Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)
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sys/netinet/tcp_timer.c
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1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 4. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95 30 */ 31 32 #include <sys/cdefs.h> 33 __FBSDID("$FreeBSD: releng/8.4/sys/netinet/tcp_timer.c 247499 2013-02-28 21:24:19Z jhb $"); 34 35 #include "opt_inet6.h" 36 #include "opt_tcpdebug.h" 37 38 #include <sys/param.h> 39 #include <sys/kernel.h> 40 #include <sys/lock.h> 41 #include <sys/mbuf.h> 42 #include <sys/mutex.h> 43 #include <sys/protosw.h> 44 #include <sys/socket.h> 45 #include <sys/socketvar.h> 46 #include <sys/sysctl.h> 47 #include <sys/systm.h> 48 49 #include <net/if.h> 50 #include <net/route.h> 51 #include <net/vnet.h> 52 53 #include <netinet/cc.h> 54 #include <netinet/in.h> 55 #include <netinet/in_pcb.h> 56 #include <netinet/in_systm.h> 57 #ifdef INET6 58 #include <netinet6/in6_pcb.h> 59 #endif 60 #include <netinet/ip_var.h> 61 #include <netinet/tcp_fsm.h> 62 #include <netinet/tcp_timer.h> 63 #include <netinet/tcp_var.h> 64 #include <netinet/tcpip.h> 65 #ifdef TCPDEBUG 66 #include <netinet/tcp_debug.h> 67 #endif 68 69 int tcp_keepinit; 70 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW, 71 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", "time to establish connection"); 72 73 int tcp_keepidle; 74 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW, 75 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", "time before keepalive probes begin"); 76 77 int tcp_keepintvl; 78 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW, 79 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", "time between keepalive probes"); 80 81 int tcp_delacktime; 82 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, CTLTYPE_INT|CTLFLAG_RW, 83 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I", 84 "Time before a delayed ACK is sent"); 85 86 int tcp_msl; 87 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW, 88 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime"); 89 90 int tcp_rexmit_min; 91 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW, 92 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", 93 "Minimum Retransmission Timeout"); 94 95 int tcp_rexmit_slop; 96 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW, 97 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", 98 "Retransmission Timer Slop"); 99 100 static int always_keepalive = 1; 101 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, 102 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); 103 104 int tcp_fast_finwait2_recycle = 0; 105 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW, 106 &tcp_fast_finwait2_recycle, 0, 107 "Recycle closed FIN_WAIT_2 connections faster"); 108 109 int tcp_finwait2_timeout; 110 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, CTLTYPE_INT|CTLFLAG_RW, 111 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", "FIN-WAIT2 timeout"); 112 113 114 static int tcp_keepcnt = TCPTV_KEEPCNT; 115 /* max idle probes */ 116 int tcp_maxpersistidle; 117 /* max idle time in persist */ 118 int tcp_maxidle; 119 120 static int tcp_rexmit_drop_options = 1; 121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW, 122 &tcp_rexmit_drop_options, 0, 123 "Drop TCP options from 3rd and later retransmitted SYN"); 124 125 /* 126 * Tcp protocol timeout routine called every 500 ms. 127 * Updates timestamps used for TCP 128 * causes finite state machine actions if timers expire. 