netdev - Re: [RFC] bridge: if no STP then forward all BPDU's

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Date:	Tue, 24 Apr 2007 16:20:27 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	shemminger@...ux-foundation.org
Cc:	netdev@...r.kernel.org
Subject: Re: [RFC] bridge: if no STP then forward all BPDU's

From: Stephen Hemminger <shemminger@...ux-foundation.org>
Date: Tue, 24 Apr 2007 16:12:26 -0700

> The bridge code by default captures all spanning tree packets and
> doesn't forward them. I propose that this might not be a good idea.
> 
> If a bridge is not running STP, then it has no way to detect a cycle
> in the network (by itself). But if some other machine is running STP,
> then if STP BPDU's get forwarded to the STP can detect the cycle
> (and turn off that link).  
> 
>               +------------+ <-BPDU-  +--------+
>               | transparent|==========| STP    |
>               |  bridge    |==========| bridge |=== ...
>               +------------+ -BPDU->  +--------+
>  
> 
> Signed-off-by: Stephen Hemminger <shemminger@...ux-foundation.org>

This makes a lot of sense, but I wonder about something:

old code:

> -	if (unlikely(is_link_local(dest))) {
> -		skb->pkt_type = PACKET_HOST;

new code:

> +	if (p->br->stp_enabled != BR_NO_STP && is_link_local(dest)) {
> +		/* skb->pkt_type should already be PACKET_MULTICAST */

So what is the true deal wrt. skb->pkt_type.  The original
code must have been setting it to PACKET_HOST for a reason,
won't leaving it at PACKET_MULTICAST break something?
-
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