Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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FreeBSD/Linux Kernel Cross Reference
sys/net/ipv4/tcp_timer.c
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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 <linux/gfp.h> 23 #include <net/tcp.h> 24 25 int sysctl_tcp_syn_retries __read_mostly = TCP_SYN_RETRIES; 26 int sysctl_tcp_synack_retries __read_mostly = TCP_SYNACK_RETRIES; 27 int sysctl_tcp_keepalive_time __read_mostly = TCP_KEEPALIVE_TIME; 28 int sysctl_tcp_keepalive_probes __read_mostly = TCP_KEEPALIVE_PROBES; 29 int sysctl_tcp_keepalive_intvl __read_mostly = TCP_KEEPALIVE_INTVL; 30 int sysctl_tcp_retries1 __read_mostly = TCP_RETR1; 31 int sysctl_tcp_retries2 __read_mostly = TCP_RETR2; 32 int sysctl_tcp_orphan_retries __read_mostly; 33 int sysctl_tcp_thin_linear_timeouts __read_mostly; 34 35 static void tcp_write_err(struct sock *sk) 36 { 37 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT; 38 sk->sk_error_report(sk); 39 40 tcp_done(sk); 41 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); 42 } 43 44 /* Do not allow orphaned sockets to eat all our resources. 45 * This is direct violation of TCP specs, but it is required 46 * to prevent DoS attacks. It is called when a retransmission timeout 47 * or zero probe timeout occurs on orphaned socket. 48 * 49 * Criteria is still not confirmed experimentally and may change. 50 * We kill the socket, if: 51 * 1. If number of orphaned sockets exceeds an administratively configured 52 * limit. 53 * 2. If we have strong memory pressure. 54 */ 55 static int tcp_out_of_resources(struct sock *sk, int do_reset) 56 { 57 struct tcp_sock *tp = tcp_sk(sk); 58 int shift = 0; 59 60 /* If peer does not open window for long time, or did not transmit 61 * anything for long time, penalize it. */ 62 if ((s32)(tcp_time_stamp - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset) 63 shift++; 64 65 /* If some dubious ICMP arrived, penalize even more. */ 66 if (sk->sk_err_soft) 67 shift++; 68 69 if (tcp_check_oom(sk, shift)) { 70 /* Catch exceptional cases, when connection requires reset. 71 * 1. Last segment was sent recently. */ 72 if ((s32)(tcp_time_stamp - tp->lsndtime) <= TCP_TIMEWAIT_LEN || 73 /* 2. Window is closed. */ 74 (!tp->snd_wnd && !tp->packets_out)) 75 do_reset = 1; 76 if (do_reset) 77 tcp_send_active_reset(sk, GFP_ATOMIC); 78 tcp_done(sk); 79 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY); 80 return 1; 81 } 82 return 0; 83 } 84 85 /* Calculate maximal number or retries on an orphaned socket. */ 86 static int tcp_orphan_retries(struct sock *sk, int alive) 87 { 88 int retries = sysctl_tcp_orphan_retries; /* May be zero. */ 89 90 /* We know from an ICMP that something is wrong. */ 91 if (sk->sk_err_soft && !alive) 92 retries = 0; 93 94 /* However, if socket sent something recently, select some safe 95 * number of retries. 8 corresponds to >100 seconds with minimal 96 * RTO of 200msec. */ 97 if (retries == 0 && alive) 98 retries = 8; 99 return retries; 100 } 101 102 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 103 { 104 /* Black hole detection */ 105 if (sysctl_tcp_mtu_probing) { 106 if (!icsk->icsk_mtup.enabled) { 107 icsk->icsk_mtup.enabled = 1; 108 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 109 } else { 110 struct tcp_sock *tp = tcp_sk(sk); 111 int mss; 112 113 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; 114 mss = min(sysctl_tcp_base_mss, mss); 115 mss = max(mss, 68 - tp->tcp_header_len); 116 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); 117 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 118 } 119 } 120 } 121 122 /* This function calculates a "timeout" which is equivalent to the timeout of a 123 * TCP connection after "boundary" unsuccessful, exponentially backed-off 124 * retransmissions with an initial RTO of