netfilter: xt_connlimit: use hotdrop jump mark
[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 };
39
40 struct xt_connlimit_data {
41         struct list_head iphash[256];
42         spinlock_t lock;
43 };
44
45 static u_int32_t connlimit_rnd __read_mostly;
46 static bool connlimit_rnd_inited __read_mostly;
47
48 static inline unsigned int connlimit_iphash(__be32 addr)
49 {
50         return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF;
51 }
52
53 static inline unsigned int
54 connlimit_iphash6(const union nf_inet_addr *addr,
55                   const union nf_inet_addr *mask)
56 {
57         union nf_inet_addr res;
58         unsigned int i;
59
60         for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i)
61                 res.ip6[i] = addr->ip6[i] & mask->ip6[i];
62
63         return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF;
64 }
65
66 static inline bool already_closed(const struct nf_conn *conn)
67 {
68         if (nf_ct_protonum(conn) == IPPROTO_TCP)
69                 return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT ||
70                        conn->proto.tcp.state == TCP_CONNTRACK_CLOSE;
71         else
72                 return 0;
73 }
74
75 static inline unsigned int
76 same_source_net(const union nf_inet_addr *addr,
77                 const union nf_inet_addr *mask,
78                 const union nf_inet_addr *u3, u_int8_t family)
79 {
80         if (family == NFPROTO_IPV4) {
81                 return (addr->ip & mask->ip) == (u3->ip & mask->ip);
82         } else {
83                 union nf_inet_addr lh, rh;
84                 unsigned int i;
85
86                 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) {
87                         lh.ip6[i] = addr->ip6[i] & mask->ip6[i];
88                         rh.ip6[i] = u3->ip6[i] & mask->ip6[i];
89                 }
90
91                 return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0;
92         }
93 }
94
95 static int count_them(struct net *net,
96                       struct xt_connlimit_data *data,
97                       const struct nf_conntrack_tuple *tuple,
98                       const union nf_inet_addr *addr,
99                       const union nf_inet_addr *mask,
100                       u_int8_t family)
101 {
102         const struct nf_conntrack_tuple_hash *found;
103         struct xt_connlimit_conn *conn;
104         struct xt_connlimit_conn *tmp;
105         struct nf_conn *found_ct;
106         struct list_head *hash;
107         bool addit = true;
108         int matches = 0;
109
110         if (family == NFPROTO_IPV6)
111                 hash = &data->iphash[connlimit_iphash6(addr, mask)];
112         else
113                 hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)];
114
115         rcu_read_lock();
116
117         /* check the saved connections */
118         list_for_each_entry_safe(conn, tmp, hash, list) {
119                 found    = nf_conntrack_find_get(net, NF_CT_DEFAULT_ZONE,
120                                                  &conn->tuple);
121                 found_ct = NULL;
122
123                 if (found != NULL)
124                         found_ct = nf_ct_tuplehash_to_ctrack(found);
125
126                 if (found_ct != NULL &&
127                     nf_ct_tuple_equal(&conn->tuple, tuple) &&
128                     !already_closed(found_ct))
129                         /*
130                          * Just to be sure we have it only once in the list.
131                          * We should not see tuples twice unless someone hooks
132                          * this into a table without "-p tcp --syn".
