net/netfilter/core.c

   1 /* netfilter.c: look after the filters for various protocols.
   2  * Heavily influenced by the old firewall.c by David Bonn and Alan Cox.
   3  *
   4  * Thanks to Rob `CmdrTaco' Malda for not influencing this code in any
   5  * way.
   6  *
   7  * This code is GPL.
   8  */
   9 #include <linux/kernel.h>
  10 #include <linux/netfilter.h>
  11 #include <net/protocol.h>
  12 #include <linux/init.h>
  13 #include <linux/skbuff.h>
  14 #include <linux/wait.h>
  15 #include <linux/module.h>
  16 #include <linux/interrupt.h>
  17 #include <linux/if.h>
  18 #include <linux/netdevice.h>
  19 #include <linux/netfilter_ipv6.h>
  20 #include <linux/inetdevice.h>
  21 #include <linux/proc_fs.h>
  22 #include <linux/mutex.h>
  23 #include <linux/mm.h>
  24 #include <linux/rcupdate.h>
  25 #include <net/net_namespace.h>
  26 #include <net/sock.h>
  27
  28 #include "nf_internals.h"
  29
  30 const struct nf_ipv6_ops __rcu *nf_ipv6_ops __read_mostly;
  31 EXPORT_SYMBOL_GPL(nf_ipv6_ops);
  32
  33 DEFINE_PER_CPU(bool, nf_skb_duplicated);
  34 EXPORT_SYMBOL_GPL(nf_skb_duplicated);
  35
  36 #ifdef HAVE_JUMP_LABEL
  37 struct static_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
  38 EXPORT_SYMBOL(nf_hooks_needed);
  39 #endif
  40
  41 static DEFINE_MUTEX(nf_hook_mutex);
  42
  43 /* max hooks per family/hooknum */
  44 #define MAX_HOOK_COUNT          1024
  45
  46 #define nf_entry_dereference(e) \
  47         rcu_dereference_protected(e, lockdep_is_held(&nf_hook_mutex))
  48
  49 static struct nf_hook_entries *allocate_hook_entries_size(u16 num)
  50 {
  51         struct nf_hook_entries *e;
  52         size_t alloc = sizeof(*e) +
  53                        sizeof(struct nf_hook_entry) * num +
  54                        sizeof(struct nf_hook_ops *) * num +
  55                        sizeof(struct nf_hook_entries_rcu_head);
  56
  57         if (num == 0)
  58                 return NULL;
  59
  60         e = kvzalloc(alloc, GFP_KERNEL);
  61         if (e)
  62                 e->num_hook_entries = num;
  63         return e;
  64 }
  65
  66 static void __nf_hook_entries_free(struct rcu_head *h)
  67 {
  68         struct nf_hook_entries_rcu_head *head;
  69
  70         head = container_of(h, struct nf_hook_entries_rcu_head, head);
  71         kvfree(head->allocation);
  72 }
  73
  74 static void nf_hook_entries_free(struct nf_hook_entries *e)
  75 {
  76         struct nf_hook_entries_rcu_head *head;
  77         struct nf_hook_ops **ops;
  78         unsigned int num;
  79
  80         if (!e)
  81                 return;
  82
  83         num = e->num_hook_entries;
  84         ops = nf_hook_entries_get_hook_ops(e);
  85         head = (void *)&ops[num];
  86         head->allocation = e;
  87         call_rcu(&head->head, __nf_hook_entries_free);
  88 }
  89
  90 static unsigned int accept_all(void *priv,
  91                                struct sk_buff *skb,
  92                                const struct nf_hook_state *state)
  93 {
  94         return NF_ACCEPT; /* ACCEPT makes nf_hook_slow call next hook */
  95 }
  96
  97 static const struct nf_hook_ops dummy_ops = {
  98         .hook = accept_all,
  99         .priority = INT_MIN,
 100 };
 101
 102 static struct nf_hook_entries *
 103 nf_hook_entries_grow(const struct nf_hook_entries *old,
 104                      const struct nf_hook_ops *reg)
