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

Arınç ÜNAL
2023-06-04T09:40:50Z

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.

Arınç