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 static unsigned int nf_ct_expect_next_id;
  45
  46 /* nf_conntrack_expect helper functions */
  47 void nf_ct_unlink_expect(struct nf_conntrack_expect *exp)
  48 {
  49         struct nf_conn_help *master_help = nfct_help(exp->master);
  50
  51         NF_CT_ASSERT(master_help);
  52         NF_CT_ASSERT(!timer_pending(&exp->timeout));
  53
  54         hlist_del(&exp->hnode);
  55         nf_ct_expect_count--;
  56
  57         hlist_del(&exp->lnode);
  58         master_help->expecting--;
  59         nf_ct_expect_put(exp);
  60
  61         NF_CT_STAT_INC(expect_delete);
  62 }
  63 EXPORT_SYMBOL_GPL(nf_ct_unlink_expect);
  64
  65 static void nf_ct_expectation_timed_out(unsigned long ul_expect)
  66 {
  67         struct nf_conntrack_expect *exp = (void *)ul_expect;
  68
  69         write_lock_bh(&nf_conntrack_lock);
  70         nf_ct_unlink_expect(exp);
  71         write_unlock_bh(&nf_conntrack_lock);
  72         nf_ct_expect_put(exp);
  73 }
  74
  75 static unsigned int nf_ct_expect_dst_hash(const struct nf_conntrack_tuple *tuple)
  76 {
  77         if (unlikely(!nf_ct_expect_hash_rnd_initted)) {
  78                 get_random_bytes(&nf_ct_expect_hash_rnd, 4);
  79                 nf_ct_expect_hash_rnd_initted = 1;
  80         }
  81
  82         return jhash2(tuple->dst.u3.all, ARRAY_SIZE(tuple->dst.u3.all),
  83                       (((tuple->dst.protonum ^ tuple->src.l3num) << 16) |
  84                        (__force __u16)tuple->dst.u.all) ^ nf_ct_expect_hash_rnd) %
  85                nf_ct_expect_hsize;
  86 }
  87
  88 struct nf_conntrack_expect *
  89 __nf_ct_expect_find(const struct nf_conntrack_tuple *tuple)
  90 {
  91         struct nf_conntrack_expect *i;
  92         struct hlist_node *n;
  93         unsigned int h;
  94
  95         if (!nf_ct_expect_count)
  96                 return NULL;
  97
  98         h = nf_ct_expect_dst_hash(tuple);
  99         hlist_for_each_entry(i, n, &nf_ct_expect_hash[h], hnode) {
 100                 if (nf_ct_tuple_mask_cmp(tuple, &i->tuple, &i->mask))
 101                         return i;
 102         }
 103         return NULL;
 104 }
 105 EXPORT_SYMBOL_GPL(__nf_ct_expect_find);
 106
 107 /* Just find a expectation corresponding to a tuple. */
 108 struct nf_conntrack_expect *
 109 nf_ct_expect_find_get(const struct nf_conntrack_tuple *tuple)
 110 {
 111         struct nf_conntrack_expect *i;
 112
 113         read_lock_bh(&nf_conntrack_lock);
 114         i = __nf_ct_expect_find(tuple);
 115         if (i)
 116                 atomic_inc(&i->use);
 117         read_unlock_bh(&nf_conntrack_lock);
 118
 119         return i;
 120 }
 121 EXPORT_SYMBOL_GPL(nf_ct_expect_find_get);
 122
 123 /* If an expectation for this connection is found, it gets delete from
 124  * global list then returned. */
 125 struct nf_conntrack_expect *
 126 nf_ct_find_expectation(const struct nf_conntrack_tuple *tuple)
 127 {
 128         struct nf_conntrack_expect *exp;
 129
 130         exp = __nf_ct_expect_find(tuple);
 131         if (!exp)
 132                 return NULL;
 133
 134         /* If master is not in hash table yet (ie. packet hasn't left
 135            this machine yet), how can other end know about expected?
