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 |
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(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 | |
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(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 | |
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(objp: 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 | |
81 | static int __init quota_mt_init(void) |
82 | { |
83 | return xt_register_match(target: "a_mt_reg); |
84 | } |
85 | |
86 | static void __exit quota_mt_exit(void) |
87 | { |
88 | xt_unregister_match(target: "a_mt_reg); |
89 | } |
90 | |
91 | module_init(quota_mt_init); |
92 | module_exit(quota_mt_exit); |
93 | |