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 static 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
  65 void inet_twsk_put(struct inet_timewait_sock *tw)
  66 {
  67         if (atomic_dec_and_test(&tw->tw_refcnt))
  68                 inet_twsk_free(tw);
  69 }
  70 EXPORT_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  */
  77 void __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
 114 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
 115
 116 struct 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
 150 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
 151
 152 /* Returns non-zero if quota exceeded.  */
 153 static 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;
 169 rescan:
 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
 201 void 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         }
 222         twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
 223         if (need_timer)
 224                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 225 out:
 226         spin_unlock(&twdr->death_lock);
 227 }
 228
 229 EXPORT_SYMBOL_GPL(inet_twdr_hangman);
 230
 231 void 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
 260 EXPORT_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. */
 267 void 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
 280 EXPORT_SYMBOL(inet_twsk_deschedule);
 281
 282 void 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
 361 EXPORT_SYMBOL_GPL(inet_twsk_schedule);
 362
 363 void 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
 413 out:
 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
 422 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);
 423
 424 void 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);
 437 restart:
 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 }
 457 EXPORT_SYMBOL_GPL(inet_twsk_purge);