nss/nsswitch.c

   1 /* Copyright (C) 1996-1999, 2001-2006, 2007 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <ctype.h>
  21 #include <dlfcn.h>
  22 #include <errno.h>
  23 #include <netdb.h>
  24 #include <bits/libc-lock.h>
  25 #include <search.h>
  26 #include <stdio.h>
  27 #include <stdio_ext.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30
  31 #include <aliases.h>
  32 #include <grp.h>
  33 #include <netinet/ether.h>
  34 #include <pwd.h>
  35 #include <shadow.h>
  36
  37 #if !defined DO_STATIC_NSS || defined SHARED
  38 # include <gnu/lib-names.h>
  39 #endif
  40
  41 #include "nsswitch.h"
  42 #include "../nscd/nscd_proto.h"
  43
  44 /* Prototypes for the local functions.  */
  45 static name_database *nss_parse_file (const char *fname) internal_function;
  46 static name_database_entry *nss_getline (char *line) internal_function;
  47 static service_user *nss_parse_service_list (const char *line)
  48      internal_function;
  49 static service_library *nss_new_service (name_database *database,
  50                                          const char *name) internal_function;
  51
  52
  53 /* Declare external database variables.  */
  54 #define DEFINE_DATABASE(name)                                                 \
  55   extern service_user *__nss_##name##_database attribute_hidden;              \
  56   weak_extern (__nss_##name##_database)
  57 #include "databases.def"
  58 #undef DEFINE_DATABASE
  59
  60 /* Structure to map database name to variable.  */
  61 static const struct
  62 {
  63   const char name[10];
  64   service_user **dbp;
  65 } databases[] =
  66 {
  67 #define DEFINE_DATABASE(name)                                                 \
  68   { #name, &__nss_##name##_database },
  69 #include "databases.def"
  70 #undef DEFINE_DATABASE
  71 };
  72 #define ndatabases (sizeof (databases) / sizeof (databases[0]))
  73
  74
  75 __libc_lock_define_initialized (static, lock)
  76
  77 #if !defined DO_STATIC_NSS || defined SHARED
  78 /* String with revision number of the shared object files.  */
  79 static const char *const __nss_shlib_revision = LIBNSS_FILES_SO + 15;
  80 #endif
  81
  82 /* The root of the whole data base.  */
  83 static name_database *service_table;
  84
  85
  86 /* -1 == database not found
  87     0 == database entry pointer stored */
  88 int
  89 __nss_database_lookup (const char *database, const char *alternate_name,
  90                        const char *defconfig, service_user **ni)
  91 {
  92   /* Prevent multiple threads to change the service table.  */
  93   __libc_lock_lock (lock);
  94
  95   /* Reconsider database variable in case some other thread called
  96      `__nss_configure_lookup' while we waited for the lock.  */
  97   if (*ni != NULL)
  98     {
  99       __libc_lock_unlock (lock);
 100       return 0;
 101     }
 102
 103   /* Are we initialized yet?  */
 104   if (service_table == NULL)
 105     /* Read config file.  */
 106     service_table = nss_parse_file (_PATH_NSSWITCH_CONF);
 107
 108   /* Test whether configuration data is available.  */
 109   if (service_table != NULL)
 110     {
 111       /* Return first `service_user' entry for DATABASE.  */
 112       name_database_entry *entry;
 113
 114       /* XXX Could use some faster mechanism here.  But each database is
 115          only requested once and so this might not be critical.  */
 116       for (entry = service_table->entry; entry != NULL; entry = entry->next)
 117         if (strcmp (database, entry->name) == 0)
 118           *ni = entry->service;
 119
 120       if (*ni == NULL && alternate_name != NULL)
 121         /* We haven't found an entry so far.  Try to find it with the
 122            alternative name.  */
 123         for (entry = service_table->entry; entry != NULL; entry = entry->next)
 124           if (strcmp (alternate_name, entry->name) == 0)
 125             *ni = entry->service;
 126     }
 127
 128   /* No configuration data is available, either because nsswitch.conf
 129      doesn't exist or because it doesn't has a line for this database.
