Imported from /home/lorry/working-area/delta_ntp/ntp-dev-4.2.7p482.tar.gz.ntp-dev-4.2.7p482

1 files changed, 1743 insertions, 0 deletions

diff --git a/ports/winnt/ntpd/nt_clockstuff.c b/ports/winnt/ntpd/nt_clockstuff.c
new file mode 100644
index 0000000..052bfcd
--- /dev/null
+++ b/ports/winnt/ntpd/nt_clockstuff.c
@@ -0,0 +1,1743 @@
+/* Windows NT Clock Routines
+ *
+ * Created by Sven Dietrich  sven@inter-yacht.com
+ *
+ * New interpolation scheme by Dave Hart <davehart@davehart.com> in
+ * February 2009 overcomes 500us-1ms inherent jitter with the older
+ * scheme, first identified by Peter Rosin (nee Ekberg)
+ * <peda@lysator.liu.se> in 2003 [Bug 216].
+ *
+ * Note:  The Windows port of ntpd uses the C99-snprintf replacement for
+ * (v)snprintf(), also used by msyslog(), which does not understand the
+ * printf format specifier %I64d, only the more common %lld.  With the
+ * minimum supported compiler raised to Visual C++ 2005 in ntp-dev in
+ * August 2011, all MS C runtime routines also understand %lld and %llu.
+ */
+
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <sys/resource.h>	/* our private version */
+
+#if defined(_MSC_VER) && _MSC_VER >= 1400	/* VS 2005 */
+#include <intrin.h>				/* for __rdtsc() */
+#endif
+
+#ifdef HAVE_PPSAPI
+#include <timepps.h>
+/*
+ * ports/winnt/include/timepps.h defines EOPNOTSUPP for compatibility
+ * with PPSAPI on other platforms.  ports/winnt/include/isc/net.h has
+ * #define EOPNOTSUPP WSAEOPNOTSUPP, so to avoid a macro redefinition
+ * warning undefine it.
+ */
+#undef EOPNOTSUPP
+#endif	/* HAVE_PPSAPI */
+
+#include "ntp_stdlib.h"
+#include "ntp_unixtime.h"
+#include "ntp_timer.h"
+#include "ntp_assert.h"
+#include "ntp_leapsec.h"
+#include "clockstuff.h"
+#include "ntservice.h"
+#include "ntpd.h"
+#include "ntpd-opts.h"
+
+extern double sys_residual;	/* residual from previous adjustment */
+
+/*
+ * Include code to possibly modify the MM timer while the service is active. 
+ */
+
+/*
+ * Whether or not MM timer modifications takes place is still controlled 
+ * by the variable below which is initialized by a default value but 
+ * might be changed depending on a command line switch.
+ */
+static int modify_mm_timer = MM_TIMER_LORES;
+
+#define MM_TIMER_INTV   1  /* the interval we'd want to set the MM timer to [ms] */
+
+static UINT wTimerRes;
+
+BOOL init_randfile();
+
+static long last_Adj = 0;
+
+#define LS_CORR_INTV_SECS  2   /* seconds to apply leap second correction */
+#define LS_CORR_INTV   ( (LONGLONG) HECTONANOSECONDS * LS_CORR_INTV_SECS )  
+#define LS_CORR_LIMIT  ( (LONGLONG) HECTONANOSECONDS / 2 )  // half a second
+
+typedef union ft_ull {
+	FILETIME ft;
+	ULONGLONG ull;
+	LONGLONG ll;
+	LARGE_INTEGER li;
+} FT_ULL;
+
+/* leap second stuff */
+static FT_ULL ls_ft;
+static DWORD ls_time_adjustment;
+static ULONGLONG ls_ref_perf_cnt;
+static LONGLONG ls_elapsed;
+
+static BOOL winnt_time_initialized = FALSE;
+static BOOL winnt_use_interpolation = FALSE;
+static unsigned clock_thread_id;
+
+
+void WINAPI GetInterpTimeAsFileTime(LPFILETIME pft);
+static void StartClockThread(void);
+static void tune_ctr_freq(LONGLONG, LONGLONG);
+void StopClockThread(void);
+void atexit_revert_mm_timer(void);
+void win_time_stepped(void);
+
+static HANDLE clock_thread = NULL;
+static HANDLE TimerThreadExitRequest = NULL;
+
+/*
+ * interp_time estimates time in 100ns units
+ * based on a performance counter value given.
+ * The 2nd parameter indicates if this is
+ * part of a current time-of-day calculation.
+ */
+ULONGLONG interp_time(ULONGLONG, BOOL);
+
+/*
+ * add_counter_time_pair is called by the
+ * high priority clock thread with a new
+ * sample.
+ */
+void add_counter_time_pair(ULONGLONG, LONGLONG);
+
+/*
+ * globals used by the above two functions to 
+ * implement the counter/time history
+ */
+#define BASELINES_TOT	256
+#define BASELINES_USED	64
+
+static volatile int	newest_baseline = 0;
+static volatile int	newest_baseline_gen = 0;
+static ULONGLONG	baseline_counts[BASELINES_TOT] = {0};
+static LONGLONG		baseline_times[BASELINES_TOT] = {0};
+
+#define CLOCK_BACK_THRESHOLD	100	/* < 10us unremarkable */
+static ULONGLONG	clock_backward_max = CLOCK_BACK_THRESHOLD;
+static int		clock_backward_count;
+
+/**
+ * A flag set on Windows versions which ignore small time adjustments.
+ *
+ * Windows Vista and Windows 7 ignore TimeAdjustment less than 16.
+ * @note Has to be checked for Windows Server 2008/2012 and Windows 8.
+ * Ref: http://support.microsoft.com/kb/2537623, bug #2328
+ */
+static BOOL os_ignores_small_adjustment;
+
+/*
+ * clockperiod is the period used for SetSystemTimeAdjustment 
+ * slewing calculations but does not necessarily correspond
+ * to the precision of the OS clock.  Prior to Windows Vista
+ * (6.0) the two were identical.  In 100ns units.
+ */
+static DWORD clockperiod;
+
+/*
+ * os_clock_precision is the observed precision of the OS
+ * clock, meaning the increment between discrete values. This
+ * is currently calculated once at startup.  100ns units.
+ */
+static ULONGLONG os_clock_precision;
+
+/*
+ * NomPerfCtrFreq is from QueryPerformanceFrequency and is the 
+ * number of performance counter beats per second.  PerfCtrFreq
+ * starts from NomPerfCtrFreq but is maintained using a sliding
+ * window average based on actual performance counter behavior,
+ * to allow us to better tolerate powersaving measures that
+ * alter the effective frequency of the processor cycle counter
+ * (TSC) which sometimes underlies QueryPerformanceCounter.
+ *
+ * Note that the OS is unlikely to be so subtle in its internal
+ * scheduling of waitable timers, presumably done using the
+ * performance counter.  Therefore our calculations for
+ * interpolated time should be based on PerfCtrFreq but our
+ * calculations for SetWaitableTimer should assume the OS will
+ * convert from FILETIME 100ns units to performance counter
+ * beats using the nominal frequency.
+ */
+
+volatile ULONGLONG PerfCtrFreq = 0;
+	 ULONGLONG NomPerfCtrFreq = 0;
+
+/* 
+ * If we're using RDTSC beating at the same rate as
+ * QueryPerformanceCounter, there is a systemic
+ * offset we need to account for when using
+ * counterstamps from serialpps.sys, which are
+ * always from QPC (actually KeQueryPerformanceCounter).
+ */
+static LONGLONG QPC_offset = 0;
+
+/*
+ * Substitute RDTSC for QueryPerformanceCounter()?
+ */
+static int use_pcc = -1;
+
+/*
+ * Restrict threads that call QPC/RDTSC to one CPU?
