| 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 | * (C) 2006-2012 Patrick McHardy <kaber@trash.net> |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or modify |
| 9 | * it under the terms of the GNU General Public License version 2 as |
| 10 | * published by the Free Software Foundation. |
| 11 | */ |
| 12 | |
| 13 | #include <linux/types.h> |
| 14 | #include <linux/netfilter.h> |
| 15 | #include <linux/module.h> |
| 16 | #include <linux/skbuff.h> |
| 17 | #include <linux/vmalloc.h> |
| 18 | #include <linux/stddef.h> |
| 19 | #include <linux/random.h> |
| 20 | #include <linux/err.h> |
| 21 | #include <linux/kernel.h> |
| 22 | #include <linux/netdevice.h> |
| 23 | #include <linux/rculist.h> |
| 24 | #include <linux/rtnetlink.h> |
| 25 | |
| 26 | #include <net/netfilter/nf_conntrack.h> |
| 27 | #include <net/netfilter/nf_conntrack_l3proto.h> |
| 28 | #include <net/netfilter/nf_conntrack_l4proto.h> |
| 29 | #include <net/netfilter/nf_conntrack_helper.h> |
| 30 | #include <net/netfilter/nf_conntrack_core.h> |
| 31 | #include <net/netfilter/nf_conntrack_extend.h> |
| 32 | #include <net/netfilter/nf_log.h> |
| 33 | |
| 34 | static DEFINE_MUTEX(nf_ct_helper_mutex); |
| 35 | struct hlist_head *nf_ct_helper_hash __read_mostly; |
| 36 | EXPORT_SYMBOL_GPL(nf_ct_helper_hash); |
| 37 | unsigned int nf_ct_helper_hsize __read_mostly; |
| 38 | EXPORT_SYMBOL_GPL(nf_ct_helper_hsize); |
| 39 | static unsigned int nf_ct_helper_count __read_mostly; |
| 40 | |
| 41 | static bool nf_ct_auto_assign_helper __read_mostly = true; |
| 42 | module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644); |
| 43 | MODULE_PARM_DESC(nf_conntrack_helper, |
| 44 | "Enable automatic conntrack helper assignment (default 1)"); |
| 45 | |
| 46 | #ifdef CONFIG_SYSCTL |
| 47 | static struct ctl_table helper_sysctl_table[] = { |
| 48 | { |
| 49 | .procname = "nf_conntrack_helper", |
| 50 | .data = &init_net.ct.sysctl_auto_assign_helper, |
| 51 | .maxlen = sizeof(unsigned int), |
| 52 | .mode = 0644, |
| 53 | .proc_handler = proc_dointvec, |
| 54 | }, |
| 55 | {} |
| 56 | }; |
| 57 | |
| 58 | static int nf_conntrack_helper_init_sysctl(struct net *net) |
| 59 | { |
| 60 | struct ctl_table *table; |
| 61 | |
| 62 | table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table), |
| 63 | GFP_KERNEL); |
| 64 | if (!table) |
| 65 | goto out; |
| 66 | |
| 67 | table[0].data = &net->ct.sysctl_auto_assign_helper; |
| 68 | |
| 69 | /* Don't export sysctls to unprivileged users */ |
| 70 | if (net->user_ns != &init_user_ns) |
| 71 | table[0].procname = NULL; |
| 72 | |
| 73 | net->ct.helper_sysctl_header = |
| 74 | register_net_sysctl(net, "net/netfilter", table); |
| 75 | |
| 76 | if (!net->ct.helper_sysctl_header) { |
| 77 | pr_err("nf_conntrack_helper: can't register to sysctl.\n"); |
| 78 | goto out_register; |
| 79 | } |
| 80 | return 0; |
| 81 | |
| 82 | out_register: |
| 83 | kfree(table); |
| 84 | out: |
| 85 | return -ENOMEM; |
| 86 | } |
| 87 | |
| 88 | static void nf_conntrack_helper_fini_sysctl(struct net *net) |
| 89 | { |
| 90 | struct ctl_table *table; |
| 91 | |
| 92 | table = net->ct.helper_sysctl_header->ctl_table_arg; |
| 93 | unregister_net_sysctl_table(net->ct.helper_sysctl_header); |
| 94 | kfree(table); |
| 95 | } |
| 96 | #else |
| 97 | static int nf_conntrack_helper_init_sysctl(struct net *net) |
| 98 | { |
| 99 | return 0; |
| 100 | } |
| 101 | |
| 102 | static void nf_conntrack_helper_fini_sysctl(struct net *net) |
| 103 | { |
| 104 | } |
