/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * 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.
 */

/*
 * 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) __dead2;

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;
        /* 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);

        (void) signal(SIGHUP, SIG_IGN);

        if (init && daemon(0,
#ifdef DEBUG
            1
#else
            0
#endif
            )) {
                syslog(LOG_ERR, "daemon: %m");
                return 1;
        }

again:
        (void) sigprocmask(SIG_BLOCK, &mask, NULL);
        (void) 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;
        }

        tzset();

        len = sizeof(kern_offset);
        if (sysctlbyname("machdep.adjkerntz", &kern_offset, &len, NULL, 0) == -1) {
                syslog(LOG_ERR, "sysctl(\"machdep.adjkerntz\"): %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);
                (void) signal(SIGTERM, SIG_DFL);
                (void) sigprocmask(SIG_UNBLOCK, &mask, NULL);
                (void) 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);
                        (void) signal(SIGTERM, SIG_DFL);
                        (void) sigprocmask(SIG_UNBLOCK, &mask, NULL);
                        (void) 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)
           ) {
                len = sizeof(disrtcset);
                if (sysctlbyname("machdep.disable_rtc_set", &disrtcset, &len, NULL, 0) == -1) {
                        syslog(LOG_ERR, "sysctl(get: \"machdep.disable_rtc_set\"): %m");
                        return 1;
                }
                if (disrtcset == 0) {
                        disrtcset = 1;
                        need_restore = True;
                        if (sysctlbyname("machdep.disable_rtc_set", NULL, NULL, &disrtcset, len) == -1) {
                                syslog(LOG_ERR, "sysctl(set: \"machdep.disable_rtc_set\"): %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.
                         */
                        (void)gettimeofday(&tv, NULL);
                        tv.tv_sec += diff;
                        stv = &tv;
                }
                if (settimeofday(stv, stz)) {
                        syslog(LOG_ERR, "settimeofday: %m");
                        return 1;
                }
        }

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

        if (kern_offset != offset) {
                kern_offset = offset;
                len = sizeof(kern_offset);
                if (sysctlbyname("machdep.adjkerntz", NULL, NULL, &kern_offset, len) == -1) {
                        syslog(LOG_ERR, "sysctl(set: \"machdep.adjkerntz\"): %m");
                        return 1;
                }
        }

        len = sizeof(wall_clock);
        if (sysctlbyname("machdep.wall_cmos_clock",  NULL, NULL, &wall_clock, len) == -1) {
                syslog(LOG_ERR, "sysctl(set: \"machdep.wall_cmos_clock\"): %m");
                return 1;
        }

        if (need_restore) {
                need_restore = False;
                disrtcset = 0;
                len = sizeof(disrtcset);
                if (sysctlbyname("machdep.disable_rtc_set", NULL, NULL, &disrtcset, len) == -1) {
                        syslog(LOG_ERR, "sysctl(set: \"machdep.disable_rtc_set\"): %m");
                        return 1;
                }
        }

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

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