/src/ntp-dev/ntpd/refclock_gpsdjson.c

Source
/*
 * refclock_gpsdjson.c - clock driver as GPSD JSON client
 *  Juergen Perlinger (perlinger@ntp.org)
 *  Feb 11, 2014 for the NTP project.
 *      The contents of 'html/copyright.html' apply.
 *
 *  Heavily inspired by refclock_nmea.c
 *
 * Special thanks to Gary Miller and Hal Murray for their comments and
 * ideas.
 *
 * Note: This will currently NOT work with Windows due to some
 * limitations:
 *
 *  - There is no GPSD for Windows. (There is an unofficial port to
 *    cygwin, but Windows is not officially supported.)
 *
 *  - To work properly, this driver needs PPS and TPV/TOFF sentences
 *    from GPSD. I don't see how the cygwin port should deal with the
 *    PPS signal.
 *
 *  - The device name matching must be done in a different way for
 *    Windows. (Can be done with COMxx matching, as done for NMEA.)
 *
 * Apart from those minor hickups, once GPSD has been fully ported to
 * Windows, there's no reason why this should not work there ;-) If this
 * is ever to happen at all is a different question.
 *
 * ---------------------------------------------------------------------
 *
 * This driver works slightly different from most others, as the PPS
 * information (if available) is also coming from GPSD via the data
 * connection. This makes using both the PPS data and the serial data
 * easier, but OTOH it's not possible to use the ATOM driver to feed a
 * raw PPS stream to the core of NTPD.
 *
 * To go around this, the driver can use a secondary clock unit
 * (units>=128) that operate in tandem with the primary clock unit
 * (unit%128). The primary clock unit does all the IO stuff and data
 * decoding; if a a secondary unit is attached to a primary unit, this
 * secondary unit is feed with the PPS samples only and can act as a PPS
 * source to the clock selection.
 *
 * The drawback is that the primary unit must be present for the
 * secondary unit to work.
 *
 * This design is a compromise to reduce the IO load for both NTPD and
 * GPSD; it also ensures that data is transmitted and evaluated only
 * once on the side of NTPD.
 *
 * ---------------------------------------------------------------------
 *
 * trouble shooting hints:
 *
 *   Enable and check the clock stats. Check if there are bad replies;
 *   there should be none. If there are actually bad replies, then the
 *   driver cannot parse all JSON records from GPSD, and some record
 *   types are vital for the operation of the driver. This indicates a
 *   problem on the protocol level.
 *
 *   When started on the command line with a debug level >= 2, the
 *   driver dumps the raw received data and the parser input to
 *   stdout. Since the debug level is global, NTPD starts to create a
 *   *lot* of output. It makes sense to pipe it through '(f)grep
 *   GPSD_JSON' before writing the result to disk.
 *
 *   A bit less intrusive is using netcat or telnet to connect to GPSD
 *   and snoop what NTPD would get. If you try this, you have to send a
 *   WATCH command to GPSD:
 *
 * ?WATCH={"device":"/dev/gps0","enable":true,"json":true,"pps":true};<CRLF>
 *
 *   should show you what GPSD has to say to NTPD. Replace "/dev/gps0"
 *   with the device link used by GPSD, if necessary.
 */


#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include "ntp_types.h"

#if defined(REFCLOCK) && defined(CLOCK_GPSDJSON) && !defined(SYS_WINNT)

/* =====================================================================
 * Get the little JSMN library directly into our guts. Use the 'parent
 * link' feature for maximum speed.
 */
#define JSMN_PARENT_LINKS
#include "../libjsmn/jsmn.c"

/* =====================================================================
 * JSON parsing stuff
 */

#define JSMN_MAXTOK 350
#define INVALID_TOKEN (-1)

typedef struct json_ctx {
  char        * buf;
  int           ntok;
  jsmntok_t     tok[JSMN_MAXTOK];
} json_ctx;

typedef int tok_ref;

/* Not all targets have 'long long', and not all of them have 'strtoll'.
 * Sigh. We roll our own integer number parser.
 */
#ifdef HAVE_LONG_LONG
typedef signed   long long int json_int;
typedef unsigned long long int json_uint;
#define JSON_INT_MAX LLONG_MAX
#define JSON_INT_MIN LLONG_MIN
#else
typedef signed   long int json_int;
typedef unsigned long int json_uint;
#define JSON_INT_MAX LONG_MAX
#define JSON_INT_MIN LONG_MIN
#endif

/* =====================================================================
 * header stuff we need
 */

#include <netdb.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <ctype.h>
#include <math.h>

#include <sys/types.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <netinet/tcp.h>

#if defined(HAVE_SYS_POLL_H)
# include <sys/poll.h>
#elif defined(HAVE_SYS_SELECT_H)
# include <sys/select.h>
#else
# error need poll() or select()
#endif

#include "ntpd.h"
#include "ntp_io.h"
#include "ntp_unixtime.h"
#include "ntp_refclock.h"
#include "ntp_stdlib.h"
#include "ntp_calendar.h"
#include "ntp_clockdev.h"
#include "timespecops.h"

/* get operation modes from mode word.

 * + SERIAL (default) evaluates only serial time information ('STI') as
 *   provided by TPV and TOFF records. TPV evaluation suffers from a
 *   bigger jitter than TOFF, sine it does not contain the receive time
 *   from GPSD and therefore the receive time of NTPD must be
 *   substituted for it. The network latency makes this a second rate
 *   guess.
 *
 *   If TOFF records are detected in the data stream, the timing
 *   information is gleaned from this record -- it contains the local
 *   receive time stamp from GPSD and therefore eliminates the
 *   transmission latency between GPSD and NTPD. The timing information
 *   from TPV is ignored once a TOFF is detected or expected.
 *
 *   TPV is still used to check the fix status, so the driver can stop
 *   feeding samples when GPSD says that the time information is
 *   effectively unreliable.
 *
 * + STRICT means only feed clock samples when a valid STI/PPS pair is
 *   available. Combines the reference time from STI with the pulse time
 *   from PPS. Masks the serial data jitter as long PPS is available,
 *   but can rapidly deteriorate once PPS drops out.
 *
 * + AUTO tries to use STI/PPS pairs if available for some time, and if
 *   this fails for too long switches back to STI only until the PPS
 *   signal becomes available again. See the HTML docs for this driver
 *   about the gotchas and why this is not the default.
 */
#define MODE_OP_MASK   0x03
#define MODE_OP_STI    0
#define MODE_OP_STRICT 1
#define MODE_OP_AUTO   2
#define MODE_OP_MAXVAL 2
#define MODE_OP_MODE(x)   ((x) & MODE_OP_MASK)

#define PRECISION (-9)  /* precision assumed (about 2 ms) */
#define PPS_PRECISION (-20)  /* precision assumed (about 1 us) */
#define REFID   "GPSD"  /* reference id */
#define DESCRIPTION "GPSD JSON client clock" /* who we are */

#define MAX_PDU_LEN 8192  /* multi-GNSS reports can be HUGE */
#define TICKOVER_LOW  10
#define TICKOVER_HIGH 120
#define LOGTHROTTLE 3600

/* Primary channel PPS avilability dance:
 * Every good PPS sample gets us a credit of PPS_INCCOUNT points, every
 * bad/missing PPS sample costs us a debit of PPS_DECCOUNT points. When
 * the account reaches the upper limit we change to a mode where only
 * PPS-augmented samples are fed to the core; when the account drops to
 * zero we switch to a mode where TPV-only timestamps are fed to the
 * core.
 * This reduces the chance of rapid alternation between raw and
 * PPS-augmented time stamps.
 */
#define PPS_MAXCOUNT  60  /* upper limit of account  */
#define PPS_INCCOUNT     3  /* credit for good samples */
#define PPS_DECCOUNT     1  /* debit for bad samples   */

/* The secondary (PPS) channel uses a different strategy to avoid old
 * PPS samples in the median filter.
 */
#define PPS2_MAXCOUNT 10

#ifndef BOOL
# define BOOL int
#endif
#ifndef TRUE
# define TRUE 1
#endif
#ifndef FALSE
# define FALSE 0
#endif

#define PROTO_VERSION(hi,lo) \
      ((((uint32_t)(hi) << 16) & 0xFFFF0000u) | \
       ((uint32_t)(lo) & 0x0FFFFu))

/* some local typedefs: The NTPD formatting style cries for short type
 * names, and we provide them locally. Note:the suffix '_t' is reserved
 * for the standard; I use a capital T instead.
 */
typedef struct peer         peerT;
typedef struct refclockproc clockprocT;
typedef struct addrinfo     addrinfoT;

