wpa_supplicant: Problem with freq_list scan filter

[Bojan Prtvar]

Hi Janusz,

On 08/08/2014 09:23, Janusz Dziedzic wrote:
> On 7 August 2014 16:05, Bojan Prtvar <bojan.prtvar at rt-rk.com> wrote:
>> Hello,
>>
>> Background:
>> We are using wpa_supplicant (v2.0-devel-4.2.2)on Android embedded device.
>> We had a requirement to support only networks in 5GHz range. In order to
>> support it, we back-ported [1] patch and added config option
>> freq_list=5180 5200 5220 5240 5260 5280 5300 5320 5500 5520 5540 5560
>> 5580 5600 5620 5640 5660 5680 5700
>> After this, Android only reports networks from 5GHz range and everything
>> seemed OK.
>>
> So, small change to android framework and adding
> bssid=f8:d1:11:a6:1b:b0 to network block.
> Should fix the issue.

No. Devices are planned for mass production. MAC addresses I provided in
the log, are just examples from the test lab.
Requirement is to support only networks from 5GHz range, not an AP with
a specific MAC.

>> Problem statement:
>> There is a problem in following scenario.
>> We have two networks(same ssid,same password) one in 5GHz other in 2GHz
>> range. We connect  device to supported 5GHz network, and then turn off
>> that AP. After a while, device automatically connects to unwanted 2GHz
>> network. Please find wpa_supplicant logs in [2].
>> 5GHz AP is f8:d1:11:a6:1b:b0
>> 2GHz AP is f8:d1:11:c4:4b:dc
>>
>> Could this be a wpa_supplicant issue or Android WiFi framework is to blame?
>> Any help would be highly appreciated.
>>
> Seems like supplicant bug? Back to scan all freq?
I think it is a supplicant bug, If my understanding of freq_list is correct:
"Scan _only_ frequencies which are provided, scan all frequencies if the
freq_list is not set."
So if the freq_list option is set, upper layers should never be aware of
any network from the range which is not set.

Is my understanding correct?
If so, this looks like a corner case when freq_list does not work as
intended.

Regards,
Bojan