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Date: Tue, 28 May 2024 10:21:06 +0200
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Subject: Re: [REGRESSION][BISECTED] wifi: RTL8821CE does not work in monitor
 mode
To: Johannes Berg <johannes.berg@intel.com>, regressions@lists.linux.dev
Cc: Kalle Valo <kvalo@kernel.org>, linux-wireless@vger.kernel.org,
 Savyasaachi Vanga <savyasaachiv@gmail.com>,
 Christian Heusel <christian@heusel.eu>
References: <chwoymvpzwtbmzryrlitpwmta5j6mtndocxsyqvdyikqu63lon@gfds653hkknl>
From: "Linux regression tracking (Thorsten Leemhuis)"
 <regressions@leemhuis.info>
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On 28.05.24 00:01, Christian Heusel wrote:
> 
> Savyasaachi reports that scanning for other stations in monitor mode
> does not work anymore with his RTL8821CE wireless network card for linux
> kernels after 6.8.9.
> [...]

So back to the real problem:

@wifi developers: Is there some bigger problem in 6.9.y related to
monitoring mode that is affecting a lot of drivers/users?

I'm asking because I noticed another report that sounded related. To
quote: https://bugzilla.kernel.org/show_bug.cgi?id=218884

"""
>  Michael 2024-05-24 17:04:51 UTC
> 
> Some features are broken since kernel 6.9.1 when running monitor mode.
> 
> First bug:
> Switching a channel via "NL80211_ATTR_WIPHY_FREQ" does not switch the channel/frequency.
> 
> That is not a device driver problem, because all device drivers (Mediatek, Ralink, Realtek, ...) are affected.
> 
> To reproduce:
> set monitor mode (by iw)
> change channel (by iw)
> check if channel has been changed (by iw)
> record traffic and check radiotap header (Channel frequency)
> 
> More information is here:
> https://github.com/ZerBea/hcxdumptool/discussions/454
> https://github.com/morrownr/8821au-20210708/issues/133#issuecomment-2125425552
> confirmed by other users:
> https://github.com/morrownr/8821au-20210708/issues/133#issuecomment-2125392151
> 
> 
> Second bug:
> frame injection is broken
> 
> To reproduce:
> Try to send a 80211 frame via raw socket (PF_PACKET). It is not transmitted over the air
> https://github.com/ZerBea/hcxdumptool/discussions/454
> 
> 
> In monitor mode, none of the WiFI tools (iw, Wireshark, airodump-ng, aireplay-ng, hcxdumptool, hcxlabtool is able to switshc the channel or to transmit 80211 frames since kernel 6.9
> 
> [tag] [reply] [−]
> Private
> Comment 1 Michael 2024-05-26 09:00:58 UTC
> 
> BTW:
> Testing monitor mode mode these days is no easy task, because most of the device drivers are not working as expected:
> https://bugzilla.kernel.org/show_bug.cgi?id=218528
> https://bugzilla.kernel.org/show_bug.cgi?id=217465
> https://bugzilla.kernel.org/show_bug.cgi?id=218528
> https://github.com/openwrt/mt76/issues/839
> 
> And now, since kernel 6.9.1, the mac stack is broken, too.
> 
"""

Ciao, Thorsten (wearing his 'the Linux kernel's regression tracker' hat)
--
Everything you wanna know about Linux kernel regression tracking:
https://linux-regtracking.leemhuis.info/about/#tldr
If I did something stupid, please tell me, as explained on that page.