+ */
+static int lock_interp_threads = -1;
+
+/*
+ * ppm_per_adjust_unit is parts per million effect on the OS
+ * clock per slewing adjustment unit per second.  Per haps.
+ */
+static DOUBLE ppm_per_adjust_unit;
+
+/*
+ * wintickadj emulates the functionality provided by unix tickadj,
+ * providing a baseline clock correction if needed to get the
+ * clock within a few hundred PPM of correct frequency.
+ */
+static long wintickadj;
+
+static void	choose_interp_counter(void);
+static int	is_qpc_built_on_pcc(void);
+
+/*
+ * performance counter frequency observations
+ */
+#define TUNE_CTR_DEPTH		3	/* running avg depth */
+
+static HANDLE		ctr_freq_timer = INVALID_HANDLE_VALUE;
+static ULONGLONG	tune_ctr_freq_max_interval;
+static unsigned		tune_ctr_period;
+void start_ctr_freq_timer(ULONGLONG now_time);
+void reset_ctr_freq_timer(ULONGLONG when, ULONGLONG now);
+void reset_ctr_freq_timer_abs(ULONGLONG when);
+
+/* round a Windows time to the next bottom of the second */
+
+#define ROUND_TO_NEXT_SEC_BOTTOM(t)	\
+do {	\
+	(t) += 3 * HECTONANOSECONDS / 2 - 1;	\
+	(t) /= HECTONANOSECONDS;	\
+	(t) *= HECTONANOSECONDS;	\
+	(t) -= HECTONANOSECONDS / 2;	\
+} while (0)
+
+/*
+ * NT native time format is 100's of nanoseconds since 1601-01-01.
+ * Helpers for converting between "hectonanoseconds" and the 
+ * performance counter scale from which interpolated time is
+ * derived.
+ */
+#define HNS2PERF(hns)	((hns) * PerfCtrFreq / HECTONANOSECONDS)
+#define PERF2HNS(ctr)	((ctr) * HECTONANOSECONDS / PerfCtrFreq)
+
+
+#if defined(_MSC_VER) && _MSC_VER >= 1400	/* VS 2005 */
+#define	get_pcc()	__rdtsc()
+#else
+/*
+ * something like this can be used for a compiler without __rdtsc()
+ */
+ULONGLONG __forceinline 
+get_pcc(void)
+{
+	/* RDTSC returns in EDX:EAX, same as C compiler */
+	__asm {
+		RDTSC
+	}
+}
+#endif
+
+
+/*
+ * perf_ctr() returns the current performance counter value, 
+ * from QueryPerformanceCounter or RDTSC.
+ */
+ULONGLONG WINAPI 
+perf_ctr(void)
+{
+	FT_ULL ft;
+
+	if (use_pcc)
+		return get_pcc();
+	else {
+		QueryPerformanceCounter(&ft.li);
+		return ft.ull;
+	}
+}
+
+
+/*
+ * init_small_adjustment
+ *
+ * Set variable os_ignores_small_adjustment
+ *
+ */
+static void init_small_adjustment(void)
+{
+	OSVERSIONINFO vi;
+	memset(&vi, 0, sizeof(vi));
+	vi.dwOSVersionInfoSize = sizeof(vi);
+
+	if (!GetVersionEx(&vi)) {
+		msyslog(LOG_WARNING, "GetVersionEx failed with error code %d.", GetLastError());
+		os_ignores_small_adjustment = FALSE;
+		return;
+	}
+
+	if (vi.dwMajorVersion == 6 && vi.dwMinorVersion == 1) {
+		// Windows 7 and Windows Server 2008 R2
+		//
+		// Windows 7 is documented as affected.
+		// Windows Server 2008 R2 is assumed affected.
+		os_ignores_small_adjustment = TRUE;
+	} else if (vi.dwMajorVersion == 6 && vi.dwMinorVersion == 0) {
+		// Windows Vista and Windows Server 2008
+		//
+		// Windows Vista is documented as affected.
+		// Windows Server 2008 is assumed affected.
+		os_ignores_small_adjustment = TRUE;
+	} else {
+		os_ignores_small_adjustment = FALSE;
+	}
+}
+
+
+/*
+ * choose_interp_counter - select between QueryPerformanceCounter and
+ *			   the x86 processor cycle counter (TSC).
+ */
+static void
+choose_interp_counter(void)
+{
+	const char *	ntpd_pcc_freq_text;
+	int		qpc_built_on_pcc;
+
+	/*
+	 * Regardless of whether we actually use RDTSC, first determine
+	 * if QueryPerformanceCounter is built on it, so that we can
+	 * decide whether it's prudent to lock QPC-consuming threads to
+	 * a particular CPU.
+	 */
+	qpc_built_on_pcc = is_qpc_built_on_pcc();
+	lock_interp_threads = qpc_built_on_pcc;
+
+	/*
+	 * It's time to make some more permanent knobs,
+	 * but for right now the RDTSC aka PCC dance on x86 is:
+	 *
+	 * 1.  With none of these variables defined, only QPC
+	 *     is used because there is no reliable way to
+	 *     detect counter frequency variation after ntpd
+	 *     startup implemented.
+	 * 2.  We need a better knob, but for now if you know
+	 *     your RDTSC / CPU frequency is invariant, set
+	 *     NTPD_PCC and assuming your QPC is based on the
+	 *     PCC as well, RDTSC will be substituted.
+	 * 3.  More forcefully, you can jam in a desired exact
+	 *     processor frequency, expressed in cycles per
+	 *     second by setting NTPD_PCC_FREQ=398125000, for
+	 *     example, if yor actual known CPU frequency is
+	 *     398.125 MHz, and NTPD_PCC doesn't work because
+	 *     QueryPerformanceCounter is implemented using
+	 *     another counter.  It is very easy to make ntpd
+	 *     fall down if the NTPD_PCC_FREQ value isn't very
+	 *     close to the observed RDTSC units per second.
+	 *
+	 * Items 2 and 3 could probably best be combined into one
+	 * new windows-specific command line switch such as
+	 *   ntpd --pcc
+	 * or
+	 *   ntpd --pcc=398125000
+	 *
+	 * They are currently tied to Windows because that is
+	 * the only ntpd port with its own interpolation, and
+	 * to x86/x64 because no one has ported the Windows
+	 * ntpd port to the sole remaining alternative, Intel
+	 * Itanium.
+	 */
+	if (HAVE_OPT(PCCFREQ))
+		ntpd_pcc_freq_text = OPT_ARG(PCCFREQ);
+	else
+		ntpd_pcc_freq_text = getenv("NTPD_PCC_FREQ");
+
+	if (!HAVE_OPT(USEPCC)
+	    && NULL == ntpd_pcc_freq_text
+	    && NULL == getenv("NTPD_PCC")) {
+		use_pcc = 0;
+		return;
+	}
+
+	if (!qpc_built_on_pcc && NULL == ntpd_pcc_freq_text) {
+		use_pcc = 0;
+		return;
+	}
+
+	use_pcc = 1;
+	if (ntpd_pcc_freq_text != NULL)
+		sscanf(ntpd_pcc_freq_text, 
+		       "%llu", 
+		       &NomPerfCtrFreq);
+
+	NLOG(NLOG_CLOCKINFO)
+		msyslog(LOG_INFO, 
+			"using processor cycle counter "
+			"%.3f MHz", 
+			NomPerfCtrFreq / 1e6);
+	return;
+}
+
+
+/*
+ * is_qpc_built_on_pcc - test if QueryPerformanceCounter runs at the
+ *			 same rate as the processor cycle counter (TSC).
