nscd/nscd_getai.c

   1 /* Copyright (C) 2004-2023 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 <netdb.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24 #include <not-cancel.h>
  25
  26 #include "nscd-client.h"
  27 #include "nscd_proto.h"
  28
  29
  30 /* Define in nscd_gethst_r.c.  */
  31 extern int __nss_not_use_nscd_hosts;
  32
  33
  34 /* We use the mapping from nscd_gethst.  */
  35 libc_locked_map_ptr (extern, __hst_map_handle) attribute_hidden;
  36
  37 /* Defined in nscd_gethst_r.c.  */
  38 extern int __nss_have_localdomain attribute_hidden;
  39
  40
  41 int
  42 __nscd_getai (const char *key, struct nscd_ai_result **result, int *h_errnop)
  43 {
  44   if (__glibc_unlikely (__nss_have_localdomain >= 0))
  45     {
  46       if (__nss_have_localdomain == 0)
  47         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
  48       if (__nss_have_localdomain > 0)
  49         {
  50           __nss_not_use_nscd_hosts = 1;
  51           return -1;
  52         }
  53     }
  54
  55   size_t keylen = strlen (key) + 1;
  56   int gc_cycle;
  57   int nretries = 0;
  58
  59   /* If the mapping is available, try to search there instead of
  60      communicating with the nscd.  */
  61   struct mapped_database *mapped;
  62   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
  63                                &gc_cycle);
  64
  65  retry:;
  66   struct nscd_ai_result *resultbuf = NULL;
  67   const char *recend = (const char *) ~UINTMAX_C (0);
  68   char *respdata = NULL;
  69   int retval = -1;
  70   int sock = -1;
  71   ai_response_header ai_resp;
  72
  73   if (mapped != NO_MAPPING)
  74     {
  75       struct datahead *found = __nscd_cache_search (GETAI, key, keylen,
  76                                                     mapped, sizeof ai_resp);
  77       if (found != NULL)
  78         {
  79           respdata = (char *) (&found->data[0].aidata + 1);
  80           ai_resp = found->data[0].aidata;
  81           recend = (const char *) found->data + found->recsize;
  82           /* Now check if we can trust ai_resp fields.  If GC is
  83              in progress, it can contain anything.  */
  84           if (mapped->head->gc_cycle != gc_cycle)
  85             {
  86               retval = -2;
  87               goto out;
  88             }
  89         }
  90     }
  91
  92   /* If we do not have the cache mapped, try to get the data over the
  93      socket.  */
  94   if (respdata == NULL)
  95     {
  96       sock = __nscd_open_socket (key, keylen, GETAI, &ai_resp,
  97                                  sizeof (ai_resp));
  98       if (sock == -1)
  99         {
 100           /* nscd not running or wrong version.  */
 101           __nss_not_use_nscd_hosts = 1;
 102           goto out;
 103         }
 104     }
 105
 106   if (ai_resp.found == 1)
 107     {
 108       size_t datalen = ai_resp.naddrs + ai_resp.addrslen + ai_resp.canonlen;
 109
 110       /* This check really only affects the case where the data
 111          comes from the mapped cache.  */
 112       if (respdata + datalen > recend)
 113         {
 114           assert (sock == -1);
 115           goto out;
 116         }
 117
 118       /* Create result.  */
 119       resultbuf = (struct nscd_ai_result *) malloc (sizeof (*resultbuf)
 120                                                     + datalen);
 121       if (resultbuf == NULL)
 122         {
 123           *h_errnop = NETDB_INTERNAL;
 124           goto out_close;
 125         }
 126
 127       /* Set up the data structure, including pointers.  */
 128       resultbuf->naddrs = ai_resp.naddrs;
 129       resultbuf->addrs = (char *) (resultbuf + 1);
 130       resultbuf->family = (uint8_t *) (resultbuf->addrs + ai_resp.addrslen);
 131       if (ai_resp.canonlen != 0)
 132         resultbuf->canon = (char *) (resultbuf->family + resultbuf->naddrs);
 133       else
 134         resultbuf->canon = NULL;
 135
 136       if (respdata == NULL)
 137         {
 138           /* Read the data from the socket.  */
 139           if ((size_t) __readall (sock, resultbuf + 1, datalen) == datalen)
 140             {
 141               retval = 0;
 142               *result = resultbuf;
 143             }
 144           else
 145             {
 146               free (resultbuf);
 147               *h_errnop = NETDB_INTERNAL;
 148             }
 149         }
 150       else
 151         {
 152           /* Copy the data in the block.  */
 153           memcpy (resultbuf + 1, respdata, datalen);
 154
 155           /* Try to detect corrupt databases.  */
 156           if (resultbuf->canon != NULL
 157               && resultbuf->canon[ai_resp.canonlen - 1] != '\0')
 158             /* We cannot use the database.  */
 159             {
 160               if (mapped->head->gc_cycle != gc_cycle)
 161                 retval = -2;
 162               else
 163                 free (resultbuf);
 164               goto out_close;
 165             }
 166
 167           retval = 0;
 168           *result = resultbuf;
 169         }
 170     }
 171   else
 172     {
 173       if (__glibc_unlikely (ai_resp.found == -1))
 174         {
 175           /* The daemon does not cache this database.  */
 176           __nss_not_use_nscd_hosts = 1;
 177           goto out_close;
 178         }
 179
 180       /* Store the error number.  */
 181       *h_errnop = ai_resp.error;
 182
 183       /* Set errno to 0 to indicate no error, just no found record.  */
 184       __set_errno (0);
 185       /* Even though we have not found anything, the result is zero.  */
 186       retval = 0;
 187     }
 188
 189  out_close:
 190   if (sock != -1)
 191     __close_nocancel_nostatus (sock);
 192  out:
 193   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 194     {
 195       /* When we come here this means there has been a GC cycle while we
 196          were looking for the data.  This means the data might have been
 197          inconsistent.  Retry if possible.  */
 198       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 199         {
 200           /* nscd is just running gc now.  Disable using the mapping.  */
 201           if (atomic_fetch_add_relaxed (&mapped->counter, -1) == 1)
 202             __nscd_unmap (mapped);
 203           mapped = NO_MAPPING;
 204         }
 205
 206       if (retval != -1)
 207         {
 208           *result = NULL;
 209           free (resultbuf);
 210           goto retry;
 211         }
 212     }
 213
 214   return retval;
 215 }