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 #include <net/rstreason.h> 26 27 static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk) 28 { 29 const struct inet_connection_sock *icsk = inet_csk(sk); 30 const struct tcp_sock *tp = tcp_sk(sk); 31 u32 elapsed, user_timeout; 32 s32 remaining; 33 34 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 35 if (!user_timeout) 36 return icsk->icsk_rto; 37 38 elapsed = tcp_time_stamp_ts(tp) - tp->retrans_stamp; 39 if (tp->tcp_usec_ts) 40 elapsed /= USEC_PER_MSEC; 41 42 remaining = user_timeout - elapsed; 43 if (remaining <= 0) 44 return 1; /* user timeout has passed; fire ASAP */ 45 46 return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining)); 47 } 48 49 u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when) 50 { 51 const struct inet_connection_sock *icsk = inet_csk(sk); 52 u32 remaining, user_timeout; 53 s32 elapsed; 54 55 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 56 if (!user_timeout || !icsk->icsk_probes_tstamp) 57 return when; 58 59 elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp; 60 if (unlikely(elapsed < 0)) 61 elapsed = 0; 62 remaining = msecs_to_jiffies(user_timeout) - elapsed; 63 remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN); 64 65 return min_t(u32, remaining, when); 66 } 67 68 /** 69 * tcp_write_err() - close socket and save error info 70 * @sk: The socket the error has appeared on. 71 * 72 * Returns: Nothing (void) 73 */ 74 75 static void tcp_write_err(struct sock *sk) 76 { 77 tcp_done_with_error(sk, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT); 78 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); 79 } 80 81 /** 82 * tcp_out_of_resources() - Close socket if out of resources 83 * @sk: pointer to current socket 84 * @do_reset: send a last packet with reset flag 85 * 86 * Do not allow orphaned sockets to eat all our resources. 87 * This is direct violation of TCP specs, but it is required 88 * to prevent DoS attacks. It is called when a retransmission timeout 89 * or zero probe timeout occurs on orphaned socket. 90 * 91 * Also close if our net namespace is exiting; in that case there is no 92 * hope of ever communicating again since all netns interfaces are already 93 * down (or about to be down), and we need to release our dst references, 94 * which have been moved to the netns loopback interface, so the namespace 95 * can finish exiting. This condition is only possible if we are a kernel 96 * socket, as those do not hold references to the namespace. 97 * 98 * Criteria is still not confirmed experimentally and may change. 99 * We kill the socket, if: 100 * 1. If number of orphaned sockets exceeds an administratively configured 101 * limit. 102 * 2. If we have strong memory pressure. 103 * 3. If our net namespace is exiting. 104 */ 105 static int tcp_out_of_resources(struct sock *sk, bool do_reset) 106 { 107 struct tcp_sock *tp = tcp_sk(sk); 108 int shift = 0; 109 110 /* If peer does not open window for long time, or did not transmit 111 * anything for long time, penalize it. */ 112 if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*tcp_rto_max(sk) || !do_reset) 113 shift++; 114 115 /* If some dubious ICMP arrived, penalize even more. */ 116 if (READ_ONCE(sk->sk_err_soft)) 117 shift++; 118 119 if (tcp_check_oom(sk, shift)) { 120 /* Catch exceptional cases, when connection requires reset. 121 * 1. Last segment was sent recently. */ 122 if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN || 123 /* 2. Window is closed. */ 124 (!tp->snd_wnd && !tp->packets_out)) 125 do_reset = true; 126 if (do_reset) 127 tcp_send_active_reset(sk, GFP_ATOMIC, 128 SK_RST_REASON_TCP_ABORT_ON_MEMORY); 129 tcp_done(sk); 130 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY); 131 return 1; 132 } 133 134 if (!check_net(sock_net(sk))) { 135 /* Not possible to send reset; just close */ 136 tcp_done(sk); 137 return 1; 138 } 139 140 return 0; 141 } 142 143 /** 144 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket 145 * @sk: Pointer to the current socket. 