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/config.h>
  12
  13 #include <net/inet_hashtables.h>
  14 #include <net/inet_timewait_sock.h>
  15 #include <net/ip.h>
  16
  17 /* Must be called with locally disabled BHs. */
  18 void __inet_twsk_kill(struct inet_timewait_sock *tw, struct inet_hashinfo *hashinfo)
  19 {
  20         struct inet_bind_hashbucket *bhead;
  21         struct inet_bind_bucket *tb;
  22         /* Unlink from established hashes. */
  23         struct inet_ehash_bucket *ehead = &hashinfo->ehash[tw->tw_hashent];
  24
  25         write_lock(&ehead->lock);
  26         if (hlist_unhashed(&tw->tw_node)) {
  27                 write_unlock(&ehead->lock);
  28                 return;
  29         }
  30         __hlist_del(&tw->tw_node);
  31         sk_node_init(&tw->tw_node);
  32         write_unlock(&ehead->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 EXPORT_SYMBOL_GPL(__inet_twsk_kill);
  52
  53 /*
  54  * Enter the time wait state. This is called with locally disabled BH.
  55  * Essentially we whip up a timewait bucket, copy the relevant info into it
  56  * from the SK, and mess with hash chains and list linkage.
  57  */
  58 void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
  59                            struct inet_hashinfo *hashinfo)
  60 {
  61         const struct inet_sock *inet = inet_sk(sk);
  62         const struct inet_connection_sock *icsk = inet_csk(sk);
  63         struct inet_ehash_bucket *ehead = &hashinfo->ehash[sk->sk_hashent];
  64         struct inet_bind_hashbucket *bhead;
  65         /* Step 1: Put TW into bind hash. Original socket stays there too.
  66            Note, that any socket with inet->num != 0 MUST be bound in
  67            binding cache, even if it is closed.
  68          */
  69         bhead = &hashinfo->bhash[inet_bhashfn(inet->num, hashinfo->bhash_size)];
  70         spin_lock(&bhead->lock);
  71         tw->tw_tb = icsk->icsk_bind_hash;
  72         BUG_TRAP(icsk->icsk_bind_hash);
  73         inet_twsk_add_bind_node(tw, &tw->tw_tb->owners);
  74         spin_unlock(&bhead->lock);
  75
  76         write_lock(&ehead->lock);
  77
  78         /* Step 2: Remove SK from established hash. */
  79         if (__sk_del_node_init(sk))
  80                 sock_prot_dec_use(sk->sk_prot);
  81
  82         /* Step 3: Hash TW into TIMEWAIT half of established hash table. */
  83         inet_twsk_add_node(tw, &(ehead + hashinfo->ehash_size)->chain);
  84         atomic_inc(&tw->tw_refcnt);
  85
  86         write_unlock(&ehead->lock);
  87 }
  88
  89 EXPORT_SYMBOL_GPL(__inet_twsk_hashdance);
  90
  91 struct inet_timewait_sock *inet_twsk_alloc(const struct sock *sk, const int state)
  92 {
  93         struct inet_timewait_sock *tw = kmem_cache_alloc(sk->sk_prot_creator->twsk_slab,
  94                                                          SLAB_ATOMIC);
  95         if (tw != NULL) {
  96                 const struct inet_sock *inet = inet_sk(sk);
  97
  98                 /* Give us an identity. */
  99                 tw->tw_daddr        = inet->daddr;
 100                 tw->tw_rcv_saddr    = inet->rcv_saddr;
 101                 tw->tw_bound_dev_if = sk->sk_bound_dev_if;
 102                 tw->tw_num          = inet->num;
 103                 tw->tw_state        = TCP_TIME_WAIT;
 104                 tw->tw_substate     = state;
 105                 tw->tw_sport        = inet->sport;
 106                 tw->tw_dport        = inet->dport;
 107                 tw->tw_family       = sk->sk_family;
 108                 tw->tw_reuse        = sk->sk_reuse;
 109                 tw->tw_hashent      = sk->sk_hashent;
 110                 tw->tw_ipv6only     = 0;
 111                 tw->tw_prot         = sk->sk_prot_creator;
 112                 atomic_set(&tw->tw_refcnt, 1);
 113                 inet_twsk_dead_node_init(tw);
 114         }
 115
 116         return tw;
 117 }
 118
 119 EXPORT_SYMBOL_GPL(inet_twsk_alloc);
 120
 121 /* Returns non-zero if quota exceeded.  */
 122 static int inet_twdr_do_twkill_work(struct inet_timewait_death_row *twdr,
 123                                     const int slot)
 124 {
 125         struct inet_timewait_sock *tw;
 126         struct hlist_node *node;
 127         unsigned int killed;
 128         int ret;
 129
 130         /* NOTE: compare this to previous version where lock
 131          * was released after detaching chain. It was racy,
 132          * because tw buckets are scheduled in not serialized context
 133          * in 2.3 (with netfilter), and with softnet it is common, because
 134          * soft irqs are not sequenced.
