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Date:   Fri, 11 Sep 2020 21:35:56 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Florian Fainelli <f.fainelli@...il.com>
Cc:     davem@...emloft.net, vivien.didelot@...il.com, andrew@...n.ch,
        netdev@...r.kernel.org
Subject: Re: [PATCH net-next 4/4] net: dsa: set
 configure_vlan_while_not_filtering to true by default

On Fri, Sep 11, 2020 at 11:23:28AM -0700, Florian Fainelli wrote:
> On 9/11/2020 8:43 AM, Vladimir Oltean wrote:
> > > The slightly confusing part is that a vlan_filtering=1 bridge accepts the
> > > default_pvid either tagged or untagged whereas a vlan_filtering=0 bridge
> > > does not, except for DHCP for instance. I would have to add a br0.1 802.1Q
> > > upper to take care of the default_pvid being egress tagged on the CPU port.
> > >
> > > We could solve this in the DSA receive path, or the Broadcom tag receive
> > > path as you say since that is dependent on the tagging format and switch
> > > properties.
> > >
> > > With Broadcom tags enabled now, all is well since we can differentiate
> > > traffic from different source ports using that 4 bytes tag.
> > >
> > > Where this broke was when using a 802.1Q separation because all frames that
> > > egressed the CPU were egress tagged and it was no longer possible to
> > > differentiate whether they came from the LAN group in VID 1 or the WAN group
> > > in VID 2. But all of this should be a thing of the past now, ok, all is
> > > clear again now.
> >
> > Or we could do this, what do you think?
>
> Yes, this would be working, and I just tested it with the following delta on
> top of my b53 patch:
>
> diff --git a/drivers/net/dsa/b53/b53_common.c
> b/drivers/net/dsa/b53/b53_common.c
> index 46ac8875f870..73507cff3bc4 100644
> --- a/drivers/net/dsa/b53/b53_common.c
> +++ b/drivers/net/dsa/b53/b53_common.c
> @@ -1427,7 +1427,7 @@ void b53_vlan_add(struct dsa_switch *ds, int port,
>                         untagged = true;
>
>                 vl->members |= BIT(port);
> -               if (untagged)
> +               if (untagged && !dsa_is_cpu_port(ds, port))
>                         vl->untag |= BIT(port);
>                 else
>                         vl->untag &= ~BIT(port);
> @@ -1465,7 +1465,7 @@ int b53_vlan_del(struct dsa_switch *ds, int port,
>                 if (pvid == vid)
>                         pvid = b53_default_pvid(dev);
>
> -               if (untagged)
> +               if (untagged && !dsa_is_cpu_port(ds, port))
>                         vl->untag &= ~(BIT(port));
>
>                 b53_set_vlan_entry(dev, vid, vl);
>
> and it works, thanks!
>

I'm conflicted. So you prefer having the CPU port as egress-tagged?

Also, I think I'll also experiment with a version of this patch that is
local to the DSA RX path. The bridge people may not like it, and as far
as I understand, only DSA has this situation where pvid-tagged traffic
may end up with a vlan tag on ingress.

Thanks,
-Vladimir

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