1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * INET An implementation of the TCP/IP protocol suite for the LINUX 4 * operating system. INET is implemented using the BSD Socket 5 * interface as the means of communication with the user level. 6 * 7 * Implementation of the Transmission Control Protocol(TCP). 8 * 9 * Authors: Ross Biro 10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 11 * Mark Evans, <evansmp@uhura.aston.ac.uk> 12 * Corey Minyard <wf-rch!minyard@relay.EU.net> 13 * Florian La Roche, <flla@stud.uni-sb.de> 14 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> 15 * Linus Torvalds, <torvalds@cs.helsinki.fi> 16 * Alan Cox, <gw4pts@gw4pts.ampr.org> 17 * Matthew Dillon, <dillon@apollo.west.oic.com> 18 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 19 * Jorge Cwik, <jorge@laser.satlink.net> 20 */ 21 22 #include <linux/module.h> 23 #include <linux/gfp.h> 24 #include <net/tcp.h> 25 26 static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk) 27 { 28 struct inet_connection_sock *icsk = inet_csk(sk); 29 u32 elapsed, start_ts; 30 s32 remaining; 31 32 start_ts = tcp_sk(sk)->retrans_stamp; 33 if (!icsk->icsk_user_timeout) 34 return icsk->icsk_rto; 35 elapsed = tcp_time_stamp(tcp_sk(sk)) - start_ts; 36 remaining = icsk->icsk_user_timeout - elapsed; 37 if (remaining <= 0) 38 return 1; /* user timeout has passed; fire ASAP */ 39 40 return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining)); 41 } 42 43 u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when) 44 { 45 struct inet_connection_sock *icsk = inet_csk(sk); 46 u32 remaining; 47 s32 elapsed; 48 49 if (!icsk->icsk_user_timeout || !icsk->icsk_probes_tstamp) 50 return when; 51 52 elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp; 53 if (unlikely(elapsed < 0)) 54 elapsed = 0; 55 remaining = msecs_to_jiffies(icsk->icsk_user_timeout) - elapsed; 56 remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN); 57 58 return min_t(u32, remaining, when); 59 } 60 61 /** 62 * tcp_write_err() - close socket and save error info 63 * @sk: The socket the error has appeared on. 64 * 65 * Returns: Nothing (void) 66 */ 67 68 static void tcp_write_err(struct sock *sk) 69 { 70 sk->sk_err = sk->sk_err_soft ? : ETIMEDOUT; 71 sk_error_report(sk); 72 73 tcp_write_queue_purge(sk); 74 tcp_done(sk); 75 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); 76 } 77 78 /** 79 * tcp_out_of_resources() - Close socket if out of resources 80 * @sk: pointer to current socket 81 * @do_reset: send a last packet with reset flag 82 * 83 * Do not allow orphaned sockets to eat all our resources. 84 * This is direct violation of TCP specs, but it is required 85 * to prevent DoS attacks. It is called when a retransmission timeout 86 * or zero probe timeout occurs on orphaned socket. 87 * 88 * Also close if our net namespace is exiting; in that case there is no 89 * hope of ever communicating again since all netns interfaces are already 90 * down (or about to be down), and we need to release our dst references, 91 * which have been moved to the netns loopback interface, so the namespace 92 * can finish exiting. This condition is only possible if we are a kernel 93 * socket, as those do not hold references to the namespace. 94 * 95 * Criteria is still not confirmed experimentally and may change. 96 * We kill the socket, if: 97 * 1. If number of orphaned sockets exceeds an administratively configured 98 * limit. 99 * 2. If we have strong memory pressure. 100 * 3. If our net namespace is exiting. 