nfs/lib/daemon.c

	daemon.c revision 250a073308fb9258903f57b76eeb2470c6926efe
/*
 * 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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/* LINTLIBRARY */
/* PROTOLIB1 */

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

/* NFS server */

#include <sys/param.h>
#include <sys/types.h>
#include <errno.h>
#include <stdio.h>
#include <stdio_ext.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <libscf.h>

/*
 * The parent never returns from this function. It sits
 * and waits for the child to send status on whether it
 * loaded or not.
 *
 * We do not close down the standard file descriptors until
 * we know the child is going to run.
 */
int
daemonize_init(void)
{
    int status, pfds[2];
    sigset_t set, oset;
    pid_t pid;

    /*
     * Block all signals prior to the fork and leave them blocked in the
     * parent so we don't get in a situation where the parent gets SIGINT
     * and returns non-zero exit status and the child is actually running.
     * In the child, restore the signal mask once we've done our setsid().
     */
    (void) sigfillset(&set);
    (void) sigdelset(&set, SIGABRT);
    (void) sigprocmask(SIG_BLOCK, &set, &oset);

    /*
     * We need to do this before we open the pipe - it makes things
     * easier in the long run.
     */
    closefrom(STDERR_FILENO + 1);

    if (pipe(pfds) == -1) {
        fprintf(stderr, "failed to create pipe for daemonize");
        exit(SMF_EXIT_ERR_FATAL);
    }

    if ((pid = fork()) == -1) {
        fprintf(stderr, "failed to fork into background");
        exit(SMF_EXIT_ERR_FATAL);
    }

    if (pid != 0) {
        (void) close(pfds[1]);

        if (read(pfds[0], &status, sizeof (status)) == sizeof (status))
            exit(status);

        if (waitpid(pid, &status, 0) == pid && WIFEXITED(status))
            exit(WEXITSTATUS(status));

        exit(SMF_EXIT_ERR_FATAL);
    }

    /*
     * All child from here on...
     */
    (void) setsid();
    (void) sigprocmask(SIG_SETMASK, &oset, NULL);
    (void) close(pfds[0]);

    return (pfds[1]);
}

/*
 * We are only a daemon if the file descriptor is valid.
 */
void
daemonize_fini(int fd)
{
    int status = 0;

    if (fd != -1) {
        (void) write(fd, &status, sizeof (status));

        (void) close(fd);

        if ((fd = open("/dev/null", O_RDWR)) >= 0) {
            (void) fcntl(fd, F_DUP2FD, STDIN_FILENO);
            (void) fcntl(fd, F_DUP2FD, STDOUT_FILENO);
            (void) fcntl(fd, F_DUP2FD, STDERR_FILENO);
            (void) close(fd);
        }
    }
}