Receiving your own wifi beacons

Receiving your own wifi beacons

[Avery Pennarun]

Hi all,

We're currently investigating a problem where the ath10k AP will
seemingly stop sending out beacons, with no other obvious symptoms
(hostapd is still working fine).  There's not much I can report
because, of course, no symptoms.

We would like to detect this situation automatically by watching for
outgoing beacons, but we've noticed that when we create a monitor
interface, we can see all the beacons *except* ones generated by the
local AP.  This seems to also be true with ath9k, so it may not be an
ath10k-specific problem, but we'd like some way to see them going out
(at the expense of some wasted CPU, of course).

Is there any magic incantation that can un-hide the beacons?

Thanks,

Avery

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Re: Receiving your own wifi beacons

[Yeoh Chun-Yeow]

Haven't encounter this before. Which firmware are you using?

----
Chun-Yeow

On Wed, May 7, 2014 at 7:42 AM, Avery Pennarun <apenwarr@gmail.com> wrote:
> Hi all,
>
> We're currently investigating a problem where the ath10k AP will
> seemingly stop sending out beacons, with no other obvious symptoms
> (hostapd is still working fine).  There's not much I can report
> because, of course, no symptoms.
>
> We would like to detect this situation automatically by watching for
> outgoing beacons, but we've noticed that when we create a monitor
> interface, we can see all the beacons *except* ones generated by the
> local AP.  This seems to also be true with ath9k, so it may not be an
> ath10k-specific problem, but we'd like some way to see them going out
> (at the expense of some wasted CPU, of course).
>
> Is there any magic incantation that can un-hide the beacons?
>
> Thanks,
>
> Avery
>
> _______________________________________________
> ath10k mailing list
> ath10k@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/ath10k

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Re: Receiving your own wifi beacons

[Avery Pennarun]

On Tue, May 6, 2014 at 9:18 PM, Yeoh Chun-Yeow <yeohchunyeow@gmail.com> wrote:
> On Wed, May 7, 2014 at 7:42 AM, Avery Pennarun <apenwarr@gmail.com> wrote:
>> We're currently investigating a problem where the ath10k AP will
>> seemingly stop sending out beacons, with no other obvious symptoms
>> (hostapd is still working fine).  There's not much I can report
>> because, of course, no symptoms.
>>
>> We would like to detect this situation automatically by watching for
>> outgoing beacons, but we've noticed that when we create a monitor
>> interface, we can see all the beacons *except* ones generated by the
>> local AP.  This seems to also be true with ath9k, so it may not be an
>> ath10k-specific problem, but we'd like some way to see them going out
>> (at the expense of some wasted CPU, of course).
>>
>> Is there any magic incantation that can un-hide the beacons?
>
> Haven't encounter this before. Which firmware are you using?

This is with firmware 10.1.467.2-1.

Avery

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Re: Receiving your own wifi beacons

[Michal Kazior]

On 7 May 2014 01:42, Avery Pennarun <apenwarr@gmail.com> wrote:
> Hi all,
>
> We're currently investigating a problem where the ath10k AP will
> seemingly stop sending out beacons, with no other obvious symptoms
> (hostapd is still working fine).  There's not much I can report
> because, of course, no symptoms.
>
> We would like to detect this situation automatically by watching for
> outgoing beacons, but we've noticed that when we create a monitor
> interface, we can see all the beacons *except* ones generated by the
> local AP.  This seems to also be true with ath9k, so it may not be an
> ath10k-specific problem, but we'd like some way to see them going out
> (at the expense of some wasted CPU, of course).
>
> Is there any magic incantation that can un-hide the beacons?

I don't think you can do that.

Beacons have no tx completion in mac80211 and it's the driver that
requests beacon sk_buffs, not the other way around so there's no way
to sniff them.

Your best option is to look at ath10k debug logs. Each beacon is
submitted upon receiving an SWBA event from firmware.

If you want to be verify if beacons are on air you need an extra
device to act as a sniffer though.


Michał

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Re: Receiving your own wifi beacons

[Kalle Valo]

Avery Pennarun <apenwarr@gmail.com> writes:

> We're currently investigating a problem where the ath10k AP will
> seemingly stop sending out beacons, with no other obvious symptoms
> (hostapd is still working fine).  There's not much I can report
> because, of course, no symptoms.

Can you still provide more information about the problem, please? How
often do you see it? What kind of setup do you have? With or without
DFS? How many BSS?

