nscd/nscd_gethst_r.c

   1 /* Copyright (C) 1998-2005, 2006, 2007 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   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 <resolv.h>
  24 #include <stdint.h>
  25 #include <stdio.h>
  26 #include <stdlib.h>
  27 #include <string.h>
  28 #include <unistd.h>
  29 #include <arpa/nameser.h>
  30 #include <not-cancel.h>
  31
  32 #include "nscd-client.h"
  33 #include "nscd_proto.h"
  34
  35 int __nss_not_use_nscd_hosts;
  36
  37 static int nscd_gethst_r (const char *key, size_t keylen, request_type type,
  38                           struct hostent *resultbuf, char *buffer,
  39                           size_t buflen, struct hostent **result,
  40                           int *h_errnop) internal_function;
  41
  42
  43 int
  44 __nscd_gethostbyname_r (const char *name, struct hostent *resultbuf,
  45                         char *buffer, size_t buflen, struct hostent **result,
  46                         int *h_errnop)
  47 {
  48   request_type reqtype;
  49
  50   reqtype = (_res.options & RES_USE_INET6) ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  51
  52   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  53                         buffer, buflen, result, h_errnop);
  54 }
  55
  56
  57 int
  58 __nscd_gethostbyname2_r (const char *name, int af, struct hostent *resultbuf,
  59                          char *buffer, size_t buflen, struct hostent **result,
  60                          int *h_errnop)
  61 {
  62   request_type reqtype;
  63
  64   reqtype = af == AF_INET6 ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  65
  66   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  67                         buffer, buflen, result, h_errnop);
  68 }
  69
  70
  71 int
  72 __nscd_gethostbyaddr_r (const void *addr, socklen_t len, int type,
  73                         struct hostent *resultbuf, char *buffer, size_t buflen,
  74                         struct hostent **result, int *h_errnop)
  75 {
  76   request_type reqtype;
  77
  78   if (!((len == INADDRSZ && type == AF_INET)
  79         || (len == IN6ADDRSZ && type == AF_INET6)))
  80     /* LEN and TYPE do not match.  */
  81     return -1;
  82
  83   reqtype = type == AF_INET6 ? GETHOSTBYADDRv6 : GETHOSTBYADDR;
  84
  85   return nscd_gethst_r (addr, len, reqtype, resultbuf, buffer, buflen, result,
  86                         h_errnop);
  87 }
  88
  89
  90 libc_locked_map_ptr (, __hst_map_handle) attribute_hidden;
  91 /* Note that we only free the structure if necessary.  The memory
  92    mapping is not removed since it is not visible to the malloc
  93    handling.  */
  94 libc_freeres_fn (hst_map_free)
  95 {
  96   if (__hst_map_handle.mapped != NO_MAPPING)
  97     {
  98       void *p = __hst_map_handle.mapped;
  99       __hst_map_handle.mapped = NO_MAPPING;
 100       free (p);
 101     }
 102 }
 103
 104
 105 static int
 106 internal_function
 107 nscd_gethst_r (const char *key, size_t keylen, request_type type,
 108                struct hostent *resultbuf, char *buffer, size_t buflen,
 109                struct hostent **result, int *h_errnop)
 110 {
 111   int gc_cycle;
 112   int nretries = 0;
 113
 114   /* If the mapping is available, try to search there instead of
 115      communicating with the nscd.  */
 116   struct mapped_database *mapped;
 117   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
 118                                &gc_cycle);
 119
 120  retry:;
 121   const char *h_name = NULL;
 122   const uint32_t *aliases_len = NULL;
 123   const char *addr_list = NULL;
 124   size_t addr_list_len = 0;
 125   int retval = -1;
 126   const char *recend = (const char *) ~UINTMAX_C (0);
 127   int sock = -1;
 128   hst_response_header hst_resp;
 129   if (mapped != NO_MAPPING)
 130     {
 131       /* No const qualifier, as it can change during garbage collection.  */
 132       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped);
 133       if (found != NULL)
 134         {
 135           h_name = (char *) (&found->data[0].hstdata + 1);
 136           hst_resp = found->data[0].hstdata;
 137           aliases_len = (uint32_t *) (h_name + hst_resp.h_name_len);
 138           addr_list = ((char *) aliases_len
 139                        + hst_resp.h_aliases_cnt * sizeof (uint32_t));
 140           addr_list_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 141           recend = (const char *) found->data + found->recsize;
 142           /* Now check if we can trust hst_resp fields.  If GC is
 143              in progress, it can contain anything.  */
 144           if (mapped->head->gc_cycle != gc_cycle)
 145             {
 146               retval = -2;
 147               goto out;
 148             }
 149
 150 #ifndef _STRING_ARCH_unaligned
 151           /* The aliases_len array in the mapped database might very
