net/ipv4/inet_connection_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  *              Support for INET connection oriented protocols.
   7  *
   8  * Authors:     See the TCP sources
   9  *
  10  *              This program is free software; you can redistribute it and/or
  11  *              modify it under the terms of the GNU General Public License
  12  *              as published by the Free Software Foundation; either version
  13  *              2 of the License, or(at your option) any later version.
  14  */
  15
  16 #include <linux/config.h>
  17 #include <linux/module.h>
  18 #include <linux/jhash.h>
  19
  20 #include <net/inet_connection_sock.h>
  21 #include <net/inet_hashtables.h>
  22 #include <net/inet_timewait_sock.h>
  23 #include <net/ip.h>
  24 #include <net/route.h>
  25 #include <net/tcp_states.h>
  26 #include <net/xfrm.h>
  27
  28 #ifdef INET_CSK_DEBUG
  29 const char inet_csk_timer_bug_msg[] = "inet_csk BUG: unknown timer value\n";
  30 EXPORT_SYMBOL(inet_csk_timer_bug_msg);
  31 #endif
  32
  33 /*
  34  * This array holds the first and last local port number.
  35  * For high-usage systems, use sysctl to change this to
  36  * 32768-61000
  37  */
  38 int sysctl_local_port_range[2] = { 1024, 4999 };
  39
  40 static inline int inet_csk_bind_conflict(struct sock *sk, struct inet_bind_bucket *tb)
  41 {
  42         const u32 sk_rcv_saddr = inet_rcv_saddr(sk);
  43         struct sock *sk2;
  44         struct hlist_node *node;
  45         int reuse = sk->sk_reuse;
  46
  47         sk_for_each_bound(sk2, node, &tb->owners) {
  48                 if (sk != sk2 &&
  49                     !inet_v6_ipv6only(sk2) &&
  50                     (!sk->sk_bound_dev_if ||
  51                      !sk2->sk_bound_dev_if ||
  52                      sk->sk_bound_dev_if == sk2->sk_bound_dev_if)) {
  53                         if (!reuse || !sk2->sk_reuse ||
  54                             sk2->sk_state == TCP_LISTEN) {
  55                                 const u32 sk2_rcv_saddr = inet_rcv_saddr(sk2);
  56                                 if (!sk2_rcv_saddr || !sk_rcv_saddr ||
  57                                     sk2_rcv_saddr == sk_rcv_saddr)
  58                                         break;
  59                         }
  60                 }
  61         }
  62         return node != NULL;
  63 }
  64
  65 /* Obtain a reference to a local port for the given sock,
  66  * if snum is zero it means select any available local port.
  67  */
  68 int inet_csk_get_port(struct inet_hashinfo *hashinfo,
  69                       struct sock *sk, unsigned short snum)
  70 {
  71         struct inet_bind_hashbucket *head;
  72         struct hlist_node *node;
  73         struct inet_bind_bucket *tb;
  74         int ret;
  75
  76         local_bh_disable();
  77         if (!snum) {
  78                 int low = sysctl_local_port_range[0];
  79                 int high = sysctl_local_port_range[1];
  80                 int remaining = (high - low) + 1;
  81                 int rover = net_random() % (high - low) + low;
  82
  83                 do {
  84                         head = &hashinfo->bhash[inet_bhashfn(rover, hashinfo->bhash_size)];
  85                         spin_lock(&head->lock);
  86                         inet_bind_bucket_for_each(tb, node, &head->chain)
  87                                 if (tb->port == rover)
  88                                         goto next;
  89                         break;
  90                 next:
  91                         spin_unlock(&head->lock);
  92                         if (++rover > high)
  93                                 rover = low;
  94                 } while (--remaining > 0);
  95
  96                 /* Exhausted local port range during search?  It is not
  97                  * possible for us to be holding one of the bind hash
  98                  * locks if this test triggers, because if 'remaining'
  99                  * drops to zero, we broke out of the do/while loop at
 100                  * the top level, not from the 'break;' statement.
 101                  */
 102                 ret = 1;
 103                 if (remaining <= 0)
 104                         goto fail;
 105
 106                 /* OK, here is the one we will use.  HEAD is
 107                  * non-NULL and we hold it's mutex.
