2
0
mirror of https://github.com/openvswitch/ovs synced 2025-08-23 02:17:42 +00:00
ovs/lib/daemon.c

584 lines
16 KiB
C
Raw Normal View History

/*
* Copyright (c) 2008, 2009, 2010, 2011 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 <signal.h>
#include <stdlib.h>
#include <string.h>
#include <sys/resource.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <unistd.h>
#include "command-line.h"
#include "fatal-signal.h"
#include "dirs.h"
#include "lockfile.h"
#include "process.h"
#include "socket-util.h"
#include "timeval.h"
#include "util.h"
#include "vlog.h"
VLOG_DEFINE_THIS_MODULE(daemon);
/* --detach: Should we run in the background? */
static bool detach;
/* --pidfile: Name of pidfile (null if none). */
static char *pidfile;
/* Device and inode of pidfile, so we can avoid reopening it. */
static dev_t pidfile_dev;
static ino_t pidfile_ino;
/* --overwrite-pidfile: Create pidfile even if one already exists and is
locked? */
static bool overwrite_pidfile;
/* --no-chdir: Should we chdir to "/"? */
static bool chdir_ = true;
/* File descriptor used by daemonize_start() and daemonize_complete(). */
static int daemonize_fd = -1;
/* --monitor: Should a supervisory process monitor the daemon and restart it if
* it dies due to an error signal? */
static bool monitor;
/* 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)
: abs_file_name(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;
}
/* Sets that we do not chdir to "/". */
void
set_no_chdir(void)
{
chdir_ = false;
}
/* Will we chdir to "/" as part of daemonizing? */
bool
is_chdir_enabled(void)
{
return chdir_;
}
/* Normally, daemonize() or damonize_start() will terminate the program with a
* message if a locked pidfile already exists. If this function is called, an
* existing pidfile will be replaced, with a warning. */
void
ignore_existing_pidfile(void)
{
overwrite_pidfile = 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;
}
/* Will daemonize() really detach? */
bool
get_detach(void)
{
return detach;
}
/* Sets up a following call to daemonize() to fork a supervisory process to
* monitor the daemon and restart it if it dies due to an error signal. */
void
daemon_set_monitor(void)
{
monitor = true;
}
/* If a locked pidfile exists, issue a warning message and, unless
* ignore_existing_pidfile() has been called, terminate the program. */
static void
die_if_already_running(void)
{
pid_t pid;
if (!pidfile) {
return;
}
pid = read_pidfile_if_exists(pidfile);
if (pid > 0) {
if (!overwrite_pidfile) {
VLOG_ERR("%s: %s already running as pid %ld, aborting",
get_pidfile(), program_name, (long int) pid);
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's pid in it. 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. */
struct stat s;
if (!fstat(fd, &s)) {
pidfile_dev = s.st_dev;
pidfile_ino = s.st_ino;
} else {
VLOG_ERR("%s: fstat failed: %s",
pidfile, strerror(errno));
}
}
} else {
VLOG_ERR("%s: write failed: %s", tmpfile, strerror(errno));
close(fd);
}
free(text);
} 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)
{
daemonize_start();
daemonize_complete();
}
static pid_t
fork_and_wait_for_startup(int *fdp)
{
int fds[2];
pid_t pid;
xpipe(fds);
pid = fork();
if (pid > 0) {
/* Running in parent process. */
size_t bytes_read;
char c;
close(fds[1]);
fatal_signal_fork();
if (read_fully(fds[0], &c, 1, &bytes_read) != 0) {
int retval;
int status;
do {
retval = waitpid(pid, &status, 0);
} while (retval == -1 && errno == EINTR);
if (retval == pid
&& WIFEXITED(status)
&& WEXITSTATUS(status)) {
/* Child exited with an error. Convey the same error to
* our parent process as a courtesy. */
exit(WEXITSTATUS(status));
}
VLOG_FATAL("fork child failed to signal startup (%s)",
strerror(errno));
}
close(fds[0]);
*fdp = -1;
} else if (!pid) {
/* Running in child process. */
close(fds[0]);
time_postfork();
lockfile_postfork();
*fdp = fds[1];
} else {
VLOG_FATAL("fork failed (%s)", strerror(errno));
}
return pid;
}
static void
fork_notify_startup(int fd)
{
if (fd != -1) {
size_t bytes_written;
int error;
error = write_fully(fd, "", 1, &bytes_written);
if (error) {
VLOG_FATAL("pipe write failed (%s)", strerror(error));
}
close(fd);
}
}
static bool
should_restart(int status)
{
if (WIFSIGNALED(status)) {
static const int error_signals[] = {
SIGABRT, SIGALRM, SIGBUS, SIGFPE, SIGILL, SIGPIPE, SIGSEGV,
SIGXCPU, SIGXFSZ
};
size_t i;
for (i = 0; i < ARRAY_SIZE(error_signals); i++) {
if (error_signals[i] == WTERMSIG(status)) {
return true;
}
}
}
return false;
}
static void
monitor_daemon(pid_t daemon_pid)
{
/* XXX Should log daemon's stderr output at startup time. */
const char *saved_program_name;
time_t last_restart;
char *status_msg;
int crashes;
saved_program_name = program_name;
program_name = xasprintf("monitor(%s)", program_name);
