pidfile.h revision 243750 
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 * Derived from FreeBSD head/lib/libutil/pidfile.c r231938
27 * $P4: //depot/projects/trustedbsd/openbsm/compat/pidfile.h#1 $
28 */
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 <time.h>
40#include <err.h>
41#include <errno.h>
42
43#include "flopen.h"
44
45struct pidfh {
46	int	pf_fd;
47	char	pf_path[MAXPATHLEN + 1];
48	dev_t	pf_dev;
49	ino_t	pf_ino;
50};
51
52static int _pidfile_remove(struct pidfh *pfh, int freeit);
53
54static int
55pidfile_verify(const struct pidfh *pfh)
56{
57	struct stat sb;
58
59	if (pfh == NULL || pfh->pf_fd == -1)
60		return (EINVAL);
61	/*
62	 * Check remembered descriptor.
63	 */
64	if (fstat(pfh->pf_fd, &sb) == -1)
65		return (errno);
66	if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino)
67		return (EINVAL);
68	return (0);
69}
70
71static int
72pidfile_read(const char *path, pid_t *pidptr)
73{
74	char buf[16], *endptr;
75	int error, fd, i;
76
77	fd = open(path, O_RDONLY);
78	if (fd == -1)
79		return (errno);
80
81	i = read(fd, buf, sizeof(buf) - 1);
82	error = errno;	/* Remember errno in case close() wants to change it. */
83	close(fd);
84	if (i == -1)
85		return (error);
86	else if (i == 0)
87		return (EAGAIN);
88	buf[i] = '\0';
89
90	*pidptr = strtol(buf, &endptr, 10);
91	if (endptr != &buf[i])
92		return (EINVAL);
93
94	return (0);
95}
96
97static struct pidfh *
98pidfile_open(const char *path, mode_t mode, pid_t *pidptr)
99{
100	struct pidfh *pfh;
101	struct stat sb;
102	int error, fd, len, count;
103	struct timespec rqtp;
104
105	if (pidptr != NULL)
106		*pidptr = -1;
107
108	if (path == NULL)
109		return (NULL);
110
111	pfh = malloc(sizeof(*pfh));
112	if (pfh == NULL)
113		return (NULL);
114
115	len = snprintf(pfh->pf_path, sizeof(pfh->pf_path),
116	    "%s", path);
117	if (len >= (int)sizeof(pfh->pf_path)) {
118		free(pfh);
119		errno = ENAMETOOLONG;
120		return (NULL);
121	}
122
123	/*
124	 * Open the PID file and obtain exclusive lock.
125	 * We truncate PID file here only to remove old PID immediatelly,
126	 * PID file will be truncated again in pidfile_write(), so
127	 * pidfile_write() can be called multiple times.
128	 */
129	fd = flopen(pfh->pf_path,
130#ifdef O_CLOEXEC
131	    O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK | O_CLOEXEC, mode);
132#else
133	    O_WRONLY | O_CREAT | O_TRUNC | O_NONBLOCK, mode);
134#endif
135	if (fd == -1) {
136		if (errno == EWOULDBLOCK && pidptr != NULL) {
137			count = 20;
138			rqtp.tv_sec = 0;
139			rqtp.tv_nsec = 5000000;
140			for (;;) {
141				errno = pidfile_read(pfh->pf_path, pidptr);
142				if (errno != EAGAIN || --count == 0)
143					break;
144				nanosleep(&rqtp, 0);
145			}
146			if (errno == EAGAIN)
147				*pidptr = -1;
148			if (errno == 0 || errno == EAGAIN)
149				errno = EEXIST;
150		}
151		free(pfh);
152		return (NULL);
153	}
154
155#ifndef O_CLOEXEC
156	if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) {
157		error = errno;
158		unlink(pfh->pf_path);
159		close(fd);
160		free(pfh);
161		errno = error;
162		return (NULL);
163	}
164#endif
165
166	/*
167	 * Remember file information, so in pidfile_write() we are sure we write
168	 * to the proper descriptor.
169	 */
170	if (fstat(fd, &sb) == -1) {
171		error = errno;
172		unlink(pfh->pf_path);
173		close(fd);
174		free(pfh);
175		errno = error;
176		return (NULL);
177	}
178
179	pfh->pf_fd = fd;
180	pfh->pf_dev = sb.st_dev;
181	pfh->pf_ino = sb.st_ino;
182
183	return (pfh);
184}
185
186static int
187pidfile_write(struct pidfh *pfh)
188{
189	char pidstr[16];
190	int error, fd;
191
192	/*
193	 * Check remembered descriptor, so we don't overwrite some other
194	 * file if pidfile was closed and descriptor reused.
195	 */
196	errno = pidfile_verify(pfh);
197	if (errno != 0) {
198		/*
199		 * Don't close descriptor, because we are not sure if it's ours.
200		 */
201		return (-1);
202	}
203	fd = pfh->pf_fd;
204
205	/*
206	 * Truncate PID file, so multiple calls of pidfile_write() are allowed.
207	 */
208	if (ftruncate(fd, 0) == -1) {
209		error = errno;
210		_pidfile_remove(pfh, 0);
211		errno = error;
212		return (-1);
213	}
214
215	snprintf(pidstr, sizeof(pidstr), "%u", getpid());
216	if (pwrite(fd, pidstr, strlen(pidstr), 0) != (ssize_t)strlen(pidstr)) {
217		error = errno;
218		_pidfile_remove(pfh, 0);
219		errno = error;
220		return (-1);
221	}
222
223	return (0);
224}
225
226static int
227pidfile_close(struct pidfh *pfh)
228{
229	int error;
230
231	error = pidfile_verify(pfh);
232	if (error != 0) {
233		errno = error;
234		return (-1);
235	}
236
237	if (close(pfh->pf_fd) == -1)
238		error = errno;
239	free(pfh);
240	if (error != 0) {
241		errno = error;
242		return (-1);
243	}
244	return (0);
245}
246
247static int
248_pidfile_remove(struct pidfh *pfh, int freeit)
249{
250	int error;
251
252	error = pidfile_verify(pfh);
253	if (error != 0) {
254		errno = error;
255		return (-1);
256	}
257
258	if (unlink(pfh->pf_path) == -1)
259		error = errno;
260	if (close(pfh->pf_fd) == -1) {
261		if (error == 0)
262			error = errno;
263	}
264	if (freeit)
265		free(pfh);
266	else
267		pfh->pf_fd = -1;
268	if (error != 0) {
269		errno = error;
270		return (-1);
271	}
272	return (0);
273}
274
275static int
276pidfile_remove(struct pidfh *pfh)
277{
278
279	return (_pidfile_remove(pfh, 1));
280}
281
282#if 0
283static int
284pidfile_fileno(const struct pidfh *pfh)
285{
286
287	if (pfh == NULL || pfh->pf_fd == -1) {
288		errno = EINVAL;
289		return (-1);
290	}
291	return (pfh->pf_fd);
292}
293#endif
294