dcfd.c

网络时间协议NTP 源码 版本v4.2.0b 该源码用于linux平台下

	 */
	if (highmax)
	{
		lowmax /= highmax;
	}
	else
	{
		lowmax = 0;
	}

	highmax = 0; /* weighted sum of upper bits counts */
	cutoff = 0;  /* bitcount */

	/*
	 * collect weighted sum of lower bits (right of initial guess)
	 */
	for (; i < BITS; i++)
	{
		highmax+=histbuf[i] * i;
		cutoff +=histbuf[i];
		dprintf((" %d", histbuf[i]));
	}
	dprintf(("\n"));

	/*
	 * determine upper maximum (weighted sum / bit count)
	 */
	if (cutoff)
	{
		highmax /= cutoff;
	}
	else
	{
		highmax = BITS-1;
	}

	/*
	 * following now holds:
	 * lowmax <= cutoff(initial guess) <= highmax
	 * best cutoff is the minimum nearest to higher bits
	 */

	/*
	 * find the minimum between lowmax and highmax (detecting
	 * possibly a minimum span)
	 */
	span = cutoff = lowmax;
	for (i = lowmax; i <= highmax; i++)
	{
		if (histbuf[cutoff] > histbuf[i])
		{
			/*
			 * got a new minimum move beginning of minimum (cutoff) and
			 * end of minimum (span) there
			 */
			cutoff = span = i;
		}
		else
		    if (histbuf[cutoff] == histbuf[i])
		    {
			    /*
			     * minimum not better yet - but it spans more than
			     * one bit value - follow it
			     */
			    span = i;
		    }
	}

	/*
	 * cutoff point for 1/0 decision is the middle of the minimum section
	 * in the histogram
	 */
	cutoff = (cutoff + span) / 2;

	dprintf(("parse: cvt_rawdcf: lower maximum %d, higher maximum %d, cutoff %d\n", lowmax, highmax, cutoff));

	/*
	 * convert the bit counts to symbolic 1/0 information for data conversion
	 */
	s = buffer;
	while ((s < e) && *c && *b)
	{
		if (*s == (unsigned char)~0)
		{
			/*
			 * invalid character
			 */
			*s = '?';
		}
		else
		{
			/*
			 * symbolic 1/0 representation
			 */
			*s = (*s >= cutoff) ? *b : *c;
		}
		s++;
		b++;
		c++;
	}

	/*
	 * if everything went well so far return the result of the symbolic
	 * conversion routine else just the accumulated errors
	 */
	if (rtc != CVT_NONE) 
	{
		PRINTF("%-30s", "*** BAD DATA");
	}

	return (rtc == CVT_NONE) ? convert_rawdcf(buffer, size, clock_time) : rtc;
}

/*-----------------------------------------------------------------------
 * convert a wall clock time description of DCF77 to a Unix time (seconds
 * since 1.1. 1970 UTC)
 */
static time_t
dcf_to_unixtime(
		clocktime_t   *clock_time,
		unsigned *cvtrtc
		)
{
#define SETRTC(_X_)	{ if (cvtrtc) *cvtrtc = (_X_); }
	static int days_of_month[] = 
	{
		0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31
	};
	register int i;
	time_t t;
  
	/*
	 * map 2 digit years to 19xx (DCF77 is a 20th century item)
	 */
	if ( clock_time->year < YEAR_PIVOT ) 	/* in case of	   Y2KFixes [ */
		clock_time->year += 100;	/* *year%100, make tm_year */
						/* *(do we need this?) */
	if ( clock_time->year < YEAR_BREAK )	/* (failsafe if) */
	    clock_time->year += 1900;				/* Y2KFixes ] */

	/*
	 * must have been a really bad year code - drop it
	 */
	if (clock_time->year < (YEAR_PIVOT + 1900) )		/* Y2KFixes */
	{
		SETRTC(CVT_FAIL|CVT_BADDATE);
		return -1;
	}
	/*
	 * sorry, slow section here - but it's not time critical anyway
	 */

	/*
	 * calculate days since 1970 (watching leap years)
	 */
	t = julian0( clock_time->year ) - julian0( 1970 );

  				/* month */
	if (clock_time->month <= 0 || clock_time->month > 12)
	{
		SETRTC(CVT_FAIL|CVT_BADDATE);
		return -1;		/* bad month */
	}
				/* adjust current leap year */
#if 0
	if (clock_time->month < 3 && days_per_year(clock_time->year) == 366)
	    t--;
#endif

