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