[ovs.git] / lib / daemon.c

/*
 * Copyright (c) 2008, 2009 Nicira Networks.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at:
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include <config.h>
#include "daemon.h"
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "fatal-signal.h"
#include "dirs.h"
#include "util.h"

#define THIS_MODULE VLM_daemon
#include "vlog.h"

/* Should we run in the background? */
static bool detach;

/* Name of pidfile (null if none). */
static char *pidfile;

/* Create pidfile even if one already exists and is locked? */
static bool force;

/* Returns the file name that would be used for a pidfile if 'name' were
 * provided to set_pidfile().  The caller must free the returned string. */
char *
make_pidfile_name(const char *name) 
{
    return (!name ? xasprintf("%s/%s.pid", ovs_rundir, program_name)
            : *name == '/' ? xstrdup(name)
            : xasprintf("%s/%s", ovs_rundir, name));
}

/* Sets up a following call to daemonize() to create a pidfile named 'name'.
 * If 'name' begins with '/', then it is treated as an absolute path.
 * Otherwise, it is taken relative to RUNDIR, which is $(prefix)/var/run by
 * default.
 *
 * If 'name' is null, then program_name followed by ".pid" is used. */
void
set_pidfile(const char *name)
{
    free(pidfile);
    pidfile = make_pidfile_name(name);
}

/* Returns an absolute path to the configured pidfile, or a null pointer if no
 * pidfile is configured.  The caller must not modify or free the returned
 * string. */
const char *
get_pidfile(void)
{
    return pidfile;
}

/* Normally, die_if_already_running() will terminate the program with a message
 * if a locked pidfile already exists.  If this function is called,
 * die_if_already_running() will merely log a warning. */
void
ignore_existing_pidfile(void)
{
    force = true;
}

/* Sets up a following call to daemonize() to detach from the foreground
 * session, running this process in the background.  */
void
set_detach(void)
{
    detach = true;
}

/* If a pidfile has been configured and that pidfile already exists and is
 * locked by a running process, returns the pid of the running process.
 * Otherwise, returns 0. */
static pid_t
already_running(void)
{
    pid_t pid = 0;
    if (pidfile) {
        int fd = open(pidfile, O_RDWR);
        if (fd >= 0) {
            struct flock lck;
            lck.l_type = F_WRLCK;
            lck.l_whence = SEEK_SET;
            lck.l_start = 0;
            lck.l_len = 0;
            if (fcntl(fd, F_GETLK, &lck) != -1 && lck.l_type != F_UNLCK) {
                pid = lck.l_pid;
            }
            close(fd);
        }
    }
    return pid;
}

/* If a locked pidfile exists, issue a warning message and, unless
 * ignore_existing_pidfile() has been called, terminate the program. */
void
die_if_already_running(void)
{
    pid_t pid = already_running();
    if (pid) {
        if (!force) {
            ovs_fatal(0, "%s: already running as pid %ld",
                      get_pidfile(), (long int) pid);
        } else {
            VLOG_WARN("%s: %s already running as pid %ld",
                      get_pidfile(), program_name, (long int) pid);
        }
    }
}

/* If a pidfile has been configured, creates it and stores the running process'
 * pid init.  Ensures that the pidfile will be deleted when the process
 * exits. */
static void
make_pidfile(void)
{
    if (pidfile) {
        /* Create pidfile via temporary file, so that observers never see an
         * empty pidfile or an unlocked pidfile. */
        long int pid = getpid();
        char *tmpfile;
        int fd;

        tmpfile = xasprintf("%s.tmp%ld", pidfile, pid);
        fatal_signal_add_file_to_unlink(tmpfile);
        fd = open(tmpfile, O_CREAT | O_WRONLY | O_TRUNC, 0666);
        if (fd >= 0) {
            struct flock lck;
            lck.l_type = F_WRLCK;
            lck.l_whence = SEEK_SET;
            lck.l_start = 0;
            lck.l_len = 0;
            if (fcntl(fd, F_SETLK, &lck) != -1) {
                char *text = xasprintf("%ld\n", pid);
                if (write(fd, text, strlen(text)) == strlen(text)) {
                    fatal_signal_add_file_to_unlink(pidfile);
                    if (rename(tmpfile, pidfile) < 0) {
                        VLOG_ERR("failed to rename \"%s\" to \"%s\": %s",
                                 tmpfile, pidfile, strerror(errno));
                        fatal_signal_remove_file_to_unlink(pidfile);
                        close(fd);
                    } else {
                        /* Keep 'fd' open to retain the lock. */
                    }
                    free(text);
                } else {
                    VLOG_ERR("%s: write failed: %s", tmpfile, strerror(errno));
                    close(fd);
                }
            } else {
                VLOG_ERR("%s: fcntl failed: %s", tmpfile, strerror(errno));
                close(fd);
            }
        } else {
            VLOG_ERR("%s: create failed: %s", tmpfile, strerror(errno));
        }
        fatal_signal_remove_file_to_unlink(tmpfile);
        free(tmpfile);
    }
    free(pidfile);
    pidfile = NULL;
}

