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  *      inet_twsk_unhash - unhash a timewait socket from established hash
  20  *      @tw: timewait socket
  21  *
  22  *      unhash a timewait socket from established hash, if hashed.
  23  *      ehash lock must be held by caller.
  24  *      Returns 1 if caller should call inet_twsk_put() after lock release.
  25  */
  26 int inet_twsk_unhash(struct inet_timewait_sock *tw)
  27 {
  28         if (hlist_nulls_unhashed(&tw->tw_node))
  29                 return 0;
  30
  31         hlist_nulls_del_rcu(&tw->tw_node);
  32         sk_nulls_node_init(&tw->tw_node);
  33         /*
  34          * We cannot call inet_twsk_put() ourself under lock,
  35          * caller must call it for us.
  36          */
  37         return 1;
  38 }
  39
  40 /**
  41  *      inet_twsk_bind_unhash - unhash a timewait socket from bind hash
  42  *      @tw: timewait socket
  43  *      @hashinfo: hashinfo pointer
  44  *
  45  *      unhash a timewait socket from bind hash, if hashed.
  46  *      bind hash lock must be held by caller.
  47  *      Returns 1 if caller should call inet_twsk_put() after lock release.
  48  */
  49 int inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
  50                           struct inet_hashinfo *hashinfo)
  51 {
  52         struct inet_bind_bucket *tb = tw->tw_tb;
  53
  54         if (!tb)
  55                 return 0;
  56
  57         __hlist_del(&tw->tw_bind_node);
  58         tw->tw_tb = NULL;
  59         inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
  60         /*
  61          * We cannot call inet_twsk_put() ourself under lock,
  62          * caller must call it for us.
  63          */
  64         return 1;
  65 }
  66
  67 /* Must be called with locally disabled BHs. */
  68 static void __inet_twsk_kill(struct inet_timewait_sock *tw,
  69                              struct inet_hashinfo *hashinfo)
  70 {
  71         struct inet_bind_hashbucket *bhead;
  72         int refcnt;
  73         /* Unlink from established hashes. */
  74         spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
  75
  76         spin_lock(lock);
  77         refcnt = inet_twsk_unhash(tw);
  78         spin_unlock(lock);
  79
  80         /* Disassociate with bind bucket. */
  81         bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
  82                         hashinfo->bhash_size)];
  83
  84         spin_lock(&bhead->lock);
  85         refcnt += inet_twsk_bind_unhash(tw, hashinfo);
  86         spin_unlock(&bhead->lock);
  87
  88 #ifdef SOCK_REFCNT_DEBUG
  89         if (atomic_read(&tw->tw_refcnt) != 1) {
  90                 printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n",
  91                        tw->tw_prot->name, tw, atomic_read(&tw->tw_refcnt));
  92         }
  93 #endif
  94         while (refcnt) {
  95                 inet_twsk_put(tw);
  96                 refcnt--;
  97         }
  98 }
  99
 100 static noinline void inet_twsk_free(struct inet_timewait_sock *tw)
 101 {
 102         struct module *owner = tw->tw_prot->owner;
 103         twsk_destructor((struct sock *)tw);
 104 #ifdef SOCK_REFCNT_DEBUG
 105         pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
 106 #endif
 107         release_net(twsk_net(tw));
 108         kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
 109         module_put(owner);
 110 }
 111
 112 void inet_twsk_put(struct inet_timewait_sock *tw)
 113 {
 114         if (atomic_dec_and_test(&tw->tw_refcnt))
 115                 inet_twsk_free(tw);
 116 }
 117 EXPORT_SYMBOL_GPL(inet_twsk_put);
 118
 119 /*
 120  * Enter the time wait state. This is called with locally disabled BH.
 121  * Essentially we whip up a timewait bucket, copy the relevant info into it
 122  * from the SK, and mess with hash chains and list linkage.
 123  */
 124 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
 125                            struct inet_hashinfo *hashinfo)
 126 {
 127         const struct inet_sock *inet = inet_sk(sk);
 128         const struct inet_connection_sock *icsk = inet_csk(sk);
 129         struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
 130         spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
 131         struct inet_bind_hashbucket *bhead;
 132         /* Step 1: Put TW into bind hash. Original socket stays there too.
 133            Note, that any socket with inet->num != 0 MUST be bound in
 134            binding cache, even if it is closed.
 135          */
 136         bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
 137                         hashinfo->bhash_size)];
 138         spin_lock(&bhead->lock);
 139         tw->tw_tb = icsk->icsk_bind_hash;
 140         WARN_ON(!icsk->icsk_bind_hash);
 141         inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
 142         spin_unlock(&bhead->lock);
 143
 144         spin_lock(lock);
 145
 146         /*
 147          * Step 2: Hash TW into TIMEWAIT chain.
