You can check the EVENT_NEW_STA in drv_callbacks.c. This will call hostapd_event_new_sta()->hostapd_new_assoc_sta() to notify that a new station associated with the AP.
Thank you for your reply.
I don't think the 4-way handshake offloading is complete when the EVENT_NEW_STA event occurs.
I want to detect that the STA is connected to the AP, same as the AP-STA-CONNECTED event.
(That means the 4-way handshake is complete and the connection is successful.)