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 * $FreeBSD$ 31 */ 32 33 #include "opt_inet6.h" 34 #include "opt_tcpdebug.h" 35 #include "opt_tcp_sack.h" 36 37 #include <sys/param.h> 38 #include <sys/kernel.h> 39 #include <sys/lock.h> 40 #include <sys/mbuf.h> 41 #include <sys/mutex.h> 42 #include <sys/protosw.h> 43 #include <sys/socket.h> 44 #include <sys/socketvar.h> 45 #include <sys/sysctl.h> 46 #include <sys/systm.h> 47 48 #include <net/route.h> 49 50 #include <netinet/in.h> 51 #include <netinet/in_pcb.h> 52 #include <netinet/in_systm.h> 53 #ifdef INET6 54 #include <netinet6/in6_pcb.h> 55 #endif 56 #include <netinet/ip_var.h> 57 #include <netinet/tcp.h> 58 #include <netinet/tcp_fsm.h> 59 #include <netinet/tcp_timer.h> 60 #include <netinet/tcp_var.h> 61 #include <netinet/tcpip.h> 62 #ifdef TCPDEBUG 63 #include <netinet/tcp_debug.h> 64 #endif 65 66 int tcp_keepinit; 67 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW, 68 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", ""); 69 70 int tcp_keepidle; 71 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW, 72 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", ""); 73 74 int tcp_keepintvl; 75 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW, 76 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", ""); 77 78 int tcp_delacktime; 79 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, 80 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I", 81 "Time before a delayed ACK is sent"); 82 83 int tcp_msl; 84 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW, 85 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime"); 86 87 int tcp_rexmit_min; 88 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW, 89 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout"); 90 91 int tcp_rexmit_slop; 92 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW, 93 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", "Retransmission Timer Slop"); 94 95 static int always_keepalive = 1; 96 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, 97 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); 98 99 static int tcp_keepcnt = TCPTV_KEEPCNT; 100 /* max idle probes */ 101 int tcp_maxpersistidle; 102 /* max idle time in persist */ 103 int tcp_maxidle; 104 105 /* 106 * Tcp protocol timeout routine called every 500 ms. 107 * Updates timestamps used for TCP 108 * causes finite state machine actions if timers expire. 109 */ 110 void 111 tcp_slowtimo() 112 { 113 114 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 115 INP_INFO_WLOCK(&tcbinfo); 116 (void) tcp_timer_2msl_tw(0); 117 INP_INFO_WUNLOCK(&tcbinfo); 118 } 119 120 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 121 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 122 123 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 124 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 }; 125 126 static int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */ 127 128 /* 129 * TCP timer processing. 130 */ 131 132 void 133 tcp_timer_delack(xtp) 134 void *xtp; 135 { 136 struct tcpcb *tp = xtp; 137 struct inpcb *inp; 138 139 INP_INFO_RLOCK(&tcbinfo); 140 inp = tp->t_inpcb; 141 if (inp == NULL) { 142 INP_INFO_RUNLOCK(&tcbinfo); 143 return; 144 } 145 INP_LOCK(inp); 146 INP_INFO_RUNLOCK(&tcbinfo); 147 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { 148 INP_UNLOCK(inp); 149 return; 150 } 151 callout_deactivate(tp->tt_delack); 152 153 tp->t_flags |= TF_ACKNOW; 154 tcpstat.tcps_delack++; 155 (void) tcp_output(tp); 156 INP_UNLOCK(inp); 157 } 158 159 void 160 tcp_timer_2msl(xtp) 161 void *xtp; 162 { 163 struct tcpcb *tp = xtp; 164 struct inpcb *inp; 165 #ifdef TCPDEBUG 166 int ostate; 167 168 ostate = tp->t_state; 169 #endif 170 INP_INFO_WLOCK(&tcbinfo); 171 inp = tp->t_inpcb; 172 if (inp == NULL) { 173 INP_INFO_WUNLOCK(&tcbinfo); 