netdev - Re: [PATCH net-next] net: bridge: pop vlan from skb if filtering is disabled but it's a pvid

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Date:   Sat, 12 Sep 2020 10:23:02 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Nikolay Aleksandrov <nikolay@...dia.com>
Cc:     "stephen@...workplumber.org" <stephen@...workplumber.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        Roopa Prabhu <roopa@...dia.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "andrew@...n.ch" <andrew@...n.ch>
Subject: Re: [PATCH net-next] net: bridge: pop vlan from skb if filtering is
 disabled but it's a pvid

On Sat, Sep 12, 2020 at 06:56:12AM +0000, Nikolay Aleksandrov wrote:
> Could you point me to a thread where these problems were discussed and why
> they couldn't be resolved within DSA in detail ?

See my discussion with Florian in this thread:
http://patchwork.ozlabs.org/project/netdev/patch/20200907182910.1285496-5-olteanv@gmail.com/
There's a bunch of unrelated stuff going on there, hope you'll manage.

> > - the bridge API only offers a race-free API for determining the pvid of
> >   a port, br_vlan_get_pvid(), under RTNL.
> >
>
> The API can be easily extended.
>

If you can help, cool.

> > And in fact this might not even be a situation unique to DSA. Any driver
> > that receives untagged frames as pvid-tagged is now able to communicate
> > without needing an 8021q upper for the pvid.
> >
>
> I would prefer we don't add hardware/driver-specific fixes in the bridge, when
> vlan filtering is disabled there should be no vlan manipulation/filtering done
> by the bridge. This could potentially break users who have added 8021q devices
> as bridge ports. At the very least this needs to be hidden behind a new option,
> but I would like to find a way to actually push it back to DSA. But again adding
> hardware/driver-specific options should be avoided.
>
> Can you use tc to pop the vlan on ingress ? I mean the cases above are visible
> to the user, so they might decide to add the ingress vlan rule.
>
> Thanks,
>  Nik

I can, but I think that all in all it's a bit strange for the bridge to
not untag pvid-tagged frames.

Thanks!
-Vladimir