bp_watchdog.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <syslog.h>
#include <errno.h>
#include <pwd.h>
#include <signal.h>

/* Change this to whatever your daemon is called */
#define DAEMON_NAME "bp_watchdog"

/* Change this to the user under which to run */
#define RUN_AS_USER "root"

#define EXIT_SUCCESS 0
#define EXIT_FAILURE 1

static void finish_app(){
    syslog( LOG_NOTICE, "terminated" );
    closelog();
}

static void child_handler(int signum) {
    switch(signum) {
        case SIGALRM: 
            exit(EXIT_FAILURE); 
            break;
	case SIGUSR1:
            exit(EXIT_SUCCESS); 
            break;
	case SIGCHLD: 
            exit(EXIT_FAILURE); 
            break;
	case SIGTERM:
            finish_app(); 
            exit(EXIT_SUCCESS); 
            break;
    }
}

static void daemonize() {
    pid_t pid, sid, parent;
    int lfp = -1;

    /* already a daemon */
    if ( getppid() == 1 ) return;

    /* Drop user if there is one, and we were run as root */
    if ( getuid() == 0 || geteuid() == 0 ) {
        struct passwd *pw = getpwnam(RUN_AS_USER);
        if ( pw ) {
            syslog( LOG_NOTICE, "setting user to " RUN_AS_USER );
            setuid( pw->pw_uid );
        }
    }

    /* Trap signals that we expect to recieve */
    signal(SIGCHLD,child_handler);
    signal(SIGUSR1,child_handler);
    signal(SIGALRM,child_handler);
    signal(SIGTERM,child_handler);

    /* Fork off the parent process */
    pid = fork();
    if (pid < 0) {
        syslog( LOG_ERR, "unable to fork daemon, code=%d (%s)", errno, strerror(errno) );
        exit(EXIT_FAILURE);
    }

    /* If we got a good PID, then we can exit the parent process. */
    if (pid > 0) {
        /* Wait for confirmation from the child via SIGTERM or SIGCHLD, or
           for two seconds to elapse (SIGALRM).  pause() should not return. */
        alarm(2);
        pause();
        exit(EXIT_FAILURE);
    }

    /* At this point we are executing as the child process */
    parent = getppid();

    /* Cancel certain signals */
    signal(SIGCHLD,SIG_DFL); /* A child process dies */
    signal(SIGTSTP,SIG_IGN); /* Various TTY signals */
    signal(SIGTTOU,SIG_IGN);
    signal(SIGTTIN,SIG_IGN);
    signal(SIGHUP, SIG_IGN); /* Ignore hangup signal */
    //signal(SIGTERM,SIG_DFL); /* Die on SIGTERM */

    /* Change the file mode mask */
    umask(0);

    /* Create a new SID for the child process */
    sid = setsid();
    if (sid < 0) {
        syslog( LOG_ERR, "unable to create a new session, code %d (%s)", errno, strerror(errno) );
        exit(EXIT_FAILURE);
    }

    /* Change the current working directory.  This prevents the current
       directory from being locked; hence not being able to remove it. */
    if ((chdir("/")) < 0) {
        syslog( LOG_ERR, "unable to change directory to %s, code %d (%s)", "/", errno, strerror(errno) );
        exit(EXIT_FAILURE);
    }

    /* Redirect standard files to /dev/null */
    freopen( "/dev/null", "r", stdin);
    freopen( "/dev/null", "w", stdout);
    freopen( "/dev/null", "w", stderr);

    /* Tell the parent process that we are A-okay */
    kill( parent, SIGUSR1 );
}


int main( int argc, char *argv[] ) {
    /* Initialize the logging interface */
    openlog( DAEMON_NAME, LOG_PID, LOG_LOCAL5 );
    syslog( LOG_INFO, "starting" );

    /* One may wish to process command line arguments here */

    /* Daemonize */
    daemonize();

    /* Now we are a daemon -- do the work for which we were paid */
    while (1){
        system("/usr/bin/bpctl_util all reset_bypass_wd");
        sleep(5);
    }

    /* Finish up */
    finish_app();
    return EXIT_SUCCESS;
}