SAFE public projects git trees. - safe/jmp/linux-2.6/blob - net/ipv4/tcp_timer.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  *              Implementation of the Transmission Control Protocol(TCP).
   7  *
   8  * Authors:     Ross Biro
   9  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
  10  *              Mark Evans, <evansmp@uhura.aston.ac.uk>
  11  *              Corey Minyard <wf-rch!minyard@relay.EU.net>
  12  *              Florian La Roche, <flla@stud.uni-sb.de>
  13  *              Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
  14  *              Linus Torvalds, <torvalds@cs.helsinki.fi>
  15  *              Alan Cox, <gw4pts@gw4pts.ampr.org>
  16  *              Matthew Dillon, <dillon@apollo.west.oic.com>
  17  *              Arnt Gulbrandsen, <agulbra@nvg.unit.no>
  18  *              Jorge Cwik, <jorge@laser.satlink.net>
  19  */
  20
  21 #include <linux/module.h>
  22 #include <net/tcp.h>
  23
  24 int sysctl_tcp_syn_retries __read_mostly = TCP_SYN_RETRIES;
  25 int sysctl_tcp_synack_retries __read_mostly = TCP_SYNACK_RETRIES;
  26 int sysctl_tcp_keepalive_time __read_mostly = TCP_KEEPALIVE_TIME;
  27 int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES;
  28 int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL;
  29 int sysctl_tcp_retries1 __read_mostly = TCP_RETR1;
  30 int sysctl_tcp_retries2 __read_mostly = TCP_RETR2;
  31 int sysctl_tcp_orphan_retries __read_mostly;
  32
  33 static void tcp_write_timer(unsigned long);
  34 static void tcp_delack_timer(unsigned long);
  35 static void tcp_keepalive_timer (unsigned long data);
  36
  37 void tcp_init_xmit_timers(struct sock *sk)
  38 {
  39         inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer,
  40                                   &tcp_keepalive_timer);
  41 }
  42
  43 EXPORT_SYMBOL(tcp_init_xmit_timers);
  44
  45 static void tcp_write_err(struct sock *sk)
  46 {
  47         sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT;
  48         sk->sk_error_report(sk);
  49
  50         tcp_done(sk);
  51         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT);
  52 }
  53
  54 /* Do not allow orphaned sockets to eat all our resources.
  55  * This is direct violation of TCP specs, but it is required
  56  * to prevent DoS attacks. It is called when a retransmission timeout
  57  * or zero probe timeout occurs on orphaned socket.
  58  *
  59  * Criteria is still not confirmed experimentally and may change.
  60  * We kill the socket, if:
  61  * 1. If number of orphaned sockets exceeds an administratively configured
  62  *    limit.
  63  * 2. If we have strong memory pressure.
  64  */
  65 static int tcp_out_of_resources(struct sock *sk, int do_reset)
  66 {
  67         struct tcp_sock *tp = tcp_sk(sk);
  68         int orphans = percpu_counter_read_positive(&tcp_orphan_count);
  69
  70         /* If peer does not open window for long time, or did not transmit
  71          * anything for long time, penalize it. */
  72         if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset)
  73                 orphans <<= 1;
  74
  75         /* If some dubious ICMP arrived, penalize even more. */
  76         if (sk->sk_err_soft)
  77                 orphans <<= 1;
  78
  79         if (tcp_too_many_orphans(sk, orphans)) {
  80                 if (net_ratelimit())
  81                         printk(KERN_INFO "Out of socket memory\n");
  82
  83                 /* Catch exceptional cases, when connection requires reset.