 108                  */
 109                 snum = rover;
 110         } else {
 111                 head = &hashinfo->bhash[inet_bhashfn(snum, hashinfo->bhash_size)];
 112                 spin_lock(&head->lock);
 113                 inet_bind_bucket_for_each(tb, node, &head->chain)
 114                         if (tb->port == snum)
 115                                 goto tb_found;
 116         }
 117         tb = NULL;
 118         goto tb_not_found;
 119 tb_found:
 120         if (!hlist_empty(&tb->owners)) {
 121                 if (sk->sk_reuse > 1)
 122                         goto success;
 123                 if (tb->fastreuse > 0 &&
 124                     sk->sk_reuse && sk->sk_state != TCP_LISTEN) {
 125                         goto success;
 126                 } else {
 127                         ret = 1;
 128                         if (inet_csk_bind_conflict(sk, tb))
 129                                 goto fail_unlock;
 130                 }
 131         }
 132 tb_not_found:
 133         ret = 1;
 134         if (!tb && (tb = inet_bind_bucket_create(hashinfo->bind_bucket_cachep, head, snum)) == NULL)
 135                 goto fail_unlock;
 136         if (hlist_empty(&tb->owners)) {
 137                 if (sk->sk_reuse && sk->sk_state != TCP_LISTEN)
 138                         tb->fastreuse = 1;
 139                 else
 140                         tb->fastreuse = 0;
 141         } else if (tb->fastreuse &&
 142                    (!sk->sk_reuse || sk->sk_state == TCP_LISTEN))
 143                 tb->fastreuse = 0;
 144 success:
 145         if (!inet_csk(sk)->icsk_bind_hash)
 146                 inet_bind_hash(sk, tb, snum);
 147         BUG_TRAP(inet_csk(sk)->icsk_bind_hash == tb);
 148         ret = 0;
 149
 150 fail_unlock:
 151         spin_unlock(&head->lock);
 152 fail:
 153         local_bh_enable();
 154         return ret;
 155 }
 156
 157 EXPORT_SYMBOL_GPL(inet_csk_get_port);
 158
 159 /*
 160  * Wait for an incoming connection, avoid race conditions. This must be called
 161  * with the socket locked.
 162  */
 163 static int inet_csk_wait_for_connect(struct sock *sk, long timeo)
 164 {
 165         struct inet_connection_sock *icsk = inet_csk(sk);
 166         DEFINE_WAIT(wait);
 167         int err;
 168
 169         /*
 170          * True wake-one mechanism for incoming connections: only
 171          * one process gets woken up, not the 'whole herd'.
 172          * Since we do not 'race & poll' for established sockets
 173          * anymore, the common case will execute the loop only once.
 174          *
 175          * Subtle issue: "add_wait_queue_exclusive()" will be added
 176          * after any current non-exclusive waiters, and we know that
 177          * it will always _stay_ after any new non-exclusive waiters
 178          * because all non-exclusive waiters are added at the
 179          * beginning of the wait-queue. As such, it's ok to "drop"
 180          * our exclusiveness temporarily when we get woken up without
 181          * having to remove and re-insert us on the wait queue.
 182          */
 183         for (;;) {
 184                 prepare_to_wait_exclusive(sk->sk_sleep, &wait,
 185                                           TASK_INTERRUPTIBLE);
 186                 release_sock(sk);
 187                 if (reqsk_queue_empty(&icsk->icsk_accept_queue))
 188                         timeo = schedule_timeout(timeo);
 189                 lock_sock(sk);
 190                 err = 0;
 191                 if (!reqsk_queue_empty(&icsk->icsk_accept_queue))
 192                         break;
 193                 err = -EINVAL;
 194                 if (sk->sk_state != TCP_LISTEN)
 195                         break;
 196                 err = sock_intr_errno(timeo);
 197                 if (signal_pending(current))
 198                         break;
 199                 err = -EAGAIN;
 200                 if (!timeo)
 201                         break;
 202         }
 203         finish_wait(sk->sk_sleep, &wait);
 204         return err;
 205 }
 206
 207 /*
 208  * This will accept the next outstanding connection.
 209  */
 210 struct sock *inet_csk_accept(struct sock *sk, int flags, int *err)
 211 {
 212         struct inet_connection_sock *icsk = inet_csk(sk);
 213         struct sock *newsk;
 214         int error;
 215
 216         lock_sock(sk);
 217
 218         /* We need to make sure that this socket is listening,
 219          * and that it has something pending.
