/* $NetBSD: refclock_nmea.c,v 1.15 2024/08/18 20:47:18 christos Exp $ */

/* $NetBSD: refclock_nmea.c,v 1.15 2024/08/18 20:47:18 christos Exp $ */

/*
* 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
* [email protected], [email protected]
*
* 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
* [email protected], [email protected]
*/

#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>
#ifdef HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif

#include "ntpd.h"
#include "ntp_io.h"
#include "ntp_unixtime.h"
#include "ntp_refclock.h"
#include "ntp_stdlib.h"
#include "ntp_calgps.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 0x00000080U
#define NMEA_EXTLOG_MASK 0x00010000U
#define NMEA_QUIETPPS_MASK 0x00020000U
#define NMEA_DATETRUST_MASK 0x00040000U
#define NMEA_IGNSTATUS_MASK 0x00080000U

#define NMEA_PROTO_IDLEN 4 /* tag name must be at least 4 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 DATE_HOLD 16 /* seconds to hold on provided GPS date */
#define DATE_HLIM 4 /* when do we take ANY date format */
#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_PUBX04 6
#define NMEA_ARRAY_SIZE (NMEA_PUBX04 + 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
#define USE_PUBX04 0x00000200u

/* 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,
USE_PUBX04
};

/* 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 */
};

/* date type */
enum date_type {
DTYP_NONE,
DTYP_Y2D, /* 2-digit year */
DTYP_W10B, /* 10-bit week in GPS epoch */
DTYP_Y4D, /* 4-digit (full) year */
DTYP_WEXT /* extended week in GPS epoch */
};

/* 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
*/
struct refclock_atom;
typedef struct refclock_atom TAtomUnit;
typedef struct {
# ifdef HAVE_PPSAPI
TAtomUnit 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 */
# endif /* HAVE_PPSAPI */
uint16_t rcvtout; /* one-shot for sample expiration */
u_char ppsapi_gate; /* system is on PPS */
u_char gps_time; /* use GPS time, not UTC */
l_fp last_reftime; /* last processed reference stamp */
TNtpDatum last_gpsdate; /* last processed split date/time */
u_short hold_gpsdate; /* validity ticker for above */
u_short type_gpsdate; /* date info type for above */
/* 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];

/* line assembly buffer (NMEAD support) */
u_short lb_len;
char lb_buf[BMAX]; /* assembly buffer */
} 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;

/*
* Function prototypes
*/
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 *);
static void nmea_procrec (struct peer * const, l_fp);
#ifdef HAVE_PPSAPI
static double tabsdiffd (l_fp, l_fp);
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 (TCivilDate * jd, l_fp * fofs,
nmea_data *, int idx);
static int parse_date (TCivilDate * jd, nmea_data *,
int idx, enum date_fmt fmt);
static int parse_gpsw (TGpsDatum *, nmea_data *,
int weekidx, int timeidx, int leapidx);

static int nmead_open (const char * device);

/*
* If we want the driver to output 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 *);
#endif /* NMEA_WRITE_SUPPORT */

/*
* -------------------------------------------------------------------
* 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 */
noentry, /* initialize driver */
noentry, /* buginfo */
nmea_timer /* called once per second */
};

/*
* -------------------------------------------------------------------
* 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;

/* Get baudrate choice from mode byte bits 4/5/6 */
rate = (peer->ttl & NMEA_BAUDRATE_MASK) >> NMEA_BAUDRATE_SHIFT;

switch (rate) {
default:
case 0:
baudrate = SPEED232;
break;
case 1:
baudrate = B9600;
break;
case 2:
baudrate = B19200;
break;
case 3:
baudrate = B38400;
break;
# ifdef B57600
case 4:
baudrate = B57600;
break;
# endif
# ifdef B115200
case 5:
baudrate = B115200;
break;
# endif
}

