1f4b9f9da496f24cf840ea96226d26b6179757a5
[linux-2.6.git] / net / netfilter / xt_connlimit.c
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 #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/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>
33
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;
39 };
40
41 struct xt_connlimit_data {
42         struct list_head iphash[256];
43         spinlock_t lock;
44 };
45
46 static u_int32_t connlimit_rnd __read_mostly;
47 static bool connlimit_rnd_inited __read_mostly;
48
49 static inline unsigned int connlimit_iphash(__be32 addr)
50 {
51         return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF;
52 }
53
54 static inline unsigned int
55 connlimit_iphash6(const union nf_inet_addr *addr,
56                   const union nf_inet_addr *mask)
57 {
58         union nf_inet_addr res;
59         unsigned int i;
60
61         for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
62                 res.ip6[i] = addr->ip6[i] & mask->ip6[i];
63
64         return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF;
65 }
66
67 static inline bool already_closed(const struct nf_conn *conn)
68 {
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;
72         else
73                 return 0;
74 }
75
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)
80 {
81         if (family == NFPROTO_IPV4) {
82                 return (addr->ip & mask->ip) == (u3->ip & mask->ip);
83         } else {
84                 union nf_inet_addr lh, rh;
85                 unsigned int i;
86
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];
90                 }
91
92                 return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0;
93         }
94 }
95
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,
101                       u_int8_t family)
102 {
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;
108         bool addit = true;
109         int matches = 0;
110
111         if (family == NFPROTO_IPV6)
112                 hash = &data->iphash[connlimit_iphash6(addr, mask)];
113         else
114                 hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
115
116         rcu_read_lock();
117
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,
121                                                  &conn->tuple);
122                 found_ct = NULL;
123
124                 if (found != NULL)
125                         found_ct = nf_ct_tuplehash_to_ctrack(found);
126
127                 if (found_ct != NULL &&
128                     nf_ct_tuple_equal(&conn->tuple, tuple) &&
129                     !already_closed(found_ct))
130                         /*
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".
134                          */
135                         addit = false;
136
137                 if (found == NULL) {
138                         /* this one is gone */
139                         list_del(&conn->list);
140                         kfree(conn);
141                         continue;
142                 }
143
144                 if (already_closed(found_ct)) {
145                         /*
146                          * we do not care about connections which are
147                          * closed already -> ditch it
148                          */
149                         nf_ct_put(found_ct);
150                         list_del(&conn->list);
151                         kfree(conn);
152                         continue;
153                 }
154
155                 if (same_source_net(addr, mask, &conn->addr, family))
156                         /* same source network -> be counted! */
157                         ++matches;
158                 nf_ct_put(found_ct);
159         }
160
161         rcu_read_unlock();
162
163         if (addit) {
164                 /* save the new connection in our list */
165                 conn = kzalloc(sizeof(*conn), GFP_ATOMIC);
166                 if (conn == NULL)
167                         return -ENOMEM;
168                 conn->tuple = *tuple;
169                 conn->addr = *addr;
170                 list_add(&conn->list, hash);
171                 ++matches;
172         }
173
174         return matches;
175 }
176
177 static bool
178 connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
179 {
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;
187         int connections;
188
189         ct = nf_ct_get(skb, &ctinfo);
190         if (ct != NULL)
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))
194                 goto hotdrop;
195
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));
200         } else {
201                 const struct iphdr *iph = ip_hdr(skb);
202                 addr.ip = (info->flags & XT_CONNLIMIT_DADDR) ?
203                           iph->daddr : iph->saddr;
204         }
205
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);
210
211         if (connections < 0)
212                 /* kmalloc failed, drop it entirely */
213                 goto hotdrop;
214
215         return (connections > info->limit) ^
216                !!(info->flags & XT_CONNLIMIT_INVERT);
217
218  hotdrop:
219         par->hotdrop = true;
220         return false;
221 }
222
223 static int connlimit_mt_check(const struct xt_mtchk_param *par)
224 {
225         struct xt_connlimit_info *info = par->matchinfo;
226         unsigned int i;
227         int ret;
228
229         if (unlikely(!connlimit_rnd_inited)) {
230                 get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
231                 connlimit_rnd_inited = true;
232         }
233         ret = nf_ct_l3proto_try_module_get(par->family);
234         if (ret < 0) {
235                 pr_info("cannot load conntrack support for "
236                         "address family %u\n", par->family);
237                 return ret;
238         }
239
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);
244                 return -ENOMEM;
245         }
246
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]);
250
251         return 0;
252 }
253
254 static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
255 {
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;
260         unsigned int i;
261
262         nf_ct_l3proto_module_put(par->family);
263
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);
267                         kfree(conn);
268                 }
269         }
270
271         kfree(info->data);
272 }
273
274 static struct xt_match connlimit_mt_reg[] __read_mostly = {
275         {
276                 .name       = "connlimit",
277                 .revision   = 0,
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,
283                 .me         = THIS_MODULE,
284         },
285         {
286                 .name       = "connlimit",
287                 .revision   = 1,
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,
293                 .me         = THIS_MODULE,
294         },
295 };
296
297 static int __init connlimit_mt_init(void)
298 {
299         return xt_register_matches(connlimit_mt_reg,
300                ARRAY_SIZE(connlimit_mt_reg));
301 }
302
303 static void __exit connlimit_mt_exit(void)
304 {
305         xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg));
306 }
307
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");