 105 {
 106         unsigned int i, alloc_entries, nhooks, old_entries;
 107         struct nf_hook_ops **orig_ops = NULL;
 108         struct nf_hook_ops **new_ops;
 109         struct nf_hook_entries *new;
 110         bool inserted = false;
 111
 112         alloc_entries = 1;
 113         old_entries = old ? old->num_hook_entries : 0;
 114
 115         if (old) {
 116                 orig_ops = nf_hook_entries_get_hook_ops(old);
 117
 118                 for (i = 0; i < old_entries; i++) {
 119                         if (orig_ops[i] != &dummy_ops)
 120                                 alloc_entries++;
 121                 }
 122         }
 123
 124         if (alloc_entries > MAX_HOOK_COUNT)
 125                 return ERR_PTR(-E2BIG);
 126
 127         new = allocate_hook_entries_size(alloc_entries);
 128         if (!new)
 129                 return ERR_PTR(-ENOMEM);
 130
 131         new_ops = nf_hook_entries_get_hook_ops(new);
 132
 133         i = 0;
 134         nhooks = 0;
 135         while (i < old_entries) {
 136                 if (orig_ops[i] == &dummy_ops) {
 137                         ++i;
 138                         continue;
 139                 }
 140
 141                 if (reg->nat_hook && orig_ops[i]->nat_hook) {
 142                         kvfree(new);
 143                         return ERR_PTR(-EBUSY);
 144                 }
 145
 146                 if (inserted || reg->priority > orig_ops[i]->priority) {
 147                         new_ops[nhooks] = (void *)orig_ops[i];
 148                         new->hooks[nhooks] = old->hooks[i];
 149                         i++;
 150                 } else {
 151                         new_ops[nhooks] = (void *)reg;
 152                         new->hooks[nhooks].hook = reg->hook;
 153                         new->hooks[nhooks].priv = reg->priv;
 154                         inserted = true;
 155                 }
 156                 nhooks++;
 157         }
 158
 159         if (!inserted) {
 160                 new_ops[nhooks] = (void *)reg;
 161                 new->hooks[nhooks].hook = reg->hook;
 162                 new->hooks[nhooks].priv = reg->priv;
 163         }
 164
 165         return new;
 166 }
 167
 168 static void hooks_validate(const struct nf_hook_entries *hooks)
 169 {
 170 #ifdef CONFIG_DEBUG_KERNEL
 171         struct nf_hook_ops **orig_ops;
 172         int prio = INT_MIN;
 173         size_t i = 0;
 174
 175         orig_ops = nf_hook_entries_get_hook_ops(hooks);
 176
 177         for (i = 0; i < hooks->num_hook_entries; i++) {
 178                 if (orig_ops[i] == &dummy_ops)
 179                         continue;
 180
 181                 WARN_ON(orig_ops[i]->priority < prio);
 182
 183                 if (orig_ops[i]->priority > prio)
 184                         prio = orig_ops[i]->priority;
 185         }
 186 #endif
 187 }
 188
 189 /*
 190  * __nf_hook_entries_try_shrink - try to shrink hook array
 191  *
 192  * @pp -- location of hook blob
 193  *
 194  * Hook unregistration must always succeed, so to-be-removed hooks
 195  * are replaced by a dummy one that will just move to next hook.
 196  *
 197  * This counts the current dummy hooks, attempts to allocate new blob,
 198  * copies the live hooks, then replaces and discards old one.
 199  *
 200  * return values:
 201  *
 202  * Returns address to free, or NULL.
