batman-adv: send GW_DEL event when the gw client mode is deselected

Whenever the GW client mode is deselected, a DEL event has
to be sent in order to tell userspace that the current
gateway has been lost. Send the uevent on state change only
if a gateway was currently selected.
Reported-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Antonio Quartulli <antonio@open-mesh.com>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>

net/batman-adv/gateway_client.c

@@ -190,6 +190,33 @@ batadv_gw_get_best_gw_node(struct batadv_priv *bat_priv)
 	return curr_gw;
 }
 
+/**
+ * batadv_gw_check_client_stop - check if client mode has been switched off
+ * @bat_priv: the bat priv with all the soft interface information
+ *
+ * This function assumes the caller has checked that the gw state *is actually
+ * changing*. This function is not supposed to be called when there is no state
+ * change.
+ */
+void batadv_gw_check_client_stop(struct batadv_priv *bat_priv)
+{
+	struct batadv_gw_node *curr_gw;
+
+	if (atomic_read(&bat_priv->gw_mode) != BATADV_GW_MODE_CLIENT)
+		return;
+
+	curr_gw = batadv_gw_get_selected_gw_node(bat_priv);
+	if (!curr_gw)
+		return;
+
+	/* if batman-adv is switching the gw client mode off and a gateway was
+	 * already selected, send a DEL uevent
+	 */
+	batadv_throw_uevent(bat_priv, BATADV_UEV_GW, BATADV_UEV_DEL, NULL);
+
+	batadv_gw_node_free_ref(curr_gw);
+}
+
 void batadv_gw_election(struct batadv_priv *bat_priv)
 {
 	struct batadv_gw_node *curr_gw = NULL, *next_gw = NULL;

net/batman-adv/gateway_client.h

@@ -20,6 +20,7 @@
 #ifndef _NET_BATMAN_ADV_GATEWAY_CLIENT_H_
 #define _NET_BATMAN_ADV_GATEWAY_CLIENT_H_
 
+void batadv_gw_check_client_stop(struct batadv_priv *bat_priv);
 void batadv_gw_deselect(struct batadv_priv *bat_priv);
 void batadv_gw_election(struct batadv_priv *bat_priv);
 struct batadv_orig_node *

net/batman-adv/sysfs.c

@@ -385,6 +385,10 @@ static ssize_t batadv_store_gw_mode(struct kobject *kobj,
 		    curr_gw_mode_str, buff);
 
 	batadv_gw_deselect(bat_priv);
+	/* always call batadv_gw_check_client_stop() before changing the gateway
+	 * state
+	 */
+	batadv_gw_check_client_stop(bat_priv);
 	atomic_set(&bat_priv->gw_mode, (unsigned int)gw_mode_tmp);
 	return count;
 }