src/plugins/mailmbox/maillock.c

   1 /*
   2  * libEtPan! -- a mail stuff library
   3  *
   4  * Copyright (C) 2001, 2002 - DINH Viet Hoa
   5  * All rights reserved.
   6  *
   7  * Redistribution and use in source and binary forms, with or without
   8  * modification, are permitted provided that the following conditions
   9  * are met:
  10  * 1. Redistributions of source code must retain the above copyright
  11  *    notice, this list of conditions and the following disclaimer.
  12  * 2. Redistributions in binary form must reproduce the above copyright
  13  *    notice, this list of conditions and the following disclaimer in the
  14  *    documentation and/or other materials provided with the distribution.
  15  * 3. Neither the name of the libEtPan! project nor the names of its
  16  *    contributors may be used to endorse or promote products derived
  17  *    from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  29  * SUCH DAMAGE.
  30  */
  31
  32 /*
  33  * $Id $
  34  */
  35
  36 #include "config.h"
  37
  38 #include "maillock.h"
  39
  40 #include <sys/types.h>
  41 #include <sys/stat.h>
  42 #include <fcntl.h>
  43 #include <limits.h>
  44 #include <unistd.h>
  45 #include <stdio.h>
  46 #include <time.h>
  47 #include <string.h>
  48
  49 #include "utils.h"
  50
  51 /* ********************************************************************** */
  52
  53 /* lock primitives */
  54
  55 /* the lock code is modified from the dot lock file code from mail.local.c */
  56
  57 /*
  58                              SENDMAIL LICENSE
  59
  60 The following license terms and conditions apply, unless a different
  61 license is obtained from Sendmail, Inc., 6425 Christie Ave, Fourth Floor,
  62 Emeryville, CA 94608, or by electronic mail at license@sendmail.com.
  63
  64 License Terms:
  65
  66 Use, Modification and Redistribution (including distribution of any
  67 modified or derived work) in source and binary forms is permitted only if
  68 each of the following conditions is met:
  69
  70 1. Redistributions qualify as "freeware" or "Open Source Software" under
  71    one of the following terms:
  72
  73    (a) Redistributions are made at no charge beyond the reasonable cost of
  74        materials and delivery.
  75
  76    (b) Redistributions are accompanied by a copy of the Source Code or by an
  77        irrevocable offer to provide a copy of the Source Code for up to three
  78        years at the cost of materials and delivery.  Such redistributions
  79        must allow further use, modification, and redistribution of the Source
  80        Code under substantially the same terms as this license.  For the
  81        purposes of redistribution "Source Code" means the complete compilable
  82        and linkable source code of sendmail including all modifications.
  83
  84 2. Redistributions of source code must retain the copyright notices as they
  85    appear in each source code file, these license terms, and the
  86    disclaimer/limitation of liability set forth as paragraph 6 below.
  87
  88 3. Redistributions in binary form must reproduce the Copyright Notice,
  89    these license terms, and the disclaimer/limitation of liability set
  90    forth as paragraph 6 below, in the documentation and/or other materials
  91    provided with the distribution.  For the purposes of binary distribution
  92    the "Copyright Notice" refers to the following language:
  93    "Copyright (c) 1998-2002 Sendmail, Inc.  All rights reserved."
  94
  95 4. Neither the name of Sendmail, Inc. nor the University of California nor
  96    the names of their contributors may be used to endorse or promote
  97    products derived from this software without specific prior written
  98    permission.  The name "sendmail" is a trademark of Sendmail, Inc.
  99
 100 5. All redistributions must comply with the conditions imposed by the
 101    University of California on certain embedded code, whose copyright
 102    notice and conditions for redistribution are as follows:
 103
 104    (a) Copyright (c) 1988, 1993 The Regents of the University of
 105        California.  All rights reserved.
 106
 107    (b) Redistribution and use in source and binary forms, with or without
 108        modification, are permitted provided that the following conditions
 109        are met:
 110
 111       (i)   Redistributions of source code must retain the above copyright
 112             notice, this list of conditions and the following disclaimer.
 113
 114       (ii)  Redistributions in binary form must reproduce the above
 115             copyright notice, this list of conditions and the following
 116             disclaimer in the documentation and/or other materials provided
 117             with the distribution.
 118
 119       (iii) Neither the name of the University nor the names of its
 120             contributors may be used to endorse or promote products derived
 121             from this software without specific prior written permission.
