batman-adv: make sure ELP/OGM orig MAC is updated on address change

When the MAC address of the primary interface is changed,
update the originator address in the ELP and OGM skb buffers as
well in order to reflect the change.

Fixes: d6f94d91f766 ("batman-adv: ELP - adding basic infrastructure")
Reported-by: Marek Lindner <marek@neomailbox.ch>
Signed-off-by: Antonio Quartulli <a@unstable.cc>

net/batman-adv/bat_v.c

@@ -73,16 +73,34 @@ static void batadv_v_iface_disable(struct batadv_hard_iface *hard_iface)
 	batadv_v_elp_iface_disable(hard_iface);
 }
 
-static void batadv_v_iface_update_mac(struct batadv_hard_iface *hard_iface)
-{
-}
-
 static void batadv_v_primary_iface_set(struct batadv_hard_iface *hard_iface)
 {
 	batadv_v_elp_primary_iface_set(hard_iface);
 	batadv_v_ogm_primary_iface_set(hard_iface);
 }
 
+/**
+ * batadv_v_iface_update_mac - react to hard-interface MAC address change
+ * @hard_iface: the modified interface
+ *
+ * If the modified interface is the primary one, update the originator
+ * address in the ELP and OGM messages to reflect the new MAC address.
+ */
+static void batadv_v_iface_update_mac(struct batadv_hard_iface *hard_iface)
+{
+	struct batadv_priv *bat_priv = netdev_priv(hard_iface->soft_iface);
+	struct batadv_hard_iface *primary_if;
+
+	primary_if = batadv_primary_if_get_selected(bat_priv);
+	if (primary_if != hard_iface)
+		goto out;
+
+	batadv_v_primary_iface_set(hard_iface);
+out:
+	if (primary_if)
+		batadv_hardif_put(primary_if);
+}
+
 static void
 batadv_v_hardif_neigh_init(struct batadv_hardif_neigh_node *hardif_neigh)
 {