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, bool 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 = true; 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 struct net *net = sock_net(sk); 105 106 /* Black hole detection */ 107 if (net->ipv4.sysctl_tcp_mtu_probing) { 108 if (!icsk->icsk_mtup.enabled) { 109 icsk->icsk_mtup.enabled = 1; 110 icsk->icsk_mtup.probe_timestamp = tcp_time_stamp; 111 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 112 } else { 113 struct net *net = sock_net(sk); 114 struct tcp_sock *tp = tcp_sk(sk); 115 int mss; 116 117 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; 118 mss = min(net->ipv4.sysctl_tcp_base_mss, mss); 119 mss = max(mss, 68 - tp->tcp_header_len); 120 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); 121 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 122 } 123 } 124 } 125 126 /* This function calculates a "timeout" which is equivalent to the timeout of a 127 * TCP connection after "boundary" unsuccessful, exponentially backed-off 128 * retransmissions with an initial RTO of TCP_RTO_MIN or TCP_TIMEOUT_INIT if 129 * syn_set flag is set. 130 */ 131 static bool retransmits_timed_out(struct sock *sk, 132 unsigned int boundary, 133 unsigned int timeout, 134 bool syn_set) 135 { 136 unsigned int linear_backoff_thresh, start_ts; 137 unsigned int rto_base = syn_set ? TCP_TIMEOUT_INIT : TCP_RTO_MIN; 138 139 if (!inet_csk(sk)->icsk_retransmits) 140 return false; 141 142 start_ts = tcp_sk(sk)->retrans_stamp; 143 if (unlikely(!start_ts)) 144 start_ts = tcp_skb_timestamp(tcp_write_queue_head(sk)); 145 146 if (likely(timeout == 0)) { 147 linear_backoff_thresh = ilog2(TCP_RTO_MAX/rto_base); 148 149 if (boundary <= linear_backoff_thresh) 150 timeout = ((2 << boundary) - 1) * rto_base; 151 else 152 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + 153 (boundary - linear_backoff_thresh) * TCP_RTO_MAX; 154 } 155 return (tcp_time_stamp - start_ts) >= timeout; 156 } 157 158 /* A write timeout has occurred. Process the after effects. */ 159 static int tcp_write_timeout(struct sock *sk) 160 { 161 struct inet_connection_sock *icsk = inet_csk(sk); 162 struct tcp_sock *tp = tcp_sk(sk); 163 int retry_until; 164 bool do_reset, syn_set = false; 165 166 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { 167 if (icsk->icsk_retransmits) { 168 dst_negative_advice(sk); 169 if (tp->syn_fastopen || tp->syn_data) 170 tcp_fastopen_cache_set(sk, 0, NULL, true, 0); 171 if (tp->syn_data) 172 NET_INC_STATS_BH(sock_net(sk), 173 LINUX_MIB_TCPFASTOPENACTIVEFAIL); 174 } 175 retry_until = icsk->icsk_syn_retries ? : sysctl_tcp_syn_retries; 176 syn_set = true; 177 } else { 178 if (retransmits_timed_out(sk, sysctl_tcp_retries1, 0, 0)) { 179 /* Black hole detection */ 180 tcp_mtu_probing(icsk, sk); 181 182 dst_negative_advice(sk); 183 } 184 185 retry_until = sysctl_tcp_retries2; 186 if (sock_flag(sk, SOCK_DEAD)) { 187 const int alive = icsk->icsk_rto < TCP_RTO_MAX; 188 189 retry_until = tcp_orphan_retries(sk, alive); 190 do_reset = alive || 191 !retransmits_timed_out(sk, retry_until, 0, 0); 192 193 if (tcp_out_of_resources(sk, do_reset)) 194 return 1; 195 } 196 } 197 198 if (retransmits_timed_out(sk, retry_until, 199 syn_set ? 0 : icsk->icsk_user_timeout, syn_set)) { 200 /* Has it gone just too far? */ 201 tcp_write_err(sk); 202 return 1; 203 } 204 return 0; 205 } 206 207 void tcp_delack_timer_handler(struct sock *sk) 208 { 209 struct tcp_sock *tp = tcp_sk(sk); 210 struct inet_connection_sock *icsk = inet_csk(sk); 211 212 sk_mem_reclaim_partial(sk); 213 214 if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 215 goto out; 216 217 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 218 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); 219 goto out; 220 } 221 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 222 223 if (!skb_queue_empty(&tp->ucopy.prequeue)) { 224 struct sk_buff *skb; 225 226 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSCHEDULERFAILED); 227 228 while ((skb = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) 229 sk_backlog_rcv(sk, skb); 230 231 tp->ucopy.memory = 0; 232 } 233 234 if (inet_csk_ack_scheduled(sk)) { 235 if (!icsk->icsk_ack.pingpong) { 236 /* Delayed ACK missed: inflate ATO. */ 237 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto); 238 } else { 239 /* Delayed ACK missed: leave pingpong mode and 240 * deflate ATO. 241 */ 242 icsk->icsk_ack.pingpong = 0; 243 icsk->icsk_ack.ato = TCP_ATO_MIN; 244 } 245 tcp_send_ack(sk); 246 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKS); 247 } 248 249 out: 250 if (tcp_under_memory_pressure(sk)) 251 sk_mem_reclaim(sk); 252 } 253 254 static void tcp_delack_timer(unsigned long data) 255 { 256 struct sock *sk = (struct sock *)data; 257 258 bh_lock_sock(sk); 259 if (!sock_owned_by_user(sk)) { 260 tcp_delack_timer_handler(sk); 261 } else { 262 inet_csk(sk)->icsk_ack.blocked = 1; 263 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 264 /* deleguate our work to tcp_release_cb() */ 265 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags)) 266 sock_hold(sk); 267 } 268 bh_unlock_sock(sk); 269 sock_put(sk); 270 } 271 272 static void tcp_probe_timer(struct sock *sk) 273 { 274 struct inet_connection_sock *icsk = inet_csk(sk); 275 struct tcp_sock *tp = tcp_sk(sk); 276 int max_probes; 277 u32 start_ts; 278 279 if (tp->packets_out || !tcp_send_head(sk)) { 280 icsk->icsk_probes_out = 0; 281 return; 282 } 283 284 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as 285 * long as the receiver continues to respond probes. We support this by 286 * default and reset icsk_probes_out with incoming ACKs. But if the 287 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we 288 * kill the socket when the retry count and the time exceeds the 289 * corresponding system limit. We also implement similar policy when 290 * we use RTO to probe window in tcp_retransmit_timer(). 291 */ 292 start_ts = tcp_skb_timestamp(tcp_send_head(sk)); 293 if (!start_ts) 294 skb_mstamp_get(&tcp_send_head(sk)->skb_mstamp); 295 else if (icsk->icsk_user_timeout && 296 (s32)(tcp_time_stamp - start_ts) > icsk->icsk_user_timeout) 297 goto abort; 298 299 max_probes = sysctl_tcp_retries2; 300 if (sock_flag(sk, SOCK_DEAD)) { 301 const int alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX; 302 303 max_probes = tcp_orphan_retries(sk, alive); 304 if (!alive && icsk->icsk_backoff >= max_probes) 305 goto abort; 306 if (tcp_out_of_resources(sk, true)) 307 return; 308 } 309 310 if (icsk->icsk_probes_out > max_probes) { 311 abort: tcp_write_err(sk); 312 } else { 313 /* Only send another probe if we didn't close things up. */ 314 tcp_send_probe0(sk); 315 } 316 } 317 318 /* 319 * Timer for Fast Open socket to retransmit SYNACK. Note that the 320 * sk here is the child socket, not the parent (listener) socket. 321 */ 322 static void tcp_fastopen_synack_timer(struct sock *sk) 323 { 324 struct inet_connection_sock *icsk = inet_csk(sk); 325 int max_retries = icsk->icsk_syn_retries ? : 326 sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */ 327 struct request_sock *req; 328 329 req = tcp_sk(sk)->fastopen_rsk; 330 req->rsk_ops->syn_ack_timeout(req); 331 332 if (req->num_timeout >= max_retries) { 333 tcp_write_err(sk); 334 return; 335 } 336 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error 337 * returned from rtx_syn_ack() to make it more persistent like 338 * regular retransmit because if the child socket has been accepted 339 * it's not good to give up too easily. 340 */ 341 inet_rtx_syn_ack(sk, req); 342 req->num_timeout++; 343 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 344 TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX); 345 } 346 347 /* 348 * The TCP retransmit timer. 349 */ 350 351 void tcp_retransmit_timer(struct sock *sk) 352 { 353 struct tcp_sock *tp = tcp_sk(sk); 354 struct inet_connection_sock *icsk = inet_csk(sk); 355 356 if (tp->fastopen_rsk) { 357 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && 358 sk->sk_state != TCP_FIN_WAIT1); 359 tcp_fastopen_synack_timer(sk); 360 /* Before we receive ACK to our SYN-ACK don't retransmit 361 * anything else (e.g., data or FIN segments). 