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 <linux/slab.h>
  14 #include <linux/module.h>
  15 #include <net/inet_hashtables.h>
  16 #include <net/inet_timewait_sock.h>
  17 #include <net/ip.h>
  18
  19
  20 /**
  21  *      inet_twsk_unhash - unhash a timewait socket from established hash
  22  *      @tw: timewait socket
  23  *
  24  *      unhash a timewait socket from established hash, if hashed.
  25  *      ehash lock must be held by caller.
  26  *      Returns 1 if caller should call inet_twsk_put() after lock release.
  27  */
  28 int inet_twsk_unhash(struct inet_timewait_sock *tw)
  29 {
  30         if (hlist_nulls_unhashed(&tw->tw_node))
  31                 return 0;
  32
  33         hlist_nulls_del_rcu(&tw->tw_node);
  34         sk_nulls_node_init(&tw->tw_node);
  35         /*
  36          * We cannot call inet_twsk_put() ourself under lock,
  37          * caller must call it for us.
  38          */
  39         return 1;
  40 }
  41
  42 /**
  43  *      inet_twsk_bind_unhash - unhash a timewait socket from bind hash
  44  *      @tw: timewait socket
  45  *      @hashinfo: hashinfo pointer
  46  *
  47  *      unhash a timewait socket from bind hash, if hashed.
  48  *      bind hash lock must be held by caller.
  49  *      Returns 1 if caller should call inet_twsk_put() after lock release.
  50  */
  51 int inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
  52                           struct inet_hashinfo *hashinfo)
  53 {
  54         struct inet_bind_bucket *tb = tw->tw_tb;
  55
  56         if (!tb)
  57                 return 0;
  58
  59         __hlist_del(&tw->tw_bind_node);
  60         tw->tw_tb = NULL;
  61         inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
  62         /*
  63          * We cannot call inet_twsk_put() ourself under lock,
  64          * caller must call it for us.
  65          */
  66         return 1;
  67 }
  68
  69 /* Must be called with locally disabled BHs. */
  70 static void __inet_twsk_kill(struct inet_timewait_sock *tw,
  71                              struct inet_hashinfo *hashinfo)
  72 {
  73         struct inet_bind_hashbucket *bhead;
  74         int refcnt;
  75         /* Unlink from established hashes. */
  76         spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
  77
  78         spin_lock(lock);
  79         refcnt = inet_twsk_unhash(tw);
  80         spin_unlock(lock);
  81
  82         /* Disassociate with bind bucket. */
  83         bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
  84                         hashinfo->bhash_size)];
  85
  86         spin_lock(&bhead->lock);
  87         refcnt += inet_twsk_bind_unhash(tw, hashinfo);
  88         spin_unlock(&bhead->lock);
  89
  90         BUG_ON(refcnt >= atomic_read(&tw->tw_refcnt));
  91         atomic_sub(refcnt, &tw->tw_refcnt);
  92 }
  93
  94 void inet_twsk_free(struct inet_timewait_sock *tw)
  95 {
  96         struct module *owner = tw->tw_prot->owner;
  97         twsk_destructor((struct sock *)tw);
  98 #ifdef SOCK_REFCNT_DEBUG
  99         pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
 100 #endif
 101         release_net(twsk_net(tw));
 102         kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
 103         module_put(owner);
 104 }
 105
 106 void inet_twsk_put(struct inet_timewait_sock *tw)
 107 {
 108         if (atomic_dec_and_test(&tw->tw_refcnt))
 109                 inet_twsk_free(tw);
 110 }
 111 EXPORT_SYMBOL_GPL(inet_twsk_put);
 112
 113 static void inet_twsk_add_node_rcu(struct inet_timewait_sock *tw,
 114                                    struct hlist_nulls_head *list)
 115 {
 116         hlist_nulls_add_head_rcu(&tw->tw_node, list);
 117 }
 118
 119 static void inet_twsk_add_bind_node(struct inet_timewait_sock *tw,
 120                                     struct hlist_head *list)
 121 {
 122         hlist_add_head(&tw->tw_bind_node, list);
 123 }
 124
 125 /*
 126  * Enter the time wait state. This is called with locally disabled BH.
