blob: d5b26dab9e26de074a99cd75c7ab5bd53674244b [file] [log] [blame]
Jan Engelhardt370786f2007-07-14 20:47:26 -07001/*
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
Jan Engelhardtba5dc272007-11-05 20:35:56 -08007 * (C) CC Computer Consultants GmbH, 2007
Jan Engelhardt370786f2007-07-14 20:47:26 -07008 *
9 * based on ...
10 *
11 * Kernel module to match connection tracking information.
12 * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au).
13 */
Jan Engelhardt8bee4ba2010-03-17 16:04:40 +010014#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
Jan Engelhardt370786f2007-07-14 20:47:26 -070015#include <linux/in.h>
16#include <linux/in6.h>
17#include <linux/ip.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>
Patrick McHardy5d0aa2c2010-02-15 18:13:33 +010031#include <net/netfilter/nf_conntrack_zones.h>
Jan Engelhardt370786f2007-07-14 20:47:26 -070032
33/* we will save the tuples of all connections we care about */
34struct xt_connlimit_conn {
35 struct list_head list;
36 struct nf_conntrack_tuple tuple;
37};
38
39struct xt_connlimit_data {
40 struct list_head iphash[256];
41 spinlock_t lock;
42};
43
Jan Engelhardt294188a2010-01-04 16:28:38 +010044static u_int32_t connlimit_rnd __read_mostly;
45static bool connlimit_rnd_inited __read_mostly;
Jan Engelhardt370786f2007-07-14 20:47:26 -070046
Al Viroa34c4582007-07-26 17:33:19 +010047static inline unsigned int connlimit_iphash(__be32 addr)
Jan Engelhardt370786f2007-07-14 20:47:26 -070048{
Al Viroa34c4582007-07-26 17:33:19 +010049 return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF;
Jan Engelhardt370786f2007-07-14 20:47:26 -070050}
51
52static inline unsigned int
Jan Engelhardt643a2c12007-12-17 22:43:50 -080053connlimit_iphash6(const union nf_inet_addr *addr,
54 const union nf_inet_addr *mask)
Jan Engelhardt370786f2007-07-14 20:47:26 -070055{
Jan Engelhardt643a2c12007-12-17 22:43:50 -080056 union nf_inet_addr res;
Jan Engelhardt370786f2007-07-14 20:47:26 -070057 unsigned int i;
58
Jan Engelhardt370786f2007-07-14 20:47:26 -070059 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
60 res.ip6[i] = addr->ip6[i] & mask->ip6[i];
61
Al Viroa34c4582007-07-26 17:33:19 +010062 return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF;
Jan Engelhardt370786f2007-07-14 20:47:26 -070063}
64
65static inline bool already_closed(const struct nf_conn *conn)
66{
Patrick McHardy5e8fbe22008-04-14 11:15:52 +020067 if (nf_ct_protonum(conn) == IPPROTO_TCP)
Dong Weid2ee3f22008-06-04 09:57:51 -070068 return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT ||
69 conn->proto.tcp.state == TCP_CONNTRACK_CLOSE;
Jan Engelhardt370786f2007-07-14 20:47:26 -070070 else
71 return 0;
72}
73
74static inline unsigned int
Jan Engelhardt643a2c12007-12-17 22:43:50 -080075same_source_net(const union nf_inet_addr *addr,
76 const union nf_inet_addr *mask,
Jan Engelhardt76108ce2008-10-08 11:35:00 +020077 const union nf_inet_addr *u3, u_int8_t family)
Jan Engelhardt370786f2007-07-14 20:47:26 -070078{
Jan Engelhardtee999d82008-10-08 11:35:01 +020079 if (family == NFPROTO_IPV4) {
Jan Engelhardt370786f2007-07-14 20:47:26 -070080 return (addr->ip & mask->ip) == (u3->ip & mask->ip);
81 } else {
Jan Engelhardt643a2c12007-12-17 22:43:50 -080082 union nf_inet_addr lh, rh;
Jan Engelhardt370786f2007-07-14 20:47:26 -070083 unsigned int i;
84
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];
88 }
89
90 return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0;
91 }
92}
93
Alexey Dobriyan83fc8102010-01-18 08:07:50 +010094static int count_them(struct net *net,
95 struct xt_connlimit_data *data,
Jan Engelhardt370786f2007-07-14 20:47:26 -070096 const struct nf_conntrack_tuple *tuple,
Jan Engelhardt643a2c12007-12-17 22:43:50 -080097 const union nf_inet_addr *addr,
98 const union nf_inet_addr *mask,
Jan Engelhardt539054a2009-11-06 18:08:32 -080099 u_int8_t family)
Jan Engelhardt370786f2007-07-14 20:47:26 -0700100{
