Re: [regression] STP on 80211s is broken in 6.4-rc4

["Nicolas Escande" <nico.escande@gmail.com>]

On Thu Jun 15, 2023 at 2:54 PM CEST, Linux regression tracking (Thorsten Leemhuis) wrote:
> 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.

I haven't seen mails from felix on the list for a few days, I'm guessing he's
unavailable for now but I'll hapilly wait.

>
> 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/

Well this series already landed in 6.4 and that is the version I did my initial
testing with. So no luck there.

>
> Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
> --
> Everything you wanna know about Linux kernel regression tracking:
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