net/netfilter/xt_LED.c

   1 /*
   2  * xt_LED.c - netfilter target to make LEDs blink upon packet matches
   3  *
   4  * Copyright (C) 2008 Adam Nielsen <a.nielsen@shikadi.net>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; version 2 of the License.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  18  * 02110-1301 USA.
  19  *
  20  */
  21 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  22 #include <linux/module.h>
  23 #include <linux/skbuff.h>
  24 #include <linux/netfilter/x_tables.h>
  25 #include <linux/slab.h>
  26 #include <linux/leds.h>
  27 #include <linux/mutex.h>
  28
  29 #include <linux/netfilter/xt_LED.h>
  30
  31 MODULE_LICENSE("GPL");
  32 MODULE_AUTHOR("Adam Nielsen <a.nielsen@shikadi.net>");
  33 MODULE_DESCRIPTION("Xtables: trigger LED devices on packet match");
  34
  35 static LIST_HEAD(xt_led_triggers);
  36 static DEFINE_MUTEX(xt_led_mutex);
  37
  38 /*
  39  * This is declared in here (the kernel module) only, to avoid having these
  40  * dependencies in userspace code.  This is what xt_led_info.internal_data
  41  * points to.
  42  */
  43 struct xt_led_info_internal {
  44         struct list_head list;
  45         int refcnt;
  46         char *trigger_id;
  47         struct led_trigger netfilter_led_trigger;
  48         struct timer_list timer;
  49 };
  50
  51 static unsigned int
  52 led_tg(struct sk_buff *skb, const struct xt_action_param *par)
  53 {
  54         const struct xt_led_info *ledinfo = par->targinfo;
  55         struct xt_led_info_internal *ledinternal = ledinfo->internal_data;
  56
  57         /*
  58          * If "always blink" is enabled, and there's still some time until the
  59          * LED will switch off, briefly switch it off now.
  60          */
  61         if ((ledinfo->delay > 0) && ledinfo->always_blink &&
  62             timer_pending(&ledinternal->timer))
  63                 led_trigger_event(&ledinternal->netfilter_led_trigger, LED_OFF);
  64
  65         led_trigger_event(&ledinternal->netfilter_led_trigger, LED_FULL);
  66
  67         /* If there's a positive delay, start/update the timer */
  68         if (ledinfo->delay > 0) {
  69                 mod_timer(&ledinternal->timer,
  70                           jiffies + msecs_to_jiffies(ledinfo->delay));
  71
  72         /* Otherwise if there was no delay given, blink as fast as possible */
  73         } else if (ledinfo->delay == 0) {
  74                 led_trigger_event(&ledinternal->netfilter_led_trigger, LED_OFF);
  75         }
  76
  77         /* else the delay is negative, which means switch on and stay on */
  78
  79         return XT_CONTINUE;
  80 }
  81
  82 static void led_timeout_callback(unsigned long data)
  83 {
  84         struct xt_led_info_internal *ledinternal = (struct xt_led_info_internal *)data;
  85
  86         led_trigger_event(&ledinternal->netfilter_led_trigger, LED_OFF);
  87 }
  88
  89 static struct xt_led_info_internal *led_trigger_lookup(const char *name)
  90 {
  91         struct xt_led_info_internal *ledinternal;
  92
  93         list_for_each_entry(ledinternal, &xt_led_triggers, list) {
  94                 if (!strcmp(name, ledinternal->netfilter_led_trigger.name)) {
  95                         return ledinternal;
  96                 }
  97         }
  98         return NULL;
  99 }
 100
 101 static int led_tg_check(const struct xt_tgchk_param *par)
 102 {
 103         struct xt_led_info *ledinfo = par->targinfo;
 104         struct xt_led_info_internal *ledinternal;
 105         int err;
 106
 107         if (ledinfo->id[0] == '\0') {
 108                 pr_info("No 'id' parameter given.\n");
 109                 return -EINVAL;
 110         }
 111
 112         mutex_lock(&xt_led_mutex);
 113
 114         ledinternal = led_trigger_lookup(ledinfo->id);
 115         if (ledinternal) {
 116                 ledinternal->refcnt++;
 117                 goto out;
 118         }
 119
 120         err = -ENOMEM;
 121         ledinternal = kzalloc(sizeof(struct xt_led_info_internal), GFP_KERNEL);
 122         if (!ledinternal)
 123                 goto exit_mutex_only;
 124
 125         ledinternal->trigger_id = kstrdup(ledinfo->id, GFP_KERNEL);
 126         if (!ledinternal->trigger_id)
 127                 goto exit_internal_alloc;
 128
 129         ledinternal->refcnt = 1;
 130         ledinternal->netfilter_led_trigger.name = ledinternal->trigger_id;
 131
 132         err = led_trigger_register(&ledinternal->netfilter_led_trigger);
 133         if (err) {
 134                 pr_warning("led_trigger_register() failed\n");
 135                 if (err == -EEXIST)
 136                         pr_warning("Trigger name is already in use.\n");
 137                 goto exit_alloc;
 138         }
 139
 140         /* See if we need to set up a timer */
 141         if (ledinfo->delay > 0)
 142                 setup_timer(&ledinternal->timer, led_timeout_callback,
 143                             (unsigned long)ledinternal);
 144
 145         list_add_tail(&ledinternal->list, &xt_led_triggers);
 146
 147 out:
 148         mutex_unlock(&xt_led_mutex);
 149
 150         ledinfo->internal_data = ledinternal;
 151
 152         return 0;
 153
 154 exit_alloc:
 155         kfree(ledinternal->trigger_id);
 156
 157 exit_internal_alloc:
 158         kfree(ledinternal);
 159
 160 exit_mutex_only:
 161         mutex_unlock(&xt_led_mutex);
 162
 163         return err;
 164 }
 165
 166 static void led_tg_destroy(const struct xt_tgdtor_param *par)
 167 {
 168         const struct xt_led_info *ledinfo = par->targinfo;
 169         struct xt_led_info_internal *ledinternal = ledinfo->internal_data;
 170
 171         mutex_lock(&xt_led_mutex);
 172
 173         if (--ledinternal->refcnt) {
 174                 mutex_unlock(&xt_led_mutex);
 175                 return;
 176         }
 177
 178         list_del(&ledinternal->list);
 179
 180         if (ledinfo->delay > 0)
 181                 del_timer_sync(&ledinternal->timer);
 182
 183         led_trigger_unregister(&ledinternal->netfilter_led_trigger);
 184
 185         mutex_unlock(&xt_led_mutex);
 186
 187         kfree(ledinternal->trigger_id);
 188         kfree(ledinternal);
 189 }
 190
 191 static struct xt_target led_tg_reg __read_mostly = {
 192         .name           = "LED",
 193         .revision       = 0,
 194         .family         = NFPROTO_UNSPEC,
 195         .target         = led_tg,
 196         .targetsize     = sizeof(struct xt_led_info),
 197         .checkentry     = led_tg_check,
 198         .destroy        = led_tg_destroy,
 199         .me             = THIS_MODULE,
 200 };
 201
 202 static int __init led_tg_init(void)
 203 {
 204         return xt_register_target(&led_tg_reg);
 205 }
 206
 207 static void __exit led_tg_exit(void)
 208 {
 209         xt_unregister_target(&led_tg_reg);
 210 }
 211
 212 module_init(led_tg_init);
 213 module_exit(led_tg_exit);