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