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/*
 * Copyright (c) 2001-2002 Packet Design, LLC.
 * All rights reserved.
 * 
 * Subject to the following obligations and disclaimer of warranty,
 * use and redistribution of this software, in source or object code
 * forms, with or without modifications are expressly permitted by
 * Packet Design; provided, however, that:
 * 
 *    (i)  Any and all reproductions of the source or object code
 *         must include the copyright notice above and the following
 *         disclaimer of warranties; and
 *    (ii) No rights are granted, in any manner or form, to use
 *         Packet Design trademarks, including the mark "PACKET DESIGN"
 *         on advertising, endorsements, or otherwise except as such
 *         appears in the above copyright notice or in the software.
 * 
 * THIS SOFTWARE IS BEING PROVIDED BY PACKET DESIGN "AS IS", AND
 * TO THE MAXIMUM EXTENT PERMITTED BY LAW, PACKET DESIGN MAKES NO
 * REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED, REGARDING
 * THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY AND ALL IMPLIED
 * WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE,
 * OR NON-INFRINGEMENT.  PACKET DESIGN DOES NOT WARRANT, GUARANTEE,
 * OR MAKE ANY REPRESENTATIONS REGARDING THE USE OF, OR THE RESULTS
 * OF THE USE OF THIS SOFTWARE IN TERMS OF ITS CORRECTNESS, ACCURACY,
 * RELIABILITY OR OTHERWISE.  IN NO EVENT SHALL PACKET DESIGN BE
 * LIABLE FOR ANY DAMAGES RESULTING FROM OR ARISING OUT OF ANY USE
 * OF THIS SOFTWARE, INCLUDING WITHOUT LIMITATION, ANY DIRECT,
 * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, PUNITIVE, OR CONSEQUENTIAL
 * DAMAGES, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES, LOSS OF
 * USE, DATA OR PROFITS, HOWEVER CAUSED AND UNDER ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF PACKET DESIGN IS ADVISED OF
 * THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Author: Archie Cobbs <archie@freebsd.org>
 */

#include <sys/types.h>
#include <sys/stat.h>

#include <netinet/in.h>

#include <stdio.h>
#include <assert.h>
#include <signal.h>
#include <errno.h>
#include <syslog.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdarg.h>

#include "structs/structs.h"
#include "structs/type/array.h"
#include "util/typed_mem.h"
#include "config/app_config.h"
#include "sys/alog.h"

/************************************************************************
			PIDFILE SUBSYSTEM
************************************************************************/

static app_ss_startup_t		app_pidfile_start;
static app_ss_shutdown_t	app_pidfile_stop;
static app_ss_willrun_t		app_pidfile_willrun;
static app_ss_changed_t		app_pidfile_changed;

static int			app_pidfile_fd = -1;
static int			app_pidfile_pid;

const struct app_subsystem	app_config_pidfile_subsystem = {
	"pidfile",
	NULL,
	app_pidfile_start,
	app_pidfile_stop,
	app_pidfile_willrun,
	app_pidfile_changed,
	NULL
};

/*
 * PID file startup
 */
static int
app_pidfile_start(struct app_config_ctx *ctx,
	const struct app_subsystem *ss, const void *config)
{
	const char *const name = ss->arg;
	char *path;
	char buf[32];

	/* Get PID file name */
	if ((path = structs_get_string(app_config_get_type(ctx),
	    name, config, TYPED_MEM_TEMP)) == NULL) {
		alogf(LOG_ERR, "%s: %m", "structs_get_string");
		return (-1);
	}

	/* Create new PID file, or reset old one */
	if (app_pidfile_fd != -1) {
		alog(LOG_DEBUG, "rewriting pidfile \"%s\"", path);
		(void)ftruncate(app_pidfile_fd, 0);
	} else {
#ifdef O_EXLOCK
		const int flags = O_CREAT|O_WRONLY|O_EXLOCK|O_NONBLOCK;
#else
		const int flags = O_CREAT|O_WRONLY|O_NONBLOCK;
#endif