 152              well be unaligned.  We will access it word-wise so on
 153              platforms which do not tolerate unaligned accesses we
 154              need to make an aligned copy.  */
 155           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 156               != 0)
 157             {
 158               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 159                                       * sizeof (uint32_t));
 160               aliases_len = memcpy (tmp, aliases_len,
 161                                     hst_resp.h_aliases_cnt
 162                                     * sizeof (uint32_t));
 163             }
 164 #endif
 165           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 166             {
 167               if (hst_resp.h_length == INADDRSZ)
 168                 addr_list += addr_list_len;
 169               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 170             }
 171           if (__builtin_expect ((const char *) addr_list + addr_list_len
 172                                 > recend, 0))
 173             goto out;
 174         }
 175     }
 176
 177   if (h_name == NULL)
 178     {
 179       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 180                                  sizeof (hst_resp));
 181       if (sock == -1)
 182         {
 183           __nss_not_use_nscd_hosts = 1;
 184           goto out;
 185         }
 186     }
 187
 188   /* No value found so far.  */
 189   *result = NULL;
 190
 191   if (__builtin_expect (hst_resp.found == -1, 0))
 192     {
 193       /* The daemon does not cache this database.  */
 194       __nss_not_use_nscd_hosts = 1;
 195       goto out_close;
 196     }
 197
 198   if (hst_resp.found == 1)
 199     {
 200       struct iovec vec[4];
 201       char *cp = buffer;
 202       uintptr_t align1;
 203       uintptr_t align2;
 204       size_t total_len;
 205       ssize_t cnt;
 206       char *ignore;
 207       int n;
 208
 209       /* A first check whether the buffer is sufficiently large is possible.  */
 210       /* Now allocate the buffer the array for the group members.  We must
 211          align the pointer and the base of the h_addr_list pointers.  */
 212       align1 = ((__alignof__ (char *) - (cp - ((char *) 0)))
 213                 & (__alignof__ (char *) - 1));
 214       align2 = ((__alignof__ (char *) - ((cp + align1 + hst_resp.h_name_len)
 215                                          - ((char *) 0)))
 216                 & (__alignof__ (char *) - 1));
 217       if (buflen < (align1 + hst_resp.h_name_len + align2
 218                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 219                         + 2)
 220                        * sizeof (char *))
 221                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 222                                                   ? INADDRSZ : IN6ADDRSZ)))
 223         {
 224         no_room:
 225           *h_errnop = NETDB_INTERNAL;
 226           __set_errno (ERANGE);
 227           retval = ERANGE;
 228           goto out_close;
 229         }
 230       cp += align1;
 231
 232       /* Prepare the result as far as we can.  */
 233       resultbuf->h_aliases = (char **) cp;
 234       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 235       resultbuf->h_addr_list = (char **) cp;
 236       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 237
 238       resultbuf->h_name = cp;
 239       cp += hst_resp.h_name_len + align2;
 240
 241       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 242         {
 243           resultbuf->h_addrtype = AF_INET;
 244           resultbuf->h_length = INADDRSZ;
 245         }
 246       else
 247         {
 248           resultbuf->h_addrtype = AF_INET6;
 249           resultbuf->h_length = IN6ADDRSZ;
 250         }
 251       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 252         {
 253           resultbuf->h_addr_list[cnt] = cp;
 254           cp += resultbuf->h_length;
 255         }
 256       resultbuf->h_addr_list[cnt] = NULL;
 257
 258       if (h_name == NULL)
 259         {
 260           vec[0].iov_base = resultbuf->h_name;
 261           vec[0].iov_len = hst_resp.h_name_len;
 262           total_len = hst_resp.h_name_len;
 263           n = 1;
 264
 265           if (hst_resp.h_aliases_cnt > 0)
 266             {
 267               aliases_len = alloca (hst_resp.h_aliases_cnt
 268                                     * sizeof (uint32_t));
 269               vec[n].iov_base = (void *) aliases_len;
 270               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 271
 272               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 273               ++n;
 274             }
 275
 276           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 277             {
 278               vec[n].iov_base = resultbuf->h_addr_list[0];