 203  */
 204 static void *__nf_hook_entries_try_shrink(struct nf_hook_entries __rcu **pp)
 205 {
 206         struct nf_hook_entries *old, *new = NULL;
 207         unsigned int i, j, skip = 0, hook_entries;
 208         struct nf_hook_ops **orig_ops;
 209         struct nf_hook_ops **new_ops;
 210
 211         old = nf_entry_dereference(*pp);
 212         if (WARN_ON_ONCE(!old))
 213                 return NULL;
 214
 215         orig_ops = nf_hook_entries_get_hook_ops(old);
 216         for (i = 0; i < old->num_hook_entries; i++) {
 217                 if (orig_ops[i] == &dummy_ops)
 218                         skip++;
 219         }
 220
 221         /* if skip == hook_entries all hooks have been removed */
 222         hook_entries = old->num_hook_entries;
 223         if (skip == hook_entries)
 224                 goto out_assign;
 225
 226         if (skip == 0)
 227                 return NULL;
 228
 229         hook_entries -= skip;
 230         new = allocate_hook_entries_size(hook_entries);
 231         if (!new)
 232                 return NULL;
 233
 234         new_ops = nf_hook_entries_get_hook_ops(new);
 235         for (i = 0, j = 0; i < old->num_hook_entries; i++) {
 236                 if (orig_ops[i] == &dummy_ops)
 237                         continue;
 238                 new->hooks[j] = old->hooks[i];
 239                 new_ops[j] = (void *)orig_ops[i];
 240                 j++;
 241         }
 242         hooks_validate(new);
 243 out_assign:
 244         rcu_assign_pointer(*pp, new);
 245         return old;
 246 }
 247
 248 static struct nf_hook_entries __rcu **
 249 nf_hook_entry_head(struct net *net, int pf, unsigned int hooknum,
 250                    struct net_device *dev)
 251 {
 252         switch (pf) {
 253         case NFPROTO_NETDEV:
 254                 break;
 255 #ifdef CONFIG_NETFILTER_FAMILY_ARP
 256         case NFPROTO_ARP:
 257                 if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_arp) <= hooknum))
 258                         return NULL;
 259                 return net->nf.hooks_arp + hooknum;
 260 #endif
 261 #ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
 262         case NFPROTO_BRIDGE:
 263                 if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_bridge) <= hooknum))
 264                         return NULL;
 265                 return net->nf.hooks_bridge + hooknum;
 266 #endif
 267         case NFPROTO_IPV4:
 268                 if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_ipv4) <= hooknum))
 269                         return NULL;
 270                 return net->nf.hooks_ipv4 + hooknum;
 271         case NFPROTO_IPV6:
 272                 if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_ipv6) <= hooknum))
 273                         return NULL;
 274                 return net->nf.hooks_ipv6 + hooknum;
 275 #if IS_ENABLED(CONFIG_DECNET)
 276         case NFPROTO_DECNET:
 277                 if (WARN_ON_ONCE(ARRAY_SIZE(net->nf.hooks_decnet) <= hooknum))
 278                         return NULL;
 279                 return net->nf.hooks_decnet + hooknum;
 280 #endif
 281         default:
 282                 WARN_ON_ONCE(1);
 283                 return NULL;
 284         }
 285
 286 #ifdef CONFIG_NETFILTER_INGRESS
 287         if (hooknum == NF_NETDEV_INGRESS) {
 288                 if (dev && dev_net(dev) == net)
 289                         return &dev->nf_hooks_ingress;
 290         }
 291 #endif
 292         WARN_ON_ONCE(1);
 293         return NULL;
 294 }
 295
 296 static int __nf_register_net_hook(struct net *net, int pf,
 297                                   const struct nf_hook_ops *reg)
 298 {
 299         struct nf_hook_entries *p, *new_hooks;
 300         struct nf_hook_entries __rcu **pp;
 301
 302         if (pf == NFPROTO_NETDEV) {
 303 #ifndef CONFIG_NETFILTER_INGRESS
 304                 if (reg->hooknum == NF_NETDEV_INGRESS)
 305                         return -EOPNOTSUPP;
 306 #endif
 307                 if (reg->hooknum != NF_NETDEV_INGRESS ||
 308                     !reg->dev || dev_net(reg->dev) != net)
 309                         return -EINVAL;
 310         }
 311
 312         pp = nf_hook_entry_head(net, pf, reg->hooknum, reg->dev);
 313         if (!pp)
 314                 return -EINVAL;
 315
 316         mutex_lock(&nf_hook_mutex);
 317
 318         p = nf_entry_dereference(*pp);
 319         new_hooks = nf_hook_entries_grow(p, reg);
 320
 321         if (!IS_ERR(new_hooks))
 322                 rcu_assign_pointer(*pp, new_hooks);
 323
 324         mutex_unlock(&nf_hook_mutex);
 325         if (IS_ERR(new_hooks))
 326                 return PTR_ERR(new_hooks);
 327
 328         hooks_validate(new_hooks);
 329 #ifdef CONFIG_NETFILTER_INGRESS
 330         if (pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_INGRESS)
 331                 net_inc_ingress_queue();
 332 #endif
 333 #ifdef HAVE_JUMP_LABEL
 334         static_key_slow_inc(&nf_hooks_needed[pf][reg->hooknum]);
 335 #endif
 336         BUG_ON(p == new_hooks);
 337         nf_hook_entries_free(p);
 338         return 0;
 339 }
 340
 341 /*
 342  * nf_remove_net_hook - remove a hook from blob
 343  *
 344  * @oldp: current address of hook blob
 345  * @unreg: hook to unregister
 346  *
 347  * This cannot fail, hook unregistration must always succeed.
