/*-
 * 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/time.h>
#include <sys/ioctl.h>
#include <sys/param.h>
#include <sys/linker.h>
#include <sys/mount.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/utsname.h>
#include <assert.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <libgen.h>
#include <libutil.h>
#include <netdb.h>
#include <signal.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "autofs_ioctl.h"

#include "common.h"

#define AUTOMOUNTD_PIDFILE      "/var/run/automountd.pid"

static int nchildren = 0;
static int autofs_fd;
static int request_id;

static void
done(int request_error, bool wildcards)
{
        struct autofs_daemon_done add;
        int error;

        memset(&add, 0, sizeof(add));
        add.add_id = request_id;
        add.add_wildcards = wildcards;
        add.add_error = request_error;

        log_debugx("completing request %d with error %d",
            request_id, request_error);

        error = ioctl(autofs_fd, AUTOFSDONE, &add);
        if (error != 0)
                log_warn("AUTOFSDONE");
}

/*
 * Remove "fstype=whatever" from optionsp and return the "whatever" part.
 */
static char *
pick_option(const char *option, char **optionsp)
{
        char *tofree, *pair, *newoptions;
        char *picked = NULL;
        bool first = true;

        tofree = *optionsp;

        newoptions = calloc(1, strlen(*optionsp) + 1);
        if (newoptions == NULL)
                log_err(1, "calloc");

        while ((pair = strsep(optionsp, ",")) != NULL) {
                /*
                 * XXX: strncasecmp(3) perhaps?
                 */
                if (strncmp(pair, option, strlen(option)) == 0) {
                        picked = checked_strdup(pair + strlen(option));
                } else {
                        if (first == false)
                                strcat(newoptions, ",");
                        else
                                first = false;
                        strcat(newoptions, pair);
                }
        }

        free(tofree);
        *optionsp = newoptions;

        return (picked);
}

static void
create_subtree(const struct node *node, bool incomplete)
{
        const struct node *child;
        char *path;
        bool wildcard_found = false;

        /*
         * Skip wildcard nodes.
         */
        if (strcmp(node->n_key, "*") == 0)
                return;

        path = node_path(node);
        log_debugx("creating subtree at %s", path);
        create_directory(path);

        if (incomplete) {
                TAILQ_FOREACH(child, &node->n_children, n_next) {
                        if (strcmp(child->n_key, "*") == 0) {
                                wildcard_found = true;
                                break;
                        }
                }

                if (wildcard_found) {
                        log_debugx("node %s contains wildcard entry; "
                            "not creating its subdirectories due to -d flag",
                            path);
                        free(path);
                        return;
                }
        }

        free(path);

        TAILQ_FOREACH(child, &node->n_children, n_next)
                create_subtree(child, incomplete);
}

static void
exit_callback(void)
{

        done(EIO, true);
}

static void
handle_request(const struct autofs_daemon_request *adr, char *cmdline_options,
    bool incomplete_hierarchy)
{
        const char *map;
        struct node *root, *parent, *node;
        FILE *f;
        char *key, *options, *fstype, *nobrowse, *retrycnt, *tmp;
        int error;
        bool wildcards;

        log_debugx("got request %d: from %s, path %s, prefix \"%s\", "
            "key \"%s\", options \"%s\"", adr->adr_id, adr->adr_from,
            adr->adr_path, adr->adr_prefix, adr->adr_key, adr->adr_options);

        /*
         * Try to notify the kernel about any problems.
         */
        request_id = adr->adr_id;
        atexit(exit_callback);

        if (strncmp(adr->adr_from, "map ", 4) != 0) {
                log_errx(1, "invalid mountfrom \"%s\"; failing request",
                    adr->adr_from);
        }

        map = adr->adr_from + 4; /* 4 for strlen("map "); */
        root = node_new_root();
        if (adr->adr_prefix[0] == '\0' || strcmp(adr->adr_prefix, "/") == 0) {
                /*
                 * Direct map.  autofs(4) doesn't have a way to determine
                 * correct map key, but since it's a direct map, we can just
                 * use adr_path instead.
                 */
                parent = root;
                key = checked_strdup(adr->adr_path);
        } else {
                /*
                 * Indirect map.
                 */
                parent = node_new_map(root, checked_strdup(adr->adr_prefix),
                    NULL,  checked_strdup(map),
                    checked_strdup("[kernel request]"), lineno);

                if (adr->adr_key[0] == '\0')
                        key = NULL;
                else
                        key = checked_strdup(adr->adr_key);
        }