101 */ 102 static int tcp_out_of_resources(struct sock *sk, bool do_reset) 103 { 104 struct tcp_sock *tp = tcp_sk(sk); 105 int shift = 0; 106 107 /* If peer does not open window for long time, or did not transmit 108 * anything for long time, penalize it. */ 109 if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset) 110 shift++; 111 112 /* If some dubious ICMP arrived, penalize even more. */ 113 if (sk->sk_err_soft) 114 shift++; 115 116 if (tcp_check_oom(sk, shift)) { 117 /* Catch exceptional cases, when connection requires reset. 118 * 1. Last segment was sent recently. */ 119 if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN || 120 /* 2. Window is closed. */ 121 (!tp->snd_wnd && !tp->packets_out)) 122 do_reset = true; 123 if (do_reset) 124 tcp_send_active_reset(sk, GFP_ATOMIC); 125 tcp_done(sk); 126 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY); 127 return 1; 128 } 129 130 if (!check_net(sock_net(sk))) { 131 /* Not possible to send reset; just close */ 132 tcp_done(sk); 133 return 1; 134 } 135 136 return 0; 137 } 138 139 /** 140 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket 141 * @sk: Pointer to the current socket. 142 * @alive: bool, socket alive state 143 */ 144 static int tcp_orphan_retries(struct sock *sk, bool alive) 145 { 146 int retries = sock_net(sk)->ipv4.sysctl_tcp_orphan_retries; /* May be zero. */ 147 148 /* We know from an ICMP that something is wrong. */ 149 if (sk->sk_err_soft && !alive) 150 retries = 0; 151 152 /* However, if socket sent something recently, select some safe 153 * number of retries. 8 corresponds to >100 seconds with minimal 154 * RTO of 200msec. */ 155 if (retries == 0 && alive) 156 retries = 8; 157 return retries; 158 } 159 160 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 161 { 162 const struct net *net = sock_net(sk); 163 int mss; 164 165 /* Black hole detection */ 166 if (!net->ipv4.sysctl_tcp_mtu_probing) 167 return; 168 169 if (!icsk->icsk_mtup.enabled) { 170 icsk->icsk_mtup.enabled = 1; 171 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; 172 } else { 173 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; 174 mss = min(net->ipv4.sysctl_tcp_base_mss, mss); 175 mss = max(mss, net->ipv4.sysctl_tcp_mtu_probe_floor); 176 mss = max(mss, net->ipv4.sysctl_tcp_min_snd_mss); 177 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); 178 } 179 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 180 } 181 182 static unsigned int tcp_model_timeout(struct sock *sk, 183 unsigned int boundary, 184 unsigned int rto_base) 185 { 186 unsigned int linear_backoff_thresh, timeout; 187 188 linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base); 189 if (boundary <= linear_backoff_thresh) 190 timeout = ((2 << boundary) - 1) * rto_base; 191 else 192 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + 193 (boundary - linear_backoff_thresh) * TCP_RTO_MAX; 194 return jiffies_to_msecs(timeout); 195 } 196 /** 197 * retransmits_timed_out() - returns true if this connection has timed out 198 * @sk: The current socket 199 * @boundary: max number of retransmissions 200 * @timeout: A custom timeout value. 201 * If set to 0 the default timeout is calculated and used. 202 * Using TCP_RTO_MIN and the number of unsuccessful retransmits. 