net/netfilter/nf_conntrack_expect.c

   1 /* Expectation handling for nf_conntrack. */
   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/skbuff.h>
  15 #include <linux/proc_fs.h>
  16 #include <linux/seq_file.h>
  17 #include <linux/stddef.h>
  18 #include <linux/slab.h>
  19 #include <linux/err.h>
  20 #include <linux/percpu.h>
  21 #include <linux/kernel.h>
  22 #include <linux/jhash.h>
  23 #include <net/net_namespace.h>
  24
  25 #include <net/netfilter/nf_conntrack.h>
  26 #include <net/netfilter/nf_conntrack_core.h>
  27 #include <net/netfilter/nf_conntrack_expect.h>
  28 #include <net/netfilter/nf_conntrack_helper.h>
  29 #include <net/netfilter/nf_conntrack_tuple.h>
  30
  31 struct hlist_head *nf_ct_expect_hash __read_mostly;
  32 EXPORT_SYMBOL_GPL(nf_ct_expect_hash);
  33
  34 unsigned int nf_ct_expect_hsize __read_mostly;
  35 EXPORT_SYMBOL_GPL(nf_ct_expect_hsize);
  36
  37 static unsigned int nf_ct_expect_hash_rnd __read_mostly;
  38 static unsigned int nf_ct_expect_count;
  39 unsigned int nf_ct_expect_max __read_mostly;
  40 static int nf_ct_expect_hash_rnd_initted __read_mostly;
  41 static int nf_ct_expect_vmalloc;
  42
  43 static struct kmem_cache *nf_ct_expect_cachep __read_mostly;
  44
  45 /* nf_conntrack_expect helper functions */
  46 void nf_ct_unlink_expect(struct nf_conntrack_expect *exp)
  47 {
  48         struct nf_conn_help *master_help = nfct_help(exp->master);
  49
  50         NF_CT_ASSERT(master_help);
  51         NF_CT_ASSERT(!timer_pending(&exp->timeout));
  52
  53         hlist_del(&exp->hnode);
  54         nf_ct_expect_count--;
  55
  56         hlist_del(&exp->lnode);
  57         master_help->expecting--;
  58         nf_ct_expect_put(exp);
  59
  60         NF_CT_STAT_INC(expect_delete);
  61 }
  62 EXPORT_SYMBOL_GPL(nf_ct_unlink_expect);
  63
  64 static void nf_ct_expectation_timed_out(unsigned long ul_expect)
  65 {
  66         struct nf_conntrack_expect *exp = (void *)ul_expect;
  67
  68         write_lock_bh(&nf_conntrack_lock);
  69         nf_ct_unlink_expect(exp);
  70         write_unlock_bh(&nf_conntrack_lock);
  71         nf_ct_expect_put(exp);
  72 }
  73
  74 static unsigned int nf_ct_expect_dst_hash(const struct nf_conntrack_tuple *tuple)
  75 {
  76         if (unlikely(!nf_ct_expect_hash_rnd_initted)) {
  77                 get_random_bytes(&nf_ct_expect_hash_rnd, 4);
  78                 nf_ct_expect_hash_rnd_initted = 1;
  79         }
  80
  81         return jhash2(tuple->dst.u3.all, ARRAY_SIZE(tuple->dst.u3.all),
  82                       (((tuple->dst.protonum ^ tuple->src.l3num) << 16) |
  83                        (__force __u16)tuple->dst.u.all) ^ nf_ct_expect_hash_rnd) %
  84                nf_ct_expect_hsize;
  85 }
  86
  87 struct nf_conntrack_expect *
  88 __nf_ct_expect_find(const struct nf_conntrack_tuple *tuple)
  89 {
  90         struct nf_conntrack_expect *i;
  91         struct hlist_node *n;
  92         unsigned int h;
  93
  94         if (!nf_ct_expect_count)
  95                 return NULL;
  96
  97         h = nf_ct_expect_dst_hash(tuple);
  98         hlist_for_each_entry(i, n, &nf_ct_expect_hash[h], hnode) {
  99                 if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask))
 100                         return i;
 101         }
 102         return NULL;
 103 }
 104 EXPORT_SYMBOL_GPL(__nf_ct_expect_find);
 105
 106 /* Just find a expectation corresponding to a tuple. */
 107 struct nf_conntrack_expect *
 108 nf_ct_expect_find_get(const struct nf_conntrack_tuple *tuple)
 109 {
 110         struct nf_conntrack_expect *i;
 111
 112         read_lock_bh(&nf_conntrack_lock);
 113         i = __nf_ct_expect_find(tuple);
 114         if (i)
 115                 atomic_inc(&i->use);
 116         read_unlock_bh(&nf_conntrack_lock);
 117
 118         return i;
 119 }
 120 EXPORT_SYMBOL_GPL(nf_ct_expect_find_get);
 121
 122 /* If an expectation for this connection is found, it gets delete from
 123  * global list then returned. */
 124 struct nf_conntrack_expect *
 125 nf_ct_find_expectation(const struct nf_conntrack_tuple *tuple)
 126 {
 127         struct nf_conntrack_expect *exp;
 128
 129         exp = __nf_ct_expect_find(tuple);
 130         if (!exp)
 131                 return NULL;
 132
 133         /* If master is not in hash table yet (ie. packet hasn't left
 134            this machine yet), how can other end know about expected?