 348  * Therefore replace the to-be-removed hook with a dummy hook.
 349  */
 350 static void nf_remove_net_hook(struct nf_hook_entries *old,
 351                                const struct nf_hook_ops *unreg, int pf)
 352 {
 353         struct nf_hook_ops **orig_ops;
 354         bool found = false;
 355         unsigned int i;
 356
 357         orig_ops = nf_hook_entries_get_hook_ops(old);
 358         for (i = 0; i < old->num_hook_entries; i++) {
 359                 if (orig_ops[i] != unreg)
 360                         continue;
 361                 WRITE_ONCE(old->hooks[i].hook, accept_all);
 362                 WRITE_ONCE(orig_ops[i], &dummy_ops);
 363                 found = true;
 364                 break;
 365         }
 366
 367         if (found) {
 368 #ifdef CONFIG_NETFILTER_INGRESS
 369                 if (pf == NFPROTO_NETDEV && unreg->hooknum == NF_NETDEV_INGRESS)
 370                         net_dec_ingress_queue();
 371 #endif
 372 #ifdef HAVE_JUMP_LABEL
 373                 static_key_slow_dec(&nf_hooks_needed[pf][unreg->hooknum]);
 374 #endif
 375         } else {
 376                 WARN_ONCE(1, "hook not found, pf %d num %d", pf, unreg->hooknum);
 377         }
 378 }
 379
 380 static void __nf_unregister_net_hook(struct net *net, int pf,
 381                                      const struct nf_hook_ops *reg)
 382 {
 383         struct nf_hook_entries __rcu **pp;
 384         struct nf_hook_entries *p;
 385
 386         pp = nf_hook_entry_head(net, pf, reg->hooknum, reg->dev);
 387         if (!pp)
 388                 return;
 389
 390         mutex_lock(&nf_hook_mutex);
 391
 392         p = nf_entry_dereference(*pp);
 393         if (WARN_ON_ONCE(!p)) {
 394                 mutex_unlock(&nf_hook_mutex);
 395                 return;
 396         }
 397
 398         nf_remove_net_hook(p, reg, pf);
 399
 400         p = __nf_hook_entries_try_shrink(pp);
 401         mutex_unlock(&nf_hook_mutex);
 402         if (!p)
 403                 return;
 404
 405         nf_queue_nf_hook_drop(net);
 406         nf_hook_entries_free(p);
 407 }
 408
 409 void nf_unregister_net_hook(struct net *net, const struct nf_hook_ops *reg)
 410 {
 411         if (reg->pf == NFPROTO_INET) {
 412                 __nf_unregister_net_hook(net, NFPROTO_IPV4, reg);
 413                 __nf_unregister_net_hook(net, NFPROTO_IPV6, reg);
 414         } else {
 415                 __nf_unregister_net_hook(net, reg->pf, reg);
 416         }
 417 }
 418 EXPORT_SYMBOL(nf_unregister_net_hook);
 419
 420 int nf_register_net_hook(struct net *net, const struct nf_hook_ops *reg)
 421 {
 422         int err;
 423
 424         if (reg->pf == NFPROTO_INET) {
 425                 err = __nf_register_net_hook(net, NFPROTO_IPV4, reg);
 426                 if (err < 0)
 427                         return err;
 428
 429                 err = __nf_register_net_hook(net, NFPROTO_IPV6, reg);
 430                 if (err < 0) {
 431                         __nf_unregister_net_hook(net, NFPROTO_IPV4, reg);
 432                         return err;
 433                 }
 434         } else {
 435                 err = __nf_register_net_hook(net, reg->pf, reg);
 436                 if (err < 0)
 437                         return err;
 438         }
 439
 440         return 0;
 441 }
