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