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 * Contact: <jengelh@computergmbh.de>
12 * Kernel module to match connection tracking information.
13 * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au).
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>
32 /* we will save the tuples of all connections we care about */
33 struct xt_connlimit_conn {
34 struct list_head list;
35 struct nf_conntrack_tuple tuple;
38 struct xt_connlimit_data {
39 struct list_head iphash[256];
43 static u_int32_t connlimit_rnd;
44 static bool connlimit_rnd_inited;
46 static inline unsigned int connlimit_iphash(__be32 addr)
48 if (unlikely(!connlimit_rnd_inited)) {
49 get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
50 connlimit_rnd_inited = true;
52 return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF;
55 static inline unsigned int
56 connlimit_iphash6(const union nf_conntrack_address *addr,
57 const union nf_conntrack_address *mask)
59 union nf_conntrack_address res;
62 if (unlikely(!connlimit_rnd_inited)) {
63 get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
64 connlimit_rnd_inited = true;
67 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
68 res.ip6[i] = addr->ip6[i] & mask->ip6[i];
70 return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF;
73 static inline bool already_closed(const struct nf_conn *conn)
75 u_int16_t proto = conn->tuplehash[0].tuple.dst.protonum;
77 if (proto == IPPROTO_TCP)
78 return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT;
83 static inline unsigned int
84 same_source_net(const union nf_conntrack_address *addr,
85 const union nf_conntrack_address *mask,
86 const union nf_conntrack_address *u3, unsigned int family)
88 if (family == AF_INET) {
89 return (addr->ip & mask->ip) == (u3->ip & mask->ip);
91 union nf_conntrack_address lh, rh;
94 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) {
95 lh.ip6[i] = addr->ip6[i] & mask->ip6[i];
96 rh.ip6[i] = u3->ip6[i] & mask->ip6[i];
99 return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0;
103 static int count_them(struct xt_connlimit_data *data,
104 const struct nf_conntrack_tuple *tuple,
105 const union nf_conntrack_address *addr,
106 const union nf_conntrack_address *mask,
107 const struct xt_match *match)
109 struct nf_conntrack_tuple_hash *found;
110 struct xt_connlimit_conn *conn;
111 struct xt_connlimit_conn *tmp;
112 struct nf_conn *found_ct;
113 struct list_head *hash;
118 if (match->family == AF_INET6)
119 hash = &data->iphash[connlimit_iphash6(addr, mask)];
121 hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
123 read_lock_bh(&nf_conntrack_lock);
125 /* check the saved connections */
126 list_for_each_entry_safe(conn, tmp, hash, list) {
127 found = __nf_conntrack_find(&conn->tuple, NULL);
131 found_ct = nf_ct_tuplehash_to_ctrack(found);
133 if (found_ct != NULL &&
134 nf_ct_tuple_equal(&conn->tuple, tuple) &&
135 !already_closed(found_ct))
137 * Just to be sure we have it only once in the list.
138 * We should not see tuples twice unless someone hooks
139 * this into a table without "-p tcp --syn".
144 /* this one is gone */
145 list_del(&conn->list);
150 if (already_closed(found_ct)) {
152 * we do not care about connections which are
153 * closed already -> ditch it
155 list_del(&conn->list);
160 if (same_source_net(addr, mask, &conn->tuple.src.u3,
162 /* same source network -> be counted! */
166 read_unlock_bh(&nf_conntrack_lock);
169 /* save the new connection in our list */
170 conn = kzalloc(sizeof(*conn), GFP_ATOMIC);
173 conn->tuple = *tuple;
174 list_add(&conn->list, hash);
181 static bool connlimit_match(const struct sk_buff *skb,
182 const struct net_device *in,
183 const struct net_device *out,
184 const struct xt_match *match,
185 const void *matchinfo, int offset,
186 unsigned int protoff, bool *hotdrop)
188 const struct xt_connlimit_info *info = matchinfo;
189 union nf_conntrack_address addr, mask;
190 struct nf_conntrack_tuple tuple;
191 const struct nf_conntrack_tuple *tuple_ptr = &tuple;
192 enum ip_conntrack_info ctinfo;
193 const struct nf_conn *ct;
196 ct = nf_ct_get(skb, &ctinfo);
198 tuple_ptr = &ct->tuplehash[0].tuple;
199 else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
200 match->family, &tuple))
203 if (match->family == AF_INET6) {
204 const struct ipv6hdr *iph = ipv6_hdr(skb);
205 memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr));
206 memcpy(&mask.ip6, info->v6_mask, sizeof(info->v6_mask));
208 const struct iphdr *iph = ip_hdr(skb);
209 addr.ip = iph->saddr;
210 mask.ip = info->v4_mask;
213 spin_lock_bh(&info->data->lock);
214 connections = count_them(info->data, tuple_ptr, &addr, &mask, match);
215 spin_unlock_bh(&info->data->lock);
217 if (connections < 0) {
218 /* kmalloc failed, drop it entirely */
223 return (connections > info->limit) ^ info->inverse;
230 static bool connlimit_check(const char *tablename, const void *ip,
231 const struct xt_match *match, void *matchinfo,
232 unsigned int hook_mask)
234 struct xt_connlimit_info *info = matchinfo;
237 if (nf_ct_l3proto_try_module_get(match->family) < 0) {
238 printk(KERN_WARNING "cannot load conntrack support for "
239 "address family %u\n", match->family);
243 /* init private data */
244 info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL);
245 if (info->data == NULL) {
246 nf_ct_l3proto_module_put(match->family);
250 spin_lock_init(&info->data->lock);
251 for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i)
252 INIT_LIST_HEAD(&info->data->iphash[i]);
257 static void connlimit_destroy(const struct xt_match *match, void *matchinfo)
259 struct xt_connlimit_info *info = matchinfo;
260 struct xt_connlimit_conn *conn;
261 struct xt_connlimit_conn *tmp;
262 struct list_head *hash = info->data->iphash;
265 nf_ct_l3proto_module_put(match->family);
267 for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) {
268 list_for_each_entry_safe(conn, tmp, &hash[i], list) {
269 list_del(&conn->list);
277 static struct xt_match connlimit_reg[] __read_mostly = {
281 .checkentry = connlimit_check,
282 .match = connlimit_match,
283 .matchsize = sizeof(struct xt_connlimit_info),
284 .destroy = connlimit_destroy,
290 .checkentry = connlimit_check,
291 .match = connlimit_match,
292 .matchsize = sizeof(struct xt_connlimit_info),
293 .destroy = connlimit_destroy,
298 static int __init xt_connlimit_init(void)
300 return xt_register_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg));
303 static void __exit xt_connlimit_exit(void)
305 xt_unregister_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg));
308 module_init(xt_connlimit_init);
309 module_exit(xt_connlimit_exit);
310 MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>");
311 MODULE_DESCRIPTION("netfilter xt_connlimit match module");
312 MODULE_LICENSE("GPL");
313 MODULE_ALIAS("ipt_connlimit");
314 MODULE_ALIAS("ip6t_connlimit");