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