/* =====================================================================
 * We use the same device name scheme as does the NMEA driver; since
 * GPSD supports the same links, we can select devices by a fixed name.
 */
static const char * s_dev_stem = "/dev/gps";

/* =====================================================================
 * forward declarations for transfer vector and the vector itself
 */

static  void  gpsd_init (void);
static  int gpsd_start  (int, peerT *);
static  void  gpsd_shutdown (int, peerT *);
static  void  gpsd_receive  (struct recvbuf *);
static  void  gpsd_poll (int, peerT *);
static  void  gpsd_control  (int, const struct refclockstat *,
         struct refclockstat *, peerT *);
static  void  gpsd_timer  (int, peerT *);

static  int     myasprintf(char**, char const*, ...) NTP_PRINTF(2, 3);

static void     enter_opmode(peerT *peer, int mode);
static void leave_opmode(peerT *peer, int mode);

struct refclock refclock_gpsdjson = {
  gpsd_start,   /* start up driver */
  gpsd_shutdown,    /* shut down driver */
  gpsd_poll,    /* transmit poll message */
  gpsd_control,   /* fudge control */
  gpsd_init,    /* initialize driver */
  noentry,    /* buginfo */
  gpsd_timer    /* called once per second */
};

/* =====================================================================
 * our local clock unit and data
 */
struct gpsd_unit;
typedef struct gpsd_unit gpsd_unitT;

struct gpsd_unit {
  /* links for sharing between master/slave units */
  gpsd_unitT *next_unit;
  size_t      refcount;

  /* data for the secondary PPS channel */
  peerT      *pps_peer;

  /* unit and operation modes */
  int      unit;
  int      mode;
  char    *logname; /* cached name for log/print */
  char    * device; /* device name of unit */

  /* current line protocol version */
  uint32_t proto_version;

  /* PPS time stamps primary + secondary channel */
  l_fp pps_local; /* when we received the PPS message */
  l_fp pps_stamp; /* related reference time */
  l_fp pps_recvt; /* when GPSD detected the pulse */
  l_fp pps_stamp2;/* related reference time (secondary) */
  l_fp pps_recvt2;/* when GPSD detected the pulse (secondary)*/
  int  ppscount;  /* PPS counter (primary unit) */
  int  ppscount2; /* PPS counter (secondary unit) */

  /* TPV or TOFF serial time information */
  l_fp sti_local; /* when we received the TPV/TOFF message */
  l_fp sti_stamp; /* effective GPS time stamp */
  l_fp sti_recvt; /* when GPSD got the fix */

  /* precision estimates */
  int16_t     sti_prec; /* serial precision based on EPT */
  int16_t     pps_prec; /* PPS precision from GPSD or above */

  /* fudge values for correction, mirrored as 'l_fp' */
  l_fp pps_fudge;   /* PPS fudge primary channel */
  l_fp pps_fudge2;  /* PPS fudge secondary channel */
  l_fp sti_fudge;   /* TPV/TOFF serial data fudge */

  /* Flags to indicate available data */
  int fl_nosync: 1; /* GPSD signals bad quality */
  int fl_sti   : 1; /* valid TPV/TOFF seen (have time) */
  int fl_pps   : 1; /* valid pulse seen */
  int fl_pps2  : 1; /* valid pulse seen for PPS channel */
  int fl_rawsti: 1; /* permit raw TPV/TOFF time stamps */
  int fl_vers  : 1; /* have protocol version */
  int fl_watch : 1; /* watch reply seen */
  /* protocol flags */
  int pf_nsec  : 1; /* have nanosec PPS info */
  int pf_toff  : 1; /* have TOFF record for timing */

  /* admin stuff for sockets and device selection */
  int         fdt;  /* current connecting socket */
  addrinfoT * addr; /* next address to try */
  u_int       tickover; /* timeout countdown */
  u_int       tickpres; /* timeout preset */

  /* tallies for the various events */
  u_int       tc_recv;  /* received known records */
  u_int       tc_breply;  /* bad replies / parsing errors */
  u_int       tc_nosync;  /* TPV / sample cycles w/o fix */
  u_int       tc_sti_recv;/* received serial time info records */
  u_int       tc_sti_used;/* used        --^-- */
  u_int       tc_pps_recv;/* received PPS timing info records */
  u_int       tc_pps_used;/* used        --^-- */

  /* log bloat throttle */
  u_int       logthrottle;/* seconds to next log slot */

  /* The parse context for the current record */
  json_ctx    json_parse;

  /* record assemby buffer and saved length */
  int  buflen;
  char buffer[MAX_PDU_LEN];
};

/* =====================================================================
 * static local helpers forward decls
 */
static void gpsd_init_socket(peerT * const peer);
static void gpsd_test_socket(peerT * const peer);
static void gpsd_stop_socket(peerT * const peer);

static void gpsd_parse(peerT * const peer,
           const l_fp  * const rtime);
static BOOL convert_ascii_time(l_fp * fp, const char * gps_time);
static void save_ltc(clockprocT * const pp, const char * const tc);
static int  syslogok(clockprocT * const pp, gpsd_unitT * const up);
static void log_data(peerT *peer, int level, const char *what,
         const char *buf, size_t len);
static int16_t clamped_precision(int rawprec);

/* =====================================================================
 * local / static stuff
 */

static const char * const s_req_version =
    "?VERSION;\r\n";

/* We keep a static list of network addresses for 'localhost:gpsd' or a
 * fallback alias of it, and we try to connect to them in round-robin
 * fashion. The service lookup is done during the driver init
 * function to minmise the impact of 'getaddrinfo()'.
 *
 * Alas, the init function is called even if there are no clocks
 * configured for this driver. So it makes sense to defer the logging of
 * any errors or other notifications until the first clock unit is
 * started -- otherwise there might be syslog entries from a driver that
 * is not used at all.
 */
static addrinfoT  *s_gpsd_addr;
static gpsd_unitT *s_clock_units;

/* list of service/socket names we want to resolve against */
static const char * const s_svctab[][2] = {
  { "localhost", "gpsd" },
  { "localhost", "2947" },
  { "127.0.0.1", "2947" },
  { NULL, NULL }
};

/* list of address resolution errors and index of service entry that
 * finally worked.
 */
static int s_svcerr[sizeof(s_svctab)/sizeof(s_svctab[0])];
static int s_svcidx;

/* =====================================================================
 * log throttling
 */
static int/*BOOL*/
syslogok(
  clockprocT * const pp,
  gpsd_unitT * const up)
{
  int res = (0 != (pp->sloppyclockflag & CLK_FLAG3))
         || (0           == up->logthrottle )
         || (LOGTHROTTLE == up->logthrottle );
  if (res)
    up->logthrottle = LOGTHROTTLE;
  return res;
}

/* =====================================================================
 * the clock functions
 */

/* ---------------------------------------------------------------------
 * Init: This currently just gets the socket address for the GPS daemon
 */
static void
gpsd_init(void)
{
  addrinfoT   hints;
  int         rc, idx;

  memset(s_svcerr, 0, sizeof(s_svcerr));
  memset(&hints, 0, sizeof(hints));
  hints.ai_family   = AF_UNSPEC;
  hints.ai_protocol = IPPROTO_TCP;
  hints.ai_socktype = SOCK_STREAM;

  for (idx = 0; s_svctab[idx][0] && !s_gpsd_addr; idx++) {
    rc = getaddrinfo(s_svctab[idx][0], s_svctab[idx][1],
         &hints, &s_gpsd_addr);
    s_svcerr[idx] = rc;
    if (0 == rc)
      break;
    s_gpsd_addr = NULL;
  }
  s_svcidx = idx;
}

/* ---------------------------------------------------------------------
 * Init Check: flush pending log messages and check if we can proceed
 */
static int/*BOOL*/
gpsd_init_check(void)
{
  int idx;

  /* Check if there is something to log */
  if (s_svcidx == 0)
    return (s_gpsd_addr != NULL);

  /* spool out the resolver errors */
  for (idx = 0; idx < s_svcidx; ++idx) {
    msyslog(LOG_WARNING,
      "GPSD_JSON: failed to resolve '%s:%s', rc=%d (%s)",
      s_svctab[idx][0], s_svctab[idx][1],
      s_svcerr[idx], gai_strerror(s_svcerr[idx]));
  }

