xt_LED.c

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/*
 * xt_LED.c - netfilter target to make LEDs blink upon packet matches
 *
 * Copyright (C) 2008 Adam Nielsen <[email protected]>
 *
 * 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 <[email protected]>");
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(unsigned long data)
{
    struct xt_led_info_internal *ledinternal = (struct xt_led_info_internal *)data;

    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;
    }

    /* See if we need to set up a timer */
    if (ledinfo->delay > 0)
        setup_timer(&ledinternal->timer, led_timeout_callback,
                (unsigned long)ledinternal);

    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);

    if (ledinfo->delay > 0)
        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);