1 /* 2 * Copyright (c) 2003, 2004 Jeffrey M. Hsu. All rights reserved. 3 * Copyright (c) 2003, 2004 The DragonFly Project. All rights reserved. 4 * 5 * This code is derived from software contributed to The DragonFly Project 6 * by Jeffrey M. Hsu. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. Neither the name of The DragonFly Project nor the names of its 17 * contributors may be used to endorse or promote products derived 18 * from this software without specific, prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 21 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 23 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 24 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 25 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 26 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 27 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 28 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 29 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 30 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 */ 33 34 /* 35 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 36 * The Regents of the University of California. All rights reserved. 37 * 38 * Redistribution and use in source and binary forms, with or without 39 * modification, are permitted provided that the following conditions 40 * are met: 41 * 1. Redistributions of source code must retain the above copyright 42 * notice, this list of conditions and the following disclaimer. 43 * 2. Redistributions in binary form must reproduce the above copyright 44 * notice, this list of conditions and the following disclaimer in the 45 * documentation and/or other materials provided with the distribution. 46 * 3. All advertising materials mentioning features or use of this software 47 * must display the following acknowledgement: 48 * This product includes software developed by the University of 49 * California, Berkeley and its contributors. 50 * 4. Neither the name of the University nor the names of its contributors 51 * may be used to endorse or promote products derived from this software 52 * without specific prior written permission. 53 * 54 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 55 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 56 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 57 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 58 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 59 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 60 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 61 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 62 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 63 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 64 * SUCH DAMAGE. 65 * 66 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95 67 * $FreeBSD: src/sys/netinet/tcp_timer.c,v 1.34.2.14 2003/02/03 02:33:41 hsu Exp $ 68 * $DragonFly: src/sys/netinet/tcp_timer.c,v 1.17 2008/03/30 20:39:01 dillon Exp $ 69 */ 70 71 #include "opt_compat.h" 72 #include "opt_inet6.h" 73 #include "opt_tcpdebug.h" 74 75 #include <sys/param.h> 76 #include <sys/systm.h> 77 #include <sys/kernel.h> 78 #include <sys/mbuf.h> 79 #include <sys/sysctl.h> 80 #include <sys/socket.h> 81 #include <sys/socketvar.h> 82 #include <sys/protosw.h> 83 #include <sys/thread.h> 84 #include <sys/globaldata.h> 85 #include <sys/thread2.h> 86 #include <sys/msgport2.h> 87 88 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 89 90 #include <net/route.h> 91 #include <net/netmsg2.h> 92 93 #include <netinet/in.h> 94 #include <netinet/in_systm.h> 95 #include <netinet/in_pcb.h> 96 #ifdef INET6 97 #include <netinet6/in6_pcb.h> 98 #endif 99 #include <netinet/ip_var.h> 100 #include <netinet/tcp.h> 101 #include <netinet/tcp_fsm.h> 102 #include <netinet/tcp_seq.h> 103 #include <netinet/tcp_timer.h> 104 #include <netinet/tcp_timer2.h> 105 #include <netinet/tcp_var.h> 106 #include <netinet/tcpip.h> 107 #ifdef TCPDEBUG 108 #include <netinet/tcp_debug.h> 109 #endif 110 111 #define TCP_TIMER_REXMT 0x01 112 #define TCP_TIMER_PERSIST 0x02 113 #define TCP_TIMER_KEEP 0x04 114 #define TCP_TIMER_2MSL 0x08 115 #define TCP_TIMER_DELACK 0x10 116 117 static struct tcpcb *tcp_timer_rexmt_handler(struct tcpcb *); 118 static struct tcpcb *tcp_timer_persist_handler(struct tcpcb *); 119 static struct tcpcb *tcp_timer_keep_handler(struct tcpcb *); 120 static struct tcpcb *tcp_timer_2msl_handler(struct tcpcb *); 121 static struct tcpcb *tcp_timer_delack_handler(struct tcpcb *); 122 123 static const struct tcp_timer { 124 uint32_t tt_task; 125 struct tcpcb *(*tt_handler)(struct tcpcb *); 126 } tcp_timer_handlers[] = { 127 { TCP_TIMER_DELACK, tcp_timer_delack_handler }, 128 { TCP_TIMER_REXMT, tcp_timer_rexmt_handler }, 129 { TCP_TIMER_PERSIST, tcp_timer_persist_handler }, 130 { TCP_TIMER_KEEP, tcp_timer_keep_handler }, 131 { TCP_TIMER_2MSL, tcp_timer_2msl_handler }, 132 { 0, NULL } 133 }; 134 135 static int 136 sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS) 137 { 138 int error, s, tt; 139 140 tt = *(int *)oidp->oid_arg1; 141 s = (int)((int64_t)tt * 1000 / hz); 142 143 error = sysctl_handle_int(oidp, &s, 0, req); 144 if (error || !req->newptr) 145 return (error); 146 147 tt = (int)((int64_t)s * hz / 1000); 148 if (tt < 1) 149 return (EINVAL); 150 151 *(int *)oidp->oid_arg1 = tt; 152 return (0); 153 } 154 155 int tcp_keepinit; 156 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW, 157 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", ""); 158 159 int tcp_keepidle; 160 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW, 161 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", ""); 162 163 int tcp_keepintvl; 164 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW, 165 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", ""); 166 167 int tcp_delacktime; 168 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, 169 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I", 170 "Time before a delayed ACK is sent"); 171 172 int tcp_msl; 173 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW, 174 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime"); 175 176 int tcp_rexmit_min; 177 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW, 178 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout"); 179 180 int tcp_rexmit_slop; 181 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW, 182 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", 183 "Retransmission Timer Slop"); 184 185 static int always_keepalive = 1; 186 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, 187 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); 188 189 static int tcp_keepcnt = TCPTV_KEEPCNT; 190 /* max idle probes */ 191 int tcp_maxpersistidle; 192 /* max idle time in persist */ 193 int tcp_maxidle; 194 195 /* 196 * Tcp protocol timeout routine called every 500 ms. 197 * Updates timestamps used for TCP 198 * causes finite state machine actions if timers expire. 