run_kannel_box.c

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/* ==================================================================== 
 * The Kannel Software License, Version 1.0 
 * 
 * Copyright (c) 2001-2008 Kannel Group  
 * Copyright (c) 1998-2001 WapIT Ltd.   
 * All rights reserved. 
 * 
 * Redistribution and use in source and binary forms, with or without 
 * modification, are permitted provided that the following conditions 
 * are met: 
 * 
 * 1. Redistributions of source code must retain the above copyright 
 *    notice, this list of conditions and the following disclaimer. 
 * 
 * 2. Redistributions in binary form must reproduce the above copyright 
 *    notice, this list of conditions and the following disclaimer in 
 *    the documentation and/or other materials provided with the 
 *    distribution. 
 * 
 * 3. The end-user documentation included with the redistribution, 
 *    if any, must include the following acknowledgment: 
 *       "This product includes software developed by the 
 *        Kannel Group (http://www.kannel.org/)." 
 *    Alternately, this acknowledgment may appear in the software itself, 
 *    if and wherever such third-party acknowledgments normally appear. 
 * 
 * 4. The names "Kannel" and "Kannel Group" must not be used to 
 *    endorse or promote products derived from this software without 
 *    prior written permission. For written permission, please  
 *    contact org@kannel.org. 
 * 
 * 5. Products derived from this software may not be called "Kannel", 
 *    nor may "Kannel" appear in their name, without prior written 
 *    permission of the Kannel Group. 
 * 
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED 
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE 
 * DISCLAIMED.  IN NO EVENT SHALL THE KANNEL GROUP OR ITS CONTRIBUTORS 
 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,  
 * OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT  
 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR  
 * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,  
 * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE  
 * OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,  
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 * ==================================================================== 
 * 
 * This software consists of voluntary contributions made by many 
 * individuals on behalf of the Kannel Group.  For more information on  
 * the Kannel Group, please see <http://www.kannel.org/>. 
 * 
 * Portions of this software are based upon software originally written at  
 * WapIT Ltd., Helsinki, Finland for the Kannel project.  
 */ 

#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <limits.h>

#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <time.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <signal.h>

static char *progname;  /* The name of this program (for error messages) */
static char **box_arglist;
static int min_restart_delay = 60; /* in seconds */
static pid_t child_box; /* used in main_loop, available to signal handlers */
static char *pidfile; /* The name of the pidfile to use.  NULL if no pidfile */
static int use_extra_args = 1; /* Add "extra_arguments" list to argv? */

/* Extra arguments to pass to the box */
static char *extra_arguments[] = {
    "-v", "4",   /* Minimal output on stderr, goes to /dev/null anyway */
};
#define NUM_EXTRA ((int) (sizeof(extra_arguments) / sizeof(*extra_arguments)))

static void print_usage(FILE *stream)
{
    fprintf(stream,
        "Usage: %s [--pidfile PIDFILE] [--min-delay SECONDS] BOXPATH [boxoptions...]\n",
        progname);
}

/* Create the argument list to pass to the box process, and put it
 * in the box_arglist global variable.  This is also the right place
 * to add any standard arguments that we want to pass. */
static void build_box_arglist(char *boxfile, int argc, char **argv)
{
    int i;
    char **argp;

    if (box_arglist) {
        free(box_arglist);
    }

    /* one for the boxfile name itself, one for each extra argument,
     * one for each normal argument, and one for the terminating NULL */
    box_arglist = malloc((1 + NUM_EXTRA + argc + 1) * sizeof(*box_arglist));
    if (!box_arglist) {
        fprintf(stderr, "%s: malloc: %s\n", progname, strerror(errno));
        exit(1);
    }

    /* Have argp walk down box_arglist and set each argument. */
    argp = box_arglist;