129 */ 130 void 131 tcp_slowtimo(void) 132 { 133 VNET_ITERATOR_DECL(vnet_iter); 134 135 VNET_LIST_RLOCK_NOSLEEP(); 136 VNET_FOREACH(vnet_iter) { 137 CURVNET_SET(vnet_iter); 138 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 139 INP_INFO_WLOCK(&V_tcbinfo); 140 (void) tcp_tw_2msl_scan(0); 141 INP_INFO_WUNLOCK(&V_tcbinfo); 142 CURVNET_RESTORE(); 143 } 144 VNET_LIST_RUNLOCK_NOSLEEP(); 145 } 146 147 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 148 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 149 150 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 151 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 }; 152 153 static int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */ 154 155 static int tcp_timer_race; 156 SYSCTL_INT(_net_inet_tcp, OID_AUTO, timer_race, CTLFLAG_RD, &tcp_timer_race, 157 0, "Count of t_inpcb races on tcp_discardcb"); 158 159 /* 160 * TCP timer processing. 161 */ 162 163 void 164 tcp_timer_delack(void *xtp) 165 { 166 struct tcpcb *tp = xtp; 167 struct inpcb *inp; 168 CURVNET_SET(tp->t_vnet); 169 170 inp = tp->t_inpcb; 171 /* 172 * XXXRW: While this assert is in fact correct, bugs in the tcpcb 173 * tear-down mean we need it as a work-around for races between 174 * timers and tcp_discardcb(). 175 * 176 * KASSERT(inp != NULL, ("tcp_timer_delack: inp == NULL")); 177 */ 178 if (inp == NULL) { 179 tcp_timer_race++; 180 CURVNET_RESTORE(); 181 return; 182 } 183 INP_WLOCK(inp); 184 if (callout_pending(&tp->t_timers->tt_delack) || 185 !callout_active(&tp->t_timers->tt_delack)) { 186 INP_WUNLOCK(inp); 187 CURVNET_RESTORE(); 188 return; 189 } 190 callout_deactivate(&tp->t_timers->tt_delack); 191 if ((inp->inp_flags & INP_DROPPED) != 0) { 192 INP_WUNLOCK(inp); 193 CURVNET_RESTORE(); 194 return; 195 } 196 197 tp->t_flags |= TF_ACKNOW; 198 TCPSTAT_INC(tcps_delack); 199 (void) tcp_output(tp); 200 INP_WUNLOCK(inp); 201 CURVNET_RESTORE(); 202 } 203 204 void 205 tcp_timer_2msl(void *xtp) 206 { 207 struct tcpcb *tp = xtp; 208 struct inpcb *inp; 209 CURVNET_SET(tp->t_vnet); 210 #ifdef TCPDEBUG 211 int ostate; 212 213 ostate = tp->t_state; 214 #endif 215 /* 216 * XXXRW: Does this actually happen? 217 */ 218 INP_INFO_WLOCK(&V_tcbinfo); 219 inp = tp->t_inpcb; 220 /* 221 * XXXRW: While this assert is in fact correct, bugs in the tcpcb 222 * tear-down mean we need it as a work-around for races between 223 * timers and tcp_discardcb(). 224 * 225 * KASSERT(inp != NULL, ("tcp_timer_2msl: inp == NULL")); 226 */ 227 if (inp == NULL) { 228 tcp_timer_race++; 229 INP_INFO_WUNLOCK(&V_tcbinfo); 230 CURVNET_RESTORE(); 231 return; 232 } 233 INP_WLOCK(inp); 234 tcp_free_sackholes(tp); 235 if (callout_pending(&tp->t_timers->tt_2msl) || 236 !callout_active(&tp->t_timers->tt_2msl)) { 237 INP_WUNLOCK(tp->t_inpcb); 238 INP_INFO_WUNLOCK(&V_tcbinfo); 239 CURVNET_RESTORE(); 240 return; 241 } 242 callout_deactivate(&tp->t_timers->tt_2msl); 243 if ((inp->inp_flags & INP_DROPPED) != 0) { 244 INP_WUNLOCK(inp); 245 INP_INFO_WUNLOCK(&V_tcbinfo); 246 CURVNET_RESTORE(); 247 return; 248 } 249 /* 250 * 2 MSL timeout in shutdown went off. If we're closed but 251 * still waiting for peer to close and connection has been idle 252 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 253 * control block. Otherwise, check again in a bit. 254 * 255 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed, 256 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it. 257 * Ignore fact that there were recent incoming segments. 