/* If configured with set_pidfile() or set_detach(), creates the pid file and
 * detaches from the foreground session.  */
void
daemonize(void)
{
    if (detach) {
        char c = 0;
        int fds[2];
        if (pipe(fds) < 0) {
            ovs_fatal(errno, "pipe failed");
        }

        switch (fork()) {
        default:
            /* Parent process: wait for child to create pidfile, then exit. */
            close(fds[1]);
            fatal_signal_fork();
            if (read(fds[0], &c, 1) != 1) {
                ovs_fatal(errno, "daemon child failed to signal startup");
            }
            exit(0);

        case 0:
            /* Child process. */
            close(fds[0]);
            make_pidfile();
            write(fds[1], &c, 1);
            close(fds[1]);
            setsid();
            chdir("/");
            break;

        case -1:
            /* Error. */
            ovs_fatal(errno, "could not fork");
            break;
        }
    } else {
        make_pidfile();
    }
}

void
daemon_usage(void)
{
    printf(
        "\nDaemon options:\n"
        "  -D, --detach            run in background as daemon\n"
        "  -P, --pidfile[=FILE]    create pidfile (default: %s/%s.pid)\n"
        "  -f, --force             with -P, start even if already running\n",
        ovs_rundir, program_name);
}

/* Opens and reads a PID from 'pidfile'.  Returns the nonnegative PID if
 * successful, otherwise a negative errno value. */
pid_t
read_pidfile(const char *pidfile)
{
    char line[128];
    struct flock lck;
    FILE *file;
    int error;

    file = fopen(pidfile, "r");
    if (!file) {
        error = errno;
        VLOG_WARN("%s: open: %s", pidfile, strerror(error));
        goto error;
    }

    lck.l_type = F_WRLCK;
    lck.l_whence = SEEK_SET;
    lck.l_start = 0;
    lck.l_len = 0;
    if (fcntl(fileno(file), F_GETLK, &lck)) {
        error = errno;
        VLOG_WARN("%s: fcntl: %s", pidfile, strerror(error));
        goto error;
    }
    if (lck.l_type == F_UNLCK) {
        error = ESRCH;
        VLOG_WARN("%s: pid file is not locked", pidfile);
        goto error;
    }

    if (!fgets(line, sizeof line, file)) {
        if (ferror(file)) {
            error = errno;
            VLOG_WARN("%s: read: %s", pidfile, strerror(error));
        } else {
            error = ESRCH;
            VLOG_WARN("%s: read: unexpected end of file", pidfile);
        }
        goto error;
    }

    if (lck.l_pid != strtoul(line, NULL, 10)) {
        error = ESRCH;
        VLOG_WARN("l_pid (%ld) != %s pid (%s)",
                   (long int) lck.l_pid, pidfile, line);
        goto error;
    }

    fclose(file);
    return lck.l_pid;

