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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/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 | #include <net/netfilter/nf_conntrack_zones.h> | |
32 | ||
33 | /* we will save the tuples of all connections we care about */ | |
34 | struct xt_connlimit_conn { | |
35 | struct list_head list; | |
36 | struct nf_conntrack_tuple tuple; | |
37 | }; | |
38 | ||
39 | struct xt_connlimit_data { | |
40 | struct list_head iphash[256]; | |
41 | spinlock_t lock; | |
42 | }; | |
43 | ||
44 | static u_int32_t connlimit_rnd __read_mostly; | |
45 | static bool connlimit_rnd_inited __read_mostly; | |
46 | ||
47 | static inline unsigned int connlimit_iphash(__be32 addr) | |
48 | { | |
49 | return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; | |
50 | } | |
51 | ||
52 | static inline unsigned int | |
53 | connlimit_iphash6(const union nf_inet_addr *addr, | |
54 | const union nf_inet_addr *mask) | |
55 | { | |
56 | union nf_inet_addr res; | |
57 | unsigned int i; | |
58 | ||
59 | for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) | |
60 | res.ip6[i] = addr->ip6[i] & mask->ip6[i]; | |
61 | ||
62 | return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; | |
63 | } | |
64 | ||
65 | static inline bool already_closed(const struct nf_conn *conn) | |
66 | { | |
67 | if (nf_ct_protonum(conn) == IPPROTO_TCP) | |
68 | return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT || | |
69 | conn->proto.tcp.state == TCP_CONNTRACK_CLOSE; | |
70 | else | |
71 | return 0; | |
72 | } | |
73 | ||
74 | static inline unsigned int | |
75 | same_source_net(const union nf_inet_addr *addr, | |
76 | const union nf_inet_addr *mask, | |
77 | const union nf_inet_addr *u3, u_int8_t family) | |
78 | { | |
79 | if (family == NFPROTO_IPV4) { | |
80 | return (addr->ip & mask->ip) == (u3->ip & mask->ip); | |
81 | } else { | |
82 | union nf_inet_addr lh, rh; | |
83 | unsigned int i; | |
84 | ||
85 | for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) { | |
86 | lh.ip6[i] = addr->ip6[i] & mask->ip6[i]; | |
87 | rh.ip6[i] = u3->ip6[i] & mask->ip6[i]; | |
88 | } | |
89 | ||
90 | return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0; | |
91 | } | |
92 | } | |
93 | ||
94 | static int count_them(struct net *net, | |
95 | struct xt_connlimit_data *data, | |
96 | const struct nf_conntrack_tuple *tuple, | |
97 | const union nf_inet_addr *addr, | |
98 | const union nf_inet_addr *mask, | |
99 | u_int8_t family) | |
100 | { | |
101 | const struct nf_conntrack_tuple_hash *found; | |
102 | struct xt_connlimit_conn *conn; | |
103 | struct xt_connlimit_conn *tmp; | |
104 | struct nf_conn *found_ct; | |
105 | struct list_head *hash; | |
106 | bool addit = true; | |
107 | int matches = 0; | |
108 | ||
109 | if (family == NFPROTO_IPV6) | |
110 | hash = &data->iphash[connlimit_iphash6(addr, mask)]; | |
111 | else | |
112 | hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; | |
113 | ||
114 | rcu_read_lock(); | |
115 | ||
116 | /* check the saved connections */ | |
117 | list_for_each_entry_safe(conn, tmp, hash, list) { | |
118 | found = nf_conntrack_find_get(net, NF_CT_DEFAULT_ZONE, | |
119 | &conn->tuple); | |
120 | found_ct = NULL; | |
121 | ||
122 | if (found != NULL) | |
123 | found_ct = nf_ct_tuplehash_to_ctrack(found); | |
124 | ||
125 | if (found_ct != NULL && | |
126 | nf_ct_tuple_equal(&conn->tuple, tuple) && | |
127 | !already_closed(found_ct)) | |
128 | /* | |
129 | * Just to be sure we have it only once in the list. | |
130 | * We should not see tuples twice unless someone hooks | |
131 | * this into a table without "-p tcp --syn". | |
132 | */ | |
133 | addit = false; | |
134 | ||
135 | if (found == NULL) { | |
136 | /* this one is gone */ | |
137 | list_del(&conn->list); | |
138 | kfree(conn); | |
139 | continue; | |
140 | } | |
141 | ||
142 | if (already_closed(found_ct)) { | |
143 | /* | |
144 | * we do not care about connections which are | |
145 | * closed already -> ditch it | |
146 | */ | |
147 | nf_ct_put(found_ct); | |
148 | list_del(&conn->list); | |
149 | kfree(conn); | |
150 | continue; | |
151 | } | |
152 | ||
153 | if (same_source_net(addr, mask, &conn->tuple.src.u3, family)) | |
154 | /* same source network -> be counted! */ | |
155 | ++matches; | |
156 | nf_ct_put(found_ct); | |
157 | } | |
158 | ||
159 | rcu_read_unlock(); | |
160 | ||
161 | if (addit) { | |
162 | /* save the new connection in our list */ | |
