mac80211: IBSS join rework

I hold back this patch for around a week to avoid
confusion. This is the second step of
"mac80211: Fixed BSSID handling revisited".

With it, in the situation of a strange merge to the
same BSSID (e.g. caused by a TSF overflow) only
reset_tsf() is called.

And sta_info_flush_delayed() is only called if you
change the network manually, not on an automatic
BSSID merge.
Signed-off-by: Alina Friedrichsen <x-alina@gmx.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/mlme.c

@@ -1503,13 +1503,22 @@ static int ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 				   struct ieee80211_bss *bss)
 {
 	struct ieee80211_local *local = sdata->local;
-	int res, rates, i, j;
+	int res = 0, rates, i, j;
 	struct sk_buff *skb;
 	struct ieee80211_mgmt *mgmt;
 	u8 *pos;
 	struct ieee80211_supported_band *sband;
 	union iwreq_data wrqu;
 
+	if (local->ops->reset_tsf) {
+		/* Reset own TSF to allow time synchronization work. */
+		local->ops->reset_tsf(local_to_hw(local));
+	}
+
+	if ((ifsta->flags & IEEE80211_STA_PREV_BSSID_SET) &&
+	   memcmp(ifsta->bssid, bss->bssid, ETH_ALEN) == 0)
+		return res;
+
 	skb = dev_alloc_skb(local->hw.extra_tx_headroom + 400 +
 			    sdata->u.sta.ie_proberesp_len);
 	if (!skb) {
@@ -1520,13 +1529,11 @@ static int ieee80211_sta_join_ibss(struct ieee80211_sub_if_data *sdata,
 
 	sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
 
+	if (!(ifsta->flags & IEEE80211_STA_PREV_BSSID_SET)) {
 		/* Remove possible STA entries from other IBSS networks. */
 		sta_info_flush_delayed(sdata);
-
-	if (local->ops->reset_tsf) {
-		/* Reset own TSF to allow time synchronization work. */
-		local->ops->reset_tsf(local_to_hw(local));
 	}
+
 	memcpy(ifsta->bssid, bss->bssid, ETH_ALEN);
 	res = ieee80211_if_config(sdata, IEEE80211_IFCC_BSSID);
 	if (res)