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370786f9 JE |
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 | * Copyright © Jan Engelhardt <jengelh@gmx.de>, 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 | #include <linux/in.h> | |
15 | #include <linux/in6.h> | |
16 | #include <linux/ip.h> | |
17 | #include <linux/ipv6.h> | |
18 | #include <linux/jhash.h> | |
19 | #include <linux/list.h> | |
20 | #include <linux/module.h> | |
21 | #include <linux/random.h> | |
22 | #include <linux/skbuff.h> | |
23 | #include <linux/spinlock.h> | |
24 | #include <linux/netfilter/nf_conntrack_tcp.h> | |
25 | #include <linux/netfilter/x_tables.h> | |
26 | #include <linux/netfilter/xt_connlimit.h> | |
27 | #include <net/netfilter/nf_conntrack.h> | |
28 | #include <net/netfilter/nf_conntrack_core.h> | |
29 | #include <net/netfilter/nf_conntrack_tuple.h> | |
30 | ||
31 | /* we will save the tuples of all connections we care about */ | |
32 | struct xt_connlimit_conn { | |
33 | struct list_head list; | |
34 | struct nf_conntrack_tuple tuple; | |
35 | }; | |
36 | ||
37 | struct xt_connlimit_data { | |
38 | struct list_head iphash[256]; | |
39 | spinlock_t lock; | |
40 | }; | |
41 | ||
42 | static u_int32_t connlimit_rnd; | |
43 | static bool connlimit_rnd_inited; | |
44 | ||
a34c4589 | 45 | static inline unsigned int connlimit_iphash(__be32 addr) |
370786f9 JE |
46 | { |
47 | if (unlikely(!connlimit_rnd_inited)) { | |
48 | get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); | |
49 | connlimit_rnd_inited = true; | |
50 | } | |
a34c4589 | 51 | return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; |
370786f9 JE |
52 | } |
53 | ||
54 | static inline unsigned int | |
55 | connlimit_iphash6(const union nf_conntrack_address *addr, | |
56 | const union nf_conntrack_address *mask) | |
57 | { | |
58 | union nf_conntrack_address res; | |
59 | unsigned int i; | |
60 | ||
61 | if (unlikely(!connlimit_rnd_inited)) { | |
62 | get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); | |
63 | connlimit_rnd_inited = true; | |
64 | } | |
65 | ||
66 | for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) | |
67 | res.ip6[i] = addr->ip6[i] & mask->ip6[i]; | |
68 | ||
a34c4589 | 69 | return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; |
370786f9 JE |
70 | } |
71 | ||
72 | static inline bool already_closed(const struct nf_conn *conn) | |
73 | { | |
74 | u_int16_t proto = conn->tuplehash[0].tuple.dst.protonum; | |
75 | ||
76 | if (proto == IPPROTO_TCP) | |
77 | return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT; | |
78 | else | |
79 | return 0; | |
80 | } | |
81 | ||
82 | static inline unsigned int | |
83 | same_source_net(const union nf_conntrack_address *addr, | |
84 | const union nf_conntrack_address *mask, | |
85 | const union nf_conntrack_address *u3, unsigned int family) | |
86 | { | |
87 | if (family == AF_INET) { | |
88 | return (addr->ip & mask->ip) == (u3->ip & mask->ip); | |
89 | } else { | |
90 | union nf_conntrack_address 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_conntrack_address *addr, | |
105 | const union nf_conntrack_address *mask, | |
106 | const struct xt_match *match) | |
107 | { | |
108 | struct nf_conntrack_tuple_hash *found; | |
109 | struct xt_connlimit_conn *conn; | |
110 | struct xt_connlimit_conn *tmp; | |
111 | struct nf_conn *found_ct; | |
112 | struct list_head *hash; | |
113 | bool addit = true; | |
114 | int matches = 0; | |
115 | ||
116 | ||
117 | if (match->family == AF_INET6) | |
118 | hash = &data->iphash[connlimit_iphash6(addr, mask)]; | |
119 | else | |
120 | hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; | |
121 | ||
122 | read_lock_bh(&nf_conntrack_lock); | |
123 | ||
124 | /* check the saved connections */ | |
125 | list_for_each_entry_safe(conn, tmp, hash, list) { | |
126 | found = __nf_conntrack_find(&conn->tuple, NULL); | |
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 | read_unlock_bh(&nf_conntrack_lock); | |
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 connlimit_match(const struct sk_buff *skb, | |
181 | const struct net_device *in, | |
182 | const struct net_device *out, | |
183 | const struct xt_match *match, | |
184 | const void *matchinfo, int offset, | |
185 | unsigned int protoff, bool *hotdrop) | |
186 | { | |
187 | const struct xt_connlimit_info *info = matchinfo; | |
