CC3351: Failure to connect to hidden SSID on DFS channel

Dean Ramsier

Part Number: CC3351

Tool/software:

The CC3351 (release 1.0.0.8) fails to connect to an AP that is configured with a hidden SSID on a DFS channel. It is able to connect on a DFS channel if the SSID is broadcast, and it is able to connect to hidden SSIDs on a non-DFS channel.

Repro steps:

1. Configure AP on channel 64 with open security

2. Configure the SSID to be hidden ('no guest-mode' on Cisco APs). Note that the AP still beacons, but the SSID element is zero length

3. Attempt to connect.

Observe via sniffer that the CC3351 never sends a probe request, even though beacons are present enabling use of the channel.

4. Enable the ssid

5. Attempt to connect

Observe via sniffer that the CC3351 probes and connects successfully.

Expectation: CC3351 should connect to a hidden SSID on both regular and DFS channels.

4 days ago

0 Shlomi Itzhak 3 days ago

TI__Guru 60695 points

Hi,

When enabling hidden SSID on an AP, the SSID is not sent on beacons and if it is set as a DFS, stations are not allowed to transmit on this channel as well.

Since the station can only find APs via passive scanning and the SSID is not being transmitted, the station will never find the AP it is looking for.

Let me look into it internally and see if there is a way around it.

Shlomi

0 Dean Ramsier 1 day ago in reply to Shlomi Itzhak

Intellectual 360 points

The beacon is still being broadcast. The SSID element is of zero length but the rest of the beacon content is still present.

The station is passively scanning and can see the beacon - the SSID doesn't have to be in the beacon for that. Since it can see the beacon, it should be able to go active and issue a directed probe and connect. It isn't doing that.

Regards,

Dean

0 Shlomi Itzhak 1 day ago in reply to Dean Ramsier

TI__Guru 60695 points

I am still on it. The fact that we see the beacon might not be enough since we look for specific SSID and not any SSID.

0 Dean Ramsier 1 day ago in reply to Shlomi Itzhak

Intellectual 360 points

That seems to be a bug, does it not? The channel can be used once the station determines the AP is on it regardless of the SSID - it should not need to stay passive.

0 Shlomi Itzhak 1 day ago in reply to Dean Ramsier

TI__Guru 60695 points

As I mentioned, I am pending on some feedback from experts to verify the expected behavior.

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CC3351: Failure to connect to hidden SSID on DFS channel