1  /* Mapping NSS services to action lists.
       2     Copyright (C) 2020-2023 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  /* Internal type.  Exposed only for fork handling purposes.  */
      68  struct nss_database_data
      69  {
      70    struct file_change_detection nsswitch_conf;
      71    nss_action_list services[NSS_DATABASE_COUNT];
      72    int reload_disabled;          /* Actually bool; int for atomic access.  */
      73    bool initialized;
      74  };
      75  
      76  /* Called by fork in the parent process, before forking.  */
      77  void __nss_database_fork_prepare_parent (struct nss_database_data *data)
      78    attribute_hidden;
      79  
      80  /* Called by fork in the new subprocess, after forking.  */
      81  void __nss_database_fork_subprocess (struct nss_database_data *data)
      82    attribute_hidden;
      83  
      84  #endif /* _NSS_DATABASE_H */