netdev - Re: [virtio-dev] Re: net_failover slave udev renaming (was Re: [RFC PATCH net-next v6 4/4] netvsc: refactor notifier/event handling code to use the bypass framework)

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Date:   Thu, 21 Feb 2019 19:33:23 -0800
From:   si-wei liu <si-wei.liu@...cle.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>,
        Siwei Liu <loseweigh@...il.com>
Cc:     Jiri Pirko <jiri@...nulli.us>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Sridhar Samudrala <sridhar.samudrala@...el.com>,
        David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        virtualization@...ts.linux-foundation.org,
        virtio-dev <virtio-dev@...ts.oasis-open.org>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        Alexander Duyck <alexander.h.duyck@...el.com>,
        Jakub Kicinski <kubakici@...pl>,
        Jason Wang <jasowang@...hat.com>, liran.alon@...cle.com
Subject: Re: [virtio-dev] Re: net_failover slave udev renaming (was Re: [RFC
 PATCH net-next v6 4/4] netvsc: refactor notifier/event handling code to use
 the bypass framework)



On 2/21/2019 5:39 PM, Michael S. Tsirkin wrote:
> On Thu, Feb 21, 2019 at 05:14:44PM -0800, Siwei Liu wrote:
>> Sorry for replying to this ancient thread. There was some remaining
>> issue that I don't think the initial net_failover patch got addressed
>> cleanly, see:
>>
>> https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1815268
>>
>> The renaming of 'eth0' to 'ens4' fails because the udev userspace was
>> not specifically writtten for such kernel automatic enslavement.
>> Specifically, if it is a bond or team, the slave would typically get
>> renamed *before* virtual device gets created, that's what udev can
>> control (without getting netdev opened early by the other part of
>> kernel) and other userspace components for e.g. initramfs,
>> init-scripts can coordinate well in between. The in-kernel
>> auto-enslavement of net_failover breaks this userspace convention,
>> which don't provides a solution if user care about consistent naming
>> on the slave netdevs specifically.
>>
>> Previously this issue had been specifically called out when IFF_HIDDEN
>> and the 1-netdev was proposed, but no one gives out a solution to this
>> problem ever since. Please share your mind how to proceed and solve
>> this userspace issue if netdev does not welcome a 1-netdev model.
> Above says:
>
> 	there's no motivation in the systemd/udevd community at
> 	this point to refactor the rename logic and make it work well with
> 	3-netdev.
>
> What would the fix be? Skip slave devices?
>
There's nothing user can get if just skipping slave devices - the name 
is still unchanged and unpredictable e.g. eth0, or eth1 the next reboot, 
while the rest may conform to the naming scheme (ens3 and such). There's 
no way one can fix this in userspace alone - when the failover is 
created the enslaved netdev was opened by the kernel earlier than the 
userspace is made aware of, and there's no negotiation protocol for 
kernel to know when userspace has done initial renaming of the 
interface. I would expect netdev list should at least provide the 
direction in general for how this can be solved...

-Siwei