xt_quota.c revision acc738fec03bdaa5b77340c32a82fbfedaaabef0 
1/*
2 * netfilter module to enforce network quotas
3 *
4 * Sam Johnston <samj@samj.net>
5 */
6#include <linux/skbuff.h>
7#include <linux/spinlock.h>
8
9#include <linux/netfilter/x_tables.h>
10#include <linux/netfilter/xt_quota.h>
11
12struct xt_quota_priv {
13	uint64_t quota;
14};
15
16MODULE_LICENSE("GPL");
17MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
18MODULE_DESCRIPTION("Xtables: countdown quota match");
19MODULE_ALIAS("ipt_quota");
20MODULE_ALIAS("ip6t_quota");
21
22static DEFINE_SPINLOCK(quota_lock);
23
24static bool
25quota_mt(const struct sk_buff *skb, const struct xt_match_param *par)
26{
27	struct xt_quota_info *q = (void *)par->matchinfo;
28	struct xt_quota_priv *priv = q->master;
29	bool ret = q->flags & XT_QUOTA_INVERT;
30
31	spin_lock_bh(&quota_lock);
32	if (priv->quota >= skb->len) {
33		priv->quota -= skb->len;
34		ret = !ret;
35	} else {
36		/* we do not allow even small packets from now on */
37		priv->quota = 0;
38	}
39	/* Copy quota back to matchinfo so that iptables can display it */
40	q->quota = priv->quota;
41	spin_unlock_bh(&quota_lock);
42
43	return ret;
44}
45
46static bool quota_mt_check(const struct xt_mtchk_param *par)
47{
48	struct xt_quota_info *q = par->matchinfo;
49
50	if (q->flags & ~XT_QUOTA_MASK)
51		return false;
52
53	q->master = kmalloc(sizeof(*q->master), GFP_KERNEL);
54	if (q->master == NULL)
55		return -ENOMEM;
56
57	return true;
58}
59
60static void quota_mt_destroy(const struct xt_mtdtor_param *par)
61{
62	const struct xt_quota_info *q = par->matchinfo;
63
64	kfree(q->master);
65}
66
67static struct xt_match quota_mt_reg __read_mostly = {
68	.name       = "quota",
69	.revision   = 0,
70	.family     = NFPROTO_UNSPEC,
71	.match      = quota_mt,
72	.checkentry = quota_mt_check,
73	.destroy    = quota_mt_destroy,
74	.matchsize  = sizeof(struct xt_quota_info),
75	.me         = THIS_MODULE,
76};
77
78static int __init quota_mt_init(void)
79{
80	return xt_register_match(&quota_mt_reg);
81}
82
83static void __exit quota_mt_exit(void)
84{
85	xt_unregister_match(&quota_mt_reg);
86}
87
88module_init(quota_mt_init);
89module_exit(quota_mt_exit);
90