nscd/nscd_gethst_r.c

   1 /* Copyright (C) 1998-2005, 2006, 2007, 2008 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 int __nss_have_localdomain attribute_hidden;
 101
 102 static int
 103 internal_function
 104 nscd_gethst_r (const char *key, size_t keylen, request_type type,
 105                struct hostent *resultbuf, char *buffer, size_t buflen,
 106                struct hostent **result, int *h_errnop)
 107 {
 108   if (__builtin_expect (__nss_have_localdomain >= 0, 0))
 109     {
 110       if (__nss_have_localdomain == 0)
 111         __nss_have_localdomain = getenv ("LOCALDOMAIN") != NULL ? 1 : -1;
 112       if (__nss_have_localdomain > 0)
 113         {
 114           __nss_not_use_nscd_hosts = 1;
 115           return -1;
 116         }
 117     }
 118
 119   int gc_cycle;
 120   int nretries = 0;
 121
 122   /* If the mapping is available, try to search there instead of
 123      communicating with the nscd.  */
 124   struct mapped_database *mapped;
 125   mapped = __nscd_get_map_ref (GETFDHST, "hosts", &__hst_map_handle,
 126                                &gc_cycle);
 127
 128  retry:;
 129   const char *h_name = NULL;
 130   const uint32_t *aliases_len = NULL;
 131   const char *addr_list = NULL;
 132   size_t addr_list_len = 0;
 133   int retval = -1;
 134   const char *recend = (const char *) ~UINTMAX_C (0);
 135   int sock = -1;
 136   hst_response_header hst_resp;
 137   if (mapped != NO_MAPPING)
 138     {
 139       /* No const qualifier, as it can change during garbage collection.  */
 140       struct datahead *found = __nscd_cache_search (type, key, keylen, mapped);
 141       if (found != NULL)
 142         {
 143           h_name = (char *) (&found->data[0].hstdata + 1);
 144           hst_resp = found->data[0].hstdata;
 145           aliases_len = (uint32_t *) (h_name + hst_resp.h_name_len);
 146           addr_list = ((char *) aliases_len
 147                        + hst_resp.h_aliases_cnt * sizeof (uint32_t));
 148           addr_list_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 149           recend = (const char *) found->data + found->recsize;
 150           /* Now check if we can trust hst_resp fields.  If GC is
 151              in progress, it can contain anything.  */
 152           if (mapped->head->gc_cycle != gc_cycle)
 153             {
 154               retval = -2;
 155               goto out;
 156             }
 157
 158 #ifndef _STRING_ARCH_unaligned
 159           /* The aliases_len array in the mapped database might very
 160              well be unaligned.  We will access it word-wise so on
 161              platforms which do not tolerate unaligned accesses we
 162              need to make an aligned copy.  */
 163           if (((uintptr_t) aliases_len & (__alignof__ (*aliases_len) - 1))
 164               != 0)
 165             {
 166               uint32_t *tmp = alloca (hst_resp.h_aliases_cnt
 167                                       * sizeof (uint32_t));
 168               aliases_len = memcpy (tmp, aliases_len,
 169                                     hst_resp.h_aliases_cnt
 170                                     * sizeof (uint32_t));
 171             }
 172 #endif
 173           if (type != GETHOSTBYADDR && type != GETHOSTBYNAME)
 174             {
 175               if (hst_resp.h_length == INADDRSZ)
 176                 addr_list += addr_list_len;
 177               addr_list_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 178             }
 179           if (__builtin_expect ((const char *) addr_list + addr_list_len
 180                                 > recend, 0))
 181             goto out;
 182         }
 183     }
 184
 185   if (h_name == NULL)
 186     {
 187       sock = __nscd_open_socket (key, keylen, type, &hst_resp,
 188                                  sizeof (hst_resp));
 189       if (sock == -1)
 190         {
 191           __nss_not_use_nscd_hosts = 1;
 192           goto out;
 193         }
 194     }
 195
 196   /* No value found so far.  */
 197   *result = NULL;
 198
 199   if (__builtin_expect (hst_resp.found == -1, 0))
