Really handle SIG_TERM outside the signal handler

[bpdyndnsd] / src / main.cpp

/** @file
 * @brief The main function.
 *
 *
 *
 * @copyright Intra2net AG
 * @license GPLv2
*/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#define PIDFILE "/var/run/bpdyndnsd/bpdyndnsd.pid"

#include <iostream>
#include <fstream>
#include <list>
#include <string>
#include <boost/foreach.hpp>
#include <sys/types.h>
#include <signal.h>

#include "updater.hpp"

using namespace std;

Updater::Ptr updater;
volatile bool need_config_reload = false;
volatile bool exit_now = false;

volatile bool caught_sig_term = false;
volatile bool caught_sig_usr1 = false;
volatile bool caught_sig_usr2 = false;
volatile bool caught_sig_rtmin1 = false;

/**
 * Checks if a bpdyndnsd process is already running.
 * @param updater Shared Pointer to updater, needed for logging.
 * @return 0 if process not running already or pid of already running process.
 */
int check_for_running_process()
{
    ifstream pidfile(PIDFILE);
    if ( pidfile.is_open() )
    {
        int pid;
        pidfile >> pid;
        if ( pid > 0 )
            updater->get_logger()->print_pid_found(pid);
        else
            return 0;

        // check if process still running ret_val==-1 -> not runnig, ret_val==0 -> running
        if ( kill(pid,0) == 0)
        {
            updater->get_logger()->print_process_already_running(pid);
            pidfile.close();
            return pid;
        }
    }
    pidfile.close();
    return 0;
}


/**
 * Writes the pid into the pidfile.
 * @param pid The process's pid.
 */
int write_pidfile(int pid)
{
    ofstream pidfile(PIDFILE);
    if ( pidfile.is_open() )
    {
        pidfile << pid << endl;
    }
    else
    {
        updater->get_logger()->print_error_opening_rw(PIDFILE);
        return -1;
    }
    pidfile.close();
    return 0;
}


/**
 * Parent shutdown function
 * @return 0 if all is fine, -1 otherwise
 */
int shutdown_parent(bool remove_pid, int ret_val)
{
    // starting shutdown_parent
    updater->get_logger()->print_starting_shutdown_parent();

    // remove pidfile if requested
    if(remove_pid)
        unlink(PIDFILE);

    // shutdown parent complete
    updater->get_logger()->print_shutdown_parent_succeeded();

    // release shared pointer
    updater.reset();

    exit(ret_val);
}


/**
 * Shutdown function
 * @return 0 if all is fine, -1 otherwise
 */
int shutdown()
{
    int ret_val = 0;

    // starting shutdown
    updater->get_logger()->print_starting_shutdown();

    // serialize actual service objects
    if ( updater->get_service_holder()->serialize_services() != 0 )
        ret_val = -1;

    // unlink pidfile
    unlink(PIDFILE);

    // shutdown complete
    updater->get_logger()->print_shutdown_succeeded();

    // release shared pointer
    updater.reset();

    return ret_val;
}


/**
 * Signal SIGTERM caught, releasing resources and exit.
 * @param param Parameter from the signal interface.
 */
void terminate(int param)
{
    caught_sig_term = true;
} /*lint !e715 */


/**
 * Signal SIGUSR1 caught, switching to offline mode.
 * @param param Parameter from the signal interface.
 */
void switch_to_offline(int param)
{
    caught_sig_usr1 = true;
} /*lint !e715 */


/**
 * Signal SIGHUP caught, reloading config.
 * @param param Parameter from the signal interface.
 */
void reload_config(int param)
{
    need_config_reload = true;
} /*lint !e715 */


/**
 * Signal SIGUSR2 caught, switching to online mode.
 * @param param Parameter from the signal interface.
 */
void switch_to_online(int param)
{
    caught_sig_usr2 = true;
} /*lint !e715 */


/**
 * Signal SIGRTMIN caught, switching to online mode with webcheck enabled.
 * @param param Parameter from the signal interface.
 */
void switch_to_online_webcheck(int param)
{
    caught_sig_rtmin1 = true;
} /*lint !e715 */


