Pileus Git - ~andy/linux/blob - net/netfilter/nf_conntrack_helper.c

   1 /* Helper handling for netfilter. */
   2
   3 /* (C) 1999-2001 Paul `Rusty' Russell
   4  * (C) 2002-2006 Netfilter Core Team <coreteam@netfilter.org>
   5  * (C) 2003,2004 USAGI/WIDE Project <http://www.linux-ipv6.org>
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License version 2 as
   9  * published by the Free Software Foundation.
  10  */
  11
  12 #include <linux/types.h>
  13 #include <linux/netfilter.h>
  14 #include <linux/module.h>
  15 #include <linux/skbuff.h>
  16 #include <linux/vmalloc.h>
  17 #include <linux/stddef.h>
  18 #include <linux/random.h>
  19 #include <linux/err.h>
  20 #include <linux/kernel.h>
  21 #include <linux/netdevice.h>
  22 #include <linux/rculist.h>
  23 #include <linux/rtnetlink.h>
  24
  25 #include <net/netfilter/nf_conntrack.h>
  26 #include <net/netfilter/nf_conntrack_l3proto.h>
  27 #include <net/netfilter/nf_conntrack_l4proto.h>
  28 #include <net/netfilter/nf_conntrack_helper.h>
  29 #include <net/netfilter/nf_conntrack_core.h>
  30 #include <net/netfilter/nf_conntrack_extend.h>
  31 #include <net/netfilter/nf_log.h>
  32
  33 static DEFINE_MUTEX(nf_ct_helper_mutex);
  34 struct hlist_head *nf_ct_helper_hash __read_mostly;
  35 EXPORT_SYMBOL_GPL(nf_ct_helper_hash);
  36 unsigned int nf_ct_helper_hsize __read_mostly;
  37 EXPORT_SYMBOL_GPL(nf_ct_helper_hsize);
  38 static unsigned int nf_ct_helper_count __read_mostly;
  39
  40 static bool nf_ct_auto_assign_helper __read_mostly = true;
  41 module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
  42 MODULE_PARM_DESC(nf_conntrack_helper,
  43                  "Enable automatic conntrack helper assignment (default 1)");
  44
  45 #ifdef CONFIG_SYSCTL
  46 static struct ctl_table helper_sysctl_table[] = {
  47         {
  48                 .procname       = "nf_conntrack_helper",
  49                 .data           = &init_net.ct.sysctl_auto_assign_helper,
  50                 .maxlen         = sizeof(unsigned int),
  51                 .mode           = 0644,
  52                 .proc_handler   = proc_dointvec,
  53         },
  54         {}
  55 };
  56
  57 static int nf_conntrack_helper_init_sysctl(struct net *net)
  58 {
  59         struct ctl_table *table;
  60
  61         table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table),
  62                         GFP_KERNEL);
  63         if (!table)
  64                 goto out;
  65
  66         table[0].data = &net->ct.sysctl_auto_assign_helper;
  67
  68         /* Don't export sysctls to unprivileged users */
  69         if (net->user_ns != &init_user_ns)
  70                 table[0].procname = NULL;
  71
  72         net->ct.helper_sysctl_header =
  73                 register_net_sysctl(net, "net/netfilter", table);
  74
  75         if (!net->ct.helper_sysctl_header) {
  76                 pr_err("nf_conntrack_helper: can't register to sysctl.\n");
  77                 goto out_register;
  78         }
  79         return 0;
  80
  81 out_register:
  82         kfree(table);
  83 out:
  84         return -ENOMEM;
  85 }
  86
  87 static void nf_conntrack_helper_fini_sysctl(struct net *net)
  88 {
  89         struct ctl_table *table;
  90
  91         table = net->ct.helper_sysctl_header->ctl_table_arg;
  92         unregister_net_sysctl_table(net->ct.helper_sysctl_header);
  93         kfree(table);
  94 }
  95 #else
  96 static int nf_conntrack_helper_init_sysctl(struct net *net)
  97 {
  98         return 0;
  99 }
 100
 101 static void nf_conntrack_helper_fini_sysctl(struct net *net)
 102 {
 103 }
 104 #endif /* CONFIG_SYSCTL */
 105
 106 /* Stupid hash, but collision free for the default registrations of the
 107  * helpers currently in the kernel. */
 108 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
 109 {
 110         return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
 111                 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
 112 }
 113
 114 static struct nf_conntrack_helper *
 115 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
 116 {
 117         struct nf_conntrack_helper *helper;
 118         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
 119         struct hlist_node *n;
 120         unsigned int h;
 121
 122         if (!nf_ct_helper_count)
 123                 return NULL;
 124
 125         h = helper_hash(tuple);
 126         hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
