net: Add netif_is_l3_slave

IPv6 addrconf keys off of IFF_SLAVE so can not use it for L3 slave.
Add a new private flag and add netif_is_l3_slave function for checking
it.

Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/l3mdev/l3mdev.c b/net/l3mdev/l3mdev.c
index ddf75ad..8e5ead3 100644
--- a/net/l3mdev/l3mdev.c
+++ b/net/l3mdev/l3mdev.c
@@ -26,11 +26,11 @@
 
 	if (netif_is_l3_master(dev)) {
 		ifindex = dev->ifindex;
-	} else if (dev->flags & IFF_SLAVE) {
+	} else if (netif_is_l3_slave(dev)) {
 		struct net_device *master;
 
 		master = netdev_master_upper_dev_get_rcu(dev);
-		if (master && netif_is_l3_master(master))
+		if (master)
 			ifindex = master->ifindex;
 	}
 
@@ -54,7 +54,7 @@
 	if (netif_is_l3_master(dev)) {
 		if (dev->l3mdev_ops->l3mdev_fib_table)
 			tb_id = dev->l3mdev_ops->l3mdev_fib_table(dev);
-	} else if (dev->flags & IFF_SLAVE) {
+	} else if (netif_is_l3_slave(dev)) {
 		/* Users of netdev_master_upper_dev_get_rcu need non-const,
 		 * but current inet_*type functions take a const
 		 */
@@ -62,7 +62,7 @@
 		const struct net_device *master;
 
 		master = netdev_master_upper_dev_get_rcu(_dev);
-		if (master && netif_is_l3_master(master) &&
+		if (master &&
 		    master->l3mdev_ops->l3mdev_fib_table)
 			tb_id = master->l3mdev_ops->l3mdev_fib_table(master);
 	}