 122
 123 6. Disclaimer/Limitation of Liability: THIS SOFTWARE IS PROVIDED BY
 124    SENDMAIL, INC. AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
 125    WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 126    MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN
 127    NO EVENT SHALL SENDMAIL, INC., THE REGENTS OF THE UNIVERSITY OF
 128    CALIFORNIA OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 129    INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 130    NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 131    USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
 132    ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 133    (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 134    THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 135 */
 136
 137 /*
 138   TODO : lock, prefer fcntl() over flock()
 139          AND use dotlock code above
 140 */
 141
 142 #define LOCKTO_RM       300     /* timeout for stale lockfile removal */
 143 #define LOCKTO_GLOB     400     /* global timeout for lockfile creation */
 144
 145 static int lock_common(const char * filename, int fd, short locktype)
 146 {
 147   char lockfilename[PATH_MAX];
 148   struct flock lock;
 149   /* dot lock file */
 150   int statfailed = 0;
 151   time_t start;
 152   int r;
 153   int res;
 154
 155   lock.l_start = 0;
 156   lock.l_len = 0;
 157   lock.l_pid = getpid();
 158   lock.l_type = locktype;
 159   lock.l_whence = SEEK_SET;
 160
 161   r = fcntl(fd, F_SETLKW, &lock);
 162   if (r < 0) {
 163     /* WARNING POSIX lock could not be applied */
 164     perror("lock");
 165   }
 166
 167   /* dot lock file */
 168
 169   if (strlen(filename) + 6 > PATH_MAX) {
 170     res = -1;
 171     goto unlock;
 172   }
 173
 174   snprintf(lockfilename, PATH_MAX, "%s.lock", filename);
 175
 176   time(&start);
 177   while (1) {
 178     int fd;
 179     GStatBuf st;
 180     time_t now;
 181
 182     /* global timeout */
 183     time(&now);
 184     if (now > start + LOCKTO_GLOB) {
 185       res = -1;
 186       goto unlock;
 187     }
 188
 189     fd = open(lockfilename, O_WRONLY|O_EXCL|O_CREAT, 0);
 190     if (fd >= 0) {
 191       /* defeat lock checking programs which test pid */
 192       if (write(fd, "0", 2) < 0)
 193           FILE_OP_ERROR(lockfilename, "write");
 194       close(fd);
 195       break;
 196     } else {
 197       FILE_OP_ERROR(lockfilename, "open");
 198     }
 199
 200     /* libEtPan! - adds a delay of 5 seconds between each tries */
 201     sleep(5);
 202
 203     if (g_stat(lockfilename, &st) < 0) {
 204       if (statfailed++ > 5) {
 205         res = -1;
 206         goto unlock;
 207       }
 208       continue;
 209     }
 210     statfailed = 0;
 211     time(&now);
 212
 213     if (now < st.st_ctime + LOCKTO_RM)
 214       continue;
 215
 216     /* try to remove stale lockfile */
 217     if (unlink(lockfilename) < 0) {
 218       res = -1;
 219       goto unlock;
 220     }
 221
 222     /*
 223       libEtPan! - removes this delay of 5 seconds,
 224        maybe it was misplaced ?
 225     */
 226 #if 0
 227     sleep(5);
 228 #endif
 229   }
 230
 231   return 0;
 232
 233  unlock:
 234   lock.l_start = 0;
 235   lock.l_len = 0;
 236   lock.l_pid = getpid();
 237   lock.l_type = F_UNLCK;
 238   lock.l_whence = SEEK_SET;
 239
 240   r = fcntl(fd, F_SETLK, &lock);
 241   if (r < 0) {
 242     /* WARNING POSIX lock could not be applied */
 243     perror("lock");
 244   }
 245   return res;
 246 }
 247
 248 static int unlock_common(const char * filename, int fd)
 249 {
 250   char lockfilename[PATH_MAX];
 251   struct flock lock;
 252   int r;
 253
 254   if (strlen(filename) + 6 > PATH_MAX)
 255     return -1;
 256
 257   snprintf(lockfilename, PATH_MAX, "%s.lock", filename);
 258
 259   unlink(lockfilename);
 260
 261   lock.l_start = 0;
 262   lock.l_len = 0;
 263   lock.l_pid = getpid();
 264   lock.l_type = F_UNLCK;
 265   lock.l_whence = SEEK_SET;
 266
 267   r = fcntl(fd, F_SETLK, &lock);
 268   if (r < 0) {
 269     /* WARNING POSIX lock could not be applied */
 270   }
 271
 272   return 0;
 273 }
 274
 275 int maillock_read_lock(const char * filename, int fd)
 276 {
 277   return lock_common(filename, fd, F_RDLCK);
 278 }
 279
 280 int maillock_read_unlock(const char * filename, int fd)
 281 {
 282   return unlock_common(filename, fd);
 283 }
 284
 285 int maillock_write_lock(const char * filename, int fd)
 286 {
 287   return lock_common(filename, fd, F_WRLCK);
 288 }
 289
 290 int maillock_write_unlock(const char * filename, int fd)
 291 {
 292   return unlock_common(filename, fd);
 293 }