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/slab.h> 21 #include <linux/list.h> 22 #include <linux/rbtree.h> 23 #include <linux/module.h> 24 #include <linux/random.h> 25 #include <linux/skbuff.h> 26 #include <linux/spinlock.h> 27 #include <linux/netfilter/nf_conntrack_tcp.h> 28 #include <linux/netfilter/x_tables.h> 29 #include <linux/netfilter/xt_connlimit.h> 30 #include <net/netfilter/nf_conntrack.h> 31 #include <net/netfilter/nf_conntrack_core.h> 32 #include <net/netfilter/nf_conntrack_tuple.h> 33 #include <net/netfilter/nf_conntrack_zones.h> 34 35 #define CONNLIMIT_SLOTS 256U 36 37 #ifdef CONFIG_LOCKDEP 38 #define CONNLIMIT_LOCK_SLOTS 8U 39 #else 40 #define CONNLIMIT_LOCK_SLOTS 256U 41 #endif 42 43 #define CONNLIMIT_GC_MAX_NODES 8 44 45 /* we will save the tuples of all connections we care about */ 46 struct xt_connlimit_conn { 47 struct hlist_node node; 48 struct nf_conntrack_tuple tuple; 49 union nf_inet_addr addr; 50 }; 51 52 struct xt_connlimit_rb { 53 struct rb_node node; 54 struct hlist_head hhead; /* connections/hosts in same subnet */ 55 union nf_inet_addr addr; /* search key */ 56 }; 57 58 static spinlock_t xt_connlimit_locks[CONNLIMIT_LOCK_SLOTS] __cacheline_aligned_in_smp; 59 60 struct xt_connlimit_data { 61 struct rb_root climit_root4[CONNLIMIT_SLOTS]; 62 struct rb_root climit_root6[CONNLIMIT_SLOTS]; 63 }; 64 65 static u_int32_t connlimit_rnd __read_mostly; 66 static struct kmem_cache *connlimit_rb_cachep __read_mostly; 67 static struct kmem_cache *connlimit_conn_cachep __read_mostly; 68 69 static inline unsigned int connlimit_iphash(__be32 addr) 70 { 71 return jhash_1word((__force __u32)addr, 72 connlimit_rnd) % CONNLIMIT_SLOTS; 73 } 74 75 static inline unsigned int 76 connlimit_iphash6(const union nf_inet_addr *addr, 77 const union nf_inet_addr *mask) 78 { 79 union nf_inet_addr res; 80 unsigned int i; 81 82 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) 83 res.ip6[i] = addr->ip6[i] & mask->ip6[i]; 84 85 return jhash2((u32 *)res.ip6, ARRAY_SIZE(res.ip6), 86 connlimit_rnd) % CONNLIMIT_SLOTS; 87 } 88 89 static inline bool already_closed(const struct nf_conn *conn) 90 { 91 if (nf_ct_protonum(conn) == IPPROTO_TCP) 92 return conn->proto.tcp.state == TCP_CONNTRACK_TIME_WAIT || 93 conn->proto.tcp.state == TCP_CONNTRACK_CLOSE; 94 else 95 return 0; 96 } 97 98 static int 99 same_source_net(const union nf_inet_addr *addr, 100 const union nf_inet_addr *mask, 101 const union nf_inet_addr *u3, u_int8_t family) 102 { 103 if (family == NFPROTO_IPV4) { 104 return ntohl(addr->ip & mask->ip) - 105 ntohl(u3->ip & mask->ip); 106 } else { 107 union nf_inet_addr lh, rh; 108 unsigned int i; 109 110 for (i = 0; i < ARRAY_SIZE(addr->ip6); ++i) { 111 lh.ip6[i] = addr->ip6[i] & mask->ip6[i]; 112 rh.ip6[i] = u3->ip6[i] & mask->ip6[i]; 113 } 114 115 return memcmp(&lh.ip6, &rh.ip6, sizeof(lh.ip6)); 116 } 117 } 118 119 static bool add_hlist(struct hlist_head *head, 120 const struct nf_conntrack_tuple *tuple, 121 const union nf_inet_addr *addr) 122 { 123 struct xt_connlimit_conn *conn; 124 125 conn = kmem_cache_alloc(connlimit_conn_cachep, GFP_ATOMIC); 126 if (conn == NULL) 127 return false; 128 conn->tuple = *tuple; 129 conn->addr = *addr; 130 hlist_add_head(&conn->node, head); 131 return true; 132 } 133 134 static unsigned int check_hlist(struct