    *argp++ = boxfile;
        if (use_extra_args) {
        for (i = 0; i < NUM_EXTRA; i++) {
            *argp++ = extra_arguments[i];
        }
    }
    for (i = 0; i < argc; i++) {
        *argp++ = argv[i];
    }
    *argp++ = (char *)NULL;
}

static void write_pidfile(void)
{
    int fd;
    FILE *f;

    if (!pidfile)
        return;

    fd = open(pidfile, O_WRONLY|O_NOCTTY|O_TRUNC|O_CREAT, 0644);
    if (fd < 0) {
        fprintf(stderr, "%s: open: %s: %s\n", progname, pidfile, strerror(errno));
        exit(1);
    }

    f = fdopen(fd, "w");
    if (!f) {
        fprintf(stderr, "%s: fdopen: %s\n", progname, strerror(errno));
        exit(1);
    }

    fprintf(f, "%ld\n", (long)getpid());
    if (fclose(f) < 0) {
        fprintf(stderr, "%s: writing %s: %s\n", progname, pidfile, strerror(errno));
        exit(1);
    }
}

static void remove_pidfile(void)
{
    if (!pidfile)
        return;

    unlink(pidfile);
}

/* Set 0 (stdin) to /dev/null, and 1 and 2 (stdout and stderr) to /dev/full
 * if it's available and /dev/null otherwise. */
static void rebind_standard_streams(void)
{
    int devnullfd;
    int devfullfd;

    devnullfd = open("/dev/null", O_RDONLY);
    if (devnullfd < 0) {
        fprintf(stderr, "%s: cannot open /dev/null: %s\n",
            progname, strerror(errno));
        exit(2);
    }
    devfullfd = open("/dev/full", O_WRONLY);
    if (devfullfd < 0) {
        devfullfd = devnullfd;
    }

    /* Alert: The dup on stderr is done last, so that the error message
     * works regardless of which dup fails. */
    if (dup2(devnullfd, 0) < 0 ||
        dup2(devfullfd, 1) < 0 ||
        dup2(devfullfd, 2) < 0) {
        fprintf(stderr, "%s: dup2: %s\n", progname, strerror(errno));
        exit(1);
    }
}

/* Some code to determine the highest possible file descriptor number,
 * so that we can close them all.  */
static int open_max(void)
{
#ifdef OPEN_MAX
    return OPEN_MAX;
#else
    int max;

    max = sysconf(_SC_OPEN_MAX);
    if (max <= 0) {
        return 1024;  /* guess */
    }
    return max;
#endif
}

/* Close all file descriptors other than 0, 1, and 2. */
static void close_extra_files(void)
{
    int max = open_max();
    int fd;

    for (fd = 3; fd < max; fd++) {
        close(fd);
    }
}

/* We received a signal that we should pass on to the child box.
 * We ignore it ourselves. */
static void signal_transfer(int signum)
{
    if (child_box > 0) {
        kill(child_box, signum);
    }
}

/* We received a signal that we should pass on to the child box,
 * and then die from ourselves.  It has to be a signal that
 * terminates the process as its default action! */
static void signal_transfer_and_die(int signum)
{
    /* First send it to the child process */
    if (child_box > 0) {
        kill(child_box, signum);
    }

    /* Prepare to die.  Normally the atexit handler would take care
     * of this when we exit(), but we're going to die from a signal. */
    remove_pidfile();

    /* Then send it to self.  First set the default handler, to
     * avoid catching the signal with this handler again.  This
     * is not a race, because it doesn't matter if we die from
     * the signal we're going to send or from a different one.  */
    signal(signum, SIG_DFL);
    kill(getpid(), signum);
}

static void setup_signals(void)
{
    signal(SIGHUP, &signal_transfer);
    signal(SIGINT, &signal_transfer_and_die);
    signal(SIGQUIT, &signal_transfer_and_die);
    signal(SIGTERM, &signal_transfer_and_die);
    signal(SIGUSR1, &signal_transfer);
    signal(SIGUSR2, &signal_transfer);
}

