/*

 * systime -- routines to fiddle a UNIX clock.

 *

 * ATTENTION: Get approval from Dave Mills on all changes to this file!

 *

 */

#include <config.h>

#include <math.h>

#include "ntp.h"

#include "ntpd.h"

#include "ntp_syslog.h"

#include "ntp_stdlib.h"

#include "ntp_random.h"

#include "iosignal.h"

#include "timevalops.h"

#include "timespecops.h"

#include "ntp_calendar.h"

#ifdef HAVE_SYS_PARAM_H

# include <sys/param.h>

#endif

#ifdef HAVE_UTMP_H

# include <utmp.h>

#endif /* HAVE_UTMP_H */

#ifdef HAVE_UTMPX_H

# include <utmpx.h>

#endif /* HAVE_UTMPX_H */

int allow_panic = FALSE;    /* allow panic correction (-g) */

int enable_panic_check = TRUE;  /* Can we check allow_panic's state? */

u_long  sys_lamport;      /* Lamport violation */

u_long  sys_tsrounding;     /* timestamp rounding errors */

#ifndef USE_COMPILETIME_PIVOT

# define USE_COMPILETIME_PIVOT 1

#endif

/*

 * These routines (get_systime, step_systime, adj_systime) implement an

 * interface between the system independent NTP clock and the Unix

 * system clock in various architectures and operating systems. Time is

 * a precious quantity in these routines and every effort is made to

 * minimize errors by unbiased rounding and amortizing adjustment

 * residues.

 *

 * In order to improve the apparent resolution, provide unbiased

 * rounding and most importantly ensure that the readings cannot be

 * predicted, the low-order unused portion of the time below the minimum

 * time to read the clock is filled with an unbiased random fuzz.

 *

 * The sys_tick variable specifies the system clock tick interval in

 * seconds, for stepping clocks, defined as those which return times

 * less than MINSTEP greater than the previous reading. For systems that

 * use a high-resolution counter such that each clock reading is always

 * at least MINSTEP greater than the prior, sys_tick is the time to read

 * the system clock.

 *

 * The sys_fuzz variable measures the minimum time to read the system

 * clock, regardless of its precision.  When reading the system clock

 * using get_systime() after sys_tick and sys_fuzz have been determined,

 * ntpd ensures each unprocessed clock reading is no less than sys_fuzz

 * later than the prior unprocessed reading, and then fuzzes the bits

 * below sys_fuzz in the timestamp returned, ensuring each of its

 * resulting readings is strictly later than the previous.

 *

 * When slewing the system clock using adj_systime() (with the kernel

 * loop discipline unavailable or disabled), adjtime() offsets are

 * quantized to sys_tick, if sys_tick is greater than sys_fuzz, which

 * is to say if the OS presents a stepping clock.  Otherwise, offsets

 * are quantized to the microsecond resolution of adjtime()'s timeval

 * input.  The remaining correction sys_residual is carried into the

 * next adjtime() and meanwhile is also factored into get_systime()

 * readings.

 */

double  sys_tick = 0;   /* tick size or time to read (s) */

double  sys_fuzz = 0;   /* min. time to read the clock (s) */

long  sys_fuzz_nsec = 0;  /* min. time to read the clock (ns) */

double  measured_tick;    /* non-overridable sys_tick (s) */

double  sys_residual = 0; /* adjustment residue (s) */

int trunc_os_clock;   /* sys_tick > measured_tick */

time_stepped_callback step_callback;

#ifndef SIM

/* perlinger@ntp.org: As 'get_sysime()' does it's own check for clock

 * backstepping, this could probably become a local variable in

 * 'get_systime()' and the cruft associated with communicating via a

 * static value could be removed after the v4.2.8 release.