net *net, 135 struct hlist_head *head, 136 const struct nf_conntrack_tuple *tuple, 137 const struct nf_conntrack_zone *zone, 138 bool *addit) 139 { 140 const struct nf_conntrack_tuple_hash *found; 141 struct xt_connlimit_conn *conn; 142 struct hlist_node *n; 143 struct nf_conn *found_ct; 144 unsigned int length = 0; 145 146 *addit = true; 147 rcu_read_lock(); 148 149 /* check the saved connections */ 150 hlist_for_each_entry_safe(conn, n, head, node) { 151 found = nf_conntrack_find_get(net, zone, &conn->tuple); 152 if (found == NULL) { 153 hlist_del(&conn->node); 154 kmem_cache_free(connlimit_conn_cachep, conn); 155 continue; 156 } 157 158 found_ct = nf_ct_tuplehash_to_ctrack(found); 159 160 if (nf_ct_tuple_equal(&conn->tuple, tuple)) { 161 /* 162 * Just to be sure we have it only once in the list. 163 * We should not see tuples twice unless someone hooks 164 * this into a table without "-p tcp --syn". 165 */ 166 *addit = false; 167 } else if (already_closed(found_ct)) { 168 /* 169 * we do not care about connections which are 170 * closed already -> ditch it 171 */ 172 nf_ct_put(found_ct); 173 hlist_del(&conn->node); 174 kmem_cache_free(connlimit_conn_cachep, conn); 175 continue; 176 } 177 178 nf_ct_put(found_ct); 179 length++; 180 } 181 182 rcu_read_unlock(); 183 184 return length; 185 } 186 187 static void tree_nodes_free(struct rb_root *root, 188 struct xt_connlimit_rb *gc_nodes[], 189 unsigned int gc_count) 190 { 191 struct xt_connlimit_rb *rbconn; 192 193 while (gc_count) { 194 rbconn = gc_nodes[--gc_count]; 195 rb_erase(&rbconn->node, root); 196 kmem_cache_free(connlimit_rb_cachep, rbconn); 197 } 198 } 199 200 static unsigned int 201 count_tree(struct net *net, struct rb_root *root, 202 const struct nf_conntrack_tuple *tuple, 203 const union nf_inet_addr *addr, const union nf_inet_addr *mask, 204 u8 family, const struct nf_conntrack_zone *zone) 205 { 206 struct xt_connlimit_rb *gc_nodes[CONNLIMIT_GC_MAX_NODES]; 207 struct rb_node **rbnode, *parent; 208 struct xt_connlimit_rb *rbconn; 209 struct xt_connlimit_conn *conn; 210 unsigned int gc_count; 211 bool no_gc = false; 212 213 restart: 214 gc_count = 0; 215 parent = NULL; 216 rbnode = &(root->rb_node); 217 while (*rbnode) { 218 int diff; 219 bool addit; 220 221 rbconn = rb_entry(*rbnode, struct xt_connlimit_rb, node); 222 223 parent = *rbnode; 224 diff = same_source_net(addr, mask, &rbconn->addr, family); 225 if (diff < 0) { 226 rbnode = &((*rbnode)->rb_left); 227 } else if (diff > 0) { 228 rbnode = &((*rbnode)->rb_right); 229 } else { 230 /* same source network -> be counted! */ 231 unsigned int count; 232 count = check_hlist(net, &rbconn->hhead, tuple, zone, &addit); 233 234 tree_nodes_free(root, gc_nodes, gc_count); 235 if (!addit) 236 return count; 237 238 if (!add_hlist(&rbconn->hhead, tuple, addr)) 239 return 0; /* hotdrop */ 240 241 return count + 1; 242 } 243 244 if (no_gc || gc_count >= ARRAY_SIZE(gc_nodes)) 245 continue; 246 247 /* only used for GC on hhead, retval and 'addit' ignored */ 248 check_hlist(net, &rbconn->hhead, tuple, zone, &addit); 249 if (hlist_empty(&rbconn->hhead)) 250 gc_nodes[gc_count++] = rbconn; 251 } 252 253 if (gc_count) { 254 no_gc = true; 255 tree_nodes_free(root, gc_nodes, gc_count); 256 /* tree_node_free before new allocation permits 257 * allocator to re-use newly free'd object. 