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  * Rusty Russell (C)2000 -- This code is GPL.
   8  * Patrick McHardy (c) 2006-2012
   9  */
  10 #include <linux/kernel.h>
  11 #include <linux/netfilter.h>
  12 #include <net/protocol.h>
  13 #include <linux/init.h>
  14 #include <linux/skbuff.h>
  15 #include <linux/wait.h>
  16 #include <linux/module.h>
  17 #include <linux/interrupt.h>
  18 #include <linux/if.h>
  19 #include <linux/netdevice.h>
  20 #include <linux/netfilter_ipv6.h>
  21 #include <linux/inetdevice.h>
  22 #include <linux/proc_fs.h>
  23 #include <linux/mutex.h>
  24 #include <linux/slab.h>
  25 #include <net/net_namespace.h>
  26 #include <net/sock.h>
  27
  28 #include "nf_internals.h"
  29
  30 static DEFINE_MUTEX(afinfo_mutex);
  31
  32 const struct nf_afinfo __rcu *nf_afinfo[NFPROTO_NUMPROTO] __read_mostly;
  33 EXPORT_SYMBOL(nf_afinfo);
  34 const struct nf_ipv6_ops __rcu *nf_ipv6_ops __read_mostly;
  35 EXPORT_SYMBOL_GPL(nf_ipv6_ops);
  36
  37 DEFINE_PER_CPU(bool, nf_skb_duplicated);
  38 EXPORT_SYMBOL_GPL(nf_skb_duplicated);
  39
  40 int nf_register_afinfo(const struct nf_afinfo *afinfo)
  41 {
  42         mutex_lock(&afinfo_mutex);
  43         RCU_INIT_POINTER(nf_afinfo[afinfo->family], afinfo);
  44         mutex_unlock(&afinfo_mutex);
  45         return 0;
  46 }
  47 EXPORT_SYMBOL_GPL(nf_register_afinfo);
  48
  49 void nf_unregister_afinfo(const struct nf_afinfo *afinfo)
  50 {
  51         mutex_lock(&afinfo_mutex);
  52         RCU_INIT_POINTER(nf_afinfo[afinfo->family], NULL);
  53         mutex_unlock(&afinfo_mutex);
  54         synchronize_rcu();
  55 }
  56 EXPORT_SYMBOL_GPL(nf_unregister_afinfo);
  57
  58 #ifdef HAVE_JUMP_LABEL
  59 struct static_key nf_hooks_needed[NFPROTO_NUMPROTO][NF_MAX_HOOKS];
  60 EXPORT_SYMBOL(nf_hooks_needed);
  61 #endif
  62
  63 static DEFINE_MUTEX(nf_hook_mutex);
  64
  65 static struct list_head *nf_find_hook_list(struct net *net,
  66                                            const struct nf_hook_ops *reg)
  67 {
  68         struct list_head *hook_list = NULL;
  69
  70         if (reg->pf != NFPROTO_NETDEV)
  71                 hook_list = &net->nf.hooks[reg->pf][reg->hooknum];
  72         else if (reg->hooknum == NF_NETDEV_INGRESS) {
  73 #ifdef CONFIG_NETFILTER_INGRESS
  74                 if (reg->dev && dev_net(reg->dev) == net)
  75                         hook_list = &reg->dev->nf_hooks_ingress;
  76 #endif
  77         }
  78         return hook_list;
  79 }
  80
  81 struct nf_hook_entry {
  82         const struct nf_hook_ops        *orig_ops;
  83         struct nf_hook_ops              ops;
  84 };
  85
  86 int nf_register_net_hook(struct net *net, const struct nf_hook_ops *reg)
  87 {
  88         struct list_head *hook_list;
  89         struct nf_hook_entry *entry;
  90         struct nf_hook_ops *elem;
  91
  92         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
  93         if (!entry)
  94                 return -ENOMEM;
  95
  96         entry->orig_ops = reg;
  97         entry->ops      = *reg;
  98
  99         hook_list = nf_find_hook_list(net, reg);
 100         if (!hook_list) {
 101                 kfree(entry);
 102                 return -ENOENT;
 103         }
 104
 105         mutex_lock(&nf_hook_mutex);
 106         list_for_each_entry(elem, hook_list, list) {
 107                 if (reg->priority < elem->priority)
 108                         break;
 109         }
 110         list_add_rcu(&entry->ops.list, elem->list.prev);
 111         mutex_unlock(&nf_hook_mutex);
 112 #ifdef CONFIG_NETFILTER_INGRESS
 113         if (reg->pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_INGRESS)
 114                 net_inc_ingress_queue();
 115 #endif
 116 #ifdef HAVE_JUMP_LABEL
 117         static_key_slow_inc(&nf_hooks_needed[reg->pf][reg->hooknum]);
 118 #endif
 119         return 0;
 120 }
 121 EXPORT_SYMBOL(nf_register_net_hook);
 122
 123 void nf_unregister_net_hook(struct net *net, const struct nf_hook_ops *reg)
 124 {
 125         struct list_head *hook_list;
 126         struct nf_hook_entry *entry;
 127         struct nf_hook_ops *elem;
 128
 129         hook_list = nf_find_hook_list(net, reg);