	/*
	 * collect days from months excluding the current one
	 */
	for (i = 1; i < clock_time->month; i++)
	{
		t += days_of_month[i];
	}
				/* day */
	if (clock_time->day < 1 || ((clock_time->month == 2 && days_per_year(clock_time->year) == 366) ?
			       clock_time->day > 29 : clock_time->day > days_of_month[clock_time->month]))
	{
		SETRTC(CVT_FAIL|CVT_BADDATE);
		return -1;		/* bad day */
	}

	/*
	 * collect days from date excluding the current one
	 */
	t += clock_time->day - 1;

				/* hour */
	if (clock_time->hour < 0 || clock_time->hour >= 24)
	{
		SETRTC(CVT_FAIL|CVT_BADTIME);
		return -1;		/* bad hour */
	}

	/*
	 * calculate hours from 1. 1. 1970
	 */
	t = TIMES24(t) + clock_time->hour;

  				/* min */
	if (clock_time->minute < 0 || clock_time->minute > 59)
	{
		SETRTC(CVT_FAIL|CVT_BADTIME);
		return -1;		/* bad min */
	}

	/*
	 * calculate minutes from 1. 1. 1970
	 */
	t = TIMES60(t) + clock_time->minute;
				/* sec */
  
	/*
	 * calculate UTC in minutes
	 */
	t += clock_time->utcoffset;

	if (clock_time->second < 0 || clock_time->second > 60)	/* allow for LEAPs */
	{
		SETRTC(CVT_FAIL|CVT_BADTIME);
		return -1;		/* bad sec */
	}

	/*
	 * calculate UTC in seconds - phew !
	 */
	t  = TIMES60(t) + clock_time->second;
				/* done */
	return t;
}

/*-----------------------------------------------------------------------
 * cheap half baked 1/0 decision - for interactive operation only
 */
static char
type(
     unsigned int c
     )
{
	c ^= 0xFF;
	return (c > 0xF);
}

/*-----------------------------------------------------------------------
 * week day representation
 */
static const char *wday[8] =
{
	"??",
	"Mo",
	"Tu",
	"We",
	"Th",
	"Fr",
	"Sa",
	"Su"
};

/*-----------------------------------------------------------------------
 * generate a string representation for a timeval
 */
static char *
pr_timeval(
	   struct timeval *val
	   )
{
	static char buf[20];

	if (val->tv_sec == 0)
	    sprintf(buf, "%c0.%06ld", (val->tv_usec < 0) ? '-' : '+', (long int)l_abs(val->tv_usec));
	else
	    sprintf(buf, "%ld.%06ld", (long int)val->tv_sec, (long int)l_abs(val->tv_usec));
	return buf;
}

/*-----------------------------------------------------------------------
 * correct the current time by an offset by setting the time rigorously
 */
static void
set_time(
	 struct timeval *offset
	 )
{
	struct timeval the_time;

	if (no_set)
	    return;

	LPRINTF("set_time: %s ", pr_timeval(offset));
	syslog(LOG_NOTICE, "setting time (offset %s)", pr_timeval(offset));

	if (gettimeofday(&the_time, 0L) == -1)
	{
		perror("gettimeofday()");
	}
	else
	{
		timeradd(&the_time, offset);
		if (settimeofday(&the_time, 0L) == -1)
		{
			perror("settimeofday()");
		}
	}
}

/*-----------------------------------------------------------------------
 * slew the time by a given offset
 */
static void
adj_time(
	 long offset
	 )
{
	struct timeval time_offset;

	if (no_set)
	    return;

	time_offset.tv_sec  = offset / 1000000;
	time_offset.tv_usec = offset % 1000000;

	LPRINTF("adj_time: %ld us ", (long int)offset);
	if (adjtime(&time_offset, 0L) == -1)
	    perror("adjtime()");
}

/*-----------------------------------------------------------------------
 * read in a possibly previously written drift value
 */
static void
read_drift(
	   const char *drift_file
	   )
{
	FILE *df;

	df = fopen(drift_file, "r");
	if (df != NULL)
	{
		int idrift = 0, fdrift = 0;

		fscanf(df, "%4d.%03d", &idrift, &fdrift);
		fclose(df);
		LPRINTF("read_drift: %d.%03d ppm ", idrift, fdrift);

		accum_drift = idrift << USECSCALE;
		fdrift     = (fdrift << USECSCALE) / 1000;
		accum_drift += fdrift & (1<<USECSCALE);
		LPRINTF("read_drift: drift_comp %ld ", (long int)accum_drift);
	}
}

