Subject: Re: [patch net-next 01/15] net: introduce upper device lists

From: Stephen Hemminger <[email-masked]>
Date: Sun, 30 Dec 2012 20:56:33 -0800

On Sun, 30 Dec 2012 12:58:08 +0100
Jiri Pirko <[email-masked]> wrote:

> This lists are supposed to serve for storing pointers to all upper devices.
> Eventually it will replace dev->master pointer which is used for
> bonding, bridge, team but it cannot be used for vlan, macvlan where
> there might be multiple upper present. In case the upper link is
> replacement for dev->master, it is marked with "master" flag.
> 
> New upper device list resolves this limitation. Also, the information
> stored in lists is used for preventing looping setups like
> "bond->somethingelse->samebond"
> 
> Signed-off-by: Jiri Pirko <[email-masked]>

What is the use case for this?
Could you describe a topology that the new upper device list supports,
that the old scheme does not?

I am concerned that it may open up many new possibilities for user
error that were not possible before. For example how does it prevent
an ethernet from being assigned to both a bonding and bridge at the
same time?