mqprio: Avoid panic if no options are provided
[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 hlist_node               node;
37         struct nf_conntrack_tuple       tuple;
38         union nf_inet_addr              addr;
39 };
40
41 struct xt_connlimit_data {
42         struct hlist_head       iphash[256];
43         spinlock_t              lock;
44 };
45
46 static u_int32_t connlimit_rnd __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 hlist_node *pos, *n;
105         struct nf_conn *found_ct;
106         struct hlist_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         hlist_for_each_entry_safe(conn, pos, n, hash, node) {
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                         hlist_del(&conn->node);
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                         hlist_del(&conn->node);
150                         kfree(conn);
151                         continue;
152                 }
153
154                 if (same_source_net(addr, mask, &conn->addr, 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 = kmalloc(sizeof(*conn), GFP_ATOMIC);
165                 if (conn == NULL)
166                         return -ENOMEM;
167                 conn->tuple = *tuple;
168                 conn->addr = *addr;
169                 hlist_add_head(&conn->node, hash);
170                 ++matches;
171         }
172
173         return matches;
174 }
175
176 static bool
177 connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par)
178 {
179         struct net *net = dev_net(par->in ? par->in : par->out);
180         const struct xt_connlimit_info *info = par->matchinfo;
181         union nf_inet_addr addr;
182         struct nf_conntrack_tuple tuple;
183         const struct nf_conntrack_tuple *tuple_ptr = &tuple;
184         enum ip_conntrack_info ctinfo;
185         const struct nf_conn *ct;
186         int connections;
187
188         ct = nf_ct_get(skb, &ctinfo);
189         if (ct != NULL)
190                 tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple;
191         else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb),
192                                     par->family, &tuple))
193                 goto hotdrop;
194
195         if (par->family == NFPROTO_IPV6) {
196                 const struct ipv6hdr *iph = ipv6_hdr(skb);
197                 memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ?
198                        &iph->daddr : &iph->saddr, sizeof(addr.ip6));
199         } else {
200                 const struct iphdr *iph = ip_hdr(skb);
201                 addr.ip = (info->flags & XT_CONNLIMIT_DADDR) ?
202                           iph->daddr : iph->saddr;
203         }
204
205         spin_lock_bh(&info->data->lock);
206         connections = count_them(net, info->data, tuple_ptr, &addr,
207                                  &info->mask, par->family);
208         spin_unlock_bh(&info->data->lock);
209
210         if (connections < 0)
211                 /* kmalloc failed, drop it entirely */
212                 goto hotdrop;
213
214         return (connections > info->limit) ^
215                !!(info->flags & XT_CONNLIMIT_INVERT);
216
217  hotdrop:
218         par->hotdrop = true;
219         return false;
220 }
221
222 static int connlimit_mt_check(const struct xt_mtchk_param *par)
223 {
224         struct xt_connlimit_info *info = par->matchinfo;
225         unsigned int i;
226         int ret;
227
228         if (unlikely(!connlimit_rnd)) {
229                 u_int32_t rand;
230
231                 do {
232                         get_random_bytes(&rand, sizeof(rand));
233                 } while (!rand);
234                 cmpxchg(&connlimit_rnd, 0, rand);
235         }
236         ret = nf_ct_l3proto_try_module_get(par->family);
237         if (ret < 0) {
238                 pr_info("cannot load conntrack support for "
239                         "address family %u\n", par->family);
240                 return ret;
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(par->family);
247                 return -ENOMEM;
248         }
249
250         spin_lock_init(&info->data->lock);
251         for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i)
252                 INIT_HLIST_HEAD(&info->data->iphash[i]);
253
254         return 0;
255 }
256
257 static void connlimit_mt_destroy(const struct xt_mtdtor_param *par)
258 {
259         const struct xt_connlimit_info *info = par->matchinfo;
260         struct xt_connlimit_conn *conn;
261         struct hlist_node *pos, *n;
262         struct hlist_head *hash = info->data->iphash;
263         unsigned int i;
264
265         nf_ct_l3proto_module_put(par->family);
266
267         for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) {
268                 hlist_for_each_entry_safe(conn, pos, n, &hash[i], node) {
269                         hlist_del(&conn->node);
270                         kfree(conn);
271                 }
272         }
273
274         kfree(info->data);
275 }
276
277 static struct xt_match connlimit_mt_reg[] __read_mostly = {
278         {
279                 .name       = "connlimit",
280                 .revision   = 0,
281                 .family     = NFPROTO_UNSPEC,
282                 .checkentry = connlimit_mt_check,
283                 .match      = connlimit_mt,
284                 .matchsize  = sizeof(struct xt_connlimit_info),
285                 .destroy    = connlimit_mt_destroy,
286                 .me         = THIS_MODULE,
287         },
288         {
289                 .name       = "connlimit",
290                 .revision   = 1,
291                 .family     = NFPROTO_UNSPEC,
292                 .checkentry = connlimit_mt_check,
293                 .match      = connlimit_mt,
294                 .matchsize  = sizeof(struct xt_connlimit_info),
295                 .destroy    = connlimit_mt_destroy,
296                 .me         = THIS_MODULE,
297         },
298 };
299
300 static int __init connlimit_mt_init(void)
301 {
302         return xt_register_matches(connlimit_mt_reg,
303                ARRAY_SIZE(connlimit_mt_reg));
304 }
305
306 static void __exit connlimit_mt_exit(void)
307 {
308         xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg));
309 }
310
311 module_init(connlimit_mt_init);
312 module_exit(connlimit_mt_exit);
313 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
314 MODULE_DESCRIPTION("Xtables: Number of connections matching");
315 MODULE_LICENSE("GPL");
316 MODULE_ALIAS("ipt_connlimit");
317 MODULE_ALIAS("ip6t_connlimit");