/*
 * Copyright (C) 1993-1998 by Andrey A. Chernov, Moscow, Russia.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON 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 ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * @(#)Copyright (C) 1993-1996 by Andrey A. Chernov, Moscow, Russia. All rights reserved.
 * $FreeBSD: src/sbin/adjkerntz/adjkerntz.c,v 1.25.2.1 2001/07/30 10:38:04 dd Exp $
 * $DragonFly: src/sbin/adjkerntz/adjkerntz.c,v 1.6 2005/11/06 12:03:15 swildner Exp $
 */

/*
 * Andrey A. Chernov   <ache@astral.msk.su>    Dec 20 1993
 *
 * Fix kernel time value if machine run wall CMOS clock
 * (and /etc/wall_cmos_clock file present)
 * using zoneinfo rules or direct TZ environment variable set.
 * Use Joerg Wunsch idea for seconds accurate offset calculation
 * with Garrett Wollman and Bruce Evans fixes.
 *
 */
#include <stdio.h>
#include <signal.h>
#include <stdlib.h>
#include <unistd.h>
#include <syslog.h>
#include <sys/time.h>
#include <sys/param.h>
#include <machine/cpu.h>
#include <sys/sysctl.h>

#include "pathnames.h"

/*#define DEBUG*/

#define True (1)
#define False (0)
#define Unknown (-1)

#define REPORT_PERIOD (30*60)

static void fake(int);
static void usage(void);

static void
fake(int unused __unused)
{

	/* Do nothing. */
}

int
main(int argc, char **argv)
{
	struct tm local;
	struct timeval tv, *stv;
	struct timezone tz, *stz;
	int kern_offset, wall_clock, disrtcset;
	size_t len;
	int mib[2];
	/* Avoid time_t here, can be unsigned long or worse */
	long offset, localsec, diff;
	time_t initial_sec, final_sec;
	int ch;
	int initial_isdst = -1, final_isdst;
	int need_restore = False, sleep_mode = False, looping,
	    init = Unknown;
	sigset_t mask, emask;

	while ((ch = getopt(argc, argv, "ais")) != -1)
		switch((char)ch) {
		case 'i':               /* initial call, save offset */
			if (init != Unknown)
				usage();
			init = True;
			break;
		case 'a':               /* adjustment call, use saved offset */
			if (init != Unknown)
				usage();
			init = False;
			break;
		case 's':
			sleep_mode = True;
			break;
		default:
			usage();
		}
	if (init == Unknown)
		usage();

	if (access(_PATH_CLOCK, F_OK) != 0)
		return 0;

	if (init)
		sleep_mode = True;

	sigemptyset(&mask);
	sigemptyset(&emask);
	sigaddset(&mask, SIGTERM);

	openlog("adjkerntz", LOG_PID|LOG_PERROR, LOG_DAEMON);

	signal(SIGHUP, SIG_IGN);

	if (init && daemon(0, 1)) {
		syslog(LOG_ERR, "daemon: %m");
		return 1;
	}

again:
	sigprocmask(SIG_BLOCK, &mask, NULL);
	signal(SIGTERM, fake);

	diff = 0;
	stv = NULL;
	stz = NULL;
	looping = False;

	wall_clock = (access(_PATH_CLOCK, F_OK) == 0);
	if (init && !sleep_mode) {
		init = False;
		if (!wall_clock)
			return 0;
	}

	mib[0] = CTL_MACHDEP;
	mib[1] = CPU_ADJKERNTZ;
	len = sizeof(kern_offset);
	if (sysctl(mib, 2, &kern_offset, &len, NULL, 0) == -1) {
		syslog(LOG_ERR, "sysctl(get_offset): %m");
		return 1;
	}

/****** Critical section, do all things as fast as possible ******/

	/* get local CMOS clock and possible kernel offset */
	if (gettimeofday(&tv, &tz)) {
		syslog(LOG_ERR, "gettimeofday: %m");
		return 1;
	}

	/* get the actual local timezone difference */
	initial_sec = tv.tv_sec;

recalculate:
	local = *localtime(&initial_sec);
	if (diff == 0)
		initial_isdst = local.tm_isdst;
	local.tm_isdst = initial_isdst;

	/* calculate local CMOS diff from GMT */

	localsec = mktime(&local);
	if (localsec == -1) {
		/*
		 * XXX user can only control local time, and it is
		 * unacceptable to fail here for init.  2:30 am in the
		 * middle of the nonexistent hour means 3:30 am.
		 */
		if (!sleep_mode) {
			syslog(LOG_WARNING,
			"Warning: nonexistent local time, try to run later.");
			syslog(LOG_WARNING, "Giving up.");
			return 1;
		}
		syslog(LOG_WARNING,
			"Warning: nonexistent local time.");
		syslog(LOG_WARNING, "Will retry after %d minutes.",
			REPORT_PERIOD / 60);
		signal(SIGTERM, SIG_DFL);
		sigprocmask(SIG_UNBLOCK, &mask, NULL);
		sleep(REPORT_PERIOD);
		goto again;
	}
	offset = -local.tm_gmtoff;
#ifdef DEBUG
	fprintf(stderr, "Initial offset: %ld secs\n", offset);
#endif

	/* correct the kerneltime for this diffs */
	/* subtract kernel offset, if present, old offset too */

	diff = offset - tz.tz_minuteswest * 60 - kern_offset;

	if (diff != 0) {
#ifdef DEBUG
		fprintf(stderr, "Initial diff: %ld secs\n", diff);
#endif
		/* Yet one step for final time */

		final_sec = initial_sec + diff;

