nscd/nscd_helper.c

   1 /* Copyright (C) 1998-2002,2003,2004,2005,2006,2007
   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 <assert.h>
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <stdbool.h>
  25 #include <string.h>
  26 #include <time.h>
  27 #include <unistd.h>
  28 #include <sys/mman.h>
  29 #include <sys/poll.h>
  30 #include <sys/socket.h>
  31 #include <sys/stat.h>
  32 #include <sys/time.h>
  33 #include <sys/uio.h>
  34 #include <sys/un.h>
  35 #include <not-cancel.h>
  36 #include <nis/rpcsvc/nis.h>
  37
  38 #include "nscd-client.h"
  39
  40
  41 ssize_t
  42 __readall (int fd, void *buf, size_t len)
  43 {
  44   size_t n = len;
  45   ssize_t ret;
  46   do
  47     {
  48       ret = TEMP_FAILURE_RETRY (__read (fd, buf, n));
  49       if (ret <= 0)
  50         break;
  51       buf = (char *) buf + ret;
  52       n -= ret;
  53     }
  54   while (n > 0);
  55   return ret < 0 ? ret : len - n;
  56 }
  57
  58
  59 ssize_t
  60 __readvall (int fd, const struct iovec *iov, int iovcnt)
  61 {
  62   ssize_t ret = TEMP_FAILURE_RETRY (__readv (fd, iov, iovcnt));
  63   if (ret <= 0)
  64     return ret;
  65
  66   size_t total = 0;
  67   for (int i = 0; i < iovcnt; ++i)
  68     total += iov[i].iov_len;
  69
  70   if (ret < total)
  71     {
  72       struct iovec iov_buf[iovcnt];
  73       ssize_t r = ret;
  74
  75       struct iovec *iovp = memcpy (iov_buf, iov, iovcnt * sizeof (*iov));
  76       do
  77         {
  78           while (iovp->iov_len <= r)
  79             {
  80               r -= iovp->iov_len;
  81               --iovcnt;
  82               ++iovp;
  83             }
  84           iovp->iov_base = (char *) iovp->iov_base + r;
  85           iovp->iov_len -= r;
  86           r = TEMP_FAILURE_RETRY (__readv (fd, iovp, iovcnt));
  87           if (r <= 0)
  88             break;
  89           ret += r;
  90         }
  91       while (ret < total);
  92       if (r < 0)
  93         ret = r;
  94     }
  95   return ret;
  96 }
  97
  98
  99 static int
 100 open_socket (request_type type, const char *key, size_t keylen)
 101 {
 102   int sock = __socket (PF_UNIX, SOCK_STREAM, 0);
 103   if (sock < 0)
 104     return -1;
 105
 106   struct
 107   {
 108     request_header req;
 109     char key[keylen];
 110   } reqdata;
 111   size_t real_sizeof_reqdata = sizeof (request_header) + keylen;
 112
 113   /* Make socket non-blocking.  */
 114   __fcntl (sock, F_SETFL, O_RDWR | O_NONBLOCK);
 115
 116   struct sockaddr_un sun;
 117   sun.sun_family = AF_UNIX;
 118   strcpy (sun.sun_path, _PATH_NSCDSOCKET);
 119   if (__connect (sock, (struct sockaddr *) &sun, sizeof (sun)) < 0
 120       && errno != EINPROGRESS)
 121     goto out;
 122
 123   reqdata.req.version = NSCD_VERSION;
 124   reqdata.req.type = type;
 125   reqdata.req.key_len = keylen;
 126
 127   memcpy (reqdata.key, key, keylen);
 128
 129   bool first_try = true;
 130   struct timeval tvend;
 131   /* Fake initializing tvend.  */
 132   asm ("" : "=m" (tvend));
 133   while (1)
 134     {
 135 #ifndef MSG_NOSIGNAL
 136 # define MSG_NOSIGNAL 0
 137 #endif
 138       ssize_t wres = TEMP_FAILURE_RETRY (__send (sock, &reqdata,
 139                                                  real_sizeof_reqdata,
 140                                                  MSG_NOSIGNAL));
 141       if (__builtin_expect (wres == (ssize_t) real_sizeof_reqdata, 1))
 142         /* We managed to send the request.  */
 143         return sock;
 144
 145       if (wres != -1 || errno != EAGAIN)
 146         /* Something is really wrong, no chance to continue.  */
 147         break;
 148