 130
 131      DEFCONFIG specifies the default service list for this database,
 132      or null to use the most common default.  */
 133   if (*ni == NULL)
 134     *ni = nss_parse_service_list (defconfig
 135                                   ?: "nis [NOTFOUND=return] files");
 136
 137   __libc_lock_unlock (lock);
 138
 139   return 0;
 140 }
 141 libc_hidden_def (__nss_database_lookup)
 142
 143
 144 /* -1 == not found
 145     0 == function found
 146     1 == finished */
 147 int
 148 __nss_lookup (service_user **ni, const char *fct_name, const char *fct2_name,
 149               void **fctp)
 150 {
 151   *fctp = __nss_lookup_function (*ni, fct_name);
 152   if (*fctp == NULL && fct2_name != NULL)
 153     *fctp = __nss_lookup_function (*ni, fct2_name);
 154
 155   while (*fctp == NULL
 156          && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
 157          && (*ni)->next != NULL)
 158     {
 159       *ni = (*ni)->next;
 160
 161       *fctp = __nss_lookup_function (*ni, fct_name);
 162       if (*fctp == NULL && fct2_name != NULL)
 163         *fctp = __nss_lookup_function (*ni, fct2_name);
 164     }
 165
 166   return *fctp != NULL ? 0 : (*ni)->next == NULL ? 1 : -1;
 167 }
 168
 169
 170 /* -1 == not found
 171     0 == adjusted for next function
 172     1 == finished */
 173 int
 174 __nss_next2 (service_user **ni, const char *fct_name, const char *fct2_name,
 175              void **fctp, int status, int all_values)
 176 {
 177   if (all_values)
 178     {
 179       if (nss_next_action (*ni, NSS_STATUS_TRYAGAIN) == NSS_ACTION_RETURN
 180           && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_RETURN
 181           && nss_next_action (*ni, NSS_STATUS_NOTFOUND) == NSS_ACTION_RETURN
 182           && nss_next_action (*ni, NSS_STATUS_SUCCESS) == NSS_ACTION_RETURN)
 183         return 1;
 184     }
 185   else
 186     {
 187       /* This is really only for debugging.  */
 188       if (__builtin_expect (NSS_STATUS_TRYAGAIN > status
 189                             || status > NSS_STATUS_RETURN, 0))
 190          __libc_fatal ("illegal status in __nss_next");
 191
 192        if (nss_next_action (*ni, status) == NSS_ACTION_RETURN)
 193          return 1;
 194     }
 195
 196   if ((*ni)->next == NULL)
 197     return -1;
 198
 199   do
 200     {
 201       *ni = (*ni)->next;
 202
 203       *fctp = __nss_lookup_function (*ni, fct_name);
 204       if (*fctp == NULL && fct2_name != NULL)
 205         *fctp = __nss_lookup_function (*ni, fct2_name);
 206     }
 207   while (*fctp == NULL
 208          && nss_next_action (*ni, NSS_STATUS_UNAVAIL) == NSS_ACTION_CONTINUE
 209          && (*ni)->next != NULL);
 210
 211   return *fctp != NULL ? 0 : -1;
 212 }
 213 libc_hidden_def (__nss_next2)
 214
 215
 216 int
 217 attribute_compat_text_section
 218 __nss_next (service_user **ni, const char *fct_name, void **fctp, int status,
 219             int all_values)
 220 {
 221   return __nss_next2 (ni, fct_name, NULL, fctp, status, all_values);
 222 }
 223
 224
 225 int
 226 __nss_configure_lookup (const char *dbname, const char *service_line)
 227 {
 228   service_user *new_db;
 229   size_t cnt;
 230
 231   for (cnt = 0; cnt < ndatabases; ++cnt)
 232     {
 233       int cmp = strcmp (dbname, databases[cnt].name);
 234       if (cmp == 0)
 235         break;
 236       if (cmp < 0)
 237         {
 238           __set_errno (EINVAL);
 239           return -1;
 240         }
 241     }
 242
 243   if (cnt == ndatabases)
 244     {
 245       __set_errno (EINVAL);
 246       return -1;
 247     }
 248
 249   /* Test whether it is really used.  */
 250   if (databases[cnt].dbp == NULL)
 251     /* Nothing to do, but we could do.  */
 252     return 0;
 253
 254   /* Try to generate new data.  */
 255   new_db = nss_parse_service_list (service_line);
 256   if (new_db == NULL)
 257     {
 258       /* Illegal service specification.  */
 259       __set_errno (EINVAL);
 260       return -1;
 261     }
 262
 263   /* Prevent multiple threads to change the service table.  */
 264   __libc_lock_lock (lock);
 265
 266   /* Install new rules.  */
 267   *databases[cnt].dbp = new_db;
 268
 269   __libc_lock_unlock (lock);
 270
 271   return 0;
 272 }
 273
 274
 275 /* Comparison function for searching NI->known tree.  */
 276 static int
 277 known_compare (const void *p1, const void *p2)
 278 {