 200     {
 201       /* The daemon does not cache this database.  */
 202       __nss_not_use_nscd_hosts = 1;
 203       goto out_close;
 204     }
 205
 206   if (hst_resp.found == 1)
 207     {
 208       char *cp = buffer;
 209       uintptr_t align1;
 210       uintptr_t align2;
 211       size_t total_len;
 212       ssize_t cnt;
 213       char *ignore;
 214       int n;
 215
 216       /* A first check whether the buffer is sufficiently large is possible.  */
 217       /* Now allocate the buffer the array for the group members.  We must
 218          align the pointer and the base of the h_addr_list pointers.  */
 219       align1 = ((__alignof__ (char *) - (cp - ((char *) 0)))
 220                 & (__alignof__ (char *) - 1));
 221       align2 = ((__alignof__ (char *) - ((cp + align1 + hst_resp.h_name_len)
 222                                          - ((char *) 0)))
 223                 & (__alignof__ (char *) - 1));
 224       if (buflen < (align1 + hst_resp.h_name_len + align2
 225                     + ((hst_resp.h_aliases_cnt + hst_resp.h_addr_list_cnt
 226                         + 2)
 227                        * sizeof (char *))
 228                     + hst_resp.h_addr_list_cnt * (type == AF_INET
 229                                                   ? INADDRSZ : IN6ADDRSZ)))
 230         {
 231         no_room:
 232           *h_errnop = NETDB_INTERNAL;
 233           __set_errno (ERANGE);
 234           retval = ERANGE;
 235           goto out_close;
 236         }
 237       cp += align1;
 238
 239       /* Prepare the result as far as we can.  */
 240       resultbuf->h_aliases = (char **) cp;
 241       cp += (hst_resp.h_aliases_cnt + 1) * sizeof (char *);
 242       resultbuf->h_addr_list = (char **) cp;
 243       cp += (hst_resp.h_addr_list_cnt + 1) * sizeof (char *);
 244
 245       resultbuf->h_name = cp;
 246       cp += hst_resp.h_name_len + align2;
 247
 248       if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 249         {
 250           resultbuf->h_addrtype = AF_INET;
 251           resultbuf->h_length = INADDRSZ;
 252         }
 253       else
 254         {
 255           resultbuf->h_addrtype = AF_INET6;
 256           resultbuf->h_length = IN6ADDRSZ;
 257         }
 258       for (cnt = 0; cnt < hst_resp.h_addr_list_cnt; ++cnt)
 259         {
 260           resultbuf->h_addr_list[cnt] = cp;
 261           cp += resultbuf->h_length;
 262         }
 263       resultbuf->h_addr_list[cnt] = NULL;
 264
 265       if (h_name == NULL)
 266         {
 267           struct iovec vec[4];
 268
 269           vec[0].iov_base = resultbuf->h_name;
 270           vec[0].iov_len = hst_resp.h_name_len;
 271           total_len = hst_resp.h_name_len;
 272           n = 1;
 273
 274           if (hst_resp.h_aliases_cnt > 0)
 275             {
 276               aliases_len = alloca (hst_resp.h_aliases_cnt
 277                                     * sizeof (uint32_t));
 278               vec[n].iov_base = (void *) aliases_len;
 279               vec[n].iov_len = hst_resp.h_aliases_cnt * sizeof (uint32_t);
 280
 281               total_len += hst_resp.h_aliases_cnt * sizeof (uint32_t);
 282               ++n;
 283             }
 284
 285           if (type == GETHOSTBYADDR || type == GETHOSTBYNAME)
 286             {
 287               vec[n].iov_base = resultbuf->h_addr_list[0];
 288               vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 289
 290               total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 291
 292               ++n;
 293             }
 294           else
 295             {
 296               if (hst_resp.h_length == INADDRSZ)
 297                 {
 298                   ignore = alloca (hst_resp.h_addr_list_cnt * INADDRSZ);
 299                   vec[n].iov_base = ignore;
 300                   vec[n].iov_len = hst_resp.h_addr_list_cnt * INADDRSZ;
 301
 302                   total_len += hst_resp.h_addr_list_cnt * INADDRSZ;
 303
 304                   ++n;
 305                 }
 306
