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, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <assert.h>
  21 #include <errno.h>
  22 #include <netdb.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26 #include <not-cancel.h>
  27
  28 #include "nscd-client.h"
  29 #include "nscd_proto.h"
  30
  31
  32 /* Define in nscd_gethst_r.c.  */
  33 extern int __nss_not_use_nscd_hosts;
  34
  35
  36 /* We use the mapping from nscd_gethst.  */
  37 libc_locked_map_ptr (extern, __hst_map_handle) attribute_hidden;
  38
  39 /* Defined in nscd_gethst_r.c.  */
  40 extern int __nss_have_localdomain attribute_hidden;
  41
  42
  43 int
  44 __nscd_getai (const char *key, struct nscd_ai_result **result, int *h_errnop)
  45 {
  46   if (__builtin_expect (__nss_have_localdomain >= 0, 0))
  47     {
  48       if (__nss_have_localdomain == 0)
  49         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
  50       if (__nss_have_localdomain > 0)
  51         {
  52           __nss_not_use_nscd_hosts = 1;
  53           return -1;
  54         }
  55     }
  56
  57   size_t keylen = strlen (key) + 1;
  58   int gc_cycle;
  59   int nretries = 0;
  60
  61   /* If the mapping is available, try to search there instead of
  62      communicating with the nscd.  */
  63   struct mapped_database *mapped;
  64   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
  65                                &gc_cycle);
  66
  67  retry:;
  68   struct nscd_ai_result *resultbuf = NULL;
  69   const char *recend = (const char *) ~UINTMAX_C (0);
  70   char *respdata = NULL;
  71   int retval = -1;
  72   int sock = -1;
  73   ai_response_header ai_resp;
  74
  75   if (mapped != NO_MAPPING)
  76     {
  77       struct datahead *found = __nscd_cache_search (GETAI, key, keylen,
  78                                                     mapped, sizeof ai_resp);
  79       if (found != NULL)
  80         {
  81           respdata = (char *) (&found->data[0].aidata + 1);
  82           ai_resp = found->data[0].aidata;
  83           recend = (const char *) found->data + found->recsize;
  84           /* Now check if we can trust ai_resp fields.  If GC is
  85              in progress, it can contain anything.  */
  86           if (mapped->head->gc_cycle != gc_cycle)
  87             {
  88               retval = -2;
  89               goto out;
  90             }
  91         }
  92     }
  93
  94   /* If we do not have the cache mapped, try to get the data over the
  95      socket.  */
  96   if (respdata == NULL)
  97     {
  98       sock = __nscd_open_socket (key, keylen, GETAI, &ai_resp,
  99                                  sizeof (ai_resp));
 100       if (sock == -1)
 101         {
 102           /* nscd not running or wrong version.  */
 103           __nss_not_use_nscd_hosts = 1;
 104           goto out;
 105         }
 106     }
 107
 108   if (ai_resp.found == 1)
 109     {
 110       size_t datalen = ai_resp.naddrs + ai_resp.addrslen + ai_resp.canonlen;
 111
 112       /* This check really only affects the case where the data
 113          comes from the mapped cache.  */
 114       if (respdata + datalen > recend)
 115         {
 116           assert (sock == -1);
 117           goto out;
 118         }
 119
 120       /* Create result.  */
 121       resultbuf = (struct nscd_ai_result *) malloc (sizeof (*resultbuf)
 122                                                     + datalen);
 123       if (resultbuf == NULL)
 124         {
 125           *h_errnop = NETDB_INTERNAL;
 126           goto out_close;
 127         }
 128
 129       /* Set up the data structure, including pointers.  */
 130       resultbuf->naddrs = ai_resp.naddrs;
 131       resultbuf->addrs = (char *) (resultbuf + 1);
 132       resultbuf->family = (uint8_t *) (resultbuf->addrs + ai_resp.addrslen);
 133       if (ai_resp.canonlen != 0)
 134         resultbuf->canon = (char *) (resultbuf->family + resultbuf->naddrs);
 135       else
 136         resultbuf->canon = NULL;
 137
 138       if (respdata == NULL)
 139         {
 140           /* Read the data from the socket.  */
 141           if ((size_t) __readall (sock, resultbuf + 1, datalen) == datalen)
 142             {
 143               retval = 0;
 144               *result = resultbuf;
 145             }
 146           else
 147             {
 148               free (resultbuf);
 149               *h_errnop = NETDB_INTERNAL;
 150             }
 151         }
 152       else
 153         {
 154           /* Copy the data in the block.  */
 155           memcpy (resultbuf + 1, respdata, datalen);
 156
 157           /* Try to detect corrupt databases.  */
 158           if (resultbuf->canon != NULL
 159               && resultbuf->canon[ai_resp.canonlen - 1] != '\0')
 160             /* We cannot use the database.  */
 161             {
 162               if (mapped->head->gc_cycle != gc_cycle)
 163                 retval = -2;
 164               else
 165                 free (resultbuf);
 166               goto out_close;
 167             }
 168
 169           retval = 0;
 170           *result = resultbuf;
 171         }
 172     }
 173   else
 174     {
 175       if (__builtin_expect (ai_resp.found == -1, 0))
 176         {
 177           /* The daemon does not cache this database.  */
 178           __nss_not_use_nscd_hosts = 1;
 179           goto out_close;
 180         }
 181
 182       /* Store the error number.  */
 183       *h_errnop = ai_resp.error;
 184
 185       /* Set errno to 0 to indicate no error, just no found record.  */
 186       __set_errno (0);
 187       /* Even though we have not found anything, the result is zero.  */
 188       retval = 0;
 189     }
 190
 191  out_close:
 192   if (sock != -1)
 193     close_not_cancel_no_status (sock);
 194  out:
 195   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 196     {
 197       /* When we come here this means there has been a GC cycle while we
 198          were looking for the data.  This means the data might have been
 199          inconsistent.  Retry if possible.  */
 200       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 201         {
 202           /* nscd is just running gc now.  Disable using the mapping.  */
 203           if (atomic_decrement_val (&mapped->counter) == 0)
 204             __nscd_unmap (mapped);
 205           mapped = NO_MAPPING;
 206         }
 207
 208       if (retval != -1)
 209         {
 210           *result = NULL;
 211           free (resultbuf);
 212           goto retry;
 213         }
 214     }
 215
 216   return retval;
 217 }