 135          */
 136         killed = 0;
 137         ret = 0;
 138 rescan:
 139         inet_twsk_for_each_inmate(tw, node, &twdr->cells[slot]) {
 140                 __inet_twsk_del_dead_node(tw);
 141                 spin_unlock(&twdr->death_lock);
 142                 __inet_twsk_kill(tw, twdr->hashinfo);
 143                 inet_twsk_put(tw);
 144                 killed++;
 145                 spin_lock(&twdr->death_lock);
 146                 if (killed > INET_TWDR_TWKILL_QUOTA) {
 147                         ret = 1;
 148                         break;
 149                 }
 150
 151                 /* While we dropped twdr->death_lock, another cpu may have
 152                  * killed off the next TW bucket in the list, therefore
 153                  * do a fresh re-read of the hlist head node with the
 154                  * lock reacquired.  We still use the hlist traversal
 155                  * macro in order to get the prefetches.
 156                  */
 157                 goto rescan;
 158         }
 159
 160         twdr->tw_count -= killed;
 161         NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITED, killed);
 162
 163         return ret;
 164 }
 165
 166 void inet_twdr_hangman(unsigned long data)
 167 {
 168         struct inet_timewait_death_row *twdr;
 169         int unsigned need_timer;
 170
 171         twdr = (struct inet_timewait_death_row *)data;
 172         spin_lock(&twdr->death_lock);
 173
 174         if (twdr->tw_count == 0)
 175                 goto out;
 176
 177         need_timer = 0;
 178         if (inet_twdr_do_twkill_work(twdr, twdr->slot)) {
 179                 twdr->thread_slots |= (1 << twdr->slot);
 180                 mb();
 181                 schedule_work(&twdr->twkill_work);
 182                 need_timer = 1;
 183         } else {
 184                 /* We purged the entire slot, anything left?  */
 185                 if (twdr->tw_count)
 186                         need_timer = 1;
 187         }
 188         twdr->slot = ((twdr->slot + 1) & (INET_TWDR_TWKILL_SLOTS - 1));
 189         if (need_timer)
 190                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 191 out:
 192         spin_unlock(&twdr->death_lock);
 193 }
 194
 195 EXPORT_SYMBOL_GPL(inet_twdr_hangman);
 196
 197 extern void twkill_slots_invalid(void);
 198
 199 void inet_twdr_twkill_work(void *data)
 200 {
 201         struct inet_timewait_death_row *twdr = data;
 202         int i;
 203
 204         if ((INET_TWDR_TWKILL_SLOTS - 1) > (sizeof(twdr->thread_slots) * 8))
 205                 twkill_slots_invalid();
 206
 207         while (twdr->thread_slots) {
 208                 spin_lock_bh(&twdr->death_lock);
 209                 for (i = 0; i < INET_TWDR_TWKILL_SLOTS; i++) {
 210                         if (!(twdr->thread_slots & (1 << i)))
 211                                 continue;
 212
 213                         while (inet_twdr_do_twkill_work(twdr, i) != 0) {
 214                                 if (need_resched()) {
 215                                         spin_unlock_bh(&twdr->death_lock);
 216                                         schedule();
 217                                         spin_lock_bh(&twdr->death_lock);
 218                                 }
 219                         }
 220
 221                         twdr->thread_slots &= ~(1 << i);
 222                 }
 223                 spin_unlock_bh(&twdr->death_lock);
 224         }
 225 }
 226
 227 EXPORT_SYMBOL_GPL(inet_twdr_twkill_work);
 228
 229 /* These are always called from BH context.  See callers in
 230  * tcp_input.c to verify this.