174 return; 175 } 176 INP_LOCK(inp); 177 tcp_free_sackholes(tp); 178 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { 179 INP_UNLOCK(tp->t_inpcb); 180 INP_INFO_WUNLOCK(&tcbinfo); 181 return; 182 } 183 callout_deactivate(tp->tt_2msl); 184 /* 185 * 2 MSL timeout in shutdown went off. If we're closed but 186 * still waiting for peer to close and connection has been idle 187 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 188 * control block. Otherwise, check again in a bit. 189 */ 190 if (tp->t_state != TCPS_TIME_WAIT && 191 (ticks - tp->t_rcvtime) <= tcp_maxidle) 192 callout_reset(tp->tt_2msl, tcp_keepintvl, 193 tcp_timer_2msl, tp); 194 else 195 tp = tcp_close(tp); 196 197 #ifdef TCPDEBUG 198 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 199 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 200 PRU_SLOWTIMO); 201 #endif 202 if (tp) 203 INP_UNLOCK(inp); 204 INP_INFO_WUNLOCK(&tcbinfo); 205 } 206 207 /* 208 * The timed wait lists contain references to each of the TCP sessions 209 * currently TIME_WAIT state. The list pointers, including the list pointers 210 * in each tcptw structure, are protected using the global tcbinfo lock, 211 * which must be held over list iteration and modification. 212 */ 213 struct twlist { 214 LIST_HEAD(, tcptw) tw_list; 215 struct tcptw tw_tail; 216 }; 217 #define TWLIST_NLISTS 2 218 static struct twlist twl_2msl[TWLIST_NLISTS]; 219 static struct twlist *tw_2msl_list[] = { &twl_2msl[0], &twl_2msl[1], NULL }; 220 221 void 222 tcp_timer_init(void) 223 { 224 int i; 225 struct twlist *twl; 226 227 for (i = 0; i < TWLIST_NLISTS; i++) { 228 twl = &twl_2msl[i]; 229 LIST_INIT(&twl->tw_list); 230 LIST_INSERT_HEAD(&twl->tw_list, &twl->tw_tail, tw_2msl); 231 } 232 } 233 234 void 235 tcp_timer_2msl_reset(struct tcptw *tw, int timeo) 236 { 237 int i; 238 struct tcptw *tw_tail; 239 240 INP_INFO_WLOCK_ASSERT(&tcbinfo); 241 INP_LOCK_ASSERT(tw->tw_inpcb); 242 if (tw->tw_time != 0) 243 LIST_REMOVE(tw, tw_2msl); 244 tw->tw_time = timeo + ticks; 245 i = timeo > tcp_msl ? 1 : 0; 246 tw_tail = &twl_2msl[i].tw_tail; 247 LIST_INSERT_BEFORE(tw_tail, tw, tw_2msl); 248 } 249 250 void 251 tcp_timer_2msl_stop(struct tcptw *tw) 252 { 253 254 INP_INFO_WLOCK_ASSERT(&tcbinfo); 255 if (tw->tw_time != 0) 256 LIST_REMOVE(tw, tw_2msl); 257 } 258 259 struct tcptw * 260 tcp_timer_2msl_tw(int reuse) 261 { 262 struct tcptw *tw, *tw_tail; 263 struct twlist *twl; 264 int i; 265 266 INP_INFO_WLOCK_ASSERT(&tcbinfo); 267 for (i = 0; i < 2; i++) { 268 twl = tw_2msl_list[i]; 269 tw_tail = &twl->tw_tail; 270 for (;;) { 271 tw = LIST_FIRST(&twl->tw_list); 272 if (tw == tw_tail || (!reuse && tw->tw_time > ticks)) 273 break; 274 INP_LOCK(tw->tw_inpcb); 275 if (tcp_twclose(tw, reuse) != NULL) 276 return (tw); 277 } 278 } 279 return (NULL); 280 } 281 282 void 283 tcp_timer_keep(xtp) 284 void *xtp; 285 { 286 struct tcpcb *tp = xtp; 287 struct tcptemp *t_template; 288 struct inpcb *inp; 289 #ifdef TCPDEBUG 290 int ostate; 291 292 ostate = tp->t_state; 293 #endif 294 INP_INFO_WLOCK(&tcbinfo); 295 inp = tp->t_inpcb; 296 if (!inp) { 297 INP_INFO_WUNLOCK(&tcbinfo); 298 return; 299 } 300 INP_LOCK(inp); 301 if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) { 302 INP_UNLOCK(inp); 303 INP_INFO_WUNLOCK(&tcbinfo); 304 return; 305 } 306 callout_deactivate(tp->tt_keep); 307 /* 308 * Keep-alive timer went off; send something 309 * or drop connection if idle for too long. 310 */ 311 tcpstat.tcps_keeptimeo++; 312 if (tp->t_state < TCPS_ESTABLISHED) 313 goto dropit; 314 if ((always_keepalive || inp->inp_socket->so_options & SO_KEEPALIVE) && 315 tp->t_state <= TCPS_CLOSING) { 316 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 317 goto dropit; 318 /* 319 * Send a packet designed to force a response 320 * if the peer is up and reachable: 321 * either an ACK if the connection is still alive, 322 * or an RST if the peer has closed the connection 323 * due to timeout or reboot. 