1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * INET An implementation of the TCP/IP protocol suite for the LINUX 4 * operating system. INET is implemented using the BSD Socket 5 * interface as the means of communication with the user level. 6 * 7 * Implementation of the Transmission Control Protocol(TCP). 8 * 9 * Authors: Ross Biro 10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 11 * Mark Evans, <evansmp@uhura.aston.ac.uk> 12 * Corey Minyard <wf-rch!minyard@relay.EU.net> 13 * Florian La Roche, <flla@stud.uni-sb.de> 14 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> 15 * Linus Torvalds, <torvalds@cs.helsinki.fi> 16 * Alan Cox, <gw4pts@gw4pts.ampr.org> 17 * Matthew Dillon, <dillon@apollo.west.oic.com> 18 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 19 * Jorge Cwik, <jorge@laser.satlink.net> 20 */ 21 22 #include <linux/module.h> 23 #include <linux/gfp.h> 24 #include <net/tcp.h> 25 26 static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk) 27 { 28 struct inet_connection_sock *icsk = inet_csk(sk); 29 u32 elapsed, start_ts; 30 s32 remaining; 31 32 start_ts = tcp_sk(sk)->retrans_stamp; 33 if (!icsk->icsk_user_timeout) 34 return icsk->icsk_rto; 35 elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts; 36 remaining = icsk->icsk_user_timeout - elapsed; 37 if (remaining <= 0) 38 return 1; /* user timeout has passed; fire ASAP */ 39 40 return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining)); 41 } 42 43 /** 44 * tcp_write_err() - close socket and save error info 45 * @sk: The socket the error has appeared on. 46 * 47 * Returns: Nothing (void) 48 */ 49 50 static void tcp_write_err(struct sock *sk) 51 { 52 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT; 53 sk->sk_error_report(sk); 54 55 tcp_write_queue_purge(sk); 56 tcp_done(sk); 57 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); 58 } 59 60 /** 61 * tcp_out_of_resources() - Close socket if out of resources 62 * @sk: pointer to current socket 63 * @do_reset: send a last packet with reset flag 64 * 65 * Do not allow orphaned sockets to eat all our resources. 66 * This is direct violation of TCP specs, but it is required 67 * to prevent DoS attacks. It is called when a retransmission timeout 68 * or zero probe timeout occurs on orphaned socket. 69 * 70 * Also close if our net namespace is exiting; in that case there is no 71 * hope of ever communicating again since all netns interfaces are already 72 * down (or about to be down), and we need to release our dst references, 73 * which have been moved to the netns loopback interface, so the namespace 74 * can finish exiting. This condition is only possible if we are a kernel 75 * socket, as those do not hold references to the namespace. 76 * 77 * Criteria is still not confirmed experimentally and may change. 78 * We kill the socket, if: 79 * 1. If number of orphaned sockets exceeds an administratively configured 80 * limit. 81 * 2. If we have strong memory pressure. 82 * 3. If our net namespace is exiting. 83 */ 84 static int tcp_out_of_resources(struct sock *sk, bool do_reset) 85 { 86 struct tcp_sock *tp = tcp_sk(sk); 87 int shift = 0; 88 89 /* If peer does not open window for long time, or did not transmit 90 * anything for long time, penalize it. */ 91 if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset) 92 shift++; 93 94 /* If some dubious ICMP arrived, penalize even more. */ 95 if (sk->sk_err_soft) 96 shift++; 97 98 if (tcp_check_oom(sk, shift)) { 99 /* Catch exceptional cases, when connection requires reset. 100 * 1. Last segment was sent recently. */ 101 if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN || 102 /* 2. Window is closed. */ 103 (!tp->snd_wnd && !tp->packets_out)) 104 do_reset = true; 105 if (do_reset) 106 tcp_send_active_reset(sk, GFP_ATOMIC); 107 tcp_done(sk); 108 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY); 109 return 1; 110 } 111 112 if (!check_net(sock_net(sk))) { 113 /* Not possible to send reset; just close */ 114 tcp_done(sk); 115 return 1; 116 } 117 118 return 0; 119 } 120 121 /** 122 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket 123 * @sk: Pointer to the current socket. 