How to clear scan cache.

Raghavendra. S raghavendra.akkasali at gmail.com
Fri Jan 11 10:41:32 EST 2008


On 1/11/08, Dan Williams <dcbw at redhat.com> wrote:
> On Fri, 2008-01-11 at 07:31 +0530, Raghavendra. S wrote:
> > Hi,
> >
> >  In my case, I will enable wpa supplicant and in wpa_cli I issue
> > "SCAN" command. Then I will sleep for 5-7 seconds. Later I will issue
> > "SCAN_RESULT" command to get scan result.
> >
> > Here I have few  doubts?
> >
> > 1. what is the optimal value for this sleep?
>
> If wpa_supplicant's control interface doesn't give you a notification of
> new scan results (it really should if it doesn't), then you can use
> netlink to monitor the wireless driver's event stream and look for
> SIOCGIWSCAN events.  That means the driver has found new access points.
>
> Or, if you don't want to watch netlink (it's not trivial code to do so)
> then use a value of around 7 - 10 seconds to be sure.
>
> > 2. In  wpa_ctrl_request(ctrl_conn, "SCAN_RESULTS",
> >                      os_strlen("SCAN_RESULTS"), scanbuf, &len, NULL);
> >
> >   Currently in wpa_cli size of "scanbuf" is defined as char array of
> > 2048 bytes. So it will hardly accomodate scan result for 15-16 APs.
> >
> >  Can I increase this size from 2048 to higher value? say 3072, so that
> > it can hold 24-25 scanned AP information?
>
> Yeah, probably.  That looks like a limitation of the socket-based
> control interface.

  It means that even if I increase scanbuf size to 3072, I will end up
receiving max 2048. Am I right?


>
> Dan
>
> > 3. I have following config file for scan
> >
> > # cat /tmp/wpa_supplicant.conf.tmp
> > ctrl_interface=/var/run/wpa_supplicant
> > ap_scan=1
> >
> > network={
> >                 bssid=00:00:00:00:00:00
> >                 key_mgmt=NONE
> > }
> >
> > This will never connect to any AP, but will remain in scan state. Is
> > there any issue in using this kind of configuration?
> >
> >
> > -Raghu.
> >
> >
> > On 1/10/08, Dan Williams <dcbw at redhat.com> wrote:
> > > On Thu, 2008-01-10 at 14:42 +0530, Raghavendra. S wrote:
> > > > Hi All,
> > > >
> > > >  Can any body tell me how to clear scan cache?
> > >
> > > Any particular reason you'd want to do this?  Scan results should be
> > > expired fairly quickly anyway, like a matter of seconds.  The drivers
> > > themselves may cache scan results for up to 15 seconds.
> > >
> > > Dan
> > >
> > >
> > >
> >
> >
>
>


-- 
Regards & Thanks
Raghavendra. S


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