Kernel: Linux 4.9.84 armv7l on board
Bluez: 5.65
Peer: Android 12 & IOS 16.6
Role: Central is my phone, Peripheral is my board
Application:

• use btmgmt create a bondable agent and io-cap set to NoInputNoOutput

btmgmt power off
btmgmt connectable on
btmgmt pairable on
btmgmt le on
btmgmt bondable on
btmgmt power on
btmgmt advertising on

• use phone to pair the board.

Result:

My phone successfully connected to my board and added encryption to the link, but after the pairing process, the IRK was not distributed by the central device. Without the IRK, I cannot resolve the central resolvable MAC address.

Expectation:
I want to use the LTK, which was generated last time, to handle re-pairing issues. However, without the IRK, I can’t index those LTKs. Therefore, I want to get the IRK distributed and store it locally to handle re-pairing issues.

I already know that if the initiator key distribution of the peripheral do not include IdKey, the central device will not send the IRK.
I have already tried changing the peripheral’s IO capability and pairing mode (from Legacy to Secure Connections), but I still cannot change the initiator key distribution of the peripheral.

ps: See at Core v5.4 vol3,Part H. page 1602

Any help on this matter would be greatly appreciated!