 136            Hence these are not the droids you are looking for (if
 137            master ct never got confirmed, we'd hold a reference to it
 138            and weird things would happen to future packets). */
 139         if (!nf_ct_is_confirmed(exp->master))
 140                 return NULL;
 141
 142         if (exp->flags & NF_CT_EXPECT_PERMANENT) {
 143                 atomic_inc(&exp->use);
 144                 return exp;
 145         } else if (del_timer(&exp->timeout)) {
 146                 nf_ct_unlink_expect(exp);
 147                 return exp;
 148         }
 149
 150         return NULL;
 151 }
 152
 153 /* delete all expectations for this conntrack */
 154 void nf_ct_remove_expectations(struct nf_conn *ct)
 155 {
 156         struct nf_conn_help *help = nfct_help(ct);
 157         struct nf_conntrack_expect *exp;
 158         struct hlist_node *n, *next;
 159
 160         /* Optimization: most connection never expect any others. */
 161         if (!help || help->expecting == 0)
 162                 return;
 163
 164         hlist_for_each_entry_safe(exp, n, next, &help->expectations, lnode) {
 165                 if (del_timer(&exp->timeout)) {
 166                         nf_ct_unlink_expect(exp);
 167                         nf_ct_expect_put(exp);
 168                 }
 169         }
 170 }
 171 EXPORT_SYMBOL_GPL(nf_ct_remove_expectations);
 172
 173 /* Would two expected things clash? */
 174 static inline int expect_clash(const struct nf_conntrack_expect *a,
 175                                const struct nf_conntrack_expect *b)
 176 {
 177         /* Part covered by intersection of masks must be unequal,
 178            otherwise they clash */
 179         struct nf_conntrack_tuple_mask intersect_mask;
 180         int count;
 181
 182         intersect_mask.src.u.all = a->mask.src.u.all & b->mask.src.u.all;
 183
 184         for (count = 0; count < NF_CT_TUPLE_L3SIZE; count++){
 185                 intersect_mask.src.u3.all[count] =
 186                         a->mask.src.u3.all[count] & b->mask.src.u3.all[count];
 187         }
 188
 189         return nf_ct_tuple_mask_cmp(&a->tuple, &b->tuple, &intersect_mask);
 190 }
 191
 192 static inline int expect_matches(const struct nf_conntrack_expect *a,
 193                                  const struct nf_conntrack_expect *b)
 194 {
 195         return a->master == b->master
 196                 && nf_ct_tuple_equal(&a->tuple, &b->tuple)
 197                 && nf_ct_tuple_mask_equal(&a->mask, &b->mask);
 198 }
 199
 200 /* Generally a bad idea to call this: could have matched already. */
 201 void nf_ct_unexpect_related(struct nf_conntrack_expect *exp)
 202 {
 203         write_lock_bh(&nf_conntrack_lock);
 204         if (del_timer(&exp->timeout)) {
 205                 nf_ct_unlink_expect(exp);
 206                 nf_ct_expect_put(exp);
 207         }
 208         write_unlock_bh(&nf_conntrack_lock);
 209 }
 210 EXPORT_SYMBOL_GPL(nf_ct_unexpect_related);
 211
 212 /* We don't increase the master conntrack refcount for non-fulfilled
 213  * conntracks. During the conntrack destruction, the expectations are
 214  * always killed before the conntrack itself */
 215 struct nf_conntrack_expect *nf_ct_expect_alloc(struct nf_conn *me)
 216 {
 217         struct nf_conntrack_expect *new;
 218
 219         new = kmem_cache_alloc(nf_ct_expect_cachep, GFP_ATOMIC);
 220         if (!new)
 221                 return NULL;
 222
 223         new->master = me;
 224         atomic_set(&new->use, 1);
 225         return new;
 226 }
 227 EXPORT_SYMBOL_GPL(nf_ct_expect_alloc);
 228
 229 void nf_ct_expect_init(struct nf_conntrack_expect *exp, int family,
 230                        union nf_conntrack_address *saddr,
 231                        union nf_conntrack_address *daddr,
 232                        u_int8_t proto, __be16 *src, __be16 *dst)
 233 {
 234         int len;
 235
 236         if (family == AF_INET)
 237                 len = 4;
