net/ipv4/udp_tunnel: prefer SO_BINDTOIFINDEX over SO_BINDTODEVICE

The udp-tunnel setup allows binding sockets to a network device. Prefer
the new SO_BINDTOIFINDEX to avoid temporarily resolving the device-name
just to look it up in the ioctl again.
Reviewed-by: Tom Gundersen <teg@jklm.no>
Signed-off-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/udp_tunnel.c

@@ -21,18 +21,9 @@ int udp_sock_create4(struct net *net, struct udp_port_cfg *cfg,
 		goto error;
 
 	if (cfg->bind_ifindex) {
-		struct net_device *dev;
-
-		dev = dev_get_by_index(net, cfg->bind_ifindex);
-		if (!dev) {
-			err = -ENODEV;
-			goto error;
-		}
-
-		err = kernel_setsockopt(sock, SOL_SOCKET, SO_BINDTODEVICE,
-					dev->name, strlen(dev->name) + 1);
-		dev_put(dev);
-
+		err = kernel_setsockopt(sock, SOL_SOCKET, SO_BINDTOIFINDEX,
+					(void *)&cfg->bind_ifindex,
+					sizeof(cfg->bind_ifindex));
 		if (err < 0)
 			goto error;
 	}