[PATCH] AP: Do not reply to probe request with DS IE mismatch

Jouni Malinen j at w1.fi
Sat Feb 7 04:03:23 EST 2015

On Thu, Feb 05, 2015 at 08:37:04PM -0500, Ilan Peer wrote:
> Do not reply to a probe request with a DS IE in which the channel
> is different than the operating channel of the AP, as the sending
> station is not found on the AP's operating channel.

Strictly speaking, this seems to be non-compliant with IEEE Std
802.11-2012. The AP shall do this if dot11RadioMeasurementActivated is
true (so yes, for that case, this change is indeed required), but the
standard language seems to imply that the AP shall reply to the Probe
Request that matches all the described rules and in case of
dot11RadioMeasurementActivated false, that would include the case of DSS
Parameter Set element value not matching the current channel..

I'm not sure this is really the real intent behind the design that was
added in 802.11k, but that's what the current standard says. In addition
to that, I've heard of some scanning optimizations that would
potentially depend on the AP replying on neighboring channel. That said,
it is also desirable to reduce the number of unnecessary Probe Response
frames (whether that response is unnecessary or not depends on whether
the STA is likely to receive it).

Jouni Malinen                                            PGP id EFC895FA

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