 220          */
 221         error = -EINVAL;
 222         if (sk->sk_state != TCP_LISTEN)
 223                 goto out_err;
 224
 225         /* Find already established connection */
 226         if (reqsk_queue_empty(&icsk->icsk_accept_queue)) {
 227                 long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK);
 228
 229                 /* If this is a non blocking socket don't sleep */
 230                 error = -EAGAIN;
 231                 if (!timeo)
 232                         goto out_err;
 233
 234                 error = inet_csk_wait_for_connect(sk, timeo);
 235                 if (error)
 236                         goto out_err;
 237         }
 238
 239         newsk = reqsk_queue_get_child(&icsk->icsk_accept_queue, sk);
 240         BUG_TRAP(newsk->sk_state != TCP_SYN_RECV);
 241 out:
 242         release_sock(sk);
 243         return newsk;
 244 out_err:
 245         newsk = NULL;
 246         *err = error;
 247         goto out;
 248 }
 249
 250 EXPORT_SYMBOL(inet_csk_accept);
 251
 252 /*
 253  * Using different timers for retransmit, delayed acks and probes
 254  * We may wish use just one timer maintaining a list of expire jiffies
 255  * to optimize.
 256  */
 257 void inet_csk_init_xmit_timers(struct sock *sk,
 258                                void (*retransmit_handler)(unsigned long),
 259                                void (*delack_handler)(unsigned long),
 260                                void (*keepalive_handler)(unsigned long))
 261 {
 262         struct inet_connection_sock *icsk = inet_csk(sk);
 263
 264         init_timer(&icsk->icsk_retransmit_timer);
 265         init_timer(&icsk->icsk_delack_timer);
 266         init_timer(&sk->sk_timer);
 267
 268         icsk->icsk_retransmit_timer.function = retransmit_handler;
 269         icsk->icsk_delack_timer.function     = delack_handler;
 270         sk->sk_timer.function                = keepalive_handler;
 271
 272         icsk->icsk_retransmit_timer.data =
 273                 icsk->icsk_delack_timer.data =
 274                         sk->sk_timer.data  = (unsigned long)sk;
 275
 276         icsk->icsk_pending = icsk->icsk_ack.pending = 0;
 277 }
 278
 279 EXPORT_SYMBOL(inet_csk_init_xmit_timers);
 280
 281 void inet_csk_clear_xmit_timers(struct sock *sk)
 282 {
 283         struct inet_connection_sock *icsk = inet_csk(sk);
 284
 285         icsk->icsk_pending = icsk->icsk_ack.pending = icsk->icsk_ack.blocked = 0;
 286
 287         sk_stop_timer(sk, &icsk->icsk_retransmit_timer);
 288         sk_stop_timer(sk, &icsk->icsk_delack_timer);
 289         sk_stop_timer(sk, &sk->sk_timer);
 290 }
 291
 292 EXPORT_SYMBOL(inet_csk_clear_xmit_timers);
 293
 294 void inet_csk_delete_keepalive_timer(struct sock *sk)
 295 {
 296         sk_stop_timer(sk, &sk->sk_timer);
 297 }
 298
 299 EXPORT_SYMBOL(inet_csk_delete_keepalive_timer);
 300
 301 void inet_csk_reset_keepalive_timer(struct sock *sk, unsigned long len)
 302 {
 303         sk_reset_timer(sk, &sk->sk_timer, jiffies + len);
 304 }
 305
 306 EXPORT_SYMBOL(inet_csk_reset_keepalive_timer);
 307
 308 struct dst_entry* inet_csk_route_req(struct sock *sk,
 309                                      const struct request_sock *req)
 310 {
 311         struct rtable *rt;
 312         const struct inet_request_sock *ireq = inet_rsk(req);
 313         struct ip_options *opt = inet_rsk(req)->opt;
 314         struct flowi fl = { .oif = sk->sk_bound_dev_if,
 315                             .nl_u = { .ip4_u =
 316                                       { .daddr = ((opt && opt->srr) ?
