netdev - Re: bonding (IEEE 802.3ad) not working with qemu/virtio

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Date:	Sat, 30 Jan 2016 12:41:16 +0100
From:	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
To:	David Miller <davem@...emloft.net>
Cc:	jay.vosburgh@...onical.com, bjornar.ness@...il.com,
	netdev@...r.kernel.org, vfalico@...il.com,
	gospo@...ulusnetworks.com, jiri@...nulli.us, mst@...hat.com,
	virtualization@...ts.linux-foundation.org
Subject: Re: bonding (IEEE 802.3ad) not working with qemu/virtio

On 01/30/2016 07:59 AM, David Miller wrote:
> From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
> Date: Fri, 29 Jan 2016 22:48:26 +0100
> 
>> On 01/29/2016 10:45 PM, Jay Vosburgh wrote:
>>> Nikolay Aleksandrov <nikolay@...ulusnetworks.com> wrote:
>>>
>>>> On 01/25/2016 05:24 PM, Bjørnar Ness wrote:
>>>>> As subject says, 802.3ad bonding is not working with virtio network model.
>>>>>
>>>>> The only errors I see is:
>>>>>
>>>>> No 802.3ad response from the link partner for any adapters in the bond.
>>>>>
>>>>> Dumping the network traffic shows that no LACP packets are sent from the
>>>>> host running with virtio driver, changing to for example e1000 solves
>>>>> this problem
>>>>> with no configuration changes.
>>>>>
>>>>> Is this a known problem?
>>>>>
>>>> [Including bonding maintainers for comments]
>>>>
>>>> Hi,
>>>> Here's a workaround patch for virtio_net devices that "cheats" the
>>>> duplex test (which is the actual problem). I've tested this locally
>>>> and it works for me.
>>>> I'd let the others comment on the implementation, there're other signs
>>>> that can be used to distinguish a virtio_net device so I'm open to suggestions.
>>>> Also feedback if this is at all acceptable would be appreciated.
>>>
>>> 	Should virtio instead provide an arbitrary speed and full duplex
>>> to ethtool, as veth does?
>>>
>>> 	Creating a magic whitelist of devices deep inside the 802.3ad
>>> implementation seems less desirable.
>>>
>> TBH, I absolutely agree. In fact here's what we've been doing:
>> add set_settings which allows the user to set any speed/duplex
>> and get_settings of course to retrieve that. This is also useful
>> for testing other stuff that requires speed and duplex, not only
>> for the bonding case.
> 
> I also agree.  Having a whitelist is just rediculous.
> 
> There should be a default speed/duplex setting for such devices as well.
> We can pick one that will be use universally for these kinds of devices.
> 
Yes, that's the other thing - the default setting, from a brief grepping
I see that veth uses 10Gbps, tun uses 10Mbps and batman-adv uses 10Mbps.

If we add a default get_settings that can be used by virtual devices
in ethtool that returns 10Gbps with the settings set like veth does
sounds good to me. What do you think ?

In fact they all set the same settings (apart from speed) so we can
consolidate them in a single default setting init function and for the
ones using different speed do something like:
__ethtool_init_settings(); <- sets everything like veth would with 10Mbps speed
__ethtool_cmd_speed_set(cmd, SPEED_10000);
And we're done.