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