net/netfilter/nfnetlink.c

   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 int nfnetlink_send(struct sk_buff *skb, struct net *net, u32 portid,
 131                    unsigned int group, int echo, gfp_t flags)
 132 {
 133         return nlmsg_notify(net->nfnl, skb, portid, group, echo, flags);
 134 }
 135 EXPORT_SYMBOL_GPL(nfnetlink_send);
 136
 137 int nfnetlink_set_err(struct net *net, u32 portid, u32 group, int error)
 138 {
 139         return netlink_set_err(net->nfnl, portid, group, error);
 140 }
 141 EXPORT_SYMBOL_GPL(nfnetlink_set_err);
 142
 143 int nfnetlink_unicast(struct sk_buff *skb, struct net *net, u32 portid,
 144                       int flags)
 145 {
 146         return netlink_unicast(net->nfnl, skb, portid, flags);
 147 }
 148 EXPORT_SYMBOL_GPL(nfnetlink_unicast);
 149
 150 /* Process one complete nfnetlink message. */
 151 static int nfnetlink_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
 152 {
 153         struct net *net = sock_net(skb->sk);
 154         const struct nfnl_callback *nc;
 155         const struct nfnetlink_subsystem *ss;
 156         int type, err;
 157
 158         /* All the messages must at least contain nfgenmsg */
 159         if (nlmsg_len(nlh) < sizeof(struct nfgenmsg))
 160                 return 0;
 161
 162         type = nlh->nlmsg_type;
 163 replay:
 164         rcu_read_lock();
 165         ss = nfnetlink_get_subsys(type);
 166         if (!ss) {
 167 #ifdef CONFIG_MODULES
 168                 rcu_read_unlock();
 169                 request_module("nfnetlink-subsys-%d", NFNL_SUBSYS_ID(type));
 170                 rcu_read_lock();
 171                 ss = nfnetlink_get_subsys(type);
 172                 if (!ss)
 173 #endif
 174                 {
 175                         rcu_read_unlock();
 176                         return -EINVAL;
 177                 }
 178         }
 179
 180         nc = nfnetlink_find_client(type, ss);
 181         if (!nc) {
 182                 rcu_read_unlock();
 183                 return -EINVAL;
 184         }
 185
 186         {
 187                 int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 188                 u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 189                 struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 190                 struct nlattr *attr = (void *)nlh + min_len;
 191                 int attrlen = nlh->nlmsg_len - min_len;
 192                 __u8 subsys_id = NFNL_SUBSYS_ID(type);
 193
 194                 err = nla_parse(cda, ss->cb[cb_id].attr_count,
 195                                 attr, attrlen, ss->cb[cb_id].policy);
 196                 if (err < 0) {
 197                         rcu_read_unlock();
 198                         return err;
 199                 }
 200
 201                 if (nc->call_rcu) {
 202                         err = nc->call_rcu(net, net->nfnl, skb, nlh,
 203                                            (const struct nlattr **)cda);
 204                         rcu_read_unlock();
 205                 } else {
 206                         rcu_read_unlock();
 207                         nfnl_lock(subsys_id);
 208                         if (nfnl_dereference_protected(subsys_id) != ss ||
 209                             nfnetlink_find_client(type, ss) != nc)
 210                                 err = -EAGAIN;
 211                         else if (nc->call)
 212                                 err = nc->call(net, net->nfnl, skb, nlh,
 213                                                (const struct nlattr **)cda);
 214                         else
 215                                 err = -EINVAL;
 216                         nfnl_unlock(subsys_id);
 217                 }
 218                 if (err == -EAGAIN)
 219                         goto replay;
 220                 return err;
 221         }
 222 }
 223
 224 struct nfnl_err {
 225         struct list_head        head;
 226         struct nlmsghdr         *nlh;
 227         int                     err;
 228 };
 229
 230 static int nfnl_err_add(struct list_head *list, struct nlmsghdr *nlh, int err)
 231 {
 232         struct nfnl_err *nfnl_err;
 233