 148          * Should be done before removing sk from established chain
 149          * because readers are lockless and search established first.
 150          */
 151         inet_twsk_add_node_rcu(tw, &ehead->twchain);
 152
 153         /* Step 3: Remove SK from established hash. */
 154         if (__sk_nulls_del_node_init_rcu(sk))
 155                 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 156
 157         /*
 158          * Notes :
 159          * - We initially set tw_refcnt to 0 in inet_twsk_alloc()
 160          * - We add one reference for the bhash link
 161          * - We add one reference for the ehash link
 162          * - We want this refcnt update done before allowing other
 163          *   threads to find this tw in ehash chain.
 164          */
 165         atomic_add(1 + 1 + 1, &tw->tw_refcnt);
 166
 167         spin_unlock(lock);
 168 }
 169 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
 170
 171 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state)
 172 {
 173         struct inet_timewait_sock *tw =
 174                 kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
 175                                  GFP_ATOMIC);
 176         if (tw != NULL) {
 177                 const struct inet_sock *inet = inet_sk(sk);
 178
 179                 kmemcheck_annotate_bitfield(tw, flags);
 180
 181                 /* Give us an identity. */
 182                 tw->tw_daddr        = inet->inet_daddr;
 183                 tw->tw_rcv_saddr    = inet->inet_rcv_saddr;
 184                 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
 185                 tw->tw_num          = inet->inet_num;
 186                 tw->tw_state        = TCP_TIME_WAIT;
 187                 tw->tw_substate     = state;
 188                 tw->tw_sport        = inet->inet_sport;
 189                 tw->tw_dport        = inet->inet_dport;
 190                 tw->tw_family       = sk->sk_family;
 191                 tw->tw_reuse        = sk->sk_reuse;
 192                 tw->tw_hash         = sk->sk_hash;
 193                 tw->tw_ipv6only     = 0;
 194                 tw->tw_transparent  = inet->transparent;
 195                 tw->tw_prot         = sk->sk_prot_creator;
 196                 twsk_net_set(tw, hold_net(sock_net(sk)));
 197                 /*
 198                  * Because we use RCU lookups, we should not set tw_refcnt
 199                  * to a non null value before everything is setup for this
 200                  * timewait socket.
 201                  */
 202                 atomic_set(&tw->tw_refcnt, 0);
 203                 inet_twsk_dead_node_init(tw);
 204                 __module_get(tw->tw_prot->owner);
 205         }
 206
 207         return tw;
 208 }
 209 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
 210
 211 /* Returns non-zero if quota exceeded.  */
 212 static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
 213                                     const int slot)
 214 {
 215         struct inet_timewait_sock *tw;
 216         struct hlist_node *node;
 217         unsigned int killed;
 218         int ret;
 219
 220         /* NOTE: compare this to previous version where lock
 221          * was released after detaching chain. It was racy,
 222          * because tw buckets are scheduled in not serialized context
 223          * in 2.3 (with netfilter), and with softnet it is common, because
 224          * soft irqs are not sequenced.
 225          */
 226         killed = 0;
 227         ret = 0;
 228 rescan:
 229         inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) {
 230                 __inet_twsk_del_dead_node(tw);
 231                 spin_unlock(&twdr->death_lock);
 232                 __inet_twsk_kill(tw, twdr->hashinfo);
 233 #ifdef CONFIG_NET_NS
 234                 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED);
 235 #endif
 236                 inet_twsk_put(tw);
 237                 killed++;
 238                 spin_lock(&twdr->death_lock);
 239                 if (killed > INET_TWDR_TWKILL_QUOTA) {
 240                         ret = 1;
 241                         break;
 242                 }
 243
 244                 /* While we dropped twdr->death_lock, another cpu may have
 245                  * killed off the next TW bucket in the list, therefore
 246                  * do a fresh re-read of the hlist head node with the
 247                  * lock reacquired.  We still use the hlist traversal
 248                  * macro in order to get the prefetches.
