batman-adv: Fix change mac address of soft iface.

Into function interface_set_mac_addr, the function tt_local_add was
invoked before updating dev->dev_addr. The new MAC address was not
tagged as NoPurge.
Signed-off-by: NDef <def@laposte.net>

net/batman-adv/soft-interface.c

@@ -100,18 +100,21 @@ static int batadv_interface_set_mac_addr(struct net_device *dev, void *p)
 {
 	struct batadv_priv *bat_priv = netdev_priv(dev);
 	struct sockaddr *addr = p;
+	uint8_t old_addr[ETH_ALEN];
 
 	if (!is_valid_ether_addr(addr->sa_data))
 		return -EADDRNOTAVAIL;
 
+	memcpy(old_addr, dev->dev_addr, ETH_ALEN);
+	memcpy(dev->dev_addr, addr->sa_data, ETH_ALEN);
+
 	/* only modify transtable if it has been initialized before */
 	if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_ACTIVE) {
-		batadv_tt_local_remove(bat_priv, dev->dev_addr,
+		batadv_tt_local_remove(bat_priv, old_addr,
 				       "mac address changed", false);
 		batadv_tt_local_add(dev, addr->sa_data, BATADV_NULL_IFINDEX);
 	}
 
-	memcpy(dev->dev_addr, addr->sa_data, ETH_ALEN);
 	dev->addr_assign_type &= ~NET_ADDR_RANDOM;
 	return 0;
 }