 130         if (!hook_list)
 131                 return;
 132
 133         mutex_lock(&nf_hook_mutex);
 134         list_for_each_entry(elem, hook_list, list) {
 135                 entry = container_of(elem, struct nf_hook_entry, ops);
 136                 if (entry->orig_ops == reg) {
 137                         list_del_rcu(&entry->ops.list);
 138                         break;
 139                 }
 140         }
 141         mutex_unlock(&nf_hook_mutex);
 142         if (&elem->list == hook_list) {
 143                 WARN(1, "nf_unregister_net_hook: hook not found!\n");
 144                 return;
 145         }
 146 #ifdef CONFIG_NETFILTER_INGRESS
 147         if (reg->pf == NFPROTO_NETDEV && reg->hooknum == NF_NETDEV_INGRESS)
 148                 net_dec_ingress_queue();
 149 #endif
 150 #ifdef HAVE_JUMP_LABEL
 151         static_key_slow_dec(&nf_hooks_needed[reg->pf][reg->hooknum]);
 152 #endif
 153         synchronize_net();
 154         nf_queue_nf_hook_drop(net, &entry->ops);
 155         kfree(entry);
 156 }
 157 EXPORT_SYMBOL(nf_unregister_net_hook);
 158
 159 int nf_register_net_hooks(struct net *net, const struct nf_hook_ops *reg,
 160                           unsigned int n)
 161 {
 162         unsigned int i;
 163         int err = 0;
 164
 165         for (i = 0; i < n; i++) {
 166                 err = nf_register_net_hook(net, &reg[i]);
 167                 if (err)
 168                         goto err;
 169         }
 170         return err;
 171
 172 err:
 173         if (i > 0)
 174                 nf_unregister_net_hooks(net, reg, i);
 175         return err;
 176 }
 177 EXPORT_SYMBOL(nf_register_net_hooks);
 178
 179 void nf_unregister_net_hooks(struct net *net, const struct nf_hook_ops *reg,
 180                              unsigned int n)
 181 {
 182         while (n-- > 0)
 183                 nf_unregister_net_hook(net, &reg[n]);
 184 }
 185 EXPORT_SYMBOL(nf_unregister_net_hooks);
 186
 187 static LIST_HEAD(nf_hook_list);
 188
 189 int nf_register_hook(struct nf_hook_ops *reg)
 190 {
 191         struct net *net, *last;
 192         int ret;
 193
 194         rtnl_lock();
 195         for_each_net(net) {
 196                 ret = nf_register_net_hook(net, reg);
 197                 if (ret && ret != -ENOENT)
 198                         goto rollback;
 199         }
 200         list_add_tail(&reg->list, &nf_hook_list);
 201         rtnl_unlock();
 202
 203         return 0;
 204 rollback:
 205         last = net;
 206         for_each_net(net) {
 207                 if (net == last)
 208                         break;
 209                 nf_unregister_net_hook(net, reg);
 210         }
 211         rtnl_unlock();
 212         return ret;
 213 }
 214 EXPORT_SYMBOL(nf_register_hook);
 215
 216 void nf_unregister_hook(struct nf_hook_ops *reg)
 217 {
 218         struct net *net;
 219
 220         rtnl_lock();
 221         list_del(&reg->list);
 222         for_each_net(net)
 223                 nf_unregister_net_hook(net, reg);
 224         rtnl_unlock();
 225 }
 226 EXPORT_SYMBOL(nf_unregister_hook);
 227
 228 int nf_register_hooks(struct nf_hook_ops *reg, unsigned int n)
 229 {
 230         unsigned int i;
 231         int err = 0;
 232
 233         for (i = 0; i < n; i++) {
 234                 err = nf_register_hook(&reg[i]);
 235                 if (err)
 236                         goto err;
 237         }
 238         return err;
 239
 240 err:
 241         if (i > 0)
 242                 nf_unregister_hooks(reg, i);
 243         return err;
 244 }
 245 EXPORT_SYMBOL(nf_register_hooks);
 246
 247 void nf_unregister_hooks(struct nf_hook_ops *reg, unsigned int n)
 248 {
 249         while (n-- > 0)
 250                 nf_unregister_hook(&reg[n]);
 251 }
 252 EXPORT_SYMBOL(nf_unregister_hooks);
 253
 254 unsigned int nf_iterate(struct list_head *head,
 255                         struct sk_buff *skb,
 256                         struct nf_hook_state *state,
 257                         struct nf_hook_ops **elemp)
 258 {
 259         unsigned int verdict;
 260
 261         /*
 262          * The caller must not block between calls to this
 263          * function because of risk of continuing from deleted element.
