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 u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when) 44 { 45 struct inet_connection_sock *icsk = inet_csk(sk); 46 u32 remaining; 47 s32 elapsed; 48 49 if (!icsk->icsk_user_timeout || !icsk->icsk_probes_tstamp) 50 return when; 51 52 elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp; 53 if (unlikely(elapsed < 0)) 54 elapsed = 0; 55 remaining = msecs_to_jiffies(icsk->icsk_user_timeout) - elapsed; 56 remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN); 57 58 return min_t(u32, remaining, when); 59 } 60 61 /** 62 * tcp_write_err() - close socket and save error info 63 * @sk: The socket the error has appeared on. 64 * 65 * Returns: Nothing (void) 66 */ 67 68 static void tcp_write_err(struct sock *sk) 69 { 70 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT; 71 sk_error_report(sk); 72 73 tcp_write_queue_purge(sk); 74 tcp_done(sk); 75 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); 76 } 77 78 /** 79 * tcp_out_of_resources() - Close socket if out of resources 80 * @sk: pointer to current socket 81 * @do_reset: send a last packet with reset flag 82 * 83 * Do not allow orphaned sockets to eat all our resources. 84 * This is direct violation of TCP specs, but it is required 85 * to prevent DoS attacks. It is called when a retransmission timeout 86 * or zero probe timeout occurs on orphaned socket. 87 * 88 * Also close if our net namespace is exiting; in that case there is no 89 * hope of ever communicating again since all netns interfaces are already 90 * down (or about to be down), and we need to release our dst references, 91 * which have been moved to the netns loopback interface, so the namespace 92 * can finish exiting. This condition is only possible if we are a kernel 93 * socket, as those do not hold references to the namespace. 94 * 95 * Criteria is still not confirmed experimentally and may change. 96 * We kill the socket, if: 97 * 1. If number of orphaned sockets exceeds an administratively configured 98 * limit. 99 * 2. If we have strong memory pressure. 100 * 3. If our net namespace is exiting. 101 */ 102 static int tcp_out_of_resources(struct sock *sk, bool do_reset) 103 { 104 struct tcp_sock *tp = tcp_sk(sk); 105 int shift = 0; 106 107 /* If peer does not open window for long time, or did not transmit 108 * anything for long time, penalize it. */ 109 if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset) 110 shift++; 111 112 /* If some dubious ICMP arrived, penalize even more. */ 113 if (sk->sk_err_soft) 114 shift++; 115 116 if (tcp_check_oom(sk, shift)) { 117 /* Catch exceptional cases, when connection requires reset. 118 * 1. Last segment was sent recently. */ 119 if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN || 120 /* 2. Window is closed. */ 121 (!tp->snd_wnd && !tp->packets_out)) 122 do_reset = true; 123 if (do_reset) 124 tcp_send_active_reset(sk, GFP_ATOMIC); 125 tcp_done(sk); 126 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY); 127 return 1; 128 } 129 130 if (!check_net(sock_net(sk))) { 131 /* Not possible to send reset; just close */ 132 tcp_done(sk); 133 return 1; 134 } 135 136 return 0; 137 } 138 139 /** 140 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket 141 * @sk: Pointer to the current socket. 142 * @alive: bool, socket alive state 143 */ 144 static int tcp_orphan_retries(struct sock *sk, bool alive) 145 { 146 int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */ 147 148 /* We know from an ICMP that something is wrong. */ 149 if (sk->sk_err_soft && !alive) 150 retries = 0; 151 152 /* However, if socket sent something recently, select some safe 153 * number of retries. 