status_msg = xstrdup("healthy");
last_restart = TIME_MIN;
crashes = 0;
for (;;) {
int retval;
int status;
proctitle_set("%s: monitoring pid %lu (%s)",
saved_program_name, (unsigned long int) daemon_pid,
status_msg);
do {
retval = waitpid(daemon_pid, &status, 0);
} while (retval == -1 && errno == EINTR);
if (retval == -1) {
VLOG_FATAL("waitpid failed (%s)", strerror(errno));
} else if (retval == daemon_pid) {
char *s = process_status_msg(status);
if (should_restart(status)) {
free(status_msg);
status_msg = xasprintf("%d crashes: pid %lu died, %s",
++crashes,
(unsigned long int) daemon_pid, s);
free(s);
if (WCOREDUMP(status)) {
/* Disable further core dumps to save disk space. */
struct rlimit r;
r.rlim_cur = 0;
r.rlim_max = 0;
if (setrlimit(RLIMIT_CORE, &r) == -1) {
VLOG_WARN("failed to disable core dumps: %s",
strerror(errno));
}
}
/* Throttle restarts to no more than once every 10 seconds. */
if (time(NULL) < last_restart + 10) {
VLOG_WARN("%s, waiting until 10 seconds since last "
"restart", status_msg);
for (;;) {
time_t now = time(NULL);
time_t wakeup = last_restart + 10;
if (now >= wakeup) {
break;
}
sleep(wakeup - now);
}
}
last_restart = time(NULL);
VLOG_ERR("%s, restarting", status_msg);
daemon_pid = fork_and_wait_for_startup(&daemonize_fd);
if (!daemon_pid) {
break;
}
} else {
VLOG_INFO("pid %lu died, %s, exiting",
(unsigned long int) daemon_pid, s);
free(s);
exit(0);
}
}
}
free(status_msg);
/* Running in new daemon process. */
proctitle_restore();
free((char *) program_name);
program_name = saved_program_name;
}
/* Close stdin, stdout, stderr. If we're started from e.g. an SSH session,
* then this keeps us from holding that session open artificially. */
static void
close_standard_fds(void)
{
int null_fd = get_null_fd();
if (null_fd >= 0) {
dup2(null_fd, STDIN_FILENO);
dup2(null_fd, STDOUT_FILENO);
dup2(null_fd, STDERR_FILENO);
}
}
/* If daemonization is configured, then starts daemonization, by forking and
* returning in the child process. The parent process hangs around until the
* child lets it know either that it completed startup successfully (by calling
* daemon_complete()) or that it failed to start up (by exiting with a nonzero
* exit code). */
void
daemonize_start(void)
{
daemonize_fd = -1;
if (detach) {
if (fork_and_wait_for_startup(&daemonize_fd) > 0) {
/* Running in parent process. */
exit(0);
}
/* Running in daemon or monitor process. */
}
if (monitor) {
int saved_daemonize_fd = daemonize_fd;
pid_t daemon_pid;
daemon_pid = fork_and_wait_for_startup(&daemonize_fd);
if (daemon_pid > 0) {
/* Running in monitor process. */
fork_notify_startup(saved_daemonize_fd);
close_standard_fds();
monitor_daemon(daemon_pid);
}
/* Running in daemon process. */
}
die_if_already_running();
make_pidfile();
/* Make sure that the unixctl commands for vlog get registered in a
* daemon, even before the first log message. */
vlog_init();
}
/* If daemonization is configured, then this function notifies the parent
* process that the child process has completed startup successfully.
*
* Calling this function more than once has no additional effect. */
void
daemonize_complete(void)
{
fork_notify_startup(daemonize_fd);
daemonize_fd = -1;
if (detach) {
setsid();
if (chdir_) {
ignore(chdir("/"));
}
close_standard_fds();
detach = false;
}
}
void
daemon_usage(void)
{
printf(
"\nDaemon options:\n"
" --detach run in background as daemon\n"
" --no-chdir do not chdir to '/'\n"
" --pidfile[=FILE] create pidfile (default: %s/%s.pid)\n"
" --overwrite-pidfile with --pidfile, start even if already "
"running\n",
ovs_rundir(), program_name);
}
static pid_t
read_pidfile__(const char *pidfile, bool must_exist)
{
char line[128];
struct flock lck;
struct stat s;
FILE *file;
int error;
if ((pidfile_ino || pidfile_dev)
&& !stat(pidfile, &s)
&& s.st_ino == pidfile_ino && s.st_dev == pidfile_dev) {
/* It's our own pidfile. We can't afford to open it, because closing
* *any* fd for a file that a process has locked also releases all the
* locks on that file.
*
* Fortunately, we know the associated pid anyhow: */
return getpid();
}
file = fopen(pidfile, "r");
if (!file) {
if (errno == ENOENT && !must_exist) {
return 0;
}
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;
lck.l_pid = 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;
}
/* Opens and reads a PID from 'pidfile'. Returns the positive PID if
* successful, otherwise a negative errno value. */
pid_t
read_pidfile(const char *pidfile)
{
return read_pidfile__(pidfile, true);
}
/* Opens and reads a PID from 'pidfile', if it exists. Returns 0 if 'pidfile'
* doesn't exist, the positive PID if successful, otherwise a negative errno
* value. */
pid_t
read_pidfile_if_exists(const char *pidfile)
{
return read_pidfile__(pidfile, false);
}