 */

static int lamport_violated;  /* clock was stepped back */

#endif  /* !SIM */

#ifdef DEBUG

static int systime_init_done;

# define DONE_SYSTIME_INIT()  systime_init_done = TRUE

#else

# define DONE_SYSTIME_INIT()  do {} while (FALSE)

#endif

#ifdef HAVE_SIGNALED_IO

int using_sigio;

#endif

#ifdef SYS_WINNT

CRITICAL_SECTION get_systime_cs;

#endif

void

set_sys_fuzz(

  double  fuzz_val

  )

{

  sys_fuzz = fuzz_val;

  INSIST(sys_fuzz >= 0);

  INSIST(sys_fuzz <= 1.0);

  /* [Bug 3450] ensure nsec fuzz >= sys_fuzz to reduce chance of

   * short-falling fuzz advance

   */

  sys_fuzz_nsec = (long)ceil(sys_fuzz * 1e9);

}

void

init_systime(void)

{

  INIT_GET_SYSTIME_CRITSEC();

  INIT_WIN_PRECISE_TIME();

  DONE_SYSTIME_INIT();

}

#ifndef SIM /* ntpsim.c has get_systime() and friends for sim */

static inline void

get_ostime(

  struct timespec * tsp

  )

{

  int rc;

  long  ticks;

#if defined(HAVE_CLOCK_GETTIME)

  rc = clock_gettime(CLOCK_REALTIME, tsp);

#elif defined(HAVE_GETCLOCK)

  rc = getclock(TIMEOFDAY, tsp);

#else

  struct timeval    tv;

  rc = GETTIMEOFDAY(&tv, NULL);

  tsp->tv_sec = tv.tv_sec;

  tsp->tv_nsec = tv.tv_usec * 1000;

#endif

  if (rc < 0) {

    msyslog(LOG_ERR, "read system clock failed: %m (%d)",

      errno);

    exit(1);

  }

  if (trunc_os_clock) {

    ticks = (long)((tsp->tv_nsec * 1e-9) / sys_tick);

    tsp->tv_nsec = (long)(ticks * 1e9 * sys_tick);

  }

}

/*

 * get_systime - return system time in NTP timestamp format.

 */

void

get_systime(

  l_fp *now   /* system time */

  )

{

        static struct timespec  ts_last;        /* last sampled os time */

  static struct timespec  ts_prev;  /* prior os time */

  static l_fp   lfp_prev; /* prior result */

  struct timespec ts; /* seconds and nanoseconds */

  struct timespec ts_min; /* earliest permissible */

  struct timespec ts_lam; /* lamport fictional increment */

  double  dfuzz;

  l_fp  result;

  l_fp  lfpfuzz;

  l_fp  lfpdelta;

  get_ostime(&ts);

  DEBUG_REQUIRE(systime_init_done);

  ENTER_GET_SYSTIME_CRITSEC();

        /* First check if here was a Lamport violation, that is, two

         * successive calls to 'get_ostime()' resulted in negative

         * time difference. Use a few milliseconds of permissible

         * tolerance -- being too sharp can hurt here. (This is intented

         * for the Win32 target, where the HPC interpolation might

         * introduce small steps backward. It should not be an issue on

         * systems where get_ostime() results in a true syscall.)

         */

        if (cmp_tspec(add_tspec_ns(ts, 50000000), ts_last) < 0) {

                lamport_violated = 1;

                sys_lamport++;

  }

        ts_last = ts;

  /*

   * After default_get_precision() has set a nonzero sys_fuzz,

   * ensure every reading of the OS clock advances by at least

   * sys_fuzz over the prior reading, thereby assuring each

   * fuzzed result is strictly later than the prior.  Limit the

   * necessary fiction to 1 second.