+ */
+static int
+is_qpc_built_on_pcc(void)
+{
+	LONGLONG	offset;
+	FT_ULL		ft1;
+	FT_ULL		ft2;
+	FT_ULL		ft3;
+	FT_ULL		ft4;
+	FT_ULL		ft5;
+
+	NTP_REQUIRE(NomPerfCtrFreq != 0);
+
+	QueryPerformanceCounter(&ft1.li);
+	ft2.ull = get_pcc();
+	Sleep(1);
+	QueryPerformanceCounter(&ft3.li);
+	Sleep(1);
+	ft4.ull = get_pcc();
+	Sleep(1);
+	QueryPerformanceCounter(&ft5.li);
+
+	offset = ft2.ull - ft1.ull;
+	ft3.ull += offset;
+	ft5.ull += offset;
+
+	if (ft2.ull <= ft3.ull &&
+	    ft3.ull <= ft4.ull &&
+	    ft4.ull <= ft5.ull) {
+
+		QPC_offset = offset;
+		return TRUE;
+	}
+
+	return FALSE;
+}
+
+
+/*
+ * Request Multimedia Timer
+ */
+void
+set_mm_timer(
+	int timerres
+	)
+{
+	modify_mm_timer = timerres;
+}
+
+/*
+ * adj_systime - called once every second to discipline system clock.
+ * Normally, the offset passed in (parameter now) is in the range
+ * [-NTP_MAXFREQ, NTP_MAXFREQ].  However, at EVNT_NSET, a much larger
+ * slew is requested if the initial offset is less than the step
+ * threshold, in the range [-step, step] where step is the step
+ * threshold, 128 msec by default.  For the remainder of the frequency
+ * training interval, adj_systime is called with 0 offset each second
+ * and slew the large offset at 500 PPM (500 usec/sec).
+ * Returns 1 if okay, 0 if trouble.
+ */
+int
+adj_systime(
+	double now
+	)
+{
+        /* ntp time scale origin as ticks since 1601-01-01 */
+        static const ULONGLONG HNS_JAN_1900 = 94354848000000000ull;
+
+	static double	adjtime_carry;
+	double		dtemp;
+	u_char		isneg;
+	BOOL		rc;
+	long		TimeAdjustment;
+	SYSTEMTIME	st;
+	ULONGLONG	this_perf_count;
+	FT_ULL		curr_ft;
+        leap_result_t   lsi;
+
+	/*
+	 * Add the residual from the previous adjustment to the new
+	 * adjustment, bound and round.
+	 */
+	dtemp = adjtime_carry + sys_residual + now;
+	adjtime_carry = 0.;
+	sys_residual = 0.;
+	if (dtemp < 0) {
+		isneg = TRUE;
+		dtemp = -dtemp;
+	} else {
+		isneg = FALSE;
+	}
+
+	if (dtemp > NTP_MAXFREQ) {
+		adjtime_carry = dtemp - NTP_MAXFREQ;
+		dtemp = NTP_MAXFREQ;
+	}
+
+	if (isneg) {
+		dtemp = -dtemp;
+		adjtime_carry = -adjtime_carry;
+	}
+
+	dtemp = dtemp * 1e6;
+
+	/* 
+	 * dtemp is in micro seconds. NT uses 100 ns units,
+	 * so a unit change in TimeAdjustment corresponds
+	 * to slewing 10 ppm on a 100 Hz system. Calculate
+	 * the number of 100ns units to add, using OS tick
+	 * frequency as per suggestion from Harry Pyle,
+	 * and leave the remainder in dtemp
+	 */
+	TimeAdjustment = (long)(dtemp / ppm_per_adjust_unit +
+				((isneg)
+				     ? -0.5
+				     : 0.5));
+
+	if (os_ignores_small_adjustment) {
+		/*
+		 * As the OS ignores adjustments smaller than 16, we need to
+		 * leave these small adjustments in sys_residual, causing
+		 * the small values to be averaged over time.
+		 */
+		if (TimeAdjustment > -16 && TimeAdjustment < 16) {
+			TimeAdjustment = 0;
+		}
+	}
+
+	dtemp -= TimeAdjustment * ppm_per_adjust_unit;	
+
+
+	/* If a piping-hot close leap second is pending for the end
+         * of this day, determine the UTC time stamp when the transition
+         * must take place. (Calculated in the current leap era!) 
+	 */
+	if (leapsec >= LSPROX_ALERT) {
+                if (0 == ls_ft.ull && leapsec_frame(&lsi)) {
+                        if (lsi.tai_diff > 0) {
+                                /* A leap second insert is scheduled at the end
+                                 * of the day. Since we have not yet computed the
+                                 * time stamp, do it now. Signal electric mode
+                                 * for this insert.
+                                 */
+                                ls_ft.ull = lsi.ttime.Q_s * HECTONANOSECONDS
+                                          + HNS_JAN_1900;
+                                FileTimeToSystemTime(&ls_ft.ft, &st);
+			        msyslog(LOG_NOTICE,
+				        "Detected positive leap second announcement "
+				        "for %04d-%02d-%02d %02d:%02d:%02d UTC",
+				        st.wYear, st.wMonth, st.wDay,
+				        st.wHour, st.wMinute, st.wSecond);
+                                leapsec_electric(TRUE);
+                        } else if (lsi.tai_diff < 0) {
+                                /* Do not handle negative leap seconds here. If this
+                                 * happens, let the system step.
+                                 */
+                                leapsec_electric(FALSE);
+                        }
+                }
+        } else {
+                /* The leap second announcement is gone. Happens primarily after
+                 * the leap transition, but can also be due to a clock step.
+                 * Disarm the leap second, but only if there is one scheduled
+                 * and not currently in progress!
+                 */
+		if (ls_ft.ull != 0 && ls_time_adjustment == 0) {
+			ls_ft.ull = 0;
+			msyslog(LOG_NOTICE, "Leap second announcement disarmed");
+		}
+	}
+
+	/*
+	 * If the time stamp for the next leap second has been set
+	 * then check if the leap second must be handled
+	 */
+	if (ls_ft.ull != 0) {
+		this_perf_count = perf_ctr();
+
+		if (0 == ls_time_adjustment) { /* has not yet been scheduled */
+
+	 		GetSystemTimeAsFileTime(&curr_ft.ft);
+			if (curr_ft.ull >= ls_ft.ull) {
+				ls_time_adjustment = clockperiod / LS_CORR_INTV_SECS;
+				ls_ref_perf_cnt = this_perf_count;
+				ls_elapsed = 0;
+				msyslog(LOG_NOTICE, "Inserting positive leap second.");
+			}
+		} else {  /* leap sec adjustment has been scheduled previously */
+			ls_elapsed = (this_perf_count - ls_ref_perf_cnt) 
+				     * HECTONANOSECONDS / PerfCtrFreq;
+		}
+
+		if (ls_time_adjustment != 0) {  /* leap second adjustment is currently active */
+			if (ls_elapsed > (LS_CORR_INTV - LS_CORR_LIMIT)) {
+				ls_time_adjustment = 0;  /* leap second adjustment done */
+				ls_ft.ull = 0;
+			}
+
+			/* 
+			 * NOTE: While the system time is slewed during the leap second 
+			 * the interpolation function which is based on the performance 
+			 * counter does not account for the slew.
