d7becf08a93a3481fe587842f47f60d871f882d3
[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  *   Contact: <jengelh@computergmbh.de>
9  *
10  * based on ...
11  *
12  * Kernel module to match connection tracking information.
13  * GPL (C) 1999  Rusty Russell (rusty@rustcorp.com.au).
14  */
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/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
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;
36 };
37
38 struct xt_connlimit_data {
39         struct list_head iphash[256];
40         spinlock_t lock;
41 };
42
43 static u_int32_t connlimit_rnd;
44 static bool connlimit_rnd_inited;
45
46 static inline unsigned int connlimit_iphash(__be32 addr)
47 {
48         if (unlikely(!connlimit_rnd_inited)) {
49                 get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
50                 connlimit_rnd_inited = true;
51         }
52         return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF;
53 }
54
55 static inline unsigned int
56 connlimit_iphash6(const union nf_conntrack_address *addr,
57                   const union nf_conntrack_address *mask)
58 {
59         union nf_conntrack_address res;
60         unsigned int i;
61
62         if (unlikely(!connlimit_rnd_inited)) {
63                 get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
64                 connlimit_rnd_inited = true;
65         }
66
67         for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
68                 res.ip6[i] = addr->ip6[i] & mask->ip6[i];
69
70         return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF;
71 }
72
73 static inline bool already_closed(const struct nf_conn *conn)
74 {
75         u_int16_t proto = conn->tuplehash[0].tuple.dst.protonum;
76
77         if (proto == IPPROTO_TCP)
78                 return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT;
79         else
80                 return 0;
81 }
82
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)
87 {
88         if (family == AF_INET) {
89                 return (addr->ip & mask->ip) == (u3->ip & mask->ip);
90         } else {
91                 union nf_conntrack_address lh, rh;
92                 unsigned int i;
93
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];
97                 }
98
99                 return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0;
100         }
101 }
102
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)
108 {
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;
114         bool addit = true;
115         int matches = 0;
116
117
118         if (match->family == AF_INET6)
119                 hash = &data->iphash[connlimit_iphash6(addr, mask)];
120         else
121                 hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
122
123         read_lock_bh(&nf_conntrack_lock);
124
125         /* check the saved connections */
126         list_for_each_entry_safe(conn, tmp, hash, list) {
127                 found    = __nf_conntrack_find(&conn->tuple, NULL);
128                 found_ct = NULL;
129
130                 if (found != NULL)
131                         found_ct = nf_ct_tuplehash_to_ctrack(found);
132
133                 if (found_ct != NULL &&
134                     nf_ct_tuple_equal(&conn->tuple, tuple) &&
135                     !already_closed(found_ct))
136                         /*
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".
140                          */
141                         addit = false;
142
143                 if (found == NULL) {
144                         /* this one is gone */
145                         list_del(&conn->list);
146                         kfree(conn);
147                         continue;
148                 }
149
150                 if (already_closed(found_ct)) {
151                         /*
152                          * we do not care about connections which are
153                          * closed already -> ditch it
154                          */
155                         list_del(&conn->list);
156                         kfree(conn);
157                         continue;
158                 }
159
160                 if (same_source_net(addr, mask, &conn->tuple.src.u3,
161                     match->family))
162                         /* same source network -> be counted! */
163                         ++matches;
164         }
165
166         read_unlock_bh(&nf_conntrack_lock);
167
168         if (addit) {
169                 /* save the new connection in our list */
170                 conn = kzalloc(sizeof(*conn), GFP_ATOMIC);
171                 if (conn == NULL)
172                         return -ENOMEM;
173                 conn->tuple = *tuple;
174                 list_add(&conn->list, hash);
175                 ++matches;
176         }
177
178         return matches;
179 }
180
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)
187 {
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;
194         int connections;
195
196         ct = nf_ct_get(skb, &ctinfo);
197         if (ct != NULL)
198                 tuple_ptr = &ct->tuplehash[0].tuple;
199         else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
200                                     match->family, &tuple))
201                 goto hotdrop;
202
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));
207         } else {
208                 const struct iphdr *iph = ip_hdr(skb);
209                 addr.ip = iph->saddr;
210                 mask.ip = info->v4_mask;
211         }
212
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);
216
217         if (connections < 0) {
218                 /* kmalloc failed, drop it entirely */
219                 *hotdrop = true;
220                 return false;
221         }
222
223         return (connections > info->limit) ^ info->inverse;
224
225  hotdrop:
226         *hotdrop = true;
227         return false;
228 }
229
230 static bool connlimit_check(const char *tablename, const void *ip,
231                             const struct xt_match *match, void *matchinfo,
232                             unsigned int hook_mask)
233 {
234         struct xt_connlimit_info *info = matchinfo;
235         unsigned int i;
236
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);
240                 return false;
241         }
242
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);
247                 return false;
248         }
249
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]);
253
254         return true;
255 }
256
257 static void connlimit_destroy(const struct xt_match *match, void *matchinfo)
258 {
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;
263         unsigned int i;
264
265         nf_ct_l3proto_module_put(match->family);
266
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);
270                         kfree(conn);
271                 }
272         }
273
274         kfree(info->data);
275 }
276
277 static struct xt_match connlimit_reg[] __read_mostly = {
278         {
279                 .name       = "connlimit",
280                 .family     = AF_INET,
281                 .checkentry = connlimit_check,
282                 .match      = connlimit_match,
283                 .matchsize  = sizeof(struct xt_connlimit_info),
284                 .destroy    = connlimit_destroy,
285                 .me         = THIS_MODULE,
286         },
287         {
288                 .name       = "connlimit",
289                 .family     = AF_INET6,
290                 .checkentry = connlimit_check,
291                 .match      = connlimit_match,
292                 .matchsize  = sizeof(struct xt_connlimit_info),
293                 .destroy    = connlimit_destroy,
294                 .me         = THIS_MODULE,
295         },
296 };
297
298 static int __init xt_connlimit_init(void)
299 {
300         return xt_register_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg));
301 }
302
303 static void __exit xt_connlimit_exit(void)
304 {
305         xt_unregister_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg));
306 }
307
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");