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         BUG_TRAP(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_prot         = sk->sk_prot_creator;
 130                 twsk_net_set(tw, hold_net(sock_net(sk)));
 131                 atomic_set(&tw->tw_refcnt, 1);
 132                 inet_twsk_dead_node_init(tw);
 133                 __module_get(tw->tw_prot->owner);
 134         }
 135
 136         return tw;
 137 }
 138
 139 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
 140
 141 /* Returns non-zero if quota exceeded.  */
 142 static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
 143                                     const int slot)
 144 {
 145         struct inet_timewait_sock *tw;
 146         struct hlist_node *node;
 147         unsigned int killed;
 148         int ret;
 149
 150         /* NOTE: compare this to previous version where lock
 151          * was released after detaching chain. It was racy,
 152          * because tw buckets are scheduled in not serialized context
 153          * in 2.3 (with netfilter), and with softnet it is common, because
 154          * soft irqs are not sequenced.
 155          */
 156         killed = 0;
 157         ret = 0;
 158 rescan:
 159         inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) {
 160                 __inet_twsk_del_dead_node(tw);
 161                 spin_unlock(&twdr->death_lock);
 162                 __inet_twsk_kill(tw, twdr->hashinfo);
 163                 inet_twsk_put(tw);
 164                 killed++;
 165                 spin_lock(&twdr->death_lock);
 166                 if (killed > INET_TWDR_TWKILL_QUOTA) {
 167                         ret = 1;
 168                         break;
 169                 }
 170
 171                 /* While we dropped twdr->death_lock, another cpu may have
 172                  * killed off the next TW bucket in the list, therefore
 173                  * do a fresh re-read of the hlist head node with the
 174                  * lock reacquired.  We still use the hlist traversal
 175                  * macro in order to get the prefetches.
 176                  */
 177                 goto rescan;
 178         }
 179
 180         twdr->tw_count -= killed;
 181         NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed);
 182
 183         return ret;
 184 }
 185
 186 void inet_twdr_hangman(unsigned long data)
 187 {
 188         struct inet_timewait_death_row *twdr;
 189         int unsigned need_timer;
 190
 191         twdr = (struct inet_timewait_death_row *)data;
 192         spin_lock(&twdr->death_lock);
 193
 194         if (twdr->tw_count == 0)
 195                 goto out;
 196
 197         need_timer = 0;
 198         if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
 199                 twdr->thread_slots |= (1 << twdr->slot);
 200                 schedule_work(&twdr->twkill_work);
 201                 need_timer = 1;
 202         } else {
 203                 /* We purged the entire slot, anything left?  */
 204                 if (twdr->tw_count)
 205                         need_timer = 1;
 206         }
 207         twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
 208         if (need_timer)
 209                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 210 out:
 211         spin_unlock(&twdr->death_lock);
 212 }
 213
 214 EXPORT_SYMBOL_GPL(inet_twdr_hangman);
 215
 216 void inet_twdr_twkill_work(struct work_struct *work)
 217 {
 218         struct inet_timewait_death_row *twdr =
 219                 container_of(work, struct inet_timewait_death_row, twkill_work);
 220         int i;
 221
 222         BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) >
 223                         (sizeof(twdr->thread_slots) * 8));
 224
 225         while (twdr->thread_slots) {
 226                 spin_lock_bh(&twdr->death_lock);
 227                 for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
 228                         if (!(twdr->thread_slots & (1 << i)))
 229                                 continue;
 230
 231                         while (inet_twdr_do_twkill_work(twdr, i) != 0) {
 232                                 if (need_resched()) {
 233                                         spin_unlock_bh(&twdr->death_lock);
 234                                         schedule();
 235                                         spin_lock_bh(&twdr->death_lock);
 236                                 }
 237                         }
 238
 239                         twdr->thread_slots &= ~(1 << i);
 240                 }
 241                 spin_unlock_bh(&twdr->death_lock);
 242         }
 243 }
 244
 245 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);
 246
 247 /* These are always called from BH context.  See callers in
 248  * tcp_input.c to verify this.
 249  */
 250
 251 /* This is for handling early-kills of TIME_WAIT sockets. */
 252 void inet_twsk_deschedule(struct inet_timewait_sock *tw,
 253                           struct inet_timewait_death_row *twdr)
 254 {
 255         spin_lock(&twdr->death_lock);
 256         if (inet_twsk_del_dead_node(tw)) {
 257                 inet_twsk_put(tw);
 258                 if (--twdr->tw_count == 0)
 259                         del_timer(&twdr->tw_timer);
 260         }
 261         spin_unlock(&twdr->death_lock);
 262         __inet_twsk_kill(tw, twdr->hashinfo);
 263 }
 264
 265 EXPORT_SYMBOL(inet_twsk_deschedule);
 266
 267 void inet_twsk_schedule(struct inet_timewait_sock *tw,
 268                        struct inet_timewait_death_row *twdr,
 269                        const int timeo, const int timewait_len)
 270 {
 271         struct hlist_head *list;
 272         int slot;
 273
 274         /* timeout := RTO * 3.5
 275          *
 276          * 3.5 = 1+2+0.5 to wait for two retransmits.