 149       /* The daemon is busy wait for it.  */
 150       int to;
 151       struct timeval now;
 152       (void) __gettimeofday (&now, NULL);
 153       if (first_try)
 154         {
 155           tvend.tv_usec = now.tv_usec;
 156           tvend.tv_sec = now.tv_sec + 5;
 157           to = 5 * 1000;
 158           first_try = false;
 159         }
 160       else
 161         to = ((tvend.tv_sec - now.tv_sec) * 1000
 162               + (tvend.tv_usec - now.tv_usec) / 1000);
 163
 164       struct pollfd fds[1];
 165       fds[0].fd = sock;
 166       fds[0].events = POLLOUT | POLLERR | POLLHUP;
 167       if (__poll (fds, 1, to) <= 0)
 168         /* The connection timed out or broke down.  */
 169         break;
 170
 171       /* We try to write again.  */
 172     }
 173
 174  out:
 175   close_not_cancel_no_status (sock);
 176
 177   return -1;
 178 }
 179
 180
 181 void
 182 __nscd_unmap (struct mapped_database *mapped)
 183 {
 184   assert (mapped->counter == 0);
 185   __munmap ((void *) mapped->head, mapped->mapsize);
 186   free (mapped);
 187 }
 188
 189
 190 static int
 191 wait_on_socket (int sock)
 192 {
 193   struct pollfd fds[1];
 194   fds[0].fd = sock;
 195   fds[0].events = POLLIN | POLLERR | POLLHUP;
 196   int n = __poll (fds, 1, 5 * 1000);
 197   if (n == -1 && __builtin_expect (errno == EINTR, 0))
 198     {
 199       /* Handle the case where the poll() call is interrupted by a
 200          signal.  We cannot just use TEMP_FAILURE_RETRY since it might
 201          lead to infinite loops.  */
 202       struct timeval now;
 203       (void) __gettimeofday (&now, NULL);
 204       long int end = (now.tv_sec + 5) * 1000 + (now.tv_usec + 500) / 1000;
 205       while (1)
 206         {
 207           long int timeout = end - (now.tv_sec * 1000
 208                                     + (now.tv_usec + 500) / 1000);
 209           n = __poll (fds, 1, timeout);
 210           if (n != -1 || errno != EINTR)
 211             break;
 212           (void) __gettimeofday (&now, NULL);
 213         }
 214     }
 215
 216   return n;
 217 }
 218
 219
 220 /* Try to get a file descriptor for the shared meory segment
 221    containing the database.  */
 222 static struct mapped_database *
 223 get_mapping (request_type type, const char *key,
 224              struct mapped_database **mappedp)
 225 {
 226   struct mapped_database *result = NO_MAPPING;
 227 #ifdef SCM_RIGHTS
 228   const size_t keylen = strlen (key) + 1;
 229   int saved_errno = errno;
 230
 231   int mapfd = -1;
 232   char resdata[keylen];
 233
 234   /* Open a socket and send the request.  */
 235   int sock = open_socket (type, key, keylen);
 236   if (sock < 0)
 237     goto out;
 238
 239   /* Room for the data sent along with the file descriptor.  We expect
 240      the key name back.  */
 241   struct iovec iov[1];
 242   iov[0].iov_base = resdata;
 243   iov[0].iov_len = keylen;
 244
 245   union
 246   {
 247     struct cmsghdr hdr;
 248     char bytes[CMSG_SPACE (sizeof (int))];
 249   } buf;
 250   struct msghdr msg = { .msg_iov = iov, .msg_iovlen = 1,
 251                         .msg_control = buf.bytes,
 252                         .msg_controllen = sizeof (buf) };
 253   struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg);
 254
 255   cmsg->cmsg_level = SOL_SOCKET;
 256   cmsg->cmsg_type = SCM_RIGHTS;
 257   cmsg->cmsg_len = CMSG_LEN (sizeof (int));
 258
 259   /* This access is well-aligned since BUF is correctly aligned for an
 260      int and CMSG_DATA preserves this alignment.  */
 261   *(int *) CMSG_DATA (cmsg) = -1;
 262
 263   msg.msg_controllen = cmsg->cmsg_len;
 264
