Scanning regression since "cfg80211: use DS or HT operation IEs to determine BSS channel"

Rafał Miłecki zajec5 at
Tue Mar 26 17:58:49 EDT 2013

2013/3/26 Johannes Berg <johannes at>:
> On Tue, 2013-03-26 at 18:10 +0100, Rafał Miłecki wrote:
>> I've just finished bisecting wireless scanning regression I'm
>> experiencing with my 14e4:432b (BCM4322) and b43 driver.
> Hmmm.
>> The problem is getting my network visible in scanning results (iw dev
>> wlan0 scan). I've to repeat scanning dozens of time to notice my AP.
>> It's also well visible when using wpa_supplicant. It takes from 20s to
>> 100s before I get the "Trying to authenticate with".
> That's strange.
>> After going back to the kernel before that commit it takes
>> wpa_supplicant less than 2 seconds to connect to my WiFi network.
>> My network is at channel 13, I still have to verify if it matters.
>> Any thought about that?
>> The first bad commit (I've verified manually after bisecting) appears to be:
> "verified manually" how? By reverting the commit? But anyway the commit
> is clearly scanning related, so ...

Oh, that was just about
1) git checkout 0172bb75073e11a5aa9d8a953bdaefb8709f00c8
2) test
3) git revert 0172bb75073e11a5aa9d8a953bdaefb8709f00c8
4) test

> Can you check your channel list? (iw list or iw phy0 info)

Sure, attaching iw.list.log.

> Also can you show the full data including beacon data from the AP (iw
> wlan0 scan dump -b) please?

Hm, first of all, above command doesn't seem to perform real scanning.
It returns too quick to actually scan anything. It's result is empty
as long as I don't use standard "iw dev wlan0 scan".  After scanning a
normal way once ("iw dev wlan0 scan"), executing "dump -b" results in
the output at the one produced by "iw dev wlan0 scan" (only TSF and
last seen differ).

Is there anything special about "iw dev wlan0 scan dump -b" I should know of?

> Does reverting just the mac80211 change fix it?

Yes. Reverting just a change in net/mac80211/scan.c fixes the problem
for me. I've tested this with the latest wireless-testing.

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