 279   return p1 == p2 ? 0 : strcmp (*(const char *const *) p1,
 280                                 *(const char *const *) p2);
 281 }
 282
 283
 284 void *
 285 __nss_lookup_function (service_user *ni, const char *fct_name)
 286 {
 287   void **found, *result;
 288
 289   /* We now modify global data.  Protect it.  */
 290   __libc_lock_lock (lock);
 291
 292   /* Search the tree of functions previously requested.  Data in the
 293      tree are `known_function' structures, whose first member is a
 294      `const char *', the lookup key.  The search returns a pointer to
 295      the tree node structure; the first member of the is a pointer to
 296      our structure (i.e. what will be a `known_function'); since the
 297      first member of that is the lookup key string, &FCT_NAME is close
 298      enough to a pointer to our structure to use as a lookup key that
 299      will be passed to `known_compare' (above).  */
 300
 301   found = __tsearch (&fct_name, &ni->known, &known_compare);
 302   if (*found != &fct_name)
 303     /* The search found an existing structure in the tree.  */
 304     result = ((known_function *) *found)->fct_ptr;
 305   else
 306     {
 307       /* This name was not known before.  Now we have a node in the tree
 308          (in the proper sorted position for FCT_NAME) that points to
 309          &FCT_NAME instead of any real `known_function' structure.
 310          Allocate a new structure and fill it in.  */
 311
 312       known_function *known = malloc (sizeof *known);
 313       if (! known)
 314         {
 315         remove_from_tree:
 316           /* Oops.  We can't instantiate this node properly.
 317              Remove it from the tree.  */
 318           __tdelete (&fct_name, &ni->known, &known_compare);
 319           result = NULL;
 320         }
 321       else
 322         {
 323           /* Point the tree node at this new structure.  */
 324           *found = known;
 325           known->fct_name = fct_name;
 326
 327           if (ni->library == NULL)
 328             {
 329               /* This service has not yet been used.  Fetch the service
 330                  library for it, creating a new one if need be.  If there
 331                  is no service table from the file, this static variable
 332                  holds the head of the service_library list made from the
 333                  default configuration.  */
 334               static name_database default_table;
 335               ni->library = nss_new_service (service_table ?: &default_table,
 336                                              ni->name);
 337               if (ni->library == NULL)
 338                 {
 339                   /* This only happens when out of memory.  */
 340                   free (known);
 341                   goto remove_from_tree;
 342                 }
 343             }
 344
 345 #if !defined DO_STATIC_NSS || defined SHARED
 346           if (ni->library->lib_handle == NULL)
 347             {
 348               /* Load the shared library.  */
 349               size_t shlen = (7 + strlen (ni->library->name) + 3
 350                               + strlen (__nss_shlib_revision) + 1);
 351               int saved_errno = errno;
 352               char shlib_name[shlen];
 353
 354               /* Construct shared object name.  */
 355               __stpcpy (__stpcpy (__stpcpy (__stpcpy (shlib_name,
 356                                                       "libnss_"),
 357                                             ni->library->name),
 358                                   ".so"),
 359                         __nss_shlib_revision);
 360
 361               ni->library->lib_handle = __libc_dlopen (shlib_name);
 362               if (ni->library->lib_handle == NULL)
 363                 {
 364                   /* Failed to load the library.  */
 365                   ni->library->lib_handle = (void *) -1l;
 366                   __set_errno (saved_errno);
 367                 }
 368             }
 369
 370           if (ni->library->lib_handle == (void *) -1l)
 371             /* Library not found => function not found.  */
 372             result = NULL;
 373           else
 374             {
 375               /* Get the desired function.  */
 376               size_t namlen = (5 + strlen (ni->library->name) + 1
 377                                + strlen (fct_name) + 1);
