mac80211: Give it some time to do the TSF sync

Give slow hardware some time to do the TSF sync, to not run into an
IBSS merging endless loop in some rarely situations.
Signed-off-by: Alina Friedrichsen <x-alina@gmx.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/ibss.c

@@ -29,6 +29,7 @@
 #define IEEE80211_IBSS_JOIN_TIMEOUT (7 * HZ)
 
 #define IEEE80211_IBSS_MERGE_INTERVAL (30 * HZ)
+#define IEEE80211_IBSS_MERGE_DELAY 0x400000
 #define IEEE80211_IBSS_INACTIVITY_LIMIT (60 * HZ)
 
 #define IEEE80211_IBSS_MAX_STA_ENTRIES 128
@@ -336,6 +337,10 @@ static void ieee80211_rx_bss_info(struct ieee80211_sub_if_data *sdata,
 	       jiffies);
 #endif
 
+	/* give slow hardware some time to do the TSF sync */
+	if (rx_timestamp < IEEE80211_IBSS_MERGE_DELAY)
+		goto put_bss;
+
 	if (beacon_timestamp > rx_timestamp) {
 #ifdef CONFIG_MAC80211_IBSS_DEBUG
 		printk(KERN_DEBUG "%s: beacon TSF higher than "