 231  */
 232
 233 /* This is for handling early-kills of TIME_WAIT sockets. */
 234 void inet_twsk_deschedule(struct inet_timewait_sock *tw,
 235                           struct inet_timewait_death_row *twdr)
 236 {
 237         spin_lock(&twdr->death_lock);
 238         if (inet_twsk_del_dead_node(tw)) {
 239                 inet_twsk_put(tw);
 240                 if (--twdr->tw_count == 0)
 241                         del_timer(&twdr->tw_timer);
 242         }
 243         spin_unlock(&twdr->death_lock);
 244         __inet_twsk_kill(tw, twdr->hashinfo);
 245 }
 246
 247 EXPORT_SYMBOL(inet_twsk_deschedule);
 248
 249 void inet_twsk_schedule(struct inet_timewait_sock *tw,
 250                        struct inet_timewait_death_row *twdr,
 251                        const int timeo, const int timewait_len)
 252 {
 253         struct hlist_head *list;
 254         int slot;
 255
 256         /* timeout := RTO * 3.5
 257          *
 258          * 3.5 = 1+2+0.5 to wait for two retransmits.
 259          *
 260          * RATIONALE: if FIN arrived and we entered TIME-WAIT state,
 261          * our ACK acking that FIN can be lost. If N subsequent retransmitted
 262          * FINs (or previous seqments) are lost (probability of such event
 263          * is p^(N+1), where p is probability to lose single packet and
 264          * time to detect the loss is about RTO*(2^N - 1) with exponential
 265          * backoff). Normal timewait length is calculated so, that we
 266          * waited at least for one retransmitted FIN (maximal RTO is 120sec).
 267          * [ BTW Linux. following BSD, violates this requirement waiting
 268          *   only for 60sec, we should wait at least for 240 secs.
 269          *   Well, 240 consumes too much of resources 8)
 270          * ]
 271          * This interval is not reduced to catch old duplicate and
 272          * responces to our wandering segments living for two MSLs.
 273          * However, if we use PAWS to detect
 274          * old duplicates, we can reduce the interval to bounds required
 275          * by RTO, rather than MSL. So, if peer understands PAWS, we
 276          * kill tw bucket after 3.5*RTO (it is important that this number
 277          * is greater than TS tick!) and detect old duplicates with help
 278          * of PAWS.
