linux: import more network related headers from v6.11-rc6

Hopefully, no effective change.

src/basic/linux/net_namespace.h

@@ -0,0 +1,26 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* Copyright (c) 2015 6WIND S.A.
+ * Author: Nicolas Dichtel <nicolas.dichtel@6wind.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ */
+#ifndef _LINUX_NET_NAMESPACE_H_
+#define _LINUX_NET_NAMESPACE_H_
+
+/* Attributes of RTM_NEWNSID/RTM_GETNSID messages */
+enum {
+	NETNSA_NONE,
+#define NETNSA_NSID_NOT_ASSIGNED -1
+	NETNSA_NSID,
+	NETNSA_PID,
+	NETNSA_FD,
+	NETNSA_TARGET_NSID,
+	NETNSA_CURRENT_NSID,
+	__NETNSA_MAX,
+};
+
+#define NETNSA_MAX		(__NETNSA_MAX - 1)
+
+#endif /* _LINUX_NET_NAMESPACE_H_ */