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