linux/net/ipv4/inet_timewait_sock.c
<<
>>
Prefs
   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 <net/inet_hashtables.h>
  15#include <net/inet_timewait_sock.h>
  16#include <net/ip.h>
  17
  18
  19/**
  20 *      inet_twsk_unhash - unhash a timewait socket from established hash
  21 *      @tw: timewait socket
  22 *
  23 *      unhash a timewait socket from established hash, if hashed.
  24 *      ehash lock must be held by caller.
  25 *      Returns 1 if caller should call inet_twsk_put() after lock release.
  26 */
  27int inet_twsk_unhash(struct inet_timewait_sock *tw)
  28{
  29        if (hlist_nulls_unhashed(&tw->tw_node))
  30                return 0;
  31
  32        hlist_nulls_del_rcu(&tw->tw_node);
  33        sk_nulls_node_init(&tw->tw_node);
  34        /*
  35         * We cannot call inet_twsk_put() ourself under lock,
  36         * caller must call it for us.
  37         */
  38        return 1;
  39}
  40
  41/**
  42 *      inet_twsk_bind_unhash - unhash a timewait socket from bind hash
  43 *      @tw: timewait socket
  44 *      @hashinfo: hashinfo pointer
  45 *
  46 *      unhash a timewait socket from bind hash, if hashed.
  47 *      bind hash lock must be held by caller.
  48 *      Returns 1 if caller should call inet_twsk_put() after lock release.
  49 */
  50int inet_twsk_bind_unhash(struct inet_timewait_sock *tw,
  51                          struct inet_hashinfo *hashinfo)
  52{
  53        struct inet_bind_bucket *tb = tw->tw_tb;
  54
  55        if (!tb)
  56                return 0;
  57
  58        __hlist_del(&tw->tw_bind_node);
  59        tw->tw_tb = NULL;
  60        inet_bind_bucket_destroy(hashinfo->bind_bucket_cachep, tb);
  61        /*
  62         * We cannot call inet_twsk_put() ourself under lock,
  63         * caller must call it for us.
  64         */
  65        return 1;
  66}
  67
  68/* Must be called with locally disabled BHs. */
  69static void __inet_twsk_kill(struct inet_timewait_sock *tw,
  70                             struct inet_hashinfo *hashinfo)
  71{
  72        struct inet_bind_hashbucket *bhead;
  73        int refcnt;
  74        /* Unlink from established hashes. */
  75        spinlock_t *lock = inet_ehash_lockp(hashinfo, tw->tw_hash);
  76
  77        spin_lock(lock);
  78        refcnt = inet_twsk_unhash(tw);
  79        spin_unlock(lock);
  80
  81        /* Disassociate with bind bucket. */
  82        bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), tw->tw_num,
  83                        hashinfo->bhash_size)];
  84
  85        spin_lock(&bhead->lock);
  86        refcnt += inet_twsk_bind_unhash(tw, hashinfo);
  87        spin_unlock(&bhead->lock);
  88
  89#ifdef SOCK_REFCNT_DEBUG
  90        if (atomic_read(&tw->tw_refcnt) != 1) {
  91                printk(KERN_DEBUG "%s timewait_sock %p refcnt=%d\n",
  92                       tw->tw_prot->name, tw, atomic_read(&tw->tw_refcnt));
  93        }
  94#endif
  95        while (refcnt) {
  96                inet_twsk_put(tw);
  97                refcnt--;
  98        }
  99}
 100
 101static noinline void inet_twsk_free(struct inet_timewait_sock *tw)
 102{
 103        struct module *owner = tw->tw_prot->owner;
 104        twsk_destructor((struct sock *)tw);
 105#ifdef SOCK_REFCNT_DEBUG
 106        pr_debug("%s timewait_sock %p released\n", tw->tw_prot->name, tw);
 107#endif
 108        release_net(twsk_net(tw));
 109        kmem_cache_free(tw->tw_prot->twsk_prot->twsk_slab, tw);
 110        module_put(owner);
 111}
 112
 113void inet_twsk_put(struct inet_timewait_sock *tw)
 114{
 115        if (atomic_dec_and_test(&tw->tw_refcnt))
 116                inet_twsk_free(tw);
 117}
 118EXPORT_SYMBOL_GPL(inet_twsk_put);
 119
 120/*
 121 * Enter the time wait state. This is called with locally disabled BH.
 122 * Essentially we whip up a timewait bucket, copy the relevant info into it
 123 * from the SK, and mess with hash chains and list linkage.
 124 */
 125void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
 126                           struct inet_hashinfo *hashinfo)
 127{
 128        const struct inet_sock *inet = inet_sk(sk);
 129        const struct inet_connection_sock *icsk = inet_csk(sk);
 130        struct inet_ehash_bucket *ehead = inet_ehash_bucket(hashinfo, sk->sk_hash);
 131        spinlock_t *lock = inet_ehash_lockp(hashinfo, sk->sk_hash);
 132        struct inet_bind_hashbucket *bhead;
 133        /* Step 1: Put TW into bind hash. Original socket stays there too.
 134           Note, that any socket with inet->num != 0 MUST be bound in
 135           binding cache, even if it is closed.
