From: Thomas Graf <tgraf@suug.ch>
Subject: Re: [RFC IPv6] Disabling IPv6 autoconf
Date: Tue, 29 Aug 2006 20:10:21 +0200
Message-ID: <20060829181021.GA3470@postel.suug.ch>
References: <20060829082435.GA2676@suse.de>
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Cc: netdev@vger.kernel.org, Jan Beulich <jbeulich@suse.de>
To: Olaf Kirch <okir@suse.de>
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In-Reply-To: <20060829082435.GA2676@suse.de>
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* Olaf Kirch <okir@suse.de> 2006-08-29 10:24
> we had bug reports from people seeing lots of spurious messages
> like the following:
> 
> kernel: peth0: received packet with own address as source address.
> 
> and
> 
> xenbr0: duplicate address detected!
> 
> This is on a Xen enabled machine, with lots of Xen machines on the
> same network.
> 
> When the Xen code configures the bridge device, this will do IPv6
> autoconfiguration for the interface, and since they use synthetic MAC
> addresses, there will be DAD collisions.
> 
> When the Xen people looked for a way to disable IPv6 autoconf of the
> bridge, they didn't find any way to do it without bringing up the
> device first (and thereby triggering DAD).

They didn't find any because there is no need to disable it. I
hardly think that the network stack should fix things that Xen
got wrong. Setting dev_addr to -1 is just plain wrong, other
virtual ethernet devices call random_ether_addr(), it's not a
new problem at all.