SAFE public projects git trees. - safe/jmp/linux-2.6/blob - net/ipv4/inet_timewait_sock.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 TIME_WAIT sockets functions
   7  *
   8  *              From code orinally in TCP
   9  */
  10
  11 #include <linux/kernel.h>
  12 #include <linux/kmemcheck.h>
  13 #include <net/inet_hashtables.h>
  14 #include <net/inet_timewait_sock.h>
  15 #include <net/ip.h>
  16
  17
  18 /*
  19  * unhash a timewait socket from established hash
  20  * lock must be hold by caller
  21  */
  22 int inet_twsk_unhash(struct inet_timewait_sock *tw)
  23 {
  24         if (hlist_nulls_unhashed(&tw->tw_node))
  25                 return 0;
  26
  27         hlist_nulls_del_rcu(&tw->tw_node);
  28         sk_nulls_node_init(&tw->tw_node);
  29         return 1;
  30 }
  31
  32 /* Must be called with locally disabled BHs. */
  33 static void __inet_twsk_kill(struct inet_timewait_sock *tw,
  34                              struct inet_hashinfo *hashinfo)
  35 {
  36         struct inet_bind_hashbucket *bhead;
  37         struct inet_bind_bucket *tb;
  38         int refcnt;
  39         /* Unlink from established hashes. */
  40         spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
  41
  42         spin_lock(lock);
  43         refcnt = inet_twsk_unhash(tw);
  44         spin_unlock(lock);
  45
  46         /* Disassociate with bind bucket. */
  47         bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
  48                         hashinfo->bhash_size)];
  49         spin_lock(&bhead->lock);
  50         tb = tw->tw_tb;
  51         if (tb) {
  52                 __hlist_del(&tw->tw_bind_node);
  53                 tw->tw_tb = NULL;
  54                 inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
  55                 refcnt++;
  56         }
  57         spin_unlock(&bhead->lock);
  58 #ifdef SOCK_REFCNT_DEBUG
  59         if (atomic_read(&tw->tw_refcnt) != 1) {
  60                 printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n",
  61                        tw->tw_prot->name, tw, atomic_read(&tw->tw_refcnt));
  62         }
  63 #endif
  64         while (refcnt) {
  65                 inet_twsk_put(tw);
  66                 refcnt--;
  67         }
  68 }
  69
  70 static noinline void inet_twsk_free(struct inet_timewait_sock *tw)
  71 {
  72         struct module *owner = tw->tw_prot->owner;
  73         twsk_destructor((struct sock *)tw);
  74 #ifdef SOCK_REFCNT_DEBUG
  75         pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
  76 #endif
  77         release_net(twsk_net(tw));
  78         kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
  79         module_put(owner);
  80 }
  81
  82 void inet_twsk_put(struct inet_timewait_sock *tw)
  83 {
  84         if (atomic_dec_and_test(&tw->tw_refcnt))
  85                 inet_twsk_free(tw);
  86 }
  87 EXPORT_SYMBOL_GPL(inet_twsk_put);
  88
  89 /*
  90  * Enter the time wait state. This is called with locally disabled BH.
  91  * Essentially we whip up a timewait bucket, copy the relevant info into it
  92  * from the SK, and mess with hash chains and list linkage.
  93  */
  94 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
  95                            struct inet_hashinfo *hashinfo)
  96 {
  97         const struct inet_sock *inet = inet_sk(sk);
  98         const struct inet_connection_sock *icsk = inet_csk(sk);
  99         struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
 100         spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
 101         struct inet_bind_hashbucket *bhead;
 102         /* Step 1: Put TW into bind hash. Original socket stays there too.
 103            Note, that any socket with inet->num != 0 MUST be bound in
 104            binding cache, even if it is closed.
 105          */
 106         bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
 107                         hashinfo->bhash_size)];
 108         spin_lock(&bhead->lock);
 109         tw->tw_tb = icsk->icsk_bind_hash;
 110         WARN_ON(!icsk->icsk_bind_hash);
 111         inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
 112         spin_unlock(&bhead->lock);
 113
 114         spin_lock(lock);
 115
 116         /*
 117          * Step 2: Hash TW into TIMEWAIT chain.
 118          * Should be done before removing sk from established chain
 119          * because readers are lockless and search established first.
 120          */
 121         inet_twsk_add_node_rcu(tw, &ehead->twchain);
 122
 123         /* Step 3: Remove SK from established hash. */
 124         if (__sk_nulls_del_node_init_rcu(sk))
 125                 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 126
 127         /*
 128          * Notes :
 129          * - We initially set tw_refcnt to 0 in inet_twsk_alloc()
 130          * - We add one reference for the bhash link
 131          * - We add one reference for the ehash link
 132          * - We want this refcnt update done before allowing other
 133          *   threads to find this tw in ehash chain.
