netdev - Re: [PATCH net-next v2] bridge: fix setlink/dellink notifications

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Date:	Sat, 17 Jan 2015 23:50:29 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	roopa@...ulusnetworks.com
Cc:	netdev@...r.kernel.org, shemminger@...tta.com, vyasevic@...hat.com,
	john.fastabend@...il.com, tgraf@...g.ch, jhs@...atatu.com,
	sfeldma@...il.com, jiri@...nulli.us, wkok@...ulusnetworks.com,
	ronen.arad@...el.com
Subject: Re: [PATCH net-next v2] bridge: fix setlink/dellink notifications

From: roopa@...ulusnetworks.com
Date: Wed, 14 Jan 2015 20:02:25 -0800

> problems with bridge getlink/setlink notifications today:
>         - bridge setlink generates two notifications to userspace
>                 - one from the bridge driver
>                 - one from rtnetlink.c (rtnl_bridge_notify)
>         - dellink generates one notification from rtnetlink.c. Which
> 	means bridge setlink and dellink notifications are not
> 	consistent
> 
>         - Looking at the code it appears,
> 	If both BRIDGE_FLAGS_MASTER and BRIDGE_FLAGS_SELF were set,
>         the size calculation in rtnl_bridge_notify can be wrong.
>         Example: if you set both BRIDGE_FLAGS_MASTER and BRIDGE_FLAGS_SELF
>         in a setlink request to rocker dev, rtnl_bridge_notify will
> 	allocate skb for one set of bridge attributes, but,
> 	both the bridge driver and rocker dev will try to add
> 	attributes resulting in twice the number of attributes
> 	being added to the skb.  (rocker dev calls ndo_dflt_bridge_getlink)
> 
> There are multiple options:
> 1) Generate one notification including all attributes from master and self:
>    But, I don't think it will work, because both master and self may use
>    the same attributes/policy. Cannot pack the same set of attributes in a
>    single notification from both master and slave (duplicate attributes).
> 
> 2) Generate one notification from master and the other notification from
>    self (This seems to be ideal):
>      For master: the master driver will send notification (bridge in this
> 	example)
>      For self: the self driver will send notification (rocker in the above
> 	example. It can use helpers from rtnetlink.c to do so. Like the
> 	ndo_dflt_bridge_getlink api).
> 
> This patch implements 2) (leaving the 'rtnl_bridge_notify' around to be used
> with 'self').
...
> Signed-off-by: Roopa Prabhu <roopa@...ulusnetworks.com>

Applied, thanks.
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