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 struct tcp_sock *tp = tcp_sk(sk); 160 int retry_until; 161 bool do_reset, syn_set = false; 162 163 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { 164 if (icsk->icsk_retransmits) { 165 dst_negative_advice(sk); 166 if (tp->syn_fastopen || tp->syn_data) 167 tcp_fastopen_cache_set(sk, 0, NULL, true); 168 if (tp->syn_data) 169 NET_INC_STATS_BH(sock_net(sk), 170 LINUX_MIB_TCPFASTOPENACTIVEFAIL); 171 } 172 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries; 173 syn_set = true; 174 } else { 175 if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0, 0)) { 176 /* Black hole detection */ 177 tcp_mtu_probing(icsk, sk); 178 179 dst_negative_advice(sk); 180 } 181 182 retry_until = sysctl_tcp_retries2; 183 if (sock_flag(sk, SOCK_DEAD)) { 184 const int alive = (icsk->icsk_rto < TCP_RTO_MAX); 185 186 retry_until = tcp_orphan_retries(sk, alive); 187 do_reset = alive || 188 !retransmits_timed_out(sk, retry_until, 0, 0); 189 190 if (tcp_out_of_resources(sk, do_reset)) 191 return 1; 192 } 193 } 194 195 if (retransmits_timed_out(sk, retry_until, 196 syn_set ? 0 : icsk->icsk_user_timeout, syn_set)) { 197 /* Has it gone just too far? */ 198 tcp_write_err(sk); 199 return 1; 200 } 201 return 0; 202 } 203 204 void tcp_delack_timer_handler(struct sock *sk) 205 { 206 struct tcp_sock *tp = tcp_sk(sk); 207 struct inet_connection_sock *icsk = inet_csk(sk); 208 209 sk_mem_reclaim_partial(sk); 210 211 if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 212 goto out; 213 214 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 215 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); 216 goto out; 217 } 218 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 219 220 if (!skb_queue_empty(&tp->ucopy.prequeue)) { 221 struct sk_buff *skb; 222 223 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED); 224 225 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) 226 sk_backlog_rcv(sk, skb); 227 228 tp->ucopy.memory = 0; 229 } 230 231 if (inet_csk_ack_scheduled(sk)) { 232 if (!icsk->icsk_ack.pingpong) { 233 /* Delayed ACK missed: inflate ATO. */ 234 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto); 235 } else { 236 /* Delayed ACK missed: leave pingpong mode and 237 * deflate ATO. 238 */ 239 icsk->icsk_ack.pingpong = 0; 240 icsk->icsk_ack.ato = TCP_ATO_MIN; 241 } 242 tcp_send_ack(sk); 243 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS); 244 } 245 246 out: 247 if (sk_under_memory_pressure(sk)) 248 sk_mem_reclaim(sk); 249 } 250 251 static void tcp_delack_timer(unsigned long data) 252 { 253 struct sock *sk = (struct sock *)data; 254 255 bh_lock_sock(sk); 256 if (!sock_owned_by_user(sk)) { 257 tcp_delack_timer_handler(sk); 258 } else { 259 inet_csk(sk)->icsk_ack.blocked = 1; 260 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 261 /* deleguate our work to tcp_release_cb() */ 262 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags)) 263 sock_hold(sk); 264 } 265 bh_unlock_sock(sk); 266 sock_put(sk); 267 } 268 269 static void tcp_probe_timer(struct sock *sk) 270 { 271 struct inet_connection_sock *icsk = inet_csk(sk); 272 struct tcp_sock *tp = tcp_sk(sk); 273 int max_probes; 274 275 if (tp->packets_out || !tcp_send_head(sk)) { 276 icsk->icsk_probes_out = 0; 277 return; 278 } 279 280 /* *WARNING* RFC 1122 forbids this 281 * 282 * It doesn't AFAIK, because we kill the retransmit timer -AK 283 * 284 * FIXME: We ought not to do it, Solaris 2.5 actually has fixing 285 * this behaviour in Solaris down as a bug fix. [AC] 286 * 287 * Let me to explain. icsk_probes_out is zeroed by incoming ACKs 288 * even if they advertise zero window. Hence, connection is killed only 289 * if we received no ACKs for normal connection timeout. It is not killed 290 * only because window stays zero for some time, window may be zero 291 * until armageddon and even later. We are in full accordance 292 * with RFCs, only probe timer combines both retransmission timeout 293 * and probe timeout in one bottle. --ANK 294 */ 295 max_probes = sysctl_tcp_retries2; 296 297 if (sock_flag(sk, SOCK_DEAD)) { 298 const int alive = ((icsk->icsk_rto << icsk->icsk_backoff) < TCP_RTO_MAX); 299 300 max_probes = tcp_orphan_retries(sk, alive); 301 302 if (tcp_out_of_resources(sk, alive || icsk->icsk_probes_out <= max_probes)) 303 return; 304 } 305 306 if (icsk->icsk_probes_out > max_probes) { 307 tcp_write_err(sk); 308 } else { 309 /* Only send another probe if we didn't close things up. */ 310 tcp_send_probe0(sk); 311 } 312 } 313 314 /* 315 * Timer for Fast Open socket to retransmit SYNACK. Note that the 316 * sk here is the child socket, not the parent (listener) socket. 317 */ 318 static void tcp_fastopen_synack_timer(struct sock *sk) 319 { 320 struct inet_connection_sock *icsk = inet_csk(sk); 321 int max_retries = icsk->icsk_syn_retries ? : 322 sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */ 323 struct request_sock *req; 324 325 req = tcp_sk(sk)->fastopen_rsk; 326 req->rsk_ops->syn_ack_timeout(sk, req); 327 328 if (req->num_timeout >= max_retries) { 329 tcp_write_err(sk); 330 return; 331 } 332 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error 333 * returned from rtx_syn_ack() to make it more persistent like 334 * regular retransmit because if the child socket has been accepted 335 * it's not good to give up too easily. 336 */ 337 inet_rtx_syn_ack(sk, req); 338 req->num_timeout++; 339 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 340 TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX); 341 } 342 343 /* 344 * The TCP retransmit timer. 345 */ 346 347 void tcp_retransmit_timer(struct sock *sk) 348 { 349 struct tcp_sock *tp = tcp_sk(sk); 350 struct inet_connection_sock *icsk = inet_csk(sk); 351 352 if (tp->fastopen_rsk) { 353 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && 354 sk->sk_state != TCP_FIN_WAIT1); 355 tcp_fastopen_synack_timer(sk); 356 /* Before we receive ACK to our SYN-ACK don't retransmit 357 * anything else (e.g., data or FIN segments). 358 */ 359 return; 360 } 361 if (!tp->packets_out) 362 goto out; 363 364 WARN_ON(tcp_write_queue_empty(sk)); 365 366 tp->tlp_high_seq = 0; 367 368 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && 369 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { 370 /* Receiver dastardly shrinks window. Our retransmits 371 * become zero probes, but we should not timeout this 372 * connection. If the socket is an orphan, time it out, 373 * we cannot allow such beasts to hang infinitely. 374 */ 375 struct inet_sock *inet = inet_sk(sk); 376 if (sk->sk_family == AF_INET) { 377 LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"), 378 &inet->inet_daddr, 379 ntohs(inet->inet_dport), inet->inet_num, 380 tp->snd_una, tp->snd_nxt); 381 } 382 #if IS_ENABLED(CONFIG_IPV6) 383 else if (sk->sk_family == AF_INET6) { 384 LIMIT_NETDEBUG(KERN_DEBUG pr_fmt("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n"), 385 &sk->sk_v6_daddr, 386 ntohs(inet->inet_dport), inet->inet_num, 387 tp->snd_una, tp->snd_nxt); 388 } 389 #endif 390 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) { 391 tcp_write_err(sk); 392 goto out; 393 } 394 tcp_enter_loss(sk); 395 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 396 __sk_dst_reset(sk); 397 goto out_reset_timer; 398 } 399 400 if (tcp_write_timeout(sk)) 401 goto out; 402 403 if (icsk->icsk_retransmits == 0) { 404 int mib_idx; 405 406 if (icsk->icsk_ca_state == TCP_CA_Recovery) { 407 if (tcp_is_sack(tp)) 408 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; 409 else 410 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; 411 } else if (icsk->icsk_ca_state == TCP_CA_Loss) { 412 mib_idx = LINUX_MIB_TCPLOSSFAILURES; 413 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || 414 tp->sacked_out) { 415 if (tcp_is_sack(tp)) 416 mib_idx = LINUX_MIB_TCPSACKFAILURES; 417 else 418 mib_idx = LINUX_MIB_TCPRENOFAILURES; 419 } else { 420 mib_idx = LINUX_MIB_TCPTIMEOUTS; 421 } 422 