// SPDX-License-Identifier: GPL-2.0-only
/*
 * linux/net/netfilter/xt_IDLETIMER.c
 *
 * Netfilter module to trigger a timer when packet matches.
 * After timer expires a kevent will be sent.
 *
 * Copyright (C) 2004, 2010 Nokia Corporation
 * Written by Timo Teras <ext-timo.teras@nokia.com>
 *
 * Converted to x_tables and reworked for upstream inclusion
 * by Luciano Coelho <luciano.coelho@nokia.com>
 *
 * Contact: Luciano Coelho <luciano.coelho@nokia.com>
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/timer.h>
#include <linux/alarmtimer.h>
#include <linux/list.h>
#include <linux/mutex.h>
#include <linux/netfilter.h>
#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_IDLETIMER.h>
#include <linux/kdev_t.h>
#include <linux/kobject.h>
#include <linux/workqueue.h>
#include <linux/sysfs.h>

struct idletimer_tg {
        struct list_head entry;
        struct alarm alarm;
        struct timer_list timer;
        struct work_struct work;

        struct kobject *kobj;
        struct device_attribute attr;

        unsigned int refcnt;
        u8 timer_type;
};

static LIST_HEAD(idletimer_tg_list);
static DEFINE_MUTEX(list_mutex);

static struct kobject *idletimer_tg_kobj;

static
struct idletimer_tg *__idletimer_tg_find_by_label(const char *label)
{
        struct idletimer_tg *entry;

        list_for_each_entry(entry, &idletimer_tg_list, entry) {
                if (!strcmp(label, entry->attr.attr.name))
                        return entry;
        }

        return NULL;
}

static ssize_t idletimer_tg_show(struct device *dev,
                                 struct device_attribute *attr, char *buf)
{
        struct idletimer_tg *timer;
        unsigned long expires = 0;
        struct timespec64 ktimespec = {};
        long time_diff = 0;

        mutex_lock(&list_mutex);

        timer = __idletimer_tg_find_by_label(attr->attr.name);
        if (timer) {
                if (timer->timer_type & XT_IDLETIMER_ALARM) {
                        ktime_t expires_alarm = alarm_expires_remaining(&timer->alarm);
                        ktimespec = ktime_to_timespec64(expires_alarm);
                        time_diff = ktimespec.tv_sec;
                } else {
                        expires = timer->timer.expires;
                        time_diff = jiffies_to_msecs(expires - jiffies) / 1000;
                }
        }

        mutex_unlock(&list_mutex);

        if (time_after(expires, jiffies) || ktimespec.tv_sec > 0)
                return sysfs_emit(buf, "%ld\n", time_diff);

        return sysfs_emit(buf, "0\n");
}

static void idletimer_tg_work(struct work_struct *work)
{
        struct idletimer_tg *timer = container_of(work, struct idletimer_tg,
                                                  work);

        sysfs_notify(idletimer_tg_kobj, NULL, timer->attr.attr.name);
}

static void idletimer_tg_expired(struct timer_list *t)
{
        struct idletimer_tg *timer = timer_container_of(timer, t, timer);

        pr_debug("timer %s expired\n", timer->attr.attr.name);

        schedule_work(&timer->work);
}

static void idletimer_tg_alarmproc(struct alarm *alarm, ktime_t now)
{
        struct idletimer_tg *timer = alarm->data;

        pr_debug("alarm %s expired\n", timer->attr.attr.name);
        schedule_work(&timer->work);
}

static int idletimer_check_sysfs_name(const char *name, unsigned int size)
{
        int ret;

        ret = xt_check_proc_name(name, size);
        if (ret < 0)
                return ret;

        if (!strcmp(name, "power") ||
            !strcmp(name, "subsystem") ||
            !strcmp(name, "uevent"))
                return -EINVAL;

        return 0;
}

static int idletimer_tg_create(struct idletimer_tg_info *info)
{
        int ret;

        info->timer = kzalloc_obj(*info->timer);
        if (!info->timer) {
                ret = -ENOMEM;
                goto out;
        }

        ret = idletimer_check_sysfs_name(info->label, sizeof(info->label));
        if (ret < 0)
                goto out_free_timer;

        sysfs_attr_init(&info->timer->attr.attr);
        info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
        if (!info->timer->attr.attr.name) {
                ret = -ENOMEM;
                goto out_free_timer;
        }
        info->timer->attr.attr.mode = 0444;
        info->timer->attr.show = idletimer_tg_show;

        ret = sysfs_create_file(idletimer_tg_kobj, &info->timer->attr.attr);
        if (ret < 0) {
                pr_debug("couldn't add file to sysfs");
                goto out_free_attr;
        }

        list_add(&info->timer->entry, &idletimer_tg_list);

        timer_setup(&info->timer->timer, idletimer_tg_expired, 0);
        info->timer->refcnt = 1;

