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
  32 static DEFINE_MUTEX(nf_ct_helper_mutex);
  33 static struct hlist_head *nf_ct_helper_hash __read_mostly;
  34 static unsigned int nf_ct_helper_hsize __read_mostly;
  35 static unsigned int nf_ct_helper_count __read_mostly;
  36
  37 static bool nf_ct_auto_assign_helper __read_mostly = true;
  38 module_param_named(nf_conntrack_helper, nf_ct_auto_assign_helper, bool, 0644);
  39 MODULE_PARM_DESC(nf_conntrack_helper,
  40                  "Enable automatic conntrack helper assignment (default 1)");
  41
  42 #ifdef CONFIG_SYSCTL
  43 static struct ctl_table helper_sysctl_table[] = {
  44         {
  45                 .procname       = "nf_conntrack_helper",
  46                 .data           = &init_net.ct.sysctl_auto_assign_helper,
  47                 .maxlen         = sizeof(unsigned int),
  48                 .mode           = 0644,
  49                 .proc_handler   = proc_dointvec,
  50         },
  51         {}
  52 };
  53
  54 static int nf_conntrack_helper_init_sysctl(struct net *net)
  55 {
  56         struct ctl_table *table;
  57
  58         table = kmemdup(helper_sysctl_table, sizeof(helper_sysctl_table),
  59                         GFP_KERNEL);
  60         if (!table)
  61                 goto out;
  62
  63         table[0].data = &net->ct.sysctl_auto_assign_helper;
  64
  65         net->ct.helper_sysctl_header =
  66                 register_net_sysctl(net, "net/netfilter", table);
  67
  68         if (!net->ct.helper_sysctl_header) {
  69                 pr_err("nf_conntrack_helper: can't register to sysctl.\n");
  70                 goto out_register;
  71         }
  72         return 0;
  73
  74 out_register:
  75         kfree(table);
  76 out:
  77         return -ENOMEM;
  78 }
  79
  80 static void nf_conntrack_helper_fini_sysctl(struct net *net)
  81 {
  82         struct ctl_table *table;
  83
  84         table = net->ct.helper_sysctl_header->ctl_table_arg;
  85         unregister_net_sysctl_table(net->ct.helper_sysctl_header);
  86         kfree(table);
  87 }
  88 #else
  89 static int nf_conntrack_helper_init_sysctl(struct net *net)
  90 {
  91         return 0;
  92 }
  93
  94 static void nf_conntrack_helper_fini_sysctl(struct net *net)
  95 {
  96 }
  97 #endif /* CONFIG_SYSCTL */
  98
  99 /* Stupid hash, but collision free for the default registrations of the
 100  * helpers currently in the kernel. */
 101 static unsigned int helper_hash(const struct nf_conntrack_tuple *tuple)
 102 {
 103         return (((tuple->src.l3num << 8) | tuple->dst.protonum) ^
 104                 (__force __u16)tuple->src.u.all) % nf_ct_helper_hsize;
 105 }
 106
 107 static struct nf_conntrack_helper *
 108 __nf_ct_helper_find(const struct nf_conntrack_tuple *tuple)
 109 {
 110         struct nf_conntrack_helper *helper;
 111         struct nf_conntrack_tuple_mask mask = { .src.u.all = htons(0xFFFF) };
 112         struct hlist_node *n;
 113         unsigned int h;
 114
 115         if (!nf_ct_helper_count)
 116                 return NULL;
 117
 118         h = helper_hash(tuple);
 119         hlist_for_each_entry_rcu(helper, n, &nf_ct_helper_hash[h], hnode) {
 120                 if (nf_ct_tuple_src_mask_cmp(tuple, &helper->tuple, &mask))
 121                         return helper;
 122         }
 123         return NULL;
 124 }
 125
 126 struct nf_conntrack_helper *
 127 __nf_conntrack_helper_find(const char *name, u16 l3num, u8 protonum)
 128 {
 129         struct nf_conntrack_helper *h;
 130         struct hlist_node *n;
 131         unsigned int i;
 132
 133         for (i = 0; i < nf_ct_helper_hsize; i++) {