| 105 | #endif /* CONFIG_SYSCTL */ |
| 106 | |
| 107 | /* Stupid hash, but collision free for the default registrations of the |
| 108 | * helpers currently in the kernel. */ |
| 109 | static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple) |
| 110 | { |
| 111 | return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^ |
| 112 | (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize; |
| 113 | } |
| 114 | |
| 115 | static struct nf_conntrack_helper * |
| 116 | __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple) |
| 117 | { |
| 118 | struct nf_conntrack_helper *helper; |
| 119 | struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) }; |
| 120 | unsigned int h; |
| 121 | |
| 122 | if (!nf_ct_helper_count) |
| 123 | return NULL; |
| 124 | |
| 125 | h = helper_hash(tuple); |
| 126 | hlist_for_each_entry_rcu(helper, &nf_ct_helper_hash[h], hnode) { |
| 127 | if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask)) |
| 128 | return helper; |
| 129 | } |
| 130 | return NULL; |
| 131 | } |
| 132 | |
| 133 | struct nf_conntrack_helper * |
| 134 | __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum) |
| 135 | { |
| 136 | struct nf_conntrack_helper *h; |
| 137 | unsigned int i; |
| 138 | |
| 139 | for (i = 0; i < nf_ct_helper_hsize; i++) { |
| 140 | hlist_for_each_entry_rcu(h, &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 | } |
| 149 | EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find); |
| 150 | |
| 151 | struct nf_conntrack_helper * |
| 152 | nf_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 | } |
| 168 | EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get); |
| 169 | |
| 170 | struct nf_conn_help * |
| 171 | nf_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 | } |
| 184 | EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add); |
| 185 | |
| 186 | int __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 | struct nf_conntrack_helper *tmp = rcu_dereference(help->helper); |
| 240 | |
| 241 | if (tmp && tmp->help != helper->help) { |
| 242 | RCU_INIT_POINTER(help->helper, NULL); |
| 243 | goto out; |
| 244 | } |
| 245 | } |
| 246 | |
| 247 | rcu_assign_pointer(help->helper, helper); |
| 248 | out: |
| 249 | return ret; |
| 250 | } |
| 251 | EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper); |
| 252 | |
| 253 | static inline int unhelp(struct nf_conntrack_tuple_hash *i, |
| 254 | const struct nf_conntrack_helper *me) |
| 255 | { |
| 256 | struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i); |
| 257 | struct nf_conn_help *help = nfct_help(ct); |
| 258 | |
| 259 | if (help && rcu_dereference_protected( |
| 260 | help->helper, |
| 261 | lockdep_is_held(&nf_conntrack_lock) |
| 262 | ) == me) { |
| 263 | nf_conntrack_event(IPCT_HELPER, ct); |
| 264 | RCU_INIT_POINTER(help->helper, NULL); |
| 265 | } |
| 266 | return 0; |
| 267 | } |
| 268 | |
| 269 | void nf_ct_helper_destroy(struct nf_conn *ct) |
| 270 | { |
| 271 | struct nf_conn_help *help = nfct_help(ct); |
| 272 | struct nf_conntrack_helper *helper; |
| 273 | |
| 274 | if (help) { |
| 275 | rcu_read_lock(); |
| 276 | helper = rcu_dereference(help->helper); |
| 277 | if (helper && helper->destroy) |
| 278 | helper->destroy(ct); |
| 279 | rcu_read_unlock(); |
| 280 | } |
| 281 | } |
| 282 | |
| 283 | static LIST_HEAD(nf_ct_helper_expectfn_list); |
| 284 | |
| 285 | void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n) |
| 286 | { |
| 287 | spin_lock_bh(&nf_conntrack_lock); |
| 288 | list_add_rcu(&n->head, &nf_ct_helper_expectfn_list); |