        INIT_WORK(&info->timer->work, idletimer_tg_work);

        mod_timer(&info->timer->timer,
                  secs_to_jiffies(info->timeout) + jiffies);

        return 0;

out_free_attr:
        kfree(info->timer->attr.attr.name);
out_free_timer:
        kfree(info->timer);
out:
        return ret;
}

static int idletimer_tg_create_v1(struct idletimer_tg_info_v1 *info)
{
        int ret;

        info->timer = kmalloc_obj(*info->timer);
        if (!info->timer) {
                ret = -ENOMEM;
                goto out;
        }

        ret = idletimer_check_sysfs_name(info->label, sizeof(info->label));
        if (ret < 0)
                goto out_free_timer;

        sysfs_attr_init(&info->timer->attr.attr);
        info->timer->attr.attr.name = kstrdup(info->label, GFP_KERNEL);
        if (!info->timer->attr.attr.name) {
                ret = -ENOMEM;
                goto out_free_timer;
        }
        info->timer->attr.attr.mode = 0444;
        info->timer->attr.show = idletimer_tg_show;

        ret = sysfs_create_file(idletimer_tg_kobj, &info->timer->attr.attr);
        if (ret < 0) {
                pr_debug("couldn't add file to sysfs");
                goto out_free_attr;
        }

        /*  notify userspace  */
        kobject_uevent(idletimer_tg_kobj,KOBJ_ADD);

        list_add(&info->timer->entry, &idletimer_tg_list);
        pr_debug("timer type value is %u", info->timer_type);
        info->timer->timer_type = info->timer_type;
        info->timer->refcnt = 1;

        INIT_WORK(&info->timer->work, idletimer_tg_work);

        if (info->timer->timer_type & XT_IDLETIMER_ALARM) {
                ktime_t tout;
                alarm_init(&info->timer->alarm, ALARM_BOOTTIME,
                           idletimer_tg_alarmproc);
                info->timer->alarm.data = info->timer;
                tout = ktime_set(info->timeout, 0);
                alarm_start_relative(&info->timer->alarm, tout);
        } else {
                timer_setup(&info->timer->timer, idletimer_tg_expired, 0);
                mod_timer(&info->timer->timer,
                                secs_to_jiffies(info->timeout) + jiffies);
        }

        return 0;

out_free_attr:
        kfree(info->timer->attr.attr.name);
out_free_timer:
        kfree(info->timer);
out:
        return ret;
}

/*
 * The actual xt_tables plugin.
 */
static unsigned int idletimer_tg_target(struct sk_buff *skb,
                                         const struct xt_action_param *par)
{
        const struct idletimer_tg_info *info = par->targinfo;

        pr_debug("resetting timer %s, timeout period %u\n",
                 info->label, info->timeout);

        mod_timer(&info->timer->timer,
                  secs_to_jiffies(info->timeout) + jiffies);

        return XT_CONTINUE;
}

/*
 * The actual xt_tables plugin.
 */
static unsigned int idletimer_tg_target_v1(struct sk_buff *skb,
                                         const struct xt_action_param *par)
{
        const struct idletimer_tg_info_v1 *info = par->targinfo;

        pr_debug("resetting timer %s, timeout period %u\n",
                 info->label, info->timeout);

        if (info->timer->timer_type & XT_IDLETIMER_ALARM) {
                ktime_t tout = ktime_set(info->timeout, 0);
                alarm_start_relative(&info->timer->alarm, tout);
        } else {
                mod_timer(&info->timer->timer,
                                secs_to_jiffies(info->timeout) + jiffies);
        }

        return XT_CONTINUE;
}

static int idletimer_tg_helper(struct idletimer_tg_info *info)
{
        if (info->timeout == 0) {
                pr_debug("timeout value is zero\n");
                return -EINVAL;
        }
        if (info->timeout >= INT_MAX / 1000) {
                pr_debug("timeout value is too big\n");
                return -EINVAL;
        }
        if (info->label[0] == '\0' ||
            strnlen(info->label,
                    MAX_IDLETIMER_LABEL_SIZE) == MAX_IDLETIMER_LABEL_SIZE) {
                pr_debug("label is empty or not nul-terminated\n");
                return -EINVAL;
        }
        return 0;
}


