linux-kernel - Re: Multicast: handling of STA disconnect

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Message-ID: <14361063-5005-4dd6-a314-737aaea7bf2c@blackwall.org>
Date:   Mon, 20 Mar 2023 19:33:43 +0200
From:   Nikolay Aleksandrov <razor@...ckwall.org>
To:     Ujjal Roy <royujjal@...il.com>
Cc:     roopa@...dia.com, netdev@...r.kernel.org,
        Kernel <linux-kernel@...r.kernel.org>,
        bridge@...ts.linux-foundation.org
Subject: Re: Multicast: handling of STA disconnect

On 20/03/2023 19:25, Ujjal Roy wrote:
> Hi Nik,
> 
> Flushing MDB can only be done when we are managing it per station not
> per port. For that we need to have MCAST_TO_UCAST, EHT and FAST_LEAVE.
> 
> Here one more point is - some vendors may offload MCAST_TO_UCAST
> conversion in their own FW to reduce CPU.
> 
> So, the best way is to have MCAST_TO_UCAST enabled and MDB will become
> per station, so we can delete MDB on disconnect. Shall, I create one
> patch for review?
> 
> Thanks,
> UjjaL Roy
> 
> On Mon, Mar 20, 2023 at 5:38 PM Nikolay Aleksandrov <razor@...ckwall.org> wrote:
>>
>> On 20/03/2023 13:45, Ujjal Roy wrote:
>>> Hi Nikolay,
>>>
>>> I have some query on multicast. When streams running on an STA and STA
>>> disconnected due to some reason. So, until the MDB is timed out the
>>> stream will be forwarded to the port and in turn to the driver and
>>> dropps there as no such STA.
>>>
>>> So, is the multicast_eht handling this scenario to take any action
>>> immediately? If not, can we do this to take quick action to reduce
>>> overhead of memory and driver?
>>>
>>> I have an idea on this. Can we mark this port group (MDB entry) as
>>> INACTIVE from the WiFi disconnect event and skip forwarding the stream
>>> to this port in br_multicast_flood by applying the check? I can share
>>> the patch on this.
>>>
>>> Thanks,
>>> UjjaL Roy
>>
>> Hi,
>> Fast leave and EHT (as that's v3's fast leave version) are about quickly converging when
>> a leave is received (e.g. when there are no listeners to quickly remove the mdb). They
>> don't deal with interface states (IIUC). Why don't you just flush the port's mdb entries
>> on disconnect? That would stop fwding.
>>
>> Cheers,
>>  Nik
>>
>>

Hi,
Alright, let's see the patch to better understand what is necessary.
Also please don't top post on netdev@.

Cheers,
 Nik