 134                 hlist_for_each_entry_rcu(h, n, &nf_ct_helper_hash[i], hnode) {
 135                         if (!strcmp(h->name, name) &&
 136                             h->tuple.src.l3num == l3num &&
 137                             h->tuple.dst.protonum == protonum)
 138                                 return h;
 139                 }
 140         }
 141         return NULL;
 142 }
 143 EXPORT_SYMBOL_GPL(__nf_conntrack_helper_find);
 144
 145 struct nf_conntrack_helper *
 146 nf_conntrack_helper_try_module_get(const char *name, u16 l3num, u8 protonum)
 147 {
 148         struct nf_conntrack_helper *h;
 149
 150         h = __nf_conntrack_helper_find(name, l3num, protonum);
 151 #ifdef CONFIG_MODULES
 152         if (h == NULL) {
 153                 if (request_module("nfct-helper-%s", name) == 0)
 154                         h = __nf_conntrack_helper_find(name, l3num, protonum);
 155         }
 156 #endif
 157         if (h != NULL && !try_module_get(h->me))
 158                 h = NULL;
 159
 160         return h;
 161 }
 162 EXPORT_SYMBOL_GPL(nf_conntrack_helper_try_module_get);
 163
 164 struct nf_conn_help *nf_ct_helper_ext_add(struct nf_conn *ct, gfp_t gfp)
 165 {
 166         struct nf_conn_help *help;
 167
 168         help = nf_ct_ext_add(ct, NF_CT_EXT_HELPER, gfp);
 169         if (help)
 170                 INIT_HLIST_HEAD(&help->expectations);
 171         else
 172                 pr_debug("failed to add helper extension area");
 173         return help;
 174 }
 175 EXPORT_SYMBOL_GPL(nf_ct_helper_ext_add);
 176
 177 int __nf_ct_try_assign_helper(struct nf_conn *ct, struct nf_conn *tmpl,
 178                               gfp_t flags)
 179 {
 180         struct nf_conntrack_helper *helper = NULL;
 181         struct nf_conn_help *help;
 182         struct net *net = nf_ct_net(ct);
 183         int ret = 0;
 184
 185         if (tmpl != NULL) {
 186                 help = nfct_help(tmpl);
 187                 if (help != NULL)
 188                         helper = help->helper;
 189         }
 190
 191         help = nfct_help(ct);
 192         if (net->ct.sysctl_auto_assign_helper && helper == NULL) {
 193                 helper = __nf_ct_helper_find(&ct->tuplehash[IP_CT_DIR_REPLY].tuple);
 194                 if (unlikely(!net->ct.auto_assign_helper_warned && helper)) {
 195                         pr_info("nf_conntrack: automatic helper "
 196                                 "assignment is deprecated and it will "
 197                                 "be removed soon. Use the iptables CT target "
 198                                 "to attach helpers instead.\n");
 199                         net->ct.auto_assign_helper_warned = true;
 200                 }
 201         }
 202
 203         if (helper == NULL) {
 204                 if (help)
 205                         RCU_INIT_POINTER(help->helper, NULL);
 206                 goto out;
 207         }
 208
 209         if (help == NULL) {
 210                 help = nf_ct_helper_ext_add(ct, flags);
 211                 if (help == NULL) {
 212                         ret = -ENOMEM;
 213                         goto out;
 214                 }
 215         } else {
 216                 memset(&help->help, 0, sizeof(help->help));
 217         }
 218
 219         rcu_assign_pointer(help->helper, helper);
 220 out:
 221         return ret;
 222 }
 223 EXPORT_SYMBOL_GPL(__nf_ct_try_assign_helper);
 224
 225 static inline int unhelp(struct nf_conntrack_tuple_hash *i,
 226                          const struct nf_conntrack_helper *me)
 227 {
 228         struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(i);
 229         struct nf_conn_help *help = nfct_help(ct);
 230