 317                                                   opt->faddr :
 318                                                   ireq->rmt_addr),
 319                                         .saddr = ireq->loc_addr,
 320                                         .tos = RT_CONN_FLAGS(sk) } },
 321                             .proto = sk->sk_protocol,
 322                             .uli_u = { .ports =
 323                                        { .sport = inet_sk(sk)->sport,
 324                                          .dport = ireq->rmt_port } } };
 325
 326         if (ip_route_output_flow(&rt, &fl, sk, 0)) {
 327                 IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
 328                 return NULL;
 329         }
 330         if (opt && opt->is_strictroute && rt->rt_dst != rt->rt_gateway) {
 331                 ip_rt_put(rt);
 332                 IP_INC_STATS_BH(IPSTATS_MIB_OUTNOROUTES);
 333                 return NULL;
 334         }
 335         return &rt->u.dst;
 336 }
 337
 338 EXPORT_SYMBOL_GPL(inet_csk_route_req);
 339
 340 static inline u32 inet_synq_hash(const u32 raddr, const u16 rport,
 341                                  const u32 rnd, const u16 synq_hsize)
 342 {
 343         return jhash_2words(raddr, (u32)rport, rnd) & (synq_hsize - 1);
 344 }
 345
 346 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 347 #define AF_INET_FAMILY(fam) ((fam) == AF_INET)
 348 #else
 349 #define AF_INET_FAMILY(fam) 1
 350 #endif
 351
 352 struct request_sock *inet_csk_search_req(const struct sock *sk,
 353                                          struct request_sock ***prevp,
 354                                          const __u16 rport, const __u32 raddr,
 355                                          const __u32 laddr)
 356 {
 357         const struct inet_connection_sock *icsk = inet_csk(sk);
 358         struct listen_sock *lopt = icsk->icsk_accept_queue.listen_opt;
 359         struct request_sock *req, **prev;
 360
 361         for (prev = &lopt->syn_table[inet_synq_hash(raddr, rport, lopt->hash_rnd,
 362                                                     lopt->nr_table_entries)];
 363              (req = *prev) != NULL;
 364              prev = &req->dl_next) {
 365                 const struct inet_request_sock *ireq = inet_rsk(req);
 366
 367                 if (ireq->rmt_port == rport &&
 368                     ireq->rmt_addr == raddr &&
 369                     ireq->loc_addr == laddr &&
 370                     AF_INET_FAMILY(req->rsk_ops->family)) {
 371                         BUG_TRAP(!req->sk);
 372                         *prevp = prev;
 373                         break;
 374                 }
 375         }
 376
 377         return req;
 378 }
 379
 380 EXPORT_SYMBOL_GPL(inet_csk_search_req);
 381
 382 void inet_csk_reqsk_queue_hash_add(struct sock *sk, struct request_sock *req,
 383                                    const unsigned timeout)
 384 {
 385         struct inet_connection_sock *icsk = inet_csk(sk);
 386         struct listen_sock *lopt = icsk->icsk_accept_queue.listen_opt;
 387         const u32 h = inet_synq_hash(inet_rsk(req)->rmt_addr, inet_rsk(req)->rmt_port,
 388                                      lopt->hash_rnd, lopt->nr_table_entries);
 389
 390         reqsk_queue_hash_req(&icsk->icsk_accept_queue, h, req, timeout);
 391         inet_csk_reqsk_queue_added(sk, timeout);
 392 }
 393
 394 /* Only thing we need from tcp.h */
 395 extern int sysctl_tcp_synack_retries;
 396
 397 EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_hash_add);
 398
 399 void inet_csk_reqsk_queue_prune(struct sock *parent,
 400                                 const unsigned long interval,
 401                                 const unsigned long timeout,
 402                                 const unsigned long max_rto)
 403 {
 404         struct inet_connection_sock *icsk = inet_csk(parent);
 405         struct request_sock_queue *queue = &icsk->icsk_accept_queue;
 406         struct listen_sock *lopt = queue->listen_opt;
 407         int max_retries = icsk->icsk_syn_retries ? : sysctl_tcp_synack_retries;
 408         int thresh = max_retries;
 409         unsigned long now = jiffies;
 410         struct request_sock **reqp, *req;
 411         int i, budget;
 412
 413         if (lopt == NULL || lopt->qlen == 0)
 414                 return;
 415
 416         /* Normally all the openreqs are young and become mature
 417          * (i.e. converted to established socket) for first timeout.
