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

Jouni Malinen j at w1.fi
Tue Mar 7 10:51:10 PST 2023

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?

> 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.

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.

Jouni Malinen                                            PGP id EFC895FA

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