P2P Connection Channel Issues

Chris Furlough ChrisFurlough at smarttech.com
Tue Apr 2 09:10:28 PDT 2019


For P2P, you don't NEED a STA connection.  Try to connect the devices WITHOUT the station connection.  There's also an option to tell the supplicant to prefer the P2P connection, which will cause it to disconnect the STA connection first.  

It's possible that you have a single band radio, and you're trying to do 2 bands, and it just can't handle it.



From: Hostap <hostap-bounces at lists.infradead.org> on behalf of Andreea Lutac <andreea.lutac at fixposition.ch>
Sent: 02 April 2019 03:08
To: hostap at lists.infradead.org
Subject: P2P Connection Channel Issues
 
Hello all,
I'm trying to connect two devices via P2P (an embedded Linux board and an Android tablet), but I'm having some trouble which I think is related to the communication channels. It would be great if anyone could shed some light as to what's happening here.

My setup is the following: the Android tablet is connected to an AP that operates on a 5 GHz channel chosen at boot by the device providing the AP (a camera). The tablet then finds and sends a GO negotiation request to the embedded Linux board. The board responds via the wpa_cli command:
p2p_connect <tablet MAC> pbc go_intent=0

The GO negotiation succeeds, with the tablet always ending up as the group owner, as intended.
Now the problem is that a lot of the time the group formation step times out. On its end, the tablet seems to set up the DIRECT-xy-<name> group usually on the same frequency as the AP, but on the board wpa_cli shows:
<3>P2P-GO-NEG-SUCCESS role=client freq=5220 ht40=0 peer_dev=e2:b6:f5:82:18:b5 peer_iface=e2:b6:f5:82:18:b5 wps_method=PBC
<3>CTRL-EVENT-SCAN-RESULTS
<3>CTRL-EVENT-SCAN-RESULTS
<3>CTRL-EVENT-SCAN-RESULTS
<3>CTRL-EVENT-SCAN-RESULTS
<3>CTRL-EVENT-SCAN-RESULTS
<3>CTRL-EVENT-SCAN-RESULTS
<3>CTRL-EVENT-SCAN-RESULTS
<3>P2P-GROUP-FORMATION-FAILURE
<3>P2P-GROUP-REMOVED p2p-wlan0-32 client reason=FORMATION_FAILED

I think I have narrowed this down to an issue with the operating channels, where the board's wpa_supplicant tries to scan the various channels during provisioning, but doesn't find the right one before formation times out.
I have tried to add freq=<AP freq> to the p2p_connect command and with some frequencies (5745, 5765) this fixes the timeout and the connection is instant, but with others (5700, 5560, 5580), I get the error message:
FAIL-CHANNEL-UNSUPPORTED
 
Running "iw reg get" on both the tablet and the board shows that the country is unset (00), so I don't think there should be any restriction on the channels. I have however noticed that the operating frequency of the tablet (as reported by p2p_peer) is often different from that of the AP. But adding this operating frequency to p2p_connect still results in timeouts.

What could be causing the "channel usupported" message? Is there a way to tell wpa_supplicant which channels to scan during the provisioning phase?

Thank you and I look forward to your advice.

Best,
Andreea



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