netfilter: xtables: move extension arguments into compound structure (1/6)
[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_inet_addr *addr,
57                   const union nf_inet_addr *mask)
58 {
59         union nf_inet_addr 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         if (nf_ct_protonum(conn) == IPPROTO_TCP)
76                 return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT ||
77                        conn->proto.tcp.state == TCP_CONNTRACK_CLOSE;
78         else
79                 return 0;
80 }
81
82 static inline unsigned int
83 same_source_net(const union nf_inet_addr *addr,
84                 const union nf_inet_addr *mask,
85                 const union nf_inet_addr *u3, u_int8_t family)
86 {
87         if (family == NFPROTO_IPV4) {
88                 return (addr->ip & mask->ip) == (u3->ip & mask->ip);
89         } else {
90                 union nf_inet_addr lh, rh;
91                 unsigned int i;
92
93                 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) {
94                         lh.ip6[i] = addr->ip6[i] & mask->ip6[i];
95                         rh.ip6[i] = u3->ip6[i] & mask->ip6[i];
96                 }
97
98                 return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0;
99         }
100 }
101
102 static int count_them(struct xt_connlimit_data *data,
103                       const struct nf_conntrack_tuple *tuple,
104                       const union nf_inet_addr *addr,
105                       const union nf_inet_addr *mask,
106                       const struct xt_match *match)
107 {
108         const struct nf_conntrack_tuple_hash *found;
109         struct xt_connlimit_conn *conn;
110         struct xt_connlimit_conn *tmp;
111         const struct nf_conn *found_ct;
112         struct list_head *hash;
113         bool addit = true;
114         int matches = 0;
115
116
117         if (match->family == NFPROTO_IPV6)
118                 hash = &data->iphash[connlimit_iphash6(addr, mask)];
119         else
120                 hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
121
122         rcu_read_lock();
123
124         /* check the saved connections */
125         list_for_each_entry_safe(conn, tmp, hash, list) {
126                 found    = __nf_conntrack_find(&init_net, &conn->tuple);
127                 found_ct = NULL;
128
129                 if (found != NULL)
130                         found_ct = nf_ct_tuplehash_to_ctrack(found);
131
132                 if (found_ct != NULL &&
133                     nf_ct_tuple_equal(&conn->tuple, tuple) &&
134                     !already_closed(found_ct))
135                         /*
136                          * Just to be sure we have it only once in the list.
137                          * We should not see tuples twice unless someone hooks
138                          * this into a table without "-p tcp --syn".
139                          */
140                         addit = false;
141
142                 if (found == NULL) {
143                         /* this one is gone */
144                         list_del(&conn->list);
145                         kfree(conn);
146                         continue;
147                 }
148
149                 if (already_closed(found_ct)) {
150                         /*
151                          * we do not care about connections which are
152                          * closed already -> ditch it
153                          */
154                         list_del(&conn->list);
155                         kfree(conn);
156                         continue;
157                 }
158
159                 if (same_source_net(addr, mask, &conn->tuple.src.u3,
160                     match->family))
161                         /* same source network -> be counted! */
162                         ++matches;
163         }
164
165         rcu_read_unlock();
166
167         if (addit) {
168                 /* save the new connection in our list */
169                 conn = kzalloc(sizeof(*conn), GFP_ATOMIC);
170                 if (conn == NULL)
171                         return -ENOMEM;
172                 conn->tuple = *tuple;
173                 list_add(&conn->list, hash);
174                 ++matches;
175         }
176
177         return matches;
178 }
179
180 static bool
181 connlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par)
182 {
183         const struct xt_connlimit_info *info = par->matchinfo;
184         union nf_inet_addr addr;
185         struct nf_conntrack_tuple tuple;
