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freebsd-dev/ntpd/refclock_nmea.c
Cy Schubert b5e14a1344 Vendor import ntp 4.2.8. 
Reviewed by:	roberto
Security:	VUXML: 4033d826-87dd-11e4-9079-3c970e169bc2
Security:	http://www.kb.cert.org/vuls/id/852879
Security:	CVE-2014-9293
Security	CVE-2014-9294
Security	CVE-2014-9295
Security	CVE-2014-9296
2014-12-20 22:52:39 +00:00

1957 lines
57 KiB
C
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/*
* refclock_nmea.c - clock driver for an NMEA GPS CLOCK
* Michael Petry Jun 20, 1994
* based on refclock_heathn.c
*
* Updated to add support for Accord GPS Clock
* Venu Gopal Dec 05, 2007
* neo.venu@gmail.com, venugopal_d@pgad.gov.in
*
* Updated to process 'time1' fudge factor
* Venu Gopal May 05, 2008
*
* Converted to common PPSAPI code, separate PPS fudge time1
* from serial timecode fudge time2.
* Dave Hart July 1, 2009
* hart@ntp.org, davehart@davehart.com
*/
#ifdef HAVE_CONFIG_H
#include <config.h>
#endif
#include "ntp_types.h"
#if defined(REFCLOCK) && defined(CLOCK_NMEA)
#define NMEA_WRITE_SUPPORT 0 /* no write support at the moment */
#include <sys/stat.h>
#include <stdio.h>
#include <ctype.h>
#include "ntpd.h"
#include "ntp_io.h"
#include "ntp_unixtime.h"
#include "ntp_refclock.h"
#include "ntp_stdlib.h"
#include "ntp_calendar.h"
#include "timespecops.h"
#ifdef HAVE_PPSAPI
# include "ppsapi_timepps.h"
# include "refclock_atom.h"
#endif /* HAVE_PPSAPI */
/*
* This driver supports NMEA-compatible GPS receivers
*
* Prototype was refclock_trak.c, Thanks a lot.
*
* The receiver used spits out the NMEA sentences for boat navigation.
* And you thought it was an information superhighway. Try a raging river
* filled with rapids and whirlpools that rip away your data and warp time.
*
* If HAVE_PPSAPI is defined code to use the PPSAPI will be compiled in.
* On startup if initialization of the PPSAPI fails, it will fall back
* to the "normal" timestamps.
*
* The PPSAPI part of the driver understands fudge flag2 and flag3. If
* flag2 is set, it will use the clear edge of the pulse. If flag3 is
* set, kernel hardpps is enabled.
*
* GPS sentences other than RMC (the default) may be enabled by setting
* the relevent bits of 'mode' in the server configuration line
* server 127.127.20.x mode X
*
* bit 0 - enables RMC (1)
* bit 1 - enables GGA (2)
* bit 2 - enables GLL (4)
* bit 3 - enables ZDA (8) - Standard Time & Date
* bit 3 - enables ZDG (8) - Accord GPS Clock's custom sentence with GPS time
* very close to standard ZDA
*
* Multiple sentences may be selected except when ZDG/ZDA is selected.
*
* bit 4/5/6 - selects the baudrate for serial port :
* 0 for 4800 (default)
* 1 for 9600
* 2 for 19200
* 3 for 38400
* 4 for 57600
* 5 for 115200
*/
#define NMEA_MESSAGE_MASK 0x0000FF0FU
#define NMEA_BAUDRATE_MASK 0x00000070U
#define NMEA_BAUDRATE_SHIFT 4
#define NMEA_DELAYMEAS_MASK 0x80
#define NMEA_EXTLOG_MASK 0x00010000U
#define NMEA_DATETRUST_MASK 0x02000000U
#define NMEA_PROTO_IDLEN 5 /* tag name must be at least 5 chars */
#define NMEA_PROTO_MINLEN 6 /* min chars in sentence, excluding CS */
#define NMEA_PROTO_MAXLEN 80 /* max chars in sentence, excluding CS */
#define NMEA_PROTO_FIELDS 32 /* not official; limit on fields per record */
/*
* We check the timecode format and decode its contents. We only care
* about a few of them, the most important being the $GPRMC format:
*
* $GPRMC,hhmmss,a,fddmm.xx,n,dddmmm.xx,w,zz.z,yyy.,ddmmyy,dd,v*CC
*
* mode (0,1,2,3) selects sentence ANY/ALL, RMC, GGA, GLL, ZDA
* $GPGLL,3513.8385,S,14900.7851,E,232420.594,A*21
* $GPGGA,232420.59,3513.8385,S,14900.7851,E,1,05,3.4,00519,M,,,,*3F
* $GPRMC,232418.19,A,3513.8386,S,14900.7853,E,00.0,000.0,121199,12.,E*77
*
* Defining GPZDA to support Standard Time & Date
* sentence. The sentence has the following format
*
* $--ZDA,HHMMSS.SS,DD,MM,YYYY,TH,TM,*CS<CR><LF>
*
* Apart from the familiar fields,
* 'TH' Time zone Hours
* 'TM' Time zone Minutes
*
* Defining GPZDG to support Accord GPS Clock's custom NMEA
* sentence. The sentence has the following format
*
* $GPZDG,HHMMSS.S,DD,MM,YYYY,AA.BB,V*CS<CR><LF>
*
* It contains the GPS timestamp valid for next PPS pulse.
* Apart from the familiar fields,
* 'AA.BB' denotes the signal strength( should be < 05.00 )
* 'V' denotes the GPS sync status :
* '0' indicates INVALID time,
* '1' indicates accuracy of +/-20 ms
* '2' indicates accuracy of +/-100 ns
*
* Defining PGRMF for Garmin GPS Fix Data
* $PGRMF,WN,WS,DATE,TIME,LS,LAT,LAT_DIR,LON,LON_DIR,MODE,FIX,SPD,DIR,PDOP,TDOP
* WN -- GPS week number (weeks since 1980-01-06, mod 1024)
* WS -- GPS seconds in week
* LS -- GPS leap seconds, accumulated ( UTC + LS == GPS )
* FIX -- Fix type: 0=nofix, 1=2D, 2=3D
* DATE/TIME are standard date/time strings in UTC time scale
*
* The GPS time can be used to get the full century for the truncated
* date spec.
*/
/*
* Definitions
*/
#define DEVICE "/dev/gps%d" /* GPS serial device */
#define PPSDEV "/dev/gpspps%d" /* PPSAPI device override */
#define SPEED232 B4800 /* uart speed (4800 bps) */
#define PRECISION (-9) /* precision assumed (about 2 ms) */
#define PPS_PRECISION (-20) /* precision assumed (about 1 us) */
#define REFID "GPS\0" /* reference id */
#define DESCRIPTION "NMEA GPS Clock" /* who we are */
#ifndef O_NOCTTY
#define M_NOCTTY 0
#else
#define M_NOCTTY O_NOCTTY
#endif
#ifndef O_NONBLOCK
#define M_NONBLOCK 0
#else
#define M_NONBLOCK O_NONBLOCK
#endif
#define PPSOPENMODE (O_RDWR | M_NOCTTY | M_NONBLOCK)
/* NMEA sentence array indexes for those we use */
#define NMEA_GPRMC 0 /* recommended min. nav. */
#define NMEA_GPGGA 1 /* fix and quality */
#define NMEA_GPGLL 2 /* geo. lat/long */
#define NMEA_GPZDA 3 /* date/time */
/*
* $GPZDG is a proprietary sentence that violates the spec, by not
* using $P and an assigned company identifier to prefix the sentence
* identifier. When used with this driver, the system needs to be
* isolated from other NTP networks, as it operates in GPS time, not
* UTC as is much more common. GPS time is >15 seconds different from
* UTC due to not respecting leap seconds since 1970 or so. Other
* than the different timebase, $GPZDG is similar to $GPZDA.