 442 EXPORT_SYMBOL(nf_register_net_hook);
 443
 444 int nf_register_net_hooks(struct net *net, const struct nf_hook_ops *reg,
 445                           unsigned int n)
 446 {
 447         unsigned int i;
 448         int err = 0;
 449
 450         for (i = 0; i < n; i++) {
 451                 err = nf_register_net_hook(net, &reg[i]);
 452                 if (err)
 453                         goto err;
 454         }
 455         return err;
 456
 457 err:
 458         if (i > 0)
 459                 nf_unregister_net_hooks(net, reg, i);
 460         return err;
 461 }
 462 EXPORT_SYMBOL(nf_register_net_hooks);
 463
 464 void nf_unregister_net_hooks(struct net *net, const struct nf_hook_ops *reg,
 465                              unsigned int hookcount)
 466 {
 467         unsigned int i;
 468
 469         for (i = 0; i < hookcount; i++)
 470                 nf_unregister_net_hook(net, &reg[i]);
 471 }
 472 EXPORT_SYMBOL(nf_unregister_net_hooks);
 473
 474 /* Returns 1 if okfn() needs to be executed by the caller,
 475  * -EPERM for NF_DROP, 0 otherwise.  Caller must hold rcu_read_lock. */
 476 int nf_hook_slow(struct sk_buff *skb, struct nf_hook_state *state,
 477                  const struct nf_hook_entries *e, unsigned int s)
 478 {
 479         unsigned int verdict;
 480         int ret;
 481
 482         for (; s < e->num_hook_entries; s++) {
 483                 verdict = nf_hook_entry_hookfn(&e->hooks[s], skb, state);
 484                 switch (verdict & NF_VERDICT_MASK) {
 485                 case NF_ACCEPT:
 486                         break;
 487                 case NF_DROP:
 488                         kfree_skb(skb);
 489                         ret = NF_DROP_GETERR(verdict);
 490                         if (ret == 0)
 491                                 ret = -EPERM;
 492                         return ret;
 493                 case NF_QUEUE:
 494                         ret = nf_queue(skb, state, e, s, verdict);
 495                         if (ret == 1)
 496                                 continue;
 497                         return ret;
 498                 default:
 499                         /* Implicit handling for NF_STOLEN, as well as any other
 500                          * non conventional verdicts.
 501                          */
 502                         return 0;
 503                 }
 504         }
 505
 506         return 1;
 507 }
 508 EXPORT_SYMBOL(nf_hook_slow);
 509
 510
 511 int skb_make_writable(struct sk_buff *skb, unsigned int writable_len)
 512 {
 513         if (writable_len > skb->len)
 514                 return 0;
 515
 516         /* Not exclusive use of packet?  Must copy. */
 517         if (!skb_cloned(skb)) {
 518                 if (writable_len <= skb_headlen(skb))
 519                         return 1;
 520         } else if (skb_clone_writable(skb, writable_len))
 521                 return 1;
 522
 523         if (writable_len <= skb_headlen(skb))
 524                 writable_len = 0;
 525         else
 526                 writable_len -= skb_headlen(skb);
 527
 528         return !!__pskb_pull_tail(skb, writable_len);
 529 }
 530 EXPORT_SYMBOL(skb_make_writable);
 531
 532 /* This needs to be compiled in any case to avoid dependencies between the
 533  * nfnetlink_queue code and nf_conntrack.
