[NET]: Add a dev_ioctl() fallback to sock_ioctl()

Currently all network protocols need to call dev_ioctl as the default
fallback in their ioctl implementations.  This patch adds a fallback
to dev_ioctl to sock_ioctl if the protocol returned -ENOIOCTLCMD.
This way all the procotol ioctl handlers can be simplified and we don't
need to export dev_ioctl.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/socket.c

@@ -900,6 +900,13 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
 			break;
 		default:
 			err = sock->ops->ioctl(sock, cmd, arg);
+
+			/*
+			 * If this ioctl is unknown try to hand it down
+			 * to the NIC driver.
+			 */
+			if (err == -ENOIOCTLCMD)
+				err = dev_ioctl(cmd, argp);
 			break;
 	}
 	return err;