*/
#define NMEA_GPZDG 4
#define NMEA_PGRMF 5
#define NMEA_ARRAY_SIZE (NMEA_PGRMF + 1)
/*
* Sentence selection mode bits
*/
#define USE_GPRMC 0x00000001u
#define USE_GPGGA 0x00000002u
#define USE_GPGLL 0x00000004u
#define USE_GPZDA 0x00000008u
#define USE_PGRMF 0x00000100u
/* mapping from sentence index to controlling mode bit */
static const u_int32 sentence_mode[NMEA_ARRAY_SIZE] =
{
USE_GPRMC,
USE_GPGGA,
USE_GPGLL,
USE_GPZDA,
USE_GPZDA,
USE_PGRMF
};
/* date formats we support */
enum date_fmt {
DATE_1_DDMMYY, /* use 1 field with 2-digit year */
DATE_3_DDMMYYYY /* use 3 fields with 4-digit year */
};
/* results for 'field_init()'
*
* Note: If a checksum is present, the checksum test must pass OK or the
* sentence is tagged invalid.
*/
#define CHECK_EMPTY -1 /* no data */
#define CHECK_INVALID 0 /* not a valid NMEA sentence */
#define CHECK_VALID 1 /* valid but without checksum */
#define CHECK_CSVALID 2 /* valid with checksum OK */
/*
* Unit control structure
*/
typedef struct {
#ifdef HAVE_PPSAPI
struct refclock_atom atom; /* PPSAPI structure */
int ppsapi_fd; /* fd used with PPSAPI */
u_char ppsapi_tried; /* attempt PPSAPI once */
u_char ppsapi_lit; /* time_pps_create() worked */
u_char ppsapi_gate; /* system is on PPS */
#endif /* HAVE_PPSAPI */
u_char gps_time; /* use GPS time, not UTC */
u_short century_cache; /* cached current century */
l_fp last_reftime; /* last processed reference stamp */
short epoch_warp; /* last epoch warp, for logging */
/* tally stats, reset each poll cycle */
struct
{
u_int total;
u_int accepted;
u_int rejected; /* GPS said not enough signal */
u_int malformed; /* Bad checksum, invalid date or time */
u_int filtered; /* mode bits, not GPZDG, same second */
u_int pps_used;
}
tally;
/* per sentence checksum seen flag */
u_char cksum_type[NMEA_ARRAY_SIZE];
} nmea_unit;
/*
* helper for faster field access
*/
typedef struct {
char *base; /* buffer base */
char *cptr; /* current field ptr */
int blen; /* buffer length */
int cidx; /* current field index */
} nmea_data;
/*
* NMEA gps week/time information
* This record contains the number of weeks since 1980-01-06 modulo
* 1024, the seconds elapsed since start of the week, and the number of
* leap seconds that are the difference between GPS and UTC time scale.
*/
typedef struct {
u_int32 wt_time; /* seconds since weekstart */
u_short wt_week; /* week number */
short wt_leap; /* leap seconds */
} gps_weektm;
/*
* The GPS week time scale starts on Sunday, 1980-01-06. We need the
* rata die number of this day.
*/
#ifndef DAY_GPS_STARTS
#define DAY_GPS_STARTS 722820
#endif
/*
* Function prototypes
*/
static void nmea_init (void);
static int nmea_start (int, struct peer *);
static void nmea_shutdown (int, struct peer *);
static void nmea_receive (struct recvbuf *);
static void nmea_poll (int, struct peer *);
#ifdef HAVE_PPSAPI
static void nmea_control (int, const struct refclockstat *,
struct refclockstat *, struct peer *);
#define NMEA_CONTROL nmea_control
#else
#define NMEA_CONTROL noentry
#endif /* HAVE_PPSAPI */
static void nmea_timer (int, struct peer *);
/* parsing helpers */
static int field_init (nmea_data * data, char * cp, int len);
static char * field_parse (nmea_data * data, int fn);
static void field_wipe (nmea_data * data, ...);
static u_char parse_qual (nmea_data * data, int idx,
char tag, int inv);
static int parse_time (struct calendar * jd, long * nsec,
nmea_data *, int idx);
static int parse_date (struct calendar *jd, nmea_data*,
int idx, enum date_fmt fmt);
static int parse_weekdata (gps_weektm *, nmea_data *,
int weekidx, int timeidx, int leapidx);
/* calendar / date helpers */
static int unfold_day (struct calendar * jd, u_int32 rec_ui);
static int unfold_century (struct calendar * jd, u_int32 rec_ui);
static int gpsfix_century (struct calendar * jd, const gps_weektm * wd,
u_short * ccentury);
static l_fp eval_gps_time (struct peer * peer, const struct calendar * gpst,
const struct timespec * gpso, const l_fp * recv);
static int nmead_open (const char * device);
static void save_ltc (struct refclockproc * const, const char * const,
size_t);
/*
* If we want the driver to ouput sentences, too: re-enable the send
* support functions by defining NMEA_WRITE_SUPPORT to non-zero...
*/
#if NMEA_WRITE_SUPPORT
static void gps_send(int, const char *, struct peer *);
# ifdef SYS_WINNT
# undef write /* ports/winnt/include/config.h: #define write _write */
extern int async_write(int, const void *, unsigned int);
# define write(fd, data, octets) async_write(fd, data, octets)
# endif /* SYS_WINNT */
#endif /* NMEA_WRITE_SUPPORT */
static int32_t g_gpsMinBase;
static int32_t g_gpsMinYear;
/*
* -------------------------------------------------------------------
* Transfer vector
* -------------------------------------------------------------------
*/
struct refclock refclock_nmea = {
nmea_start, /* start up driver */
nmea_shutdown, /* shut down driver */
nmea_poll, /* transmit poll message */
NMEA_CONTROL, /* fudge control */
nmea_init, /* initialize driver */
noentry, /* buginfo */
nmea_timer /* called once per second */
};
/*
* -------------------------------------------------------------------
* nmea_init - initialise data
*
* calculates a few runtime constants that cannot be made compile time
* constants.
* -------------------------------------------------------------------
*/
static void
nmea_init(void)
{
struct calendar date;
/* - calculate min. base value for GPS epoch & century unfolding
* This assumes that the build system was roughly in sync with
* the world, and that really synchronising to a time before the
* program was created would be unsafe or insane. If the build
* date cannot be stablished, at least use the start of GPS
* (1980-01-06) as minimum, because GPS can surely NOT
* synchronise beyond it's own big bang. We add a little safety
* margin for the fuzziness of the build date, which is in an
* undefined time zone. */
if (ntpcal_get_build_date(&date))
g_gpsMinBase = ntpcal_date_to_rd(&date) - 2;
else
g_gpsMinBase = 0;
if (g_gpsMinBase < DAY_GPS_STARTS)
g_gpsMinBase = DAY_GPS_STARTS;
ntpcal_rd_to_date(&date, g_gpsMinBase);
g_gpsMinYear = date.year;
g_gpsMinBase -= DAY_NTP_STARTS;
}
/*
* -------------------------------------------------------------------
* nmea_start - open the GPS devices and initialize data for processing
*
* return 0 on error, 1 on success. Even on error the peer structures
* must be in a state that permits 'nmea_shutdown()' to clean up all
* resources, because it will be called immediately to do so.