203 * 204 * The default "timeout" value this function can calculate and use 205 * is equivalent to the timeout of a TCP Connection 206 * after "boundary" unsuccessful, exponentially backed-off 207 * retransmissions with an initial RTO of TCP_RTO_MIN. 208 */ 209 static bool retransmits_timed_out(struct sock *sk, 210 unsigned int boundary, 211 unsigned int timeout) 212 { 213 unsigned int start_ts; 214 215 if (!inet_csk(sk)->icsk_retransmits) 216 return false; 217 218 start_ts = tcp_sk(sk)->retrans_stamp; 219 if (likely(timeout == 0)) { 220 unsigned int rto_base = TCP_RTO_MIN; 221 222 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) 223 rto_base = tcp_timeout_init(sk); 224 timeout = tcp_model_timeout(sk, boundary, rto_base); 225 } 226 227 return (s32)(tcp_time_stamp(tcp_sk(sk)) - start_ts - timeout) >= 0; 228 } 229 230 /* A write timeout has occurred. Process the after effects. */ 231 static int tcp_write_timeout(struct sock *sk) 232 { 233 struct inet_connection_sock *icsk = inet_csk(sk); 234 struct tcp_sock *tp = tcp_sk(sk); 235 struct net *net = sock_net(sk); 236 bool expired = false, do_reset; 237 int retry_until; 238 239 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { 240 if (icsk->icsk_retransmits) 241 __dst_negative_advice(sk); 242 retry_until = icsk->icsk_syn_retries ? : net->ipv4.sysctl_tcp_syn_retries; 243 expired = icsk->icsk_retransmits >= retry_until; 244 } else { 245 if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1, 0)) { 246 /* Black hole detection */ 247 tcp_mtu_probing(icsk, sk); 248 249 __dst_negative_advice(sk); 250 } 251 252 retry_until = net->ipv4.sysctl_tcp_retries2; 253 if (sock_flag(sk, SOCK_DEAD)) { 254 const bool alive = icsk->icsk_rto < TCP_RTO_MAX; 255 256 retry_until = tcp_orphan_retries(sk, alive); 257 do_reset = alive || 258 !retransmits_timed_out(sk, retry_until, 0); 259 260 if (tcp_out_of_resources(sk, do_reset)) 261 return 1; 262 } 263 } 264 if (!expired) 265 expired = retransmits_timed_out(sk, retry_until, 266 icsk->icsk_user_timeout); 267 tcp_fastopen_active_detect_blackhole(sk, expired); 268 269 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG)) 270 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB, 271 icsk->icsk_retransmits, 272 icsk->icsk_rto, (int)expired); 273 274 if (expired) { 275 /* Has it gone just too far? */ 276 tcp_write_err(sk); 277 return 1; 278 } 279 280 if (sk_rethink_txhash(sk)) { 281 tp->timeout_rehash++; 282 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH); 283 } 284 285 return 0; 286 } 287 288 /* Called with BH disabled */ 289 void tcp_delack_timer_handler(struct sock *sk) 290 { 291 struct inet_connection_sock *icsk = inet_csk(sk); 292 293 sk_mem_reclaim_partial(sk); 294 295 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || 296 !(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 297 goto out; 298 299 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 300 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); 301 goto out; 302 } 303 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 304 305 if (inet_csk_ack_scheduled(sk)) { 306 if (!inet_csk_in_pingpong_mode(sk)) { 307 /* Delayed ACK missed: inflate ATO. */ 308 icsk->icsk_ack.ato = min(icsk->icsk_ack.ato << 1, icsk->icsk_rto); 309 } else { 310 /* Delayed ACK missed: leave pingpong mode and 311 * deflate ATO. 312 */ 313 inet_csk_exit_pingpong_mode(sk); 314 icsk->icsk_ack.ato = TCP_ATO_MIN; 315 } 316 tcp_mstamp_refresh(tcp_sk(sk)); 317 tcp_send_ack(sk); 318 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS); 319 } 320 321 out: 322 if (tcp_under_memory_pressure(sk)) 323 sk_mem_reclaim(sk); 324 } 325 326 327 /** 328 * tcp_delack_timer() - The TCP delayed ACK timeout handler 329 * @t: Pointer to the timer. (gets casted to struct sock *) 330 * 331 * This function gets (indirectly) called when the kernel timer for a TCP packet 332 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work. 333 * 