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