 134          */
 135         atomic_add(1 + 1 + 1, &tw->tw_refcnt);
 136
 137         spin_unlock(lock);
 138 }
 139
 140 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
 141
 142 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state)
 143 {
 144         struct inet_timewait_sock *tw =
 145                 kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
 146                                  GFP_ATOMIC);
 147         if (tw != NULL) {
 148                 const struct inet_sock *inet = inet_sk(sk);
 149
 150                 kmemcheck_annotate_bitfield(tw, flags);
 151
 152                 /* Give us an identity. */
 153                 tw->tw_daddr        = inet->inet_daddr;
 154                 tw->tw_rcv_saddr    = inet->inet_rcv_saddr;
 155                 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
 156                 tw->tw_num          = inet->inet_num;
 157                 tw->tw_state        = TCP_TIME_WAIT;
 158                 tw->tw_substate     = state;
 159                 tw->tw_sport        = inet->inet_sport;
 160                 tw->tw_dport        = inet->inet_dport;
 161                 tw->tw_family       = sk->sk_family;
 162                 tw->tw_reuse        = sk->sk_reuse;
 163                 tw->tw_hash         = sk->sk_hash;
 164                 tw->tw_ipv6only     = 0;
 165                 tw->tw_transparent  = inet->transparent;
 166                 tw->tw_prot         = sk->sk_prot_creator;
 167                 twsk_net_set(tw, hold_net(sock_net(sk)));
 168                 /*
 169                  * Because we use RCU lookups, we should not set tw_refcnt
 170                  * to a non null value before everything is setup for this
 171                  * timewait socket.
 172                  */
 173                 atomic_set(&tw->tw_refcnt, 0);
 174                 inet_twsk_dead_node_init(tw);
 175                 __module_get(tw->tw_prot->owner);
 176         }
 177
 178         return tw;
 179 }
 180
 181 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
 182
 183 /* Returns non-zero if quota exceeded.  */
 184 static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
 185                                     const int slot)
 186 {
 187         struct inet_timewait_sock *tw;
 188         struct hlist_node *node;
 189         unsigned int killed;
 190         int ret;
 191
 192         /* NOTE: compare this to previous version where lock
 193          * was released after detaching chain. It was racy,
 194          * because tw buckets are scheduled in not serialized context
 195          * in 2.3 (with netfilter), and with softnet it is common, because
 196          * soft irqs are not sequenced.
 197          */
 198         killed = 0;
 199         ret = 0;
 200 rescan:
 201         inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) {
 202                 __inet_twsk_del_dead_node(tw);
 203                 spin_unlock(&twdr->death_lock);
 204                 __inet_twsk_kill(tw, twdr->hashinfo);
 205 #ifdef CONFIG_NET_NS
 206                 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED);
 207 #endif
 208                 inet_twsk_put(tw);
 209                 killed++;
 210                 spin_lock(&twdr->death_lock);
 211                 if (killed > INET_TWDR_TWKILL_QUOTA) {
 212                         ret = 1;
 213                         break;
 214                 }
 215
 216                 /* While we dropped twdr->death_lock, another cpu may have
 217                  * killed off the next TW bucket in the list, therefore
 218                  * do a fresh re-read of the hlist head node with the
 219                  * lock reacquired.  We still use the hlist traversal
 220                  * macro in order to get the prefetches.
