1 /* Netfilter messages via netlink socket. Allows for user space 2 * protocol helpers and general trouble making from userspace. 3 * 4 * (C) 2001 by Jay Schulist <jschlst@samba.org>, 5 * (C) 2002-2005 by Harald Welte <laforge@gnumonks.org> 6 * (C) 2005,2007 by Pablo Neira Ayuso <pablo@netfilter.org> 7 * 8 * Initial netfilter messages via netlink development funded and 9 * generally made possible by Network Robots, Inc. (www.networkrobots.com) 10 * 11 * Further development of this code funded by Astaro AG (http://www.astaro.com) 12 * 13 * This software may be used and distributed according to the terms 14 * of the GNU General Public License, incorporated herein by reference. 15 */ 16 17 #include <linux/module.h> 18 #include <linux/types.h> 19 #include <linux/socket.h> 20 #include <linux/kernel.h> 21 #include <linux/string.h> 22 #include <linux/sockios.h> 23 #include <linux/net.h> 24 #include <linux/skbuff.h> 25 #include <asm/uaccess.h> 26 #include <net/sock.h> 27 #include <linux/init.h> 28 29 #include <net/netlink.h> 30 #include <linux/netfilter/nfnetlink.h> 31 32 MODULE_LICENSE("GPL"); 33 MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>"); 34 MODULE_ALIAS_NET_PF_PROTO(PF_NETLINK, NETLINK_NETFILTER); 35 36 static char __initdata nfversion[] = "0.30"; 37 38 static struct { 39 struct mutex mutex; 40 const struct nfnetlink_subsystem __rcu *subsys; 41 } table[NFNL_SUBSYS_COUNT]; 42 43 static const int nfnl_group2type[NFNLGRP_MAX+1] = { 44 [NFNLGRP_CONNTRACK_NEW] = NFNL_SUBSYS_CTNETLINK, 45 [NFNLGRP_CONNTRACK_UPDATE] = NFNL_SUBSYS_CTNETLINK, 46 [NFNLGRP_CONNTRACK_DESTROY] = NFNL_SUBSYS_CTNETLINK, 47 [NFNLGRP_CONNTRACK_EXP_NEW] = NFNL_SUBSYS_CTNETLINK_EXP, 48 [NFNLGRP_CONNTRACK_EXP_UPDATE] = NFNL_SUBSYS_CTNETLINK_EXP, 49 [NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP, 50 [NFNLGRP_NFTABLES] = NFNL_SUBSYS_NFTABLES, 51 [NFNLGRP_ACCT_QUOTA] = NFNL_SUBSYS_ACCT, 52 }; 53 54 void nfnl_lock(__u8 subsys_id) 55 { 56 mutex_lock(&table[subsys_id].mutex); 57 } 58 EXPORT_SYMBOL_GPL(nfnl_lock); 59 60 void nfnl_unlock(__u8 subsys_id) 61 { 62 mutex_unlock(&table[subsys_id].mutex); 63 } 64 EXPORT_SYMBOL_GPL(nfnl_unlock); 65 66 #ifdef CONFIG_PROVE_LOCKING 67 int lockdep_nfnl_is_held(u8 subsys_id) 68 { 69 return lockdep_is_held(&table[subsys_id].mutex); 70 } 71 EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held); 72 #endif 73 74 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n) 75 { 76 nfnl_lock(n->subsys_id); 77 if (table[n->subsys_id].subsys) { 78 nfnl_unlock(n->subsys_id); 79 return -EBUSY; 80 } 81 rcu_assign_pointer(table[n->subsys_id].subsys, n); 82 nfnl_unlock(n->subsys_id); 83 84 return 0; 85 } 86 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register); 87 88 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n) 89 { 90 nfnl_lock(n->subsys_id); 91 table[n->subsys_id].subsys = NULL; 92 nfnl_unlock(n->subsys_id); 93 synchronize_rcu(); 94 return 0; 95 } 96 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister); 97 98 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type) 99 { 100 u_int8_t subsys_id = NFNL_SUBSYS_ID(type); 101 102 if (subsys_id >= NFNL_SUBSYS_COUNT) 103 return NULL; 104 105 return rcu_dereference(table[subsys_id].subsys); 106 } 107 108 static inline const struct nfnl_callback * 109 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss) 110 { 111 u_int8_t cb_id = NFNL_MSG_TYPE(type); 112 113 if (cb_id >= ss->cb_count) 114 return NULL; 115 116 return &ss->cb[cb_id]; 117 } 118 119 int nfnetlink_has_listeners(struct net *net, unsigned int group) 120 { 121 return netlink_has_listeners(net->nfnl, group); 122 } 123 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners); 124 125 struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size, 