 238         else
 239                 len = 16;
 240
 241         exp->flags = 0;
 242         exp->expectfn = NULL;
 243         exp->helper = NULL;
 244         exp->tuple.src.l3num = family;
 245         exp->tuple.dst.protonum = proto;
 246
 247         if (saddr) {
 248                 memcpy(&exp->tuple.src.u3, saddr, len);
 249                 if (sizeof(exp->tuple.src.u3) > len)
 250                         /* address needs to be cleared for nf_ct_tuple_equal */
 251                         memset((void *)&exp->tuple.src.u3 + len, 0x00,
 252                                sizeof(exp->tuple.src.u3) - len);
 253                 memset(&exp->mask.src.u3, 0xFF, len);
 254                 if (sizeof(exp->mask.src.u3) > len)
 255                         memset((void *)&exp->mask.src.u3 + len, 0x00,
 256                                sizeof(exp->mask.src.u3) - len);
 257         } else {
 258                 memset(&exp->tuple.src.u3, 0x00, sizeof(exp->tuple.src.u3));
 259                 memset(&exp->mask.src.u3, 0x00, sizeof(exp->mask.src.u3));
 260         }
 261
 262         if (src) {
 263                 exp->tuple.src.u.all = *src;
 264                 exp->mask.src.u.all = htons(0xFFFF);
 265         } else {
 266                 exp->tuple.src.u.all = 0;
 267                 exp->mask.src.u.all = 0;
 268         }
 269
 270         memcpy(&exp->tuple.dst.u3, daddr, len);
 271         if (sizeof(exp->tuple.dst.u3) > len)
 272                 /* address needs to be cleared for nf_ct_tuple_equal */
 273                 memset((void *)&exp->tuple.dst.u3 + len, 0x00,
 274                        sizeof(exp->tuple.dst.u3) - len);
 275
 276         exp->tuple.dst.u.all = *dst;
 277 }
 278 EXPORT_SYMBOL_GPL(nf_ct_expect_init);
 279
 280 void nf_ct_expect_put(struct nf_conntrack_expect *exp)
 281 {
 282         if (atomic_dec_and_test(&exp->use))
 283                 kmem_cache_free(nf_ct_expect_cachep, exp);
 284 }
 285 EXPORT_SYMBOL_GPL(nf_ct_expect_put);
 286
 287 static void nf_ct_expect_insert(struct nf_conntrack_expect *exp)
 288 {
 289         struct nf_conn_help *master_help = nfct_help(exp->master);
 290         unsigned int h = nf_ct_expect_dst_hash(&exp->tuple);
 291
 292         atomic_inc(&exp->use);
 293
 294         hlist_add_head(&exp->lnode, &master_help->expectations);
 295         master_help->expecting++;
 296
 297         hlist_add_head(&exp->hnode, &nf_ct_expect_hash[h]);
 298         nf_ct_expect_count++;
 299
 300         setup_timer(&exp->timeout, nf_ct_expectation_timed_out,
 301                     (unsigned long)exp);
 302         exp->timeout.expires = jiffies + master_help->helper->timeout * HZ;
 303         add_timer(&exp->timeout);
 304
 305         exp->id = ++nf_ct_expect_next_id;
 306         atomic_inc(&exp->use);
 307         NF_CT_STAT_INC(expect_create);
 308 }
 309
 310 /* Race with expectations being used means we could have none to find; OK. */
 311 static void evict_oldest_expect(struct nf_conn *master)
 312 {
 313         struct nf_conn_help *master_help = nfct_help(master);
 314         struct nf_conntrack_expect *exp = NULL;
 315         struct hlist_node *n;
 316
 317         hlist_for_each_entry(exp, n, &master_help->expectations, lnode)
 318                 ; /* nothing */
 319
 320         if (exp && del_timer(&exp->timeout)) {
 321                 nf_ct_unlink_expect(exp);
 322                 nf_ct_expect_put(exp);
 323         }
 324 }
 325
 326 static inline int refresh_timer(struct nf_conntrack_expect *i)
 327 {
 328         struct nf_conn_help *master_help = nfct_help(i->master);
 329
 330         if (!del_timer(&i->timeout))
 331                 return 0;
 332
 333         i->timeout.expires = jiffies + master_help->helper->timeout*HZ;
 334         add_timer(&i->timeout);
 335         return 1;
 336 }
 337
 338 int nf_ct_expect_related(struct nf_conntrack_expect *expect)
 339 {
 340         struct nf_conntrack_expect *i;
