Loading...
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 | /*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* Implementation of the Transmission Control Protocol(TCP).
*
* Version: $Id: tcp_timer.c,v 1.76 2000/05/03 06:37:07 davem Exp $
*
* Authors: Ross Biro, <bir7@leland.Stanford.Edu>
* Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
* Mark Evans, <evansmp@uhura.aston.ac.uk>
* Corey Minyard <wf-rch!minyard@relay.EU.net>
* Florian La Roche, <flla@stud.uni-sb.de>
* Charles Hedrick, <hedrick@klinzhai.rutgers.edu>
* Linus Torvalds, <torvalds@cs.helsinki.fi>
* Alan Cox, <gw4pts@gw4pts.ampr.org>
* Matthew Dillon, <dillon@apollo.west.oic.com>
* Arnt Gulbrandsen, <agulbra@nvg.unit.no>
* Jorge Cwik, <jorge@laser.satlink.net>
*/
#include <net/tcp.h>
int sysctl_tcp_syn_retries = TCP_SYN_RETRIES;
int sysctl_tcp_synack_retries = TCP_SYNACK_RETRIES;
int sysctl_tcp_keepalive_time = TCP_KEEPALIVE_TIME;
int sysctl_tcp_keepalive_probes = TCP_KEEPALIVE_PROBES;
int sysctl_tcp_keepalive_intvl = TCP_KEEPALIVE_INTVL;
int sysctl_tcp_retries1 = TCP_RETR1;
int sysctl_tcp_retries2 = TCP_RETR2;
int sysctl_tcp_orphan_retries = TCP_ORPHAN_RETRIES;
static void tcp_retransmit_timer(unsigned long);
static void tcp_delack_timer(unsigned long);
static void tcp_probe_timer(unsigned long);
static void tcp_keepalive_timer (unsigned long data);
static void tcp_twkill(unsigned long);
const char timer_bug_msg[] = KERN_DEBUG "tcpbug: unknown timer value\n";
/*
* Using different timers for retransmit, delayed acks and probes
* We may wish use just one timer maintaining a list of expire jiffies
* to optimize.
*/
void tcp_init_xmit_timers(struct sock *sk)
{
struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
init_timer(&tp->retransmit_timer);
tp->retransmit_timer.function=&tcp_retransmit_timer;
tp->retransmit_timer.data = (unsigned long) sk;
init_timer(&tp->delack_timer);
tp->delack_timer.function=&tcp_delack_timer;
tp->delack_timer.data = (unsigned long) sk;
init_timer(&tp->probe_timer);
tp->probe_timer.function=&tcp_probe_timer;
tp->probe_timer.data = (unsigned long) sk;
init_timer(&sk->timer);
sk->timer.function=&tcp_keepalive_timer;
sk->timer.data = (unsigned long) sk;
}
/*
* Reset the retransmission timer
*/
void tcp_reset_xmit_timer(struct sock *sk, int what, unsigned long when)
{
struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
switch (what) {
case TCP_TIME_RETRANS:
/* When seting the transmit timer the probe timer
* should not be set.
* The delayed ack timer can be set if we are changing the
* retransmit timer when removing acked frames.
