AW: [PATCH] wpasupplicant: Only advertise MSCS and SCS in association request if supported by bss

Sebastian Priebe sebastian.priebe at
Fri Mar 10 01:54:02 PST 2023

> -----Ursprüngliche Nachricht-----
> Von: Jouni Malinen <j at>
> Gesendet: Dienstag, 7. März 2023 19:51
> An: Sebastian Priebe <sebastian.priebe at>
> Cc: hostap at
> Betreff: Re: [PATCH] wpasupplicant: Only advertise MSCS and SCS in
> association request if supported by bss
> On Fri, Mar 03, 2023 at 08:43:39AM +0000, Sebastian Priebe wrote:
> > Since version 2.10 the extended capabilities MSCS and SCS are
> > advertised in the association request.
> > This causes the assiciation request to be rejected by several access
> > points. Issue was observed with:
> > - D-Link DIR600
> > - Tp-Link AC1900
> > - Synology MR2200ac
> > To avoid this issue the extended capabilites MSCS and SCS shall only
> > be added if the bss also supports them.
> Would you happen to know what is the exact trigger for the listed APs
> failed to reject the association, i.e., is this because of the length of
> the Extended Capabilities element being "unexpectedly" long or is there
> something specific about these two particular capability bits or is this
> just because of included the Extended Capabilities element in the first
> place, regardless of its length?

I tested this with the Synology MR2200ac: it seem that this AP can't handle
the Extended Capabilities element in the association request at all. I tried
different lengths/contents and it got rejected every time. The status code
was always 1.

> > Note: The extended capabilites are only included in the association
> > request if the bss also sent it's extended capabilities (see
> > wpas_populate_assoc_ies). This workaround exists since verion 2.1.
> > ---
> This is strictly speaking non-compliant with the IEEE 802.11 standard,
> but I guess this would be an acceptable compromise to avoid
> interoperability issues with deployed APs.

I completely agree.

> Please see the top level CONTRIBUTIONS file for the description of the
> Signed-off-by: line. I'd need to get this patch resubmitted with that
> added to be able to consider applying it.

I will do that. Thanks.

> --
> Jouni Malinen                                            PGP id EFC895FA

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