  84                  *      1. Last segment was sent recently. */
  85                 if ((s32)(tcp_time_stamp - tp->lsndtime) <= TCP_TIMEWAIT_LEN ||
  86                     /*  2. Window is closed. */
  87                     (!tp->snd_wnd && !tp->packets_out))
  88                         do_reset = 1;
  89                 if (do_reset)
  90                         tcp_send_active_reset(sk, GFP_ATOMIC);
  91                 tcp_done(sk);
  92                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY);
  93                 return 1;
  94         }
  95         return 0;
  96 }
  97
  98 /* Calculate maximal number or retries on an orphaned socket. */
  99 static int tcp_orphan_retries(struct sock *sk, int alive)
 100 {
 101         int retries = sysctl_tcp_orphan_retries; /* May be zero. */
 102
 103         /* We know from an ICMP that something is wrong. */
 104         if (sk->sk_err_soft && !alive)
 105                 retries = 0;
 106
 107         /* However, if socket sent something recently, select some safe
 108          * number of retries. 8 corresponds to >100 seconds with minimal
 109          * RTO of 200msec. */
 110         if (retries == 0 && alive)
 111                 retries = 8;
 112         return retries;
 113 }
 114
 115 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
 116 {
 117         /* Black hole detection */
 118         if (sysctl_tcp_mtu_probing) {
 119                 if (!icsk->icsk_mtup.enabled) {
 120                         icsk->icsk_mtup.enabled = 1;
 121                         tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 122                 } else {
 123                         struct tcp_sock *tp = tcp_sk(sk);
 124                         int mss;
 125
 126                         mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1;
 127                         mss = min(sysctl_tcp_base_mss, mss);
 128                         mss = max(mss, 68 - tp->tcp_header_len);
 129                         icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss);
 130                         tcp_sync_mss(sk, icsk->icsk_pmtu_cookie);
 131                 }
 132         }
 133 }
 134
 135 /* This function calculates a "timeout" which is equivalent to the timeout of a
 136  * TCP connection after "boundary" unsucessful, exponentially backed-off
 137  * retransmissions with an initial RTO of TCP_RTO_MIN.
 138  */
 139 static bool retransmits_timed_out(struct sock *sk,
 140                                   unsigned int boundary)
 141 {
 142         unsigned int timeout, linear_backoff_thresh;
 143         unsigned int start_ts;
 144
 145         if (!inet_csk(sk)->icsk_retransmits)
 146                 return false;
 147
 148         if (unlikely(!tcp_sk(sk)->retrans_stamp))
 149                 start_ts = TCP_SKB_CB(tcp_write_queue_head(sk))->when;
 150         else
 151                 start_ts = tcp_sk(sk)->retrans_stamp;
 152
 153         linear_backoff_thresh = ilog2(TCP_RTO_MAX/TCP_RTO_MIN);
 154
 155         if (boundary <= linear_backoff_thresh)
 156                 timeout = ((2 << boundary) - 1) * TCP_RTO_MIN;
 157         else
 158                 timeout = ((2 << linear_backoff_thresh) - 1) * TCP_RTO_MIN +
 159                           (boundary - linear_backoff_thresh) * TCP_RTO_MAX;
 160
 161         return (tcp_time_stamp - start_ts) >= timeout;
 162 }
 163
 164 /* A write timeout has occurred. Process the after effects. */
 165 static int tcp_write_timeout(struct sock *sk)
 166 {
 167         struct inet_connection_sock *icsk = inet_csk(sk);
 168         int retry_until;
 169         bool do_reset;
 170
 171         if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) {
 172                 if (icsk->icsk_retransmits)
 173                         dst_negative_advice(&sk->sk_dst_cache, sk);
 174                 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries;
 175         } else {
 176                 if (retransmits_timed_out(sk, sysctl_tcp_retries1)) {
 177                         /* Black hole detection */
 178                         tcp_mtu_probing(icsk, sk);
 179
 180                         dst_negative_advice(&sk->sk_dst_cache, sk);
 181                 }
 182
 183                 retry_until = sysctl_tcp_retries2;
 184                 if (sock_flag(sk, SOCK_DEAD)) {
 185                         const int alive = (icsk->icsk_rto < TCP_RTO_MAX);
 186
 187                         retry_until = tcp_orphan_retries(sk, alive);
 188                         do_reset = alive ||
 189                                    !retransmits_timed_out(sk, retry_until);
 190
 191                         if (tcp_out_of_resources(sk, do_reset))
 192                                 return 1;
 193                 }
 194         }
 195
 196         if (retransmits_timed_out(sk, retry_until)) {
 197                 /* Has it gone just too far? */
 198                 tcp_write_err(sk);
 199                 return 1;
 200         }
 201         return 0;
 202 }
 203
 204 static void tcp_delack_timer(unsigned long data)
 205 {
 206         struct sock *sk = (struct sock *)data;
 207         struct tcp_sock *tp = tcp_sk(sk);
 208         struct inet_connection_sock *icsk = inet_csk(sk);
 209
 210         bh_lock_sock(sk);
 211         if (sock_owned_by_user(sk)) {
 212                 /* Try again later. */
 213                 icsk->icsk_ack.blocked = 1;
 214                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED);
 215                 sk_reset_timer(sk, &icsk->icsk_delack_timer, jiffies + TCP_DELACK_MIN);
 216                 goto out_unlock;
 217         }
 218
 219         sk_mem_reclaim_partial(sk);
 220
 221         if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
 222                 goto out;
 223
 224         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
 225                 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout);
 226                 goto out;
 227         }
 228         icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER;
 229
 230         if (!skb_queue_empty(&tp->ucopy.prequeue)) {
 231                 struct sk_buff *skb;
 232
 233                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED);
 234
 235                 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL)
 236                         sk_backlog_rcv(sk, skb);
 237
 238                 tp->ucopy.memory = 0;
 239         }
 240
 241         if (inet_csk_ack_scheduled(sk)) {
 242                 if (!icsk->icsk_ack.pingpong) {
 243                         /* Delayed ACK missed: inflate ATO. */
 244                         icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto);
 245                 } else {
 246                         /* Delayed ACK missed: leave pingpong mode and
 247                          * deflate ATO.
