[NET] dev_change_name: ignore changes to same name

Prevent error/backtrace from dev_rename() when changing
name of network device to the same name. This is a common
situation with udev and other scripts that bind addr to device.

Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -883,6 +883,9 @@ int dev_change_name(struct net_device *dev, char *newname)
 	if (!dev_valid_name(newname))
 		return -EINVAL;
 
+	if (strncmp(newname, dev->name, IFNAMSIZ) == 0)
+		return 0;
+
 	memcpy(oldname, dev->name, IFNAMSIZ);
 
 	if (strchr(newname, '%')) {