gps-watchdog is a small tool that will connect to gpsd as a client using libgps. If no data is received for a configurable timeout, a configurable systemd service will be killed via 'systemctl kill'. The idea is that this will restart gpsd, and some ExecStartPre of the gpsd service is then re-initializing the gps receiver hardware.master
parent
cb50b4bb9f
commit
8c0f608643
@ -1,11 +1,16 @@
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CFLAGS=-Wall -O2
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all: gpsdate gps-watchdog
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gpsdate: gpsdate.o
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$(CC) $(LDFLAGS) -o $@ $^ -lgps
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gps-watchdog: gps-watchdog.o
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$(CC) $(LDFLAGS) -o $@ $^ -lgps
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%.o: %.c
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$(CC) $(CFLAGS) -o $@ -c $^
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clean:
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@rm -f gpsdate *.o
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@rm -f gpsdate gps-watchdog *.o
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@ -0,0 +1,277 @@
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/* gps-wd - small utility to restart gpsd if no data is received
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* (C) 2013-2015 by sysmocom - s.f.m.c. GmbH, Author: Harald Welte
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* All Rights Reserved
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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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/* The idea of this program is that you run it once at system boot time,
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* to set the local RTC to the time received by GPS. Further synchronization
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* during system runtime is then handled by ntpd, interfacing with gpsd using
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* the ntp shared memory protocol.
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*
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* However, ntpd is unable to accept a GPS time that's off by more than four
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* hours from the system RTC, so initial synchronization has to be done
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* externally. 'ntpdate' is the usual option, but doesn't work if you're
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* offline. Thus, this gpsdate utilith was created to fill the gap.
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*/
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#include <stdlib.h>
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#include <stdio.h>
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#include <errno.h>
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#include <unistd.h>
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#include <string.h>
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#include <syslog.h>
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#include <getopt.h>
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#include <sys/time.h>
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <gps.h>
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#define NUM_RETRIES 60 /* Number of gpsd re-connects */
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#define RETRY_SLEEP 1 /* Seconds to sleep between re-connects */
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#define TIMEOUT 10 /* max Number of seconds without sentence */
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static int no_detach = 0;
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static int timeout = TIMEOUT;
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static struct gps_data_t gpsdata;
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static char *service_name = "gpsd.service";
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static void callback(struct gps_data_t *gpsdata)
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{
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/* we received some data but gpsd itself believes the receiver
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* to be offline */
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if (gpsdata->online == 0)
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return;
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/* re-set the alarm to the timeout */
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alarm(timeout);
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}
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static int osmo_daemonize(void)
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{
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int rc;
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pid_t pid, sid;
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/* Check if parent PID == init, in which case we are already a daemon */
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if (getppid() == 1)
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return -EEXIST;
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/* Fork from the parent process */
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pid = fork();
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if (pid < 0) {
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/* some error happened */
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return pid;
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}
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if (pid > 0) {
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/* if we have received a positive PID, then we are the parent
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* and can exit */
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exit(0);
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}
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/* FIXME: do we really want this? */
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umask(0);
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/* Create a new session and set process group ID */
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sid = setsid();
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if (sid < 0)
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return sid;
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/* Change to the /tmp directory, which prevents the CWD from being locked
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* and unable to remove it */
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rc = chdir("/tmp");
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if (rc < 0)
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return rc;
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/* Redirect stdio to /dev/null */
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/* since C89/C99 says stderr is a macro, we can safely do this! */
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#ifdef stderr
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freopen("/dev/null", "r", stdin);
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freopen("/dev/null", "w", stdout);
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freopen("/dev/null", "w", stderr);
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#endif
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return 0;
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}
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/* local copy, as the libgps official version ignores gps_read() result */
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static int my_gps_mainloop(struct gps_data_t *gdata,
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int timeout,
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void (*hook)(struct gps_data_t *gdata))
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{
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int rc;
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for (;;) {
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if (!gps_waiting(gdata, timeout)) {
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return -1;
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} else {
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rc = gps_read(gdata);
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if (rc < 0)
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return rc;
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(*hook)(gdata);
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}
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}
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return 0;
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}
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static int attempt_reconnect(const char *host, const char *port,