 264          */
 265         list_for_each_entry_continue_rcu((*elemp), head, list) {
 266                 if (state->thresh > (*elemp)->priority)
 267                         continue;
 268
 269                 /* Optimization: we don't need to hold module
 270                    reference here, since function can't sleep. --RR */
 271 repeat:
 272                 verdict = (*elemp)->hook(*elemp, skb, state);
 273                 if (verdict != NF_ACCEPT) {
 274 #ifdef CONFIG_NETFILTER_DEBUG
 275                         if (unlikely((verdict & NF_VERDICT_MASK)
 276                                                         > NF_MAX_VERDICT)) {
 277                                 NFDEBUG("Evil return from %p(%u).\n",
 278                                         (*elemp)->hook, state->hook);
 279                                 continue;
 280                         }
 281 #endif
 282                         if (verdict != NF_REPEAT)
 283                                 return verdict;
 284                         goto repeat;
 285                 }
 286         }
 287         return NF_ACCEPT;
 288 }
 289
 290
 291 /* Returns 1 if okfn() needs to be executed by the caller,
 292  * -EPERM for NF_DROP, 0 otherwise. */
 293 int nf_hook_slow(struct sk_buff *skb, struct nf_hook_state *state)
 294 {
 295         struct nf_hook_ops *elem;
 296         unsigned int verdict;
 297         int ret = 0;
 298
 299         /* We may already have this, but read-locks nest anyway */
 300         rcu_read_lock();
 301
 302         elem = list_entry_rcu(state->hook_list, struct nf_hook_ops, list);
 303 next_hook:
 304         verdict = nf_iterate(state->hook_list, skb, state, &elem);
 305         if (verdict == NF_ACCEPT || verdict == NF_STOP) {
 306                 ret = 1;
 307         } else if ((verdict & NF_VERDICT_MASK) == NF_DROP) {
 308                 kfree_skb(skb);
 309                 ret = NF_DROP_GETERR(verdict);
 310                 if (ret == 0)
 311                         ret = -EPERM;
 312         } else if ((verdict & NF_VERDICT_MASK) == NF_QUEUE) {
 313                 int err = nf_queue(skb, elem, state,
 314                                    verdict >> NF_VERDICT_QBITS);
 315                 if (err < 0) {
 316                         if (err == -ECANCELED)
 317                                 goto next_hook;
 318                         if (err == -ESRCH &&
 319                            (verdict & NF_VERDICT_FLAG_QUEUE_BYPASS))
 320                                 goto next_hook;
 321                         kfree_skb(skb);
 322                 }
 323         }
 324         rcu_read_unlock();
 325         return ret;
 326 }
 327 EXPORT_SYMBOL(nf_hook_slow);
 328
 329
 330 int skb_make_writable(struct sk_buff *skb, unsigned int writable_len)
 331 {
 332         if (writable_len > skb->len)
 333                 return 0;
 334
 335         /* Not exclusive use of packet?  Must copy. */
 336         if (!skb_cloned(skb)) {
 337                 if (writable_len <= skb_headlen(skb))
 338                         return 1;
 339         } else if (skb_clone_writable(skb, writable_len))
 340                 return 1;
 341
 342         if (writable_len <= skb_headlen(skb))
 343                 writable_len = 0;
 344         else
 345                 writable_len -= skb_headlen(skb);
 346
 347         return !!__pskb_pull_tail(skb, writable_len);
 348 }
 349 EXPORT_SYMBOL(skb_make_writable);
 350
 351 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 352 /* This does not belong here, but locally generated errors need it if connection
 353    tracking in use: without this, connection may not be in hash table, and hence
 354    manufactured ICMP or RST packets will not be associated with it. */
 355 void (*ip_ct_attach)(struct sk_buff *, const struct sk_buff *)
 356                 __rcu __read_mostly;
 357 EXPORT_SYMBOL(ip_ct_attach);
 358
 359 void nf_ct_attach(struct sk_buff *new, const struct sk_buff *skb)
 360 {
