netdev - Re: [PATCH net-next] bonding,vlan: propagate MAC failover changes to VLANs

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Date:	Wed, 18 Apr 2012 19:17:59 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Jay Vosburgh <fubar@...ibm.com>
CC:	<netdev@...r.kernel.org>, "David S. Miller" <davem@...emloft.net>,
	Patrick McHardy <kaber@...sh.net>,
	Andy Gospodarek <andy@...yhouse.net>
Subject: Re: [PATCH net-next] bonding,vlan: propagate MAC failover changes
 to VLANs

On Wed, 2012-04-18 at 11:02 -0700, Jay Vosburgh wrote:
> 	With bonding's fail_over_mac=active, during failover the MAC
> address of the bond itself changes to match that of the slave.
> 
> 	This patch adds a notifier call to cause VLANs stacked atop the
> bonding to also change their MAC addresses to the new address when a
> failover occurs.
> 
> 	While it is legal for a VLAN to have a MAC address that differs
> from the underlying device, at least one device (qeth) that requires the
> use of fail_over_mac for bonding cannot handle the VLAN's MAC differing
> from that of the bond; thus, it needs the MAC change to propagate up
> to any VLANs when fail_over_mac is set to active.
[...]

This doesn't make sense to me.  You're applying the behaviour to all
VLANs on top of a bond, whether or not the underlying device is driven
by qeth, and ignoring any MAC address changes that don't involve the
bonding driver.

I think either of these would be better fixes:
1. Make VLAN devices follow changes to the parent device's MAC address
unless they are assigned an address of their own.
2. Add a configuration flag for VLAN devices to follow changes to the
parent device's MAC address.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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