 234         nfnl_err = kmalloc(sizeof(struct nfnl_err), GFP_KERNEL);
 235         if (nfnl_err == NULL)
 236                 return -ENOMEM;
 237
 238         nfnl_err->nlh = nlh;
 239         nfnl_err->err = err;
 240         list_add_tail(&nfnl_err->head, list);
 241
 242         return 0;
 243 }
 244
 245 static void nfnl_err_del(struct nfnl_err *nfnl_err)
 246 {
 247         list_del(&nfnl_err->head);
 248         kfree(nfnl_err);
 249 }
 250
 251 static void nfnl_err_reset(struct list_head *err_list)
 252 {
 253         struct nfnl_err *nfnl_err, *next;
 254
 255         list_for_each_entry_safe(nfnl_err, next, err_list, head)
 256                 nfnl_err_del(nfnl_err);
 257 }
 258
 259 static void nfnl_err_deliver(struct list_head *err_list, struct sk_buff *skb)
 260 {
 261         struct nfnl_err *nfnl_err, *next;
 262
 263         list_for_each_entry_safe(nfnl_err, next, err_list, head) {
 264                 netlink_ack(skb, nfnl_err->nlh, nfnl_err->err);
 265                 nfnl_err_del(nfnl_err);
 266         }
 267 }
 268
 269 enum {
 270         NFNL_BATCH_FAILURE      = (1 << 0),
 271         NFNL_BATCH_DONE         = (1 << 1),
 272         NFNL_BATCH_REPLAY       = (1 << 2),
 273 };
 274
 275 static void nfnetlink_rcv_batch(struct sk_buff *skb, struct nlmsghdr *nlh,
 276                                 u_int16_t subsys_id)
 277 {
 278         struct sk_buff *oskb = skb;
 279         struct net *net = sock_net(skb->sk);
 280         const struct nfnetlink_subsystem *ss;
 281         const struct nfnl_callback *nc;
 282         static LIST_HEAD(err_list);
 283         u32 status;
 284         int err;
 285
 286         if (subsys_id >= NFNL_SUBSYS_COUNT)
 287                 return netlink_ack(skb, nlh, -EINVAL);
 288 replay:
 289         status = 0;
 290
 291         skb = netlink_skb_clone(oskb, GFP_KERNEL);
 292         if (!skb)
 293                 return netlink_ack(oskb, nlh, -ENOMEM);
 294
 295         nfnl_lock(subsys_id);
 296         ss = nfnl_dereference_protected(subsys_id);
 297         if (!ss) {
 298 #ifdef CONFIG_MODULES
 299                 nfnl_unlock(subsys_id);
 300                 request_module("nfnetlink-subsys-%d", subsys_id);
 301                 nfnl_lock(subsys_id);
 302                 ss = nfnl_dereference_protected(subsys_id);
 303                 if (!ss)
 304 #endif
 305                 {
 306                         nfnl_unlock(subsys_id);
 307                         netlink_ack(skb, nlh, -EOPNOTSUPP);
 308                         return kfree_skb(skb);
 309                 }
 310         }
 311
 312         if (!ss->commit || !ss->abort) {
 313                 nfnl_unlock(subsys_id);
 314                 netlink_ack(skb, nlh, -EOPNOTSUPP);
 315                 return kfree_skb(skb);
 316         }
 317
 318         while (skb->len >= nlmsg_total_size(0)) {
 319                 int msglen, type;
 320
 321                 nlh = nlmsg_hdr(skb);
 322                 err = 0;
 323
 324                 if (nlmsg_len(nlh) < sizeof(struct nfgenmsg) ||
 325                     skb->len < nlh->nlmsg_len) {
 326                         err = -EINVAL;
 327                         goto ack;
 328                 }
 329
 330                 /* Only requests are handled by the kernel */
 331                 if (!(nlh->nlmsg_flags & NLM_F_REQUEST)) {
 332                         err = -EINVAL;
 333                         goto ack;
 334                 }
 335
 336                 type = nlh->nlmsg_type;
 337                 if (type == NFNL_MSG_BATCH_BEGIN) {
 338                         /* Malformed: Batch begin twice */
 339                         nfnl_err_reset(&err_list);
 340                         status |= NFNL_BATCH_FAILURE;
 341                         goto done;
 342                 } else if (type == NFNL_MSG_BATCH_END) {
 343                         status |= NFNL_BATCH_DONE;
 344                         goto done;
 345                 } else if (type < NLMSG_MIN_TYPE) {
 346                         err = -EINVAL;
 347                         goto ack;
 348                 }
 349
 350                 /* We only accept a batch with messages for the same
 351                  * subsystem.