186         const struct nf_conntrack_tuple *tuple_ptr = &tuple;
187         enum ip_conntrack_info ctinfo;
188         const struct nf_conn *ct;
189         int connections;
190
191         ct = nf_ct_get(skb, &ctinfo);
192         if (ct != NULL)
193                 tuple_ptr = &ct->tuplehash[0].tuple;
194         else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
195                                     par->match->family, &tuple))
196                 goto hotdrop;
197
198         if (par->match->family == NFPROTO_IPV6) {
199                 const struct ipv6hdr *iph = ipv6_hdr(skb);
200                 memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr));
201         } else {
202                 const struct iphdr *iph = ip_hdr(skb);
203                 addr.ip = iph->saddr;
204         }
205
206         spin_lock_bh(&info->data->lock);
207         connections = count_them(info->data, tuple_ptr, &addr,
208                                  &info->mask, par->match);
209         spin_unlock_bh(&info->data->lock);
210
211         if (connections < 0) {
212                 /* kmalloc failed, drop it entirely */
213                 *par->hotdrop = true;
214                 return false;
215         }
216
217         return (connections > info->limit) ^ info->inverse;
218
219  hotdrop:
220         *par->hotdrop = true;
221         return false;
222 }
223
224 static bool
225 connlimit_mt_check(const char *tablename, const void *ip,
226                    const struct xt_match *match, void *matchinfo,
227                    unsigned int hook_mask)
228 {
229         struct xt_connlimit_info *info = matchinfo;
230         unsigned int i;
231
232         if (nf_ct_l3proto_try_module_get(match->family) < 0) {
233                 printk(KERN_WARNING "cannot load conntrack support for "
234                        "address family %u\n", match->family);
235                 return false;
236         }
237
238         /* init private data */
239         info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL);
240         if (info->data == NULL) {
241                 nf_ct_l3proto_module_put(match->family);
242                 return false;
243         }
244
245         spin_lock_init(&info->data->lock);
246         for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i)
247                 INIT_LIST_HEAD(&info->data->iphash[i]);
248
249         return true;
250 }
251
252 static void
253 connlimit_mt_destroy(const struct xt_match *match, void *matchinfo)
254 {
255         const struct xt_connlimit_info *info = matchinfo;
256         struct xt_connlimit_conn *conn;
257         struct xt_connlimit_conn *tmp;
258         struct list_head *hash = info->data->iphash;
259         unsigned int i;
260
261         nf_ct_l3proto_module_put(match->family);
262
263         for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) {
264                 list_for_each_entry_safe(conn, tmp, &hash[i], list) {
265                         list_del(&conn->list);
266                         kfree(conn);
267                 }
268         }
269
270         kfree(info->data);
271 }
272
273 static struct xt_match connlimit_mt_reg[] __read_mostly = {
274         {
275                 .name       = "connlimit",
276                 .family     = NFPROTO_IPV4,
277                 .checkentry = connlimit_mt_check,
278                 .match      = connlimit_mt,
279                 .matchsize  = sizeof(struct xt_connlimit_info),
280                 .destroy    = connlimit_mt_destroy,
281                 .me         = THIS_MODULE,
282         },
283         {
284                 .name       = "connlimit",
285                 .family     = NFPROTO_IPV6,
286                 .checkentry = connlimit_mt_check,
287                 .match      = connlimit_mt,
288                 .matchsize  = sizeof(struct xt_connlimit_info),
289                 .destroy    = connlimit_mt_destroy,
290                 .me         = THIS_MODULE,
291         },
292 };
293
294 static int __init connlimit_mt_init(void)
295 {
296         return xt_register_matches(connlimit_mt_reg,
297                ARRAY_SIZE(connlimit_mt_reg));
298 }
299
300 static void __exit connlimit_mt_exit(void)
301 {
302         xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg));
303 }
304
305 module_init(connlimit_mt_init);
306 module_exit(connlimit_mt_exit);
307 MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>");
308 MODULE_DESCRIPTION("Xtables: Number of connections matching");
309 MODULE_LICENSE("GPL");
310 MODULE_ALIAS("ipt_connlimit");
311 MODULE_ALIAS("ip6t_connlimit");