sbin/dhcpagent/script_handler.c

	script_handler.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <time.h>
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <signal.h>
#include <fcntl.h>
#include <dhcpmsg.h>
#include "script_handler.h"

/*
 * scripts are directly managed by a script helper process. dhcpagent creates
 * the helper process and it, in turn, creates a process to run the script
 * dhcpagent owns one end of a pipe and the helper process owns the other end
 * the helper process calls waitpid to wait for the script to exit. an alarm
 * is set for SCRIPT_TIMEOUT seconds. If the alarm fires, SIGTERM is sent to
 * the script process and a second alarm is set for SCRIPT_TIMEOUT_GRACE. if
 * the second alarm fires, SIGKILL is sent to forcefully kill the script. when
 * script exits, the helper process notifies dhcpagent by closing its end
 * of the pipe.
 */

unsigned int    script_count;

/*
 * the signal to send to the script process. it is a global variable
 * to this file as sigterm_handler needs it.
 */

static int  script_signal = SIGTERM;

/*
 * script's absolute timeout value. the first timeout is set to SCRIPT_TIMEOUT
 * seconds from the time it is started. SIGTERM is sent on the first timeout
 * the second timeout is set to SCRIPT_TIMEOUT_GRACE from the first timeout
 * and SIGKILL is sent on the second timeout.
 */
static time_t       timeout;

/*
 * sigalarm_handler(): signal handler for SIGARLM
 *
 *   input: int: signal the handler was called with
 *  output: void
 */

/* ARGSUSED */
static void
sigalarm_handler(int sig)
{
    time_t  now;

    /* set a another alarm if it fires too early */
    now = time(NULL);
    if (now < timeout)
        (void) alarm(timeout - now);
}

/*
 * sigterm_handler(): signal handler for SIGTERM, fired when dhcpagent wants
 *            to stop the script
 *   input: int: signal the handler was called with
 *  output: void
 */

/* ARGSUSED */
static void
sigterm_handler(int sig)
{
    if (script_signal != SIGKILL) {
        /* send SIGKILL SCRIPT_TIMEOUT_GRACE seconds from now */
        script_signal = SIGKILL;
        timeout = time(NULL) + SCRIPT_TIMEOUT_GRACE;
        (void) alarm(SCRIPT_TIMEOUT_GRACE);
    }
}

/*
 * run_script(): it forks a process to execute the script
 *
 *   input: struct ifslist *: the interface
 *      const char *: the event name
 *      int: the pipe end owned by the script helper process
 *  output: void
 */
static void
run_script(struct ifslist *ifsp, const char *event, int fd)
{
    int     n;
    char        c;
    char        *name;
    pid_t       pid;
    time_t      now;
    extern int  errno;

    if ((pid = fork()) == -1) {
        return;
    }
    if (pid == 0) {
        name = strrchr(SCRIPT_PATH, '/') + 1;

        /* close all files */
        closefrom(0);

        /* redirect stdin, stdout and stderr to /dev/null */
        if ((n = open("/dev/null", O_RDWR)) < 0)
            exit(-1);

        (void) dup2(n, STDOUT_FILENO);
        (void) dup2(n, STDERR_FILENO);

        (void) execl(SCRIPT_PATH, name, ifsp->if_name, event, NULL);
        _exit(127);
    }

    /*
     * the first timeout fires SCRIPT_TIMEOUT seconds from now.
     */
    timeout = time(NULL) + SCRIPT_TIMEOUT;
    (void) sigset(SIGALRM, sigalarm_handler);
    (void) alarm(SCRIPT_TIMEOUT);

    /*
     * pass script's pid to dhcpagent.
     */
    (void) write(fd, &pid, sizeof (pid));

    for (;;) {
        if (waitpid(pid, NULL, 0) >= 0) {
            /* script has exited */
            c = SCRIPT_OK;
            break;
        }

        if (errno != EINTR) {
            return;
        }

        now = time(NULL);
        if (now >= timeout) {
            (void) kill(pid, script_signal);
            if (script_signal == SIGKILL) {
                c = SCRIPT_KILLED;
                break;
            }

            script_signal = SIGKILL;
            timeout = now + SCRIPT_TIMEOUT_GRACE;
            (void) alarm(SCRIPT_TIMEOUT_GRACE);
        }
    }

    (void) write(fd, &c, 1);
}

/*
 * script_cleanup(): cleanup helper function
 *
 *   input: struct ifslist *: the interface
 *  output: void
 */

static void
script_cleanup(struct ifslist *ifsp)
{
    ifsp->if_script_helper_pid = -1;
    ifsp->if_script_pid = -1;

    if (ifsp->if_script_fd != -1) {
        assert(ifsp->if_script_event_id != -1);
        assert(ifsp->if_script_callback != NULL);

