1 /*
2 * netfilter module to limit the number of parallel tcp
3 * connections per IP address.
4 * (c) 2000 Gerd Knorr <kraxel@bytesex.org>
5 * Nov 2002: Martin Bene <martin.bene@icomedias.com>:
6 * only ignore TIME_WAIT or gone connections
7 * (C) CC Computer Consultants GmbH, 2007
8 *
9 * based on ...
10 *
11 * Kernel module to match connection tracking information.
12 * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au).
13 */
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
15
16 #include <linux/module.h>
17 #include <linux/skbuff.h>
18 #include <linux/netfilter/x_tables.h>
19 #include <linux/netfilter/xt_connlimit.h>
20
21 #include <net/netfilter/nf_conntrack.h>
22 #include <net/netfilter/nf_conntrack_core.h>
23 #include <net/netfilter/nf_conntrack_tuple.h>
24 #include <net/netfilter/nf_conntrack_zones.h>
25 #include <net/netfilter/nf_conntrack_count.h>
26
27 static bool
connlimit_mt(const struct sk_buff * skb,struct xt_action_param * par)28 connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
29 {
30 struct net *net = xt_net(par);
31 const struct xt_connlimit_info *info = par->matchinfo;
32 struct nf_conntrack_tuple tuple;
33 const struct nf_conntrack_tuple *tuple_ptr = &tuple;
34 const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt;
35 enum ip_conntrack_info ctinfo;
36 const struct nf_conn *ct;
37 unsigned int connections;
38 u32 key[5];
39
40 ct = nf_ct_get(skb, &ctinfo);
41 if (ct != NULL) {
42 tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
43 zone = nf_ct_zone(ct);
44 } else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
45 xt_family(par), net, &tuple)) {
46 goto hotdrop;
47 }
48
49 if (xt_family(par) == NFPROTO_IPV6) {
50 const struct ipv6hdr *iph = ipv6_hdr(skb);
51 union nf_inet_addr addr;
52 unsigned int i;
53
54 memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ?
55 &iph->daddr : &iph->saddr, sizeof(addr.ip6));
56
57 for (i = 0; i < ARRAY_SIZE(addr.ip6); ++i)
58 addr.ip6[i] &= info->mask.ip6[i];
59 memcpy(key, &addr, sizeof(addr.ip6));
60 key[4] = zone->id;
61 } else {
62 const struct iphdr *iph = ip_hdr(skb);
63 key[0] = (info->flags & XT_CONNLIMIT_DADDR) ?
64 iph->daddr : iph->saddr;
65
66 key[0] &= info->mask.ip;
67 key[1] = zone->id;
68 }
69
70 connections = nf_conncount_count(net, info->data, key, tuple_ptr,
71 zone);
72 if (connections == 0)
73 /* kmalloc failed, drop it entirely */
74 goto hotdrop;
75
76 return (connections > info->limit) ^ !!(info->flags & XT_CONNLIMIT_INVERT);
77
78 hotdrop:
79 par->hotdrop = true;
80 return false;
81 }
82
connlimit_mt_check(const struct xt_mtchk_param * par)83 static int connlimit_mt_check(const struct xt_mtchk_param *par)
84 {
85 struct xt_connlimit_info *info = par->matchinfo;
86 unsigned int keylen;
87
88 keylen = sizeof(u32);
89 if (par->family == NFPROTO_IPV6)
90 keylen += sizeof(struct in6_addr);
91 else
92 keylen += sizeof(struct in_addr);
93
94 /* init private data */
95 info->data = nf_conncount_init(par->net, par->family, keylen);
96
97 return PTR_ERR_OR_ZERO(info->data);
98 }
99
connlimit_mt_destroy(const struct xt_mtdtor_param * par)100 static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
101 {
102 const struct xt_connlimit_info *info = par->matchinfo;
103
104 nf_conncount_destroy(par->net, par->family, info->data);
105 }
106
107 static struct xt_match connlimit_mt_reg __read_mostly = {
108 .name = "connlimit",
109 .revision = 1,
110 .family = NFPROTO_UNSPEC,
111 .checkentry = connlimit_mt_check,
112 .match = connlimit_mt,
113 .matchsize = sizeof(struct xt_connlimit_info),
114 .usersize = offsetof(struct xt_connlimit_info, data),
115 .destroy = connlimit_mt_destroy,
116 .me = THIS_MODULE,
117 };
118
connlimit_mt_init(void)119 static int __init connlimit_mt_init(void)
120 {
121 return xt_register_match(&connlimit_mt_reg);
122 }
123
connlimit_mt_exit(void)124 static void __exit connlimit_mt_exit(void)
125 {
126 xt_unregister_match(&connlimit_mt_reg);
127 }
128
129 module_init(connlimit_mt_init);
130 module_exit(connlimit_mt_exit);
131 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
132 MODULE_DESCRIPTION("Xtables: Number of connections matching");
133 MODULE_LICENSE("GPL");
134 MODULE_ALIAS("ipt_connlimit");
135 MODULE_ALIAS("ip6t_connlimit");
136