| 289 | spin_unlock_bh(&nf_conntrack_lock); |
| 290 | } |
| 291 | EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register); |
| 292 | |
| 293 | void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n) |
| 294 | { |
| 295 | spin_lock_bh(&nf_conntrack_lock); |
| 296 | list_del_rcu(&n->head); |
| 297 | spin_unlock_bh(&nf_conntrack_lock); |
| 298 | } |
| 299 | EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister); |
| 300 | |
| 301 | struct nf_ct_helper_expectfn * |
| 302 | nf_ct_helper_expectfn_find_by_name(const char *name) |
| 303 | { |
| 304 | struct nf_ct_helper_expectfn *cur; |
| 305 | bool found = false; |
| 306 | |
| 307 | rcu_read_lock(); |
| 308 | list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) { |
| 309 | if (!strcmp(cur->name, name)) { |
| 310 | found = true; |
| 311 | break; |
| 312 | } |
| 313 | } |
| 314 | rcu_read_unlock(); |
| 315 | return found ? cur : NULL; |
| 316 | } |
| 317 | EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name); |
| 318 | |
| 319 | struct nf_ct_helper_expectfn * |
| 320 | nf_ct_helper_expectfn_find_by_symbol(const void *symbol) |
| 321 | { |
| 322 | struct nf_ct_helper_expectfn *cur; |
| 323 | bool found = false; |
| 324 | |
| 325 | rcu_read_lock(); |
| 326 | list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) { |
| 327 | if (cur->expectfn == symbol) { |
| 328 | found = true; |
| 329 | break; |
| 330 | } |
| 331 | } |
| 332 | rcu_read_unlock(); |
| 333 | return found ? cur : NULL; |
| 334 | } |
| 335 | EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol); |
| 336 | |
| 337 | __printf(3, 4) |
| 338 | void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct, |
| 339 | const char *fmt, ...) |
| 340 | { |
| 341 | const struct nf_conn_help *help; |
| 342 | const struct nf_conntrack_helper *helper; |
| 343 | struct va_format vaf; |
| 344 | va_list args; |
| 345 | |
| 346 | va_start(args, fmt); |
| 347 | |
| 348 | vaf.fmt = fmt; |
| 349 | vaf.va = &args; |
| 350 | |
| 351 | /* Called from the helper function, this call never fails */ |
| 352 | help = nfct_help(ct); |
| 353 | |
| 354 | /* rcu_read_lock()ed by nf_hook_slow */ |
| 355 | helper = rcu_dereference(help->helper); |
| 356 | |
| 357 | nf_log_packet(nf_ct_net(ct), nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL, |
| 358 | "nf_ct_%s: dropping packet: %pV ", helper->name, &vaf); |
| 359 | |
| 360 | va_end(args); |
| 361 | } |
| 362 | EXPORT_SYMBOL_GPL(nf_ct_helper_log); |
| 363 | |
| 364 | int nf_conntrack_helper_register(struct nf_conntrack_helper *me) |
| 365 | { |
| 366 | int ret = 0; |
| 367 | struct nf_conntrack_helper *cur; |
| 368 | unsigned int h = helper_hash(&me->tuple); |
| 369 | |
| 370 | BUG_ON(me->expect_policy == NULL); |
| 371 | BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES); |
| 372 | BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1); |
| 373 | |
| 374 | mutex_lock(&nf_ct_helper_mutex); |
| 375 | hlist_for_each_entry(cur, &nf_ct_helper_hash[h], hnode) { |
| 376 | if (strncmp(cur->name, me->name, NF_CT_HELPER_NAME_LEN) == 0 && |
| 377 | cur->tuple.src.l3num == me->tuple.src.l3num && |
| 378 | cur->tuple.dst.protonum == me->tuple.dst.protonum) { |
| 379 | ret = -EEXIST; |
| 380 | goto out; |
| 381 | } |
| 382 | } |
| 383 | hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]); |
| 384 | nf_ct_helper_count++; |
| 385 | out: |
| 386 | mutex_unlock(&nf_ct_helper_mutex); |
| 387 | return ret; |
| 388 | } |
| 389 | EXPORT_SYMBOL_GPL(nf_conntrack_helper_register); |