 341         struct nf_conn *master = expect->master;
 342         struct nf_conn_help *master_help = nfct_help(master);
 343         struct hlist_node *n;
 344         unsigned int h;
 345         int ret;
 346
 347         NF_CT_ASSERT(master_help);
 348
 349         write_lock_bh(&nf_conntrack_lock);
 350         if (!master_help->helper) {
 351                 ret = -ESHUTDOWN;
 352                 goto out;
 353         }
 354         h = nf_ct_expect_dst_hash(&expect->tuple);
 355         hlist_for_each_entry(i, n, &nf_ct_expect_hash[h], hnode) {
 356                 if (expect_matches(i, expect)) {
 357                         /* Refresh timer: if it's dying, ignore.. */
 358                         if (refresh_timer(i)) {
 359                                 ret = 0;
 360                                 goto out;
 361                         }
 362                 } else if (expect_clash(i, expect)) {
 363                         ret = -EBUSY;
 364                         goto out;
 365                 }
 366         }
 367         /* Will be over limit? */
 368         if (master_help->helper->max_expected &&
 369             master_help->expecting >= master_help->helper->max_expected)
 370                 evict_oldest_expect(master);
 371
 372         if (nf_ct_expect_count >= nf_ct_expect_max) {
 373                 if (net_ratelimit())
 374                         printk(KERN_WARNING
 375                                "nf_conntrack: expectation table full");
 376                 ret = -EMFILE;
 377                 goto out;
 378         }
 379
 380         nf_ct_expect_insert(expect);
 381         nf_ct_expect_event(IPEXP_NEW, expect);
 382         ret = 0;
 383 out:
 384         write_unlock_bh(&nf_conntrack_lock);
 385         return ret;
 386 }
 387 EXPORT_SYMBOL_GPL(nf_ct_expect_related);
 388
 389 #ifdef CONFIG_PROC_FS
 390 struct ct_expect_iter_state {
 391         unsigned int bucket;
 392 };
 393
 394 static struct hlist_node *ct_expect_get_first(struct seq_file *seq)
 395 {
 396         struct ct_expect_iter_state *st = seq->private;
 397
 398         for (st->bucket = 0; st->bucket < nf_ct_expect_hsize; st->bucket++) {
 399                 if (!hlist_empty(&nf_ct_expect_hash[st->bucket]))
 400                         return nf_ct_expect_hash[st->bucket].first;
 401         }
 402         return NULL;
 403 }
 404
 405 static struct hlist_node *ct_expect_get_next(struct seq_file *seq,
 406                                              struct hlist_node *head)
 407 {
 408         struct ct_expect_iter_state *st = seq->private;
 409
 410         head = head->next;
 411         while (head == NULL) {
 412                 if (++st->bucket >= nf_ct_expect_hsize)
 413                         return NULL;
 414                 head = nf_ct_expect_hash[st->bucket].first;
 415         }
 416         return head;
 417 }
 418
 419 static struct hlist_node *ct_expect_get_idx(struct seq_file *seq, loff_t pos)
 420 {
 421         struct hlist_node *head = ct_expect_get_first(seq);
 422
 423         if (head)
 424                 while (pos && (head = ct_expect_get_next(seq, head)))
 425                         pos--;
 426         return pos ? NULL : head;
 427 }
 428
 429 static void *exp_seq_start(struct seq_file *seq, loff_t *pos)
 430 {
 431         read_lock_bh(&nf_conntrack_lock);
 432         return ct_expect_get_idx(seq, *pos);
 433 }
 434
 435 static void *exp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
 436 {
 437         (*pos)++;
 438         return ct_expect_get_next(seq, v);
 439 }
 440
 441 static void exp_seq_stop(struct seq_file *seq, void *v)
 442 {
 443         read_unlock_bh(&nf_conntrack_lock);
 444 }
 445
 446 static int exp_seq_show(struct seq_file *s, void *v)
 447 {
 448         struct nf_conntrack_expect *expect;
 449         struct hlist_node *n = v;
 450
 451         expect = hlist_entry(n, struct nf_conntrack_expect, hnode);
 452
 453         if (expect->timeout.function)