   */

  if (!USING_SIGIO()) {

    ts_min = add_tspec_ns(ts_prev, sys_fuzz_nsec);

    if (cmp_tspec(ts, ts_min) < 0) {

      ts_lam = sub_tspec(ts_min, ts);

      if (ts_lam.tv_sec > 0 && !lamport_violated) {

        msyslog(LOG_ERR,

          "get_systime Lamport advance exceeds one second (%.9f)",

          ts_lam.tv_sec +

              1e-9 * ts_lam.tv_nsec);

        exit(1);

      }

      if (!lamport_violated)

        ts = ts_min;

    }

    ts_prev = ts;

  }

  /* convert from timespec to l_fp fixed-point */

  result = tspec_stamp_to_lfp(ts);

  /*

   * Add in the fuzz. 'ntp_random()' returns [0..2**31-1] so we

   * must scale up the result by 2.0 to cover the full fractional

   * range.

   */

  dfuzz = ntp_uurandom() * sys_fuzz;

  DTOLFP(dfuzz, &lfpfuzz);

  L_ADD(&result, &lfpfuzz);

  /*

   * Ensure result is strictly greater than prior result (ignoring

   * sys_residual's effect for now) once sys_fuzz has been

   * determined.

   *

   * [Bug 3450] Rounding errors and time slew can lead to a

   * violation of the expected postcondition. This is bound to

   * happen from time to time (depending on state of the random

   * generator, the current slew and the closeness of system time

   * stamps drawn) and does not warrant a syslog entry. Instead it

   * makes much more sense to ensure the postcondition and hop

   * along silently.

   */

  if (!USING_SIGIO()) {

    if (   !L_ISZERO(&lfp_prev)

        && !lamport_violated

        && (sys_fuzz > 0.0)

       ) {

      lfpdelta = result;

      L_SUB(&lfpdelta, &lfp_prev);

      L_SUBUF(&lfpdelta, 1);

      if (lfpdelta.l_i < 0)

      {

        L_NEG(&lfpdelta);

        DPRINTF(1, ("get_systime: postcond failed by %s secs, fixed\n",

              lfptoa(&lfpdelta, 9)));

        result = lfp_prev;

        L_ADDUF(&result, 1);

        sys_tsrounding++;

      }

    }

    lfp_prev = result;

    if (lamport_violated) 

      lamport_violated = FALSE;

  }

  LEAVE_GET_SYSTIME_CRITSEC();

  *now = result;

}

/*

 * adj_systime - adjust system time by the argument.

 */

#if !defined SYS_WINNT

int       /* 0 okay, 1 error */

adj_systime(

  double now    /* adjustment (s) */

  )

{

  struct timeval adjtv; /* new adjustment */

  struct timeval oadjtv;  /* residual adjustment */

  double  quant;    /* quantize to multiples of */

  double  dtemp;

  long  ticks;

  int isneg = 0;

  /*

   * The Windows port adj_systime() depends on being called each

   * second even when there's no additional correction, to allow

   * emulation of adjtime() behavior on top of an API that simply

   * sets the current rate.  This POSIX implementation needs to

   * ignore invocations with zero correction, otherwise ongoing

   * EVNT_NSET adjtime() can be aborted by a tiny adjtime()

   * triggered by sys_residual.

   */

  if (0. == now) {

    if (enable_panic_check && allow_panic) {

      msyslog(LOG_ERR, "adj_systime: allow_panic is TRUE!");

      INSIST(!allow_panic);

    }

    return TRUE;

  }

  /*

   * Most Unix adjtime() implementations adjust the system clock

   * in microsecond quanta, but some adjust in 10-ms quanta. We

   * carefully round the adjustment to the nearest quantum, then

   * adjust in quanta and keep the residue for later.

   */

  dtemp = now + sys_residual;

  if (dtemp < 0) {

    isneg = 1;

    dtemp = -dtemp;

  }

  adjtv.tv_sec = (long)dtemp;

  dtemp -= adjtv.tv_sec;

  if (sys_tick > sys_fuzz)

    quant = sys_tick;

  else

    quant = 1e-6;

  ticks = (long)(dtemp / quant + .5);

  adjtv.tv_usec = (long)(ticks * quant * 1.e6 + .5);

  /* The rounding in the conversions could us push over the

   * limits: make sure the result is properly normalised!