*/
if (timer_pending(&tp->probe_timer) && del_timer(&tp->probe_timer))
__sock_put(sk);
if (when > TCP_RTO_MAX) {
printk(KERN_DEBUG "reset_xmit_timer sk=%p when=0x%lx, caller=%p\n", sk, when, NET_CALLER(sk));
when = TCP_RTO_MAX;
}
if (!mod_timer(&tp->retransmit_timer, jiffies+when))
sock_hold(sk);
break;
case TCP_TIME_DACK:
if (!mod_timer(&tp->delack_timer, jiffies+when))
sock_hold(sk);
break;
case TCP_TIME_PROBE0:
if (!mod_timer(&tp->probe_timer, jiffies+when))
sock_hold(sk);
break;
default:
printk(KERN_DEBUG "bug: unknown timer value\n");
};
}
void tcp_clear_xmit_timers(struct sock *sk)
{
struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
if(timer_pending(&tp->retransmit_timer) && del_timer(&tp->retransmit_timer))
__sock_put(sk);
if(timer_pending(&tp->delack_timer) && del_timer(&tp->delack_timer))
__sock_put(sk);
tp->ack.blocked = 0;
if(timer_pending(&tp->probe_timer) && del_timer(&tp->probe_timer))
__sock_put(sk);
if(timer_pending(&sk->timer) && del_timer(&sk->timer))
__sock_put(sk);
}
static void tcp_write_err(struct sock *sk)
{
sk->err = sk->err_soft ? : ETIMEDOUT;
sk->error_report(sk);
tcp_done(sk);
}
/* Do not allow orphaned sockets to eat all our resources.
* This is direct violation of TCP specs, but it is required
* to prevent DoS attacks. It is called when a retransmission timeout
* or zero probe timeout occurs on orphaned socket.
*
* Criterium is still not confirmed experimentally and may change.
* We kill the socket, if:
* 1. If number of orphaned sockets exceeds an administratively configured
* limit.
* 2. Under pessimistic assumption that all the orphans eat memory not
* less than this one, total consumed memory exceeds all
* the available memory.
*/
static int tcp_out_of_resources(struct sock *sk, int do_reset)
{
int orphans = atomic_read(&tcp_orphan_count);
if (orphans >= sysctl_tcp_max_orphans ||
((orphans*atomic_read(&sk->wmem_alloc))>>PAGE_SHIFT) >= num_physpages) {
if (net_ratelimit())
printk(KERN_INFO "Out of socket memory\n");
if (do_reset)
tcp_send_active_reset(sk, GFP_ATOMIC);
tcp_done(sk);
return 1;
}
return 0;
}
/* A write timeout has occurred. Process the after effects. */
static int tcp_write_timeout(struct sock *sk)
{
struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
int retry_until;
if ((1<<sk->state)&(TCPF_SYN_SENT|TCPF_SYN_RECV)) {
if (tp->retransmits)
dst_negative_advice(&sk->dst_cache);
retry_until = tp->syn_retries ? : sysctl_tcp_syn_retries;
} else {
if (tp->retransmits >= sysctl_tcp_retries1) {
/* NOTE. draft-ietf-tcpimpl-pmtud-01.txt requires pmtu black
hole detection. :-(
It is place to make it. It is not made. I do not want
to make it. It is disguisting. It does not work in any
case. Let me to cite the same draft, which requires for
us to implement this:
"The one security concern raised by this memo is that ICMP black holes
are often caused by over-zealous security administrators who block
all ICMP messages. It is vitally important that those who design and
deploy security systems understand the impact of strict filtering on
upper-layer protocols. The safest web site in the world is worthless
if most TCP implementations cannot transfer data from it. It would
be far nicer to have all of the black holes fixed rather than fixing
all of the TCP implementations."
Golden words :-).
*/
dst_negative_advice(&sk->dst_cache);
}
retry_until = sysctl_tcp_retries2;
if (sk->dead) {
if (tcp_out_of_resources(sk, tp->retransmits < retry_until))
return 1;
retry_until = sysctl_tcp_orphan_retries;
}
}
if (tp->retransmits >= retry_until) {
/* Has it gone just too far? */
tcp_write_err(sk);
return 1;
}
return 0;
}
static void tcp_delack_timer(unsigned long data)
{
struct sock *sk = (struct sock*)data;
struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
bh_lock_sock(sk);
if (sk->lock.users) {
/* Try again later. */
tp->ack.blocked = 1;
NET_INC_STATS_BH(DelayedACKLocked);
tcp_reset_xmit_timer(sk, TCP_TIME_DACK, TCP_DELACK_MIN);
goto out_unlock;
}
if (tp->ack.pending) {
if (!tp->ack.pingpong) {
/* Delayed ACK missed: inflate ATO. */
tp->ack.ato = min(tp->ack.ato<<1, TCP_ATO_MAX);
} else {
/* Delayed ACK missed: leave pingpong mode and
* deflate ATO.
