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 | */ | |
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> | |
5d0aa2cc | 30 | #include <net/netfilter/nf_conntrack_zones.h> |
370786f9 JE |
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 | ||
294188ae JE |
43 | static u_int32_t connlimit_rnd __read_mostly; |
44 | static bool connlimit_rnd_inited __read_mostly; | |
370786f9 | 45 | |
a34c4589 | 46 | static inline unsigned int connlimit_iphash(__be32 addr) |
370786f9 | 47 | { |
a34c4589 | 48 | return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; |
370786f9 JE |
49 | } |
50 | ||
51 | static inline unsigned int | |
643a2c15 JE |
52 | connlimit_iphash6(const union nf_inet_addr *addr, |
53 | const union nf_inet_addr *mask) | |
370786f9 | 54 | { |
643a2c15 | 55 | union nf_inet_addr res; |
370786f9 JE |
56 | unsigned int i; |
57 | ||
370786f9 JE |
58 | for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) |
59 | res.ip6[i] = addr->ip6[i] & mask->ip6[i]; | |
60 | ||
a34c4589 | 61 | return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; |
370786f9 JE |
62 | } |
63 | ||
64 | static inline bool already_closed(const struct nf_conn *conn) | |
65 | { | |
5e8fbe2a | 66 | if (nf_ct_protonum(conn) == IPPROTO_TCP) |
d2ee3f2c DW |
67 | return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT || |
68 | conn->proto.tcp.state == TCP_CONNTRACK_CLOSE; | |
370786f9 JE |
69 | else |
70 | return 0; | |
71 | } | |
72 | ||
73 | static inline unsigned int | |
643a2c15 JE |
74 | same_source_net(const union nf_inet_addr *addr, |
75 | const union nf_inet_addr *mask, | |
76108cea | 76 | const union nf_inet_addr *u3, u_int8_t family) |
370786f9 | 77 | { |
ee999d8b | 78 | if (family == NFPROTO_IPV4) { |
370786f9 JE |
79 | return (addr->ip & mask->ip) == (u3->ip & mask->ip); |
80 | } else { | |
643a2c15 | 81 | union nf_inet_addr lh, rh; |
370786f9 JE |
82 | unsigned int i; |
83 | ||
84 | for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) { | |
85 | lh.ip6[i] = addr->ip6[i] & mask->ip6[i]; | |
86 | rh.ip6[i] = u3->ip6[i] & mask->ip6[i]; | |
87 | } | |
88 | ||
89 | return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)) == 0; | |
90 | } | |
91 | } | |
92 | ||
83fc8102 AD |
93 | static int count_them(struct net *net, |
94 | struct xt_connlimit_data *data, | |
370786f9 | 95 | const struct nf_conntrack_tuple *tuple, |
643a2c15 JE |
96 | const union nf_inet_addr *addr, |
97 | const union nf_inet_addr *mask, | |
539054a8 | 98 | u_int8_t family) |
370786f9 | 99 | { |
3cf93c96 | 100 | const struct nf_conntrack_tuple_hash *found; |
370786f9 JE |
101 | struct xt_connlimit_conn *conn; |
102 | struct xt_connlimit_conn *tmp; | |
ea781f19 | 103 | struct nf_conn *found_ct; |
370786f9 JE |
104 | struct list_head *hash; |
105 | bool addit = true; | |
106 | int matches = 0; | |
107 | ||
539054a8 | 108 | if (family == NFPROTO_IPV6) |
370786f9 JE |
109 | hash = &data->iphash[connlimit_iphash6(addr, mask)]; |
110 | else | |
111 | hash = &data->iphash[connlimit_iphash(addr->ip & mask->ip)]; | |
112 | ||
76507f69 | 113 | rcu_read_lock(); |
370786f9 JE |
114 | |
115 | /* check the saved connections */ | |
116 | list_for_each_entry_safe(conn, tmp, hash, list) { | |
5d0aa2cc PM |
