IssueTracker

The easiest way to reproduce the issue is by using an app like Nordic's nRF Connect for Mobile from Google Play.

Prerequisites:
Any BLE device you can create a GATT connection to

Steps to reproduce:

1. Open nRF Connect for Mobile
2. Discover the BLE device
3. Create a connection to the BLE device
4. Pull from the left side of the screen in nRF to reveal the log window (or look at logcat on a connected computer)
5. Terminate the BLE connection by powering off or taking the BLE device out of range

Expected result:
If the BLE device is taken out of range, the GATT status value in onConnectionStateChanged() should be '8' (GATT_CONN_TIMEOUT), like on all previous Android versions with BLE support.
If the BLE device terminates the connection, the GATT status value in onConnectionStateChanged() should be '19' (GATT_CONN_TERMINATE_PEER_USER), like on all previous Android versions with BLE support.

The GATT status should only be '0' when the app closes the connection via a call to BluetoothGatt#disconnect().

Actual result:
In Android 12, regardless how the BLE connection is terminated the GATT status is always '0'.

See attached screen shot ('Comparison.png') for a comparison between an older Android version and Android 12.

Pixel 12:
GATT_CONN_TIMEOUT, disconnect reason 8:
2021-11-29 11:48:13.635 13689-13722/? D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=9 device=xx:xx:xx:xx:xx:xx

GATT_CONN_TERMINATE_PEER_USER, disconnect reason 19:
2021-11-29 11:53:02.644 13689-21741/? D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=9 device=xx:xx:xx:xx:xx:xx

Bugreport
https://drive.google.com/file/d/19ASZ6bVYXRuhRt_NjsRs_-YnWOiUGcyN/view?usp=drive_web (bugreport-flame-SP1A.210812.015-2021-11-29-11-53-20.zip)

We have shared this with our product and engineering team and will update this issue with more information as it becomes available.

If you look into the HCI snoop log, you can see that the disconnect reasons (0x08 and 0x13), are correctly shown there. Though I noticed that in the HCI log, there is a 'Status: Success (0x00)' field. Is this the one which is now passed on to the onClientConnectionState() / onConnectionStateChanged() methods?
If that is the case, then how do we get the 'disconnect reason' through the API in Android 12?

Android 12:

GATT_CONN_TIMEOUT, disconnect reason 8 ((0x08):
HCI log:

44563	10:48:13.617287	0.000839	controller	host	HCI_EVT	7	Rcvd Disconnect Complete
Frame 44563: 7 bytes on wire (56 bits), 7 bytes captured (56 bits)
Bluetooth
Bluetooth HCI H4
Bluetooth HCI Event - Disconnect Complete
    Event Code: Disconnect Complete (0x05)
    Parameter Total Length: 4
    Status: Success (0x00)
    Connection Handle: 0x0002
    Reason: Connection Timeout (0x08)

Log cat:
2021-11-29 11:48:13.635 13689-13722/? D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=9 device=xx:xx:xx:xx:xx:xx

GATT_CONN_TERMINATE_PEER_USER, disconnect reason 19 (0x13):
HCI log:

45054	10:53:02.634023	16.743903	controller	host	HCI_EVT	7	Rcvd Disconnect Complete
Frame 45054: 7 bytes on wire (56 bits), 7 bytes captured (56 bits)
Bluetooth
Bluetooth HCI H4
Bluetooth HCI Event - Disconnect Complete
    Event Code: Disconnect Complete (0x05)
    Parameter Total Length: 4
    Status: Success (0x00)
    Connection Handle: 0x0003
    Reason: Remote User Terminated Connection (0x13)

Log cat:
2021-11-29 11:53:02.644 13689-21741/? D/BluetoothGatt: onClientConnectionState() - status=0 clientIf=9 device=xx:xx:xx:xx:xx:xx

Android 11:

GATT_CONN_TIMEOUT, disconnect reason 8 ((0x08):
HCI log:

19997	11:20:16.335340	0.001857	controller	host	HCI_EVT	7	Rcvd Disconnect Complete
Frame 19997: 7 bytes on wire (56 bits), 7 bytes captured (56 bits)
Bluetooth
Bluetooth HCI H4
Bluetooth HCI Event - Disconnect Complete
    Event Code: Disconnect Complete (0x05)
    Parameter Total Length: 4
    Status: Success (0x00)
    Connection Handle: 0x0040
    Reason: Connection Timeout (0x08)

Log cat:
12-02 11:20:16.348 10268 25440 26308 D BluetoothGatt: onClientConnectionState() - status=8 clientIf=11 device=52:31:2C:E1:EF:82

12-02 11:20:16.349--BluetoothRemoteDevices -- ACTION_ACL_DISCONNECTED, device is 52312C, reason is 8, linktype is 2

GATT_CONN_TERMINATE_PEER_USER, disconnect reason 19 (0x13):
HCI log:

20386	11:21:13.816370	3.541896	controller	host	HCI_EVT	7	Rcvd Disconnect Complete
Frame 20386: 7 bytes on wire (56 bits), 7 bytes captured (56 bits)
Bluetooth
Bluetooth HCI H4
Bluetooth HCI Event - Disconnect Complete
    Event Code: Disconnect Complete (0x05)
    Parameter Total Length: 4
    Status: Success (0x00)
    Connection Handle: 0x0040
    Reason: Remote User Terminated Connection (0x13)

Log cat:
12-02 11:21:13.826 10268 25440 26126 D BluetoothGatt: onClientConnectionState() - status=19 clientIf=11 device=52:31:2C:E1:EF:82

12-02 11:21:13.828--BluetoothRemoteDevices -- ACTION_ACL_DISCONNECTED, device is 52312C, reason is 19, linktype is 2

Same situation with Android 12L Beta on Pixel 4 :( - still always returns 'status = 0'.

Pixel 4, SB1.211112.006

...and also still a problem on Pixel 6 with the January patch: SQ1D.220105.007

...and on Pixel 4 with Android 13 developer preview: TPP1.220114.016

The situation is unchanged for 12.1.0 (SP2A.220305.012, Mar 2022) :(

Nope. Same problem in Android 12.1 May and Android 13 beta 2 😣

In packages/modules/Bluetooth/android/app/src/com/android/bluetooth/btservice/AdapterService.java there is a nice mapping of HCI disconnect reasons to Android disconnect reasons. But for some reason, they are not being passed all the way up to BluetoothGattCallback#onConnectionStateChange() - as they used to for Android 11 and older.

We still need these disconnect reasons in order help our customers when something goes wrong. As it is now, we have no way of knowing if a disconnect was caused by the the user walking out of range, a phone error, a device error etc, so we cannot guide the user on how to recover, when the connection breaks.