 135            Hence these are not the droids you are looking for (if
 136            master ct never got confirmed, we'd hold a reference to it
 137            and weird things would happen to future packets). */
 138         if (!nf_ct_is_confirmed(exp->master))
 139                 return NULL;
 140
 141         if (exp->flags & NF_CT_EXPECT_PERMANENT) {
 142                 atomic_inc(&exp->use);
 143                 return exp;
 144         } else if (del_timer(&exp->timeout)) {
 145                 nf_ct_unlink_expect(exp);
 146                 return exp;
 147         }
 148
 149         return NULL;
 150 }
 151
 152 /* delete all expectations for this conntrack */
 153 void nf_ct_remove_expectations(struct nf_conn *ct)
 154 {
 155         struct nf_conn_help *help = nfct_help(ct);
 156         struct nf_conntrack_expect *exp;
 157         struct hlist_node *n, *next;
 158
 159         /* Optimization: most connection never expect any others. */
 160         if (!help || help->expecting == 0)
 161                 return;
 162
 163         hlist_for_each_entry_safe(exp, n, next, &help->expectations, lnode) {
 164                 if (del_timer(&exp->timeout)) {
 165                         nf_ct_unlink_expect(exp);
 166                         nf_ct_expect_put(exp);
 167                 }
 168         }
 169 }
 170 EXPORT_SYMBOL_GPL(nf_ct_remove_expectations);
 171
 172 /* Would two expected things clash? */
 173 static inline int expect_clash(const struct nf_conntrack_expect *a,
 174                                const struct nf_conntrack_expect *b)
 175 {
 176         /* Part covered by intersection of masks must be unequal,
 177            otherwise they clash */
 178         struct nf_conntrack_tuple_mask intersect_mask;
 179         int count;
 180
 181         intersect_mask.src.u.all = a->mask.src.u.all & b->mask.src.u.all;
 182
 183         for (count = 0; count < NF_CT_TUPLE_L3SIZE; count++){
 184                 intersect_mask.src.u3.all[count] =
 185                         a->mask.src.u3.all[count] & b->mask.src.u3.all[count];
 186         }
 187
 188         return nf_ct_tuple_mask_cmp(&a->tuple, &b->tuple, &intersect_mask);
 189 }
 190
 191 static inline int expect_matches(const struct nf_conntrack_expect *a,
 192                                  const struct nf_conntrack_expect *b)
 193 {
 194         return a->master == b->master
 195                 && nf_ct_tuple_equal(&a->tuple, &b->tuple)
 196                 && nf_ct_tuple_mask_equal(&a->mask, &b->mask);
 197 }
 198
 199 /* Generally a bad idea to call this: could have matched already. */
 200 void nf_ct_unexpect_related(struct nf_conntrack_expect *exp)
 201 {
 202         write_lock_bh(&nf_conntrack_lock);
 203         if (del_timer(&exp->timeout)) {
 204                 nf_ct_unlink_expect(exp);
 205                 nf_ct_expect_put(exp);
 206         }
 207         write_unlock_bh(&nf_conntrack_lock);
 208 }
 209 EXPORT_SYMBOL_GPL(nf_ct_unexpect_related);
 210
 211 /* We don't increase the master conntrack refcount for non-fulfilled
 212  * conntracks. During the conntrack destruction, the expectations are
 213  * always killed before the conntrack itself */
 214 struct nf_conntrack_expect *nf_ct_expect_alloc(struct nf_conn *me)
 215 {
 216         struct nf_conntrack_expect *new;
 217
 218         new = kmem_cache_alloc(nf_ct_expect_cachep, GFP_ATOMIC);
 219         if (!new)
 220                 return NULL;
 221
 222         new->master = me;
 223         atomic_set(&new->use, 1);
 224         return new;
 225 }
 226 EXPORT_SYMBOL_GPL(nf_ct_expect_alloc);
 227
 228 void nf_ct_expect_init(struct nf_conntrack_expect *exp, int family,
 229                        union nf_conntrack_address *saddr,
 230                        union nf_conntrack_address *daddr,
 231                        u_int8_t proto, __be16 *src, __be16 *dst)
