/*
 * xt_LED.c - netfilter target to make LEDs blink upon packet matches
 *
 * Copyright (C) 2008 Adam Nielsen <a.nielsen@shikadi.net>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 *
 */
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/netfilter/x_tables.h>
#include <linux/slab.h>
#include <linux/leds.h>
#include <linux/mutex.h>

#include <linux/netfilter/xt_LED.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Adam Nielsen <a.nielsen@shikadi.net>");
MODULE_DESCRIPTION("Xtables: trigger LED devices on packet match");
MODULE_ALIAS("ipt_LED");
MODULE_ALIAS("ip6t_LED");

static LIST_HEAD(xt_led_triggers);
static DEFINE_MUTEX(xt_led_mutex);

/*
 * This is declared in here (the kernel module) only, to avoid having these
 * dependencies in userspace code.  This is what xt_led_info.internal_data
 * points to.
 */
struct xt_led_info_internal {
        struct list_head list;
        int refcnt;
        char *trigger_id;
        struct led_trigger netfilter_led_trigger;
        struct timer_list timer;
};

static unsigned int
led_tg(struct sk_buff *skb, const struct xt_action_param *par)
{
        const struct xt_led_info *ledinfo = par->targinfo;
        struct xt_led_info_internal *ledinternal = ledinfo->internal_data;

        /*
         * If "always blink" is enabled, and there's still some time until the
         * LED will switch off, briefly switch it off now.
         */
        if ((ledinfo->delay > 0) && ledinfo->always_blink &&
            timer_pending(&ledinternal->timer))
                led_trigger_event(&ledinternal->netfilter_led_trigger, LED_OFF);

        led_trigger_event(&ledinternal->netfilter_led_trigger, LED_FULL);

        /* If there's a positive delay, start/update the timer */
        if (ledinfo->delay > 0) {
                mod_timer(&ledinternal->timer,
                          jiffies + msecs_to_jiffies(ledinfo->delay));

        /* Otherwise if there was no delay given, blink as fast as possible */
        } else if (ledinfo->delay == 0) {
                led_trigger_event(&ledinternal->netfilter_led_trigger, LED_OFF);
        }

        /* else the delay is negative, which means switch on and stay on */

        return XT_CONTINUE;
}

static void led_timeout_callback(struct timer_list *t)
{
        struct xt_led_info_internal *ledinternal = from_timer(ledinternal, t,
                                                               timer);

        led_trigger_event(&ledinternal->netfilter_led_trigger, LED_OFF);
}

static struct xt_led_info_internal *led_trigger_lookup(const char *name)
{
        struct xt_led_info_internal *ledinternal;

        list_for_each_entry(ledinternal, &xt_led_triggers, list) {
                if (!strcmp(name, ledinternal->netfilter_led_trigger.name)) {
                        return ledinternal;
                }
        }
        return NULL;
}

static int led_tg_check(const struct xt_tgchk_param *par)
{
        struct xt_led_info *ledinfo = par->targinfo;
        struct xt_led_info_internal *ledinternal;
        int err;

        if (ledinfo->id[0] == '\0') {
                pr_info("No 'id' parameter given.\n");
                return -EINVAL;
        }

        mutex_lock(&xt_led_mutex);

        ledinternal = led_trigger_lookup(ledinfo->id);
        if (ledinternal) {
                ledinternal->refcnt++;
                goto out;
        }

        err = -ENOMEM;
        ledinternal = kzalloc(sizeof(struct xt_led_info_internal), GFP_KERNEL);
        if (!ledinternal)
                goto exit_mutex_only;

        ledinternal->trigger_id = kstrdup(ledinfo->id, GFP_KERNEL);
        if (!ledinternal->trigger_id)
                goto exit_internal_alloc;

        ledinternal->refcnt = 1;
        ledinternal->netfilter_led_trigger.name = ledinternal->trigger_id;

        err = led_trigger_register(&ledinternal->netfilter_led_trigger);
        if (err) {
                pr_warning("led_trigger_register() failed\n");
                if (err == -EEXIST)
                        pr_warning("Trigger name is already in use.\n");
                goto exit_alloc;
        }

        /* Since the letinternal timer can be shared between multiple targets,
         * always set it up, even if the current target does not need it
         */
        timer_setup(&ledinternal->timer, led_timeout_callback, 0);

        list_add_tail(&ledinternal->list, &xt_led_triggers);

out:
        mutex_unlock(&xt_led_mutex);

        ledinfo->internal_data = ledinternal;

        return 0;

exit_alloc:
        kfree(ledinternal->trigger_id);

exit_internal_alloc:
        kfree(ledinternal);

exit_mutex_only:
        mutex_unlock(&xt_led_mutex);

        return err;
}

static void led_tg_destroy(const struct xt_tgdtor_param *par)
{
        const struct xt_led_info *ledinfo = par->targinfo;
        struct xt_led_info_internal *ledinternal = ledinfo->internal_data;

        mutex_lock(&xt_led_mutex);

        if (--ledinternal->refcnt) {
                mutex_unlock(&xt_led_mutex);
                return;
        }

        list_del(&ledinternal->list);

        del_timer_sync(&ledinternal->timer);

        led_trigger_unregister(&ledinternal->netfilter_led_trigger);

        mutex_unlock(&xt_led_mutex);

        kfree(ledinternal->trigger_id);
        kfree(ledinternal);
}

static struct xt_target led_tg_reg __read_mostly = {
        .name           = "LED",
        .revision       = 0,
        .family         = NFPROTO_UNSPEC,
        .target         = led_tg,
        .targetsize     = sizeof(struct xt_led_info),
        .checkentry     = led_tg_check,
        .destroy        = led_tg_destroy,
        .me             = THIS_MODULE,
};

static int __init led_tg_init(void)
{
        return xt_register_target(&led_tg_reg);
}

static void __exit led_tg_exit(void)
{
        xt_unregister_target(&led_tg_reg);
}

module_init(led_tg_init);
module_exit(led_tg_exit);