/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2014 The FreeBSD Foundation
 *
 * This software was developed by Edward Tomasz Napierala under sponsorship
 * from the FreeBSD Foundation.
 *
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS 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 AUTHOR OR 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.
 *
 */

#include <sys/types.h>
#include <sys/event.h>
#include <sys/mount.h>
#include <sys/time.h>
#include <assert.h>
#include <errno.h>
#include <libutil.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "common.h"

#define AUTOUNMOUNTD_PIDFILE    "/var/run/autounmountd.pid"

struct automounted_fs {
        TAILQ_ENTRY(automounted_fs)     af_next;
        time_t                          af_mount_time;
        bool                            af_mark;
        fsid_t                          af_fsid;
        char                            af_mountpoint[MNAMELEN];
};

static TAILQ_HEAD(, automounted_fs)     automounted;

static struct automounted_fs *
automounted_find(fsid_t fsid)
{
        struct automounted_fs *af;

        TAILQ_FOREACH(af, &automounted, af_next) {
                if (fsidcmp(&af->af_fsid, &fsid) == 0)
                        return (af);
        }

        return (NULL);
}

static struct automounted_fs *
automounted_add(fsid_t fsid, const char *mountpoint)
{
        struct automounted_fs *af;

        af = calloc(1, sizeof(*af));
        if (af == NULL)
                log_err(1, "calloc");
        af->af_mount_time = time(NULL);
        af->af_fsid = fsid;
        strlcpy(af->af_mountpoint, mountpoint, sizeof(af->af_mountpoint));

        TAILQ_INSERT_TAIL(&automounted, af, af_next);

        return (af);
}

static void
automounted_remove(struct automounted_fs *af)
{

        TAILQ_REMOVE(&automounted, af, af_next);
        free(af);
}

static void
refresh_automounted(void)
{
        struct automounted_fs *af, *tmpaf;
        struct statfs *mntbuf;
        int i, nitems;

        nitems = getmntinfo(&mntbuf, MNT_WAIT);
        if (nitems <= 0)
                log_err(1, "getmntinfo");

        log_debugx("refreshing list of automounted filesystems");

        TAILQ_FOREACH(af, &automounted, af_next)
                af->af_mark = false;

        for (i = 0; i < nitems; i++) {
                if (strcmp(mntbuf[i].f_fstypename, "autofs") == 0) {
                        log_debugx("skipping %s, filesystem type is autofs",
                            mntbuf[i].f_mntonname);
                        continue;
                }

                if ((mntbuf[i].f_flags & MNT_AUTOMOUNTED) == 0) {
                        log_debugx("skipping %s, not automounted",
                            mntbuf[i].f_mntonname);
                        continue;
                }

                af = automounted_find(mntbuf[i].f_fsid);
                if (af == NULL) {
                        log_debugx("new automounted filesystem found on %s "
                            "(FSID:%d:%d)", mntbuf[i].f_mntonname,
                            mntbuf[i].f_fsid.val[0], mntbuf[i].f_fsid.val[1]);
                        af = automounted_add(mntbuf[i].f_fsid,
                            mntbuf[i].f_mntonname);
                } else {
                        log_debugx("already known automounted filesystem "
                            "found on %s (FSID:%d:%d)", mntbuf[i].f_mntonname,
                            mntbuf[i].f_fsid.val[0], mntbuf[i].f_fsid.val[1]);
                }
                af->af_mark = true;
        }

        TAILQ_FOREACH_SAFE(af, &automounted, af_next, tmpaf) {
                if (af->af_mark)
                        continue;
                log_debugx("lost filesystem mounted on %s (FSID:%d:%d)",
                    af->af_mountpoint, af->af_fsid.val[0], af->af_fsid.val[1]);
                automounted_remove(af);
        }
}

static int
unmount_by_fsid(const fsid_t fsid, const char *mountpoint)
{
        char *fsid_str;
        int error, ret;

        ret = asprintf(&fsid_str, "FSID:%d:%d", fsid.val[0], fsid.val[1]);
        if (ret < 0)
                log_err(1, "asprintf");

        error = unmount(fsid_str, MNT_NONBUSY | MNT_BYFSID);
        if (error != 0) {
                if (errno == EBUSY) {
                        log_debugx("cannot unmount %s (%s): %s",
                            mountpoint, fsid_str, strerror(errno));
                } else {
                        log_warn("cannot unmount %s (%s)",
                            mountpoint, fsid_str);
                }
        } else
                rpc_umntall();

        free(fsid_str);

        return (error);
}

static time_t
expire_automounted(time_t expiration_time)
{
        struct automounted_fs *af, *tmpaf;
        time_t now;
        time_t mounted_for, mounted_max = -1;
        int error;

        now = time(NULL);

        log_debugx("expiring automounted filesystems");

