nf_conntrack_helper.c revision 5e615b220087c5551f486c967831cecdfd338dbe
1/* Helper handling for netfilter. */ 2 3/* (C) 1999-2001 Paul `Rusty' Russell 4 * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org> 5 * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License version 2 as 9 * published by the Free Software Foundation. 10 */ 11 12#include <linux/types.h> 13#include <linux/netfilter.h> 14#include <linux/module.h> 15#include <linux/skbuff.h> 16#include <linux/vmalloc.h> 17#include <linux/stddef.h> 18#include <linux/random.h> 19#include <linux/err.h> 20#include <linux/kernel.h> 21#include <linux/netdevice.h> 22#include <linux/rculist.h> 23#include <linux/rtnetlink.h> 24 25#include <net/netfilter/nf_conntrack.h> 26#include <net/netfilter/nf_conntrack_l3proto.h> 27#include <net/netfilter/nf_conntrack_l4proto.h> 28#include <net/netfilter/nf_conntrack_helper.h> 29#include <net/netfilter/nf_conntrack_core.h> 30#include <net/netfilter/nf_conntrack_extend.h> 31 32static DEFINE_MUTEX(nf_ct_helper_mutex); 33struct hlist_head *nf_ct_helper_hash __read_mostly; 34EXPORT_SYMBOL_GPL(nf_ct_helper_hash); 35unsigned int nf_ct_helper_hsize __read_mostly; 36EXPORT_SYMBOL_GPL(nf_ct_helper_hsize); 37static unsigned int nf_ct_helper_count __read_mostly; 38 39static bool nf_ct_auto_assign_helper __read_mostly = true; 40module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644); 41MODULE_PARM_DESC(nf_conntrack_helper, 42 "Enable automatic conntrack helper assignment (default 1)"); 43 44#ifdef CONFIG_SYSCTL 45static struct ctl_table helper_sysctl_table[] = { 46 { 47 .procname = "nf_conntrack_helper", 48 .data = &init_net.ct.sysctl_auto_assign_helper, 49 .maxlen = sizeof(unsigned int), 50 .mode = 0644, 51 .proc_handler = proc_dointvec, 52 }, 53 {} 54}; 55 56static int nf_conntrack_helper_init_sysctl(struct net *net) 57{ 58 struct ctl_table *table; 59 60 table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table), 61 GFP_KERNEL); 62 if (!table) 63 goto out; 64 65 table[0].data = &net->ct.sysctl_auto_assign_helper; 66 67 /* Don't export sysctls to unprivileged users */ 68 if (net->user_ns != &init_user_ns) 69 table[0].procname = NULL; 70 71 net->ct.helper_sysctl_header = 72 register_net_sysctl(net, "net/netfilter", table); 73 74 if (!net->ct.helper_sysctl_header) { 75 pr_err("nf_conntrack_helper: can't register to sysctl.\n"); 76 goto out_register; 77 } 78 return 0; 79 80out_register: 81 kfree(table); 82out: 83 return -ENOMEM; 84} 85 86static void nf_conntrack_helper_fini_sysctl(struct net *net) 87{ 88 struct ctl_table *table; 89 90 table = net->ct.helper_sysctl_header->ctl_table_arg; 91 unregister_net_sysctl_table(net->ct.helper_sysctl_header); 92 kfree(table); 93} 94#else 95static int nf_conntrack_helper_init_sysctl(struct net *net) 96{ 97 return 0; 98} 99 100static void nf_conntrack_helper_fini_sysctl(struct net *net) 101{ 102} 103#endif /* CONFIG_SYSCTL */ 104 105/* Stupid hash, but collision free for the default registrations of the 106 * helpers currently in the kernel. */ 107static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple) 108{ 109 return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^ 110 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize; 111} 112 113static struct nf_conntrack_helper * 114__nf_ct_helper_find(const struct nf_conntrack_tuple *tuple) 115{ 116 struct nf_conntrack_helper *helper; 117 struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) }; 118 struct hlist_node *n; 119 unsigned int h; 120 121 if (!nf_ct_helper_count) 122 return NULL; 123 124 h = helper_hash(tuple); 125 hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) { 126 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask)) 127 return helper; 128 } 129 return NULL; 130} 131 132struct nf_conntrack_helper * 133__nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum) 134{ 135 struct nf_conntrack_helper *h; 136 struct hlist_node *n; 137 unsigned int i; 138 139 for (i = 0; i < nf_ct_helper_hsize; i++) { 140 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) { 141 if (!strcmp(h->name, name) && 142 h->tuple.src.l3num == l3num && 143 h->tuple.dst.protonum == protonum) 144 return h; 145 } 146 } 147 return NULL; 148} 149EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find); 150 151struct nf_conntrack_helper * 152nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum) 153{ 154 struct