  /* check if it was fatal, or if we can proceed */
  if (s_gpsd_addr == NULL)
    msyslog(LOG_ERR, "%s",
      "GPSD_JSON: failed to get socket address, giving up.");
  else if (idx != 0)
    msyslog(LOG_WARNING,
      "GPSD_JSON: using '%s:%s' instead of '%s:%s'",
      s_svctab[idx][0], s_svctab[idx][1],
      s_svctab[0][0], s_svctab[0][1]);

  /* make sure this gets logged only once and tell if we can
   * proceed or not
   */
  s_svcidx = 0;
  return (s_gpsd_addr != NULL);
}

/* ---------------------------------------------------------------------
 * Start: allocate a unit pointer and set up the runtime data
 */
static int
gpsd_start(
  int     unit,
  peerT * peer)
{
  clockprocT  * const pp = peer->procptr;
  gpsd_unitT  * up;
  gpsd_unitT ** uscan    = &s_clock_units;
  const char  *tmpName;

  struct stat sb;
  char *    devname = NULL;

  /* check if we can proceed at all or if init failed */
  if ( ! gpsd_init_check())
    return FALSE;

  /* search for matching unit */
  while ((up = *uscan) != NULL && up->unit != (unit & 0x7F))
    uscan = &up->next_unit;
  if (up == NULL) {
    /* alloc unit, add to list and increment use count ASAP. */
    up = emalloc_zero(sizeof(*up));
    *uscan = up;
    ++up->refcount;

    /* initialize the unit structure */
    up->logname  = estrdup(refnumtoa(&peer->srcadr));
    up->unit     = unit & 0x7F;
    up->fdt      = -1;
    up->addr     = s_gpsd_addr;
    up->tickpres = TICKOVER_LOW;

    /* Create the device name and check for a Character
     * Device. It's assumed that GPSD was started with the
     * same link, so the names match. (If this is not
     * practicable, we will have to read the symlink, if
     * any, so we can get the true device file.)
     */
    tmpName = clockdev_lookup(&peer->srcadr, 0);
    if (NULL != tmpName) {
      up->device = estrdup(tmpName);
    } else if (-1 == myasprintf(&up->device, "%s%u", s_dev_stem, up->unit)) {
      msyslog(LOG_ERR, "%s: clock device name too long",
        up->logname);
      goto dev_fail;
    }
    devname = up->device;
    up->device = ntp_realpath(devname);
    if (NULL == up->device) {
      msyslog(LOG_ERR, "%s: '%s' has no absolute path",
        up->logname, devname);
      goto dev_fail;
    }
    free(devname);
    devname = NULL;
    if (-1 == lstat(up->device, &sb)) {
      msyslog(LOG_ERR, "%s: '%s' not accessible",
        up->logname, up->device);
      goto dev_fail;
    }
    if (!S_ISCHR(sb.st_mode)) {
      msyslog(LOG_ERR, "%s: '%s' is not a character device",
        up->logname, up->device);
      goto dev_fail;
    }
  } else {
    /* All set up, just increment use count. */
    ++up->refcount;
  }
  
  /* setup refclock processing */
  pp->unitptr = (caddr_t)up;
  pp->io.fd         = -1;
  pp->io.clock_recv = gpsd_receive;
  pp->io.srcclock   = peer;
  pp->io.datalen    = 0;
  pp->a_lastcode[0] = '\0';
  pp->lencode       = 0;
  pp->clockdesc     = DESCRIPTION;
  memcpy(&pp->refid, REFID, 4);

  /* Initialize miscellaneous variables */
  if (unit >= 128)
    peer->precision = PPS_PRECISION;
  else
    peer->precision = PRECISION;

  /* If the daemon name lookup failed, just give up now. */
  if (NULL == up->addr) {
    msyslog(LOG_ERR, "%s: no GPSD socket address, giving up",
      up->logname);
    goto dev_fail;
  }

  LOGIF(CLOCKINFO,
        (LOG_NOTICE, "%s: startup, device is '%s'",
         refnumtoa(&peer->srcadr), up->device));
  up->mode = MODE_OP_MODE(peer->ttl);
  if (up->mode > MODE_OP_MAXVAL)
    up->mode = 0;
  if (unit >= 128)
    up->pps_peer = peer;
  else
    enter_opmode(peer, up->mode);
  return TRUE;

dev_fail:
  /* On failure, remove all UNIT ressources and declare defeat. */
  free(devname);
  INSIST (up);
  if (!--up->refcount) {
    *uscan = up->next_unit;
    free(up->device);
    free(up);
  }

  pp->unitptr = (caddr_t)NULL;
  return FALSE;
}

/* ------------------------------------------------------------------ */

static void
gpsd_shutdown(
  int     unit,
  peerT * peer)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;
  gpsd_unitT ** uscan   = &s_clock_units;

  UNUSED_ARG(unit);

  /* The unit pointer might have been removed already. */
  if (up == NULL)
    return;

  /* now check if we must close IO resources */
  if (peer != up->pps_peer) {
    if (-1 != pp->io.fd) {
      DPRINTF(1, ("%s: closing clock, fd=%d\n",
            up->logname, pp->io.fd));
      io_closeclock(&pp->io);
      pp->io.fd = -1;
    }
    if (up->fdt != -1)
      close(up->fdt);
  }
  /* decrement use count and eventually remove this unit. */
  if (!--up->refcount) {
    /* unlink this unit */
    while (*uscan != NULL)
      if (*uscan == up)
        *uscan = up->next_unit;
      else
        uscan = &(*uscan)->next_unit;
    free(up->logname);
    free(up->device);
    free(up);
  }
  pp->unitptr = (caddr_t)NULL;
  LOGIF(CLOCKINFO,
        (LOG_NOTICE, "%s: shutdown", refnumtoa(&peer->srcadr)));
}

/* ------------------------------------------------------------------ */

static void
gpsd_receive(
  struct recvbuf * rbufp)
{
  /* declare & init control structure ptrs */
  peerT    * const peer = rbufp->recv_peer;
  clockprocT * const pp   = peer->procptr;
  gpsd_unitT * const up   = (gpsd_unitT *)pp->unitptr;

  const char *psrc, *esrc;
  char       *pdst, *edst, ch;

  /* log the data stream, if this is enabled */
  log_data(peer, 3, "recv", (const char*)rbufp->recv_buffer,
     (size_t)rbufp->recv_length);


  /* Since we're getting a raw stream data, we must assemble lines
   * in our receive buffer. We can't use neither 'refclock_gtraw'
   * not 'refclock_gtlin' here...  We process chars until we reach
   * an EoL (that is, line feed) but we truncate the message if it
   * does not fit the buffer.  GPSD might truncate messages, too,
   * so dealing with truncated buffers is necessary anyway.
   */
  psrc = (const char*)rbufp->recv_buffer;
  esrc = psrc + rbufp->recv_length;

  pdst = up->buffer + up->buflen;
  edst = up->buffer + sizeof(up->buffer) - 1; /* for trailing NUL */

  while (psrc != esrc) {
    ch = *psrc++;
    if (ch == '\n') {
      /* trim trailing whitespace & terminate buffer */
      while (pdst != up->buffer && pdst[-1] <= ' ')
        --pdst;
      *pdst = '\0';
      /* process data and reset buffer */
      up->buflen = pdst - up->buffer;
      gpsd_parse(peer, &rbufp->recv_time);
      pdst = up->buffer;
    } else if (pdst != edst) {
      /* add next char, ignoring leading whitespace */
      if (ch > ' ' || pdst != up->buffer)
        *pdst++ = ch;
    }
  }
  up->buflen   = pdst - up->buffer;
  up->tickover = TICKOVER_LOW;
}

/* ------------------------------------------------------------------ */

static void
poll_primary(
  peerT      * const peer ,
  clockprocT * const pp   ,
  gpsd_unitT * const up   )
{
  if (pp->coderecv != pp->codeproc) {
    /* all is well */
    pp->lastref = pp->lastrec;
    refclock_report(peer, CEVNT_NOMINAL);
    refclock_receive(peer);
  } else {
    /* Not working properly, admit to it. If we have no
     * connection to GPSD, declare the clock as faulty. If
     * there were bad replies, this is handled as the major
     * cause, and everything else is just a timeout.
     */
    peer->precision = PRECISION;
    if (-1 == pp->io.fd)
      refclock_report(peer, CEVNT_FAULT);
    else if (0 != up->tc_breply)
      refclock_report(peer, CEVNT_BADREPLY);
    else
      refclock_report(peer, CEVNT_TIMEOUT);
  }

  if (pp->sloppyclockflag & CLK_FLAG4)
    mprintf_clock_stats(
      &peer->srcadr,"%u %u %u %u %u %u %u",
      up->tc_recv,
      up->tc_breply, up->tc_nosync,
      up->tc_sti_recv, up->tc_sti_used,
      up->tc_pps_recv, up->tc_pps_used);

