nss/nss_database.h

   1 /* Mapping NSS services to action lists.
   2    Copyright (C) 2020-2022 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _NSS_DATABASE_H
  20 #define _NSS_DATABASE_H
  21
  22 #include <file_change_detection.h>
  23
  24 /* Each "line" in nsswitch.conf maps a supported database (example:
  25    passwd) to one or more name service providers (example: files dns).
  26    Internally, each name service provider (example: dns) is a
  27    dynamically loadable module (i.e. libnss_dns.so), managed by
  28    nss_module.h.  The sequence of providers and rules (example: files
  29    [SUCCESS=RETURN] dns) is mapped by nss_action.h to a cached entry
  30    which encodes the sequence of modules and rules.  Keeping track of
  31    all supported databases and their corresponding actions is done
  32    here.
  33
  34    The key entry is __nss_database_get, which provides a set of
  35    actions which can be used with nss_lookup_function() and
  36    nss_next().  Callers should assume that these functions are fast,
  37    and should not cache the result longer than needed.  */
  38
  39 #include "nss_action.h"
  40
  41 /* The enumeration literal in enum nss_database for the database NAME
  42    (e.g., nss_database_hosts for hosts).  */
  43 #define NSS_DATABASE_LITERAL(name) nss_database_##name
  44
  45 enum nss_database
  46 {
  47 #define DEFINE_DATABASE(name) NSS_DATABASE_LITERAL (name),
  48 #include "databases.def"
  49 #undef DEFINE_DATABASE
  50
  51   /* Total number of databases.  */
  52   NSS_DATABASE_COUNT
  53 };
  54
  55 /* Looks up the action list for DB and stores it in *ACTIONS.  Returns
  56    true on success or false on failure.  Success can mean that
  57    *ACTIONS is NULL.  */
  58 bool __nss_database_get (enum nss_database db, nss_action_list *actions);
  59 libc_hidden_proto (__nss_database_get)
  60
  61 /* Like __nss_database_get, but does not reload /etc/nsswitch.conf
  62    from disk.  This assumes that there has been a previous successful
  63    __nss_database_get call (which may not have returned any data).  */
  64 nss_action_list __nss_database_get_noreload (enum nss_database db)
  65   attribute_hidden;
  66
  67 /* Called from __libc_freeres.  */
  68 void __nss_database_freeres (void) attribute_hidden;
  69
  70 /* Internal type.  Exposed only for fork handling purposes.  */
  71 struct nss_database_data
  72 {
  73   struct file_change_detection nsswitch_conf;
  74   nss_action_list services[NSS_DATABASE_COUNT];
  75   int reload_disabled;          /* Actually bool; int for atomic access.  */
  76   bool initialized;
  77 };
  78
  79 /* Called by fork in the parent process, before forking.  */
  80 void __nss_database_fork_prepare_parent (struct nss_database_data *data)
  81   attribute_hidden;
  82
  83 /* Called by fork in the new subprocess, after forking.  */
  84 void __nss_database_fork_subprocess (struct nss_database_data *data)
  85   attribute_hidden;
  86
  87 #endif /* _NSS_DATABASE_H */