netdev - Re: [PATCH 2/2] bridge: allow forwarding some link local frames

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Date:	Wed, 05 Oct 2011 20:40:19 +0100
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] bridge: allow forwarding some link local frames

On Mon, 2011-10-03 at 21:14 -0700, Stephen Hemminger wrote:
> plain text document attachment (bridge-multicast-filter.patch)
> This is based on an earlier patch by Nick Carter with comments
> by David Lamparter but with some refinements. Thanks for their patience
> this is a confusing area with overlap of standards, user requirements,
> and compatibility with earlier releases.
> 
> It adds a new sysfs attribute 
>    /sys/class/net/brX/bridge/group_fwd_mask
> that controls forwarding of frames with address of: 01-80-C2-00-00-0X
> The default setting has no forwarding to retain compatibility.
> 
> One change from earlier releases is that forwarding of group
> addresses is not dependent on STP being enabled or disabled. This
> choice was made based on interpretation of tie 802.1 standards.
> I expect complaints will arise because of this, but better to follow
> the standard than continue acting incorrectly by default.
> 
> The filtering mask is writeable, but only values that don't forward
> known control frames are allowed. It intentionally blocks attempts
> to filter control protocols. For example: writing a 8 allows
> forwarding 802.1X PAE addresses which is the most common request.
[...]

I wonder why you don't forbid forwarding frames sent to reserved
destination addresses?  The standards seem pretty clear that this should
not be allowed.

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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