146 * @alive: bool, socket alive state 147 */ 148 static int tcp_orphan_retries(struct sock *sk, bool alive) 149 { 150 int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */ 151 152 /* We know from an ICMP that something is wrong. */ 153 if (READ_ONCE(sk->sk_err_soft) && !alive) 154 retries = 0; 155 156 /* However, if socket sent something recently, select some safe 157 * number of retries. 8 corresponds to >100 seconds with minimal 158 * RTO of 200msec. */ 159 if (retries == 0 && alive) 160 retries = 8; 161 return retries; 162 } 163 164 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 165 { 166 const struct net *net = sock_net(sk); 167 int mss; 168 169 /* Black hole detection */ 170 if (!READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing)) 171 return; 172 173 if (!icsk->icsk_mtup.enabled) { 174 icsk->icsk_mtup.enabled = 1; 175 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; 176 } else { 177 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; 178 mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss); 179 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_mtu_probe_floor)); 180 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss)); 181 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); 182 } 183 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 184 } 185 186 static unsigned int tcp_model_timeout(struct sock *sk, 187 unsigned int boundary, 188 unsigned int rto_base) 189 { 190 unsigned int linear_backoff_thresh, timeout; 191 192 linear_backoff_thresh = ilog2(tcp_rto_max(sk) / rto_base); 193 if (boundary <= linear_backoff_thresh) 194 timeout = ((2 << boundary) - 1) * rto_base; 195 else 196 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + 197 (boundary - linear_backoff_thresh) * tcp_rto_max(sk); 198 return jiffies_to_msecs(timeout); 199 } 200 /** 201 * retransmits_timed_out() - returns true if this connection has timed out 202 * @sk: The current socket 203 * @boundary: max number of retransmissions 204 * @timeout: A custom timeout value. 205 * If set to 0 the default timeout is calculated and used. 206 * Using TCP_RTO_MIN and the number of unsuccessful retransmits. 207 * 208 * The default "timeout" value this function can calculate and use 209 * is equivalent to the timeout of a TCP Connection 210 * after "boundary" unsuccessful, exponentially backed-off 211 * retransmissions with an initial RTO of TCP_RTO_MIN. 212 */ 213 static bool retransmits_timed_out(struct sock *sk, 214 unsigned int boundary, 215 unsigned int timeout) 216 { 217 struct tcp_sock *tp = tcp_sk(sk); 218 unsigned int start_ts, delta; 219 220 if (!inet_csk(sk)->icsk_retransmits) 221 return false; 222 223 start_ts = tp->retrans_stamp; 224 if (likely(timeout == 0)) { 225 unsigned int rto_base = TCP_RTO_MIN; 226 227 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) 228 rto_base = tcp_timeout_init(sk); 229 timeout = tcp_model_timeout(sk, boundary, rto_base); 230 } 231 232 if (tp->tcp_usec_ts) { 233 /* delta maybe off up to a jiffy due to timer granularity. */ 234 delta = tp->tcp_mstamp - start_ts + jiffies_to_usecs(1); 235 return (s32)(delta - timeout * USEC_PER_MSEC) >= 0; 236 } 237 return (s32)(tcp_time_stamp_ts(tp) - start_ts - timeout) >= 0; 238 } 239 240 /* A write timeout has occurred. Process the after effects. */ 241 static int tcp_write_timeout(struct sock *sk) 242 { 243 struct inet_connection_sock *icsk = inet_csk(sk); 244 struct tcp_sock *tp = tcp_sk(sk); 245 struct net *net = sock_net(sk); 246 bool expired = false, do_reset; 247 int retry_until, max_retransmits; 248 249 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { 250 if (icsk->icsk_retransmits) 251 __dst_negative_advice(sk); 252 /* Paired with WRITE_ONCE() in tcp_sock_set_syncnt() */ 253 retry_until = READ_ONCE(icsk->icsk_syn_retries) ? : 254 READ_ONCE(net->ipv4.sysctl_tcp_syn_retries); 255 256 max_retransmits = retry_until; 257 if (sk->sk_state == TCP_SYN_SENT) 258 max_retransmits += READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts); 259 260 expired = icsk->icsk_retransmits >= max_retransmits; 261 } else { 262 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1), 0)) { 263 /* Black hole detection */ 264 tcp_mtu_probing(icsk, sk); 265 266 __dst_negative_advice(sk); 267 } 268 269 retry_until = READ_ONCE(net->ipv4.sysctl_tcp_retries2); 270 if (sock_flag(sk, SOCK_DEAD)) { 271 const bool alive = icsk->icsk_rto < tcp_rto_max(sk); 272 273 retry_until = tcp_orphan_retries(sk, alive); 274 do_reset = alive || 275 !retransmits_timed_out(sk, retry_until, 0); 276 277 if (tcp_out_of_resources(sk, do_reset)) 278 return 1; 279 } 280 } 281 if (!expired) 282 expired = retransmits_timed_out(sk, retry_until, 283 READ_ONCE(icsk->icsk_user_timeout)); 284 tcp_fastopen_active_detect_blackhole(sk, expired); 285 mptcp_active_detect_blackhole(sk, expired); 286 287 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG)) 288 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB, 289 icsk->icsk_retransmits, 290 icsk->icsk_rto, (int)expired); 291 292 if (expired) { 293 /* Has it gone just too far? */ 294 tcp_write_err(sk); 295 return 1; 296 } 297 298 if (sk_rethink_txhash(sk)) { 299 tp->timeout_rehash++; 300 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH); 301 } 302 303 return 0; 304 } 305 306 /* Called with BH disabled */ 307 void tcp_delack_timer_handler(struct sock *sk) 308 { 309 struct inet_connection_sock *icsk = inet_csk(sk); 310 struct tcp_sock *tp = tcp_sk(sk); 311 312 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 313 return; 314 315 /* Handling the sack compression case */ 316 if (tp->compressed_ack) { 317 tcp_mstamp_refresh(tp); 318 tcp_sack_compress_send_ack(sk); 319 return; 320 } 321 322 if (!(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 323 return; 324 325 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 326 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); 327 return; 328 } 329 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 330 331 if (inet_csk_ack_scheduled(sk)) { 332 if (!inet_csk_in_pingpong_mode(sk)) { 333 /* Delayed ACK missed: inflate ATO. */ 334 icsk->icsk_ack.ato = min_t(u32, icsk->icsk_ack.ato << 1, icsk->icsk_rto); 335 } else { 336 /* Delayed ACK missed: leave pingpong mode and 337 * deflate ATO. 338 */ 339 inet_csk_exit_pingpong_mode(sk); 340 icsk->icsk_ack.ato = TCP_ATO_MIN; 341 } 342 tcp_mstamp_refresh(tp); 343 tcp_send_ack(sk); 344 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS); 345 } 346 } 347 348 349 /** 350 * tcp_delack_timer() - The TCP delayed ACK timeout handler 351 * @t: Pointer to the timer. (gets casted to struct sock *) 352 * 353 * This function gets (indirectly) called when the kernel timer for a TCP packet 354 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work. 355 * 356 * Returns: Nothing (void) 357 */ 358 static void tcp_delack_timer(struct timer_list *t) 359 { 360 struct inet_connection_sock *icsk = 361 from_timer(icsk, t, icsk_delack_timer); 362 struct sock *sk = &icsk->icsk_inet.sk; 363 364 /* Avoid taking socket spinlock if there is no ACK to send. 365 * The compressed_ack check is racy, but a separate hrtimer 366 * will take care of it eventually. 367 */ 368 if (!(smp_load_acquire(&icsk->icsk_ack.pending) & ICSK_ACK_TIMER) && 369 !READ_ONCE(tcp_sk(sk)->compressed_ack)) 370 goto out; 371 372 bh_lock_sock(sk); 373 if (!sock_owned_by_user(sk)) { 374 tcp_delack_timer_handler(sk); 375 } else { 376 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 377 /* deleguate our work to tcp_release_cb() */ 378 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags)) 379 sock_hold(sk); 380 } 381 bh_unlock_sock(sk); 382 out: 383 sock_put(sk); 384 } 385 386 static void tcp_probe_timer(struct sock *sk) 387 { 388 struct inet_connection_sock *icsk = inet_csk(sk); 389 struct sk_buff *skb = tcp_send_head(sk); 390 struct tcp_sock *tp = tcp_sk(sk); 391 int max_probes; 392 393 if (tp->packets_out || !skb) { 394 icsk->icsk_probes_out = 0; 395 icsk->icsk_probes_tstamp = 0; 396 return; 397 } 398 399 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as 400 * long as the receiver continues to respond probes. We support this by 401 * default and reset icsk_probes_out with incoming ACKs. But if the 402 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we 403 * kill the socket when the retry count and the time exceeds the 404 * corresponding system limit. We also implement similar policy when 405 * we use RTO to probe window in tcp_retransmit_timer(). 