199 */ 200 void 201 tcp_slowtimo(void) 202 { 203 crit_enter(); 204 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 205 crit_exit(); 206 } 207 208 /* 209 * Cancel all timers for TCP tp. 210 */ 211 void 212 tcp_canceltimers(struct tcpcb *tp) 213 { 214 tcp_callout_stop(tp, tp->tt_2msl); 215 tcp_callout_stop(tp, tp->tt_persist); 216 tcp_callout_stop(tp, tp->tt_keep); 217 tcp_callout_stop(tp, tp->tt_rexmt); 218 } 219 220 /* 221 * Caller should be in critical section 222 */ 223 static void 224 tcp_send_timermsg(struct tcpcb *tp, uint32_t task) 225 { 226 struct netmsg_tcp_timer *tmsg = tp->tt_msg; 227 228 KKASSERT(tmsg != NULL && tmsg->tt_cpuid == mycpuid && 229 tmsg->tt_tcb != NULL); 230 231 tmsg->tt_tasks |= task; 232 if (tmsg->tt_nmsg.nm_lmsg.ms_flags & MSGF_DONE) 233 lwkt_sendmsg(tmsg->tt_msgport, &tmsg->tt_nmsg.nm_lmsg); 234 } 235 236 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 237 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 238 239 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 240 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 241 242 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 243 244 /* Caller should be in critical section */ 245 static struct tcpcb * 246 tcp_timer_delack_handler(struct tcpcb *tp) 247 { 248 tp->t_flags |= TF_ACKNOW; 249 tcpstat.tcps_delack++; 250 tcp_output(tp); 251 return tp; 252 } 253 254 /* 255 * TCP timer processing. 256 */ 257 void 258 tcp_timer_delack(void *xtp) 259 { 260 struct tcpcb *tp = xtp; 261 struct callout *co = &tp->tt_delack->tc_callout; 262 263 crit_enter(); 264 if (callout_pending(co) || !callout_active(co)) { 265 crit_exit(); 266 return; 267 } 268 callout_deactivate(co); 269 tcp_send_timermsg(tp, TCP_TIMER_DELACK); 270 crit_exit(); 271 } 272 273 /* Caller should be in critical section */ 274 static struct tcpcb * 275 tcp_timer_2msl_handler(struct tcpcb *tp) 276 { 277 #ifdef TCPDEBUG 278 int ostate; 279 #endif 280 281 #ifdef TCPDEBUG 282 ostate = tp->t_state; 283 #endif 284 /* 285 * 2 MSL timeout in shutdown went off. If we're closed but 286 * still waiting for peer to close and connection has been idle 287 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 288 * control block. Otherwise, check again in a bit. 289 */ 290 if (tp->t_state != TCPS_TIME_WAIT && 291 (ticks - tp->t_rcvtime) <= tcp_maxidle) { 292 tcp_callout_reset(tp, tp->tt_2msl, tcp_keepintvl, 293 tcp_timer_2msl); 294 } else { 295 tp = tcp_close(tp); 296 } 297 298 #ifdef TCPDEBUG 299 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 300 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO); 301 #endif 302 return tp; 303 } 304 305 void 306 tcp_timer_2msl(void *xtp) 307 { 308 struct tcpcb *tp = xtp; 309 struct callout *co = &tp->tt_2msl->tc_callout; 310 311 crit_enter(); 312 if (callout_pending(co) || !callout_active(co)) { 313 crit_exit(); 314 return; 315 } 316 callout_deactivate(co); 317 tcp_send_timermsg(tp, TCP_TIMER_2MSL); 318 crit_exit(); 319 } 320 321 /* Caller should be in critical section */ 322 static struct tcpcb * 323 tcp_timer_keep_handler(struct tcpcb *tp) 324 { 325 struct tcptemp *t_template; 326 #ifdef TCPDEBUG 327 int ostate; 328 #endif 329 330 #ifdef TCPDEBUG 331 ostate = tp->t_state; 332 #endif 333 /* 334 * Keep-alive timer went off; send something 335 * or drop connection if idle for too long. 336 */ 337 tcpstat.tcps_keeptimeo++; 338 if (tp->t_state < TCPS_ESTABLISHED) 339 goto dropit; 340 if ((always_keepalive || (tp->t_flags & TF_KEEPALIVE) || 341 (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE)) && 342 tp->t_state <= TCPS_CLOSING) { 343 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 344 goto dropit; 345 /* 346 * Send a packet designed to force a response 347 * if the peer is up and reachable: 348 * either an ACK if the connection is still alive, 349 * or an RST if the peer has closed the connection 350 * due to timeout or reboot. 351 * Using sequence number tp->snd_una-1 352 * causes the transmitted zero-length segment 353 * to lie outside the receive window; 354 * by the protocol spec, this requires the 355 * correspondent TCP to respond. 