/* 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));
memset(&up->last_gpsdate, 0x00, sizeof(up->last_gpsdate));
/* force checksum on GPRMC, see below */
up->cksum_type[NMEA_GPRMC] = CHECK_CSVALID;
# ifdef HAVE_PPSAPI
up->ppsapi_fd = -1;
# endif /* HAVE_PPSAPI */
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(&peer->srcadr, device, baudrate, LDISC_CLK);
if (0 >= pp->io.fd) {
pp->io.fd = nmead_open(device);
if (-1 == pp->io.fd)
return FALSE;
}

/* 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);
ppsdev_close(pp->io.fd, 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$UNIT can be opened that will be used for
* PPSAPI. On Linux, a PPS device mathing the TTY will be
* searched for and possibly created on the fly. Otherwise, the
* GPS serial device /dev/gps$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) {
const char *ppsname = device;
up->ppsapi_tried = TRUE;
/* get FD for the pps device; might be the tty itself! */
devlen = snprintf(device, sizeof(device), PPSDEV, unit);
if (devlen >= sizeof(device)) {
msyslog(LOG_ERR, "%s PPS device name too long",
refnumtoa(&peer->srcadr));
ppsname = NULL;
}
up->ppsapi_fd = ppsdev_reopen(
&peer->srcadr,
pp->io.fd, up->ppsapi_fd,
ppsname, PPSOPENMODE, (S_IRUSR|S_IWUSR));
/* note 1: the pps fd might be the same as the tty fd
* note 2: the current PPS fd remains valid until
* - the clock is shut down
* - flag1 is set again after being cleared
*/
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));
}
} 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;
/* do !!NOT!! close/drop PPS fd here! */

/* 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
*
* 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.
*
* Also takes care of sample expiration if the receiver fails to
* provide new input data.
* -------------------------------------------------------------------
*/
static void
nmea_timer(
int unit,
struct peer * peer
)
{
struct refclockproc * const pp = peer->procptr;
nmea_unit * const up = (nmea_unit *)pp->unitptr;

UNUSED_ARG(unit);

# if NMEA_WRITE_SUPPORT

if (-1 != pp->io.fd) /* any mode bits to evaluate here? */
gps_send(pp->io.fd, "$PMOTG,RMC,0000*1D\r\n", peer);

# endif /* NMEA_WRITE_SUPPORT */

/* receive timeout occurred? */
if (up->rcvtout) {
--up->rcvtout;
} else if (pp->codeproc != pp->coderecv) {
/* expire one (the oldest) sample, if any */
refclock_samples_expire(pp, 1);
/* reset message assembly buffer */
up->lb_buf[0] = '\0';
up->lb_len = 0;
}

if (up->hold_gpsdate && (--up->hold_gpsdate < DATE_HLIM))
up->type_gpsdate = DTYP_NONE;
}

/*
* -------------------------------------------------------------------
* nmea_procrec - 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 date, 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.
*
* This function assumes a non-empty line in the unit line buffer.
* -------------------------------------------------------------------
*/
static void
nmea_procrec(
struct peer * const peer,
l_fp rd_timestamp
)
{
/* declare & init control structure pointers */
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;
l_fp rd_reftime;

/* working stuff */
TCivilDate date; /* to keep & convert the time stamp */
TGpsDatum wgps; /* week time storage */
TNtpDatum dntp;
l_fp tofs; /* offset to full-second reftime */
/* results of sentence/date/time parsing */
u_char sentence; /* sentence tag */
int checkres;
int warp; /* warp to GPS base date */
char * cp;
int rc_date, rc_time;
u_short rc_dtyp;
# ifdef HAVE_PPSAPI
int withpps = 0;
# endif /* HAVE_PPSAPI */

/* make sure data has defined pristine state */
ZERO(tofs);
ZERO(date);
ZERO(wgps);
ZERO(dntp);

/*
* Read the timecode and timestamp, then initialize 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.
*/
checkres = field_init(&rdata, up->lb_buf, up->lb_len);
switch (checkres) {

case CHECK_INVALID:
DPRINTF(1, ("%s invalid data: '%s'\n",
refnumtoa(&peer->srcadr), up->lb_buf));
refclock_report(peer, CEVNT_BADREPLY);
return;

case CHECK_EMPTY:
return;

default:
DPRINTF(1, ("%s gpsread: %d '%s'\n",
refnumtoa(&peer->srcadr), up->lb_len,
up->lb_buf));
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 if (strncmp(cp, "PUBX,04,", 8) == 0)
sentence = NMEA_PUBX04;
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(up->lb_buf, ',') - up->lb_buf),
up->lb_buf);
}

