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Message-ID: <4bb71d8a-daf1-5f60-daf0-44aa8afcfdc3@nbd.name>
Date:   Tue, 11 Jul 2023 13:12:22 +0200
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Subject: Re: [regression] STP on 80211s is broken in 6.4-rc4
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To:     Nicolas Escande <nico.escande@gmail.com>,
        Linux regressions mailing list <regressions@lists.linux.dev>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rg?= =?UTF-8?Q?ensen?= 
        <toke@toke.dk>, Kalle Valo <kvalo@kernel.org>,
        Johannes Berg <johannes.berg@intel.com>
Cc:     linux-wireless@vger.kernel.org
References: <CT5GNZSK28AI.2K6M69OXM9RW5@syracuse> <ZIQbs0wqdRh7c0Kx@debian.me>
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 <CTDWJJDKSYYD.XBG1CAZB3A5W@syracuse>
 <809500b6-4eec-7a5e-5930-00e7eeebcc5e@leemhuis.info>
 <CTYNAK10A6AJ.1I4W9V78VG1NB@syracuse>
From:   Felix Fietkau <nbd@nbd.name>
In-Reply-To: <CTYNAK10A6AJ.1I4W9V78VG1NB@syracuse>
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On 10.07.23 18:50, Nicolas Escande wrote:
> On Mon Jul 10, 2023 at 1:32 PM CEST, Linux regression tracking (Thorsten Leemhuis) wrote:
>> On 16.06.23 09:45, Nicolas Escande wrote:
>> > 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:
>> >>>>
>> >>>> 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.
>> >> [...]
>> >> 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.
>>
>> Still no progress. Hmmm. Are you still okay with that? I've seen no
>> other reports about this, so waiting is somewhat (albeit not completely)
>> fine for me if it is for you.
> I'm not so surprised no one else reported it, using STP on wifi (and 802.11s) is
> not a really common thing to do, to be honest (and STP on wifi is unreliable).
> Even though some openwrt guys do it for sure, I'm guessing their kernel version
> is lagging behind...
>>
>> But in any case it might be good if you could recheck 6.5-rc1.
> Testing on 6.5 as a whole won't be as easy for me as testing a single patch on
> top of 6.4. I'll do my best to try but from what I saw nothing got merged that
> would even remotely help me on this issue.
> 
> I am not loosing hope that Felix or someone that understands this stuff better
> finds the time to look into this. I'm guessing it's the summer vacation effet.

Sorry for the delay. This should fix the regression, please test.
I will submit it for 6.5 soon.
---
--- a/net/wireless/util.c
+++ b/net/wireless/util.c
@@ -580,6 +580,8 @@ int ieee80211_strip_8023_mesh_hdr(struct
  		hdrlen += ETH_ALEN + 2;
  	else if (!pskb_may_pull(skb, hdrlen))
  		return -EINVAL;
+	else
+		payload.eth.h_proto = htons(skb->len - hdrlen);

  	mesh_addr = skb->data + sizeof(payload.eth) + ETH_ALEN;
  	switch (payload.flags & MESH_FLAGS_AE) {