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 #define nfnl_dereference_protected(id) \ 37 rcu_dereference_protected(table[(id)].subsys, \ 38 lockdep_nfnl_is_held((id))) 39 40 static char __initdata nfversion[] = "0.30"; 41 42 static struct { 43 struct mutex mutex; 44 const struct nfnetlink_subsystem __rcu *subsys; 45 } table[NFNL_SUBSYS_COUNT]; 46 47 static const int nfnl_group2type[NFNLGRP_MAX+1] = { 48 [NFNLGRP_CONNTRACK_NEW] = NFNL_SUBSYS_CTNETLINK, 49 [NFNLGRP_CONNTRACK_UPDATE] = NFNL_SUBSYS_CTNETLINK, 50 [NFNLGRP_CONNTRACK_DESTROY] = NFNL_SUBSYS_CTNETLINK, 51 [NFNLGRP_CONNTRACK_EXP_NEW] = NFNL_SUBSYS_CTNETLINK_EXP, 52 [NFNLGRP_CONNTRACK_EXP_UPDATE] = NFNL_SUBSYS_CTNETLINK_EXP, 53 [NFNLGRP_CONNTRACK_EXP_DESTROY] = NFNL_SUBSYS_CTNETLINK_EXP, 54 [NFNLGRP_NFTABLES] = NFNL_SUBSYS_NFTABLES, 55 [NFNLGRP_ACCT_QUOTA] = NFNL_SUBSYS_ACCT, 56 [NFNLGRP_NFTRACE] = NFNL_SUBSYS_NFTABLES, 57 }; 58 59 void nfnl_lock(__u8 subsys_id) 60 { 61 mutex_lock(&table[subsys_id].mutex); 62 } 63 EXPORT_SYMBOL_GPL(nfnl_lock); 64 65 void nfnl_unlock(__u8 subsys_id) 66 { 67 mutex_unlock(&table[subsys_id].mutex); 68 } 69 EXPORT_SYMBOL_GPL(nfnl_unlock); 70 71 #ifdef CONFIG_PROVE_LOCKING 72 bool lockdep_nfnl_is_held(u8 subsys_id) 73 { 74 return lockdep_is_held(&table[subsys_id].mutex); 75 } 76 EXPORT_SYMBOL_GPL(lockdep_nfnl_is_held); 77 #endif 78 79 int nfnetlink_subsys_register(const struct nfnetlink_subsystem *n) 80 { 81 nfnl_lock(n->subsys_id); 82 if (table[n->subsys_id].subsys) { 83 nfnl_unlock(n->subsys_id); 84 return -EBUSY; 85 } 86 rcu_assign_pointer(table[n->subsys_id].subsys, n); 87 nfnl_unlock(n->subsys_id); 88 89 return 0; 90 } 91 EXPORT_SYMBOL_GPL(nfnetlink_subsys_register); 92 93 int nfnetlink_subsys_unregister(const struct nfnetlink_subsystem *n) 94 { 95 nfnl_lock(n->subsys_id); 96 table[n->subsys_id].subsys = NULL; 97 nfnl_unlock(n->subsys_id); 98 synchronize_rcu(); 99 return 0; 100 } 101 EXPORT_SYMBOL_GPL(nfnetlink_subsys_unregister); 102 103 static inline const struct nfnetlink_subsystem *nfnetlink_get_subsys(u_int16_t type) 104 { 105 u_int8_t subsys_id = NFNL_SUBSYS_ID(type); 106 107 if (subsys_id >= NFNL_SUBSYS_COUNT) 108 return NULL; 109 110 return rcu_dereference(table[subsys_id].subsys); 111 } 112 113 static inline const struct nfnl_callback * 114 nfnetlink_find_client(u_int16_t type, const struct nfnetlink_subsystem *ss) 115 { 116 u_int8_t cb_id = NFNL_MSG_TYPE(type); 117 118 if (cb_id >= ss->cb_count) 119 return NULL; 120 121 return &ss->cb[cb_id]; 122 } 123 124 int nfnetlink_has_listeners(struct net *net, unsigned int group) 125 { 126 return netlink_has_listeners(net->nfnl, group); 127 } 128 EXPORT_SYMBOL_GPL(nfnetlink_has_listeners); 129 130 struct sk_buff *nfnetlink_alloc_skb(struct net *net, unsigned int size, 131 u32 dst_portid, gfp_t gfp_mask) 132 { 133 return netlink_alloc_skb(net->nfnl, size, dst_portid, gfp_mask); 134 } 135 EXPORT_SYMBOL_GPL(nfnetlink_alloc_skb); 136 137 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid, 138 unsigned int group, int echo, gfp_t flags) 139 { 140 return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags); 141 } 142 EXPORT_SYMBOL_GPL(nfnetlink_send); 143 144 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error) 145 { 146 return netlink_set_err(net->nfnl, portid, group, error); 147 } 148 EXPORT_SYMBOL_GPL(nfnetlink_set_err); 149 150 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid, 151 int flags) 152 { 153 return netlink_unicast(net->nfnl, skb, portid, flags); 154 } 155 EXPORT_SYMBOL_GPL(nfnetlink_unicast); 156 157 /* Process one complete nfnetlink message. */ 158 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh) 159 { 160 struct net *net = sock_net(skb->sk); 161 const struct nfnl_callback *nc; 162 const struct nfnetlink_subsystem *ss; 163 int type, err; 164 165 /* All the messages must at least contain nfgenmsg */ 166 if (nlmsg_len(nlh) < sizeof(struct nfgenmsg)) 167 return 0; 168 169 type = nlh->nlmsg_type; 170 replay: 171 rcu_read_lock(); 172 ss = nfnetlink_get_subsys(type); 173 if (!ss) { 174 #ifdef CONFIG_MODULES 175 rcu_read_unlock(); 176 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type)); 177 rcu_read_lock(); 178 ss = nfnetlink_get_subsys(type); 179 if (!ss) 180 #endif 181 { 182 rcu_read_unlock(); 183 return -EINVAL; 184 } 185 } 186 187 nc = nfnetlink_find_client(type, ss); 188 if (!nc) { 189 rcu_read_unlock(); 190 return -EINVAL; 191 } 192 193 { 194 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg)); 195 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type); 196 struct nlattr *cda[ss->cb[cb_id].attr_count + 1]; 197 struct nlattr *attr = (void *)nlh + min_len; 198 int attrlen = nlh->nlmsg_len - min_len; 199 __u8 subsys_id = NFNL_SUBSYS_ID(type); 200 201 err = nla_parse(cda, ss->cb[cb_id].attr_count, 202 attr, attrlen, ss->cb[cb_id].policy); 203 if (err < 0) { 204 rcu_read_unlock(); 205 return err; 206 } 207 208 if (nc->call_rcu) { 209 err = nc->call_rcu(net, net->nfnl, skb, nlh, 210 (const struct nlattr **)cda); 211 rcu_read_unlock(); 212 } else { 213 rcu_read_unlock(); 214 nfnl_lock(subsys_id); 215 if (nfnl_dereference_protected(subsys_id) != ss || 216 nfnetlink_find_client(type, ss) != nc) 217 err = -EAGAIN; 218 else if (nc->call) 219 err = nc->call(net, net->nfnl, skb, nlh, 220 (const struct nlattr **)cda); 221 else 222 err = -EINVAL; 223 nfnl_unlock(subsys_id); 224 } 225 if (err == -EAGAIN) 226 goto replay; 227 return err; 228 } 229 } 230 231 struct nfnl_err { 232 struct list_head head; 233 struct nlmsghdr *nlh; 234 int err; 235 }; 236 237 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err) 238 { 239 struct nfnl_err *nfnl_err; 240 241 nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL); 242 if (nfnl_err == NULL) 243 return -ENOMEM; 244 245 nfnl_err->nlh = nlh; 246 nfnl_err->err = err; 247 list_add_tail(&nfnl_err->head, list); 248 249 return 0; 250 } 251 252 static void nfnl_err_del(struct nfnl_err *nfnl_err) 253 { 254 list_del(&nfnl_err->head); 255 kfree(nfnl_err); 256 } 257 258 static void nfnl_err_reset(struct list_head *err_list) 259 { 260 struct nfnl_err *nfnl_err, *next; 261 262 list_for_each_entry_safe(nfnl_err, next, err_list, head) 263 nfnl_err_del(nfnl_err); 264 } 265 266 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb) 267 { 268 struct nfnl_err *nfnl_err, *next; 269 270 list_for_each_entry_safe(nfnl_err, next, err_list, head) { 271 netlink_ack(skb, nfnl_err->nlh, nfnl_err->err); 272 nfnl_err_del(nfnl_err); 273 } 274 } 275 276 enum { 277 NFNL_BATCH_FAILURE = (1 << 0), 278 NFNL_BATCH_DONE = (1 << 1), 279 NFNL_BATCH_REPLAY = (1 << 2), 280 }; 281 282 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh, 283 u_int16_t subsys_id) 284 { 285 struct sk_buff *oskb = skb; 286 struct net *net = sock_net(skb->sk); 287 const struct nfnetlink_subsystem *ss; 288 const struct nfnl_callback *nc; 289 static LIST_HEAD(err_list); 290 u32 status; 291 int err; 292 293 if (subsys_id >= NFNL_SUBSYS_COUNT) 294 return netlink_ack(skb, nlh, -EINVAL); 295 replay: 296 status = 0; 297 298 skb = netlink_skb_clone(oskb, GFP_KERNEL); 299 if (!skb) 300 return netlink_ack(oskb, nlh, -ENOMEM); 301 302 nfnl_lock(subsys_id); 303 ss = nfnl_dereference_protected(subsys_id); 304 if (!ss) { 305 #ifdef CONFIG_MODULES 306 nfnl_unlock(subsys_id); 307 request_module("nfnetlink-subsys-%d", subsys_id); 308 nfnl_lock(subsys_id); 309 ss = nfnl_dereference_protected(subsys_id); 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, 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(net, 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(net, oskb); 435 } else { 436 ss->abort(net, 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 << 8); 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