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 = tt * 1000 / hz; 78 79 error = sysctl_handle_int(oidp, &s, 0, req); 80 if (error || !req->newptr) 81 return (error); 82 83 tt = 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 static int always_keepalive = 1; 113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, 114 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); 115 116 static int tcp_keepcnt = TCPTV_KEEPCNT; 117 /* max idle probes */ 118 int tcp_maxpersistidle; 119 /* max idle time in persist */ 120 int tcp_maxidle; 121 122 /* 123 * Tcp protocol timeout routine called every 500 ms. 124 * Updates timestamps used for TCP 125 * causes finite state machine actions if timers expire. 126 */ 127 void 128 tcp_slowtimo() 129 { 130 int s; 131 132 s = splnet(); 133 134 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 135 136 splx(s); 137 } 138 139 /* 140 * Cancel all timers for TCP tp. 141 */ 142 void 143 tcp_canceltimers(tp) 144 struct tcpcb *tp; 145 { 146 callout_stop(tp->tt_2msl); 147 callout_stop(tp->tt_persist); 148 callout_stop(tp->tt_keep); 149 callout_stop(tp->tt_rexmt); 150 } 151 152 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 153 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 154 155 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 156 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 157 158 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 159 160 /* 161 * TCP timer processing. 162 */ 163 164 void 165 tcp_timer_delack(xtp) 166 void *xtp; 167 { 168 struct tcpcb *tp = xtp; 169 int s; 170 struct inpcb *inp; 171 172 s = splnet(); 173 INP_INFO_RLOCK(&tcbinfo); 174 inp = tp->t_inpcb; 175 INP_LOCK(inp); 176 INP_INFO_RUNLOCK(&tcbinfo); 177 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { 178 INP_UNLOCK(inp); 179 splx(s); 180 return; 181 } 182 callout_deactivate(tp->tt_delack); 183 184 tp->t_flags |= TF_ACKNOW; 185 tcpstat.tcps_delack++; 186 (void) tcp_output(tp); 187 INP_UNLOCK(inp); 188 splx(s); 189 } 190 191 void 192 tcp_timer_2msl(xtp) 193 void *xtp; 194 { 195 struct tcpcb *tp = xtp; 196 int s; 197 struct inpcb *inp; 198 #ifdef TCPDEBUG 199 int ostate; 200 201 ostate = tp->t_state; 202 #endif 203 s = splnet(); 204 INP_INFO_WLOCK(&tcbinfo); 205 inp = tp->t_inpcb; 206 INP_LOCK(inp); 207 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { 208 INP_UNLOCK(tp->t_inpcb); 209 INP_INFO_WUNLOCK(&tcbinfo); 210 splx(s); 211 return; 212 } 213 callout_deactivate(tp->tt_2msl); 214 /* 215 * 2 MSL timeout in shutdown went off. If we're closed but 216 * still waiting for peer to close and connection has been idle 217 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 218 * control block. Otherwise, check again in a bit. 219 */ 220 if (tp->t_state != TCPS_TIME_WAIT && 221 (ticks - tp->t_rcvtime) <= tcp_maxidle) 222 callout_reset(tp->tt_2msl, tcp_keepintvl, 223 tcp_timer_2msl, tp); 224 else 225 tp = tcp_close(tp); 226 227 #ifdef TCPDEBUG 228 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 229 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 230 PRU_SLOWTIMO); 231 #endif 232 if (tp) 233 INP_UNLOCK(inp); 234 INP_INFO_WUNLOCK(&tcbinfo); 235 splx(s); 236 } 237 238 void 239 tcp_timer_keep(xtp) 240 void *xtp; 241 { 242 struct tcpcb *tp = xtp; 243 struct tcptemp *t_template; 244 int s; 245 struct inpcb *inp; 246 #ifdef TCPDEBUG 247 int ostate; 248 249 ostate = tp->t_state; 250 #endif 251 s = splnet(); 252 INP_INFO_WLOCK(&tcbinfo); 253 inp = tp->t_inpcb; 254 INP_LOCK(inp); 255 if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) { 256 INP_UNLOCK(inp); 257 INP_INFO_WUNLOCK(&tcbinfo); 258 splx(s); 259 return; 260 } 261 callout_deactivate(tp->tt_keep); 262 /* 263 * Keep-alive timer went off; send something 264 * or drop connection if idle for too long. 265 */ 266 tcpstat.tcps_keeptimeo++; 267 if (tp->t_state < TCPS_ESTABLISHED) 268 goto dropit; 269 if ((always_keepalive || 270 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 271 tp->t_state <= TCPS_CLOSING) { 272 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 273 goto dropit; 274 /* 275 * Send a packet designed to force a response 276 * if the peer is up and reachable: 277 * either an ACK if the connection is still alive, 278 * or an RST if the peer has closed the connection 279 * due to timeout or reboot. 