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 | 7 | * (C) CC Computer Consultants GmbH, 2007 |
370786f9 JE |
8 | * |
9 | * based on ... | |
10 | * | |
11 | * Kernel module to match connection tracking information. | |
12 | * GPL (C) 1999 Rusty Russell (rusty@rustcorp.com.au). | |
13 | */ | |
8bee4bad | 14 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
370786f9 JE |
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> | |
5d0aa2cc | 31 | #include <net/netfilter/nf_conntrack_zones.h> |
370786f9 JE |
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 | ||
294188ae JE |
44 | static u_int32_t connlimit_rnd __read_mostly; |
45 | static bool connlimit_rnd_inited __read_mostly; | |
370786f9 | 46 | |
a34c4589 | 47 | static inline unsigned int connlimit_iphash(__be32 addr) |
370786f9 | 48 | { |
a34c4589 | 49 | return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; |
370786f9 JE |
50 | } |
51 | ||
52 | static inline unsigned int | |
643a2c15 JE |
53 | connlimit_iphash6(const union nf_inet_addr *addr, |
54 | const union nf_inet_addr *mask) | |
370786f9 | 55 | { |
643a2c15 | 56 | union nf_inet_addr res; |
370786f9 JE |
57 | unsigned int i; |
58 | ||
370786f9 JE |
59 | for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) |
60 | res.ip6[i] = addr->ip6[i] & mask->ip6[i]; | |
61 | ||
a34c4589 | 62 | return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; |
370786f9 JE |
63 | } |
64 | ||
65 | static inline bool already_closed(const struct nf_conn *conn) | |
66 | { | |
5e8fbe2a | 67 | if (nf_ct_protonum(conn) == IPPROTO_TCP) |
d2ee3f2c DW |
68 | return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT || |
69 | conn->proto.tcp.state == TCP_CONNTRACK_CLOSE; | |
370786f9 JE |
70 | else |
71 | return 0; | |
72 | } | |
73 | ||
74 | static inline unsigned int | |
643a2c15 JE |
75 | same_source_net(const union nf_inet_addr *addr, |
76 | const union nf_inet_addr *mask, | |
76108cea | 77 | const union nf_inet_addr *u3, u_int8_t family) |
370786f9 | 78 | { |
ee999d8b | 79 | if (family == NFPROTO_IPV4) { |
370786f9 JE |
80 | return (addr->ip & mask->ip) == (u3->ip & mask->ip); |
81 | } else { | |
643a2c15 | 82 | union nf_inet_addr lh, rh; |
370786f9 JE |
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 | ||
83fc8102 AD |
94 | static int count_them(struct net *net, |
95 | struct xt_connlimit_data *data, | |
370786f9 | 96 | const struct nf_conntrack_tuple *tuple, |
643a2c15 JE |
97 | const union nf_inet_addr *addr, |
98 | const union nf_inet_addr *mask, | |
539054a8 | 99 | u_int8_t family) |
370786f9 | 100 | { |
3cf93c96 | 101 | const struct nf_conntrack_tuple_hash *found; |
370786f9 JE |
102 | struct xt_connlimit_conn *conn; |
103 | struct xt_connlimit_conn *tmp; | |
ea781f19 | 104 | struct nf_conn *found_ct; |
370786f9 JE |
105 | struct list_head *hash; |
106 | bool addit = true; | |
107 | int matches = 0; | |
108 | ||
539054a8 | 109 | if (family == NFPROTO_IPV6) |
370786f9 JE |
110 | hash = &data->iphash[connlimit_iphash6(addr, mask)]; |
111 | else | |
112 | hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; | |
113 | ||
76507f69 | 114 | rcu_read_lock(); |
370786f9 JE |
115 | |
116 | /* check the saved connections */ | |
117 | list_for_each_entry_safe(conn, tmp, hash, list) { | |
5d0aa2cc PM |
118 | found = nf_conntrack_find_get(net, NF_CT_DEFAULT_ZONE, |
119 | &conn->tuple); | |
370786f9 JE |
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 | */ | |
ea781f19 | 147 | nf_ct_put(found_ct); |
370786f9 JE |
148 | list_del(&conn->list); |
149 | kfree(conn); | |
150 | continue; | |
151 | } | |
152 | ||
539054a8 | 153 | if (same_source_net(addr, mask, &conn->tuple.src.u3, family)) |
370786f9 JE |
154 | /* same source network -> be counted! */ |
155 | ++matches; | |
ea781f19 | 156 | nf_ct_put(found_ct); |
370786f9 JE |
