netdev - Re: IPv6 route to gateway on fe80::1%eth0 when I have fe80::1%br0 locally

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Message-ID: <20160222192039.GC26042@torres.zugschlus.de>
Date:	Mon, 22 Feb 2016 20:20:39 +0100
From:	Marc Haber <mh+netdev@...schlus.de>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>
Cc:	netdev@...r.kernel.org
Subject: Re: IPv6 route to gateway on fe80::1%eth0 when I have fe80::1%br0
 locally

On Mon, Feb 22, 2016 at 05:15:41PM +0100, Hannes Frederic Sowa wrote:
> On 22.02.2016 16:47, Marc Haber wrote:
> >Can you reproduce the behavior with accept_ra_from_local =0 as well?
> >Unfortunately, the debugging VM I build works fine, it's just the
> >physical host showing this behavior. This is really strange.
> 
> Same here. Debugging VM didn't show this error at all and other systems
> didn't show this symptom either (4.4.2 as well as net-next).
> 
> With which kernel did you see this behavior for the first time and what was
> the last working version?

Thanks for motivating me to investigate this further.

I have to apologize. It is not a kernel issue.

It has turned out that systemd, starting with version 229, has placed
a "Not invented here" stamp on route advertisement processing in the
kernel and has implemented its own userspace code to handle router
advertisements.

And, of course, they did it wrong.

Setting IPv6AcceptRouterAdvertisements=0 in eth0.network seems to
disable enough code that this issue does not show any more.

Sorry for the rumble, I debugged the wrong piece of software. Bugs in
Debian are filed, #815582, #815586. I don't file bugs with systemd
upstream any more since I got silenced on systemd-devel for losing my
temper.

Greetings
Marc

-- 
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