linux-kernel - Re: [PATCH v2 net-next 04/11] net: bridge: offload initial and final port flags through switchdev

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Message-ID: <20210211074443.GB324421@shredder.lan>
Date:   Thu, 11 Feb 2021 09:44:43 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Andrew Lunn <andrew@...n.ch>,
        Vivien Didelot <vivien.didelot@...il.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        bridge@...ts.linux-foundation.org, Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <nikolay@...dia.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        UNGLinuxDriver@...rochip.com, Vadym Kochan <vkochan@...vell.com>,
        Taras Chornyi <tchornyi@...vell.com>,
        Grygorii Strashko <grygorii.strashko@...com>,
        Ioana Ciornei <ioana.ciornei@....com>,
        Ivan Vecera <ivecera@...hat.com>, linux-omap@...r.kernel.org
Subject: Re: [PATCH v2 net-next 04/11] net: bridge: offload initial and final
 port flags through switchdev

On Thu, Feb 11, 2021 at 01:23:52AM +0200, Vladimir Oltean wrote:
> On Wed, Feb 10, 2021 at 12:59:49PM +0200, Ido Schimmel wrote:
> > > > The reverse, during unlinking, would be to refuse unlinking if the upper
> > > > has uppers of its own. netdev_upper_dev_unlink() needs to learn to
> > > > return an error and callers such as team/bond need to learn to handle
> > > > it, but it seems patchable.
> > >
> > > Again, this was treated prior to my deletion in this series and not by
> > > erroring out, I just really didn't think it through.
> > >
> > > So you're saying that if we impose that all switchdev drivers restrict
> > > the house of cards to be constructed from the bottom up, and destructed
> > > from the top down, then the notification of bridge port flags can stay
> > > in the bridge layer?
> >
> > I actually don't think it's a good idea to have this in the bridge in
> > any case. I understand that it makes sense for some devices where
> > learning, flooding, etc are port attributes, but in other devices these
> > can be {port,vlan} attributes and then you need to take care of them
> > when a vlan is added / deleted and not only when a port is removed from
> > the bridge. So for such devices this really won't save anything. I would
> > thus leave it to the lower levels to decide.
> 
> Just for my understanding, how are per-{port,vlan} attributes such as
> learning and flooding managed by the Linux bridge? How can I disable
> flooding only in a certain VLAN?

You can't (currently). But it does not change the fact that in some
devices these are {port,vlan} attributes and we are talking here about
the interface towards these devices. Having these as {port,vlan}
attributes allows you to support use cases such as a port being enslaved
to a VLAN-aware bridge and its VLAN upper(s) enslaved to VLAN unaware
bridge(s). Obviously you need to ensure there is no conflict between the
VLANs used by the VLAN-aware bridge and the VLAN device(s).