324 * Using sequence number tp->snd_una-1 325 * causes the transmitted zero-length segment 326 * to lie outside the receive window; 327 * by the protocol spec, this requires the 328 * correspondent TCP to respond. 329 */ 330 tcpstat.tcps_keepprobe++; 331 t_template = tcpip_maketemplate(inp); 332 if (t_template) { 333 tcp_respond(tp, t_template->tt_ipgen, 334 &t_template->tt_t, (struct mbuf *)NULL, 335 tp->rcv_nxt, tp->snd_una - 1, 0); 336 (void) m_free(dtom(t_template)); 337 } 338 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 339 } else 340 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 341 342 #ifdef TCPDEBUG 343 if (inp->inp_socket->so_options & SO_DEBUG) 344 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 345 PRU_SLOWTIMO); 346 #endif 347 INP_UNLOCK(inp); 348 INP_INFO_WUNLOCK(&tcbinfo); 349 return; 350 351 dropit: 352 tcpstat.tcps_keepdrops++; 353 tp = tcp_drop(tp, ETIMEDOUT); 354 355 #ifdef TCPDEBUG 356 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 357 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 358 PRU_SLOWTIMO); 359 #endif 360 if (tp) 361 INP_UNLOCK(tp->t_inpcb); 362 INP_INFO_WUNLOCK(&tcbinfo); 363 } 364 365 void 366 tcp_timer_persist(xtp) 367 void *xtp; 368 { 369 struct tcpcb *tp = xtp; 370 struct inpcb *inp; 371 #ifdef TCPDEBUG 372 int ostate; 373 374 ostate = tp->t_state; 375 #endif 376 INP_INFO_WLOCK(&tcbinfo); 377 inp = tp->t_inpcb; 378 if (!inp) { 379 INP_INFO_WUNLOCK(&tcbinfo); 380 return; 381 } 382 INP_LOCK(inp); 383 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ 384 INP_UNLOCK(inp); 385 INP_INFO_WUNLOCK(&tcbinfo); 386 return; 387 } 388 callout_deactivate(tp->tt_persist); 389 /* 390 * Persistance timer into zero window. 391 * Force a byte to be output, if possible. 392 */ 393 tcpstat.tcps_persisttimeo++; 394 /* 395 * Hack: if the peer is dead/unreachable, we do not 396 * time out if the window is closed. After a full 397 * backoff, drop the connection if the idle time 398 * (no responses to probes) reaches the maximum 399 * backoff that we would use if retransmitting. 400 */ 401 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 402 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 403 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 404 tcpstat.tcps_persistdrop++; 405 tp = tcp_drop(tp, ETIMEDOUT); 406 goto out; 407 } 408 tcp_setpersist(tp); 409 tp->t_flags |= TF_FORCEDATA; 410 (void) tcp_output(tp); 411 tp->t_flags &= ~TF_FORCEDATA; 412 413 out: 414 #ifdef TCPDEBUG 415 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 416 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 417 PRU_SLOWTIMO); 418 #endif 419 if (tp) 420 INP_UNLOCK(inp); 421 INP_INFO_WUNLOCK(&tcbinfo); 422 } 423 424 void 425 tcp_timer_rexmt(xtp) 426 void *xtp; 427 { 428 struct tcpcb *tp = xtp; 429 int rexmt; 430 int headlocked; 431 struct inpcb *inp; 432 #ifdef TCPDEBUG 433 int ostate; 434 435 ostate = tp->t_state; 436 #endif 437 INP_INFO_WLOCK(&tcbinfo); 438 headlocked = 1; 439 inp = tp->t_inpcb; 440 if (!inp) { 441 INP_INFO_WUNLOCK(&tcbinfo); 442 return; 443 } 444 INP_LOCK(inp); 445 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { 446 INP_UNLOCK(inp); 447 INP_INFO_WUNLOCK(&tcbinfo); 448 return; 449 } 450 callout_deactivate(tp->tt_rexmt); 451 tcp_free_sackholes(tp); 452 /* 453 * Retransmission timer went off. Message has not 454 * been acked within retransmit interval. Back off 455 * to a longer retransmit interval and retransmit one segment. 456 */ 457 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 458 tp->t_rxtshift = TCP_MAXRXTSHIFT; 459 tcpstat.tcps_timeoutdrop++; 460 tp = tcp_drop(tp, tp->t_softerror ? 