nf_conntrack_helper *h; 155 156 h = __nf_conntrack_helper_find(name, l3num, protonum); 157#ifdef CONFIG_MODULES 158 if (h == NULL) { 159 if (request_module("nfct-helper-%s", name) == 0) 160 h = __nf_conntrack_helper_find(name, l3num, protonum); 161 } 162#endif 163 if (h != NULL && !try_module_get(h->me)) 164 h = NULL; 165 166 return h; 167} 168EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get); 169 170struct nf_conn_help * 171nf_ct_helper_ext_add(struct nf_conn *ct, 172 struct nf_conntrack_helper *helper, gfp_t gfp) 173{ 174 struct nf_conn_help *help; 175 176 help = nf_ct_ext_add_length(ct, NF_CT_EXT_HELPER, 177 helper->data_len, gfp); 178 if (help) 179 INIT_HLIST_HEAD(&help->expectations); 180 else 181 pr_debug("failed to add helper extension area"); 182 return help; 183} 184EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add); 185 186int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl, 187 gfp_t flags) 188{ 189 struct nf_conntrack_helper *helper = NULL; 190 struct nf_conn_help *help; 191 struct net *net = nf_ct_net(ct); 192 int ret = 0; 193 194 /* We already got a helper explicitly attached. The function 195 * nf_conntrack_alter_reply - in case NAT is in use - asks for looking 196 * the helper up again. Since now the user is in full control of 197 * making consistent helper configurations, skip this automatic 198 * re-lookup, otherwise we'll lose the helper. 199 */ 200 if (test_bit(IPS_HELPER_BIT, &ct->status)) 201 return 0; 202 203 if (tmpl != NULL) { 204 help = nfct_help(tmpl); 205 if (help != NULL) { 206 helper = help->helper; 207 set_bit(IPS_HELPER_BIT, &ct->status); 208 } 209 } 210 211 help = nfct_help(ct); 212 if (net->ct.sysctl_auto_assign_helper && helper == NULL) { 213 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple); 214 if (unlikely(!net->ct.auto_assign_helper_warned && helper)) { 215 pr_info("nf_conntrack: automatic helper " 216 "assignment is deprecated and it will " 217 "be removed soon. Use the iptables CT target " 218 "to attach helpers instead.\n"); 219 net->ct.auto_assign_helper_warned = true; 220 } 221 } 222 223 if (helper == NULL) { 224 if (help) 225 RCU_INIT_POINTER(help->helper, NULL); 226 goto out; 227 } 228 229 if (help == NULL) { 230 help = nf_ct_helper_ext_add(ct, helper, flags); 231 if (help == NULL) { 232 ret = -ENOMEM; 233 goto out; 234 } 235 } else { 236 /* We only allow helper re-assignment of the same sort since 237 * we cannot reallocate the helper extension area. 238 */ 239 if (help->helper != helper) { 240 RCU_INIT_POINTER(help->helper, NULL); 241 goto out; 242 } 243 } 244 245 rcu_assign_pointer(help->helper, helper); 246out: 247 return ret; 248} 249EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper); 250 251static inline int unhelp(struct nf_conntrack_tuple_hash *i, 252 const struct nf_conntrack_helper *me) 253{ 254 struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i); 255 struct nf_conn_help *help = nfct_help(ct); 256 257 if (help && rcu_dereference_protected( 258 help->helper, 259 lockdep_is_held(&nf_conntrack_lock) 260 ) == me) { 261 nf_conntrack_event(IPCT_HELPER, ct); 262 RCU_INIT_POINTER(help->helper, NULL); 263 } 264 return 0; 265} 266 267void nf_ct_helper_destroy(struct nf_conn *ct) 268{ 269 struct nf_conn_help *help = nfct_help(ct); 270 struct nf_conntrack_helper *helper; 271 272 if (help) { 273 rcu_read_lock(); 274 helper = rcu_dereference(help->helper); 275 if (helper && helper->destroy) 276 helper->destroy(ct); 277 rcu_read_unlock(); 278 } 279} 280 281static LIST_HEAD(nf_ct_helper_expectfn_list); 282 283void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n) 284{ 285 spin_lock_bh(&nf_conntrack_lock); 286 list_add_rcu(&n->head, &nf_ct_helper_expectfn_list); 287 spin_unlock_bh(&nf_conntrack_lock); 288} 289EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register); 290 291void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n) 292{ 293 spin_lock_bh(&nf_conntrack_lock); 294 list_del_rcu(&n->head); 295 spin_unlock_bh(&nf_conntrack_lock); 296} 297EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister); 298 299struct nf_ct_helper_expectfn * 300nf_ct_helper_expectfn_find_by_name(const char *name) 301{ 302 struct nf_ct_helper_expectfn *cur; 303 bool found = false; 304 305 rcu_read_lock(); 306 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) { 307 if (!strcmp(cur->name, name)) { 308 found = true; 309 break; 310 } 311 } 312 rcu_read_unlock(); 313 return found ? cur : NULL; 314} 315EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name); 316 317struct nf_ct_helper_expectfn * 318nf_ct_helper_expectfn_find_by_symbol(const void *symbol) 319{ 320 struct nf_ct_helper_expectfn *cur; 321 bool found = false; 322 323 rcu_read_lock(); 324 list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) { 325 if (cur->expectfn == symbol) { 326 found = true; 327 break; 328 } 329 } 330 rcu_read_unlock(); 331 return found ? cur : NULL; 332} 333EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol); 334 335int nf_conntrack_helper_register(struct nf_conntrack_helper *me) 336{ 337 int ret = 0; 338 struct nf_conntrack_helper *cur; 339 struct hlist_node *n; 340 unsigned int h = helper_hash(&me->tuple); 341 342 BUG_ON(me->expect_policy == NULL); 343 BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES); 344 BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1); 345 346 mutex_lock(&nf_ct_helper_mutex); 347 hlist_for_each_entry(cur, n, &nf_ct_helper_hash[h], hnode) { 348 if (strncmp(cur->name, me->name, NF_CT_HELPER_NAME_LEN) == 0 && 349 cur->tuple.src.l3num == me->tuple.src.l3num && 350 cur->tuple.dst.protonum == me->tuple.dst.protonum) { 351 ret = -EEXIST; 352 goto out; 353 } 354 } 355 hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]); 356 nf_ct_helper_count++; 357out: 358 mutex_unlock(&nf_ct_helper_mutex); 359 return ret; 360} 361EXPORT_SYMBOL_GPL(nf_conntrack_helper_register); 362 363static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me, 364 struct net *net) 365{ 366 struct nf_conntrack_tuple_hash *h; 367 struct nf_conntrack_expect *exp; 368 const struct hlist_node *n, *next; 369 const struct hlist_nulls_node *nn; 370 unsigned int i; 371 372 /* Get rid of expectations */ 373 for (i = 0; i < nf_ct_expect_hsize; i++) { 374 hlist_for_each_entry_safe(exp, n, next, 375 &net->ct.expect_hash[i], hnode) { 376 struct nf_conn_help *help = nfct_help(exp->master); 377 if ((rcu_dereference_protected( 378 help->helper, 379 lockdep_is_held(&nf_conntrack_lock) 380 ) == me || exp->helper == me) && 381 del_timer(&exp->timeout)) { 382 nf_ct_unlink_expect(exp); 383 nf_ct_expect_put(exp); 384 } 385 } 386 } 387 388 /* Get rid of expecteds, set helpers to NULL. */ 389 hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode) 390 unhelp(h, me); 391 for (i = 0; i < net->ct.htable_size; i++) { 392 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode) 393 unhelp(h, me); 394 } 395} 396 397void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me) 398{ 399 struct net *net; 400 401 mutex_lock(&nf_ct_helper_mutex); 402 hlist_del_rcu(&me->hnode); 403 nf_ct_helper_count--; 404 mutex_unlock(&nf_ct_helper_mutex); 405 406 /* Make sure every nothing is still using the helper unless its a 407 * connection in the hash. 408 */ 409 synchronize_rcu(); 410 411 rtnl_lock(); 412 spin_lock_bh(&nf_conntrack_lock); 413 for_each_net(net) 414 __nf_conntrack_helper_unregister(me, net); 415 spin_unlock_bh(&nf_conntrack_lock); 416 rtnl_unlock(); 417} 418EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister); 419 420static struct nf_ct_ext_type helper_extend __read_mostly = { 421 .len = sizeof(struct nf_conn_help), 422 .align = __alignof__(struct nf_conn_help), 423 .id = NF_CT_EXT_HELPER, 424}; 425 426int nf_conntrack_helper_pernet_init(struct net *net) 427{ 428 net->ct.auto_assign_helper_warned = false; 429 net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper; 430 return nf_conntrack_helper_init_sysctl(net); 431} 432 433void nf_conntrack_helper_pernet_fini(struct net *net) 434{ 435 nf_conntrack_helper_fini_sysctl(net); 436} 437 438int nf_conntrack_helper_init(void) 439{ 440 int ret; 441 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */ 442 nf_ct_helper_hash = 443 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0); 444 if (!nf_ct_helper_hash) 445 return -ENOMEM; 446 447 ret = nf_ct_extend_register(&helper_extend); 448 if (ret < 0) { 449 pr_err("nf_ct_helper: Unable to register helper extension.\n"); 450 goto out_extend; 451 } 452 453 return 0; 454out_extend: 455 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize); 456 return ret; 457} 458 459void nf_conntrack_helper_fini(void) 460{ 461 nf_ct_extend_unregister(&helper_extend); 462 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize); 463} 464