133                          */
134                         addit = false;
135
136                 if (found == NULL) {
137                         /* this one is gone */
138                         list_del(&conn->list);
139                         kfree(conn);
140                         continue;
141                 }
142
143                 if (already_closed(found_ct)) {
144                         /*
145                          * we do not care about connections which are
146                          * closed already -> ditch it
147                          */
148                         nf_ct_put(found_ct);
149                         list_del(&conn->list);
150                         kfree(conn);
151                         continue;
152                 }
153
154                 if (same_source_net(addr, mask, &conn->tuple.src.u3, family))
155                         /* same source network -> be counted! */
156                         ++matches;
157                 nf_ct_put(found_ct);
158         }
159
160         rcu_read_unlock();
161
162         if (addit) {
163                 /* save the new connection in our list */
164                 conn = kzalloc(sizeof(*conn), GFP_ATOMIC);
165                 if (conn == NULL)
166                         return -ENOMEM;
167                 conn->tuple = *tuple;
168                 list_add(&conn->list, hash);
169                 ++matches;
170         }
171
172         return matches;
173 }
174
175 static bool
176 connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
177 {
178         struct net *net = dev_net(par->in ? par->in : par->out);
179         const struct xt_connlimit_info *info = par->matchinfo;
180         union nf_inet_addr addr;
181         struct nf_conntrack_tuple tuple;
182         const struct nf_conntrack_tuple *tuple_ptr = &tuple;
183         enum ip_conntrack_info ctinfo;
184         const struct nf_conn *ct;
185         int connections;
186
187         ct = nf_ct_get(skb, &ctinfo);
188         if (ct != NULL)
189                 tuple_ptr = &ct->tuplehash[0].tuple;
190         else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
191                                     par->family, &tuple))
192                 goto hotdrop;
193
194         if (par->family == NFPROTO_IPV6) {
195                 const struct ipv6hdr *iph = ipv6_hdr(skb);
196                 memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr));
197         } else {
198                 const struct iphdr *iph = ip_hdr(skb);
199                 addr.ip = iph->saddr;
200         }
201
202         spin_lock_bh(&info->data->lock);
203         connections = count_them(net, info->data, tuple_ptr, &addr,
204                                  &info->mask, par->family);
205         spin_unlock_bh(&info->data->lock);
206
207         if (connections < 0)
208                 /* kmalloc failed, drop it entirely */
209                 goto hotdrop;
210
211         return (connections > info->limit) ^ info->inverse;
212
213  hotdrop:
214         par->hotdrop = true;
215         return false;
216 }
217
218 static int connlimit_mt_check(const struct xt_mtchk_param *par)
219 {
220         struct xt_connlimit_info *info = par->matchinfo;
221         unsigned int i;
222         int ret;
223
224         if (unlikely(!connlimit_rnd_inited)) {
225                 get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd));
226                 connlimit_rnd_inited = true;
227         }
228         ret = nf_ct_l3proto_try_module_get(par->family);
229         if (ret < 0) {
230                 pr_info("cannot load conntrack support for "
231                         "address family %u\n", par->family);
232                 return ret;
233         }
234
235         /* init private data */
236         info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL);
237         if (info->data == NULL) {
238                 nf_ct_l3proto_module_put(par->family);
239                 return -ENOMEM;
240         }
241
242         spin_lock_init(&info->data->lock);
243         for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i)
244                 INIT_LIST_HEAD(&info->data->iphash[i]);
245
246         return 0;
247 }
248
249 static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
250 {
251         const struct xt_connlimit_info *info = par->matchinfo;
252         struct xt_connlimit_conn *conn;
253         struct xt_connlimit_conn *tmp;
254         struct list_head *hash = info->data->iphash;
255         unsigned int i;
256
257         nf_ct_l3proto_module_put(par->family);
258
259         for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) {
260                 list_for_each_entry_safe(conn, tmp, &hash[i], list) {
261                         list_del(&conn->list);
262                         kfree(conn);
263                 }
264         }
265
266         kfree(info->data);
267 }
268
269 static struct xt_match connlimit_mt_reg __read_mostly = {
270         .name       = "connlimit",
271         .revision   = 0,
272         .family     = NFPROTO_UNSPEC,
273         .checkentry = connlimit_mt_check,
274         .match      = connlimit_mt,
275         .matchsize  = sizeof(struct xt_connlimit_info),
276         .destroy    = connlimit_mt_destroy,
277         .me         = THIS_MODULE,
278 };
279
280 static int __init connlimit_mt_init(void)
281 {
282         return xt_register_match(&connlimit_mt_reg);
283 }
284
285 static void __exit connlimit_mt_exit(void)
286 {
287         xt_unregister_match(&connlimit_mt_reg);
288 }
289
290 module_init(connlimit_mt_init);
291 module_exit(connlimit_mt_exit);
292 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
293 MODULE_DESCRIPTION("Xtables: Number of connections matching");
294 MODULE_LICENSE("GPL");
295 MODULE_ALIAS("ipt_connlimit");
296 MODULE_ALIAS("ip6t_connlimit");