 378               char name[namlen];
 379
 380               /* Construct the function name.  */
 381               __stpcpy (__stpcpy (__stpcpy (__stpcpy (name, "_nss_"),
 382                                             ni->library->name),
 383                                   "_"),
 384                         fct_name);
 385
 386               /* Look up the symbol.  */
 387               result = __libc_dlsym (ni->library->lib_handle, name);
 388             }
 389 #else
 390           /* We can't get function address dynamically in static linking. */
 391           {
 392 # define DEFINE_ENT(h,nm)                                                     \
 393             { #h"_get"#nm"ent_r", _nss_##h##_get##nm##ent_r },                \
 394             { #h"_end"#nm"ent", _nss_##h##_end##nm##ent },                    \
 395             { #h"_set"#nm"ent", _nss_##h##_set##nm##ent },
 396 # define DEFINE_GET(h,nm)                                                     \
 397             { #h"_get"#nm"_r", _nss_##h##_get##nm##_r },
 398 # define DEFINE_GETBY(h,nm,ky)                                                \
 399             { #h"_get"#nm"by"#ky"_r", _nss_##h##_get##nm##by##ky##_r },
 400             static struct fct_tbl { const char *fname; void *fp; } *tp, tbl[] =
 401               {
 402 # include "function.def"
 403                 { NULL, NULL }
 404               };
 405             size_t namlen = (5 + strlen (ni->library->name) + 1
 406                              + strlen (fct_name) + 1);
 407             char name[namlen];
 408
 409             /* Construct the function name.  */
 410             __stpcpy (__stpcpy (__stpcpy (name, ni->library->name),
 411                                 "_"),
 412                       fct_name);
 413
 414             result = NULL;
 415             for (tp = &tbl[0]; tp->fname; tp++)
 416               if (strcmp (tp->fname, name) == 0)
 417                 {
 418                   result = tp->fp;
 419                   break;
 420                 }
 421           }
 422 #endif
 423
 424           /* Remember function pointer for later calls.  Even if null, we
 425              record it so a second try needn't search the library again.  */
 426           known->fct_ptr = result;
 427         }
 428     }
 429
 430   /* Remove the lock.  */
 431   __libc_lock_unlock (lock);
 432
 433   return result;
 434 }
 435 libc_hidden_def (__nss_lookup_function)
 436
 437
 438 static name_database *
 439 internal_function
 440 nss_parse_file (const char *fname)
 441 {
 442   FILE *fp;
 443   name_database *result;
 444   name_database_entry *last;
 445   char *line;
 446   size_t len;
 447
 448   /* Open the configuration file.  */
 449   fp = fopen (fname, "rc");
 450   if (fp == NULL)
 451     return NULL;
 452
 453   /* No threads use this stream.  */
 454   __fsetlocking (fp, FSETLOCKING_BYCALLER);
 455
 456   result = (name_database *) malloc (sizeof (name_database));
 457   if (result == NULL)
 458     return NULL;
 459
 460   result->entry = NULL;
 461   result->library = NULL;
 462   last = NULL;
 463   line = NULL;
 464   len = 0;
 465   do
 466     {
 467       name_database_entry *this;
 468       ssize_t n;
 469
 470       n = __getline (&line, &len, fp);
 471       if (n < 0)
 472         break;
 473       if (line[n - 1] == '\n')
 474         line[n - 1] = '\0';
 475
 476       /* Because the file format does not know any form of quoting we
 477          can search forward for the next '#' character and if found
 478          make it terminating the line.  */
 479       *__strchrnul (line, '#') = '\0';
 480
 481       /* If the line is blank it is ignored.  */
 482       if (line[0] == '\0')
 483         continue;
 484
 485       /* Each line completely specifies the actions for a database.  */
 486       this = nss_getline (line);
 487       if (this != NULL)
 488         {
 489           if (last != NULL)
 490             last->next = this;
 491           else
 492             result->entry = this;
 493
 494           last = this;
 495         }
 496     }
 497   while (!feof_unlocked (fp));
 498
 499   /* Free the buffer.  */
 500   free (line);
 501   /* Close configuration file.  */
 502   fclose (fp);
 503
 504   return result;
 505 }
 506
 507
 508 /* Read the source names:
 509         `( <source> ( "[" "!"? (<status> "=" <action> )+ "]" )? )*'