        /*
         * "Wildcards" here actually means "make autofs(4) request
         * automountd(8) action if the node being looked up does not
         * exist, even though the parent is marked as cached".  This
         * needs to be done for maps with wildcard entries, but also
         * for special and executable maps.
         */
        parse_map(parent, map, key, &wildcards);
        if (!wildcards)
                wildcards = node_has_wildcards(parent);
        if (wildcards)
                log_debugx("map may contain wildcard entries");
        else
                log_debugx("map does not contain wildcard entries");

        if (key != NULL)
                node_expand_wildcard(root, key);

        node = node_find(root, adr->adr_path);
        if (node == NULL) {
                log_errx(1, "map %s does not contain key for \"%s\"; "
                    "failing mount", map, adr->adr_path);
        }

        options = node_options(node);

        /*
         * Append options from auto_master.
         */
        options = concat(options, ',', adr->adr_options);

        /*
         * Prepend options passed via automountd(8) command line.
         */
        options = concat(cmdline_options, ',', options);

        if (node->n_location == NULL) {
                log_debugx("found node defined at %s:%d; not a mountpoint",
                    node->n_config_file, node->n_config_line);

                nobrowse = pick_option("nobrowse", &options);
                if (nobrowse != NULL && key == NULL) {
                        log_debugx("skipping map %s due to \"nobrowse\" "
                            "option; exiting", map);
                        done(0, true);

                        /*
                         * Exit without calling exit_callback().
                         */
                        quick_exit(0);
                }

                /*
                 * Not a mountpoint; create directories in the autofs mount
                 * and complete the request.
                 */
                create_subtree(node, incomplete_hierarchy);

                if (incomplete_hierarchy && key != NULL) {
                        /*
                         * We still need to create the single subdirectory
                         * user is trying to access.
                         */
                        tmp = concat(adr->adr_path, '/', key);
                        node = node_find(root, tmp);
                        if (node != NULL)
                                create_subtree(node, false);
                }

                log_debugx("nothing to mount; exiting");
                done(0, wildcards);

                /*
                 * Exit without calling exit_callback().
                 */
                quick_exit(0);
        }

        log_debugx("found node defined at %s:%d; it is a mountpoint",
            node->n_config_file, node->n_config_line);

        if (key != NULL)
                node_expand_ampersand(node, key);
        error = node_expand_defined(node);
        if (error != 0) {
                log_errx(1, "variable expansion failed for %s; "
                    "failing mount", adr->adr_path);
        }

        /*
         * Append "automounted".
         */
        options = concat(options, ',', "automounted");

        /*
         * Remove "nobrowse", mount(8) doesn't understand it.
         */
        pick_option("nobrowse", &options);

        /*
         * Figure out fstype.
         */
        fstype = pick_option("fstype=", &options);
        if (fstype == NULL) {
                log_debugx("fstype not specified in options; "
                    "defaulting to \"nfs\"");
                fstype = checked_strdup("nfs");
        }

        if (strcmp(fstype, "nfs") == 0) {
                /*
                 * The mount_nfs(8) command defaults to retry undefinitely.
                 * We do not want that behaviour, because it leaves mount_nfs(8)
                 * instances and automountd(8) children hanging forever.
                 * Disable retries unless the option was passed explicitly.
                 */
                retrycnt = pick_option("retrycnt=", &options);
                if (retrycnt == NULL) {
                        log_debugx("retrycnt not specified in options; "
                            "defaulting to 1");
                        options = concat(options, ',', "retrycnt=1");
                } else {
                        options = concat(options, ',',
                            concat("retrycnt", '=', retrycnt));
                }
        }

        f = auto_popen("mount", "-t", fstype, "-o", options,
            node->n_location, adr->adr_path, NULL);
        assert(f != NULL);
        error = auto_pclose(f);
        if (error != 0)
                log_errx(1, "mount failed");

        log_debugx("mount done; exiting");
        done(0, wildcards);

        /*
         * Exit without calling exit_callback().
         */
        quick_exit(0);
}

static void
sigchld_handler(int dummy __unused)
{

        /*
         * The only purpose of this handler is to make SIGCHLD
         * interrupt the AUTOFSREQUEST ioctl(2), so we can call
         * wait_for_children().
         */
}

static void
register_sigchld(void)
{
        struct sigaction sa;
        int error;

        bzero(&sa, sizeof(sa));
        sa.sa_handler = sigchld_handler;
        sigfillset(&sa.sa_mask);
        error = sigaction(SIGCHLD, &sa, NULL);
        if (error != 0)
                log_err(1, "sigaction");

