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 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95 34 * $FreeBSD$ 35 */ 36 37 #include "opt_compat.h" 38 #include "opt_inet6.h" 39 #include "opt_tcpdebug.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/kernel.h> 44 #include <sys/mbuf.h> 45 #include <sys/sysctl.h> 46 #include <sys/socket.h> 47 #include <sys/socketvar.h> 48 #include <sys/protosw.h> 49 50 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 51 52 #include <net/route.h> 53 54 #include <netinet/in.h> 55 #include <netinet/in_systm.h> 56 #include <netinet/in_pcb.h> 57 #ifdef INET6 58 #include <netinet6/in6_pcb.h> 59 #endif 60 #include <netinet/ip_var.h> 61 #include <netinet/tcp.h> 62 #include <netinet/tcp_fsm.h> 63 #include <netinet/tcp_seq.h> 64 #include <netinet/tcp_timer.h> 65 #include <netinet/tcp_var.h> 66 #include <netinet/tcpip.h> 67 #ifdef TCPDEBUG 68 #include <netinet/tcp_debug.h> 69 #endif 70 71 static int 72 sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS) 73 { 74 int error, s, tt; 75 76 tt = *(int *)oidp->oid_arg1; 77 s = (int)((int64_t)tt * 1000 / hz); 78 79 error = sysctl_handle_int(oidp, &s, 0, req); 80 if (error || !req->newptr) 81 return (error); 82 83 tt = (int)((int64_t)s * hz / 1000); 84 if (tt < 1) 85 return (EINVAL); 86 87 *(int *)oidp->oid_arg1 = tt; 88 return (0); 89 } 90 91 int tcp_keepinit; 92 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW, 93 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", ""); 94 95 int tcp_keepidle; 96 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW, 97 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", ""); 98 99 int tcp_keepintvl; 100 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW, 101 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", ""); 102 103 int tcp_delacktime; 104 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, 105 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I", 106 "Time before a delayed ACK is sent"); 107 108 int tcp_msl; 109 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW, 110 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime"); 111 112 int tcp_rexmit_min; 113 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW, 114 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout"); 115 116 int tcp_rexmit_slop; 117 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW, 118 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", "Retransmission Timer Slop"); 119 120 static int always_keepalive = 1; 121 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, 122 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); 123 124 static int tcp_keepcnt = TCPTV_KEEPCNT; 125 /* max idle probes */ 126 int tcp_maxpersistidle; 127 /* max idle time in persist */ 128 int tcp_maxidle; 129 130 /* 131 * Tcp protocol timeout routine called every 500 ms. 132 * Updates timestamps used for TCP 133 * causes finite state machine actions if timers expire. 134 */ 135 void 136 tcp_slowtimo() 137 { 138 int s; 139 140 s = splnet(); 141 142 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 143 144 splx(s); 145 } 146 147 /* 148 * Cancel all timers for TCP tp. 149 */ 150 void 151 tcp_canceltimers(tp) 152 struct tcpcb *tp; 153 { 154 callout_stop(tp->tt_2msl); 155 callout_stop(tp->tt_persist); 156 callout_stop(tp->tt_keep); 157 callout_stop(tp->tt_rexmt); 158 } 159 160 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 161 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 162 163 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 164 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 165 166 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 167 168 /* 169 * TCP timer processing. 170 */ 171 172 void 173 tcp_timer_delack(xtp) 174 void *xtp; 175 { 176 struct tcpcb *tp = xtp; 177 int s; 178 struct inpcb *inp; 179 180 s = splnet(); 181 INP_INFO_RLOCK(&tcbinfo); 182 inp = tp->t_inpcb; 183 INP_LOCK(inp); 184 INP_INFO_RUNLOCK(&tcbinfo); 185 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { 186 INP_UNLOCK(inp); 187 splx(s); 188 return; 189 } 190 callout_deactivate(tp->tt_delack); 191 192 tp->t_flags |= TF_ACKNOW; 193 tcpstat.tcps_delack++; 194 (void) tcp_output(tp); 195 INP_UNLOCK(inp); 196 splx(s); 197 } 198 199 void 200 tcp_timer_2msl(xtp) 201 void *xtp; 202 { 203 struct tcpcb *tp = xtp; 204 int s; 205 struct inpcb *inp; 206 #ifdef TCPDEBUG 207 int ostate; 208 209 ostate = tp->t_state; 210 #endif 211 s = splnet(); 212 INP_INFO_WLOCK(&tcbinfo); 213 inp = tp->t_inpcb; 214 INP_LOCK(inp); 215 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { 216 INP_UNLOCK(tp->t_inpcb); 217 INP_INFO_WUNLOCK(&tcbinfo); 218 splx(s); 219 return; 220 } 221 callout_deactivate(tp->tt_2msl); 