net/ipv4/inet_hashtables.c

   1 /*
   2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
   3  *              operating system.  INET is implemented using the BSD Socket
   4  *              interface as the means of communication with the user level.
   5  *
   6  *              Generic INET transport hashtables
   7  *
   8  * Authors:     Lotsa people, from code originally in tcp
   9  *
  10  *      This program is free software; you can redistribute it and/or
  11  *      modify it under the terms of the GNU General Public License
  12  *      as published by the Free Software Foundation; either version
  13  *      2 of the License, or (at your option) any later version.
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/random.h>
  18 #include <linux/sched.h>
  19 #include <linux/slab.h>
  20 #include <linux/wait.h>
  21
  22 #include <net/inet_connection_sock.h>
  23 #include <net/inet_hashtables.h>
  24 #include <net/ip.h>
  25
  26 /*
  27  * Allocate and initialize a new local port bind bucket.
  28  * The bindhash mutex for snum's hash chain must be held here.
  29  */
  30 struct inet_bind_bucket *inet_bind_bucket_create(struct kmem_cache *cachep,
  31                                                  struct net *net,
  32                                                  struct inet_bind_hashbucket *head,
  33                                                  const unsigned short snum)
  34 {
  35         struct inet_bind_bucket *tb = kmem_cache_alloc(cachep, GFP_ATOMIC);
  36
  37         if (tb != NULL) {
  38                 tb->ib_net       = net;
  39                 tb->port      = snum;
  40                 tb->fastreuse = 0;
  41                 INIT_HLIST_HEAD(&tb->owners);
  42                 hlist_add_head(&tb->node, &head->chain);
  43         }
  44         return tb;
  45 }
  46
  47 /*
  48  * Caller must hold hashbucket lock for this tb with local BH disabled
  49  */
  50 void inet_bind_bucket_destroy(struct kmem_cache *cachep, struct inet_bind_bucket *tb)
  51 {
  52         if (hlist_empty(&tb->owners)) {
  53                 __hlist_del(&tb->node);
  54                 kmem_cache_free(cachep, tb);
  55         }
  56 }
  57
  58 void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
  59                     const unsigned short snum)
  60 {
  61         inet_sk(sk)->num = snum;
  62         sk_add_bind_node(sk, &tb->owners);
  63         inet_csk(sk)->icsk_bind_hash = tb;
  64 }
  65
  66 /*
  67  * Get rid of any references to a local port held by the given sock.
  68  */
  69 static void __inet_put_port(struct sock *sk)
  70 {
  71         struct inet_hashinfo *hashinfo = sk->sk_prot->hashinfo;
  72         const int bhash = inet_bhashfn(inet_sk(sk)->num, hashinfo->bhash_size);
  73         struct inet_bind_hashbucket *head = &hashinfo->bhash[bhash];
  74         struct inet_bind_bucket *tb;
  75
  76         spin_lock(&head->lock);
  77         tb = inet_csk(sk)->icsk_bind_hash;
  78         __sk_del_bind_node(sk);
  79         inet_csk(sk)->icsk_bind_hash = NULL;
  80         inet_sk(sk)->num = 0;
  81         inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
  82         spin_unlock(&head->lock);
  83 }
  84
  85 void inet_put_port(struct sock *sk)
  86 {
  87         local_bh_disable();
  88         __inet_put_port(sk);
  89         local_bh_enable();
  90 }
  91
  92 EXPORT_SYMBOL(inet_put_port);
  93
  94 /*
  95  * This lock without WQ_FLAG_EXCLUSIVE is good on UP and it can be very bad on SMP.
  96  * Look, when several writers sleep and reader wakes them up, all but one
  97  * immediately hit write lock and grab all the cpus. Exclusive sleep solves
  98  * this, _but_ remember, it adds useless work on UP machines (wake up each
  99  * exclusive lock release). It should be ifdefed really.