* -------------------------------------------------------------------
*/
static int
nmea_start(
int unit,
struct peer * peer
)
{
struct refclockproc * const pp = peer->procptr;
nmea_unit * const up = emalloc_zero(sizeof(*up));
char device[20];
size_t devlen;
u_int32 rate;
int baudrate;
char * baudtext;
/* Get baudrate choice from mode byte bits 4/5/6 */
rate = (peer->ttl & NMEA_BAUDRATE_MASK) >> NMEA_BAUDRATE_SHIFT;
switch (rate) {
case 0:
baudrate = SPEED232;
baudtext = "4800";
break;
case 1:
baudrate = B9600;
baudtext = "9600";
break;
case 2:
baudrate = B19200;
baudtext = "19200";
break;
case 3:
baudrate = B38400;
baudtext = "38400";
break;
#ifdef B57600
case 4:
baudrate = B57600;
baudtext = "57600";
break;
#endif
#ifdef B115200
case 5:
baudrate = B115200;
baudtext = "115200";
break;
#endif
default:
baudrate = SPEED232;
baudtext = "4800 (fallback)";
break;
}
/* Allocate and initialize unit structure */
pp->unitptr = (caddr_t)up;
pp->io.fd = -1;
pp->io.clock_recv = nmea_receive;
pp->io.srcclock = peer;
pp->io.datalen = 0;
/* force change detection on first valid message */
memset(&up->last_reftime, 0xFF, sizeof(up->last_reftime));
/* force checksum on GPRMC, see below */
up->cksum_type[NMEA_GPRMC] = CHECK_CSVALID;
#ifdef HAVE_PPSAPI
up->ppsapi_fd = -1;
#endif
ZERO(up->tally);
/* Initialize miscellaneous variables */
peer->precision = PRECISION;
pp->clockdesc = DESCRIPTION;
memcpy(&pp->refid, REFID, 4);
/* Open serial port. Use CLK line discipline, if available. */
devlen = snprintf(device, sizeof(device), DEVICE, unit);
if (devlen >= sizeof(device)) {
msyslog(LOG_ERR, "%s clock device name too long",
refnumtoa(&peer->srcadr));
return FALSE; /* buffer overflow */
}
pp->io.fd = refclock_open(device, baudrate, LDISC_CLK);
if (0 >= pp->io.fd) {
pp->io.fd = nmead_open(device);
if (-1 == pp->io.fd)
return FALSE;
}
LOGIF(CLOCKINFO, (LOG_NOTICE, "%s serial %s open at %s bps",
refnumtoa(&peer->srcadr), device, baudtext));
/* succeed if this clock can be added */
return io_addclock(&pp->io) != 0;
}
/*
* -------------------------------------------------------------------
* nmea_shutdown - shut down a GPS clock
*
* NOTE this routine is called after nmea_start() returns failure,
* as well as during a normal shutdown due to ntpq :config unpeer.
* -------------------------------------------------------------------
*/
static void
nmea_shutdown(
int unit,
struct peer * peer
)
{
struct refclockproc * const pp = peer->procptr;
nmea_unit * const up = (nmea_unit *)pp->unitptr;
UNUSED_ARG(unit);
if (up != NULL) {
#ifdef HAVE_PPSAPI
if (up->ppsapi_lit)
time_pps_destroy(up->atom.handle);
if (up->ppsapi_tried && up->ppsapi_fd != pp->io.fd)
close(up->ppsapi_fd);
#endif
free(up);
}
pp->unitptr = (caddr_t)NULL;
if (-1 != pp->io.fd)
io_closeclock(&pp->io);
pp->io.fd = -1;
}
/*
* -------------------------------------------------------------------
* nmea_control - configure fudge params
* -------------------------------------------------------------------
*/
#ifdef HAVE_PPSAPI
static void
nmea_control(
int unit,
const struct refclockstat * in_st,
struct refclockstat * out_st,
struct peer * peer
)
{
struct refclockproc * const pp = peer->procptr;
nmea_unit * const up = (nmea_unit *)pp->unitptr;
char device[32];
size_t devlen;
UNUSED_ARG(in_st);
UNUSED_ARG(out_st);
/*
* PPS control
*
* If /dev/gpspps$UNIT can be opened that will be used for
* PPSAPI. Otherwise, the GPS serial device /dev/gps$UNIT
* already opened is used for PPSAPI as well. (This might not
* work, in which case the PPS API remains unavailable...)
*/
/* Light up the PPSAPI interface if not yet attempted. */
if ((CLK_FLAG1 & pp->sloppyclockflag) && !up->ppsapi_tried) {
up->ppsapi_tried = TRUE;
devlen = snprintf(device, sizeof(device), PPSDEV, unit);
if (devlen < sizeof(device)) {
up->ppsapi_fd = open(device, PPSOPENMODE,
S_IRUSR | S_IWUSR);
} else {
up->ppsapi_fd = -1;
msyslog(LOG_ERR, "%s PPS device name too long",
refnumtoa(&peer->srcadr));
}
if (-1 == up->ppsapi_fd)
up->ppsapi_fd = pp->io.fd;
if (refclock_ppsapi(up->ppsapi_fd, &up->atom)) {
/* use the PPS API for our own purposes now. */
up->ppsapi_lit = refclock_params(
pp->sloppyclockflag, &up->atom);
if (!up->ppsapi_lit) {
/* failed to configure, drop PPS unit */
time_pps_destroy(up->atom.handle);
msyslog(LOG_WARNING,
"%s set PPSAPI params fails",
refnumtoa(&peer->srcadr));
}
/* note: the PPS I/O handle remains valid until
* flag1 is cleared or the clock is shut down.
*/
} else {
msyslog(LOG_WARNING,
"%s flag1 1 but PPSAPI fails",
refnumtoa(&peer->srcadr));
}
}
/* shut down PPS API if activated */
if (!(CLK_FLAG1 & pp->sloppyclockflag) && up->ppsapi_tried) {
/* shutdown PPS API */
if (up->ppsapi_lit)
time_pps_destroy(up->atom.handle);
up->atom.handle = 0;
/* close/drop PPS fd */
if (up->ppsapi_fd != pp->io.fd)
close(up->ppsapi_fd);
up->ppsapi_fd = -1;
/* clear markers and peer items */
up->ppsapi_gate = FALSE;
up->ppsapi_lit = FALSE;
up->ppsapi_tried = FALSE;
peer->flags &= ~FLAG_PPS;
peer->precision = PRECISION;
}
}
#endif /* HAVE_PPSAPI */
/*
* -------------------------------------------------------------------
* nmea_timer - called once per second
* this only polls (older?) Oncore devices now
*
* Usually 'nmea_receive()' can get a timestamp every second, but at
* least one Motorola unit needs prompting each time. Doing so in
* 'nmea_poll()' gives only one sample per poll cycle, which actually
* defeats the purpose of the median filter. Polling once per second
* seems a much better idea.
* -------------------------------------------------------------------
*/
static void
nmea_timer(
int unit,
struct peer * peer
)
{
#if NMEA_WRITE_SUPPORT
struct refclockproc * const pp = peer->procptr;
UNUSED_ARG(unit);
if (-1 != pp->io.fd) /* any mode bits to evaluate here? */
gps_send(pp->io.fd, "$PMOTG,RMC,0000*1D\r\n", peer);
#else
UNUSED_ARG(unit);
UNUSED_ARG(peer);
#endif /* NMEA_WRITE_SUPPORT */
}
#ifdef HAVE_PPSAPI
/*
* -------------------------------------------------------------------
* refclock_ppsrelate(...) -- correlate with PPS edge
*
* This function is used to correlate a receive time stamp and a
* reference time with a PPS edge time stamp. It applies the necessary
* fudges (fudge1 for PPS, fudge2 for receive time) and then tries to
* move the receive time stamp to the corresponding edge. This can warp
* into future, if a transmission delay of more than 500ms is not
* compensated with a corresponding fudge time2 value, because then the
* next PPS edge is nearer than the last. (Similiar to what the PPS ATOM
* driver does, but we deal with full time stamps here, not just phase
* shift information.) Likewise, a negative fudge time2 value must be
* used if the reference time stamp correlates with the *following* PPS
* pulse.
*
* Note that the receive time fudge value only needs to move the receive
* stamp near a PPS edge but that close proximity is not required;
* +/-100ms precision should be enough. But since the fudge value will
* probably also be used to compensate the transmission delay when no
* PPS edge can be related to the time stamp, it's best to get it as
* close as possible.
*
* It should also be noted that the typical use case is matching to the
* preceeding edge, as most units relate their sentences to the current
* second.
*
* The function returns PPS_RELATE_NONE (0) if no PPS edge correlation
* can be fixed; PPS_RELATE_EDGE (1) when a PPS edge could be fixed, but
* the distance to the reference time stamp is too big (exceeds
* +/-400ms) and the ATOM driver PLL cannot be used to fix the phase;
* and PPS_RELATE_PHASE (2) when the ATOM driver PLL code can be used.
*
* On output, the receive time stamp is replaced with the corresponding
* PPS edge time if a fix could be made; the PPS fudge is updated to
* reflect the proper fudge time to apply. (This implies that
* 'refclock_process_offset()' must be used!)