 136         */
 137        bhead = &hashinfo->bhash[inet_bhashfn(twsk_net(tw), inet->inet_num,
 138                        hashinfo->bhash_size)];
 139        spin_lock(&bhead->lock);
 140        tw->tw_tb = icsk->icsk_bind_hash;
 141        WARN_ON(!icsk->icsk_bind_hash);
 142        inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
 143        spin_unlock(&bhead->lock);
 144
 145        spin_lock(lock);
 146
 147        /*
 148         * Step 2: Hash TW into TIMEWAIT chain.
 149         * Should be done before removing sk from established chain
 150         * because readers are lockless and search established first.
 151         */
 152        inet_twsk_add_node_rcu(tw, &ehead->twchain);
 153
 154        /* Step 3: Remove SK from established hash. */
 155        if (__sk_nulls_del_node_init_rcu(sk))
 156                sock_prot_inuse_add(sock_net(sk), sk->sk_prot, -1);
 157
 158        /*
 159         * Notes :
 160         * - We initially set tw_refcnt to 0 in inet_twsk_alloc()
 161         * - We add one reference for the bhash link
 162         * - We add one reference for the ehash link
 163         * - We want this refcnt update done before allowing other
 164         *   threads to find this tw in ehash chain.
 165         */
 166        atomic_add(1 + 1 + 1, &tw->tw_refcnt);
 167
 168        spin_unlock(lock);
 169}
 170EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
 171
 172struct 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_num          = inet->inet_num;
 187                tw->tw_state        = TCP_TIME_WAIT;
 188                tw->tw_substate     = state;
 189                tw->tw_sport        = inet->inet_sport;
 190                tw->tw_dport        = inet->inet_dport;
 191                tw->tw_family       = sk->sk_family;
 192                tw->tw_reuse        = sk->sk_reuse;
 193                tw->tw_hash         = sk->sk_hash;
 194                tw->tw_ipv6only     = 0;
 195                tw->tw_transparent  = inet->transparent;
 196                tw->tw_prot         = sk->sk_prot_creator;
 197                twsk_net_set(tw, hold_net(sock_net(sk)));
 198                /*
 199                 * Because we use RCU lookups, we should not set tw_refcnt
 200                 * to a non null value before everything is setup for this
 201                 * timewait socket.
 202                 */
 203                atomic_set(&tw->tw_refcnt, 0);
 204                inet_twsk_dead_node_init(tw);
 205                __module_get(tw->tw_prot->owner);
 206        }
 207
 208        return tw;
 209}
 210EXPORT_SYMBOL_GPL(inet_twsk_alloc);
 211
 212/* Returns non-zero if quota exceeded.  */
 213static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
 214                                    const int slot)
 215{
 216        struct inet_timewait_sock *tw;
 217        struct hlist_node *node;
 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;
 229rescan:
 230        inet_twsk_for_each_inmate(tw, node, &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
 261void inet_twdr_hangman(unsigned long data)
 262{
 263        struct inet_timewait_death_row *twdr;
 264        int unsigned 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);
 285out:
 286        spin_unlock(&twdr->death_lock);
 287}
 288EXPORT_SYMBOL_GPL(inet_twdr_hangman);
 289
 290void 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}
 318EXPORT_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. */
 325void 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}
 337EXPORT_SYMBOL(inet_twsk_deschedule);
 338
 339void 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 = jiffies + timeo;
 390                slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
 391                list = &twdr->cells[slot];
 392        } else {
 393                tw->tw_ttd = jiffies + (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}
 417EXPORT_SYMBOL_GPL(inet_twsk_schedule);
 418
 419void 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 *node, *safe;
 440                        struct inet_timewait_sock *tw;
 441
 442                        inet_twsk_for_each_inmate_safe(tw, node, 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
 469out:
 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}
 477EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);
 478
 479void 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];
 489restart_rcu:
 490                rcu_read_lock();
 491restart:
 492                sk_nulls_for_each_rcu(sk, node, &head->twchain) {
 493                        tw = inet_twsk(sk);
 494                        if ((tw->tw_family != family) ||
 495                                atomic_read(&twsk_net(tw)->count))
 496                                continue;
 497
 498                        if (unlikely(!atomic_inc_not_zero(&tw->tw_refcnt)))
 499                                continue;
 500
 501                        if (unlikely((tw->tw_family != family) ||
 502                                     atomic_read(&twsk_net(tw)->count))) {
 503                                inet_twsk_put(tw);
 504                                goto restart;
 505                        }
 506
 507                        rcu_read_unlock();
 508                        inet_twsk_deschedule(tw, twdr);
 509                        inet_twsk_put(tw);
 510                        goto restart_rcu;
 511                }
 512                /* If the nulls value we got at the end of this lookup is
 513                 * not the expected one, we must restart lookup.
 514                 * We probably met an item that was moved to another chain.
 515                 */
 516                if (get_nulls_value(node) != slot)
 517                        goto restart;
 518                rcu_read_unlock();
 519        }
 520}
 521EXPORT_SYMBOL_GPL(inet_twsk_purge);
 522