nscd/nscd_helper.c

   1 /* Copyright (C) 1998-2002, 2003, 2004 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 <assert.h>
  21 #include <errno.h>
  22 #include <fcntl.h>
  23 #include <stdbool.h>
  24 #include <unistd.h>
  25 #include <sys/mman.h>
  26 #include <sys/poll.h>
  27 #include <sys/socket.h>
  28 #include <sys/stat.h>
  29 #include <sys/uio.h>
  30 #include <sys/un.h>
  31 #include <not-cancel.h>
  32 #include <nis/rpcsvc/nis.h>
  33
  34 #include "nscd-client.h"
  35
  36
  37 ssize_t
  38 __readall (int fd, void *buf, size_t len)
  39 {
  40   size_t n = len;
  41   ssize_t ret;
  42   do
  43     {
  44       ret = TEMP_FAILURE_RETRY (__read (fd, buf, n));
  45       if (ret <= 0)
  46         break;
  47       buf = (char *) buf + ret;
  48       n -= ret;
  49     }
  50   while (n > 0);
  51   return ret < 0 ? ret : len - n;
  52 }
  53
  54
  55 ssize_t
  56 __readvall (int fd, const struct iovec *iov, int iovcnt)
  57 {
  58   ssize_t ret = TEMP_FAILURE_RETRY (__readv (fd, iov, iovcnt));
  59   if (ret <= 0)
  60     return ret;
  61
  62   size_t total = 0;
  63   for (int i = 0; i < iovcnt; ++i)
  64     total += iov[i].iov_len;
  65
  66   if (ret < total)
  67     {
  68       struct iovec iov_buf[iovcnt];
  69       ssize_t r = ret;
  70
  71       struct iovec *iovp = memcpy (iov_buf, iov, iovcnt * sizeof (*iov));
  72       do
  73         {
  74           while (iovp->iov_len <= r)
  75             {
  76               r -= iovp->iov_len;
  77               --iovcnt;
  78               ++iovp;
  79             }
  80           iovp->iov_base = (char *) iovp->iov_base + r;
  81           iovp->iov_len -= r;
  82           r = TEMP_FAILURE_RETRY (__readv (fd, iovp, iovcnt));
  83           if (r <= 0)
  84             break;
  85           ret += r;
  86         }
  87       while (ret < total);
  88       if (r < 0)
  89         ret = r;
  90     }
  91   return ret;
  92 }
  93
  94
  95 static int
  96 open_socket (void)
  97 {
  98   int sock = __socket (PF_UNIX, SOCK_STREAM, 0);
  99   if (sock < 0)
 100     return -1;
 101
 102   /* Make socket non-blocking.  */
 103   int fl = __fcntl (sock, F_GETFL);
 104   if (fl != -1)
 105     __fcntl (sock, F_SETFL, fl | O_NONBLOCK);
 106
 107   struct sockaddr_un sun;
 108   sun.sun_family = AF_UNIX;
 109   strcpy (sun.sun_path, _PATH_NSCDSOCKET);
 110   if (__connect (sock, (struct sockaddr *) &sun, sizeof (sun)) < 0
 111       && errno != EINPROGRESS)
 112     goto out;
 113
 114   struct pollfd fds[1];
 115   fds[0].fd = sock;
 116   fds[0].events = POLLOUT | POLLERR | POLLHUP;
 117   if (__poll (fds, 1, 5 * 1000) > 0)
 118     /* Success.  We do not check for success of the connect call here.