   * note: sign comes later, all numbers non-negative here.

   */

  if (adjtv.tv_usec >= 1000000) {

    adjtv.tv_sec  += 1;

    adjtv.tv_usec -= 1000000;

    dtemp         -= 1.;

  }

  /* set the new residual with leftover from correction */

  sys_residual = dtemp - adjtv.tv_usec * 1.e-6;

  /*

   * Convert to signed seconds and microseconds for the Unix

   * adjtime() system call. Note we purposely lose the adjtime()

   * leftover.

   */

  if (isneg) {

    adjtv.tv_sec = -adjtv.tv_sec;

    adjtv.tv_usec = -adjtv.tv_usec;

    sys_residual = -sys_residual;

  }

  if (adjtv.tv_sec != 0 || adjtv.tv_usec != 0) {

    if (adjtime(&adjtv, &oadjtv) < 0) {

      msyslog(LOG_ERR, "adj_systime: %m");

      if (enable_panic_check && allow_panic) {

        msyslog(LOG_ERR, "adj_systime: allow_panic is TRUE!");

      }

      return FALSE;

    }

  }

  if (enable_panic_check && allow_panic) {

    msyslog(LOG_ERR, "adj_systime: allow_panic is TRUE!");

  }

  return TRUE;

}

#endif

/*

 * helper to keep utmp/wtmp up to date

 */

static void

update_uwtmp(

  struct timeval timetv,

  struct timeval tvlast

  )

{

  struct timeval tvdiff;

  /*

   * FreeBSD, for example, has:

   * struct utmp {

   *     char    ut_line[UT_LINESIZE];

   *     char    ut_name[UT_NAMESIZE];

   *     char    ut_host[UT_HOSTSIZE];

   *     long    ut_time;

   * };

   * and appends line="|", name="date", host="", time for the OLD

   * and appends line="{", name="date", host="", time for the NEW // }

   * to _PATH_WTMP .

   *

   * Some OSes have utmp, some have utmpx.

   */

  /*

   * Write old and new time entries in utmp and wtmp if step

   * adjustment is greater than one second.

   *

   * This might become even Uglier...

   */

  tvdiff = abs_tval(sub_tval(timetv, tvlast));

  if (tvdiff.tv_sec > 0) {

#ifdef HAVE_UTMP_H

    struct utmp ut;

#endif

#ifdef HAVE_UTMPX_H

    struct utmpx utx;

#endif

#ifdef HAVE_UTMP_H

    ZERO(ut);

#endif

#ifdef HAVE_UTMPX_H

    ZERO(utx);

#endif

    /* UTMP */

#ifdef UPDATE_UTMP

# ifdef HAVE_PUTUTLINE

#  ifndef _PATH_UTMP

#   define _PATH_UTMP UTMP_FILE

#  endif

    utmpname(_PATH_UTMP);

    ut.ut_type = OLD_TIME;

    strlcpy(ut.ut_line, OTIME_MSG, sizeof(ut.ut_line));

    ut.ut_time = tvlast.tv_sec;

    setutent();

    pututline(&ut);

    ut.ut_type = NEW_TIME;

    strlcpy(ut.ut_line, NTIME_MSG, sizeof(ut.ut_line));

    ut.ut_time = timetv.tv_sec;

    setutent();

    pututline(&ut);

    endutent();

# else /* not HAVE_PUTUTLINE */

# endif /* not HAVE_PUTUTLINE */

#endif /* UPDATE_UTMP */

    /* UTMPX */

#ifdef UPDATE_UTMPX

# ifdef HAVE_PUTUTXLINE

    utx.ut_type = OLD_TIME;

    strlcpy(utx.ut_line, OTIME_MSG, sizeof(utx.ut_line));

    utx.ut_tv = tvlast;

    setutxent();

    pututxline(&utx);

    utx.ut_type = NEW_TIME;

    strlcpy(utx.ut_line, NTIME_MSG, sizeof(utx.ut_line));

    utx.ut_tv = timetv;

    setutxent();

    pututxline(&utx);

    endutxent();