188 | union nf_conntrack_address addr, mask; | |
189 | struct nf_conntrack_tuple tuple; | |
190 | const struct nf_conntrack_tuple *tuple_ptr = &tuple; | |
191 | enum ip_conntrack_info ctinfo; | |
192 | const struct nf_conn *ct; | |
193 | int connections; | |
194 | ||
195 | ct = nf_ct_get(skb, &ctinfo); | |
196 | if (ct != NULL) | |
197 | tuple_ptr = &ct->tuplehash[0].tuple; | |
198 | else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), | |
199 | match->family, &tuple)) | |
200 | goto hotdrop; | |
201 | ||
202 | if (match->family == AF_INET6) { | |
203 | const struct ipv6hdr *iph = ipv6_hdr(skb); | |
204 | memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); | |
205 | memcpy(&mask.ip6, info->v6_mask, sizeof(info->v6_mask)); | |
206 | } else { | |
207 | const struct iphdr *iph = ip_hdr(skb); | |
208 | addr.ip = iph->saddr; | |
209 | mask.ip = info->v4_mask; | |
210 | } | |
211 | ||
212 | spin_lock_bh(&info->data->lock); | |
213 | connections = count_them(info->data, tuple_ptr, &addr, &mask, match); | |
214 | spin_unlock_bh(&info->data->lock); | |
215 | ||
216 | if (connections < 0) { | |
217 | /* kmalloc failed, drop it entirely */ | |
218 | *hotdrop = true; | |
219 | return false; | |
220 | } | |
221 | ||
222 | return (connections > info->limit) ^ info->inverse; | |
223 | ||
224 | hotdrop: | |
225 | *hotdrop = true; | |
226 | return false; | |
227 | } | |
228 | ||
229 | static bool connlimit_check(const char *tablename, const void *ip, | |
230 | const struct xt_match *match, void *matchinfo, | |
231 | unsigned int hook_mask) | |
232 | { | |
233 | struct xt_connlimit_info *info = matchinfo; | |
234 | unsigned int i; | |
235 | ||
236 | if (nf_ct_l3proto_try_module_get(match->family) < 0) { | |
237 | printk(KERN_WARNING "cannot load conntrack support for " | |
238 | "address family %u\n", match->family); | |
239 | return false; | |
240 | } | |
241 | ||
242 | /* init private data */ | |
243 | info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); | |
244 | if (info->data == NULL) { | |
245 | nf_ct_l3proto_module_put(match->family); | |
246 | return false; | |
247 | } | |
248 | ||
249 | spin_lock_init(&info->data->lock); | |
250 | for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) | |
251 | INIT_LIST_HEAD(&info->data->iphash[i]); | |
252 | ||
253 | return true; | |
254 | } | |
255 | ||
256 | static void connlimit_destroy(const struct xt_match *match, void *matchinfo) | |
257 | { | |
258 | struct xt_connlimit_info *info = matchinfo; | |
259 | struct xt_connlimit_conn *conn; | |
260 | struct xt_connlimit_conn *tmp; | |
261 | struct list_head *hash = info->data->iphash; | |
262 | unsigned int i; | |
263 | ||
264 | nf_ct_l3proto_module_put(match->family); | |
265 | ||
266 | for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { | |
267 | list_for_each_entry_safe(conn, tmp, &hash[i], list) { | |
268 | list_del(&conn->list); | |
269 | kfree(conn); | |
270 | } | |
271 | } | |
272 | ||
273 | kfree(info->data); | |
274 | } | |
275 | ||
276 | static struct xt_match connlimit_reg[] __read_mostly = { | |
277 | { | |
278 | .name = "connlimit", | |
279 | .family = AF_INET, | |
280 | .checkentry = connlimit_check, | |
281 | .match = connlimit_match, | |
282 | .matchsize = sizeof(struct xt_connlimit_info), | |
283 | .destroy = connlimit_destroy, | |
284 | .me = THIS_MODULE, | |
285 | }, | |
286 | { | |
287 | .name = "connlimit", | |
288 | .family = AF_INET6, | |
289 | .checkentry = connlimit_check, | |
290 | .match = connlimit_match, | |
291 | .matchsize = sizeof(struct xt_connlimit_info), | |
292 | .destroy = connlimit_destroy, | |
293 | .me = THIS_MODULE, | |
294 | }, | |
295 | }; | |
296 | ||
297 | static int __init xt_connlimit_init(void) | |
298 | { | |
299 | return xt_register_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg)); | |
300 | } | |
301 | ||
302 | static void __exit xt_connlimit_exit(void) | |
303 | { | |
304 | xt_unregister_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg)); | |
305 | } | |
306 | ||
307 | module_init(xt_connlimit_init); | |
308 | module_exit(xt_connlimit_exit); | |
309 | MODULE_AUTHOR("Jan Engelhardt <jengelh@gmx.de>"); | |
310 | MODULE_DESCRIPTION("netfilter xt_connlimit match module"); | |
311 | MODULE_LICENSE("GPL"); | |
312 | MODULE_ALIAS("ipt_connlimit"); | |
313 | MODULE_ALIAS("ip6t_connlimit"); |