 119        If it failed, the following operations will fail.  */
 120     return sock;
 121
 122  out:
 123   close_not_cancel_no_status (sock);
 124
 125   return -1;
 126 }
 127
 128
 129 void
 130 __nscd_unmap (struct mapped_database *mapped)
 131 {
 132   assert (mapped->counter == 0);
 133   __munmap ((void *) mapped->head, mapped->mapsize);
 134   free (mapped);
 135 }
 136
 137
 138 /* Try to get a file descriptor for the shared meory segment
 139    containing the database.  */
 140 static struct mapped_database *
 141 get_mapping (request_type type, const char *key,
 142              struct mapped_database **mappedp)
 143 {
 144   struct mapped_database *result = NO_MAPPING;
 145 #ifdef SCM_RIGHTS
 146   const size_t keylen = strlen (key) + 1;
 147   char resdata[keylen];
 148   int saved_errno = errno;
 149
 150   int mapfd = -1;
 151
 152   /* Send the request.  */
 153   struct iovec iov[2];
 154   request_header req;
 155
 156   int sock = open_socket ();
 157   if (sock < 0)
 158     goto out;
 159
 160   req.version = NSCD_VERSION;
 161   req.type = type;
 162   req.key_len = keylen;
 163
 164   iov[0].iov_base = &req;
 165   iov[0].iov_len = sizeof (req);
 166   iov[1].iov_base = (void *) key;
 167   iov[1].iov_len = keylen;
 168
 169   if (TEMP_FAILURE_RETRY (__writev (sock, iov, 2))
 170       != iov[0].iov_len + iov[1].iov_len)
 171     /* We cannot even write the request.  */
 172     goto out_close2;
 173
 174   /* Room for the data sent along with the file descriptor.  We expect
 175      the key name back.  */
 176   iov[0].iov_base = resdata;
 177   iov[0].iov_len = keylen;
 178
 179   char buf[CMSG_SPACE (sizeof (int))];
 180   struct msghdr msg = { .msg_iov = iov, .msg_iovlen = 1,
 181                         .msg_control = buf, .msg_controllen = sizeof (buf) };
 182   struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg);
 183
 184   cmsg->cmsg_level = SOL_SOCKET;
 185   cmsg->cmsg_type = SCM_RIGHTS;
 186   cmsg->cmsg_len = CMSG_LEN (sizeof (int));
 187
 188   *(int *) CMSG_DATA (cmsg) = -1;
 189
 190   msg.msg_controllen = cmsg->cmsg_len;
 191
 192   struct pollfd fds[1];
 193   fds[0].fd = sock;
 194   fds[0].events = POLLIN | POLLERR | POLLHUP;
 195   if (__poll (fds, 1, 5 * 1000) <= 0)
 196     /* Failure or timeout.  */
 197     goto out_close2;
 198
 199   if (TEMP_FAILURE_RETRY (__recvmsg (sock, &msg, 0)) != keylen)
 200     goto out_close2;
 201
 202   mapfd = *(int *) CMSG_DATA (cmsg);
 203
 204   if (CMSG_FIRSTHDR (&msg)->cmsg_len != CMSG_LEN (sizeof (int)))
 205     goto out_close;
 206
 207   struct stat64 st;
 208   if (strcmp (resdata, key) != 0
 209       || fstat64 (mapfd, &st) != 0
 210       || st.st_size < sizeof (struct database_pers_head))
 211     goto out_close;
 212
 213   struct database_pers_head head;
 214   if (TEMP_FAILURE_RETRY (__pread (mapfd, &head, sizeof (head), 0))
 215       != sizeof (head))
 216     goto out_close;
 217
 218   if (head.version != DB_VERSION || head.header_size != sizeof (head)
 219       /* This really should not happen but who knows, maybe the update
 220          thread got stuck.  */
 221       || (! head.nscd_certainly_running
 222           && head.timestamp + MAPPING_TIMEOUT < time (NULL)))
 223     goto out_close;
 224
 225   size_t size = (sizeof (head) + roundup (head.module * sizeof (ref_t), ALIGN)
 226                  + head.data_size);
 227
 228   if (st.st_size < size)
 229     goto out_close;
 230
 231   /* The file is large enough, map it now.  */
 232   void *mapping = __mmap (NULL, size, PROT_READ, MAP_SHARED, mapfd, 0);
 233   if (mapping != MAP_FAILED)
 234     {
 235       /* Allocate a record for the mapping.  */
 236       struct mapped_database *newp;
 237
 238       newp = malloc (sizeof (*newp));
 239       if (newp == NULL)
 240         {
 241           /* Ugh, after all we went through the memory allocation failed.  */
 242           __munmap (result, size);
 243           goto out_close;
 244         }
 245
 246       newp->head = mapping;
 247       newp->data = ((char *) mapping + head.header_size
 248                     + roundup (head.module * sizeof (ref_t), ALIGN));
 249       newp->mapsize = size;
 250       /* Set counter to 1 to show it is usable.  */
 251       newp->counter = 1;
 252
 253       result = newp;
 254     }
 255
 256  out_close:
 257   __close (mapfd);
 258  out_close2:
 259   __close (sock);
 260  out:
 261   __set_errno (saved_errno);
 262 #endif  /* SCM_RIGHTS */
 263
 264   struct mapped_database *oldval = *mappedp;
 265   *mappedp = result;
 266
 267   if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
 268     __nscd_unmap (oldval);
 269
 270   return result;
 271 }
 272
 273
 274 struct mapped_database *
 275 __nscd_get_map_ref (request_type type, const char *name,
 276                     struct locked_map_ptr *mapptr, int *gc_cyclep)
 277 {
 278   struct mapped_database *cur = mapptr->mapped;
 279   if (cur == NO_MAPPING)
 280     return cur;
 281
 282   int cnt = 0;
 283   while (atomic_compare_and_exchange_val_acq (&mapptr->lock, 1, 0) != 0)
 284     {
 285       // XXX Best number of rounds?