334 * Returns: Nothing (void) 335 */ 336 static void tcp_delack_timer(struct timer_list *t) 337 { 338 struct inet_connection_sock *icsk = 339 from_timer(icsk, t, icsk_delack_timer); 340 struct sock *sk = &icsk->icsk_inet.sk; 341 342 bh_lock_sock(sk); 343 if (!sock_owned_by_user(sk)) { 344 tcp_delack_timer_handler(sk); 345 } else { 346 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 347 /* deleguate our work to tcp_release_cb() */ 348 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags)) 349 sock_hold(sk); 350 } 351 bh_unlock_sock(sk); 352 sock_put(sk); 353 } 354 355 static void tcp_probe_timer(struct sock *sk) 356 { 357 struct inet_connection_sock *icsk = inet_csk(sk); 358 struct sk_buff *skb = tcp_send_head(sk); 359 struct tcp_sock *tp = tcp_sk(sk); 360 int max_probes; 361 362 if (tp->packets_out || !skb) { 363 icsk->icsk_probes_out = 0; 364 icsk->icsk_probes_tstamp = 0; 365 return; 366 } 367 368 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as 369 * long as the receiver continues to respond probes. We support this by 370 * default and reset icsk_probes_out with incoming ACKs. But if the 371 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we 372 * kill the socket when the retry count and the time exceeds the 373 * corresponding system limit. We also implement similar policy when 374 * we use RTO to probe window in tcp_retransmit_timer(). 375 */ 376 if (!icsk->icsk_probes_tstamp) 377 icsk->icsk_probes_tstamp = tcp_jiffies32; 378 else if (icsk->icsk_user_timeout && 379 (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >= 380 msecs_to_jiffies(icsk->icsk_user_timeout)) 381 goto abort; 382 383 max_probes = sock_net(sk)->ipv4.sysctl_tcp_retries2; 384 if (sock_flag(sk, SOCK_DEAD)) { 385 const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX; 386 387 max_probes = tcp_orphan_retries(sk, alive); 388 if (!alive && icsk->icsk_backoff >= max_probes) 389 goto abort; 390 if (tcp_out_of_resources(sk, true)) 391 return; 392 } 393 394 if (icsk->icsk_probes_out >= max_probes) { 395 abort: tcp_write_err(sk); 396 } else { 397 /* Only send another probe if we didn't close things up. */ 398 tcp_send_probe0(sk); 399 } 400 } 401 402 /* 403 * Timer for Fast Open socket to retransmit SYNACK. Note that the 404 * sk here is the child socket, not the parent (listener) socket. 405 */ 406 static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req) 407 { 408 struct inet_connection_sock *icsk = inet_csk(sk); 409 int max_retries = icsk->icsk_syn_retries ? : 410 sock_net(sk)->ipv4.sysctl_tcp_synack_retries + 1; /* add one more retry for fastopen */ 411 struct tcp_sock *tp = tcp_sk(sk); 412 413 req->rsk_ops->syn_ack_timeout(req); 414 415 if (req->num_timeout >= max_retries) { 416 tcp_write_err(sk); 417 return; 418 } 419 /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */ 420 if (icsk->icsk_retransmits == 1) 421 tcp_enter_loss(sk); 422 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error 423 * returned from rtx_syn_ack() to make it more persistent like 424 * regular retransmit because if the child socket has been accepted 425 * it's not good to give up too easily. 426 */ 427 inet_rtx_syn_ack(sk, req); 428 req->num_timeout++; 429 icsk->icsk_retransmits++; 430 if (!tp->retrans_stamp) 431 tp->retrans_stamp = tcp_time_stamp(tp); 432 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 433 TCP_TIMEOUT_INIT << req->num_timeout, TCP_RTO_MAX); 434 } 435 436 437 /** 438 * tcp_retransmit_timer() - The TCP retransmit timeout handler 439 * @sk: Pointer to the current socket. 