* -------------------------------------------------------------------
*/
#define PPS_RELATE_NONE 0 /* no pps correlation possible */
#define PPS_RELATE_EDGE 1 /* recv time fixed, no phase lock */
#define PPS_RELATE_PHASE 2 /* recv time fixed, phase lock ok */
static int
refclock_ppsrelate(
const struct refclockproc * pp , /* for sanity */
const struct refclock_atom * ap , /* for PPS io */
const l_fp * reftime ,
l_fp * rd_stamp, /* i/o read stamp */
double pp_fudge, /* pps fudge */
double * rd_fudge /* i/o read fudge */
)
{
pps_info_t pps_info;
struct timespec timeout;
l_fp pp_stamp, pp_delta;
double delta, idelta;
if (pp->leap == LEAP_NOTINSYNC)
return PPS_RELATE_NONE; /* clock is insane, no chance */
ZERO(timeout);
ZERO(pps_info);
if (time_pps_fetch(ap->handle, PPS_TSFMT_TSPEC,
&pps_info, &timeout) < 0)
return PPS_RELATE_NONE; /* can't get time stamps */
/* get last active PPS edge before receive */
if (ap->pps_params.mode & PPS_CAPTUREASSERT)
timeout = pps_info.assert_timestamp;
else if (ap->pps_params.mode & PPS_CAPTURECLEAR)
timeout = pps_info.clear_timestamp;
else
return PPS_RELATE_NONE; /* WHICH edge, please?!? */
/* get delta between receive time and PPS time */
pp_stamp = tspec_stamp_to_lfp(timeout);
pp_delta = *rd_stamp;
L_SUB(&pp_delta, &pp_stamp);
LFPTOD(&pp_delta, delta);
delta += pp_fudge - *rd_fudge;
if (fabs(delta) > 1.5)
return PPS_RELATE_NONE; /* PPS timeout control */
/* eventually warp edges, check phase */
idelta = floor(delta + 0.5);
pp_fudge -= idelta;
delta -= idelta;
if (fabs(delta) > 0.45)
return PPS_RELATE_NONE; /* dead band control */
/* we actually have a PPS edge to relate with! */
*rd_stamp = pp_stamp;
*rd_fudge = pp_fudge;
/* if whole system out-of-sync, do not try to PLL */
if (sys_leap == LEAP_NOTINSYNC)
return PPS_RELATE_EDGE; /* cannot PLL with atom code */
/* check against reftime if ATOM PLL can be used */
pp_delta = *reftime;
L_SUB(&pp_delta, &pp_stamp);
LFPTOD(&pp_delta, delta);
delta += pp_fudge;
if (fabs(delta) > 0.45)
return PPS_RELATE_EDGE; /* cannot PLL with atom code */
/* all checks passed, gets an AAA rating here! */
return PPS_RELATE_PHASE; /* can PLL with atom code */
}
#endif /* HAVE_PPSAPI */
/*
* -------------------------------------------------------------------
* nmea_receive - receive data from the serial interface
*
* This is the workhorse for NMEA data evaluation:
*
* + it checks all NMEA data, and rejects sentences that are not valid
* NMEA sentences
* + it checks whether a sentence is known and to be used
* + it parses the time and date data from the NMEA data string and
* augments the missing bits. (century in dat, whole date, ...)
* + it rejects data that is not from the first accepted sentence in a
* burst
* + it eventually replaces the receive time with the PPS edge time.
* + it feeds the data to the internal processing stages.
* -------------------------------------------------------------------
*/
static void
nmea_receive(
struct recvbuf * rbufp
)
{
/* declare & init control structure ptrs */
struct peer * const peer = rbufp->recv_peer;
struct refclockproc * const pp = peer->procptr;
nmea_unit * const up = (nmea_unit*)pp->unitptr;
/* Use these variables to hold data until we decide its worth keeping */
nmea_data rdata;
char rd_lastcode[BMAX];
l_fp rd_timestamp, rd_reftime;
int rd_lencode;
double rd_fudge;
/* working stuff */
struct calendar date; /* to keep & convert the time stamp */
struct timespec tofs; /* offset to full-second reftime */
gps_weektm gpsw; /* week time storage */
/* results of sentence/date/time parsing */
u_char sentence; /* sentence tag */
int checkres;
char * cp;
int rc_date;
int rc_time;
/* make sure data has defined pristine state */
ZERO(tofs);
ZERO(date);
ZERO(gpsw);
sentence = 0;
rc_date = 0;
rc_time = 0;
/*
* Read the timecode and timestamp, then initialise field
* processing. The <CR><LF> at the NMEA line end is translated
* to <LF><LF> by the terminal input routines on most systems,
* and this gives us one spurious empty read per record which we
* better ignore silently.
*/
rd_lencode = refclock_gtlin(rbufp, rd_lastcode,
sizeof(rd_lastcode), &rd_timestamp);
checkres = field_init(&rdata, rd_lastcode, rd_lencode);
switch (checkres) {
case CHECK_INVALID:
DPRINTF(1, ("%s invalid data: '%s'\n",
refnumtoa(&peer->srcadr), rd_lastcode));
refclock_report(peer, CEVNT_BADREPLY);
return;
case CHECK_EMPTY:
return;
default:
DPRINTF(1, ("%s gpsread: %d '%s'\n",
refnumtoa(&peer->srcadr), rd_lencode,
rd_lastcode));
break;
}
up->tally.total++;
/*
* --> below this point we have a valid NMEA sentence <--
*
* Check sentence name. Skip first 2 chars (talker ID) in most
* cases, to allow for $GLGGA and $GPGGA etc. Since the name
* field has at least 5 chars we can simply shift the field
* start.
*/
cp = field_parse(&rdata, 0);
if (strncmp(cp + 2, "RMC,", 4) == 0)
sentence = NMEA_GPRMC;
else if (strncmp(cp + 2, "GGA,", 4) == 0)
sentence = NMEA_GPGGA;
else if (strncmp(cp + 2, "GLL,", 4) == 0)
sentence = NMEA_GPGLL;
else if (strncmp(cp + 2, "ZDA,", 4) == 0)
sentence = NMEA_GPZDA;
else if (strncmp(cp + 2, "ZDG,", 4) == 0)
sentence = NMEA_GPZDG;
else if (strncmp(cp, "PGRMF,", 6) == 0)
sentence = NMEA_PGRMF;
else
return; /* not something we know about */
/* Eventually output delay measurement now. */
if (peer->ttl & NMEA_DELAYMEAS_MASK) {
mprintf_clock_stats(&peer->srcadr, "delay %0.6f %.*s",
ldexp(rd_timestamp.l_uf, -32),
(int)(strchr(rd_lastcode, ',') - rd_lastcode),
rd_lastcode);
}
/* See if I want to process this message type */
if ((peer->ttl & NMEA_MESSAGE_MASK) &&
!(peer->ttl & sentence_mode[sentence])) {
up->tally.filtered++;
return;
}
/*
* make sure it came in clean
*
* Apparently, older NMEA specifications (which are expensive)
* did not require the checksum for all sentences. $GPMRC is
* the only one so far identified which has always been required
* to include a checksum.
*
* Today, most NMEA GPS receivers checksum every sentence. To
* preserve its error-detection capabilities with modern GPSes
* while allowing operation without checksums on all but $GPMRC,
* we keep track of whether we've ever seen a valid checksum on
* a given sentence, and if so, reject future instances without
* checksum. ('up->cksum_type[NMEA_GPRMC]' is set in
* 'nmea_start()' to enforce checksums for $GPRMC right from the
* start.)
*/
if (up->cksum_type[sentence] <= (u_char)checkres) {
up->cksum_type[sentence] = (u_char)checkres;
} else {
DPRINTF(1, ("%s checksum missing: '%s'\n",
refnumtoa(&peer->srcadr), rd_lastcode));
refclock_report(peer, CEVNT_BADREPLY);
up->tally.malformed++;
return;
}
/*
* $GPZDG provides GPS time not UTC, and the two mix poorly.
* Once have processed a $GPZDG, do not process any further UTC
* sentences (all but $GPZDG currently).