 454                 seq_printf(s, "%ld ", timer_pending(&expect->timeout)
 455                            ? (long)(expect->timeout.expires - jiffies)/HZ : 0);
 456         else
 457                 seq_printf(s, "- ");
 458         seq_printf(s, "l3proto = %u proto=%u ",
 459                    expect->tuple.src.l3num,
 460                    expect->tuple.dst.protonum);
 461         print_tuple(s, &expect->tuple,
 462                     __nf_ct_l3proto_find(expect->tuple.src.l3num),
 463                     __nf_ct_l4proto_find(expect->tuple.src.l3num,
 464                                        expect->tuple.dst.protonum));
 465         return seq_putc(s, '\n');
 466 }
 467
 468 static const struct seq_operations exp_seq_ops = {
 469         .start = exp_seq_start,
 470         .next = exp_seq_next,
 471         .stop = exp_seq_stop,
 472         .show = exp_seq_show
 473 };
 474
 475 static int exp_open(struct inode *inode, struct file *file)
 476 {
 477         struct seq_file *seq;
 478         struct ct_expect_iter_state *st;
 479         int ret;
 480
 481         st = kzalloc(sizeof(struct ct_expect_iter_state), GFP_KERNEL);
 482         if (!st)
 483                 return -ENOMEM;
 484         ret = seq_open(file, &exp_seq_ops);
 485         if (ret)
 486                 goto out_free;
 487         seq          = file->private_data;
 488         seq->private = st;
 489         return ret;
 490 out_free:
 491         kfree(st);
 492         return ret;
 493 }
 494
 495 static const struct file_operations exp_file_ops = {
 496         .owner   = THIS_MODULE,
 497         .open    = exp_open,
 498         .read    = seq_read,
 499         .llseek  = seq_lseek,
 500         .release = seq_release_private,
 501 };
 502 #endif /* CONFIG_PROC_FS */
 503
 504 static int __init exp_proc_init(void)
 505 {
 506 #ifdef CONFIG_PROC_FS
 507         struct proc_dir_entry *proc;
 508
 509         proc = proc_net_fops_create(&init_net, "nf_conntrack_expect", 0440, &exp_file_ops);
 510         if (!proc)
 511                 return -ENOMEM;
 512 #endif /* CONFIG_PROC_FS */
 513         return 0;
 514 }
 515
 516 static void exp_proc_remove(void)
 517 {
 518 #ifdef CONFIG_PROC_FS
 519         proc_net_remove(&init_net, "nf_conntrack_expect");
 520 #endif /* CONFIG_PROC_FS */
 521 }
 522
 523 module_param_named(expect_hashsize, nf_ct_expect_hsize, uint, 0600);
 524
 525 int __init nf_conntrack_expect_init(void)
 526 {
 527         int err = -ENOMEM;
 528
 529         if (!nf_ct_expect_hsize) {
 530                 nf_ct_expect_hsize = nf_conntrack_htable_size / 256;
 531                 if (!nf_ct_expect_hsize)
 532                         nf_ct_expect_hsize = 1;
 533         }
 534         nf_ct_expect_max = nf_ct_expect_hsize * 4;
 535
 536         nf_ct_expect_hash = nf_ct_alloc_hashtable(&nf_ct_expect_hsize,
 537                                                   &nf_ct_expect_vmalloc);
 538         if (nf_ct_expect_hash == NULL)
 539                 goto err1;
 540
 541         nf_ct_expect_cachep = kmem_cache_create("nf_conntrack_expect",
 542                                         sizeof(struct nf_conntrack_expect),
 543                                         0, 0, NULL);
 544         if (!nf_ct_expect_cachep)
 545                 goto err2;
 546
 547         err = exp_proc_init();
 548         if (err < 0)
 549                 goto err3;
 550
 551         return 0;
 552
 553 err3:
 554         nf_ct_free_hashtable(nf_ct_expect_hash, nf_ct_expect_vmalloc,
 555                              nf_ct_expect_hsize);
 556 err2:
 557         kmem_cache_destroy(nf_ct_expect_cachep);
 558 err1:
 559         return err;
 560 }
 561
 562 void nf_conntrack_expect_fini(void)
 563 {
 564         exp_proc_remove();
 565         kmem_cache_destroy(nf_ct_expect_cachep);
 566         nf_ct_free_hashtable(nf_ct_expect_hash, nf_ct_expect_vmalloc,
 567                              nf_ct_expect_hsize);
 568 }