wpa_supplicant's p2p wouldn't connect to Sony Bravia TV

Jouni Malinen j at w1.fi
Fri Dec 2 16:17:34 EST 2011


On Wed, Nov 30, 2011 at 01:03:55AM +0100, Vitaly Wool wrote:
> Notable is, if I switch the TV to automatic mode (no confirmation), it
> works just fine. So I investigated this deeper, including getting /
> analyzing air logs and it turns out the problem is the following.

Would you be able to send me capture files from both the success
(automatic mode) and failure cases?

> Before the connection is confirmed, TV responds to probe requests with
> responses that don't include active session attribute (which is quite fine
> IMO). So connection process on my prototype device is not started and the
> scan is rescheduled. But after the connection has been confirmed, the TV
> would not respond to probe requests at all so that's why nothing happens.
> And it actually turns out to be the valid behavior also: according to the
> specification, a Wi-Fi Direct device should not answer to probe requests
> that either do not contain P2P wildcard SSID or do not contain this
> device's SSID while in listen mode.

Well, there are some restrictions on when the GO should not answer, but
I don't think that what's described above is one of those cases (there
may be some other reasons and that's why I would like to see the capture
files myself).

> And the scan wpa_supplicant runs in this case is just plain wildcard scan
> (no SSID at all). This is of course valid for basic WPS case but is not
> going to work with P2P.

Well, it is supposed to work in this particular case with P2P.. ;-)

> So what's next? I'm eager to come back with a patch but it looks like we
> need to have a common ground on how to fix this. I suggest that we run
> specific scan in P2P case for this SSID (it is known by p2p_supplicant), it
> will require very minimal changes in the whole flow. Alternatively, P2P
> wildcard SSID can be used but then there should be some additional logic in
> picking up the right session (e. g. if the scan was run for P2P wildcard,
> do not request exact SSID match). Of course one may have a better idea :)

Can you provide more information about the device you used in this test?
Does the driver use mac80211? Or cfg80211?

As far as changing scanning behavior is concerned, I need to understand
which exact Probe Request frame is the one that is not getting a
response. If this is the one sent in the beginning of p2p_connect join
command, it should be fine to force the Probe Request to use P2P
wildcard SSID (and include P2P IE).

-- 
Jouni Malinen                                            PGP id EFC895FA


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