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Subject: Re: [RFC PATCH] cfg80211: fix duplicated scan entries after channel
 switch
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Sergey Matyukevich <sergey.matyukevich.os@quantenna.com>
Cc:     "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
        Igor Mitsyanko <igor.mitsyanko.os@quantenna.com>,
        Mikhail Karpenko <mkarpenko@quantenna.com>
Date:   Tue, 02 Jul 2019 14:40:57 +0200
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Hi Sergey,

On Tue, 2019-07-02 at 11:50 +0000, Sergey Matyukevich wrote:

> Thanks for review! Summarizing your comments, here are the options
> and some of their highlights:
> 
> 1. replace old entry with the new entry
>    - no easy way to update ifmgd->associated w/o rework of mac80211 csa

Yes, this one's the tricky one. I don't think you can make this work
easily.

> 2. keep old entry, remove new entry
>    - this is what suggested RFC patch does
>    - works, but update of current_bss entry after csa may be delayed

Correct.

> 3. keep old entry, update it using data from new entry, then remove new entry
>    - this looks like a better approach
> 
> Unless I am missing something, the last option can be implemented on top of
> the current RFC patch w/o extra complexity. The required bss entry update is
> what cfg80211_bss_update function does when bss in question already exists.
> So it should be possible to reuse that code.

Agree, you just need to sort of invert it, or call it like this:

 * relink the old entry, unlink a new entry (if any)
 * bss_update() with the new entry if there was one
 * it should free one of the entries if I remember correctly

> I will post RFC patch v2 after more testing for both mac80211 and
> fullmac cases.

Sounds good, thanks a lot for working on this!

johannes