[RFC,16/23] batman-adv: ELP - read estimated throughput from cfg80211

diff --git a/bat_v_elp.c b/bat_v_elp.c
index 14a1e15..31190af 100644
--- a/bat_v_elp.c
+++ b/bat_v_elp.c
@@ -18,6 +18,8 @@ 
  *
  */
 
+#include <net/cfg80211.h>
+
 #include "main.h"
 #include "hard-interface.h"
 #include "send.h"
@@ -64,19 +66,56 @@  batadv_v_elp_get_throughput(struct batadv_elp_neigh_node *neigh)
 {
 	struct batadv_hard_iface *hard_iface = neigh->hard_iface;
 	struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
+	struct station_info sinfo;
 	uint32_t throughput;
+	int r;
 
-	/* get the customised user value for the throughput */
-	throughput = atomic_read(&hard_iface->bat_v.user_throughput);
-	/* if the user specified a value, let's return it */
+	/* if the user specified a customised value for this interface, then
+	 * return it directly
+	 */
+	throughput =  atomic_read(&hard_iface->bat_v.user_throughput);
 	if (throughput != 0)
 		return throughput;
 
-	/* throughput cannot be computed right now. Return base value */
+	/* if this is a wireless device, then ask its throughput through
+	 * cfg80211 API
+	 */
+	if (hard_iface->net_dev->ieee80211_ptr) {
+		r = cfg80211_get_station(hard_iface->net_dev, neigh->addr,
+					 &sinfo);
+		if (r == -ENOENT) {
+			/* node is not associated anymore! it would be possible
+			 * to delete this neighbor. for now set metric to 0
+			 */
+			return 0;
+		}
+		if (!r)
+			return sinfo.expected_throughput;
+	}
+
+	/* if none of the above cases apply, return the base_throughput */
 	return atomic_read(&bat_priv->bat_v.base_throughput);
 }
 
 /**
+ * batadv_v_elp_metric_update - worker updating the metric of one neighbour
+ * @work: the work queue item
+ */
+static void batadv_v_elp_metric_update(struct work_struct *work)
+{
+	struct batadv_elp_neigh_node *neigh;
+
+	neigh = container_of(work, struct batadv_elp_neigh_node, metric_work);
+
+	ewma_add(&neigh->metric, batadv_v_elp_get_throughput(neigh));
+
+	/* decrement refcounter to balance increment performed before scheduling
+	 * this task
+	 */
+	batadv_elp_neigh_node_free_ref(neigh);
+}
+
+/**
  * batadv_v_elp_neigh_new - create a new ELP neighbour node
  * @hard_iface: the interface the neighbour is connected to
  * @neigh_addr: the neighbour interface address
@@ -108,6 +147,8 @@  batadv_v_elp_neigh_new(struct batadv_hard_iface *hard_iface,
 	spin_unlock_bh(&hard_iface->bat_v.neigh_list_lock);
 	atomic_inc(&hard_iface->bat_v.num_neighbors);
 
+	INIT_WORK(&neigh->metric_work, batadv_v_elp_metric_update);
+
 	return neigh;
 }
 
@@ -192,7 +233,7 @@  static int batadv_v_elp_wifi_neigh_probe(struct batadv_hard_iface *hard_iface,
 	int probe_len, i;
 
 	/* this probing routine is for Wifi neighbours only */
-	if (batadv_is_wifi_netdev(hard_iface->net_dev))
+	if (!batadv_is_wifi_netdev(hard_iface->net_dev))
 		return 0;
 
 	/* probe the neighbor only if no unicast packets have been sent
@@ -310,7 +351,14 @@  static void batadv_v_elp_periodic_work(struct work_struct *work)
 			 */
 			break;
 
-		ewma_add(&neigh->metric, batadv_v_elp_get_throughput(neigh));
+		if (!atomic_inc_not_zero(&neigh->refcount))
+			continue;
+
+		/* reading the estimated throughput from cfg80211 is a task that
+		 * may sleep and that is not allowed in an rcu protected
+		 * context. Therefore schedule a task for that.
+		 */
+		queue_work(batadv_event_workqueue, &neigh->metric_work);
 	}
 	rcu_read_unlock();
 
@@ -442,7 +490,6 @@  static void batadv_v_elp_neigh_update(struct batadv_priv *bat_priv,
 
 	neigh->last_seen = jiffies;
 	neigh->last_recv_seqno = ntohl(elp_packet->seqno);
-	ewma_add(&neigh->metric, batadv_v_elp_get_throughput(neigh));
 
 out:
 	if (neigh)
diff --git a/compat.h b/compat.h
index 12bc8d8..9f71f51 100644
--- a/compat.h
+++ b/compat.h
@@ -407,4 +407,24 @@  static int __batadv_interface_kill_vid(struct net_device *dev, __be16 proto,\
 
 #endif /* < KERNEL_VERSION(3, 14, 0) */
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(3, 15, 0)
+
+/* NOTE: shall I put this ifndef outside of every #if block ? */
+#ifndef cfg80211_get_station
+
+/* the expected behaviour of this function is to return 0 on success, therefore
+ * it is possible to define it as 1 so that batman-adv thinks like something
+ * went wrong. It will then decide what to do.
+ */
+#define cfg80211_get_station(_a, _b, _c) (1)
+/* the following define substitute the expected_throughput field with a random
+ * one existing in the station_info struct. It can be random because due to the
+ * define above it will never be used. We need it only to make the code compile
+ */
+#define expected_throughput filled
+
+#endif /* cfg80211_get_station */
+
+#endif /* < KERNEL_VERSION(3, 15, 0) */
+
 #endif /* _NET_BATMAN_ADV_COMPAT_H_ */
diff --git a/types.h b/types.h
index 948d5dc..6f05d99 100644
--- a/types.h
+++ b/types.h
@@ -346,6 +346,7 @@  struct batadv_gw_node {
  * @refcount: number of contexts the object is used
  * @rcu: struct used for freeing in an RCU-safe manner
  * @hard_iface: the interface where this neighbor is connected to
+ * @metric_work: work queue callback item for metric update
  */
 struct batadv_elp_neigh_node {
 	struct hlist_node list;
@@ -359,6 +360,7 @@  struct batadv_elp_neigh_node {
 	atomic_t refcount;
 	struct rcu_head rcu;
 	struct batadv_hard_iface *hard_iface;
+	struct work_struct metric_work;
 };
 
 /**