linux-kernel - Re: [PATCH] wifi: mwifiex: fix parsing of more than two AKM suites

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Date: Thu, 30 May 2024 14:01:21 +0200
From: Sascha Hauer <s.hauer@...gutronix.de>
To: Kalle Valo <kvalo@...nel.org>
Cc: linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	Brian Norris <briannorris@...omium.org>,
	Francesco Dolcini <francesco@...cini.it>,
	David Lin <yu-hao.lin@....com>
Subject: Re: [PATCH] wifi: mwifiex: fix parsing of more than two AKM suites

On Sat, May 25, 2024 at 12:15:22PM +0300, Kalle Valo wrote:
> Sascha Hauer <s.hauer@...gutronix.de> writes:
> 
> > params->crypto.n_akm_suites seems to be limited to two AKM suites. Once
> > there are more they will be passed as extra elements of type WLAN_EID_RSN
> > or WLAN_EID_VENDOR_SPECIFIC.
> >
> > This takes some snippets from the downstream vendor driver to parse
> > these elements and to set the correct protocol and key_mgmt bits to
> > enable the desired key managements algorithms in the hardware.
> >
> > This patch is not a request for inclusion, more a heads up that there's
> > something missing and the question if the approach taken is the right
> > one or if there are other preferred ways to fix this issue.
> 
> Please mark patches like this as "[PATCH RFC]", that way we maintainers
> know to drop them automatically.

Yes, will do. I should have known that.

The question I had with this patch is more like whether the approach is
fine.

I wonder why I have to parse the WLAN_EID_RSN element in driver specific
code and why I do not find similar code in other drivers which should
suffer from the same problem.

Looking deeper at it the Kernel by default only supports two AKM suites.
wiphy->max_num_akm_suites is initialized to NL80211_MAX_NR_AKM_SUITES
(which is 2). Whenever wpa_supplicant/hostapd specify more AKM suites
the suites exceeding 2 are encoded in the WLAN_EID_RSN element and I
would expect other drivers to handle this as well.

I realized that the Kernel can handle up to 10 AKM suites by setting
wiphy->max_num_akm_suites to CFG80211_MAX_NUM_AKM_SUITES and that
seems to do the trick as well, at least when I patch wpa_supplicant
to actually use this increased number.

Sascha

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