8 corresponds to >100 seconds with minimal 154 * RTO of 200msec. */ 155 if (retries == 0 && alive) 156 retries = 8; 157 return retries; 158 } 159 160 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 161 { 162 const struct net *net = sock_net(sk); 163 int mss; 164 165 /* Black hole detection */ 166 if (!READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing)) 167 return; 168 169 if (!icsk->icsk_mtup.enabled) { 170 icsk->icsk_mtup.enabled = 1; 171 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; 172 } else { 173 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; 174 mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss); 175 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_mtu_probe_floor)); 176 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss)); 177 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); 178 } 179 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 180 } 181 182 static unsigned int tcp_model_timeout(struct sock *sk, 183 unsigned int boundary, 184 unsigned int rto_base) 185 { 186 unsigned int linear_backoff_thresh, timeout; 187 188 linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base); 189 if (boundary <= linear_backoff_thresh) 190 timeout = ((2 << boundary) - 1) * rto_base; 191 else 192 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + 193 (boundary - linear_backoff_thresh) * TCP_RTO_MAX; 194 return jiffies_to_msecs(timeout); 195 } 196 /** 197 * retransmits_timed_out() - returns true if this connection has timed out 198 * @sk: The current socket 199 * @boundary: max number of retransmissions 200 * @timeout: A custom timeout value. 201 * If set to 0 the default timeout is calculated and used. 202 * Using TCP_RTO_MIN and the number of unsuccessful retransmits. 203 * 204 * The default "timeout" value this function can calculate and use 205 * is equivalent to the timeout of a TCP Connection 206 * after "boundary" unsuccessful, exponentially backed-off 207 * retransmissions with an initial RTO of TCP_RTO_MIN. 208 */ 209 static bool retransmits_timed_out(struct sock *sk, 210 unsigned int boundary, 211 unsigned int timeout) 212 { 213 unsigned int start_ts; 214 215 if (!inet_csk(sk)->icsk_retransmits) 216 return false; 217 218 start_ts = tcp_sk(sk)->retrans_stamp; 219 if (likely(timeout == 0)) { 220 unsigned int rto_base = TCP_RTO_MIN; 221 222 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) 223 rto_base = tcp_timeout_init(sk); 224 timeout = tcp_model_timeout(sk, boundary, rto_base); 225 } 226 227 return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0; 228 } 229 230 /* A write timeout has occurred. Process the after effects. */ 231 static int tcp_write_timeout(struct sock *sk) 232 { 233 struct inet_connection_sock *icsk = inet_csk(sk); 234 struct tcp_sock *tp = tcp_sk(sk); 235 struct net *net = sock_net(sk); 236 bool expired = false, do_reset; 237 int retry_until; 238 239 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { 240 if (icsk->icsk_retransmits) 241 __dst_negative_advice(sk); 242 retry_until = icsk->icsk_syn_retries ? : 243 READ_ONCE(net->ipv4.sysctl_tcp_syn_retries); 244 expired = icsk->icsk_retransmits >= retry_until; 245 } else { 246 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1), 0)) { 247 /* Black hole detection */ 248 tcp_mtu_probing(icsk, sk); 249 250 __dst_negative_advice(sk); 251 } 252 253 retry_until = READ_ONCE(net->ipv4.sysctl_tcp_retries2); 254 if (sock_flag(sk, SOCK_DEAD)) { 255 const bool alive = icsk->icsk_rto < TCP_RTO_MAX; 256 257 retry_until = tcp_orphan_retries(sk, alive); 258 do_reset = alive || 259 !retransmits_timed_out(sk, retry_until, 0); 260 261 if (tcp_out_of_resources(sk, do_reset)) 262 return 1; 263 } 264 } 265 if (!expired) 266 expired = retransmits_timed_out(sk, retry_until, 267 icsk->icsk_user_timeout); 268 tcp_fastopen_active_detect_blackhole(sk, expired); 269 270 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG)) 271 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB, 272 icsk->icsk_retransmits, 273 icsk->icsk_rto, (int)expired); 274 275 if (expired) { 276 /* Has it gone just too far? */ 277 tcp_write_err(sk); 278 return 1; 279 } 280 281 if (sk_rethink_txhash(sk)) { 282 tp->timeout_rehash++; 283 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH); 284 } 285 286 return 0; 287 } 288 289 /* Called with BH disabled */ 290 void tcp_delack_timer_handler(struct sock *sk) 291 { 292 struct inet_connection_sock *icsk = inet_csk(sk); 293 294 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || 295 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 296 return; 297 298 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 299 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); 300 return; 301 } 302 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 303 304 if (inet_csk_ack_scheduled(sk)) { 305 if (!inet_csk_in_pingpong_mode(sk)) { 306 /* Delayed ACK missed: inflate ATO. */ 307 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto); 308 } else { 309 /* Delayed ACK missed: leave pingpong mode and 310 * deflate ATO. 311 */ 312 inet_csk_exit_pingpong_mode(sk); 313 icsk->icsk_ack.ato = TCP_ATO_MIN; 314 } 315 tcp_mstamp_refresh(tcp_sk(sk)); 316 tcp_send_ack(sk); 317 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS); 318 } 319 } 320 321 322 /** 323 * tcp_delack_timer() - The TCP delayed ACK timeout handler 324 * @t: Pointer to the timer. (gets casted to struct sock *) 325 * 326 * This function gets (indirectly) called when the kernel timer for a TCP packet 327 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work. 328 * 329 * Returns: Nothing (void) 330 */ 331 static void tcp_delack_timer(struct timer_list *t) 332 { 333 struct inet_connection_sock *icsk = 334 from_timer(icsk, t, icsk_delack_timer); 335 struct sock *sk = &icsk->icsk_inet.sk; 336 337 bh_lock_sock(sk); 338 if (!sock_owned_by_user(sk)) { 339 tcp_delack_timer_handler(sk); 340 } else { 341 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 342 /* deleguate our work to tcp_release_cb() */ 343 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags)) 344 sock_hold(sk); 345 } 346 bh_unlock_sock(sk); 347 sock_put(sk); 348 } 349 350 static void tcp_probe_timer(struct sock *sk) 351 { 352 struct inet_connection_sock *icsk = inet_csk(sk); 353 struct sk_buff *skb = tcp_send_head(sk); 354 struct tcp_sock *tp = tcp_sk(sk); 355 int max_probes; 356 357 if (tp->packets_out || !skb) { 358 icsk->icsk_probes_out = 0; 359 icsk->icsk_probes_tstamp = 0; 360 return; 361 } 362 363 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as 364 * long as the receiver continues to respond probes. We support this by 365 * default and reset icsk_probes_out with incoming ACKs. But if the 366 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we 367 * kill the socket when the retry count and the time exceeds the 368 * corresponding system limit. We also implement similar policy when 369 * we use RTO to probe window in tcp_retransmit_timer(). 370 */ 371 if (!icsk->icsk_probes_tstamp) 372 icsk->icsk_probes_tstamp = tcp_jiffies32; 373 else if (icsk->icsk_user_timeout && 374 (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >= 375 msecs_to_jiffies(icsk->icsk_user_timeout)) 376 goto abort; 377 378 max_probes = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retries2); 379 if (sock_flag(sk, SOCK_DEAD)) { 380 const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX; 381 382 max_probes = tcp_orphan_retries(sk, alive); 383 if (!alive && icsk->icsk_backoff >= max_probes) 384 goto abort; 385 if (tcp_out_of_resources(sk, true)) 386 return; 387 } 388 389 if (icsk->icsk_probes_out >= max_probes) { 390 abort: tcp_write_err(sk); 391 } else { 392 /* Only send another probe if we didn't close things up. */ 393 tcp_send_probe0(sk); 394 } 395 } 396 397 /* 398 * Timer for Fast Open socket to retransmit SYNACK. Note that the 399 * sk here is the child socket, not the parent (listener) socket. 