/* 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), up->lb_buf));
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 (sentence == NMEA_GPZDG) {
if (!up->gps_time) {
msyslog(LOG_INFO,
"%s using GPS time as if it were UTC",
refnumtoa(&peer->srcadr));
up->gps_time = 1;
}
} else {
if (up->gps_time) {
up->tally.filtered++;
return;
}
}

DPRINTF(1, ("%s processing %d bytes, timecode '%s'\n",
refnumtoa(&peer->srcadr), up->lb_len, up->lb_buf));

/*
* Grab fields depending on clock string type and possibly wipe
* sensitive data from the last timecode.
*/
rc_date = -1; /* assume we have to do day-time mapping */
rc_dtyp = DTYP_NONE;
switch (sentence) {

case NMEA_GPRMC:
/* Check quality byte, fetch data & time */
rc_time = parse_time(&date, &tofs, &rdata, 1);
pp->leap = parse_qual(&rdata, 2, 'A', 0);
if (up->type_gpsdate <= DTYP_Y2D) {
rc_date = parse_date(&date, &rdata, 9, DATE_1_DDMMYY);
rc_dtyp = DTYP_Y2D;
}
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, &rdata, 1);
pp->leap = parse_qual(&rdata, 6, '0', 1);
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, &rdata, 5);
pp->leap = parse_qual(&rdata, 6, 'A', 0);
if (CLK_FLAG4 & pp->sloppyclockflag)
field_wipe(&rdata, 1, 3, -1);
break;

case NMEA_GPZDA:
/* No quality. Assume best, fetch time & full date */
rc_time = parse_time(&date, &tofs, &rdata, 1);
if (up->type_gpsdate <= DTYP_Y4D) {
rc_date = parse_date(&date, &rdata, 2, DATE_3_DDMMYYYY);
rc_dtyp = DTYP_Y4D;
}
break;

case NMEA_GPZDG:
/* Check quality byte, fetch time & full date */
rc_time = parse_time(&date, &tofs, &rdata, 1);
pp->leap = parse_qual(&rdata, 4, '0', 1);
--tofs.l_ui; /* GPZDG gives *following* second */
if (up->type_gpsdate <= DTYP_Y4D) {
rc_date = parse_date(&date, &rdata, 2, DATE_3_DDMMYYYY);
rc_dtyp = DTYP_Y4D;
}
break;

case NMEA_PGRMF:
/* get time, qualifier and GPS weektime. */
rc_time = parse_time(&date, &tofs, &rdata, 4);
if (up->type_gpsdate <= DTYP_W10B) {
rc_date = parse_gpsw(&wgps, &rdata, 1, 2, 5);
rc_dtyp = DTYP_W10B;
}
pp->leap = parse_qual(&rdata, 11, '0', 1);
if (CLK_FLAG4 & pp->sloppyclockflag)
field_wipe(&rdata, 6, 8, -1);
break;

case NMEA_PUBX04:
/* PUBX,04 is peculiar. The UTC time-of-week is the *internal*
* time base, which is not exactly on par with the fix time.
*/
rc_time = parse_time(&date, &tofs, &rdata, 2);
if (up->type_gpsdate <= DTYP_WEXT) {
rc_date = parse_gpsw(&wgps, &rdata, 5, 4, -1);
rc_dtyp = DTYP_WEXT;
}
break;

default:
INVARIANT(0); /* Coverity 97123 */
return;
}

/* ignore receiver status? [bug 3694] */
if (peer->ttl & NMEA_IGNSTATUS_MASK) { /* assume always good? */
pp->leap = LEAP_NOWARNING;
}

/* check clock sanity; [bug 2143] */
if (pp->leap == LEAP_NOTINSYNC) { /* no good status? */
checkres = CEVNT_PROP;
up->tally.rejected++;
}
/* Check sanity of time-of-day. */
else 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++;
}
else {
checkres = -1;
}

if (checkres != -1) {
refclock_save_lcode(pp, up->lb_buf, up->lb_len);
refclock_report(peer, checkres);
return;
}

