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Import from old repository commit 61ef2b42a9c4ba8e1600f15bb0236765edc2ad45.

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Ben Pfaff
2009-07-08 13:19:16 -07:00
commit 064af42167
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lib/daemon.c Normal file
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/*
* Copyright (c) 2008, 2009 Nicira Networks.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#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;
}