362 */ 363 return; 364 } 365 if (!tp->packets_out) 366 goto out; 367 368 WARN_ON(tcp_write_queue_empty(sk)); 369 370 tp->tlp_high_seq = 0; 371 372 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && 373 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { 374 /* Receiver dastardly shrinks window. Our retransmits 375 * become zero probes, but we should not timeout this 376 * connection. If the socket is an orphan, time it out, 377 * we cannot allow such beasts to hang infinitely. 378 */ 379 struct inet_sock *inet = inet_sk(sk); 380 if (sk->sk_family == AF_INET) { 381 net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", 382 &inet->inet_daddr, 383 ntohs(inet->inet_dport), 384 inet->inet_num, 385 tp->snd_una, tp->snd_nxt); 386 } 387 #if IS_ENABLED(CONFIG_IPV6) 388 else if (sk->sk_family == AF_INET6) { 389 net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", 390 &sk->sk_v6_daddr, 391 ntohs(inet->inet_dport), 392 inet->inet_num, 393 tp->snd_una, tp->snd_nxt); 394 } 395 #endif 396 if (tcp_time_stamp - tp->rcv_tstamp > TCP_RTO_MAX) { 397 tcp_write_err(sk); 398 goto out; 399 } 400 tcp_enter_loss(sk); 401 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 402 __sk_dst_reset(sk); 403 goto out_reset_timer; 404 } 405 406 if (tcp_write_timeout(sk)) 407 goto out; 408 409 if (icsk->icsk_retransmits == 0) { 410 int mib_idx; 411 412 if (icsk->icsk_ca_state == TCP_CA_Recovery) { 413 if (tcp_is_sack(tp)) 414 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; 415 else 416 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; 417 } else if (icsk->icsk_ca_state == TCP_CA_Loss) { 418 mib_idx = LINUX_MIB_TCPLOSSFAILURES; 419 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || 420 tp->sacked_out) { 421 if (tcp_is_sack(tp)) 422 mib_idx = LINUX_MIB_TCPSACKFAILURES; 423 else 424 mib_idx = LINUX_MIB_TCPRENOFAILURES; 425 } else { 426 mib_idx = LINUX_MIB_TCPTIMEOUTS; 427 } 428 NET_INC_STATS_BH(sock_net(sk), mib_idx); 429 } 430 431 tcp_enter_loss(sk); 432 433 if (tcp_retransmit_skb(sk, tcp_write_queue_head(sk)) > 0) { 434 /* Retransmission failed because of local congestion, 435 * do not backoff. 436 */ 437 if (!icsk->icsk_retransmits) 438 icsk->icsk_retransmits = 1; 439 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 440 min(icsk->icsk_rto, TCP_RESOURCE_PROBE_INTERVAL), 441 TCP_RTO_MAX); 442 goto out; 443 } 444 445 /* Increase the timeout each time we retransmit. Note that 446 * we do not increase the rtt estimate. rto is initialized 447 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests 448 * that doubling rto each time is the least we can get away with. 449 * In KA9Q, Karn uses this for the first few times, and then 450 * goes to quadratic. netBSD doubles, but only goes up to *64, 451 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is 452 * defined in the protocol as the maximum possible RTT. I guess 453 * we'll have to use something other than TCP to talk to the 454 * University of Mars. 455 * 456 * PAWS allows us longer timeouts and large windows, so once 457 * implemented ftp to mars will work nicely. We will have to fix 458 * the 120 second clamps though! 459 */ 460 icsk->icsk_backoff++; 461 icsk->icsk_retransmits++; 462 463 out_reset_timer: 464 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is 465 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this 466 * might be increased if the stream oscillates between thin and thick, 467 * thus the old value might already be too high compared to the value 468 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without 469 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating 470 * exponential backoff behaviour to avoid continue hammering 471 * linear-timeout retransmissions into a black hole 472 */ 473 if (sk->sk_state == TCP_ESTABLISHED && 474 (tp->thin_lto || sysctl_tcp_thin_linear_timeouts) && 475 tcp_stream_is_thin(tp) && 476 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { 477 icsk->icsk_backoff = 0; 478 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX); 479 } else { 480 /* Use normal (exponential) backoff */ 481 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); 482 } 483 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, icsk->icsk_rto, TCP_RTO_MAX); 484 if (retransmits_timed_out(sk, sysctl_tcp_retries1 + 1, 