 127                 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
 128                         return helper;
 129         }
 130         return NULL;
 131 }
 132
 133 struct nf_conntrack_helper *
 134 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
 135 {
 136         struct nf_conntrack_helper *h;
 137         struct hlist_node *n;
 138         unsigned int i;
 139
 140         for (i = 0; i < nf_ct_helper_hsize; i++) {
 141                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
 142                         if (!strcmp(h->name, name) &&
 143                             h->tuple.src.l3num == l3num &&
 144                             h->tuple.dst.protonum == protonum)
 145                                 return h;
 146                 }
 147         }
 148         return NULL;
 149 }
 150 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
 151
 152 struct nf_conntrack_helper *
 153 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
 154 {
 155         struct nf_conntrack_helper *h;
 156
 157         h = __nf_conntrack_helper_find(name, l3num, protonum);
 158 #ifdef CONFIG_MODULES
 159         if (h == NULL) {
 160                 if (request_module("nfct-helper-%s", name) == 0)
 161                         h = __nf_conntrack_helper_find(name, l3num, protonum);
 162         }
 163 #endif
 164         if (h != NULL && !try_module_get(h->me))
 165                 h = NULL;
 166
 167         return h;
 168 }
 169 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
 170
 171 struct nf_conn_help *
 172 nf_ct_helper_ext_add(struct nf_conn *ct,
 173                      struct nf_conntrack_helper *helper, gfp_t gfp)
 174 {
 175         struct nf_conn_help *help;
 176
 177         help = nf_ct_ext_add_length(ct, NF_CT_EXT_HELPER,
 178                                     helper->data_len, gfp);
 179         if (help)
 180                 INIT_HLIST_HEAD(&help->expectations);
 181         else
 182                 pr_debug("failed to add helper extension area");
 183         return help;
 184 }
 185 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
 186
 187 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 188                               gfp_t flags)
 189 {
 190         struct nf_conntrack_helper *helper = NULL;
 191         struct nf_conn_help *help;
 192         struct net *net = nf_ct_net(ct);
 193         int ret = 0;
 194
 195         /* We already got a helper explicitly attached. The function
 196          * nf_conntrack_alter_reply - in case NAT is in use - asks for looking
 197          * the helper up again. Since now the user is in full control of
 198          * making consistent helper configurations, skip this automatic
 199          * re-lookup, otherwise we'll lose the helper.
 200          */
 201         if (test_bit(IPS_HELPER_BIT, &ct->status))
 202                 return 0;
 203
 204         if (tmpl != NULL) {
 205                 help = nfct_help(tmpl);
 206                 if (help != NULL) {
 207                         helper = help->helper;
 208                         set_bit(IPS_HELPER_BIT, &ct->status);
 209                 }
 210         }
 211
 212         help = nfct_help(ct);
 213         if (net->ct.sysctl_auto_assign_helper && helper == NULL) {
 214                 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 215                 if (unlikely(!net->ct.auto_assign_helper_warned && helper)) {
 216                         pr_info("nf_conntrack: automatic helper "
 217                                 "assignment is deprecated and it will "
 218                                 "be removed soon. Use the iptables CT target "
 219                                 "to attach helpers instead.\n");
 220                         net->ct.auto_assign_helper_warned = true;
 221                 }
 222         }
 223
 224         if (helper == NULL) {
 225                 if (help)
 226                         RCU_INIT_POINTER(help->helper, NULL);
 227                 goto out;
 228         }
 229
 230         if (help == NULL) {
 231                 help = nf_ct_helper_ext_add(ct, helper, flags);
 232                 if (help == NULL) {
 233                         ret = -ENOMEM;
 234                         goto out;
 235                 }
 236         } else {
 237                 /* We only allow helper re-assignment of the same sort since
 238                  * we cannot reallocate the helper extension area.