 361         void (*attach)(struct sk_buff *, const struct sk_buff *);
 362
 363         if (skb->nfct) {
 364                 rcu_read_lock();
 365                 attach = rcu_dereference(ip_ct_attach);
 366                 if (attach)
 367                         attach(new, skb);
 368                 rcu_read_unlock();
 369         }
 370 }
 371 EXPORT_SYMBOL(nf_ct_attach);
 372
 373 void (*nf_ct_destroy)(struct nf_conntrack *) __rcu __read_mostly;
 374 EXPORT_SYMBOL(nf_ct_destroy);
 375
 376 void nf_conntrack_destroy(struct nf_conntrack *nfct)
 377 {
 378         void (*destroy)(struct nf_conntrack *);
 379
 380         rcu_read_lock();
 381         destroy = rcu_dereference(nf_ct_destroy);
 382         BUG_ON(destroy == NULL);
 383         destroy(nfct);
 384         rcu_read_unlock();
 385 }
 386 EXPORT_SYMBOL(nf_conntrack_destroy);
 387
 388 struct nfq_ct_hook __rcu *nfq_ct_hook __read_mostly;
 389 EXPORT_SYMBOL_GPL(nfq_ct_hook);
 390
 391 /* Built-in default zone used e.g. by modules. */
 392 const struct nf_conntrack_zone nf_ct_zone_dflt = {
 393         .id     = NF_CT_DEFAULT_ZONE_ID,
 394         .dir    = NF_CT_DEFAULT_ZONE_DIR,
 395 };
 396 EXPORT_SYMBOL_GPL(nf_ct_zone_dflt);
 397 #endif /* CONFIG_NF_CONNTRACK */
 398
 399 #ifdef CONFIG_NF_NAT_NEEDED
 400 void (*nf_nat_decode_session_hook)(struct sk_buff *, struct flowi *);
 401 EXPORT_SYMBOL(nf_nat_decode_session_hook);
 402 #endif
 403
 404 static int nf_register_hook_list(struct net *net)
 405 {
 406         struct nf_hook_ops *elem;
 407         int ret;
 408
 409         rtnl_lock();
 410         list_for_each_entry(elem, &nf_hook_list, list) {
 411                 ret = nf_register_net_hook(net, elem);
 412                 if (ret && ret != -ENOENT)
 413                         goto out_undo;
 414         }
 415         rtnl_unlock();
 416         return 0;
 417
 418 out_undo:
 419         list_for_each_entry_continue_reverse(elem, &nf_hook_list, list)
 420                 nf_unregister_net_hook(net, elem);
 421         rtnl_unlock();
 422         return ret;
 423 }
 424
 425 static void nf_unregister_hook_list(struct net *net)
 426 {
 427         struct nf_hook_ops *elem;
 428
 429         rtnl_lock();
 430         list_for_each_entry(elem, &nf_hook_list, list)
 431                 nf_unregister_net_hook(net, elem);
 432         rtnl_unlock();
 433 }
 434
 435 static int __net_init netfilter_net_init(struct net *net)
 436 {
 437         int i, h, ret;
 438
 439         for (i = 0; i < ARRAY_SIZE(net->nf.hooks); i++) {
 440                 for (h = 0; h < NF_MAX_HOOKS; h++)
 441                         INIT_LIST_HEAD(&net->nf.hooks[i][h]);
 442         }
 443
 444 #ifdef CONFIG_PROC_FS
 445         net->nf.proc_netfilter = proc_net_mkdir(net, "netfilter",
 446                                                 net->proc_net);
 447         if (!net->nf.proc_netfilter) {
 448                 if (!net_eq(net, &init_net))
 449                         pr_err("cannot create netfilter proc entry");
 450
 451                 return -ENOMEM;
 452         }
 453 #endif
 454         ret = nf_register_hook_list(net);
 455         if (ret)
 456                 remove_proc_entry("netfilter", net->proc_net);
 457
 458         return ret;
 459 }
 460
 461 static void __net_exit netfilter_net_exit(struct net *net)
 462 {
 463         nf_unregister_hook_list(net);
 464         remove_proc_entry("netfilter", net->proc_net);
 465 }
 466
 467 static struct pernet_operations netfilter_net_ops = {
 468         .init = netfilter_net_init,
 469         .exit = netfilter_net_exit,
 470 };
 471
 472 int __init netfilter_init(void)
 473 {
 474         int ret;
 475
 476         ret = register_pernet_subsys(&netfilter_net_ops);
 477         if (ret < 0)
 478                 goto err;
 479
 480         ret = netfilter_log_init();
 481         if (ret < 0)
 482                 goto err_pernet;
 483
 484         return 0;
 485 err_pernet:
 486         unregister_pernet_subsys(&netfilter_net_ops);
 487 err:
 488         return ret;
 489 }