 127  * Essentially we whip up a timewait bucket, copy the relevant info into it
 128  * from the SK, and mess with hash chains and list linkage.
 129  */
 130 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
 131                            struct inet_hashinfo *hashinfo)
 132 {
 133         const struct inet_sock *inet = inet_sk(sk);
 134         const struct inet_connection_sock *icsk = inet_csk(sk);
 135         struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
 136         spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
 137         struct inet_bind_hashbucket *bhead;
 138         /* Step 1: Put TW into bind hash. Original socket stays there too.
 139            Note, that any socket with inet->num != 0 MUST be bound in
 140            binding cache, even if it is closed.
 141          */
 142         bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
 143                         hashinfo->bhash_size)];
 144         spin_lock(&bhead->lock);
 145         tw->tw_tb = icsk->icsk_bind_hash;
 146         WARN_ON(!icsk->icsk_bind_hash);
 147         inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
 148         spin_unlock(&bhead->lock);
 149
 150         spin_lock(lock);
 151
 152         /*
 153          * Step 2: Hash TW into tcp ehash chain.
 154          * Notes :
 155          * - tw_refcnt is set to 3 because :
 156          * - We have one reference from bhash chain.
 157          * - We have one reference from ehash chain.
 158          * We can use atomic_set() because prior spin_lock()/spin_unlock()
 159          * committed into memory all tw fields.
 160          */
 161         atomic_set(&tw->tw_refcnt, 1 + 1 + 1);
 162         inet_twsk_add_node_rcu(tw, &ehead->chain);
 163
 164         /* Step 3: Remove SK from hash chain */
 165         if (__sk_nulls_del_node_init_rcu(sk))
 166                 sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 167
 168         spin_unlock(lock);
 169 }
 170 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
 171
 172 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state)
 173 {
 174         struct inet_timewait_sock *tw =
 175                 kmem_cache_alloc(sk->sk_prot_creator->twsk_prot->twsk_slab,
 176                                  GFP_ATOMIC);
 177         if (tw != NULL) {
 178                 const struct inet_sock *inet = inet_sk(sk);
 179
 180                 kmemcheck_annotate_bitfield(tw, flags);
 181
 182                 /* Give us an identity. */
 183                 tw->tw_daddr        = inet->inet_daddr;
 184                 tw->tw_rcv_saddr    = inet->inet_rcv_saddr;
 185                 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
 186                 tw->tw_tos          = inet->tos;
 187                 tw->tw_num          = inet->inet_num;
 188                 tw->tw_state        = TCP_TIME_WAIT;
 189                 tw->tw_substate     = state;
 190                 tw->tw_sport        = inet->inet_sport;
 191                 tw->tw_dport        = inet->inet_dport;
 192                 tw->tw_family       = sk->sk_family;
 193                 tw->tw_reuse        = sk->sk_reuse;
 194                 tw->tw_hash         = sk->sk_hash;
 195                 tw->tw_ipv6only     = 0;
 196                 tw->tw_transparent  = inet->transparent;
 197                 tw->tw_prot         = sk->sk_prot_creator;
 198                 twsk_net_set(tw, hold_net(sock_net(sk)));
 199                 /*
 200                  * Because we use RCU lookups, we should not set tw_refcnt
 201                  * to a non null value before everything is setup for this
 202                  * timewait socket.
 203                  */
 204                 atomic_set(&tw->tw_refcnt, 0);
 205                 inet_twsk_dead_node_init(tw);
 206                 __module_get(tw->tw_prot->owner);
 207         }
 208
 209         return tw;
 210 }
 211 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
 212
 213 /* Returns non-zero if quota exceeded.  */
 214 static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
 215                                     const int slot)
 216 {
 217         struct inet_timewait_sock *tw;
 218         unsigned int killed;
 219         int ret;
 220
 221         /* NOTE: compare this to previous version where lock
 222          * was released after detaching chain. It was racy,
 223          * because tw buckets are scheduled in not serialized context
 224          * in 2.3 (with netfilter), and with softnet it is common, because
 225          * soft irqs are not sequenced.
