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 #ifdef CONFIG_NET_NS
 164                 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITED);
 165 #endif
 166                 inet_twsk_put(tw);
 167                 killed++;
 168                 spin_lock(&twdr->death_lock);
 169                 if (killed > INET_TWDR_TWKILL_QUOTA) {
 170                         ret = 1;
 171                         break;
 172                 }
 173
 174                 /* While we dropped twdr->death_lock, another cpu may have
 175                  * killed off the next TW bucket in the list, therefore
 176                  * do a fresh re-read of the hlist head node with the
 177                  * lock reacquired.  We still use the hlist traversal
 178                  * macro in order to get the prefetches.
 179                  */
 180                 goto rescan;
 181         }
 182
 183         twdr->tw_count -= killed;
 184 #ifndef CONFIG_NET_NS
 185         NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITED, killed);
 186 #endif
 187         return ret;
 188 }
 189
 190 void inet_twdr_hangman(unsigned long data)
 191 {
 192         struct inet_timewait_death_row *twdr;
 193         int unsigned need_timer;
 194
 195         twdr = (struct inet_timewait_death_row *)data;
 196         spin_lock(&twdr->death_lock);
 197
 198         if (twdr->tw_count == 0)
 199                 goto out;
 200
 201         need_timer = 0;
 202         if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
 203                 twdr->thread_slots |= (1 << twdr->slot);
 204                 schedule_work(&twdr->twkill_work);
 205                 need_timer = 1;
 206         } else {
 207                 /* We purged the entire slot, anything left?  */
 208                 if (twdr->tw_count)
 209                         need_timer = 1;
 210         }
 211         twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
 212         if (need_timer)
 213                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 214 out:
 215         spin_unlock(&twdr->death_lock);
 216 }
 217
 218 EXPORT_SYMBOL_GPL(inet_twdr_hangman);
 219
 220 void inet_twdr_twkill_work(struct work_struct *work)
 221 {
 222         struct inet_timewait_death_row *twdr =
 223                 container_of(work, struct inet_timewait_death_row, twkill_work);
 224         int i;
 225
 226         BUILD_BUG_ON((INET_TWDR_TWKILL_SLOTS - 1) >
 227                         (sizeof(twdr->thread_slots) * 8));
 228
 229         while (twdr->thread_slots) {
 230                 spin_lock_bh(&twdr->death_lock);
 231                 for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
 232                         if (!(twdr->thread_slots & (1 << i)))
 233                                 continue;
 234
 235                         while (inet_twdr_do_twkill_work(twdr, i) != 0) {
 236                                 if (need_resched()) {
 237                                         spin_unlock_bh(&twdr->death_lock);
 238                                         schedule();
 239                                         spin_lock_bh(&twdr->death_lock);
 240                                 }
 241                         }
 242
 243                         twdr->thread_slots &= ~(1 << i);
 244                 }
 245                 spin_unlock_bh(&twdr->death_lock);
 246         }
 247 }
 248
 249 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);
 250
 251 /* These are always called from BH context.  See callers in
 252  * tcp_input.c to verify this.
 253  */
 254
 255 /* This is for handling early-kills of TIME_WAIT sockets. */
 256 void inet_twsk_deschedule(struct inet_timewait_sock *tw,
 257                           struct inet_timewait_death_row *twdr)
 258 {
 259         spin_lock(&twdr->death_lock);
 260         if (inet_twsk_del_dead_node(tw)) {
 261                 inet_twsk_put(tw);
 262                 if (--twdr->tw_count == 0)
 263                         del_timer(&twdr->tw_timer);
 264         }
 265         spin_unlock(&twdr->death_lock);
 266         __inet_twsk_kill(tw, twdr->hashinfo);
 267 }
 268
 269 EXPORT_SYMBOL(inet_twsk_deschedule);
 270
 271 void inet_twsk_schedule(struct inet_timewait_sock *tw,
 272                        struct inet_timewait_death_row *twdr,
 273                        const int timeo, const int timewait_len)
 274 {
 275         struct hlist_head *list;
 276         int slot;
 277
 278         /* timeout := RTO * 3.5
 279          *
 280          * 3.5 = 1+2+0.5 to wait for two retransmits.
 281          *
 282          * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
 283          * our ACK acking that FIN can be lost. If N subsequent retransmitted
 284          * FINs (or previous seqments) are lost (probability of such event
 285          * is p^(N+1), where p is probability to lose single packet and
 286          * time to detect the loss is about RTO*(2^N - 1) with exponential
 287          * backoff). Normal timewait length is calculated so, that we
 288          * waited at least for one retransmitted FIN (maximal RTO is 120sec).
 289          * [ BTW Linux. following BSD, violates this requirement waiting
 290          *   only for 60sec, we should wait at least for 240 secs.
