scanning/wpa client while in hostapd mode

Dan Williams dcbw at
Tue Mar 8 14:50:16 PST 2016

On Tue, 2016-03-08 at 21:35 +0000, Fred Ollinger wrote:
> Thanks for the kind response.
> First, I'd like to say that I believe I was wrong about Android
> phones hosting an access point and scanning at the same time.
> I'll answer the other questions in hopes that perhaps this can be
> done on my platform.
> I'm running Yocto on an arm:
> Linux csplus_cm 3.10.53-1.1.0+g04cae56 #1 SMP Tue Mar 1 11:01:22 PST
> 2016 armv7l GNU/Linux
> The driver is a for wl1831:

The driver may not support it.  Run "iw phy phy0 info" and look for a
line near the end with "Device supports AP scan".  If you don't see
that, the driver doesn't support it, or your 'iw' tool doesn't know
about that feature.

The upstream kernel's wl18xx driver implements the mac80211 hw_scan
hook, which means that the driver must specifically
declare NL80211_FEATURE_AP_SCAN support.  wl18xx doesn't do that, so at
least the upstream wl18xx driver doesn't appear to support scanning
while in AP mode.  I have no idea if the driver you're using is that
one or a different one though.


> The version of wpa_supplicant is here:
> git://;destsuffix=compat-
> wireless;name=compat-wireless;branch=upstream_312 
> The supplicant is run with the following parameters:
> /usr/sbin/wpa_supplicant -B -P /var/run/ -i
> wlan0 -c /etc/wpa_supplicant.conf -D nl80211
> I'll be happy to answer any other questions to help solve this
> problem.
> Wishing you well,
> Frederick
> _________________________________
> From: Jouni Malinen <j at>
> Sent: Tuesday, March 8, 2016 1:24 PM
> To: Fred Ollinger
> Cc: hostap at
> Subject: Re: scanning/wpa client while in hostapd mode
> On Mon, Mar 07, 2016 at 06:25:57PM +0000, Fred Ollinger wrote:
> > 
> > Most Android phones allow for one to connect to an access point as
> > a client and to serve an access point at the same time to allow a
> > computer with wifi to connect to the Internet via one's mobile
> > plan.
> > 
> > I'm trying to do the same with hostapd, but it seems like when
> > wpa_supplicant is running, hostapd fails.
> Could you please provide more details on how this fails, which
> netdevs
> you are using and how they were created, and which WLAN driver are
> you
> using?
> > 
> > Is there a workaround? If so, can you please point out where in the
> > documentation? If there is no documentation, but this is a feature
> > we have, I'll be happy to document this from the source code if
> > pointed in the right direction.
> It is difficult to say much more without knowing more about the
> details
> of how exactly the configuration is done. With number of drivers, it
> should be possible to do this with wpa_supplicant and hostapd, but it
> would also be possible to use wpa_supplicant to control both the
> station
> and AP mode interfaces concurrently.
> --
> Jouni Malinen                                            PGP id
> EFC895FA
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