/*-----------------------------------------------------------------------
 * write out the current drift value
 */
static void
update_drift(
	     const char *drift_file,
	     long offset,
	     time_t reftime
	     )
{
	FILE *df;

	df = fopen(drift_file, "w");
	if (df != NULL)
	{
		int idrift = R_SHIFT(accum_drift, USECSCALE);
		int fdrift = accum_drift & ((1<<USECSCALE)-1);

		LPRINTF("update_drift: drift_comp %ld ", (long int)accum_drift);
		fdrift = (fdrift * 1000) / (1<<USECSCALE);
		fprintf(df, "%4d.%03d %c%ld.%06ld %.24s\n", idrift, fdrift,
			(offset < 0) ? '-' : '+', (long int)(l_abs(offset) / 1000000),
			(long int)(l_abs(offset) % 1000000), asctime(localtime(&reftime)));
		fclose(df);
		LPRINTF("update_drift: %d.%03d ppm ", idrift, fdrift);
	}
}

/*-----------------------------------------------------------------------
 * process adjustments derived from the DCF77 observation
 * (controls clock PLL)
 */
static void
adjust_clock(
	     struct timeval *offset,
	     const char *drift_file,
	     time_t reftime
	     )
{
	struct timeval toffset;
	register long usecoffset;
	int tmp;

	if (no_set)
	    return;

	if (skip_adjust)
	{
		skip_adjust = 0;
		return;
	}

	toffset = *offset;
	toffset.tv_sec  = l_abs(toffset.tv_sec);
	toffset.tv_usec = l_abs(toffset.tv_usec);
	if (timercmp(&toffset, &max_adj_offset, >))
	{
		/*
		 * hopeless - set the clock - and clear the timing
		 */
		set_time(offset);
		clock_adjust = 0;
		skip_adjust  = 1;
		return;
	}

	usecoffset   = offset->tv_sec * 1000000 + offset->tv_usec;

	clock_adjust = R_SHIFT(usecoffset, TIMECONSTANT);	/* adjustment to make for next period */

	tmp = 0;
	while (adjustments > (1 << tmp))
	    tmp++;
	adjustments = 0;
	if (tmp > FREQ_WEIGHT)
	    tmp = FREQ_WEIGHT;

	accum_drift  += R_SHIFT(usecoffset << USECSCALE, TIMECONSTANT+TIMECONSTANT+FREQ_WEIGHT-tmp);

	if (accum_drift > MAX_DRIFT)		/* clamp into interval */
	    accum_drift = MAX_DRIFT;
	else
	    if (accum_drift < -MAX_DRIFT)
		accum_drift = -MAX_DRIFT;

	update_drift(drift_file, usecoffset, reftime);
	LPRINTF("clock_adjust: %s, clock_adjust %ld, drift_comp %ld(%ld) ",
		pr_timeval(offset),(long int) R_SHIFT(clock_adjust, USECSCALE),
		(long int)R_SHIFT(accum_drift, USECSCALE), (long int)accum_drift);
}

/*-----------------------------------------------------------------------
 * adjust the clock by a small mount to simulate frequency correction
 */
static void
periodic_adjust(
		void
		)
{
	register long adjustment;

	adjustments++;

	adjustment = R_SHIFT(clock_adjust, PHASE_WEIGHT);

	clock_adjust -= adjustment;

	adjustment += R_SHIFT(accum_drift, USECSCALE+ADJINTERVAL);

	adj_time(adjustment);
}

/*-----------------------------------------------------------------------
 * control synchronisation status (warnings) and do periodic adjusts
 * (frequency control simulation)
 */
static void
tick(
     int signum
     )
{
	static unsigned long last_notice = 0;

#if !defined(HAVE_SIGACTION) && !defined(HAVE_SIGVEC)
	(void)signal(SIGALRM, tick);
#endif

	periodic_adjust();

	ticks += 1<<ADJINTERVAL;

	if ((ticks - last_sync) > MAX_UNSYNC)
	{
		/*
		 * not getting time for a while
		 */
		if (sync_state == SYNC)
		{
			/*
			 * completely lost information
			 */
			sync_state = NO_SYNC;
			syslog(LOG_INFO, "DCF77 reception lost (timeout)");
			last_notice = ticks;
		}
		else
		    /*
		     * in NO_SYNC state - look whether its time to speak up again
		     */
		    if ((ticks - last_notice) > NOTICE_INTERVAL)
		    {
			    syslog(LOG_NOTICE, "still not synchronized to DCF77 - check receiver/signal");
			    last_notice = ticks;
		    }
	}

