[PATCH] Treat '' in SSIDs param of DBus Interface.Scan as a request for braodcast scan.

Daniel Kurtz djkurtz at google.com
Fri Oct 8 11:39:43 EDT 2010

To put it another way, this patch adds a feature that allows simultaneous
active scanning for both broadcast SSID, and a list of specific SSIDs.  This
is useful when searching for available networks, including some known hidden
SSIDs, that only respond to directed ProbeRequests.

Not sending an explicit SSIDs field with a Scan request is merely a shortcut
for requesting a ProbeRequests with SSID=''.  This patch allows the caller
to request this explicitly.

Thanks for the info.  I guess you are literally answering Dan's question:
"Does not sending any SSIDs somehow not work?"


On Thu, Oct 7, 2010 at 9:15 AM, Blaise Gassend <blaise at willowgarage.com>wrote:

> On Wed, Oct 6, 2010 at 11:06 PM, Dan Williams <dcbw at redhat.com> wrote:
> > On Wed, 2010-10-06 at 15:46 -0700, Daniel Kurtz wrote:
> >> This patch changes wpa_supplicant policy for handling '' in SSIDs field
> of Interface.SSID DBus message.
> >> It treats '' (zero-length) SSID as a request for a broadcast scan,
> instead of ignoring it.
> >
> > Does not sending any SSIDs somehow not work?  This seems like a pretty
> > big kludge.  The behavior should be that if no SSID property is sent,
> > then no specific scan is performed.  A zero-length SSID should actually
> > be rejected with an error.
> If I recall, iw's scan command sends an empty SSID when no ssid is
> explicitely specified. A while ago iwlagn was not doing the broadcast
> scan if the empty ssid wasn't there. However, I believe that was a
> bug, and it has been corrected in recent versions of iwlagn.
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