pidfile.c revision 171706 
1/*-
2 * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org>
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 *    notice, this list of conditions and the following disclaimer in the
12 *    documentation and/or other materials provided with the distribution.
13 *
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
15 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
16 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
17 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
18 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
19 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
20 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
21 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
22 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
23 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
24 * SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD: head/lib/libutil/pidfile.c 171706 2007-08-03 09:20:28Z des $");
29
30#include <sys/param.h>
31#include <sys/file.h>
32#include <sys/stat.h>
33
34#include <stdio.h>
35#include <stdlib.h>
36#include <unistd.h>
37#include <fcntl.h>
38#include <string.h>
39#include <err.h>
40#include <errno.h>
41#include <libutil.h>
42
43static int _pidfile_remove(struct pidfh *pfh, int freeit);
44
45static int
46pidfile_verify(struct pidfh *pfh)
47{
48	struct stat sb;
49
50	if (pfh == NULL || pfh->pf_fd == -1)
51		return (EDOOFUS);
52	/*
53	 * Check remembered descriptor.
54	 */
55	if (fstat(pfh->pf_fd, &sb) == -1)
56		return (errno);
57	if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino)
58		return (EDOOFUS);
59	return (0);
60}
61
62static int
63pidfile_read(const char *path, pid_t *pidptr)
64{
65	char buf[16], *endptr;
66	int error, fd, i;
67
68	fd = open(path, O_RDONLY);
69	if (fd == -1)
70		return (errno);
71
72	i = read(fd, buf, sizeof(buf) - 1);
73	error = errno;	/* Remember errno in case close() wants to change it. */
74	close(fd);
75	if (i == -1)
76		return (error);
77	buf[i] = '\0';
78
79	*pidptr = strtol(buf, &endptr, 10);
80	if (endptr != &buf[i])
81		return (EINVAL);
82
83	return (0);
84}
85
86struct pidfh *
87pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
88{
89	struct pidfh *pfh;
90	struct stat sb;
91	int error, fd, len;
92
93	pfh = malloc(sizeof(*pfh));
94	if (pfh == NULL)
95		return (NULL);
96
97	if (path == NULL)
98		len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
99		    "/var/run/%s.pid", getprogname());
100	else
101		len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
102		    "%s", path);
103	if (len >= (int)sizeof(pfh->pf_path)) {
104		free(pfh);
105		errno = ENAMETOOLONG;
106		return (NULL);
107	}
108
109	/*
110	 * Open the PID file and obtain exclusive lock.
111	 * We truncate PID file here only to remove old PID immediatelly,
112	 * PID file will be truncated again in pidfile_write(), so
113	 * pidfile_write() can be called multiple times.
114	 */
115	fd = flopen(pfh->pf_path,
116	    O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, mode);
117	if (fd == -1) {
118		if (errno == EWOULDBLOCK && pidptr != NULL) {
119			errno = pidfile_read(pfh->pf_path, pidptr);
120			if (errno == 0)
121				errno = EEXIST;
122		}
123		free(pfh);
124		return (NULL);
125	}
126	/*
127	 * Remember file information, so in pidfile_write() we are sure we write
128	 * to the proper descriptor.
129	 */
130	if (fstat(fd, &sb) == -1) {
131		error = errno;
132		unlink(pfh->pf_path);
133		close(fd);
134		free(pfh);
135		errno = error;
136		return (NULL);
137	}
138
139	pfh->pf_fd = fd;
140	pfh->pf_dev = sb.st_dev;
141	pfh->pf_ino = sb.st_ino;
142
143	return (pfh);
144}
145
146int
147pidfile_write(struct pidfh *pfh)
148{
149	char pidstr[16];
150	int error, fd;
151
152	/*
153	 * Check remembered descriptor, so we don't overwrite some other
154	 * file if pidfile was closed and descriptor reused.
155	 */
156	errno = pidfile_verify(pfh);
157	if (errno != 0) {
158		/*
159		 * Don't close descriptor, because we are not sure if it's ours.
160		 */
161		return (-1);
162	}
163	fd = pfh->pf_fd;
164
165	/*
166	 * Truncate PID file, so multiple calls of pidfile_write() are allowed.
167	 */
168	if (ftruncate(fd, 0) == -1) {
169		error = errno;
170		_pidfile_remove(pfh, 0);
171		errno = error;
172		return (-1);
173	}
174
175	snprintf(pidstr, sizeof(pidstr), "%u", getpid());
176	if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) {
177		error = errno;
178		_pidfile_remove(pfh, 0);
179		errno = error;
180		return (-1);
181	}
182
183	return (0);
184}
185
186int
187pidfile_close(struct pidfh *pfh)
188{
189	int error;
190
191	error = pidfile_verify(pfh);
192	if (error != 0) {
193		errno = error;
194		return (-1);
195	}
196
197	if (close(pfh->pf_fd) == -1)
198		error = errno;
199	free(pfh);
200	if (error != 0) {
201		errno = error;
202		return (-1);
203	}
204	return (0);
205}
206
207static int
208_pidfile_remove(struct pidfh *pfh, int freeit)
209{
210	int error;
211
212	error = pidfile_verify(pfh);
213	if (error != 0) {
214		errno = error;
215		return (-1);
216	}
217
218	if (unlink(pfh->pf_path) == -1)
219		error = errno;
220	if (flock(pfh->pf_fd, LOCK_UN) == -1) {
221		if (error == 0)
222			error = errno;
223	}
224	if (close(pfh->pf_fd) == -1) {
225		if (error == 0)
226			error = errno;
227	}
228	if (freeit)
229		free(pfh);
230	else
231		pfh->pf_fd = -1;
232	if (error != 0) {
233		errno = error;
234		return (-1);
235	}
236	return (0);
237}
238
239int
240pidfile_remove(struct pidfh *pfh)
241{
242
243	return (_pidfile_remove(pfh, 1));
244}
245