		/* Open file */
		alog(LOG_DEBUG, "creating pidfile \"%s\"", path);
		if ((app_pidfile_fd = open(path, flags, 0644)) == -1)
		    	goto failed;
#ifdef O_EXLOCK
		goto got_lock;
#else
	    {
		struct flock f;

		memset(&f, 0, sizeof(f));
		f.l_pid = getpid();
		f.l_type = F_WRLCK;
		f.l_whence = SEEK_SET;
		if (fcntl(app_pidfile_fd, F_SETLK, &f) != -1)
		    	goto got_lock;
	    }
#endif
failed:
		/* Failed to open and lock pidfile */
		switch (errno) {
		case EWOULDBLOCK:
			alog(LOG_ERR, "%s: file locked: exiting", path);
			(void)kill(getpid(), SIGTERM);
			FREE(TYPED_MEM_TEMP, path);
			return (-1);
		default:
			alog(LOG_ERR, "%s: %m", path);
			FREE(TYPED_MEM_TEMP, path);
			return (-1);
		}
got_lock:
		(void)fcntl(app_pidfile_fd, F_SETFD, 1);
		if (ftruncate(app_pidfile_fd, 0) == -1) {
			alog(LOG_ERR, "%s: can't truncate: %m", path);
			FREE(TYPED_MEM_TEMP, path);
			return (-1);
		}
	}

	/* Write PID into file */
	snprintf(buf, sizeof(buf), "%d\n", getpid());
	if (write(app_pidfile_fd, buf, strlen(buf)) != strlen(buf)) {
		alog(LOG_ERR, "%s: write error: %m", path);
		(void)close(app_pidfile_fd);
		app_pidfile_fd = -1;
		FREE(TYPED_MEM_TEMP, path);
		return (-1);
	}

	/* Leave file open so it stays locked */
	FREE(TYPED_MEM_TEMP, path);
	app_pidfile_pid = getpid();
	return (0);
}

/*
 * PID file shutdown
 */
static void
app_pidfile_stop(struct app_config_ctx *ctx,
	const struct app_subsystem *ss, const void *config)
{
	const char *const name = ss->arg;
	char *path;

	/* Get PID file name */
	if ((path = structs_get_string(app_config_get_type(ctx),
	    name, config, TYPED_MEM_TEMP)) == NULL) {
		alogf(LOG_ERR, "%s: %m", "structs_get_string");
		return;
	}

	/* Remove old PID file */
	alog(LOG_DEBUG, "removing pidfile \"%s\"", path);
	(void)unlink(path);
	(void)close(app_pidfile_fd);
	app_pidfile_fd = -1;
	app_pidfile_pid = -1;
	FREE(TYPED_MEM_TEMP, path);
}

/*
 * PID file necessity check
 */
static int
app_pidfile_willrun(struct app_config_ctx *ctx,
	const struct app_subsystem *ss, const void *config)
{
	const char *const name = ss->arg;
	char *path;
	int r;

	/* Get PID file name */
	assert(name != NULL);
	if ((path = structs_get_string(app_config_get_type(ctx),
	    name, config, TYPED_MEM_TEMP)) == NULL) {
		alogf(LOG_ERR, "%s: %m", "structs_get_string");
		return (-1);
	}

	/* Check if not NULL */
	r = (*path != '\0');
	FREE(TYPED_MEM_TEMP, path);
	return (r);
}

/*
 * PID file configuration changed check
 */
static int
app_pidfile_changed(struct app_config_ctx *ctx,
	const struct app_subsystem *ss, const void *config1,
	const void *config2)
{
	const char *const name = ss->arg;
	int equal;

	/* Compare PID file names as well as PID itself */
	if ((equal = structs_equal(app_config_get_type(ctx),
	    name, config1, config2)) == -1) {
		alogf(LOG_ERR, "%s: %m", "structs_equal");
		return (-1);
	}
	return (!equal || getpid() != app_pidfile_pid);
}