400 */ 401 static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req) 402 { 403 struct inet_connection_sock *icsk = inet_csk(sk); 404 struct tcp_sock *tp = tcp_sk(sk); 405 int max_retries; 406 407 req->rsk_ops->syn_ack_timeout(req); 408 409 /* add one more retry for fastopen */ 410 max_retries = icsk->icsk_syn_retries ? : 411 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1; 412 413 if (req->num_timeout >= max_retries) { 414 tcp_write_err(sk); 415 return; 416 } 417 /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */ 418 if (icsk->icsk_retransmits == 1) 419 tcp_enter_loss(sk); 420 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error 421 * returned from rtx_syn_ack() to make it more persistent like 422 * regular retransmit because if the child socket has been accepted 423 * it's not good to give up too easily. 424 */ 425 inet_rtx_syn_ack(sk, req); 426 req->num_timeout++; 427 icsk->icsk_retransmits++; 428 if (!tp->retrans_stamp) 429 tp->retrans_stamp = tcp_time_stamp(tp); 430 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 431 req->timeout << req->num_timeout, TCP_RTO_MAX); 432 } 433 434 435 /** 436 * tcp_retransmit_timer() - The TCP retransmit timeout handler 437 * @sk: Pointer to the current socket. 438 * 439 * This function gets called when the kernel timer for a TCP packet 440 * of this socket expires. 441 * 442 * It handles retransmission, timer adjustment and other necessary measures. 443 * 444 * Returns: Nothing (void) 445 */ 446 void tcp_retransmit_timer(struct sock *sk) 447 { 448 struct tcp_sock *tp = tcp_sk(sk); 449 struct net *net = sock_net(sk); 450 struct inet_connection_sock *icsk = inet_csk(sk); 451 struct request_sock *req; 452 struct sk_buff *skb; 453 454 req = rcu_dereference_protected(tp->fastopen_rsk, 455 lockdep_sock_is_held(sk)); 456 if (req) { 457 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && 458 sk->sk_state != TCP_FIN_WAIT1); 459 tcp_fastopen_synack_timer(sk, req); 460 /* Before we receive ACK to our SYN-ACK don't retransmit 461 * anything else (e.g., data or FIN segments). 462 */ 463 return; 464 } 465 466 if (!tp->packets_out) 467 return; 468 469 skb = tcp_rtx_queue_head(sk); 470 if (WARN_ON_ONCE(!skb)) 471 return; 472 473 tp->tlp_high_seq = 0; 474 475 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && 476 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { 477 /* Receiver dastardly shrinks window. Our retransmits 478 * become zero probes, but we should not timeout this 479 * connection. If the socket is an orphan, time it out, 480 * we cannot allow such beasts to hang infinitely. 481 */ 482 struct inet_sock *inet = inet_sk(sk); 483 if (sk->sk_family == AF_INET) { 484 net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", 485 &inet->inet_daddr, 486 ntohs(inet->inet_dport), 487 inet->inet_num, 488 tp->snd_una, tp->snd_nxt); 489 } 490 #if IS_ENABLED(CONFIG_IPV6) 491 else if (sk->sk_family == AF_INET6) { 492 net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", 493 &sk->sk_v6_daddr, 494 ntohs(inet->inet_dport), 495 inet->inet_num, 496 tp->snd_una, tp->snd_nxt); 497 } 498 #endif 499 if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) { 500 tcp_write_err(sk); 501 goto out; 502 } 503 tcp_enter_loss(sk); 504 tcp_retransmit_skb(sk, skb, 1); 505 __sk_dst_reset(sk); 506 goto out_reset_timer; 507 } 508 509 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); 510 if (tcp_write_timeout(sk)) 511 goto out; 512 513 if (icsk->icsk_retransmits == 0) { 514 int mib_idx = 0; 515 516 if (icsk->icsk_ca_state == TCP_CA_Recovery) { 517 if (tcp_is_sack(tp)) 518 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; 519 else 520 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; 521 } else if (icsk->icsk_ca_state == TCP_CA_Loss) { 522 mib_idx = LINUX_MIB_TCPLOSSFAILURES; 523 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || 524 tp->sacked_out) { 525 if (tcp_is_sack(tp)) 526 mib_idx = LINUX_MIB_TCPSACKFAILURES; 527 else 528 mib_idx = LINUX_MIB_TCPRENOFAILURES; 529 } 530 if (mib_idx) 531 __NET_INC_STATS(sock_net(sk), mib_idx); 532 } 533 534 tcp_enter_loss(sk); 535 536 icsk->icsk_retransmits++; 537 if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) { 538 /* Retransmission failed because of local congestion, 539 * Let senders fight for local resources conservatively. 