/* See if we can augment the receive time stamp. If not, apply
* fudge time 2 to the receive time stamp directly.
*/
# ifdef HAVE_PPSAPI
if (up->ppsapi_lit && pp->leap != LEAP_NOTINSYNC)
withpps = refclock_ppsaugment(
&up->atom, &rd_timestamp,
pp->fudgetime2, pp->fudgetime1);
else
# endif /* HAVE_PPSAPI */
rd_timestamp = ntpfp_with_fudge(
rd_timestamp, pp->fudgetime2);

/* set the GPS base date, if possible */
warp = !(peer->ttl & NMEA_DATETRUST_MASK);
if (rc_dtyp != DTYP_NONE) {
DPRINTF(1, ("%s saving date, type=%hu\n",
refnumtoa(&peer->srcadr), rc_dtyp));
switch (rc_dtyp) {
case DTYP_W10B:
up->last_gpsdate = gpsntp_from_gpscal_ex(
&wgps, (warp = TRUE));
break;
case DTYP_WEXT:
up->last_gpsdate = gpsntp_from_gpscal_ex(
&wgps, warp);
break;
default:
up->last_gpsdate = gpsntp_from_calendar_ex(
&date, tofs, warp);
break;
}
up->type_gpsdate = rc_dtyp;
up->hold_gpsdate = DATE_HOLD;
}
/* now convert and possibly extend/expand the time stamp. */
if (up->hold_gpsdate) { /* time of day, based */
dntp = gpsntp_from_daytime2_ex(
&date, tofs, &up->last_gpsdate, warp);
} else { /* time of day, floating */
dntp = gpsntp_from_daytime1_ex(
&date, tofs, rd_timestamp, warp);
}

if (debug) {
/* debug print time stamp */
gpsntp_to_calendar(&date, &dntp);
# ifdef HAVE_PPSAPI
DPRINTF(1, ("%s effective timecode: %s (%s PPS)\n",
refnumtoa(&peer->srcadr),
ntpcal_iso8601std(NULL, 0, &date),
(withpps ? "with" : "without")));
# else /* ?HAVE_PPSAPI */
DPRINTF(1, ("%s effective timecode: %s\n",
refnumtoa(&peer->srcadr),
ntpcal_iso8601std(NULL, 0, &date)));
# endif /* !HAVE_PPSAPI */
}

/* 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 = ntpfp_from_ntpdatum(&dntp);
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;

DPRINTF(1, ("%s using '%s'\n",
refnumtoa(&peer->srcadr), up->lb_buf));

/* Data will be accepted. Update stats & log data. */
up->tally.accepted++;
refclock_save_lcode(pp, up->lb_buf, up->lb_len);
pp->lastrec = rd_timestamp;

/* If we have PPS augmented receive time, we *must* have a
* working PPS source and we must set the flags accordingly.
*/
# ifdef HAVE_PPSAPI
if (withpps) {
up->ppsapi_gate = TRUE;
peer->precision = PPS_PRECISION;
if (tabsdiffd(rd_reftime, rd_timestamp) < 0.5) {
if ( ! (peer->ttl & NMEA_QUIETPPS_MASK))
peer->flags |= FLAG_PPS;
DPRINTF(2, ("%s PPS_RELATE_PHASE\n",
refnumtoa(&peer->srcadr)));
up->tally.pps_used++;
} else {
DPRINTF(2, ("%s PPS_RELATE_EDGE\n",
refnumtoa(&peer->srcadr)));
}
/* !Note! 'FLAG_PPS' is reset in 'nmea_poll()' */
}
# endif /* HAVE_PPSAPI */
/* Whether the receive time stamp is PPS-augmented or not,
* the proper fudge offset is already applied. There's no
* residual fudge to process.
*/
refclock_process_offset(pp, rd_reftime, rd_timestamp, 0.0);
up->rcvtout = 2;
}

