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 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   if (TEMP_FAILURE_RETRY (__recvmsg (sock, &msg, 0)) != keylen)
 142     goto out_close2;
 143
 144   mapfd = *(int *) CMSG_DATA (cmsg);
 145
 146   if (CMSG_FIRSTHDR (&msg)->cmsg_len != CMSG_LEN (sizeof (int)))
 147     goto out_close;
 148
 149   struct stat64 st;
 150   if (strcmp (resdata, key) != 0
 151       || fstat64 (mapfd, &st) != 0
 152       || st.st_size < sizeof (struct database_pers_head))
 153     goto out_close;
 154
 155   struct database_pers_head head;
 156   if (TEMP_FAILURE_RETRY (__pread (mapfd, &head, sizeof (head), 0))
 157       != sizeof (head))
 158     goto out_close;
 159
 160   if (head.version != DB_VERSION || head.header_size != sizeof (head)
 161       /* This really should not happen but who knows, maybe the update
 162          thread got stuck.  */
 163       || (! head.nscd_certainly_running
 164           && head.timestamp + MAPPING_TIMEOUT < time (NULL)))
 165     goto out_close;
 166
 167   size_t size = (sizeof (head) + roundup (head.module * sizeof (ref_t), ALIGN)
 168                  + head.data_size);
 169
 170   if (st.st_size < size)
 171     goto out_close;
 172
 173   /* The file is large enough, map it now.  */
 174   void *mapping = __mmap (NULL, size, PROT_READ, MAP_SHARED, mapfd, 0);
 175   if (mapping != MAP_FAILED)
 176     {
 177       /* Allocate a record for the mapping.  */
 178       struct mapped_database *newp;
 179
 180       newp = malloc (sizeof (*newp));
 181       if (newp == NULL)
 182         {
 183           /* Ugh, after all we went through the memory allocation failed.  */
 184           __munmap (result, size);
 185           goto out_close;
 186         }
 187
 188       newp->head = mapping;
 189       newp->data = ((char *) mapping + head.header_size
 190                     + roundup (head.module * sizeof (ref_t), ALIGN));
 191       newp->mapsize = size;
 192       /* Set counter to 1 to show it is usable.  */
 193       newp->counter = 1;
 194
 195       result = newp;
 196     }
 197
 198  out_close:
 199   __close (mapfd);
 200  out_close2:
 201   __close (sock);
 202  out:
 203   __set_errno (saved_errno);
 204 #endif  /* SCM_RIGHTS */
 205
 206   struct mapped_database *oldval = *mappedp;
 207   *mappedp = result;
 208
 209   if (oldval != NULL && atomic_decrement_val (&oldval->counter) == 0)
 210     __nscd_unmap (oldval);
 211
 212   return result;
 213 }
 214
 215
 216 struct mapped_database *
 217 __nscd_get_map_ref (request_type type, const char *name,
 218                     struct locked_map_ptr *mapptr, int *gc_cyclep)
 219 {
 220   struct mapped_database *cur = mapptr->mapped;
 221   if (cur == NO_MAPPING)
 222     return cur;
 223
 224   int cnt = 0;
 225   while (atomic_compare_and_exchange_val_acq (&mapptr->lock, 1, 0) != 0)
 226     {
 227       // XXX Best number of rounds?
 228       if (++cnt > 5)
 229         return NO_MAPPING;
 230
 231       atomic_delay ();
 232     }
 233
 234   cur = mapptr->mapped;
 235
 236   if (__builtin_expect (cur != NO_MAPPING, 1))
 237     {
 238       /* If not mapped or timestamp not updated, request new map.  */
 239       if (cur == NULL
 240           || (cur->head->nscd_certainly_running == 0
 241               && cur->head->timestamp + MAPPING_TIMEOUT < time (NULL)))
 242         cur = get_mapping (type, name, &mapptr->mapped);
 243
 244       if (__builtin_expect (cur != NO_MAPPING, 1))
 245         {
 246           if (__builtin_expect (((*gc_cyclep = cur->head->gc_cycle) & 1) != 0,
 247                                 0))
 248             cur = NO_MAPPING;
 249           else
 250             atomic_increment (&cur->counter);
 251         }
 252     }
 253
 254   mapptr->lock = 0;
 255
 256   return cur;
 257 }
 258
 259
 260 const struct datahead *
 261 __nscd_cache_search (request_type type, const char *key, size_t keylen,
 262                      const struct mapped_database *mapped)
 263 {
 264   unsigned long int hash = __nis_hash (key, keylen) % mapped->head->module;
 265
 266   ref_t work = mapped->head->array[hash];
 267   while (work != ENDREF)
 268     {
 269       struct hashentry *here = (struct hashentry *) (mapped->data + work);
 270
 271       if (type == here->type && keylen == here->len
 272           && memcmp (key, mapped->data + here->key, keylen) == 0)
 273         {
 274           /* We found the entry.  Increment the appropriate counter.  */
 275           const struct datahead *dh
 276             = (struct datahead *) (mapped->data + here->packet);
 277
 278           /* See whether we must ignore the entry or whether something
 279              is wrong because garbage collection is in progress.  */
 280           if (dh->usable && ((char *) dh + dh->allocsize
 281                              <= (char *) mapped->head + mapped->mapsize))
 282             return dh;
 283         }
 284
 285       work = here->next;
 286     }
 287
 288   return NULL;
 289 }
 290
 291
 292 /* Create a socket connected to a name. */
 293 int
 294 __nscd_open_socket (const char *key, size_t keylen, request_type type,
 295                     void *response, size_t responselen)
 296 {
 297   int saved_errno = errno;
 298
 299   int sock = open_socket ();
 300   if (sock >= 0)
 301     {
 302       request_header req;
 303       req.version = NSCD_VERSION;
 304       req.type = type;
 305       req.key_len = keylen;
 306
 307       struct iovec vec[2];
 308       vec[0].iov_base = &req;
 309       vec[0].iov_len = sizeof (request_header);
 310       vec[1].iov_base = (void *) key;
 311       vec[1].iov_len = keylen;
 312
 313       ssize_t nbytes = TEMP_FAILURE_RETRY (__writev (sock, vec, 2));
 314       if (nbytes == (ssize_t) (sizeof (request_header) + keylen))
 315         {
 316           /* Wait for data.  */
 317           struct pollfd fds[1];
 318           fds[0].fd = sock;
 319           fds[0].events = POLLIN | POLLERR | POLLHUP;
 320           if (__poll (fds, 1, 5 * 1000) > 0)
 321             {
 322               nbytes = TEMP_FAILURE_RETRY (__read (sock, response,
 323                                                    responselen));
 324               if (nbytes == (ssize_t) responselen)
 325                 return sock;
 326             }
 327         }
 328
 329       close_not_cancel_no_status (sock);
 330     }
 331
 332   __set_errno (saved_errno);
 333
 334   return -1;
 335 }