didn't
seem as clean.  I don't have strong feelings one way or the other,
though.

Greg
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