nscd/nscd_helper.c

   1 /* Copyright (C) 1998-2002, 2003, 2004, 2005 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 static int
  38 open_socket (void)
  39 {
  40   int sock = __socket (PF_UNIX, SOCK_STREAM, 0);
  41   if (sock < 0)
  42     return -1;
  43
  44   /* Make socket non-blocking.  */
  45   int fl = __fcntl (sock, F_GETFL);
  46   if (fl != -1)
  47     __fcntl (sock, F_SETFL, fl | O_NONBLOCK);
  48
  49   struct sockaddr_un sun;
  50   sun.sun_family = AF_UNIX;
  51   strcpy (sun.sun_path, _PATH_NSCDSOCKET);
  52   if (__connect (sock, (struct sockaddr *) &sun, sizeof (sun)) < 0
  53       && errno != EINPROGRESS)
  54     goto out;
  55
  56   struct pollfd fds[1];
  57   fds[0].fd = sock;
  58   fds[0].events = POLLOUT | POLLERR | POLLHUP;
  59   if (__poll (fds, 1, 5 * 1000) > 0)
  60     /* Success.  We do not check for success of the connect call here.
  61        If it failed, the following operations will fail.  */
  62     return sock;
  63
  64  out:
  65   close_not_cancel_no_status (sock);
  66
  67   return -1;
  68 }
  69
  70
  71 void
  72 __nscd_unmap (struct mapped_database *mapped)
  73 {
  74   assert (mapped->counter == 0);
  75   __munmap ((void *) mapped->head, mapped->mapsize);
  76   free (mapped);
  77 }
  78
  79
  80 /* Try to get a file descriptor for the shared meory segment
  81    containing the database.  */
  82 static struct mapped_database *
  83 get_mapping (request_type type, const char *key,
  84              struct mapped_database **mappedp)
  85 {
  86   struct mapped_database *result = NO_MAPPING;
  87 #ifdef SCM_RIGHTS
  88   const size_t keylen = strlen (key) + 1;
  89   char resdata[keylen];
  90   int saved_errno = errno;
  91
  92   int mapfd = -1;
  93
  94   /* Send the request.  */
  95   struct iovec iov[2];
  96   request_header req;
  97
  98   int sock = open_socket ();
  99   if (sock < 0)
 100     goto out;
 101
 102   req.version = NSCD_VERSION;
 103   req.type = type;
 104   req.key_len = keylen;
 105
 106   iov[0].iov_base = &req;
 107   iov[0].iov_len = sizeof (req);
 108   iov[1].iov_base = (void *) key;
 109   iov[1].iov_len = keylen;
 110
 111   if (TEMP_FAILURE_RETRY (__writev (sock, iov, 2))
 112       != iov[0].iov_len + iov[1].iov_len)
 113     /* We cannot even write the request.  */
 114     goto out_close2;
 115
 116   /* Room for the data sent along with the file descriptor.  We expect
 117      the key name back.  */
 118   iov[0].iov_base = resdata;
 119   iov[0].iov_len = keylen;
 120
 121   char buf[CMSG_SPACE (sizeof (int))];
 122   struct msghdr msg = { .msg_iov = iov, .msg_iovlen = 1,
 123                         .msg_control = buf, .msg_controllen = sizeof (buf) };
 124   struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg);
 125
 126   cmsg->cmsg_level = SOL_SOCKET;
 127   cmsg->cmsg_type = SCM_RIGHTS;
 128   cmsg->cmsg_len = CMSG_LEN (sizeof (int));
 129
 130   *(int *) CMSG_DATA (cmsg) = -1;
 131
 132   msg.msg_controllen = cmsg->cmsg_len;
 133
 134   struct pollfd fds[1];
 135   fds[0].fd = sock;
 136   fds[0].events = POLLIN | POLLERR | POLLHUP;
 137   if (__poll (fds, 1, 5 * 1000) <= 0)
 138     /* Failure or timeout.  */
 139     goto out_close2;
 140
 141 #ifndef MSG_NOSIGNAL
 142 # define MSG_NOSIGNAL 0
 143 #endif
 144   if (TEMP_FAILURE_RETRY (__recvmsg (sock, &msg, MSG_NOSIGNAL)) != keylen)
 145     goto out_close2;
 146
 147   mapfd = *(int *) CMSG_DATA (cmsg);
 148
 149   if (CMSG_FIRSTHDR (&msg)->cmsg_len != CMSG_LEN (sizeof (int)))
 150     goto out_close;
 151
 152   struct stat64 st;
 153   if (strcmp (resdata, key) != 0
 154       || fstat64 (mapfd, &st) != 0
 155       || st.st_size < sizeof (struct database_pers_head))
 156     goto out_close;
 157
 158   struct database_pers_head head;
 159   if (TEMP_FAILURE_RETRY (__pread (mapfd, &head, sizeof (head), 0))
 160       != sizeof (head))
 161     goto out_close;
 162
 163   if (head.version != DB_VERSION || head.header_size != sizeof (head)
 164       /* This really should not happen but who knows, maybe the update
 165          thread got stuck.  */
 166       || (! head.nscd_certainly_running
 167           && head.timestamp + MAPPING_TIMEOUT < time (NULL)))
 168     goto out_close;
 169
 170   size_t size = (sizeof (head) + roundup (head.module * sizeof (ref_t), ALIGN)
 171                  + head.data_size);
 172
 173   if (st.st_size < size)
 174     goto out_close;
 175
 176   /* The file is large enough, map it now.  */
 177   void *mapping = __mmap (NULL, size, PROT_READ, MAP_SHARED, mapfd, 0);
 178   if (mapping != MAP_FAILED)
 179     {
 180       /* Allocate a record for the mapping.  */
 181       struct mapped_database *newp;
 182
 183       newp = malloc (sizeof (*newp));
 184       if (newp == NULL)
 185         {