*/
if (up->gps_time && NMEA_GPZDG != sentence) {
up->tally.filtered++;
return;
}
DPRINTF(1, ("%s processing %d bytes, timecode '%s'\n",
refnumtoa(&peer->srcadr), rd_lencode, rd_lastcode));
/*
* Grab fields depending on clock string type and possibly wipe
* sensitive data from the last timecode.
*/
switch (sentence) {
case NMEA_GPRMC:
/* Check quality byte, fetch data & time */
rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 1);
pp->leap = parse_qual(&rdata, 2, 'A', 0);
rc_date = parse_date(&date, &rdata, 9, DATE_1_DDMMYY)
&& unfold_century(&date, rd_timestamp.l_ui);
if (CLK_FLAG4 & pp->sloppyclockflag)
field_wipe(&rdata, 3, 4, 5, 6, -1);
break;
case NMEA_GPGGA:
/* Check quality byte, fetch time only */
rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 1);
pp->leap = parse_qual(&rdata, 6, '0', 1);
rc_date = unfold_day(&date, rd_timestamp.l_ui);
if (CLK_FLAG4 & pp->sloppyclockflag)
field_wipe(&rdata, 2, 4, -1);
break;
case NMEA_GPGLL:
/* Check quality byte, fetch time only */
rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 5);
pp->leap = parse_qual(&rdata, 6, 'A', 0);
rc_date = unfold_day(&date, rd_timestamp.l_ui);
if (CLK_FLAG4 & pp->sloppyclockflag)
field_wipe(&rdata, 1, 3, -1);
break;
case NMEA_GPZDA:
/* No quality. Assume best, fetch time & full date */
pp->leap = LEAP_NOWARNING;
rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 1);
rc_date = parse_date(&date, &rdata, 2, DATE_3_DDMMYYYY);
break;
case NMEA_GPZDG:
/* Check quality byte, fetch time & full date */
rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 1);
rc_date = parse_date(&date, &rdata, 2, DATE_3_DDMMYYYY);
pp->leap = parse_qual(&rdata, 4, '0', 1);
tofs.tv_sec = -1; /* GPZDG is following second */
break;
case NMEA_PGRMF:
/* get date, time, qualifier and GPS weektime. We need
* date and time-of-day for the century fix, so we read
* them first.
*/
rc_date = parse_weekdata(&gpsw, &rdata, 1, 2, 5)
&& parse_date(&date, &rdata, 3, DATE_1_DDMMYY);
rc_time = parse_time(&date, &tofs.tv_nsec, &rdata, 4);
pp->leap = parse_qual(&rdata, 11, '0', 1);
rc_date = rc_date
&& gpsfix_century(&date, &gpsw, &up->century_cache);
if (CLK_FLAG4 & pp->sloppyclockflag)
field_wipe(&rdata, 6, 8, -1);
break;
default:
INVARIANT(0); /* Coverity 97123 */
return;
}
/* Check sanity of time-of-day. */
if (rc_time == 0) { /* no time or conversion error? */
checkres = CEVNT_BADTIME;
up->tally.malformed++;
}
/* Check sanity of date. */
else if (rc_date == 0) {/* no date or conversion error? */
checkres = CEVNT_BADDATE;
up->tally.malformed++;
}
/* check clock sanity; [bug 2143] */
else if (pp->leap == LEAP_NOTINSYNC) { /* no good status? */
checkres = CEVNT_BADREPLY;
up->tally.rejected++;
}
else
checkres = -1;
if (checkres != -1) {
save_ltc(pp, rd_lastcode, rd_lencode);
refclock_report(peer, checkres);
return;
}
DPRINTF(1, ("%s effective timecode: %04u-%02u-%02u %02d:%02d:%02d\n",
refnumtoa(&peer->srcadr),
date.year, date.month, date.monthday,
date.hour, date.minute, date.second));
/* Check if we must enter GPS time mode; log so if we do */
if (!up->gps_time && (sentence == NMEA_GPZDG)) {
msyslog(LOG_INFO, "%s using GPS time as if it were UTC",
refnumtoa(&peer->srcadr));
up->gps_time = 1;
}
/*
* Get the reference time stamp from the calendar buffer.
* Process the new sample in the median filter and determine the
* timecode timestamp, but only if the PPS is not in control.
* Discard sentence if reference time did not change.
*/
rd_reftime = eval_gps_time(peer, &date, &tofs, &rd_timestamp);
if (L_ISEQU(&up->last_reftime, &rd_reftime)) {
/* Do not touch pp->a_lastcode on purpose! */
up->tally.filtered++;
return;
}
up->last_reftime = rd_reftime;
rd_fudge = pp->fudgetime2;
DPRINTF(1, ("%s using '%s'\n",
refnumtoa(&peer->srcadr), rd_lastcode));
/* Data will be accepted. Update stats & log data. */
up->tally.accepted++;
save_ltc(pp, rd_lastcode, rd_lencode);
pp->lastrec = rd_timestamp;
#ifdef HAVE_PPSAPI
/*
* If we have PPS running, we try to associate the sentence
* with the last active edge of the PPS signal.
*/
if (up->ppsapi_lit)
switch (refclock_ppsrelate(
pp, &up->atom, &rd_reftime, &rd_timestamp,
pp->fudgetime1, &rd_fudge))
{
case PPS_RELATE_PHASE:
up->ppsapi_gate = TRUE;
peer->precision = PPS_PRECISION;
peer->flags |= FLAG_PPS;
DPRINTF(2, ("%s PPS_RELATE_PHASE\n",
refnumtoa(&peer->srcadr)));
up->tally.pps_used++;
break;
case PPS_RELATE_EDGE:
up->ppsapi_gate = TRUE;
peer->precision = PPS_PRECISION;
DPRINTF(2, ("%s PPS_RELATE_EDGE\n",
refnumtoa(&peer->srcadr)));
break;
case PPS_RELATE_NONE:
default:
/*
* Resetting precision and PPS flag is done in
* 'nmea_poll', since it might be a glitch. But
* at the end of the poll cycle we know...
*/
DPRINTF(2, ("%s PPS_RELATE_NONE\n",
refnumtoa(&peer->srcadr)));
break;
}
#endif /* HAVE_PPSAPI */
refclock_process_offset(pp, rd_reftime, rd_timestamp, rd_fudge);
}
/*
* -------------------------------------------------------------------
* nmea_poll - called by the transmit procedure
*
* Does the necessary bookkeeping stuff to keep the reported state of
* the clock in sync with reality.
*
* We go to great pains to avoid changing state here, since there may
* be more than one eavesdropper receiving the same timecode.
* -------------------------------------------------------------------
*/
static void
nmea_poll(
int unit,
struct peer * peer
)
{
struct refclockproc * const pp = peer->procptr;
nmea_unit * const up = (nmea_unit *)pp->unitptr;
/*
* Process median filter samples. If none received, declare a
* timeout and keep going.
*/
#ifdef HAVE_PPSAPI
/*
* If we don't have PPS pulses and time stamps, turn PPS down
* for now.
*/
if (!up->ppsapi_gate) {
peer->flags &= ~FLAG_PPS;
peer->precision = PRECISION;
} else {
up->ppsapi_gate = FALSE;
}
#endif /* HAVE_PPSAPI */
/*
* If the median filter is empty, claim a timeout. Else process
* the input data and keep the stats going.
*/
if (pp->coderecv == pp->codeproc) {
refclock_report(peer, CEVNT_TIMEOUT);
} else {
pp->polls++;
pp->lastref = pp->lastrec;
refclock_receive(peer);
}
/*
* If extended logging is required, write the tally stats to the
* clockstats file; otherwise just do a normal clock stats
* record. Clear the tally stats anyway.
*/
if (peer->ttl & NMEA_EXTLOG_MASK) {
/* Log & reset counters with extended logging */
char *nmea = pp->a_lastcode;
if (*nmea == '\0') nmea = "(none)";
mprintf_clock_stats(
&peer->srcadr, "%s %u %u %u %u %u %u",
nmea,
up->tally.total, up->tally.accepted,
up->tally.rejected, up->tally.malformed,
up->tally.filtered, up->tally.pps_used);
} else {
record_clock_stats(&peer->srcadr, pp->a_lastcode);
}
ZERO(up->tally);
}
/*
* -------------------------------------------------------------------
* Save the last timecode string, making sure it's properly truncated
* if necessary and NUL terminated in any case.