0, 0)) 485 __sk_dst_reset(sk); 486 487 out:; 488 } 489 490 void tcp_write_timer_handler(struct sock *sk) 491 { 492 struct inet_connection_sock *icsk = inet_csk(sk); 493 int event; 494 495 if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending) 496 goto out; 497 498 if (time_after(icsk->icsk_timeout, jiffies)) { 499 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); 500 goto out; 501 } 502 503 event = icsk->icsk_pending; 504 505 switch (event) { 506 case ICSK_TIME_EARLY_RETRANS: 507 tcp_resume_early_retransmit(sk); 508 break; 509 case ICSK_TIME_LOSS_PROBE: 510 tcp_send_loss_probe(sk); 511 break; 512 case ICSK_TIME_RETRANS: 513 icsk->icsk_pending = 0; 514 tcp_retransmit_timer(sk); 515 break; 516 case ICSK_TIME_PROBE0: 517 icsk->icsk_pending = 0; 518 tcp_probe_timer(sk); 519 break; 520 } 521 522 out: 523 sk_mem_reclaim(sk); 524 } 525 526 static void tcp_write_timer(unsigned long data) 527 { 528 struct sock *sk = (struct sock *)data; 529 530 bh_lock_sock(sk); 531 if (!sock_owned_by_user(sk)) { 532 tcp_write_timer_handler(sk); 533 } else { 534 /* deleguate our work to tcp_release_cb() */ 535 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &tcp_sk(sk)->tsq_flags)) 536 sock_hold(sk); 537 } 538 bh_unlock_sock(sk); 539 sock_put(sk); 540 } 541 542 void tcp_syn_ack_timeout(const struct request_sock *req) 543 { 544 struct net *net = read_pnet(&inet_rsk(req)->ireq_net); 545 546 NET_INC_STATS_BH(net, LINUX_MIB_TCPTIMEOUTS); 547 } 548 EXPORT_SYMBOL(tcp_syn_ack_timeout); 549 550 void tcp_set_keepalive(struct sock *sk, int val) 551 { 552 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 553 return; 554 555 if (val && !sock_flag(sk, SOCK_KEEPOPEN)) 556 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); 557 else if (!val) 558 inet_csk_delete_keepalive_timer(sk); 559 } 560 561 562 static void tcp_keepalive_timer (unsigned long data) 563 { 564 struct sock *sk = (struct sock *) data; 565 struct inet_connection_sock *icsk = inet_csk(sk); 566 struct tcp_sock *tp = tcp_sk(sk); 567 u32 elapsed; 568 569 /* Only process if socket is not in use. */ 570 bh_lock_sock(sk); 571 if (sock_owned_by_user(sk)) { 572 /* Try again later. */ 573 inet_csk_reset_keepalive_timer (sk, HZ/20); 574 goto out; 575 } 576 577 if (sk->sk_state == TCP_LISTEN) { 578 pr_err("Hmm... keepalive on a LISTEN ???\n"); 579 goto out; 580 } 581 582 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { 583 if (tp->linger2 >= 0) { 584 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; 585 586 if (tmo > 0) { 587 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 588 goto out; 589 } 590 } 591 tcp_send_active_reset(sk, GFP_ATOMIC); 592 goto death; 593 } 594 595 if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE) 596 goto out; 597 598 elapsed = keepalive_time_when(tp); 599 600 /* It is alive without keepalive 8) */ 601 if (tp->packets_out || tcp_send_head(sk)) 602 goto resched; 603 604 elapsed = keepalive_time_elapsed(tp); 605 606 if (elapsed >= keepalive_time_when(tp)) { 607 /* If the TCP_USER_TIMEOUT option is enabled, use that 608 * to determine when to timeout instead. 609 */ 610 if ((icsk->icsk_user_timeout != 0 && 611 elapsed >= icsk->icsk_user_timeout && 612 icsk->icsk_probes_out > 0) || 613 (icsk->icsk_user_timeout == 0 && 614 icsk->icsk_probes_out >= keepalive_probes(tp))) { 615 tcp_send_active_reset(sk, GFP_ATOMIC); 616 tcp_write_err(sk); 617 goto out; 618 } 619 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) { 620 icsk->icsk_probes_out++; 621 elapsed = keepalive_intvl_when(tp); 622 } else { 623 /* If keepalive was lost due to local congestion, 624 * try harder. 625 */ 626 elapsed = TCP_RESOURCE_PROBE_INTERVAL; 627 } 628 } else { 629 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ 630 elapsed = keepalive_time_when(tp) - elapsed; 631 } 632 633 sk_mem_reclaim(sk); 634 635 resched: 636 inet_csk_reset_keepalive_timer (sk, elapsed); 637 goto out; 638 639 death: 640 tcp_done(sk); 641 642 out: 643 bh_unlock_sock(sk); 644 sock_put(sk); 645 } 646 647 void tcp_init_xmit_timers(struct sock *sk) 648 { 649 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, 650 &tcp_keepalive_timer); 651 } 652