+			 */
+			TimeAdjustment -= ls_time_adjustment;
+		}
+	}
+
+
+	sys_residual = dtemp / 1e6;
+	DPRINTF(3, ("adj_systime: %.9f -> %.9f residual %.9f", 
+		    now, 1e-6 * (TimeAdjustment * ppm_per_adjust_unit),
+		    sys_residual));
+	if (0. == adjtime_carry)
+		DPRINTF(3, ("\n"));
+	else
+		DPRINTF(3, (" adjtime %.9f\n", adjtime_carry));
+
+	/* only adjust the clock if adjustment changes */
+	TimeAdjustment += wintickadj;
+	if (last_Adj != TimeAdjustment) {
+		last_Adj = TimeAdjustment;
+		DPRINTF(2, ("SetSystemTimeAdjustment(%+ld)\n", TimeAdjustment));
+		rc = SetSystemTimeAdjustment(clockperiod + TimeAdjustment, FALSE);
+		if (!rc)
+			msyslog(LOG_ERR, "Can't adjust time: %m");
+	} else {
+		rc = TRUE;
+	}
+
+	return rc;
+}
+
+
+void 
+init_winnt_time(void)
+{
+	static const char settod[] = "settimeofday=\"SetSystemTime\"";
+	char szMsgPath[MAX_PATH+1];
+	HANDLE hToken = INVALID_HANDLE_VALUE;
+	TOKEN_PRIVILEGES tkp;
+	TIMECAPS tc;
+	BOOL noslew;
+	DWORD adjclockperiod;
+	LARGE_INTEGER Freq;
+	FT_ULL initial_hectonanosecs;
+	FT_ULL next_hectonanosecs;
+	double adjppm;
+	double rawadj;
+	char * pch;
+
+	if (winnt_time_initialized)
+		return;
+
+	/*
+	 * Make sure the service is initialized
+	 * before we do anything else
+	 */
+	ntservice_init();
+
+	/* Set up the Console Handler */
+	if (!SetConsoleCtrlHandler(OnConsoleEvent, TRUE)) {
+		msyslog(LOG_ERR, "Can't set console control handler: %m");
+	}
+
+	/* Set the Event-ID message-file name. */
+	if (!GetModuleFileName(NULL, szMsgPath, sizeof(szMsgPath))) {
+		msyslog(LOG_ERR, "GetModuleFileName(PGM_EXE_FILE) failed: %m");
+		exit(1);
+	}
+
+	/* Initialize random file before OpenSSL checks */
+	if (!init_randfile())
+		msyslog(LOG_ERR, "Unable to initialize .rnd file");
+
+#pragma warning(push)
+#pragma warning(disable: 4127) /* conditional expression is constant */
+
+#ifdef DEBUG
+	if (SIZEOF_TIME_T != sizeof(time_t)
+	    || SIZEOF_INT != sizeof(int)
+	    || SIZEOF_SIGNED_CHAR != sizeof(char)) {
+		msyslog(LOG_ERR, "config.h SIZEOF_* macros wrong, fatal");
+		exit(1);
+	}
+#endif
+
+#pragma warning(pop)
+
+	init_small_adjustment();
+        leapsec_electric(TRUE);
+
+	/*
+	 * Get privileges needed for fiddling with the clock
+	 */
+
+	/* get the current process token handle */
+	if (!OpenProcessToken(
+		GetCurrentProcess(),
+		TOKEN_ADJUST_PRIVILEGES | TOKEN_QUERY,
+		&hToken)) {
+		msyslog(LOG_ERR, "OpenProcessToken failed: %m");
+		exit(-1);
+	}
+	/* get the LUID for system-time privilege. */
+	LookupPrivilegeValue(NULL, SE_SYSTEMTIME_NAME, &tkp.Privileges[0].Luid);
+	tkp.PrivilegeCount = 1;  /* one privilege to set */
+	tkp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
+
+	/* get set-time privilege for this process. */
+	AdjustTokenPrivileges(hToken, FALSE, &tkp, 0,
+	 	(PTOKEN_PRIVILEGES) NULL, 0);
+
+	/* cannot use return value of AdjustTokenPrivileges. */
+	/* (success does not indicate all privileges were set) */
+	if (GetLastError() != ERROR_SUCCESS) {
+		msyslog(LOG_ERR, "AdjustTokenPrivileges failed: %m");
+	 	/* later set time call will probably fail */
+	}
+
+	CloseHandle(hToken);
+	hToken = INVALID_HANDLE_VALUE;
+
+	/*
+	 * Say how we're setting the time of day
+	 */
+	set_sys_var(settod, sizeof(settod), RO);
+
+	/*
+	 * ntpd on Windows has always raised its priority, without
+	 * requiring -N as on Unix.  Since Windows ntpd doesn't share
+	 * the history of unix ntpd of once having no -N and therefore
+	 * needing to be invoked under nice, there is no reason to
+	 * bring it in line with the Unix version in this regard.
+	 * Instsrv assumes ntpd is invoked with no arguments, and
+	 * upgrading users would be negatively surprised by the 
+	 * poor timekeeping if they failed to add -N as part of 
+	 * upgrading were we to correct this platform difference.
+	 */
+	if (-1 == setpriority(PRIO_PROCESS, 0, NTP_PRIO))
+		exit(-1);
+
+	/* Determine the existing system time slewing */
+	if (!GetSystemTimeAdjustment(&adjclockperiod, &clockperiod, &noslew)) {
+		msyslog(LOG_ERR, "GetSystemTimeAdjustment failed: %m");
+		exit(-1);
+	}
+
+	/*
+	 * If there is no slewing before ntpd, adjclockperiod and clockperiod
+	 * will be equal.  Any difference is carried into adj_systime's first
+	 * pass as the previous adjustment.
+	 */
+	last_Adj = adjclockperiod - clockperiod;
+	
+	if (last_Adj)
+		msyslog(LOG_INFO, 
+			"Clock interrupt period %.3f msec "
+			"(startup slew %.1f usec/period)",
+			clockperiod / 1e4,
+			last_Adj / 10.);
+	else
+		msyslog(LOG_INFO, 
+			"Clock interrupt period %.3f msec", 
+			clockperiod / 1e4);
+
+	/*
+	 * Calculate the time adjustment resulting from incrementing
+	 * units per tick by 1 unit for 1 second 
+	 */
+	ppm_per_adjust_unit = 1e6 / clockperiod;
+
+	pch = getenv("NTPD_TICKADJ_PPM");
+	if (pch != NULL && 1 == sscanf(pch, "%lf", &adjppm)) {
+		rawadj = adjppm / ppm_per_adjust_unit;
+		rawadj += (rawadj < 0)
+			      ? -0.5
+			      : 0.5;
+		wintickadj = (long)rawadj;
+		msyslog(LOG_INFO,
+			"Using NTPD_TICKADJ_PPM %+g ppm (%+ld)",
+			adjppm, wintickadj);
+	}
+
+	/* get the performance counter ticks per second */
+	if (!QueryPerformanceFrequency(&Freq) || !Freq.QuadPart) {
+		msyslog(LOG_ERR, "QueryPerformanceFrequency failed: %m");
+		exit(-1);
+	}
+
+	NomPerfCtrFreq = PerfCtrFreq = Freq.QuadPart;
+	msyslog(LOG_INFO, 
+		"Performance counter frequency %.3f MHz",
+		PerfCtrFreq / 1e6);
+
+	/*
+	 * With a precise system clock, our interpolation decision is
+	 * a slam dunk.
+	 */
+	if (NULL != pGetSystemTimePreciseAsFileTime) {
+		winnt_use_interpolation = FALSE;
+		winnt_time_initialized = TRUE;
+
+		return;
+	}
+
+	/* 
+	 * Implement any multimedia timer manipulation requested via -M
+	 * option.  This is rumored to be unneeded on Win8 with the
+	 * introduction of the precise (interpolated) system clock.
+	 */
+	if (modify_mm_timer) {
+		if (timeGetDevCaps(&tc, sizeof(tc)) == TIMERR_NOERROR) {
+			wTimerRes = min(max(tc.wPeriodMin, MM_TIMER_INTV), tc.wPeriodMax);
+			timeBeginPeriod(wTimerRes);
+			atexit(atexit_revert_mm_timer);
+			
+			msyslog(LOG_INFO, "MM timer resolution: %u..%u msec, set to %u msec",
+				tc.wPeriodMin, tc.wPeriodMax, wTimerRes );
+		} else {
+			msyslog(LOG_ERR, "Multimedia timer unavailable");
+		}
+	}
+	
+	/*
+	 * Spin on GetSystemTimeAsFileTime to determine its
+	 * granularity.  Prior to Windows Vista this is 
+	 * typically the same as the clock period.
