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
15struct xt_quota_priv {
16 spinlock_t lock;
17 uint64_t quota;
18};
19
20MODULE_LICENSE("GPL");
21MODULE_AUTHOR("Sam Johnston <samj@samj.net>");
22MODULE_DESCRIPTION("Xtables: countdown quota match");
23MODULE_ALIAS("ipt_quota");
24MODULE_ALIAS("ip6t_quota");
25
26static bool
27quota_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(lock: &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(lock: &priv->lock);
42
43 return ret;
44}
45
46static 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(size: 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
62static void quota_mt_destroy(const struct xt_mtdtor_param *par)
63{
64 const struct xt_quota_info *q = par->matchinfo;
65
66 kfree(objp: q->master);
67}
68
69static 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
81static int __init quota_mt_init(void)
82{
83 return xt_register_match(target: &quota_mt_reg);
84}
85
86static void __exit quota_mt_exit(void)
87{
88 xt_unregister_match(target: &quota_mt_reg);
89}
90
91module_init(quota_mt_init);
92module_exit(quota_mt_exit);
93

source code of linux/net/netfilter/xt_quota.c