tcp_timer.c revision 1.65
1 /* $NetBSD: tcp_timer.c,v 1.65 2003/10/27 07:43:01 itojun Exp $ */ 2 3 /* 4 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the project nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 */ 31 32 /*- 33 * Copyright (c) 1997, 1998, 2001 The NetBSD Foundation, Inc. 34 * All rights reserved. 35 * 36 * This code is derived from software contributed to The NetBSD Foundation 37 * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation 38 * Facility, NASA Ames Research Center. 39 * 40 * Redistribution and use in source and binary forms, with or without 41 * modification, are permitted provided that the following conditions 42 * are met: 43 * 1. Redistributions of source code must retain the above copyright 44 * notice, this list of conditions and the following disclaimer. 45 * 2. Redistributions in binary form must reproduce the above copyright 46 * notice, this list of conditions and the following disclaimer in the 47 * documentation and/or other materials provided with the distribution. 48 * 3. All advertising materials mentioning features or use of this software 49 * must display the following acknowledgement: 50 * This product includes software developed by the NetBSD 51 * Foundation, Inc. and its contributors. 52 * 4. Neither the name of The NetBSD Foundation nor the names of its 53 * contributors may be used to endorse or promote products derived 54 * from this software without specific prior written permission. 55 * 56 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 57 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 58 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 59 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 60 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 61 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 62 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 63 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 64 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 65 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 66 * POSSIBILITY OF SUCH DAMAGE. 67 */ 68 69 /* 70 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 71 * The Regents of the University of California. All rights reserved. 72 * 73 * Redistribution and use in source and binary forms, with or without 74 * modification, are permitted provided that the following conditions 75 * are met: 76 * 1. Redistributions of source code must retain the above copyright 77 * notice, this list of conditions and the following disclaimer. 78 * 2. Redistributions in binary form must reproduce the above copyright 79 * notice, this list of conditions and the following disclaimer in the 80 * documentation and/or other materials provided with the distribution. 81 * 3. Neither the name of the University nor the names of its contributors 82 * may be used to endorse or promote products derived from this software 83 * without specific prior written permission. 84 * 85 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 86 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 87 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 88 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 89 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 90 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 91 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 92 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 93 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 94 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 95 * SUCH DAMAGE. 