163 | conn = kzalloc(sizeof(*conn), GFP_ATOMIC); | |
164 | if (conn == NULL) | |
165 | return -ENOMEM; | |
166 | conn->tuple = *tuple; | |
167 | list_add(&conn->list, hash); | |
168 | ++matches; | |
169 | } | |
170 | ||
171 | return matches; | |
172 | } | |
173 | ||
174 | static bool | |
175 | connlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par) | |
176 | { | |
177 | struct net *net = dev_net(par->in ? par->in : par->out); | |
178 | const struct xt_connlimit_info *info = par->matchinfo; | |
179 | union nf_inet_addr addr; | |
180 | struct nf_conntrack_tuple tuple; | |
181 | const struct nf_conntrack_tuple *tuple_ptr = &tuple; | |
182 | enum ip_conntrack_info ctinfo; | |
183 | const struct nf_conn *ct; | |
184 | int connections; | |
185 | ||
186 | ct = nf_ct_get(skb, &ctinfo); | |
187 | if (ct != NULL) | |
188 | tuple_ptr = &ct->tuplehash[0].tuple; | |
189 | else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), | |
190 | par->family, &tuple)) | |
191 | goto hotdrop; | |
192 | ||
193 | if (par->family == NFPROTO_IPV6) { | |
194 | const struct ipv6hdr *iph = ipv6_hdr(skb); | |
195 | memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); | |
196 | } else { | |
197 | const struct iphdr *iph = ip_hdr(skb); | |
198 | addr.ip = iph->saddr; | |
199 | } | |
200 | ||
201 | spin_lock_bh(&info->data->lock); | |
202 | connections = count_them(net, info->data, tuple_ptr, &addr, | |
203 | &info->mask, par->family); | |
204 | spin_unlock_bh(&info->data->lock); | |
205 | ||
206 | if (connections < 0) { | |
207 | /* kmalloc failed, drop it entirely */ | |
208 | *par->hotdrop = true; | |
209 | return false; | |
210 | } | |
211 | ||
212 | return (connections > info->limit) ^ info->inverse; | |
213 | ||
214 | hotdrop: | |
215 | *par->hotdrop = true; | |
216 | return false; | |
217 | } | |
218 | ||
219 | static int connlimit_mt_check(const struct xt_mtchk_param *par) | |
220 | { | |
221 | struct xt_connlimit_info *info = par->matchinfo; | |
222 | unsigned int i; | |
223 | ||
224 | if (unlikely(!connlimit_rnd_inited)) { | |
225 | get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); | |
226 | connlimit_rnd_inited = true; | |
227 | } | |
228 | if (nf_ct_l3proto_try_module_get(par->family) < 0) { | |
229 | pr_info("cannot load conntrack support for " | |
230 | "address family %u\n", par->family); | |
231 | return -EINVAL; | |
232 | } | |
233 | ||
234 | /* init private data */ | |
235 | info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); | |
236 | if (info->data == NULL) { | |
237 | nf_ct_l3proto_module_put(par->family); | |
238 | return -EINVAL; | |
239 | } | |
240 | ||
241 | spin_lock_init(&info->data->lock); | |
242 | for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) | |
243 | INIT_LIST_HEAD(&info->data->iphash[i]); | |
244 | ||
245 | return 0; | |
246 | } | |
247 | ||
248 | static void connlimit_mt_destroy(const struct xt_mtdtor_param *par) | |
249 | { | |
250 | const struct xt_connlimit_info *info = par->matchinfo; | |
251 | struct xt_connlimit_conn *conn; | |
252 | struct xt_connlimit_conn *tmp; | |
253 | struct list_head *hash = info->data->iphash; | |
254 | unsigned int i; | |
255 | ||
256 | nf_ct_l3proto_module_put(par->family); | |
257 | ||
258 | for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { | |
259 | list_for_each_entry_safe(conn, tmp, &hash[i], list) { | |
260 | list_del(&conn->list); | |
261 | kfree(conn); | |
262 | } | |
263 | } | |
264 | ||
265 | kfree(info->data); | |
266 | } | |
267 | ||
268 | static struct xt_match connlimit_mt_reg __read_mostly = { | |
269 | .name = "connlimit", | |
270 | .revision = 0, | |
271 | .family = NFPROTO_UNSPEC, | |
272 | .checkentry = connlimit_mt_check, | |
273 | .match = connlimit_mt, | |
274 | .matchsize = sizeof(struct xt_connlimit_info), | |
275 | .destroy = connlimit_mt_destroy, | |
276 | .me = THIS_MODULE, | |
277 | }; | |
278 | ||
279 | static int __init connlimit_mt_init(void) | |
280 | { | |
281 | return xt_register_match(&connlimit_mt_reg); | |
282 | } | |
283 | ||
284 | static void __exit connlimit_mt_exit(void) | |
285 | { | |
286 | xt_unregister_match(&connlimit_mt_reg); | |
287 | } | |
288 | ||
289 | module_init(connlimit_mt_init); | |
290 | module_exit(connlimit_mt_exit); | |
291 | MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); | |
292 | MODULE_DESCRIPTION("Xtables: Number of connections matching"); | |
293 | MODULE_LICENSE("GPL"); | |
294 | MODULE_ALIAS("ipt_connlimit"); | |
295 | MODULE_ALIAS("ip6t_connlimit"); |