static int idletimer_tg_checkentry(const struct xt_tgchk_param *par)
{
        struct idletimer_tg_info *info = par->targinfo;
        int ret;

        pr_debug("checkentry targinfo%s\n", info->label);

        ret = idletimer_tg_helper(info);
        if(ret < 0)
        {
                pr_debug("checkentry helper return invalid\n");
                return -EINVAL;
        }
        mutex_lock(&list_mutex);

        info->timer = __idletimer_tg_find_by_label(info->label);
        if (info->timer) {
                if (info->timer->timer_type & XT_IDLETIMER_ALARM) {
                        pr_debug("Adding/Replacing rule with same label and different timer type is not allowed\n");
                        mutex_unlock(&list_mutex);
                        return -EINVAL;
                }

                info->timer->refcnt++;
                mod_timer(&info->timer->timer,
                          secs_to_jiffies(info->timeout) + jiffies);

                pr_debug("increased refcnt of timer %s to %u\n",
                         info->label, info->timer->refcnt);
        } else {
                ret = idletimer_tg_create(info);
                if (ret < 0) {
                        pr_debug("failed to create timer\n");
                        mutex_unlock(&list_mutex);
                        return ret;
                }
        }

        mutex_unlock(&list_mutex);
        return 0;
}

static int idletimer_tg_checkentry_v1(const struct xt_tgchk_param *par)
{
        struct idletimer_tg_info_v1 *info = par->targinfo;
        int ret;

        pr_debug("checkentry targinfo%s\n", info->label);

        if (info->send_nl_msg)
                return -EOPNOTSUPP;

        ret = idletimer_tg_helper((struct idletimer_tg_info *)info);
        if(ret < 0)
        {
                pr_debug("checkentry helper return invalid\n");
                return -EINVAL;
        }

        if (info->timer_type > XT_IDLETIMER_ALARM) {
                pr_debug("invalid value for timer type\n");
                return -EINVAL;
        }

        mutex_lock(&list_mutex);

        info->timer = __idletimer_tg_find_by_label(info->label);
        if (info->timer) {
                if (info->timer->timer_type != info->timer_type) {
                        pr_debug("Adding/Replacing rule with same label and different timer type is not allowed\n");
                        mutex_unlock(&list_mutex);
                        return -EINVAL;
                }

                info->timer->refcnt++;
                if (info->timer_type & XT_IDLETIMER_ALARM) {
                        /* calculate remaining expiry time */
                        ktime_t tout = alarm_expires_remaining(&info->timer->alarm);
                        struct timespec64 ktimespec = ktime_to_timespec64(tout);

                        if (ktimespec.tv_sec > 0) {
                                pr_debug("time_expiry_remaining %lld\n",
                                         ktimespec.tv_sec);
                                alarm_start_relative(&info->timer->alarm, tout);
                        }
                } else {
                                mod_timer(&info->timer->timer,
                                        secs_to_jiffies(info->timeout) + jiffies);
                }
                pr_debug("increased refcnt of timer %s to %u\n",
                         info->label, info->timer->refcnt);
        } else {
                ret = idletimer_tg_create_v1(info);
                if (ret < 0) {
                        pr_debug("failed to create timer\n");
                        mutex_unlock(&list_mutex);
                        return ret;
                }
        }

        mutex_unlock(&list_mutex);
        return 0;
}

static void idletimer_tg_destroy(const struct xt_tgdtor_param *par)
{
        const struct idletimer_tg_info *info = par->targinfo;

        pr_debug("destroy targinfo %s\n", info->label);

        mutex_lock(&list_mutex);

        if (--info->timer->refcnt > 0) {
                pr_debug("decreased refcnt of timer %s to %u\n",
                         info->label, info->timer->refcnt);
                mutex_unlock(&list_mutex);
                return;
        }

        pr_debug("deleting timer %s\n", info->label);

        list_del(&info->timer->entry);
        mutex_unlock(&list_mutex);

        timer_shutdown_sync(&info->timer->timer);
        cancel_work_sync(&info->timer->work);
        sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr);
        kfree(info->timer->attr.attr.name);
        kfree(info->timer);
}

static void idletimer_tg_destroy_v1(const struct xt_tgdtor_param *par)
{
        const struct idletimer_tg_info_v1 *info = par->targinfo;

        pr_debug("destroy targinfo %s\n", info->label);

        mutex_lock(&list_mutex);

        if (--info->timer->refcnt > 0) {
                pr_debug("decreased refcnt of timer %s to %u\n",
                         info->label, info->timer->refcnt);
                mutex_unlock(&list_mutex);
                return;
        }