440 * 441 * This function gets called when the kernel timer for a TCP packet 442 * of this socket expires. 443 * 444 * It handles retransmission, timer adjustment and other necessary measures. 445 * 446 * Returns: Nothing (void) 447 */ 448 void tcp_retransmit_timer(struct sock *sk) 449 { 450 struct tcp_sock *tp = tcp_sk(sk); 451 struct net *net = sock_net(sk); 452 struct inet_connection_sock *icsk = inet_csk(sk); 453 struct request_sock *req; 454 struct sk_buff *skb; 455 456 req = rcu_dereference_protected(tp->fastopen_rsk, 457 lockdep_sock_is_held(sk)); 458 if (req) { 459 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && 460 sk->sk_state != TCP_FIN_WAIT1); 461 tcp_fastopen_synack_timer(sk, req); 462 /* Before we receive ACK to our SYN-ACK don't retransmit 463 * anything else (e.g., data or FIN segments). 464 */ 465 return; 466 } 467 468 if (!tp->packets_out) 469 return; 470 471 skb = tcp_rtx_queue_head(sk); 472 if (WARN_ON_ONCE(!skb)) 473 return; 474 475 tp->tlp_high_seq = 0; 476 477 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && 478 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { 479 /* Receiver dastardly shrinks window. Our retransmits 480 * become zero probes, but we should not timeout this 481 * connection. If the socket is an orphan, time it out, 482 * we cannot allow such beasts to hang infinitely. 483 */ 484 struct inet_sock *inet = inet_sk(sk); 485 if (sk->sk_family == AF_INET) { 486 net_dbg_ratelimited("Peer %pI4:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", 487 &inet->inet_daddr, 488 ntohs(inet->inet_dport), 489 inet->inet_num, 490 tp->snd_una, tp->snd_nxt); 491 } 492 #if IS_ENABLED(CONFIG_IPV6) 493 else if (sk->sk_family == AF_INET6) { 494 net_dbg_ratelimited("Peer %pI6:%u/%u unexpectedly shrunk window %u:%u (repaired)\n", 495 &sk->sk_v6_daddr, 496 ntohs(inet->inet_dport), 497 inet->inet_num, 498 tp->snd_una, tp->snd_nxt); 499 } 500 #endif 501 if (tcp_jiffies32 - tp->rcv_tstamp > TCP_RTO_MAX) { 502 tcp_write_err(sk); 503 goto out; 504 } 505 tcp_enter_loss(sk); 506 tcp_retransmit_skb(sk, skb, 1); 507 __sk_dst_reset(sk); 508 goto out_reset_timer; 509 } 510 511 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); 512 if (tcp_write_timeout(sk)) 513 goto out; 514 515 if (icsk->icsk_retransmits == 0) { 516 int mib_idx = 0; 517 518 if (icsk->icsk_ca_state == TCP_CA_Recovery) { 519 if (tcp_is_sack(tp)) 520 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; 521 else 522 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; 523 } else if (icsk->icsk_ca_state == TCP_CA_Loss) { 524 mib_idx = LINUX_MIB_TCPLOSSFAILURES; 525 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || 526 tp->sacked_out) { 527 if (tcp_is_sack(tp)) 528 mib_idx = LINUX_MIB_TCPSACKFAILURES; 529 else 530 mib_idx = LINUX_MIB_TCPRENOFAILURES; 531 } 532 if (mib_idx) 533 __NET_INC_STATS(sock_net(sk), mib_idx); 534 } 535 536 tcp_enter_loss(sk); 537 538 icsk->icsk_retransmits++; 539 if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) { 540 /* Retransmission failed because of local congestion, 541 * Let senders fight for local resources conservatively. 542 */ 543 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 544 TCP_RESOURCE_PROBE_INTERVAL, 545 TCP_RTO_MAX); 546 goto out; 547 } 548 549 /* Increase the timeout each time we retransmit. Note that 550 * we do not increase the rtt estimate. rto is initialized 551 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests 552 * that doubling rto each time is the least we can get away with. 553 * In KA9Q, Karn uses this for the first few times, and then 554 * goes to quadratic. netBSD doubles, but only goes up to *64, 555 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is 556 * defined in the protocol as the maximum possible RTT. I guess 557 * we'll have to use something other than TCP to talk to the 558 * University of Mars. 559 * 560 * PAWS allows us longer timeouts and large windows, so once 561 * implemented ftp to mars will work nicely. We will have to fix 562 * the 120 second clamps though! 