126 u32 dst_portid, gfp_t gfp_mask) 127 { 128 return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask); 129 } 130 EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb); 131 132 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid, 133 unsigned int group, int echo, gfp_t flags) 134 { 135 return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags); 136 } 137 EXPORT_SYMBOL_GPL(nfnetlink_send); 138 139 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error) 140 { 141 return netlink_set_err(net->nfnl, portid, group, error); 142 } 143 EXPORT_SYMBOL_GPL(nfnetlink_set_err); 144 145 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid, 146 int flags) 147 { 148 return netlink_unicast(net->nfnl, skb, portid, flags); 149 } 150 EXPORT_SYMBOL_GPL(nfnetlink_unicast); 151 152 /* Process one complete nfnetlink message. */ 153 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) 154 { 155 struct net *net = sock_net(skb->sk); 156 const struct nfnl_callback *nc; 157 const struct nfnetlink_subsystem *ss; 158 int type, err; 159 160 /* All the messages must at least contain nfgenmsg */ 161 if (nlmsg_len(nlh) < sizeof(struct nfgenmsg)) 162 return 0; 163 164 type = nlh->nlmsg_type; 165 replay: 166 rcu_read_lock(); 167 ss = nfnetlink_get_subsys(type); 168 if (!ss) { 169 #ifdef CONFIG_MODULES 170 rcu_read_unlock(); 171 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type)); 172 rcu_read_lock(); 173 ss = nfnetlink_get_subsys(type); 174 if (!ss) 175 #endif 176 { 177 rcu_read_unlock(); 178 return -EINVAL; 179 } 180 } 181 182 nc = nfnetlink_find_client(type, ss); 183 if (!nc) { 184 rcu_read_unlock(); 185 return -EINVAL; 186 } 187 188 { 189 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); 190 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); 191 struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; 192 struct nlattr *attr = (void *)nlh + min_len; 193 int attrlen = nlh->nlmsg_len - min_len; 194 __u8 subsys_id = NFNL_SUBSYS_ID(type); 195 196 err = nla_parse(cda, ss->cb[cb_id].attr_count, 197 attr, attrlen, ss->cb[cb_id].policy); 198 if (err < 0) { 199 rcu_read_unlock(); 200 return err; 201 } 202 203 if (nc->call_rcu) { 204 err = nc->call_rcu(net->nfnl, skb, nlh, 205 (const struct nlattr **)cda); 206 rcu_read_unlock(); 207 } else { 208 rcu_read_unlock(); 209 nfnl_lock(subsys_id); 210 if (rcu_dereference_protected(table[subsys_id].subsys, 211 lockdep_is_held(&table[subsys_id].mutex)) != ss || 212 nfnetlink_find_client(type, ss) != nc) 213 err = -EAGAIN; 214 else if (nc->call) 215 err = nc->call(net->nfnl, skb, nlh, 216 (const struct nlattr **)cda); 217 else 218 err = -EINVAL; 219 nfnl_unlock(subsys_id); 220 } 221 if (err == -EAGAIN) 222 goto replay; 223 return err; 224 } 225 } 226 227 struct nfnl_err { 228 struct list_head head; 229 struct nlmsghdr *nlh; 230 int err; 231 }; 232 233 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err) 234 { 235 struct nfnl_err *nfnl_err; 236 237 nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL); 238 if (nfnl_err == NULL) 239 return -ENOMEM; 240 241 nfnl_err->nlh = nlh; 242 nfnl_err->err = err; 243 list_add_tail(&nfnl_err->head, list); 244 245 return 0; 246 } 247 248 static void nfnl_err_del(struct nfnl_err *nfnl_err) 249 { 250 list_del(&nfnl_err->head); 251 kfree(nfnl_err); 252 } 253 254 static void nfnl_err_reset(struct list_head *err_list) 255 { 256 struct nfnl_err *nfnl_err, *next; 257 258 list_for_each_entry_safe(nfnl_err, next, err_list, head) 259 nfnl_err_del(nfnl_err); 260 } 261 262 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb) 263 { 264 struct nfnl_err *nfnl_err, *next; 265 266 list_for_each_entry_safe(nfnl_err, next, err_list, head) { 267 netlink_ack(skb, nfnl_err->nlh, nfnl_err->err); 