-- 
Kalle Valo

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Re: Receiving your own wifi beacons

[Avery Pennarun]

On Mon, May 12, 2014 at 12:50 AM, Kalle Valo <kvalo@qca.qualcomm.com> wrote:
> Avery Pennarun <apenwarr@gmail.com> writes:
>> We're currently investigating a problem where the ath10k AP will
>> seemingly stop sending out beacons, with no other obvious symptoms
>> (hostapd is still working fine).  There's not much I can report
>> because, of course, no symptoms.
>
> Can you still provide more information about the problem, please? How
> often do you see it? What kind of setup do you have? With or without
> DFS? How many BSS?

It doesn't happen often.  We haven't been able to reproduce it in a
lab, only at a small number of our test sites at people's homes, and
even then only rarely (although some people apparently experience it
more than others).  We aren't using DFS (does ath10k even support DFS
yet?).  We are using 20 MHz channel, 5 GHz for all these test users.
There is only a single BSS configured for our APs right now, although
other APs may be nearby.

Based on Michal's suggestion, we've added some code to enable minimal
debug messages from the firmware and log whenever a beacon is sent.
This seems to work, so we'll deploy it to all our test users in the
next week or so and, if the problem triggers, at least this should
give us a clue (such as whether the firmware thinks it's still sending
beacons, and exactly what the dmesg looks like at the time that it
stops).

If you have any other suggestions, please let us know.

Thanks!

Avery

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Re: Receiving your own wifi beacons

[Kalle Valo]

Avery Pennarun <apenwarr@gmail.com> writes:

> On Mon, May 12, 2014 at 12:50 AM, Kalle Valo <kvalo@qca.qualcomm.com> wrote:
>> Avery Pennarun <apenwarr@gmail.com> writes:
>>> We're currently investigating a problem where the ath10k AP will
>>> seemingly stop sending out beacons, with no other obvious symptoms
>>> (hostapd is still working fine).  There's not much I can report
>>> because, of course, no symptoms.
>>
>> Can you still provide more information about the problem, please? How
>> often do you see it? What kind of setup do you have? With or without
>> DFS? How many BSS?
>
> It doesn't happen often.  We haven't been able to reproduce it in a
> lab, only at a small number of our test sites at people's homes, and
> even then only rarely (although some people apparently experience it
> more than others).

Ok, so this will a tricky problem to solve.

> We aren't using DFS (does ath10k even support DFS yet?). 

Yes, ath10k supports DFS on ETSI channels but only with one BSS. Michal
has been working on mac80211 DFS with multiple BSS support and he is
getting close to finish that. And I'm hoping to get FCC and MKK support
to ath.ko soon.

> We are using 20 MHz channel, 5 GHz for all these test users. There is
> only a single BSS configured for our APs right now, although other APs
> may be nearby.

The only thing out of ordinary is the 20 MHz channel, as I think most of
users use VHT80 configuration. But I'm having hard time to believe that
would be reason why only you see it. (This is the first time I hear
about a problem like this with ath10k.)

> Based on Michal's suggestion, we've added some code to enable minimal
> debug messages from the firmware and log whenever a beacon is sent.
> This seems to work, so we'll deploy it to all our test users in the
> next week or so and, if the problem triggers, at least this should
> give us a clue (such as whether the firmware thinks it's still sending
> beacons, and exactly what the dmesg looks like at the time that it
> stops).

Good.

> If you have any other suggestions, please let us know.

Do you know if interrupts are still working when the problem appears?
What about other ath10k functionality and driver's communication to the
firmware, is that working normally? For example, can you retrieve stats
from firmware when the issue happens?

-- 
Kalle Valo

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Re: Receiving your own wifi beacons

[Avery Pennarun]

On Mon, May 12, 2014 at 1:47 AM, Kalle Valo <kvalo@qca.qualcomm.com> wrote:
> Avery Pennarun <apenwarr@gmail.com> writes:
>> We aren't using DFS (does ath10k even support DFS yet?).
>
> Yes, ath10k supports DFS on ETSI channels but only with one BSS. Michal
> has been working on mac80211 DFS with multiple BSS support and he is
> getting close to finish that. And I'm hoping to get FCC and MKK support
> to ath.ko soon.

Oh good :)  We don't need that immediately but it'll be good to have
when it's ready.

>> If you have any other suggestions, please let us know.
>
> Do you know if interrupts are still working when the problem appears?
> What about other ath10k functionality and driver's communication to the
> firmware, is that working normally? For example, can you retrieve stats
> from firmware when the issue happens?

Not sure.  hostapd doesn't seem upset, and the driver doesn't seem to
be complaining about anything.

What's a good command to retrieve the firmware stats?  We can have
that run periodically and see if it ever starts failing.

Thanks,

Avery

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