258 * 259 * This is a rare event; in most cases we will find 260 * existing node to re-use. (or gc_count is 0). 261 */ 262 goto restart; 263 } 264 265 /* no match, need to insert new node */ 266 rbconn = kmem_cache_alloc(connlimit_rb_cachep, GFP_ATOMIC); 267 if (rbconn == NULL) 268 return 0; 269 270 conn = kmem_cache_alloc(connlimit_conn_cachep, GFP_ATOMIC); 271 if (conn == NULL) { 272 kmem_cache_free(connlimit_rb_cachep, rbconn); 273 return 0; 274 } 275 276 conn->tuple = *tuple; 277 conn->addr = *addr; 278 rbconn->addr = *addr; 279 280 INIT_HLIST_HEAD(&rbconn->hhead); 281 hlist_add_head(&conn->node, &rbconn->hhead); 282 283 rb_link_node(&rbconn->node, parent, rbnode); 284 rb_insert_color(&rbconn->node, root); 285 return 1; 286 } 287 288 static int count_them(struct net *net, 289 struct xt_connlimit_data *data, 290 const struct nf_conntrack_tuple *tuple, 291 const union nf_inet_addr *addr, 292 const union nf_inet_addr *mask, 293 u_int8_t family, 294 const struct nf_conntrack_zone *zone) 295 { 296 struct rb_root *root; 297 int count; 298 u32 hash; 299 300 if (family == NFPROTO_IPV6) { 301 hash = connlimit_iphash6(addr, mask); 302 root = &data->climit_root6[hash]; 303 } else { 304 hash = connlimit_iphash(addr->ip & mask->ip); 305 root = &data->climit_root4[hash]; 306 } 307 308 spin_lock_bh(&xt_connlimit_locks[hash % CONNLIMIT_LOCK_SLOTS]); 309 310 count = count_tree(net, root, tuple, addr, mask, family, zone); 311 312 spin_unlock_bh(&xt_connlimit_locks[hash % CONNLIMIT_LOCK_SLOTS]); 313 314 return count; 315 } 316 317 static bool 318 connlimit_mt(const struct sk_buff *skb, struct xt_action_param *par) 319 { 320 struct net *net = xt_net(par); 321 const struct xt_connlimit_info *info = par->matchinfo; 322 union nf_inet_addr addr; 323 struct nf_conntrack_tuple tuple; 324 const struct nf_conntrack_tuple *tuple_ptr = &tuple; 325 const struct nf_conntrack_zone *zone = &nf_ct_zone_dflt; 326 enum ip_conntrack_info ctinfo; 327 const struct nf_conn *ct; 328 unsigned int connections; 329 330 ct = nf_ct_get(skb, &ctinfo); 331 if (ct != NULL) { 332 tuple_ptr = &ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple; 333 zone = nf_ct_zone(ct); 334 } else if (!nf_ct_get_tuplepr(skb, skb_network_offset(skb), 335 xt_family(par), net, &tuple)) { 336 goto hotdrop; 337 } 338 339 if (xt_family(par) == NFPROTO_IPV6) { 340 const struct ipv6hdr *iph = ipv6_hdr(skb); 341 memcpy(&addr.ip6, (info->flags & XT_CONNLIMIT_DADDR) ? 342 &iph->daddr : &iph->saddr, sizeof(addr.ip6)); 343 } else { 344 const struct iphdr *iph = ip_hdr(skb); 345 addr.ip = (info->flags & XT_CONNLIMIT_DADDR) ? 346 iph->daddr : iph->saddr; 347 } 348 349 connections = count_them(net, info->data, tuple_ptr, &addr, 350 &info->mask, xt_family(par), zone); 351 if (connections == 0) 352 /* kmalloc failed, drop it entirely */ 353 goto hotdrop; 354 355 return (connections > info->limit) ^ 356 !!