Jan Engelhardt | 370786f | 2007-07-14 20:47:26 -0700 | [diff] [blame] | 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 |
Jan Engelhardt | ba5dc27 | 2007-11-05 20:35:56 -0800 | [diff] [blame^] | 7 | * (C) CC Computer Consultants GmbH, 2007 |
| 8 | * Contact: <jengelh@computergmbh.de> |
Jan Engelhardt | 370786f | 2007-07-14 20:47:26 -0700 | [diff] [blame] | 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 | |
Al Viro | a34c458 | 2007-07-26 17:33:19 +0100 | [diff] [blame] | 46 | static inline unsigned int connlimit_iphash(__be32 addr) |
Jan Engelhardt | 370786f | 2007-07-14 20:47:26 -0700 | [diff] [blame] | 47 | { |
| 48 | if (unlikely(!connlimit_rnd_inited)) { |
| 49 | get_random_bytes(&connlimit_rnd, sizeof(connlimit_rnd)); |
| 50 | connlimit_rnd_inited = true; |
| 51 | } |
Al Viro | a34c458 | 2007-07-26 17:33:19 +0100 | [diff] [blame] | 52 | return jhash_1word((__force __u32)addr, connlimit_rnd) & 0xFF; |
Jan Engelhardt | 370786f | 2007-07-14 20:47:26 -0700 | [diff] [blame] | 53 | } |
| 54 | |
| 55 | static inline unsigned int |
| 56 | connlimit_iphash6(const union nf_conntrack_address *addr, |
| 57 | const union nf_conntrack_address *mask) |
| 58 | { |
| 59 | union nf_conntrack_address res; |
| 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 | |
Al Viro | a34c458 | 2007-07-26 17:33:19 +0100 | [diff] [blame] | 70 | return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), connlimit_rnd) & 0xFF; |
Jan Engelhardt | 370786f | 2007-07-14 20:47:26 -0700 | [diff] [blame] | 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 |
| 84 | same_source_net(const union nf_conntrack_address *addr, |
| 85 | const union nf_conntrack_address *mask, |
| 86 | const union nf_conntrack_address *u3, unsigned int family) |
| 87 | { |
| 88 | if (family == AF_INET) { |
| 89 | return (addr->ip & mask->ip) == (u3->ip & mask->ip); |
| 90 | } else { |
| 91 | union nf_conntrack_address lh, rh; |
| 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, |
| 105 | const union nf_conntrack_address *addr, |
| 106 | const union nf_conntrack_address *mask, |
| 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 | |
| 181 | static bool connlimit_match(const struct sk_buff *skb, |
| 182 | const struct net_device *in, |
| 183 | const struct net_device *out, |
| 184 | const struct xt_match *match, |
| 185 | const void *matchinfo, int offset, |
| 186 | unsigned int protoff, bool *hotdrop) |
| 187 | { |
| 188 | const struct xt_connlimit_info *info = matchinfo; |
| 189 | union nf_conntrack_address addr, mask; |
| 190 | struct nf_conntrack_tuple tuple; |
| 191 | const struct nf_conntrack_tuple *tuple_ptr = &tuple; |
| 192 | enum ip_conntrack_info ctinfo; |
| 193 | const struct nf_conn *ct; |
| 194 | int connections; |
| 195 | |
| 196 | ct = nf_ct_get(skb, &ctinfo); |
| 197 | if (ct != NULL) |
| 198 | tuple_ptr = &ct->tuplehash[0].tuple; |
| 199 | else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), |
| 200 | match->family, &tuple)) |
| 201 | goto hotdrop; |
| 202 | |
| 203 | if (match->family == AF_INET6) { |
| 204 | const struct ipv6hdr *iph = ipv6_hdr(skb); |
| 205 | memcpy(&addr.ip6, &iph->saddr, sizeof(iph->saddr)); |
| 206 | memcpy(&mask.ip6, info->v6_mask, sizeof(info->v6_mask)); |