 248                          */
 249                         icsk->icsk_ack.pingpong = 0;
 250                         icsk->icsk_ack.ato      = TCP_ATO_MIN;
 251                 }
 252                 tcp_send_ack(sk);
 253                 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS);
 254         }
 255         TCP_CHECK_TIMER(sk);
 256
 257 out:
 258         if (tcp_memory_pressure)
 259                 sk_mem_reclaim(sk);
 260 out_unlock:
 261         bh_unlock_sock(sk);
 262         sock_put(sk);
 263 }
 264
 265 static void tcp_probe_timer(struct sock *sk)
 266 {
 267         struct inet_connection_sock *icsk = inet_csk(sk);
 268         struct tcp_sock *tp = tcp_sk(sk);
 269         int max_probes;
 270
 271         if (tp->packets_out || !tcp_send_head(sk)) {
 272                 icsk->icsk_probes_out = 0;
 273                 return;
 274         }
 275
 276         /* *WARNING* RFC 1122 forbids this
 277          *
 278          * It doesn't AFAIK, because we kill the retransmit timer -AK
 279          *
 280          * FIXME: We ought not to do it, Solaris 2.5 actually has fixing
 281          * this behaviour in Solaris down as a bug fix. [AC]
 282          *
 283          * Let me to explain. icsk_probes_out is zeroed by incoming ACKs
 284          * even if they advertise zero window. Hence, connection is killed only
 285          * if we received no ACKs for normal connection timeout. It is not killed
 286          * only because window stays zero for some time, window may be zero
 287          * until armageddon and even later. We are in full accordance
 288          * with RFCs, only probe timer combines both retransmission timeout
 289          * and probe timeout in one bottle.                             --ANK
 290          */
 291         max_probes = sysctl_tcp_retries2;
 292
 293         if (sock_flag(sk, SOCK_DEAD)) {
 294                 const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX);
 295
 296                 max_probes = tcp_orphan_retries(sk, alive);
 297
 298                 if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes))
 299                         return;
 300         }
 301
 302         if (icsk->icsk_probes_out > max_probes) {
 303                 tcp_write_err(sk);
 304         } else {
 305                 /* Only send another probe if we didn't close things up. */
 306                 tcp_send_probe0(sk);
 307         }
 308 }
 309
 310 /*
 311  *      The TCP retransmit timer.
 312  */
 313
 314 void tcp_retransmit_timer(struct sock *sk)
 315 {
 316         struct tcp_sock *tp = tcp_sk(sk);
 317         struct inet_connection_sock *icsk = inet_csk(sk);
 318
 319         if (!tp->packets_out)
 320                 goto out;
 321
 322         WARN_ON(tcp_write_queue_empty(sk));
 323
 324         if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) &&
 325             !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) {
 326                 /* Receiver dastardly shrinks window. Our retransmits
 327                  * become zero probes, but we should not timeout this
 328                  * connection. If the socket is an orphan, time it out,
 329                  * we cannot allow such beasts to hang infinitely.