 279               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 280
 281               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 282
 283               ++n;
 284             }
 285           else
 286             {
 287               if (hst_resp.h_length == INADDRSZ)
 288                 {
 289                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 290                   vec[n].iov_base = ignore;
 291                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 292
 293                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 294
 295                   ++n;
 296                 }
 297
 298               vec[n].iov_base = resultbuf->h_addr_list[0];
 299               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 300
 301               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 302
 303               ++n;
 304             }
 305
 306           if ((size_t) __readvall (sock, vec, n) != total_len)
 307             goto out_close;
 308         }
 309       else
 310         {
 311           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 312           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 313         }
 314
 315       /*  Now we also can read the aliases.  */
 316       total_len = 0;
 317       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 318         {
 319           resultbuf->h_aliases[cnt] = cp;
 320           cp += aliases_len[cnt];
 321           total_len += aliases_len[cnt];
 322         }
 323       resultbuf->h_aliases[cnt] = NULL;
 324
 325       if (__builtin_expect ((const char *) addr_list + addr_list_len
 326                             + total_len > recend, 0))
 327         {
 328           /* aliases_len array might contain garbage during nscd GC cycle,
 329              retry rather than fail in that case.  */
 330           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 331             retval = -2;
 332           goto out_close;
 333         }
 334       /* See whether this would exceed the buffer capacity.  */
 335       if (__builtin_expect (cp > buffer + buflen, 0))
 336         {
 337           /* aliases_len array might contain garbage during nscd GC cycle,
 338              retry rather than fail in that case.  */
 339           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 340             {
 341               retval = -2;
 342               goto out_close;
 343             }
 344           goto no_room;
 345         }
 346
 347       /* And finally read the aliases.  */
 348       if (addr_list == NULL)
 349         {
 350           if (total_len == 0
 351               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 352                   == total_len))
 353             {
 354               retval = 0;
 355               *result = resultbuf;
 356             }
 357         }
 358       else
 359         {
 360           memcpy (resultbuf->h_aliases[0],
 361                   (const char *) addr_list + addr_list_len, total_len);
 362
 363           /* Try to detect corrupt databases.  */
 364           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 365               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 366                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 367                          != '\0')
 368                        break;
 369                    cnt < hst_resp.h_aliases_cnt; }))
 370             {
 371               /* We cannot use the database.  */
 372               if (mapped->head->gc_cycle != gc_cycle)
 373                 retval = -2;
 374               goto out_close;
 375             }
 376
 377           retval = 0;
 378           *result = resultbuf;
 379         }
 380     }
 381   else
 382     {
 383       /* Store the error number.  */
 384       *h_errnop = hst_resp.error;
 385
 386       /* The `errno' to some value != ERANGE.  */
 387       __set_errno (ENOENT);
 388       /* Even though we have not found anything, the result is zero.  */
 389       retval = 0;
 390     }
 391
 392  out_close:
 393   if (sock != -1)
 394     close_not_cancel_no_status (sock);
 395  out:
 396   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 397     {
 398       /* When we come here this means there has been a GC cycle while we
 399          were looking for the data.  This means the data might have been
 400          inconsistent.  Retry if possible.  */
 401       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 402         {
 403           /* nscd is just running gc now.  Disable using the mapping.  */
 404           if (atomic_decrement_val (&mapped->counter) == 0)
 405             __nscd_unmap (mapped);
 406           mapped = NO_MAPPING;
 407         }
 408
 409       if (retval != -1)
 410         goto retry;
 411     }
 412
 413   return retval;
 414 }