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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
35struct xt_connlimit_conn {
36 struct hlist_node node;
37 struct nf_conntrack_tuple tuple;
38 union nf_inet_addr addr;
39};
40
41struct xt_connlimit_data {
42 struct hlist_head iphash[256];
43 spinlock_t lock;
44};
45
46static u_int32_t connlimit_rnd __read_mostly;
47
48static inline unsigned int connlimit_iphash(__be32 addr)
49{
50 return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF;
51}
52
53static inline unsigned int
54connlimit_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
66static 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
75static inline unsigned int
76same_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
95static 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
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
131
132
133
134 addit = false;
135
136 if (found == NULL) {
137
138 hlist_del(&conn->node);
139 kfree(conn);
140 continue;
141 }
142
143 if (already_closed(found_ct)) {
144
145
146
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
156 ++matches;
157 nf_ct_put(found_ct);
158 }
159
160 rcu_read_unlock();
161
162 if (addit) {
163
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
176static bool
177connlimit_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
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
222static 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
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
257static 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
277static 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
300static int __init connlimit_mt_init(void)
301{
302 return xt_register_matches(connlimit_mt_reg,
303 ARRAY_SIZE(connlimit_mt_reg));
304}
305
306static void __exit connlimit_mt_exit(void)
307{
308 xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg));
309}
310
311module_init(connlimit_mt_init);
312module_exit(connlimit_mt_exit);
313MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>");
314MODULE_DESCRIPTION("Xtables: Number of connections matching");
315MODULE_LICENSE("GPL");
316MODULE_ALIAS("ipt_connlimit");
317MODULE_ALIAS("ip6t_connlimit");
318
