Commit | Line | Data |
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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 | |
ba5dc275 JE |
7 | * (C) CC Computer Consultants GmbH, 2007 |
8 | * Contact: <jengelh@computergmbh.de> | |
370786f9 JE |
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 | ||
a34c4589 | 46 | static inline unsigned int connlimit_iphash(__be32 addr) |
370786f9 JE |
47 | { |
48 | if (unlikely(!connlimit_rnd_inited)) { | |
49 | get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); | |
50 | connlimit_rnd_inited = true; | |
51 | } | |
a34c4589 | 52 | return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; |
370786f9 JE |
53 | } |
54 | ||
55 | static inline unsigned int | |
643a2c15 JE |
56 | connlimit_iphash6(const union nf_inet_addr *addr, |
57 | const union nf_inet_addr *mask) | |
370786f9 | 58 | { |
643a2c15 | 59 | union nf_inet_addr res; |
370786f9 JE |
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 | ||
a34c4589 | 70 | return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; |
370786f9 JE |
71 | } |
72 | ||
73 | static inline bool already_closed(const struct nf_conn *conn) | |
74 | { | |
75 | u_int16_t proto = conn->tuplehash[0].tuple.dst.protonum; | |
76 | ||
77 | if (proto == IPPROTO_TCP) | |
78 | return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT; | |
79 | else | |
80 | return 0; | |
81 | } | |
82 | ||
83 | static inline unsigned int | |
643a2c15 JE |
84 | same_source_net(const union nf_inet_addr *addr, |
85 | const union nf_inet_addr *mask, | |
86 | const union nf_inet_addr *u3, unsigned int family) | |
370786f9 JE |
87 | { |
88 | if (family == AF_INET) { | |
89 | return (addr->ip & mask->ip) == (u3->ip & mask->ip); | |
90 | } else { | |
643a2c15 | 91 | union nf_inet_addr lh, rh; |
370786f9 JE |
92 | unsigned int i; |
93 | ||
94 | for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) { | |
95 | lh.ip6[i] = addr->ip6[i] & mask->ip6[i]; | |
96 | rh.ip6[i] = u3->ip6[i] & mask->ip6[i]; | |
97 | } | |
98 | ||
99 | return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0; | |
100 | } | |
101 | } | |
102 | ||
103 | static int count_them(struct xt_connlimit_data *data, | |
104 | const struct nf_conntrack_tuple *tuple, | |
643a2c15 JE |
105 | const union nf_inet_addr *addr, |
106 | const union nf_inet_addr *mask, | |
370786f9 JE |
107 | const struct xt_match *match) |
108 | { | |
109 | struct nf_conntrack_tuple_hash *found; | |
110 | struct xt_connlimit_conn *conn; | |
111 | struct xt_connlimit_conn *tmp; | |
112 | struct nf_conn *found_ct; | |
113 | struct list_head *hash; | |
114 | bool addit = true; | |
115 | int matches = 0; | |
116 | ||
117 | ||
118 | if (match->family == AF_INET6) | |
119 | hash = &data->iphash[connlimit_iphash6(addr, mask)]; | |
120 | else | |
121 | hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; | |
122 | ||
123 | read_lock_bh(&nf_conntrack_lock); | |
124 | ||
125 | /* check the saved connections */ | |
126 | list_for_each_entry_safe(conn, tmp, hash, list) { | |
127 | found = __nf_conntrack_find(&conn->tuple, NULL); | |
128 | found_ct = NULL; | |
129 | ||
130 | if (found != NULL) | |
131 | found_ct = nf_ct_tuplehash_to_ctrack(found); | |
132 | ||
133 | if (found_ct != NULL && | |
134 | nf_ct_tuple_equal(&conn->tuple, tuple) && | |
135 | !already_closed(found_ct)) | |
136 | /* | |
137 | * Just to be sure we have it only once in the list. | |
138 | * We should not see tuples twice unless someone hooks | |
139 | * this into a table without "-p tcp --syn". | |
140 | */ | |
141 | addit = false; | |
142 | ||
143 | if (found == NULL) { | |
144 | /* this one is gone */ | |
145 | list_del(&conn->list); | |
146 | kfree(conn); | |
147 | continue; | |
148 | } | |
149 | ||
150 | if (already_closed(found_ct)) { | |
151 | /* | |
152 | * we do not care about connections which are | |
153 | * closed already -> ditch it | |
154 | */ | |
155 | list_del(&conn->list); | |
156 | kfree(conn); | |
157 | continue; | |
158 | } | |
159 | ||
160 | if (same_source_net(addr, mask, &conn->tuple.src.u3, | |
161 | match->family)) | |
162 | /* same source network -> be counted! */ | |
