Re: broadcast ssid in scheduled scan

[Luca Coelho <luca@coelho.fi>]

On Tue, 2015-03-31 at 16:21 +0200, Johannes Berg wrote:
> On Mon, 2015-03-23 at 19:38 +0100, Arend van Spriel wrote:
> > Johannes, Jouni,
> > 
> > I have noticed that under some circumstances wpa_supplicant initiates a 
> > scheduled scan with broadcast ssid. This is something our firmware can 
> > not do so could this be avoided? Maybe by adding a feature flag for it. 
> 
> I guess this would be difficult to do since you'd basically have to
> "remove" support for normal scheduled scan (that assumes this ability)
> and add support for another scheduled scan (that doesn't assume it) in
> nl80211 ... just to be compatible with older implementations of
> wpa_supplicant etc.
> 
> I do wonder why the firmware cannot do this though - there's no
> fundamental reason the 0-length SSID is all that different from a 1-byte
> one?

Is the problem in having a 0-length SSID in the probe_reqs or is it in
having it in the matches (i.e. it doesn't support "pass all")? The
latter makes a bit more sense, since filtering on a 0-length SSID, if
not treated specially, would return nothing (since it would never match,
unless an AP does send an SSID IE with 0-length).

It doesn't make much sense to have a "match all" scheduled scan though,
unless wpa_s needs to find more SSIDs than what the driver supports.
Even in that case, it wouldn't make much difference than using a normal
scan periodically...

--
Luca.