		/* get the actual local timezone difference */
		local = *localtime(&final_sec);
		final_isdst = diff < 0 ? initial_isdst : local.tm_isdst;
		if (diff > 0 && initial_isdst != final_isdst) {
			if (looping)
				goto bad_final;
			looping = True;
			initial_isdst = final_isdst;
			goto recalculate;
		}
		local.tm_isdst =  final_isdst;

		localsec = mktime(&local);
		if (localsec == -1) {
		bad_final:
			/*
			 * XXX as above.  The user has even less control,
			 * but perhaps we never get here.
			 */
			if (!sleep_mode) {
				syslog(LOG_WARNING,
					"Warning: nonexistent final local time, try to run later.");
				syslog(LOG_WARNING, "Giving up.");
				return 1;
			}
			syslog(LOG_WARNING,
				"Warning: nonexistent final local time.");
			syslog(LOG_WARNING, "Will retry after %d minutes.",
				REPORT_PERIOD / 60);
			signal(SIGTERM, SIG_DFL);
			sigprocmask(SIG_UNBLOCK, &mask, NULL);
			sleep(REPORT_PERIOD);
			goto again;
		}
		offset = -local.tm_gmtoff;
#ifdef DEBUG
		fprintf(stderr, "Final offset: %ld secs\n", offset);
#endif

		/* correct the kerneltime for this diffs */
		/* subtract kernel offset, if present, old offset too */

		diff = offset - tz.tz_minuteswest * 60 - kern_offset;

		if (diff != 0) {
#ifdef DEBUG
			fprintf(stderr, "Final diff: %ld secs\n", diff);
#endif
			/*
			 * stv is abused as a flag.  The important value
			 * is in `diff'.
			 */
			stv = &tv;
		}
	}

	if (tz.tz_dsttime != 0 || tz.tz_minuteswest != 0) {
		tz.tz_dsttime = tz.tz_minuteswest = 0;  /* zone info is garbage */
		stz = &tz;
	}
	if (!wall_clock && stz == NULL)
		stv = NULL;

	/* if init or UTC clock and offset/date will be changed, */
	/* disable RTC modification for a while.                      */

	if (   (init && stv != NULL)
	    || ((init || !wall_clock) && kern_offset != offset)
	   ) {
		mib[0] = CTL_MACHDEP;
		mib[1] = CPU_DISRTCSET;
		len = sizeof(disrtcset);
		if (sysctl(mib, 2, &disrtcset, &len, NULL, 0) == -1) {
			syslog(LOG_ERR, "sysctl(get_disrtcset): %m");
			return 1;
		}
		if (disrtcset == 0) {
			disrtcset = 1;
			need_restore = True;
			if (sysctl(mib, 2, NULL, NULL, &disrtcset, len) == -1) {
				syslog(LOG_ERR, "sysctl(set_disrtcset): %m");
				return 1;
			}
		}
	}

	if (   (init && (stv != NULL || stz != NULL))
	    || (stz != NULL && stv == NULL)
	   ) {
		if (stv != NULL) {
			/*
			 * Get the time again, as close as possible to
			 * adjusting it, to minimise drift.
			 * XXX we'd better not fail between here and
			 * restoring disrtcset, since we don't clean up
			 * anything.
			 */
			if (gettimeofday(&tv, NULL)) {
				syslog(LOG_ERR, "gettimeofday: %m");
				return 1;
			}
			tv.tv_sec += diff;
			stv = &tv;
		}
		if (settimeofday(stv, stz)) {
			syslog(LOG_ERR, "settimeofday: %m");
			return 1;
		}
	}

	/* setting CPU_ADJKERNTZ have a side effect: resettodr(), which */
	/* can be disabled by CPU_DISRTCSET, so if init or UTC clock    */
	/* -- don't write RTC, else write RTC.                          */

	if (kern_offset != offset) {
		kern_offset = offset;
		mib[0] = CTL_MACHDEP;
		mib[1] = CPU_ADJKERNTZ;
		len = sizeof(kern_offset);
		if (sysctl(mib, 2, NULL, NULL, &kern_offset, len) == -1) {
			syslog(LOG_ERR, "sysctl(update_offset): %m");
			return 1;
		}
	}

	mib[0] = CTL_MACHDEP;
	mib[1] = CPU_WALLCLOCK;
	len = sizeof(wall_clock);
	if (sysctl(mib, 2, NULL, NULL, &wall_clock, len) == -1) {
		syslog(LOG_ERR, "sysctl(put_wallclock): %m");
		return 1;
	}

	if (need_restore) {
		need_restore = False;
		mib[0] = CTL_MACHDEP;
		mib[1] = CPU_DISRTCSET;
		disrtcset = 0;
		len = sizeof(disrtcset);
		if (sysctl(mib, 2, NULL, NULL, &disrtcset, len) == -1) {
			syslog(LOG_ERR, "sysctl(restore_disrtcset): %m");
			return 1;
		}
	}

/****** End of critical section ******/

	if (init && wall_clock) {
		sleep_mode = False;
		/* wait for signals and acts like -a */
		sigsuspend(&emask);
		goto again;
	}

	return 0;
}

static void
usage(void)
{
	fprintf(stderr, "%s\n%s\n%s\n%s\n",
		"usage: adjkerntz -i",
		"\t\t(initial call from /etc/rc)",
		"       adjkerntz -a [-s]",
		"\t\t(adjustment call, -s for sleep/retry mode)");
	exit(2);
}