 232 {
 233         int len;
 234
 235         if (family == AF_INET)
 236                 len = 4;
 237         else
 238                 len = 16;
 239
 240         exp->flags = 0;
 241         exp->expectfn = NULL;
 242         exp->helper = NULL;
 243         exp->tuple.src.l3num = family;
 244         exp->tuple.dst.protonum = proto;
 245
 246         if (saddr) {
 247                 memcpy(&exp->tuple.src.u3, saddr, len);
 248                 if (sizeof(exp->tuple.src.u3) > len)
 249                         /* address needs to be cleared for nf_ct_tuple_equal */
 250                         memset((void *)&exp->tuple.src.u3 + len, 0x00,
 251                                sizeof(exp->tuple.src.u3) - len);
 252                 memset(&exp->mask.src.u3, 0xFF, len);
 253                 if (sizeof(exp->mask.src.u3) > len)
 254                         memset((void *)&exp->mask.src.u3 + len, 0x00,
 255                                sizeof(exp->mask.src.u3) - len);
 256         } else {
 257                 memset(&exp->tuple.src.u3, 0x00, sizeof(exp->tuple.src.u3));
 258                 memset(&exp->mask.src.u3, 0x00, sizeof(exp->mask.src.u3));
 259         }
 260
 261         if (src) {
 262                 exp->tuple.src.u.all = *src;
 263                 exp->mask.src.u.all = htons(0xFFFF);
 264         } else {
 265                 exp->tuple.src.u.all = 0;
 266                 exp->mask.src.u.all = 0;
 267         }
 268
 269         memcpy(&exp->tuple.dst.u3, daddr, len);
 270         if (sizeof(exp->tuple.dst.u3) > len)
 271                 /* address needs to be cleared for nf_ct_tuple_equal */
 272                 memset((void *)&exp->tuple.dst.u3 + len, 0x00,
 273                        sizeof(exp->tuple.dst.u3) - len);
 274
 275         exp->tuple.dst.u.all = *dst;
 276 }
 277 EXPORT_SYMBOL_GPL(nf_ct_expect_init);
 278
 279 void nf_ct_expect_put(struct nf_conntrack_expect *exp)
 280 {
 281         if (atomic_dec_and_test(&exp->use))
 282                 kmem_cache_free(nf_ct_expect_cachep, exp);
 283 }
 284 EXPORT_SYMBOL_GPL(nf_ct_expect_put);
 285
 286 static void nf_ct_expect_insert(struct nf_conntrack_expect *exp)
 287 {
 288         struct nf_conn_help *master_help = nfct_help(exp->master);
 289         unsigned int h = nf_ct_expect_dst_hash(&exp->tuple);
 290
 291         atomic_inc(&exp->use);
 292
 293         hlist_add_head(&exp->lnode, &master_help->expectations);
 294         master_help->expecting++;
 295
 296         hlist_add_head(&exp->hnode, &nf_ct_expect_hash[h]);
 297         nf_ct_expect_count++;
 298
 299         setup_timer(&exp->timeout, nf_ct_expectation_timed_out,
 300                     (unsigned long)exp);
 301         exp->timeout.expires = jiffies + master_help->helper->timeout * HZ;
 302         add_timer(&exp->timeout);
 303
 304         atomic_inc(&exp->use);
 305         NF_CT_STAT_INC(expect_create);
 306 }
 307
 308 /* Race with expectations being used means we could have none to find; OK. */
 309 static void evict_oldest_expect(struct nf_conn *master)
 310 {
 311         struct nf_conn_help *master_help = nfct_help(master);
 312         struct nf_conntrack_expect *exp = NULL;
 313         struct hlist_node *n;
 314
 315         hlist_for_each_entry(exp, n, &master_help->expectations, lnode)
 316                 ; /* nothing */
 317
 318         if (exp && del_timer(&exp->timeout)) {
 319                 nf_ct_unlink_expect(exp);
 320                 nf_ct_expect_put(exp);
 321         }
 322 }
 323
 324 static inline int refresh_timer(struct nf_conntrack_expect *i)
 325 {
 326         struct nf_conn_help *master_help = nfct_help(i->master);
 327
 328         if (!del_timer(&i->timeout))
 329                 return 0;
 330
 331         i->timeout.expires = jiffies + master_help->helper->timeout*HZ;
 332         add_timer(&i->timeout);
