sbin/adjkerntz/adjkerntz.c

/*
 * Copyright (C) 1993 by Andrew 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 DEVELOPERS ``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.
 */

#ifndef lint
char copyright[] =
"@(#)Copyright (C) 1993 by Andrew A. Chernov, Moscow, Russia.\n\
 All rights reserved.\n";
#endif /* not lint */

/*
 * Andrew A. Chernov   <ache@astral.msk.su>    Dec 15 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 <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <sys/time.h>

#include "pathnames.h"

char storage[] = _PATH_OFFSET;

int main(argc, argv)
        int argc;
        char **argv;
{
        struct tm local, utc;
        struct timeval tv, *stv;
        struct timezone tz, *stz;
        /* Avoid time_t here, can be unsigned long */
        long offset, oldoffset, utcsec, localsec, diff;
        int ch, init = -1, verbose = 0;
        FILE *f;

        while ((ch = getopt(argc, argv, "aiv")) != EOF)
                switch((char)ch) {
                case 'i':               /* initial call, save offset */
                        if (init != -1)
                                goto usage;
                        init = 1;
                        break;
                case 'a':               /* adjustment call, use saved offset */
                        if (init != -1)
                                goto usage;
                        init = 0;
                        break;
                case 'v':               /* verbose */
                        verbose = 1;
                        break;
                default:
                usage:
                        fprintf(stderr, "Usage:\n\
\tadjkerntz -i [-v]\t(initial call from /etc/rc)\n\
\tadjkerntz -a [-v]\t(adjustment call from crontab)\n");
                        return 2;
                }
        if (init == -1)
                goto usage;

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

        /* Restore saved offset */

        if (!init) {
                if ((f = fopen(storage, "r")) == NULL) {
                        perror(storage);
                        return 1;
                }
                if (fscanf(f, "%ld", &oldoffset) != 1) {
                        fprintf(stderr, "Incorrect offset in %s\n", storage);
                        return 1;
                }
                (void) fclose(f);
        }
        else
                oldoffset = 0;

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

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

        /* get the actual local timezone difference */
        local = *localtime(&tv.tv_sec);
        utc = *gmtime(&tv.tv_sec);
        utc.tm_isdst = local.tm_isdst; /* Use current timezone for mktime(), */
                                       /* because it assumed local time */

        /* calculate local CMOS diff from GMT */

        utcsec = mktime(&utc);
        localsec = mktime(&local);
        if (utcsec == -1 || localsec == -1) {
                fprintf(stderr, "Wrong hour to call\n");
                return 1;
        }
        offset = utcsec - localsec;

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

        diff = oldoffset + tz.tz_minuteswest * 60 - offset;
        if (diff != 0) {
                tv.tv_sec += diff;
                tv.tv_usec = 0;       /* we are restarting here... */
                stv = &tv;
        }
        else
                stv = NULL;

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

        if (stz != NULL || stv != NULL) {
                if (settimeofday(stv, stz)) {
                        perror("settimeofday");
                        return 1;
                }
        }

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

        if (verbose)
                printf("Calculated zone offset diffs: %ld seconds\n", diff);

        if (offset != oldoffset) {
                (void) umask(022);
                /* Save offset for next calls from crontab */
                if ((f = fopen(storage, "w")) == NULL) {
                        perror(storage);
                        return 1;
                }
                fprintf(f, "%ld\n", offset);
                if (fclose(f)) {
                        perror(storage);
                        return 1;
                }
        }

        return 0;
}