/*
* -------------------------------------------------------------------
* nmea_receive - receive data from the serial interface
*
* With serial IO only, a single call to 'refclock_gtlin()' to get the
* string would suffice to get the NMEA data. When using NMEAD, this
* does unfortunately no longer hold, since TCP is stream oriented and
* not line oriented, and there's no one to do the line-splitting work
* of the TTY driver in line/cooked mode.
*
* So we have to do this manually here, and we have to live with the
* fact that there could be more than one sentence in a receive buffer.
* Likewise, there can be partial messages on either end. (Strictly
* speaking, a receive buffer could also contain just a single fragment,
* though that's unlikely.)
*
* We deal with that by scanning the input buffer, copying bytes from
* the receive buffer to the assembly buffer as we go and calling the
* record processor every time we hit a CR/LF, provided the resulting
* line is not empty. Any leftovers are kept for the next round.
*
* Note: When used with a serial data stream, there's no change to the
* previous line-oriented input: One line is copied to the buffer and
* processed per call. Only with NMEAD the behavior changes, and the
* timing is badly affected unless a PPS channel is also associated with
* the clock instance. TCP leaves us nothing to improve on here.
* -------------------------------------------------------------------
*/
static void
nmea_receive(
struct recvbuf * rbufp
)
{
/* declare & init control structure pointers */
struct peer * const peer = rbufp->recv_peer;
struct refclockproc * const pp = peer->procptr;
nmea_unit * const up = (nmea_unit*)pp->unitptr;

const char *sp, *se;
char *dp, *de;

/* paranoia check: */
if (up->lb_len >= sizeof(up->lb_buf))
up->lb_len = 0;

/* pick up last assembly position; leave room for NUL */
dp = up->lb_buf + up->lb_len;
de = up->lb_buf + sizeof(up->lb_buf) - 1;
/* set up input range */
sp = (const char *)rbufp->recv_buffer;
se = sp + rbufp->recv_length;

/* walk over the input data, dropping parity bits and control
* chars as we go, and calling the record processor for each
* complete non-empty line.
*/
while (sp != se) {
char ch = (*sp++ & 0x7f);
if (dp == up->lb_buf) {
if (ch == '$')
*dp++ = ch;
} else if (dp > de) {
dp = up->lb_buf;
} else if (ch == '\n' || ch == '\r') {
*dp = '\0';
up->lb_len = (int)(dp - up->lb_buf);
dp = up->lb_buf;
nmea_procrec(peer, rbufp->recv_time);
} else if (ch >= 0x20 && ch < 0x7f) {
*dp++ = ch;
}
}
/* update state to keep for next round */
*dp = '\0';
up->lb_len = (int)(dp - up->lb_buf);
}

/*
* -------------------------------------------------------------------
* 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) {
peer->flags &= ~FLAG_PPS;
if (pp->currentstatus < CEVNT_TIMEOUT)
refclock_report(peer, CEVNT_TIMEOUT);
memset(&up->last_gpsdate, 0, sizeof(up->last_gpsdate));
} else {
pp->polls++;
pp->lastref = pp->lastrec;
refclock_receive(peer);
if (pp->currentstatus > CEVNT_NOMINAL)
refclock_report(peer, CEVNT_NOMINAL);
}

/*
* 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 */
const 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);
}

#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 (refclock_fdwrite(peer, fd, cmd, len) != len)
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
* $GPVTG,089.0,T,,,15.2,N,,*7F
*
* Some other constraints:
* + The field name must be at least 5 upcase characters or digits and
* must start with a character.
* + The checksum (if present) must be uppercase hex digits.
* + The length of a sentence is limited to 80 characters (not including
* the final CR/LF nor the checksum, but including the leading '$')
*
* 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, preferably 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
* -------------------------------------------------------------------
*/
typedef unsigned char const UCC;

static char const * const s_eof_chars = ",*\r\n";

#ifdef DEBUG
static int field_length(UCC *cp, unsigned int nfields)
{
char const * ep = (char const*)cp;
ep = strpbrk(ep, s_eof_chars);
if (ep && nfields)
while (--nfields && ep && *ep == ',')
ep = strpbrk(ep + 1, s_eof_chars);
return (ep)
? (int)((UCC*)ep - cp)
: (int)strlen((char const*)cp);
}
#endif /* DEBUG */

