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
11 * Kernel module to match connection tracking information.
12 * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au).
14 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
16 #include <linux/in6.h>
18 #include <linux/ipv6.h>
19 #include <linux/jhash.h>
20 #include <linux/list.h>
21 #include <linux/module.h>
22 #include <linux/random.h>
23 #include <linux/skbuff.h>
24 #include <linux/spinlock.h>
25 #include <linux/netfilter/nf_conntrack_tcp.h>
26 #include <linux/netfilter/x_tables.h>
27 #include <linux/netfilter/xt_connlimit.h>
28 #include <net/netfilter/nf_conntrack.h>
29 #include <net/netfilter/nf_conntrack_core.h>
30 #include <net/netfilter/nf_conntrack_tuple.h>
31 #include <net/netfilter/nf_conntrack_zones.h>
33 /* we will save the tuples of all connections we care about */
34 struct xt_connlimit_conn {
35 struct list_head list;
36 struct nf_conntrack_tuple tuple;
39 struct xt_connlimit_data {
40 struct list_head iphash[256];
44 static u_int32_t connlimit_rnd __read_mostly;
45 static bool connlimit_rnd_inited __read_mostly;
47 static inline unsigned int connlimit_iphash(__be32 addr)
49 return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF;
52 static inline unsigned int
53 connlimit_iphash6(const union nf_inet_addr *addr,
54 const union nf_inet_addr *mask)
56 union nf_inet_addr res;
59 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
60 res.ip6[i] = addr->ip6[i] & mask->ip6[i];
62 return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF;
65 static inline bool already_closed(const struct nf_conn *conn)
67 if (nf_ct_protonum(conn) == IPPROTO_TCP)
68 return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT ||
69 conn->proto.tcp.state == TCP_CONNTRACK_CLOSE;
74 static inline unsigned int
75 same_source_net(const union nf_inet_addr *addr,
76 const union nf_inet_addr *mask,
77 const union nf_inet_addr *u3, u_int8_t family)
79 if (family == NFPROTO_IPV4) {
80 return (addr->ip & mask->ip) == (u3->ip & mask->ip);
82 union nf_inet_addr lh, rh;
85 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) {
86 lh.ip6[i] = addr->ip6[i] & mask->ip6[i];
87 rh.ip6[i] = u3->ip6[i] & mask->ip6[i];
90 return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0;
94 static int count_them(struct net *net,
95 struct xt_connlimit_data *data,
96 const struct nf_conntrack_tuple *tuple,
97 const union nf_inet_addr *addr,
98 const union nf_inet_addr *mask,
101 const struct nf_conntrack_tuple_hash *found;
102 struct xt_connlimit_conn *conn;
103 struct xt_connlimit_conn *tmp;
104 struct nf_conn *found_ct;
105 struct list_head *hash;
109 if (family == NFPROTO_IPV6)
110 hash = &data->iphash[connlimit_iphash6(addr, mask)];
112 hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
116 /* check the saved connections */
117 list_for_each_entry_safe(conn, tmp, hash, list) {
118 found = nf_conntrack_find_get(net, NF_CT_DEFAULT_ZONE,
123 found_ct = nf_ct_tuplehash_to_ctrack(found);
125 if (found_ct != NULL &&
126 nf_ct_tuple_equal(&conn->tuple, tuple) &&
127 !already_closed(found_ct))
129 * Just to be sure we have it only once in the list.
130 * We should not see tuples twice unless someone hooks
131 * this into a table without "-p tcp --syn".
136 /* this one is gone */
137 list_del(&conn->list);
142 if (already_closed(found_ct)) {
144 * we do not care about connections which are
145 * closed already -> ditch it
148 list_del(&conn->list);
153 if (same_source_net(addr, mask, &conn->tuple.src.u3, family))
154 /* same source network -> be counted! */
162 /* save the new connection in our list */
163 conn = kzalloc(sizeof(*conn), GFP_ATOMIC);
166 conn->tuple = *tuple;
167 list_add(&conn->list, hash);
175 connlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par)
177 struct net *net = dev_net(par->in ? par->in : par->out);
178 const struct xt_connlimit_info *info = par->matchinfo;
179 union nf_inet_addr addr;
180 struct nf_conntrack_tuple tuple;
181 const struct nf_conntrack_tuple *tuple_ptr = &tuple;
182 enum ip_conntrack_info ctinfo;
183 const struct nf_conn *ct;
186 ct = nf_ct_get(skb, &ctinfo);
188 tuple_ptr = &ct->tuplehash[0].tuple;
189 else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
190 par->family, &tuple))
193 if (par->family == NFPROTO_IPV6) {
194 const struct ipv6hdr *iph = ipv6_hdr(skb);
195 memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr));
197 const struct iphdr *iph = ip_hdr(skb);
198 addr.ip = iph->saddr;
201 spin_lock_bh(&info->data->lock);
202 connections = count_them(net, info->data, tuple_ptr, &addr,
203 &info->mask, par->family);
204 spin_unlock_bh(&info->data->lock);
206 if (connections < 0) {
207 /* kmalloc failed, drop it entirely */
208 *par->hotdrop = true;
212 return (connections > info->limit) ^ info->inverse;
215 *par->hotdrop = true;
219 static int connlimit_mt_check(const struct xt_mtchk_param *par)
221 struct xt_connlimit_info *info = par->matchinfo;
224 if (unlikely(!connlimit_rnd_inited)) {
225 get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
226 connlimit_rnd_inited = true;
228 if (nf_ct_l3proto_try_module_get(par->family) < 0) {
229 pr_info("cannot load conntrack support for "
230 "address family %u\n", par->family);
234 /* init private data */
235 info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL);
236 if (info->data == NULL) {
237 nf_ct_l3proto_module_put(par->family);
241 spin_lock_init(&info->data->lock);
242 for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i)
243 INIT_LIST_HEAD(&info->data->iphash[i]);
248 static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
250 const struct xt_connlimit_info *info = par->matchinfo;
251 struct xt_connlimit_conn *conn;
252 struct xt_connlimit_conn *tmp;
253 struct list_head *hash = info->data->iphash;
256 nf_ct_l3proto_module_put(par->family);
258 for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) {
259 list_for_each_entry_safe(conn, tmp, &hash[i], list) {
260 list_del(&conn->list);
268 static struct xt_match connlimit_mt_reg __read_mostly = {
271 .family = NFPROTO_UNSPEC,
272 .checkentry = connlimit_mt_check,
273 .match = connlimit_mt,
274 .matchsize = sizeof(struct xt_connlimit_info),
275 .destroy = connlimit_mt_destroy,
279 static int __init connlimit_mt_init(void)
281 return xt_register_match(&connlimit_mt_reg);
284 static void __exit connlimit_mt_exit(void)
286 xt_unregister_match(&connlimit_mt_reg);
289 module_init(connlimit_mt_init);
290 module_exit(connlimit_mt_exit);
291 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
292 MODULE_DESCRIPTION("Xtables: Number of connections matching");
293 MODULE_LICENSE("GPL");
294 MODULE_ALIAS("ipt_connlimit");
295 MODULE_ALIAS("ip6t_connlimit");