461 tp->t_softerror : ETIMEDOUT); 462 goto out; 463 } 464 INP_INFO_WUNLOCK(&tcbinfo); 465 headlocked = 0; 466 if (tp->t_rxtshift == 1) { 467 /* 468 * first retransmit; record ssthresh and cwnd so they can 469 * be recovered if this turns out to be a "bad" retransmit. 470 * A retransmit is considered "bad" if an ACK for this 471 * segment is received within RTT/2 interval; the assumption 472 * here is that the ACK was already in flight. See 473 * "On Estimating End-to-End Network Path Properties" by 474 * Allman and Paxson for more details. 475 */ 476 tp->snd_cwnd_prev = tp->snd_cwnd; 477 tp->snd_ssthresh_prev = tp->snd_ssthresh; 478 tp->snd_recover_prev = tp->snd_recover; 479 if (IN_FASTRECOVERY(tp)) 480 tp->t_flags |= TF_WASFRECOVERY; 481 else 482 tp->t_flags &= ~TF_WASFRECOVERY; 483 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 484 } 485 tcpstat.tcps_rexmttimeo++; 486 if (tp->t_state == TCPS_SYN_SENT) 487 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; 488 else 489 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 490 TCPT_RANGESET(tp->t_rxtcur, rexmt, 491 tp->t_rttmin, TCPTV_REXMTMAX); 492 /* 493 * Disable rfc1323 if we havn't got any response to 494 * our third SYN to work-around some broken terminal servers 495 * (most of which have hopefully been retired) that have bad VJ 496 * header compression code which trashes TCP segments containing 497 * unknown-to-them TCP options. 498 */ 499 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3)) 500 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP); 501 /* 502 * If we backed off this far, our srtt estimate is probably bogus. 503 * Clobber it so we'll take the next rtt measurement as our srtt; 504 * move the current srtt into rttvar to keep the current 505 * retransmit times until then. 506 */ 507 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 508 #ifdef INET6 509 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 510 in6_losing(tp->t_inpcb); 511 else 512 #endif 513 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 514 tp->t_srtt = 0; 515 } 516 tp->snd_nxt = tp->snd_una; 517 tp->snd_recover = tp->snd_max; 518 /* 519 * Force a segment to be sent. 520 */ 521 tp->t_flags |= TF_ACKNOW; 522 /* 523 * If timing a segment in this window, stop the timer. 524 */ 525 tp->t_rtttime = 0; 526 /* 527 * Close the congestion window down to one segment 528 * (we'll open it by one segment for each ack we get). 529 * Since we probably have a window's worth of unacked 530 * data accumulated, this "slow start" keeps us from 531 * dumping all that data as back-to-back packets (which 532 * might overwhelm an intermediate gateway). 533 * 534 * There are two phases to the opening: Initially we 535 * open by one mss on each ack. This makes the window 536 * size increase exponentially with time. If the 537 * window is larger than the path can handle, this 538 * exponential growth results in dropped packet(s) 539 * almost immediately. To get more time between 540 * drops but still "push" the network to take advantage 541 * of improving conditions, we switch from exponential 542 * to linear window opening at some threshhold size. 543 * For a threshhold, we use half the current window 544 * size, truncated to a multiple of the mss. 545 * 546 * (the minimum cwnd that will give us exponential 547 * growth is 2 mss. We don't allow the threshhold 548 * to go below this.) 549 */ 550 { 551 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 552 if (win < 2) 553 win = 2; 554 tp->snd_cwnd = tp->t_maxseg; 555 tp->snd_ssthresh = win * tp->t_maxseg; 556 tp->t_dupacks = 0; 557 } 558 EXIT_FASTRECOVERY(tp); 559 (void) tcp_output(tp); 560 561 out: 562 #ifdef TCPDEBUG 563 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 564 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 565 PRU_SLOWTIMO); 566 #endif 567 if (tp) 568 INP_UNLOCK(inp); 569 if (headlocked) 570 INP_INFO_WUNLOCK(&tcbinfo); 571 } 572