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:   Wed, 27 Feb 2019 17:52:18 -0800
From:   Jakub Kicinski <kubakici@...pl>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     si-wei liu <si-wei.liu@...cle.com>,
        "Samudrala, Sridhar" <sridhar.samudrala@...el.com>,
        Siwei Liu <loseweigh@...il.com>, Jiri Pirko <jiri@...nulli.us>,
        Stephen Hemminger <stephen@...workplumber.org>,
        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>,
        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 Wed, 27 Feb 2019 20:26:02 -0500, Michael S. Tsirkin wrote:
> On Wed, Feb 27, 2019 at 04:52:05PM -0800, Jakub Kicinski wrote:
> > On Wed, 27 Feb 2019 19:41:32 -0500, Michael S. Tsirkin wrote:  
> > > > As this scheme adds much complexity to the kernel naming convention
> > > > (currently it's just ethX names) that no userspace can understand.    
> > > 
> > > Anything that pokes at slaves needs to be specially designed anyway.
> > > Naming seems like a minor issue.  
> > 
> > Can the users who care about the naming put net_failover into
> > "user space will do the bond enslavement" mode, and do the bond
> > creation/management themselves from user space (in systemd/ 
> > Network Manager) based on the failover flag?  
> 
> Putting issues of compatibility aside (userspace tends to be confused if
> you give it two devices with same MAC), how would you have it work in
> practice? Timer based hacks like netvsc where if userspace didn't
> respond within X seconds we assume it won't and do everything ourselves?

Well, what I'm saying is basically if user space knows how to deal with
the auto-bonding, we can put aside net_failover for the most part.  It
can either be blacklisted or it can have some knob which will
effectively disable the auto-enslavement.

Auto-bonding capable user space can do the renames, spawn the bond,
etc. all by itself.  I'm basically going back to my initial proposal
here :)  There is a RedHat bugzilla for the NetworkManager team to do
this, but we merged net_failover before those folks got around to
implementing it.

IOW if NM/systemd is capable of doing the auto-bonding itself it can
disable the kernel mechanism and take care of it all.  If kernel is
booted with an old user space which doesn't have capable NM/systemd -
net_failover will kick in and do its best.