Subject: LINKMODE & OPERSTATE thoughts
To: Johannes Berg <johannes@sipsolutions.net>,
        "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
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Cc: j@w1.fi
From: Denis Kenzior <denkenz@gmail.com>
Message-ID: <ad95b6e5-9220-3eca-bf93-8ba1d89bde3b@gmail.com> (sfid-20170609_234209_112071_67F4575C)
Date: Fri, 9 Jun 2017 16:42:03 -0500
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Sender: linux-wireless-owner@vger.kernel.org

Hi Johannes,

Let me start a separate thread on this:

>> Also, while we're on this subject.  Should the kernel auto-manage
>> the LINKMODE and OPERSTATE flags?  It would seem that it already has
>> the information to do so, and having userspace manage this just
>> introduces another source of latency / possibility of race
>> conditions, etc.
>
> I'm not convinced that it does have that information in all cases, and
> I don't see how that causes race conditions or much latency, since for
> client mode userspace would probably just set that together with the
> NL80211_STA_FLAG_AUTHORIZED flag?

Well right there is a race condition.  You have 2 sockets and both 
conveying the same information?

If we can optimize away an extra kernel trap, isn't that worthwhile 
thing to do?

The most common case is issuing Dormant + UP after setting keys & 
issuing the set_station command.  Isn't setting STA_FLAG_AUTHORIZED and 
operstate to IF_OPER_UP in effect equivalent?

Oh, by the way, some drivers don't implement set_station for normal 
links (e.g. setting STA_FLAG_AUTHORIZED returns an error), should they?

The only other cases where we mess with setting linkmode I can think of are:

1. After connecting to an open network
2. After a fast transition

For 1, it would seem that the kernel can easily infer that the 
IF_OPER_UP flag should be tweaked.
For 2, this needs to be done after the new TK is installed.  Can we 
combine these steps somehow?

Regards,
-Denis