 510    */
 511 static service_user *
 512 internal_function
 513 nss_parse_service_list (const char *line)
 514 {
 515   service_user *result = NULL, **nextp = &result;
 516
 517   while (1)
 518     {
 519       service_user *new_service;
 520       const char *name;
 521
 522       while (isspace (line[0]))
 523         ++line;
 524       if (line[0] == '\0')
 525         /* No source specified.  */
 526         return result;
 527
 528       /* Read <source> identifier.  */
 529       name = line;
 530       while (line[0] != '\0' && !isspace (line[0]) && line[0] != '[')
 531         ++line;
 532       if (name == line)
 533         return result;
 534
 535
 536       new_service = (service_user *) malloc (sizeof (service_user)
 537                                              + (line - name + 1));
 538       if (new_service == NULL)
 539         return result;
 540
 541       *((char *) __mempcpy (new_service->name, name, line - name)) = '\0';
 542
 543       /* Set default actions.  */
 544       new_service->actions[2 + NSS_STATUS_TRYAGAIN] = NSS_ACTION_CONTINUE;
 545       new_service->actions[2 + NSS_STATUS_UNAVAIL] = NSS_ACTION_CONTINUE;
 546       new_service->actions[2 + NSS_STATUS_NOTFOUND] = NSS_ACTION_CONTINUE;
 547       new_service->actions[2 + NSS_STATUS_SUCCESS] = NSS_ACTION_RETURN;
 548       new_service->actions[2 + NSS_STATUS_RETURN] = NSS_ACTION_RETURN;
 549       new_service->library = NULL;
 550       new_service->known = NULL;
 551       new_service->next = NULL;
 552
 553       while (isspace (line[0]))
 554         ++line;
 555
 556       if (line[0] == '[')
 557         {
 558           /* Read criterions.  */
 559           do
 560             ++line;
 561           while (line[0] != '\0' && isspace (line[0]));
 562
 563           do
 564             {
 565               int not;
 566               enum nss_status status;
 567               lookup_actions action;
 568
 569               /* Grok ! before name to mean all statii but that one.  */
 570               not = line[0] == '!';
 571               if (not)
 572                 ++line;
 573
 574               /* Read status name.  */
 575               name = line;
 576               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 577                      && line[0] != ']')
 578                 ++line;
 579
 580               /* Compare with known statii.  */
 581               if (line - name == 7)
 582                 {
 583                   if (__strncasecmp (name, "SUCCESS", 7) == 0)
 584                     status = NSS_STATUS_SUCCESS;
 585                   else if (__strncasecmp (name, "UNAVAIL", 7) == 0)
 586                     status = NSS_STATUS_UNAVAIL;
 587                   else
 588                     return result;
 589                 }
 590               else if (line - name == 8)
 591                 {
 592                   if (__strncasecmp (name, "NOTFOUND", 8) == 0)
 593                     status = NSS_STATUS_NOTFOUND;
 594                   else if (__strncasecmp (name, "TRYAGAIN", 8) == 0)
 595                     status = NSS_STATUS_TRYAGAIN;
 596                   else
 597                     return result;
 598                 }
 599               else
 600                 return result;
 601
 602               while (isspace (line[0]))
 603                 ++line;
 604               if (line[0] != '=')
 605                 return result;
 606               do
 607                 ++line;
 608               while (isspace (line[0]));
 609
 610               name = line;
 611               while (line[0] != '\0' && !isspace (line[0]) && line[0] != '='
 612                      && line[0] != ']')
 613                 ++line;
 614
 615               if (line - name == 6 && __strncasecmp (name, "RETURN", 6) == 0)
 616                 action = NSS_ACTION_RETURN;
 617               else if (line - name == 8
 618                        && __strncasecmp (name, "CONTINUE", 8) == 0)
 619                 action = NSS_ACTION_CONTINUE;
 620               else
 621                 return result;
 622
 623               if (not)
 624                 {
 625                   /* Save the current action setting for this status,
 626                      set them all to the given action, and reset this one.  */
 627                   const lookup_actions save = new_service->actions[2 + status];