124 * @alive: bool, socket alive state 125 */ 126 static int tcp_orphan_retries(struct sock *sk, bool alive) 127 { 128 int retries = sock_net(sk)->ipv4.sysctl_tcp_orphan_retries; /* May be zero. */ 129 130 /* We know from an ICMP that something is wrong. */ 131 if (sk->sk_err_soft && !alive) 132 retries = 0; 133 134 /* However, if socket sent something recently, select some safe 135 * number of retries. 8 corresponds to >100 seconds with minimal 136 * RTO of 200msec. */ 137 if (retries == 0 && alive) 138 retries = 8; 139 return retries; 140 } 141 142 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 143 { 144 const struct net *net = sock_net(sk); 145 int mss; 146 147 /* Black hole detection */ 148 if (!net->ipv4.sysctl_tcp_mtu_probing) 149 return; 150 151 if (!icsk->icsk_mtup.enabled) { 152 icsk->icsk_mtup.enabled = 1; 153 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; 154 } else { 155 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; 156 mss = min(net->ipv4.sysctl_tcp_base_mss, mss); 157 mss = max(mss, net->ipv4.sysctl_tcp_mtu_probe_floor); 158 mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss); 159 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); 160 } 161 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 162 } 163 164 static unsigned int tcp_model_timeout(struct sock *sk, 165 unsigned int boundary, 166 unsigned int rto_base) 167 { 168 unsigned int linear_backoff_thresh, timeout; 169 170 linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base); 171 if (boundary <= linear_backoff_thresh) 172 timeout = ((2 << boundary) - 1) * rto_base; 173 else 174 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + 175 (boundary - linear_backoff_thresh) * TCP_RTO_MAX; 176 return jiffies_to_msecs(timeout); 177 } 178 /** 179 * retransmits_timed_out() - returns true if this connection has timed out 180 * @sk: The current socket 181 * @boundary: max number of retransmissions 182 * @timeout: A custom timeout value. 183 * If set to 0 the default timeout is calculated and used. 184 * Using TCP_RTO_MIN and the number of unsuccessful retransmits. 185 * 186 * The default "timeout" value this function can calculate and use 187 * is equivalent to the timeout of a TCP Connection 188 * after "boundary" unsuccessful, exponentially backed-off 189 * retransmissions with an initial RTO of TCP_RTO_MIN. 190 */ 191 static bool retransmits_timed_out(struct sock *sk, 192 unsigned int boundary, 193 unsigned int timeout) 194 { 195 unsigned int start_ts; 196 197 if (!inet_csk(sk)->icsk_retransmits) 198 return false; 199 200 start_ts = tcp_sk(sk)->retrans_stamp; 201 if (likely(timeout == 0)) { 202 unsigned int rto_base = TCP_RTO_MIN; 203 204 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) 205 rto_base = tcp_timeout_init(sk); 206 timeout = tcp_model_timeout(sk, boundary, rto_base); 207 } 208 209 return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0; 210 } 211 212 /* A write timeout has occurred. Process the after effects. */ 213 static int tcp_write_timeout(struct sock *sk) 214 { 215 struct inet_connection_sock *icsk = inet_csk(sk); 216 struct tcp_sock *tp = tcp_sk(sk); 217 struct net *net = sock_net(sk); 218 bool expired = false, do_reset; 219 int retry_until; 220 221 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { 222 if (icsk->icsk_retransmits) { 223 dst_negative_advice(sk); 224 } else { 225 sk_rethink_txhash(sk); 226 } 227 retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries; 228 expired = icsk->icsk_retransmits >= retry_until; 229 } else { 230 if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0)) { 231 /* Black hole detection */ 232 tcp_mtu_probing(icsk, sk); 233 234 dst_negative_advice(sk); 235 } else { 236 sk_rethink_txhash(sk); 237 } 238 239 retry_until = net->ipv4.sysctl_tcp_retries2; 240 if (sock_flag(sk, SOCK_DEAD)) { 241 const bool alive = icsk->icsk_rto < TCP_RTO_MAX; 242 243 retry_until = tcp_orphan_retries(sk, alive); 244 do_reset = alive || 245 !retransmits_timed_out(sk, retry_until, 0); 246 247 if (tcp_out_of_resources(sk, do_reset)) 248 return 1; 249 } 250 } 251 if (!expired) 252 expired = retransmits_timed_out(sk, retry_until, 253 icsk->icsk_user_timeout); 254 tcp_fastopen_active_detect_blackhole(sk, expired); 255 256 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG)) 257 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB, 258 icsk->icsk_retransmits, 259 icsk->icsk_rto, (int)expired); 260 261 if (expired) { 262 /* Has it gone just too far? */ 263 tcp_write_err(sk); 264 return 1; 265 } 266 267 return 0; 268 } 269 270 /* Called with BH disabled */ 271 void tcp_delack_timer_handler(struct sock *sk) 272 { 273 struct inet_connection_sock *icsk = inet_csk(sk); 274 275 sk_mem_reclaim_partial(sk); 276 277 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || 278 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 279 goto out; 280 281 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 282 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); 283 goto out; 284 } 285 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 286 287 if (inet_csk_ack_scheduled(sk)) { 288 if (!inet_csk_in_pingpong_mode(sk)) { 289 /* Delayed ACK missed: inflate ATO. */ 290 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto); 291 } else { 292 /* Delayed ACK missed: leave pingpong mode and 293 * deflate ATO. 294 */ 295 inet_csk_exit_pingpong_mode(sk); 296 icsk->icsk_ack.ato = TCP_ATO_MIN; 297 } 298 tcp_mstamp_refresh(tcp_sk(sk)); 299 tcp_send_ack(sk); 300 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS); 301 } 302 303 out: 304 if (tcp_under_memory_pressure(sk)) 305 sk_mem_reclaim(sk); 306 } 307 308 309 /** 310 * tcp_delack_timer() - The TCP delayed ACK timeout handler 311 * @data: Pointer to the current socket. (gets casted to struct sock *) 312 * 313 * This function gets (indirectly) called when the kernel timer for a TCP packet 314 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work. 315 * 316 * Returns: Nothing (void) 317 */ 318 static void tcp_delack_timer(struct timer_list *t) 319 { 320 struct inet_connection_sock *icsk = 321 from_timer(icsk, t, icsk_delack_timer); 322 struct sock *sk = &icsk->icsk_inet.sk; 323 324 bh_lock_sock(sk); 325 if (!sock_owned_by_user(sk)) { 326 tcp_delack_timer_handler(sk); 327 } else { 328 icsk->icsk_ack.blocked = 1; 329 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 330 /* deleguate our work to tcp_release_cb() */ 331 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags)) 332 sock_hold(sk); 333 } 334 bh_unlock_sock(sk); 335 sock_put(sk); 336 } 337 338 static void tcp_probe_timer(struct sock *sk) 339 { 340 struct inet_connection_sock *icsk = inet_csk(sk); 341 struct sk_buff *skb = tcp_send_head(sk); 342 struct tcp_sock *tp = tcp_sk(sk); 343 int max_probes; 344 345 if (tp->packets_out || !skb) { 346 icsk->icsk_probes_out = 0; 347 return; 348 } 349 350 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as 351 * long as the receiver continues to respond probes. We support this by 352 * default and reset icsk_probes_out with incoming ACKs. But if the 353 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we 354 * kill the socket when the retry count and the time exceeds the 355 * corresponding system limit. We also implement similar policy when 356 * we use RTO to probe window in tcp_retransmit_timer(). 357 */ 358 if (icsk->icsk_user_timeout) { 359 u32 elapsed = tcp_model_timeout(sk, icsk->icsk_probes_out, 360 tcp_probe0_base(sk)); 361 362 if (elapsed >= icsk->icsk_user_timeout) 363 goto abort; 364 } 365 366 max_probes = sock_net(sk)->ipv4.sysctl_tcp_retries2; 367 if (sock_flag(sk, SOCK_DEAD)) { 368 const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX; 369 370 max_probes = tcp_orphan_retries(sk, alive); 371 if (!alive && icsk->icsk_backoff >= max_probes) 372 goto abort; 373 if (tcp_out_of_resources(sk, true)) 374 return; 375 } 376 377 if (icsk->icsk_probes_out >= max_probes) { 378 abort: tcp_write_err(sk); 379 } else { 380 /* Only send another probe if we didn't close things up. */ 381 tcp_send_probe0(sk); 382 } 383 } 384 385 /* 386 * Timer for Fast Open socket to retransmit SYNACK. Note that the 387 * sk here is the child socket, not the parent (listener) socket. 