nscd/aicache.c

   1 /* Cache handling for host lookup.
   2    Copyright (C) 2004-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published
   7    by the Free Software Foundation; version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program 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
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, see <https://www.gnu.org/licenses/>.  */
  17
  18 #include <assert.h>
  19 #include <errno.h>
  20 #include <libintl.h>
  21 #include <netdb.h>
  22 #include <nss.h>
  23 #include <string.h>
  24 #include <time.h>
  25 #include <unistd.h>
  26 #include <sys/mman.h>
  27 #include <resolv/resolv-internal.h>
  28 #include <resolv/resolv_context.h>
  29 #include <scratch_buffer.h>
  30
  31 #include "dbg_log.h"
  32 #include "nscd.h"
  33
  34
  35 static const ai_response_header notfound =
  36 {
  37   .version = NSCD_VERSION,
  38   .found = 0,
  39   .naddrs = 0,
  40   .addrslen = 0,
  41   .canonlen = 0,
  42   .error = 0
  43 };
  44
  45
  46 static time_t
  47 addhstaiX (struct database_dyn *db, int fd, request_header *req,
  48            void *key, uid_t uid, struct hashentry *const he,
  49            struct datahead *dh)
  50 {
  51   /* Search for the entry matching the key.  Please note that we don't
  52      look again in the table whether the dataset is now available.  We
  53      simply insert it.  It does not matter if it is in there twice.  The
  54      pruning function only will look at the timestamp.  */
  55
  56   /* We allocate all data in one memory block: the iov vector,
  57      the response header and the dataset itself.  */
  58   struct dataset
  59   {
  60     struct datahead head;
  61     ai_response_header resp;
  62     char strdata[0];
  63   } *dataset = NULL;
  64
  65   if (__glibc_unlikely (debug_level > 0))
  66     {
  67       if (he == NULL)
  68         dbg_log (_("Haven't found \"%s\" in hosts cache!"), (char *) key);
  69       else
  70         dbg_log (_("Reloading \"%s\" in hosts cache!"), (char *) key);
  71     }
  72
  73   nss_action_list nip;
  74   int no_more;
  75   int rc6 = 0;
  76   int rc4 = 0;
  77   int herrno = 0;
  78
  79   no_more = !__nss_database_get (nss_database_hosts, &nip);
  80
  81   /* Initialize configurations.  */
  82   struct resolv_context *ctx = __resolv_context_get ();
  83   if (ctx == NULL)
  84     no_more = 1;
  85
  86   struct scratch_buffer tmpbuf6;
  87   scratch_buffer_init (&tmpbuf6);
  88   struct scratch_buffer tmpbuf4;
  89   scratch_buffer_init (&tmpbuf4);
  90   struct scratch_buffer canonbuf;
  91   scratch_buffer_init (&canonbuf);
  92
  93   int32_t ttl = INT32_MAX;
  94   ssize_t total = 0;
  95   char *key_copy = NULL;
  96   bool alloca_used = false;
  97   time_t timeout = MAX_TIMEOUT_VALUE;
  98
  99   while (!no_more)
 100     {
 101       void *cp;
 102       int status[2] = { NSS_STATUS_UNAVAIL, NSS_STATUS_UNAVAIL };
 103       int naddrs = 0;
 104       size_t addrslen = 0;
 105
 106       char *canon = NULL;
 107       size_t canonlen;
 108
 109       nss_gethostbyname4_r *fct4 = __nss_lookup_function (nip,
 110                                                           "gethostbyname4_r");
 111       if (fct4 != NULL)
 112         {
 113           struct gaih_addrtuple atmem;
 114           struct gaih_addrtuple *at;
 115           while (1)
 116             {
 117               at = &atmem;
 118               rc6 = 0;
 119               herrno = 0;
 120               status[1] = DL_CALL_FCT (fct4, (key, &at,
 121                                               tmpbuf6.data, tmpbuf6.length,
 122                                               &rc6, &herrno, &ttl));
 123               if (rc6 != ERANGE || (herrno != NETDB_INTERNAL
 124                                     && herrno != TRY_AGAIN))
 125                 break;
 126               if (!scratch_buffer_grow (&tmpbuf6))
 127                 {
 128                   rc6 = ENOMEM;
 129                   break;
 130                 }
 131             }
 132
 133           if (rc6 != 0 && herrno == NETDB_INTERNAL)
 134             goto out;
 135
 136           if (status[1] != NSS_STATUS_SUCCESS)
 137             goto next_nip;
 138
 139           /* We found the data.  Count the addresses and the size.  */
 140           for (const struct gaih_addrtuple *at2 = at = &atmem; at2 != NULL;
 141                at2 = at2->next)
 142             {
 143               ++naddrs;
 144               /* We do not handle anything other than IPv4 and IPv6
 145                  addresses.  The getaddrinfo implementation does not
 146                  either so it is not worth trying to do more.  */
 147               if (at2->family == AF_INET)
 148                 addrslen += INADDRSZ;
 149               else if (at2->family == AF_INET6)
 150                 addrslen += IN6ADDRSZ;
 151             }
 152           canon = at->name;
 153           canonlen = strlen (canon) + 1;
 154
 155           total = sizeof (*dataset) + naddrs + addrslen + canonlen;