 186           /* Ugh, after all we went through the memory allocation failed.  */
 187           __munmap (result, size);
 188           goto out_close;
 189         }
 190
 191       newp->head = mapping;
 192       newp->data = ((char *) mapping + head.header_size
 193                     + roundup (head.module * sizeof (ref_t), ALIGN));
 194       newp->mapsize = size;
 195       /* Set counter to 1 to show it is usable.  */
 196       newp->counter = 1;
 197
 198       result = newp;
 199     }
 200
 201  out_close:
 202   __close (mapfd);
 203  out_close2:
 204   __close (sock);
 205  out:
 206   __set_errno (saved_errno);
 207 #endif  /* SCM_RIGHTS */
 208
 209   struct mapped_database *oldval = *mappedp;
 210   *mappedp = result;
 211
 212   if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
 213     __nscd_unmap (oldval);
 214
 215   return result;
 216 }
 217
 218
 219 struct mapped_database *
 220 __nscd_get_map_ref (request_type type, const char *name,
 221                     struct locked_map_ptr *mapptr, int *gc_cyclep)
 222 {
 223   struct mapped_database *cur = mapptr->mapped;
 224   if (cur == NO_MAPPING)
 225     return cur;
 226
 227   int cnt = 0;
 228   while (atomic_compare_and_exchange_val_acq (&mapptr->lock, 1, 0) != 0)
 229     {
 230       // XXX Best number of rounds?
 231       if (++cnt > 5)
 232         return NO_MAPPING;
 233
 234       atomic_delay ();
 235     }
 236
 237   cur = mapptr->mapped;
 238
 239   if (__builtin_expect (cur != NO_MAPPING, 1))
 240     {
 241       /* If not mapped or timestamp not updated, request new map.  */
 242       if (cur == NULL
 243           || (cur->head->nscd_certainly_running == 0
 244               && cur->head->timestamp + MAPPING_TIMEOUT < time (NULL)))
 245         cur = get_mapping (type, name, &mapptr->mapped);
 246
 247       if (__builtin_expect (cur != NO_MAPPING, 1))
 248         {
 249           if (__builtin_expect (((*gc_cyclep = cur->head->gc_cycle) & 1) != 0,
 250                                 0))
 251             cur = NO_MAPPING;
 252           else
 253             atomic_increment (&cur->counter);
 254         }
 255     }
 256
 257   mapptr->lock = 0;
 258
 259   return cur;
 260 }
 261
 262
 263 const struct datahead *
 264 __nscd_cache_search (request_type type, const char *key, size_t keylen,
 265                      const struct mapped_database *mapped)
 266 {
 267   unsigned long int hash = __nis_hash (key, keylen) % mapped->head->module;
 268
 269   ref_t work = mapped->head->array[hash];
 270   while (work != ENDREF)
 271     {
 272       struct hashentry *here = (struct hashentry *) (mapped->data + work);
 273
 274       if (type == here->type && keylen == here->len
 275           && memcmp (key, mapped->data + here->key, keylen) == 0)
 276         {
 277           /* We found the entry.  Increment the appropriate counter.  */
 278           const struct datahead *dh
 279             = (struct datahead *) (mapped->data + here->packet);
 280
 281           /* See whether we must ignore the entry or whether something
 282              is wrong because garbage collection is in progress.  */
 283           if (dh->usable && ((char *) dh + dh->allocsize
 284                              <= (char *) mapped->head + mapped->mapsize))
 285             return dh;
 286         }
 287
 288       work = here->next;
 289     }
 290
 291   return NULL;
 292 }
 293
 294
 295 /* Create a socket connected to a name. */
 296 int
 297 __nscd_open_socket (const char *key, size_t keylen, request_type type,
 298                     void *response, size_t responselen)
 299 {
 300   int saved_errno = errno;
 301
 302   int sock = open_socket ();
 303   if (sock >= 0)
 304     {
 305       request_header req;
 306       req.version = NSCD_VERSION;
 307       req.type = type;
 308       req.key_len = keylen;
 309
 310       struct iovec vec[2];
 311       vec[0].iov_base = &req;
 312       vec[0].iov_len = sizeof (request_header);
 313       vec[1].iov_base = (void *) key;
 314       vec[1].iov_len = keylen;
 315
 316       ssize_t nbytes = TEMP_FAILURE_RETRY (__writev (sock, vec, 2));
 317       if (nbytes == (ssize_t) (sizeof (request_header) + keylen))
 318         {
 319           /* Wait for data.  */
 320           struct pollfd fds[1];
 321           fds[0].fd = sock;
 322           fds[0].events = POLLIN | POLLERR | POLLHUP;
 323           if (__poll (fds, 1, 5 * 1000) > 0)
 324             {
 325               nbytes = TEMP_FAILURE_RETRY (__read (sock, response,
 326                                                    responselen));
 327               if (nbytes == (ssize_t) responselen)
 328                 return sock;
 329             }
 330         }
 331
 332       close_not_cancel_no_status (sock);
 333     }
 334
 335   __set_errno (saved_errno);
 336
 337   return -1;
 338 }