 330                  */
 331 #ifdef TCP_DEBUG
 332                 struct inet_sock *inet = inet_sk(sk);
 333                 if (sk->sk_family == AF_INET) {
 334                         LIMIT_NETDEBUG(KERN_DEBUG "TCP: Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
 335                                &inet->inet_daddr, ntohs(inet->inet_dport),
 336                                inet->inet_num, tp->snd_una, tp->snd_nxt);
 337                 }
 338 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE)
 339                 else if (sk->sk_family == AF_INET6) {
 340                         struct ipv6_pinfo *np = inet6_sk(sk);
 341                         LIMIT_NETDEBUG(KERN_DEBUG "TCP: Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n",
 342                                &np->daddr, ntohs(inet->inet_dport),
 343                                inet->inet_num, tp->snd_una, tp->snd_nxt);
 344                 }
 345 #endif
 346 #endif
 347                 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) {
 348                         tcp_write_err(sk);
 349                         goto out;
 350                 }
 351                 tcp_enter_loss(sk, 0);
 352                 tcp_retransmit_skb(sk, tcp_write_queue_head(sk));
 353                 __sk_dst_reset(sk);
 354                 goto out_reset_timer;
 355         }
 356
 357         if (tcp_write_timeout(sk))
 358                 goto out;
 359
 360         if (icsk->icsk_retransmits == 0) {
 361                 int mib_idx;
 362
 363                 if (icsk->icsk_ca_state == TCP_CA_Disorder) {
 364                         if (tcp_is_sack(tp))
 365                                 mib_idx = LINUX_MIB_TCPSACKFAILURES;
 366                         else
 367                                 mib_idx = LINUX_MIB_TCPRENOFAILURES;
 368                 } else if (icsk->icsk_ca_state == TCP_CA_Recovery) {
 369                         if (tcp_is_sack(tp))
 370                                 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL;
 371                         else
 372                                 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL;
 373                 } else if (icsk->icsk_ca_state == TCP_CA_Loss) {
 374                         mib_idx = LINUX_MIB_TCPLOSSFAILURES;
 375                 } else {
 376                         mib_idx = LINUX_MIB_TCPTIMEOUTS;
 377                 }
 378                 NET_INC_STATS_BH(sock_net(sk), mib_idx);
 379         }
 380
 381         if (tcp_use_frto(sk)) {
 382                 tcp_enter_frto(sk);
 383         } else {
 384                 tcp_enter_loss(sk, 0);
 385         }
 386
 387         if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) {
 388                 /* Retransmission failed because of local congestion,
 389                  * do not backoff.
 390                  */
 391                 if (!icsk->icsk_retransmits)
 392                         icsk->icsk_retransmits = 1;
 393                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 394                                           min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL),
 395                                           TCP_RTO_MAX);
 396                 goto out;
 397         }
 398
 399         /* Increase the timeout each time we retransmit.  Note that
 400          * we do not increase the rtt estimate.  rto is initialized
 401          * from rtt, but increases here.  Jacobson (SIGCOMM 88) suggests
 402          * that doubling rto each time is the least we can get away with.
 403          * In KA9Q, Karn uses this for the first few times, and then
 404          * goes to quadratic.  netBSD doubles, but only goes up to *64,
 405          * and clamps at 1 to 64 sec afterwards.  Note that 120 sec is
 406          * defined in the protocol as the maximum possible RTT.  I guess
 407          * we'll have to use something other than TCP to talk to the
 408          * University of Mars.
 409          *
 410          * PAWS allows us longer timeouts and large windows, so once
 411          * implemented ftp to mars will work nicely. We will have to fix
 412          * the 120 second clamps though!
