daemon.c revision 231912 
1/*-
2 * Copyright (c) 1999 Berkeley Software Design, Inc. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 *    notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 *    notice, this list of conditions and the following disclaimer in the
11 *    documentation and/or other materials provided with the distribution.
12 * 3. Berkeley Software Design Inc's name may not be used to endorse or
13 *    promote products derived from this software without specific prior
14 *    written permission.
15 *
16 * THIS SOFTWARE IS PROVIDED BY BERKELEY SOFTWARE DESIGN INC ``AS IS'' AND
17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
19 * ARE DISCLAIMED.  IN NO EVENT SHALL BERKELEY SOFTWARE DESIGN INC BE LIABLE
20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
26 * SUCH DAMAGE.
27 *
28 *	From BSDI: daemon.c,v 1.2 1996/08/15 01:11:09 jch Exp
29 */
30
31#include <sys/cdefs.h>
32__FBSDID("$FreeBSD: head/usr.sbin/daemon/daemon.c 231912 2012-02-19 10:38:55Z trociny $");
33
34#include <sys/param.h>
35#include <sys/mman.h>
36#include <sys/wait.h>
37
38#include <err.h>
39#include <errno.h>
40#include <libutil.h>
41#include <login_cap.h>
42#include <pwd.h>
43#include <signal.h>
44#include <stdio.h>
45#include <stdlib.h>
46#include <unistd.h>
47
48static void dummy_sighandler(int);
49static void restrict_process(const char *);
50static int  wait_child(pid_t pid, sigset_t *mask);
51static void usage(void);
52
53int
54main(int argc, char *argv[])
55{
56	struct pidfh *pfh = NULL;
57	sigset_t mask, oldmask;
58	int ch, nochdir, noclose, restart;
59	const char *pidfile, *user;
60	pid_t otherpid, pid;
61
62	nochdir = noclose = 1;
63	restart = 0;
64	pidfile = user = NULL;
65	while ((ch = getopt(argc, argv, "-cfp:ru:")) != -1) {
66		switch (ch) {
67		case 'c':
68			nochdir = 0;
69			break;
70		case 'f':
71			noclose = 0;
72			break;
73		case 'p':
74			pidfile = optarg;
75			break;
76		case 'r':
77			restart = 1;
78			break;
79		case 'u':
80			user = optarg;
81			break;
82		default:
83			usage();
84		}
85	}
86	argc -= optind;
87	argv += optind;
88
89	if (argc == 0)
90		usage();
91
92	pfh = NULL;
93	/*
94	 * Try to open the pidfile before calling daemon(3),
95	 * to be able to report the error intelligently
96	 */
97	if (pidfile != NULL) {
98		pfh = pidfile_open(pidfile, 0600, &otherpid);
99		if (pfh == NULL) {
100			if (errno == EEXIST) {
101				errx(3, "process already running, pid: %d",
102				    otherpid);
103			}
104			err(2, "pidfile ``%s''", pidfile);
105		}
106	}
107
108	if (daemon(nochdir, noclose) == -1)
109		err(1, NULL);
110
111	/*
112	 * If the pidfile or restart option is specified the daemon
113	 * executes the command in a forked process and wait on child
114	 * exit to remove the pidfile or restart the command. Normally
115	 * we don't want the monitoring daemon to be terminated
116	 * leaving the running process and the stale pidfile, so we
117	 * catch SIGTERM and forward it to the children expecting to
118	 * get SIGCHLD eventually.
119	 */
120	pid = -1;
121	if (pidfile != NULL || restart) {
122		/*
123		 * Restore default action for SIGTERM in case the
124		 * parent process decided to ignore it.
125		 */
126		if (signal(SIGTERM, SIG_DFL) == SIG_ERR)
127			err(1, "signal");
128		/*
129		 * Because SIGCHLD is ignored by default, setup dummy handler
130		 * for it, so we can mask it.
131		 */
132		if (signal(SIGCHLD, dummy_sighandler) == SIG_ERR)
133			err(1, "signal");
134		/*
135		 * Block interesting signals.
136		 */
137		sigemptyset(&mask);
138		sigaddset(&mask, SIGTERM);
139		sigaddset(&mask, SIGCHLD);
140		if (sigprocmask(SIG_SETMASK, &mask, &oldmask) == -1)
141			err(1, "sigprocmask");
142		/*
143		 * Try to protect against pageout kill. Ignore the
144		 * error, madvise(2) will fail only if a process does
145		 * not have superuser privileges.
146		 */
147		(void)madvise(NULL, 0, MADV_PROTECT);
148restart:
149		/*
150		 * Spawn a child to exec the command, so in the parent
151		 * we could wait for it to exit and remove pidfile.
152		 */
153		pid = fork();
154		if (pid == -1) {
155			pidfile_remove(pfh);
156			err(1, "fork");
157		}
158	}
159	if (pid <= 0) {
160		if (pid == 0) {
161			/* Restore old sigmask in the child. */
162			if (sigprocmask(SIG_SETMASK, &oldmask, NULL) == -1)
163				err(1, "sigprocmask");
164		}
165		/* Now that we are the child, write out the pid. */
166		pidfile_write(pfh);
167
168		if (user != NULL)
169			restrict_process(user);
170
171		execvp(argv[0], argv);
172
173		/*
174		 * execvp() failed -- report the error. The child is
175		 * now running, so the exit status doesn't matter.
176		 */
177		err(1, "%s", argv[0]);
178	}
179	setproctitle("%s[%d]", argv[0], pid);
180	if (wait_child(pid, &mask) == 0 && restart) {
181		sleep(1);
182		goto restart;
183	}
184	pidfile_remove(pfh);
185	exit(0); /* Exit status does not matter. */
186}
187
188static void
189dummy_sighandler(int sig __unused)
190{
191	/* Nothing to do. */
192}
193
194static void
195restrict_process(const char *user)
196{
197	struct passwd *pw = NULL;
198
199	pw = getpwnam(user);
200	if (pw == NULL)
201		errx(1, "unknown user: %s", user);
202
203	if (setusercontext(NULL, pw, pw->pw_uid, LOGIN_SETALL) != 0)
204		errx(1, "failed to set user environment");
205}
206
207static int
208wait_child(pid_t pid, sigset_t *mask)
209{
210	int terminate, signo;
211
212	terminate = 0;
213	for (;;) {
214		if (sigwait(mask, &signo) == -1) {
215			warn("sigwaitinfo");
216			return (-1);
217		}
218		switch (signo) {
219		case SIGCHLD:
220			return (terminate);
221		case SIGTERM:
222			terminate = 1;
223			if (kill(pid, signo) == -1) {
224				warn("kill");
225				return (-1);
226			}
227			continue;
228		default:
229			warnx("sigwaitinfo: invalid signal: %d", signo);
230			return (-1);
231		}
232	}
233}
234
235static void
236usage(void)
237{
238	(void)fprintf(stderr,
239	    "usage: daemon [-cf] [-p pidfile] [-u user] command "
240		"arguments ...\n");
241	exit(1);
242}
243