mac80211: Fix mesh estab_plinks counting in STA removal case

If a user space program (e.g., wpa_supplicant) deletes a STA entry that
is currently in NL80211_PLINK_ESTAB state, the number of established
plinks counter was not decremented and this could result in rejecting
new plink establishment before really hitting the real maximum plink
limit. For !user_mpm case, this decrementation is handled by
mesh_plink_deactive().

Fix this by decrementing estab_plinks on STA deletion
(mesh_sta_cleanup() gets called from there) so that the counter has a
correct value and the Beacon frame advertisement in Mesh Configuration
element shows the proper value for capability to accept additional
peers.

Cc: stable@vger.kernel.org
Signed-off-by: Jouni Malinen <j@w1.fi>
Signed-off-by: Johannes Berg <johannes@sipsolutions.net>

net/mac80211/mesh.c

@@ -148,14 +148,17 @@ u32 mesh_accept_plinks_update(struct ieee80211_sub_if_data *sdata)
 void mesh_sta_cleanup(struct sta_info *sta)
 {
 	struct ieee80211_sub_if_data *sdata = sta->sdata;
-	u32 changed;
+	u32 changed = 0;
 
 	/*
 	 * maybe userspace handles peer allocation and peering, but in either
 	 * case the beacon is still generated by the kernel and we might need
 	 * an update.
 	 */
-	changed = mesh_accept_plinks_update(sdata);
+	if (sdata->u.mesh.user_mpm &&
+	    sta->mesh->plink_state == NL80211_PLINK_ESTAB)
+		changed |= mesh_plink_dec_estab_count(sdata);
+	changed |= mesh_accept_plinks_update(sdata);
 	if (!sdata->u.mesh.user_mpm) {
 		changed |= mesh_plink_deactivate(sta);
 		del_timer_sync(&sta->mesh->plink_timer);