        (void) iu_unregister_event(eh, ifsp->if_script_event_id, NULL);
        (void) close(ifsp->if_script_fd);
        ifsp->if_script_event_id = -1;
        ifsp->if_script_fd = -1;
        ifsp->if_script_callback(ifsp, ifsp->if_callback_msg);
        ifsp->if_script_callback = NULL;
        ifsp->if_script_event = NULL;
        ifsp->if_callback_msg = NULL;

        (void) release_ifs(ifsp);
        script_count--;
    }
}

/*
 * script_exit(): does cleanup and invokes callback when script exits
 *
 *   input: eh_t *: unused
 *      int: the end of pipe owned by dhcpagent
 *      short: unused
 *      eh_event_id_t: unused
 *      void *: the interface
 *  output: void
 */

/* ARGSUSED */
static void
script_exit(iu_eh_t *ehp, int fd, short events, iu_event_id_t id, void *arg)
{
    char        c;

    if (read(fd, &c, 1) <= 0) {
        c = SCRIPT_FAILED;
    }

    if (c == SCRIPT_OK) {
        dhcpmsg(MSG_DEBUG, "script ok");
    } else if (c == SCRIPT_KILLED) {
        dhcpmsg(MSG_DEBUG, "script killed");
    } else {
        dhcpmsg(MSG_DEBUG, "script failed");
    }

    script_cleanup(arg);
}

/*
 * script_start(): tries to run the script
 *
 *   input: struct ifslist *: the interface
 *      const char *: the event name
 *      script_callback_t: callback function
 *      void *: data to the callback function
 *  output: int: 1 if script starts successfully
 *      int *: the returned value of the callback function if script
 *      starts unsuccessfully
 */
int
script_start(struct ifslist *ifsp, const char *event,
        script_callback_t *callback, const char *msg, int *status)
{
    int     n;
    int     fds[2];
    pid_t       pid;
    iu_event_id_t   event_id;

    assert(callback != NULL);

    if (access(SCRIPT_PATH, X_OK) == -1) {
        /* script does not exist */
        goto out;
    }
    if (ifsp->if_script_pid != -1) {
        /* script is running, stop it */
        dhcpmsg(MSG_ERROR, "script_start: stop script");
        script_stop(ifsp);
    }

    /*
     * dhcpagent owns one end of the pipe and script helper process
     * owns the other end. dhcpagent reads on the pipe; and the helper
     * process notifies it when the script exits.
     */
    if (pipe(fds) < 0) {
        dhcpmsg(MSG_ERROR, "script_start: can't create pipe");
        goto out;
    }

    if ((pid = fork()) < 0) {
        dhcpmsg(MSG_ERROR, "script_start: can't fork");
        (void) close(fds[0]);
        (void) close(fds[1]);
        goto out;
    }

    if (pid == 0) {
        /*
         * SIGCHLD is ignored in dhcpagent, the helper process
         * needs it. it calls waitpid to wait for the script to exit.
         */
        (void) close(fds[0]);
        (void) sigset(SIGCHLD, SIG_DFL);
        (void) sigset(SIGTERM, sigterm_handler);
        run_script(ifsp, event, fds[1]);
        exit(0);
    }

    (void) close(fds[1]);

    /* get the script's pid */
    if (read(fds[0], &ifsp->if_script_pid, sizeof (pid_t)) !=
        sizeof (pid_t)) {
        (void) kill(pid, SIGKILL);
        ifsp->if_script_pid = -1;
        (void) close(fds[0]);
        goto out;
    }

    ifsp->if_script_helper_pid = pid;
    event_id = iu_register_event(eh, fds[0], POLLIN, script_exit, ifsp);
    if (event_id == -1) {
        (void) close(fds[0]);
        script_stop(ifsp);
        goto out;
    }

    script_count++;
    ifsp->if_script_event_id = event_id;
    ifsp->if_script_callback = callback;
    ifsp->if_script_event = event;
    ifsp->if_callback_msg = msg;
    ifsp->if_script_fd = fds[0];
    hold_ifs(ifsp);
    return (1);

out:
    /* callback won't be called in script_exit, so call it here */
    n = callback(ifsp, msg);
    if (status != NULL)
        *status = n;

    return (0);
}

/*
 * script_stop(): stops the script if it is running
 *
 *   input: struct ifslist *: the interface
 *  output: void
 */
void
script_stop(struct ifslist *ifsp)
{
    if (ifsp->if_script_pid != -1) {
        assert(ifsp->if_script_helper_pid != -1);

        /*
         * sends SIGTERM to the script and asks the helper process
         * to send SIGKILL if it does not exit after
         * SCRIPT_TIMEOUT_GRACE seconds.
         */
        (void) kill(ifsp->if_script_pid, SIGTERM);
        (void) kill(ifsp->if_script_helper_pid, SIGTERM);
    }

    script_cleanup(ifsp);
}