TCP_RTO_MIN or TCP_TIMEOUT_INIT if 125 * syn_set flag is set. 126 */ 127 static bool retransmits_timed_out(struct sock *sk, 128 unsigned int boundary, 129 unsigned int timeout, 130 bool syn_set) 131 { 132 unsigned int linear_backoff_thresh, start_ts; 133 unsigned int rto_base = syn_set ? TCP_TIMEOUT_INIT : TCP_RTO_MIN; 134 135 if (!inet_csk(sk)->icsk_retransmits) 136 return false; 137 138 if (unlikely(!tcp_sk(sk)->retrans_stamp)) 139 start_ts = TCP_SKB_CB(tcp_write_queue_head(sk))->when; 140 else 141 start_ts = tcp_sk(sk)->retrans_stamp; 142 143 if (likely(timeout == 0)) { 144 linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base); 145 146 if (boundary <= linear_backoff_thresh) 147 timeout = ((2 << boundary) - 1) * rto_base; 148 else 149 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + 150 (boundary - linear_backoff_thresh) * TCP_RTO_MAX; 151 } 152 return (tcp_time_stamp - start_ts) >= timeout; 153 } 154 155 /* A write timeout has occurred. Process the after effects. */ 156 static int tcp_write_timeout(struct sock *sk) 157 { 158 struct inet_connection_sock *icsk = inet_csk(sk); 159 int retry_until; 160 bool do_reset, syn_set = false; 161 162 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { 163 if (icsk->icsk_retransmits) 164 dst_negative_advice(sk); 165 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries; 166 syn_set = true; 167 } else { 168 if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0, 0)) { 169 /* Black hole detection */ 170 tcp_mtu_probing(icsk, sk); 171 172 dst_negative_advice(sk); 173 } 174 175 retry_until = sysctl_tcp_retries2; 176 if (sock_flag(sk, SOCK_DEAD)) { 177 const int alive = (icsk->icsk_rto < TCP_RTO_MAX); 178 179 retry_until = tcp_orphan_retries(sk, alive); 180 do_reset = alive || 181 !retransmits_timed_out(sk, retry_until, 0, 0); 182 183 if (tcp_out_of_resources(sk, do_reset)) 184 return 1; 185 } 186 } 187 188 if (retransmits_timed_out(sk, retry_until, 189 syn_set ? 0 : icsk->icsk_user_timeout, syn_set)) { 190 /* Has it gone just too far? */ 191 tcp_write_err(sk); 192 return 1; 193 } 194 return 0; 195 } 196 197 void tcp_delack_timer_handler(struct sock *sk) 198 { 199 struct tcp_sock *tp = tcp_sk(sk); 200 struct inet_connection_sock *icsk = inet_csk(sk); 201 202 sk_mem_reclaim_partial(sk); 203 204 if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 205 goto out; 206 207 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 208 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); 209 goto out; 210 } 211 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 212 213 if (!skb_queue_empty(&tp->ucopy.prequeue)) { 214 struct sk_buff *skb; 215 216 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED); 217 218 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) 219 sk_backlog_rcv(sk, skb); 220 221 tp->ucopy.memory = 0; 222 } 223 224 if (inet_csk_ack_scheduled(sk)) { 225 if (!icsk->icsk_ack.pingpong) { 226 /* Delayed ACK missed: inflate ATO. */ 227 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto); 228 } else { 229 /* Delayed ACK missed: leave pingpong mode and 230 * deflate ATO. 231 */ 232 icsk->icsk_ack.pingpong = 0; 233 icsk->icsk_ack.ato = TCP_ATO_MIN; 234 } 235 tcp_send_ack(sk); 236 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS); 237 } 238 239 out: 240 if (sk_under_memory_pressure(sk)) 241 sk_mem_reclaim(sk); 242 } 243 244 static void tcp_delack_timer(unsigned long data) 245 { 246 struct sock *sk = (struct sock *)data; 247 248 bh_lock_sock(sk); 249 if (!sock_owned_by_user(sk)) { 250 tcp_delack_timer_handler(sk); 251 } else { 252 inet_csk(sk)->icsk_ack.blocked = 1; 253 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 254 /* deleguate our work to tcp_release_cb() */ 255 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags)) 256 sock_hold(sk); 257 } 258 bh_unlock_sock(sk); 259 sock_put(sk); 260 } 261 262 static void