 418          * If synack was not acknowledged for 3 seconds, it means
 419          * one of the following things: synack was lost, ack was lost,
 420          * rtt is high or nobody planned to ack (i.e. synflood).
 421          * When server is a bit loaded, queue is populated with old
 422          * open requests, reducing effective size of queue.
 423          * When server is well loaded, queue size reduces to zero
 424          * after several minutes of work. It is not synflood,
 425          * it is normal operation. The solution is pruning
 426          * too old entries overriding normal timeout, when
 427          * situation becomes dangerous.
 428          *
 429          * Essentially, we reserve half of room for young
 430          * embrions; and abort old ones without pity, if old
 431          * ones are about to clog our table.
 432          */
 433         if (lopt->qlen>>(lopt->max_qlen_log-1)) {
 434                 int young = (lopt->qlen_young<<1);
 435
 436                 while (thresh > 2) {
 437                         if (lopt->qlen < young)
 438                                 break;
 439                         thresh--;
 440                         young <<= 1;
 441                 }
 442         }
 443
 444         if (queue->rskq_defer_accept)
 445                 max_retries = queue->rskq_defer_accept;
 446
 447         budget = 2 * (lopt->nr_table_entries / (timeout / interval));
 448         i = lopt->clock_hand;
 449
 450         do {
 451                 reqp=&lopt->syn_table[i];
 452                 while ((req = *reqp) != NULL) {
 453                         if (time_after_eq(now, req->expires)) {
 454                                 if ((req->retrans < thresh ||
 455                                      (inet_rsk(req)->acked && req->retrans < max_retries))
 456                                     && !req->rsk_ops->rtx_syn_ack(parent, req, NULL)) {
 457                                         unsigned long timeo;
 458
 459                                         if (req->retrans++ == 0)
 460                                                 lopt->qlen_young--;
 461                                         timeo = min((timeout << req->retrans), max_rto);
 462                                         req->expires = now + timeo;
 463                                         reqp = &req->dl_next;
 464                                         continue;
 465                                 }
 466
 467                                 /* Drop this request */
 468                                 inet_csk_reqsk_queue_unlink(parent, req, reqp);
 469                                 reqsk_queue_removed(queue, req);
 470                                 reqsk_free(req);
 471                                 continue;
 472                         }
 473                         reqp = &req->dl_next;
 474                 }
 475
 476                 i = (i + 1) & (lopt->nr_table_entries - 1);
 477
 478         } while (--budget > 0);
 479
 480         lopt->clock_hand = i;
 481
 482         if (lopt->qlen)
 483                 inet_csk_reset_keepalive_timer(parent, interval);
 484 }
 485
 486 EXPORT_SYMBOL_GPL(inet_csk_reqsk_queue_prune);
 487
 488 struct sock *inet_csk_clone(struct sock *sk, const struct request_sock *req,
 489                             const gfp_t priority)
 490 {
 491         struct sock *newsk = sk_clone(sk, priority);
 492
 493         if (newsk != NULL) {
 494                 struct inet_connection_sock *newicsk = inet_csk(newsk);
 495
 496                 newsk->sk_state = TCP_SYN_RECV;
 497                 newicsk->icsk_bind_hash = NULL;
 498
 499                 inet_sk(newsk)->dport = inet_rsk(req)->rmt_port;
 500                 newsk->sk_write_space = sk_stream_write_space;
 501
 502                 newicsk->icsk_retransmits = 0;
 503                 newicsk->icsk_backoff     = 0;
 504                 newicsk->icsk_probes_out  = 0;
 505
 506                 /* Deinitialize accept_queue to trap illegal accesses. */
 507                 memset(&newicsk->icsk_accept_queue, 0, sizeof(newicsk->icsk_accept_queue));
 508         }
 509         return newsk;
 510 }
 511
 512 EXPORT_SYMBOL_GPL(inet_csk_clone);
 513
 514 /*
 515  * At this point, there should be no process reference to this
 516  * socket, and thus no user references at all.  Therefore we
 517  * can assume the socket waitqueue is inactive and nobody will
 518  * try to jump onto it.
