inet/getipnodebyad.c

   1 /* Copyright (C) 1999, 2000 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 Library General Public License as
   6    published by the Free Software Foundation; either version 2 of the
   7    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    Library General Public License for more details.
  13
  14    You should have received a copy of the GNU Library General Public
  15    License along with the GNU C Library; see the file COPYING.LIB.  If not,
  16    write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  17    Boston, MA 02111-1307, USA.  */
  18
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <netdb.h>
  22 #include <stdlib.h>
  23
  24 #include "nsswitch.h"
  25
  26 /* We avoid using a too large buffer in case the user is accumulating the
  27    results and there is lots of unused space in the allocated buffer.  */
  28 #define BUFLEN  512
  29
  30
  31 struct hostent *
  32 getipnodebyaddr (const void *addr, socklen_t len, int type, int *error_num)
  33 {
  34   size_t buffer_size;
  35   char *buffer;
  36   struct hostent *result;
  37
  38   buffer_size = BUFLEN;
  39   buffer = malloc (buffer_size);
  40
  41   while (buffer != NULL
  42          && __gethostbyaddr_r (addr, len, type, (struct hostent *) buffer,
  43                                (char *) ((struct hostent *) buffer + 1),
  44                                buffer_size - sizeof (struct hostent),
  45                                &result, error_num) == ERANGE
  46          && *error_num == NETDB_INTERNAL)
  47     {
  48       buffer_size += BUFLEN;
  49       buffer = realloc (buffer, buffer_size);
  50       if (buffer == NULL)
  51         {
  52           *error_num = TRY_AGAIN;
  53           assert (result == NULL);
  54           return NULL;
  55         }
  56     }
  57
  58   return buffer == NULL ? NULL : result;
  59 }