 265   if (wait_on_socket (sock) <= 0)
 266     goto out_close2;
 267
 268 # ifndef MSG_CMSG_CLOEXEC
 269 #  define MSG_CMSG_CLOEXEC 0
 270 # endif
 271   if (__builtin_expect (TEMP_FAILURE_RETRY (__recvmsg (sock, &msg,
 272                                                        MSG_CMSG_CLOEXEC))
 273                         != keylen, 0))
 274     goto out_close2;
 275
 276   if (__builtin_expect (CMSG_FIRSTHDR (&msg) == NULL
 277                         || (CMSG_FIRSTHDR (&msg)->cmsg_len
 278                             != CMSG_LEN (sizeof (int))), 0))
 279     goto out_close2;
 280
 281   mapfd = *(int *) CMSG_DATA (cmsg);
 282
 283   struct stat64 st;
 284   if (__builtin_expect (strcmp (resdata, key) != 0, 0)
 285       || __builtin_expect (fstat64 (mapfd, &st) != 0, 0)
 286       || __builtin_expect (st.st_size < sizeof (struct database_pers_head), 0))
 287     goto out_close;
 288
 289   struct database_pers_head head;
 290   if (__builtin_expect (TEMP_FAILURE_RETRY (__pread (mapfd, &head,
 291                                                      sizeof (head), 0))
 292                         != sizeof (head), 0))
 293     goto out_close;
 294
 295   if (__builtin_expect (head.version != DB_VERSION, 0)
 296       || __builtin_expect (head.header_size != sizeof (head), 0)
 297       /* This really should not happen but who knows, maybe the update
 298          thread got stuck.  */
 299       || __builtin_expect (! head.nscd_certainly_running
 300                            && head.timestamp + MAPPING_TIMEOUT < time (NULL),
 301                            0))
 302     goto out_close;
 303
 304   size_t size = (sizeof (head) + roundup (head.module * sizeof (ref_t), ALIGN)
 305                  + head.data_size);
 306
 307   if (__builtin_expect (st.st_size < size, 0))
 308     goto out_close;
 309
 310   /* The file is large enough, map it now.  */
 311   void *mapping = __mmap (NULL, size, PROT_READ, MAP_SHARED, mapfd, 0);
 312   if (__builtin_expect (mapping != MAP_FAILED, 1))
 313     {
 314       /* Allocate a record for the mapping.  */
 315       struct mapped_database *newp = malloc (sizeof (*newp));
 316       if (newp == NULL)
 317         {
 318           /* Ugh, after all we went through the memory allocation failed.  */
 319           __munmap (mapping, size);
 320           goto out_close;
 321         }
 322
 323       newp->head = mapping;
 324       newp->data = ((char *) mapping + head.header_size
 325                     + roundup (head.module * sizeof (ref_t), ALIGN));
 326       newp->mapsize = size;
 327       newp->datasize = head.data_size;
 328       /* Set counter to 1 to show it is usable.  */
 329       newp->counter = 1;
 330
 331       result = newp;
 332     }
 333
 334  out_close:
 335   __close (mapfd);
 336  out_close2:
 337   __close (sock);
 338  out:
 339   __set_errno (saved_errno);
 340 #endif  /* SCM_RIGHTS */
 341
 342   struct mapped_database *oldval = *mappedp;
 343   *mappedp = result;
 344
 345   if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
 346     __nscd_unmap (oldval);
 347
 348   return result;
 349 }
 350
 351
 352 struct mapped_database *
 353 __nscd_get_map_ref (request_type type, const char *name,
 354                     volatile struct locked_map_ptr *mapptr, int *gc_cyclep)
 355 {
 356   struct mapped_database *cur = mapptr->mapped;
 357   if (cur == NO_MAPPING)
 358     return cur;
 359
 360   int cnt = 0;
 361   while (__builtin_expect (atomic_compare_and_exchange_val_acq (&mapptr->lock,
 362                                                                 1, 0) != 0, 0))
 363     {
 364       // XXX Best number of rounds?
