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/**
* @file ntpshm.c
* @brief Implements a servo providing the NTP SHM reference clock to
* send the samples to another process.
* @note Copyright (C) 2014 Miroslav Lichvar <mlichvar@redhat.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#include <stdlib.h>
#include <sys/types.h>
#include <sys/shm.h>
#include "config.h"
#include "print.h"
#include "ntpshm.h"
#include "servo_private.h"
/* NTP leap values */
#define LEAP_NORMAL 0x0
#define LEAP_INSERT 0x1
#define LEAP_DELETE 0x2
/* Key of the first SHM segment */
#define SHMKEY 0x4e545030
/* Declaration of the SHM segment from ntp (ntpd/refclock_shm.c) */
struct shmTime {
int mode; /* 0 - if valid set
* use values,
* clear valid
* 1 - if valid set
* if count before and after read of values is equal,
* use values
* clear valid
*/
volatile int count;
time_t clockTimeStampSec;
int clockTimeStampUSec;
time_t receiveTimeStampSec;
int receiveTimeStampUSec;
int leap;
int precision;
int nsamples;
volatile int valid;
int clockTimeStampNSec;
int receiveTimeStampNSec;
int dummy[8];
};
struct ntpshm_servo {
struct servo servo;
struct shmTime *shm;
int leap;
};
static void ntpshm_destroy(struct servo *servo)
{
struct ntpshm_servo *s = container_of(servo, struct ntpshm_servo, servo);
/* Invalidate the SHM data before exiting */
s->shm->valid = 0;
shmdt(s->shm);
free(s);
}
static double ntpshm_sample(struct servo *servo,
int64_t offset,
uint64_t local_ts,
double weight,
enum servo_state *state)
{
struct ntpshm_servo *s = container_of(servo, struct ntpshm_servo, servo);
uint64_t clock_ts = local_ts - offset;
s->shm->mode = 1;
s->shm->count++;
s->shm->valid = 0;
/* TODO: write memory barrier */
s->shm->clockTimeStampSec = clock_ts / NS_PER_SEC;
s->shm->clockTimeStampNSec = clock_ts % NS_PER_SEC;
s->shm->clockTimeStampUSec = s->shm->clockTimeStampNSec / 1000;
s->shm->receiveTimeStampSec = local_ts / NS_PER_SEC;
s->shm->receiveTimeStampNSec = local_ts % NS_PER_SEC;
s->shm->receiveTimeStampUSec = s->shm->receiveTimeStampNSec / 1000;
s->shm->precision = -30; /* 1 nanosecond */
switch (s->leap) {
case -1:
s->shm->leap = LEAP_DELETE;
break;
case 1:
s->shm->leap = LEAP_INSERT;
break;
default:
s->shm->leap = LEAP_NORMAL;
}
/* TODO: write memory barrier */
s->shm->count++;
s->shm->valid = 1;
*state = SERVO_UNLOCKED;
return 0.0;
}
static void ntpshm_sync_interval(struct servo *servo, double interval)
{
}
static void ntpshm_reset(struct servo *servo)
{
}
static void ntpshm_leap(struct servo *servo, int leap)
{
struct ntpshm_servo *s = container_of(servo, struct ntpshm_servo, servo);
s->leap = leap;
}
struct servo *ntpshm_servo_create(struct config *cfg)
{
struct ntpshm_servo *s;
int ntpshm_segment = config_get_int(cfg, NULL, "ntpshm_segment");
int shmid;
s = calloc(1, sizeof(*s));
if (!s)
return NULL;
s->servo.destroy = ntpshm_destroy;
s->servo.sample = ntpshm_sample;
s->servo.sync_interval = ntpshm_sync_interval;
s->servo.reset = ntpshm_reset;
s->servo.leap = ntpshm_leap;
shmid = shmget(SHMKEY + ntpshm_segment, sizeof (struct shmTime),
IPC_CREAT | 0600);
if (shmid == -1) {
pr_err("ntpshm: shmget failed: %m");
free(s);
return NULL;
}
s->shm = (struct shmTime *)shmat(shmid, 0, 0);
if (s->shm == (void *)-1) {
pr_err("ntpshm: shmat failed: %m");
free(s);
return NULL;
}
return &s->servo;
}
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