        TAILQ_FOREACH_SAFE(af, &automounted, af_next, tmpaf) {
                mounted_for = difftime(now, af->af_mount_time);

                if (mounted_for < expiration_time) {
                        log_debugx("skipping %s (FSID:%d:%d), mounted "
                            "for %jd  seconds", af->af_mountpoint,
                            af->af_fsid.val[0], af->af_fsid.val[1],
                            (intmax_t)mounted_for);

                        if (mounted_for > mounted_max)
                                mounted_max = mounted_for;

                        continue;
                }

                log_debugx("filesystem mounted on %s (FSID:%d:%d), "
                    "was mounted for %ld seconds; unmounting",
                    af->af_mountpoint, af->af_fsid.val[0], af->af_fsid.val[1],
                    (long)mounted_for);
                error = unmount_by_fsid(af->af_fsid, af->af_mountpoint);
                if (error != 0) {
                        if (mounted_for > mounted_max)
                                mounted_max = mounted_for;
                }
        }

        return (mounted_max);
}

static void
usage_autounmountd(void)
{

        fprintf(stderr, "usage: autounmountd [-r time][-t time][-dv]\n");
        exit(1);
}

static void
do_wait(int kq, time_t sleep_time)
{
        struct timespec timeout;
        struct kevent unused;
        int nevents;

        if (sleep_time != -1) {
                assert(sleep_time > 0);
                timeout.tv_sec = sleep_time;
                timeout.tv_nsec = 0;

                log_debugx("waiting for filesystem event for %ld seconds",
                    (long)sleep_time);
                nevents = kevent(kq, NULL, 0, &unused, 1, &timeout);
        } else {
                log_debugx("waiting for filesystem event");
                nevents = kevent(kq, NULL, 0, &unused, 1, NULL);
        }
        if (nevents < 0) {
                if (errno == EINTR)
                        return;
                log_err(1, "kevent");
        }

        if (nevents == 0) {
                log_debugx("timeout reached");
                assert(sleep_time > 0);
        } else {
                log_debugx("got filesystem event");
        }
}

int
main_autounmountd(int argc, char **argv)
{
        struct kevent event;
        struct pidfh *pidfh;
        pid_t otherpid;
        const char *pidfile_path = AUTOUNMOUNTD_PIDFILE;
        int ch, debug = 0, error, kq;
        time_t expiration_time = 600, retry_time = 600, mounted_max, sleep_time;
        bool dont_daemonize = false;

        while ((ch = getopt(argc, argv, "dr:t:v")) != -1) {
                switch (ch) {
                case 'd':
                        dont_daemonize = true;
                        debug++;
                        break;
                case 'r':
                        retry_time = atoi(optarg);
                        break;
                case 't':
                        expiration_time = atoi(optarg);
                        break;
                case 'v':
                        debug++;
                        break;
                case '?':
                default:
                        usage_autounmountd();
                }
        }
        argc -= optind;
        if (argc != 0)
                usage_autounmountd();

        if (retry_time <= 0)
                log_errx(1, "retry time must be greater than zero");
        if (expiration_time <= 0)
                log_errx(1, "expiration time must be greater than zero");

        log_init(debug);

        pidfh = pidfile_open(pidfile_path, 0600, &otherpid);
        if (pidfh == NULL) {
                if (errno == EEXIST) {
                        log_errx(1, "daemon already running, pid: %jd.",
                            (intmax_t)otherpid);
                }
                log_err(1, "cannot open or create pidfile \"%s\"",
                    pidfile_path);
        }

        if (dont_daemonize == false) {
                if (daemon(0, 0) == -1) {
                        log_warn("cannot daemonize");
                        pidfile_remove(pidfh);
                        exit(1);
                }
        }

        pidfile_write(pidfh);

        TAILQ_INIT(&automounted);

        kq = kqueue();
        if (kq < 0)
                log_err(1, "kqueue");

        EV_SET(&event, 0, EVFILT_FS, EV_ADD | EV_CLEAR, VQ_MOUNT | VQ_UNMOUNT, 0, NULL);
        error = kevent(kq, &event, 1, NULL, 0, NULL);
        if (error < 0)
                log_err(1, "kevent");

        for (;;) {
                refresh_automounted();
                mounted_max = expire_automounted(expiration_time);
                if (mounted_max == -1) {
                        sleep_time = mounted_max;
                        log_debugx("no filesystems to expire");
                } else if (mounted_max < expiration_time) {
                        sleep_time = difftime(expiration_time, mounted_max);
                        log_debugx("some filesystems expire in %ld  seconds",
                            (long)sleep_time);
                } else {
                        sleep_time = retry_time;
                        log_debugx("some expired filesystems remain mounted, "
                            "will retry in %ld  seconds", (long)sleep_time);
                }

                do_wait(kq, sleep_time);
        }

        return (0);
}