 365       if (__builtin_expect (++cnt > 5, 0))
 366         return NO_MAPPING;
 367
 368       atomic_delay ();
 369     }
 370
 371   cur = mapptr->mapped;
 372
 373   if (__builtin_expect (cur != NO_MAPPING, 1))
 374     {
 375       /* If not mapped or timestamp not updated, request new map.  */
 376       if (cur == NULL
 377           || (cur->head->nscd_certainly_running == 0
 378               && cur->head->timestamp + MAPPING_TIMEOUT < time (NULL))
 379           || cur->head->data_size > cur->datasize)
 380         cur = get_mapping (type, name,
 381                            (struct mapped_database **) &mapptr->mapped);
 382
 383       if (__builtin_expect (cur != NO_MAPPING, 1))
 384         {
 385           if (__builtin_expect (((*gc_cyclep = cur->head->gc_cycle) & 1) != 0,
 386                                 0))
 387             cur = NO_MAPPING;
 388           else
 389             atomic_increment (&cur->counter);
 390         }
 391     }
 392
 393   mapptr->lock = 0;
 394
 395   return cur;
 396 }
 397
 398
 399 /* Don't return const struct datahead *, as eventhough the record
 400    is normally constant, it can change arbitrarily during nscd
 401    garbage collection.  */
 402 struct datahead *
 403 __nscd_cache_search (request_type type, const char *key, size_t keylen,
 404                      const struct mapped_database *mapped)
 405 {
 406   unsigned long int hash = __nis_hash (key, keylen) % mapped->head->module;
 407   size_t datasize = mapped->datasize;
 408
 409   ref_t work = mapped->head->array[hash];
 410   while (work != ENDREF && work + sizeof (struct hashentry) <= datasize)
 411     {
 412       struct hashentry *here = (struct hashentry *) (mapped->data + work);
 413
 414 #ifndef _STRING_ARCH_unaligned
 415       /* Although during garbage collection when moving struct hashentry
 416          records around we first copy from old to new location and then
 417          adjust pointer from previous hashentry to it, there is no barrier
 418          between those memory writes.  It is very unlikely to hit it,
 419          so check alignment only if a misaligned load can crash the
 420          application.  */
 421       if ((uintptr_t) here & (__alignof__ (*here) - 1))
 422         return NULL;
 423 #endif
 424
 425       if (type == here->type
 426           && keylen == here->len
 427           && here->key + keylen <= datasize
 428           && memcmp (key, mapped->data + here->key, keylen) == 0
 429           && here->packet + sizeof (struct datahead) <= datasize)
 430         {
 431           /* We found the entry.  Increment the appropriate counter.  */
 432           struct datahead *dh
 433             = (struct datahead *) (mapped->data + here->packet);
 434
 435 #ifndef _STRING_ARCH_unaligned
 436           if ((uintptr_t) dh & (__alignof__ (*dh) - 1))
 437             return NULL;
 438 #endif
 439
 440           /* See whether we must ignore the entry or whether something
 441              is wrong because garbage collection is in progress.  */
 442           if (dh->usable && here->packet + dh->allocsize <= datasize)
 443             return dh;
 444         }
 445
 446       work = here->next;
 447     }
 448
 449   return NULL;
 450 }
 451
 452
 453 /* Create a socket connected to a name. */
 454 int
 455 __nscd_open_socket (const char *key, size_t keylen, request_type type,
 456                     void *response, size_t responselen)
 457 {
 458   /* This should never happen and it is something the nscd daemon
 459      enforces, too.  He it helps to limit the amount of stack
 460      used.  */
 461   if (keylen > MAXKEYLEN)
 462     return -1;
 463
 464   int saved_errno = errno;
 465
 466   int sock = open_socket (type, key, keylen);
 467   if (sock >= 0)
 468     {
 469       /* Wait for data.  */
 470       if (wait_on_socket (sock) > 0)
 471         {
 472           ssize_t nbytes = TEMP_FAILURE_RETRY (__read (sock, response,
 473                                                        responselen));
 474           if (nbytes == (ssize_t) responselen)
 475             return sock;
 476         }
 477
 478       close_not_cancel_no_status (sock);
 479     }
 480
 481   __set_errno (saved_errno);
 482
 483   return -1;
 484 }