 100  */
 101 void inet_listen_wlock(struct inet_hashinfo *hashinfo)
 102         __acquires(hashinfo->lhash_lock)
 103 {
 104         write_lock(&hashinfo->lhash_lock);
 105
 106         if (atomic_read(&hashinfo->lhash_users)) {
 107                 DEFINE_WAIT(wait);
 108
 109                 for (;;) {
 110                         prepare_to_wait_exclusive(&hashinfo->lhash_wait,
 111                                                   &wait, TASK_UNINTERRUPTIBLE);
 112                         if (!atomic_read(&hashinfo->lhash_users))
 113                                 break;
 114                         write_unlock_bh(&hashinfo->lhash_lock);
 115                         schedule();
 116                         write_lock_bh(&hashinfo->lhash_lock);
 117                 }
 118
 119                 finish_wait(&hashinfo->lhash_wait, &wait);
 120         }
 121 }
 122
 123 /*
 124  * Don't inline this cruft. Here are some nice properties to exploit here. The
 125  * BSD API does not allow a listening sock to specify the remote port nor the
 126  * remote address for the connection. So always assume those are both
 127  * wildcarded during the search since they can never be otherwise.
 128  */
 129 static struct sock *inet_lookup_listener_slow(struct net *net,
 130                                               const struct hlist_head *head,
 131                                               const __be32 daddr,
 132                                               const unsigned short hnum,
 133                                               const int dif)
 134 {
 135         struct sock *result = NULL, *sk;
 136         const struct hlist_node *node;
 137         int hiscore = -1;
 138
 139         sk_for_each(sk, node, head) {
 140                 const struct inet_sock *inet = inet_sk(sk);
 141
 142                 if (sk->sk_net == net && inet->num == hnum &&
 143                                 !ipv6_only_sock(sk)) {
 144                         const __be32 rcv_saddr = inet->rcv_saddr;
 145                         int score = sk->sk_family == PF_INET ? 1 : 0;
 146
 147                         if (rcv_saddr) {
 148                                 if (rcv_saddr != daddr)
 149                                         continue;
 150                                 score += 2;
 151                         }
 152                         if (sk->sk_bound_dev_if) {
 153                                 if (sk->sk_bound_dev_if != dif)
 154                                         continue;
 155                                 score += 2;
 156                         }
 157                         if (score == 5)
 158                                 return sk;
 159                         if (score > hiscore) {
 160                                 hiscore = score;
 161                                 result  = sk;
 162                         }
 163                 }
 164         }
 165         return result;
 166 }
 167
 168 /* Optimize the common listener case. */
 169 struct sock *__inet_lookup_listener(struct net *net,
 170                                     struct inet_hashinfo *hashinfo,
 171                                     const __be32 daddr, const unsigned short hnum,
 172                                     const int dif)
 173 {
 174         struct sock *sk = NULL;
 175         const struct hlist_head *head;
 176
 177         read_lock(&hashinfo->lhash_lock);
 178         head = &hashinfo->listening_hash[inet_lhashfn(hnum)];
 179         if (!hlist_empty(head)) {
 180                 const struct inet_sock *inet = inet_sk((sk = __sk_head(head)));
 181
 182                 if (inet->num == hnum && !sk->sk_node.next &&
 183                     (!inet->rcv_saddr || inet->rcv_saddr == daddr) &&
 184                     (sk->sk_family == PF_INET || !ipv6_only_sock(sk)) &&
 185                     !sk->sk_bound_dev_if && sk->sk_net == net)
 186                         goto sherry_cache;
 187                 sk = inet_lookup_listener_slow(net, head, daddr, hnum, dif);
 188         }
 189         if (sk) {
 190 sherry_cache:
 191                 sock_hold(sk);
 192         }
 193         read_unlock(&hashinfo->lhash_lock);
 194         return sk;
 195 }
 196 EXPORT_SYMBOL_GPL(__inet_lookup_listener);
 197
 198 struct sock * __inet_lookup_established(struct net *net,
 199                                   struct inet_hashinfo *hashinfo,
 200                                   const __be32 saddr, const __be16 sport,
 201                                   const __be32 daddr, const u16 hnum,
 202                                   const int dif)
 203 {
 204         INET_ADDR_COOKIE(acookie, saddr, daddr)
 205         const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
 206         struct sock *sk;
 207         const struct hlist_node *node;
 208         /* Optimize here for direct hit, only listening connections can
 209          * have wildcards anyways.
