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 s32 rcv_delta; 489 490 /* Note: timer interrupt might have been delayed by at least one jiffy, 491 * and tp->rcv_tstamp might very well have been written recently. 492 * rcv_delta can thus be negative. 493 */ 494 rcv_delta = inet_csk(sk)->icsk_timeout - tp->rcv_tstamp; 495 if (rcv_delta <= timeout) 496 return false; 497 498 return msecs_to_jiffies(rtx_delta) > timeout; 499 } 500 501 /** 502 * tcp_retransmit_timer() - The TCP retransmit timeout handler 503 * @sk: Pointer to the current socket. 504 * 505 * This function gets called when the kernel timer for a TCP packet 506 * of this socket expires. 507 * 508 * It handles retransmission, timer adjustment and other necessary measures. 509 * 510 * Returns: Nothing (void) 511 */ 512 void tcp_retransmit_timer(struct sock *sk) 513 { 514 struct tcp_sock *tp = tcp_sk(sk); 515 struct net *net = sock_net(sk); 516 struct inet_connection_sock *icsk = inet_csk(sk); 517 struct request_sock *req; 518 struct sk_buff *skb; 519 520 req = rcu_dereference_protected(tp->fastopen_rsk, 521 lockdep_sock_is_held(sk)); 522 if (req) { 523 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && 524 sk->sk_state != TCP_FIN_WAIT1); 525 tcp_fastopen_synack_timer(sk, req); 526 /* Before we receive ACK to our SYN-ACK don't retransmit 527 * anything else (e.g., data or FIN segments). 528 */ 529 return; 530 } 531 532 if (!tp->packets_out) 533 return; 534 535 skb = tcp_rtx_queue_head(sk); 536 if (WARN_ON_ONCE(!skb)) 537 return; 538 539 tp->tlp_high_seq = 0; 540 541 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && 542 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { 543 /* Receiver dastardly shrinks window. Our retransmits 544 * become zero probes, but we should not timeout this 545 * connection. If the socket is an orphan, time it out, 546 * we cannot allow such beasts to hang infinitely. 547 */ 548 struct inet_sock *inet = inet_sk(sk); 549 u32 rtx_delta; 550 551 rtx_delta = tcp_time_stamp_ts(tp) - (tp->retrans_stamp ?: 552 tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb)); 553 if (tp->tcp_usec_ts) 554 rtx_delta /= USEC_PER_MSEC; 555 556 if (sk->sk_family == AF_INET) { 557 net_dbg_ratelimited("Probing zero-window on %pI4:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n", 558 &inet->inet_daddr, ntohs(inet->inet_dport), 559 inet->inet_num, tp->snd_una, tp->snd_nxt, 560 jiffies_to_msecs(jiffies - tp->rcv_tstamp), 561 rtx_delta); 562 } 563 #if IS_ENABLED(CONFIG_IPV6) 564 else if (sk->sk_family == AF_INET6) { 565 net_dbg_ratelimited("Probing zero-window on %pI6:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n", 566 &sk->sk_v6_daddr, ntohs(inet->inet_dport), 567 inet->inet_num, tp->snd_una, tp->snd_nxt, 568 jiffies_to_msecs(jiffies - tp->rcv_tstamp), 569 rtx_delta); 570 } 571 #endif 572 if (tcp_rtx_probe0_timed_out(sk, skb, rtx_delta)) { 573 tcp_write_err(sk); 574 goto out; 575 } 576 tcp_enter_loss(sk); 577 tcp_retransmit_skb(sk, skb, 1); 578 __sk_dst_reset(sk); 579 goto out_reset_timer; 580 } 581 582 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); 583 if (tcp_write_timeout(sk)) 584 goto out; 585 586 if (icsk->icsk_retransmits == 0) { 587 int mib_idx = 0; 588 589 if (icsk->icsk_ca_state == TCP_CA_Recovery) { 590 if (tcp_is_sack(tp)) 591 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; 592 else 593 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; 594 } else if (icsk->icsk_ca_state == TCP_CA_Loss) { 595 mib_idx = LINUX_MIB_TCPLOSSFAILURES; 596 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || 597 tp->sacked_out) { 598 if (tcp_is_sack(tp)) 599 mib_idx = LINUX_MIB_TCPSACKFAILURES; 600 else 601 mib_idx = LINUX_MIB_TCPRENOFAILURES; 602 } 603 if (mib_idx) 604 __NET_INC_STATS(sock_net(sk), mib_idx); 605 } 606 607 tcp_enter_loss(sk); 608 609 tcp_update_rto_stats(sk); 610 if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) { 611 /* Retransmission failed because of local congestion, 612 * Let senders fight for local resources conservatively. 