Jan Engelhardt3cf93c92008-04-14 09:56:05 +0200101 const struct nf_conntrack_tuple_hash *found;
Jan Engelhardt370786f2007-07-14 20:47:26 -0700102 struct xt_connlimit_conn *conn;
103 struct xt_connlimit_conn *tmp;
Eric Dumazetea781f12009-03-25 21:05:46 +0100104 struct nf_conn *found_ct;
Jan Engelhardt370786f2007-07-14 20:47:26 -0700105 struct list_head *hash;
106 bool addit = true;
107 int matches = 0;
108
Jan Engelhardt539054a2009-11-06 18:08:32 -0800109 if (family == NFPROTO_IPV6)
Jan Engelhardt370786f2007-07-14 20:47:26 -0700110 hash = &data->iphash[connlimit_iphash6(addr, mask)];
111 else
112 hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
113
Patrick McHardy76507f62008-01-31 04:38:38 -0800114 rcu_read_lock();
Jan Engelhardt370786f2007-07-14 20:47:26 -0700115
116 /* check the saved connections */
117 list_for_each_entry_safe(conn, tmp, hash, list) {
Patrick McHardy5d0aa2c2010-02-15 18:13:33 +0100118 found = nf_conntrack_find_get(net, NF_CT_DEFAULT_ZONE,
119 &conn->tuple);
Jan Engelhardt370786f2007-07-14 20:47:26 -0700120 found_ct = NULL;
121
122 if (found != NULL)
123 found_ct = nf_ct_tuplehash_to_ctrack(found);
124
125 if (found_ct != NULL &&
126 nf_ct_tuple_equal(&conn->tuple, tuple) &&
127 !already_closed(found_ct))
128 /*
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".
132 */
133 addit = false;
134
135 if (found == NULL) {
136 /* this one is gone */
137 list_del(&conn->list);
138 kfree(conn);
139 continue;
140 }
141
142 if (already_closed(found_ct)) {
143 /*
144 * we do not care about connections which are
145 * closed already -> ditch it
146 */
Eric Dumazetea781f12009-03-25 21:05:46 +0100147 nf_ct_put(found_ct);
Jan Engelhardt370786f2007-07-14 20:47:26 -0700148 list_del(&conn->list);
149 kfree(conn);
150 continue;
151 }
152
Jan Engelhardt539054a2009-11-06 18:08:32 -0800153 if (same_source_net(addr, mask, &conn->tuple.src.u3, family))
Jan Engelhardt370786f2007-07-14 20:47:26 -0700154 /* same source network -> be counted! */
155 ++matches;
Eric Dumazetea781f12009-03-25 21:05:46 +0100156 nf_ct_put(found_ct);
Jan Engelhardt370786f2007-07-14 20:47:26 -0700157 }
158
Patrick McHardy76507f62008-01-31 04:38:38 -0800159 rcu_read_unlock();
Jan Engelhardt370786f2007-07-14 20:47:26 -0700160
161 if (addit) {
162 /* save the new connection in our list */
163 conn = kzalloc(sizeof(*conn), GFP_ATOMIC);
164 if (conn == NULL)
165 return -ENOMEM;
166 conn->tuple = *tuple;
167 list_add(&conn->list, hash);
168 ++matches;
169 }
170
171 return matches;
172}
173
Jan Engelhardtd3c5ee62007-12-04 23:24:03 -0800174static bool
Jan Engelhardtf7108a202008-10-08 11:35:18 +0200175connlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par)
Jan Engelhardt370786f2007-07-14 20:47:26 -0700176{
Alexey Dobriyan83fc8102010-01-18 08:07:50 +0100177 struct net *net = dev_net(par->in ? par->in : par->out);
Jan Engelhardtf7108a202008-10-08 11:35:18 +0200178 const struct xt_connlimit_info *info = par->matchinfo;
Jan Engelhardt22c2d8b2007-12-17 22:44:47 -0800179 union nf_inet_addr addr;
Jan Engelhardt370786f2007-07-14 20:47:26 -0700180 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;
184 int connections;
185
186 ct = nf_ct_get(skb, &ctinfo);
187 if (ct != NULL)
188 tuple_ptr = &ct->tuplehash[0].tuple;
189 else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
Jan Engelhardt92f3b2b2008-10-08 11:35:20 +0200190 par->family, &tuple))
Jan Engelhardt370786f2007-07-14 20:47:26 -0700191 goto hotdrop;
192
Jan Engelhardt92f3b2b2008-10-08 11:35:20 +0200193 if (par->family == NFPROTO_IPV6) {
Jan Engelhardt370786f2007-07-14 20:47:26 -0700194 const struct ipv6hdr *iph = ipv6_hdr(skb);
195 memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr));
Jan Engelhardt370786f2007-07-14 20:47:26 -0700196 } else {
197 const struct iphdr *iph = ip_hdr(skb);
198 addr.ip = iph->saddr;
Jan Engelhardt370786f2007-07-14 20:47:26 -0700199 }
200
201 spin_lock_bh(&info->data->lock);
