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Message-ID: <616a319e4b8623508f6cd00fcfca8303f494a2de.camel@sipsolutions.net>
Subject: Re: mac80211_hwsim (kernel 4.18+): wmediumd + 2.4Ghz
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Ramon Fontes <ramonreisfontes@gmail.com>,
        Bob Copeland <me@bobcopeland.com>
Cc:     Krishna Chaitanya <chaitanya.mgit@gmail.com>,
        linux-wireless <linux-wireless@vger.kernel.org>
Date:   Tue, 01 Oct 2019 15:49:33 +0200
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On Tue, 2019-10-01 at 10:19 -0300, Ramon Fontes wrote:
> > Do they also have the same version of wmediumd?
> 
> Yes, they have the same version. As you can also see through the
> video, I only change the kernel and all the packages have the same
> version. I also tried to check the latest commits of mac80211_hwsim,
> but haven't found a reason for the problem yet.

I had been looking, but didn't consider that where you say "4.18" you
probably meant "4.18.xyz" for some stable version of 4.18 ...

Now that I look at that, I think most likely the reason is commit
119f94a6fefc ("cfg80211: Address some corner cases in scan result
channel updating") which was backported to the 4.18 series.

Before this commit, we'd have used the DS element all the time, after
this commit we'd trust the RX channel on 5 GHz...

Here's a test to reproduce this:

https://p.sipsolutions.net/63b37d07fd52179c.txt

However, I think the only reasonable way to fix this is in wmediumd:

https://p.sipsolutions.net/6c52392b5e31d9d1.txt

Bob, what do you think?

johannes