613 */ 614 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 615 TCP_RESOURCE_PROBE_INTERVAL, 616 TCP_RTO_MAX); 617 goto out; 618 } 619 620 /* Increase the timeout each time we retransmit. Note that 621 * we do not increase the rtt estimate. rto is initialized 622 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests 623 * that doubling rto each time is the least we can get away with. 624 * In KA9Q, Karn uses this for the first few times, and then 625 * goes to quadratic. netBSD doubles, but only goes up to *64, 626 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is 627 * defined in the protocol as the maximum possible RTT. I guess 628 * we'll have to use something other than TCP to talk to the 629 * University of Mars. 630 * 631 * PAWS allows us longer timeouts and large windows, so once 632 * implemented ftp to mars will work nicely. We will have to fix 633 * the 120 second clamps though! 634 */ 635 636 out_reset_timer: 637 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is 638 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this 639 * might be increased if the stream oscillates between thin and thick, 640 * thus the old value might already be too high compared to the value 641 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without 642 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating 643 * exponential backoff behaviour to avoid continue hammering 644 * linear-timeout retransmissions into a black hole 645 */ 646 if (sk->sk_state == TCP_ESTABLISHED && 647 (tp->thin_lto || READ_ONCE(net->ipv4.sysctl_tcp_thin_linear_timeouts)) && 648 tcp_stream_is_thin(tp) && 649 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { 650 icsk->icsk_backoff = 0; 651 icsk->icsk_rto = clamp(__tcp_set_rto(tp), 652 tcp_rto_min(sk), 653 TCP_RTO_MAX); 654 } else if (sk->sk_state != TCP_SYN_SENT || 655 tp->total_rto > 656 READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts)) { 657 /* Use normal (exponential) backoff unless linear timeouts are 658 * activated. 659 */ 660 icsk->icsk_backoff++; 661 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); 662 } 663 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 664 tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX); 665 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0)) 666 __sk_dst_reset(sk); 667 668 out:; 669 } 670 671 /* Called with bottom-half processing disabled. 672 Called by tcp_write_timer() */ 673 void tcp_write_timer_handler(struct sock *sk) 674 { 675 struct inet_connection_sock *icsk = inet_csk(sk); 676 int event; 677 678 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || 679 !icsk->icsk_pending) 680 return; 681 682 if (time_after(icsk->icsk_timeout, jiffies)) { 683 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); 684 return; 685 } 686 687 tcp_mstamp_refresh(tcp_sk(sk)); 688 event = icsk->icsk_pending; 689 690 switch (event) { 691 case ICSK_TIME_REO_TIMEOUT: 692 tcp_rack_reo_timeout(sk); 693 break; 694 case ICSK_TIME_LOSS_PROBE: 695 tcp_send_loss_probe(sk); 696 break; 697 case ICSK_TIME_RETRANS: 698 icsk->icsk_pending = 0; 699 tcp_retransmit_timer(sk); 700 break; 701 case ICSK_TIME_PROBE0: 702 icsk->icsk_pending = 0; 703 tcp_probe_timer(sk); 704 break; 705 } 706 } 707 708 static void tcp_write_timer(struct timer_list *t) 709 { 710 struct inet_connection_sock *icsk = 711 from_timer(icsk, t, icsk_retransmit_timer); 712 struct sock *sk = &icsk->icsk_inet.sk; 713 714 bh_lock_sock(sk); 715 if (!sock_owned_by_user(sk)) { 716 tcp_write_timer_handler(sk); 717 } else { 718 /* delegate our work to tcp_release_cb() */ 719 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags)) 720 sock_hold(sk); 721 } 722 bh_unlock_sock(sk); 723 sock_put(sk); 724 } 725 726 void tcp_syn_ack_timeout(const struct request_sock *req) 727 { 728 struct net *net = read_pnet(&inet_rsk(req)->ireq_net); 729 730 