*/
tp->ack.pingpong = 0;
tp->ack.ato = TCP_ATO_MIN;
}
tcp_send_ack(sk);
NET_INC_STATS_BH(DelayedACKs);
}
TCP_CHECK_TIMER(sk);
out_unlock:
timer_exit(&tp->delack_timer);
bh_unlock_sock(sk);
sock_put(sk);
}
static void tcp_probe_timer(unsigned long data)
{
struct sock *sk = (struct sock*)data;
struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
int max_probes;
bh_lock_sock(sk);
if (sk->lock.users) {
/* Try again later. */
tcp_reset_xmit_timer(sk, TCP_TIME_PROBE0, HZ/5);
goto out_unlock;
}
if (sk->state == TCP_CLOSE)
goto out_unlock;
if (tp->packets_out || !tp->send_head) {
tp->probes_out = 0;
goto out_unlock;
}
/* *WARNING* RFC 1122 forbids this
*
* It doesn't AFAIK, because we kill the retransmit timer -AK
*
* FIXME: We ought not to do it, Solaris 2.5 actually has fixing
* this behaviour in Solaris down as a bug fix. [AC]
*
* Let me to explain. probes_out is zeroed by incoming ACKs
* even if they advertise zero window. Hence, connection is killed only
* if we received no ACKs for normal connection timeout. It is not killed
* only because window stays zero for some time, window may be zero
* until armageddon and even later. We are in full accordance
* with RFCs, only probe timer combines both retransmission timeout
* and probe timeout in one bottle. --ANK
*/
max_probes = sysctl_tcp_retries2;
if (sk->dead) {
if (tcp_out_of_resources(sk, tp->probes_out <= max_probes))
goto out_unlock;
max_probes = sysctl_tcp_orphan_retries;
}
if (tp->probes_out > max_probes) {
tcp_write_err(sk);
} else {
/* Only send another probe if we didn't close things up. */
tcp_send_probe0(sk);
TCP_CHECK_TIMER(sk);
}
out_unlock:
timer_exit(&tp->probe_timer);
bh_unlock_sock(sk);
sock_put(sk);
}
/* Kill off TIME_WAIT sockets once their lifetime has expired. */
static int tcp_tw_death_row_slot = 0;
int tcp_tw_count = 0;
static struct tcp_tw_bucket *tcp_tw_death_row[TCP_TWKILL_SLOTS];
static spinlock_t tw_death_lock = SPIN_LOCK_UNLOCKED;
static struct timer_list tcp_tw_timer = { function: tcp_twkill };
static void SMP_TIMER_NAME(tcp_twkill)(unsigned long dummy)
{
struct tcp_tw_bucket *tw;
int killed = 0;
/* NOTE: compare this to previous version where lock
* was released after detaching chain. It was racy,
* because tw buckets are scheduled in not serialized context
* in 2.3 (with netfilter), and with softnet it is common, because
* soft irqs are not sequenced.
*/
spin_lock(&tw_death_lock);
if (tcp_tw_count == 0)
goto out;
while((tw = tcp_tw_death_row[tcp_tw_death_row_slot]) != NULL) {
tcp_tw_death_row[tcp_tw_death_row_slot] = tw->next_death;
tw->pprev_death = NULL;
spin_unlock(&tw_death_lock);
tcp_timewait_kill(tw);
tcp_tw_put(tw);
killed++;
spin_lock(&tw_death_lock);
}
tcp_tw_death_row_slot =
((tcp_tw_death_row_slot + 1) & (TCP_TWKILL_SLOTS - 1));
if ((tcp_tw_count -= killed) != 0)
mod_timer(&tcp_tw_timer, jiffies+TCP_TWKILL_PERIOD);
net_statistics[smp_processor_id()*2].TimeWaited += killed;
out:
spin_unlock(&tw_death_lock);
}
SMP_TIMER_DEFINE(tcp_twkill, tcp_twkill_task);
/* These are always called from BH context. See callers in
* tcp_input.c to verify this.
