nscd/nscd_getai.c

   1 /* Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <assert.h>
  22 #include <errno.h>
  23 #include <netdb.h>
  24 #include <stdlib.h>
  25 #include <string.h>
  26 #include <unistd.h>
  27 #include <not-cancel.h>
  28
  29 #include "nscd-client.h"
  30 #include "nscd_proto.h"
  31
  32
  33 /* Define in nscd_gethst_r.c.  */
  34 extern int __nss_not_use_nscd_hosts;
  35
  36
  37 /* We use the mapping from nscd_gethst.  */
  38 libc_locked_map_ptr (extern, __hst_map_handle) attribute_hidden;
  39
  40 /* Defined in nscd_gethst_r.c.  */
  41 extern int __nss_have_localdomain attribute_hidden;
  42
  43
  44 int
  45 __nscd_getai (const char *key, struct nscd_ai_result **result, int *h_errnop)
  46 {
  47   if (__builtin_expect (__nss_have_localdomain >= 0, 0))
  48     {
  49       if (__nss_have_localdomain == 0)
  50         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
  51       if (__nss_have_localdomain > 0)
  52         {
  53           __nss_not_use_nscd_hosts = 1;
  54           return -1;
  55         }
  56     }
  57
  58   size_t keylen = strlen (key) + 1;
  59   int gc_cycle;
  60   int nretries = 0;
  61
  62   /* If the mapping is available, try to search there instead of
  63      communicating with the nscd.  */
  64   struct mapped_database *mapped;
  65   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
  66                                &gc_cycle);
  67
  68  retry:;
  69   struct nscd_ai_result *resultbuf = NULL;
  70   const char *recend = (const char *) ~UINTMAX_C (0);
  71   char *respdata = NULL;
  72   int retval = -1;
  73   int sock = -1;
  74   ai_response_header ai_resp;
  75
  76   if (mapped != NO_MAPPING)
  77     {
  78       struct datahead *found = __nscd_cache_search (GETAI, key, keylen,
  79                                                     mapped, sizeof ai_resp);
  80       if (found != NULL)
  81         {
  82           respdata = (char *) (&found->data[0].aidata + 1);
  83           ai_resp = found->data[0].aidata;
  84           recend = (const char *) found->data + found->recsize;
  85           /* Now check if we can trust ai_resp fields.  If GC is
  86              in progress, it can contain anything.  */
  87           if (mapped->head->gc_cycle != gc_cycle)
  88             {
  89               retval = -2;
  90               goto out;
  91             }
  92         }
  93     }
  94
  95   /* If we do not have the cache mapped, try to get the data over the
  96      socket.  */
  97   if (respdata == NULL)
  98     {
  99       sock = __nscd_open_socket (key, keylen, GETAI, &ai_resp,
 100                                  sizeof (ai_resp));
 101       if (sock == -1)
 102         {
 103           /* nscd not running or wrong version.  */
 104           __nss_not_use_nscd_hosts = 1;
 105           goto out;
 106         }
 107     }
 108
 109   if (ai_resp.found == 1)
 110     {
 111       size_t datalen = ai_resp.naddrs + ai_resp.addrslen + ai_resp.canonlen;
 112
 113       /* This check really only affects the case where the data
 114          comes from the mapped cache.  */
 115       if (respdata + datalen > recend)
 116         {
 117           assert (sock == -1);
 118           goto out;
 119         }
 120
 121       /* Create result.  */
 122       resultbuf = (struct nscd_ai_result *) malloc (sizeof (*resultbuf)
 123                                                     + datalen);
 124       if (resultbuf == NULL)
 125         {
 126           *h_errnop = NETDB_INTERNAL;
 127           goto out_close;
 128         }
 129
 130       /* Set up the data structure, including pointers.  */
 131       resultbuf->naddrs = ai_resp.naddrs;
 132       resultbuf->addrs = (char *) (resultbuf + 1);
 133       resultbuf->family = (uint8_t *) (resultbuf->addrs + ai_resp.addrslen);
 134       if (ai_resp.canonlen != 0)
 135         resultbuf->canon = (char *) (resultbuf->family + resultbuf->naddrs);
 136       else
 137         resultbuf->canon = NULL;
 138
 139       if (respdata == NULL)
 140         {
 141           /* Read the data from the socket.  */
 142           if ((size_t) __readall (sock, resultbuf + 1, datalen) == datalen)
 143             {
 144               retval = 0;
 145               *result = resultbuf;
 146             }
 147           else
 148             {
 149               free (resultbuf);
 150               *h_errnop = NETDB_INTERNAL;
 151             }
 152         }
 153       else
 154         {
 155           /* Copy the data in the block.  */
 156           memcpy (resultbuf + 1, respdata, datalen);
 157
 158           /* Try to detect corrupt databases.  */
 159           if (resultbuf->canon != NULL
 160               && resultbuf->canon[ai_resp.canonlen - 1] != '\0')
 161             /* We cannot use the database.  */
 162             {
 163               if (mapped->head->gc_cycle != gc_cycle)
 164                 retval = -2;
 165               else
 166                 free (resultbuf);
 167               goto out_close;
 168             }
 169
 170           retval = 0;
 171           *result = resultbuf;
 172         }
 173     }
 174   else
 175     {
 176       if (__builtin_expect (ai_resp.found == -1, 0))
 177         {
 178           /* The daemon does not cache this database.  */
 179           __nss_not_use_nscd_hosts = 1;
 180           goto out_close;
 181         }
 182
 183       /* Store the error number.  */
 184       *h_errnop = ai_resp.error;
 185
 186       /* Set errno to 0 to indicate no error, just no found record.  */
 187       __set_errno (0);
 188       /* Even though we have not found anything, the result is zero.  */
 189       retval = 0;
 190     }
 191
 192  out_close:
 193   if (sock != -1)
 194     close_not_cancel_no_status (sock);
 195  out:
 196   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 197     {
 198       /* When we come here this means there has been a GC cycle while we
 199          were looking for the data.  This means the data might have been
 200          inconsistent.  Retry if possible.  */
 201       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 202         {
 203           /* nscd is just running gc now.  Disable using the mapping.  */
 204           if (atomic_decrement_val (&mapped->counter) == 0)
 205             __nscd_unmap (mapped);
 206           mapped = NO_MAPPING;
 207         }
 208
 209       if (retval != -1)
 210         {
 211           *result = NULL;
 212           free (resultbuf);
 213           goto retry;
 214         }
 215     }
 216
 217   return retval;
 218 }