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS); 731 } 732 EXPORT_SYMBOL(tcp_syn_ack_timeout); 733 734 void tcp_set_keepalive(struct sock *sk, int val) 735 { 736 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 737 return; 738 739 if (val && !sock_flag(sk, SOCK_KEEPOPEN)) 740 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); 741 else if (!val) 742 inet_csk_delete_keepalive_timer(sk); 743 } 744 EXPORT_SYMBOL_GPL(tcp_set_keepalive); 745 746 747 static void tcp_keepalive_timer (struct timer_list *t) 748 { 749 struct sock *sk = from_timer(sk, t, sk_timer); 750 struct inet_connection_sock *icsk = inet_csk(sk); 751 struct tcp_sock *tp = tcp_sk(sk); 752 u32 elapsed; 753 754 /* Only process if socket is not in use. */ 755 bh_lock_sock(sk); 756 if (sock_owned_by_user(sk)) { 757 /* Try again later. */ 758 inet_csk_reset_keepalive_timer (sk, HZ/20); 759 goto out; 760 } 761 762 if (sk->sk_state == TCP_LISTEN) { 763 pr_err("Hmm... keepalive on a LISTEN ???\n"); 764 goto out; 765 } 766 767 tcp_mstamp_refresh(tp); 768 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { 769 if (READ_ONCE(tp->linger2) >= 0) { 770 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; 771 772 if (tmo > 0) { 773 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 774 goto out; 775 } 776 } 777 tcp_send_active_reset(sk, GFP_ATOMIC, SK_RST_REASON_NOT_SPECIFIED); 778 goto death; 779 } 780 781 if (!sock_flag(sk, SOCK_KEEPOPEN) || 782 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT))) 783 goto out; 784 785 elapsed = keepalive_time_when(tp); 786 787 /* It is alive without keepalive 8) */ 788 if (tp->packets_out || !tcp_write_queue_empty(sk)) 789 goto resched; 790 791 elapsed = keepalive_time_elapsed(tp); 792 793 if (elapsed >= keepalive_time_when(tp)) { 794 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 795 796 /* If the TCP_USER_TIMEOUT option is enabled, use that 797 * to determine when to timeout instead. 798 */ 799 if ((user_timeout != 0 && 800 elapsed >= msecs_to_jiffies(user_timeout) && 801 icsk->icsk_probes_out > 0) || 802 (user_timeout == 0 && 803 icsk->icsk_probes_out >= keepalive_probes(tp))) { 804 tcp_send_active_reset(sk, GFP_ATOMIC, 805 SK_RST_REASON_NOT_SPECIFIED); 806 tcp_write_err(sk); 807 goto out; 808 } 809 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) { 810 icsk->icsk_probes_out++; 811 elapsed = keepalive_intvl_when(tp); 812 } else { 813 /* If keepalive was lost due to local congestion, 814 * try harder. 815 */ 816 elapsed = TCP_RESOURCE_PROBE_INTERVAL; 817 } 818 } else { 819 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ 820 elapsed = keepalive_time_when(tp) - elapsed; 821 } 822 823 resched: 824 inet_csk_reset_keepalive_timer (sk, elapsed); 825 goto out; 826 827 death: 828 tcp_done(sk); 829 830 out: 831 bh_unlock_sock(sk); 832 sock_put(sk); 833 } 834 835 static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer) 836 { 837 struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer); 838 struct sock *sk = (struct sock *)tp; 839 840 bh_lock_sock(sk); 841 if (!sock_owned_by_user(sk)) { 842 if (tp->compressed_ack) { 843 /* Since we have to send one ack finally, 844 * subtract one from tp->compressed_ack to keep 845 * LINUX_MIB_TCPACKCOMPRESSED accurate. 846 */ 847 tp->compressed_ack--; 848 tcp_send_ack(sk); 849 } 850 } else { 851 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, 852 &sk->sk_tsq_flags)) 853 sock_hold(sk); 854 } 855 bh_unlock_sock(sk); 856 857 sock_put(sk); 858 859 return HRTIMER_NORESTART; 860 } 861 862 void tcp_init_xmit_timers(struct sock *sk) 863 { 864 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, 865 &tcp_keepalive_timer); 866 hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC, 867 HRTIMER_MODE_ABS_PINNED_SOFT); 868 tcp_sk(sk)->pacing_timer.function = tcp_pace_kick; 869 870 hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC, 871 HRTIMER_MODE_REL_PINNED_SOFT); 872 tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick; 873 } 874