netdev - Re: [PATCH net-next 27/30] net: dsa: mt7530: introduce BPDU trapping for MT7530 switch

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Message-ID: <6a64db9e-ac6c-c571-fb8b-ae3aa2da07b7@arinc9.com>
Date: Sat, 10 Jun 2023 11:32:45 +0300
From: Arınç ÜNAL <arinc.unal@...nc9.com>
To: Vladimir Oltean <olteanv@...il.com>
Cc: Sean Wang <sean.wang@...iatek.com>, Landen Chao
 <Landen.Chao@...iatek.com>, DENG Qingfang <dqfext@...il.com>,
 Daniel Golle <daniel@...rotopia.org>, Andrew Lunn <andrew@...n.ch>,
 Florian Fainelli <f.fainelli@...il.com>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Russell King <linux@...linux.org.uk>,
 Richard van Schagen <richard@...terhints.com>,
 Richard van Schagen <vschagen@...com>,
 Frank Wunderlich <frank-w@...lic-files.de>,
 Bartel Eerdekens <bartel.eerdekens@...stell8.be>, erkin.bozoglu@...ont.com,
 mithat.guner@...ont.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH net-next 27/30] net: dsa: mt7530: introduce BPDU trapping
 for MT7530 switch

On 4.06.2023 15:47, Vladimir Oltean wrote:
> On Sun, Jun 04, 2023 at 12:39:33PM +0300, Arınç ÜNAL wrote:
>> On 4.06.2023 12:23, Vladimir Oltean wrote:
>>> On Sun, Jun 04, 2023 at 11:51:33AM +0300, Arınç ÜNAL wrote:
>>>>> If the switch doesn't currently trap BPDUs, isn't STP broken?
>>>>
>>>> No, the BPDU_PORT_FW bits are 0 after reset. The MT7620 programming guide
>>>> states that frames with 01:80:C2:00:00:00 MAC DA (which is how the BPDU
>>>> distinction is being made) will follow the system default which means the
>>>> BPDUs will be treated as normal multicast frames.
>>>>
>>>> Only if all 3 bits are set will the BPDUs be dropped.
>>>
>>> Right, if you don't trap BPDUs just to the CPU but flood them, I believe
>>> the STP protocol won't behave properly with switching loops. Worth testing.
>>
>> I've got no interest spending time playing around with STP at the moment so
>> I'm going to pass.
> 
> You can at the very least move it towards the beginning of the net-next patch
> set, so that we can be sure it doesn't depend on the other refactoring work,
> in case someone in the future makes a request for the patch to be backported
> to stable.

Maybe I should submit this and LLDP trapping to net? Currently, the 
MT7530 subdriver on the stable kernels treat LLDP frames and BPDUs as 
regular multicast frames, therefore flooding them to user ports, which 
is wrong. These patches could count as bug fixes.

Arınç