 239                  */
 240                 struct nf_conntrack_helper *tmp = rcu_dereference(help->helper);
 241
 242                 if (tmp && tmp->help != helper->help) {
 243                         RCU_INIT_POINTER(help->helper, NULL);
 244                         goto out;
 245                 }
 246         }
 247
 248         rcu_assign_pointer(help->helper, helper);
 249 out:
 250         return ret;
 251 }
 252 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
 253
 254 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
 255                          const struct nf_conntrack_helper *me)
 256 {
 257         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 258         struct nf_conn_help *help = nfct_help(ct);
 259
 260         if (help && rcu_dereference_protected(
 261                         help->helper,
 262                         lockdep_is_held(&nf_conntrack_lock)
 263                         ) == me) {
 264                 nf_conntrack_event(IPCT_HELPER, ct);
 265                 RCU_INIT_POINTER(help->helper, NULL);
 266         }
 267         return 0;
 268 }
 269
 270 void nf_ct_helper_destroy(struct nf_conn *ct)
 271 {
 272         struct nf_conn_help *help = nfct_help(ct);
 273         struct nf_conntrack_helper *helper;
 274
 275         if (help) {
 276                 rcu_read_lock();
 277                 helper = rcu_dereference(help->helper);
 278                 if (helper && helper->destroy)
 279                         helper->destroy(ct);
 280                 rcu_read_unlock();
 281         }
 282 }
 283
 284 static LIST_HEAD(nf_ct_helper_expectfn_list);
 285
 286 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
 287 {
 288         spin_lock_bh(&nf_conntrack_lock);
 289         list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
 290         spin_unlock_bh(&nf_conntrack_lock);
 291 }
 292 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
 293
 294 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
 295 {
 296         spin_lock_bh(&nf_conntrack_lock);
 297         list_del_rcu(&n->head);
 298         spin_unlock_bh(&nf_conntrack_lock);
 299 }
 300 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
 301
 302 struct nf_ct_helper_expectfn *
 303 nf_ct_helper_expectfn_find_by_name(const char *name)
 304 {
 305         struct nf_ct_helper_expectfn *cur;
 306         bool found = false;
 307
 308         rcu_read_lock();
 309         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
 310                 if (!strcmp(cur->name, name)) {
 311                         found = true;
 312                         break;
 313                 }
 314         }
 315         rcu_read_unlock();
 316         return found ? cur : NULL;
 317 }
 318 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
 319
 320 struct nf_ct_helper_expectfn *
 321 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
 322 {
 323         struct nf_ct_helper_expectfn *cur;
 324         bool found = false;
 325
 326         rcu_read_lock();
 327         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
 328                 if (cur->expectfn == symbol) {
 329                         found = true;
 330                         break;
 331                 }
 332         }
 333         rcu_read_unlock();
 334         return found ? cur : NULL;
 335 }
 336 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
 337
 338 __printf(3, 4)
 339 void nf_ct_helper_log(struct sk_buff *skb, const struct nf_conn *ct,
 340                       const char *fmt, ...)
