1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  * netfilter module to enforce network quotas
4  *
5  * Sam Johnston <samj@samj.net>
6  */
7 #include <linux/skbuff.h>
8 #include <linux/slab.h>
9 #include <linux/spinlock.h>
10 
11 #include <linux/netfilter/x_tables.h>
12 #include <linux/netfilter/xt_quota.h>
13 #include <linux/module.h>
14 
15 struct xt_quota_priv {
16 	spinlock_t	lock;
17 	uint64_t	quota;
18 };
19 
20 MODULE_LICENSE("GPL");
21 MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
22 MODULE_DESCRIPTION("Xtables: countdown quota match");
23 MODULE_ALIAS("ipt_quota");
24 MODULE_ALIAS("ip6t_quota");
25 
26 static bool
quota_mt(const struct sk_buff * skb,struct xt_action_param * par)27 quota_mt(const struct sk_buff *skb, struct xt_action_param *par)
28 {
29 	struct xt_quota_info *q = (void *)par->matchinfo;
30 	struct xt_quota_priv *priv = q->master;
31 	bool ret = q->flags & XT_QUOTA_INVERT;
32 
33 	spin_lock_bh(&priv->lock);
34 	if (priv->quota >= skb->len) {
35 		priv->quota -= skb->len;
36 		ret = !ret;
37 	} else {
38 		/* we do not allow even small packets from now on */
39 		priv->quota = 0;
40 	}
41 	spin_unlock_bh(&priv->lock);
42 
43 	return ret;
44 }
45 
quota_mt_check(const struct xt_mtchk_param * par)46 static int 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 -EINVAL;
52 
53 	q->master = kmalloc(sizeof(*q->master), GFP_KERNEL);
54 	if (q->master == NULL)
55 		return -ENOMEM;
56 
57 	spin_lock_init(&q->master->lock);
58 	q->master->quota = q->quota;
59 	return 0;
60 }
61 
quota_mt_destroy(const struct xt_mtdtor_param * par)62 static void quota_mt_destroy(const struct xt_mtdtor_param *par)
63 {
64 	const struct xt_quota_info *q = par->matchinfo;
65 
66 	kfree(q->master);
67 }
68 
69 static struct xt_match quota_mt_reg __read_mostly = {
70 	.name       = "quota",
71 	.revision   = 0,
72 	.family     = NFPROTO_UNSPEC,
73 	.match      = quota_mt,
74 	.checkentry = quota_mt_check,
75 	.destroy    = quota_mt_destroy,
76 	.matchsize  = sizeof(struct xt_quota_info),
77 	.usersize   = offsetof(struct xt_quota_info, master),
78 	.me         = THIS_MODULE,
79 };
80 
quota_mt_init(void)81 static int __init quota_mt_init(void)
82 {
83 	return xt_register_match(&quota_mt_reg);
84 }
85 
quota_mt_exit(void)86 static void __exit quota_mt_exit(void)
87 {
88 	xt_unregister_match(&quota_mt_reg);
89 }
90 
91 module_init(quota_mt_init);
92 module_exit(quota_mt_exit);
93