258 */ 259 if (tcp_fast_finwait2_recycle && tp->t_state == TCPS_FIN_WAIT_2 && 260 tp->t_inpcb && tp->t_inpcb->inp_socket && 261 (tp->t_inpcb->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) { 262 TCPSTAT_INC(tcps_finwait2_drops); 263 tp = tcp_close(tp); 264 } else { 265 if (tp->t_state != TCPS_TIME_WAIT && 266 ticks - tp->t_rcvtime <= tcp_maxidle) 267 callout_reset(&tp->t_timers->tt_2msl, tcp_keepintvl, 268 tcp_timer_2msl, tp); 269 else 270 tp = tcp_close(tp); 271 } 272 273 #ifdef TCPDEBUG 274 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 275 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 276 PRU_SLOWTIMO); 277 #endif 278 if (tp != NULL) 279 INP_WUNLOCK(inp); 280 INP_INFO_WUNLOCK(&V_tcbinfo); 281 CURVNET_RESTORE(); 282 } 283 284 void 285 tcp_timer_keep(void *xtp) 286 { 287 struct tcpcb *tp = xtp; 288 struct tcptemp *t_template; 289 struct inpcb *inp; 290 CURVNET_SET(tp->t_vnet); 291 #ifdef TCPDEBUG 292 int ostate; 293 294 ostate = tp->t_state; 295 #endif 296 INP_INFO_WLOCK(&V_tcbinfo); 297 inp = tp->t_inpcb; 298 /* 299 * XXXRW: While this assert is in fact correct, bugs in the tcpcb 300 * tear-down mean we need it as a work-around for races between 301 * timers and tcp_discardcb(). 302 * 303 * KASSERT(inp != NULL, ("tcp_timer_keep: inp == NULL")); 304 */ 305 if (inp == NULL) { 306 tcp_timer_race++; 307 INP_INFO_WUNLOCK(&V_tcbinfo); 308 CURVNET_RESTORE(); 309 return; 310 } 311 INP_WLOCK(inp); 312 if (callout_pending(&tp->t_timers->tt_keep) || 313 !callout_active(&tp->t_timers->tt_keep)) { 314 INP_WUNLOCK(inp); 315 INP_INFO_WUNLOCK(&V_tcbinfo); 316 CURVNET_RESTORE(); 317 return; 318 } 319 callout_deactivate(&tp->t_timers->tt_keep); 320 if ((inp->inp_flags & INP_DROPPED) != 0) { 321 INP_WUNLOCK(inp); 322 INP_INFO_WUNLOCK(&V_tcbinfo); 323 CURVNET_RESTORE(); 324 return; 325 } 326 /* 327 * Keep-alive timer went off; send something 328 * or drop connection if idle for too long. 329 */ 330 TCPSTAT_INC(tcps_keeptimeo); 331 if (tp->t_state < TCPS_ESTABLISHED) 332 goto dropit; 333 if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) && 334 tp->t_state <= TCPS_CLOSING) { 335 if (ticks - tp->t_rcvtime >= tcp_keepidle + tcp_maxidle) 336 goto dropit; 337 /* 338 * Send a packet designed to force a response 339 * if the peer is up and reachable: 340 * either an ACK if the connection is still alive, 341 * or an RST if the peer has closed the connection 342 * due to timeout or reboot. 343 * Using sequence number tp->snd_una-1 344 * causes the transmitted zero-length segment 345 * to lie outside the receive window; 346 * by the protocol spec, this requires the 347 * correspondent TCP to respond. 348 */ 349 TCPSTAT_INC(tcps_keepprobe); 350 t_template = tcpip_maketemplate(inp); 351 if (t_template) { 352 tcp_respond(tp, t_template->tt_ipgen, 353 &t_template->tt_t, (struct mbuf *)NULL, 354 tp->rcv_nxt, tp->snd_una - 1, 0); 355 free(t_template, M_TEMP); 356 } 357 callout_reset(&tp->t_timers->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 358 } else 359 callout_reset(&tp->t_timers->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 360 361 #ifdef TCPDEBUG 362 if (inp->inp_socket->so_options & SO_DEBUG) 363 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 364 PRU_SLOWTIMO); 365 #endif 366 INP_WUNLOCK(inp); 367 INP_INFO_WUNLOCK(&V_tcbinfo); 368 CURVNET_RESTORE(); 369 return; 370 371 dropit: 372 TCPSTAT_INC(tcps_keepdrops); 373 tp = tcp_drop(tp, ETIMEDOUT); 374 375 #ifdef TCPDEBUG 376 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 377 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 378 PRU_SLOWTIMO); 379 #endif 380 if (tp != NULL) 381 INP_WUNLOCK(tp->t_inpcb); 382 INP_INFO_WUNLOCK(&V_tcbinfo); 383 CURVNET_RESTORE(); 384 } 385 386 void 387 tcp_timer_persist(void *xtp) 388 { 389 struct tcpcb *tp = xtp; 390 struct inpcb *inp; 391 CURVNET_SET(tp->t_vnet); 392 #ifdef TCPDEBUG 393 int ostate; 394 395 ostate = tp->t_state; 396 #endif 397 INP_INFO_WLOCK(&V_tcbinfo); 398 inp = tp->t_inpcb; 399 /* 400 * XXXRW: While this assert is in fact correct, bugs in the tcpcb 401 * tear-down mean we need it as a work-around for races between 402 * timers and tcp_discardcb(). 