*/
static void
save_ltc(
struct refclockproc * const pp,
const char * const tc,
size_t len
)
{
if (len >= sizeof(pp->a_lastcode))
len = sizeof(pp->a_lastcode) - 1;
pp->lencode = (u_short)len;
memcpy(pp->a_lastcode, tc, len);
pp->a_lastcode[len] = '\0';
}
#if NMEA_WRITE_SUPPORT
/*
* -------------------------------------------------------------------
* gps_send(fd, cmd, peer) Sends a command to the GPS receiver.
* as in gps_send(fd, "rqts,u", peer);
*
* If 'cmd' starts with a '$' it is assumed that this command is in raw
* format, that is, starts with '$', ends with '<cr><lf>' and that any
* checksum is correctly provided; the command will be send 'as is' in
* that case. Otherwise the function will create the necessary frame
* (start char, chksum, final CRLF) on the fly.
*
* We don't currently send any data, but would like to send RTCM SC104
* messages for differential positioning. It should also give us better
* time. Without a PPS output, we're Just fooling ourselves because of
* the serial code paths
* -------------------------------------------------------------------
*/
static void
gps_send(
int fd,
const char * cmd,
struct peer * peer
)
{
/* $...*xy<CR><LF><NUL> add 7 */
char buf[NMEA_PROTO_MAXLEN + 7];
int len;
u_char dcs;
const u_char *beg, *end;
if (*cmd != '$') {
/* get checksum and length */
beg = end = (const u_char*)cmd;
dcs = 0;
while (*end >= ' ' && *end != '*')
dcs ^= *end++;
len = end - beg;
/* format into output buffer with overflow check */
len = snprintf(buf, sizeof(buf), "$%.*s*%02X\r\n",
len, beg, dcs);
if ((size_t)len >= sizeof(buf)) {
DPRINTF(1, ("%s gps_send: buffer overflow for command '%s'\n",
refnumtoa(&peer->srcadr), cmd));
return; /* game over player 1 */
}
cmd = buf;
} else {
len = strlen(cmd);
}
DPRINTF(1, ("%s gps_send: '%.*s'\n", refnumtoa(&peer->srcadr),
len - 2, cmd));
/* send out the whole stuff */
if (write(fd, cmd, len) == -1)
refclock_report(peer, CEVNT_FAULT);
}
#endif /* NMEA_WRITE_SUPPORT */
/*
* -------------------------------------------------------------------
* helpers for faster field splitting
* -------------------------------------------------------------------
*
* set up a field record, check syntax and verify checksum
*
* format is $XXXXX,1,2,3,4*ML
*
* 8-bit XOR of characters between $ and * noninclusive is transmitted
* in last two chars M and L holding most and least significant nibbles
* in hex representation such as:
*
* $GPGLL,5057.970,N,00146.110,E,142451,A*27
* $GPVTG,089.0,T,,,15.2,N,,*7F
*
* Some other constraints:
* + The field name must at least 5 upcase characters or digits and must
* start with a character.
* + The checksum (if present) must be uppercase hex digits.
* + The length of a sentence is limited to 80 characters (not including
* the final CR/LF nor the checksum, but including the leading '$')
*
* Return values:
* + CHECK_INVALID
* The data does not form a valid NMEA sentence or a checksum error
* occurred.
* + CHECK_VALID
* The data is a valid NMEA sentence but contains no checksum.
* + CHECK_CSVALID
* The data is a valid NMEA sentence and passed the checksum test.
* -------------------------------------------------------------------
*/
static int
field_init(
nmea_data * data, /* context structure */
char * cptr, /* start of raw data */
int dlen /* data len, not counting trailing NUL */
)
{
u_char cs_l; /* checksum local computed */
u_char cs_r; /* checksum remote given */
char * eptr; /* buffer end end pointer */
char tmp; /* char buffer */
cs_l = 0;
cs_r = 0;
/* some basic input constraints */
if (dlen < 0)
dlen = 0;
eptr = cptr + dlen;
*eptr = '\0';
/* load data context */
data->base = cptr;
data->cptr = cptr;
data->cidx = 0;
data->blen = dlen;
/* syntax check follows here. check allowed character
* sequences, updating the local computed checksum as we go.
*
* regex equiv: '^\$[A-Z][A-Z0-9]{4,}[^*]*(\*[0-9A-F]{2})?$'
*/
/* -*- start character: '^\$' */
if (*cptr == '\0')
return CHECK_EMPTY;
if (*cptr++ != '$')
return CHECK_INVALID;
/* -*- advance context beyond start character */
data->base++;
data->cptr++;
data->blen--;
/* -*- field name: '[A-Z][A-Z0-9]{4,},' */
if (*cptr < 'A' || *cptr > 'Z')
return CHECK_INVALID;
cs_l ^= *cptr++;
while ((*cptr >= 'A' && *cptr <= 'Z') ||
(*cptr >= '0' && *cptr <= '9') )
cs_l ^= *cptr++;
if (*cptr != ',' || (cptr - data->base) < NMEA_PROTO_IDLEN)
return CHECK_INVALID;
cs_l ^= *cptr++;
/* -*- data: '[^*]*' */
while (*cptr && *cptr != '*')
cs_l ^= *cptr++;
/* -*- checksum field: (\*[0-9A-F]{2})?$ */
if (*cptr == '\0')
return CHECK_VALID;
if (*cptr != '*' || cptr != eptr - 3 ||
(cptr - data->base) >= NMEA_PROTO_MAXLEN)
return CHECK_INVALID;
for (cptr++; (tmp = *cptr) != '\0'; cptr++) {
if (tmp >= '0' && tmp <= '9')
cs_r = (cs_r << 4) + (tmp - '0');
else if (tmp >= 'A' && tmp <= 'F')
cs_r = (cs_r << 4) + (tmp - 'A' + 10);
else
break;
}
/* -*- make sure we are at end of string and csum matches */
if (cptr != eptr || cs_l != cs_r)
return CHECK_INVALID;
return CHECK_CSVALID;
}
/*
* -------------------------------------------------------------------
* fetch a data field by index, zero being the name field. If this
* function is called repeatedly with increasing indices, the total load
* is O(n), n being the length of the string; if it is called with
* decreasing indices, the total load is O(n^2). Try not to go backwards
* too often.
* -------------------------------------------------------------------
*/
static char *
field_parse(
nmea_data * data,
int fn
)
{
char tmp;
if (fn < data->cidx) {
data->cidx = 0;
data->cptr = data->base;
}
while ((fn > data->cidx) && (tmp = *data->cptr) != '\0') {
data->cidx += (tmp == ',');
data->cptr++;
}
return data->cptr;
}
/*
* -------------------------------------------------------------------
* Wipe (that is, overwrite with '_') data fields and the checksum in
* the last timecode. The list of field indices is given as integers
* in a varargs list, preferrably in ascending order, in any case
* terminated by a negative field index.
*
* A maximum number of 8 fields can be overwritten at once to guard
* against runaway (that is, unterminated) argument lists.
*
* This function affects what a remote user can see with
*
* ntpq -c clockvar <server>
*
* Note that this also removes the wiped fields from any clockstats
* log. Some NTP operators monitor their NMEA GPS using the change in
* location in clockstats over time as as a proxy for the quality of
* GPS reception and thereby time reported.
* -------------------------------------------------------------------
*/
static void
field_wipe(
nmea_data * data,
...