163 | ++matches; | |
164 | } | |
165 | ||
166 | read_unlock_bh(&nf_conntrack_lock); | |
167 | ||
168 | if (addit) { | |
169 | /* save the new connection in our list */ | |
170 | conn = kzalloc(sizeof(*conn), GFP_ATOMIC); | |
171 | if (conn == NULL) | |
172 | return -ENOMEM; | |
173 | conn->tuple = *tuple; | |
174 | list_add(&conn->list, hash); | |
175 | ++matches; | |
176 | } | |
177 | ||
178 | return matches; | |
179 | } | |
180 | ||
d3c5ee6d JE |
181 | static bool |
182 | connlimit_mt(const struct sk_buff *skb, const struct net_device *in, | |
183 | const struct net_device *out, const struct xt_match *match, | |
184 | const void *matchinfo, int offset, unsigned int protoff, | |
185 | bool *hotdrop) | |
370786f9 JE |
186 | { |
187 | const struct xt_connlimit_info *info = matchinfo; | |
22c2d8bc | 188 | union nf_inet_addr addr; |
370786f9 JE |
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)); | |
370786f9 JE |
205 | } else { |
206 | const struct iphdr *iph = ip_hdr(skb); | |
207 | addr.ip = iph->saddr; | |
370786f9 JE |
208 | } |
209 | ||
210 | spin_lock_bh(&info->data->lock); | |
22c2d8bc JE |
211 | connections = count_them(info->data, tuple_ptr, &addr, |
212 | &info->mask, match); | |
370786f9 JE |
213 | spin_unlock_bh(&info->data->lock); |
214 | ||
215 | if (connections < 0) { | |
216 | /* kmalloc failed, drop it entirely */ | |
217 | *hotdrop = true; | |
218 | return false; | |
219 | } | |
220 | ||
221 | return (connections > info->limit) ^ info->inverse; | |
222 | ||
223 | hotdrop: | |
224 | *hotdrop = true; | |
225 | return false; | |
226 | } | |
227 | ||
d3c5ee6d JE |
228 | static bool |
229 | connlimit_mt_check(const char *tablename, const void *ip, | |
230 | const struct xt_match *match, void *matchinfo, | |
231 | unsigned int hook_mask) | |
370786f9 JE |
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 | ||
d3c5ee6d JE |
256 | static void |
257 | connlimit_mt_destroy(const struct xt_match *match, void *matchinfo) | |
370786f9 JE |
258 | { |
259 | struct xt_connlimit_info *info = matchinfo; | |
260 | struct xt_connlimit_conn *conn; | |
261 | struct xt_connlimit_conn *tmp; | |
262 | struct list_head *hash = info->data->iphash; | |
263 | unsigned int i; | |
264 | ||
265 | nf_ct_l3proto_module_put(match->family); | |
266 | ||
267 | for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { | |
268 | list_for_each_entry_safe(conn, tmp, &hash[i], list) { | |
269 | list_del(&conn->list); | |
270 | kfree(conn); | |
271 | } | |
272 | } | |
273 | ||
274 | kfree(info->data); | |
275 | } | |
276 | ||
d3c5ee6d | 277 | static struct xt_match connlimit_mt_reg[] __read_mostly = { |
370786f9 JE |
278 | { |
279 | .name = "connlimit", | |
280 | .family = AF_INET, | |
d3c5ee6d JE |
281 | .checkentry = connlimit_mt_check, |
282 | .match = connlimit_mt, | |
370786f9 | 283 | .matchsize = sizeof(struct xt_connlimit_info), |
d3c5ee6d | 284 | .destroy = connlimit_mt_destroy, |
370786f9 JE |
285 | .me = THIS_MODULE, |
286 | }, | |
287 | { | |
288 | .name = "connlimit", | |
289 | .family = AF_INET6, | |
d3c5ee6d JE |
290 | .checkentry = connlimit_mt_check, |
291 | .match = connlimit_mt, | |
370786f9 | 292 | .matchsize = sizeof(struct xt_connlimit_info), |
d3c5ee6d | 293 | .destroy = connlimit_mt_destroy, |
370786f9 JE |
294 | .me = THIS_MODULE, |
295 | }, | |
296 | }; | |
297 | ||
d3c5ee6d | 298 | static int __init connlimit_mt_init(void) |
370786f9 | 299 | { |
d3c5ee6d JE |
300 | return xt_register_matches(connlimit_mt_reg, |
301 | ARRAY_SIZE(connlimit_mt_reg)); | |
370786f9 JE |
302 | } |
303 | ||
d3c5ee6d | 304 | static void __exit connlimit_mt_exit(void) |
370786f9 | 305 | { |
d3c5ee6d | 306 | xt_unregister_matches(connlimit_mt_reg, ARRAY_SIZE(connlimit_mt_reg)); |
370786f9 JE |
307 | } |
308 | ||
d3c5ee6d JE |
309 | module_init(connlimit_mt_init); |
310 | module_exit(connlimit_mt_exit); | |
ba5dc275 | 311 | MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>"); |
370786f9 JE |
312 | MODULE_DESCRIPTION("netfilter xt_connlimit match module"); |
313 | MODULE_LICENSE("GPL"); | |
314 | MODULE_ALIAS("ipt_connlimit"); | |
315 | MODULE_ALIAS("ip6t_connlimit"); |