tcp_probe_timer(struct sock *sk) 263 { 264 struct inet_connection_sock *icsk = inet_csk(sk); 265 struct tcp_sock *tp = tcp_sk(sk); 266 int max_probes; 267 268 if (tp->packets_out || !tcp_send_head(sk)) { 269 icsk->icsk_probes_out = 0; 270 return; 271 } 272 273 /* *WARNING* RFC 1122 forbids this 274 * 275 * It doesn't AFAIK, because we kill the retransmit timer -AK 276 * 277 * FIXME: We ought not to do it, Solaris 2.5 actually has fixing 278 * this behaviour in Solaris down as a bug fix. [AC] 279 * 280 * Let me to explain. icsk_probes_out is zeroed by incoming ACKs 281 * even if they advertise zero window. Hence, connection is killed only 282 * if we received no ACKs for normal connection timeout. It is not killed 283 * only because window stays zero for some time, window may be zero 284 * until armageddon and even later. We are in full accordance 285 * with RFCs, only probe timer combines both retransmission timeout 286 * and probe timeout in one bottle. --ANK 287 */ 288 max_probes = sysctl_tcp_retries2; 289 290 if (sock_flag(sk, SOCK_DEAD)) { 291 const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX); 292 293 max_probes = tcp_orphan_retries(sk, alive); 294 295 if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes)) 296 return; 297 } 298 299 if (icsk->icsk_probes_out > max_probes) { 300 tcp_write_err(sk); 301 } else { 302 /* Only send another probe if we didn't close things up. */ 303 tcp_send_probe0(sk); 304 } 305 } 306 307 /* 308 * Timer for Fast Open socket to retransmit SYNACK. Note that the 309 * sk here is the child socket, not the parent (listener) socket. 310 */ 311 static void tcp_fastopen_synack_timer(struct sock *sk) 312 { 313 struct inet_connection_sock *icsk = inet_csk(sk); 314 int max_retries = icsk->icsk_syn_retries ? : 315 sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */ 316 struct request_sock *req; 317 318 req = tcp_sk(sk)->fastopen_rsk; 319 req->rsk_ops->syn_ack_timeout(sk, req); 320 321 if (req->num_timeout >= max_retries) { 322 tcp_write_err(sk); 323 return; 324 } 325 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error 326 * returned from rtx_syn_ack() to make it more persistent like 327 * regular retransmit because if the child socket has been accepted 328 * it's not good to give up too easily. 329 */ 330 inet_rtx_syn_ack(sk, req); 331 req->num_timeout++; 332 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 333 TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX); 334 } 335 336 /* 337 * The TCP retransmit timer. 338 */ 339 340 void tcp_retransmit_timer(struct sock *sk) 341 { 342 struct tcp_sock *tp = tcp_sk(sk); 343 struct inet_connection_sock *icsk = inet_csk(sk); 344 345 if (tp->early_retrans_delayed) { 346 tcp_resume_early_retransmit(sk); 347 return; 348 } 349 if (tp->fastopen_rsk) { 350 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && 351 sk->sk_state != TCP_FIN_WAIT1); 352 tcp_fastopen_synack_timer(sk); 353 /* Before we receive ACK to our SYN-ACK don't retransmit 354 * anything else (e.g., data or FIN segments). 355 */ 356 return; 357 } 358 if (!tp->packets_out) 359 goto out; 360 361 WARN_ON(tcp_write_queue_empty(sk)); 362 363 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && 364 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { 365 /* Receiver dastardly shrinks window. Our retransmits 366 * become zero probes, but we should not timeout this 367 * connection. If the socket is an orphan, time it out, 368 * we cannot allow such beasts to hang infinitely. 