 226          */
 227         killed = 0;
 228         ret = 0;
 229 rescan:
 230         inet_twsk_for_each_inmate(tw, &twdr->cells[slot]) {
 231                 __inet_twsk_del_dead_node(tw);
 232                 spin_unlock(&twdr->death_lock);
 233                 __inet_twsk_kill(tw, twdr->hashinfo);
 234 #ifdef CONFIG_NET_NS
 235                 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED);
 236 #endif
 237                 inet_twsk_put(tw);
 238                 killed++;
 239                 spin_lock(&twdr->death_lock);
 240                 if (killed > INET_TWDR_TWKILL_QUOTA) {
 241                         ret = 1;
 242                         break;
 243                 }
 244
 245                 /* While we dropped twdr->death_lock, another cpu may have
 246                  * killed off the next TW bucket in the list, therefore
 247                  * do a fresh re-read of the hlist head node with the
 248                  * lock reacquired.  We still use the hlist traversal
 249                  * macro in order to get the prefetches.
 250                  */
 251                 goto rescan;
 252         }
 253
 254         twdr->tw_count -= killed;
 255 #ifndef CONFIG_NET_NS
 256         NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITED, killed);
 257 #endif
 258         return ret;
 259 }
 260
 261 void inet_twdr_hangman(unsigned long data)
 262 {
 263         struct inet_timewait_death_row *twdr;
 264         unsigned int need_timer;
 265
 266         twdr = (struct inet_timewait_death_row *)data;
 267         spin_lock(&twdr->death_lock);
 268
 269         if (twdr->tw_count == 0)
 270                 goto out;
 271
 272         need_timer = 0;
 273         if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
 274                 twdr->thread_slots |= (1 << twdr->slot);
 275                 schedule_work(&twdr->twkill_work);
 276                 need_timer = 1;
 277         } else {
 278                 /* We purged the entire slot, anything left?  */
 279                 if (twdr->tw_count)
 280                         need_timer = 1;
 281                 twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
 282         }
 283         if (need_timer)
 284                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 285 out:
 286         spin_unlock(&twdr->death_lock);
 287 }
 288 EXPORT_SYMBOL_GPL(inet_twdr_hangman);
 289
 290 void inet_twdr_twkill_work(struct work_struct *work)
 291 {
 292         struct inet_timewait_death_row *twdr =
 293                 container_of(work, struct inet_timewait_death_row, twkill_work);
 294         int i;
 295
 296         BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) >
 297                         (sizeof(twdr->thread_slots) * 8));
 298
 299         while (twdr->thread_slots) {
 300                 spin_lock_bh(&twdr->death_lock);
 301                 for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
 302                         if (!(twdr->thread_slots & (1 << i)))
 303                                 continue;
 304
 305                         while (inet_twdr_do_twkill_work(twdr, i) != 0) {
 306                                 if (need_resched()) {
 307                                         spin_unlock_bh(&twdr->death_lock);
 308                                         schedule();
 309                                         spin_lock_bh(&twdr->death_lock);
 310                                 }
 311                         }
 312
 313                         twdr->thread_slots &= ~(1 << i);
 314                 }
 315                 spin_unlock_bh(&twdr->death_lock);
 316         }
 317 }
 318 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);
 319
 320 /* These are always called from BH context.  See callers in
 321  * tcp_input.c to verify this.