 534  */
 535 struct nfnl_ct_hook __rcu *nfnl_ct_hook __read_mostly;
 536 EXPORT_SYMBOL_GPL(nfnl_ct_hook);
 537
 538 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 539 /* This does not belong here, but locally generated errors need it if connection
 540    tracking in use: without this, connection may not be in hash table, and hence
 541    manufactured ICMP or RST packets will not be associated with it. */
 542 void (*ip_ct_attach)(struct sk_buff *, const struct sk_buff *)
 543                 __rcu __read_mostly;
 544 EXPORT_SYMBOL(ip_ct_attach);
 545
 546 void nf_ct_attach(struct sk_buff *new, const struct sk_buff *skb)
 547 {
 548         void (*attach)(struct sk_buff *, const struct sk_buff *);
 549
 550         if (skb->_nfct) {
 551                 rcu_read_lock();
 552                 attach = rcu_dereference(ip_ct_attach);
 553                 if (attach)
 554                         attach(new, skb);
 555                 rcu_read_unlock();
 556         }
 557 }
 558 EXPORT_SYMBOL(nf_ct_attach);
 559
 560 void (*nf_ct_destroy)(struct nf_conntrack *) __rcu __read_mostly;
 561 EXPORT_SYMBOL(nf_ct_destroy);
 562
 563 void nf_conntrack_destroy(struct nf_conntrack *nfct)
 564 {
 565         void (*destroy)(struct nf_conntrack *);
 566
 567         rcu_read_lock();
 568         destroy = rcu_dereference(nf_ct_destroy);
 569         BUG_ON(destroy == NULL);
 570         destroy(nfct);
 571         rcu_read_unlock();
 572 }
 573 EXPORT_SYMBOL(nf_conntrack_destroy);
 574
 575 /* Built-in default zone used e.g. by modules. */
 576 const struct nf_conntrack_zone nf_ct_zone_dflt = {
 577         .id     = NF_CT_DEFAULT_ZONE_ID,
 578         .dir    = NF_CT_DEFAULT_ZONE_DIR,
 579 };
 580 EXPORT_SYMBOL_GPL(nf_ct_zone_dflt);
 581 #endif /* CONFIG_NF_CONNTRACK */
 582
 583 #ifdef CONFIG_NF_NAT_NEEDED
 584 void (*nf_nat_decode_session_hook)(struct sk_buff *, struct flowi *);
 585 EXPORT_SYMBOL(nf_nat_decode_session_hook);
 586 #endif
 587
 588 static void __net_init __netfilter_net_init(struct nf_hook_entries **e, int max)
 589 {
 590         int h;
 591
 592         for (h = 0; h < max; h++)
 593                 RCU_INIT_POINTER(e[h], NULL);
 594 }
 595
 596 static int __net_init netfilter_net_init(struct net *net)
 597 {
 598         __netfilter_net_init(net->nf.hooks_ipv4, ARRAY_SIZE(net->nf.hooks_ipv4));
 599         __netfilter_net_init(net->nf.hooks_ipv6, ARRAY_SIZE(net->nf.hooks_ipv6));
 600 #ifdef CONFIG_NETFILTER_FAMILY_ARP
 601         __netfilter_net_init(net->nf.hooks_arp, ARRAY_SIZE(net->nf.hooks_arp));
 602 #endif
 603 #ifdef CONFIG_NETFILTER_FAMILY_BRIDGE
 604         __netfilter_net_init(net->nf.hooks_bridge, ARRAY_SIZE(net->nf.hooks_bridge));
 605 #endif
 606 #if IS_ENABLED(CONFIG_DECNET)
 607         __netfilter_net_init(net->nf.hooks_decnet, ARRAY_SIZE(net->nf.hooks_decnet));
 608 #endif
 609
 610 #ifdef CONFIG_PROC_FS
 611         net->nf.proc_netfilter = proc_net_mkdir(net, "netfilter",
 612                                                 net->proc_net);
 613         if (!net->nf.proc_netfilter) {
 614                 if (!net_eq(net, &init_net))
 615                         pr_err("cannot create netfilter proc entry");
 616
 617                 return -ENOMEM;
 618         }
 619 #endif
 620
 621         return 0;
 622 }
 623
 624 static void __net_exit netfilter_net_exit(struct net *net)
 625 {
 626         remove_proc_entry("netfilter", net->proc_net);
 627 }
 628
 629 static struct pernet_operations netfilter_net_ops = {
 630         .init = netfilter_net_init,
 631         .exit = netfilter_net_exit,
 632 };
 633
 634 int __init netfilter_init(void)
 635 {
 636         int ret;
 637
 638         ret = register_pernet_subsys(&netfilter_net_ops);
 639         if (ret < 0)
 640                 goto err;
 641
 642         ret = netfilter_log_init();
 643         if (ret < 0)
 644                 goto err_pernet;
 645
 646         return 0;
 647 err_pernet:
 648         unregister_pernet_subsys(&netfilter_net_ops);
 649 err:
 650         return ret;
 651 }