 519  */
 520 void inet_csk_destroy_sock(struct sock *sk)
 521 {
 522         BUG_TRAP(sk->sk_state == TCP_CLOSE);
 523         BUG_TRAP(sock_flag(sk, SOCK_DEAD));
 524
 525         /* It cannot be in hash table! */
 526         BUG_TRAP(sk_unhashed(sk));
 527
 528         /* If it has not 0 inet_sk(sk)->num, it must be bound */
 529         BUG_TRAP(!inet_sk(sk)->num || inet_csk(sk)->icsk_bind_hash);
 530
 531         sk->sk_prot->destroy(sk);
 532
 533         sk_stream_kill_queues(sk);
 534
 535         xfrm_sk_free_policy(sk);
 536
 537         sk_refcnt_debug_release(sk);
 538
 539         atomic_dec(sk->sk_prot->orphan_count);
 540         sock_put(sk);
 541 }
 542
 543 EXPORT_SYMBOL(inet_csk_destroy_sock);
 544
 545 int inet_csk_listen_start(struct sock *sk, const int nr_table_entries)
 546 {
 547         struct inet_sock *inet = inet_sk(sk);
 548         struct inet_connection_sock *icsk = inet_csk(sk);
 549         int rc = reqsk_queue_alloc(&icsk->icsk_accept_queue, nr_table_entries);
 550
 551         if (rc != 0)
 552                 return rc;
 553
 554         sk->sk_max_ack_backlog = 0;
 555         sk->sk_ack_backlog = 0;
 556         inet_csk_delack_init(sk);
 557
 558         /* There is race window here: we announce ourselves listening,
 559          * but this transition is still not validated by get_port().
 560          * It is OK, because this socket enters to hash table only
 561          * after validation is complete.
 562          */
 563         sk->sk_state = TCP_LISTEN;
 564         if (!sk->sk_prot->get_port(sk, inet->num)) {
 565                 inet->sport = htons(inet->num);
 566
 567                 sk_dst_reset(sk);
 568                 sk->sk_prot->hash(sk);
 569
 570                 return 0;
 571         }
 572
 573         sk->sk_state = TCP_CLOSE;
 574         __reqsk_queue_destroy(&icsk->icsk_accept_queue);
 575         return -EADDRINUSE;
 576 }
 577
 578 EXPORT_SYMBOL_GPL(inet_csk_listen_start);
 579
 580 /*
 581  *      This routine closes sockets which have been at least partially
 582  *      opened, but not yet accepted.
 583  */
 584 void inet_csk_listen_stop(struct sock *sk)
 585 {
 586         struct inet_connection_sock *icsk = inet_csk(sk);
 587         struct request_sock *acc_req;
 588         struct request_sock *req;
 589
 590         inet_csk_delete_keepalive_timer(sk);
 591
 592         /* make all the listen_opt local to us */
 593         acc_req = reqsk_queue_yank_acceptq(&icsk->icsk_accept_queue);
 594
 595         /* Following specs, it would be better either to send FIN
 596          * (and enter FIN-WAIT-1, it is normal close)
 597          * or to send active reset (abort).
 598          * Certainly, it is pretty dangerous while synflood, but it is
 599          * bad justification for our negligence 8)
 600          * To be honest, we are not able to make either
 601          * of the variants now.                 --ANK
 602          */
 603         reqsk_queue_destroy(&icsk->icsk_accept_queue);
 604
 605         while ((req = acc_req) != NULL) {
 606                 struct sock *child = req->sk;
 607
 608                 acc_req = req->dl_next;
 609
 610                 local_bh_disable();
 611                 bh_lock_sock(child);
 612                 BUG_TRAP(!sock_owned_by_user(child));
 613                 sock_hold(child);
 614
 615                 sk->sk_prot->disconnect(child, O_NONBLOCK);
 616
 617                 sock_orphan(child);
 618
 619                 atomic_inc(sk->sk_prot->orphan_count);
 620
 621                 inet_csk_destroy_sock(child);
 622
 623                 bh_unlock_sock(child);
 624                 local_bh_enable();
 625                 sock_put(child);
 626
 627                 sk_acceptq_removed(sk);
 628                 __reqsk_free(req);
 629         }
 630         BUG_TRAP(!sk->sk_ack_backlog);
 631 }
 632
 633 EXPORT_SYMBOL_GPL(inet_csk_listen_stop);