 352                  */
 353                 if (NFNL_SUBSYS_ID(type) != subsys_id) {
 354                         err = -EINVAL;
 355                         goto ack;
 356                 }
 357
 358                 nc = nfnetlink_find_client(type, ss);
 359                 if (!nc) {
 360                         err = -EINVAL;
 361                         goto ack;
 362                 }
 363
 364                 {
 365                         int min_len = nlmsg_total_size(sizeof(struct nfgenmsg));
 366                         u_int8_t cb_id = NFNL_MSG_TYPE(nlh->nlmsg_type);
 367                         struct nlattr *cda[ss->cb[cb_id].attr_count + 1];
 368                         struct nlattr *attr = (void *)nlh + min_len;
 369                         int attrlen = nlh->nlmsg_len - min_len;
 370
 371                         err = nla_parse(cda, ss->cb[cb_id].attr_count,
 372                                         attr, attrlen, ss->cb[cb_id].policy);
 373                         if (err < 0)
 374                                 goto ack;
 375
 376                         if (nc->call_batch) {
 377                                 err = nc->call_batch(net, net->nfnl, skb, nlh,
 378                                                      (const struct nlattr **)cda);
 379                         }
 380
 381                         /* The lock was released to autoload some module, we
 382                          * have to abort and start from scratch using the
 383                          * original skb.
 384                          */
 385                         if (err == -EAGAIN) {
 386                                 status |= NFNL_BATCH_REPLAY;
 387                                 goto next;
 388                         }
 389                 }
 390 ack:
 391                 if (nlh->nlmsg_flags & NLM_F_ACK || err) {
 392                         /* Errors are delivered once the full batch has been
 393                          * processed, this avoids that the same error is
 394                          * reported several times when replaying the batch.
 395                          */
 396                         if (nfnl_err_add(&err_list, nlh, err) < 0) {
 397                                 /* We failed to enqueue an error, reset the
 398                                  * list of errors and send OOM to userspace
 399                                  * pointing to the batch header.
 400                                  */
 401                                 nfnl_err_reset(&err_list);
 402                                 netlink_ack(skb, nlmsg_hdr(oskb), -ENOMEM);
 403                                 status |= NFNL_BATCH_FAILURE;
 404                                 goto done;
 405                         }
 406                         /* We don't stop processing the batch on errors, thus,
 407                          * userspace gets all the errors that the batch
 408                          * triggers.
 409                          */
 410                         if (err)
 411                                 status |= NFNL_BATCH_FAILURE;
 412                 }
 413 next:
 414                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 415                 if (msglen > skb->len)
 416                         msglen = skb->len;
 417                 skb_pull(skb, msglen);
 418         }
 419 done:
 420         if (status & NFNL_BATCH_REPLAY) {
 421                 ss->abort(net, oskb);
 422                 nfnl_err_reset(&err_list);
 423                 nfnl_unlock(subsys_id);
 424                 kfree_skb(skb);
 425                 goto replay;
 426         } else if (status == NFNL_BATCH_DONE) {
 427                 ss->commit(net, oskb);
 428         } else {
 429                 ss->abort(net, oskb);
 430         }
 431
 432         nfnl_err_deliver(&err_list, oskb);
 433         nfnl_unlock(subsys_id);
 434         kfree_skb(skb);
 435 }
 436
