mac80211: select an AID when creating new mesh STAs

Instead of using peer link id for AID, generate a new
AID when creating mesh STAs in the kernel peering manager.
This enables smaller TIM elements and more closely follows
the standard, and it also enables mesh to work on drivers
that require a valid AID when the STA is inserted (ath10k
firmware has this requirement, for example).

In the case of userspace-managed stations, we use the AID
from NL80211_CMD_NEW_STATION.

Signed-off-by: Bob Copeland <me@bobcopeland.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mesh_plink.c

@@ -422,20 +422,54 @@ out:
 	spin_unlock_bh(&sta->mesh->plink_lock);
 }
 
+static int mesh_allocate_aid(struct ieee80211_sub_if_data *sdata)
+{
+	struct sta_info *sta;
+	unsigned long *aid_map;
+	int aid;
+
+	aid_map = kcalloc(BITS_TO_LONGS(IEEE80211_MAX_AID + 1),
+			  sizeof(*aid_map), GFP_KERNEL);
+	if (!aid_map)
+		return -ENOMEM;
+
+	/* reserve aid 0 for mcast indication */
+	__set_bit(0, aid_map);
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(sta, &sdata->local->sta_list, list)
+		__set_bit(sta->sta.aid, aid_map);
+	rcu_read_unlock();
+
+	aid = find_first_zero_bit(aid_map, IEEE80211_MAX_AID + 1);
+	kfree(aid_map);
+
+	if (aid > IEEE80211_MAX_AID)
+		return -ENOBUFS;
+
+	return aid;
+}
+
 static struct sta_info *
 __mesh_sta_info_alloc(struct ieee80211_sub_if_data *sdata, u8 *hw_addr)
 {
 	struct sta_info *sta;
+	int aid;
 
 	if (sdata->local->num_sta >= MESH_MAX_PLINKS)
 		return NULL;
 
+	aid = mesh_allocate_aid(sdata);
+	if (aid < 0)
+		return NULL;
+
 	sta = sta_info_alloc(sdata, hw_addr, GFP_KERNEL);
 	if (!sta)
 		return NULL;
 
 	sta->mesh->plink_state = NL80211_PLINK_LISTEN;
 	sta->sta.wme = true;
+	sta->sta.aid = aid;
 
 	sta_info_pre_move_state(sta, IEEE80211_STA_AUTH);
 	sta_info_pre_move_state(sta, IEEE80211_STA_ASSOC);
@@ -659,8 +693,6 @@ static u16 mesh_get_new_llid(struct ieee80211_sub_if_data *sdata)
 
 	do {
 		get_random_bytes(&llid, sizeof(llid));
-		/* for mesh PS we still only have the AID range for TIM bits */
-		llid = (llid % IEEE80211_MAX_AID) + 1;
 	} while (llid_in_use(sdata, llid));
 
 	return llid;
@@ -1069,7 +1101,6 @@ mesh_process_plink_frame(struct ieee80211_sub_if_data *sdata,
 			goto unlock_rcu;
 		}
 		sta->mesh->plid = plid;
-		sta->sta.aid = plid;
 	} else if (!sta && event == OPN_RJCT) {
 		mesh_plink_frame_tx(sdata, NULL, WLAN_SP_MESH_PEERING_CLOSE,
 				    mgmt->sa, 0, plid,
@@ -1082,10 +1113,8 @@ mesh_process_plink_frame(struct ieee80211_sub_if_data *sdata,
 
 	if (event == CNF_ACPT) {
 		/* 802.11-2012 13.3.7.2 - update plid on CNF if not set */
-		if (!sta->mesh->plid) {
+		if (!sta->mesh->plid)
 			sta->mesh->plid = plid;
-			sta->sta.aid = sta->mesh->plid;
-		}
 
 		sta->mesh->aid = get_unaligned_le16(PLINK_CNF_AID(mgmt));
 	}