[PATCH v4 1/4] nl80211: set NL80211_SCAN_FLAG_COLOCATED_6GHZ in scan

Jouni Malinen j at w1.fi
Mon Apr 18 08:15:46 PDT 2022

On Mon, Apr 11, 2022 at 05:21:58PM +0300, Ilan Peer wrote:
> Set NL80211_SCAN_FLAG_COLOCATED_6GHZ in the scan params to enable
> scanning for co-located AP's found in 2.4/5 GHz bands when
> not scanning passively. Do so only when collocated scanning
> is not disabled by higher layer logic.

Where does this "not scanning passively" part comes from? nl80211.h
documents this flag in the following way:

"NL80211_SCAN_FLAG_COLOCATED_6GHZ: scan for colocated APs reported by
2.4/5 GHz APs"

Is that incorrect or just incomplete? They way I read that nl80211.h
comment is that this flag is or adding some additional steps to
scanning, but the comment in this proposed hostap.git change says

> diff --git a/src/drivers/driver_nl80211_scan.c b/src/drivers/driver_nl80211_scan.c
> @@ -203,6 +203,17 @@ nl80211_scan_common(struct i802_bss *bss, u8 cmd,
> +		/*
> +		 * If allowed, scan for 6GHz APs that are reported by other
> +		 * APs. If the flag is not set and 6GHz channels are to be
> +		 * scanned, they will be scanned passively.
> +		 */
> +		wpa_printf(MSG_DEBUG, "nl80211: non_coloc_6ghz=%u",
> +			   params->non_coloc_6ghz);
> +
> +		if (!params->non_coloc_6ghz)
> +			scan_flags |= NL80211_SCAN_FLAG_COLOCATED_6GHZ;

This seems to imply that if the flag is there, there would actually be
less scanning rather than the other way around..

What exactly is the expected behavior here? What is that "6 GHz channels
are to be scanned" referring to?

Should the nl80211.h documentation be extended to cover all the details
that this flag is really doing? I cannot really figure out whether this
proposed hostap.git patch is doing what the flag is supposed to do..

Is this somehow connected to the preferred scanning channels (PSC)?

Jouni Malinen                                            PGP id EFC895FA

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