369 */ 370 struct inet_sock *inet = inet_sk(sk); 371 if (sk->sk_family == AF_INET) { 372 LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"), 373 &inet->inet_daddr, 374 ntohs(inet->inet_dport), inet->inet_num, 375 tp->snd_una, tp->snd_nxt); 376 } 377 #if IS_ENABLED(CONFIG_IPV6) 378 else if (sk->sk_family == AF_INET6) { 379 struct ipv6_pinfo *np = inet6_sk(sk); 380 LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"), 381 &np->daddr, 382 ntohs(inet->inet_dport), inet->inet_num, 383 tp->snd_una, tp->snd_nxt); 384 } 385 #endif 386 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) { 387 tcp_write_err(sk); 388 goto out; 389 } 390 tcp_enter_loss(sk, 0); 391 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 392 __sk_dst_reset(sk); 393 goto out_reset_timer; 394 } 395 396 if (tcp_write_timeout(sk)) 397 goto out; 398 399 if (icsk->icsk_retransmits == 0) { 400 int mib_idx; 401 402 if (icsk->icsk_ca_state == TCP_CA_Recovery) { 403 if (tcp_is_sack(tp)) 404 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; 405 else 406 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; 407 } else if (icsk->icsk_ca_state == TCP_CA_Loss) { 408 mib_idx = LINUX_MIB_TCPLOSSFAILURES; 409 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || 410 tp->sacked_out) { 411 if (tcp_is_sack(tp)) 412 mib_idx = LINUX_MIB_TCPSACKFAILURES; 413 else 414 mib_idx = LINUX_MIB_TCPRENOFAILURES; 415 } else { 416 mib_idx = LINUX_MIB_TCPTIMEOUTS; 417 } 418 NET_INC_STATS_BH(sock_net(sk), mib_idx); 419 } 420 421 if (tcp_use_frto(sk)) { 422 tcp_enter_frto(sk); 423 } else { 424 tcp_enter_loss(sk, 0); 425 } 426 427 if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) { 428 /* Retransmission failed because of local congestion, 429 * do not backoff. 430 */ 431 if (!icsk->icsk_retransmits) 432 icsk->icsk_retransmits = 1; 433 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 434 min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL), 435 TCP_RTO_MAX); 436 goto out; 437 } 438 439 /* Increase the timeout each time we retransmit. Note that 440 * we do not increase the rtt estimate. rto is initialized 441 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests 442 * that doubling rto each time is the least we can get away with. 443 * In KA9Q, Karn uses this for the first few times, and then 444 * goes to quadratic. netBSD doubles, but only goes up to *64, 445 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is 446 * defined in the protocol as the maximum possible RTT. I guess 447 * we'll have to use something other than TCP to talk to the 448 * University of Mars. 449 * 450 * PAWS allows us longer timeouts and large windows, so once 451 * implemented ftp to mars will work nicely. We will have to fix 452 * the 120 second clamps though! 453 */ 454 icsk->icsk_backoff++; 455 icsk->icsk_retransmits++; 456 457 out_reset_timer: 458 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is 459 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this 460 * might be increased if the stream oscillates between thin and thick, 461 * thus the old value might already be too high compared to the value 462 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without 463 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating 464 * exponential backoff behaviour to avoid continue hammering 465 * linear-timeout retransmissions into a black hole 466 */ 467 if (sk->sk_state == TCP_ESTABLISHED && 468 (tp->thin_lto || sysctl_tcp_thin_linear_timeouts) && 469 tcp_stream_is_thin(tp) && 470 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { 471 icsk->icsk_backoff = 0; 472 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX); 473 } else { 474 /* Use normal (exponential) backoff */ 475 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); 476 } 477 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX); 478 if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1, 0, 0)) 479 __sk_dst_reset(sk); 480 481 out:; 482 } 483 484 void tcp_write_timer_handler(struct sock *sk) 485 { 486 struct inet_connection_sock *icsk = inet_csk(sk); 487 int event; 488 489 if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending) 490 goto out; 491 492 if (time_after(icsk->icsk_timeout, jiffies)) { 493 