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Subject: Re: [PATCH 2/2] mac80211: Support LIVE_ADDRESS_CHANGE feature
From:   Johannes Berg <johannes@sipsolutions.net>
To:     Denis Kenzior <denkenz@gmail.com>,
        James Prestwood <prestwoj@gmail.com>,
        linux-wireless@vger.kernel.org
Date:   Tue, 08 Oct 2019 18:24:32 +0200
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Hi,

> > The scan_req struct contains a reference to which interface is scanning,
> > so it should very well be possible to have
> > 
> > phy0:
> >   wlan0: IFF_UP & scanning
> >   wlan1: IFF_UP & change MAC address all the time
> > 
> > just like it's possible to change the MAC address when wlan1 *isn't*
> > IFF_UP even if wlan0 is scanning, right?
> > 
> 
> Indeed.  But that is not what you were suggesting earlier with just 
> checking local->scanning.  So if scan_req contains a wdev, then yes it 
> should be possible to compare the scan_req->wdev to the interface being 
> changed.

Well, yes, but only because I was incrementally going from James's
patch, which was checking that only.

Similar with the other local-> things being checked here, btw, though in
some cases it might be harder to actually determine which wdev is doing
something and which isn't.

> > No, this typically cannot be fixed, and it doesn't really make sense.
> > The NIC cannot possibly do two scans at a time since it has only a
> > single radio resource :-)
> 
> So why is the scan request not per phy then?  And should mac address 
> even affect the ongoing scan?  Can we simply change it with the scan 
> ongoing?

There are things that affect the scan from the interface, e.g.
capability overrides, (extended) capabilities, the MAC address is used
unless randomization is requested, etc.

johannes