 249                  */
 250                 goto rescan;
 251         }
 252
 253         twdr->tw_count -= killed;
 254 #ifndef CONFIG_NET_NS
 255         NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITED, killed);
 256 #endif
 257         return ret;
 258 }
 259
 260 void inet_twdr_hangman(unsigned long data)
 261 {
 262         struct inet_timewait_death_row *twdr;
 263         int unsigned need_timer;
 264
 265         twdr = (struct inet_timewait_death_row *)data;
 266         spin_lock(&twdr->death_lock);
 267
 268         if (twdr->tw_count == 0)
 269                 goto out;
 270
 271         need_timer = 0;
 272         if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
 273                 twdr->thread_slots |= (1 << twdr->slot);
 274                 schedule_work(&twdr->twkill_work);
 275                 need_timer = 1;
 276         } else {
 277                 /* We purged the entire slot, anything left?  */
 278                 if (twdr->tw_count)
 279                         need_timer = 1;
 280                 twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
 281         }
 282         if (need_timer)
 283                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 284 out:
 285         spin_unlock(&twdr->death_lock);
 286 }
 287 EXPORT_SYMBOL_GPL(inet_twdr_hangman);
 288
 289 void inet_twdr_twkill_work(struct work_struct *work)
 290 {
 291         struct inet_timewait_death_row *twdr =
 292                 container_of(work, struct inet_timewait_death_row, twkill_work);
 293         int i;
 294
 295         BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) >
 296                         (sizeof(twdr->thread_slots) * 8));
 297
 298         while (twdr->thread_slots) {
 299                 spin_lock_bh(&twdr->death_lock);
 300                 for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
 301                         if (!(twdr->thread_slots & (1 << i)))
 302                                 continue;
 303
 304                         while (inet_twdr_do_twkill_work(twdr, i) != 0) {
 305                                 if (need_resched()) {
 306                                         spin_unlock_bh(&twdr->death_lock);
 307                                         schedule();
 308                                         spin_lock_bh(&twdr->death_lock);
 309                                 }
 310                         }
 311
 312                         twdr->thread_slots &= ~(1 << i);
 313                 }
 314                 spin_unlock_bh(&twdr->death_lock);
 315         }
 316 }
 317 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);
 318
 319 /* These are always called from BH context.  See callers in
 320  * tcp_input.c to verify this.
 321  */
 322
 323 /* This is for handling early-kills of TIME_WAIT sockets. */
 324 void inet_twsk_deschedule(struct inet_timewait_sock *tw,
 325                           struct inet_timewait_death_row *twdr)
 326 {
 327         spin_lock(&twdr->death_lock);
 328         if (inet_twsk_del_dead_node(tw)) {
 329                 inet_twsk_put(tw);
 330                 if (--twdr->tw_count == 0)
 331                         del_timer(&twdr->tw_timer);
 332         }
 333         spin_unlock(&twdr->death_lock);
 334         __inet_twsk_kill(tw, twdr->hashinfo);
 335 }
 336 EXPORT_SYMBOL(inet_twsk_deschedule);
 337
 338 void inet_twsk_schedule(struct inet_timewait_sock *tw,
 339                        struct inet_timewait_death_row *twdr,
 340                        const int timeo, const int timewait_len)
 341 {
 342         struct hlist_head *list;
 343         int slot;
 344
 345         /* timeout := RTO * 3.5
 346          *
 347          * 3.5 = 1+2+0.5 to wait for two retransmits.
 348          *
 349          * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
 350          * our ACK acking that FIN can be lost. If N subsequent retransmitted
 351          * FINs (or previous seqments) are lost (probability of such event
 352          * is p^(N+1), where p is probability to lose single packet and
 353          * time to detect the loss is about RTO*(2^N - 1) with exponential
 354          * backoff). Normal timewait length is calculated so, that we
 355          * waited at least for one retransmitted FIN (maximal RTO is 120sec).
 356          * [ BTW Linux. following BSD, violates this requirement waiting
 357          *   only for 60sec, we should wait at least for 240 secs.
 358          *   Well, 240 consumes too much of resources 8)
 359          * ]
 360          * This interval is not reduced to catch old duplicate and
 361          * responces to our wandering segments living for two MSLs.
 362          * However, if we use PAWS to detect
 363          * old duplicates, we can reduce the interval to bounds required
 364          * by RTO, rather than MSL. So, if peer understands PAWS, we
 365          * kill tw bucket after 3.5*RTO (it is important that this number
 366          * is greater than TS tick!) and detect old duplicates with help
 367          * of PAWS.