| 390 | |
| 391 | static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me, |
| 392 | struct net *net) |
| 393 | { |
| 394 | struct nf_conntrack_tuple_hash *h; |
| 395 | struct nf_conntrack_expect *exp; |
| 396 | const struct hlist_node *next; |
| 397 | const struct hlist_nulls_node *nn; |
| 398 | unsigned int i; |
| 399 | |
| 400 | /* Get rid of expectations */ |
| 401 | for (i = 0; i < nf_ct_expect_hsize; i++) { |
| 402 | hlist_for_each_entry_safe(exp, next, |
| 403 | &net->ct.expect_hash[i], hnode) { |
| 404 | struct nf_conn_help *help = nfct_help(exp->master); |
| 405 | if ((rcu_dereference_protected( |
| 406 | help->helper, |
| 407 | lockdep_is_held(&nf_conntrack_lock) |
| 408 | ) == me || exp->helper == me) && |
| 409 | del_timer(&exp->timeout)) { |
| 410 | nf_ct_unlink_expect(exp); |
| 411 | nf_ct_expect_put(exp); |
| 412 | } |
| 413 | } |
| 414 | } |
| 415 | |
| 416 | /* Get rid of expecteds, set helpers to NULL. */ |
| 417 | hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode) |
| 418 | unhelp(h, me); |
| 419 | for (i = 0; i < net->ct.htable_size; i++) { |
| 420 | hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode) |
| 421 | unhelp(h, me); |
| 422 | } |
| 423 | } |
| 424 | |
| 425 | void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me) |
| 426 | { |
| 427 | struct net *net; |
| 428 | |
| 429 | mutex_lock(&nf_ct_helper_mutex); |
| 430 | hlist_del_rcu(&me->hnode); |
| 431 | nf_ct_helper_count--; |
| 432 | mutex_unlock(&nf_ct_helper_mutex); |
| 433 | |
| 434 | /* Make sure every nothing is still using the helper unless its a |
| 435 | * connection in the hash. |
| 436 | */ |
| 437 | synchronize_rcu(); |
| 438 | |
| 439 | rtnl_lock(); |
| 440 | spin_lock_bh(&nf_conntrack_lock); |
| 441 | for_each_net(net) |
| 442 | __nf_conntrack_helper_unregister(me, net); |
| 443 | spin_unlock_bh(&nf_conntrack_lock); |
| 444 | rtnl_unlock(); |
| 445 | } |
| 446 | EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister); |
| 447 | |
| 448 | static struct nf_ct_ext_type helper_extend __read_mostly = { |
| 449 | .len = sizeof(struct nf_conn_help), |
| 450 | .align = __alignof__(struct nf_conn_help), |
| 451 | .id = NF_CT_EXT_HELPER, |
| 452 | }; |
| 453 | |
| 454 | int nf_conntrack_helper_pernet_init(struct net *net) |
| 455 | { |
| 456 | net->ct.auto_assign_helper_warned = false; |
| 457 | net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper; |
| 458 | return nf_conntrack_helper_init_sysctl(net); |
| 459 | } |
| 460 | |
| 461 | void nf_conntrack_helper_pernet_fini(struct net *net) |
| 462 | { |
| 463 | nf_conntrack_helper_fini_sysctl(net); |
| 464 | } |
| 465 | |
| 466 | int nf_conntrack_helper_init(void) |
| 467 | { |
| 468 | int ret; |
| 469 | nf_ct_helper_hsize = 1; /* gets rounded up to use one page */ |
| 470 | nf_ct_helper_hash = |
| 471 | nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0); |
| 472 | if (!nf_ct_helper_hash) |
| 473 | return -ENOMEM; |
| 474 | |
| 475 | ret = nf_ct_extend_register(&helper_extend); |
| 476 | if (ret < 0) { |
| 477 | pr_err("nf_ct_helper: Unable to register helper extension.\n"); |
| 478 | goto out_extend; |
| 479 | } |
| 480 | |
| 481 | return 0; |
| 482 | out_extend: |
| 483 | nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize); |
| 484 | return ret; |
| 485 | } |
| 486 | |
| 487 | void nf_conntrack_helper_fini(void) |
| 488 | { |
| 489 | nf_ct_extend_unregister(&helper_extend); |
| 490 | nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize); |
| 491 | } |