[PATCH 0/3] hostapd: introduce Automatic Channel Selection (ACS)

Michal Kazior michal.kazior at tieto.com
Mon Aug 26 02:32:49 EDT 2013


On 23 August 2013 10:56, Helmut Schaa <helmut.schaa at googlemail.com> wrote:
> Hi Michal,
>
> On Fri, Aug 23, 2013 at 9:19 AM, Michal Kazior <michal.kazior at tieto.com> wrote:
>> Hi,
>>
>> This is an attempt at ressurecting ACS effort for hostapd.
>>
>> This is based on the work done by Luis R. Rodriguez
>> <lrodriguez at qca.qualcomm.com>.
>>
>> I've rebased and improved the patchset. Notable changes:
>>
>>  * Interference factor calculation has been modified.
>>
>>    The formula now includes the relative channel noise floor so a channel with
>>    lower noise floor should be preferred in case channel load evaluates to 0.
>>
>>    The formula now spits out positive values that can be summed up, which is
>>    needed for:
>>
>>  * Overlapping/primary/secondary channels are all used when calculating total
>>    intereference factor for a given connection type (2.4Ghz, HT40, VHT80).
>>    This most likely still needs tuning but it's a good start I think.
>>
>> RFC v2:
>>  * remain-on-channel replaced in favour of scan-based survey data gathering
>>    (hostapd: Add offchannel support -- dropped)
>>
>>  * chan_time scan parameter patch is introduced
>>
>>  * tested with ath9k and ath10k
>>
>> RFC v3:
>>  * chan_time patch is dropped in favour of doing a couple of passive scans
>>    this should still allow gathering enough data for ACS
>>
>>  * lots of cleanups and some small fixes
>>
>>  * trimmed down main ACS patch commit message
>>    all details are already in code comments or on wiki page [1]
>>
>> PATCH v1:
>>  * rebased on latest master branch
>>
>> The following link is a git patchbomb that has all 3 patches in case the
>> mailing list server decides to spam-block my patchset.
>>
>>   http://ix.io/7vF
>
> Just gave your patches a quick try (with ath9k).
>
> One thing I noticed was that hostapd tries to respond to probe
> requests while doing the ACS channel scan
> resulting in a couple of "handle_probe_req: send: Resource temporarily
> unavailable" errors:
>
> 1377247507.112841: Configuration file: /var/run/hostapd-phy1.conf
> 1377247507.223379: ACS: Automatic channel selection started, this may take a bit
> handle_probe_req: send: Resource temporarily unavailable
> handle_probe_req: send: Resource temporarily unavailable
> handle_probe_req: send: Resource temporarily unavailable
> handle_probe_req: send: Resource temporarily unavailable
> 1377247513.287024: Using interface wlan1 with hwaddr 00:03:7f:11:20:08
> and ssid "OpenWrt"

Hi,

Hmm.. The overlapping BSS scan should probably yield the same issue,
no? Should hostapd ignore all management frames until all BSSes have
beacon_set == 1? Won't that break anything?

Anyway I think this should be (if at all) dealt with in a separate patch.


Pozdrawiam / Best regards,
Michał Kazior.


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