 322  */
 323
 324 /* This is for handling early-kills of TIME_WAIT sockets. */
 325 void inet_twsk_deschedule(struct inet_timewait_sock *tw,
 326                           struct inet_timewait_death_row *twdr)
 327 {
 328         spin_lock(&twdr->death_lock);
 329         if (inet_twsk_del_dead_node(tw)) {
 330                 inet_twsk_put(tw);
 331                 if (--twdr->tw_count == 0)
 332                         del_timer(&twdr->tw_timer);
 333         }
 334         spin_unlock(&twdr->death_lock);
 335         __inet_twsk_kill(tw, twdr->hashinfo);
 336 }
 337 EXPORT_SYMBOL(inet_twsk_deschedule);
 338
 339 void inet_twsk_schedule(struct inet_timewait_sock *tw,
 340                        struct inet_timewait_death_row *twdr,
 341                        const int timeo, const int timewait_len)
 342 {
 343         struct hlist_head *list;
 344         int slot;
 345
 346         /* timeout := RTO * 3.5
 347          *
 348          * 3.5 = 1+2+0.5 to wait for two retransmits.
 349          *
 350          * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
 351          * our ACK acking that FIN can be lost. If N subsequent retransmitted
 352          * FINs (or previous seqments) are lost (probability of such event
 353          * is p^(N+1), where p is probability to lose single packet and
 354          * time to detect the loss is about RTO*(2^N - 1) with exponential
 355          * backoff). Normal timewait length is calculated so, that we
 356          * waited at least for one retransmitted FIN (maximal RTO is 120sec).
 357          * [ BTW Linux. following BSD, violates this requirement waiting
 358          *   only for 60sec, we should wait at least for 240 secs.
 359          *   Well, 240 consumes too much of resources 8)
 360          * ]
 361          * This interval is not reduced to catch old duplicate and
 362          * responces to our wandering segments living for two MSLs.
 363          * However, if we use PAWS to detect
 364          * old duplicates, we can reduce the interval to bounds required
 365          * by RTO, rather than MSL. So, if peer understands PAWS, we
 366          * kill tw bucket after 3.5*RTO (it is important that this number
 367          * is greater than TS tick!) and detect old duplicates with help
 368          * of PAWS.
 369          */
 370         slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
 371
 372         spin_lock(&twdr->death_lock);
 373
 374         /* Unlink it, if it was scheduled */
 375         if (inet_twsk_del_dead_node(tw))
 376                 twdr->tw_count--;
 377         else
 378                 atomic_inc(&tw->tw_refcnt);
 379
 380         if (slot >= INET_TWDR_RECYCLE_SLOTS) {
 381                 /* Schedule to slow timer */
 382                 if (timeo >= timewait_len) {
 383                         slot = INET_TWDR_TWKILL_SLOTS - 1;
 384                 } else {
 385                         slot = DIV_ROUND_UP(timeo, twdr->period);
 386                         if (slot >= INET_TWDR_TWKILL_SLOTS)
 387                                 slot = INET_TWDR_TWKILL_SLOTS - 1;
 388                 }
 389                 tw->tw_ttd = inet_tw_time_stamp() + timeo;
 390                 slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
 391                 list = &twdr->cells[slot];
 392         } else {
 393                 tw->tw_ttd = inet_tw_time_stamp() + (slot << INET_TWDR_RECYCLE_TICK);
 394
 395                 if (twdr->twcal_hand < 0) {
 396                         twdr->twcal_hand = 0;
 397                         twdr->twcal_jiffie = jiffies;
 398                         twdr->twcal_timer.expires = twdr->twcal_jiffie +
 399                                               (slot << INET_TWDR_RECYCLE_TICK);
 400                         add_timer(&twdr->twcal_timer);
 401                 } else {
 402                         if (time_after(twdr->twcal_timer.expires,
 403                                        jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
 404                                 mod_timer(&twdr->twcal_timer,
 405                                           jiffies + (slot << INET_TWDR_RECYCLE_TICK));
 406                         slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
 407                 }
 408                 list = &twdr->twcal_row[slot];
 409         }
 410
 411         hlist_add_head(&tw->tw_death_node, list);
 412
 413         if (twdr->tw_count++ == 0)
 414                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 415         spin_unlock(&twdr->death_lock);