*/
/* This is for handling early-kills of TIME_WAIT sockets. */
void tcp_tw_deschedule(struct tcp_tw_bucket *tw)
{
spin_lock(&tw_death_lock);
if (tw->pprev_death) {
if(tw->next_death)
tw->next_death->pprev_death = tw->pprev_death;
*tw->pprev_death = tw->next_death;
tw->pprev_death = NULL;
tcp_tw_put(tw);
if (--tcp_tw_count == 0)
del_timer(&tcp_tw_timer);
}
spin_unlock(&tw_death_lock);
}
/* Short-time timewait calendar */
static int tcp_twcal_hand = -1;
static int tcp_twcal_jiffie;
static void tcp_twcal_tick(unsigned long);
static struct timer_list tcp_twcal_timer = {function: tcp_twcal_tick};
static struct tcp_tw_bucket *tcp_twcal_row[TCP_TW_RECYCLE_SLOTS];
void tcp_tw_schedule(struct tcp_tw_bucket *tw, int timeo)
{
struct tcp_tw_bucket **tpp;
int slot;
/* timeout := RTO * 3.5
*
* 3.5 = 1+2+0.5 to wait for two retransmits.
*
* RATIONALE: if FIN arrived and we entered TIME-WAIT state,
* our ACK acking that FIN can be lost. If N subsequent retransmitted
* FINs (or previous seqments) are lost (probability of such event
* is p^(N+1), where p is probability to lose single packet and
* time to detect the loss is about RTO*(2^N - 1) with exponential
* backoff). Normal timewait length is calculated so, that we
* waited at least for one retransmitted FIN (maximal RTO is 120sec).
* [ BTW Linux. following BSD, violates this requirement waiting
* only for 60sec, we should wait at least for 240 secs.
* Well, 240 consumes too much of resources 8)
* ]
* This interval is not reduced to catch old duplicate and
* responces to our wandering segments living for two MSLs.
* However, if we use PAWS to detect
* old duplicates, we can reduce the interval to bounds required
* by RTO, rather than MSL. So, if peer understands PAWS, we
* kill tw bucket after 3.5*RTO (it is important that this number
* is greater than TS tick!) and detect old duplicates with help
* of PAWS.
*/
slot = (timeo + (1<<TCP_TW_RECYCLE_TICK) - 1) >> TCP_TW_RECYCLE_TICK;
spin_lock(&tw_death_lock);
/* Unlink it, if it was scheduled */
if (tw->pprev_death) {
if(tw->next_death)
tw->next_death->pprev_death = tw->pprev_death;
*tw->pprev_death = tw->next_death;
tw->pprev_death = NULL;
tcp_tw_count--;
} else
atomic_inc(&tw->refcnt);
if (slot >= TCP_TW_RECYCLE_SLOTS) {
/* Schedule to slow timer */
if (timeo >= TCP_TIMEWAIT_LEN) {
slot = TCP_TWKILL_SLOTS-1;
} else {
slot = (timeo + TCP_TWKILL_PERIOD-1) / TCP_TWKILL_PERIOD;
if (slot >= TCP_TWKILL_SLOTS)
slot = TCP_TWKILL_SLOTS-1;
}
tw->ttd = jiffies + timeo;
slot = (tcp_tw_death_row_slot + slot) & (TCP_TWKILL_SLOTS - 1);
tpp = &tcp_tw_death_row[slot];
} else {
tw->ttd = jiffies + (slot<<TCP_TW_RECYCLE_TICK);
if (tcp_twcal_hand < 0) {
tcp_twcal_hand = 0;
tcp_twcal_jiffie = jiffies;
tcp_twcal_timer.expires = tcp_twcal_jiffie + (slot<<TCP_TW_RECYCLE_TICK);
