Sending chr changed valued directly with out notification?

[stophin]

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Issue or Suggestion Description

I'm using nimble as esp-blufi components in esp32c6.
And I'm not using EspBluFi apk: https://github.com/EspressifApp/EspBlufiForAndroid
but created a new apk which follows BlueFi protocol stack: https://github.com/espressif/esp-idf/blob/v4.3/docs/en/api-guides/blufi.rst
and give no notification (say not calling android.bluetooth.BluetoothGatt.setCharacteristicNotification)

I'm not quiet sure, but following the revoking thread it indeed act as the subject of this issue.
ble_att_clt_tx_notify
ble_gatts_notify_custom

1.Any event (like gatt) calls ble_gatts_notify_custom
2.ble_gatts_notify_custom calls ble_att_clt_tx_notify
3.ble_att_clt_tx_notify use BLE_ATT_OP_NOTIFY_REQ(Handle Value Notification PDU(0x1B)) to send notify
4.the whole proceduer can be tested without client sending notification(0x100)!
5.client got the chr changed value with out notification enabled.

I assume there's no CCCD check in nimble (maybe wrong? Please Tell me why and where?)
and need confirmation or some guidance in this issue.
The apk without notification can hardly adapt to other BLE stack utils like bluez5 in linux,
which actually had strong cccd check (see bluez issue: bluez/bluez#2007)

[Singh-Sumeet]

Hi @stophin ,
Currently in esp-nimble, there isn't a hard check on the value of the CCCD if the server initiates a notification using ble_gatts_notify_custom. This is intended behavior. The application / profile has control over when to send notifications, even if the corresponding bit in the CCCD is 0. The effect of setting a CCCD bit to 1 is that the server will automatically notify when the value of the characteristic updates, however, the server may send a notification / indication manually as well, using ble_gatts_notify_custom.