117 | found = nf_conntrack_find_get(net, NF_CT_DEFAULT_ZONE, |
118 | &conn->tuple); | |
370786f9 JE |
119 | found_ct = NULL; |
120 | ||
121 | if (found != NULL) | |
122 | found_ct = nf_ct_tuplehash_to_ctrack(found); | |
123 | ||
124 | if (found_ct != NULL && | |
125 | nf_ct_tuple_equal(&conn->tuple, tuple) && | |
126 | !already_closed(found_ct)) | |
127 | /* | |
128 | * Just to be sure we have it only once in the list. | |
129 | * We should not see tuples twice unless someone hooks | |
130 | * this into a table without "-p tcp --syn". | |
131 | */ | |
132 | addit = false; | |
133 | ||
134 | if (found == NULL) { | |
135 | /* this one is gone */ | |
136 | list_del(&conn->list); | |
137 | kfree(conn); | |
138 | continue; | |
139 | } | |
140 | ||
141 | if (already_closed(found_ct)) { | |
142 | /* | |
143 | * we do not care about connections which are | |
144 | * closed already -> ditch it | |
145 | */ | |
ea781f19 | 146 | nf_ct_put(found_ct); |
370786f9 JE |
147 | list_del(&conn->list); |
148 | kfree(conn); | |
149 | continue; | |
150 | } | |
151 | ||
539054a8 | 152 | if (same_source_net(addr, mask, &conn->tuple.src.u3, family)) |
370786f9 JE |
153 | /* same source network -> be counted! */ |
154 | ++matches; | |
ea781f19 | 155 | nf_ct_put(found_ct); |
370786f9 JE |
156 | } |
157 | ||
76507f69 | 158 | rcu_read_unlock(); |
370786f9 JE |
159 | |
160 | if (addit) { | |
161 | /* save the new connection in our list */ | |
162 | conn = kzalloc(sizeof(*conn), GFP_ATOMIC); | |
163 | if (conn == NULL) | |
164 | return -ENOMEM; | |
165 | conn->tuple = *tuple; | |
166 | list_add(&conn->list, hash); | |
167 | ++matches; | |
168 | } | |
169 | ||
170 | return matches; | |
171 | } | |
172 | ||
d3c5ee6d | 173 | static bool |
f7108a20 | 174 | connlimit_mt(const struct sk_buff *skb, const struct xt_match_param *par) |
370786f9 | 175 | { |
83fc8102 | 176 | struct net *net = dev_net(par->in ? par->in : par->out); |
f7108a20 | 177 | const struct xt_connlimit_info *info = par->matchinfo; |
22c2d8bc | 178 | union nf_inet_addr addr; |
370786f9 JE |
179 | struct nf_conntrack_tuple tuple; |
180 | const struct nf_conntrack_tuple *tuple_ptr = &tuple; | |
181 | enum ip_conntrack_info ctinfo; | |
182 | const struct nf_conn *ct; | |
183 | int connections; | |
184 | ||
185 | ct = nf_ct_get(skb, &ctinfo); | |
186 | if (ct != NULL) | |
187 | tuple_ptr = &ct->tuplehash[0].tuple; | |
188 | else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), | |
92f3b2b1 | 189 | par->family, &tuple)) |
370786f9 JE |
190 | goto hotdrop; |
191 | ||
92f3b2b1 | 192 | if (par->family == NFPROTO_IPV6) { |
370786f9 JE |
193 | const struct ipv6hdr *iph = ipv6_hdr(skb); |
194 | memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); | |
370786f9 JE |
195 | } else { |
196 | const struct iphdr *iph = ip_hdr(skb); | |
197 | addr.ip = iph->saddr; | |
370786f9 JE |
198 | } |
199 | ||
200 | spin_lock_bh(&info->data->lock); | |
83fc8102 | 201 | connections = count_them(net, info->data, tuple_ptr, &addr, |
539054a8 | 202 | &info->mask, par->family); |
370786f9 JE |
203 | spin_unlock_bh(&info->data->lock); |
204 | ||
205 | if (connections < 0) { | |
206 | /* kmalloc failed, drop it entirely */ | |
f7108a20 | 207 | *par->hotdrop = true; |
370786f9 JE |