/**
     * Converts HCI disconnect reasons to Android disconnect reasons.
     * <p>
     * The HCI Error Codes used for ACL disconnect reasons propagated up from native code were
     * copied from: packages/modules/Bluetooth/system/stack/include/hci_error_code.h
     * <p>
     * These error codes are specified and described in Bluetooth Core Spec v5.1, Vol 2, Part D.
     *
     * @param hciReason is the raw HCI disconnect reason from native.
     * @return the Android disconnect reason for apps.
     */
    static @BluetoothAdapter.BluetoothConnectionCallback.DisconnectReason int
            hciToAndroidDisconnectReason(int hciReason) {
        switch(hciReason) {
            case /*HCI_SUCCESS*/ 0x00:
            case /*HCI_ERR_UNSPECIFIED*/ 0x1F:
            case /*HCI_ERR_UNDEFINED*/ 0xff:
                return BluetoothStatusCodes.ERROR_UNKNOWN;
            case /*HCI_ERR_ILLEGAL_COMMAND*/ 0x01:
            case /*HCI_ERR_NO_CONNECTION*/ 0x02:
            case /*HCI_ERR_HW_FAILURE*/ 0x03:
            case /*HCI_ERR_DIFF_TRANSACTION_COLLISION*/ 0x2A:
            case /*HCI_ERR_ROLE_SWITCH_PENDING*/ 0x32:
            case /*HCI_ERR_ROLE_SWITCH_FAILED*/ 0x35:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_LOCAL;
            case /*HCI_ERR_PAGE_TIMEOUT*/ 0x04:
            case /*HCI_ERR_CONNECTION_TOUT*/ 0x08:
            case /*HCI_ERR_HOST_TIMEOUT*/ 0x10:
            case /*HCI_ERR_LMP_RESPONSE_TIMEOUT*/ 0x22:
            case /*HCI_ERR_ADVERTISING_TIMEOUT*/ 0x3C:
            case /*HCI_ERR_CONN_FAILED_ESTABLISHMENT*/ 0x3E:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_TIMEOUT;
            case /*HCI_ERR_AUTH_FAILURE*/ 0x05:
            case /*HCI_ERR_KEY_MISSING*/ 0x06:
            case /*HCI_ERR_HOST_REJECT_SECURITY*/ 0x0E:
            case /*HCI_ERR_REPEATED_ATTEMPTS*/ 0x17:
            case /*HCI_ERR_PAIRING_NOT_ALLOWED*/ 0x18:
            case /*HCI_ERR_ENCRY_MODE_NOT_ACCEPTABLE*/ 0x25:
            case /*HCI_ERR_UNIT_KEY_USED*/ 0x26:
            case /*HCI_ERR_PAIRING_WITH_UNIT_KEY_NOT_SUPPORTED*/ 0x29:
            case /*HCI_ERR_INSUFFCIENT_SECURITY*/ 0x2F:
            case /*HCI_ERR_HOST_BUSY_PAIRING*/ 0x38:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_SECURITY;
            case /*HCI_ERR_MEMORY_FULL*/ 0x07:
            case /*HCI_ERR_MAX_NUM_OF_CONNECTIONS*/ 0x09:
            case /*HCI_ERR_MAX_NUM_OF_SCOS*/ 0x0A:
            case /*HCI_ERR_COMMAND_DISALLOWED*/ 0x0C:
            case /*HCI_ERR_HOST_REJECT_RESOURCES*/ 0x0D:
            case /*HCI_ERR_LIMIT_REACHED*/ 0x43:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_RESOURCE_LIMIT_REACHED;
            case /*HCI_ERR_CONNECTION_EXISTS*/ 0x0B:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_CONNECTION_ALREADY_EXISTS;
            case /*HCI_ERR_HOST_REJECT_DEVICE*/ 0x0F:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_SYSTEM_POLICY;
            case /*HCI_ERR_ILLEGAL_PARAMETER_FMT*/ 0x12:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_BAD_PARAMETERS;
            case /*HCI_ERR_PEER_USER*/ 0x13:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_REMOTE_REQUEST;
            case /*HCI_ERR_CONN_CAUSE_LOCAL_HOST*/ 0x16:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_LOCAL_REQUEST;
            case /*HCI_ERR_UNSUPPORTED_REM_FEATURE*/ 0x1A:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_REMOTE;
            case /*HCI_ERR_UNACCEPT_CONN_INTERVAL*/ 0x3B:
                return BluetoothStatusCodes.ERROR_DISCONNECT_REASON_BAD_PARAMETERS;
            default:
                Log.e(TAG, "Invalid HCI disconnect reason: " + hciReason);
                return BluetoothStatusCodes.ERROR_UNKNOWN;
        }
    }

I just noticed that OnePlus has solved this in their latest Android 13 release - but it is still not working on Pixel phones.

Working, i.e. disconnect reasons are provided:
OnePlus 8T, Android 13, KB2003_11_F.15 (December 5, 2022, security patch)

Still not working:
Pixel 6, Android 13, T2B2.221216.008

Sounds great. Can you provide a change ID? Any news about ud this will go into Android 13, or if we will have to wait for Android 14?

I just checked QPR3 beta2, and the fix is in!

We are now finally again getting GATT disconnect reasons:

11:48:05.801 [Callback] Connection state changed with status: 8 and new state: DISCONNECTED(0)
11:48:05.802 Error 8 (0x8): GATT CONN TIMEOUT
11:48:05.802 Disconnected
11:48:06.001 [Broadcast] Action received: android.bluetooth.device.action.ACL_DISCONNECTED