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/slab.h>
21 #include <linux/list.h>
22 #include <linux/module.h>
23 #include <linux/random.h>
24 #include <linux/skbuff.h>
25 #include <linux/spinlock.h>
26 #include <linux/netfilter/nf_conntrack_tcp.h>
27 #include <linux/netfilter/x_tables.h>
28 #include <linux/netfilter/xt_connlimit.h>
29 #include <net/netfilter/nf_conntrack.h>
30 #include <net/netfilter/nf_conntrack_core.h>
31 #include <net/netfilter/nf_conntrack_tuple.h>
32 #include <net/netfilter/nf_conntrack_zones.h>
34 /* we will save the tuples of all connections we care about */
35 struct xt_connlimit_conn {
36 struct list_head list;
37 struct nf_conntrack_tuple tuple;
38 union nf_inet_addr addr;
41 struct xt_connlimit_data {
42 struct list_head iphash[256];
46 static u_int32_t connlimit_rnd __read_mostly;
47 static bool connlimit_rnd_inited __read_mostly;
49 static inline unsigned int connlimit_iphash(__be32 addr)
51 return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF;
54 static inline unsigned int
55 connlimit_iphash6(const union nf_inet_addr *addr,
56 const union nf_inet_addr *mask)
58 union nf_inet_addr res;
61 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
62 res.ip6[i] = addr->ip6[i] & mask->ip6[i];
64 return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF;
67 static inline bool already_closed(const struct nf_conn *conn)
69 if (nf_ct_protonum(conn) == IPPROTO_TCP)
70 return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT ||
71 conn->proto.tcp.state == TCP_CONNTRACK_CLOSE;
76 static inline unsigned int
77 same_source_net(const union nf_inet_addr *addr,
78 const union nf_inet_addr *mask,
79 const union nf_inet_addr *u3, u_int8_t family)
81 if (family == NFPROTO_IPV4) {
82 return (addr->ip & mask->ip) == (u3->ip & mask->ip);
84 union nf_inet_addr lh, rh;
87 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) {
88 lh.ip6[i] = addr->ip6[i] & mask->ip6[i];
89 rh.ip6[i] = u3->ip6[i] & mask->ip6[i];
92 return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0;
96 static int count_them(struct net *net,
97 struct xt_connlimit_data *data,
98 const struct nf_conntrack_tuple *tuple,
99 const union nf_inet_addr *addr,
100 const union nf_inet_addr *mask,
103 const struct nf_conntrack_tuple_hash *found;
104 struct xt_connlimit_conn *conn;
105 struct xt_connlimit_conn *tmp;
106 struct nf_conn *found_ct;
107 struct list_head *hash;
111 if (family == NFPROTO_IPV6)
112 hash = &data->iphash[connlimit_iphash6(addr, mask)];
114 hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
118 /* check the saved connections */
119 list_for_each_entry_safe(conn, tmp, hash, list) {
120 found = nf_conntrack_find_get(net, NF_CT_DEFAULT_ZONE,
125 found_ct = nf_ct_tuplehash_to_ctrack(found);
127 if (found_ct != NULL &&
128 nf_ct_tuple_equal(&conn->tuple, tuple) &&
129 !already_closed(found_ct))
131 * Just to be sure we have it only once in the list.
132 * We should not see tuples twice unless someone hooks
133 * this into a table without "-p tcp --syn".
138 /* this one is gone */
139 list_del(&conn->list);
144 if (already_closed(found_ct)) {
146 * we do not care about connections which are
147 * closed already -> ditch it
150 list_del(&conn->list);
155 if (same_source_net(addr, mask, &conn->addr, family))
156 /* same source network -> be counted! */
164 /* save the new connection in our list */
165 conn = kmalloc(sizeof(*conn), GFP_ATOMIC);
168 conn->tuple = *tuple;
170 list_add(&conn->list, hash);
178 connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
180 struct net *net = dev_net(par->in ? par->in : par->out);
181 const struct xt_connlimit_info *info = par->matchinfo;
182 union nf_inet_addr addr;
183 struct nf_conntrack_tuple tuple;
184 const struct nf_conntrack_tuple *tuple_ptr = &tuple;
185 enum ip_conntrack_info ctinfo;
186 const struct nf_conn *ct;
189 ct = nf_ct_get(skb, &ctinfo);
191 tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
192 else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
193 par->family, &tuple))
196 if (par->family == NFPROTO_IPV6) {
197 const struct ipv6hdr *iph = ipv6_hdr(skb);
198 memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ?
199 &iph->daddr : &iph->saddr, sizeof(addr.ip6));
201 const struct iphdr *iph = ip_hdr(skb);
202 addr.ip = (info->flags & XT_CONNLIMIT_DADDR) ?
203 iph->daddr : iph->saddr;
206 spin_lock_bh(&info->data->lock);
207 connections = count_them(net, info->data, tuple_ptr, &addr,
208 &info->mask, par->family);
209 spin_unlock_bh(&info->data->lock);
212 /* kmalloc failed, drop it entirely */
215 return (connections > info->limit) ^
216 !!(info->flags & XT_CONNLIMIT_INVERT);
223 static int connlimit_mt_check(const struct xt_mtchk_param *par)
225 struct xt_connlimit_info *info = par->matchinfo;
229 if (unlikely(!connlimit_rnd_inited)) {
230 get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
231 connlimit_rnd_inited = true;
233 ret = nf_ct_l3proto_try_module_get(par->family);
235 pr_info("cannot load conntrack support for "
236 "address family %u\n", par->family);
240 /* init private data */
241 info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL);
242 if (info->data == NULL) {
243 nf_ct_l3proto_module_put(par->family);
247 spin_lock_init(&info->data->lock);
248 for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i)
249 INIT_LIST_HEAD(&info->data->iphash[i]);
254 static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
256 const struct xt_connlimit_info *info = par->matchinfo;
257 struct xt_connlimit_conn *conn;
258 struct xt_connlimit_conn *tmp;
259 struct list_head *hash = info->data->iphash;
262 nf_ct_l3proto_module_put(par->family);
264 for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) {
265 list_for_each_entry_safe(conn, tmp, &hash[i], list) {
266 list_del(&conn->list);
274 static struct xt_match connlimit_mt_reg[] __read_mostly = {
278 .family = NFPROTO_UNSPEC,
279 .checkentry = connlimit_mt_check,
280 .match = connlimit_mt,
281 .matchsize = sizeof(struct xt_connlimit_info),
282 .destroy = connlimit_mt_destroy,
288 .family = NFPROTO_UNSPEC,
289 .checkentry = connlimit_mt_check,
290 .match = connlimit_mt,
291 .matchsize = sizeof(struct xt_connlimit_info),
292 .destroy = connlimit_mt_destroy,
297 static int __init connlimit_mt_init(void)
299 return xt_register_matches(connlimit_mt_reg,
300 ARRAY_SIZE(connlimit_mt_reg));
303 static void __exit connlimit_mt_exit(void)
305 xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg));
308 module_init(connlimit_mt_init);
309 module_exit(connlimit_mt_exit);
310 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
311 MODULE_DESCRIPTION("Xtables: Number of connections matching");
312 MODULE_LICENSE("GPL");
313 MODULE_ALIAS("ipt_connlimit");
314 MODULE_ALIAS("ip6t_connlimit");