)
{
va_list va; /* vararg index list */
int fcnt; /* safeguard against runaway arglist */
int fidx; /* field to nuke, or -1 for checksum */
char * cp; /* overwrite destination */
fcnt = 8;
cp = NULL;
va_start(va, data);
do {
fidx = va_arg(va, int);
if (fidx >= 0 && fidx <= NMEA_PROTO_FIELDS) {
cp = field_parse(data, fidx);
} else {
cp = data->base + data->blen;
if (data->blen >= 3 && cp[-3] == '*')
cp -= 2;
}
for ( ; '\0' != *cp && '*' != *cp && ',' != *cp; cp++)
if ('.' != *cp)
*cp = '_';
} while (fcnt-- && fidx >= 0);
va_end(va);
}
/*
* -------------------------------------------------------------------
* PARSING HELPERS
* -------------------------------------------------------------------
*
* Check sync status
*
* If the character at the data field start matches the tag value,
* return LEAP_NOWARNING and LEAP_NOTINSYNC otherwise. If the 'inverted'
* flag is given, just the opposite value is returned. If there is no
* data field (*cp points to the NUL byte) the result is LEAP_NOTINSYNC.
* -------------------------------------------------------------------
*/
static u_char
parse_qual(
nmea_data * rd,
int idx,
char tag,
int inv
)
{
static const u_char table[2] =
{ LEAP_NOTINSYNC, LEAP_NOWARNING };
char * dp;
dp = field_parse(rd, idx);
return table[ *dp && ((*dp == tag) == !inv) ];
}
/*
* -------------------------------------------------------------------
* Parse a time stamp in HHMMSS[.sss] format with error checking.
*
* returns 1 on success, 0 on failure
* -------------------------------------------------------------------
*/
static int
parse_time(
struct calendar * jd, /* result calendar pointer */
long * ns, /* storage for nsec fraction */
nmea_data * rd,
int idx
)
{
static const unsigned long weight[4] = {
0, 100000000, 10000000, 1000000
};
int rc;
u_int h;
u_int m;
u_int s;
int p1;
int p2;
u_long f;
char * dp;
dp = field_parse(rd, idx);
rc = sscanf(dp, "%2u%2u%2u%n.%3lu%n", &h, &m, &s, &p1, &f, &p2);
if (rc < 3 || p1 != 6) {
DPRINTF(1, ("nmea: invalid time code: '%.6s'\n", dp));
return FALSE;
}
/* value sanity check */
if (h > 23 || m > 59 || s > 60) {
DPRINTF(1, ("nmea: invalid time spec %02u:%02u:%02u\n",
h, m, s));
return FALSE;
}
jd->hour = (u_char)h;
jd->minute = (u_char)m;
jd->second = (u_char)s;
/* if we have a fraction, scale it up to nanoseconds. */
if (rc == 4)
*ns = f * weight[p2 - p1 - 1];
else
*ns = 0;
return TRUE;
}
/*
* -------------------------------------------------------------------
* Parse a date string from an NMEA sentence. This could either be a
* partial date in DDMMYY format in one field, or DD,MM,YYYY full date
* spec spanning three fields. This function does some extensive error
* checking to make sure the date string was consistent.
*
* returns 1 on success, 0 on failure
* -------------------------------------------------------------------
*/
static int
parse_date(
struct calendar * jd, /* result pointer */
nmea_data * rd,
int idx,
enum date_fmt fmt
)
{
int rc;
u_int y;
u_int m;
u_int d;
int p;
char * dp;
dp = field_parse(rd, idx);
switch (fmt) {
case DATE_1_DDMMYY:
rc = sscanf(dp, "%2u%2u%2u%n", &d, &m, &y, &p);
if (rc != 3 || p != 6) {
DPRINTF(1, ("nmea: invalid date code: '%.6s'\n",
dp));
return FALSE;
}
break;
case DATE_3_DDMMYYYY:
rc = sscanf(dp, "%2u,%2u,%4u%n", &d, &m, &y, &p);
if (rc != 3 || p != 10) {
DPRINTF(1, ("nmea: invalid date code: '%.10s'\n",
dp));
return FALSE;
}
break;
default:
DPRINTF(1, ("nmea: invalid parse format: %d\n", fmt));
return FALSE;
}
/* value sanity check */
if (d < 1 || d > 31 || m < 1 || m > 12) {
DPRINTF(1, ("nmea: invalid date spec (YMD) %04u:%02u:%02u\n",
y, m, d));
return FALSE;
}
/* store results */
jd->monthday = (u_char)d;
jd->month = (u_char)m;
jd->year = (u_short)y;
return TRUE;
}
/*
* -------------------------------------------------------------------
* Parse GPS week time info from an NMEA sentence. This info contains
* the GPS week number, the GPS time-of-week and the leap seconds GPS
* to UTC.
*
* returns 1 on success, 0 on failure
* -------------------------------------------------------------------
*/
static int
parse_weekdata(
gps_weektm * wd,
nmea_data * rd,
int weekidx,
int timeidx,
int leapidx
)
{
u_long secs;
int fcnt;
/* parse fields and count success */
fcnt = sscanf(field_parse(rd, weekidx), "%hu", &wd->wt_week);
fcnt += sscanf(field_parse(rd, timeidx), "%lu", &secs);
fcnt += sscanf(field_parse(rd, leapidx), "%hd", &wd->wt_leap);
if (fcnt != 3 || wd->wt_week >= 1024 || secs >= 7*SECSPERDAY) {
DPRINTF(1, ("nmea: parse_weekdata: invalid weektime spec\n"));
return FALSE;
}
wd->wt_time = (u_int32)secs;
return TRUE;
}
/*
* -------------------------------------------------------------------
* funny calendar-oriented stuff -- perhaps a bit hard to grok.
* -------------------------------------------------------------------
*
* Unfold a time-of-day (seconds since midnight) around the current
* system time in a manner that guarantees an absolute difference of
* less than 12hrs.
*
* This function is used for NMEA sentences that contain no date
* information. This requires the system clock to be in +/-12hrs
* around the true time, or the clock will synchronize the system 1day
* off if not augmented with a time sources that also provide the
* necessary date information.
*
* The function updates the calendar structure it also uses as
* input to fetch the time from.
*
* returns 1 on success, 0 on failure
* -------------------------------------------------------------------
*/
static int
unfold_day(
struct calendar * jd,
u_int32 rec_ui
)
{
vint64 rec_qw;
ntpcal_split rec_ds;
/*
* basically this is the peridiodic extension of the receive
* time - 12hrs to the time-of-day with a period of 1 day.
* But we would have to execute this in 64bit arithmetic, and we
* cannot assume we can do this; therefore this is done
* in split representation.
*/
rec_qw = ntpcal_ntp_to_ntp(rec_ui - SECSPERDAY/2, NULL);
rec_ds = ntpcal_daysplit(&rec_qw);
rec_ds.lo = ntpcal_periodic_extend(rec_ds.lo,
ntpcal_date_to_daysec(jd),
SECSPERDAY);
rec_ds.hi += ntpcal_daysec_to_date(jd, rec_ds.lo);
return (ntpcal_rd_to_date(jd, rec_ds.hi + DAY_NTP_STARTS) >= 0);
}
/*
* -------------------------------------------------------------------
* A 2-digit year is expanded into full year spec around the year found
* in 'jd->year'. This should be in +79/-19 years around the system time,
* or the result will be off by 100 years. The assymetric behaviour was
* chosen to enable inital sync for systems that do not have a
* battery-backup clock and start with a date that is typically years in
* the past.
*
* Since the GPS epoch starts at 1980-01-06, the resulting year will be
* not be before 1980 in any case.
*
* returns 1 on success, 0 on failure
* -------------------------------------------------------------------
*/
static int
unfold_century(
struct calendar * jd,
u_int32 rec_ui
)
{
struct calendar rec;
int32 baseyear;
ntpcal_ntp_to_date(&rec, rec_ui, NULL);
baseyear = rec.year - 20;
if (baseyear < g_gpsMinYear)
baseyear = g_gpsMinYear;
jd->year = (u_short)ntpcal_periodic_extend(baseyear, jd->year,
100);
return ((baseyear <= jd->year) && (baseyear + 100 > jd->year));
}
/*
* -------------------------------------------------------------------
* A 2-digit year is expanded into a full year spec by correlation with
* a GPS week number and the current leap second count.
*
* The GPS week time scale counts weeks since Sunday, 1980-01-06, modulo
* 1024 and seconds since start of the week. The GPS time scale is based
* on international atomic time (TAI), so the leap second difference to
* UTC is also needed for a proper conversion.
