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

[Helmut Schaa]

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"

Helmut