netdev - Re: [PATCH] bonding: correct the MAC address for "follow" fail_over

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Message-Id: <20150720.203009.2006764612728170046.davem@davemloft.net>
Date:	Mon, 20 Jul 2015 20:30:09 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	dingtianhong@...wei.com
Cc:	j.vosburgh@...il.com, vfalico@...il.com, gospo@...ulusnetworks.com,
	netdev@...r.kernel.org, fengtiantian@...wei.com,
	hahaer.guo@...wei.com
Subject: Re: [PATCH] bonding: correct the MAC address for "follow"
 fail_over_mac policy

From: Ding Tianhong <dingtianhong@...wei.com>
Date: Thu, 16 Jul 2015 16:30:02 +0800

> The "follow" fail_over_mac policy is useful for multiport devices that
> either become confused or incur a performance penalty when multiple
> ports are programmed with the same MAC address, but the same MAC
> address still may happened by this steps for this policy:
> 
> 1) echo +eth0 > /sys/class/net/bond0/bonding/slaves
>    bond0 has the same mac address with eth0, it is MAC1.
> 
> 2) echo +eth1 > /sys/class/net/bond0/bonding/slaves
>    eth1 is backup, eth1 has MAC2.
> 
> 3) ifconfig eth0 down
>    eth1 became active slave, bond will swap MAC for eth0 and eth1,
>    so eth1 has MAC1, and eth0 has MAC2.
> 
> 4) ifconfig eth1 down
>    there is no active slave, and eth1 still has MAC1, eth2 has MAC2.
> 
> 5) ifconfig eth0 up
>    the eth0 became active slave again, the bond set eth0 to MAC1.
> 
> Something wrong here, then if you set eth1 up, the eth0 and eth1 will have the same
> MAC address, it will break this policy for ACTIVE_BACKUP mode.
> 
> This patch will fix this problem by finding the old active slave and
> swap them MAC address before change active slave.
> 
> Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>

Applied and queued up for -stable, thanks.
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