403 * 404 * KASSERT(inp != NULL, ("tcp_timer_persist: inp == NULL")); 405 */ 406 if (inp == NULL) { 407 tcp_timer_race++; 408 INP_INFO_WUNLOCK(&V_tcbinfo); 409 CURVNET_RESTORE(); 410 return; 411 } 412 INP_WLOCK(inp); 413 if (callout_pending(&tp->t_timers->tt_persist) || 414 !callout_active(&tp->t_timers->tt_persist)) { 415 INP_WUNLOCK(inp); 416 INP_INFO_WUNLOCK(&V_tcbinfo); 417 CURVNET_RESTORE(); 418 return; 419 } 420 callout_deactivate(&tp->t_timers->tt_persist); 421 if ((inp->inp_flags & INP_DROPPED) != 0) { 422 INP_WUNLOCK(inp); 423 INP_INFO_WUNLOCK(&V_tcbinfo); 424 CURVNET_RESTORE(); 425 return; 426 } 427 /* 428 * Persistance timer into zero window. 429 * Force a byte to be output, if possible. 430 */ 431 TCPSTAT_INC(tcps_persisttimeo); 432 /* 433 * Hack: if the peer is dead/unreachable, we do not 434 * time out if the window is closed. After a full 435 * backoff, drop the connection if the idle time 436 * (no responses to probes) reaches the maximum 437 * backoff that we would use if retransmitting. 438 */ 439 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 440 (ticks - tp->t_rcvtime >= tcp_maxpersistidle || 441 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 442 TCPSTAT_INC(tcps_persistdrop); 443 tp = tcp_drop(tp, ETIMEDOUT); 444 goto out; 445 } 446 tcp_setpersist(tp); 447 tp->t_flags |= TF_FORCEDATA; 448 (void) tcp_output(tp); 449 tp->t_flags &= ~TF_FORCEDATA; 450 451 out: 452 #ifdef TCPDEBUG 453 if (tp != NULL && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 454 tcp_trace(TA_USER, ostate, tp, NULL, NULL, PRU_SLOWTIMO); 455 #endif 456 if (tp != NULL) 457 INP_WUNLOCK(inp); 458 INP_INFO_WUNLOCK(&V_tcbinfo); 459 CURVNET_RESTORE(); 460 } 461 462 void 463 tcp_timer_rexmt(void * xtp) 464 { 465 struct tcpcb *tp = xtp; 466 CURVNET_SET(tp->t_vnet); 467 int rexmt; 468 int headlocked; 469 struct inpcb *inp; 470 #ifdef TCPDEBUG 471 int ostate; 472 473 ostate = tp->t_state; 474 #endif 475 INP_INFO_WLOCK(&V_tcbinfo); 476 headlocked = 1; 477 inp = tp->t_inpcb; 478 /* 479 * XXXRW: While this assert is in fact correct, bugs in the tcpcb 480 * tear-down mean we need it as a work-around for races between 481 * timers and tcp_discardcb(). 482 * 483 * KASSERT(inp != NULL, ("tcp_timer_rexmt: inp == NULL")); 484 */ 485 if (inp == NULL) { 486 tcp_timer_race++; 487 INP_INFO_WUNLOCK(&V_tcbinfo); 488 CURVNET_RESTORE(); 489 return; 490 } 491 INP_WLOCK(inp); 492 if (callout_pending(&tp->t_timers->tt_rexmt) || 493 !callout_active(&tp->t_timers->tt_rexmt)) { 494 INP_WUNLOCK(inp); 495 INP_INFO_WUNLOCK(&V_tcbinfo); 496 CURVNET_RESTORE(); 497 return; 498 } 499 callout_deactivate(&tp->t_timers->tt_rexmt); 500 if ((inp->inp_flags & INP_DROPPED) != 0) { 501 INP_WUNLOCK(inp); 502 INP_INFO_WUNLOCK(&V_tcbinfo); 503 CURVNET_RESTORE(); 504 return; 505 } 506 tcp_free_sackholes(tp); 507 /* 508 * Retransmission timer went off. Message has not 509 * been acked within retransmit interval. Back off 510 * to a longer retransmit interval and retransmit one segment. 511 */ 512 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 513 tp->t_rxtshift = TCP_MAXRXTSHIFT; 514 TCPSTAT_INC(tcps_timeoutdrop); 515 tp = tcp_drop(tp, tp->t_softerror ? 516 tp->t_softerror : ETIMEDOUT); 517 goto out; 518 } 519 INP_INFO_WUNLOCK(&V_tcbinfo); 520 headlocked = 0; 521 if (tp->t_rxtshift == 1) { 522 /* 523 * first retransmit; record ssthresh and cwnd so they can 524 * be recovered if this turns out to be a "bad" retransmit. 525 * A retransmit is considered "bad" if an ACK for this 526 * segment is received within RTT/2 interval; the assumption 527 * here is that the ACK was already in flight. See 528 * "On Estimating End-to-End Network Path Properties" by 529 * Allman and Paxson for more details. 