netdev - Re: fe80::/64 route missing on GRE tunnels

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Message-ID: <20140215121027.GC8634@order.stressinduktion.org>
Date:	Sat, 15 Feb 2014 13:10:27 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	nicolas.dichtel@...nd.com
Cc:	netdev@...r.kernel.org, itk-intern@...fundet.no, sesse@...fundet.no
Subject: Re: fe80::/64 route missing on GRE tunnels

Hi Nicolas!

On Sat, Feb 15, 2014 at 08:45:59AM +0100, Hannes Frederic Sowa wrote:
> On Tue, Feb 11, 2014 at 10:59:28PM +0100, Steinar H. Gunderson wrote:
> > On Tue, Feb 11, 2014 at 10:55:11PM +0100, Steinar H. Gunderson wrote:
> > > but on 3.13.1, no such route shows up. I can add it manually, though.
> > 
> > Correction; I can add it manually, but only to one GRE device at a time:
> > 
> >   root@...ersex:~$ ip -6 route add fe80::/64 dev k_molvenfinnoy
> >   root@...ersex:~$ ip -6 route add fe80::/64 dev k_sessesveits
> >   RTNETLINK answers: File exists
> >   root@...ersex:~$ ip -6 route del fe80::/64 dev k_molvenfinnoy
> >   root@...ersex:~$ ip -6 route add fe80::/64 dev k_sessesveits
> >   root@...ersex:~$
> 
> Sorry for the long delay, I was busy with other stuff...
> 
> So basically a workaround you can do for the time being is to add the tunnel
> with a local address:
> 
> ip tunnel add foo mode gre local 4.3.2.1 remote 1.2.3.4 ttl 64
> 
> The reason is that link local address generation fails in ipv6/addrconf as
> long as dev->dev_addr is zero.
> 
> I have not yet found the change which causes this change in behaviour, but
> will do so soon.

f7cb8886335dea ("sit/gre6: don't try to add the same route two times") causes
this problem, because dev->dev_addr will never get initialized and thus
ipv6_generate_eui64 and addrconf_add_linklocal will never get called.

Ok for revert or do you have a better idea?

Greetings,

  Hannes

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