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("a_mt_reg);
84 }
85
quota_mt_exit(void)86 static void __exit quota_mt_exit(void)
87 {
88 xt_unregister_match("a_mt_reg);
89 }
90
91 module_init(quota_mt_init);
92 module_exit(quota_mt_exit);
93