add_timer(&tcp_twcal_timer);
} else {
if ((long)(tcp_twcal_timer.expires - jiffies) > (slot<<TCP_TW_RECYCLE_TICK))
mod_timer(&tcp_twcal_timer, jiffies + (slot<<TCP_TW_RECYCLE_TICK));
slot = (tcp_twcal_hand + slot)&(TCP_TW_RECYCLE_SLOTS-1);
}
tpp = &tcp_twcal_row[slot];
}
if((tw->next_death = *tpp) != NULL)
(*tpp)->pprev_death = &tw->next_death;
*tpp = tw;
tw->pprev_death = tpp;
if (tcp_tw_count++ == 0)
mod_timer(&tcp_tw_timer, jiffies+TCP_TWKILL_PERIOD);
spin_unlock(&tw_death_lock);
}
void SMP_TIMER_NAME(tcp_twcal_tick)(unsigned long dummy)
{
int n, slot;
unsigned long j;
unsigned long now = jiffies;
int killed = 0;
int adv = 0;
spin_lock(&tw_death_lock);
if (tcp_twcal_hand < 0)
goto out;
slot = tcp_twcal_hand;
j = tcp_twcal_jiffie;
for (n=0; n<TCP_TW_RECYCLE_SLOTS; n++) {
if ((long)(j - now) <= 0) {
struct tcp_tw_bucket *tw;
while((tw = tcp_twcal_row[slot]) != NULL) {
tcp_twcal_row[slot] = tw->next_death;
tw->pprev_death = NULL;
tcp_timewait_kill(tw);
tcp_tw_put(tw);
killed++;
}
} else {
if (!adv) {
adv = 1;
tcp_twcal_jiffie = j;
tcp_twcal_hand = slot;
}
if (tcp_twcal_row[slot] != NULL) {
mod_timer(&tcp_twcal_timer, j);
goto out;
}
}
j += (1<<TCP_TW_RECYCLE_TICK);
slot = (slot+1)&(TCP_TW_RECYCLE_SLOTS-1);
}
tcp_twcal_hand = -1;
out:
if ((tcp_tw_count -= killed) == 0)
del_timer(&tcp_tw_timer);
net_statistics[smp_processor_id()*2].TimeWaitKilled += killed;
spin_unlock(&tw_death_lock);
}
SMP_TIMER_DEFINE(tcp_twcal_tick, tcp_twcal_tasklet);
/*
* The TCP retransmit timer.
*/
static void tcp_retransmit_timer(unsigned long data)
{
struct sock *sk = (struct sock*)data;
struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
bh_lock_sock(sk);
if (sk->lock.users) {
/* Try again later */
tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, HZ/20);
goto out_unlock;
}
if (sk->state == TCP_CLOSE || tp->packets_out == 0)
goto out_unlock;
BUG_TRAP(!skb_queue_empty(&sk->write_queue));
if (tcp_write_timeout(sk))
goto out_unlock;
/* RFC 2018, clear all 'sacked' flags in retransmission queue,
* the sender may have dropped out of order frames and we must
* send them out should this timer fire on us.
*/
if(tp->sack_ok) {
struct sk_buff *skb = skb_peek(&sk->write_queue);
while((skb != NULL) &&
(skb != tp->send_head) &&
(skb != (struct sk_buff *)&sk->write_queue)) {
TCP_SKB_CB(skb)->sacked &=
~(TCPCB_SACKED_ACKED | TCPCB_SACKED_RETRANS);
skb = skb->next;
}
}
/* Retransmission. */
tp->retrans_head = NULL;
tp->rexmt_done = 0;
tp->fackets_out = 0;
tp->retrans_out = 0;
if (tp->retransmits == 0) {
/* Remember window where we lost:
* "one half of the current window but at least 2 segments"
*
* Here "current window" means the effective one, which
* means it must be an accurate representation of our current
* sending rate _and_ the snd_wnd.
