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/*
* Daemonization & pidfile handling.
*
* Copyright (c) 2007-2009 Marko Kreen, Skype Technologies OÜ
*
* 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 <usual/daemon.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <stdio.h>
#include <usual/logging.h>
#include <usual/signal.h>
/*
* pidfile management.
*/
static char *g_pidfile;
static void remove_pidfile(void)
{
if (!g_pidfile)
return;
unlink(g_pidfile);
free(g_pidfile);
g_pidfile = NULL;
}
/*
* Reads pid from pidfile and sends a signal to it.
*
* true - signaling was successful.
* false - ENOENT / ESRCH
*
* fatal() otherwise.
*/
bool signal_pidfile(const char *pidfile, int sig)
{
char buf[128 + 1];
struct stat st;
pid_t pid = 0;
int fd, res;
if (!pidfile || !pidfile[0])
return false;
intr_loop:
/* check if pidfile exists */
if (stat(pidfile, &st) < 0)
goto fail;
/* read old pid */
fd = open(pidfile, O_RDONLY);
if (fd < 0)
goto fail;
res = read(fd, buf, sizeof(buf) - 1);
close(fd);
if (res <= 0)
goto fail;
/* parse pid */
buf[res] = 0;
errno = 0;
pid = strtoul(buf, NULL, 10);
if (errno) {
/* should we panic, or say no such process exists? */
if (0)
errno = ESRCH;
goto fail;
}
/* send the signal */
res = kill(pid, sig);
if (res == 0)
return true;
fail:
/* decide error seriousness */
if (errno == EINTR)
goto intr_loop;
if (errno == ENOENT || errno == ESRCH)
return false;
fatal_perror("signal_pidfile: Unexpected error");
}
static void check_pidfile(const char *pidfile)
{
if (signal_pidfile(pidfile, 0))
fatal("pidfile exists, another instance running?");
if (errno == ESRCH) {
log_info("Stale pidfile, removing");
unlink(pidfile);
}
}
static void write_pidfile(const char *pidfile, bool first_write)
{
char buf[64];
pid_t pid;
int res, fd, len;
static int atexit_hook = 0;
int flags = O_WRONLY | O_CREAT;
if (!pidfile || !pidfile[0])
return;
if (g_pidfile)
free(g_pidfile);
g_pidfile = strdup(pidfile);
if (!g_pidfile)
fatal_perror("cannot alloc pidfile");
pid = getpid();
snprintf(buf, sizeof(buf), "%u\n", (unsigned)pid);
/* don't allow overwrite on first write */
if (first_write)
flags |= O_EXCL;
fd = open(pidfile, flags, 0644);
if (fd < 0)
fatal_perror("Cannot write pidfile: '%s'", pidfile);
len = strlen(buf);
loop:
res = write(fd, buf, len);
if (res < 0) {
if (errno == EINTR)
goto loop;
fatal_perror("Write to pidfile failed: '%s'", pidfile);
} else if (res < len) {
len -= res;
goto loop;
}
close(fd);
if (!atexit_hook) {
/* only remove when we have it actually written */
atexit(remove_pidfile);
atexit_hook = 1;
}
}
/*
* Function: daemonize
*
* Handle pidfile and daemonization.
*
* If pidfile is given, check if old process is running.
*
* If going background is required, require non-empty pidfile
* and logfile. Then fork to background and write pidfile.
*/
void daemonize(const char *pidfile, bool go_background)
{
int pid, fd;
if (pidfile && pidfile[0]) {
check_pidfile(pidfile);
/* write pidfile twice, to be able to show problems to user */
write_pidfile(pidfile, true);
} else if (go_background)
fatal("daemon needs pidfile configured");
if (!go_background)
return;
if ((!cf_logfile || !cf_logfile[0]) && !cf_syslog)
fatal("daemon needs logging configured");
/* send stdin, stdout, stderr to /dev/null */
fd = open("/dev/null", O_RDWR);
if (fd < 0)
fatal_perror("/dev/null");
dup2(fd, 0);
dup2(fd, 1);
dup2(fd, 2);
if (fd > 2)
close(fd);
/* fork new process */
pid = fork();
if (pid < 0)
fatal_perror("fork");
if (pid > 0)
_exit(0);
/* create new session */
pid = setsid();
if (pid < 0)
fatal_perror("setsid");
/* fork again to avoid being session leader */
pid = fork();
if (pid < 0)
fatal_perror("fork");
if (pid > 0)
_exit(0);
write_pidfile(pidfile, false);
}
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