netdev - Re: IPv6 FIB related crash with MACVLANs in 3.9.11+ kernel.

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Message-ID: <CAGCdqXHh6AvabW2JwQEK5NcnTuxw9eMdRwd+JvYZUYqyHW4K7Q@mail.gmail.com>
Date:	Sun, 12 Oct 2014 07:42:24 -0400
From:	Vladislav Yasevich <vyasevich@...il.com>
To:	Ben Greear <greearb@...delatech.com>
Cc:	Cong Wang <cwang@...pensource.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Hongmei Li <duckcncn@...il.com>,
	netdev <netdev@...r.kernel.org>
Subject: Re: IPv6 FIB related crash with MACVLANs in 3.9.11+ kernel.

On Mon, Sep 29, 2014 at 5:24 PM, Ben Greear <greearb@...delatech.com> wrote:
> On 09/29/2014 01:39 PM, Cong Wang wrote:
>> On Mon, Sep 29, 2014 at 12:48 PM, Ben Greear <greearb@...delatech.com> wrote:
>>>
>>> We are going to be running up to 20 concurrent scripts that
>>> will be dumping routes & ips, and configuring ip addresses
>>> and routes during bringup.
>>>
>>> I don't have a simple stand-alone way to reproduce this,
>>> but at least when we reported the problem is was very easy
>>> for us to reproduce with our tool.
>>>
>>> Maybe 20 scripts running in parallel that randomly configured and dumped routes
>>> and ip addresses on random interfaces would do the trick?
>>>
>>
>> I think the most important question is why is this related with macvlan?
>> IPv6 is L3 while macvlan pure L2, if this is a IPv6 routing bug, it should
>> not be limited to macvlan.
>
> We saw it using mac-vlans on top of ixgbe.  Probably it can be reproduced
> elsewhere, but since we had a good test case, we didn't bother trying lots
> of other combinations.
>
> Just enabling some debug code caused the problem to be much harder
> to reproduce, so it is probably some sort of race.  Maybe lots of mac-vlans
> make it easier to hit.
>
>> What does your IPv6 routing table look like? And how do you configure those
>> macvlan interfaces?
>
> Each interface would have it's own routing table, with at least as subnet
> route.  I'm not sure we were adding a default gateway or not.
>
> The main routing table would also have some auto-created routes
> I think.
>
> It is configured using 'ip' to add and dump routes.
>

Ben

Just saw this thread.  Can you check if this commit makes a difference:
commit 40b8fe45d1f094e3babe7b2dc2b71557ab71401d
Author: Vlad Yasevich <vyasevich@...il.com>
Date:   Mon Sep 22 16:34:17 2014 -0400

    macvtap: Fix race between device delete and open.

Thanks
-vlad

> Thanks,
> Ben
>
> --
> Ben Greear <greearb@...delatech.com>
> Candela Technologies Inc  http://www.candelatech.com
>
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