nscd/nscd_getai.c

   1 /* Copyright (C) 2004-2021 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, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <assert.h>
  20 #include <errno.h>
  21 #include <netdb.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <unistd.h>
  25 #include <not-cancel.h>
  26
  27 #include "nscd-client.h"
  28 #include "nscd_proto.h"
  29
  30
  31 /* Define in nscd_gethst_r.c.  */
  32 extern int __nss_not_use_nscd_hosts;
  33
  34
  35 /* We use the mapping from nscd_gethst.  */
  36 libc_locked_map_ptr (extern, __hst_map_handle) attribute_hidden;
  37
  38 /* Defined in nscd_gethst_r.c.  */
  39 extern int __nss_have_localdomain attribute_hidden;
  40
  41
  42 int
  43 __nscd_getai (const char *key, struct nscd_ai_result **result, int *h_errnop)
  44 {
  45   if (__glibc_unlikely (__nss_have_localdomain >= 0))
  46     {
  47       if (__nss_have_localdomain == 0)
  48         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
  49       if (__nss_have_localdomain > 0)
  50         {
  51           __nss_not_use_nscd_hosts = 1;
  52           return -1;
  53         }
  54     }
  55
  56   size_t keylen = strlen (key) + 1;
  57   int gc_cycle;
  58   int nretries = 0;
  59
  60   /* If the mapping is available, try to search there instead of
  61      communicating with the nscd.  */
  62   struct mapped_database *mapped;
  63   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
  64                                &gc_cycle);
  65
  66  retry:;
  67   struct nscd_ai_result *resultbuf = NULL;
  68   const char *recend = (const char *) ~UINTMAX_C (0);
  69   char *respdata = NULL;
  70   int retval = -1;
  71   int sock = -1;
  72   ai_response_header ai_resp;
  73
  74   if (mapped != NO_MAPPING)
  75     {
  76       struct datahead *found = __nscd_cache_search (GETAI, key, keylen,
  77                                                     mapped, sizeof ai_resp);
  78       if (found != NULL)
  79         {
  80           respdata = (char *) (&found->data[0].aidata + 1);
  81           ai_resp = found->data[0].aidata;
  82           recend = (const char *) found->data + found->recsize;
  83           /* Now check if we can trust ai_resp fields.  If GC is
  84              in progress, it can contain anything.  */
  85           if (mapped->head->gc_cycle != gc_cycle)
  86             {
  87               retval = -2;
  88               goto out;
  89             }
  90         }
  91     }
  92
  93   /* If we do not have the cache mapped, try to get the data over the
  94      socket.  */
  95   if (respdata == NULL)
  96     {
  97       sock = __nscd_open_socket (key, keylen, GETAI, &ai_resp,
  98                                  sizeof (ai_resp));
  99       if (sock == -1)
 100         {
 101           /* nscd not running or wrong version.  */
 102           __nss_not_use_nscd_hosts = 1;
 103           goto out;
 104         }
 105     }
 106
 107   if (ai_resp.found == 1)
 108     {
 109       size_t datalen = ai_resp.naddrs + ai_resp.addrslen + ai_resp.canonlen;
 110
 111       /* This check really only affects the case where the data
 112          comes from the mapped cache.  */
 113       if (respdata + datalen > recend)
 114         {
 115           assert (sock == -1);
 116           goto out;
 117         }
 118
 119       /* Create result.  */
 120       resultbuf = (struct nscd_ai_result *) malloc (sizeof (*resultbuf)
 121                                                     + datalen);
 122       if (resultbuf == NULL)
 123         {
 124           *h_errnop = NETDB_INTERNAL;
 125           goto out_close;
 126         }
 127
 128       /* Set up the data structure, including pointers.  */
 129       resultbuf->naddrs = ai_resp.naddrs;
 130       resultbuf->addrs = (char *) (resultbuf + 1);
 131       resultbuf->family = (uint8_t *) (resultbuf->addrs + ai_resp.addrslen);
 132       if (ai_resp.canonlen != 0)
 133         resultbuf->canon = (char *) (resultbuf->family + resultbuf->naddrs);
 134       else
 135         resultbuf->canon = NULL;
 136
 137       if (respdata == NULL)
 138         {
 139           /* Read the data from the socket.  */
 140           if ((size_t) __readall (sock, resultbuf + 1, datalen) == datalen)
 141             {
 142               retval = 0;
 143               *result = resultbuf;
 144             }
 145           else
 146             {
 147               free (resultbuf);
 148               *h_errnop = NETDB_INTERNAL;
 149             }
 150         }
 151       else
 152         {
 153           /* Copy the data in the block.  */
 154           memcpy (resultbuf + 1, respdata, datalen);
 155
 156           /* Try to detect corrupt databases.  */
 157           if (resultbuf->canon != NULL
 158               && resultbuf->canon[ai_resp.canonlen - 1] != '\0')
 159             /* We cannot use the database.  */
 160             {
 161               if (mapped->head->gc_cycle != gc_cycle)
 162                 retval = -2;
 163               else
 164                 free (resultbuf);
 165               goto out_close;
 166             }
 167
 168           retval = 0;
 169           *result = resultbuf;
 170         }
 171     }
 172   else
 173     {
 174       if (__glibc_unlikely (ai_resp.found == -1))
 175         {
 176           /* The daemon does not cache this database.  */
 177           __nss_not_use_nscd_hosts = 1;
 178           goto out_close;
 179         }
 180
 181       /* Store the error number.  */
 182       *h_errnop = ai_resp.error;
 183
 184       /* Set errno to 0 to indicate no error, just no found record.  */
 185       __set_errno (0);
 186       /* Even though we have not found anything, the result is zero.  */
 187       retval = 0;
 188     }
 189
 190  out_close:
 191   if (sock != -1)
 192     __close_nocancel_nostatus (sock);
 193  out:
 194   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 195     {
 196       /* When we come here this means there has been a GC cycle while we
 197          were looking for the data.  This means the data might have been
 198          inconsistent.  Retry if possible.  */
 199       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 200         {
 201           /* nscd is just running gc now.  Disable using the mapping.  */
 202           if (atomic_decrement_val (&mapped->counter) == 0)
 203             __nscd_unmap (mapped);
 204           mapped = NO_MAPPING;
 205         }
 206
 207       if (retval != -1)
 208         {
 209           *result = NULL;
 210           free (resultbuf);
 211           goto retry;
 212         }
 213     }
 214
 215   return retval;
 216 }