nscd/nscd_gethst_r.c

   1 /* Copyright (C) 1998-2005, 2006, 2007, 2008, 2009
   2    Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, write to the Free
  18    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  19    02111-1307 USA.  */
  20
  21 #include <errno.h>
  22 #include <resolv.h>
  23 #include <stdio.h>
  24 #include <string.h>
  25 #include <arpa/nameser.h>
  26 #include <not-cancel.h>
  27
  28 #include "nscd-client.h"
  29 #include "nscd_proto.h"
  30
  31 int __nss_not_use_nscd_hosts;
  32
  33 static int nscd_gethst_r (const char *key, size_t keylen, request_type type,
  34                           struct hostent *resultbuf, char *buffer,
  35                           size_t buflen, struct hostent **result,
  36                           int *h_errnop) internal_function;
  37
  38
  39 int
  40 __nscd_gethostbyname_r (const char *name, struct hostent *resultbuf,
  41                         char *buffer, size_t buflen, struct hostent **result,
  42                         int *h_errnop)
  43 {
  44   request_type reqtype;
  45
  46   reqtype = (_res.options & RES_USE_INET6) ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  47
  48   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  49                         buffer, buflen, result, h_errnop);
  50 }
  51
  52
  53 int
  54 __nscd_gethostbyname2_r (const char *name, int af, struct hostent *resultbuf,
  55                          char *buffer, size_t buflen, struct hostent **result,
  56                          int *h_errnop)
  57 {
  58   request_type reqtype;
  59
  60   reqtype = af == AF_INET6 ? GETHOSTBYNAMEv6 : GETHOSTBYNAME;
  61
  62   return nscd_gethst_r (name, strlen (name) + 1, reqtype, resultbuf,
  63                         buffer, buflen, result, h_errnop);
  64 }
  65
  66
  67 int
  68 __nscd_gethostbyaddr_r (const void *addr, socklen_t len, int type,
  69                         struct hostent *resultbuf, char *buffer, size_t buflen,
  70                         struct hostent **result, int *h_errnop)
  71 {
  72   request_type reqtype;
  73
  74   if (!((len == INADDRSZ && type == AF_INET)
  75         || (len == IN6ADDRSZ && type == AF_INET6)))
  76     /* LEN and TYPE do not match.  */
  77     return -1;
  78
  79   reqtype = type == AF_INET6 ? GETHOSTBYADDRv6 : GETHOSTBYADDR;
  80
  81   return nscd_gethst_r (addr, len, reqtype, resultbuf, buffer, buflen, result,
  82                         h_errnop);
  83 }
  84
  85
  86 libc_locked_map_ptr (, __hst_map_handle) attribute_hidden;
  87 /* Note that we only free the structure if necessary.  The memory
  88    mapping is not removed since it is not visible to the malloc
  89    handling.  */
  90 libc_freeres_fn (hst_map_free)
  91 {
  92   if (__hst_map_handle.mapped != NO_MAPPING)
  93     {
  94       void *p = __hst_map_handle.mapped;
  95       __hst_map_handle.mapped = NO_MAPPING;
  96       free (p);
  97     }
  98 }
  99
 100
 101 int __nss_have_localdomain attribute_hidden;
 102
 103 static int
 104 internal_function
 105 nscd_gethst_r (const char *key, size_t keylen, request_type type,
 106                struct hostent *resultbuf, char *buffer, size_t buflen,
 107                struct hostent **result, int *h_errnop)
 108 {
 109   if (__builtin_expect (__nss_have_localdomain >= 0, 0))
 110     {
 111       if (__nss_have_localdomain == 0)
 112         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
 113       if (__nss_have_localdomain > 0)
 114         {
 115           __nss_not_use_nscd_hosts = 1;
 116           return -1;
 117         }
 118     }
 119
 120   int gc_cycle;
 121   int nretries = 0;
 122
 123   /* If the mapping is available, try to search there instead of
 124      communicating with the nscd.  */
 125   struct mapped_database *mapped;
 126   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
 127                                &gc_cycle);
 128
 129  retry:;
 130   const char *h_name = NULL;
 131   const uint32_t *aliases_len = NULL;
 132   const char *addr_list = NULL;
 133   size_t addr_list_len = 0;
 134   int retval = -1;
 135   const char *recend = (const char *) ~UINTMAX_C (0);
 136   int sock = -1;
 137   hst_response_header hst_resp;
 138   if (mapped != NO_MAPPING)
 139     {
 140       /* No const qualifier, as it can change during garbage collection.  */
 141       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped,
 142                                                     sizeof hst_resp);
 143       if (found != NULL)
 144         {
 145           h_name = (char *) (&found->data[0].hstdata + 1);
 146           hst_resp = found->data[0].hstdata;
 147           aliases_len = (uint32_t *) (h_name + hst_resp.h_name_len);
 148           addr_list = ((char *) aliases_len
 149                        + hst_resp.h_aliases_cnt * sizeof (uint32_t));
 150           addr_list_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 151           recend = (const char *) found->data + found->recsize;
 152           /* Now check if we can trust hst_resp fields.  If GC is
