gpsd/ntpshmmon.c

/* ntpshmmon.c -- monitor the inner end of an ntpshmwrite.connection
 *
 * This file is Copyright (c) 2010-2018 by the GPSD project
 * SPDX-License-Identifier: BSD-2-clause
 *
 */

#include "gpsd_config.h"  /* must be before all includes */

#include <getopt.h>
#include <limits.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>     /* for memset() */
#include <unistd.h>

#include "gps.h"	/* for safe_atof() */
#include "ntpshm.h"
#include "revision.h"
#include "timespec.h"
#include "os_compat.h"

#define NTPSEGMENTS	256	/* NTPx for x any byte */

static struct shmTime *segments[NTPSEGMENTS + 1];

int main(int argc, char **argv)
{
    int option;
    int	i;
    bool killall = false;
    bool offset = false;            /* show offset, not seen */
    bool verbose = false;
    int nsamples = INT_MAX;
    time_t timeout = (time_t)0, starttime = time(NULL);
    /* a copy of all old segments */
    struct shm_stat_t	shm_stat_old[NTPSEGMENTS + 1];
    char *whoami;

    /* strip path from program name */
    (whoami = strrchr(argv[0], '/')) ? ++whoami : (whoami = argv[0]);

    memset( shm_stat_old, 0 ,sizeof( shm_stat_old));

    while ((option = getopt(argc, argv, "?hn:ost:vV")) != -1) {
	switch (option) {
	case '?':
	case 'h':
	    (void)fprintf(
	        stderr,
                "usage: ntpshmmon [-?] [-h] [-n nsamples] [-o] [-s] [-t nseconds] [-v] [-V]\n"
                "  -?           print this help\n"
                "  -h           print this help\n"
                "  -n nsamples  exit after nsamples\n"
                "  -o           replace Seen@ with Offset\n"
                "  -s           remove SHMs and exit\n"
                "  -t nseconds  exit after nseconds\n"
                "  -v           be verbose\n"
                "  -V           print version and exit\n"
		);
	    exit(EXIT_SUCCESS);
	case 'n':
	    nsamples = atoi(optarg);
	    break;
	case 'o':
	    offset = true;
	    break;
	case 's':
	    killall = true;
	    break;
	case 't':
	    timeout = (time_t)atoi(optarg);
	    break;
	case 'v':
	    verbose = true;
	    break;
	case 'V':
	    (void)fprintf(stderr, "%s: version %s (revision %s)\n",
			  whoami, VERSION, REVISION);
	    exit(EXIT_SUCCESS);
	default:
	    /* no option, just go and do it */
	    break;
	}
    }

    /* grab all segments, keep the non-null ones */
    for (i = 0; i < NTPSEGMENTS; i++) {
	segments[i] = shm_get(i, false, true);
	if (verbose && segments[i] != NULL)
	    (void)fprintf(stderr, "unit %d opened\n", i);
    }

    if (killall) {
	struct shmTime **pp;

	for (pp = segments; pp < segments + NTPSEGMENTS; pp++)
	    if (*pp != NULL)
		(void)shmdt((void *)(*pp));
	exit(EXIT_SUCCESS);
    }

    /*
     * We want line buffering even if stdout is going to a file.  This
     * is a (possibly futile) attempt to avoid writing an incomplete
     * line on interrupt.
     */
    setvbuf(stdout, NULL, _IOLBF, 0);

    (void)printf("%s: version %s\n", whoami, VERSION);
    if (offset) {
	(void)printf("#      Name     Offset           Clock                Real                 L Prc\n");
    } else {
	(void)printf("#      Name Seen@                Clock                Real                 L Prc\n");
    }

    do {
	/* the current segment */
	struct shm_stat_t	shm_stat;
	struct timespec delay;
        char ts_buf1[TIMESPEC_LEN];
        char ts_buf2[TIMESPEC_LEN];
        char ts_buf3[TIMESPEC_LEN];

	for (i = 0; i < NTPSEGMENTS; i++) {
	    long long diff;  /* 32 bit long is too short for a timespec */
	    enum segstat_t status = ntp_read(segments[i], &shm_stat, false);
	    if (verbose)
		(void)fprintf(stderr, "unit %d status %d\n", i, status);
	    switch(status) {
	    case OK:
		/* ntpd can slew the clock at 120% real time
                 * so do not lock out slightly short cycles
		 * use 50% of cycle time as lock out limit.
                 * ignore that system time may jump. */
		diff = timespec_diff_ns(shm_stat.tvr, shm_stat_old[i].tvr);
		if ( 0 == diff) {
		    /* no change in tvr */
		    break;
		}
		diff = timespec_diff_ns(shm_stat.tvt, shm_stat_old[i].tvt);
		if ( 0 == diff) {
		    /* no change in tvt */
		    break;
		}
		/* time stamp it */
		clock_gettime(CLOCK_REALTIME, &shm_stat.tvc);
                if (offset) {
		    diff = timespec_diff_ns(shm_stat.tvr, shm_stat.tvt);
		    printf("sample %s %20.9f %s %s %d %3d\n",
			   ntp_name(i),
			   (double)diff * 1e-9,
                           timespec_str(&shm_stat.tvr, ts_buf1,
                                        sizeof(ts_buf1)),
                           timespec_str(&shm_stat.tvt, ts_buf2,
                                        sizeof(ts_buf2)),
			   shm_stat.leap, shm_stat.precision);
                } else {
		    printf("sample %s %s %s %s %d %3d\n",
			   ntp_name(i),
                           timespec_str(&shm_stat.tvc, ts_buf1,
                                        sizeof(ts_buf1)),
                           timespec_str(&shm_stat.tvr, ts_buf2,
                                        sizeof(ts_buf2)),
                           timespec_str(&shm_stat.tvt, ts_buf3,
                                        sizeof(ts_buf3)),
			   shm_stat.leap, shm_stat.precision);
                }
		--nsamples;
		/* save the new time stamp */
		shm_stat_old[i] = shm_stat; /* structure copy */

		break;
	    case NO_SEGMENT:
		break;
	    case NOT_READY:
		/* do nothing, data not ready, wait another cycle */
		break;
	    case BAD_MODE:
		(void)fprintf(stderr,
		              "ntpshmmon: unknown mode %d on segment %s\n",
		              shm_stat.status, ntp_name(i));
		break;
	    case CLASH:
		/* do nothing, data is corrupt, wait another cycle */
		break;
	    default:
		(void)fprintf(stderr,
		              "ntpshmmon: unknown status %d on segment %s\n",
		              status, ntp_name(i));
		break;
	    }
	}
	/* all segments now checked */

	/*
	 * Even on a 1 Hz PPS, a sleep(1) may end up
         * being sleep(1.1) and missing a beat.  Since
	 * we're ignoring duplicates via timestamp, polling
	 * at fast intervals should not be a problem
	 *
	 * PPS is not always one pulse per second.
	 * the Garmin GPS 18x-5Hz outputs 5 pulses per second.
         * That is a 200 millSec cycle, minimum 20 milliSec duration
         * we will wait 1 milliSec out of caution
         *
         * and, of course, nanosleep() may sleep a lot longer than we ask...
	 */
	if ( timeout ) {
	    /* do not read time unless it matters */
	    if ( time(NULL) > (starttime + timeout ) ) {
		/* time to exit */
		break;
	    }
	}

        /* wait 1,000 uSec */
	delay.tv_sec = 0;
	delay.tv_nsec = 1000000L;
	nanosleep(&delay, NULL);
    } while ( 0 < nsamples );

    exit(EXIT_SUCCESS);
}

/* end */