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

Daniel Kurtz djkurtz at google.com
Thu Oct 7 02:29:38 EDT 2010


How do you perform both Broadcast and directed scan over channels at the
same time?
For example, when looking for a network to join, including some hidden
SSIDs.

-Dan

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.
>
> Dan
>
> > This patch updates DBus API .Scan() logic per the test cases listed
> below:
> >
> > 1) Interface.Scan({'Type':'active', 'Channel':(2412, 20)})
> >    Request:     Active scan with only '' SSID (1 channel)
> >    Should be:   1 broadcast ProbeRequest on specified channel
> >    Previous:    1 broadcast ProbeRequest on specified channel
> >    This Patch:  1 broadcast ProbeRequest on specified channel
> >
> > 2) Interface.Scan({'Type':'active', 'Channel':(2412, 20), 'SSIDs':['']})
> >    Request:     Active scan with only '' SSID (1 channel)
> >    Should be:   1 broadcast ProbeRequest on specified channel
> >    Previous:    No ProbeRequests; passive scan results for specified
> channel
> >    This Patch:  FIXED: 1 broadcast ProbeRequest on specified channel
> >
> > 3) Interface.Scan({'Type':'active', 'Channel':(2412, 20),
> 'SSIDs':['MySSID']})
> >    Request:     Active scan with only non-'' SSIDs (1 channel)
> >    Should be:   1 directed ProbeRequest for each SSID on specified
> channel, no broadcast ProbeRequest
> >    Previous:    1 directed ProbeRequest for each SSID on specified
> channel, no broadcast ProbeRequest
> >    This Patch:  1 directed ProbeRequest for each SSID on specified
> channel, no broadcast ProbeRequest
> >
> > 4) Interface.Scan({'Type':'active', 'Channel':(2412, 20), 'SSIDs':['',
> 'MySSID']})
> >    Request:     Active scan with SSIDs, including 1 '' SSID (1 channel)
> >    Should be:   1 broadcast ProbeRequest, 1 directed ProbeRequest for
> each non-'' SSID on specified channel
> >    Previous:    1 directed ProbeRequest for each non-'' SSID on specified
> channel
> >    This Patch:  FIXED: 1 broadcast ProbeRequest, 1 directed ProbeRequest
> for each non-'' SSID on specified channel
> > ---
> >  wpa_supplicant/dbus/dbus_new_handlers.c |   30
> +++++++++++++++++-------------
> >  1 files changed, 17 insertions(+), 13 deletions(-)
> >
> > diff --git a/wpa_supplicant/dbus/dbus_new_handlers.c
> b/wpa_supplicant/dbus/dbus_new_handlers.c
> > index e2b5e50..36eb917 100644
> > --- a/wpa_supplicant/dbus/dbus_new_handlers.c
> > +++ b/wpa_supplicant/dbus/dbus_new_handlers.c
> > @@ -987,21 +987,25 @@ static int wpas_dbus_get_scan_ssids(DBusMessage
> *message, DBusMessageIter *var,
> >               dbus_message_iter_recurse(&array_iter, &sub_array_iter);
> >
> >               dbus_message_iter_get_fixed_array(&sub_array_iter, &val,
> &len);
> > -             if (len == 0) {
> > -                     dbus_message_iter_next(&array_iter);
> > -                     continue;
> > -             }
> >
> > -             ssid = os_malloc(len);
> > -             if (ssid == NULL) {
> > -                     wpa_printf(MSG_DEBUG,
> "wpas_dbus_handler_scan[dbus]: "
> > -                                "out of memory. Cannot allocate memory
> for "
> > -                                "SSID");
> > -                     *reply = dbus_message_new_error(
> > -                             message, DBUS_ERROR_NO_MEMORY, NULL);
> > -                     return -1;
> > +             if (len != 0) {
> > +                     ssid = os_malloc(len);
> > +                     if (ssid == NULL) {
> > +                             wpa_printf(MSG_DEBUG,
> > +                                        "wpas_dbus_handler_scan[dbus]: "
> > +                                        "out of memory. Cannot allocate
> "
> > +                                        "memory for SSID");
> > +                             *reply = dbus_message_new_error(
> > +                                             message,
> DBUS_ERROR_NO_MEMORY,
> > +                                             NULL);
> > +                             return -1;
> > +                     }
> > +                     os_memcpy(ssid, val, len);
> > +             } else {
> > +                     /* Allow zero-length SSIDs */
> > +                     ssid = NULL;
> >               }
> > -             os_memcpy(ssid, val, len);
> > +
> >               ssids[ssids_num].ssid = ssid;
> >               ssids[ssids_num].ssid_len = len;
> >
>
>
>
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