+	 */
+	GetSystemTimeAsFileTime(&initial_hectonanosecs.ft);
+	do {
+		GetSystemTimeAsFileTime(&next_hectonanosecs.ft);
+	} while (initial_hectonanosecs.ull == next_hectonanosecs.ull);
+
+	os_clock_precision = next_hectonanosecs.ull -
+		initial_hectonanosecs.ull;
+
+	msyslog(LOG_INFO,
+		"Windows clock precision %.3f msec, min. slew %.3f ppm/s",
+		os_clock_precision / 1e4, ppm_per_adjust_unit);
+
+	winnt_time_initialized = TRUE;
+
+	choose_interp_counter();
+
+	if (getenv("NTPD_USE_SYSTEM_CLOCK") ||
+	    (os_clock_precision < 4 * 10000 &&
+	     !getenv("NTPD_USE_INTERP_DANGEROUS"))) {
+		msyslog(LOG_INFO, "using Windows clock directly");
+	} else {
+		winnt_use_interpolation = TRUE;
+		get_sys_time_as_filetime = GetInterpTimeAsFileTime;
+		StartClockThread();
+	}
+}
+
+
+void
+atexit_revert_mm_timer(void)
+{
+	timeEndPeriod(wTimerRes); 
+	DPRINTF(1, ("MM timer resolution reset\n"));
+}
+
+
+void 
+reset_winnt_time(void)
+{
+	SYSTEMTIME st;
+
+	/*
+	 * If we're in the 2-second slew right after a leap second, 
+	 * we don't want to continue that extreme slew, in that case
+	 * disable our slewing and return clock discipline to the 
+	 * kernel.  Similarly if we are not yet synchronized, 
+	 * our current slew may not be a good ongoing trim.
+	 * Otherwise, our leave in place the last SetSystemTimeAdjustment
+	 * as an ongoing frequency correction, better than nothing.
+	 * TODO:
+	 * Verify this will not call SetSystemTimeAdjustment if
+	 * ntpd is running in ntpdate mode.
+	 */
+	if (sys_leap == LEAP_NOTINSYNC || ls_time_adjustment != 0)
+		SetSystemTimeAdjustment(0, TRUE);	 
+
+	/*
+	 * Read the current system time, and write it back to
+	 * force CMOS update, only if we are exiting because
+	 * the computer is shutting down and we are already
+	 * synchronized.
+	 */
+	 if (ntservice_systemisshuttingdown() && sys_leap != LEAP_NOTINSYNC) {
+		GetSystemTime(&st);
+		SetSystemTime(&st);
+		NLOG(NLOG_SYSEVENT | NLOG_CLOCKINFO)
+			msyslog(LOG_NOTICE, "system is shutting down, CMOS time reset.");
+	}
+}
+
+
+/*
+ * GetSystemTimeAsFileTime() interface clone is used by getclock() in ntpd.
+ */
+
+void WINAPI 
+GetInterpTimeAsFileTime(
+	LPFILETIME pft
+	)
+{
+	static ULONGLONG last_interp_time;
+	FT_ULL now_time;
+	FT_ULL now_count;
+	ULONGLONG clock_backward;
+
+	/*
+	 * Mark a mark ASAP.  The latency to here should be reasonably
+	 * deterministic
+	 */
+
+	now_count.ull = perf_ctr();
+	now_time.ull = interp_time(now_count.ull, TRUE);
+
+	if (last_interp_time <= now_time.ull) {
+		last_interp_time = now_time.ull;
+	} else {
+		clock_backward = last_interp_time - now_time.ull;
+		if (clock_backward > clock_backward_max) {
+			clock_backward_max = clock_backward;
+			clock_backward_count++;
+		}
+		now_time.ull = last_interp_time;
+	}
+	*pft = now_time.ft;
+
+	return;
+}
+
+
+/*
+ * TimerApcFunction is invoked on the high-priority clock
+ * thread to capture a new  baseline system time and
+ * performance counter correlation every 43 msec (64Hz 
+ * OS clock precision).
+ */
+static void CALLBACK
+TimerApcFunction(
+	LPVOID lpArgToCompletionRoutine,
+	DWORD dwTimerLowValue,
+	DWORD dwTimerHighValue
+	)
+{
+	static BOOL		ctr_freq_timer_started = FALSE;
+	static ULONGLONG	prev_count;
+	ULONGLONG		now_time;
+	FT_ULL			now_count;
+
+	/* Grab the counter first of all */
+	now_count.ull = perf_ctr();
+
+	now_time = (((ULONGLONG)dwTimerHighValue << 32) |
+				dwTimerLowValue);
+
+	/*
+	 * Save this correlation in the history.
+	 */
+	add_counter_time_pair(now_count.ull, now_time);
+
+	/*
+	 * Once we're synchronized start the counter frequency
+	 * tuning timer.
+	 */
+	if (INVALID_HANDLE_VALUE == ctr_freq_timer &&
+	    LEAP_NOTINSYNC != sys_leap)
+		start_ctr_freq_timer(now_time);
+}
+
+
+unsigned WINAPI 
+ClockThread(
+	void *arg
+	)
+{
+	LARGE_INTEGER	DueTime;
+	HANDLE		timer;
+	double		HZ;
+	double		TimerHz;
+	DWORD		timer_period_msec;
+	DWORD		res;
+	char		*ntpd_int_int_text;
+
+	UNUSED_ARG(arg);
+
+	timer = CreateWaitableTimer(NULL, FALSE, NULL);
+
+	ntpd_int_int_text = getenv("NTPD_INT_INT");
+
+	HZ = (double)HECTONANOSECONDS / clockperiod;
+
+	if (HZ > 63 && HZ < 65) {
+		timer_period_msec = 43;
+	} else if (HZ > 98 && HZ < 102) {
+		timer_period_msec = 27;
+		if (NULL == ntpd_int_int_text)
+			msyslog(LOG_WARNING, 
+				"%.3f Hz system clock may benefit from "
+				"custom NTPD_INT_INT env var timer interval "
+				"override between approx. 20 and 50 msecs.",
+				HZ);
+	} else {
+		timer_period_msec = (DWORD)(0.5 + (2.752 * clockperiod / 10000));
+		if (NULL == ntpd_int_int_text)
+			msyslog(LOG_WARNING, 
+				"unfamiliar %.3f Hz system clock may benefit "
+				"from custom NTPD_INT_INT env var timer "
+				"interval override between approx. 20 and 50 "
+				"msecs.",
+				HZ);
+	}
+
+	if (ntpd_int_int_text != NULL) {
+		timer_period_msec = atoi(ntpd_int_int_text);
+		timer_period_msec = max(9, timer_period_msec);
+		msyslog(LOG_NOTICE, 
+			"using NTPD_INT_INT env var override %u", 
+			timer_period_msec);
+	}
+
+	TimerHz = 1e3 / timer_period_msec;
+	msyslog(LOG_NOTICE, "HZ %.3f using %u msec timer %.3f Hz %d deep", 
+		HZ,
+		timer_period_msec,
+		TimerHz,
+		BASELINES_USED);
+
+	/* negative DueTime means relative to now */
+	DueTime.QuadPart = -(int)timer_period_msec;
+
+	SetWaitableTimer(
+		timer, 
+		&DueTime,		/* first fire */
+		timer_period_msec,	/* period thereafter */
+		TimerApcFunction,	/* callback routine */
+		&timer,			/* context for callback */
+		FALSE);			/* do not interfere with power saving */
+
+	/*
+	 * The clock thread spends the rest of its life in the TimerApcFunction
+	 * and ctr_freq_timer_fired timer APC callbacks, which can only occur 
+	 * while this thread is in an alertable wait.  Note the Ex on 
+	 * WaitForSingleObjectEx and TRUE for fAlertable.  The wait will return 
+	 * after each APC callback in which case we simply wait again.  We will
+	 * break out of the loop when StopClockThread signals our exit event.