/* /[,*\r\n]/ --> skip */
static int _parse_eof(UCC *cp, UCC ** ep)
{
int rc = (strchr(s_eof_chars, *(char const*)cp) != NULL);
*ep = cp + rc;
return rc;
}

/* /,/ --> skip */
static int _parse_sep(UCC *cp, UCC ** ep)
{
int rc = (*cp == ',');
*ep = cp + rc;
return rc;
}

/* /[[:digit:]]{2}/ --> uint16_t */
static int _parse_num2d(UCC *cp, UCC ** ep, uint16_t *into)
{
int rc = FALSE;

if (isdigit(cp[0]) && isdigit(cp[1])) {
*into = (cp[0] - '0') * 10 + (cp[1] - '0');
cp += 2;
rc = TRUE;
}
*ep = cp;
return rc;
}

/* /[[:digit:]]+/ --> uint16_t */
static int _parse_u16(UCC *cp, UCC **ep, uint16_t *into, unsigned int ndig)
{
uint16_t num = 0;
int rc = FALSE;
if (isdigit(*cp) && ndig) {
rc = TRUE;
do
num = (num * 10) + (*cp - '0');
while (isdigit(*++cp) && --ndig);
*into = num;
}
*ep = cp;
return rc;
}

/* /[[:digit:]]+/ --> uint32_t */
static int _parse_u32(UCC *cp, UCC **ep, uint32_t *into, unsigned int ndig)
{
uint32_t num = 0;
int rc = FALSE;
if (isdigit(*cp) && ndig) {
rc = TRUE;
do
num = (num * 10) + (*cp - '0');
while (isdigit(*++cp) && --ndig);
*into = num;
}
*ep = cp;
return rc;
}

/* /(\.[[:digit:]]*)?/ --> l_fp{0, f}
* read fractional seconds, convert to l_fp
*
* Only the first 9 decimal digits are evaluated; any excess is parsed
* away but silently ignored. (--> truncation to 1 nanosecond)
*/
static int _parse_frac(UCC *cp, UCC **ep, l_fp *into)
{
static const uint32_t powtab[10] = {
0,
100000000, 10000000, 1000000,
100000, 10000, 1000,
100, 10, 1
};

struct timespec ts;
ZERO(ts);
if (*cp == '.') {
uint32_t fval = 0;
UCC * sp = cp + 1;
if (_parse_u32(sp, &cp, &fval, 9))
ts.tv_nsec = fval * powtab[(size_t)(cp - sp)];
while (isdigit(*cp))
++cp;
}

*ep = cp;
*into = tspec_intv_to_lfp(ts);
return TRUE;
}

/* /[[:digit:]]{6}/ --> time-of-day
* parses a number string representing 'HHMMSS'
*/
static int _parse_time(UCC *cp, UCC ** ep, TCivilDate *into)
{
uint16_t s, m, h;
int rc;
UCC * xp = cp;

rc = _parse_num2d(cp, &cp, &h) && (h < 24)
&& _parse_num2d(cp, &cp, &m) && (m < 60)
&& _parse_num2d(cp, &cp, &s) && (s < 61); /* leap seconds! */

if (rc) {
into->hour = (uint8_t)h;
into->minute = (uint8_t)m;
into->second = (uint8_t)s;
*ep = cp;
} else {
*ep = xp;
DPRINTF(1, ("nmea: invalid time code: '%.*s'\n",
field_length(xp, 1), xp));
}
return rc;
}

/* /[[:digit:]]{6}/ --> civil date
* parses a number string representing 'ddmmyy'
*/
static int _parse_date1(UCC *cp, UCC **ep, TCivilDate *into)
{
unsigned short d, m, y;
int rc;
UCC * xp = cp;

rc = _parse_num2d(cp, &cp, &d) && (d - 1 < 31)
&& _parse_num2d(cp, &cp, &m) && (m - 1 < 12)
&& _parse_num2d(cp, &cp, &y)
&& _parse_eof(cp, ep);
if (rc) {
into->monthday = (uint8_t )d;
into->month = (uint8_t )m;
into->year = (uint16_t)y;
*ep = cp;
} else {
*ep = xp;
DPRINTF(1, ("nmea: invalid date code: '%.*s'\n",
field_length(xp, 1), xp));
}
return rc;
}

