nscd/nscd_getai.c

   1 /* Copyright (C) 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.
   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 <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
  40 int
  41 __nscd_getai (const char *key, struct nscd_ai_result **result, int *h_errnop)
  42 {
  43   size_t keylen = strlen (key) + 1;
  44   int gc_cycle;
  45   int nretries = 0;
  46
  47   /* If the mapping is available, try to search there instead of
  48      communicating with the nscd.  */
  49   struct mapped_database *mapped;
  50   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
  51                                &gc_cycle);
  52
  53  retry:;
  54   struct nscd_ai_result *resultbuf = NULL;
  55   const char *recend = (const char *) ~UINTMAX_C (0);
  56   char *respdata = NULL;
  57   int retval = -1;
  58   int sock = -1;
  59   ai_response_header ai_resp;
  60
  61   if (mapped != NO_MAPPING)
  62     {
  63       struct datahead *found = __nscd_cache_search (GETAI, key, keylen,
  64                                                     mapped);
  65       if (found != NULL)
  66         {
  67           respdata = (char *) (&found->data[0].aidata + 1);
  68           ai_resp = found->data[0].aidata;
  69           recend = (const char *) found->data + found->recsize;
  70           /* Now check if we can trust ai_resp fields.  If GC is
  71              in progress, it can contain anything.  */
  72           if (mapped->head->gc_cycle != gc_cycle)
  73             {
  74               retval = -2;
  75               goto out;
  76             }
  77         }
  78     }
  79
  80   /* If we do not have the cache mapped, try to get the data over the
  81      socket.  */
  82   if (respdata == NULL)
  83     {
  84       sock = __nscd_open_socket (key, keylen, GETAI, &ai_resp,
  85                                  sizeof (ai_resp));
  86       if (sock == -1)
  87         {
  88           /* nscd not running or wrong version.  */
  89           __nss_not_use_nscd_hosts = 1;
  90           goto out;
  91         }
  92     }
  93
  94   if (ai_resp.found == 1)
  95     {
  96       size_t datalen = ai_resp.naddrs + ai_resp.addrslen + ai_resp.canonlen;
  97
  98       /* This check really only affects the case where the data
  99          comes from the mapped cache.  */
 100       if (respdata + datalen > recend)
 101         {
 102           assert (sock == -1);
 103           goto out;
 104         }
 105
 106       /* Create result.  */
 107       resultbuf = (struct nscd_ai_result *) malloc (sizeof (*resultbuf)
 108                                                     + datalen);
 109       if (resultbuf == NULL)
 110         {
 111           *h_errnop = NETDB_INTERNAL;
 112           goto out_close;
 113         }
 114
 115       /* Set up the data structure, including pointers.  */
 116       resultbuf->naddrs = ai_resp.naddrs;
 117       resultbuf->addrs = (char *) (resultbuf + 1);
 118       resultbuf->family = (uint8_t *) (resultbuf->addrs + ai_resp.addrslen);
 119       if (ai_resp.canonlen != 0)
 120         resultbuf->canon = (char *) (resultbuf->family + resultbuf->naddrs);
 121       else
 122         resultbuf->canon = NULL;
 123
 124       if (respdata == NULL)
 125         {
 126           /* Read the data from the socket.  */
 127           if ((size_t) __readall (sock, resultbuf + 1, datalen) == datalen)
 128             {
 129               retval = 0;
 130               *result = resultbuf;
 131             }
 132           else
 133             {
 134               free (resultbuf);
 135               *h_errnop = NETDB_INTERNAL;
 136             }
 137         }
 138       else
 139         {
 140           /* Copy the data in the block.  */
 141           memcpy (resultbuf + 1, respdata, datalen);
 142
 143           /* Try to detect corrupt databases.  */
 144           if (resultbuf->canon != NULL
 145               && resultbuf->canon[ai_resp.canonlen - 1] != '\0')
 146             /* We cannot use the database.  */
 147             {
 148               if (mapped->head->gc_cycle != gc_cycle)
 149                 retval = -2;
 150               else
 151                 free (resultbuf);
 152               goto out_close;
 153             }
 154
 155           retval = 0;
 156           *result = resultbuf;
 157         }
 158     }
 159   else
 160     {
 161       if (__builtin_expect (ai_resp.found == -1, 0))
 162         {
 163           /* The daemon does not cache this database.  */
 164           __nss_not_use_nscd_hosts = 1;
 165           goto out_close;
 166         }
 167
 168       /* Store the error number.  */
 169       *h_errnop = ai_resp.error;
 170
 171       /* Set errno to 0 to indicate no error, just no found record.  */
 172       __set_errno (0);
 173       /* Even though we have not found anything, the result is zero.  */
 174       retval = 0;
 175     }
 176
 177  out_close:
 178   if (sock != -1)
 179     close_not_cancel_no_status (sock);
 180  out:
 181   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 182     {
 183       /* When we come here this means there has been a GC cycle while we
 184          were looking for the data.  This means the data might have been
 185          inconsistent.  Retry if possible.  */
 186       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 187         {
 188           /* nscd is just running gc now.  Disable using the mapping.  */
 189           if (atomic_decrement_val (&mapped->counter) == 0)
 190             __nscd_unmap (mapped);
 191           mapped = NO_MAPPING;
 192         }
 193
 194       if (retval != -1)
 195         {
 196           *result = NULL;
 197           free (resultbuf);
 198           goto retry;
 199         }
 200     }
 201
 202   return retval;
 203 }