WPA_supplicant authentication implementation - wpa-supplicant

Question

I need help from someone that have some experience in playing with wpa_supplicant code.
What i understand is that wpa_supplicant dose everything in order for a supplicant to connect to an AP (if that what you what). Hence the steps are as:
Scan
Get scan results
AUTH
ASSOC
4-hand shake
data exchange
As i understand this then the first 4 steps are only managed by wpa_supplicant. That is, wpa_supplicant simply calls the under laying driver to perform these steps and after the main event loop receives the EVENT_ASSOC msg. it starts the 4-handshake.
For my part, it is fine with the first two steps are carried out at the driver, ie., wpa_supplicant send a scan req, the driver perform the scan and feed the scan results.
My question is, is it correct that wpa_supplicant cannot generate the necessary packet and use, e.g., layer 2 (rawsocket) to send authentication request to the AP ? and followed by an associate request ?... shall one simply provides these as a handle from the driver layer ?
as i can see from the code in wpa_supplicant.c
(void wpa_supplicant_associate(struct wpa_supplicant *wpa_s,
struct wpa_bss *bss, struct wpa_ssid *ssid))
that this function calls a function pointer to the selected driver eg. ".associate = wpa_driver_nl80211_associate" and here the driver then send this down to the udnerlaying nl80211 driver code ? .... so wpa_supplicant can not generate these packet by it self ?
I hope that this make any sens, if not please ask :)

Answer 1

Yes, your understanding is correct. To send auth/assoc req, the wpa_supplicant should construct the corresponding NL80211 commands in following different scenarios:
a) in case the SME is maintained in wpa_supplicant
NL80211_CMD_AUTHENTICATE
NL80211_CMD_ASSOCIATE
b) in case the SME is maintained by driver
NL80211_CMD_CONNECT
And these commands will trigger the corresponding cfg80211_ops hooks (.auth, .assoc, .connect) registered by the wifi driver to be called to construct the frames and then send out the frames.