[PATCH v4 2/4] scan: Add a configuration option to disable 6GHz collocated scanning

Dennis Bland dennis at dbperformance.com
Mon Apr 18 10:34:43 PDT 2022

> On Mon, Apr 11, 2022 at 05:21:59PM +0300, Ilan Peer wrote:
> > This configuration option can be used to disable 6GHz collocated scan
> > logic which would result with passively scanning 6GHz non PSC channels.
> Is this really something we should do as a configuration option? Is the
> default behavior to scan only the 6 GHz channels that are either PSC or
> that have been determined to have a BSS based on neighbor report? And is
> that somehow conditional on active vs. passive scanning?
> I could understand having a need for a specific SCAN command that will
> scan all 6 GHz channels passively, but it would seem more reasonable to
> do that with a SCAN control interface command argument instead of a
> configuration parameter that applies to all scan operations. Isn't it
> way too slow to scan all non-PSC channels on the 6 GHz using a passive
> scan for normal use?
It seems s 6 GHz passive scan would only need to be done if the
desired SSID was not found from a 2.4/5 GHz collocated AP (i.e. the
scenario with a 6 GHz-only AP on a non-PSC channel).  In other words,
perform active scanning on the 2.4/5 GHz bands as usual, and if the
SSID is not found directly or via an RNR element, then perform active
scanning on the 6 GHz PSC channels if the regulatory domain allows it.
If the SSID is still not found, then perform a passive scan of the
remaining 6 GHz channels.

In the case of a 6 GHz AP with no 2.4/5 GHz neighbors to allow the STA
to obtain regulatory domain info, it seems reasonable to assume the
STA can passively scan the 6 GHz band (i.e. temporarily override the
world regulatory domain) without violating country-specific rules.
However, the WLAN driver/firmware might be the limiting factor there -
the 6 GHz channels may not be enabled at all by the driver until it
sees a beacon hint in the 2.4/5 GHz band.  That should probably be
addressed at the driver level sooner than later.

> --
> Jouni Malinen                                            PGP id EFC895FA

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