1 /*-
2 * Taken from FreeBSD libutil
3 *
4 * Copyright (c) 2007 Dag-Erling Coïdan Smørgrav
5 * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
6 * All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 * notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 * notice, this list of conditions and the following disclaimer in the
15 * documentation and/or other materials provided with the distribution.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 */
29
30 #include <sys/cdefs.h>
31 #ifdef __FBSDID
32 __FBSDID("$FreeBSD: src/lib/libutil/pidfile.c,v 1.9.2.1 2009/08/03 08:13:06 kensmith Exp $");
33 #endif
34
35 #include <sys/param.h>
36 #include <sys/file.h>
37 #include <sys/stat.h>
38
39 #include <stdarg.h>
40 #include <stdio.h>
41 #include <stdlib.h>
42 #include <unistd.h>
43 #include <fcntl.h>
44 #include <string.h>
45 #include <time.h>
46 #include <err.h>
47 #include <errno.h>
48
49 #include "pidfile.h"
50
51 #ifndef EDOOFUS
52 #define EDOOFUS EINVAL
53 #endif
54
55 int
flopen(const char * path,int flags,...)56 flopen(const char *path, int flags, ...)
57 {
58 int fd, operation, serrno, trunc;
59 struct stat sb, fsb;
60 mode_t mode;
61
62 #ifdef O_EXLOCK
63 flags &= ~O_EXLOCK;
64 #endif
65
66 mode = 0;
67 if (flags & O_CREAT) {
68 va_list ap;
69
70 va_start(ap, flags);
71 mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */
72 va_end(ap);
73 }
74
75 operation = LOCK_EX;
76 if (flags & O_NONBLOCK)
77 operation |= LOCK_NB;
78
79 trunc = (flags & O_TRUNC);
80 flags &= ~O_TRUNC;
81
82 for (;;) {
83 if ((fd = open(path, flags, mode)) == -1)
84 /* non-existent or no access */
85 return (-1);
86 if (flock(fd, operation) == -1) {
87 /* unsupported or interrupted */
88 serrno = errno;
89 (void)close(fd);
90 errno = serrno;
91 return (-1);
92 }
93 if (stat(path, &sb) == -1) {
94 /* disappeared from under our feet */
95 (void)close(fd);
96 continue;
97 }
98 if (fstat(fd, &fsb) == -1) {
99 /* can't happen [tm] */
100 serrno = errno;
101 (void)close(fd);
102 errno = serrno;
103 return (-1);
104 }
105 if (sb.st_dev != fsb.st_dev ||
106 sb.st_ino != fsb.st_ino) {
107 /* changed under our feet */
108 (void)close(fd);
109 continue;
110 }
111 if (trunc && ftruncate(fd, 0) != 0) {
112 /* can't happen [tm] */
113 serrno = errno;
114 (void)close(fd);
115 errno = serrno;
116 return (-1);
117 }
118 return (fd);
119 }
120 }
121
122 static int _pidfile_remove(struct pidfh *pfh, int freeit);
123
124 static int
pidfile_verify(struct pidfh * pfh)125 pidfile_verify(struct pidfh *pfh)
126 {
127 struct stat sb;
128
129 if (pfh == NULL || pfh->pf_fd == -1)
130 return (EDOOFUS);
131 /*
132 * Check remembered descriptor.
133 */
134 if (fstat(pfh->pf_fd, &sb) == -1)
135 return (errno);
136 if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino)
137 return (EDOOFUS);
138 return (0);
139 }
140
141 static int
pidfile_read(const char * path,pid_t * pidptr)142 pidfile_read(const char *path, pid_t *pidptr)
143 {
144 char buf[16], *endptr;
145 int error, fd, i;
146
147 fd = open(path, O_RDONLY);
148 if (fd == -1)
149 return (errno);
150
151 i = read(fd, buf, sizeof(buf) - 1);
152 error = errno; /* Remember errno in case close() wants to change it. */
153 close(fd);
154 if (i == -1)
155 return (error);
156 else if (i == 0)
157 return (EAGAIN);
158 buf[i] = '\0';
159
160 *pidptr = strtol(buf, &endptr, 10);
161 if (endptr != &buf[i])
162 return (EINVAL);
163
164 return (0);
165 }
166
167 struct pidfh *
pidfile_open(const char * path,mode_t mode,pid_t * pidptr)168 pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
169 {
170 struct pidfh *pfh;
171 struct stat sb;
172 int error, fd, len, count;
173 struct timespec rqtp;
174
175 pfh = malloc(sizeof(*pfh));
176 if (pfh == NULL)
177 return (NULL);
178
179 if (path == NULL)
180 return (NULL);
181
182 len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
183 "%s", path);
184 if (len >= (int)sizeof(pfh->pf_path)) {
185 free(pfh);
186 errno = ENAMETOOLONG;
187 return (NULL);
188 }
189
190 /*
191 * Open the PID file and obtain exclusive lock.