        pr_debug("deleting timer %s\n", info->label);

        list_del(&info->timer->entry);
        mutex_unlock(&list_mutex);

        if (info->timer->timer_type & XT_IDLETIMER_ALARM) {
                alarm_cancel(&info->timer->alarm);
        } else {
                timer_shutdown_sync(&info->timer->timer);
        }
        cancel_work_sync(&info->timer->work);
        sysfs_remove_file(idletimer_tg_kobj, &info->timer->attr.attr);
        kfree(info->timer->attr.attr.name);
        kfree(info->timer);
}


static struct xt_target idletimer_tg[] __read_mostly = {
        {
                .name           = "IDLETIMER",
                .family         = NFPROTO_IPV4,
                .target         = idletimer_tg_target,
                .targetsize     = sizeof(struct idletimer_tg_info),
                .usersize       = offsetof(struct idletimer_tg_info, timer),
                .checkentry     = idletimer_tg_checkentry,
                .destroy        = idletimer_tg_destroy,
                .me             = THIS_MODULE,
        },
        {
                .name           = "IDLETIMER",
                .family         = NFPROTO_IPV4,
                .revision       = 1,
                .target         = idletimer_tg_target_v1,
                .targetsize     = sizeof(struct idletimer_tg_info_v1),
                .usersize       = offsetof(struct idletimer_tg_info_v1, timer),
                .checkentry     = idletimer_tg_checkentry_v1,
                .destroy        = idletimer_tg_destroy_v1,
                .me             = THIS_MODULE,
        },
#if IS_ENABLED(CONFIG_IP6_NF_IPTABLES)
        {
                .name           = "IDLETIMER",
                .family         = NFPROTO_IPV6,
                .target         = idletimer_tg_target,
                .targetsize     = sizeof(struct idletimer_tg_info),
                .usersize       = offsetof(struct idletimer_tg_info, timer),
                .checkentry     = idletimer_tg_checkentry,
                .destroy        = idletimer_tg_destroy,
                .me             = THIS_MODULE,
        },
        {
                .name           = "IDLETIMER",
                .family         = NFPROTO_IPV6,
                .revision       = 1,
                .target         = idletimer_tg_target_v1,
                .targetsize     = sizeof(struct idletimer_tg_info_v1),
                .usersize       = offsetof(struct idletimer_tg_info_v1, timer),
                .checkentry     = idletimer_tg_checkentry_v1,
                .destroy        = idletimer_tg_destroy_v1,
                .me             = THIS_MODULE,
        },
#endif
};

static struct class *idletimer_tg_class;

static struct device *idletimer_tg_device;

static int __init idletimer_tg_init(void)
{
        int err;

        idletimer_tg_class = class_create("xt_idletimer");
        err = PTR_ERR(idletimer_tg_class);
        if (IS_ERR(idletimer_tg_class)) {
                pr_debug("couldn't register device class\n");
                goto out;
        }

        idletimer_tg_device = device_create(idletimer_tg_class, NULL,
                                            MKDEV(0, 0), NULL, "timers");
        err = PTR_ERR(idletimer_tg_device);
        if (IS_ERR(idletimer_tg_device)) {
                pr_debug("couldn't register system device\n");
                goto out_class;
        }

        idletimer_tg_kobj = &idletimer_tg_device->kobj;

        err = xt_register_targets(idletimer_tg, ARRAY_SIZE(idletimer_tg));

        if (err < 0) {
                pr_debug("couldn't register xt target\n");
                goto out_dev;
        }

        return 0;
out_dev:
        device_destroy(idletimer_tg_class, MKDEV(0, 0));
out_class:
        class_destroy(idletimer_tg_class);
out:
        return err;
}

static void __exit idletimer_tg_exit(void)
{
        xt_unregister_targets(idletimer_tg, ARRAY_SIZE(idletimer_tg));

        device_destroy(idletimer_tg_class, MKDEV(0, 0));
        class_destroy(idletimer_tg_class);
}

module_init(idletimer_tg_init);
module_exit(idletimer_tg_exit);

MODULE_AUTHOR("Timo Teras <ext-timo.teras@nokia.com>");
MODULE_AUTHOR("Luciano Coelho <luciano.coelho@nokia.com>");
MODULE_DESCRIPTION("Xtables: idle time monitor");
MODULE_LICENSE("GPL v2");
MODULE_ALIAS("ipt_IDLETIMER");
MODULE_ALIAS("ip6t_IDLETIMER");