406 */ 407 if (!icsk->icsk_probes_tstamp) { 408 icsk->icsk_probes_tstamp = tcp_jiffies32; 409 } else { 410 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 411 412 if (user_timeout && 413 (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >= 414 msecs_to_jiffies(user_timeout)) 415 goto abort; 416 } 417 max_probes = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retries2); 418 if (sock_flag(sk, SOCK_DEAD)) { 419 unsigned int rto_max = tcp_rto_max(sk); 420 const bool alive = inet_csk_rto_backoff(icsk, rto_max) < rto_max; 421 422 max_probes = tcp_orphan_retries(sk, alive); 423 if (!alive && icsk->icsk_backoff >= max_probes) 424 goto abort; 425 if (tcp_out_of_resources(sk, true)) 426 return; 427 } 428 429 if (icsk->icsk_probes_out >= max_probes) { 430 abort: tcp_write_err(sk); 431 } else { 432 /* Only send another probe if we didn't close things up. */ 433 tcp_send_probe0(sk); 434 } 435 } 436 437 static void tcp_update_rto_stats(struct sock *sk) 438 { 439 struct inet_connection_sock *icsk = inet_csk(sk); 440 struct tcp_sock *tp = tcp_sk(sk); 441 442 if (!icsk->icsk_retransmits) { 443 tp->total_rto_recoveries++; 444 tp->rto_stamp = tcp_time_stamp_ms(tp); 445 } 446 icsk->icsk_retransmits++; 447 tp->total_rto++; 448 } 449 450 /* 451 * Timer for Fast Open socket to retransmit SYNACK. Note that the 452 * sk here is the child socket, not the parent (listener) socket. 453 */ 454 static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req) 455 { 456 struct inet_connection_sock *icsk = inet_csk(sk); 457 struct tcp_sock *tp = tcp_sk(sk); 458 int max_retries; 459 460 req->rsk_ops->syn_ack_timeout(req); 461 462 /* Add one more retry for fastopen. 463 * Paired with WRITE_ONCE() in tcp_sock_set_syncnt() 464 */ 465 max_retries = READ_ONCE(icsk->icsk_syn_retries) ? : 466 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1; 467 468 if (req->num_timeout >= max_retries) { 469 tcp_write_err(sk); 470 return; 471 } 472 /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */ 473 if (icsk->icsk_retransmits == 1) 474 tcp_enter_loss(sk); 475 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error 476 * returned from rtx_syn_ack() to make it more persistent like 477 * regular retransmit because if the child socket has been accepted 478 * it's not good to give up too easily. 479 */ 480 inet_rtx_syn_ack(sk, req); 481 req->num_timeout++; 482 tcp_update_rto_stats(sk); 483 if (!tp->retrans_stamp) 484 tp->retrans_stamp = tcp_time_stamp_ts(tp); 485 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 486 req->timeout << req->num_timeout, false); 487 } 488 489 static bool tcp_rtx_probe0_timed_out(const struct sock *sk, 490 const struct sk_buff *skb, 491 u32 rtx_delta) 492 { 493 const struct inet_connection_sock *icsk = inet_csk(sk); 494 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 495 const struct tcp_sock *tp = tcp_sk(sk); 496 int timeout = tcp_rto_max(sk) * 2; 497 s32 rcv_delta; 498 499 if (user_timeout) { 500 /* If user application specified a TCP_USER_TIMEOUT, 501 * it does not want win 0 packets to 'reset the timer' 502 * while retransmits are not making progress. 503 */ 504 if (rtx_delta > user_timeout) 505 return true; 506 timeout = min_t(u32, timeout, msecs_to_jiffies(user_timeout)); 507 } 508 /* Note: timer interrupt might have been delayed by at least one jiffy, 509 * and tp->rcv_tstamp might very well have been written recently. 510 * rcv_delta can thus be negative. 