96 * 97 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95 98 */ 99 100 #include <sys/cdefs.h> 101 __KERNEL_RCSID(0, "$NetBSD: tcp_timer.c,v 1.65 2003/10/27 07:43:01 itojun Exp $"); 102 103 #include "opt_inet.h" 104 #include "opt_tcp_debug.h" 105 106 #include <sys/param.h> 107 #include <sys/systm.h> 108 #include <sys/malloc.h> 109 #include <sys/mbuf.h> 110 #include <sys/socket.h> 111 #include <sys/socketvar.h> 112 #include <sys/protosw.h> 113 #include <sys/errno.h> 114 #include <sys/kernel.h> 115 116 #include <net/if.h> 117 #include <net/route.h> 118 119 #include <netinet/in.h> 120 #include <netinet/in_systm.h> 121 #include <netinet/ip.h> 122 #include <netinet/in_pcb.h> 123 #include <netinet/ip_var.h> 124 125 #ifdef INET6 126 #ifndef INET 127 #include <netinet/in.h> 128 #endif 129 #include <netinet/ip6.h> 130 #include <netinet6/in6_pcb.h> 131 #endif 132 133 #include <netinet/tcp.h> 134 #include <netinet/tcp_fsm.h> 135 #include <netinet/tcp_seq.h> 136 #include <netinet/tcp_timer.h> 137 #include <netinet/tcp_var.h> 138 #include <netinet/tcpip.h> 139 #ifdef TCP_DEBUG 140 #include <netinet/tcp_debug.h> 141 #endif 142 143 /* 144 * Various tunable timer parameters. These are initialized in tcp_init(), 145 * unless they are patched. 146 */ 147 int tcp_keepidle = 0; 148 int tcp_keepintvl = 0; 149 int tcp_keepcnt = 0; /* max idle probes */ 150 int tcp_maxpersistidle = 0; /* max idle time in persist */ 151 int tcp_maxidle; /* computed in tcp_slowtimo() */ 152 153 /* 154 * Time to delay the ACK. This is initialized in tcp_init(), unless 155 * its patched. 156 */ 157 int tcp_delack_ticks = 0; 158 159 void tcp_timer_rexmt(void *); 160 void tcp_timer_persist(void *); 161 void tcp_timer_keep(void *); 162 void tcp_timer_2msl(void *); 163 164 const tcp_timer_func_t tcp_timer_funcs[TCPT_NTIMERS] = { 165 tcp_timer_rexmt, 166 tcp_timer_persist, 167 tcp_timer_keep, 168 tcp_timer_2msl, 169 }; 170 171 /* 172 * Timer state initialization, called from tcp_init(). 173 */ 174 void 175 tcp_timer_init(void) 176 { 177 178 if (tcp_keepidle == 0) 179 tcp_keepidle = TCPTV_KEEP_IDLE; 180 181 if (tcp_keepintvl == 0) 182 tcp_keepintvl = TCPTV_KEEPINTVL; 183 184 if (tcp_keepcnt == 0) 185 tcp_keepcnt = TCPTV_KEEPCNT; 186 187 if (tcp_maxpersistidle == 0) 188 tcp_maxpersistidle = TCPTV_KEEP_IDLE; 189 190 if (tcp_delack_ticks == 0) 191 tcp_delack_ticks = TCP_DELACK_TICKS; 192 } 193 194 /* 195 * Return how many timers are currently being invoked. 196 */ 197 int 198 tcp_timers_invoking(struct tcpcb *tp) 199 { 200 int i; 201 int count = 0; 202 203 for (i = 0; i < TCPT_NTIMERS; i++) 204 if (callout_invoking(&tp->t_timer[i])) 205 count++; 206 if (callout_invoking(&tp->t_delack_ch)) 207 count++; 208 209 return count; 210 } 211 212 /* 213 * Callout to process delayed ACKs for a TCPCB. 214 */ 215 void 216 tcp_delack(void *arg) 217 { 218 struct tcpcb *tp = arg; 219 int s; 220 221 /* 222 * If tcp_output() wasn't able to transmit the ACK 223 * for whatever reason, it will restart the delayed 224 * ACK callout. 225 */ 226 227 s = splsoftnet(); 228 callout_ack(&tp->t_delack_ch); 229 if (tcp_isdead(tp)) { 230 splx(s); 231 return; 232 } 233 234 tp->t_flags |= TF_ACKNOW; 235 (void) tcp_output(tp); 236 splx(s); 237 } 238 239 /* 240 * Tcp protocol timeout routine called every 500 ms. 241 * Updates the timers in all active tcb's and 242 * causes finite state machine actions if timers expire. 