  /* clear tallies for next round */
  up->tc_breply   = 0;
  up->tc_recv     = 0;
  up->tc_nosync   = 0;
  up->tc_sti_recv = 0;
  up->tc_sti_used = 0;
  up->tc_pps_recv = 0;
  up->tc_pps_used = 0;
}

static void
poll_secondary(
  peerT      * const peer ,
  clockprocT * const pp   ,
  gpsd_unitT * const up   )
{
  if (pp->coderecv != pp->codeproc) {
    /* all is well */
    pp->lastref = pp->lastrec;
    refclock_report(peer, CEVNT_NOMINAL);
    refclock_receive(peer);
  } else {
    peer->precision = PPS_PRECISION;
    peer->flags &= ~FLAG_PPS;
    refclock_report(peer, CEVNT_TIMEOUT);
  }
}

static void
gpsd_poll(
  int     unit,
  peerT * peer)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  ++pp->polls;
  if (peer == up->pps_peer)
    poll_secondary(peer, pp, up);
  else
    poll_primary(peer, pp, up);
}

/* ------------------------------------------------------------------ */

static void
gpsd_control(
  int                         unit,
  const struct refclockstat * in_st,
  struct refclockstat       * out_st,
  peerT                     * peer  )
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  if (peer == up->pps_peer) {
    DTOLFP(pp->fudgetime1, &up->pps_fudge2);
    if ( ! (pp->sloppyclockflag & CLK_FLAG1))
      peer->flags &= ~FLAG_PPS;
  } else {
    /* save preprocessed fudge times */
    DTOLFP(pp->fudgetime1, &up->pps_fudge);
    DTOLFP(pp->fudgetime2, &up->sti_fudge);

    if (MODE_OP_MODE(up->mode ^ peer->ttl)) {
      leave_opmode(peer, up->mode);
      up->mode = MODE_OP_MODE(peer->ttl);
      enter_opmode(peer, up->mode);
    }
  }
 }

/* ------------------------------------------------------------------ */

static void
timer_primary(
  peerT      * const peer ,
  clockprocT * const pp   ,
  gpsd_unitT * const up   )
{
  int rc;

  /* This is used for timeout handling. Nothing that needs
   * sub-second precison happens here, so receive/connect/retry
   * timeouts are simply handled by a count down, and then we
   * decide what to do by the socket values.
   *
   * Note that the timer stays at zero here, unless some of the
   * functions set it to another value.
   */
  if (up->logthrottle)
    --up->logthrottle;
  if (up->tickover)
    --up->tickover;
  switch (up->tickover) {
  case 4:
    /* If we are connected to GPSD, try to get a live signal
     * by querying the version. Otherwise just check the
     * socket to become ready.
     */
    if (-1 != pp->io.fd) {
      size_t rlen = strlen(s_req_version);
      DPRINTF(2, ("%s: timer livecheck: '%s'\n",
            up->logname, s_req_version));
      log_data(peer, 2, "send", s_req_version, rlen);
      rc = write(pp->io.fd, s_req_version, rlen);
      (void)rc;
    } else if (-1 != up->fdt) {
      gpsd_test_socket(peer);
    }
    break;

  case 0:
    if (-1 != pp->io.fd)
      gpsd_stop_socket(peer);
    else if (-1 != up->fdt)
      gpsd_test_socket(peer);
    else if (NULL != s_gpsd_addr)
      gpsd_init_socket(peer);
    break;

  default:
    if (-1 == pp->io.fd && -1 != up->fdt)
      gpsd_test_socket(peer);
  }
}

static void
timer_secondary(
  peerT      * const peer ,
  clockprocT * const pp   ,
  gpsd_unitT * const up   )
{
  /* Reduce the count by one. Flush sample buffer and clear PPS
   * flag when this happens.
   */
  up->ppscount2 = max(0, (up->ppscount2 - 1));
  if (0 == up->ppscount2) {
    if (pp->coderecv != pp->codeproc) {
      refclock_report(peer, CEVNT_TIMEOUT);
      pp->coderecv = pp->codeproc;
    }
    peer->flags &= ~FLAG_PPS;
  }
}

static void
gpsd_timer(
  int     unit,
  peerT * peer)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  if (peer == up->pps_peer)
    timer_secondary(peer, pp, up);
  else
    timer_primary(peer, pp, up);
}

/* =====================================================================
 * handle opmode switches
 */

static void
enter_opmode(
  peerT *peer,
  int    mode)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  DPRINTF(1, ("%s: enter operation mode %d\n",
        up->logname, MODE_OP_MODE(mode)));

  if (MODE_OP_MODE(mode) == MODE_OP_AUTO) {
    up->fl_rawsti = 0;
    up->ppscount  = PPS_MAXCOUNT / 2;
  }
  up->fl_pps = 0;
  up->fl_sti = 0;
}

/* ------------------------------------------------------------------ */

static void
leave_opmode(
  peerT *peer,
  int    mode)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  DPRINTF(1, ("%s: leaving operation mode %d\n",
        up->logname, MODE_OP_MODE(mode)));

  if (MODE_OP_MODE(mode) == MODE_OP_AUTO) {
    up->fl_rawsti = 0;
    up->ppscount  = 0;
  }
  up->fl_pps = 0;
  up->fl_sti = 0;
}

/* =====================================================================
 * operation mode specific evaluation
 */

static void
add_clock_sample(
  peerT      * const peer ,
  clockprocT * const pp   ,
  l_fp               stamp,
  l_fp               recvt)
{
  pp->lastref = stamp;
  if (pp->coderecv == pp->codeproc)
    refclock_report(peer, CEVNT_NOMINAL);
  refclock_process_offset(pp, stamp, recvt, 0.0);
}

/* ------------------------------------------------------------------ */

static void
eval_strict(
  peerT      * const peer ,
  clockprocT * const pp   ,
  gpsd_unitT * const up   )
{
  if (up->fl_sti && up->fl_pps) {
    /* use TPV reference time + PPS receive time */
    add_clock_sample(peer, pp, up->sti_stamp, up->pps_recvt);
    peer->precision = up->pps_prec;
    /* both packets consumed now... */
    up->fl_pps = 0;
    up->fl_sti = 0;
    ++up->tc_sti_used;
  }
}

/* ------------------------------------------------------------------ */
/* PPS processing for the secondary channel. GPSD provides us with full
 * timing information, so there's no danger of PLL-locking to the wrong
 * second. The belts and suspenders needed for the raw ATOM clock are
 * unnecessary here.
 */
static void
eval_pps_secondary(
  peerT      * const peer ,
  clockprocT * const pp   ,
  gpsd_unitT * const up   )
{
  if (up->fl_pps2) {
    /* feed data */
    add_clock_sample(peer, pp, up->pps_stamp2, up->pps_recvt2);
    peer->precision = up->pps_prec;
    /* PPS peer flag logic */
    up->ppscount2 = min(PPS2_MAXCOUNT, (up->ppscount2 + 2));
    if ((PPS2_MAXCOUNT == up->ppscount2) &&
        (pp->sloppyclockflag & CLK_FLAG1) )
      peer->flags |= FLAG_PPS;
    /* mark time stamp as burned... */
    up->fl_pps2 = 0;
    ++up->tc_pps_used;
  }
}

/* ------------------------------------------------------------------ */

static void
eval_serial(
  peerT      * const peer ,
  clockprocT * const pp   ,
  gpsd_unitT * const up   )
{
  if (up->fl_sti) {
    add_clock_sample(peer, pp, up->sti_stamp, up->sti_recvt);
    peer->precision = up->sti_prec;
    /* mark time stamp as burned... */
    up->fl_sti = 0;
    ++up->tc_sti_used;
  }
}

/* ------------------------------------------------------------------ */
static void
eval_auto(
  peerT      * const peer ,
  clockprocT * const pp   ,
  gpsd_unitT * const up   )
{
  /* If there's no TPV available, stop working here... */
  if (!up->fl_sti)
    return;