 333         return 1;
 334 }
 335
 336 int nf_ct_expect_related(struct nf_conntrack_expect *expect)
 337 {
 338         struct nf_conntrack_expect *i;
 339         struct nf_conn *master = expect->master;
 340         struct nf_conn_help *master_help = nfct_help(master);
 341         struct hlist_node *n;
 342         unsigned int h;
 343         int ret;
 344
 345         NF_CT_ASSERT(master_help);
 346
 347         write_lock_bh(&nf_conntrack_lock);
 348         if (!master_help->helper) {
 349                 ret = -ESHUTDOWN;
 350                 goto out;
 351         }
 352         h = nf_ct_expect_dst_hash(&expect->tuple);
 353         hlist_for_each_entry(i, n, &nf_ct_expect_hash[h], hnode) {
 354                 if (expect_matches(i, expect)) {
 355                         /* Refresh timer: if it's dying, ignore.. */
 356                         if (refresh_timer(i)) {
 357                                 ret = 0;
 358                                 goto out;
 359                         }
 360                 } else if (expect_clash(i, expect)) {
 361                         ret = -EBUSY;
 362                         goto out;
 363                 }
 364         }
 365         /* Will be over limit? */
 366         if (master_help->helper->max_expected &&
 367             master_help->expecting >= master_help->helper->max_expected)
 368                 evict_oldest_expect(master);
 369
 370         if (nf_ct_expect_count >= nf_ct_expect_max) {
 371                 if (net_ratelimit())
 372                         printk(KERN_WARNING
 373                                "nf_conntrack: expectation table full");
 374                 ret = -EMFILE;
 375                 goto out;
 376         }
 377
 378         nf_ct_expect_insert(expect);
 379         nf_ct_expect_event(IPEXP_NEW, expect);
 380         ret = 0;
 381 out:
 382         write_unlock_bh(&nf_conntrack_lock);
 383         return ret;
 384 }
 385 EXPORT_SYMBOL_GPL(nf_ct_expect_related);
 386
 387 #ifdef CONFIG_PROC_FS
 388 struct ct_expect_iter_state {
 389         unsigned int bucket;
 390 };
 391
 392 static struct hlist_node *ct_expect_get_first(struct seq_file *seq)
 393 {
 394         struct ct_expect_iter_state *st = seq->private;
 395
 396         for (st->bucket = 0; st->bucket < nf_ct_expect_hsize; st->bucket++) {
 397                 if (!hlist_empty(&nf_ct_expect_hash[st->bucket]))
 398                         return nf_ct_expect_hash[st->bucket].first;
 399         }
 400         return NULL;
 401 }
 402
 403 static struct hlist_node *ct_expect_get_next(struct seq_file *seq,
 404                                              struct hlist_node *head)
 405 {
 406         struct ct_expect_iter_state *st = seq->private;
 407
 408         head = head->next;
 409         while (head == NULL) {
 410                 if (++st->bucket >= nf_ct_expect_hsize)
 411                         return NULL;
 412                 head = nf_ct_expect_hash[st->bucket].first;
 413         }
 414         return head;
 415 }
 416
 417 static struct hlist_node *ct_expect_get_idx(struct seq_file *seq, loff_t pos)
 418 {
 419         struct hlist_node *head = ct_expect_get_first(seq);
 420
 421         if (head)
 422                 while (pos && (head = ct_expect_get_next(seq, head)))
 423                         pos--;
 424         return pos ? NULL : head;
 425 }
 426
 427 static void *exp_seq_start(struct seq_file *seq, loff_t *pos)
 428 {
 429         read_lock_bh(&nf_conntrack_lock);
 430         return ct_expect_get_idx(seq, *pos);
 431 }
 432
 433 static void *exp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 434 {
 435         (*pos)++;
 436         return ct_expect_get_next(seq, v);
 437 }
 438
 439 static void exp_seq_stop(struct seq_file *seq, void *v)
 440 {
 441         read_unlock_bh(&nf_conntrack_lock);
