Re: [PATCH net-next 4/4] net: dsa: set configure_vlan_while_not_filtering to true by default

From: Florian Fainelli <f.fainelli@gmail.com>
To: Vladimir Oltean <olteanv@gmail.com>
Cc: davem@davemloft.net, vivien.didelot@gmail.com, andrew@lunn.ch,
	netdev@vger.kernel.org
Subject: Re: [PATCH net-next 4/4] net: dsa: set configure_vlan_while_not_filtering to true by default
Date: Fri, 11 Sep 2020 12:39:00 -0700	[thread overview]
Message-ID: <ac73600d-6c1d-83a3-9b49-19f853ba0226@gmail.com> (raw)
In-Reply-To: <20200911183556.l3cazdcwkosyw45v@skbuf>

On 9/11/2020 11:35 AM, Vladimir Oltean wrote:
> 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?

I do, because I realized that some of the switches we support are still 
configured in DSA_TAG_NONE mode because the CPU port they chose is not 
Broadcom tag capable and there is an user out there who cares a lot 
about that case not to "break".

> 
> 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.

OK so something along the lines of: port is bridged, and bridge has 
vlan_filtering=0 and switch does egress tagging and VID is bridge's 
default_pvid then pop the tag?

Should this be a helper function that is utilized by the relevant tagger 
drivers or do you want this in dsa_switch_rcv()?
-- 
Florian