# else /* not HAVE_PUTUTXLINE */

# endif /* not HAVE_PUTUTXLINE */

#endif /* UPDATE_UTMPX */

    /* WTMP */

#ifdef UPDATE_WTMP

# ifdef HAVE_PUTUTLINE

#  ifndef _PATH_WTMP

#   define _PATH_WTMP WTMP_FILE

#  endif

    utmpname(_PATH_WTMP);

    ut.ut_type = OLD_TIME;

    strlcpy(ut.ut_line, OTIME_MSG, sizeof(ut.ut_line));

    ut.ut_time = tvlast.tv_sec;

    setutent();

    pututline(&ut);

    ut.ut_type = NEW_TIME;

    strlcpy(ut.ut_line, NTIME_MSG, sizeof(ut.ut_line));

    ut.ut_time = timetv.tv_sec;

    setutent();

    pututline(&ut);

    endutent();

# else /* not HAVE_PUTUTLINE */

# endif /* not HAVE_PUTUTLINE */

#endif /* UPDATE_WTMP */

    /* WTMPX */

#ifdef UPDATE_WTMPX

# ifdef HAVE_PUTUTXLINE

    utx.ut_type = OLD_TIME;

    utx.ut_tv = tvlast;

    strlcpy(utx.ut_line, OTIME_MSG, sizeof(utx.ut_line));

#  ifdef HAVE_UPDWTMPX

    updwtmpx(WTMPX_FILE, &utx);

#  else /* not HAVE_UPDWTMPX */

#  endif /* not HAVE_UPDWTMPX */

# else /* not HAVE_PUTUTXLINE */

# endif /* not HAVE_PUTUTXLINE */

# ifdef HAVE_PUTUTXLINE

    utx.ut_type = NEW_TIME;

    utx.ut_tv = timetv;

    strlcpy(utx.ut_line, NTIME_MSG, sizeof(utx.ut_line));

#  ifdef HAVE_UPDWTMPX

    updwtmpx(WTMPX_FILE, &utx);

#  else /* not HAVE_UPDWTMPX */

#  endif /* not HAVE_UPDWTMPX */

# else /* not HAVE_PUTUTXLINE */

# endif /* not HAVE_PUTUTXLINE */

#endif /* UPDATE_WTMPX */

  }

}

/*

 * step_systime - step the system clock.

 */

int

step_systime(

  double step

  )

{

  time_t pivot; /* for ntp era unfolding */

  struct timeval timetv, tvlast;

  struct timespec timets;

  l_fp fp_ofs, fp_sys; /* offset and target system time in FP */

  /*

   * Get pivot time for NTP era unfolding. Since we don't step

   * very often, we can afford to do the whole calculation from

   * scratch. And we're not in the time-critical path yet.

   */

#if SIZEOF_TIME_T > 4

  pivot = basedate_get_eracenter();

#else

  /* This makes sure the resulting time stamp is on or after

   * 1969-12-31/23:59:59 UTC and gives us additional two years,

   * from the change of NTP era in 2036 to the UNIX rollover in

   * 2038. (Minus one second, but that won't hurt.) We *really*

   * need a longer 'time_t' after that!  Or a different baseline,

   * but that would cause other serious trouble, too.

   */

  pivot = 0x7FFFFFFF;

#endif

  /* get the complete jump distance as l_fp */

  DTOLFP(sys_residual, &fp_sys);

  DTOLFP(step,         &fp_ofs);

  L_ADD(&fp_ofs, &fp_sys);

  /* ---> time-critical path starts ---> */

  /* get the current time as l_fp (without fuzz) and as struct timeval */

  get_ostime(&timets);

  fp_sys = tspec_stamp_to_lfp(timets);

  tvlast.tv_sec = timets.tv_sec;

  tvlast.tv_usec = (timets.tv_nsec + 500) / 1000;

