8322 nl: misleading-indentation

[unleashed/tickless.git] / usr / src / cmd / cmd-inet / sbin / dhcpagent / script_handler.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

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

#include "agent.h"
#include "script_handler.h"
#include "states.h"
#include "interface.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 SIGALRM
 *
 *   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: dhcp_smach_t *: the state machine
 *          const char *: the event name
 *          int: the pipe end owned by the script helper process
 *  output: void
 */

static void
run_script(dhcp_smach_t *dsmp, const char *event, int fd)
{
        int             n;
        char            c;
        char            *path;
        char            *name;
        pid_t           pid;
        time_t          now;

        if ((pid = fork()) == -1)
                return;

        if (pid == 0) {
                path = SCRIPT_PATH;
                name = strrchr(path, '/') + 1;

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

                /* redirect stdin, stdout and stderr to /dev/null */
                if ((n = open("/dev/null", O_RDWR)) < 0)
                        _exit(127);

                (void) dup2(n, STDOUT_FILENO);
                (void) dup2(n, STDERR_FILENO);
                (void) execl(path, name, dsmp->dsm_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_init(): initialize script state on a given state machine
 *
 *   input: dhcp_smach_t *: the state machine
 *  output: void
 */

void
script_init(dhcp_smach_t *dsmp)
{
        dsmp->dsm_script_pid = -1;
        dsmp->dsm_script_helper_pid = -1;
        dsmp->dsm_script_event_id = -1;
        dsmp->dsm_script_fd = -1;
        dsmp->dsm_script_callback = NULL;
        dsmp->dsm_script_event = NULL;
        dsmp->dsm_callback_arg = NULL;
}

/*
 * script_cleanup(): cleanup helper function
 *
 *   input: dhcp_smach_t *: the state machine
 *  output: void
 */

static void
script_cleanup(dhcp_smach_t *dsmp)
{
        /*
         * We must clear dsm_script_pid prior to invoking the callback or we
         * could get in an infinite loop via async_finish().
         */
        dsmp->dsm_script_pid = -1;
        dsmp->dsm_script_helper_pid = -1;

        if (dsmp->dsm_script_fd != -1) {
                assert(dsmp->dsm_script_event_id != -1);
                (void) iu_unregister_event(eh, dsmp->dsm_script_event_id, NULL);
                (void) close(dsmp->dsm_script_fd);

                assert(dsmp->dsm_script_callback != NULL);
                dsmp->dsm_script_callback(dsmp, dsmp->dsm_callback_arg);
                script_init(dsmp);
                script_count--;
                release_smach(dsmp);    /* hold from script_start() */
        }
}

/*
 * script_exit(): does cleanup and invokes the callback when the script exits
 *
 *   input: eh_t *: unused
 *          int: the end of pipe owned by dhcpagent
 *          short: unused
 *          eh_event_id_t: unused
 *          void *: the state machine
 *  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 start a script.
 *                 if a script is already running, it's stopped first.
 *
 *
 *   input: dhcp_smach_t *: the state machine
 *          const char *: the event name
 *          script_callback_t: callback function
 *          void *: data to the callback function
 *  output: boolean_t: B_TRUE if script starts successfully
 *          int *: the returned value of the callback function if script
 *              starts unsuccessfully
 */

boolean_t
script_start(dhcp_smach_t *dsmp, const char *event,
    script_callback_t *callback, void *arg, int *status)
{
        int             n;
        int             fds[2];
        pid_t           pid;
        iu_event_id_t   event_id;

        assert(callback != NULL);

        if (dsmp->dsm_script_pid != -1) {
                /* script is running, stop it */
                dhcpmsg(MSG_DEBUG, "script_start: stopping ongoing script");
                script_stop(dsmp);
        }

        if (access(SCRIPT_PATH, X_OK) == -1) {
                /* script does not exist */
                goto out;
        }

        /*
         * 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(dsmp, event, fds[1]);
                exit(0);
        }

        (void) close(fds[1]);

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

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

        script_count++;
        dsmp->dsm_script_event_id = event_id;
        dsmp->dsm_script_callback = callback;
        dsmp->dsm_script_event = event;
        dsmp->dsm_callback_arg = arg;
        dsmp->dsm_script_fd = fds[0];
        hold_smach(dsmp);
        return (B_TRUE);

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

        return (B_FALSE);
}

/*
 * script_stop(): stops the script if it is running
 *
 *   input: dhcp_smach_t *: the state machine
 *  output: void
 */

void
script_stop(dhcp_smach_t *dsmp)
{
        if (dsmp->dsm_script_pid != -1) {
                assert(dsmp->dsm_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(dsmp->dsm_script_pid, SIGTERM);
                (void) kill(dsmp->dsm_script_helper_pid, SIGTERM);
        }

        script_cleanup(dsmp);
}