 307               vec[n].iov_base = resultbuf->h_addr_list[0];
 308               vec[n].iov_len = hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 309
 310               total_len += hst_resp.h_addr_list_cnt * IN6ADDRSZ;
 311
 312               ++n;
 313             }
 314
 315           if ((size_t) __readvall (sock, vec, n) != total_len)
 316             goto out_close;
 317         }
 318       else
 319         {
 320           memcpy (resultbuf->h_name, h_name, hst_resp.h_name_len);
 321           memcpy (resultbuf->h_addr_list[0], addr_list, addr_list_len);
 322         }
 323
 324       /*  Now we also can read the aliases.  */
 325       total_len = 0;
 326       for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 327         {
 328           resultbuf->h_aliases[cnt] = cp;
 329           cp += aliases_len[cnt];
 330           total_len += aliases_len[cnt];
 331         }
 332       resultbuf->h_aliases[cnt] = NULL;
 333
 334       if (__builtin_expect ((const char *) addr_list + addr_list_len
 335                             + total_len > recend, 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             retval = -2;
 341           goto out_close;
 342         }
 343       /* See whether this would exceed the buffer capacity.  */
 344       if (__builtin_expect (cp > buffer + buflen, 0))
 345         {
 346           /* aliases_len array might contain garbage during nscd GC cycle,
 347              retry rather than fail in that case.  */
 348           if (addr_list != NULL && mapped->head->gc_cycle != gc_cycle)
 349             {
 350               retval = -2;
 351               goto out_close;
 352             }
 353           goto no_room;
 354         }
 355
 356       /* And finally read the aliases.  */
 357       if (addr_list == NULL)
 358         {
 359           if (total_len == 0
 360               || ((size_t) __readall (sock, resultbuf->h_aliases[0], total_len)
 361                   == total_len))
 362             {
 363               retval = 0;
 364               *result = resultbuf;
 365             }
 366         }
 367       else
 368         {
 369           memcpy (resultbuf->h_aliases[0],
 370                   (const char *) addr_list + addr_list_len, total_len);
 371
 372           /* Try to detect corrupt databases.  */
 373           if (resultbuf->h_name[hst_resp.h_name_len - 1] != '\0'
 374               || ({for (cnt = 0; cnt < hst_resp.h_aliases_cnt; ++cnt)
 375                      if (resultbuf->h_aliases[cnt][aliases_len[cnt] - 1]
 376                          != '\0')
 377                        break;
 378                    cnt < hst_resp.h_aliases_cnt; }))
 379             {
 380               /* We cannot use the database.  */
 381               if (mapped->head->gc_cycle != gc_cycle)
 382                 retval = -2;
 383               goto out_close;
 384             }
 385
 386           retval = 0;
 387           *result = resultbuf;
 388         }
 389     }
 390   else
 391     {
 392       /* Store the error number.  */
 393       *h_errnop = hst_resp.error;
 394
 395       /* Set errno to 0 to indicate no error, just no found record.  */
 396       __set_errno (0);
 397       /* Even though we have not found anything, the result is zero.  */
 398       retval = 0;
 399     }
 400
 401  out_close:
 402   if (sock != -1)
 403     close_not_cancel_no_status (sock);
 404  out:
 405   if (__nscd_drop_map_ref (mapped, &gc_cycle) != 0)
 406     {
 407       /* When we come here this means there has been a GC cycle while we
 408          were looking for the data.  This means the data might have been
 409          inconsistent.  Retry if possible.  */
 410       if ((gc_cycle & 1) != 0 || ++nretries == 5 || retval == -1)
 411         {
 412           /* nscd is just running gc now.  Disable using the mapping.  */
 413           if (atomic_decrement_val (&mapped->counter) == 0)
 414             __nscd_unmap (mapped);
 415           mapped = NO_MAPPING;
 416         }
 417
 418       if (retval != -1)
 419         goto retry;
 420     }
 421
 422   return retval;
 423 }