*/
tp->snd_ssthresh = tcp_recalc_ssthresh(tp);
tp->snd_cwnd_cnt = 0;
tp->snd_cwnd = 1;
}
tp->dup_acks = 0;
tp->high_seq = tp->snd_nxt;
if (tcp_retransmit_skb(sk, skb_peek(&sk->write_queue)) > 0) {
/* Retransmission failed because of local congestion,
* do not backoff.
*/
if (!tp->retransmits)
tp->retransmits=1;
tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS,
min(tp->rto, TCP_RESOURCE_PROBE_INTERVAL));
TCP_CHECK_TIMER(sk);
goto out_unlock;
}
/* Increase the timeout each time we retransmit. Note that
* we do not increase the rtt estimate. rto is initialized
* from rtt, but increases here. Jacobson (SIGCOMM 88) suggests
* that doubling rto each time is the least we can get away with.
* In KA9Q, Karn uses this for the first few times, and then
* goes to quadratic. netBSD doubles, but only goes up to *64,
* and clamps at 1 to 64 sec afterwards. Note that 120 sec is
* defined in the protocol as the maximum possible RTT. I guess
* we'll have to use something other than TCP to talk to the
* University of Mars.
*
* PAWS allows us longer timeouts and large windows, so once
* implemented ftp to mars will work nicely. We will have to fix
* the 120 second clamps though!
*/
tp->backoff++;
tp->retransmits++;
tp->rto = min(tp->rto << 1, TCP_RTO_MAX);
tcp_reset_xmit_timer(sk, TCP_TIME_RETRANS, tp->rto);
if (tp->retransmits > sysctl_tcp_retries1)
__sk_dst_reset(sk);
TCP_CHECK_TIMER(sk);
out_unlock:
timer_exit(&tp->retransmit_timer);
bh_unlock_sock(sk);
sock_put(sk);
}
/*
* Timer for listening sockets
*/
static void tcp_synack_timer(struct sock *sk)
{
struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
struct tcp_listen_opt *lopt = tp->listen_opt;
int max_retries = tp->syn_retries ? : sysctl_tcp_synack_retries;
int thresh = max_retries;
unsigned long now = jiffies;
struct open_request **reqp, *req;
int i, budget;
if (lopt == NULL || lopt->qlen == 0)
return;
/* Normally all the openreqs are young and become mature
* (i.e. converted to established socket) for first timeout.
* If synack was not acknowledged for 3 seconds, it means
* one of the following things: synack was lost, ack was lost,
* rtt is high or nobody planned to ack (i.e. synflood).
* When server is a bit loaded, queue is populated with old
* open requests, reducing effective size of queue.
* When server is well loaded, queue size reduces to zero
* after several minutes of work. It is not synflood,
* it is normal operation. The solution is pruning
* too old entries overriding normal timeout, when
* situation becomes dangerous.
*
* Essentially, we reserve half of room for young
* embrions; and abort old ones without pity, if old
* ones are about to clog our table.