 437 static void nfnetlink_rcv(struct sk_buff *skb)
 438 {
 439         struct nlmsghdr *nlh = nlmsg_hdr(skb);
 440         u_int16_t res_id;
 441         int msglen;
 442
 443         if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 444             skb->len < nlh->nlmsg_len)
 445                 return;
 446
 447         if (!netlink_net_capable(skb, CAP_NET_ADMIN)) {
 448                 netlink_ack(skb, nlh, -EPERM);
 449                 return;
 450         }
 451
 452         if (nlh->nlmsg_type == NFNL_MSG_BATCH_BEGIN) {
 453                 struct nfgenmsg *nfgenmsg;
 454
 455                 msglen = NLMSG_ALIGN(nlh->nlmsg_len);
 456                 if (msglen > skb->len)
 457                         msglen = skb->len;
 458
 459                 if (nlh->nlmsg_len < NLMSG_HDRLEN ||
 460                     skb->len < NLMSG_HDRLEN + sizeof(struct nfgenmsg))
 461                         return;
 462
 463                 nfgenmsg = nlmsg_data(nlh);
 464                 skb_pull(skb, msglen);
 465                 /* Work around old nft using host byte order */
 466                 if (nfgenmsg->res_id == NFNL_SUBSYS_NFTABLES)
 467                         res_id = NFNL_SUBSYS_NFTABLES;
 468                 else
 469                         res_id = ntohs(nfgenmsg->res_id);
 470                 nfnetlink_rcv_batch(skb, nlh, res_id);
 471         } else {
 472                 netlink_rcv_skb(skb, &nfnetlink_rcv_msg);
 473         }
 474 }
 475
 476 #ifdef CONFIG_MODULES
 477 static int nfnetlink_bind(struct net *net, int group)
 478 {
 479         const struct nfnetlink_subsystem *ss;
 480         int type;
 481
 482         if (group <= NFNLGRP_NONE || group > NFNLGRP_MAX)
 483                 return 0;
 484
 485         type = nfnl_group2type[group];
 486
 487         rcu_read_lock();
 488         ss = nfnetlink_get_subsys(type << 8);
 489         rcu_read_unlock();
 490         if (!ss)
 491                 request_module("nfnetlink-subsys-%d", type);
 492         return 0;
 493 }
 494 #endif
 495
 496 static int __net_init nfnetlink_net_init(struct net *net)
 497 {
 498         struct sock *nfnl;
 499         struct netlink_kernel_cfg cfg = {
 500                 .groups = NFNLGRP_MAX,
 501                 .input  = nfnetlink_rcv,
 502 #ifdef CONFIG_MODULES
 503                 .bind   = nfnetlink_bind,
 504 #endif
 505         };
 506
 507         nfnl = netlink_kernel_create(net, NETLINK_NETFILTER, &cfg);
 508         if (!nfnl)
 509                 return -ENOMEM;
 510         net->nfnl_stash = nfnl;
 511         rcu_assign_pointer(net->nfnl, nfnl);
 512         return 0;
 513 }
 514
 515 static void __net_exit nfnetlink_net_exit_batch(struct list_head *net_exit_list)
 516 {
 517         struct net *net;
 518
 519         list_for_each_entry(net, net_exit_list, exit_list)
 520                 RCU_INIT_POINTER(net->nfnl, NULL);
 521         synchronize_net();
 522         list_for_each_entry(net, net_exit_list, exit_list)
 523                 netlink_kernel_release(net->nfnl_stash);
 524 }
 525
 526 static struct pernet_operations nfnetlink_net_ops = {
 527         .init           = nfnetlink_net_init,
 528         .exit_batch     = nfnetlink_net_exit_batch,
 529 };
 530
 531 static int __init nfnetlink_init(void)
 532 {
 533         int i;
 534
 535         for (i = NFNLGRP_NONE + 1; i <= NFNLGRP_MAX; i++)
 536                 BUG_ON(nfnl_group2type[i] == NFNL_SUBSYS_NONE);
 537
 538         for (i=0; i<NFNL_SUBSYS_COUNT; i++)
 539                 mutex_init(&table[i].mutex);
 540
 541         pr_info("Netfilter messages via NETLINK v%s.\n", nfversion);
 542         return register_pernet_subsys(&nfnetlink_net_ops);
 543 }
 544
 545 static void __exit nfnetlink_exit(void)
 546 {
 547         pr_info("Removing netfilter NETLINK layer.\n");
 548         unregister_pernet_subsys(&nfnetlink_net_ops);
 549 }
 550 module_init(nfnetlink_init);
 551 module_exit(nfnetlink_exit);