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Message-ID: <a9d02800-2cd6-a27b-7998-4c97cf2eb692@leemhuis.info>
Date:   Thu, 15 Jun 2023 14:54:48 +0200
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Subject: Re: [regression] STP on 80211s is broken in 6.4-rc4
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To:     Bagas Sanjaya <bagasdotme@gmail.com>,
        Nicolas Escande <nico.escande@gmail.com>, nbd@nbd.name,
        =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= <toke@toke.dk>,
        Kalle Valo <kvalo@kernel.org>,
        Johannes Berg <johannes.berg@intel.com>
Cc:     linux-wireless@vger.kernel.org,
        Linux Regressions <regressions@lists.linux.dev>
References: <CT5GNZSK28AI.2K6M69OXM9RW5@syracuse> <ZIQbs0wqdRh7c0Kx@debian.me>
From:   "Linux regression tracking (Thorsten Leemhuis)" 
        <regressions@leemhuis.info>
Reply-To: Linux regressions mailing list <regressions@lists.linux.dev>
In-Reply-To: <ZIQbs0wqdRh7c0Kx@debian.me>
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On 10.06.23 08:44, Bagas Sanjaya wrote:
> On Tue, Jun 06, 2023 at 12:55:57PM +0200, Nicolas Escande wrote:
>> Hello Felix,
>>
>> As user of the mesh part of mac80211 on multiple products at work let me say
>> thank you for all the work you do on wifi, especially on 80211s, and especially
>> the recent improvements you made for mesh fast RX/TX & cross vendor AMSDU compat
>>
>> We upgraded our kernel from an older (5.15) to a newer 6.4. The problem is STP 
>> doesn't work anymore and alas we use it for now (for the better or worse).
>>
>> What I gathered so far from my setup:
>>  - we use ath9k & ath10k
>>  - in my case STP frames are received as regular packet and not as amsdu
>>  - the received packets have a wrong length of 44 in tcpdump
>>    (instead of 38 with our previous kernel)
>>  - llc_fixup_skb() tries to pull some 41 bytes out of a 35 bytes packet
>>    this makes llc_rcv() discard the frames & breaks STP
>>
>> >From bisecting the culprit seems to be 986e43b19ae9176093da35e0a844e65c8bf9ede7
>> (wifi: mac80211: fix receiving A-MSDU frames on mesh interfaces)
>>
>> I guess that your changes to handle both ampdu subframes & normal frames in the
>> same datapath ends up putting a wrong skb->len for STP (multicast) frames ?
>> Honestly I don't understand enough of the 80211 internals & spec to pinpoint the
>> exact problem.
>>
>> It seems this change was already in the 6.3 kernel so I guess someone should
>> have seen it before (but I didn't find anything..) ? Maybe I missed something...
>>
>> Anyway I'm happy to provide more info or try anything you throw at me.
>>
> 
> Thanks for the regression report. I'm adding it to regzbot:
> 
> (Felix: it looks like this regression is introcued by a commit authored by you.
> Would you like to take a look on it?)
> 
> #regzbot ^introduced: 986e43b19ae917

Hmmm, Felix did not reply. But let's ignore that for now.

Nicolas, I noticed there are a few patches in next that refer to the
culprit. Might be worth giving this series a try:

https://lore.kernel.org/all/20230314095956.62085-1-nbd@nbd.name/

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
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