netdev - Re: [PATCH net-next 0/3] VLANs, DSA switches and multiple bridges

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Message-ID: <20200218195812.GD80929@t480s.localdomain>
Date:   Tue, 18 Feb 2020 19:58:12 -0500
From:   Vivien Didelot <vivien.didelot@...il.com>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Florian Fainelli <f.fainelli@...il.com>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Ido Schimmel <idosch@...sch.org>,
        "David S. Miller" <davem@...emloft.net>,
        Ivan Vecera <ivecera@...hat.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 0/3] VLANs, DSA switches and multiple bridges

On Wed, 19 Feb 2020 00:17:37 +0000, Russell King - ARM Linux admin <linux@...linux.org.uk> wrote:
> On Tue, Feb 18, 2020 at 04:00:08PM -0800, Florian Fainelli wrote:
> > On 2/18/20 3:45 AM, Russell King - ARM Linux admin wrote:
> > > Hi,
> > > 
> > > This is a repost of the previously posted RFC back in December, which
> > > did not get fully reviewed.  I've dropped the RFC tag this time as no
> > > one really found anything too problematical in the RFC posting.
> > > 
> > > I've been trying to configure DSA for VLANs and not having much success.
> > > The setup is quite simple:
> > > 
> > > - The main network is untagged
> > > - The wifi network is a vlan tagged with id $VN running over the main
> > >   network.
> > > 
> > > I have an Armada 388 Clearfog with a PCIe wifi card which I'm trying to
> > > setup to provide wifi access to the vlan $VN network, while the switch
> > > is also part of the main network.
> > 
> > Why not just revert 2ea7a679ca2abd251c1ec03f20508619707e1749 ("net: dsa:
> > Don't add vlans when vlan filtering is disabled")? If a driver wants to
> > veto the programming of VLANs while it has ports enslaved to a bridge
> > that does not have VLAN filtering, it should have enough information to
> > not do that operation.
> 
> I do not have the knowledge to know whether reverting that commit
> would be appropriate; I do not know how the non-Marvell switches will
> behave with such a revert - what was the reason for the commit in
> the first place?
> 
> The commit says:
> 
>     This fixes at least one corner case. There are still issues in other
>     corners, such as when vlan_filtering is later enabled.
> 
> but it doesn't say what that corner case was.  So, presumably reverting
> it will cause a regression of whatever that corner case was...

It is hard to care about regression when we have no idea what these "corner
cases" are. Also things like ds->vlan_filtering* were added after if I'm
not mistaken, so the drivers might have enough information now to adapt to
or reject some unsupported bridge offload.

Getting rid of this limitation would definitely be another approach worth
trying.


Thanks,

	Vivien