--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __LINUX_NSFS_H
+#define __LINUX_NSFS_H
+
+#include <linux/ioctl.h>
+
+#define NSIO 0xb7
+
+/* Returns a file descriptor that refers to an owning user namespace */
+#define NS_GET_USERNS _IO(NSIO, 0x1)
+/* Returns a file descriptor that refers to a parent namespace */
+#define NS_GET_PARENT _IO(NSIO, 0x2)
+/* Returns the type of namespace (CLONE_NEW* value) referred to by
+ file descriptor */
+#define NS_GET_NSTYPE _IO(NSIO, 0x3)
+/* Get owner UID (in the caller's user namespace) for a user namespace */
+#define NS_GET_OWNER_UID _IO(NSIO, 0x4)
+
+#endif /* __LINUX_NSFS_H */