[PATCH 6/8] WNM: Handle BTM request with "Link Removal Imminent"

[Jouni Malinen]

On Wed, Dec 13, 2023 at 04:04:10PM +0200, Andrei Otcheretianski wrote:
> Based on Draft P802.11be_D3.0, when a station is non-AP MLD with more
> then one link and "Link Removal Imminent" is set, the "Disassociation
> Imminent" and "BSS Termination Included" can be ignored, as the station
> will not be disassociated.

That is not what the standard says.. Those two bits are not being
"ignored". In particular, there is a specific meaning for BSS
Termination Included value 0 which is clearly not supposed to be
ignored..

> diff --git a/wpa_supplicant/wnm_sta.c b/wpa_supplicant/wnm_sta.c
> +	/*
> +	 * Based on Draft P802.11be_D3.0, when a station is non-AP MLD with more
> +	 * then one link and "link removal imminent" is set, the below flags can
> +	 * be ignored, as the station will not be disassociated.
> +	 */
> +	if ((wpa_s->valid_links & (wpa_s->valid_links - 1)) != 0 &&
> +	    wpa_s->wnm_mode & WNM_BSS_TM_REQ_LINK_REMOVAL_IMMINENT &&
> +	    (wpa_s->wnm_mode & WNM_BSS_TM_REQ_DISASSOC_IMMINENT ||
> +	     wpa_s->wnm_mode & WNM_BSS_TM_REQ_BSS_TERMINATION_INCLUDED)) {
> +		wpa_printf(MSG_INFO,
> +			   "WNM: BTM request for single MLO link. ignore");
> +		return;
> +	}

So those conditions are incorrect since the link removal case applies
only if BSS Termination Included is set to 1. Furthermore, I did not
find any justification from the standard to ignore the BTM request
itself, i.e., this request still needs a response.

I fixed these and the test in the following patch to match the
functionality.

In addition, patch 8/8 broke functionality since it did not make sure
wpa_s->wnm_mode is cleared for new associations/disassociations and the
old value was incorrectly used for cases where there had been no
disassociation imminent indication.

I applied all eight patches with cleanup and fixes.

-- 
Jouni Malinen                                            PGP id EFC895FA