563 */ 564 icsk->icsk_backoff++; 565 566 out_reset_timer: 567 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is 568 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this 569 * might be increased if the stream oscillates between thin and thick, 570 * thus the old value might already be too high compared to the value 571 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without 572 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating 573 * exponential backoff behaviour to avoid continue hammering 574 * linear-timeout retransmissions into a black hole 575 */ 576 if (sk->sk_state == TCP_ESTABLISHED && 577 (tp->thin_lto || net->ipv4.sysctl_tcp_thin_linear_timeouts) && 578 tcp_stream_is_thin(tp) && 579 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { 580 icsk->icsk_backoff = 0; 581 icsk->icsk_rto = min(__tcp_set_rto(tp), TCP_RTO_MAX); 582 } else { 583 /* Use normal (exponential) backoff */ 584 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); 585 } 586 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 587 tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX); 588 if (retransmits_timed_out(sk, net->ipv4.sysctl_tcp_retries1 + 1, 0)) 589 __sk_dst_reset(sk); 590 591 out:; 592 } 593 594 /* Called with bottom-half processing disabled. 595 Called by tcp_write_timer() */ 596 void tcp_write_timer_handler(struct sock *sk) 597 { 598 struct inet_connection_sock *icsk = inet_csk(sk); 599 int event; 600 601 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || 602 !icsk->icsk_pending) 603 goto out; 604 605 if (time_after(icsk->icsk_timeout, jiffies)) { 606 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); 607 goto out; 608 } 609 610 tcp_mstamp_refresh(tcp_sk(sk)); 611 event = icsk->icsk_pending; 612 613 switch (event) { 614 case ICSK_TIME_REO_TIMEOUT: 615 tcp_rack_reo_timeout(sk); 616 break; 617 case ICSK_TIME_LOSS_PROBE: 618 tcp_send_loss_probe(sk); 619 break; 620 case ICSK_TIME_RETRANS: 621 icsk->icsk_pending = 0; 622 tcp_retransmit_timer(sk); 623 break; 624 case ICSK_TIME_PROBE0: 625 icsk->icsk_pending = 0; 626 tcp_probe_timer(sk); 627 break; 628 } 629 630 out: 631 sk_mem_reclaim(sk); 632 } 633 634 static void tcp_write_timer(struct timer_list *t) 635 { 636 struct inet_connection_sock *icsk = 637 from_timer(icsk, t, icsk_retransmit_timer); 638 struct sock *sk = &icsk->icsk_inet.sk; 639 640 bh_lock_sock(sk); 641 if (!sock_owned_by_user(sk)) { 642 tcp_write_timer_handler(sk); 643 } else { 644 /* delegate our work to tcp_release_cb() */ 645 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags)) 646 sock_hold(sk); 647 } 648 bh_unlock_sock(sk); 649 sock_put(sk); 650 } 651 652 void tcp_syn_ack_timeout(const struct request_sock *req) 653 { 654 struct net *net = read_pnet(&inet_rsk(req)->ireq_net); 655 656 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS); 657 } 658 EXPORT_SYMBOL(tcp_syn_ack_timeout); 659 660 void tcp_set_keepalive(struct sock *sk, int val) 661 { 662 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 663 return; 664 665 if (val && !sock_flag(sk, SOCK_KEEPOPEN)) 666 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); 