 210          */
 211         unsigned int hash = inet_ehashfn(daddr, hnum, saddr, sport);
 212         struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash);
 213         rwlock_t *lock = inet_ehash_lockp(hashinfo, hash);
 214
 215         prefetch(head->chain.first);
 216         read_lock(lock);
 217         sk_for_each(sk, node, &head->chain) {
 218                 if (INET_MATCH(sk, net, hash, acookie,
 219                                         saddr, daddr, ports, dif))
 220                         goto hit; /* You sunk my battleship! */
 221         }
 222
 223         /* Must check for a TIME_WAIT'er before going to listener hash. */
 224         sk_for_each(sk, node, &head->twchain) {
 225                 if (INET_TW_MATCH(sk, net, hash, acookie,
 226                                         saddr, daddr, ports, dif))
 227                         goto hit;
 228         }
 229         sk = NULL;
 230 out:
 231         read_unlock(lock);
 232         return sk;
 233 hit:
 234         sock_hold(sk);
 235         goto out;
 236 }
 237 EXPORT_SYMBOL_GPL(__inet_lookup_established);
 238
 239 /* called with local bh disabled */
 240 static int __inet_check_established(struct inet_timewait_death_row *death_row,
 241                                     struct sock *sk, __u16 lport,
 242                                     struct inet_timewait_sock **twp)
 243 {
 244         struct inet_hashinfo *hinfo = death_row->hashinfo;
 245         struct inet_sock *inet = inet_sk(sk);
 246         __be32 daddr = inet->rcv_saddr;
 247         __be32 saddr = inet->daddr;
 248         int dif = sk->sk_bound_dev_if;
 249         INET_ADDR_COOKIE(acookie, saddr, daddr)
 250         const __portpair ports = INET_COMBINED_PORTS(inet->dport, lport);
 251         unsigned int hash = inet_ehashfn(daddr, lport, saddr, inet->dport);
 252         struct inet_ehash_bucket *head = inet_ehash_bucket(hinfo, hash);
 253         rwlock_t *lock = inet_ehash_lockp(hinfo, hash);
 254         struct sock *sk2;
 255         const struct hlist_node *node;
 256         struct inet_timewait_sock *tw;
 257         struct net *net = sk->sk_net;
 258
 259         prefetch(head->chain.first);
 260         write_lock(lock);
 261
 262         /* Check TIME-WAIT sockets first. */
 263         sk_for_each(sk2, node, &head->twchain) {
 264                 tw = inet_twsk(sk2);
 265
 266                 if (INET_TW_MATCH(sk2, net, hash, acookie,
 267                                         saddr, daddr, ports, dif)) {
 268                         if (twsk_unique(sk, sk2, twp))
 269                                 goto unique;
 270                         else
 271                                 goto not_unique;
 272                 }
 273         }
 274         tw = NULL;
 275
 276         /* And established part... */
 277         sk_for_each(sk2, node, &head->chain) {
 278                 if (INET_MATCH(sk2, net, hash, acookie,
 279                                         saddr, daddr, ports, dif))
 280                         goto not_unique;
 281         }
 282
 283 unique:
 284         /* Must record num and sport now. Otherwise we will see
 285          * in hash table socket with a funny identity. */
 286         inet->num = lport;
 287         inet->sport = htons(lport);
 288         sk->sk_hash = hash;
 289         BUG_TRAP(sk_unhashed(sk));
 290         __sk_add_node(sk, &head->chain);
 291         sock_prot_inuse_add(sk->sk_prot, 1);
 292         write_unlock(lock);
 293
 294         if (twp) {
 295                 *twp = tw;
 296                 NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);
 297         } else if (tw) {
 298                 /* Silly. Should hash-dance instead... */
 299                 inet_twsk_deschedule(tw, death_row);
 300                 NET_INC_STATS_BH(LINUX_MIB_TIMEWAITRECYCLED);
