P2P: Reduce redundant PSK generation for GO

The PSK generation done by pbkdf2_sha1() is one of the longest CPU time
users according to our profiling from boot to GO started.

So I have reduced some steps.

I could boot a GO by this command sequence.
-------------
add_net
set_network 0 ssid '"DIRECT-XX"'
set_network 0 psk
'"123456789012345678901234567890123456789012345678901234567890123"'
set_network 0 proto RSN
set_network 0 key_mgmt WPA-PSK
set_network 0 pairwise CCMP
set_network 0 auth_alg OPEN
set_network 0 mode 3
set_network 0 disabled 2
p2p_group_add persistent=0 freq=2412
-------------

By this sequence, pbkdf2_sha1() was called three times and the function
calculates the same value each time. Reduce number of calls to
pbkdf2_sha1() from 3 to 1 by caching the previous result.

Signed-hostap: Masashi Honma <masashi.honma at gmail.com>

src/p2p/p2p.h

@@ -87,6 +87,16 @@ struct p2p_go_neg_results {
 	 */
 	size_t ssid_len;
 
+	/**
+	 * psk - WPA pre-shared key (256 bits) (GO only)
+	 */
+	u8 psk[32];
+
+	/**
+	 * psk_set - Whether PSK field is configured (GO only)
+	 */
+	int psk_set;
+
 	/**
 	 * passphrase - WPA2-Personal passphrase for the group (GO only)
 	 */

wpa_supplicant/ap.c

@@ -174,15 +174,15 @@ static int wpa_supplicant_conf_ap(struct wpa_supplicant *wpa_s,
 		bss->wpa = ssid->proto;
 	bss->wpa_key_mgmt = ssid->key_mgmt;
 	bss->wpa_pairwise = ssid->pairwise_cipher;
-	if (ssid->passphrase) {
-		bss->ssid.wpa_passphrase = os_strdup(ssid->passphrase);
-	} else if (ssid->psk_set) {
+	if (ssid->psk_set) {
 		os_free(bss->ssid.wpa_psk);
 		bss->ssid.wpa_psk = os_zalloc(sizeof(struct hostapd_wpa_psk));
 		if (bss->ssid.wpa_psk == NULL)
 			return -1;
 		os_memcpy(bss->ssid.wpa_psk->psk, ssid->psk, PMK_LEN);
 		bss->ssid.wpa_psk->group = 1;
+	} else if (ssid->passphrase) {
+		bss->ssid.wpa_passphrase = os_strdup(ssid->passphrase);
 	} else if (ssid->wep_key_len[0] || ssid->wep_key_len[1] ||
 		   ssid->wep_key_len[2] || ssid->wep_key_len[3]) {
 		struct hostapd_wep_keys *wep = &bss->ssid.wep;

wpa_supplicant/p2p_supplicant.c

@@ -888,7 +888,11 @@ static void wpas_start_wps_go(struct wpa_supplicant *wpa_s,
 		wpa_config_remove_network(wpa_s->conf, ssid->id);
 		return;
 	}
-	wpa_config_update_psk(ssid);
+	ssid->psk_set = params->psk_set;
+	if (ssid->psk_set)
+		os_memcpy(ssid->psk, params->psk, sizeof(ssid->psk));
+	else
+		wpa_config_update_psk(ssid);
 	ssid->ap_max_inactivity = wpa_s->parent->conf->p2p_go_max_inactivity;
 
 	wpa_s->ap_configured_cb = p2p_go_configured;
@@ -4117,6 +4121,9 @@ int wpas_p2p_group_add_persistent(struct wpa_supplicant *wpa_s,
 		return -1;
 
 	params.role_go = 1;
+	params.psk_set = ssid->psk_set;
+	if (params.psk_set)
+		os_memcpy(params.psk, ssid->psk, sizeof(params.psk));
 	if (ssid->passphrase == NULL ||
 	    os_strlen(ssid->passphrase) >= sizeof(params.passphrase)) {
 		wpa_printf(MSG_DEBUG, "P2P: Invalid passphrase in persistent "