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 <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. */
  17 static 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
  52 void 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 }
  66 EXPORT_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  */
  73 void __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
 110 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
 111
 112 struct 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
 144 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
 145
 146 /* Returns non-zero if quota exceeded.  */
 147 static 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;
 163 rescan:
 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
 195 void 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);
 219 out:
 220         spin_unlock(&twdr->death_lock);
 221 }
 222
 223 EXPORT_SYMBOL_GPL(inet_twdr_hangman);
 224
 225 void 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
 254 EXPORT_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. */
 261 void 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
 274 EXPORT_SYMBOL(inet_twsk_deschedule);
 275
 276 void 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
 355 EXPORT_SYMBOL_GPL(inet_twsk_schedule);
 356
 357 void 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
 407 out:
 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
 416 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);
 417
 418 void 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);
 431 restart:
 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 }
 451 EXPORT_SYMBOL_GPL(inet_twsk_purge);