511 */ 512 rcv_delta = icsk->icsk_timeout - tp->rcv_tstamp; 513 if (rcv_delta <= timeout) 514 return false; 515 516 return msecs_to_jiffies(rtx_delta) > timeout; 517 } 518 519 /** 520 * tcp_retransmit_timer() - The TCP retransmit timeout handler 521 * @sk: Pointer to the current socket. 522 * 523 * This function gets called when the kernel timer for a TCP packet 524 * of this socket expires. 525 * 526 * It handles retransmission, timer adjustment and other necessary measures. 527 * 528 * Returns: Nothing (void) 529 */ 530 void tcp_retransmit_timer(struct sock *sk) 531 { 532 struct tcp_sock *tp = tcp_sk(sk); 533 struct net *net = sock_net(sk); 534 struct inet_connection_sock *icsk = inet_csk(sk); 535 struct request_sock *req; 536 struct sk_buff *skb; 537 538 req = rcu_dereference_protected(tp->fastopen_rsk, 539 lockdep_sock_is_held(sk)); 540 if (req) { 541 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && 542 sk->sk_state != TCP_FIN_WAIT1); 543 tcp_fastopen_synack_timer(sk, req); 544 /* Before we receive ACK to our SYN-ACK don't retransmit 545 * anything else (e.g., data or FIN segments). 546 */ 547 return; 548 } 549 550 if (!tp->packets_out) 551 return; 552 553 skb = tcp_rtx_queue_head(sk); 554 if (WARN_ON_ONCE(!skb)) 555 return; 556 557 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && 558 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { 559 /* Receiver dastardly shrinks window. Our retransmits 560 * become zero probes, but we should not timeout this 561 * connection. If the socket is an orphan, time it out, 562 * we cannot allow such beasts to hang infinitely. 563 */ 564 struct inet_sock *inet = inet_sk(sk); 565 u32 rtx_delta; 566 567 rtx_delta = tcp_time_stamp_ts(tp) - (tp->retrans_stamp ?: 568 tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb)); 569 if (tp->tcp_usec_ts) 570 rtx_delta /= USEC_PER_MSEC; 571 572 if (sk->sk_family == AF_INET) { 573 net_dbg_ratelimited("Probing zero-window on %pI4:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n", 574 &inet->inet_daddr, ntohs(inet->inet_dport), 575 inet->inet_num, tp->snd_una, tp->snd_nxt, 576 jiffies_to_msecs(jiffies - tp->rcv_tstamp), 577 rtx_delta); 578 } 579 #if IS_ENABLED(CONFIG_IPV6) 580 else if (sk->sk_family == AF_INET6) { 581 net_dbg_ratelimited("Probing zero-window on %pI6:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n", 582 &sk->sk_v6_daddr, ntohs(inet->inet_dport), 583 inet->inet_num, tp->snd_una, tp->snd_nxt, 584 jiffies_to_msecs(jiffies - tp->rcv_tstamp), 585 rtx_delta); 586 } 587 #endif 588 if (tcp_rtx_probe0_timed_out(sk, skb, rtx_delta)) { 589 tcp_write_err(sk); 590 goto out; 591 } 592 tcp_enter_loss(sk); 593 tcp_retransmit_skb(sk, skb, 1); 594 __sk_dst_reset(sk); 595 goto out_reset_timer; 596 } 597 598 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); 599 if (tcp_write_timeout(sk)) 600 goto out; 601 602 if (icsk->icsk_retransmits == 0) { 603 int mib_idx = 0; 604 605 if (icsk->icsk_ca_state == TCP_CA_Recovery) { 606 if (tcp_is_sack(tp)) 607 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; 608 else 609 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; 610 } else if (icsk->icsk_ca_state == TCP_CA_Loss) { 611 mib_idx = LINUX_MIB_TCPLOSSFAILURES; 612 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || 613 tp->sacked_out) { 614 if (tcp_is_sack(tp)) 615 mib_idx = LINUX_MIB_TCPSACKFAILURES; 616 else 617 mib_idx = LINUX_MIB_TCPRENOFAILURES; 618 } 619 if (mib_idx) 620 __NET_INC_STATS(sock_net(sk), mib_idx); 621 } 622 623 tcp_enter_loss(sk); 624 625 tcp_update_rto_stats(sk); 626 if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) { 627 /* Retransmission failed because of local congestion, 628 * Let senders fight for local resources conservatively. 