/**
 * Initialize the signals we handle.
 * @return 0 if all is fine, -1 on error.
 */
int init_signals()
{
    sighandler_t ret_val;
    ret_val = signal(SIGTERM,terminate);
    if ( ret_val == SIG_ERR )
    {
        updater->get_logger()->print_error_setting_signal("SIGTERM");
        return -1;
    }
    ret_val = signal(SIGUSR1,switch_to_offline);
    if ( ret_val == SIG_ERR )
    {
        updater->get_logger()->print_error_setting_signal("SIGUSR1");
        return -1;
    }
    ret_val = signal(SIGHUP,reload_config);
    if ( ret_val == SIG_ERR )
    {
        updater->get_logger()->print_error_setting_signal("SIGHUP");
        return -1;
    }
    ret_val = signal(SIGUSR2,switch_to_online);
    if ( ret_val == SIG_ERR )
    {
        updater->get_logger()->print_error_setting_signal("SIGUSR2");
        return -1;
    }
    ret_val = signal(SIGRTMIN,switch_to_online_webcheck);
    if ( ret_val == SIG_ERR )
    {
        updater->get_logger()->print_error_setting_signal("SIGRTMIN");
        return -1;
    }

    return 0;
}


/**
 * Try to run in daemon mode if enabled in config.
 * @param daemon_mode True if process should detach to init (run as daemon), false if not detach to init.
 * @return 0 if all is fine, -1 on error.
 */
int init_daemon_mode(bool daemon_mode)
{
    updater->get_logger()->print_daemon_mode(daemon_mode);
    if ( daemon_mode == true )
    {
        int pid = fork();
        if ( pid < 0 )
        {
            // error fork
            updater->get_logger()->print_error_fork();
            return -1;
        }
        else if ( pid > 0 )
        {
            // parent continues here
            if ( write_pidfile(pid) != 0 )
            {
                if ( kill(pid,SIGTERM) != 0 )
                {
                    updater->get_logger()->print_error_kill_child(pid);
                    shutdown_parent(false,-1); /*lint !e534 */
                }
                else
                {
                    updater->get_logger()->print_child_killed(pid);
                    shutdown_parent(true,-1); /*lint !e534 */
                }
            }
            updater->get_logger()->print_runnig_as_daemon(pid);
            shutdown_parent(false,0); /*lint !e534 */
        }
        // child starts here
    }
    else
    {
        if ( write_pidfile(getpid()) != 0 )
        {
            shutdown(); /*lint !e534 */
            exit(-1);
        }
    }
    return 0;
}

/**
 * @brief The main part.
 * @param argc Number of arguments
 * @param argv Command line arguments
 * @return 0 if all is fine.
 */
int main(int argc, char *argv[])
{
    // initialize Updater
    updater = Updater::Ptr(new Updater);

    // load config and initialize helper classes
    if ( updater->load_config(argc,argv) != 0 )
        return -1;

    // open pidfile and check for running process
    if ( check_for_running_process() != 0)
        return -1;

    // init signal handling
    if ( init_signals() != 0)
        return -1;

    // init daemon_mode if enabled
    if ( init_daemon_mode(updater->get_config()->get_daemon_mode()) != 0 )
        return -1;

    // Should we start in offline mode?
    bool is_online = !updater->get_config()->get_start_offline();
    bool webcheck_enabled = updater->get_config()->get_webcheck_enabled();

    // One shot run if daemon mode is disabled
    if (updater->get_config()->get_daemon_mode() != 1)
        exit_now = true;

    // service processing starts here
    do
    {
        // Signal processing
        if (caught_sig_usr1)
        {
            caught_sig_usr1 = false;
            updater->get_logger()->print_caught_siguser1();

            // Go offline
            is_online = false;
        } else if (caught_sig_usr2)
        {
            caught_sig_usr2 = false;
            updater->get_logger()->print_caught_siguser2();

            // Go online
            is_online = true;
            webcheck_enabled = false;
        } else if (caught_sig_rtmin1)
        {
            caught_sig_rtmin1 = false;
            updater->get_logger()->print_caught_sigrtmin();

            // Go online - with webcheck
            is_online = true;
            webcheck_enabled = true;
        } else if (caught_sig_term)
        {
            caught_sig_term = true;
            updater->get_logger()->print_caught_sigterm();

            exit_now = true;
        }

        // State handling
        if ( is_online == true )
        {
            // Check if webcheck_enabled differs due to caught singnal then set it in config correspondingly
            if ( updater->get_config()->get_webcheck_enabled() != webcheck_enabled )    /*lint !e731 */
                updater->get_config()->set_webcheck_enabled(webcheck_enabled);

            // update all configured services
            updater->update_services();
        }
        else
        {
            // We are in offline mode, do nothing, expect printing "offline mode".
            updater->get_logger()->print_offline_mode();
        }

        if (need_config_reload)
        {
            updater->get_logger()->print_caught_sighup();
            need_config_reload = false;

            if ( updater->reload_config() != 0 )
            {
                updater->get_logger()->print_conf_reload_failed_exit();
                exit(-1);
            }
        }

        // Snore, snore... don't hog the cpu if we are in daemon_mode.
        if ( !exit_now )
            sleep(10); /*lint !e534 */
    } while ( !exit_now );

    // Serialize services to save their actual state.
    if ( shutdown() != 0 )
        return -1;

    return 0;
}