}


static int
wait_for_children(bool block)
{
        pid_t pid;
        int status;
        int num = 0;

        for (;;) {
                /*
                 * If "block" is true, wait for at least one process.
                 */
                if (block && num == 0)
                        pid = wait4(-1, &status, 0, NULL);
                else
                        pid = wait4(-1, &status, WNOHANG, NULL);
                if (pid <= 0)
                        break;
                if (WIFSIGNALED(status)) {
                        log_warnx("child process %d terminated with signal %d",
                            pid, WTERMSIG(status));
                } else if (WEXITSTATUS(status) != 0) {
                        log_debugx("child process %d terminated with exit status %d",
                            pid, WEXITSTATUS(status));
                } else {
                        log_debugx("child process %d terminated gracefully", pid);
                }
                num++;
        }

        return (num);
}

static void
usage_automountd(void)
{

        fprintf(stderr, "usage: automountd [-D name=value][-m maxproc]"
            "[-o opts][-Tidv]\n");
        exit(1);
}

int
main_automountd(int argc, char **argv)
{
        struct pidfh *pidfh;
        pid_t pid, otherpid;
        const char *pidfile_path = AUTOMOUNTD_PIDFILE;
        char *options = NULL;
        struct autofs_daemon_request request;
        int ch, debug = 0, error, maxproc = 30, retval, saved_errno;
        bool dont_daemonize = false, incomplete_hierarchy = false;

        defined_init();

        while ((ch = getopt(argc, argv, "D:Tdim:o:v")) != -1) {
                switch (ch) {
                case 'D':
                        defined_parse_and_add(optarg);
                        break;
                case 'T':
                        /*
                         * For compatibility with other implementations,
                         * such as OS X.
                         */
                        debug++;
                        break;
                case 'd':
                        dont_daemonize = true;
                        debug++;
                        break;
                case 'i':
                        incomplete_hierarchy = true;
                        break;
                case 'm':
                        maxproc = atoi(optarg);
                        break;
                case 'o':
                        options = concat(options, ',', optarg);
                        break;
                case 'v':
                        debug++;
                        break;
                case '?':
                default:
                        usage_automountd();
                }
        }
        argc -= optind;
        if (argc != 0)
                usage_automountd();

        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);
        }

        autofs_fd = open(AUTOFS_PATH, O_RDWR | O_CLOEXEC);
        if (autofs_fd < 0 && errno == ENOENT) {
                saved_errno = errno;
                retval = kldload("autofs");
                if (retval != -1)
                        autofs_fd = open(AUTOFS_PATH, O_RDWR | O_CLOEXEC);
                else
                        errno = saved_errno;
        }
        if (autofs_fd < 0)
                log_err(1, "failed to open %s", AUTOFS_PATH);

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

        pidfile_write(pidfh);

        register_sigchld();

        for (;;) {
                log_debugx("waiting for request from the kernel");

                memset(&request, 0, sizeof(request));
                error = ioctl(autofs_fd, AUTOFSREQUEST, &request);
                if (error != 0) {
                        if (errno == EINTR) {
                                nchildren -= wait_for_children(false);
                                assert(nchildren >= 0);
                                continue;
                        }

                        log_err(1, "AUTOFSREQUEST");
                }

                if (dont_daemonize) {
                        log_debugx("not forking due to -d flag; "
                            "will exit after servicing a single request");
                } else {
                        nchildren -= wait_for_children(false);
                        assert(nchildren >= 0);

                        while (maxproc > 0 && nchildren >= maxproc) {
                                log_debugx("maxproc limit of %d child processes hit; "
                                    "waiting for child process to exit", maxproc);
                                nchildren -= wait_for_children(true);
                                assert(nchildren >= 0);
                        }
                        log_debugx("got request; forking child process #%d",
                            nchildren);
                        nchildren++;

                        pid = fork();
                        if (pid < 0)
                                log_err(1, "fork");
                        if (pid > 0)
                                continue;
                }

                pidfile_close(pidfh);
                handle_request(&request, options, incomplete_hierarchy);
        }

        pidfile_close(pidfh);

        return (0);
}