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