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diff --git a/nss/nss_module.h b/nss/nss_module.h
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+/* Global list of NSS service modules.
+   Copyright (c) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _NSS_MODULE_H
+#define _NSS_MODULE_H
+
+#include <nss.h>
+#include <stdbool.h>
+
+/* See nss_database.h for a summary of how this relates.  */
+
+/* Typed function pointers for all functions that can be defined by a
+   service module.  */
+struct nss_module_functions
+{
+#undef DEFINE_NSS_FUNCTION
+#define DEFINE_NSS_FUNCTION(f) nss_##f *f;
+#include "function.def"
+};
+
+/* Untyped version of struct nss_module_functions, for consistent
+   processing purposes.  */
+typedef void *nss_module_functions_untyped[sizeof (struct nss_module_functions)
+                                           / sizeof (void *)];
+
+/* Initialization state of a NSS module.  */
+enum nss_module_state
+{
+  nss_module_uninitialized,
+  nss_module_loaded,
+  nss_module_failed,
+};
+
+/* A NSS service module (potentially unloaded).  Client code should
+   use the functions below.  */
+struct nss_module
+{
+  /* Actual type is enum nss_module_state.  Use int due to atomic
+     access.  Used in a double-checked locking idiom.  */
+  int state;
+
+  /* The function pointers in the module.  */
+  union
+  {
+    struct nss_module_functions typed;
+    nss_module_functions_untyped untyped;
+  } functions;
+
+  /* Only used for __libc_freeres unloading.  */
+  void *handle;
+
+  /* The next module in the list. */
+  struct nss_module *next;
+
+  /* The name of the module (as it appears in /etc/nsswitch.conf).  */
+  char name[];
+};
+
+/* Allocates the NSS module NAME (of NAME_LENGTH bytes) and places it
+   into the global list.  If it already exists in the list, return the
+   pre-existing module.  This does not actually load the module.
+   Returns NULL on memory allocation failure.  */
+struct nss_module *__nss_module_allocate (const char *name,
+                                          size_t name_length) attribute_hidden;
+
+/* Ensures that MODULE is in a loaded or failed state.  */
+bool __nss_module_load (struct nss_module *module) attribute_hidden;
+
+/* Ensures that MODULE is loaded and returns a pointer to the function
+   NAME defined in it.  Returns NULL if MODULE could not be loaded, or
+   if the function NAME is not defined in the module.  */
+void *__nss_module_get_function (struct nss_module *module, const char *name)
+  attribute_hidden;
+
+/* Called from __libc_freeres.  */
+void __nss_module_freeres (void) attribute_hidden;
+
+#endif /* NSS_MODULE_H */