NET_INC_STATS_BH(sock_net(sk), mib_idx); 423 } 424 425 tcp_enter_loss(sk); 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; 498 499 switch (event) { 500 case ICSK_TIME_EARLY_RETRANS: 501 tcp_resume_early_retransmit(sk); 502 break; 503 case ICSK_TIME_LOSS_PROBE: 504 tcp_send_loss_probe(sk); 505 break; 506 case ICSK_TIME_RETRANS: 507 icsk->icsk_pending = 0; 508 tcp_retransmit_timer(sk); 509 break; 510 case ICSK_TIME_PROBE0: 511 icsk->icsk_pending = 0; 512 tcp_probe_timer(sk); 513 break; 514 } 515 516 out: 517 sk_mem_reclaim(sk); 518 } 519 520 static void tcp_write_timer(unsigned long data) 521 { 522 struct sock *sk = (struct sock *)data; 523 524 bh_lock_sock(sk); 525 if (!sock_owned_by_user(sk)) { 526 tcp_write_timer_handler(sk); 527 } else { 528 /* deleguate our work to tcp_release_cb() */ 529 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags)) 530 sock_hold(sk); 531 } 532 bh_unlock_sock(sk); 533 sock_put(sk); 534 } 535 536 /* 537 * Timer for listening sockets 538 */ 539 540 static void tcp_synack_timer(struct sock *sk) 541 { 542 inet_csk_reqsk_queue_prune(sk, TCP_SYNQ_INTERVAL, 543 TCP_TIMEOUT_INIT, TCP_RTO_MAX); 544 } 545 546 void tcp_syn_ack_timeout(struct sock *sk, struct request_sock *req) 547 { 548 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); 549 } 550 EXPORT_SYMBOL(tcp_syn_ack_timeout); 551 552 void tcp_set_keepalive(struct sock *sk, int val) 553 { 554 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 555 return; 556 557 if (val && !sock_flag(sk, SOCK_KEEPOPEN)) 558 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); 559 else if (!val) 560 inet_csk_delete_keepalive_timer(sk); 561 } 562 563 564 static void tcp_keepalive_timer (unsigned long data) 565 { 566 struct sock *sk = (struct sock *) data; 567 struct inet_connection_sock *icsk = inet_csk(sk); 568 struct tcp_sock *tp = tcp_sk(sk); 569 u32 elapsed; 570 571 /* Only process if socket is not in use. */ 572 bh_lock_sock(sk); 573 if (sock_owned_by_user(sk)) { 574 /* Try again later. */ 575 inet_csk_reset_keepalive_timer (sk, HZ/20); 576 goto out; 577 } 578 579 if (sk->sk_state == TCP_LISTEN) { 580 tcp_synack_timer(sk); 581 goto out; 582 } 583 584 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { 585 if (tp->linger2 >= 0) { 586 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; 587 588 if (tmo > 0) { 589 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 590 goto out; 591 } 592 } 593 tcp_send_active_reset(sk, GFP_ATOMIC); 594 goto death; 595 } 596 597 if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE) 598 goto out; 599 600 elapsed = keepalive_time_when(tp); 601 602 /* It is alive without keepalive 8) */ 603 if (tp->packets_out || tcp_send_head(sk)) 604 goto resched; 605 606 elapsed = keepalive_time_elapsed(tp); 607 608 if (elapsed >= keepalive_time_when(tp)) { 609 /* If the TCP_USER_TIMEOUT option is enabled, use that 610 * to determine when to timeout instead. 611 */ 612 if ((icsk->icsk_user_timeout != 0 && 613 elapsed >= icsk->icsk_user_timeout && 614 icsk->icsk_probes_out > 0) || 615 (icsk->icsk_user_timeout == 0 && 616 icsk->icsk_probes_out >= keepalive_probes(tp))) { 617 tcp_send_active_reset(sk, GFP_ATOMIC); 618 tcp_write_err(sk); 619 goto out; 620 } 621 if (tcp_write_wakeup(sk) <= 0) { 622 icsk->icsk_probes_out++; 623 elapsed = keepalive_intvl_when(tp); 624 } else { 625 /* If keepalive was lost due to local congestion, 626 * try harder. 627 */ 628 elapsed = TCP_RESOURCE_PROBE_INTERVAL; 629 } 630 } else { 631 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ 632 elapsed = keepalive_time_when(tp) - elapsed; 633 } 634 635 sk_mem_reclaim(sk); 636 637 resched: 638 inet_csk_reset_keepalive_timer (sk, elapsed); 639 goto out; 640 641 death: 642 tcp_done(sk); 643 644 out: 645 bh_unlock_sock(sk); 646 sock_put(sk); 647 } 648 649 void tcp_init_xmit_timers(struct sock *sk) 650 { 651 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, 652 &tcp_keepalive_timer); 653 } 654 EXPORT_SYMBOL(tcp_init_xmit_timers); 655