Passive Scannning

Dan Williams dcbw at redhat.com
Sun Nov 9 23:22:44 EST 2008


On Fri, 2008-11-07 at 09:42 +0530, Kiran Kulkarni wrote:
> Dan Williams wrote:
> > On Thu, 2008-11-06 at 20:41 +0530, Kiran Kulkarni wrote:
> >   
> >> In wpa_supplicant I am searching for a functionality where I will put my 
> >> system in passive scan which will only listen to beacons. And if 
> >> networks are available I should get some notification on D-Bus or Socket 
> >> interface.
> >>     
> >
> > On Linux, wpa_supplicant will only request probe-scans when you have
> > "scan_ssid=1" in a network block.  Otherwise, it's up to the driver
> > whether passive or active scans are used.
> >
> > You'll get a notification on the D-Bus interface when new scan results
> > are available, not sure about the socket interface.
> >
> > Dan
> >
> >
> >
> >   
> But I found out that in wext we can set /scan_type/ field to 
> /IW_SCAN_TYPE_PASSIVE/ in /struct iw_scan_req/ and then make ioctl call 
> /SIOCSIWSCAN. /But I didnt know any method exposed to do such thing.
> 
> I agree that we get signal over D-BUS when scan results are available. 
> My question was that can we force the driver to go into passive scanning 
> through wpa_supplicant or we have to write seperate code to handle this 
> case...

You could modify wpa_supplicant to pass TYPE_PASSIVE if you like, but be
aware that only a few drivers actually support that selector.

Dan




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