[PATCH 2/2] hostapd: Add DFS CAC and radar detection

Janusz Dziedzic janusz.dziedzic at tieto.com
Fri Sep 20 05:38:48 EDT 2013


On 19 September 2013 13:51, Simon Wunderlich
<simon.wunderlich at s2003.tu-chemnitz.de> wrote:
> Hey Janusz,
>
> On Tue, Sep 17, 2013 at 08:44:37PM +0200, Janusz Dziedzic wrote:
>> On 17 September 2013 18:25, Simon Wunderlich
>> <simon.wunderlich at s2003.tu-chemnitz.de> wrote:
>> > Hey Janusz,
>> >
>> > On Mon, Sep 16, 2013 at 07:40:07AM +0200, Janusz Dziedzic wrote:
>> >> Add DFS CAC handling, radar detection.
>> >> By default after radar detected or
>> >> channel became unavailable random channel
>> >> will be choose.
>> >>
>> >> Signed-hostap: Simon Wunderlich <siwu at hrz.tu-chemnitz.de>
>> >> Signed-hostap: Janusz Dziedzic <janusz.dziedzic at tieto.com>
>> >
>> > Thanks a lot for the rewrite - looks good to me and works well here, so
>> > feel free to add:
>> >
>> > Tested-by: Simon Wunderlich <siwu at hrz.tu-chemnitz.de>
>> >
>> Thanks for review and tests.
>>
>> > Also the patch looks good in general. This series is still missing the
>> > dfs channel list patch which is in another patch Jouni has still backed
>> > up [1] (doesn't apply currently, but it's trivial to fix). Would be good
>> > to merge this as well.
>> >
>> > Just one remark: What do we do if all channels are taken? Your current
>> > implementation will then simply close hostapd, but I'm not sure if this
>> > is desired behaviour - shouldn't we rather keep it running and wait for one
>> > channel to come back (when the Non-occupancy-period is over) and try again?
>> >
>> I think we should never hit this case. Base of spec I changed getting
>> new channel little bit.
>> Currently we get random channel from list of:
>> -  "standard" 5G channels (!disabled) - defined by regdomain
>> -  DFS usable + availabe channels.
>>
>> Even all DFS channels will be unavailable we should get still
>> "standard" channels list I think.
>
> If we want to use 5 GHz outdoors we may only use outdoor channels. These must be
> limited e.g. by using the DFS channel option in the pending patch[1]. Jumping back
> to a non-DFS channel is not an option for outdoors, at least in Europe all outdoor
> channels require DFS. So it might happen that all channels become unavailable for
> some time.
>
> In this case, your current implementation will just stop the hostapd (I've tested
> after applying the channel list patch [1]), and while this is one option to handle
> it, I feel that's not the best ... :)
>

Good catch. So I think we can add this as a separate patch + proper
NOP handling. This should be quite easy.

BR
Janusz


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