error:
    if (file) {
        fclose(file);
    }
    return -error;
}
Commit	Line	Data
064af421 BP	1	/*
	2	* Copyright (c) 2008, 2009 Nicira Networks.
	3	*
a14bc59f BP	4	* Licensed under the Apache License, Version 2.0 (the "License");
	5	* you may not use this file except in compliance with the License.
	6	* You may obtain a copy of the License at:
064af421	7	*
a14bc59f BP	8	* http://www.apache.org/licenses/LICENSE-2.0
	9	*
	10	* Unless required by applicable law or agreed to in writing, software
	11	* distributed under the License is distributed on an "AS IS" BASIS,
	12	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	13	* See the License for the specific language governing permissions and
	14	* limitations under the License.
064af421 BP	15	*/
	16
	17	#include <config.h>
	18	#include "daemon.h"
	19	#include <errno.h>
	20	#include <fcntl.h>
	21	#include <stdlib.h>
	22	#include <string.h>
	23	#include <unistd.h>
	24	#include "fatal-signal.h"
	25	#include "dirs.h"
	26	#include "util.h"
	27
	28	#define THIS_MODULE VLM_daemon
	29	#include "vlog.h"
	30
	31	/* Should we run in the background? */
	32	static bool detach;
	33
	34	/* Name of pidfile (null if none). */
	35	static char *pidfile;
	36
	37	/* Create pidfile even if one already exists and is locked? */
	38	static bool force;
	39
	40	/* Returns the file name that would be used for a pidfile if 'name' were
	41	* provided to set_pidfile(). The caller must free the returned string. */
	42	char *
	43	make_pidfile_name(const char *name)
	44	{
	45	return (!name ? xasprintf("%s/%s.pid", ovs_rundir, program_name)
	46	: *name == '/' ? xstrdup(name)
	47	: xasprintf("%s/%s", ovs_rundir, name));
	48	}
	49
	50	/* Sets up a following call to daemonize() to create a pidfile named 'name'.
	51	* If 'name' begins with '/', then it is treated as an absolute path.
	52	* Otherwise, it is taken relative to RUNDIR, which is $(prefix)/var/run by
	53	* default.
	54	*
	55	* If 'name' is null, then program_name followed by ".pid" is used. */
	56	void
	57	set_pidfile(const char *name)
	58	{
	59	free(pidfile);
	60	pidfile = make_pidfile_name(name);
	61	}
	62
	63	/* Returns an absolute path to the configured pidfile, or a null pointer if no
	64	* pidfile is configured. The caller must not modify or free the returned
	65	* string. */
	66	const char *
	67	get_pidfile(void)
	68	{
	69	return pidfile;
	70	}
	71
	72	/* Normally, die_if_already_running() will terminate the program with a message
	73	* if a locked pidfile already exists. If this function is called,
	74	* die_if_already_running() will merely log a warning. */
	75	void
	76	ignore_existing_pidfile(void)
	77	{
	78	force = true;
79	}
80
81	/* Sets up a following call to daemonize() to detach from the foreground
82	* session, running this process in the background. */
83	void
84	set_detach(void)
85	{
86	detach = true;
87	}
88
89	/* If a pidfile has been configured and that pidfile already exists and is
90	* locked by a running process, returns the pid of the running process.
91	* Otherwise, returns 0. */
92	static pid_t
93	already_running(void)
94	{
95	pid_t pid = 0;
96	if (pidfile) {
97	int fd = open(pidfile, O_RDWR);
98	if (fd >= 0) {
99	struct flock lck;
100	lck.l_type = F_WRLCK;
101	lck.l_whence = SEEK_SET;
102	lck.l_start = 0;
103	lck.l_len = 0;
104	if (fcntl(fd, F_GETLK, &lck) != -1 && lck.l_type != F_UNLCK) {
105	pid = lck.l_pid;
106	}
107	close(fd);
108	}
109	}
110	return pid;
111	}
112
113	/* If a locked pidfile exists, issue a warning message and, unless
114	* ignore_existing_pidfile() has been called, terminate the program. */
115	void
116	die_if_already_running(void)
117	{
118	pid_t pid = already_running();
119	if (pid) {
120	if (!force) {
121	ovs_fatal(0, "%s: already running as pid %ld",
122	get_pidfile(), (long int) pid);
123	} else {
124	VLOG_WARN("%s: %s already running as pid %ld",
125	get_pidfile(), program_name, (long int) pid);
126	}
127	}
128	}
129
130	/* If a pidfile has been configured, creates it and stores the running process'