/* Fork off a box process and loop indefinitely, forking a new one
 * every time it dies. */
static int main_loop(char *boxfile)
{
    time_t next_fork = 0;

    /* We can't report any errors here, because we are running
     * as a daemon and we have no logfile of our own.  So we
     * exit with errno as the exit code, to offer a minimal clue. */

    for (;;) {

        /* Make sure we don't fork in an endless loop if something
         * is drastically wrong.  This code limits it to one
         * per minute (or whatever min_restart_delay is set to). */
        time_t this_time = time(NULL);
        if (this_time <= next_fork) {
            sleep(next_fork - this_time);
        }
        next_fork = this_time + min_restart_delay;

        child_box = fork();
        if (child_box < 0) {
            return errno;
        }
        if (child_box == 0) {
            /* child.  exec the box */
            execvp(boxfile, box_arglist);
            exit(127);
        }
        
        while (waitpid(child_box, (int *)NULL, 0) != child_box) {
            if (errno == ECHILD) {
                /* Something went wrong... we don't know what,
                 * but we do know that our child does not
                 * exist.  So restart it. */
                break;
            }
            if (errno == EINTR) {
                continue;
            }
            /* Something weird happened. */
            return errno;
        }
    }
}

int main(int argc, char *argv[])
{
    int i;
    char *boxfile = NULL;
    pid_t childpid;

    progname = argv[0];

    if (argc == 1) {
        print_usage(stderr);
        exit(2);
    }

    /* Parse the options meant for the wrapper, and get the name of
     * the box to wrap. */
    for (i = 1; i < argc && !boxfile; i++) {
        if (strcmp(argv[i], "--pidfile") == 0) {
            if (i+1 >= argc) {
                fprintf(stderr, "Missing argument for option %s\n", argv[i]);
                exit(2);
            }
            pidfile = argv[i+1];
            i++;
        } else if (strcmp(argv[i], "--min-delay") == 0) {
            if (i+1 >= argc) {
                fprintf(stderr, "Missing argument for option %s", argv[i]);
                exit(2);
            }
            min_restart_delay = atoi(argv[i+1]);
            i++;
        } else if (strcmp(argv[i], "--no-extra-args") == 0) {
                use_extra_args = 0;
        } else if (argv[i][0] == '-') {
            fprintf(stderr, "Unknown option %s\n", argv[i]);
            exit(2);
        } else {
            boxfile = argv[i];
        }
    }

    /* Check if we have everything */
    if (!boxfile) {
        print_usage(stderr);
        exit(2);
    }

    /* The remaining arguments should be passed to the box */
    build_box_arglist(boxfile, argc - i, argv + i);

    /* Ready to rock.  Begin daemonization. */

    /* Fork a child process and have the parent exit.
         * This makes us run in the background. */
    childpid = fork();
    if (childpid < 0) {
        fprintf(stderr, "%s: fork: %s\n", progname, strerror(errno));
        exit(1);
    }
    if (childpid != 0) {
        exit(0); /* parent exits immediately */
    }
    
    /* The child continues here.  Now call setsid() to disconnect
     * from our terminal and from the parent's session and process
     * group. */
    if (setsid() < 0) {
        fprintf(stderr, "%s: setsid: %s\n", progname, strerror(errno));
        exit(1);
    }

    /* Change to the root directory, so that we don't keep a
     * file descriptor open on an unknown directory. */
    if (chdir("/") < 0) {
        fprintf(stderr, "%s: chdir to root: %s\n", progname, strerror(errno));
        exit(1);
    }

    atexit(remove_pidfile);
    write_pidfile();

    /* Set the umask to a known value, rather than inheriting
     * an unknown one. */
    umask(077);

    /* Leave file descriptors 0, 1, and 2 pointing to harmless
     * places, and close all other file descriptors. */
    rebind_standard_streams();
    close_extra_files();

    setup_signals();
    return main_loop(boxfile);
}

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