629 */ 630 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 631 TCP_RESOURCE_PROBE_INTERVAL, 632 false); 633 goto out; 634 } 635 636 /* Increase the timeout each time we retransmit. Note that 637 * we do not increase the rtt estimate. rto is initialized 638 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests 639 * that doubling rto each time is the least we can get away with. 640 * In KA9Q, Karn uses this for the first few times, and then 641 * goes to quadratic. netBSD doubles, but only goes up to *64, 642 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is 643 * defined in the protocol as the maximum possible RTT. I guess 644 * we'll have to use something other than TCP to talk to the 645 * University of Mars. 646 * 647 * PAWS allows us longer timeouts and large windows, so once 648 * implemented ftp to mars will work nicely. We will have to fix 649 * the 120 second clamps though! 650 */ 651 652 out_reset_timer: 653 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is 654 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this 655 * might be increased if the stream oscillates between thin and thick, 656 * thus the old value might already be too high compared to the value 657 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without 658 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating 659 * exponential backoff behaviour to avoid continue hammering 660 * linear-timeout retransmissions into a black hole 661 */ 662 if (sk->sk_state == TCP_ESTABLISHED && 663 (tp->thin_lto || READ_ONCE(net->ipv4.sysctl_tcp_thin_linear_timeouts)) && 664 tcp_stream_is_thin(tp) && 665 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { 666 icsk->icsk_backoff = 0; 667 icsk->icsk_rto = clamp(__tcp_set_rto(tp), 668 tcp_rto_min(sk), 669 tcp_rto_max(sk)); 670 } else if (sk->sk_state != TCP_SYN_SENT || 671 tp->total_rto > 672 READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts)) { 673 /* Use normal (exponential) backoff unless linear timeouts are 674 * activated. 675 */ 676 icsk->icsk_backoff++; 677 icsk->icsk_rto = min(icsk->icsk_rto << 1, tcp_rto_max(sk)); 678 } 679 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 680 tcp_clamp_rto_to_user_timeout(sk), false); 681 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0)) 682 __sk_dst_reset(sk); 683 684 out:; 685 } 686 687 /* Called with bottom-half processing disabled. 688 Called by tcp_write_timer() */ 689 void tcp_write_timer_handler(struct sock *sk) 690 { 691 struct inet_connection_sock *icsk = inet_csk(sk); 692 int event; 693 694 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || 695 !icsk->icsk_pending) 696 return; 697 698 if (time_after(icsk->icsk_timeout, jiffies)) { 699 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); 700 return; 701 } 702 703 tcp_mstamp_refresh(tcp_sk(sk)); 704 event = icsk->icsk_pending; 705 706 switch (event) { 707 case ICSK_TIME_REO_TIMEOUT: 708 tcp_rack_reo_timeout(sk); 709 break; 710 case ICSK_TIME_LOSS_PROBE: 711 tcp_send_loss_probe(sk); 712 break; 713 case ICSK_TIME_RETRANS: 714 smp_store_release(&icsk->icsk_pending, 0); 715 tcp_retransmit_timer(sk); 716 break; 717 case ICSK_TIME_PROBE0: 718 smp_store_release(&icsk->icsk_pending, 0); 719 tcp_probe_timer(sk); 720 break; 721 } 722 } 723 724 static void tcp_write_timer(struct timer_list *t) 725 { 726 struct inet_connection_sock *icsk = 727 from_timer(icsk, t, icsk_retransmit_timer); 728 struct sock *sk = &icsk->icsk_inet.sk; 729 730 /* Avoid locking the socket when there is no pending event. */ 731 if (!smp_load_acquire(&icsk->icsk_pending)) 732 goto out; 733 734 bh_lock_sock(sk); 735 if (!sock_owned_by_user(sk)) { 736 tcp_write_timer_handler(sk); 737 } else { 738 /* delegate our work to tcp_release_cb() */ 739 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags)) 740 sock_hold(sk); 741 } 742 bh_unlock_sock(sk); 743 out: 744 sock_put(sk); 745 } 746 747 void tcp_syn_ack_timeout(const struct request_sock *req) 748 { 749 struct net *net = read_pnet(&inet_rsk(req)->ireq_net); 750 751 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS); 752 } 753 EXPORT_SYMBOL(tcp_syn_ack_timeout); 754 755 void tcp_reset_keepalive_timer(struct sock *sk, unsigned long len) 756 { 757 sk_reset_timer(sk, &sk->sk_timer, jiffies + len); 758 } 759 760 