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); 494 goto out; 495 } 496 497 event = icsk->icsk_pending; 498 icsk->icsk_pending = 0; 499 500 switch (event) { 501 case ICSK_TIME_RETRANS: 502 tcp_retransmit_timer(sk); 503 break; 504 case ICSK_TIME_PROBE0: 505 tcp_probe_timer(sk); 506 break; 507 } 508 509 out: 510 sk_mem_reclaim(sk); 511 } 512 513 static void tcp_write_timer(unsigned long data) 514 { 515 struct sock *sk = (struct sock *)data; 516 517 bh_lock_sock(sk); 518 if (!sock_owned_by_user(sk)) { 519 tcp_write_timer_handler(sk); 520 } else { 521 /* deleguate our work to tcp_release_cb() */ 522 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags)) 523 sock_hold(sk); 524 } 525 bh_unlock_sock(sk); 526 sock_put(sk); 527 } 528 529 /* 530 * Timer for listening sockets 531 */ 532 533 static void tcp_synack_timer(struct sock *sk) 534 { 535 inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL, 536 TCP_TIMEOUT_INIT, TCP_RTO_MAX); 537 } 538 539 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req) 540 { 541 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); 542 } 543 EXPORT_SYMBOL(tcp_syn_ack_timeout); 544 545 void tcp_set_keepalive(struct sock *sk, int val) 546 { 547 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 548 return; 549 550 if (val && !sock_flag(sk, SOCK_KEEPOPEN)) 551 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); 552 else if (!val) 553 inet_csk_delete_keepalive_timer(sk); 554 } 555 556 557 static void tcp_keepalive_timer (unsigned long data) 558 { 559 struct sock *sk = (struct sock *) data; 560 struct inet_connection_sock *icsk = inet_csk(sk); 561 struct tcp_sock *tp = tcp_sk(sk); 562 u32 elapsed; 563 564 /* Only process if socket is not in use. */ 565 bh_lock_sock(sk); 566 if (sock_owned_by_user(sk)) { 567 /* Try again later. */ 568 inet_csk_reset_keepalive_timer (sk, HZ/20); 569 goto out; 570 } 571 572 if (sk->sk_state == TCP_LISTEN) { 573 tcp_synack_timer(sk); 574 goto out; 575 } 576 577 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { 578 if (tp->linger2 >= 0) { 579 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; 580 581 if (tmo > 0) { 582 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 583 goto out; 584 } 585 } 586 tcp_send_active_reset(sk, GFP_ATOMIC); 587 goto death; 588 } 589 590 if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE) 591 goto out; 592 593 elapsed = keepalive_time_when(tp); 594 595 /* It is alive without keepalive 8) */ 596 if (tp->packets_out || tcp_send_head(sk)) 597 goto resched; 598 599 elapsed = keepalive_time_elapsed(tp); 600 601 if (elapsed >= keepalive_time_when(tp)) { 602 /* If the TCP_USER_TIMEOUT option is enabled, use that 603 * to determine when to timeout instead. 604 */ 605 if ((icsk->icsk_user_timeout != 0 && 606 elapsed >= icsk->icsk_user_timeout && 607 icsk->icsk_probes_out > 0) || 608 (icsk->icsk_user_timeout == 0 && 609 icsk->icsk_probes_out >= keepalive_probes(tp))) { 610 tcp_send_active_reset(sk, GFP_ATOMIC); 611 tcp_write_err(sk); 612 goto out; 613 } 614 if (tcp_write_wakeup(sk) <= 0) { 615 icsk->icsk_probes_out++; 616 elapsed = keepalive_intvl_when(tp); 617 } else { 618 /* If keepalive was lost due to local congestion, 619 * try harder. 620 */ 621 elapsed = TCP_RESOURCE_PROBE_INTERVAL; 622 } 623 } else { 624 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ 625 elapsed = keepalive_time_when(tp) - elapsed; 626 } 627 628 sk_mem_reclaim(sk); 629 630 resched: 631 inet_csk_reset_keepalive_timer (sk, elapsed); 632 goto out; 633 634 death: 635 tcp_done(sk); 636 637 out: 638 bh_unlock_sock(sk); 639 sock_put(sk); 640 } 641 642 void tcp_init_xmit_timers(struct sock *sk) 643 { 644 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, 645 &tcp_keepalive_timer); 646 } 647 EXPORT_SYMBOL(tcp_init_xmit_timers);
Cache object: d42d7881fc8f5ce5be42bd6c9c85975d
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