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