 279          */
 280         slot = (timeo + (1 << INET_TWDR_RECYCLE_TICK) - 1) >> INET_TWDR_RECYCLE_TICK;
 281
 282         spin_lock(&twdr->death_lock);
 283
 284         /* Unlink it, if it was scheduled */
 285         if (inet_twsk_del_dead_node(tw))
 286                 twdr->tw_count--;
 287         else
 288                 atomic_inc(&tw->tw_refcnt);
 289
 290         if (slot >= INET_TWDR_RECYCLE_SLOTS) {
 291                 /* Schedule to slow timer */
 292                 if (timeo >= timewait_len) {
 293                         slot = INET_TWDR_TWKILL_SLOTS - 1;
 294                 } else {
 295                         slot = (timeo + twdr->period - 1) / twdr->period;
 296                         if (slot >= INET_TWDR_TWKILL_SLOTS)
 297                                 slot = INET_TWDR_TWKILL_SLOTS - 1;
 298                 }
 299                 tw->tw_ttd = jiffies + timeo;
 300                 slot = (twdr->slot + slot) & (INET_TWDR_TWKILL_SLOTS - 1);
 301                 list = &twdr->cells[slot];
 302         } else {
 303                 tw->tw_ttd = jiffies + (slot << INET_TWDR_RECYCLE_TICK);
 304
 305                 if (twdr->twcal_hand < 0) {
 306                         twdr->twcal_hand = 0;
 307                         twdr->twcal_jiffie = jiffies;
 308                         twdr->twcal_timer.expires = twdr->twcal_jiffie +
 309                                               (slot << INET_TWDR_RECYCLE_TICK);
 310                         add_timer(&twdr->twcal_timer);
 311                 } else {
 312                         if (time_after(twdr->twcal_timer.expires,
 313                                        jiffies + (slot << INET_TWDR_RECYCLE_TICK)))
 314                                 mod_timer(&twdr->twcal_timer,
 315                                           jiffies + (slot << INET_TWDR_RECYCLE_TICK));
 316                         slot = (twdr->twcal_hand + slot) & (INET_TWDR_RECYCLE_SLOTS - 1);
 317                 }
 318                 list = &twdr->twcal_row[slot];
 319         }
 320
 321         hlist_add_head(&tw->tw_death_node, list);
 322
 323         if (twdr->tw_count++ == 0)
 324                 mod_timer(&twdr->tw_timer, jiffies + twdr->period);
 325         spin_unlock(&twdr->death_lock);
 326 }
 327
 328 EXPORT_SYMBOL_GPL(inet_twsk_schedule);
 329
 330 void inet_twdr_twcal_tick(unsigned long data)
 331 {
 332         struct inet_timewait_death_row *twdr;
 333         int n, slot;
 334         unsigned long j;
 335         unsigned long now = jiffies;
 336         int killed = 0;
 337         int adv = 0;
 338
 339         twdr = (struct inet_timewait_death_row *)data;
 340
 341         spin_lock(&twdr->death_lock);
 342         if (twdr->twcal_hand < 0)
 343                 goto out;
 344
 345         slot = twdr->twcal_hand;
 346         j = twdr->twcal_jiffie;
 347
 348         for (n = 0; n < INET_TWDR_RECYCLE_SLOTS; n++) {
 349                 if (time_before_eq(j, now)) {
 350                         struct hlist_node *node, *safe;
 351                         struct inet_timewait_sock *tw;
 352
 353                         inet_twsk_for_each_inmate_safe(tw, node, safe,
 354                                                        &twdr->twcal_row[slot]) {
 355                                 __inet_twsk_del_dead_node(tw);
 356                                 __inet_twsk_kill(tw, twdr->hashinfo);
 357                                 inet_twsk_put(tw);
 358                                 killed++;
 359                         }
 360                 } else {
 361                         if (!adv) {
 362                                 adv = 1;
 363                                 twdr->twcal_jiffie = j;
 364                                 twdr->twcal_hand = slot;
 365                         }
 366
 367                         if (!hlist_empty(&twdr->twcal_row[slot])) {
 368                                 mod_timer(&twdr->twcal_timer, j);
 369                                 goto out;
 370                         }
 371                 }
 372                 j += 1 << INET_TWDR_RECYCLE_TICK;
 373                 slot = (slot + 1) & (INET_TWDR_RECYCLE_SLOTS - 1);
 374         }
 375         twdr->twcal_hand = -1;
 376
 377 out:
 378         if ((twdr->tw_count -= killed) == 0)
 379                 del_timer(&twdr->tw_timer);
 380         NET_ADD_STATS_BH(LINUX_MIB_TIMEWAITKILLED, killed);
 381         spin_unlock(&twdr->death_lock);
 382 }
 383
 384 EXPORT_SYMBOL_GPL(inet_twdr_twcal_tick);