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