#ifndef ITIMER_REAL
	(void) alarm(1<<ADJINTERVAL);
#endif
}

/*-----------------------------------------------------------------------
 * break association from terminal to avoid catching terminal
 * or process group related signals (-> daemon operation)
 */
static void
detach(
       void
       )
{
#   ifdef HAVE_DAEMON
	daemon(0, 0);
#   else /* not HAVE_DAEMON */
	if (fork())
	    exit(0);

	{
		u_long s;
		int max_fd;

#if defined(HAVE_SYSCONF) && defined(_SC_OPEN_MAX)
		max_fd = sysconf(_SC_OPEN_MAX);
#else /* HAVE_SYSCONF && _SC_OPEN_MAX */
		max_fd = getdtablesize();
#endif /* HAVE_SYSCONF && _SC_OPEN_MAX */
		for (s = 0; s < max_fd; s++)
		    (void) close((int)s);
		(void) open("/", 0);
		(void) dup2(0, 1);
		(void) dup2(0, 2);
#ifdef SYS_DOMAINOS
		{
			uid_$t puid;
			status_$t st;

			proc2_$who_am_i(&puid);
			proc2_$make_server(&puid, &st);
		}
#endif /* SYS_DOMAINOS */
#if defined(HAVE_SETPGID) || defined(HAVE_SETSID)
# ifdef HAVE_SETSID
		if (setsid() == (pid_t)-1)
		    syslog(LOG_ERR, "dcfd: setsid(): %m");
# else
		if (setpgid(0, 0) == -1)
		    syslog(LOG_ERR, "dcfd: setpgid(): %m");
# endif
#else /* HAVE_SETPGID || HAVE_SETSID */
		{
			int fid;

			fid = open("/dev/tty", 2);
			if (fid >= 0)
			{
				(void) ioctl(fid, (u_long) TIOCNOTTY, (char *) 0);
				(void) close(fid);
			}
# ifdef HAVE_SETPGRP_0
			(void) setpgrp();
# else /* HAVE_SETPGRP_0 */
			(void) setpgrp(0, getpid());
# endif /* HAVE_SETPGRP_0 */
		}
#endif /* HAVE_SETPGID || HAVE_SETSID */
	}
#endif /* not HAVE_DAEMON */
}

/*-----------------------------------------------------------------------
 * list possible arguments and options
 */
static void
usage(
      char *program
      )
{
  fprintf(stderr, "usage: %s [-n] [-f] [-l] [-t] [-i] [-o] [-d <drift_file>] [-D <input delay>] <device>\n", program);
	fprintf(stderr, "\t-n              do not change time\n");
	fprintf(stderr, "\t-i              interactive\n");
	fprintf(stderr, "\t-t              trace (print all datagrams)\n");
	fprintf(stderr, "\t-f              print all databits (includes PTB private data)\n");
	fprintf(stderr, "\t-l              print loop filter debug information\n");
	fprintf(stderr, "\t-o              print offet average for current minute\n");
	fprintf(stderr, "\t-Y              make internal Y2K checks then exit\n");	/* Y2KFixes */
	fprintf(stderr, "\t-d <drift_file> specify alternate drift file\n");
	fprintf(stderr, "\t-D <input delay>specify delay from input edge to processing in micro seconds\n");
}

/*-----------------------------------------------------------------------
 * check_y2k() - internal check of Y2K logic
 *	(a lot of this logic lifted from ../ntpd/check_y2k.c)
 */
static int
check_y2k( void )
{ 
    int  year;			/* current working year */
    int  year0 = 1900;		/* sarting year for NTP time */
    int  yearend;		/* ending year we test for NTP time.
				    * 32-bit systems: through 2036, the
				      **year in which NTP time overflows.
				    * 64-bit systems: a reasonable upper
				      **limit (well, maybe somewhat beyond
				      **reasonable, but well before the
				      **max time, by which time the earth
				      **will be dead.) */
    time_t Time;
    struct tm LocalTime;

    int Fatals, Warnings;
#define Error(year) if ( (year)>=2036 && LocalTime.tm_year < 110 ) \
	Warnings++; else Fatals++

    Fatals = Warnings = 0;

    Time = time( (time_t *)NULL );
    LocalTime = *localtime( &Time );

    year = ( sizeof( u_long ) > 4 ) 	/* save max span using year as temp */
		? ( 400 * 3 ) 		/* three greater gregorian cycles */
		: ((int)(0x7FFFFFFF / 365.242 / 24/60/60)* 2 ); /*32-bit limit*/
			/* NOTE: will automacially expand test years on