 442 }
 443
 444 static int exp_seq_show(struct seq_file *s, void *v)
 445 {
 446         struct nf_conntrack_expect *expect;
 447         struct hlist_node *n = v;
 448
 449         expect = hlist_entry(n, struct nf_conntrack_expect, hnode);
 450
 451         if (expect->timeout.function)
 452                 seq_printf(s, "%ld ", timer_pending(&expect->timeout)
 453                            ? (long)(expect->timeout.expires - jiffies)/HZ : 0);
 454         else
 455                 seq_printf(s, "- ");
 456         seq_printf(s, "l3proto = %u proto=%u ",
 457                    expect->tuple.src.l3num,
 458                    expect->tuple.dst.protonum);
 459         print_tuple(s, &expect->tuple,
 460                     __nf_ct_l3proto_find(expect->tuple.src.l3num),
 461                     __nf_ct_l4proto_find(expect->tuple.src.l3num,
 462                                        expect->tuple.dst.protonum));
 463         return seq_putc(s, '\n');
 464 }
 465
 466 static const struct seq_operations exp_seq_ops = {
 467         .start = exp_seq_start,
 468         .next = exp_seq_next,
 469         .stop = exp_seq_stop,
 470         .show = exp_seq_show
 471 };
 472
 473 static int exp_open(struct inode *inode, struct file *file)
 474 {
 475         return seq_open_private(file, &exp_seq_ops,
 476                         sizeof(struct ct_expect_iter_state));
 477 }
 478
 479 static const struct file_operations exp_file_ops = {
 480         .owner   = THIS_MODULE,
 481         .open    = exp_open,
 482         .read    = seq_read,
 483         .llseek  = seq_lseek,
 484         .release = seq_release_private,
 485 };
 486 #endif /* CONFIG_PROC_FS */
 487
 488 static int __init exp_proc_init(void)
 489 {
 490 #ifdef CONFIG_PROC_FS
 491         struct proc_dir_entry *proc;
 492
 493         proc = proc_net_fops_create(&init_net, "nf_conntrack_expect", 0440, &exp_file_ops);
 494         if (!proc)
 495                 return -ENOMEM;
 496 #endif /* CONFIG_PROC_FS */
 497         return 0;
 498 }
 499
 500 static void exp_proc_remove(void)
 501 {
 502 #ifdef CONFIG_PROC_FS
 503         proc_net_remove(&init_net, "nf_conntrack_expect");
 504 #endif /* CONFIG_PROC_FS */
 505 }
 506
 507 module_param_named(expect_hashsize, nf_ct_expect_hsize, uint, 0600);
 508
 509 int __init nf_conntrack_expect_init(void)
 510 {
 511         int err = -ENOMEM;
 512
 513         if (!nf_ct_expect_hsize) {
 514                 nf_ct_expect_hsize = nf_conntrack_htable_size / 256;
 515                 if (!nf_ct_expect_hsize)
 516                         nf_ct_expect_hsize = 1;
 517         }
 518         nf_ct_expect_max = nf_ct_expect_hsize * 4;
 519
 520         nf_ct_expect_hash = nf_ct_alloc_hashtable(&nf_ct_expect_hsize,
 521                                                   &nf_ct_expect_vmalloc);
 522         if (nf_ct_expect_hash == NULL)
 523                 goto err1;
 524
 525         nf_ct_expect_cachep = kmem_cache_create("nf_conntrack_expect",
 526                                         sizeof(struct nf_conntrack_expect),
 527                                         0, 0, NULL);
 528         if (!nf_ct_expect_cachep)
 529                 goto err2;
 530
 531         err = exp_proc_init();
 532         if (err < 0)
 533                 goto err3;
 534
 535         return 0;
 536
 537 err3:
 538         nf_ct_free_hashtable(nf_ct_expect_hash, nf_ct_expect_vmalloc,
 539                              nf_ct_expect_hsize);
 540 err2:
 541         kmem_cache_destroy(nf_ct_expect_cachep);
 542 err1:
 543         return err;
 544 }
 545
 546 void nf_conntrack_expect_fini(void)
 547 {
 548         exp_proc_remove();
 549         kmem_cache_destroy(nf_ct_expect_cachep);
 550         nf_ct_free_hashtable(nf_ct_expect_hash, nf_ct_expect_vmalloc,
 551                              nf_ct_expect_hsize);
 552 }