268 nfnl_err_del(nfnl_err); 269 } 270 } 271 272 enum { 273 NFNL_BATCH_FAILURE = (1 << 0), 274 NFNL_BATCH_DONE = (1 << 1), 275 NFNL_BATCH_REPLAY = (1 << 2), 276 }; 277 278 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh, 279 u_int16_t subsys_id) 280 { 281 struct sk_buff *oskb = skb; 282 struct net *net = sock_net(skb->sk); 283 const struct nfnetlink_subsystem *ss; 284 const struct nfnl_callback *nc; 285 static LIST_HEAD(err_list); 286 u32 status; 287 int err; 288 289 if (subsys_id >= NFNL_SUBSYS_COUNT) 290 return netlink_ack(skb, nlh, -EINVAL); 291 replay: 292 status = 0; 293 294 skb = netlink_skb_clone(oskb, GFP_KERNEL); 295 if (!skb) 296 return netlink_ack(oskb, nlh, -ENOMEM); 297 298 skb->sk = oskb->sk; 299 300 nfnl_lock(subsys_id); 301 ss = rcu_dereference_protected(table[subsys_id].subsys, 302 lockdep_is_held(&table[subsys_id].mutex)); 303 if (!ss) { 304 #ifdef CONFIG_MODULES 305 nfnl_unlock(subsys_id); 306 request_module("nfnetlink-subsys-%d", subsys_id); 307 nfnl_lock(subsys_id); 308 ss = rcu_dereference_protected(table[subsys_id].subsys, 309 lockdep_is_held(&table[subsys_id].mutex)); 310 if (!ss) 311 #endif 312 { 313 nfnl_unlock(subsys_id); 314 netlink_ack(skb, nlh, -EOPNOTSUPP); 315 return kfree_skb(skb); 316 } 317 } 318 319 if (!ss->commit || !ss->abort) { 320 nfnl_unlock(subsys_id); 321 netlink_ack(skb, nlh, -EOPNOTSUPP); 322 return kfree_skb(skb); 323 } 324 325 while (skb->len >= nlmsg_total_size(0)) { 326 int msglen, type; 327 328 nlh = nlmsg_hdr(skb); 329 err = 0; 330 331 if (nlmsg_len(nlh) < sizeof(struct nfgenmsg) || 332 skb->len < nlh->nlmsg_len) { 333 err = -EINVAL; 334 goto ack; 335 } 336 337 /* Only requests are handled by the kernel */ 338 if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) { 339 err = -EINVAL; 340 goto ack; 341 } 342 343 type = nlh->nlmsg_type; 344 if (type == NFNL_MSG_BATCH_BEGIN) { 345 /* Malformed: Batch begin twice */ 346 nfnl_err_reset(&err_list); 347 status |= NFNL_BATCH_FAILURE; 348 goto done; 349 } else if (type == NFNL_MSG_BATCH_END) { 350 status |= NFNL_BATCH_DONE; 351 goto done; 352 } else if (type < NLMSG_MIN_TYPE) { 353 err = -EINVAL; 354 goto ack; 355 } 356 357 /* We only accept a batch with messages for the same 358 * subsystem. 359 */ 360 if (NFNL_SUBSYS_ID(type) != subsys_id) { 361 err = -EINVAL; 362 goto ack; 363 } 364 365 nc = nfnetlink_find_client(type, ss); 366 if (!nc) { 367 err = -EINVAL; 368 goto ack; 369 } 370 371 { 372 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); 373 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); 374 struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; 375 struct nlattr *attr = (void *)nlh + min_len; 376 int attrlen = nlh->nlmsg_len - min_len; 377 378 err = nla_parse(cda, ss->cb[cb_id].attr_count, 379 attr, attrlen, ss->cb[cb_id].policy); 380 if (err < 0) 381 goto ack; 382 383 if (nc->call_batch) { 384 err = nc->call_batch(net->nfnl, skb, nlh, 385 (const struct nlattr **)cda); 386 } 387 388 /* The lock was released to autoload some module, we 389 * have to abort and start from scratch using the 390 * original skb. 391 */ 392 if (err == -EAGAIN) { 393 status |= NFNL_BATCH_REPLAY; 394 goto next; 395 } 396 } 397 ack: 398 if (nlh->nlmsg_flags & NLM_F_ACK || err) { 399 /* Errors are delivered once the full batch has been 400 * processed, this avoids that the same error is 401 * reported several times when replaying the batch. 402 */ 403 if (nfnl_err_add(&err_list, nlh, err) < 0) { 404 /* We failed to enqueue an error, reset the 405 * list of errors and send OOM to userspace 406 * pointing to the batch header. 