Clearing the "Scan buffer": I continue to see an AP I've unplugged in the Scan Results

Dan Williams dcbw at redhat.com
Tue Sep 12 22:13:42 EDT 2006


On Tue, 2006-09-12 at 17:17 -0700, George S. Lockwood wrote:
> Hello,
> 
> Supplicant begins and is instructed by a cli-style app to periodically
> scan and scan_results.
> 
> It finds my AP.
> 
> I then unplug that AP.
> 
> The AP continues to appear in the scan_results list after subsequent
> calls to scan and scan_results.

For how long?  The card may keep the scan result in its scan list until
it times the AP out.  Is the card still "connected" to AP?  If you just
unplug the AP then it certainly isn't going to send out disconnection
events to everyone, so the card may just think it's still connected
until something times out.  Do you get disconnection events from
wpa_supplicant shortly after you unplug the access point?

> I can understand it remaining on perhaps for a scan or two after it
> was unplugged, but it never seems to leave the list.

Number of scans shouldn't matter; what matters is some timeout based on
when the last seen beacon from the AP was.  And that timeout should be
performed in the driver or firmware.

> How to "reset" or empty the list or otherwise insure an accurate list
> at all times?

That's completely driver and firmware dependent, and wpa_supplicant
shouldn't be doing _anything_ but reporting what the card and driver
say.  If the card and driver are wrong, then they need to be fixed and
not worked around in wpa_supplicant.  You can work around that in your
client.

Dan





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