 413          */
 414         icsk->icsk_backoff++;
 415         icsk->icsk_retransmits++;
 416
 417 out_reset_timer:
 418         icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX);
 419         inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX);
 420         if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1))
 421                 __sk_dst_reset(sk);
 422
 423 out:;
 424 }
 425
 426 static void tcp_write_timer(unsigned long data)
 427 {
 428         struct sock *sk = (struct sock *)data;
 429         struct inet_connection_sock *icsk = inet_csk(sk);
 430         int event;
 431
 432         bh_lock_sock(sk);
 433         if (sock_owned_by_user(sk)) {
 434                 /* Try again later */
 435                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, jiffies + (HZ / 20));
 436                 goto out_unlock;
 437         }
 438
 439         if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
 440                 goto out;
 441
 442         if (time_after(icsk->icsk_timeout, jiffies)) {
 443                 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout);
 444                 goto out;
 445         }
 446
 447         event = icsk->icsk_pending;
 448         icsk->icsk_pending = 0;
 449
 450         switch (event) {
 451         case ICSK_TIME_RETRANS:
 452                 tcp_retransmit_timer(sk);
 453                 break;
 454         case ICSK_TIME_PROBE0:
 455                 tcp_probe_timer(sk);
 456                 break;
 457         }
 458         TCP_CHECK_TIMER(sk);
 459
 460 out:
 461         sk_mem_reclaim(sk);
 462 out_unlock:
 463         bh_unlock_sock(sk);
 464         sock_put(sk);
 465 }
 466
 467 /*
 468  *      Timer for listening sockets
 469  */
 470
 471 static void tcp_synack_timer(struct sock *sk)
 472 {
 473         inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL,
 474                                    TCP_TIMEOUT_INIT, TCP_RTO_MAX);
 475 }
 476
 477 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req)
 478 {
 479         NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPTIMEOUTS);
 480 }
 481 EXPORT_SYMBOL(tcp_syn_ack_timeout);
 482
 483 void tcp_set_keepalive(struct sock *sk, int val)
 484 {
 485         if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN))
 486                 return;
 487
 488         if (val && !sock_flag(sk, SOCK_KEEPOPEN))
 489                 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk)));
 490         else if (!val)
 491                 inet_csk_delete_keepalive_timer(sk);
 492 }
 493
 494
 495 static void tcp_keepalive_timer (unsigned long data)
 496 {
 497         struct sock *sk = (struct sock *) data;
 498         struct inet_connection_sock *icsk = inet_csk(sk);
 499         struct tcp_sock *tp = tcp_sk(sk);
 500         __u32 elapsed;
 501
 502         /* Only process if socket is not in use. */
 503         bh_lock_sock(sk);
 504         if (sock_owned_by_user(sk)) {
 505                 /* Try again later. */
 506                 inet_csk_reset_keepalive_timer (sk, HZ/20);
 507                 goto out;
 508         }
 509
 510         if (sk->sk_state == TCP_LISTEN) {
 511                 tcp_synack_timer(sk);
 512                 goto out;
 513         }
 514
 515         if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) {
 516                 if (tp->linger2 >= 0) {
 517                         const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN;
 518
 519                         if (tmo > 0) {
 520                                 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
 521                                 goto out;
 522                         }
 523                 }
 524                 tcp_send_active_reset(sk, GFP_ATOMIC);
 525                 goto death;
 526         }
 527
 528         if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE)
 529                 goto out;
 530
 531         elapsed = keepalive_time_when(tp);
 532
 533         /* It is alive without keepalive 8) */
 534         if (tp->packets_out || tcp_send_head(sk))
 535                 goto resched;
 536
 537         elapsed = tcp_time_stamp - tp->rcv_tstamp;
 538
 539         if (elapsed >= keepalive_time_when(tp)) {
 540                 if (icsk->icsk_probes_out >= keepalive_probes(tp)) {
 541                         tcp_send_active_reset(sk, GFP_ATOMIC);
 542                         tcp_write_err(sk);
 543                         goto out;
 544                 }
 545                 if (tcp_write_wakeup(sk) <= 0) {
 546                         icsk->icsk_probes_out++;
 547                         elapsed = keepalive_intvl_when(tp);
 548                 } else {
 549                         /* If keepalive was lost due to local congestion,
 550                          * try harder.
 551                          */
 552                         elapsed = TCP_RESOURCE_PROBE_INTERVAL;
 553                 }
 554         } else {
 555                 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */
 556                 elapsed = keepalive_time_when(tp) - elapsed;
 557         }
 558
 559         TCP_CHECK_TIMER(sk);
 560         sk_mem_reclaim(sk);
 561
 562 resched:
 563         inet_csk_reset_keepalive_timer (sk, elapsed);
 564         goto out;
 565
 566 death:
 567         tcp_done(sk);
 568
 569 out:
 570         bh_unlock_sock(sk);
 571         sock_put(sk);
 572 }