356 */ 357 tcpstat.tcps_keepprobe++; 358 t_template = tcp_maketemplate(tp); 359 if (t_template) { 360 tcp_respond(tp, t_template->tt_ipgen, 361 &t_template->tt_t, NULL, 362 tp->rcv_nxt, tp->snd_una - 1, 0); 363 tcp_freetemplate(t_template); 364 } 365 tcp_callout_reset(tp, tp->tt_keep, tcp_keepintvl, 366 tcp_timer_keep); 367 } else { 368 tcp_callout_reset(tp, tp->tt_keep, tcp_keepidle, 369 tcp_timer_keep); 370 } 371 372 #ifdef TCPDEBUG 373 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 374 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO); 375 #endif 376 return tp; 377 378 dropit: 379 tcpstat.tcps_keepdrops++; 380 tp = tcp_drop(tp, ETIMEDOUT); 381 382 #ifdef TCPDEBUG 383 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 384 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO); 385 #endif 386 return tp; 387 } 388 389 void 390 tcp_timer_keep(void *xtp) 391 { 392 struct tcpcb *tp = xtp; 393 struct callout *co = &tp->tt_keep->tc_callout; 394 395 crit_enter(); 396 if (callout_pending(co) || !callout_active(co)) { 397 crit_exit(); 398 return; 399 } 400 callout_deactivate(co); 401 tcp_send_timermsg(tp, TCP_TIMER_KEEP); 402 crit_exit(); 403 } 404 405 /* Caller should be in critical section */ 406 static struct tcpcb * 407 tcp_timer_persist_handler(struct tcpcb *tp) 408 { 409 #ifdef TCPDEBUG 410 int ostate; 411 #endif 412 413 #ifdef TCPDEBUG 414 ostate = tp->t_state; 415 #endif 416 /* 417 * Persistance timer into zero window. 418 * Force a byte to be output, if possible. 419 */ 420 tcpstat.tcps_persisttimeo++; 421 /* 422 * Hack: if the peer is dead/unreachable, we do not 423 * time out if the window is closed. After a full 424 * backoff, drop the connection if the idle time 425 * (no responses to probes) reaches the maximum 426 * backoff that we would use if retransmitting. 427 */ 428 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 429 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 430 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 431 tcpstat.tcps_persistdrop++; 432 tp = tcp_drop(tp, ETIMEDOUT); 433 goto out; 434 } 435 tcp_setpersist(tp); 436 tp->t_flags |= TF_FORCE; 437 tcp_output(tp); 438 tp->t_flags &= ~TF_FORCE; 439 440 out: 441 #ifdef TCPDEBUG 442 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 443 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO); 444 #endif 445 return tp; 446 } 447 448 void 449 tcp_timer_persist(void *xtp) 450 { 451 struct tcpcb *tp = xtp; 452 struct callout *co = &tp->tt_persist->tc_callout; 453 454 crit_enter(); 455 if (callout_pending(co) || !callout_active(co)){ 456 crit_exit(); 457 return; 458 } 459 callout_deactivate(co); 460 tcp_send_timermsg(tp, TCP_TIMER_PERSIST); 461 crit_exit(); 462 } 463 464 void 465 tcp_save_congestion_state(struct tcpcb *tp) 466 { 467 tp->snd_cwnd_prev = tp->snd_cwnd; 468 tp->snd_wacked_prev = tp->snd_wacked; 469 tp->snd_ssthresh_prev = tp->snd_ssthresh; 470 tp->snd_recover_prev = tp->snd_recover; 471 if (IN_FASTRECOVERY(tp)) 472 tp->t_flags |= TF_WASFRECOVERY; 473 else 474 tp->t_flags &= ~TF_WASFRECOVERY; 475 if (tp->t_flags & TF_RCVD_TSTMP) { 476 tp->t_rexmtTS = ticks; 477 tp->t_flags |= TF_FIRSTACCACK; 478 } 479 #ifdef later 480 tcp_sack_save_scoreboard(&tp->scb); 481 #endif 482 } 483 484 void 485 tcp_revert_congestion_state(struct tcpcb *tp) 486 { 487 tp->snd_cwnd = tp->snd_cwnd_prev; 488 tp->snd_wacked = tp->snd_wacked_prev; 489 tp->snd_ssthresh = tp->snd_ssthresh_prev; 490 tp->snd_recover = tp->snd_recover_prev; 491 if (tp->t_flags & TF_WASFRECOVERY) 492 ENTER_FASTRECOVERY(tp); 493 if (tp->t_flags & TF_FASTREXMT) { 494 ++tcpstat.tcps_sndfastrexmitbad; 495 if (tp->t_flags & TF_EARLYREXMT) 496 ++tcpstat.tcps_sndearlyrexmitbad; 497 } else 498 ++tcpstat.tcps_sndrtobad; 499 tp->t_badrxtwin = 0; 500 tp->t_rxtshift = 0; 501 tp->snd_nxt = tp->snd_max; 502 #ifdef later 503 tcp_sack_revert_scoreboard(&tp->scb, tp->snd_una); 504 #endif 505 } 506 507 /* Caller should be in critical section */ 508 static struct tcpcb * 509 tcp_timer_rexmt_handler(struct tcpcb *tp) 510 { 511 int rexmt; 512 #ifdef TCPDEBUG 513 int ostate; 514 #endif 515 516 #ifdef TCPDEBUG 517 ostate = tp->t_state; 518 #endif 519 /* 520 * Retransmission timer went off. Message has not 521 * been acked within retransmit interval. Back off 522 * to a longer retransmit interval and retransmit one segment. 523 */ 524 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 525 tp->t_rxtshift = TCP_MAXRXTSHIFT; 526 tcpstat.tcps_timeoutdrop++; 527 tp = tcp_drop(tp, tp->t_softerror ? 528 tp->t_softerror : ETIMEDOUT); 529 goto out; 530 } 531 if (tp->t_rxtshift == 1) { 532 /* 533 * first retransmit; record ssthresh and cwnd so they can 534 * be recovered if this turns out to be a "bad" retransmit. 535 * A retransmit is considered "bad" if an ACK for this 536 * segment is received within RTT/2 interval; the assumption 537 * here is that the ACK was already in flight. See 538 * "On Estimating End-to-End Network Path Properties" by 539 * Allman and Paxson for more details. 540 */ 541 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 542 tcp_save_congestion_state(tp); 543 tp->t_flags &= ~(TF_FASTREXMT | TF_EARLYREXMT); 544 } 545 /* Throw away SACK blocks on a RTO, as specified by RFC2018. */ 546 tcp_sack_cleanup(&tp->scb); 547 tcpstat.tcps_rexmttimeo++; 548 if (tp->t_state == TCPS_SYN_SENT) 549 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; 550 else 551 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 552 TCPT_RANGESET(tp->t_rxtcur, rexmt, 553 tp->t_rttmin, TCPTV_REXMTMAX); 554 /* 555 * Disable rfc1323 and rfc1644 if we havn't got any response to 556 * our third SYN to work-around some broken terminal servers 557 * (most of which have hopefully been retired) that have bad VJ 558 * header compression code which trashes TCP segments containing 559 * unknown-to-them TCP options. 560 */ 561 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3)) 562 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC); 563 /* 564 * If losing, let the lower level know and try for 565 * a better route. Also, if we backed off this far, 566 * our srtt estimate is probably bogus. Clobber it 567 * so we'll take the next rtt measurement as our srtt; 568 * move the current srtt into rttvar to keep the current 569 * retransmit times until then. 570 */ 571 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 572 #ifdef INET6 573 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 574 in6_losing(tp->t_inpcb); 575 else 576 #endif 577 in_losing(tp->t_inpcb); 578 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 579 tp->t_srtt = 0; 580 } 581 tp->snd_nxt = tp->snd_una; 582 tp->rexmt_high = tp->snd_una; 583 tp->snd_recover = tp->snd_max; 584 /* 585 * Force a segment to be sent. 586 */ 587 tp->t_flags |= TF_ACKNOW; 588 /* 589 * If timing a segment in this window, stop the timer. 590 */ 591 tp->t_rtttime = 0; 592 /* 593 * Close the congestion window down to one segment 594 * (we'll open it by one segment for each ack we get). 595 * Since we probably have a window's worth of unacked 596 * data accumulated, this "slow start" keeps us from 597 * dumping all that data as back-to-back packets (which 598 * might overwhelm an intermediate gateway). 