xt_quota.c revision 3a9a231d977222eea36eae091df2c358e03ac839 
1/*
2 * netfilter module to enforce network quotas
3 *
4 * Sam Johnston <samj@samj.net>
5 */
6#include <linux/skbuff.h>
7#include <linux/slab.h>
8#include <linux/spinlock.h>
9
10#include <linux/netfilter/x_tables.h>
11#include <linux/netfilter/xt_quota.h>
12#include <linux/module.h>
13
14struct xt_quota_priv {
15	spinlock_t	lock;
16	uint64_t	quota;
17};
18
19MODULE_LICENSE("GPL");
20MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
21MODULE_DESCRIPTION("Xtables: countdown quota match");
22MODULE_ALIAS("ipt_quota");
23MODULE_ALIAS("ip6t_quota");
24
25static bool
26quota_mt(const struct sk_buff *skb, struct xt_action_param *par)
27{
28	struct xt_quota_info *q = (void *)par->matchinfo;
29	struct xt_quota_priv *priv = q->master;
30	bool ret = q->flags & XT_QUOTA_INVERT;
31
32	spin_lock_bh(&priv->lock);
33	if (priv->quota >= skb->len) {
34		priv->quota -= skb->len;
35		ret = !ret;
36	} else {
37		/* we do not allow even small packets from now on */
38		priv->quota = 0;
39	}
40	spin_unlock_bh(&priv->lock);
41
42	return ret;
43}
44
45static int quota_mt_check(const struct xt_mtchk_param *par)
46{
47	struct xt_quota_info *q = par->matchinfo;
48
49	if (q->flags & ~XT_QUOTA_MASK)
50		return -EINVAL;
51
52	q->master = kmalloc(sizeof(*q->master), GFP_KERNEL);
53	if (q->master == NULL)
54		return -ENOMEM;
55
56	spin_lock_init(&q->master->lock);
57	q->master->quota = q->quota;
58	return 0;
59}
60
61static void quota_mt_destroy(const struct xt_mtdtor_param *par)
62{
63	const struct xt_quota_info *q = par->matchinfo;
64
65	kfree(q->master);
66}
67
68static struct xt_match quota_mt_reg __read_mostly = {
69	.name       = "quota",
70	.revision   = 0,
71	.family     = NFPROTO_UNSPEC,
72	.match      = quota_mt,
73	.checkentry = quota_mt_check,
74	.destroy    = quota_mt_destroy,
75	.matchsize  = sizeof(struct xt_quota_info),
76	.me         = THIS_MODULE,
77};
78
79static int __init quota_mt_init(void)
80{
81	return xt_register_match(&quota_mt_reg);
82}
83
84static void __exit quota_mt_exit(void)
85{
86	xt_unregister_match(&quota_mt_reg);
87}
88
89module_init(quota_mt_init);
90module_exit(quota_mt_exit);
91