 156
 157           /* Now we can allocate the data structure.  If the TTL of the
 158              entry is reported as zero do not cache the entry at all.  */
 159           if (ttl != 0 && he == NULL)
 160             dataset = (struct dataset *) mempool_alloc (db, total
 161                                                         + req->key_len, 1);
 162
 163           if (dataset == NULL)
 164             {
 165               /* We cannot permanently add the result in the moment.  But
 166                  we can provide the result as is.  Store the data in some
 167                  temporary memory.  */
 168               dataset = (struct dataset *) alloca (total + req->key_len);
 169
 170               /* We cannot add this record to the permanent database.  */
 171               alloca_used = true;
 172             }
 173
 174           /* Fill in the address and address families.  */
 175           char *addrs = dataset->strdata;
 176           uint8_t *family = (uint8_t *) (addrs + addrslen);
 177
 178           for (const struct gaih_addrtuple *at2 = at; at2 != NULL;
 179                at2 = at2->next)
 180             {
 181               *family++ = at2->family;
 182               if (at2->family == AF_INET)
 183                 addrs = mempcpy (addrs, at2->addr, INADDRSZ);
 184               else if (at2->family == AF_INET6)
 185                 addrs = mempcpy (addrs, at2->addr, IN6ADDRSZ);
 186             }
 187
 188           cp = family;
 189         }
 190       else
 191         {
 192           /* Prefer the function which also returns the TTL and
 193              canonical name.  */
 194           nss_gethostbyname3_r *fct
 195             = __nss_lookup_function (nip, "gethostbyname3_r");
 196           if (fct == NULL)
 197             fct = __nss_lookup_function (nip, "gethostbyname2_r");
 198
 199           if (fct == NULL)
 200             goto next_nip;
 201
 202           struct hostent th[2];
 203
 204           /* Collect IPv6 information first.  */
 205           while (1)
 206             {
 207               rc6 = 0;
 208               status[0] = DL_CALL_FCT (fct, (key, AF_INET6, &th[0],
 209                                              tmpbuf6.data, tmpbuf6.length,
 210                                              &rc6, &herrno, &ttl,
 211                                              &canon));
 212               if (rc6 != ERANGE || herrno != NETDB_INTERNAL)
 213                 break;
 214               if (!scratch_buffer_grow (&tmpbuf6))
 215                 {
 216                   rc6 = ENOMEM;
 217                   break;
 218                 }
 219             }
 220
 221           if (rc6 != 0 && herrno == NETDB_INTERNAL)
 222             goto out;
 223
 224           /* Next collect IPv4 information.  */
 225           while (1)
 226             {
 227               rc4 = 0;
 228               status[1] = DL_CALL_FCT (fct, (key, AF_INET, &th[1],
 229                                              tmpbuf4.data, tmpbuf4.length,
 230                                              &rc4, &herrno,
 231                                              ttl == INT32_MAX ? &ttl : NULL,
 232                                              canon == NULL ? &canon : NULL));
 233               if (rc4 != ERANGE || herrno != NETDB_INTERNAL)
 234                 break;
 235               if (!scratch_buffer_grow (&tmpbuf4))
 236                 {
 237                   rc4 = ENOMEM;
 238                   break;
 239                 }
 240             }
 241
 242           if (rc4 != 0 && herrno == NETDB_INTERNAL)
 243             goto out;
 244
 245           if (status[0] != NSS_STATUS_SUCCESS
 246               && status[1] != NSS_STATUS_SUCCESS)
 247             goto next_nip;
 248
 249           /* We found the data.  Count the addresses and the size.  */
 250           for (int j = 0; j < 2; ++j)
 251             if (status[j] == NSS_STATUS_SUCCESS)
 252               for (int i = 0; th[j].h_addr_list[i] != NULL; ++i)
 253                 {
 254                   ++naddrs;
 255                   addrslen += th[j].h_length;
 256                 }
 257
 258           if (canon == NULL)
 259             {
 260               /* Determine the canonical name.  */
 261               nss_getcanonname_r *cfct;
 262               cfct = __nss_lookup_function (nip, "getcanonname_r");
 263               if (cfct != NULL)
 264                 {
 265                   char *s;
 266                   int rc;
 267
 268                   if (DL_CALL_FCT (cfct, (key, canonbuf.data, canonbuf.length,
 269                                           &s, &rc, &herrno))
 270                       == NSS_STATUS_SUCCESS)
 271                     canon = s;
 272                   else
 273                     /* Set to name now to avoid using gethostbyaddr.  */
 274                     canon = key;
 275                 }
 276               else
 277                 {
 278                   struct hostent *hstent = NULL;