 221                  */
 222                 goto rescan;
 223         }
 224
 225         twdr->tw_count -= killed;
 226 #ifndef CONFIG_NET_NS
 227         NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITED, killed);
 228 #endif
 229         return ret;
 230 }
 231
 232 void inet_twdr_hangman(unsigned long data)
 233 {
 234         struct inet_timewait_death_row *twdr;
 235         int unsigned need_timer;
 236
 237         twdr = (struct inet_timewait_death_row *)data;
 238         spin_lock(&twdr->death_lock);
 239
 240         if (twdr->tw_count == 0)
 241                 goto out;
 242
 243         need_timer = 0;
 244         if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
 245                 twdr->thread_slots |= (1 << twdr->slot);
 246                 schedule_work(&twdr->twkill_work);
 247                 need_timer = 1;
 248         } else {
 249                 /* We purged the entire slot, anything left?  */
 250                 if (twdr->tw_count)
 251                         need_timer = 1;
 252                 twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
 253         }
 254         if (need_timer)
 255                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 256 out:
 257         spin_unlock(&twdr->death_lock);
 258 }
 259
 260 EXPORT_SYMBOL_GPL(inet_twdr_hangman);
 261
 262 void inet_twdr_twkill_work(struct work_struct *work)
 263 {
 264         struct inet_timewait_death_row *twdr =
 265                 container_of(work, struct inet_timewait_death_row, twkill_work);
 266         int i;
 267
 268         BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) >
 269                         (sizeof(twdr->thread_slots) * 8));
 270
 271         while (twdr->thread_slots) {
 272                 spin_lock_bh(&twdr->death_lock);
 273                 for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
 274                         if (!(twdr->thread_slots & (1 << i)))
 275                                 continue;
 276
 277                         while (inet_twdr_do_twkill_work(twdr, i) != 0) {
 278                                 if (need_resched()) {
 279                                         spin_unlock_bh(&twdr->death_lock);
 280                                         schedule();
 281                                         spin_lock_bh(&twdr->death_lock);
 282                                 }
 283                         }
 284
 285                         twdr->thread_slots &= ~(1 << i);
 286                 }
 287                 spin_unlock_bh(&twdr->death_lock);
 288         }
 289 }
 290
 291 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);
 292
 293 /* These are always called from BH context.  See callers in
 294  * tcp_input.c to verify this.
 295  */
 296
 297 /* This is for handling early-kills of TIME_WAIT sockets. */
 298 void inet_twsk_deschedule(struct inet_timewait_sock *tw,
 299                           struct inet_timewait_death_row *twdr)
 300 {
 301         spin_lock(&twdr->death_lock);
 302         if (inet_twsk_del_dead_node(tw)) {
 303                 inet_twsk_put(tw);
 304                 if (--twdr->tw_count == 0)
 305                         del_timer(&twdr->tw_timer);
 306         }
 307         spin_unlock(&twdr->death_lock);
 308         __inet_twsk_kill(tw, twdr->hashinfo);
 309 }
 310
 311 EXPORT_SYMBOL(inet_twsk_deschedule);
 312
 313 void inet_twsk_schedule(struct inet_timewait_sock *tw,
 314                        struct inet_timewait_death_row *twdr,
 315                        const int timeo, const int timewait_len)
 316 {
 317         struct hlist_head *list;
 318         int slot;
 319
 320         /* timeout := RTO * 3.5
 321          *
 322          * 3.5 = 1+2+0.5 to wait for two retransmits.
 323          *
 324          * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
 325          * our ACK acking that FIN can be lost. If N subsequent retransmitted
 326          * FINs (or previous seqments) are lost (probability of such event
 327          * is p^(N+1), where p is probability to lose single packet and
 328          * time to detect the loss is about RTO*(2^N - 1) with exponential
 329          * backoff). Normal timewait length is calculated so, that we
 330          * waited at least for one retransmitted FIN (maximal RTO is 120sec).
 331          * [ BTW Linux. following BSD, violates this requirement waiting
 332          *   only for 60sec, we should wait at least for 240 secs.
 333          *   Well, 240 consumes too much of resources 8)
 334          * ]
 335          * This interval is not reduced to catch old duplicate and
 336          * responces to our wandering segments living for two MSLs.
 337          * However, if we use PAWS to detect
 338          * old duplicates, we can reduce the interval to bounds required
 339          * by RTO, rather than MSL. So, if peer understands PAWS, we
 340          * kill tw bucket after 3.5*RTO (it is important that this number
 341          * is greater than TS tick!) and detect old duplicates with help
 342          * of PAWS.