*/
if (lopt->qlen>>(lopt->max_qlen_log-1)) {
int young = (lopt->qlen_young<<1);
while (thresh > 2) {
if (lopt->qlen < young)
break;
thresh--;
young <<= 1;
}
}
if (tp->defer_accept)
max_retries = tp->defer_accept;
budget = 2*(TCP_SYNQ_HSIZE/(TCP_TIMEOUT_INIT/TCP_SYNQ_INTERVAL));
i = lopt->clock_hand;
do {
reqp=&lopt->syn_table[i];
while ((req = *reqp) != NULL) {
if ((long)(now - req->expires) >= 0) {
if ((req->retrans < thresh ||
(req->acked && req->retrans < max_retries))
&& !req->class->rtx_syn_ack(sk, req, NULL)) {
unsigned long timeo;
if (req->retrans++ == 0)
lopt->qlen_young--;
timeo = min((TCP_TIMEOUT_INIT << req->retrans),
TCP_RTO_MAX);
req->expires = now + timeo;
reqp = &req->dl_next;
continue;
}
/* Drop this request */
write_lock(&tp->syn_wait_lock);
*reqp = req->dl_next;
write_unlock(&tp->syn_wait_lock);
lopt->qlen--;
if (req->retrans == 0)
lopt->qlen_young--;
tcp_openreq_free(req);
continue;
}
reqp = &req->dl_next;
}
i = (i+1)&(TCP_SYNQ_HSIZE-1);
} while (--budget > 0);
lopt->clock_hand = i;
if (lopt->qlen)
tcp_reset_keepalive_timer(sk, TCP_SYNQ_INTERVAL);
}
void tcp_delete_keepalive_timer (struct sock *sk)
{
if (timer_pending(&sk->timer) && del_timer (&sk->timer))
__sock_put(sk);
}
void tcp_reset_keepalive_timer (struct sock *sk, unsigned long len)
{
if (!mod_timer(&sk->timer, jiffies+len))
sock_hold(sk);
}
void tcp_set_keepalive(struct sock *sk, int val)
{
if ((1<<sk->state)&(TCPF_CLOSE|TCPF_LISTEN))
return;
if (val && !sk->keepopen)
tcp_reset_keepalive_timer(sk, keepalive_time_when(&sk->tp_pinfo.af_tcp));
else if (!val)
tcp_delete_keepalive_timer(sk);
}
static void tcp_keepalive_timer (unsigned long data)
{
struct sock *sk = (struct sock *) data;
struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
__u32 elapsed;
/* Only process if socket is not in use. */
bh_lock_sock(sk);
if (sk->lock.users) {
/* Try again later. */
tcp_reset_keepalive_timer (sk, HZ/20);
goto out;
}
if (sk->state == TCP_LISTEN) {
tcp_synack_timer(sk);
goto out;
}
if (sk->state == TCP_FIN_WAIT2 && sk->dead) {
if (tp->linger2 >= 0) {
int tmo = tcp_fin_time(tp) - TCP_TIMEWAIT_LEN;
if (tmo > 0) {
tcp_time_wait(sk, TCP_FIN_WAIT2, tmo);
goto out;
}
}
tcp_send_active_reset(sk, GFP_ATOMIC);
goto death;
}
if (!sk->keepopen || sk->state == TCP_CLOSE)
goto out;
elapsed = keepalive_time_when(tp);
/* It is alive without keepalive 8) */
if (tp->packets_out || tp->send_head)
goto resched;
elapsed = tcp_time_stamp - tp->rcv_tstamp;
if (elapsed >= keepalive_time_when(tp)) {
if ((!tp->keepalive_probes && tp->probes_out >= sysctl_tcp_keepalive_probes) ||
(tp->keepalive_probes && tp->probes_out >= tp->keepalive_probes)) {
tcp_send_active_reset(sk, GFP_ATOMIC);
tcp_write_err(sk);
goto out;
}
if (tcp_write_wakeup(sk) <= 0) {
tp->probes_out++;
elapsed = keepalive_intvl_when(tp);
} else {
/* If keepalive was lost due to local congestion,
* try harder.
*/
elapsed = TCP_RESOURCE_PROBE_INTERVAL;
}
} else {
/* It is tp->rcv_tstamp + keepalive_time_when(tp) */
elapsed = keepalive_time_when(tp) - elapsed;
}
TCP_CHECK_TIMER(sk);
resched:
tcp_reset_keepalive_timer (sk, elapsed);
goto out;
death:
tcp_done(sk);
out:
timer_exit(&sk->timer);
bh_unlock_sock(sk);
sock_put(sk);
}
|