157 | } |
158 | ||
76507f69 | 159 | rcu_read_unlock(); |
370786f9 JE |
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 | ||
d3c5ee6d | 174 | static bool |
f7108a20 | 175 | connlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par) |
370786f9 | 176 | { |
83fc8102 | 177 | struct net *net = dev_net(par->in ? par->in : par->out); |
f7108a20 | 178 | const struct xt_connlimit_info *info = par->matchinfo; |
22c2d8bc | 179 | union nf_inet_addr addr; |
370786f9 JE |
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), | |
92f3b2b1 | 190 | par->family, &tuple)) |
370786f9 JE |
191 | goto hotdrop; |
192 | ||
92f3b2b1 | 193 | if (par->family == NFPROTO_IPV6) { |
370786f9 JE |
194 | const struct ipv6hdr *iph = ipv6_hdr(skb); |
195 | memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); | |
370786f9 JE |
196 | } else { |
197 | const struct iphdr *iph = ip_hdr(skb); | |
198 | addr.ip = iph->saddr; | |
370786f9 JE |
199 | } |
200 | ||
201 | spin_lock_bh(&info->data->lock); | |
83fc8102 | 202 | connections = count_them(net, info->data, tuple_ptr, &addr, |
539054a8 | 203 | &info->mask, par->family); |
370786f9 JE |
204 | spin_unlock_bh(&info->data->lock); |
205 | ||
206 | if (connections < 0) { | |
207 | /* kmalloc failed, drop it entirely */ | |
f7108a20 | 208 | *par->hotdrop = true; |
370786f9 JE |
209 | return false; |
210 | } | |
211 | ||
212 | return (connections > info->limit) ^ info->inverse; | |
213 | ||
214 | hotdrop: | |
f7108a20 | 215 | *par->hotdrop = true; |
370786f9 JE |
216 | return false; |
217 | } | |
218 | ||
b0f38452 | 219 | static int connlimit_mt_check(const struct xt_mtchk_param *par) |
370786f9 | 220 | { |
9b4fce7a | 221 | struct xt_connlimit_info *info = par->matchinfo; |
370786f9 JE |
222 | unsigned int i; |
223 | ||
294188ae JE |
224 | if (unlikely(!connlimit_rnd_inited)) { |
225 | get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); | |
226 | connlimit_rnd_inited = true; | |
227 | } | |
92f3b2b1 | 228 | if (nf_ct_l3proto_try_module_get(par->family) < 0) { |
8bee4bad JE |
229 | pr_info("cannot load conntrack support for " |
230 | "address family %u\n", par->family); | |
bd414ee6 | 231 | return -EINVAL; |
370786f9 JE |
232 | } |
233 | ||
234 | /* init private data */ | |
235 | info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); | |
236 | if (info->data == NULL) { | |
92f3b2b1 | 237 | nf_ct_l3proto_module_put(par->family); |
bd414ee6 | 238 | return -EINVAL; |
370786f9 JE |
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 | ||
bd414ee6 | 245 | return 0; |
370786f9 JE |
246 | } |
247 | ||
6be3d859 | 248 | static void connlimit_mt_destroy(const struct xt_mtdtor_param *par) |
370786f9 | 249 | { |
6be3d859 | 250 | const struct xt_connlimit_info *info = par->matchinfo; |
370786f9 JE |
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 | ||
92f3b2b1 | 256 | nf_ct_l3proto_module_put(par->family); |
370786f9 JE |
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 | ||
92f3b2b1 JE |
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, | |
370786f9 JE |
277 | }; |
278 | ||
d3c5ee6d | 279 | static int __init connlimit_mt_init(void) |
370786f9 | 280 | { |
92f3b2b1 | 281 | return xt_register_match(&connlimit_mt_reg); |
370786f9 JE |
282 | } |
283 | ||
d3c5ee6d | 284 | static void __exit connlimit_mt_exit(void) |
370786f9 | 285 | { |
92f3b2b1 | 286 | xt_unregister_match(&connlimit_mt_reg); |
370786f9 JE |
287 | } |
288 | ||
d3c5ee6d JE |
289 | module_init(connlimit_mt_init); |
290 | module_exit(connlimit_mt_exit); | |
92f3b2b1 | 291 | MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); |
2ae15b64 | 292 | MODULE_DESCRIPTION("Xtables: Number of connections matching"); |
370786f9 JE |
293 | MODULE_LICENSE("GPL"); |
294 | MODULE_ALIAS("ipt_connlimit"); | |
295 | MODULE_ALIAS("ip6t_connlimit"); |