nss/getXXbyYY.c

   1 /* Copyright (C) 1996-2019 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <assert.h>
  19 #include <errno.h>
  20 #include <libc-lock.h>
  21 #include <stdlib.h>
  22 #include <resolv.h>
  23
  24 #include "nsswitch.h"
  25
  26 /*******************************************************************\
  27 |* Here we assume several symbols to be defined:                   *|
  28 |*                                                                 *|
  29 |* LOOKUP_TYPE   - the return type of the function                 *|
  30 |*                                                                 *|
  31 |* FUNCTION_NAME - name of the non-reentrant function              *|
  32 |*                                                                 *|
  33 |* DATABASE_NAME - name of the database the function accesses      *|
  34 |*                 (e.g., host, services, ...)                     *|
  35 |*                                                                 *|
  36 |* ADD_PARAMS    - additional parameter, can vary in number        *|
  37 |*                                                                 *|
  38 |* ADD_VARIABLES - names of additional parameter                   *|
  39 |*                                                                 *|
  40 |* BUFLEN        - length of buffer allocated for the non          *|
  41 |*                 reentrant version                               *|
  42 |*                                                                 *|
  43 |* Optionally the following vars can be defined:                   *|
  44 |*                                                                 *|
  45 |* NEED_H_ERRNO  - an extra parameter will be passed to point to   *|
  46 |*                 the global `h_errno' variable.                  *|
  47 |*                                                                 *|
  48 \*******************************************************************/
  49
  50
  51 #ifdef HANDLE_DIGITS_DOTS
  52 # include <resolv/resolv_context.h>
  53 #endif
  54
  55 /* To make the real sources a bit prettier.  */
  56 #define REENTRANT_NAME APPEND_R (FUNCTION_NAME)
  57 #define APPEND_R(name) APPEND_R1 (name)
  58 #define APPEND_R1(name) name##_r
  59 #define INTERNAL(name) INTERNAL1 (name)
  60 #define INTERNAL1(name) __##name
  61
  62 /* Sometimes we need to store error codes in the `h_errno' variable.  */
  63 #ifdef NEED_H_ERRNO
  64 # define H_ERRNO_PARM , int *h_errnop
  65 # define H_ERRNO_VAR , &h_errno_tmp
  66 # define H_ERRNO_VAR_P &h_errno_tmp
  67 #else
  68 # define H_ERRNO_PARM
  69 # define H_ERRNO_VAR
  70 # define H_ERRNO_VAR_P NULL
  71 #endif
  72
  73 #ifdef HAVE_AF
  74 # define AF_VAL af
  75 #else
  76 # define AF_VAL AF_INET
  77 #endif
  78
  79 /* Prototype for reentrant version we use here.  */
  80 extern int INTERNAL (REENTRANT_NAME) (ADD_PARAMS, LOOKUP_TYPE *resbuf,
  81                                       char *buffer, size_t buflen,
  82                                       LOOKUP_TYPE **result H_ERRNO_PARM)
  83      attribute_hidden;
  84
  85 /* We need to protect the dynamic buffer handling.  */
  86 __libc_lock_define_initialized (static, lock);
  87
  88 /* This points to the static buffer used.  */
  89 libc_freeres_ptr (static char *buffer);
  90
  91
  92 LOOKUP_TYPE *
  93 FUNCTION_NAME (ADD_PARAMS)
  94 {
  95   static size_t buffer_size;
  96   static LOOKUP_TYPE resbuf;
  97   LOOKUP_TYPE *result;
  98 #ifdef NEED_H_ERRNO
  99   int h_errno_tmp = 0;
 100 #endif
 101
 102 #ifdef HANDLE_DIGITS_DOTS
 103   /* Wrap both __nss_hostname_digits_dots and the actual lookup
 104      function call in the same context.  */
 105   struct resolv_context *res_ctx = __resolv_context_get ();
 106   if (res_ctx == NULL)
 107     {
 108 # if NEED_H_ERRNO
 109       __set_h_errno (NETDB_INTERNAL);
 110 # endif
 111       return NULL;
 112     }
 113 #endif
 114
 115   /* Get lock.  */
 116   __libc_lock_lock (lock);
 117
 118   if (buffer == NULL)
 119     {
 120       buffer_size = BUFLEN;
 121       buffer = (char *) malloc (buffer_size);
 122     }
 123
 124 #ifdef HANDLE_DIGITS_DOTS
 125   if (buffer != NULL)
 126     {
 127       if (__nss_hostname_digits_dots_context
 128           (res_ctx, name, &resbuf, &buffer, &buffer_size, 0, &result, NULL,
 129            AF_VAL, H_ERRNO_VAR_P))
 130         goto done;
 131     }
 132 #endif
 133
 134   while (buffer != NULL
 135          && (INTERNAL (REENTRANT_NAME) (ADD_VARIABLES, &resbuf, buffer,
 136                                         buffer_size, &result H_ERRNO_VAR)
 137              == ERANGE)
 138 #ifdef NEED_H_ERRNO
 139          && h_errno_tmp == NETDB_INTERNAL
 140 #endif
 141          )
 142     {
 143       char *new_buf;
 144       buffer_size *= 2;
 145       new_buf = (char *) realloc (buffer, buffer_size);
 146       if (new_buf == NULL)
 147         {
 148           /* We are out of memory.  Free the current buffer so that the
 149              process gets a chance for a normal termination.  */
 150           free (buffer);
 151           __set_errno (ENOMEM);
 152         }
 153       buffer = new_buf;
 154     }
 155
 156   if (buffer == NULL)
 157     result = NULL;
 158
 159 #ifdef HANDLE_DIGITS_DOTS
 160 done:
 161 #endif
 162   /* Release lock.  */
 163   __libc_lock_unlock (lock);
 164
 165 #ifdef HANDLE_DIGITS_DOTS
 166   __resolv_context_put (res_ctx);
 167 #endif
 168
 169 #ifdef NEED_H_ERRNO
 170   if (h_errno_tmp != 0)
 171     __set_h_errno (h_errno_tmp);
 172 #endif
 173
 174   return result;
 175 }
 176
 177 nss_interface_function (FUNCTION_NAME)