iOS application connecting in the background

[Jeff]

I'm using SDK 15.3.0 and SoftDevice 6.1.1 running on an nRF52832.

The iOS application works correctly when it is running in the foreground.  It is able to connect and bond to the nRF.

After it has bonded, if I try to connect in the background, I'm seeing an BLE_GAP_EVT_AUTH_STATUS event.  I don't see that event during a foreground connection. The fields in the status event are saying that the remote side (src) returned a status of BLE_GAP_SEC_STATUS_UNSPECIFIED (0x88):

[00:01:24.056,976] <debug> ble_dcs: Event BLE_GAP_EVT_AUTH_STATUS (0x19)
[00:01:24.057,006] <info> app: BLE_GAP_EVT_AUTH_STATUS: status:0x88 bond:0x0 src:0x1 lesc:0x0
[00:01:24.057,037] <info> app: BLE_GAP_EVT_AUTH_STATUS: sm1:0000
[00:01:24.057,037] <info> app: BLE_GAP_EVT_AUTH_STATUS. sm2.0000
[00:01:24.057,067] <info> app: BLE_GAP_EVT_AUTH_STATUS: kdist_own: enc:0x0 id:0x0 sign:0x0 link:0x0
[00:01:24.057,067] <info> app: BLE_GAP_EVT_AUTH_STATUS: kdist_peer: enc:0x0 id:0x0 sign:0x0 link:0x0

I'm looking for any insight into the cause of this issue and what (if anything) can be done about it?

thanks,

Jeff

[Jeff]

Hung,

I've attached a sniffer trace that I captured of the issue.  Packet 1995 shows the pairing failure.

Let me know what you think.

thanks,

Jeff

iOS-background_connection.pcapng

[Hung Bui]

Hi Jeff, 
It looked like the Slave requested the link to be bonded and the phone just rejected it.
I'm not 100% sure why the phone did this. But have you got the link encrypted (bonded) before that ? Could you capture that connection and exchange as well ? (in one shot) 

If the phone and the device had not been paired before that I think the rejection makes sense. The phone doesn't want the end user to be disturbed by an app in the background to popup and ask for pairing.