Hidden SSID/BSSID cache

Jouni Malinen j
Fri Nov 11 13:35:02 PST 2011

On Fri, Nov 11, 2011 at 11:35:25AM -0800, Simon Barber wrote:
> The problem with active scan for that SSID is that this slows down the 
> case of finding other, non hidden SSIDs (e.g. my home AP). The 
> persistent cache allows both non hidden, and hidden (after 1st use) APs 
> to be found quickly - all in 1 step. Only first use hidden SSIDs would 
> pay the time penalty - an uncommon case. I can do some sniffing to find 
> out what the driver is actually doing right now.

Well, the extra cost of sending two Probe Request frames instead of one
in a single command is not really significant - in fact, it is unlikely
to add any latency since there is going to be a wait for the responses
anyway. Extra complexity in wpa_supplicant for this does not sound
justified with driver interfaces that can handle scanning for multiple
SSIDs at a time (e.g., nl80211) and there is not really much interest in
improving driver interfaces that don't (e.g., WEXT).

Jouni Malinen                                            PGP id EFC895FA

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