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