/*

 * Copyright (c) 2014 Nicira, Inc.

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at:

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

#include <config.h>

#include "daemon.h"

#include "daemon-private.h"

#include <errno.h>

#include <fcntl.h>

#include <unistd.h>

#include "util.h"

#include "ovs-thread.h"

#include "openvswitch/vlog.h"

VLOG_DEFINE_THIS_MODULE(daemon);

/* For each of the standard file descriptors, whether to replace it by

 * /dev/null (if false) or keep it for the daemon to use (if true). */

static bool save_fds[3];

/* Self Confinement is a security feature that introduces additional

 * layer of defense where OVS in self-denying manner would refuse to connect

 * to or create unix domain sockets outside designated 'run' directory even

 * if remote (or local) OVSDB manager asked it to do so.  This feature may

 * be disabled if Mandatory Access Control is used. */

static bool self_confine = true;

/* Will daemonize() really detach? */

bool

get_detach(void)

{

    return detach;

}

/* If configured with set_pidfile() or set_detach(), creates the pid file and

 * detaches from the foreground session.  */

void

daemonize(void)

{

    daemonize_start(false, false);

    daemonize_complete();

}

/* Sets up a following call to daemonize() to create a pidfile named 'name'.

 * If 'name' begins with '/', then it is treated as an absolute path.

 * Otherwise, it is taken relative to RUNDIR, which is $(prefix)/var/run

 * by default.

 *

 * If 'name' is null, then program_name followed by ".pid" is used. */

void

set_pidfile(const char *name)

{

    assert_single_threaded();

    free(pidfile);

    pidfile = make_pidfile_name(name);

}

/* Disables self confinement. */

void

daemon_disable_self_confinement(void)

{

    self_confine = false;

}

/* Returns true, if self-confinement should be enforced.

 * Otherwise, returns false. */

bool

daemon_should_self_confine(void)

{

    return self_confine;

}

/* A daemon doesn't normally have any use for the file descriptors for stdin,

 * stdout, and stderr after it detaches.  To keep these file descriptors from

 * e.g. holding an SSH session open, by default detaching replaces each of

 * these file descriptors by /dev/null.  But a few daemons expect the user to

 * redirect stdout or stderr to a file, in which case it is desirable to keep

 * these file descriptors.  This function, therefore, disables replacing 'fd'

 * by /dev/null when the daemon detaches. */

void

daemon_save_fd(int fd)

{

    ovs_assert(fd == STDIN_FILENO ||

               fd == STDOUT_FILENO ||

               fd == STDERR_FILENO);

    save_fds[fd] = true;

}

/* Returns a readable and writable fd for /dev/null, if successful, otherwise

 * a negative errno value.  The caller must not close the returned fd (because

 * the same fd will be handed out to subsequent callers). */

static int

get_null_fd(void)

{

    static int null_fd;

    char *device = "/dev/null";

    if (!null_fd) {

        null_fd = open(device, O_RDWR);

        if (null_fd < 0) {

            int error = errno;

            VLOG_ERR("could not open %s: %s", device, ovs_strerror(error));

            null_fd = -error;

        }

    }

    return null_fd;

}

/* Close standard file descriptors (except any that the client has requested we

 * leave open by calling daemon_save_fd()).  If we're started from e.g. an SSH

 * session, then this keeps us from holding that session open artificially. */

void

close_standard_fds(void)

{

    int null_fd = get_null_fd();

    if (null_fd >= 0) {

        int fd;

        for (fd = 0; fd < 3; fd++) {

            if (!save_fds[fd]) {

                dup2(null_fd, fd);

            }

        }

    }

    /* Disable logging to stderr to avoid wasting CPU time. */

    vlog_set_levels(NULL, VLF_CONSOLE, VLL_OFF);

}