667 else if (!val) 668 inet_csk_delete_keepalive_timer(sk); 669 } 670 EXPORT_SYMBOL_GPL(tcp_set_keepalive); 671 672 673 static void tcp_keepalive_timer (struct timer_list *t) 674 { 675 struct sock *sk = from_timer(sk, t, sk_timer); 676 struct inet_connection_sock *icsk = inet_csk(sk); 677 struct tcp_sock *tp = tcp_sk(sk); 678 u32 elapsed; 679 680 /* Only process if socket is not in use. */ 681 bh_lock_sock(sk); 682 if (sock_owned_by_user(sk)) { 683 /* Try again later. */ 684 inet_csk_reset_keepalive_timer (sk, HZ/20); 685 goto out; 686 } 687 688 if (sk->sk_state == TCP_LISTEN) { 689 pr_err("Hmm... keepalive on a LISTEN ???\n"); 690 goto out; 691 } 692 693 tcp_mstamp_refresh(tp); 694 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { 695 if (tp->linger2 >= 0) { 696 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; 697 698 if (tmo > 0) { 699 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 700 goto out; 701 } 702 } 703 tcp_send_active_reset(sk, GFP_ATOMIC); 704 goto death; 705 } 706 707 if (!sock_flag(sk, SOCK_KEEPOPEN) || 708 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT))) 709 goto out; 710 711 elapsed = keepalive_time_when(tp); 712 713 /* It is alive without keepalive 8) */ 714 if (tp->packets_out || !tcp_write_queue_empty(sk)) 715 goto resched; 716 717 elapsed = keepalive_time_elapsed(tp); 718 719 if (elapsed >= keepalive_time_when(tp)) { 720 /* If the TCP_USER_TIMEOUT option is enabled, use that 721 * to determine when to timeout instead. 722 */ 723 if ((icsk->icsk_user_timeout != 0 && 724 elapsed >= msecs_to_jiffies(icsk->icsk_user_timeout) && 725 icsk->icsk_probes_out > 0) || 726 (icsk->icsk_user_timeout == 0 && 727 icsk->icsk_probes_out >= keepalive_probes(tp))) { 728 tcp_send_active_reset(sk, GFP_ATOMIC); 729 tcp_write_err(sk); 730 goto out; 731 } 732 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) { 733 icsk->icsk_probes_out++; 734 elapsed = keepalive_intvl_when(tp); 735 } else { 736 /* If keepalive was lost due to local congestion, 737 * try harder. 738 */ 739 elapsed = TCP_RESOURCE_PROBE_INTERVAL; 740 } 741 } else { 742 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ 743 elapsed = keepalive_time_when(tp) - elapsed; 744 } 745 746 sk_mem_reclaim(sk); 747 748 resched: 749 inet_csk_reset_keepalive_timer (sk, elapsed); 750 goto out; 751 752 death: 753 tcp_done(sk); 754 755 out: 756 bh_unlock_sock(sk); 757 sock_put(sk); 758 } 759 760 static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer) 761 { 762 struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer); 763 struct sock *sk = (struct sock *)tp; 764 765 bh_lock_sock(sk); 766 if (!sock_owned_by_user(sk)) { 767 if (tp->compressed_ack) { 768 /* Since we have to send one ack finally, 769 * subtract one from tp->compressed_ack to keep 770 * LINUX_MIB_TCPACKCOMPRESSED accurate. 771 */ 772 tp->compressed_ack--; 773 tcp_send_ack(sk); 774 } 775 } else { 776 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, 777 &sk->sk_tsq_flags)) 778 sock_hold(sk); 779 } 780 bh_unlock_sock(sk); 781 782 sock_put(sk); 783 784 return HRTIMER_NORESTART; 785 } 786 787 void tcp_init_xmit_timers(struct sock *sk) 788 { 789 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, 790 &tcp_keepalive_timer); 791 hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC, 792 HRTIMER_MODE_ABS_PINNED_SOFT); 793 tcp_sk(sk)->pacing_timer.function = tcp_pace_kick; 794 795 hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC, 796 HRTIMER_MODE_REL_PINNED_SOFT); 797 tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick; 798 } 799