388 */ 389 static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req) 390 { 391 struct inet_connection_sock *icsk = inet_csk(sk); 392 int max_retries = icsk->icsk_syn_retries ? : 393 sock_net(sk)->ipv4.sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */ 394 struct tcp_sock *tp = tcp_sk(sk); 395 396 req->rsk_ops->syn_ack_timeout(req); 397 398 if (req->num_timeout >= max_retries) { 399 tcp_write_err(sk); 400 return; 401 } 402 /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */ 403 if (icsk->icsk_retransmits == 1) 404 tcp_enter_loss(sk); 405 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error 406 * returned from rtx_syn_ack() to make it more persistent like 407 * regular retransmit because if the child socket has been accepted 408 * it's not good to give up too easily. 409 */ 410 inet_rtx_syn_ack(sk, req); 411 req->num_timeout++; 412 icsk->icsk_retransmits++; 413 if (!tp->retrans_stamp) 414 tp->retrans_stamp = tcp_time_stamp(tp); 415 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 416 TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX); 417 } 418 419 420 /** 421 * tcp_retransmit_timer() - The TCP retransmit timeout handler 422 * @sk: Pointer to the current socket. 423 * 424 * This function gets called when the kernel timer for a TCP packet 425 * of this socket expires. 426 * 427 * It handles retransmission, timer adjustment and other necesarry measures. 428 * 429 * Returns: Nothing (void) 430 */ 431 void tcp_retransmit_timer(struct sock *sk) 432 { 433 struct tcp_sock *tp = tcp_sk(sk); 434 struct net *net = sock_net(sk); 435 struct inet_connection_sock *icsk = inet_csk(sk); 436 struct request_sock *req; 437 438 req = rcu_dereference_protected(tp->fastopen_rsk, 439 lockdep_sock_is_held(sk)); 440 if (req) { 441 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && 442 sk->sk_state != TCP_FIN_WAIT1); 443 tcp_fastopen_synack_timer(sk, req); 444 /* Before we receive ACK to our SYN-ACK don't retransmit 445 * anything else (e.g., data or FIN segments). 446 */ 447 return; 448 } 449 if (!tp->packets_out || WARN_ON_ONCE(tcp_rtx_queue_empty(sk))) 450 return; 451 452 tp->tlp_high_seq = 0; 453 454 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && 455 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { 456 /* Receiver dastardly shrinks window. Our retransmits 457 * become zero probes, but we should not timeout this 458 * connection. If the socket is an orphan, time it out, 459 * we cannot allow such beasts to hang infinitely. 460 */ 461 struct inet_sock *inet = inet_sk(sk); 462 if (sk->sk_family == AF_INET) { 463 net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", 464 &inet->inet_daddr, 465 ntohs(inet->inet_dport), 466 inet->inet_num, 467 tp->snd_una, tp->snd_nxt); 468 } 469 #if IS_ENABLED(CONFIG_IPV6) 470 else if (sk->sk_family == AF_INET6) { 471 net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", 472 &sk->sk_v6_daddr, 473 ntohs(inet->inet_dport), 474 inet->inet_num, 475 tp->snd_una, tp->snd_nxt); 476 } 477 #endif 478 if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) { 479 tcp_write_err(sk); 480 goto out; 481 } 482 tcp_enter_loss(sk); 483 tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1); 484 __sk_dst_reset(sk); 485 goto out_reset_timer; 486 } 487 488 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); 489 if (tcp_write_timeout(sk)) 490 goto out; 491 492 if (icsk->icsk_retransmits == 0) { 493 int mib_idx = 0; 494 495 if (icsk->icsk_ca_state == TCP_CA_Recovery) { 496 if (tcp_is_sack(tp)) 497 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; 498 else 499 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; 500 } else if (icsk->icsk_ca_state == TCP_CA_Loss) { 501 mib_idx = LINUX_MIB_TCPLOSSFAILURES; 502 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || 503 tp->sacked_out) { 504 if (tcp_is_sack(tp)) 505 mib_idx = LINUX_MIB_TCPSACKFAILURES; 506 else 507 mib_idx = LINUX_MIB_TCPRENOFAILURES; 508 } 509 if (mib_idx) 510 __NET_INC_STATS(sock_net(sk), mib_idx); 511 } 512 513 tcp_enter_loss(sk); 514 515 icsk->icsk_retransmits++; 516 if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) { 517 /* Retransmission failed because of local congestion, 518 * Let senders fight for local resources conservatively. 