 153              in progress, it can contain anything.  */
 154           if (mapped->head->gc_cycle != gc_cycle)
 155             {
 156               retval = -2;
 157               goto out;
 158             }
 159
 160 #ifndef _STRING_ARCH_unaligned
 161           /* The aliases_len array in the mapped database might very
 162              well be unaligned.  We will access it word-wise so on
 163              platforms which do not tolerate unaligned accesses we
 164              need to make an aligned copy.  */
 165           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 166               != 0)
 167             {
 168               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 169                                       * sizeof (uint32_t));
 170               aliases_len = memcpy (tmp, aliases_len,
 171                                     hst_resp.h_aliases_cnt
 172                                     * sizeof (uint32_t));
 173             }
 174 #endif
 175           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 176             {
 177               if (hst_resp.h_length == INADDRSZ)
 178                 addr_list += addr_list_len;
 179               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 180             }
 181           if (__builtin_expect ((const char *) addr_list + addr_list_len
 182                                 > recend, 0))
 183             goto out;
 184         }
 185     }
 186
 187   if (h_name == NULL)
 188     {
 189       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 190                                  sizeof (hst_resp));
 191       if (sock == -1)
 192         {
 193           __nss_not_use_nscd_hosts = 1;
 194           goto out;
 195         }
 196     }
 197
 198   /* No value found so far.  */
 199   *result = NULL;
 200
 201   if (__builtin_expect (hst_resp.found == -1, 0))
 202     {
 203       /* The daemon does not cache this database.  */
 204       __nss_not_use_nscd_hosts = 1;
 205       goto out_close;
 206     }
 207
 208   if (hst_resp.found == 1)
 209     {
 210       char *cp = buffer;
 211       uintptr_t align1;
 212       uintptr_t align2;
 213       size_t total_len;
 214       ssize_t cnt;
 215       char *ignore;
 216       int n;
 217
 218       /* A first check whether the buffer is sufficiently large is possible.  */
 219       /* Now allocate the buffer the array for the group members.  We must
 220          align the pointer and the base of the h_addr_list pointers.  */
 221       align1 = ((__alignof__ (char *) - (cp - ((char *) 0)))
 222                 & (__alignof__ (char *) - 1));
 223       align2 = ((__alignof__ (char *) - ((cp + align1 + hst_resp.h_name_len)
 224                                          - ((char *) 0)))
 225                 & (__alignof__ (char *) - 1));
 226       if (buflen < (align1 + hst_resp.h_name_len + align2
 227                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 228                         + 2)
 229                        * sizeof (char *))
 230                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 231                                                   ? INADDRSZ : IN6ADDRSZ)))
 232         {
 233         no_room:
 234           *h_errnop = NETDB_INTERNAL;
 235           __set_errno (ERANGE);
 236           retval = ERANGE;
 237           goto out_close;
 238         }
 239       cp += align1;
 240
 241       /* Prepare the result as far as we can.  */
 242       resultbuf->h_aliases = (char **) cp;
 243       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 244       resultbuf->h_addr_list = (char **) cp;
 245       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 246
 247       resultbuf->h_name = cp;
 248       cp += hst_resp.h_name_len + align2;
 249
 250       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 251         {
 252           resultbuf->h_addrtype = AF_INET;
 253           resultbuf->h_length = INADDRSZ;
 254         }
 255       else
 256         {
 257           resultbuf->h_addrtype = AF_INET6;
 258           resultbuf->h_length = IN6ADDRSZ;
 259         }
 260       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 261         {
 262           resultbuf->h_addr_list[cnt] = cp;
 263           cp += resultbuf->h_length;
 264         }
 265       resultbuf->h_addr_list[cnt] = NULL;
 266
 267       if (h_name == NULL)
 268         {
 269           struct iovec vec[4];
 270
 271           vec[0].iov_base = resultbuf->h_name;
 272           vec[0].iov_len = hst_resp.h_name_len;
 273           total_len = hst_resp.h_name_len;
 274           n = 1;
 275
 276           if (hst_resp.h_aliases_cnt > 0)
 277             {
 278               aliases_len = alloca (hst_resp.h_aliases_cnt
 279                                     * sizeof (uint32_t));
 280               vec[n].iov_base = (void *) aliases_len;
 281               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 282
 283               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 284               ++n;
