mac80211: Fix reassociation by not clearing previous BSSID

We must not clear the previous BSSID when roaming to another AP within
the same ESS for reassociation to be used properly. It is fine to
clear this when the SSID changes, so let's move the code into
ieee80211_sta_set_ssid().
Signed-off-by: Jouni Malinen <jouni.malinen@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/mlme.c

@@ -1888,8 +1888,6 @@ int ieee80211_sta_commit(struct ieee80211_sub_if_data *sdata)
 {
 	struct ieee80211_if_managed *ifmgd = &sdata->u.mgd;
 
-	ifmgd->flags &= ~IEEE80211_STA_PREV_BSSID_SET;
-
 	if (ifmgd->ssid_len)
 		ifmgd->flags |= IEEE80211_STA_SSID_SET;
 	else
@@ -1908,6 +1906,10 @@ int ieee80211_sta_set_ssid(struct ieee80211_sub_if_data *sdata, char *ssid, size
 	ifmgd = &sdata->u.mgd;
 
 	if (ifmgd->ssid_len != len || memcmp(ifmgd->ssid, ssid, len) != 0) {
+		/*
+		 * Do not use reassociation if SSID is changed (different ESS).
+		 */
+		ifmgd->flags &= ~IEEE80211_STA_PREV_BSSID_SET;
 		memset(ifmgd->ssid, 0, sizeof(ifmgd->ssid));
 		memcpy(ifmgd->ssid, ssid, len);
 		ifmgd->ssid_len = len;