Alexey Dobriyan83fc8102010-01-18 08:07:50 +0100202 connections = count_them(net, info->data, tuple_ptr, &addr,
Jan Engelhardt539054a2009-11-06 18:08:32 -0800203 &info->mask, par->family);
Jan Engelhardt370786f2007-07-14 20:47:26 -0700204 spin_unlock_bh(&info->data->lock);
205
206 if (connections < 0) {
207 /* kmalloc failed, drop it entirely */
Jan Engelhardtf7108a202008-10-08 11:35:18 +0200208 *par->hotdrop = true;
Jan Engelhardt370786f2007-07-14 20:47:26 -0700209 return false;
210 }
211
212 return (connections > info->limit) ^ info->inverse;
213
214 hotdrop:
Jan Engelhardtf7108a202008-10-08 11:35:18 +0200215 *par->hotdrop = true;
Jan Engelhardt370786f2007-07-14 20:47:26 -0700216 return false;
217}
218
Jan Engelhardt9b4fce72008-10-08 11:35:18 +0200219static bool connlimit_mt_check(const struct xt_mtchk_param *par)
Jan Engelhardt370786f2007-07-14 20:47:26 -0700220{
Jan Engelhardt9b4fce72008-10-08 11:35:18 +0200221 struct xt_connlimit_info *info = par->matchinfo;
Jan Engelhardt370786f2007-07-14 20:47:26 -0700222 unsigned int i;
223
Jan Engelhardt294188a2010-01-04 16:28:38 +0100224 if (unlikely(!connlimit_rnd_inited)) {
225 get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
226 connlimit_rnd_inited = true;
227 }
Jan Engelhardt92f3b2b2008-10-08 11:35:20 +0200228 if (nf_ct_l3proto_try_module_get(par->family) < 0) {
Jan Engelhardt8bee4ba2010-03-17 16:04:40 +0100229 pr_info("cannot load conntrack support for "
230 "address family %u\n", par->family);
Jan Engelhardt370786f2007-07-14 20:47:26 -0700231 return false;
232 }
233
234 /* init private data */
235 info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL);
236 if (info->data == NULL) {
Jan Engelhardt92f3b2b2008-10-08 11:35:20 +0200237 nf_ct_l3proto_module_put(par->family);
Jan Engelhardt370786f2007-07-14 20:47:26 -0700238 return false;
239 }
240
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]);
244
245 return true;
246}
247
Jan Engelhardt6be3d852008-10-08 11:35:19 +0200248static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
Jan Engelhardt370786f2007-07-14 20:47:26 -0700249{
Jan Engelhardt6be3d852008-10-08 11:35:19 +0200250 const struct xt_connlimit_info *info = par->matchinfo;
Jan Engelhardt370786f2007-07-14 20:47:26 -0700251 struct xt_connlimit_conn *conn;
252 struct xt_connlimit_conn *tmp;
253 struct list_head *hash = info->data->iphash;
254 unsigned int i;
255
Jan Engelhardt92f3b2b2008-10-08 11:35:20 +0200256 nf_ct_l3proto_module_put(par->family);
Jan Engelhardt370786f2007-07-14 20:47:26 -0700257
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);
261 kfree(conn);
262 }
263 }
264
265 kfree(info->data);
266}
267
Jan Engelhardt92f3b2b2008-10-08 11:35:20 +0200268static struct xt_match connlimit_mt_reg __read_mostly = {
269 .name = "connlimit",
270 .revision = 0,
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,
276 .me = THIS_MODULE,
Jan Engelhardt370786f2007-07-14 20:47:26 -0700277};
278
Jan Engelhardtd3c5ee62007-12-04 23:24:03 -0800279static int __init connlimit_mt_init(void)
Jan Engelhardt370786f2007-07-14 20:47:26 -0700280{
Jan Engelhardt92f3b2b2008-10-08 11:35:20 +0200281 return xt_register_match(&connlimit_mt_reg);
Jan Engelhardt370786f2007-07-14 20:47:26 -0700282}
283
Jan Engelhardtd3c5ee62007-12-04 23:24:03 -0800284static void __exit connlimit_mt_exit(void)
Jan Engelhardt370786f2007-07-14 20:47:26 -0700285{
Jan Engelhardt92f3b2b2008-10-08 11:35:20 +0200286 xt_unregister_match(&connlimit_mt_reg);
Jan Engelhardt370786f2007-07-14 20:47:26 -0700287}
288
Jan Engelhardtd3c5ee62007-12-04 23:24:03 -0800289module_init(connlimit_mt_init);
290module_exit(connlimit_mt_exit);
Jan Engelhardt92f3b2b2008-10-08 11:35:20 +0200291MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
Jan Engelhardt2ae15b62008-01-14 23:42:28 -0800292MODULE_DESCRIPTION("Xtables: Number of connections matching");
Jan Engelhardt370786f2007-07-14 20:47:26 -0700293MODULE_LICENSE("GPL");
294MODULE_ALIAS("ipt_connlimit");
295MODULE_ALIAS("ip6t_connlimit");