+	 */
+	do res = WaitForSingleObjectEx(
+			TimerThreadExitRequest, 
+			INFINITE, 
+			TRUE);
+	while (WAIT_OBJECT_0 != res);
+
+	CloseHandle(timer);
+
+	if (ctr_freq_timer != INVALID_HANDLE_VALUE) {
+		CloseHandle(ctr_freq_timer);
+		ctr_freq_timer = INVALID_HANDLE_VALUE;
+	}
+
+	return 0;
+}
+
+
+static void 
+StartClockThread(void)
+{
+	static BOOL done_once = FALSE;
+	FT_ULL StartTime;
+
+	/* init variables with the time now */
+	GetSystemTimeAsFileTime(&StartTime.ft);
+	baseline_times[0] = StartTime.ull;
+	baseline_counts[0] = perf_ctr();
+
+	/* init sync objects */
+	TimerThreadExitRequest = CreateEvent(NULL, FALSE, FALSE, NULL);
+
+	clock_thread = 
+		(HANDLE)_beginthreadex(
+			NULL, 
+			0, 
+			ClockThread, 
+			NULL, 
+			CREATE_SUSPENDED, 
+			&clock_thread_id);
+
+	if (clock_thread != NULL) {
+		/* remember the thread priority is only within the process class */
+		if (!SetThreadPriority(clock_thread, THREAD_PRIORITY_TIME_CRITICAL)) {
+			DPRINTF(1, ("Error setting thread priority\n"));
+		}
+
+		lock_thread_to_processor(clock_thread);
+		ResumeThread(clock_thread);
+
+		if (FALSE == done_once) {
+			done_once = TRUE;
+			lock_thread_to_processor(GetCurrentThread());
+			atexit( StopClockThread );
+		}
+
+		/*
+		 * Give the clock thread time to fill its counter/time
+		 * sample buffer.  This will underfill the buffer a
+		 * bit for sample periods over 43 msec.
+		 */
+		Sleep(BASELINES_USED * 43);
+	}
+}
+
+
+void 
+StopClockThread(void)
+{
+	/*
+	 * if the clock thread exit()s this routine
+	 * will be called on the clock thread and
+	 * we need not (and can't) use the normal
+	 * TimerThreadExitRequest event.
+	 */
+	if (GetCurrentThreadId() != clock_thread_id) {
+
+		if (!SetEvent(TimerThreadExitRequest) ||
+		    WaitForSingleObject(clock_thread, 2 * 1000) != 
+		    WAIT_OBJECT_0) {
+			msyslog(LOG_ERR, "Failed to stop clock thread.");
+		}
+	}
+	CloseHandle(TimerThreadExitRequest);
+	TimerThreadExitRequest = NULL;
+	CloseHandle(clock_thread);
+	clock_thread = NULL;
+}
+
+
+void
+lock_thread_to_processor(HANDLE thread)
+{
+	static	DWORD_PTR	ProcessAffinityMask;
+	static	DWORD_PTR	ThreadAffinityMask;
+	DWORD_PTR		SystemAffinityMask;
+	char			*cputext;
+	unsigned int		cpu;
+
+	if ( ! winnt_time_initialized) {
+		DPRINTF(1, ("init_winnt_time() must be called before "
+				"lock_thread_to_processor(), exiting\n"));
+		exit(-1);
+	}
+
+	if (!winnt_use_interpolation)
+		return;
+	
+	if (-1 == lock_interp_threads) {
+		DPRINTF(1, ("choose_interp_counter() is not called "
+			    "before lock_thread_to_processor()\n"));
+		exit(-1);
+	} else if (!lock_interp_threads)
+		return;
+
+	/*
+	 * Calculate the ThreadAffinityMask we'll use once on the
+	 * first invocation.
+	 */
+	if (!ProcessAffinityMask) {
+
+		/*
+		 * Choose which processor to nail the main and clock threads to.
+		 * If we have more than one, we simply choose the 2nd.
+		 * Randomly choosing from 2 to n would be better, but in
+		 * either case with clock and network interrupts more likely
+		 * to be serviced by the first procecssor, let's stay away 
+		 * from it.  QueryPerformanceCounter is not necessarily
+		 * consistent across CPUs, hence the need to nail the two
+		 * threads involved in QPC-based interpolation to the same
+		 * CPU.
+		 */
+
+		GetProcessAffinityMask(
+			GetCurrentProcess(), 
+			&ProcessAffinityMask,
+			&SystemAffinityMask);
+
+		/*
+		 * respect NTPD_CPU environment variable if present
+		 * for testing.  NTPD_CPU=0 means use all CPUs, 1-64
+		 * means lock threads involved in interpolation to
+		 * that CPU.  Default to 2nd if more than 1.
+		 */
+
+		cpu = 2;
+		cputext = getenv("NTPD_CPU");
+		if (cputext) {
+			cpu = (unsigned int) atoi(cputext);
+			cpu = min((8 * sizeof(DWORD_PTR)), cpu);
+		}
+
+		/* 
+		 * Clear all bits except the 2nd.  If we have only one proc
+		 * that leaves ThreadAffinityMask zeroed and we won't bother
+		 * with SetThreadAffinityMask.
+		 */
+
+		ThreadAffinityMask = (0 == cpu) ? 0 : (1 << (cpu - 1));
+
+		if (ThreadAffinityMask && 
+			!(ThreadAffinityMask & ProcessAffinityMask)) 
+
+			DPRINTF(1, ("Selected CPU %u (mask %x) is outside "
+					"process mask %x, using all CPUs.\n",
+					cpu, ThreadAffinityMask, 
+					ProcessAffinityMask));
+		else
+			DPRINTF(1, ("Wiring to processor %u (0 means all) "
+					"affinity mask %x\n",	
+					cpu, ThreadAffinityMask));
+
+		ThreadAffinityMask &= ProcessAffinityMask;
+	}
+
+	if (ThreadAffinityMask && 
+	    !SetThreadAffinityMask(thread, ThreadAffinityMask))
+		msyslog(LOG_ERR, 
+			"Unable to wire thread to mask %x: %m", 
+			ThreadAffinityMask);
+}
+
+
+#ifdef HAVE_PPSAPI
+static inline void ntp_timestamp_from_counter(l_fp *, ULONGLONG,
+					      ULONGLONG);
+
+/*
+ * helper routine for serial PPS which returns QueryPerformanceCounter
+ * timestamp and needs to interpolate it to an NTP timestamp.
