netdev - Re: [PATCH] net: Fix tentative IPv6 address due to DAD looping back

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Message-ID: <20130412200353.GA23992@order.stressinduktion.org>
Date:	Fri, 12 Apr 2013 22:03:53 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	"Meng, Jilin" <Jilin.Meng@....com>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
	"kaber@...sh.net" <kaber@...sh.net>,
	"Sun, Yinglin" <yinglin.sun@....com>,
	"Prithviraj, Lakshmanan" <lakshmanan.prithviraj@....com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH] net: Fix tentative IPv6 address due to DAD looping back

On Fri, Apr 12, 2013 at 07:51:41PM +0200, Hannes Frederic Sowa wrote:
> On Fri, Apr 12, 2013 at 07:45:54AM +0000, Meng, Jilin wrote:
> > This version accepted David's comments of coding style, Eric's comments of ether_addr_equal_64bits(), and Hannes' comments of eth_hdr(), etc.
> > 
> > we should ignore the looped-back IPv6 DAD packet to avoid configuration failure.
> > This occurs when a bonding interface with roundrobin mode is being configured an IPv6 address while the switch side isn't configured bonding/channel yet.
> [...]
> What do you think if we hook up a function which does reenable ipv6 on
> an interface as soon as 'disable_ipv6' is switched to '0'? So you could
> control reacquiring the ipv6 address from userspace without ifup&ifdown
> and the risk of disturbing ipv4 connections? This seems to be the
> easiest solution (but have not checked thoroughly).
> [...]

I just looked into it and it does already worked as expected. Didn't know why
I assumed that there was only a disable handler. So you can resolve this issue
from userspace by a timer or a small program which listens for loopback
traffic in userspace and do DAD after the loop is resolved. I think this is a
more sensible solution.

Thanks,

  Hannes

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