243 */ 244 void 245 tcp_slowtimo() 246 { 247 int s; 248 249 s = splsoftnet(); 250 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 251 tcp_iss_seq += TCP_ISSINCR; /* increment iss */ 252 tcp_now++; /* for timestamps */ 253 splx(s); 254 } 255 256 /* 257 * Cancel all timers for TCP tp. 258 */ 259 void 260 tcp_canceltimers(tp) 261 struct tcpcb *tp; 262 { 263 int i; 264 265 for (i = 0; i < TCPT_NTIMERS; i++) 266 TCP_TIMER_DISARM(tp, i); 267 } 268 269 const int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 270 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 271 272 const int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 273 274 /* 275 * TCP timer processing. 276 */ 277 278 void 279 tcp_timer_rexmt(void *arg) 280 { 281 struct tcpcb *tp = arg; 282 uint32_t rto; 283 int s; 284 #ifdef TCP_DEBUG 285 struct socket *so = NULL; 286 short ostate; 287 #endif 288 289 s = splsoftnet(); 290 callout_ack(&tp->t_timer[TCPT_KEEP]); 291 if (tcp_isdead(tp)) { 292 splx(s); 293 return; 294 } 295 296 #ifdef TCP_DEBUG 297 #ifdef INET 298 if (tp->t_inpcb) 299 so = tp->t_inpcb->inp_socket; 300 #endif 301 #ifdef INET6 302 if (tp->t_in6pcb) 303 so = tp->t_in6pcb->in6p_socket; 304 #endif 305 ostate = tp->t_state; 306 #endif /* TCP_DEBUG */ 307 308 /* 309 * Retransmission timer went off. Message has not 310 * been acked within retransmit interval. Back off 311 * to a longer retransmit interval and retransmit one segment. 312 */ 313 314 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 315 tp->t_rxtshift = TCP_MAXRXTSHIFT; 316 tcpstat.tcps_timeoutdrop++; 317 tp = tcp_drop(tp, tp->t_softerror ? 318 tp->t_softerror : ETIMEDOUT); 319 goto out; 320 } 321 tcpstat.tcps_rexmttimeo++; 322 rto = TCP_REXMTVAL(tp); 323 if (rto < tp->t_rttmin) 324 rto = tp->t_rttmin; 325 TCPT_RANGESET(tp->t_rxtcur, rto * tcp_backoff[tp->t_rxtshift], 326 tp->t_rttmin, TCPTV_REXMTMAX); 327 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 328 329 /* 330 * If we are losing and we are trying path MTU discovery, 331 * try turning it off. This will avoid black holes in 332 * the network which suppress or fail to send "packet 333 * too big" ICMP messages. We should ideally do 334 * lots more sophisticated searching to find the right 335 * value here... 336 */ 337 if (tp->t_mtudisc && tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) { 338 tcpstat.tcps_pmtublackhole++; 339 340 #ifdef INET 341 /* try turning PMTUD off */ 342 if (tp->t_inpcb) 343 tp->t_mtudisc = 0; 344 #endif 345 #ifdef INET6 346 /* try using IPv6 minimum MTU */ 347 if (tp->t_in6pcb) 348 tp->t_mtudisc = 0; 349 #endif 350 351 /* XXX: more sophisticated Black hole recovery code? */ 352 } 353 354 /* 355 * If losing, let the lower level know and try for 356 * a better route. Also, if we backed off this far, 357 * our srtt estimate is probably bogus. Clobber it 358 * so we'll take the next rtt measurement as our srtt; 359 * move the current srtt into rttvar to keep the current 360 * retransmit times until then. 361 */ 362 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 363 #ifdef INET 364 if (tp->t_inpcb) 365 in_losing(tp->t_inpcb); 366 #endif 367 #ifdef INET6 368 if (tp->t_in6pcb) 369 in6_losing(tp->t_in6pcb); 370 #endif 371 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 372 tp->t_srtt = 0; 373 } 374 tp->snd_nxt = tp->snd_una; 375 /* 376 * If timing a segment in this window, stop the timer. 