netdev - Re: [PATCH] bridge: mask forwarding of IEEE 802 local multicast groups

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Date:	Sat, 2 Jul 2011 00:37:56 +0200
From:	David Lamparter <equinox@...c24.net>
To:	Nick Carter <ncarter100@...il.com>
Cc:	netdev@...r.kernel.org,
	Michał Mirosław <mirqus@...il.com>,
	David Lamparter <equinox@...c24.net>,
	Stephen Hemminger <shemminger@...ux-foundation.org>,
	davem@...emloft.net
Subject: Re: [PATCH] bridge: mask forwarding of IEEE 802 local multicast
 groups

On Fri, Jul 01, 2011 at 10:21:44PM +0100, Nick Carter wrote:
> Introduce sysfs ../bridge/group_fwd_mask attribute so users can
> configure which group mac addresses are forwarded.
> 
> These diffs do not change the default behaviour of bridge.ko.  By
> changing the group_fwd_mask value users can select any combination of
> the 01-80-C2-00-00-00 - 01-80-C2-00-00-0F addresses to be forwarded.
> 
> Signed-off-by: Nick Carter <ncarter100@...il.com>

Hm. Makes it very easy to shoot yourself in the foot, but...

> +	br->group_fwd_mask = 0;

... but the default is safe, so we're following the unix philosophy of
handing out the gun to shoot yourself :)

Reviewed-by: David Lamparter <equinox@...c24.net>


PS:
> @@ -166,6 +166,9 @@ struct sk_buff *br_handle_frame(struct sk_buff *skb)
>  		if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
>  			goto forward;

Not sure if we still need the STP one when we have the mask, it should
probably go away for consistency. It would change existing behaviour
though... either way it can be a separate patch.

> +		if (p->br->group_fwd_mask & (1 << dest[5]))
> +			goto forward;
> +
>  		if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
>  			    NULL, br_handle_local_finish))
>  			return NULL;	/* frame consumed by filter */
--
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