 341 {
 342         const struct nf_conn_help *help;
 343         const struct nf_conntrack_helper *helper;
 344
 345         /* Called from the helper function, this call never fails */
 346         help = nfct_help(ct);
 347
 348         /* rcu_read_lock()ed by nf_hook_slow */
 349         helper = rcu_dereference(help->helper);
 350
 351         nf_log_packet(nf_ct_l3num(ct), 0, skb, NULL, NULL, NULL,
 352                       "nf_ct_%s: dropping packet: %s ", helper->name, fmt);
 353 }
 354 EXPORT_SYMBOL_GPL(nf_ct_helper_log);
 355
 356 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 357 {
 358         int ret = 0;
 359         struct nf_conntrack_helper *cur;
 360         struct hlist_node *n;
 361         unsigned int h = helper_hash(&me->tuple);
 362
 363         BUG_ON(me->expect_policy == NULL);
 364         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 365         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
 366
 367         mutex_lock(&nf_ct_helper_mutex);
 368         hlist_for_each_entry(cur, n, &nf_ct_helper_hash[h], hnode) {
 369                 if (strncmp(cur->name, me->name, NF_CT_HELPER_NAME_LEN) == 0 &&
 370                     cur->tuple.src.l3num == me->tuple.src.l3num &&
 371                     cur->tuple.dst.protonum == me->tuple.dst.protonum) {
 372                         ret = -EEXIST;
 373                         goto out;
 374                 }
 375         }
 376         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 377         nf_ct_helper_count++;
 378 out:
 379         mutex_unlock(&nf_ct_helper_mutex);
 380         return ret;
 381 }
 382 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 383
 384 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 385                                              struct net *net)
 386 {
 387         struct nf_conntrack_tuple_hash *h;
 388         struct nf_conntrack_expect *exp;
 389         const struct hlist_node *n, *next;
 390         const struct hlist_nulls_node *nn;
 391         unsigned int i;
 392
 393         /* Get rid of expectations */
 394         for (i = 0; i < nf_ct_expect_hsize; i++) {
 395                 hlist_for_each_entry_safe(exp, n, next,
 396                                           &net->ct.expect_hash[i], hnode) {
 397                         struct nf_conn_help *help = nfct_help(exp->master);
 398                         if ((rcu_dereference_protected(
 399                                         help->helper,
 400                                         lockdep_is_held(&nf_conntrack_lock)
 401                                         ) == me || exp->helper == me) &&
 402                             del_timer(&exp->timeout)) {
 403                                 nf_ct_unlink_expect(exp);
 404                                 nf_ct_expect_put(exp);
 405                         }
 406                 }
 407         }
 408
 409         /* Get rid of expecteds, set helpers to NULL. */
 410         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
 411                 unhelp(h, me);
 412         for (i = 0; i < net->ct.htable_size; i++) {
 413                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
 414                         unhelp(h, me);
 415         }
 416 }
 417
 418 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 419 {
 420         struct net *net;
 421
 422         mutex_lock(&nf_ct_helper_mutex);
 423         hlist_del_rcu(&me->hnode);
 424         nf_ct_helper_count--;
 425         mutex_unlock(&nf_ct_helper_mutex);
 426
 427         /* Make sure every nothing is still using the helper unless its a
 428          * connection in the hash.
 429          */
 430         synchronize_rcu();
 431
 432         rtnl_lock();
 433         spin_lock_bh(&nf_conntrack_lock);
 434         for_each_net(net)
 435                 __nf_conntrack_helper_unregister(me, net);
 436         spin_unlock_bh(&nf_conntrack_lock);
 437         rtnl_unlock();
 438 }
 439 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 440
 441 static struct nf_ct_ext_type helper_extend __read_mostly = {
 442         .len    = sizeof(struct nf_conn_help),
 443         .align  = __alignof__(struct nf_conn_help),
 444         .id     = NF_CT_EXT_HELPER,
 445 };
 446
 447 int nf_conntrack_helper_pernet_init(struct net *net)
 448 {
 449         net->ct.auto_assign_helper_warned = false;
 450         net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
 451         return nf_conntrack_helper_init_sysctl(net);
 452 }
 453
 454 void nf_conntrack_helper_pernet_fini(struct net *net)
 455 {
 456         nf_conntrack_helper_fini_sysctl(net);
 457 }
 458
 459 int nf_conntrack_helper_init(void)
 460 {
 461         int ret;
 462         nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 463         nf_ct_helper_hash =
 464                 nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
 465         if (!nf_ct_helper_hash)
 466                 return -ENOMEM;
 467
 468         ret = nf_ct_extend_register(&helper_extend);
 469         if (ret < 0) {
 470                 pr_err("nf_ct_helper: Unable to register helper extension.\n");
 471                 goto out_extend;
 472         }
 473
 474         return 0;
 475 out_extend:
 476         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
 477         return ret;
 478 }
 479
 480 void nf_conntrack_helper_fini(void)
 481 {
 482         nf_ct_extend_unregister(&helper_extend);
 483         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
 484 }