[PATCH 1/9] ap: switch pri/sec channels only if pri channel is idle

Jouni Malinen j
Fri Jun 19 05:48:56 PDT 2015

On Wed, Jun 17, 2015 at 04:18:13PM +0300, Ilan Peer wrote:
> IEEE Std 802.11-2012 ( states that the secondary
> channel should be a channel with no other beacons, unless
> beacons are detected on both the primary and secondary
> channels.

Yes and just before that it states that the PRI/SEC channels shall be
identical with a detected BSS unless there is already mix of different
PRI/SEC channels which is an actual requirements (shall vs. should).

> The current code doesn't check the existence of such
> beacons, resulting in unnecessary switch in case
> of HT20 ap on our primary channel + overlapping HT40 ap.

There is already a check for whether beacons are detected on SEC
channel, but not on PRI and switches own configuration based on that.
Could you please provide a more detailed example of this? I'd like to
see the list of detected PRI/SEC channels and the local configuration in
which case the unnecessary switch happens.

> Add check to consider this switch only if there are
> no beacons on the primary channel.

I'm not sure I follow the logic here taken into account !pri_bss
condition here would imply that sec_bss == 0, i.e., the earlier loop
through scan results did not find a single BSS on either our PRI or SEC
channels. How could this second loop find a match in such a case?

Jouni Malinen                                            PGP id EFC895FA

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