208 | return false; |
209 | } | |
210 | ||
211 | return (connections > info->limit) ^ info->inverse; | |
212 | ||
213 | hotdrop: | |
f7108a20 | 214 | *par->hotdrop = true; |
370786f9 JE |
215 | return false; |
216 | } | |
217 | ||
9b4fce7a | 218 | static bool connlimit_mt_check(const struct xt_mtchk_param *par) |
370786f9 | 219 | { |
9b4fce7a | 220 | struct xt_connlimit_info *info = par->matchinfo; |
370786f9 JE |
221 | unsigned int i; |
222 | ||
294188ae JE |
223 | if (unlikely(!connlimit_rnd_inited)) { |
224 | get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); | |
225 | connlimit_rnd_inited = true; | |
226 | } | |
92f3b2b1 | 227 | if (nf_ct_l3proto_try_module_get(par->family) < 0) { |
370786f9 | 228 | printk(KERN_WARNING "cannot load conntrack support for " |
92f3b2b1 | 229 | "address family %u\n", par->family); |
370786f9 JE |
230 | return false; |
231 | } | |
232 | ||
233 | /* init private data */ | |
234 | info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); | |
235 | if (info->data == NULL) { | |
92f3b2b1 | 236 | nf_ct_l3proto_module_put(par->family); |
370786f9 JE |
237 | return false; |
238 | } | |
239 | ||
240 | spin_lock_init(&info->data->lock); | |
241 | for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) | |
242 | INIT_LIST_HEAD(&info->data->iphash[i]); | |
243 | ||
244 | return true; | |
245 | } | |
246 | ||
6be3d859 | 247 | static void connlimit_mt_destroy(const struct xt_mtdtor_param *par) |
370786f9 | 248 | { |
6be3d859 | 249 | const struct xt_connlimit_info *info = par->matchinfo; |
370786f9 JE |
250 | struct xt_connlimit_conn *conn; |
251 | struct xt_connlimit_conn *tmp; | |
252 | struct list_head *hash = info->data->iphash; | |
253 | unsigned int i; | |
254 | ||
92f3b2b1 | 255 | nf_ct_l3proto_module_put(par->family); |
370786f9 JE |
256 | |
257 | for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) { | |
258 | list_for_each_entry_safe(conn, tmp, &hash[i], list) { | |
259 | list_del(&conn->list); | |
260 | kfree(conn); | |
261 | } | |
262 | } | |
263 | ||
264 | kfree(info->data); | |
265 | } | |
266 | ||
92f3b2b1 JE |
267 | static struct xt_match connlimit_mt_reg __read_mostly = { |
268 | .name = "connlimit", | |
269 | .revision = 0, | |
270 | .family = NFPROTO_UNSPEC, | |
271 | .checkentry = connlimit_mt_check, | |
272 | .match = connlimit_mt, | |
273 | .matchsize = sizeof(struct xt_connlimit_info), | |
274 | .destroy = connlimit_mt_destroy, | |
275 | .me = THIS_MODULE, | |
370786f9 JE |
276 | }; |
277 | ||
d3c5ee6d | 278 | static int __init connlimit_mt_init(void) |
370786f9 | 279 | { |
92f3b2b1 | 280 | return xt_register_match(&connlimit_mt_reg); |
370786f9 JE |
281 | } |
282 | ||
d3c5ee6d | 283 | static void __exit connlimit_mt_exit(void) |
370786f9 | 284 | { |
92f3b2b1 | 285 | xt_unregister_match(&connlimit_mt_reg); |
370786f9 JE |
286 | } |
287 | ||
d3c5ee6d JE |
288 | module_init(connlimit_mt_init); |
289 | module_exit(connlimit_mt_exit); | |
92f3b2b1 | 290 | MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); |
2ae15b64 | 291 | MODULE_DESCRIPTION("Xtables: Number of connections matching"); |
370786f9 JE |
292 | MODULE_LICENSE("GPL"); |
293 | MODULE_ALIAS("ipt_connlimit"); | |
294 | MODULE_ALIAS("ip6t_connlimit"); |