*
* A brute-force analysis (that is, test for every date) shows that a
* wrong assignment of the century can not happen between the years 1900
* to 2399 when comparing the week signatures for different
* centuries. (I *think* that will not happen for 400*1024 years, but I
* have no valid proof. -*-perlinger@ntp.org-*-)
*
* This function is bound to to work between years 1980 and 2399
* (inclusive), which should suffice for now ;-)
*
* Note: This function needs a full date&time spec on input due to the
* necessary leap second corrections!
*
* returns 1 on success, 0 on failure
* -------------------------------------------------------------------
*/
static int
gpsfix_century(
struct calendar * jd,
const gps_weektm * wd,
u_short * century
)
{
int32 days;
int32 doff;
u_short week;
u_short year;
int loop;
/* Get day offset. Assumes that the input time is in range and
* that the leap seconds do not shift more than +/-1 day.
*/
doff = ntpcal_date_to_daysec(jd) + wd->wt_leap;
doff = (doff >= SECSPERDAY) - (doff < 0);
/*
* Loop over centuries to get a match, starting with the last
* successful one. (Or with the 19th century if the cached value
* is out of range...)
*/
year = jd->year % 100;
for (loop = 5; loop > 0; loop--,(*century)++) {
if (*century < 19 || *century >= 24)
*century = 19;
/* Get days and week in GPS epoch */
jd->year = year + *century * 100;
days = ntpcal_date_to_rd(jd) - DAY_GPS_STARTS + doff;
week = (days / 7) % 1024;
if (days >= 0 && wd->wt_week == week)
return TRUE; /* matched... */
}
jd->year = year;
return FALSE; /* match failed... */
}
/*
* -------------------------------------------------------------------
* And now the final execise: Considering the fact that many (most?)
* GPS receivers cannot handle a GPS epoch wrap well, we try to
* compensate for that problem by unwrapping a GPS epoch around the
* receive stamp. Another execise in periodic unfolding, of course,
* but with enough points to take care of.
*
* Note: The integral part of 'tofs' is intended to handle small(!)
* systematic offsets, as -1 for handling $GPZDG, which gives the
* following second. (sigh...) The absolute value shall be less than a
* day (86400 seconds).
* -------------------------------------------------------------------
*/
static l_fp
eval_gps_time(
struct peer * peer, /* for logging etc */
const struct calendar * gpst, /* GPS time stamp */
const struct timespec * tofs, /* GPS frac second & offset */
const l_fp * recv /* receive time stamp */
)
{
struct refclockproc * const pp = peer->procptr;
nmea_unit * const up = (nmea_unit *)pp->unitptr;
l_fp retv;
/* components of calculation */
int32_t rcv_sec, rcv_day; /* receive ToD and day */
int32_t gps_sec, gps_day; /* GPS ToD and day in NTP epoch */
int32_t adj_day, weeks; /* adjusted GPS day and week shift */
/* some temporaries to shuffle data */
vint64 vi64;
ntpcal_split rs64;
/* evaluate time stamp from receiver. */
gps_sec = ntpcal_date_to_daysec(gpst);
gps_day = ntpcal_date_to_rd(gpst) - DAY_NTP_STARTS;
/* merge in fractional offset */
retv = tspec_intv_to_lfp(*tofs);
gps_sec += retv.l_i;
/* If we fully trust the GPS receiver, just combine days and
* seconds and be done. */
if (peer->ttl & NMEA_DATETRUST_MASK) {
retv.l_ui = ntpcal_dayjoin(gps_day, gps_sec).D_s.lo;
return retv;
}
/* So we do not trust the GPS receiver to deliver a correct date
* due to the GPS epoch changes. We map the date from the
* receiver into the +/-512 week interval around the receive
* time in that case. This would be a tad easier with 64bit
* calculations, but again, we restrict the code to 32bit ops
* when possible. */
/* - make sure the GPS fractional day is normalised
* Applying the offset value might have put us slightly over the
* edge of the allowed range for seconds-of-day. Doing a full
* division with floor correction is overkill here; a simple
* addition or subtraction step is sufficient. Using WHILE loops
* gives the right result even if the offset exceeds one day,
* which is NOT what it's intented for! */
while (gps_sec >= SECSPERDAY) {
gps_sec -= SECSPERDAY;
gps_day += 1;
}
while (gps_sec < 0) {
gps_sec += SECSPERDAY;
gps_day -= 1;
}
/* - get unfold base: day of full recv time - 512 weeks */
vi64 = ntpcal_ntp_to_ntp(recv->l_ui, NULL);
rs64 = ntpcal_daysplit(&vi64);
rcv_sec = rs64.lo;
rcv_day = rs64.hi - 512 * 7;
/* - take the fractional days into account
* If the fractional day of the GPS time is smaller than the
* fractional day of the receive time, we shift the base day for
* the unfold by 1. */
if ( gps_sec < rcv_sec
|| (gps_sec == rcv_sec && retv.l_uf < recv->l_uf))
rcv_day += 1;
/* - don't warp ahead of GPS invention! */
if (rcv_day < g_gpsMinBase)
rcv_day = g_gpsMinBase;
/* - let the magic happen: */
adj_day = ntpcal_periodic_extend(rcv_day, gps_day, 1024*7);
/* - check if we should log a GPS epoch warp */
weeks = (adj_day - gps_day) / 7;
if (weeks != up->epoch_warp) {
up->epoch_warp = weeks;
LOGIF(CLOCKINFO, (LOG_INFO,
"%s Changed GPS epoch warp to %d weeks",
refnumtoa(&peer->srcadr), weeks));
}
/* - build result and be done */
retv.l_ui = ntpcal_dayjoin(adj_day, gps_sec).D_s.lo;
return retv;
}
/*
* ===================================================================
*
* NMEAD support
*
* original nmead support added by Jon Miner (cp_n18@yahoo.com)
*
* See http://home.hiwaay.net/~taylorc/gps/nmea-server/
* for information about nmead
*
* To use this, you need to create a link from /dev/gpsX to
* the server:port where nmead is running. Something like this:
*
* ln -s server:port /dev/gps1
*
* Split into separate function by Juergen Perlinger
* (perlinger-at-ntp-dot-org)
*
* ===================================================================
*/
static int
nmead_open(
const char * device
)
{
int fd = -1; /* result file descriptor */
#ifdef HAVE_READLINK
char host[80]; /* link target buffer */
char * port; /* port name or number */
int rc; /* result code (several)*/
int sh; /* socket handle */
struct addrinfo ai_hint; /* resolution hint */
struct addrinfo *ai_list; /* resolution result */
struct addrinfo *ai; /* result scan ptr */
fd = -1;
/* try to read as link, make sure no overflow occurs */
rc = readlink(device, host, sizeof(host));
if ((size_t)rc >= sizeof(host))
return fd; /* error / overflow / truncation */
host[rc] = '\0'; /* readlink does not place NUL */
/* get port */
port = strchr(host, ':');
if (!port)
return fd; /* not 'host:port' syntax ? */
*port++ = '\0'; /* put in separator */
/* get address infos and try to open socket
*
* This getaddrinfo() is naughty in ntpd's nonblocking main
* thread, but you have to go out of your wary to use this code
* and typically the blocking is at startup where its impact is
* reduced. The same holds for the 'connect()', as it is
* blocking, too...
*/
ZERO(ai_hint);
ai_hint.ai_protocol = IPPROTO_TCP;
ai_hint.ai_socktype = SOCK_STREAM;
if (getaddrinfo(host, port, &ai_hint, &ai_list))
return fd;
for (ai = ai_list; ai && (fd == -1); ai = ai->ai_next) {
sh = socket(ai->ai_family, ai->ai_socktype,
ai->ai_protocol);
if (INVALID_SOCKET == sh)
continue;
rc = connect(sh, ai->ai_addr, ai->ai_addrlen);
if (-1 != rc)
fd = sh;
else
close(sh);
}
freeaddrinfo(ai_list);
#else
fd = -1;
#endif
return fd;
}
#else
NONEMPTY_TRANSLATION_UNIT
#endif /* REFCLOCK && CLOCK_NMEA */
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