 416 }
 417 EXPORT_SYMBOL_GPL(inet_twsk_schedule);
 418
 419 void inet_twdr_twcal_tick(unsigned long data)
 420 {
 421         struct inet_timewait_death_row *twdr;
 422         int n, slot;
 423         unsigned long j;
 424         unsigned long now = jiffies;
 425         int killed = 0;
 426         int adv = 0;
 427
 428         twdr = (struct inet_timewait_death_row *)data;
 429
 430         spin_lock(&twdr->death_lock);
 431         if (twdr->twcal_hand < 0)
 432                 goto out;
 433
 434         slot = twdr->twcal_hand;
 435         j = twdr->twcal_jiffie;
 436
 437         for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
 438                 if (time_before_eq(j, now)) {
 439                         struct hlist_node *safe;
 440                         struct inet_timewait_sock *tw;
 441
 442                         inet_twsk_for_each_inmate_safe(tw, safe,
 443                                                        &twdr->twcal_row[slot]) {
 444                                 __inet_twsk_del_dead_node(tw);
 445                                 __inet_twsk_kill(tw, twdr->hashinfo);
 446 #ifdef CONFIG_NET_NS
 447                                 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
 448 #endif
 449                                 inet_twsk_put(tw);
 450                                 killed++;
 451                         }
 452                 } else {
 453                         if (!adv) {
 454                                 adv = 1;
 455                                 twdr->twcal_jiffie = j;
 456                                 twdr->twcal_hand = slot;
 457                         }
 458
 459                         if (!hlist_empty(&twdr->twcal_row[slot])) {
 460                                 mod_timer(&twdr->twcal_timer, j);
 461                                 goto out;
 462                         }
 463                 }
 464                 j += 1 << INET_TWDR_RECYCLE_TICK;
 465                 slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
 466         }
 467         twdr->twcal_hand = -1;
 468
 469 out:
 470         if ((twdr->tw_count -= killed) == 0)
 471                 del_timer(&twdr->tw_timer);
 472 #ifndef CONFIG_NET_NS
 473         NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITKILLED, killed);
 474 #endif
 475         spin_unlock(&twdr->death_lock);
 476 }
 477 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);
 478
 479 void inet_twsk_purge(struct inet_hashinfo *hashinfo,
 480                      struct inet_timewait_death_row *twdr, int family)
 481 {
 482         struct inet_timewait_sock *tw;
 483         struct sock *sk;
 484         struct hlist_nulls_node *node;
 485         unsigned int slot;
 486
 487         for (slot = 0; slot <= hashinfo->ehash_mask; slot++) {
 488                 struct inet_ehash_bucket *head = &hashinfo->ehash[slot];
 489 restart_rcu:
 490                 rcu_read_lock();
 491 restart:
 492                 sk_nulls_for_each_rcu(sk, node, &head->chain) {
 493                         if (sk->sk_state != TCP_TIME_WAIT)
 494                                 continue;
 495                         tw = inet_twsk(sk);
 496                         if ((tw->tw_family != family) ||
 497                                 atomic_read(&twsk_net(tw)->count))
 498                                 continue;
 499
 500                         if (unlikely(!atomic_inc_not_zero(&tw->tw_refcnt)))
 501                                 continue;
 502
 503                         if (unlikely((tw->tw_family != family) ||
 504                                      atomic_read(&twsk_net(tw)->count))) {
 505                                 inet_twsk_put(tw);
 506                                 goto restart;
 507                         }
 508
 509                         rcu_read_unlock();
 510                         local_bh_disable();
 511                         inet_twsk_deschedule(tw, twdr);
 512                         local_bh_enable();
 513                         inet_twsk_put(tw);
 514                         goto restart_rcu;
 515                 }
 516                 /* If the nulls value we got at the end of this lookup is
 517                  * not the expected one, we must restart lookup.
 518                  * We probably met an item that was moved to another chain.
 519                  */
 520                 if (get_nulls_value(node) != slot)
 521                         goto restart;
 522                 rcu_read_unlock();
 523         }
 524 }
 525 EXPORT_SYMBOL_GPL(inet_twsk_purge);