+ */
+void 
+pps_ntp_timestamp_from_counter(
+	ntp_fp_t	*result, 
+	ULONGLONG	Timestamp, 
+	ULONGLONG	Counterstamp
+	)
+{
+	/*
+	 * convert between equivalent l_fp and PPSAPI ntp_fp_t
+	 */
+	ntp_timestamp_from_counter(
+		(l_fp *)result,
+		Timestamp,
+		Counterstamp);
+}
+
+
+static inline 
+void 
+ntp_timestamp_from_counter(
+	l_fp *result, 
+	ULONGLONG Timestamp, 
+	ULONGLONG Counterstamp
+	)
+{
+	FT_ULL		Now;
+	FT_ULL		Ctr;
+	LONGLONG	CtrDelta;
+	double		seconds;
+	ULONGLONG	InterpTimestamp;
+
+	if (winnt_use_interpolation) {
+		if (0 == Counterstamp) {
+			DPRINTF(1, ("ntp_timestamp_from_counter rejecting 0 counter.\n"));
+			ZERO(*result);
+			return;
+		}
+
+		InterpTimestamp = interp_time(Counterstamp + QPC_offset, FALSE);
+	} else {  /* ! winnt_use_interpolation */
+		if (NULL != pGetSystemTimePreciseAsFileTime &&
+		    0 != Counterstamp) {
+			QueryPerformanceCounter(&Ctr.li);
+			(*pGetSystemTimePreciseAsFileTime)(&Now.ft);
+			CtrDelta = Ctr.ull - Counterstamp;
+			seconds = (double)CtrDelta / PerfCtrFreq;
+			InterpTimestamp = Now.ull -
+			    (ULONGLONG)(seconds * HECTONANOSECONDS);
+		} else {
+			/* have to simply use the driver's system time timestamp */
+			InterpTimestamp = Timestamp;
+			GetSystemTimeAsFileTime(&Now.ft);
+		}
+	}
+
+	/* convert from 100ns units to NTP fixed point format */
+
+	InterpTimestamp -= FILETIME_1970;
+	result->l_ui = JAN_1970 + (u_int32)(InterpTimestamp / HECTONANOSECONDS);
+	result->l_uf = (u_int32)((InterpTimestamp % HECTONANOSECONDS) *
+				 (ULONGLONG)FRAC / HECTONANOSECONDS);
+}
+#endif  /* HAVE_PPSAPI */
+
+
+void
+win_time_stepped(void)
+{
+	/*
+	 * called back by ntp_set_tod after the system
+	 * time has been stepped (set).
+	 *
+	 * We normally prevent the reported time from going backwards
+	 * but need to allow it in this case.
+	 */
+	if (FALSE == winnt_use_interpolation)
+		return;
+
+
+	/*
+	 * Restart the clock thread to get a new baseline
+	 * time/counter correlation.
+	 */
+	StopClockThread();
+
+	/*
+	 * newest_baseline_gen is a generation counter
+	 * incremented once each time newest_baseline
+	 * is reset.
+	 */
+	newest_baseline_gen++;
+
+	clock_backward_max = CLOCK_BACK_THRESHOLD;
+	clock_backward_count = 0;
+	newest_baseline = 0;
+	ZERO(baseline_counts);
+	ZERO(baseline_times);
+
+	StartClockThread();
+}
+
+
+/*
+ * log2ull - log base 2 of a unsigned 64-bit number
+ */
+int 
+log2ull(
+	ULONGLONG n
+	)
+{
+	const ULONGLONG one = 1;
+	int log = 0;
+
+	if (n >= one<<32) { n >>= 32; log += 32; }
+	if (n >= one<<16) { n >>= 16; log += 16; }
+	if (n >= one<< 8) { n >>=  8; log +=  8; }
+	if (n >= one<< 4) { n >>=  4; log +=  4; }
+	if (n >= one<< 2) { n >>=  2; log +=  2; }
+	if (n >= one<< 1) {	      log +=  1; }
+
+	return (n) ? log : (-1);
+}
+
+
+/*
+ * ctr_freq_timer_fired is called once a few seconds before
+ * tune_ctr_period seconds have elapsed, to reset the timer
+ * and hopefully minimize error due to the system using the
+ * nominal performance counter frequency to set the timer
+ * internally, which is typically dozens of PPM from the
+ * actual performance counter rate.  A few seconds later
+ * it is called again to observe the counter and estimate the
+ * counter frequency.
+ */
+static void CALLBACK
+ctr_freq_timer_fired(
+	LPVOID arg,
+	DWORD dwTimeLow,
+	DWORD dwTimeHigh
+	)
+{
+	static	FT_ULL		begin_time = {0};
+	static	FT_ULL		begin_count = {0};
+	static	ULONGLONG	next_period_time = 0;
+	static	ULONGLONG	report_systemtime = 0;
+	const	ULONGLONG	five_minutes = 5ui64 * 60 * HECTONANOSECONDS;
+	FT_ULL			now_time;
+	FT_ULL			now_count;
+
+	if (!begin_time.ull) {
+		begin_count.ull = perf_ctr();
+		begin_time.ft.dwLowDateTime = dwTimeLow;
+		begin_time.ft.dwHighDateTime = dwTimeHigh;
+
+		/*
+		 * adapt perf ctr observation interval to the
+		 * counter frequency
+		 */
+		tune_ctr_period = 22680 / log2ull(NomPerfCtrFreq);
+
+		/*
+		 * reset timer 2s before period ends to minimize
+		 * error from OS timer routines using nominal 
+		 * performance frequency internally.
+		 */
+		tune_ctr_freq_max_interval = tune_ctr_period - 2;
+
+		next_period_time = begin_time.ull + 
+			(ULONGLONG)tune_ctr_period * HECTONANOSECONDS;
+
+		ROUND_TO_NEXT_SEC_BOTTOM(next_period_time);
+
+		reset_ctr_freq_timer(next_period_time, begin_time.ull);
+
+		return;
+	}
+
+	now_time.ft.dwLowDateTime = dwTimeLow;
+	now_time.ft.dwHighDateTime = dwTimeHigh;
+
+	if (now_time.ull >= next_period_time) {
+		now_count.ull = perf_ctr();
+		tune_ctr_freq(
+			now_count.ull - begin_count.ull,
+			now_time.ull - begin_time.ull);
+		next_period_time += (ULONGLONG)tune_ctr_period * HECTONANOSECONDS;
+		begin_count.ull = now_count.ull;
+		begin_time.ull = now_time.ull;
+	}
+
+	/* 
+	 * Log clock backward events no more often than 5 minutes.
+	 */
+	if (!report_systemtime) {
+		report_systemtime = now_time.ull + five_minutes;
+	} else if (report_systemtime <= now_time.ull) {
+		report_systemtime +=  five_minutes;
+		if (clock_backward_count) {
+			msyslog(LOG_WARNING, 
+				"clock would have gone backward %d times, "
+				"max %.1f usec",
+				clock_backward_count, 
+				clock_backward_max / 10.);
+
+			clock_backward_max = CLOCK_BACK_THRESHOLD;
+			clock_backward_count = 0;
+		}
+	}
+	reset_ctr_freq_timer(next_period_time, now_time.ull);
+}
+
+
+void
+reset_ctr_freq_timer_abs(
+	ULONGLONG when
+	)
+{
+	FT_ULL	fire_time;
+
+	fire_time.ull = when; 
+	SetWaitableTimer(
+		ctr_freq_timer,
+		&fire_time.li,		/* first fire */
+		0,			/* not periodic */
+		ctr_freq_timer_fired,	/* callback routine */
+		NULL,			/* context for callback */
+		FALSE);			/* do not interfere with power saving */
+}
+
+
+void
+reset_ctr_freq_timer(
+	ULONGLONG when,
+	ULONGLONG now
+	)
+{
+	if (when - now > 
+	    (tune_ctr_freq_max_interval * HECTONANOSECONDS + HECTONANOSECONDS))
+		when = now + tune_ctr_freq_max_interval * HECTONANOSECONDS;
+
+	reset_ctr_freq_timer_abs(when);
+}
+
+
+void
+start_ctr_freq_timer(
+	ULONGLONG now_time
+	)
+{
+	ULONGLONG when;
+
+	ctr_freq_timer = CreateWaitableTimer(NULL, FALSE, NULL);
+	when = now_time;
+	ROUND_TO_NEXT_SEC_BOTTOM(when);
+
+	reset_ctr_freq_timer_abs(when);
+}
+
+
+/*
+ * tune_ctr_freq is called once per tune_ctr_period seconds
+ * with a counter difference and time difference.
