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