sdk 1.15.3 how to set up bonding examples with DFU enabled?

[breaker]

Dears,

What I am trying to implement:

1. enable MITM and bonding
2. device IO capability:BLE_GAP_IO_CAPS_DISPLAY_ONLY; (mostly like ble_app_gls with passkey method, but different service)
3. with DFU enabled

What I did try or failed:

1. secure bootloader example and ble_app_buttonless_dfu example, with or without bonding, walked through and succeed
2. trying to set ble_app_gls to add DFU services, failed in application bootup

I need some help here:

1. Is there any procedure I can follow to add DFU feature into a current bonding example?
2. How to set ble_app_buttonless_dfu bonding with passkey entry method?(ble_app_buttonless_dfu bonding example seems only works under JUST WORK method).

[breaker]

Update some details:

1. SDK version is 15.3.0, sorry for confusing you.

2. I need to enable LE Secure connection(LE Legacy is not acceptable by my customer), seems I have to import some crypto parts?