407 */ 408 nfnl_err_reset(&err_list); 409 netlink_ack(skb, nlmsg_hdr(oskb), -ENOMEM); 410 status |= NFNL_BATCH_FAILURE; 411 goto done; 412 } 413 /* We don't stop processing the batch on errors, thus, 414 * userspace gets all the errors that the batch 415 * triggers. 416 */ 417 if (err) 418 status |= NFNL_BATCH_FAILURE; 419 } 420 next: 421 msglen = NLMSG_ALIGN(nlh->nlmsg_len); 422 if (msglen > skb->len) 423 msglen = skb->len; 424 skb_pull(skb, msglen); 425 } 426 done: 427 if (status & NFNL_BATCH_REPLAY) { 428 ss->abort(oskb); 429 nfnl_err_reset(&err_list); 430 nfnl_unlock(subsys_id); 431 kfree_skb(skb); 432 goto replay; 433 } else if (status == NFNL_BATCH_DONE) { 434 ss->commit(oskb); 435 } else { 436 ss->abort(oskb); 437 } 438 439 nfnl_err_deliver(&err_list, oskb); 440 nfnl_unlock(subsys_id); 441 kfree_skb(skb); 442 } 443 444 static void nfnetlink_rcv(struct sk_buff *skb) 445 { 446 struct nlmsghdr *nlh = nlmsg_hdr(skb); 447 u_int16_t res_id; 448 int msglen; 449 450 if (nlh->nlmsg_len < NLMSG_HDRLEN || 451 skb->len < nlh->nlmsg_len) 452 return; 453 454 if (!netlink_net_capable(skb, CAP_NET_ADMIN)) { 455 netlink_ack(skb, nlh, -EPERM); 456 return; 457 } 458 459 if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) { 460 struct nfgenmsg *nfgenmsg; 461 462 msglen = NLMSG_ALIGN(nlh->nlmsg_len); 463 if (msglen > skb->len) 464 msglen = skb->len; 465 466 if (nlh->nlmsg_len < NLMSG_HDRLEN || 467 skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg)) 468 return; 469 470 nfgenmsg = nlmsg_data(nlh); 471 skb_pull(skb, msglen); 472 /* Work around old nft using host byte order */ 473 if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES) 474 res_id = NFNL_SUBSYS_NFTABLES; 475 else 476 res_id = ntohs(nfgenmsg->res_id); 477 nfnetlink_rcv_batch(skb, nlh, res_id); 478 } else { 479 netlink_rcv_skb(skb, &nfnetlink_rcv_msg); 480 } 481 } 482 483 #ifdef CONFIG_MODULES 484 static int nfnetlink_bind(struct net *net, int group) 485 { 486 const struct nfnetlink_subsystem *ss; 487 int type; 488 489 if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX) 490 return 0; 491 492 type = nfnl_group2type[group]; 493 494 rcu_read_lock(); 495 ss = nfnetlink_get_subsys(type); 496 rcu_read_unlock(); 497 if (!ss) 498 request_module("nfnetlink-subsys-%d", type); 499 return 0; 500 } 501 #endif 502 503 static int __net_init nfnetlink_net_init(struct net *net) 504 { 505 struct sock *nfnl; 506 struct netlink_kernel_cfg cfg = { 507 .groups = NFNLGRP_MAX, 508 .input = nfnetlink_rcv, 509 #ifdef CONFIG_MODULES 510 .bind = nfnetlink_bind, 511 #endif 512 }; 513 514 nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg); 515 if (!nfnl) 516 return -ENOMEM; 517 net->nfnl_stash = nfnl; 518 rcu_assign_pointer(net->nfnl, nfnl); 519 return 0; 520 } 521 522 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list) 523 { 524 struct net *net; 525 526 list_for_each_entry(net, net_exit_list, exit_list) 527 RCU_INIT_POINTER(net->nfnl, NULL); 528 synchronize_net(); 529 list_for_each_entry(net, net_exit_list, exit_list) 530 netlink_kernel_release(net->nfnl_stash); 531 } 532 533 static struct pernet_operations nfnetlink_net_ops = { 534 .init = nfnetlink_net_init, 535 .exit_batch = nfnetlink_net_exit_batch, 536 }; 537 538 static int __init nfnetlink_init(void) 539 { 540 int i; 541 542 for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++) 543 BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE); 544 545 for (i=0; i<NFNL_SUBSYS_COUNT; i++) 546 mutex_init(&table[i].mutex); 547 548 pr_info("Netfilter messages via NETLINK v%s.\n", nfversion); 549 return register_pernet_subsys(&nfnetlink_net_ops); 550 } 551 552 static void __exit nfnetlink_exit(void) 553 { 554 pr_info("Removing netfilter NETLINK layer.\n"); 555 unregister_pernet_subsys(&nfnetlink_net_ops); 556 } 557 module_init(nfnetlink_init); 558 module_exit(nfnetlink_exit); 559