377 */ 378 tp->t_rtttime = 0; 379 /* 380 * Remember if we are retransmitting a SYN, because if 381 * we do, set the initial congestion window must be set 382 * to 1 segment. 383 */ 384 if (tp->t_state == TCPS_SYN_SENT) 385 tp->t_flags |= TF_SYN_REXMT; 386 /* 387 * Close the congestion window down to one segment 388 * (we'll open it by one segment for each ack we get). 389 * Since we probably have a window's worth of unacked 390 * data accumulated, this "slow start" keeps us from 391 * dumping all that data as back-to-back packets (which 392 * might overwhelm an intermediate gateway). 393 * 394 * There are two phases to the opening: Initially we 395 * open by one mss on each ack. This makes the window 396 * size increase exponentially with time. If the 397 * window is larger than the path can handle, this 398 * exponential growth results in dropped packet(s) 399 * almost immediately. To get more time between 400 * drops but still "push" the network to take advantage 401 * of improving conditions, we switch from exponential 402 * to linear window opening at some threshhold size. 403 * For a threshhold, we use half the current window 404 * size, truncated to a multiple of the mss. 405 * 406 * (the minimum cwnd that will give us exponential 407 * growth is 2 mss. We don't allow the threshhold 408 * to go below this.) 409 */ 410 { 411 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz; 412 if (win < 2) 413 win = 2; 414 /* Loss Window MUST be one segment. */ 415 tp->snd_cwnd = tp->t_segsz; 416 tp->snd_ssthresh = win * tp->t_segsz; 417 tp->t_dupacks = 0; 418 } 419 (void) tcp_output(tp); 420 421 out: 422 #ifdef TCP_DEBUG 423 if (tp && so->so_options & SO_DEBUG) 424 tcp_trace(TA_USER, ostate, tp, NULL, 425 PRU_SLOWTIMO | (TCPT_REXMT << 8)); 426 #endif 427 splx(s); 428 } 429 430 void 431 tcp_timer_persist(void *arg) 432 { 433 struct tcpcb *tp = arg; 434 uint32_t rto; 435 int s; 436 #ifdef TCP_DEBUG 437 struct socket *so = NULL; 438 short ostate; 439 #endif 440 441 s = splsoftnet(); 442 callout_ack(&tp->t_timer[TCPT_PERSIST]); 443 if (tcp_isdead(tp)) { 444 splx(s); 445 return; 446 } 447 448 #ifdef TCP_DEBUG 449 #ifdef INET 450 if (tp->t_inpcb) 451 so = tp->t_inpcb->inp_socket; 452 #endif 453 #ifdef INET6 454 if (tp->t_in6pcb) 455 so = tp->t_in6pcb->in6p_socket; 456 #endif 457 458 ostate = tp->t_state; 459 #endif /* TCP_DEBUG */ 460 461 /* 462 * Persistance timer into zero window. 463 * Force a byte to be output, if possible. 464 */ 465 466 /* 467 * Hack: if the peer is dead/unreachable, we do not 468 * time out if the window is closed. After a full 469 * backoff, drop the connection if the idle time 470 * (no responses to probes) reaches the maximum 471 * backoff that we would use if retransmitting. 472 */ 473 rto = TCP_REXMTVAL(tp); 474 if (rto < tp->t_rttmin) 475 rto = tp->t_rttmin; 476 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 477 ((tcp_now - tp->t_rcvtime) >= tcp_maxpersistidle || 478 (tcp_now - tp->t_rcvtime) >= rto * tcp_totbackoff)) { 479 tcpstat.tcps_persistdrops++; 480 tp = tcp_drop(tp, ETIMEDOUT); 481 goto out; 482 } 483 tcpstat.tcps_persisttimeo++; 484 tcp_setpersist(tp); 485 tp->t_force = 1; 486 (void) tcp_output(tp); 487 tp->t_force = 0; 488 489 out: 490 #ifdef TCP_DEBUG 491 if (tp && so->so_options & SO_DEBUG) 492 tcp_trace(TA_USER, ostate, tp, NULL, 493 PRU_SLOWTIMO | (TCPT_PERSIST << 8)); 494 #endif 495 splx(s); 496 } 497 498 void 499 tcp_timer_keep(void *arg) 500 { 501 