  /* check how to handle STI+PPS: Can PPS be used to augment STI
   * (or vice versae), do we drop the sample because there is a
   * temporary missing PPS signal, or do we feed on STI time
   * stamps alone?
   *
   * Do a counter/threshold dance to decide how to proceed.
   */
  if (up->fl_pps) {
    up->ppscount = min(PPS_MAXCOUNT,
           (up->ppscount + PPS_INCCOUNT));
    if ((PPS_MAXCOUNT == up->ppscount) && up->fl_rawsti) {
      up->fl_rawsti = 0;
      msyslog(LOG_INFO,
        "%s: expect valid PPS from now",
        up->logname);
    }
  } else {
    up->ppscount = max(0, (up->ppscount - PPS_DECCOUNT));
    if ((0 == up->ppscount) && !up->fl_rawsti) {
      up->fl_rawsti = -1;
      msyslog(LOG_WARNING,
        "%s: use TPV alone from now",
        up->logname);
    }
  }

  /* now eventually feed the sample */
  if (up->fl_rawsti)
    eval_serial(peer, pp, up);
  else
    eval_strict(peer, pp, up);
}

/* =====================================================================
 * JSON parsing stuff
 */

/* ------------------------------------------------------------------ */
/* Parse a decimal integer with a possible sign. Works like 'strtoll()'
 * or 'strtol()', but with a fixed base of 10 and without eating away
 * leading whitespace. For the error codes, the handling of the end
 * pointer and the return values see 'strtol()'.
 */
static json_int
strtojint(
  const char *cp, char **ep)
{
  json_uint     accu, limit_lo, limit_hi;
  int           flags; /* bit 0: overflow; bit 1: sign */
  const char  * hold;

  /* pointer union to circumvent a tricky/sticky const issue */
  union { const char * c; char * v; } vep;

  /* store initial value of 'cp' -- see 'strtol()' */
  vep.c = cp;

  /* Eat away an optional sign and set the limits accordingly: The
   * high limit is the maximum absolute value that can be returned,
   * and the low limit is the biggest value that does not cause an
   * overflow when multiplied with 10. Avoid negation overflows.
   */
  if (*cp == '-') {
    cp += 1;
    flags    = 2;
    limit_hi = (json_uint)-(JSON_INT_MIN + 1) + 1;
  } else {
    cp += (*cp == '+');
    flags    = 0;
    limit_hi = (json_uint)JSON_INT_MAX;
  }
  limit_lo = limit_hi / 10;

  /* Now try to convert a sequence of digits. */
  hold = cp;
  accu = 0;
  while (isdigit(*(const u_char*)cp)) {
    flags |= (accu > limit_lo);
    accu = accu * 10 + (*(const u_char*)cp++ - '0');
    flags |= (accu > limit_hi);
  }
  /* Check for empty conversion (no digits seen). */
  if (hold != cp)
    vep.c = cp;
  else
    errno = EINVAL; /* accu is still zero */
  /* Check for range overflow */
  if (flags & 1) {
    errno = ERANGE;
    accu  = limit_hi;
  }
  /* If possible, store back the end-of-conversion pointer */
  if (ep)
    *ep = vep.v;
  /* If negative, return the negated result if the accu is not
   * zero. Avoid negation overflows.
   */
  if ((flags & 2) && accu)
    return -(json_int)(accu - 1) - 1;
  else
    return (json_int)accu;
}

/* ------------------------------------------------------------------ */

static tok_ref
json_token_skip(
  const json_ctx * ctx,
  tok_ref          tid)
{
  if (tid >= 0 && tid < ctx->ntok) {
    int len = ctx->tok[tid].size;
    /* For arrays and objects, the size is the number of
     * ITEMS in the compound. Thats the number of objects in
     * the array, and the number of key/value pairs for
     * objects. In theory, the key must be a string, and we
     * could simply skip one token before skipping the
     * value, which can be anything. We're a bit paranoid
     * and lazy at the same time: We simply double the
     * number of tokens to skip and fall through into the
     * array processing when encountering an object.
     */
    switch (ctx->tok[tid].type) {
    case JSMN_OBJECT:
      len *= 2;
      /* FALLTHROUGH */
    case JSMN_ARRAY:
      for (++tid; len; --len)
        tid = json_token_skip(ctx, tid);
      break;
      
    default:
      ++tid;
      break;
    }
    /* The next condition should never be true, but paranoia
     * prevails...
     */
    if (tid < 0 || tid > ctx->ntok)
      tid = ctx->ntok;
  }
  return tid;
}

/* ------------------------------------------------------------------ */

static int
json_object_lookup(
  const json_ctx * ctx ,
  tok_ref          tid ,
  const char     * key ,
  int              what)
{
  int len;

  if (tid < 0 || tid >= ctx->ntok ||
      ctx->tok[tid].type != JSMN_OBJECT)
    return INVALID_TOKEN;
  
  len = ctx->tok[tid].size;
  for (++tid; len && tid+1 < ctx->ntok; --len) {
    if (ctx->tok[tid].type != JSMN_STRING) { /* Blooper! */
      tid = json_token_skip(ctx, tid); /* skip key */
      tid = json_token_skip(ctx, tid); /* skip val */
    } else if (strcmp(key, ctx->buf + ctx->tok[tid].start)) {
      tid = json_token_skip(ctx, tid+1); /* skip key+val */
    } else if (what < 0 || (u_int)what == ctx->tok[tid+1].type) {
      return tid + 1;
    } else {
      break;
    }
    /* if skipping ahead returned an error, bail out here. */
    if (tid < 0)
      break;
  }
  return INVALID_TOKEN;
}

/* ------------------------------------------------------------------ */

static const char*
json_object_lookup_primitive(
  const json_ctx * ctx,
  tok_ref          tid,
  const char     * key)
{
  tid = json_object_lookup(ctx, tid, key, JSMN_PRIMITIVE);
  if (INVALID_TOKEN  != tid)
    return ctx->buf + ctx->tok[tid].start;
  else
    return NULL;
}
/* ------------------------------------------------------------------ */
/* look up a boolean value. This essentially returns a tribool:
 * 0->false, 1->true, (-1)->error/undefined
 */
static int
json_object_lookup_bool(
  const json_ctx * ctx,
  tok_ref          tid,
  const char     * key)
{
  const char *cp;
  cp  = json_object_lookup_primitive(ctx, tid, key);
  switch ( cp ? *cp : '\0') {
  case 't': return  1;
  case 'f': return  0;
  default : return -1;
  }
}

/* ------------------------------------------------------------------ */

static const char*
json_object_lookup_string(
  const json_ctx * ctx,
  tok_ref          tid,
  const char     * key)
{
  tid = json_object_lookup(ctx, tid, key, JSMN_STRING);
  if (INVALID_TOKEN != tid)
    return ctx->buf + ctx->tok[tid].start;
  return NULL;
}

static const char*
json_object_lookup_string_default(
  const json_ctx * ctx,
  tok_ref          tid,
  const char     * key,
  const char     * def)
{
  tid = json_object_lookup(ctx, tid, key, JSMN_STRING);
  if (INVALID_TOKEN != tid)
    return ctx->buf + ctx->tok[tid].start;
  return def;
}

/* ------------------------------------------------------------------ */

static json_int
json_object_lookup_int(
  const json_ctx * ctx,
  tok_ref          tid,
  const char     * key)
{
  json_int     ret;
  const char * cp;
  char       * ep;

  cp = json_object_lookup_primitive(ctx, tid, key);
  if (NULL != cp) {
    ret = strtojint(cp, &ep);
    if (cp != ep && '\0' == *ep)
      return ret;
  } else {
    errno = EINVAL;
  }
  return 0;
}

static json_int
json_object_lookup_int_default(
  const json_ctx * ctx,
  tok_ref          tid,
  const char     * key,
  json_int         def)
{
  json_int     ret;
  const char * cp;
  char       * ep;

  cp = json_object_lookup_primitive(ctx, tid, key);
  if (NULL != cp) {
    ret = strtojint(cp, &ep);
    if (cp != ep && '\0' == *ep)
      return ret;
  }
  return def;
}

/* ------------------------------------------------------------------ */
#if 0 /* currently unused */
static double
json_object_lookup_float(
  const json_ctx * ctx,
  tok_ref          tid,
  const char     * key)
{
  double       ret;
  const char * cp;
  char       * ep;

  cp = json_object_lookup_primitive(ctx, tid, key);
  if (NULL != cp) {
    ret = strtod(cp, &ep);
    if (cp != ep && '\0' == *ep)
      return ret;
  } else {
    errno = EINVAL;
  }
  return 0.0;
}
#endif

static double
json_object_lookup_float_default(
  const json_ctx * ctx,
  tok_ref          tid,
  const char     * key,
  double           def)
{
  double       ret;
  const char * cp;
  char       * ep;

  cp = json_object_lookup_primitive(ctx, tid, key);
  if (NULL != cp) {
    ret = strtod(cp, &ep);
    if (cp != ep && '\0' == *ep)
      return ret;
  }
  return def;
}

