root/net/netfilter/xt_quota.c

DEFINITIONS

1. quota_mt
2. quota_mt_check
3. quota_mt_init
4. quota_mt_exit

/*
 * netfilter module to enforce network quotas
 *
 * Sam Johnston <samj@samj.net>
 */
#include <linux/skbuff.h>
#include <linux/spinlock.h>

#include <linux/netfilter/x_tables.h>
#include <linux/netfilter/xt_quota.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
MODULE_DESCRIPTION("Xtables: countdown quota match");
MODULE_ALIAS("ipt_quota");
MODULE_ALIAS("ip6t_quota");

static DEFINE_SPINLOCK(quota_lock);

static bool
quota_mt(const struct sk_buff *skb, const struct xt_match_param *par)
{
        struct xt_quota_info *q =
                ((const struct xt_quota_info *)par->matchinfo)->master;
        bool ret = q->flags & XT_QUOTA_INVERT;

        spin_lock_bh(&quota_lock);
        if (q->quota >= skb->len) {
                q->quota -= skb->len;
                ret = !ret;
        } else {
                /* we do not allow even small packets from now on */
                q->quota = 0;
        }
        spin_unlock_bh(&quota_lock);

        return ret;
}

static bool quota_mt_check(const struct xt_mtchk_param *par)
{
        struct xt_quota_info *q = par->matchinfo;

        if (q->flags & ~XT_QUOTA_MASK)
                return false;
        /* For SMP, we only want to use one set of counters. */
        q->master = q;
        return true;
}

static struct xt_match quota_mt_reg __read_mostly = {
        .name       = "quota",
        .revision   = 0,
        .family     = NFPROTO_UNSPEC,
        .match      = quota_mt,
        .checkentry = quota_mt_check,
        .matchsize  = sizeof(struct xt_quota_info),
        .me         = THIS_MODULE,
};

static int __init quota_mt_init(void)
{
        return xt_register_match(&quota_mt_reg);
}

static void __exit quota_mt_exit(void)
{
        xt_unregister_match(&quota_mt_reg);
}

module_init(quota_mt_init);
module_exit(quota_mt_exit);