 301
 302                 inet_twsk_put(tw);
 303         }
 304
 305         return 0;
 306
 307 not_unique:
 308         write_unlock(lock);
 309         return -EADDRNOTAVAIL;
 310 }
 311
 312 static inline u32 inet_sk_port_offset(const struct sock *sk)
 313 {
 314         const struct inet_sock *inet = inet_sk(sk);
 315         return secure_ipv4_port_ephemeral(inet->rcv_saddr, inet->daddr,
 316                                           inet->dport);
 317 }
 318
 319 void __inet_hash_nolisten(struct sock *sk)
 320 {
 321         struct inet_hashinfo *hashinfo = sk->sk_prot->hashinfo;
 322         struct hlist_head *list;
 323         rwlock_t *lock;
 324         struct inet_ehash_bucket *head;
 325
 326         BUG_TRAP(sk_unhashed(sk));
 327
 328         sk->sk_hash = inet_sk_ehashfn(sk);
 329         head = inet_ehash_bucket(hashinfo, sk->sk_hash);
 330         list = &head->chain;
 331         lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
 332
 333         write_lock(lock);
 334         __sk_add_node(sk, list);
 335         sock_prot_inuse_add(sk->sk_prot, 1);
 336         write_unlock(lock);
 337 }
 338 EXPORT_SYMBOL_GPL(__inet_hash_nolisten);
 339
 340 static void __inet_hash(struct sock *sk)
 341 {
 342         struct inet_hashinfo *hashinfo = sk->sk_prot->hashinfo;
 343         struct hlist_head *list;
 344         rwlock_t *lock;
 345
 346         if (sk->sk_state != TCP_LISTEN) {
 347                 __inet_hash_nolisten(sk);
 348                 return;
 349         }
 350
 351         BUG_TRAP(sk_unhashed(sk));
 352         list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
 353         lock = &hashinfo->lhash_lock;
 354
 355         inet_listen_wlock(hashinfo);
 356         __sk_add_node(sk, list);
 357         sock_prot_inuse_add(sk->sk_prot, 1);
 358         write_unlock(lock);
 359         wake_up(&hashinfo->lhash_wait);
 360 }
 361
 362 void inet_hash(struct sock *sk)
 363 {
 364         if (sk->sk_state != TCP_CLOSE) {
 365                 local_bh_disable();
 366                 __inet_hash(sk);
 367                 local_bh_enable();
 368         }
 369 }
 370 EXPORT_SYMBOL_GPL(inet_hash);
 371
 372 void inet_unhash(struct sock *sk)
 373 {
 374         rwlock_t *lock;
 375         struct inet_hashinfo *hashinfo = sk->sk_prot->hashinfo;
 376
 377         if (sk_unhashed(sk))
 378                 goto out;
 379
 380         if (sk->sk_state == TCP_LISTEN) {
 381                 local_bh_disable();
 382                 inet_listen_wlock(hashinfo);
 383                 lock = &hashinfo->lhash_lock;
 384         } else {
 385                 lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
 386                 write_lock_bh(lock);
 387         }
 388
 389         if (__sk_del_node_init(sk))
 390                 sock_prot_inuse_add(sk->sk_prot, -1);
 391         write_unlock_bh(lock);
 392 out:
 393         if (sk->sk_state == TCP_LISTEN)
 394                 wake_up(&hashinfo->lhash_wait);
 395 }
 396 EXPORT_SYMBOL_GPL(inet_unhash);
 397
 398 int __inet_hash_connect(struct inet_timewait_death_row *death_row,
 399                 struct sock *sk, u32 port_offset,
 400                 int (*check_established)(struct inet_timewait_death_row *,
 401                         struct sock *, __u16, struct inet_timewait_sock **),
 402                 void (*hash)(struct sock *sk))
 403 {
 404         struct inet_hashinfo *hinfo = death_row->hashinfo;
 405         const unsigned short snum = inet_sk(sk)->num;
 406         struct inet_bind_hashbucket *head;
 407         struct inet_bind_bucket *tb;
 408         int ret;
 409         struct net *net = sk->sk_net;
 410
 411         if (!snum) {
 412                 int i, remaining, low, high, port;
 413                 static u32 hint;
 414                 u32 offset = hint + port_offset;
