1/*	$NetBSD: pidfile.c,v 1.2 2016/04/05 12:28:57 christos Exp $	*/
2
3/*-
4 * Copyright (c) 1999 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Jason R. Thorpe, Matthias Scheler and Julio Merino.
9 *
10 * Redistribution and use in source and binary forms, with or without
11 * modification, are permitted provided that the following conditions
12 * are met:
13 * 1. Redistributions of source code must retain the above copyright
14 *    notice, this list of conditions and the following disclaimer.
15 * 2. Redistributions in binary form must reproduce the above copyright
16 *    notice, this list of conditions and the following disclaimer in the
17 *    documentation and/or other materials provided with the distribution.
18 *
19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 * POSSIBILITY OF SUCH DAMAGE.
30 */
31#ifdef HAVE_CONFIG_H
32#include "config.h"
33#endif
34
35#include <sys/cdefs.h>
36#if defined(LIBC_SCCS) && !defined(lint)
37__RCSID("$NetBSD: pidfile.c,v 1.2 2016/04/05 12:28:57 christos Exp $");
38#endif
39
40#include <sys/param.h>
41
42#include <paths.h>
43#include <stdbool.h>
44#include <stdlib.h>
45#include <stdio.h>
46#include <string.h>
47#include <unistd.h>
48#ifdef HAVE_LIBUTIL_H
49#include <libutil.h>
50#endif
51#ifdef HAVE_UTIL_H
52#include <util.h>
53#endif
54
55static pid_t pidfile_pid;
56static char *pidfile_path;
57
58/* Deletes an existent pidfile iff it was created by this process. */
59static void
60pidfile_cleanup(void)
61{
62
63	if ((pidfile_path != NULL) && (pidfile_pid == getpid()))
64		(void) unlink(pidfile_path);
65}
66
67/* Registers an atexit(3) handler to delete the pidfile we have generated.
68 * We only register the handler when we create a pidfile, so we can assume
69 * that the pidfile exists.
70 *
71 * Returns 0 on success or -1 if the handler could not be registered. */
72static int
73register_atexit_handler(void)
74{
75	static bool done = false;
76
77	if (!done) {
78		if (atexit(pidfile_cleanup) < 0)
79			return -1;
80		done = true;
81	}
82
83	return 0;
84}
85
86/* Given a new pidfile name in 'path', deletes any previously-created pidfile
87 * if the previous file differs to the new one.
88 *
89 * If a previous file is deleted, returns 1, which means that a new pidfile
90 * must be created.  Otherwise, this returns 0, which means that the existing
91 * file does not need to be touched. */
92static int
93cleanup_old_pidfile(const char* path)
94{
95	if (pidfile_path != NULL) {
96		if (strcmp(pidfile_path, path) != 0) {
97			pidfile_cleanup();
98
99			free(pidfile_path);
100			pidfile_path = NULL;
101
102			return 1;
103		} else
104			return 0;
105	} else
106		return 1;
107}
108
109/* Constructs a name for a pidfile in the default location (/var/run).  If
110 * 'basename' is NULL, uses the name of the current program for the name of
111 * the pidfile.
112 *
113 * Returns a pointer to a dynamically-allocatd string containing the absolute
114 * path to the pidfile; NULL on failure. */
115static char *
116generate_varrun_path(const char *bname)
117{
118	char *path;
119
120	if (bname == NULL)
121		bname = getprogname();
122
123	/* _PATH_VARRUN includes trailing / */
124	if (asprintf(&path, "%s%s.pid", _PATH_VARRUN, bname) == -1)
125		return NULL;
126	return path;
127}
128
129/* Creates a pidfile with the provided name.  The new pidfile is "registered"
130 * in the global variables pidfile_path and pidfile_pid so that any further
131 * call to pidfile(3) can check if we are recreating the same file or a new
132 * one.
133 *
134 * Returns 0 on success or -1 if there is any error. */
135static int
136create_pidfile(const char* path)
137{
138	FILE *f;
139
140	if (register_atexit_handler() == -1)
141		return -1;
142
143	if (cleanup_old_pidfile(path) == 0)
144		return 0;
145
146	pidfile_path = strdup(path);
147	if (pidfile_path == NULL)
148		return -1;
149
150	if ((f = fopen(path, "w")) == NULL) {
151		free(pidfile_path);
152		pidfile_path = NULL;
153		return -1;
154	}
155
156	pidfile_pid = getpid();
157
158	(void) fprintf(f, "%d\n", pidfile_pid);
159	(void) fclose(f);
160
161	return 0;
162}
163
164int
165pidfile(const char *path)
166{
167
168	if (path == NULL || strchr(path, '/') == NULL) {
169		char *default_path;
170
171		if ((default_path = generate_varrun_path(path)) == NULL)
172			return -1;
173
174		if (create_pidfile(default_path) == -1) {
175			free(default_path);
176			return -1;
177		}
178
179		free(default_path);
180		return 0;
181	} else
182		return create_pidfile(path);
183}
184