struct tcpcb *tp = arg; 502 struct socket *so = NULL; /* Quell compiler warning */ 503 int s; 504 #ifdef TCP_DEBUG 505 short ostate; 506 #endif 507 508 s = splsoftnet(); 509 callout_ack(&tp->t_timer[TCPT_KEEP]); 510 if (tcp_isdead(tp)) { 511 splx(s); 512 return; 513 } 514 515 #ifdef TCP_DEBUG 516 ostate = tp->t_state; 517 #endif /* TCP_DEBUG */ 518 519 /* 520 * Keep-alive timer went off; send something 521 * or drop connection if idle for too long. 522 */ 523 524 tcpstat.tcps_keeptimeo++; 525 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 526 goto dropit; 527 #ifdef INET 528 if (tp->t_inpcb) 529 so = tp->t_inpcb->inp_socket; 530 #endif 531 #ifdef INET6 532 if (tp->t_in6pcb) 533 so = tp->t_in6pcb->in6p_socket; 534 #endif 535 if (so->so_options & SO_KEEPALIVE && 536 tp->t_state <= TCPS_CLOSE_WAIT) { 537 if ((tcp_maxidle > 0) && 538 ((tcp_now - tp->t_rcvtime) >= 539 tcp_keepidle + tcp_maxidle)) 540 goto dropit; 541 /* 542 * Send a packet designed to force a response 543 * if the peer is up and reachable: 544 * either an ACK if the connection is still alive, 545 * or an RST if the peer has closed the connection 546 * due to timeout or reboot. 547 * Using sequence number tp->snd_una-1 548 * causes the transmitted zero-length segment 549 * to lie outside the receive window; 550 * by the protocol spec, this requires the 551 * correspondent TCP to respond. 552 */ 553 tcpstat.tcps_keepprobe++; 554 if (tcp_compat_42) { 555 /* 556 * The keepalive packet must have nonzero 557 * length to get a 4.2 host to respond. 558 */ 559 (void)tcp_respond(tp, tp->t_template, 560 (struct mbuf *)NULL, NULL, tp->rcv_nxt - 1, 561 tp->snd_una - 1, 0); 562 } else { 563 (void)tcp_respond(tp, tp->t_template, 564 (struct mbuf *)NULL, NULL, tp->rcv_nxt, 565 tp->snd_una - 1, 0); 566 } 567 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepintvl); 568 } else 569 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle); 570 571 #ifdef TCP_DEBUG 572 if (tp && so->so_options & SO_DEBUG) 573 tcp_trace(TA_USER, ostate, tp, NULL, 574 PRU_SLOWTIMO | (TCPT_KEEP << 8)); 575 #endif 576 splx(s); 577 return; 578 579 dropit: 580 tcpstat.tcps_keepdrops++; 581 (void) tcp_drop(tp, ETIMEDOUT); 582 splx(s); 583 } 584 585 void 586 tcp_timer_2msl(void *arg) 587 { 588 struct tcpcb *tp = arg; 589 int s; 590 #ifdef TCP_DEBUG 591 struct socket *so = NULL; 592 short ostate; 593 #endif 594 595 s = splsoftnet(); 596 callout_ack(&tp->t_timer[TCPT_2MSL]); 597 if (tcp_isdead(tp)) { 598 splx(s); 599 return; 600 } 601 602 #ifdef TCP_DEBUG 603 #ifdef INET 604 if (tp->t_inpcb) 605 so = tp->t_inpcb->inp_socket; 606 #endif 607 #ifdef INET6 608 if (tp->t_in6pcb) 609 so = tp->t_in6pcb->in6p_socket; 610 #endif 611 612 ostate = tp->t_state; 613 #endif /* TCP_DEBUG */ 614 615 /* 616 * 2 MSL timeout in shutdown went off. If we're closed but 617 * still waiting for peer to close and connection has been idle 618 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 619 * control block. Otherwise, check again in a bit. 620 */ 621 if (tp->t_state != TCPS_TIME_WAIT && 622 ((tcp_maxidle == 0) || ((tcp_now - tp->t_rcvtime) <= tcp_maxidle))) 623 TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_keepintvl); 624 else 625 tp = tcp_close(tp); 626 627 #ifdef TCP_DEBUG 628 if (tp && so->so_options & SO_DEBUG) 629 tcp_trace(TA_USER, ostate, tp, NULL, 630 PRU_SLOWTIMO | (TCPT_2MSL << 8)); 631 #endif 632 splx(s); 633 } 634
Indexes created Sun Sep 21 20:09:37 GMT 2025