 368          */
 369         slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
 370
 371         spin_lock(&twdr->death_lock);
 372
 373         /* Unlink it, if it was scheduled */
 374         if (inet_twsk_del_dead_node(tw))
 375                 twdr->tw_count--;
 376         else
 377                 atomic_inc(&tw->tw_refcnt);
 378
 379         if (slot >= INET_TWDR_RECYCLE_SLOTS) {
 380                 /* Schedule to slow timer */
 381                 if (timeo >= timewait_len) {
 382                         slot = INET_TWDR_TWKILL_SLOTS - 1;
 383                 } else {
 384                         slot = DIV_ROUND_UP(timeo, twdr->period);
 385                         if (slot >= INET_TWDR_TWKILL_SLOTS)
 386                                 slot = INET_TWDR_TWKILL_SLOTS - 1;
 387                 }
 388                 tw->tw_ttd = jiffies + timeo;
 389                 slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
 390                 list = &twdr->cells[slot];
 391         } else {
 392                 tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK);
 393
 394                 if (twdr->twcal_hand < 0) {
 395                         twdr->twcal_hand = 0;
 396                         twdr->twcal_jiffie = jiffies;
 397                         twdr->twcal_timer.expires = twdr->twcal_jiffie +
 398                                               (slot << INET_TWDR_RECYCLE_TICK);
 399                         add_timer(&twdr->twcal_timer);
 400                 } else {
 401                         if (time_after(twdr->twcal_timer.expires,
 402                                        jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
 403                                 mod_timer(&twdr->twcal_timer,
 404                                           jiffies + (slot << INET_TWDR_RECYCLE_TICK));
 405                         slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
 406                 }
 407                 list = &twdr->twcal_row[slot];
 408         }
 409
 410         hlist_add_head(&tw->tw_death_node, list);
 411
 412         if (twdr->tw_count++ == 0)
 413                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 414         spin_unlock(&twdr->death_lock);
 415 }
 416 EXPORT_SYMBOL_GPL(inet_twsk_schedule);
 417
 418 void inet_twdr_twcal_tick(unsigned long data)
 419 {
 420         struct inet_timewait_death_row *twdr;
 421         int n, slot;
 422         unsigned long j;
 423         unsigned long now = jiffies;
 424         int killed = 0;
 425         int adv = 0;
 426
 427         twdr = (struct inet_timewait_death_row *)data;
 428
 429         spin_lock(&twdr->death_lock);
 430         if (twdr->twcal_hand < 0)
 431                 goto out;
 432
 433         slot = twdr->twcal_hand;
 434         j = twdr->twcal_jiffie;
 435
 436         for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
 437                 if (time_before_eq(j, now)) {
 438                         struct hlist_node *node, *safe;
 439                         struct inet_timewait_sock *tw;
 440
 441                         inet_twsk_for_each_inmate_safe(tw, node, safe,
 442                                                        &twdr->twcal_row[slot]) {
 443                                 __inet_twsk_del_dead_node(tw);
 444                                 __inet_twsk_kill(tw, twdr->hashinfo);
 445 #ifdef CONFIG_NET_NS
 446                                 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
 447 #endif
 448                                 inet_twsk_put(tw);
 449                                 killed++;
 450                         }
 451                 } else {
 452                         if (!adv) {
 453                                 adv = 1;
 454                                 twdr->twcal_jiffie = j;
 455                                 twdr->twcal_hand = slot;
 456                         }
 457
 458                         if (!hlist_empty(&twdr->twcal_row[slot])) {
 459                                 mod_timer(&twdr->twcal_timer, j);
 460                                 goto out;
 461                         }
 462                 }
 463                 j += 1 << INET_TWDR_RECYCLE_TICK;
 464                 slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
 465         }
 466         twdr->twcal_hand = -1;
 467
 468 out:
 469         if ((twdr->tw_count -= killed) == 0)
 470                 del_timer(&twdr->tw_timer);
 471 #ifndef CONFIG_NET_NS
 472         NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITKILLED, killed);
 473 #endif
 474         spin_unlock(&twdr->death_lock);
 475 }
 476 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);
 477
 478 void inet_twsk_purge(struct inet_hashinfo *hashinfo,
 479                      struct inet_timewait_death_row *twdr, int family)
 480 {
 481         struct inet_timewait_sock *tw;
 482         struct sock *sk;
 483         struct hlist_nulls_node *node;
 484         unsigned int slot;
 485
 486         for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
 487                 struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
 488 restart_rcu:
 489                 rcu_read_lock();
 490 restart:
 491                 sk_nulls_for_each_rcu(sk, node, &head->twchain) {
 492                         tw = inet_twsk(sk);
 493                         if ((tw->tw_family != family) ||
 494                                 atomic_read(&twsk_net(tw)->count))
 495                                 continue;
 496
 497                         if (unlikely(!atomic_inc_not_zero(&tw->tw_refcnt)))
 498                                 continue;
 499
 500                         if (unlikely((tw->tw_family != family) ||
 501                                      atomic_read(&twsk_net(tw)->count))) {
 502                                 inet_twsk_put(tw);
 503                                 goto restart;
 504                         }
 505
 506                         rcu_read_unlock();
 507                         inet_twsk_deschedule(tw, twdr);
 508                         inet_twsk_put(tw);
 509                         goto restart_rcu;
 510                 }
 511                 /* If the nulls value we got at the end of this lookup is
 512                  * not the expected one, we must restart lookup.
 513                  * We probably met an item that was moved to another chain.
 514                  */
 515                 if (get_nulls_value(node) != slot)
 516                         goto restart;
 517                 rcu_read_unlock();
 518         }
 519 }
 520 EXPORT_SYMBOL_GPL(inet_twsk_purge);