 415                 struct hlist_node *node;
 416                 struct inet_timewait_sock *tw = NULL;
 417
 418                 inet_get_local_port_range(&low, &high);
 419                 remaining = (high - low) + 1;
 420
 421                 local_bh_disable();
 422                 for (i = 1; i <= remaining; i++) {
 423                         port = low + (i + offset) % remaining;
 424                         head = &hinfo->bhash[inet_bhashfn(port, hinfo->bhash_size)];
 425                         spin_lock(&head->lock);
 426
 427                         /* Does not bother with rcv_saddr checks,
 428                          * because the established check is already
 429                          * unique enough.
 430                          */
 431                         inet_bind_bucket_for_each(tb, node, &head->chain) {
 432                                 if (tb->ib_net == net && tb->port == port) {
 433                                         BUG_TRAP(!hlist_empty(&tb->owners));
 434                                         if (tb->fastreuse >= 0)
 435                                                 goto next_port;
 436                                         if (!check_established(death_row, sk,
 437                                                                 port, &tw))
 438                                                 goto ok;
 439                                         goto next_port;
 440                                 }
 441                         }
 442
 443                         tb = inet_bind_bucket_create(hinfo->bind_bucket_cachep,
 444                                         net, head, port);
 445                         if (!tb) {
 446                                 spin_unlock(&head->lock);
 447                                 break;
 448                         }
 449                         tb->fastreuse = -1;
 450                         goto ok;
 451
 452                 next_port:
 453                         spin_unlock(&head->lock);
 454                 }
 455                 local_bh_enable();
 456
 457                 return -EADDRNOTAVAIL;
 458
 459 ok:
 460                 hint += i;
 461
 462                 /* Head lock still held and bh's disabled */
 463                 inet_bind_hash(sk, tb, port);
 464                 if (sk_unhashed(sk)) {
 465                         inet_sk(sk)->sport = htons(port);
 466                         hash(sk);
 467                 }
 468                 spin_unlock(&head->lock);
 469
 470                 if (tw) {
 471                         inet_twsk_deschedule(tw, death_row);
 472                         inet_twsk_put(tw);
 473                 }
 474
 475                 ret = 0;
 476                 goto out;
 477         }
 478
 479         head = &hinfo->bhash[inet_bhashfn(snum, hinfo->bhash_size)];
 480         tb  = inet_csk(sk)->icsk_bind_hash;
 481         spin_lock_bh(&head->lock);
 482         if (sk_head(&tb->owners) == sk && !sk->sk_bind_node.next) {
 483                 hash(sk);
 484                 spin_unlock_bh(&head->lock);
 485                 return 0;
 486         } else {
 487                 spin_unlock(&head->lock);
 488                 /* No definite answer... Walk to established hash table */
 489                 ret = check_established(death_row, sk, snum, NULL);
 490 out:
 491                 local_bh_enable();
 492                 return ret;
 493         }
 494 }
 495
 496 /*
 497  * Bind a port for a connect operation and hash it.
 498  */
 499 int inet_hash_connect(struct inet_timewait_death_row *death_row,
 500                       struct sock *sk)
 501 {
 502         return __inet_hash_connect(death_row, sk, inet_sk_port_offset(sk),
 503                         __inet_check_established, __inet_hash_nolisten);
 504 }
 505
 506 EXPORT_SYMBOL_GPL(inet_hash_connect);