nl80211: add generation number to all dumps

In order for userspace to be able to figure out whether
it obtained a consistent snapshot of data or not when
using netlink dumps, we need to have a generation number
in each dump message that indicates whether the list has
changed or not -- its value is arbitrary.

This patch adds such a number to all dumps, this needs
some mac80211 involvement to keep track of a generation
number to start with when adding/removing mesh paths or
stations.

The wiphy and netdev lists can be fully handled within
cfg80211, of course, but generation numbers need to be
stored there as well.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/sta_info.c

@@ -349,6 +349,7 @@ int sta_info_insert(struct sta_info *sta)
 		goto out_free;
 	}
 	list_add(&sta->list, &local->sta_list);
+	local->sta_generation++;
 	local->num_sta++;
 	sta_info_hash_add(local, sta);
 
@@ -485,6 +486,7 @@ static void __sta_info_unlink(struct sta_info **sta)
 	}
 
 	local->num_sta--;
+	local->sta_generation++;
 
 	if (local->ops->sta_notify) {
 		if (sdata->vif.type == NL80211_IFTYPE_AP_VLAN)