 285             }
 286
 287           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 288             {
 289               vec[n].iov_base = resultbuf->h_addr_list[0];
 290               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 291
 292               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 293
 294               ++n;
 295             }
 296           else
 297             {
 298               if (hst_resp.h_length == INADDRSZ)
 299                 {
 300                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 301                   vec[n].iov_base = ignore;
 302                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 303
 304                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 305
 306                   ++n;
 307                 }
 308
 309               vec[n].iov_base = resultbuf->h_addr_list[0];
 310               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 311
 312               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 313
 314               ++n;
 315             }
 316
 317           if ((size_t) __readvall (sock, vec, n) != total_len)
 318             goto out_close;
 319         }
 320       else
 321         {
 322           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 323           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 324         }
 325
 326       /*  Now we also can read the aliases.  */
 327       total_len = 0;
 328       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 329         {
 330           resultbuf->h_aliases[cnt] = cp;
 331           cp += aliases_len[cnt];
 332           total_len += aliases_len[cnt];
 333         }
 334       resultbuf->h_aliases[cnt] = NULL;
 335
 336       if (__builtin_expect ((const char *) addr_list + addr_list_len
 337                             + total_len > recend, 0))
 338         {
 339           /* aliases_len array might contain garbage during nscd GC cycle,
 340              retry rather than fail in that case.  */
 341           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 342             retval = -2;
 343           goto out_close;
 344         }
 345       /* See whether this would exceed the buffer capacity.  */
 346       if (__builtin_expect (cp > buffer + buflen, 0))
 347         {
 348           /* aliases_len array might contain garbage during nscd GC cycle,
 349              retry rather than fail in that case.  */
 350           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 351             {
 352               retval = -2;
 353               goto out_close;
 354             }
 355           goto no_room;
 356         }
 357
 358       /* And finally read the aliases.  */
 359       if (addr_list == NULL)
 360         {
 361           if (total_len == 0
 362               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 363                   == total_len))
 364             {
 365               retval = 0;
 366               *result = resultbuf;
 367             }
 368         }
 369       else
 370         {
 371           memcpy (resultbuf->h_aliases[0],
 372                   (const char *) addr_list + addr_list_len, total_len);
 373
 374           /* Try to detect corrupt databases.  */
 375           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 376               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 377                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 378                          != '\0')
 379                        break;
 380                    cnt < hst_resp.h_aliases_cnt; }))
 381             {
 382               /* We cannot use the database.  */
 383               if (mapped->head->gc_cycle != gc_cycle)
 384                 retval = -2;
 385               goto out_close;
 386             }
 387
 388           retval = 0;
 389           *result = resultbuf;
 390         }
 391     }
 392   else
 393     {
 394       /* Store the error number.  */
 395       *h_errnop = hst_resp.error;
 396
 397       /* Set errno to 0 to indicate no error, just no found record.  */
 398       __set_errno (0);
 399       /* Even though we have not found anything, the result is zero.  */
 400       retval = 0;
 401     }
 402
 403  out_close:
 404   if (sock != -1)
 405     close_not_cancel_no_status (sock);
 406  out:
 407   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 408     {
 409       /* When we come here this means there has been a GC cycle while we
 410          were looking for the data.  This means the data might have been
 411          inconsistent.  Retry if possible.  */
 412       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 413         {
 414           /* nscd is just running gc now.  Disable using the mapping.  */
 415           if (atomic_decrement_val (&mapped->counter) == 0)
 416             __nscd_unmap (mapped);
 417           mapped = NO_MAPPING;
 418         }
 419
 420       if (retval != -1)
 421         goto retry;
 422     }
 423
 424   return retval;
 425 }