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struct gps_data_t *gpsdata)
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{
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int rc;
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rc = gps_open(host, port, gpsdata);
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if (rc)
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return -1;
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syslog(LOG_INFO, "(re)connected to gpsd\n");
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gps_stream(gpsdata, WATCH_ENABLE|WATCH_JSON, NULL);
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return 0;
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}
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enum state {
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S_CONNECTED,
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S_RECONNECT,
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};
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static void alarm_hdlr(int signal)
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{
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char buf[256];
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if (signal != SIGALRM)
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return;
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/* the timeout has expired. restart gpsd */
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syslog(LOG_ERR, "%d seconds without data from gpsd, "
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"stopping gpsd\n", timeout);
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snprintf(buf, sizeof(buf), "systemctl kill %s", service_name);
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system(buf);
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exit(EXIT_FAILURE);
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}
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int main(int argc, char **argv)
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{
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char *host = "localhost";
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char *port = DEFAULT_GPSD_PORT;
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int num_retries = NUM_RETRIES;
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int retry_sleep = RETRY_SLEEP;
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int i, rc;
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enum state state;
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openlog("gps-wd", LOG_PERROR, LOG_CRON);
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while (1) {
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int option_index = 0, c;
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static struct option long_options[] = {
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{"num-retries", 1, 0, 'n'},
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{"retry-sleep", 1, 0, 's'},
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{"no-detach", 0, 0, 'd'},
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{"timeout", 1, 0, 't'},
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{"service-name", 1, 0, 'r'},
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{0,0,0,0}
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};
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c = getopt_long(argc, argv, "n:s:dt:r:",
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long_options, &option_index);
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if (c == -1)
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break;
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switch (c) {
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case 'n':
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num_retries = atoi(optarg);
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break;
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case 's':
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retry_sleep = atoi(optarg);
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break;
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case 'd':
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no_detach = 1;
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break;
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case 't':
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timeout = atoi(optarg);
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break;
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case 'r':
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service_name = optarg;
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break;
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}
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}
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if (optind < argc)
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host = argv[optind++];
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if (optind < argc)
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port = argv[optind++];
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syslog(LOG_INFO, "starting gps-wd for %s:%s (timeout %ds, service %s)",
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host, port, timeout, service_name);
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/* attempt up to NUM_RETRIES times to connect to gpsd while we are
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* still running in foreground. The idea is that we will block the
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* boot process (init scripts) until we have a connection */
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for (i = 1; i <= num_retries; i++) {
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printf("Attempt #%d to connect to gpsd at %s...\n", i, host);
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rc = attempt_reconnect(host, port, &gpsdata);
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if (rc >= 0)
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break;
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sleep(retry_sleep);
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}
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if (rc < 0) {
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syslog(LOG_ERR, "no gpsd running or network error: %d, %s\n",
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errno, gps_errstr(errno));
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closelog();
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exit(EXIT_FAILURE);
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}
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state = S_CONNECTED;
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if (!no_detach)
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osmo_daemonize();
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signal(SIGALRM, alarm_hdlr);
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/* We run in an endless loop. The only reasonable way to exit is after
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* a correct GPS timestamp has been received in callback() */
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while (1) {
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switch (state) {
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case S_CONNECTED:
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alarm(timeout);
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rc = my_gps_mainloop(&gpsdata, INT_MAX, callback);
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if (rc < 1) {
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syslog(LOG_ERR, "connection to gpsd was "
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"closed: %d, reconnecting\n", rc);
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gps_close(&gpsdata);
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alarm(0);
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state = S_RECONNECT;
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}
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break;
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case S_RECONNECT:
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rc = attempt_reconnect(host, port, &gpsdata);
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if (rc < 0)
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sleep(RETRY_SLEEP);
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else
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state = S_CONNECTED;
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break;
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}
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}
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gps_close(&gpsdata);
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closelog();
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exit(EXIT_SUCCESS);
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}
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Loading…
Reference in new issue