Re: [PATCH] cfg80211: Fix support for flushing old scan results

[Denis Kenzior <denkenz@gmail.com>]

Hi Johannes,

On 05/22/2018 09:51 AM, Johannes Berg wrote:
> On Tue, 2018-05-22 at 16:50 +0200, Johannes Berg wrote:
>> On Tue, 2018-05-22 at 09:48 -0500, Denis Kenzior wrote:
>>> Hi Arend,
>>>
>>>>> Are you saying the first result is from the Beacon and the other is from
>>>>> the Probe Response?  Then why are the 'Information elements from Probe
>>>>> Response frame' the way they are?
>>>>
>>>> Nope. I am not saying that. I am saying that there are two probe
>>>> requests being sent. One with broadcast ssid, ie. ssid_len == 0, and
>>>> with ssid 'myssid'. But it is speculation without a sniffer capture.
>>>
>>> Ah I see what you mean now.  No, we traced this down to hostapd itself
>>> and it was receiving a single Probe Request with the ssid set and
>>> replying to it per spec.  So I'm pretty confident this scenario isn't
>>> what is happening.  Let me try to get some actual packet captures...
>>
>> Was "myssid" the real SSID, or did you hide that from us and it was
>> really 9 characters long in the original?

See the other sub-thread.  It was 9 characters long, I hand-edited it to 
protect the innocent.

>>
>> If it was really 9 characters long I could imagine that there's a
>> different bug with a beacon with all-zero-bytes having been received
>> (and getting stuck into the probe response buffer for some reason), and
>> then you *should* see both entries.
> 
> Or perhaps there's a bug with how we link the results between
> hidden/non-hidden, but it seems to me that hostapd would never have
> responded with a probe response with zeroed bytes.
> 

We suspect it is likely a bug in cfg80211_bss_update logic somewhere.

Regards,
-Denis