131	* pid init. Ensures that the pidfile will be deleted when the process
132	* exits. */
133	static void
134	make_pidfile(void)
135	{
136	if (pidfile) {
137	/* Create pidfile via temporary file, so that observers never see an
138	* empty pidfile or an unlocked pidfile. */
139	long int pid = getpid();
140	char *tmpfile;
141	int fd;
142
143	tmpfile = xasprintf("%s.tmp%ld", pidfile, pid);
144	fatal_signal_add_file_to_unlink(tmpfile);
145	fd = open(tmpfile, O_CREAT \| O_WRONLY \| O_TRUNC, 0666);
146	if (fd >= 0) {
147	struct flock lck;
148	lck.l_type = F_WRLCK;
149	lck.l_whence = SEEK_SET;
150	lck.l_start = 0;
151	lck.l_len = 0;
152	if (fcntl(fd, F_SETLK, &lck) != -1) {
153	char *text = xasprintf("%ld\n", pid);
154	if (write(fd, text, strlen(text)) == strlen(text)) {
155	fatal_signal_add_file_to_unlink(pidfile);
156	if (rename(tmpfile, pidfile) < 0) {
157	VLOG_ERR("failed to rename \"%s\" to \"%s\": %s",
158	tmpfile, pidfile, strerror(errno));
159	fatal_signal_remove_file_to_unlink(pidfile);
160	close(fd);
161	} else {
162	/* Keep 'fd' open to retain the lock. */
163	}
164	free(text);
165	} else {
166	VLOG_ERR("%s: write failed: %s", tmpfile, strerror(errno));
167	close(fd);
168	}
169	} else {
170	VLOG_ERR("%s: fcntl failed: %s", tmpfile, strerror(errno));
171	close(fd);
172	}
173	} else {
174	VLOG_ERR("%s: create failed: %s", tmpfile, strerror(errno));
175	}
176	fatal_signal_remove_file_to_unlink(tmpfile);
177	free(tmpfile);
178	}
179	free(pidfile);
180	pidfile = NULL;
181	}
182
183	/* If configured with set_pidfile() or set_detach(), creates the pid file and
184	* detaches from the foreground session. */
185	void
186	daemonize(void)
187	{
188	if (detach) {
189	char c = 0;
190	int fds[2];
191	if (pipe(fds) < 0) {
192	ovs_fatal(errno, "pipe failed");
193	}
194
195	switch (fork()) {
196	default:
197	/* Parent process: wait for child to create pidfile, then exit. */
198	close(fds[1]);
199	fatal_signal_fork();
200	if (read(fds[0], &c, 1) != 1) {
201	ovs_fatal(errno, "daemon child failed to signal startup");
202	}
203	exit(0);
204
205	case 0:
206	/* Child process. */
207	close(fds[0]);
208	make_pidfile();
209	write(fds[1], &c, 1);
210	close(fds[1]);
211	setsid();
212	chdir("/");
213	break;
214
215	case -1:
216	/* Error. */
217	ovs_fatal(errno, "could not fork");
218	break;
219	}
220	} else {
221	make_pidfile();
222	}
223	}
224
225	void
226	daemon_usage(void)
227	{
228	printf(
229	"\nDaemon options:\n"
230	" -D, --detach run in background as daemon\n"
231	" -P, --pidfile[=FILE] create pidfile (default: %s/%s.pid)\n"
232	" -f, --force with -P, start even if already running\n",
233	ovs_rundir, program_name);
234	}
235
236	/* Opens and reads a PID from 'pidfile'. Returns the nonnegative PID if
237	* successful, otherwise a negative errno value. */
238	pid_t
239	read_pidfile(const char *pidfile)
240	{
241	char line[128];
242	struct flock lck;
243	FILE *file;
244	int error;
245
246	file = fopen(pidfile, "r");
247	if (!file) {
248	error = errno;
249	VLOG_WARN("%s: open: %s", pidfile, strerror(error));
250	goto error;
251	}
252
253	lck.l_type = F_WRLCK;
254	lck.l_whence = SEEK_SET;
255	lck.l_start = 0;
256	lck.l_len = 0;
257	if (fcntl(fileno(file), F_GETLK, &lck)) {
258	error = errno;
259	VLOG_WARN("%s: fcntl: %s", pidfile, strerror(error));
260	goto error;
261	}
262	if (lck.l_type == F_UNLCK) {
263	error = ESRCH;
264	VLOG_WARN("%s: pid file is not locked", pidfile);
265	goto error;
266	}
267
268	if (!fgets(line, sizeof line, file)) {
269	if (ferror(file)) {
270	error = errno;
271	VLOG_WARN("%s: read: %s", pidfile, strerror(error));
272	} else {
273	error = ESRCH;
274	VLOG_WARN("%s: read: unexpected end of file", pidfile);
275	}
276	goto error;
277	}
278
279	if (lck.l_pid != strtoul(line, NULL, 10)) {
280	error = ESRCH;
281	VLOG_WARN("l_pid (%ld) != %s pid (%s)",
282	(long int) lck.l_pid, pidfile, line);
283	goto error;
284	}
285
286	fclose(file);
287	return lck.l_pid;
288
289	error:
290	if (file) {
291	fclose(file);
292	}
293	return -error;
294	}