 343          */
 344         slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
 345
 346         spin_lock(&twdr->death_lock);
 347
 348         /* Unlink it, if it was scheduled */
 349         if (inet_twsk_del_dead_node(tw))
 350                 twdr->tw_count--;
 351         else
 352                 atomic_inc(&tw->tw_refcnt);
 353
 354         if (slot >= INET_TWDR_RECYCLE_SLOTS) {
 355                 /* Schedule to slow timer */
 356                 if (timeo >= timewait_len) {
 357                         slot = INET_TWDR_TWKILL_SLOTS - 1;
 358                 } else {
 359                         slot = DIV_ROUND_UP(timeo, twdr->period);
 360                         if (slot >= INET_TWDR_TWKILL_SLOTS)
 361                                 slot = INET_TWDR_TWKILL_SLOTS - 1;
 362                 }
 363                 tw->tw_ttd = jiffies + timeo;
 364                 slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
 365                 list = &twdr->cells[slot];
 366         } else {
 367                 tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK);
 368
 369                 if (twdr->twcal_hand < 0) {
 370                         twdr->twcal_hand = 0;
 371                         twdr->twcal_jiffie = jiffies;
 372                         twdr->twcal_timer.expires = twdr->twcal_jiffie +
 373                                               (slot << INET_TWDR_RECYCLE_TICK);
 374                         add_timer(&twdr->twcal_timer);
 375                 } else {
 376                         if (time_after(twdr->twcal_timer.expires,
 377                                        jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
 378                                 mod_timer(&twdr->twcal_timer,
 379                                           jiffies + (slot << INET_TWDR_RECYCLE_TICK));
 380                         slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
 381                 }
 382                 list = &twdr->twcal_row[slot];
 383         }
 384
 385         hlist_add_head(&tw->tw_death_node, list);
 386
 387         if (twdr->tw_count++ == 0)
 388                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 389         spin_unlock(&twdr->death_lock);
 390 }
 391
 392 EXPORT_SYMBOL_GPL(inet_twsk_schedule);
 393
 394 void inet_twdr_twcal_tick(unsigned long data)
 395 {
 396         struct inet_timewait_death_row *twdr;
 397         int n, slot;
 398         unsigned long j;
 399         unsigned long now = jiffies;
 400         int killed = 0;
 401         int adv = 0;
 402
 403         twdr = (struct inet_timewait_death_row *)data;
 404
 405         spin_lock(&twdr->death_lock);
 406         if (twdr->twcal_hand < 0)
 407                 goto out;
 408
 409         slot = twdr->twcal_hand;
 410         j = twdr->twcal_jiffie;
 411
 412         for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
 413                 if (time_before_eq(j, now)) {
 414                         struct hlist_node *node, *safe;
 415                         struct inet_timewait_sock *tw;
 416
 417                         inet_twsk_for_each_inmate_safe(tw, node, safe,
 418                                                        &twdr->twcal_row[slot]) {
 419                                 __inet_twsk_del_dead_node(tw);
 420                                 __inet_twsk_kill(tw, twdr->hashinfo);
 421 #ifdef CONFIG_NET_NS
 422                                 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
 423 #endif
 424                                 inet_twsk_put(tw);
 425                                 killed++;
 426                         }
 427                 } else {
 428                         if (!adv) {
 429                                 adv = 1;
 430                                 twdr->twcal_jiffie = j;
 431                                 twdr->twcal_hand = slot;
 432                         }
 433
 434                         if (!hlist_empty(&twdr->twcal_row[slot])) {
 435                                 mod_timer(&twdr->twcal_timer, j);
 436                                 goto out;
 437                         }
 438                 }
 439                 j += 1 << INET_TWDR_RECYCLE_TICK;
 440                 slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
 441         }
 442         twdr->twcal_hand = -1;
 443
 444 out:
 445         if ((twdr->tw_count -= killed) == 0)
 446                 del_timer(&twdr->tw_timer);
 447 #ifndef CONFIG_NET_NS
 448         NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITKILLED, killed);
 449 #endif
 450         spin_unlock(&twdr->death_lock);
 451 }
 452
 453 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);
 454
 455 void inet_twsk_purge(struct inet_hashinfo *hashinfo,
 456                      struct inet_timewait_death_row *twdr, int family)
 457 {
 458         struct inet_timewait_sock *tw;
 459         struct sock *sk;
 460         struct hlist_nulls_node *node;
 461         unsigned int slot;
 462
 463         for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
 464                 struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
 465 restart_rcu:
 466                 rcu_read_lock();
 467 restart:
 468                 sk_nulls_for_each_rcu(sk, node, &head->twchain) {
 469                         tw = inet_twsk(sk);
 470                         if ((tw->tw_family != family) ||
 471                                 atomic_read(&twsk_net(tw)->count))
 472                                 continue;
 473
 474                         if (unlikely(!atomic_inc_not_zero(&tw->tw_refcnt)))
 475                                 continue;
 476
 477                         if (unlikely((tw->tw_family != family) ||
 478                                      atomic_read(&twsk_net(tw)->count))) {
 479                                 inet_twsk_put(tw);
 480                                 goto restart;
 481                         }
 482
 483                         rcu_read_unlock();
 484                         inet_twsk_deschedule(tw, twdr);
 485                         inet_twsk_put(tw);
 486                         goto restart_rcu;
 487                 }
 488                 /* If the nulls value we got at the end of this lookup is
 489                  * not the expected one, we must restart lookup.
 490                  * We probably met an item that was moved to another chain.
 491                  */
 492                 if (get_nulls_value(node) != slot)
 493                         goto restart;
 494                 rcu_read_unlock();
 495         }
 496 }
 497 EXPORT_SYMBOL_GPL(inet_twsk_purge);