280 * Using sequence number tp->snd_una-1 281 * causes the transmitted zero-length segment 282 * to lie outside the receive window; 283 * by the protocol spec, this requires the 284 * correspondent TCP to respond. 285 */ 286 tcpstat.tcps_keepprobe++; 287 t_template = tcp_maketemplate(tp); 288 if (t_template) { 289 tcp_respond(tp, t_template->tt_ipgen, 290 &t_template->tt_t, (struct mbuf *)NULL, 291 tp->rcv_nxt, tp->snd_una - 1, 0); 292 (void) m_free(dtom(t_template)); 293 } 294 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 295 } else 296 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 297 298 #ifdef TCPDEBUG 299 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 300 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 301 PRU_SLOWTIMO); 302 #endif 303 INP_UNLOCK(inp); 304 INP_INFO_WUNLOCK(&tcbinfo); 305 splx(s); 306 return; 307 308 dropit: 309 tcpstat.tcps_keepdrops++; 310 tp = tcp_drop(tp, ETIMEDOUT); 311 312 #ifdef TCPDEBUG 313 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 314 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 315 PRU_SLOWTIMO); 316 #endif 317 if (tp) 318 INP_UNLOCK(tp->t_inpcb); 319 INP_INFO_WUNLOCK(&tcbinfo); 320 splx(s); 321 } 322 323 void 324 tcp_timer_persist(xtp) 325 void *xtp; 326 { 327 struct tcpcb *tp = xtp; 328 int s; 329 struct inpcb *inp; 330 #ifdef TCPDEBUG 331 int ostate; 332 333 ostate = tp->t_state; 334 #endif 335 s = splnet(); 336 INP_INFO_WLOCK(&tcbinfo); 337 inp = tp->t_inpcb; 338 INP_LOCK(inp); 339 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ 340 INP_UNLOCK(inp); 341 INP_INFO_WUNLOCK(&tcbinfo); 342 splx(s); 343 return; 344 } 345 callout_deactivate(tp->tt_persist); 346 /* 347 * Persistance timer into zero window. 348 * Force a byte to be output, if possible. 349 */ 350 tcpstat.tcps_persisttimeo++; 351 /* 352 * Hack: if the peer is dead/unreachable, we do not 353 * time out if the window is closed. After a full 354 * backoff, drop the connection if the idle time 355 * (no responses to probes) reaches the maximum 356 * backoff that we would use if retransmitting. 357 */ 358 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 359 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 360 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 361 tcpstat.tcps_persistdrop++; 362 tp = tcp_drop(tp, ETIMEDOUT); 363 goto out; 364 } 365 tcp_setpersist(tp); 366 tp->t_force = 1; 367 (void) tcp_output(tp); 368 tp->t_force = 0; 369 370 out: 371 #ifdef TCPDEBUG 372 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 373 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 374 PRU_SLOWTIMO); 375 #endif 376 if (tp) 377 INP_UNLOCK(inp); 378 INP_INFO_WUNLOCK(&tcbinfo); 379 splx(s); 380 } 381 382 void 383 tcp_timer_rexmt(xtp) 384 void *xtp; 385 { 386 struct tcpcb *tp = xtp; 387 int s; 388 int rexmt; 389 int headlocked; 390 struct inpcb *inp; 391 #ifdef TCPDEBUG 392 int ostate; 393 394 ostate = tp->t_state; 395 #endif 396 s = splnet(); 397 INP_INFO_WLOCK(&tcbinfo); 398 headlocked = 1; 399 inp = tp->t_inpcb; 400 INP_LOCK(inp); 401 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { 402 INP_UNLOCK(inp); 403 INP_INFO_WUNLOCK(&tcbinfo); 404 splx(s); 405 return; 406 } 407 callout_deactivate(tp->tt_rexmt); 408 /* 409 * Retransmission timer went off. Message has not 410 * been acked within retransmit interval. Back off 411 * to a longer retransmit interval and retransmit one segment. 412 */ 413 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 414 tp->t_rxtshift = TCP_MAXRXTSHIFT; 415 tcpstat.tcps_timeoutdrop++; 416 tp = tcp_drop(tp, tp->t_softerror ? 