 279                   int herrno;
 280                   struct hostent hstent_mem;
 281                   void *addr;
 282                   size_t addrlen;
 283                   int addrfamily;
 284
 285                   if (status[1] == NSS_STATUS_SUCCESS)
 286                     {
 287                       addr = th[1].h_addr_list[0];
 288                       addrlen = sizeof (struct in_addr);
 289                       addrfamily = AF_INET;
 290                     }
 291                   else
 292                     {
 293                       addr = th[0].h_addr_list[0];
 294                       addrlen = sizeof (struct in6_addr);
 295                       addrfamily = AF_INET6;
 296                     }
 297
 298                   int rc;
 299                   while (1)
 300                     {
 301                       rc = __gethostbyaddr2_r (addr, addrlen, addrfamily,
 302                                                &hstent_mem,
 303                                                canonbuf.data, canonbuf.length,
 304                                                &hstent, &herrno, NULL);
 305                       if (rc != ERANGE || herrno != NETDB_INTERNAL)
 306                         break;
 307                       if (!scratch_buffer_grow (&canonbuf))
 308                         {
 309                           rc = ENOMEM;
 310                           break;
 311                         }
 312                     }
 313
 314                   if (rc == 0)
 315                     {
 316                       if (hstent != NULL)
 317                         canon = hstent->h_name;
 318                       else
 319                         canon = key;
 320                     }
 321                 }
 322             }
 323
 324           canonlen = canon == NULL ? 0 : (strlen (canon) + 1);
 325
 326           total = sizeof (*dataset) + naddrs + addrslen + canonlen;
 327
 328
 329           /* Now we can allocate the data structure.  If the TTL of the
 330              entry is reported as zero do not cache the entry at all.  */
 331           if (ttl != 0 && he == NULL)
 332             dataset = (struct dataset *) mempool_alloc (db, total
 333                                                         + req->key_len, 1);
 334
 335           if (dataset == NULL)
 336             {
 337               /* We cannot permanently add the result in the moment.  But
 338                  we can provide the result as is.  Store the data in some
 339                  temporary memory.  */
 340               dataset = (struct dataset *) alloca (total + req->key_len);
 341
 342               /* We cannot add this record to the permanent database.  */
 343               alloca_used = true;
 344             }
 345
 346           /* Fill in the address and address families.  */
 347           char *addrs = dataset->strdata;
 348           uint8_t *family = (uint8_t *) (addrs + addrslen);
 349
 350           for (int j = 0; j < 2; ++j)
 351             if (status[j] == NSS_STATUS_SUCCESS)
 352               for (int i = 0; th[j].h_addr_list[i] != NULL; ++i)
 353                 {
 354                   addrs = mempcpy (addrs, th[j].h_addr_list[i],
 355                                    th[j].h_length);
 356                   *family++ = th[j].h_addrtype;
 357                 }
 358
 359           cp = family;
 360         }
 361
 362       timeout = datahead_init_pos (&dataset->head, total + req->key_len,
 363                                    total - offsetof (struct dataset, resp),
 364                                    he == NULL ? 0 : dh->nreloads + 1,
 365                                    ttl == INT32_MAX ? db->postimeout : ttl);
 366
 367       /* Fill in the rest of the dataset.  */
 368       dataset->resp.version = NSCD_VERSION;
 369       dataset->resp.found = 1;
 370       dataset->resp.naddrs = naddrs;
 371       dataset->resp.addrslen = addrslen;
 372       dataset->resp.canonlen = canonlen;
 373       dataset->resp.error = NETDB_SUCCESS;
 374
 375       if (canon != NULL)
 376         cp = mempcpy (cp, canon, canonlen);
 377
 378       key_copy = memcpy (cp, key, req->key_len);
 379
 380       assert (cp == (char *) dataset + total);
 381
 382       /* Now we can determine whether on refill we have to create a
 383          new record or not.  */
 384       if (he != NULL)
 385         {
 386           assert (fd == -1);
 387
 388           if (total + req->key_len == dh->allocsize
 389               && total - offsetof (struct dataset, resp) == dh->recsize
 390               && memcmp (&dataset->resp, dh->data,
 391                          dh->allocsize - offsetof (struct dataset,
 392                                                    resp)) == 0)
 393             {
 394               /* The data has not changed.  We will just bump the
 395                  timeout value.  Note that the new record has been
 396                  allocated on the stack and need not be freed.  */