 231         if (help && rcu_dereference_protected(
 232                         help->helper,
 233                         lockdep_is_held(&nf_conntrack_lock)
 234                         ) == me) {
 235                 nf_conntrack_event(IPCT_HELPER, ct);
 236                 RCU_INIT_POINTER(help->helper, NULL);
 237         }
 238         return 0;
 239 }
 240
 241 void nf_ct_helper_destroy(struct nf_conn *ct)
 242 {
 243         struct nf_conn_help *help = nfct_help(ct);
 244         struct nf_conntrack_helper *helper;
 245
 246         if (help) {
 247                 rcu_read_lock();
 248                 helper = rcu_dereference(help->helper);
 249                 if (helper && helper->destroy)
 250                         helper->destroy(ct);
 251                 rcu_read_unlock();
 252         }
 253 }
 254
 255 static LIST_HEAD(nf_ct_helper_expectfn_list);
 256
 257 void nf_ct_helper_expectfn_register(struct nf_ct_helper_expectfn *n)
 258 {
 259         spin_lock_bh(&nf_conntrack_lock);
 260         list_add_rcu(&n->head, &nf_ct_helper_expectfn_list);
 261         spin_unlock_bh(&nf_conntrack_lock);
 262 }
 263 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_register);
 264
 265 void nf_ct_helper_expectfn_unregister(struct nf_ct_helper_expectfn *n)
 266 {
 267         spin_lock_bh(&nf_conntrack_lock);
 268         list_del_rcu(&n->head);
 269         spin_unlock_bh(&nf_conntrack_lock);
 270 }
 271 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister);
 272
 273 struct nf_ct_helper_expectfn *
 274 nf_ct_helper_expectfn_find_by_name(const char *name)
 275 {
 276         struct nf_ct_helper_expectfn *cur;
 277         bool found = false;
 278
 279         rcu_read_lock();
 280         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
 281                 if (!strcmp(cur->name, name)) {
 282                         found = true;
 283                         break;
 284                 }
 285         }
 286         rcu_read_unlock();
 287         return found ? cur : NULL;
 288 }
 289 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name);
 290
 291 struct nf_ct_helper_expectfn *
 292 nf_ct_helper_expectfn_find_by_symbol(const void *symbol)
 293 {
 294         struct nf_ct_helper_expectfn *cur;
 295         bool found = false;
 296
 297         rcu_read_lock();
 298         list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) {
 299                 if (cur->expectfn == symbol) {
 300                         found = true;
 301                         break;
 302                 }
 303         }
 304         rcu_read_unlock();
 305         return found ? cur : NULL;
 306 }
 307 EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_symbol);
 308
 309 int nf_conntrack_helper_register(struct nf_conntrack_helper *me)
 310 {
 311         unsigned int h = helper_hash(&me->tuple);
 312
 313         BUG_ON(me->expect_policy == NULL);
 314         BUG_ON(me->expect_class_max >= NF_CT_MAX_EXPECT_CLASSES);
 315         BUG_ON(strlen(me->name) > NF_CT_HELPER_NAME_LEN - 1);
 316
 317         mutex_lock(&nf_ct_helper_mutex);
 318         hlist_add_head_rcu(&me->hnode, &nf_ct_helper_hash[h]);
 319         nf_ct_helper_count++;
 320         mutex_unlock(&nf_ct_helper_mutex);
 321
 322         return 0;
 323 }
 324 EXPORT_SYMBOL_GPL(nf_conntrack_helper_register);
 325
 326 static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
 327                                              struct net *net)
 328 {
 329         struct nf_conntrack_tuple_hash *h;
 330         struct nf_conntrack_expect *exp;
 331         const struct hlist_node *n, *next;
 332         const struct hlist_nulls_node *nn;
 333         unsigned int i;
