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