 397               dh->timeout = dataset->head.timeout;
 398               dh->ttl = dataset->head.ttl;
 399               ++dh->nreloads;
 400             }
 401           else
 402             {
 403               /* We have to create a new record.  Just allocate
 404                  appropriate memory and copy it.  */
 405               struct dataset *newp
 406                 = (struct dataset *) mempool_alloc (db, total + req->key_len,
 407                                                     1);
 408               if (__glibc_likely (newp != NULL))
 409                 {
 410                   /* Adjust pointer into the memory block.  */
 411                   key_copy = (char *) newp + (key_copy - (char *) dataset);
 412
 413                   dataset = memcpy (newp, dataset, total + req->key_len);
 414                   alloca_used = false;
 415                 }
 416
 417               /* Mark the old record as obsolete.  */
 418               dh->usable = false;
 419             }
 420         }
 421       else
 422         {
 423           /* We write the dataset before inserting it to the database
 424              since while inserting this thread might block and so
 425              would unnecessarily let the receiver wait.  */
 426           assert (fd != -1);
 427
 428           writeall (fd, &dataset->resp, dataset->head.recsize);
 429         }
 430
 431       goto out;
 432
 433 next_nip:
 434       if (nss_next_action (nip, status[1]) == NSS_ACTION_RETURN)
 435         break;
 436
 437       if (nip[1].module == NULL)
 438         no_more = -1;
 439       else
 440         ++nip;
 441     }
 442
 443   /* No result found.  Create a negative result record.  */
 444   if (he != NULL && rc4 == EAGAIN)
 445     {
 446       /* If we have an old record available but cannot find one now
 447          because the service is not available we keep the old record
 448          and make sure it does not get removed.  */
 449       if (reload_count != UINT_MAX && dh->nreloads == reload_count)
 450         /* Do not reset the value if we never not reload the record.  */
 451         dh->nreloads = reload_count - 1;
 452
 453       /* Reload with the same time-to-live value.  */
 454       timeout = dh->timeout = time (NULL) + dh->ttl;
 455     }
 456   else
 457     {
 458       /* We have no data.  This means we send the standard reply for
 459          this case.  */
 460       total = sizeof (notfound);
 461
 462       if (fd != -1)
 463         TEMP_FAILURE_RETRY (send (fd, &notfound, total, MSG_NOSIGNAL));
 464
 465       /* If we have a transient error or cannot permanently store the
 466          result, so be it.  */
 467       if (rc4 == EAGAIN || __builtin_expect (db->negtimeout == 0, 0))
 468         {
 469           /* Mark the old entry as obsolete.  */
 470           if (dh != NULL)
 471             dh->usable = false;
 472           dataset = NULL;
 473         }
 474       else if ((dataset = mempool_alloc (db, (sizeof (struct dataset)
 475                                               + req->key_len), 1)) != NULL)
 476         {
 477           timeout = datahead_init_neg (&dataset->head,
 478                                        sizeof (struct dataset) + req->key_len,
 479                                        total, db->negtimeout);
 480
 481           /* This is the reply.  */
 482           memcpy (&dataset->resp, &notfound, total);
 483
 484           /* Copy the key data.  */
 485           key_copy = memcpy (dataset->strdata, key, req->key_len);
 486         }
 487    }
 488
 489  out:
 490   __resolv_context_put (ctx);
 491
 492   if (dataset != NULL && !alloca_used)
 493     {
 494       /* If necessary, we also propagate the data to disk.  */
 495       if (db->persistent)
 496         {
 497           // XXX async OK?
 498           uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
 499           msync ((void *) pval,
 500                  ((uintptr_t) dataset & pagesize_m1) + total + req->key_len,
 501                  MS_ASYNC);
 502         }
 503
 504       (void) cache_add (req->type, key_copy, req->key_len, &dataset->head,
 505                         true, db, uid, he == NULL);
 506
 507       pthread_rwlock_unlock (&db->lock);
 508
 509       /* Mark the old entry as obsolete.  */
 510       if (dh != NULL)
 511         dh->usable = false;
 512     }
 513
 514   scratch_buffer_free (&tmpbuf6);
 515   scratch_buffer_free (&tmpbuf4);
 516   scratch_buffer_free (&canonbuf);
 517
 518   return timeout;
 519 }
 520
 521
 522 void
 523 addhstai (struct database_dyn *db, int fd, request_header *req, void *key,
 524           uid_t uid)
 525 {
 526   addhstaiX (db, fd, req, key, uid, NULL, NULL);
 527 }
 528
 529
 530 time_t
 531 readdhstai (struct database_dyn *db, struct hashentry *he, struct datahead *dh)
 532 {
 533   request_header req =
 534     {
 535       .type = GETAI,
 536       .key_len = he->len
 537     };
 538
 539   return addhstaiX (db, -1, &req, db->data + he->key, he->owner, he, dh);
 540 }