599 * 600 * There are two phases to the opening: Initially we 601 * open by one mss on each ack. This makes the window 602 * size increase exponentially with time. If the 603 * window is larger than the path can handle, this 604 * exponential growth results in dropped packet(s) 605 * almost immediately. To get more time between 606 * drops but still "push" the network to take advantage 607 * of improving conditions, we switch from exponential 608 * to linear window opening at some threshhold size. 609 * For a threshhold, we use half the current window 610 * size, truncated to a multiple of the mss. 611 * 612 * (the minimum cwnd that will give us exponential 613 * growth is 2 mss. We don't allow the threshhold 614 * to go below this.) 615 */ 616 { 617 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 618 619 if (win < 2) 620 win = 2; 621 tp->snd_cwnd = tp->t_maxseg; 622 tp->snd_wacked = 0; 623 tp->snd_ssthresh = win * tp->t_maxseg; 624 tp->t_dupacks = 0; 625 } 626 EXIT_FASTRECOVERY(tp); 627 tcp_output(tp); 628 629 out: 630 #ifdef TCPDEBUG 631 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 632 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO); 633 #endif 634 return tp; 635 } 636 637 void 638 tcp_timer_rexmt(void *xtp) 639 { 640 struct tcpcb *tp = xtp; 641 struct callout *co = &tp->tt_rexmt->tc_callout; 642 643 crit_enter(); 644 if (callout_pending(co) || !callout_active(co)) { 645 crit_exit(); 646 return; 647 } 648 callout_deactivate(co); 649 tcp_send_timermsg(tp, TCP_TIMER_REXMT); 650 crit_exit(); 651 } 652 653 static void 654 tcp_timer_handler(struct netmsg *nmsg) 655 { 656 struct netmsg_tcp_timer *tmsg = (struct netmsg_tcp_timer *)nmsg; 657 const struct tcp_timer *tt; 658 struct tcpcb *tp; 659 660 crit_enter(); 661 662 KKASSERT(tmsg->tt_cpuid == mycpuid && tmsg->tt_tcb != NULL); 663 tp = tmsg->tt_tcb; 664 665 /* Save pending tasks and reset the tasks in message */ 666 tmsg->tt_running_tasks = tmsg->tt_tasks; 667 tmsg->tt_prev_tasks = tmsg->tt_tasks; 668 tmsg->tt_tasks = 0; 669 670 /* Reply ASAP */ 671 lwkt_replymsg(&tmsg->tt_nmsg.nm_lmsg, 0); 672 673 if (tmsg->tt_running_tasks == 0) { 674 /* 675 * All of the timers are cancelled when the message 676 * is pending; bail out. 677 */ 678 crit_exit(); 679 return; 680 } 681 682 for (tt = tcp_timer_handlers; tt->tt_handler != NULL; ++tt) { 683 if ((tmsg->tt_running_tasks & tt->tt_task) == 0) 684 continue; 685 686 tmsg->tt_running_tasks &= ~tt->tt_task; 687 tp = tt->tt_handler(tp); 688 if (tp == NULL) 689 break; 690 691 if (tmsg->tt_running_tasks == 0) /* nothing left to do */ 692 break; 693 } 694 695 crit_exit(); 696 } 697 698 void 699 tcp_create_timermsg(struct tcpcb *tp, struct lwkt_port *msgport) 700 { 701 struct netmsg_tcp_timer *tmsg = tp->tt_msg; 702 703 netmsg_init(&tmsg->tt_nmsg, &netisr_adone_rport, 704 MSGF_DROPABLE | MSGF_PRIORITY, tcp_timer_handler); 705 tmsg->tt_cpuid = mycpuid; 706 tmsg->tt_msgport = msgport; 707 tmsg->tt_tcb = tp; 708 tmsg->tt_tasks = 0; 709 } 710 711 void 712 tcp_destroy_timermsg(struct tcpcb *tp) 713 { 714 struct netmsg_tcp_timer *tmsg = tp->tt_msg; 715 716 if (tmsg == NULL || /* listen socket */ 717 tmsg->tt_tcb == NULL) /* only tcp_attach() is called */ 718 return; 719 720 KKASSERT(tmsg->tt_cpuid == mycpuid); 721 crit_enter(); 722 if ((tmsg->tt_nmsg.nm_lmsg.ms_flags & MSGF_DONE) == 0) { 723 /* 724 * This message is still pending to be processed; 725 * drop it. 726 */ 727 lwkt_dropmsg(&tmsg->tt_nmsg.nm_lmsg); 728 } 729 crit_exit(); 730 } 731 732 static __inline void 733 tcp_callout_init(struct tcp_callout *tc, uint32_t task) 734 { 735 callout_init(&tc->tc_callout); 736 tc->tc_task = task; 737 } 738 739 void 740 tcp_inittimers(struct tcpcb *tp) 741 { 742 tcp_callout_init(tp->tt_rexmt, TCP_TIMER_REXMT); 743 tcp_callout_init(tp->tt_persist, TCP_TIMER_PERSIST); 744 tcp_callout_init(tp->tt_keep, TCP_TIMER_KEEP); 745 tcp_callout_init(tp->tt_2msl, TCP_TIMER_2MSL); 746 tcp_callout_init(tp->tt_delack, TCP_TIMER_DELACK); 747 } 748