519 */ 520 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 521 TCP_RESOURCE_PROBE_INTERVAL, 522 TCP_RTO_MAX); 523 goto out; 524 } 525 526 /* Increase the timeout each time we retransmit. Note that 527 * we do not increase the rtt estimate. rto is initialized 528 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests 529 * that doubling rto each time is the least we can get away with. 530 * In KA9Q, Karn uses this for the first few times, and then 531 * goes to quadratic. netBSD doubles, but only goes up to *64, 532 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is 533 * defined in the protocol as the maximum possible RTT. I guess 534 * we'll have to use something other than TCP to talk to the 535 * University of Mars. 536 * 537 * PAWS allows us longer timeouts and large windows, so once 538 * implemented ftp to mars will work nicely. We will have to fix 539 * the 120 second clamps though! 540 */ 541 icsk->icsk_backoff++; 542 543 out_reset_timer: 544 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is 545 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this 546 * might be increased if the stream oscillates between thin and thick, 547 * thus the old value might already be too high compared to the value 548 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without 549 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating 550 * exponential backoff behaviour to avoid continue hammering 551 * linear-timeout retransmissions into a black hole 552 */ 553 if (sk->sk_state == TCP_ESTABLISHED && 554 (tp->thin_lto || net->ipv4.sysctl_tcp_thin_linear_timeouts) && 555 tcp_stream_is_thin(tp) && 556 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { 557 icsk->icsk_backoff = 0; 558 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX); 559 } else { 560 /* Use normal (exponential) backoff */ 561 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); 562 } 563 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 564 tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX); 565 if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1 + 1, 0)) 566 __sk_dst_reset(sk); 567 568 out:; 569 } 570 571 /* Called with bottom-half processing disabled. 572 Called by tcp_write_timer() */ 573 void tcp_write_timer_handler(struct sock *sk) 574 { 575 struct inet_connection_sock *icsk = inet_csk(sk); 576 int event; 577 578 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || 579 !icsk->icsk_pending) 580 goto out; 581 582 if (time_after(icsk->icsk_timeout, jiffies)) { 583 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); 584 goto out; 585 } 586 587 tcp_mstamp_refresh(tcp_sk(sk)); 588 event = icsk->icsk_pending; 589 590 switch (event) { 591 case ICSK_TIME_REO_TIMEOUT: 592 tcp_rack_reo_timeout(sk); 593 break; 594 case ICSK_TIME_LOSS_PROBE: 595 tcp_send_loss_probe(sk); 596 break; 597 case ICSK_TIME_RETRANS: 598 icsk->icsk_pending = 0; 599 tcp_retransmit_timer(sk); 600 break; 601 case ICSK_TIME_PROBE0: 602 icsk->icsk_pending = 0; 603 tcp_probe_timer(sk); 604 break; 605 } 606 607 out: 608 sk_mem_reclaim(sk); 609 } 610 611 static void tcp_write_timer(struct timer_list *t) 612 { 613 struct inet_connection_sock *icsk = 614 from_timer(icsk, t, icsk_retransmit_timer); 615 struct sock *sk = &icsk->icsk_inet.sk; 616 617 bh_lock_sock(sk); 618 if (!sock_owned_by_user(sk)) { 619 tcp_write_timer_handler(sk); 620 } else { 621 /* delegate our work to tcp_release_cb() */ 622 