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
12 MODULE_LICENSE("GPL");
13 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
14 MODULE_DESCRIPTION("Xtables: countdown quota match");
15 MODULE_ALIAS("ipt_quota");
16 MODULE_ALIAS("ip6t_quota");
17
18 static DEFINE_SPINLOCK(quota_lock);
19
20 static bool
quota_mt(const struct sk_buff * skb,const struct xt_match_param * par)21 quota_mt(const struct sk_buff *skb, const struct xt_match_param *par)
22 {
23 struct xt_quota_info *q =
24 ((const struct xt_quota_info *)par->matchinfo)->master;
25 bool ret = q->flags & XT_QUOTA_INVERT;
26
27 spin_lock_bh("a_lock);
28 if (q->quota >= skb->len) {
29 q->quota -= skb->len;
30 ret = !ret;
31 } else {
32 /* we do not allow even small packets from now on */
33 q->quota = 0;
34 }
35 spin_unlock_bh("a_lock);
36
37 return ret;
38 }
39
quota_mt_check(const struct xt_mtchk_param * par)40 static bool quota_mt_check(const struct xt_mtchk_param *par)
41 {
42 struct xt_quota_info *q = par->matchinfo;
43
44 if (q->flags & ~XT_QUOTA_MASK)
45 return false;
46 /* For SMP, we only want to use one set of counters. */
47 q->master = q;
48 return true;
49 }
50
51 static struct xt_match quota_mt_reg __read_mostly = {
52 .name = "quota",
53 .revision = 0,
54 .family = NFPROTO_UNSPEC,
55 .match = quota_mt,
56 .checkentry = quota_mt_check,
57 .matchsize = sizeof(struct xt_quota_info),
58 .me = THIS_MODULE,
59 };
60
quota_mt_init(void)61 static int __init quota_mt_init(void)
62 {
63 return xt_register_match("a_mt_reg);
64 }
65
quota_mt_exit(void)66 static void __exit quota_mt_exit(void)
67 {
68 xt_unregister_match("a_mt_reg);
69 }
70
71 module_init(quota_mt_init);
72 module_exit(quota_mt_exit);
73