222 /* 223 * 2 MSL timeout in shutdown went off. If we're closed but 224 * still waiting for peer to close and connection has been idle 225 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 226 * control block. Otherwise, check again in a bit. 227 */ 228 if (tp->t_state != TCPS_TIME_WAIT && 229 (ticks - tp->t_rcvtime) <= tcp_maxidle) 230 callout_reset(tp->tt_2msl, tcp_keepintvl, 231 tcp_timer_2msl, tp); 232 else 233 tp = tcp_close(tp); 234 235 #ifdef TCPDEBUG 236 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 237 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 238 PRU_SLOWTIMO); 239 #endif 240 if (tp) 241 INP_UNLOCK(inp); 242 INP_INFO_WUNLOCK(&tcbinfo); 243 splx(s); 244 } 245 246 void 247 tcp_timer_keep(xtp) 248 void *xtp; 249 { 250 struct tcpcb *tp = xtp; 251 struct tcptemp *t_template; 252 int s; 253 struct inpcb *inp; 254 #ifdef TCPDEBUG 255 int ostate; 256 257 ostate = tp->t_state; 258 #endif 259 s = splnet(); 260 INP_INFO_WLOCK(&tcbinfo); 261 inp = tp->t_inpcb; 262 INP_LOCK(inp); 263 if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) { 264 INP_UNLOCK(inp); 265 INP_INFO_WUNLOCK(&tcbinfo); 266 splx(s); 267 return; 268 } 269 callout_deactivate(tp->tt_keep); 270 /* 271 * Keep-alive timer went off; send something 272 * or drop connection if idle for too long. 273 */ 274 tcpstat.tcps_keeptimeo++; 275 if (tp->t_state < TCPS_ESTABLISHED) 276 goto dropit; 277 if ((always_keepalive || 278 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 279 tp->t_state <= TCPS_CLOSING) { 280 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 281 goto dropit; 282 /* 283 * Send a packet designed to force a response 284 * if the peer is up and reachable: 285 * either an ACK if the connection is still alive, 286 * or an RST if the peer has closed the connection 287 * due to timeout or reboot. 288 * Using sequence number tp->snd_una-1 289 * causes the transmitted zero-length segment 290 * to lie outside the receive window; 291 * by the protocol spec, this requires the 292 * correspondent TCP to respond. 293 */ 294 tcpstat.tcps_keepprobe++; 295 t_template = tcp_maketemplate(tp); 296 if (t_template) { 297 tcp_respond(tp, t_template->tt_ipgen, 298 &t_template->tt_t, (struct mbuf *)NULL, 299 tp->rcv_nxt, tp->snd_una - 1, 0); 300 (void) m_free(dtom(t_template)); 301 } 302 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 303 } else 304 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 305 306 #ifdef TCPDEBUG 307 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 308 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 309 PRU_SLOWTIMO); 310 #endif 311 INP_UNLOCK(inp); 312 INP_INFO_WUNLOCK(&tcbinfo); 313 splx(s); 314 return; 315 316 dropit: 317 tcpstat.tcps_keepdrops++; 318 tp = tcp_drop(tp, ETIMEDOUT); 319 320 #ifdef TCPDEBUG 321 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 322 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 323 PRU_SLOWTIMO); 324 #endif 325 if (tp) 326 INP_UNLOCK(tp->t_inpcb); 327 INP_INFO_WUNLOCK(&tcbinfo); 328 splx(s); 329 } 330 331 void 332 tcp_timer_persist(xtp) 333 void *xtp; 334 { 335 struct tcpcb *tp = xtp; 336 int s; 337 struct inpcb *inp; 338 #ifdef TCPDEBUG 339 int ostate; 340 341 ostate = tp->t_state; 342 #endif 343 s = splnet(); 344 INP_INFO_WLOCK(&tcbinfo); 345 inp = tp->t_inpcb; 346 INP_LOCK(inp); 347 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ 348 INP_UNLOCK(inp); 349 INP_INFO_WUNLOCK(&tcbinfo); 350 splx(s); 351 return; 352 } 353 callout_deactivate(tp->tt_persist); 354 /* 355 * Persistance timer into zero window. 356 * Force a byte to be output, if possible. 357 */ 358 tcpstat.tcps_persisttimeo++; 359 /* 360 * Hack: if the peer is dead/unreachable, we do not 361 * time out if the window is closed. After a full 362 * backoff, drop the connection if the idle time 363 * (no responses to probes) reaches the maximum 364 * backoff that we would use if retransmitting. 365 */ 366 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 367 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 368 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 369 tcpstat.tcps_persistdrop++; 370 tp = tcp_drop(tp, ETIMEDOUT); 371 goto out; 372 } 373 tcp_setpersist(tp); 374 tp->t_force = 1; 375 (void) tcp_output(tp); 376 tp->t_force = 0; 377 378 out: 379 #ifdef TCPDEBUG 380 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 381 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 382 PRU_SLOWTIMO); 383 #endif 384 if (tp) 385 INP_UNLOCK(inp); 386 INP_INFO_WUNLOCK(&tcbinfo); 387 splx(s); 388 } 389 390 void 391 tcp_timer_rexmt(xtp) 392 void *xtp; 393 { 394 struct tcpcb *tp = xtp; 395 int s; 396 int rexmt; 397 int headlocked; 398 struct inpcb *inp; 399 #ifdef TCPDEBUG 400 int ostate; 401 402 ostate = tp->t_state; 403 #endif 404 s = splnet(); 405 INP_INFO_WLOCK(&tcbinfo); 406 headlocked = 1; 407 inp = tp->t_inpcb; 408 INP_LOCK(inp); 409 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { 410 INP_UNLOCK(inp); 411 INP_INFO_WUNLOCK(&tcbinfo); 412 splx(s); 413 return; 414 } 415 callout_deactivate(tp->tt_rexmt); 416 /* 417 * Retransmission timer went off. Message has not 418 * been acked within retransmit interval. Back off 419 * to a longer retransmit interval and retransmit one segment. 