/* ------------------------------------------------------------------ */

static BOOL
json_parse_record(
  json_ctx * ctx,
  char     * buf,
  size_t     len)
{
  jsmn_parser jsm;
  int         idx, rc;

  jsmn_init(&jsm);
  rc = jsmn_parse(&jsm, buf, len, ctx->tok, JSMN_MAXTOK);
  if (rc <= 0)
    return FALSE;
  ctx->buf  = buf;
  ctx->ntok = rc;

  if (JSMN_OBJECT != ctx->tok[0].type)
    return FALSE; /* not object!?! */

  /* Make all tokens NUL terminated by overwriting the
   * terminator symbol. Makes string compares and number parsing a
   * lot easier!
   */
  for (idx = 0; idx < ctx->ntok; ++idx)
    if (ctx->tok[idx].end > ctx->tok[idx].start)
      ctx->buf[ctx->tok[idx].end] = '\0';
  return TRUE;
}


/* =====================================================================
 * static local helpers
 */
static BOOL
get_binary_time(
  l_fp       * const dest     ,
  json_ctx   * const jctx     ,
  const char * const time_name,
  const char * const frac_name,
  long               fscale   )
{
  BOOL            retv = FALSE;
  struct timespec ts;

  errno = 0;
  ts.tv_sec  = (time_t)json_object_lookup_int(jctx, 0, time_name);
  ts.tv_nsec = (long  )json_object_lookup_int(jctx, 0, frac_name);
  if (0 == errno) {
    ts.tv_nsec *= fscale;
    *dest = tspec_stamp_to_lfp(ts);
    retv  = TRUE;
  }
  return retv;
}

/* ------------------------------------------------------------------ */
/* Process a WATCH record
 *
 * Currently this is only used to recognise that the device is present
 * and that we're listed subscribers.
 */
static void
process_watch(
  peerT      * const peer ,
  json_ctx   * const jctx ,
  const l_fp * const rtime)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  const char * path;

  path = json_object_lookup_string(jctx, 0, "device");
  if (NULL == path || strcmp(path, up->device))
    return;

  if (json_object_lookup_bool(jctx, 0, "enable") > 0 &&
      json_object_lookup_bool(jctx, 0, "json"  ) > 0  )
    up->fl_watch = -1;
  else
    up->fl_watch = 0;
  DPRINTF(2, ("%s: process_watch, enabled=%d\n",
        up->logname, (up->fl_watch & 1)));
}

/* ------------------------------------------------------------------ */

static void
process_version(
  peerT      * const peer ,
  json_ctx   * const jctx ,
  const l_fp * const rtime)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  int    len;
  char * buf;
  const char *revision;
  const char *release;
  uint16_t    pvhi, pvlo;

  /* get protocol version number */
  revision = json_object_lookup_string_default(
    jctx, 0, "rev", "(unknown)");
  release  = json_object_lookup_string_default(
    jctx, 0, "release", "(unknown)");
  errno = 0;
  pvhi = (uint16_t)json_object_lookup_int(jctx, 0, "proto_major");
  pvlo = (uint16_t)json_object_lookup_int(jctx, 0, "proto_minor");

  if (0 == errno) {
    if ( ! up->fl_vers)
      msyslog(LOG_INFO,
        "%s: GPSD revision=%s release=%s protocol=%u.%u",
        up->logname, revision, release,
        pvhi, pvlo);
    up->proto_version = PROTO_VERSION(pvhi, pvlo);
    up->fl_vers = -1;
  } else {
    if (syslogok(pp, up))
      msyslog(LOG_INFO,
        "%s: could not evaluate version data",
        up->logname);
    return;
  }
  /* With the 3.9 GPSD protocol, '*_musec' vanished from the PPS
   * record and was replace by '*_nsec'.
   */
  up->pf_nsec = -(up->proto_version >= PROTO_VERSION(3,9));

  /* With the 3.10 protocol we can get TOFF records for better
   * timing information.
   */
  up->pf_toff = -(up->proto_version >= PROTO_VERSION(3,10));

  /* request watch for our GPS device if not yet watched.
   *
   * The version string is also sent as a life signal, if we have
   * seen useable data. So if we're already watching the device,
   * skip the request.
   *
   * Reuse the input buffer, which is no longer needed in the
   * current cycle. Also assume that we can write the watch
   * request in one sweep into the socket; since we do not do
   * output otherwise, this should always work.  (Unless the
   * TCP/IP window size gets lower than the length of the
   * request. We handle that when it happens.)
   */
  if (up->fl_watch)
    return;

  /* The logon string is actually the ?WATCH command of GPSD,
   * using JSON data and selecting the GPS device name we created
   * from our unit number. We have an old and a newer version that
   * request PPS (and TOFF) transmission.
   */
  snprintf(up->buffer, sizeof(up->buffer),
     "?WATCH={\"device\":\"%s\",\"enable\":true,\"json\":true%s};\r\n",
     up->device, (up->pf_toff ? ",\"pps\":true" : ""));
  buf = up->buffer;
  len = strlen(buf);
  log_data(peer, 2, "send", buf, len);
  if (len != write(pp->io.fd, buf, len) && (syslogok(pp, up))) {
    /* Note: if the server fails to read our request, the
     * resulting data timeout will take care of the
     * connection!
     */
    msyslog(LOG_ERR, "%s: failed to write watch request (%m)",
      up->logname);
  }
}

/* ------------------------------------------------------------------ */

static void
process_tpv(
  peerT      * const peer ,
  json_ctx   * const jctx ,
  const l_fp * const rtime)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  const char * gps_time;
  int          gps_mode;
  double       ept;
  int          xlog2;

  gps_mode = (int)json_object_lookup_int_default(
    jctx, 0, "mode", 0);

  gps_time = json_object_lookup_string(
    jctx, 0, "time");

  /* accept time stamps only in 2d or 3d fix */
  if (gps_mode < 2 || NULL == gps_time) {
    /* receiver has no fix; tell about and avoid stale data */
    if ( ! up->pf_toff)
      ++up->tc_sti_recv;
    ++up->tc_nosync;
    up->fl_sti    = 0;
    up->fl_pps    = 0;
    up->fl_nosync = -1;
    return;
  }
  up->fl_nosync = 0;

  /* convert clock and set resulting ref time, but only if the
   * TOFF sentence is *not* available
   */
  if ( ! up->pf_toff) {
    ++up->tc_sti_recv;
    /* save last time code to clock data */
    save_ltc(pp, gps_time);
    /* now parse the time string */
    if (convert_ascii_time(&up->sti_stamp, gps_time)) {
      DPRINTF(2, ("%s: process_tpv, stamp='%s',"
            " recvt='%s' mode=%u\n",
            up->logname,
            gmprettydate(&up->sti_stamp),
            gmprettydate(&up->sti_recvt),
            gps_mode));

      /* have to use local receive time as substitute
       * for the real receive time: TPV does not tell
       * us.
       */
      up->sti_local = *rtime;
      up->sti_recvt = *rtime;
      L_SUB(&up->sti_recvt, &up->sti_fudge);
      up->fl_sti = -1;
    } else {
      ++up->tc_breply;
      up->fl_sti = 0;
    }
  }

  /* Set the precision from the GPSD data
   * Use the ETP field for an estimation of the precision of the
   * serial data. If ETP is not available, use the default serial
   * data presion instead. (Note: The PPS branch has a different
   * precision estimation, since it gets the proper value directly
   * from GPSD!)
   */
  ept = json_object_lookup_float_default(jctx, 0, "ept", 2.0e-3);
  ept = frexp(fabs(ept)*0.70710678, &xlog2); /* ~ sqrt(0.5) */
  if (ept < 0.25)
    xlog2 = INT_MIN;
  if (ept > 2.0)
    xlog2 = INT_MAX;
  up->sti_prec = clamped_precision(xlog2);
}

/* ------------------------------------------------------------------ */

static void
process_pps(
  peerT      * const peer ,
  json_ctx   * const jctx ,
  const l_fp * const rtime)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  int xlog2;

  ++up->tc_pps_recv;