 291          *   Well, 240 consumes too much of resources 8)
 292          * ]
 293          * This interval is not reduced to catch old duplicate and
 294          * responces to our wandering segments living for two MSLs.
 295          * However, if we use PAWS to detect
 296          * old duplicates, we can reduce the interval to bounds required
 297          * by RTO, rather than MSL. So, if peer understands PAWS, we
 298          * kill tw bucket after 3.5*RTO (it is important that this number
 299          * is greater than TS tick!) and detect old duplicates with help
 300          * of PAWS.
 301          */
 302         slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
 303
 304         spin_lock(&twdr->death_lock);
 305
 306         /* Unlink it, if it was scheduled */
 307         if (inet_twsk_del_dead_node(tw))
 308                 twdr->tw_count--;
 309         else
 310                 atomic_inc(&tw->tw_refcnt);
 311
 312         if (slot >= INET_TWDR_RECYCLE_SLOTS) {
 313                 /* Schedule to slow timer */
 314                 if (timeo >= timewait_len) {
 315                         slot = INET_TWDR_TWKILL_SLOTS - 1;
 316                 } else {
 317                         slot = DIV_ROUND_UP(timeo, twdr->period);
 318                         if (slot >= INET_TWDR_TWKILL_SLOTS)
 319                                 slot = INET_TWDR_TWKILL_SLOTS - 1;
 320                 }
 321                 tw->tw_ttd = jiffies + timeo;
 322                 slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
 323                 list = &twdr->cells[slot];
 324         } else {
 325                 tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK);
 326
 327                 if (twdr->twcal_hand < 0) {
 328                         twdr->twcal_hand = 0;
 329                         twdr->twcal_jiffie = jiffies;
 330                         twdr->twcal_timer.expires = twdr->twcal_jiffie +
 331                                               (slot << INET_TWDR_RECYCLE_TICK);
 332                         add_timer(&twdr->twcal_timer);
 333                 } else {
 334                         if (time_after(twdr->twcal_timer.expires,
 335                                        jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
 336                                 mod_timer(&twdr->twcal_timer,
 337                                           jiffies + (slot << INET_TWDR_RECYCLE_TICK));
 338                         slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
 339                 }
 340                 list = &twdr->twcal_row[slot];
 341         }
 342
 343         hlist_add_head(&tw->tw_death_node, list);
 344
 345         if (twdr->tw_count++ == 0)
 346                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 347         spin_unlock(&twdr->death_lock);
 348 }
 349
 350 EXPORT_SYMBOL_GPL(inet_twsk_schedule);
 351
 352 void inet_twdr_twcal_tick(unsigned long data)
 353 {
 354         struct inet_timewait_death_row *twdr;
 355         int n, slot;
 356         unsigned long j;
 357         unsigned long now = jiffies;
 358         int killed = 0;
 359         int adv = 0;
 360
 361         twdr = (struct inet_timewait_death_row *)data;
 362
 363         spin_lock(&twdr->death_lock);
 364         if (twdr->twcal_hand < 0)
 365                 goto out;
 366
 367         slot = twdr->twcal_hand;
 368         j = twdr->twcal_jiffie;
 369
 370         for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
 371                 if (time_before_eq(j, now)) {
 372                         struct hlist_node *node, *safe;
 373                         struct inet_timewait_sock *tw;
 374
 375                         inet_twsk_for_each_inmate_safe(tw, node, safe,
 376                                                        &twdr->twcal_row[slot]) {
 377                                 __inet_twsk_del_dead_node(tw);
 378                                 __inet_twsk_kill(tw, twdr->hashinfo);
 379 #ifdef CONFIG_NET_NS
 380                                 NET_INC_STATS_BH(twsk_net(tw), LINUX_MIB_TIMEWAITKILLED);
 381 #endif
 382                                 inet_twsk_put(tw);
 383                                 killed++;
 384                         }
 385                 } else {
 386                         if (!adv) {
 387                                 adv = 1;
 388                                 twdr->twcal_jiffie = j;
 389                                 twdr->twcal_hand = slot;
 390                         }
 391
 392                         if (!hlist_empty(&twdr->twcal_row[slot])) {
 393                                 mod_timer(&twdr->twcal_timer, j);
 394                                 goto out;
 395                         }
 396                 }
 397                 j += 1 << INET_TWDR_RECYCLE_TICK;
 398                 slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
 399         }
 400         twdr->twcal_hand = -1;
 401
 402 out:
 403         if ((twdr->tw_count -= killed) == 0)
 404                 del_timer(&twdr->tw_timer);
 405 #ifndef CONFIG_NET_NS
 406         NET_ADD_STATS_BH(&init_net, LINUX_MIB_TIMEWAITKILLED, killed);
 407 #endif
 408         spin_unlock(&twdr->death_lock);
 409 }
 410
 411 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);