540 */ 541 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 542 TCP_RESOURCE_PROBE_INTERVAL, 543 TCP_RTO_MAX); 544 goto out; 545 } 546 547 /* Increase the timeout each time we retransmit. Note that 548 * we do not increase the rtt estimate. rto is initialized 549 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests 550 * that doubling rto each time is the least we can get away with. 551 * In KA9Q, Karn uses this for the first few times, and then 552 * goes to quadratic. netBSD doubles, but only goes up to *64, 553 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is 554 * defined in the protocol as the maximum possible RTT. I guess 555 * we'll have to use something other than TCP to talk to the 556 * University of Mars. 557 * 558 * PAWS allows us longer timeouts and large windows, so once 559 * implemented ftp to mars will work nicely. We will have to fix 560 * the 120 second clamps though! 561 */ 562 icsk->icsk_backoff++; 563 564 out_reset_timer: 565 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is 566 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this 567 * might be increased if the stream oscillates between thin and thick, 568 * thus the old value might already be too high compared to the value 569 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without 570 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating 571 * exponential backoff behaviour to avoid continue hammering 572 * linear-timeout retransmissions into a black hole 573 */ 574 if (sk->sk_state == TCP_ESTABLISHED && 575 (tp->thin_lto || READ_ONCE(net->ipv4.sysctl_tcp_thin_linear_timeouts)) && 576 tcp_stream_is_thin(tp) && 577 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { 578 icsk->icsk_backoff = 0; 579 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX); 580 } else { 581 /* Use normal (exponential) backoff */ 582 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); 583 } 584 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 585 tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX); 586 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0)) 587 __sk_dst_reset(sk); 588 589 out:; 590 } 591 592 /* Called with bottom-half processing disabled. 593 Called by tcp_write_timer() */ 594 void tcp_write_timer_handler(struct sock *sk) 595 { 596 struct inet_connection_sock *icsk = inet_csk(sk); 597 int event; 598 599 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || 600 !icsk->icsk_pending) 601 return; 602 603 if (time_after(icsk->icsk_timeout, jiffies)) { 604 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); 605 return; 606 } 607 608 tcp_mstamp_refresh(tcp_sk(sk)); 609 event = icsk->icsk_pending; 610 611 switch (event) { 612 case ICSK_TIME_REO_TIMEOUT: 613 tcp_rack_reo_timeout(sk); 614 break; 615 case ICSK_TIME_LOSS_PROBE: 616 tcp_send_loss_probe(sk); 617 break; 618 case ICSK_TIME_RETRANS: 619 icsk->icsk_pending = 0; 620 tcp_retransmit_timer(sk); 621 break; 622 case ICSK_TIME_PROBE0: 623 icsk->icsk_pending = 0; 624 tcp_probe_timer(sk); 625 break; 626 } 627 } 628 629 static void tcp_write_timer(struct timer_list *t) 630 { 631 struct inet_connection_sock *icsk = 632 from_timer(icsk, t, icsk_retransmit_timer); 633 struct sock *sk = &icsk->icsk_inet.sk; 634 635 bh_lock_sock(sk); 636 if (!sock_owned_by_user(sk)) { 637 tcp_write_timer_handler(sk); 638 } else { 639 /* delegate our work to tcp_release_cb() */ 640 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags)) 641 sock_hold(sk); 642 } 643 bh_unlock_sock(sk); 644 sock_put(sk); 645 } 646 647 void tcp_syn_ack_timeout(const struct request_sock *req) 648 { 649 struct net *net = read_pnet(&inet_rsk(req)->ireq_net); 650 651 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS); 652 } 653 EXPORT_SYMBOL(tcp_syn_ack_timeout); 654 655 void tcp_set_keepalive(struct sock *sk, int val) 656 { 657 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 658 return; 659 660 if (val && !sock_flag(sk, SOCK_KEEPOPEN)) 661 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); 662 else if (!val) 663 inet_csk_delete_keepalive_timer(sk); 664 } 665 EXPORT_SYMBOL_GPL(tcp_set_keepalive); 666 667 668 static void tcp_keepalive_timer (struct timer_list *t) 669 { 670 struct sock *sk = from_timer(sk, t, sk_timer); 671 struct inet_connection_sock *icsk = inet_csk(sk); 672 struct tcp_sock *tp = tcp_sk(sk); 673 u32 elapsed; 674 675 /* Only process if socket is not in use. */ 676 bh_lock_sock(sk); 677 if (sock_owned_by_user(sk)) { 678 /* Try again later. */ 679 inet_csk_reset_keepalive_timer (sk, HZ/20); 680 goto out; 681 } 682 683 if (sk->sk_state == TCP_LISTEN) { 684 pr_err("Hmm... keepalive on a LISTEN ???\n"); 685 goto out; 686 } 687 688 tcp_mstamp_refresh(tp); 689 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { 690 if (tp->linger2 >= 0) { 691 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; 692 693 if (tmo > 0) { 694 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 695 goto out; 696 } 697 } 698 tcp_send_active_reset(sk, GFP_ATOMIC); 699 goto death; 700 } 701 702 if (!sock_flag(sk, SOCK_KEEPOPEN) || 703 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT))) 704 goto out; 705 706 elapsed = keepalive_time_when(tp); 707 708 /* It is alive without keepalive 8) */ 709 if (tp->packets_out || !tcp_write_queue_empty(sk)) 710 goto resched; 711 712 elapsed = keepalive_time_elapsed(tp); 713 714 if (elapsed >= keepalive_time_when(tp)) { 715 /* If the TCP_USER_TIMEOUT option is enabled, use that 716 * to determine when to timeout instead. 717 */ 718 if ((icsk->icsk_user_timeout != 0 && 719 elapsed >= msecs_to_jiffies(icsk->icsk_user_timeout) && 720 icsk->icsk_probes_out > 0) || 721 (icsk->icsk_user_timeout == 0 && 722 icsk->icsk_probes_out >= keepalive_probes(tp))) { 723 tcp_send_active_reset(sk, GFP_ATOMIC); 724 tcp_write_err(sk); 725 goto out; 726 } 727 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) { 728 icsk->icsk_probes_out++; 729 elapsed = keepalive_intvl_when(tp); 730 } else { 731 /* If keepalive was lost due to local congestion, 732 * try harder. 733 */ 734 elapsed = TCP_RESOURCE_PROBE_INTERVAL; 735 } 736 } else { 737 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ 738 elapsed = keepalive_time_when(tp) - elapsed; 739 } 740 741 resched: 742 inet_csk_reset_keepalive_timer (sk, elapsed); 743 goto out; 744 745 death: 746 tcp_done(sk); 747 748 out: 749 bh_unlock_sock(sk); 750 sock_put(sk); 751 } 752 753 static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer) 754 { 755 struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer); 756 struct sock *sk = (struct sock *)tp; 757 758 bh_lock_sock(sk); 759 if (!sock_owned_by_user(sk)) { 760 if (tp->compressed_ack) { 761 /* Since we have to send one ack finally, 762 * subtract one from tp->compressed_ack to keep 763 * LINUX_MIB_TCPACKCOMPRESSED accurate. 764 */ 765 tp->compressed_ack--; 766 tcp_send_ack(sk); 767 } 768 } else { 769 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, 770 &sk->sk_tsq_flags)) 771 sock_hold(sk); 772 } 773 bh_unlock_sock(sk); 774 775 sock_put(sk); 776 777 return HRTIMER_NORESTART; 778 } 779 780 void tcp_init_xmit_timers(struct sock *sk) 781 { 782 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, 783 &tcp_keepalive_timer); 784 hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC, 785 HRTIMER_MODE_ABS_PINNED_SOFT); 786 tcp_sk(sk)->pacing_timer.function = tcp_pace_kick; 787 788 hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC, 789 HRTIMER_MODE_REL_PINNED_SOFT); 790 tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick; 791 } 792