  /* Bail out if there's indication that time sync is bad or
   * if we're explicitely requested to ignore PPS data.
   */
  if (up->fl_nosync)
    return;

  up->pps_local = *rtime;
  /* Now grab the time values. 'clock_*' is the event time of the
   * pulse measured on the local system clock; 'real_*' is the GPS
   * reference time GPSD associated with the pulse.
   */
  if (up->pf_nsec) {
    if ( ! get_binary_time(&up->pps_recvt2, jctx,
               "clock_sec", "clock_nsec", 1))
      goto fail;
    if ( ! get_binary_time(&up->pps_stamp2, jctx,
               "real_sec", "real_nsec", 1))
      goto fail;
  } else {
    if ( ! get_binary_time(&up->pps_recvt2, jctx,
               "clock_sec", "clock_musec", 1000))
      goto fail;
    if ( ! get_binary_time(&up->pps_stamp2, jctx,
               "real_sec", "real_musec", 1000))
      goto fail;
  }

  /* Try to read the precision field from the PPS record. If it's
   * not there, take the precision from the serial data.
   */
  xlog2 = json_object_lookup_int_default(
      jctx, 0, "precision", up->sti_prec);
  up->pps_prec = clamped_precision(xlog2);
  
  /* Get fudged receive times for primary & secondary unit */
  up->pps_recvt = up->pps_recvt2;
  L_SUB(&up->pps_recvt , &up->pps_fudge );
  L_SUB(&up->pps_recvt2, &up->pps_fudge2);
  pp->lastrec = up->pps_recvt;

  /* Map to nearest full second as reference time stamp for the
   * primary channel. Sanity checks are done in evaluation step.
   */
  up->pps_stamp = up->pps_recvt;
  L_ADDUF(&up->pps_stamp, 0x80000000u);
  up->pps_stamp.l_uf = 0;

  if (NULL != up->pps_peer)
    save_ltc(up->pps_peer->procptr,
       gmprettydate(&up->pps_stamp2));
  DPRINTF(2, ("%s: PPS record processed,"
        " stamp='%s', recvt='%s'\n",
        up->logname,
        gmprettydate(&up->pps_stamp2),
        gmprettydate(&up->pps_recvt2)));
  
  up->fl_pps  = (0 != (pp->sloppyclockflag & CLK_FLAG2)) - 1;
  up->fl_pps2 = -1;
  return;

  fail:
  DPRINTF(1, ("%s: PPS record processing FAILED\n",
        up->logname));
  ++up->tc_breply;
}

/* ------------------------------------------------------------------ */

static void
process_toff(
  peerT      * const peer ,
  json_ctx   * const jctx ,
  const l_fp * const rtime)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  ++up->tc_sti_recv;

  /* remember this! */
  up->pf_toff = -1;

  /* bail out if there's indication that time sync is bad */
  if (up->fl_nosync)
    return;

  if ( ! get_binary_time(&up->sti_recvt, jctx,
             "clock_sec", "clock_nsec", 1))
      goto fail;
  if ( ! get_binary_time(&up->sti_stamp, jctx,
             "real_sec", "real_nsec", 1))
      goto fail;
  L_SUB(&up->sti_recvt, &up->sti_fudge);
  up->sti_local = *rtime;
  up->fl_sti    = -1;

  save_ltc(pp, gmprettydate(&up->sti_stamp));
  DPRINTF(2, ("%s: TOFF record processed,"
        " stamp='%s', recvt='%s'\n",
        up->logname,
        gmprettydate(&up->sti_stamp),
        gmprettydate(&up->sti_recvt)));
  return;

  fail:
  DPRINTF(1, ("%s: TOFF record processing FAILED\n",
        up->logname));
  ++up->tc_breply;
}

/* ------------------------------------------------------------------ */

static void
gpsd_parse(
  peerT      * const peer ,
  const l_fp * const rtime)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  const char * clsid;

        DPRINTF(2, ("%s: gpsd_parse: time %s '%.*s'\n",
                    up->logname, ulfptoa(rtime, 6),
        up->buflen, up->buffer));

  /* See if we can grab anything potentially useful. JSMN does not
   * need a trailing NUL, but it needs the number of bytes to
   * process. */
  if (!json_parse_record(&up->json_parse, up->buffer, up->buflen)) {
    ++up->tc_breply;
    return;
  }
  
  /* Now dispatch over the objects we know */
  clsid = json_object_lookup_string(&up->json_parse, 0, "class");
  if (NULL == clsid) {
    ++up->tc_breply;
    return;
  }

  if      (!strcmp("TPV", clsid))
    process_tpv(peer, &up->json_parse, rtime);
  else if (!strcmp("PPS", clsid))
    process_pps(peer, &up->json_parse, rtime);
  else if (!strcmp("TOFF", clsid))
    process_toff(peer, &up->json_parse, rtime);
  else if (!strcmp("VERSION", clsid))
    process_version(peer, &up->json_parse, rtime);
  else if (!strcmp("WATCH", clsid))
    process_watch(peer, &up->json_parse, rtime);
  else
    return; /* nothing we know about... */
  ++up->tc_recv;

  /* if possible, feed the PPS side channel */
  if (up->pps_peer)
    eval_pps_secondary(
      up->pps_peer, up->pps_peer->procptr, up);

  /* check PPS vs. STI receive times:
   * If STI is before PPS, then clearly the STI is too old. If PPS
   * is before STI by more than one second, then PPS is too old.
   * Weed out stale time stamps & flags.
   */
  if (up->fl_pps && up->fl_sti) {
    l_fp diff;
    diff = up->sti_local;
    L_SUB(&diff, &up->pps_local);
    if (diff.l_i > 0)
      up->fl_pps = 0; /* pps too old */
    else if (diff.l_i < 0)
      up->fl_sti = 0; /* serial data too old */
  }

  /* dispatch to the mode-dependent processing functions */
  switch (up->mode) {
  default:
  case MODE_OP_STI:
    eval_serial(peer, pp, up);
    break;

  case MODE_OP_STRICT:
    eval_strict(peer, pp, up);
    break;

  case MODE_OP_AUTO:
    eval_auto(peer, pp, up);
    break;
  }
}

/* ------------------------------------------------------------------ */

static void
gpsd_stop_socket(
  peerT * const peer)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  if (-1 != pp->io.fd) {
    if (syslogok(pp, up))
      msyslog(LOG_INFO,
        "%s: closing socket to GPSD, fd=%d",
        up->logname, pp->io.fd);
    else
      DPRINTF(1, ("%s: closing socket to GPSD, fd=%d\n",
            up->logname, pp->io.fd));
    io_closeclock(&pp->io);
    pp->io.fd = -1;
  }
  up->tickover = up->tickpres;
  up->tickpres = min(up->tickpres + 5, TICKOVER_HIGH);
  up->fl_vers  = 0;
  up->fl_sti   = 0;
  up->fl_pps   = 0;
  up->fl_watch = 0;
}

/* ------------------------------------------------------------------ */

static void
gpsd_init_socket(
  peerT * const peer)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;
  addrinfoT  * ai;
  int          rc;
  int          ov;

  /* draw next address to try */
  if (NULL == up->addr)
    up->addr = s_gpsd_addr;
  ai = up->addr;
  up->addr = ai->ai_next;

  /* try to create a matching socket */
  up->fdt = socket(
    ai->ai_family, ai->ai_socktype, ai->ai_protocol);
  if (-1 == up->fdt) {
    if (syslogok(pp, up))
      msyslog(LOG_ERR,
        "%s: cannot create GPSD socket: %m",
        up->logname);
    goto no_socket;
  }

  /* Make sure the socket is non-blocking. Connect/reconnect and
   * IO happen in an event-driven environment, and synchronous
   * operations wreak havoc on that.
   */
  rc = fcntl(up->fdt, F_SETFL, O_NONBLOCK, 1);
  if (-1 == rc) {
    if (syslogok(pp, up))
      msyslog(LOG_ERR,
        "%s: cannot set GPSD socket to non-blocking: %m",
        up->logname);
    goto no_socket;
  }
  /* Disable nagling. The way both GPSD and NTPD handle the
   * protocol makes it record-oriented, and in most cases
   * complete records (JSON serialised objects) will be sent in
   * one sweep. Nagling gives not much advantage but adds another
   * delay, which can worsen the situation for some packets.
   */
  ov = 1;
  rc = setsockopt(up->fdt, IPPROTO_TCP, TCP_NODELAY,
      (void *)&ov, sizeof(ov));
  if (-1 == rc) {
    if (syslogok(pp, up))
      msyslog(LOG_INFO,
        "%s: cannot disable TCP nagle: %m",
        up->logname);
  }

  /* Start a non-blocking connect. There might be a synchronous
   * connection result we have to handle.
   */
  rc = connect(up->fdt, ai->ai_addr, ai->ai_addrlen);
  if (-1 == rc) {
    if (errno == EINPROGRESS) {
      DPRINTF(1, ("%s: async connect pending, fd=%d\n",
            up->logname, up->fdt));
      return;
    }

    if (syslogok(pp, up))
      msyslog(LOG_ERR,
        "%s: cannot connect GPSD socket: %m",
        up->logname);
    goto no_socket;
  }