/* /[[:digit:]]+,[[:digit:]]+,[[:digit:]]+/ --> civil date
* parses three successive numeric fields as date: day,month,year
*/
static int _parse_date3(UCC *cp, UCC **ep, TCivilDate *into)
{
uint16_t d, m, y;
int rc;
UCC * xp = cp;

rc = _parse_u16(cp, &cp, &d, 2) && (d - 1 < 31)
&& _parse_sep(cp, &cp)
&& _parse_u16(cp, &cp, &m, 2) && (m - 1 < 12)
&& _parse_sep(cp, &cp)
&& _parse_u16(cp, &cp, &y, 4) && (y > 1980)
&& _parse_eof(cp, ep);
if (rc) {
into->monthday = (uint8_t )d;
into->month = (uint8_t )m;
into->year = (uint16_t)y;
*ep = cp;
} else {
*ep = xp;
DPRINTF(1, ("nmea: invalid date code: '%.*s'\n",
field_length(xp, 3), xp));
}
return rc;
}

/*
* -------------------------------------------------------------------
* 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 = 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 */
l_fp * fofs, /* storage for nsec fraction */
nmea_data * rd,
int idx
)
{
UCC * dp = (UCC*)field_parse(rd, idx);

return _parse_time(dp, &dp, jd)
&& _parse_frac(dp, &dp, fofs)
&& _parse_eof (dp, &dp);
}

/*
* -------------------------------------------------------------------
* 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
)
{
UCC * dp = (UCC*)field_parse(rd, idx);

switch (fmt) {
case DATE_1_DDMMYY:
return _parse_date1(dp, &dp, jd);
case DATE_3_DDMMYYYY:
return _parse_date3(dp, &dp, jd);
default:
DPRINTF(1, ("nmea: invalid parse format: %d\n", fmt));
break;
}
return FALSE;
}

/*
* -------------------------------------------------------------------
* 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_gpsw(
TGpsDatum * wd,
nmea_data * rd,
int weekidx,
int timeidx,
int leapidx
)
{
uint32_t secs;
uint16_t week, leap = 0;
l_fp fofs;
int rc;

UCC * dpw = (UCC*)field_parse(rd, weekidx);
UCC * dps = (UCC*)field_parse(rd, timeidx);

rc = _parse_u16 (dpw, &dpw, &week, 5)
&& _parse_eof (dpw, &dpw)
&& _parse_u32 (dps, &dps, &secs, 9)
&& _parse_frac(dps, &dps, &fofs)
&& _parse_eof (dps, &dps)
&& (secs < 7*SECSPERDAY);
if (rc && leapidx > 0) {
UCC * dpl = (UCC*)field_parse(rd, leapidx);
rc = _parse_u16 (dpl, &dpl, &leap, 5)
&& _parse_eof (dpl, &dpl);
}
if (rc) {
fofs.l_ui -= leap;
*wd = gpscal_from_gpsweek(week, secs, fofs);
} else {
DPRINTF(1, ("nmea: parse_gpsw: invalid weektime spec\n"));
}
return rc;
}

#ifdef HAVE_PPSAPI
static double
tabsdiffd(
l_fp t1,
l_fp t2
)
{
double dd;
L_SUB(&t1, &t2);
LFPTOD(&t1, dd);
return fabs(dd);
}
#endif /* HAVE_PPSAPI */

/*
* ===================================================================
*
* NMEAD support
*
* original nmead support added by Jon Miner ([email protected])
*
* 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);
if (fd != -1)
make_socket_nonblocking(fd);
# else
fd = -1;
# endif

return fd;
}
#else
NONEMPTY_TRANSLATION_UNIT
#endif /* REFCLOCK && CLOCK_NMEA */