 286       if (++cnt > 5)
 287         return NO_MAPPING;
 288
 289       atomic_delay ();
 290     }
 291
 292   cur = mapptr->mapped;
 293
 294   if (__builtin_expect (cur != NO_MAPPING, 1))
 295     {
 296       /* If not mapped or timestamp not updated, request new map.  */
 297       if (cur == NULL
 298           || (cur->head->nscd_certainly_running == 0
 299               && cur->head->timestamp + MAPPING_TIMEOUT < time (NULL)))
 300         cur = get_mapping (type, name, &mapptr->mapped);
 301
 302       if (__builtin_expect (cur != NO_MAPPING, 1))
 303         {
 304           if (__builtin_expect (((*gc_cyclep = cur->head->gc_cycle) & 1) != 0,
 305                                 0))
 306             cur = NO_MAPPING;
 307           else
 308             atomic_increment (&cur->counter);
 309         }
 310     }
 311
 312   mapptr->lock = 0;
 313
 314   return cur;
 315 }
 316
 317
 318 const struct datahead *
 319 __nscd_cache_search (request_type type, const char *key, size_t keylen,
 320                      const struct mapped_database *mapped)
 321 {
 322   unsigned long int hash = __nis_hash (key, keylen) % mapped->head->module;
 323
 324   ref_t work = mapped->head->array[hash];
 325   while (work != ENDREF)
 326     {
 327       struct hashentry *here = (struct hashentry *) (mapped->data + work);
 328
 329       if (type == here->type && keylen == here->len
 330           && memcmp (key, mapped->data + here->key, keylen) == 0)
 331         {
 332           /* We found the entry.  Increment the appropriate counter.  */
 333           const struct datahead *dh
 334             = (struct datahead *) (mapped->data + here->packet);
 335
 336           /* See whether we must ignore the entry or whether something
 337              is wrong because garbage collection is in progress.  */
 338           if (dh->usable && ((char *) dh + dh->allocsize
 339                              <= (char *) mapped->head + mapped->mapsize))
 340             return dh;
 341         }
 342
 343       work = here->next;
 344     }
 345
 346   return NULL;
 347 }
 348
 349
 350 /* Create a socket connected to a name. */
 351 int
 352 __nscd_open_socket (const char *key, size_t keylen, request_type type,
 353                     void *response, size_t responselen)
 354 {
 355   int saved_errno = errno;
 356
 357   int sock = open_socket ();
 358   if (sock >= 0)
 359     {
 360       request_header req;
 361       req.version = NSCD_VERSION;
 362       req.type = type;
 363       req.key_len = keylen;
 364
 365       struct iovec vec[2];
 366       vec[0].iov_base = &req;
 367       vec[0].iov_len = sizeof (request_header);
 368       vec[1].iov_base = (void *) key;
 369       vec[1].iov_len = keylen;
 370
 371       ssize_t nbytes = TEMP_FAILURE_RETRY (__writev (sock, vec, 2));
 372       if (nbytes == (ssize_t) (sizeof (request_header) + keylen))
 373         {
 374           /* Wait for data.  */
 375           struct pollfd fds[1];
 376           fds[0].fd = sock;
 377           fds[0].events = POLLIN | POLLERR | POLLHUP;
 378           if (__poll (fds, 1, 5 * 1000) > 0)
 379             {
 380               nbytes = TEMP_FAILURE_RETRY (__read (sock, response,
 381                                                    responselen));
 382               if (nbytes == (ssize_t) responselen)
 383                 return sock;
 384             }
 385         }
 386
 387       close_not_cancel_no_status (sock);
 388     }
 389
 390   __set_errno (saved_errno);
 391
 392   return -1;
 393 }