420 */ 421 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 422 tp->t_rxtshift = TCP_MAXRXTSHIFT; 423 tcpstat.tcps_timeoutdrop++; 424 tp = tcp_drop(tp, tp->t_softerror ? 425 tp->t_softerror : ETIMEDOUT); 426 goto out; 427 } 428 INP_INFO_WUNLOCK(&tcbinfo); 429 headlocked = 0; 430 if (tp->t_rxtshift == 1) { 431 /* 432 * first retransmit; record ssthresh and cwnd so they can 433 * be recovered if this turns out to be a "bad" retransmit. 434 * A retransmit is considered "bad" if an ACK for this 435 * segment is received within RTT/2 interval; the assumption 436 * here is that the ACK was already in flight. See 437 * "On Estimating End-to-End Network Path Properties" by 438 * Allman and Paxson for more details. 439 */ 440 tp->snd_cwnd_prev = tp->snd_cwnd; 441 tp->snd_ssthresh_prev = tp->snd_ssthresh; 442 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 443 } 444 tcpstat.tcps_rexmttimeo++; 445 if (tp->t_state == TCPS_SYN_SENT) 446 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; 447 else 448 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 449 TCPT_RANGESET(tp->t_rxtcur, rexmt, 450 tp->t_rttmin, TCPTV_REXMTMAX); 451 /* 452 * Disable rfc1323 and rfc1644 if we havn't got any response to 453 * our third SYN to work-around some broken terminal servers 454 * (most of which have hopefully been retired) that have bad VJ 455 * header compression code which trashes TCP segments containing 456 * unknown-to-them TCP options. 457 */ 458 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3)) 459 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC); 460 /* 461 * If losing, let the lower level know and try for 462 * a better route. Also, if we backed off this far, 463 * our srtt estimate is probably bogus. Clobber it 464 * so we'll take the next rtt measurement as our srtt; 465 * move the current srtt into rttvar to keep the current 466 * retransmit times until then. 467 */ 468 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 469 #ifdef INET6 470 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 471 in6_losing(tp->t_inpcb); 472 else 473 #endif 474 in_losing(tp->t_inpcb); 475 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 476 tp->t_srtt = 0; 477 } 478 tp->snd_nxt = tp->snd_una; 479 /* 480 * Note: We overload snd_recover to function also as the 481 * snd_last variable described in RFC 2582 482 */ 483 tp->snd_recover = tp->snd_max; 484 /* 485 * Force a segment to be sent. 486 */ 487 tp->t_flags |= TF_ACKNOW; 488 /* 489 * If timing a segment in this window, stop the timer. 490 */ 491 tp->t_rtttime = 0; 492 /* 493 * Close the congestion window down to one segment 494 * (we'll open it by one segment for each ack we get). 495 * Since we probably have a window's worth of unacked 496 * data accumulated, this "slow start" keeps us from 497 * dumping all that data as back-to-back packets (which 498 * might overwhelm an intermediate gateway). 499 * 500 * There are two phases to the opening: Initially we 501 * open by one mss on each ack. This makes the window 502 * size increase exponentially with time. If the 503 * window is larger than the path can handle, this 504 * exponential growth results in dropped packet(s) 505 * almost immediately. To get more time between 506 * drops but still "push" the network to take advantage 507 * of improving conditions, we switch from exponential 508 * to linear window opening at some threshhold size. 509 * For a threshhold, we use half the current window 510 * size, truncated to a multiple of the mss. 511 * 512 * (the minimum cwnd that will give us exponential 513 * growth is 2 mss. We don't allow the threshhold 514 * to go below this.) 515 */ 516 { 517 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 518 if (win < 2) 519 win = 2; 520 tp->snd_cwnd = tp->t_maxseg; 521 tp->snd_ssthresh = win * tp->t_maxseg; 522 tp->t_dupacks = 0; 523 } 524 (void) tcp_output(tp); 525 526 out: 527 #ifdef TCPDEBUG 528 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 529 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 530 PRU_SLOWTIMO); 531 #endif 532 if (tp) 533 INP_UNLOCK(inp); 534 if (headlocked) 535 INP_INFO_WUNLOCK(&tcbinfo); 536 splx(s); 537 } 538