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags)) 623 sock_hold(sk); 624 } 625 bh_unlock_sock(sk); 626 sock_put(sk); 627 } 628 629 void tcp_syn_ack_timeout(const struct request_sock *req) 630 { 631 struct net *net = read_pnet(&inet_rsk(req)->ireq_net); 632 633 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS); 634 } 635 EXPORT_SYMBOL(tcp_syn_ack_timeout); 636 637 void tcp_set_keepalive(struct sock *sk, int val) 638 { 639 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 640 return; 641 642 if (val && !sock_flag(sk, SOCK_KEEPOPEN)) 643 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); 644 else if (!val) 645 inet_csk_delete_keepalive_timer(sk); 646 } 647 EXPORT_SYMBOL_GPL(tcp_set_keepalive); 648 649 650 static void tcp_keepalive_timer (struct timer_list *t) 651 { 652 struct sock *sk = from_timer(sk, t, sk_timer); 653 struct inet_connection_sock *icsk = inet_csk(sk); 654 struct tcp_sock *tp = tcp_sk(sk); 655 u32 elapsed; 656 657 /* Only process if socket is not in use. */ 658 bh_lock_sock(sk); 659 if (sock_owned_by_user(sk)) { 660 /* Try again later. */ 661 inet_csk_reset_keepalive_timer (sk, HZ/20); 662 goto out; 663 } 664 665 if (sk->sk_state == TCP_LISTEN) { 666 pr_err("Hmm... keepalive on a LISTEN ???\n"); 667 goto out; 668 } 669 670 tcp_mstamp_refresh(tp); 671 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { 672 if (tp->linger2 >= 0) { 673 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; 674 675 if (tmo > 0) { 676 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 677 goto out; 678 } 679 } 680 tcp_send_active_reset(sk, GFP_ATOMIC); 681 goto death; 682 } 683 684 if (!sock_flag(sk, SOCK_KEEPOPEN) || 685 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT))) 686 goto out; 687 688 elapsed = keepalive_time_when(tp); 689 690 /* It is alive without keepalive 8) */ 691 if (tp->packets_out || !tcp_write_queue_empty(sk)) 692 goto resched; 693 694 elapsed = keepalive_time_elapsed(tp); 695 696 if (elapsed >= keepalive_time_when(tp)) { 697 /* If the TCP_USER_TIMEOUT option is enabled, use that 698 * to determine when to timeout instead. 699 */ 700 if ((icsk->icsk_user_timeout != 0 && 701 elapsed >= msecs_to_jiffies(icsk->icsk_user_timeout) && 702 icsk->icsk_probes_out > 0) || 703 (icsk->icsk_user_timeout == 0 && 704 icsk->icsk_probes_out >= keepalive_probes(tp))) { 705 tcp_send_active_reset(sk, GFP_ATOMIC); 706 tcp_write_err(sk); 707 goto out; 708 } 709 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) { 710 icsk->icsk_probes_out++; 711 elapsed = keepalive_intvl_when(tp); 712 } else { 713 /* If keepalive was lost due to local congestion, 714 * try harder. 715 */ 716 elapsed = TCP_RESOURCE_PROBE_INTERVAL; 717 } 718 } else { 719 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ 720 elapsed = keepalive_time_when(tp) - elapsed; 721 } 722 723 sk_mem_reclaim(sk); 724 725 resched: 726 inet_csk_reset_keepalive_timer (sk, elapsed); 727 goto out; 728 729 death: 730 tcp_done(sk); 731 732 out: 733 bh_unlock_sock(sk); 734 sock_put(sk); 735 } 736 737 static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer) 738 { 739 struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer); 740 struct sock *sk = (struct sock *)tp; 741 742 bh_lock_sock(sk); 743 if (!sock_owned_by_user(sk)) { 744 if (tp->compressed_ack > TCP_FASTRETRANS_THRESH) 745 tcp_send_ack(sk); 746 } else { 747 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, 748 &sk->sk_tsq_flags)) 749 sock_hold(sk); 750 } 751 bh_unlock_sock(sk); 752 753 sock_put(sk); 754 755 return HRTIMER_NORESTART; 756 } 757 758 void tcp_init_xmit_timers(struct sock *sk) 759 { 760 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, 761 &tcp_keepalive_timer); 762 hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC, 763 HRTIMER_MODE_ABS_PINNED_SOFT); 764 tcp_sk(sk)->pacing_timer.function = tcp_pace_kick; 765 766 hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC, 767 HRTIMER_MODE_REL_PINNED_SOFT); 768 tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick; 769 } 770