 277          *
 278          * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
 279          * our ACK acking that FIN can be lost. If N subsequent retransmitted
 280          * FINs (or previous seqments) are lost (probability of such event
 281          * is p^(N+1), where p is probability to lose single packet and
 282          * time to detect the loss is about RTO*(2^N - 1) with exponential
 283          * backoff). Normal timewait length is calculated so, that we
 284          * waited at least for one retransmitted FIN (maximal RTO is 120sec).
 285          * [ BTW Linux. following BSD, violates this requirement waiting
 286          *   only for 60sec, we should wait at least for 240 secs.
 287          *   Well, 240 consumes too much of resources 8)
 288          * ]
 289          * This interval is not reduced to catch old duplicate and
 290          * responces to our wandering segments living for two MSLs.
 291          * However, if we use PAWS to detect
 292          * old duplicates, we can reduce the interval to bounds required
 293          * by RTO, rather than MSL. So, if peer understands PAWS, we
 294          * kill tw bucket after 3.5*RTO (it is important that this number
 295          * is greater than TS tick!) and detect old duplicates with help
 296          * of PAWS.
 297          */
 298         slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
 299
 300         spin_lock(&twdr->death_lock);
 301
 302         /* Unlink it, if it was scheduled */
 303         if (inet_twsk_del_dead_node(tw))
 304                 twdr->tw_count--;
 305         else
 306                 atomic_inc(&tw->tw_refcnt);
 307
 308         if (slot >= INET_TWDR_RECYCLE_SLOTS) {
 309                 /* Schedule to slow timer */
 310                 if (timeo >= timewait_len) {
 311                         slot = INET_TWDR_TWKILL_SLOTS - 1;
 312                 } else {
 313                         slot = DIV_ROUND_UP(timeo, twdr->period);
 314                         if (slot >= INET_TWDR_TWKILL_SLOTS)
 315                                 slot = INET_TWDR_TWKILL_SLOTS - 1;
 316                 }
 317                 tw->tw_ttd = jiffies + timeo;
 318                 slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
 319                 list = &twdr->cells[slot];
 320         } else {
 321                 tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK);
 322
 323                 if (twdr->twcal_hand < 0) {
 324                         twdr->twcal_hand = 0;
 325                         twdr->twcal_jiffie = jiffies;
 326                         twdr->twcal_timer.expires = twdr->twcal_jiffie +
 327                                               (slot << INET_TWDR_RECYCLE_TICK);
 328                         add_timer(&twdr->twcal_timer);
 329                 } else {
 330                         if (time_after(twdr->twcal_timer.expires,
 331                                        jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
 332                                 mod_timer(&twdr->twcal_timer,
 333                                           jiffies + (slot << INET_TWDR_RECYCLE_TICK));
 334                         slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
 335                 }
 336                 list = &twdr->twcal_row[slot];
 337         }
 338
 339         hlist_add_head(&tw->tw_death_node, list);
 340
 341         if (twdr->tw_count++ == 0)
 342                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 343         spin_unlock(&twdr->death_lock);
 344 }
 345
 346 EXPORT_SYMBOL_GPL(inet_twsk_schedule);
 347
 348 void inet_twdr_twcal_tick(unsigned long data)
 349 {
 350         struct inet_timewait_death_row *twdr;
 351         int n, slot;
 352         unsigned long j;
 353         unsigned long now = jiffies;
 354         int killed = 0;
 355         int adv = 0;
 356
 357         twdr = (struct inet_timewait_death_row *)data;
 358
 359         spin_lock(&twdr->death_lock);
 360         if (twdr->twcal_hand < 0)
 361                 goto out;
 362
 363         slot = twdr->twcal_hand;
 364         j = twdr->twcal_jiffie;
 365
 366         for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
 367                 if (time_before_eq(j, now)) {
 368                         struct hlist_node *node, *safe;
 369                         struct inet_timewait_sock *tw;
 370
 371                         inet_twsk_for_each_inmate_safe(tw, node, safe,
 372                                                        &twdr->twcal_row[slot]) {
 373                                 __inet_twsk_del_dead_node(tw);
 374                                 __inet_twsk_kill(tw, twdr->hashinfo);
 375                                 inet_twsk_put(tw);
 376                                 killed++;
 377                         }
 378                 } else {
 379                         if (!adv) {
 380                                 adv = 1;
 381                                 twdr->twcal_jiffie = j;
 382                                 twdr->twcal_hand = slot;
 383                         }
 384
 385                         if (!hlist_empty(&twdr->twcal_row[slot])) {
 386                                 mod_timer(&twdr->twcal_timer, j);
 387                                 goto out;
 388                         }
 389                 }
 390                 j += 1 << INET_TWDR_RECYCLE_TICK;
 391                 slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
 392         }
 393         twdr->twcal_hand = -1;
 394
 395 out:
 396         if ((twdr->tw_count -= killed) == 0)
 397                 del_timer(&twdr->tw_timer);
 398         NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed);
 399         spin_unlock(&twdr->death_lock);
 400 }
 401
 402 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);