  /* We had a successful synchronous connect, so we add the
   * refclock processing ASAP. We still have to wait for the
   * version string and apply the watch command later on, but we
   * might as well get the show on the road now.
   */
  DPRINTF(1, ("%s: new socket connection, fd=%d\n",
        up->logname, up->fdt));

  pp->io.fd = up->fdt;
  up->fdt   = -1;
  if (0 == io_addclock(&pp->io)) {
    if (syslogok(pp, up))
      msyslog(LOG_ERR,
        "%s: failed to register with I/O engine",
        up->logname);
    goto no_socket;
  }

  return;

  no_socket:
  if (-1 != pp->io.fd)
    close(pp->io.fd);
  if (-1 != up->fdt)
    close(up->fdt);
  pp->io.fd    = -1;
  up->fdt      = -1;
  up->tickover = up->tickpres;
  up->tickpres = min(up->tickpres + 5, TICKOVER_HIGH);
}

/* ------------------------------------------------------------------ */

static void
gpsd_test_socket(
  peerT * const peer)
{
  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  int       ec, rc;
  socklen_t lc;

  /* Check if the non-blocking connect was finished by testing the
   * socket for writeability. Use the 'poll()' API if available
   * and 'select()' otherwise.
   */
  DPRINTF(2, ("%s: check connect, fd=%d\n",
        up->logname, up->fdt));

#if defined(HAVE_SYS_POLL_H)
  {
    struct pollfd pfd;

    pfd.events = POLLOUT;
    pfd.fd     = up->fdt;
    rc = poll(&pfd, 1, 0);
    if (1 != rc || !(pfd.revents & POLLOUT))
      return;
  }
#elif defined(HAVE_SYS_SELECT_H)
  {
    struct timeval tout;
    fd_set         wset;

    memset(&tout, 0, sizeof(tout));
    FD_ZERO(&wset);
    FD_SET(up->fdt, &wset);
    rc = select(up->fdt+1, NULL, &wset, NULL, &tout);
    if (0 == rc || !(FD_ISSET(up->fdt, &wset)))
      return;
  }
#else
# error Blooper! That should have been found earlier!
#endif

  /* next timeout is a full one... */
  up->tickover = TICKOVER_LOW;

  /* check for socket error */
  ec = 0;
  lc = sizeof(ec);
  rc = getsockopt(up->fdt, SOL_SOCKET, SO_ERROR, (void *)&ec, &lc);
  if (-1 == rc || 0 != ec) {
    const char *errtxt;
    if (0 == ec)
      ec = errno;
    errtxt = strerror(ec);
    if (syslogok(pp, up))
      msyslog(LOG_ERR,
        "%s: async connect to GPSD failed,"
        " fd=%d, ec=%d(%s)",
        up->logname, up->fdt, ec, errtxt);
    else
      DPRINTF(1, ("%s: async connect to GPSD failed,"
        " fd=%d, ec=%d(%s)\n",
            up->logname, up->fdt, ec, errtxt));
    goto no_socket;
  } else {
    DPRINTF(1, ("%s: async connect to GPSD succeeded, fd=%d\n",
          up->logname, up->fdt));
  }

  /* swap socket FDs, and make sure the clock was added */
  pp->io.fd = up->fdt;
  up->fdt   = -1;
  if (0 == io_addclock(&pp->io)) {
    if (syslogok(pp, up))
      msyslog(LOG_ERR,
        "%s: failed to register with I/O engine",
        up->logname);
    goto no_socket;
  }
  return;

  no_socket:
  if (-1 != up->fdt) {
    DPRINTF(1, ("%s: closing socket, fd=%d\n",
          up->logname, up->fdt));
    close(up->fdt);
  }
  up->fdt      = -1;
  up->tickover = up->tickpres;
  up->tickpres = min(up->tickpres + 5, TICKOVER_HIGH);
}

/* =====================================================================
 * helper stuff
 */

/* -------------------------------------------------------------------
 * store a properly clamped precision value
 */
static int16_t
clamped_precision(
  int rawprec)
{
  if (rawprec > 0)
    rawprec = 0;
  if (rawprec < -32)
    rawprec = -32;
  return (int16_t)rawprec;
}

/* -------------------------------------------------------------------
 * Convert a GPSD timestamp (ISO8601 Format) to an l_fp
 */
static BOOL
convert_ascii_time(
  l_fp       * fp      ,
  const char * gps_time)
{
  char           *ep;
  struct tm       gd;
  struct timespec ts;
  uint32_t        dw;

  /* Use 'strptime' to take the brunt of the work, then parse
   * the fractional part manually, starting with a digit weight of
   * 10^8 nanoseconds.
   */
  ts.tv_nsec = 0;
  ep = strptime(gps_time, "%Y-%m-%dT%H:%M:%S", &gd);
  if (NULL == ep)
    return FALSE; /* could not parse the mandatory stuff! */
  if (*ep == '.') {
    dw = 100000000u;
    while (isdigit(*(u_char*)++ep)) {
      ts.tv_nsec += (*(u_char*)ep - '0') * dw;
      dw /= 10u;
    }
  }
  if (ep[0] != 'Z' || ep[1] != '\0')
    return FALSE; /* trailing garbage */

  /* Now convert the whole thing into a 'l_fp'. We do not use
   * 'mkgmtime()' since its not standard and going through the
   * calendar routines is not much effort, either.
   */
  ts.tv_sec = (ntpcal_tm_to_rd(&gd) - DAY_NTP_STARTS) * SECSPERDAY
            + ntpcal_tm_to_daysec(&gd);
  *fp = tspec_intv_to_lfp(ts);

  return TRUE;
}

/* -------------------------------------------------------------------
 * Save the last timecode string, making sure it's properly truncated
 * if necessary and NUL terminated in any case.
 */
static void
save_ltc(
  clockprocT * const pp,
  const char * const tc)
{
  size_t len = 0;
  
  if (tc) {
    len = strlen(tc);
    if (len >= sizeof(pp->a_lastcode))
      len = sizeof(pp->a_lastcode) - 1;
    memcpy(pp->a_lastcode, tc, len);
  }
  pp->lencode = (u_short)len;
  pp->a_lastcode[len] = '\0';
}

/* -------------------------------------------------------------------
 * asprintf replacement... it's not available everywhere...
 */
static int
myasprintf(
  char      ** spp,
  char const * fmt,
  ...             )
{
  size_t alen, plen;

  alen = 32;
  *spp = NULL;
  do {
    va_list va;

    alen += alen;
    free(*spp);
    *spp = (char*)malloc(alen);
    if (NULL == *spp)
      return -1;

    va_start(va, fmt);
    plen = (size_t)vsnprintf(*spp, alen, fmt, va);
    va_end(va);
  } while (plen >= alen);

  return (int)plen;
}

/* -------------------------------------------------------------------
 * dump a raw data buffer
 */

static char *
add_string(
  char *dp,
  char *ep,
  const char *sp)
{
  while (dp != ep && *sp)
    *dp++ = *sp++;
  return dp;
}

static void
log_data(
  peerT      *peer,
  int         level,
  const char *what,
  const char *buf ,
  size_t      len )
{
  /* we're running single threaded with regards to the clocks. */
  static char s_lbuf[2048];

  clockprocT * const pp = peer->procptr;
  gpsd_unitT * const up = (gpsd_unitT *)pp->unitptr;

  if (debug >= level) {
    const char *sptr = buf;
    const char *stop = buf + len;
    char       *dptr = s_lbuf;
    char       *dtop = s_lbuf + sizeof(s_lbuf) - 1; /* for NUL */

    while (sptr != stop && dptr != dtop) {
      u_char uch = (u_char)*sptr++;
      if (uch == '\\') {
        dptr = add_string(dptr, dtop, "\\\\");
      } else if (isprint(uch)) {
        *dptr++ = (char)uch;
      } else {
        char fbuf[6];
        snprintf(fbuf, sizeof(fbuf), "\\%03o", uch);
        dptr = add_string(dptr, dtop, fbuf);
      }
    }
    *dptr = '\0';
    mprintf("%s[%s]: '%s'\n", up->logname, what, s_lbuf);
  }
}


#else
NONEMPTY_TRANSLATION_UNIT
#endif /* REFCLOCK && CLOCK_GPSDJSON */

Coverage Report

Created: 2026-02-26 06:20