static void tcp_delete_keepalive_timer(struct sock *sk) 761 { 762 sk_stop_timer(sk, &sk->sk_timer); 763 } 764 765 void tcp_set_keepalive(struct sock *sk, int val) 766 { 767 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 768 return; 769 770 if (val && !sock_flag(sk, SOCK_KEEPOPEN)) 771 tcp_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); 772 else if (!val) 773 tcp_delete_keepalive_timer(sk); 774 } 775 EXPORT_SYMBOL_GPL(tcp_set_keepalive); 776 777 static void tcp_keepalive_timer(struct timer_list *t) 778 { 779 struct sock *sk = from_timer(sk, t, sk_timer); 780 struct inet_connection_sock *icsk = inet_csk(sk); 781 struct tcp_sock *tp = tcp_sk(sk); 782 u32 elapsed; 783 784 /* Only process if socket is not in use. */ 785 bh_lock_sock(sk); 786 if (sock_owned_by_user(sk)) { 787 /* Try again later. */ 788 tcp_reset_keepalive_timer(sk, HZ/20); 789 goto out; 790 } 791 792 if (sk->sk_state == TCP_LISTEN) { 793 pr_err("Hmm... keepalive on a LISTEN ???\n"); 794 goto out; 795 } 796 797 tcp_mstamp_refresh(tp); 798 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { 799 if (READ_ONCE(tp->linger2) >= 0) { 800 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; 801 802 if (tmo > 0) { 803 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 804 goto out; 805 } 806 } 807 tcp_send_active_reset(sk, GFP_ATOMIC, SK_RST_REASON_TCP_STATE); 808 goto death; 809 } 810 811 if (!sock_flag(sk, SOCK_KEEPOPEN) || 812 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT))) 813 goto out; 814 815 elapsed = keepalive_time_when(tp); 816 817 /* It is alive without keepalive 8) */ 818 if (tp->packets_out || !tcp_write_queue_empty(sk)) 819 goto resched; 820 821 elapsed = keepalive_time_elapsed(tp); 822 823 if (elapsed >= keepalive_time_when(tp)) { 824 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 825 826 /* If the TCP_USER_TIMEOUT option is enabled, use that 827 * to determine when to timeout instead. 828 */ 829 if ((user_timeout != 0 && 830 elapsed >= msecs_to_jiffies(user_timeout) && 831 icsk->icsk_probes_out > 0) || 832 (user_timeout == 0 && 833 icsk->icsk_probes_out >= keepalive_probes(tp))) { 834 tcp_send_active_reset(sk, GFP_ATOMIC, 835 SK_RST_REASON_TCP_KEEPALIVE_TIMEOUT); 836 tcp_write_err(sk); 837 goto out; 838 } 839 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) { 840 icsk->icsk_probes_out++; 841 elapsed = keepalive_intvl_when(tp); 842 } else { 843 /* If keepalive was lost due to local congestion, 844 * try harder. 845 */ 846 elapsed = TCP_RESOURCE_PROBE_INTERVAL; 847 } 848 } else { 849 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ 850 elapsed = keepalive_time_when(tp) - elapsed; 851 } 852 853 resched: 854 tcp_reset_keepalive_timer(sk, elapsed); 855 goto out; 856 857 death: 858 tcp_done(sk); 859 860 out: 861 bh_unlock_sock(sk); 862 sock_put(sk); 863 } 864 865 static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer) 866 { 867 struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer); 868 struct sock *sk = (struct sock *)tp; 869 870 bh_lock_sock(sk); 871 if (!sock_owned_by_user(sk)) { 872 if (tp->compressed_ack) { 873 /* Since we have to send one ack finally, 874 * subtract one from tp->compressed_ack to keep 875 * LINUX_MIB_TCPACKCOMPRESSED accurate. 876 */ 877 tp->compressed_ack--; 878 tcp_mstamp_refresh(tp); 879 tcp_send_ack(sk); 880 } 881 } else { 882 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, 883 &sk->sk_tsq_flags)) 884 sock_hold(sk); 885 } 886 bh_unlock_sock(sk); 887 888 sock_put(sk); 889 890 return HRTIMER_NORESTART; 891 } 892 893 void tcp_init_xmit_timers(struct sock *sk) 894 { 895 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, 896 &tcp_keepalive_timer); 897 hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC, 898 HRTIMER_MODE_ABS_PINNED_SOFT); 899 tcp_sk(sk)->pacing_timer.function = tcp_pace_kick; 900 901 hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC, 902 HRTIMER_MODE_REL_PINNED_SOFT); 903 tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick; 904 } 905