PREQ handling in hostap on Android

Jouni Malinen j
Wed Sep 26 06:02:37 PDT 2012

On Wed, Sep 26, 2012 at 02:03:54PM +0200, Benjamin Grap wrote:
> My application acts upon specific PREQ packets. For my Linux netbooks 
> with an atheros card this works. Receiving PREQs triggers the 
> handle_probe_req function in ap/beacon.c which I can then use to send 
> messages to my backend.

This would be the case with drivers that use hostapd for AP mode
MLME/SME processing.

> However in the hostapd 0.7.2. from android 4.1 on a Galaxy Nexus phone, 
> PREQs do not seem to ever trigger that function.
> I assume that those PREQs are already handled by the driver on those 
> devices and never passed to hostapd?


> But my application relies on 
> receiving those PREQ packets and I was wondering whether there was 
> something that I could do that would pass the PREQs to hostapd.

Talk to the driver maintainers or use another WLAN device.. This may not
be easily doable with the device you are using here.

> Any comments on the inner working of the Android hostapd/driver 
> combination will be much appreciated.

It's not really specific to Android in any way, but to the architecture
the WLAN design uses in the system. If Probe Request frames are
processed in firmware, there is not much hostapd can do about it. Since
information from Probe Request frames is needed to allow WPS to be
implemented correctly, you may have some luck of at least receiving
information (like WPS IE) from the received Probe Request frames, but
this depends on the driver in question.

Jouni Malinen                                            PGP id EFC895FA

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