| 207 | } else { |
| 208 | const struct iphdr *iph = ip_hdr(skb); |
| 209 | addr.ip = iph->saddr; |
| 210 | mask.ip = info->v4_mask; |
| 211 | } |
| 212 | |
| 213 | spin_lock_bh(&info->data->lock); |
| 214 | connections = count_them(info->data, tuple_ptr, &addr, &mask, match); |
| 215 | spin_unlock_bh(&info->data->lock); |
| 216 | |
| 217 | if (connections < 0) { |
| 218 | /* kmalloc failed, drop it entirely */ |
| 219 | *hotdrop = true; |
| 220 | return false; |
| 221 | } |
| 222 | |
| 223 | return (connections > info->limit) ^ info->inverse; |
| 224 | |
| 225 | hotdrop: |
| 226 | *hotdrop = true; |
| 227 | return false; |
| 228 | } |
| 229 | |
| 230 | static bool connlimit_check(const char *tablename, const void *ip, |
| 231 | const struct xt_match *match, void *matchinfo, |
| 232 | unsigned int hook_mask) |
| 233 | { |
| 234 | struct xt_connlimit_info *info = matchinfo; |
| 235 | unsigned int i; |
| 236 | |
| 237 | if (nf_ct_l3proto_try_module_get(match->family) < 0) { |
| 238 | printk(KERN_WARNING "cannot load conntrack support for " |
| 239 | "address family %u\n", match->family); |
| 240 | return false; |
| 241 | } |
| 242 | |
| 243 | /* init private data */ |
| 244 | info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); |
| 245 | if (info->data == NULL) { |
| 246 | nf_ct_l3proto_module_put(match->family); |
| 247 | return false; |
| 248 | } |
| 249 | |
| 250 | spin_lock_init(&info->data->lock); |
| 251 | for (i = 0; i < ARRAY_SIZE(info->data->iphash); ++i) |
| 252 | INIT_LIST_HEAD(&info->data->iphash[i]); |
| 253 | |
| 254 | return true; |
| 255 | } |
| 256 | |
| 257 | static void connlimit_destroy(const struct xt_match *match, void *matchinfo) |
| 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 | |
| 277 | static struct xt_match connlimit_reg[] __read_mostly = { |
| 278 | { |
| 279 | .name = "connlimit", |
| 280 | .family = AF_INET, |
| 281 | .checkentry = connlimit_check, |
| 282 | .match = connlimit_match, |
| 283 | .matchsize = sizeof(struct xt_connlimit_info), |
| 284 | .destroy = connlimit_destroy, |
| 285 | .me = THIS_MODULE, |
| 286 | }, |
| 287 | { |
| 288 | .name = "connlimit", |
| 289 | .family = AF_INET6, |
| 290 | .checkentry = connlimit_check, |
| 291 | .match = connlimit_match, |
| 292 | .matchsize = sizeof(struct xt_connlimit_info), |
| 293 | .destroy = connlimit_destroy, |
| 294 | .me = THIS_MODULE, |
| 295 | }, |
| 296 | }; |
| 297 | |
| 298 | static int __init xt_connlimit_init(void) |
| 299 | { |
| 300 | return xt_register_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg)); |
| 301 | } |
| 302 | |
| 303 | static void __exit xt_connlimit_exit(void) |
| 304 | { |
| 305 | xt_unregister_matches(connlimit_reg, ARRAY_SIZE(connlimit_reg)); |
| 306 | } |
| 307 | |
| 308 | module_init(xt_connlimit_init); |
| 309 | module_exit(xt_connlimit_exit); |
Jan Engelhardt | ba5dc27 | 2007-11-05 20:35:56 -0800 | [diff] [blame^] | 310 | MODULE_AUTHOR("Jan Engelhardt <jengelh@computergmbh.de>"); |
Jan Engelhardt | 370786f | 2007-07-14 20:47:26 -0700 | [diff] [blame] | 311 | MODULE_DESCRIPTION("netfilter xt_connlimit match module"); |
| 312 | MODULE_LICENSE("GPL"); |
| 313 | MODULE_ALIAS("ipt_connlimit"); |
| 314 | MODULE_ALIAS("ip6t_connlimit"); |