 334
 335         /* Get rid of expectations */
 336         for (i = 0; i < nf_ct_expect_hsize; i++) {
 337                 hlist_for_each_entry_safe(exp, n, next,
 338                                           &net->ct.expect_hash[i], hnode) {
 339                         struct nf_conn_help *help = nfct_help(exp->master);
 340                         if ((rcu_dereference_protected(
 341                                         help->helper,
 342                                         lockdep_is_held(&nf_conntrack_lock)
 343                                         ) == me || exp->helper == me) &&
 344                             del_timer(&exp->timeout)) {
 345                                 nf_ct_unlink_expect(exp);
 346                                 nf_ct_expect_put(exp);
 347                         }
 348                 }
 349         }
 350
 351         /* Get rid of expecteds, set helpers to NULL. */
 352         hlist_nulls_for_each_entry(h, nn, &net->ct.unconfirmed, hnnode)
 353                 unhelp(h, me);
 354         for (i = 0; i < net->ct.htable_size; i++) {
 355                 hlist_nulls_for_each_entry(h, nn, &net->ct.hash[i], hnnode)
 356                         unhelp(h, me);
 357         }
 358 }
 359
 360 void nf_conntrack_helper_unregister(struct nf_conntrack_helper *me)
 361 {
 362         struct net *net;
 363
 364         mutex_lock(&nf_ct_helper_mutex);
 365         hlist_del_rcu(&me->hnode);
 366         nf_ct_helper_count--;
 367         mutex_unlock(&nf_ct_helper_mutex);
 368
 369         /* Make sure every nothing is still using the helper unless its a
 370          * connection in the hash.
 371          */
 372         synchronize_rcu();
 373
 374         rtnl_lock();
 375         spin_lock_bh(&nf_conntrack_lock);
 376         for_each_net(net)
 377                 __nf_conntrack_helper_unregister(me, net);
 378         spin_unlock_bh(&nf_conntrack_lock);
 379         rtnl_unlock();
 380 }
 381 EXPORT_SYMBOL_GPL(nf_conntrack_helper_unregister);
 382
 383 static struct nf_ct_ext_type helper_extend __read_mostly = {
 384         .len    = sizeof(struct nf_conn_help),
 385         .align  = __alignof__(struct nf_conn_help),
 386         .id     = NF_CT_EXT_HELPER,
 387 };
 388
 389 int nf_conntrack_helper_init(struct net *net)
 390 {
 391         int err;
 392
 393         net->ct.auto_assign_helper_warned = false;
 394         net->ct.sysctl_auto_assign_helper = nf_ct_auto_assign_helper;
 395
 396         if (net_eq(net, &init_net)) {
 397                 nf_ct_helper_hsize = 1; /* gets rounded up to use one page */
 398                 nf_ct_helper_hash =
 399                         nf_ct_alloc_hashtable(&nf_ct_helper_hsize, 0);
 400                 if (!nf_ct_helper_hash)
 401                         return -ENOMEM;
 402
 403                 err = nf_ct_extend_register(&helper_extend);
 404                 if (err < 0)
 405                         goto err1;
 406         }
 407
 408         err = nf_conntrack_helper_init_sysctl(net);
 409         if (err < 0)
 410                 goto out_sysctl;
 411
 412         return 0;
 413
 414 out_sysctl:
 415         if (net_eq(net, &init_net))
 416                 nf_ct_extend_unregister(&helper_extend);
 417 err1:
 418         nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
 419         return err;
 420 }
 421
 422 void nf_conntrack_helper_fini(struct net *net)
 423 {
 424         nf_conntrack_helper_fini_sysctl(net);
 425         if (net_eq(net, &init_net)) {
 426                 nf_ct_extend_unregister(&helper_extend);
 427                 nf_ct_free_hashtable(nf_ct_helper_hash, nf_ct_helper_hsize);
 428         }
 429 }