192 * We truncate PID file here only to remove old PID immediatelly,
193 * PID file will be truncated again in pidfile_write(), so
194 * pidfile_write() can be called multiple times.
195 */
196 fd = flopen(pfh->pf_path,
197 O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, mode);
198 if (fd == -1) {
199 count = 0;
200 rqtp.tv_sec = 0;
201 rqtp.tv_nsec = 5000000;
202 if (errno == EWOULDBLOCK && pidptr != NULL) {
203 again:
204 errno = pidfile_read(pfh->pf_path, pidptr);
205 if (errno == 0)
206 errno = EEXIST;
207 else if (errno == EAGAIN) {
208 if (++count <= 3) {
209 nanosleep(&rqtp, 0);
210 goto again;
211 }
212 }
213 }
214 free(pfh);
215 return (NULL);
216 }
217 /*
218 * Remember file information, so in pidfile_write() we are sure we write
219 * to the proper descriptor.
220 */
221 if (fstat(fd, &sb) == -1) {
222 error = errno;
223 unlink(pfh->pf_path);
224 close(fd);
225 free(pfh);
226 errno = error;
227 return (NULL);
228 }
229
230 pfh->pf_fd = fd;
231 pfh->pf_dev = sb.st_dev;
232 pfh->pf_ino = sb.st_ino;
233
234 return (pfh);
235 }
236
237 int
pidfile_write(struct pidfh * pfh)238 pidfile_write(struct pidfh *pfh)
239 {
240 char pidstr[16];
241 int error, fd;
242
243 /*
244 * Check remembered descriptor, so we don't overwrite some other
245 * file if pidfile was closed and descriptor reused.
246 */
247 errno = pidfile_verify(pfh);
248 if (errno != 0) {
249 /*
250 * Don't close descriptor, because we are not sure if it's ours.
251 */
252 return (-1);
253 }
254 fd = pfh->pf_fd;
255
256 /*
257 * Truncate PID file, so multiple calls of pidfile_write() are allowed.
258 */
259 if (ftruncate(fd, 0) == -1) {
260 error = errno;
261 _pidfile_remove(pfh, 0);
262 errno = error;
263 return (-1);
264 }
265
266 snprintf(pidstr, sizeof(pidstr), "%u", getpid());
267 if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) {
268 error = errno;
269 _pidfile_remove(pfh, 0);
270 errno = error;
271 return (-1);
272 }
273
274 return (0);
275 }
276
277 int
pidfile_close(struct pidfh * pfh)278 pidfile_close(struct pidfh *pfh)
279 {
280 int error;
281
282 error = pidfile_verify(pfh);
283 if (error != 0) {
284 errno = error;
285 return (-1);
286 }
287
288 if (close(pfh->pf_fd) == -1)
289 error = errno;
290 free(pfh);
291 if (error != 0) {
292 errno = error;
293 return (-1);
294 }
295 return (0);
296 }
297
298 static int
_pidfile_remove(struct pidfh * pfh,int freeit)299 _pidfile_remove(struct pidfh *pfh, int freeit)
300 {
301 int error;
302
303 error = pidfile_verify(pfh);
304 if (error != 0) {
305 errno = error;
306 return (-1);
307 }
308
309 if (unlink(pfh->pf_path) == -1)
310 error = errno;
311 if (close(pfh->pf_fd) == -1) {
312 if (error == 0)
313 error = errno;
314 }
315 if (freeit)
316 free(pfh);
317 else
318 pfh->pf_fd = -1;
319 if (error != 0) {
320 errno = error;
321 return (-1);
322 }
323 return (0);
324 }
325
326 int
pidfile_remove(struct pidfh * pfh)327 pidfile_remove(struct pidfh *pfh)
328 {
329
330 return (_pidfile_remove(pfh, 1));
331 }
332