530 */ 531 tp->snd_cwnd_prev = tp->snd_cwnd; 532 tp->snd_ssthresh_prev = tp->snd_ssthresh; 533 tp->snd_recover_prev = tp->snd_recover; 534 if (IN_FASTRECOVERY(tp->t_flags)) 535 tp->t_flags |= TF_WASFRECOVERY; 536 else 537 tp->t_flags &= ~TF_WASFRECOVERY; 538 if (IN_CONGRECOVERY(tp->t_flags)) 539 tp->t_flags |= TF_WASCRECOVERY; 540 else 541 tp->t_flags &= ~TF_WASCRECOVERY; 542 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 543 tp->t_flags |= TF_PREVVALID; 544 } else 545 tp->t_flags &= ~TF_PREVVALID; 546 TCPSTAT_INC(tcps_rexmttimeo); 547 if (tp->t_state == TCPS_SYN_SENT) 548 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; 549 else 550 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 551 TCPT_RANGESET(tp->t_rxtcur, rexmt, 552 tp->t_rttmin, TCPTV_REXMTMAX); 553 /* 554 * Disable rfc1323 if we haven't got any response to 555 * our third SYN to work-around some broken terminal servers 556 * (most of which have hopefully been retired) that have bad VJ 557 * header compression code which trashes TCP segments containing 558 * unknown-to-them TCP options. 559 */ 560 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) && 561 (tp->t_rxtshift == 3)) 562 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP); 563 /* 564 * If we backed off this far, our srtt estimate is probably bogus. 565 * Clobber it so we'll take the next rtt measurement as our srtt; 566 * move the current srtt into rttvar to keep the current 567 * retransmit times until then. 568 */ 569 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 570 #ifdef INET6 571 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 572 in6_losing(tp->t_inpcb); 573 else 574 #endif 575 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 576 tp->t_srtt = 0; 577 } 578 tp->snd_nxt = tp->snd_una; 579 tp->snd_recover = tp->snd_max; 580 /* 581 * Force a segment to be sent. 582 */ 583 tp->t_flags |= TF_ACKNOW; 584 /* 585 * If timing a segment in this window, stop the timer. 586 */ 587 tp->t_rtttime = 0; 588 589 cc_cong_signal(tp, NULL, CC_RTO); 590 591 (void) tcp_output(tp); 592 593 out: 594 #ifdef TCPDEBUG 595 if (tp != NULL && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 596 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 597 PRU_SLOWTIMO); 598 #endif 599 if (tp != NULL) 600 INP_WUNLOCK(inp); 601 if (headlocked) 602 INP_INFO_WUNLOCK(&V_tcbinfo); 603 CURVNET_RESTORE(); 604 } 605 606 void 607 tcp_timer_activate(struct tcpcb *tp, int timer_type, u_int delta) 608 { 609 struct callout *t_callout; 610 void *f_callout; 611 612 switch (timer_type) { 613 case TT_DELACK: 614 t_callout = &tp->t_timers->tt_delack; 615 f_callout = tcp_timer_delack; 616 break; 617 case TT_REXMT: 618 t_callout = &tp->t_timers->tt_rexmt; 619 f_callout = tcp_timer_rexmt; 620 break; 621 case TT_PERSIST: 622 t_callout = &tp->t_timers->tt_persist; 623 f_callout = tcp_timer_persist; 624 break; 625 case TT_KEEP: 626 t_callout = &tp->t_timers->tt_keep; 627 f_callout = tcp_timer_keep; 628 break; 629 case TT_2MSL: 630 t_callout = &tp->t_timers->tt_2msl; 631 f_callout = tcp_timer_2msl; 632 break; 633 default: 634 panic("bad timer_type"); 635 } 636 if (delta == 0) { 637 callout_stop(t_callout); 638 } else { 639 callout_reset(t_callout, delta, f_callout, tp); 640 } 641 } 642 643 int 644 tcp_timer_active(struct tcpcb *tp, int timer_type) 645 { 646 struct callout *t_callout; 647 648 switch (timer_type) { 649 case TT_DELACK: 650 t_callout = &tp->t_timers->tt_delack; 651 break; 652 case TT_REXMT: 653 t_callout = &tp->t_timers->tt_rexmt; 654 break; 655 case TT_PERSIST: 656 t_callout = &tp->t_timers->tt_persist; 657 break; 658 case TT_KEEP: 659 t_callout = &tp->t_timers->tt_keep; 660 break; 661 case TT_2MSL: 662 t_callout = &tp->t_timers->tt_2msl; 663 break; 664 default: 665 panic("bad timer_type"); 666 } 667 return callout_active(t_callout); 668 }
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