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