l2tp: set name_assign_type for devices created by l2tp_eth.c

Export naming scheme used when creating l2tpeth interfaces
(/sys/class/net/<iface>/name_assign_type). This let userspace know if
the device's name has been generated automatically or defined manually.
Signed-off-by: Guillaume Nault <g.nault@alphalink.fr>
Acked-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_eth.c

@@ -258,6 +258,7 @@ static void l2tp_eth_adjust_mtu(struct l2tp_tunnel *tunnel,
 
 static int l2tp_eth_create(struct net *net, u32 tunnel_id, u32 session_id, u32 peer_session_id, struct l2tp_session_cfg *cfg)
 {
+	unsigned char name_assign_type;
 	struct net_device *dev;
 	char name[IFNAMSIZ];
 	struct l2tp_tunnel *tunnel;
@@ -281,8 +282,11 @@ static int l2tp_eth_create(struct net *net, u32 tunnel_id, u32 session_id, u32 p
 			goto out;
 		}
 		strlcpy(name, cfg->ifname, IFNAMSIZ);
-	} else
+		name_assign_type = NET_NAME_USER;
+	} else {
 		strcpy(name, L2TP_ETH_DEV_NAME);
+		name_assign_type = NET_NAME_ENUM;
+	}
 
 	session = l2tp_session_create(sizeof(*spriv), tunnel, session_id,
 				      peer_session_id, cfg);
@@ -291,7 +295,7 @@ static int l2tp_eth_create(struct net *net, u32 tunnel_id, u32 session_id, u32 p
 		goto out;
 	}
 
-	dev = alloc_netdev(sizeof(*priv), name, NET_NAME_UNKNOWN,
+	dev = alloc_netdev(sizeof(*priv), name, name_assign_type,
 			   l2tp_eth_dev_setup);
 	if (!dev) {
 		rc = -ENOMEM;