417 tp->t_softerror : ETIMEDOUT); 418 goto out; 419 } 420 INP_INFO_WUNLOCK(&tcbinfo); 421 headlocked = 0; 422 if (tp->t_rxtshift == 1) { 423 /* 424 * first retransmit; record ssthresh and cwnd so they can 425 * be recovered if this turns out to be a "bad" retransmit. 426 * A retransmit is considered "bad" if an ACK for this 427 * segment is received within RTT/2 interval; the assumption 428 * here is that the ACK was already in flight. See 429 * "On Estimating End-to-End Network Path Properties" by 430 * Allman and Paxson for more details. 431 */ 432 tp->snd_cwnd_prev = tp->snd_cwnd; 433 tp->snd_ssthresh_prev = tp->snd_ssthresh; 434 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 435 } 436 tcpstat.tcps_rexmttimeo++; 437 if (tp->t_state == TCPS_SYN_SENT) 438 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; 439 else 440 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 441 TCPT_RANGESET(tp->t_rxtcur, rexmt, 442 tp->t_rttmin, TCPTV_REXMTMAX); 443 /* 444 * Disable rfc1323 and rfc1644 if we havn't got any response to 445 * our third SYN to work-around some broken terminal servers 446 * (most of which have hopefully been retired) that have bad VJ 447 * header compression code which trashes TCP segments containing 448 * unknown-to-them TCP options. 449 */ 450 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3)) 451 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC); 452 /* 453 * If losing, let the lower level know and try for 454 * a better route. Also, if we backed off this far, 455 * our srtt estimate is probably bogus. Clobber it 456 * so we'll take the next rtt measurement as our srtt; 457 * move the current srtt into rttvar to keep the current 458 * retransmit times until then. 459 */ 460 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 461 #ifdef INET6 462 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 463 in6_losing(tp->t_inpcb); 464 else 465 #endif 466 in_losing(tp->t_inpcb); 467 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 468 tp->t_srtt = 0; 469 } 470 tp->snd_nxt = tp->snd_una; 471 /* 472 * Note: We overload snd_recover to function also as the 473 * snd_last variable described in RFC 2582 474 */ 475 tp->snd_recover = tp->snd_max; 476 /* 477 * Force a segment to be sent. 478 */ 479 tp->t_flags |= TF_ACKNOW; 480 /* 481 * If timing a segment in this window, stop the timer. 482 */ 483 tp->t_rtttime = 0; 484 /* 485 * Close the congestion window down to one segment 486 * (we'll open it by one segment for each ack we get). 487 * Since we probably have a window's worth of unacked 488 * data accumulated, this "slow start" keeps us from 489 * dumping all that data as back-to-back packets (which 490 * might overwhelm an intermediate gateway). 491 * 492 * There are two phases to the opening: Initially we 493 * open by one mss on each ack. This makes the window 494 * size increase exponentially with time. If the 495 * window is larger than the path can handle, this 496 * exponential growth results in dropped packet(s) 497 * almost immediately. To get more time between 498 * drops but still "push" the network to take advantage 499 * of improving conditions, we switch from exponential 500 * to linear window opening at some threshhold size. 501 * For a threshhold, we use half the current window 502 * size, truncated to a multiple of the mss. 503 * 504 * (the minimum cwnd that will give us exponential 505 * growth is 2 mss. We don't allow the threshhold 506 * to go below this.) 507 */ 508 { 509 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 510 if (win < 2) 511 win = 2; 512 tp->snd_cwnd = tp->t_maxseg; 513 tp->snd_ssthresh = win * tp->t_maxseg; 514 tp->t_dupacks = 0; 515 } 516 (void) tcp_output(tp); 517 518 out: 519 #ifdef TCPDEBUG 520 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 521 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 522 PRU_SLOWTIMO); 523 #endif 524 if (tp) 525 INP_UNLOCK(inp); 526 if (headlocked) 527 INP_INFO_WUNLOCK(&tcbinfo); 528 splx(s); 529 } 530