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Subject: Re: [PATCH] mac80211: Send deauth to STA's upon AP stop
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Shay Bar <Shay.Bar@celeno.com>,
        Ben Greear <greearb@candelatech.com>
Cc:     "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Date:   Thu, 25 Jun 2020 11:51:47 +0200
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On Sun, 2020-06-21 at 10:12 +0000, Shay Bar wrote:
> Hi Johannes and Ben,
> 
> To conclude this thread, hostapd doesn’t send any deauth/disassoc
> upon AP stop (when hostapd is killed _or_ when "ifconfig down" the
> AP interface).

Right. I'm sort of suggesting you just shouldn't be doing this, and it
doesn't seem like most people actually do, otherwise we'd have seen this
issue before?

> This is causing a situation where stations keep sending unicast frames
> to a down AP interface as it doesn’t know it's gone down.
> I tried your suggestion and sent 1 deauth/disassoc as broadcast
> (instead of unicast to each STA), but some stations (e.g. Samsung S8)
> Ignore this broadcast (while it will not ignore unicast deauth/disassoc).
> Although not indicated in the standard, I think it's better to let STA
> Know AP gone down by sending this unicast deauth to each STA
> (as this patch does).

I'm not really sure. That's a _lot_ of frames and potentially quite a
long time. In the patch, as written, I'm not even convinced you can be
sure that they will all make it out to the air?

johannes