+ */
+void 
+tune_ctr_freq(
+	LONGLONG ctr_delta,
+	LONGLONG time_delta
+	)
+{
+	static unsigned count = 0;
+	static unsigned dispcount = 0;
+	static unsigned report_at_count = 0;
+	static int disbelieved = 0;
+	static int i = 0;
+	static double nom_freq = 0;
+	static LONGLONG diffs[TUNE_CTR_DEPTH] = {0};
+	static LONGLONG sum = 0;
+	char ctr_freq_eq[64];
+	LONGLONG delta;
+	LONGLONG deltadiff;
+	ULONGLONG ObsPerfCtrFreq;
+	double freq;
+	double this_freq;
+	BOOL isneg;
+
+	/* one-time initialization */
+	if (!report_at_count) {
+		report_at_count = 24 * 60 * 60 / tune_ctr_period;
+		nom_freq = NomPerfCtrFreq / 1e6;
+	}
+
+	/* delta is the per-second observed frequency this time */
+	delta = (LONGLONG)((double)ctr_delta * HECTONANOSECONDS /
+			   time_delta);
+
+	/* disbelieve any delta more than +/- 976 PPM from nominal */
+	deltadiff = delta - NomPerfCtrFreq;
+	if (0 > deltadiff) {
+		isneg = TRUE;
+		deltadiff = -deltadiff;
+	} else {
+		isneg = FALSE;
+	}
+
+	if ((ULONGLONG)deltadiff > (NomPerfCtrFreq / 1024)) {
+		disbelieved++;
+		dispcount++;
+#ifdef DEBUG
+		msyslog(LOG_DEBUG, "ctr delta %s%lld exceeds limit %llu",
+				   (isneg) ? "-" : "",
+				   deltadiff,
+				   NomPerfCtrFreq / 1024);
+#endif
+	} else {
+
+		/*
+		 * collect average over TUNE_CTR_DEPTH samples
+		 * for our PerfCtrFreq trimming.
+		 */
+
+		if (isneg)
+			deltadiff = -deltadiff;
+		sum -= diffs[i];
+		diffs[i] = deltadiff;
+		sum += deltadiff;
+		i = (i + 1) % COUNTOF(diffs);
+		count++;
+		dispcount++;
+	}
+
+	this_freq = delta / 1e6;
+
+	ObsPerfCtrFreq = NomPerfCtrFreq + (sum / COUNTOF(diffs));
+
+#if 1	/* #if 0 to disable changing freq used */
+	/* get rid of ObsPerfCtrFreq when removing the #ifdef */
+	PerfCtrFreq = ObsPerfCtrFreq;
+#endif
+	freq = PerfCtrFreq / 1e6;
+
+	/*
+	 * make the performance counter's frequency error from its
+	 * nominal rate, expressed in PPM, available via ntpq as
+	 * system variable "ctr_frequency".  This is consistent with
+	 * "frequency" which is the system clock drift in PPM.
+	 */
+	snprintf(ctr_freq_eq, sizeof(ctr_freq_eq), "ctr_frequency=%.2f", 
+		 1e6 * (freq - nom_freq) / nom_freq);
+	set_sys_var(ctr_freq_eq, strlen(ctr_freq_eq) + 1, RO | DEF);
+
+	/* 
+	 * report observed ctr freq each time the estimate used during
+	 * startup moves toward the observed freq from the nominal.
+	 */
+
+	if (count > COUNTOF(diffs) &&
+	    /* (count % COUNTOF(diffs)) && */	/* enables reporting each */
+	    dispcount < report_at_count)	/* TUNE_CTR_DEPTH samples */
+		return;
+
+	NLOG(NLOG_CLOCKINFO)
+		if (count <= COUNTOF(diffs))
+			/* moving to observed freq. from nominal (startup) */
+			msyslog(LOG_INFO,
+				(freq > 100)
+				   ? "ctr %.3f MHz %+6.2f PPM using %.3f MHz %+6.2f PPM"
+				   : "ctr %.6f MHz %+6.2f PPM using %.6f MHz %+6.2f PPM",
+				this_freq,
+				1e6 * (this_freq - nom_freq) / nom_freq,
+				freq, 
+				1e6 * (freq - nom_freq) / nom_freq);
+		else
+			/* steady state */
+			msyslog(LOG_INFO,
+				(freq > 100)
+				   ? "ctr %.3f MHz %+.2f PPM"
+				   : "ctr %.6f MHz %+.2f PPM",
+				freq, 
+				1e6 * (freq - nom_freq) / nom_freq);
+
+	if (disbelieved) {
+		msyslog(LOG_ERR, 
+			"%d ctr samples exceed +/- 976 PPM range gate",
+			disbelieved);
+		disbelieved = 0;
+	}
+
+	dispcount = 0;
+}
+
+
+/*
+ * add_counter_time_pair is called by the
+ * high priority clock thread with each new
+ * baseline counter/time correlation.
+ */
+void
+add_counter_time_pair(
+	ULONGLONG ctr,
+	LONGLONG time
+	)
+{
+	int i;
+
+	i = (newest_baseline + 1) % BASELINES_TOT;
+
+	baseline_counts[i] = ctr;
+	baseline_times[i] = time;
+
+	newest_baseline = i;
+}
+
+
+/*
+ * interp_time estimates NT time in 100ns units
+ * based on a performance counter value given.
+ * This must tolerate recent historical counters
+ * as well as current.  When current is FALSE
+ * we can't assume ctr is the latest/highest
+ * seen.
+ */
+ULONGLONG
+interp_time(
+	ULONGLONG ctr,
+	BOOL current
+	)
+{
+	static __declspec(thread) int		last_newest = -1;
+	static __declspec(thread) int		last_newest_gen;
+	static __declspec(thread) int		best_index;
+	ULONGLONG	this_ctr;
+	LONGLONG	this_time;
+	LONGLONG	latest_time;
+	LONGLONG	ctr_diff;
+	int		i;
+	int		i_gen;
+	int		c;
+
+	/*
+	 * Use the system time (roughly synchronised to the tick, and
+	 * extrapolated using the system performance counter.
+	 *
+	 * Cache the results per thread and only repeat the
+	 * calculation when new data has arrived.
+	 */
+	i = newest_baseline;
+	i_gen = newest_baseline_gen;
+
+	if (last_newest == i && last_newest_gen == i_gen) {
+		this_time = baseline_times[best_index];
+		ctr_diff = ctr - baseline_counts[best_index];
+		this_time += (LONGLONG)PERF2HNS((double)ctr_diff);
+
+		return this_time;
+	}
+
+	last_newest = i;
+	last_newest_gen = i_gen;
+
+	latest_time = 0;
+
+	/*
+	 * Run through the history calculating the interpolated 
+	 * time based on each counter/time correlation in turn,
+	 * and believe the latest one.  This is akin to the NTP
+	 * protocol minimum delay clock filter.  Errors due to 
+	 * counter/time correlations with stale time are all 
+	 * negative.
+	 */
+	for (c = 0; c < BASELINES_USED; c++) {
+		 if (baseline_times[i]) {
+			this_time = baseline_times[i];
+			this_ctr = baseline_counts[i];
+
+			ctr_diff = ctr - this_ctr;
+
+			if (current && ctr_diff < 0) {
+				/* 
+				 * The performance counter apparently went 
+				 * backwards without rolling over.  It might 
+				 * be nice to complain but we don't want 
+				 * to do it repeatedly.
+				 */
+				ctr_diff = 0;
+			}
+
+			this_time += (LONGLONG)PERF2HNS((double)ctr_diff);
+
+			if (this_time > latest_time) {
+				latest_time = this_time;
+				best_index = i;
+			}
+		}
+		i = i ? (i - 1) : (BASELINES_TOT - 1);
+	}
+
+	return latest_time;
+}