 628                   new_service->actions[2 + NSS_STATUS_TRYAGAIN] = action;
 629                   new_service->actions[2 + NSS_STATUS_UNAVAIL] = action;
 630                   new_service->actions[2 + NSS_STATUS_NOTFOUND] = action;
 631                   new_service->actions[2 + NSS_STATUS_SUCCESS] = action;
 632                   new_service->actions[2 + status] = save;
 633                 }
 634               else
 635                 new_service->actions[2 + status] = action;
 636
 637               /* Skip white spaces.  */
 638               while (isspace (line[0]))
 639                 ++line;
 640             }
 641           while (line[0] != ']');
 642
 643           /* Skip the ']'.  */
 644           ++line;
 645         }
 646
 647       *nextp = new_service;
 648       nextp = &new_service->next;
 649     }
 650 }
 651
 652 static name_database_entry *
 653 internal_function
 654 nss_getline (char *line)
 655 {
 656   const char *name;
 657   name_database_entry *result;
 658   size_t len;
 659
 660   /* Ignore leading white spaces.  ATTENTION: this is different from
 661      what is implemented in Solaris.  The Solaris man page says a line
 662      beginning with a white space character is ignored.  We regard
 663      this as just another misfeature in Solaris.  */
 664   while (isspace (line[0]))
 665     ++line;
 666
 667   /* Recognize `<database> ":"'.  */
 668   name = line;
 669   while (line[0] != '\0' && !isspace (line[0]) && line[0] != ':')
 670     ++line;
 671   if (line[0] == '\0' || name == line)
 672     /* Syntax error.  */
 673     return NULL;
 674   *line++ = '\0';
 675
 676   len = strlen (name) + 1;
 677
 678   result = (name_database_entry *) malloc (sizeof (name_database_entry) + len);
 679   if (result == NULL)
 680     return NULL;
 681
 682   /* Save the database name.  */
 683   memcpy (result->name, name, len);
 684
 685   /* Parse the list of services.  */
 686   result->service = nss_parse_service_list (line);
 687
 688   result->next = NULL;
 689   return result;
 690 }
 691
 692
 693 static service_library *
 694 internal_function
 695 nss_new_service (name_database *database, const char *name)
 696 {
 697   service_library **currentp = &database->library;
 698
 699   while (*currentp != NULL)
 700     {
 701       if (strcmp ((*currentp)->name, name) == 0)
 702         return *currentp;
 703       currentp = &(*currentp)->next;
 704     }
 705
 706   /* We have to add the new service.  */
 707   *currentp = (service_library *) malloc (sizeof (service_library));
 708   if (*currentp == NULL)
 709     return NULL;
 710
 711   (*currentp)->name = name;
 712   (*currentp)->lib_handle = NULL;
 713   (*currentp)->next = NULL;
 714
 715   return *currentp;
 716 }
 717
 718
 719 /* Called by nscd and nscd alone.  */
 720 void
 721 __nss_disable_nscd (void)
 722 {
 723   /* Disable all uses of NSCD.  */
 724   __nss_not_use_nscd_passwd = -1;
 725   __nss_not_use_nscd_group = -1;
 726   __nss_not_use_nscd_hosts = -1;
 727   __nss_not_use_nscd_services = -1;
 728 }
 729
 730
 731 /* Free all resources if necessary.  */
 732 libc_freeres_fn (free_mem)
 733 {
 734   name_database *top = service_table;
 735   name_database_entry *entry;
 736   service_library *library;
 737
 738   if (top == NULL)
 739     /* Maybe we have not read the nsswitch.conf file.  */
 740     return;
 741
 742   /* Don't disturb ongoing other threads (if there are any).  */
 743   service_table = NULL;
 744
 745   entry = top->entry;
 746   while (entry != NULL)
 747     {
 748       name_database_entry *olde = entry;
 749       service_user *service = entry->service;
 750
 751       while (service != NULL)
 752         {
 753           service_user *olds = service;
 754
 755           if (service->known != NULL)
 756             __tdestroy (service->known, free);
 757
 758           service = service->next;
 759           free (olds);
 760         }
 761
 762       entry = entry->next;
 763       free (olde);
 764     }
 765
 766   library = top->library;
 767   while (library != NULL)
 768     {
 769       service_library *oldl = library;
 770
 771       if (library->lib_handle && library->lib_handle != (void *) -1l)
 772         __libc_dlclose (library->lib_handle);
 773
 774       library = library->next;
 775       free (oldl);
 776     }
 777
 778   free (top);
 779 }