  /* get the target time as l_fp */

  L_ADD(&fp_sys, &fp_ofs);

  /* unfold the new system time */

  timetv = lfp_stamp_to_tval(fp_sys, &pivot);

  /* now set new system time */

  if (ntp_set_tod(&timetv, NULL) != 0) {

    msyslog(LOG_ERR, "step-systime: %m");

    if (enable_panic_check && allow_panic) {

      msyslog(LOG_ERR, "step_systime: allow_panic is TRUE!");

    }

    return FALSE;

  }

  /* <--- time-critical path ended with 'ntp_set_tod()' <--- */

  sys_residual = 0;

  lamport_violated = (step < 0);

  if (step_callback)

    (*step_callback)();

#ifdef NEED_HPUX_ADJTIME

  /*

   * CHECKME: is this correct when called by ntpdate?????

   */

  _clear_adjtime();

#endif

  update_uwtmp(timetv, tvlast);

  if (enable_panic_check && allow_panic) {

    msyslog(LOG_ERR, "step_systime: allow_panic is TRUE!");

    INSIST(!allow_panic);

  }

  return TRUE;

}

#if SIZEOF_TIME_T > 4

static const char *

tv_fmt_libbuf(

  const struct timeval * ptv

  )

{

  char *    retv;

  vint64    secs;

  ntpcal_split  dds;

  struct calendar jd;

  secs = time_to_vint64(&ptv->tv_sec);

  dds  = ntpcal_daysplit(&secs);

  ntpcal_daysplit_to_date(&jd, &dds, DAY_UNIX_STARTS);

  LIB_GETBUF(retv);

  snprintf(retv, LIB_BUFLENGTH,

     "%04hu-%02hu-%02hu/%02hu:%02hu:%02hu.%06u",

     jd.year, (u_short)jd.month, (u_short)jd.monthday,

     (u_short)jd.hour, (u_short)jd.minute, (u_short)jd.second,

     (u_int)ptv->tv_usec);

  return retv;

}

#endif  /* SIZEOF_TIME_T > 4 */

int /*BOOL*/

clamp_systime(void)

{

#if SIZEOF_TIME_T > 4

  struct timeval  tvbase, tvlast;

  struct timespec timets;

  tvbase.tv_sec  = basedate_get_erabase();

  tvbase.tv_usec = 0;

  /* ---> time-critical path starts ---> */

  /* get the current time as l_fp (without fuzz) and as struct timeval */

  get_ostime(&timets);

  tvlast.tv_sec = timets.tv_sec;

  tvlast.tv_usec = (timets.tv_nsec + 500) / 1000;

  if (tvlast.tv_usec >= 1000000) {

    tvlast.tv_usec -= 1000000;

    tvlast.tv_sec  += 1;

  }

  if (tvbase.tv_sec > tvlast.tv_sec) {

    /* now set new system time */

    if (ntp_set_tod(&tvbase, NULL) != 0) {

      msyslog(LOG_ERR, "clamp-systime: %m");

      return FALSE;

    }

  } else {

    msyslog(LOG_INFO,

      "clamp-systime: clock (%s) in allowed range",

      tv_fmt_libbuf(&tvlast));

    return FALSE;

  }

  /* <--- time-critical path ended with 'ntp_set_tod()' <--- */

  sys_residual = 0;

  lamport_violated = (tvbase.tv_sec < tvlast.tv_sec);

  if (step_callback)

    (*step_callback)();

#   ifdef NEED_HPUX_ADJTIME

  /*

   * CHECKME: is this correct when called by ntpdate?????

   */

  _clear_adjtime();

#   endif

  update_uwtmp(tvbase, tvlast);

  msyslog(LOG_WARNING,

    "clamp-systime: clock stepped from %s to %s!",

    tv_fmt_libbuf(&tvlast), tv_fmt_libbuf(&tvbase));

  return TRUE;

#else

  return FALSE;

#endif

}

#endif  /* !SIM */