nss/nss_action.h

   1 /* NSS actions, elements in a nsswitch.conf configuration line.
   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_ACTION_H
  20 #define _NSS_ACTION_H
  21
  22 #include <stddef.h>
  23
  24 /* See nss_database.h for a summary of how this relates.  */
  25
  26 #include "nsswitch.h" /* For lookup_actions.  */
  27
  28 struct nss_module;
  29
  30 /* A NSS action pairs a service module with the action for each result
  31    state.  */
  32 struct nss_action
  33 {
  34   /* The service module that provides the functionality (potentially
  35      not yet loaded).  */
  36   struct nss_module *module;
  37
  38   /* Action according to result.  Two bits for each lookup_actions
  39      value (from nsswitch.h), indexed by enum nss_status (from nss.h).  */
  40   unsigned int action_bits;
  41 };
  42
  43 /* Value to add to first nss_status value to get zero.  */
  44 #define NSS_STATUS_BIAS 2
  45 /* Number of bits per lookup action.  */
  46 #define NSS_BPL 2
  47 #define NSS_BPL_MASK ((1 << NSS_BPL) - 1)
  48
  49 /* Index in actions of an NSS status.  Note that in nss/nss.h the
  50    status starts at -2, and we shift that up to zero by adding 2.
  51    Thus for example NSS_STATUS_TRYAGAIN, which is -2, would index into
  52    the 0th bit place as expected.  */
  53 static inline int
  54 nss_actions_bits_index (enum nss_status status)
  55 {
  56   return NSS_BPL * (NSS_STATUS_BIAS + status);
  57 }
  58
  59 /* Returns the lookup_action value for STATUS in ACTION.  */
  60 static inline lookup_actions
  61 nss_action_get (const struct nss_action *action, enum nss_status status)
  62 {
  63   return ((action->action_bits >> nss_actions_bits_index (status))
  64           & NSS_BPL_MASK);
  65 }
  66
  67 /* Sets the lookup_action value for STATUS in ACTION.  */
  68 static inline void
  69 nss_action_set (struct nss_action *action,
  70                 enum nss_status status, lookup_actions actions)
  71 {
  72   int offset = nss_actions_bits_index (status);
  73   unsigned int mask = NSS_BPL_MASK << offset;
  74   action->action_bits = ((action->action_bits & ~mask)
  75                          | ((unsigned int) actions << offset));
  76 }
  77
  78 static inline void
  79 nss_action_set_all (struct nss_action *action, lookup_actions actions)
  80 {
  81   unsigned int bits = actions & NSS_BPL_MASK;
  82   action->action_bits = (   bits
  83                          | (bits << (NSS_BPL * 1))
  84                          | (bits << (NSS_BPL * 2))
  85                          | (bits << (NSS_BPL * 3))
  86                          | (bits << (NSS_BPL * 4))
  87                          );
  88 }
  89
  90 /* A list of struct nss_action objects in array terminated by an
  91    action with a NULL module.  */
  92 typedef struct nss_action *nss_action_list;
  93
  94 /* Returns a pointer to an allocated NSS action list that has COUNT
  95    actions that matches the array at ACTIONS.  */
  96 nss_action_list __nss_action_allocate (struct nss_action *actions,
  97                                        size_t count) attribute_hidden;
  98
  99 /* Returns a pointer to a list allocated by __nss_action_allocate, or
 100    NULL on error.  ENOMEM means a (temporary) memory allocation error,
 101    EINVAL means that LINE is syntactically invalid.  */
 102 nss_action_list __nss_action_parse (const char *line);
 103
 104 /* Called from __libc_freeres.  */
 105 void __nss_action_freeres (void) attribute_hidden;
 106
 107
 108 #endif /* _NSS_ACTION_H */