BLE pairing issue when BT_SECURITY_L4 with nRF5340

[SanketC]

Hello,

I am using SDK1.5.1 with one nRf5340 as central and another nRf5340 as peripheral. My use case is, I am setting security level 4 (BT_SECURITY_L4) after establishing the connection.  In a normal scenario, it is working and I am able to establish a secure connection. Now the problem I am facing is some time during pairing if peripheral or central is unable to call bt_conn_auth_passkey_confirm() and after again restarting the scan, at the central device I am getting the following warning message:

"Found valid connection in the disconnected state"

post this, paring is not happening. I have to forcefully restart the central and start the process again to get successful pair. I can see bt_conn_unref(conn); is already called after the warning message.

Request you to help me to clear the whole stuff during the run time for such types of errors so that I can start the fresh pair process without actually restarting the central device. 

 Best Regards,

SC

[Hung Bui]

Hi Sanket,

Can the issue be reproduced using the peripheral_sc_only example ? So we can test here. 

You mentioned "if peripheral or central is unable to call bt_conn_auth_passkey_confirm() ", what exactly happened there ? Was bt_conn_auth_cancel() called or the connection simply dropped from one side at that time ? 

We have a case with similar error, could you have a look and check if the solution there can help ? 
https://devzone.nordicsemi.com/f/nordic-q-a/68150/bluetooth-codded-phy-couldn-t-connect-after-disconnecting-w-found-valid-connection-in-disconnected-state

[SanketC]

Hello Hung,

I have already gone through the case shared by you. Please see my reply below for your question:

You mentioned "if peripheral or central is unable to call bt_conn_auth_passkey_confirm() ", what exactly happened there ? Was bt_conn_auth_cancel() called or the connection simply dropped from one side at that time ? 

SC: basically there is one use case because of that central and peripheral is not able to call bt_conn_auth_passkey_confirm() so after approx 10seconds I get " SMP time out " and "security failed" log I get from security_changed() call back. After this, if If I try to again pair then I get "Found valid connection in the disconnected state".

So, I want to clear out this reference and start fresh pair.

Best Regards,

SC

[Hung Bui]

Hi SC, 

Could you provide the sample that can reproduce the issue so I can test here ? 
I did a quick test with the peripheral_sc_only and the nRF Connect Desktop but couldn't reproduce the issue on the peripheral side. The central was able to re-connect after disconnect. 

[SanketC]

Hi Hung,

Actually, I have not used peripheral_sc_only example. I am using central_uart and peripheral_uart in which I have enabled the security. I shall try to provide the file with minimum changes on which you can reproduce this issue. Give me some time. I shall get back to you on this.

Regards,

SC

[Hung Bui]

Thanks, I would suggest to test with the peripheral_sc_only, just in case if it works, then you can use it as the reference.