(info->flags & XT_CONNLIMIT_INVERT); 357 358 hotdrop: 359 par->hotdrop = true; 360 return false; 361 } 362 363 static int connlimit_mt_check(const struct xt_mtchk_param *par) 364 { 365 struct xt_connlimit_info *info = par->matchinfo; 366 unsigned int i; 367 int ret; 368 369 net_get_random_once(&connlimit_rnd, sizeof(connlimit_rnd)); 370 371 ret = nf_ct_netns_get(par->net, par->family); 372 if (ret < 0) { 373 pr_info("cannot load conntrack support for " 374 "address family %u\n", par->family); 375 return ret; 376 } 377 378 /* init private data */ 379 info->data = kmalloc(sizeof(struct xt_connlimit_data), GFP_KERNEL); 380 if (info->data == NULL) { 381 nf_ct_netns_put(par->net, par->family); 382 return -ENOMEM; 383 } 384 385 for (i = 0; i < ARRAY_SIZE(info->data->climit_root4); ++i) 386 info->data->climit_root4[i] = RB_ROOT; 387 for (i = 0; i < ARRAY_SIZE(info->data->climit_root6); ++i) 388 info->data->climit_root6[i] = RB_ROOT; 389 390 return 0; 391 } 392 393 static void destroy_tree(struct rb_root *r) 394 { 395 struct xt_connlimit_conn *conn; 396 struct xt_connlimit_rb *rbconn; 397 struct hlist_node *n; 398 struct rb_node *node; 399 400 while ((node = rb_first(r)) != NULL) { 401 rbconn = rb_entry(node, struct xt_connlimit_rb, node); 402 403 rb_erase(node, r); 404 405 hlist_for_each_entry_safe(conn, n, &rbconn->hhead, node) 406 kmem_cache_free(connlimit_conn_cachep, conn); 407 408 kmem_cache_free(connlimit_rb_cachep, rbconn); 409 } 410 } 411 412 static void connlimit_mt_destroy(const struct xt_mtdtor_param *par) 413 { 414 const struct xt_connlimit_info *info = par->matchinfo; 415 unsigned int i; 416 417 nf_ct_netns_put(par->net, par->family); 418 419 for (i = 0; i < ARRAY_SIZE(info->data->climit_root4); ++i) 420 destroy_tree(&info->data->climit_root4[i]); 421 for (i = 0; i < ARRAY_SIZE(info->data->climit_root6); ++i) 422 destroy_tree(&info->data->climit_root6[i]); 423 424 kfree(info->data); 425 } 426 427 static struct xt_match connlimit_mt_reg __read_mostly = { 428 .name = "connlimit", 429 .revision = 1, 430 .family = NFPROTO_UNSPEC, 431 .checkentry = connlimit_mt_check, 432 .match = connlimit_mt, 433 .matchsize = sizeof(struct xt_connlimit_info), 434 .usersize = offsetof(struct xt_connlimit_info, data), 435 .destroy = connlimit_mt_destroy, 436 .me = THIS_MODULE, 437 }; 438 439 static int __init connlimit_mt_init(void) 440 { 441 int ret, i; 442 443 BUILD_BUG_ON(CONNLIMIT_LOCK_SLOTS > CONNLIMIT_SLOTS); 444 BUILD_BUG_ON((CONNLIMIT_SLOTS % CONNLIMIT_LOCK_SLOTS) != 0); 445 446 for (i = 0; i < CONNLIMIT_LOCK_SLOTS; ++i) 447 spin_lock_init(&xt_connlimit_locks[i]); 448 449 connlimit_conn_cachep = kmem_cache_create("xt_connlimit_conn", 450 sizeof(struct xt_connlimit_conn), 451 0, 0, NULL); 452 if (!connlimit_conn_cachep) 453 return -ENOMEM; 454 455 connlimit_rb_cachep = kmem_cache_create("xt_connlimit_rb", 456 sizeof(struct xt_connlimit_rb), 457 0, 0, NULL); 458 if (!connlimit_rb_cachep) { 459 kmem_cache_destroy(connlimit_conn_cachep); 460 return -ENOMEM; 461 } 462 ret = xt_register_match(&connlimit_mt_reg); 463 if (ret != 0) { 464 kmem_cache_destroy(connlimit_conn_cachep); 465 kmem_cache_destroy(connlimit_rb_cachep); 466 } 467 return ret; 468 } 469 470 static void __exit connlimit_mt_exit(void) 471 { 472 xt_unregister_match(&connlimit_mt_reg); 473 kmem_cache_destroy(connlimit_conn_cachep); 474 kmem_cache_destroy(connlimit_rb_cachep); 475 } 476 477 module_init(connlimit_mt_init); 478 module_exit(connlimit_mt_exit); 479 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); 480 MODULE_DESCRIPTION("Xtables: Number of connections matching"); 481 MODULE_LICENSE("GPL"); 482 MODULE_ALIAS("ipt_connlimit"); 483 MODULE_ALIAS("ip6t_connlimit"); 484