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_inet6.h" 38 #include "opt_tcpdebug.h" 39 40 #include <sys/param.h> 41 #include <sys/kernel.h> 42 #include <sys/lock.h> 43 #include <sys/mbuf.h> 44 #include <sys/mutex.h> 45 #include <sys/protosw.h> 46 #include <sys/socket.h> 47 #include <sys/socketvar.h> 48 #include <sys/sysctl.h> 49 #include <sys/systm.h> 50 51 #include <net/route.h> 52 53 #include <netinet/in.h> 54 #include <netinet/in_pcb.h> 55 #include <netinet/in_systm.h> 56 #ifdef INET6 57 #include <netinet6/in6_pcb.h> 58 #endif 59 #include <netinet/ip_var.h> 60 #include <netinet/tcp.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 static int 70 sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS) 71 { 72 int error, s, tt; 73 74 tt = *(int *)oidp->oid_arg1; 75 s = (int)((int64_t)tt * 1000 / hz); 76 77 error = sysctl_handle_int(oidp, &s, 0, req); 78 if (error || !req->newptr) 79 return (error); 80 81 tt = (int)((int64_t)s * hz / 1000); 82 if (tt < 1) 83 return (EINVAL); 84 85 *(int *)oidp->oid_arg1 = tt; 86 return (0); 87 } 88 89 int tcp_keepinit; 90 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW, 91 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", ""); 92 93 int tcp_keepidle; 94 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW, 95 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", ""); 96 97 int tcp_keepintvl; 98 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW, 99 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", ""); 100 101 int tcp_delacktime; 102 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, 103 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I", 104 "Time before a delayed ACK is sent"); 105 106 int tcp_msl; 107 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW, 108 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime"); 109 110 int tcp_rexmit_min; 111 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW, 112 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout"); 113 114 int tcp_rexmit_slop; 115 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW, 116 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", "Retransmission Timer Slop"); 117 118 static int always_keepalive = 1; 119 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, 120 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); 121 122 static int tcp_keepcnt = TCPTV_KEEPCNT; 123 /* max idle probes */ 124 int tcp_maxpersistidle; 125 /* max idle time in persist */ 126 int tcp_maxidle; 127 128 /* 129 * Tcp protocol timeout routine called every 500 ms. 130 * Updates timestamps used for TCP 131 * causes finite state machine actions if timers expire. 132 */ 133 void 134 tcp_slowtimo() 135 { 136 int s; 137 138 s = splnet(); 139 140 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 141 142 splx(s); 143 } 144 145 /* 146 * Cancel all timers for TCP tp. 147 */ 148 void 149 tcp_canceltimers(tp) 150 struct tcpcb *tp; 151 { 152 callout_stop(tp->tt_2msl); 153 callout_stop(tp->tt_persist); 154 callout_stop(tp->tt_keep); 155 callout_stop(tp->tt_rexmt); 156 } 157 158 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 159 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 160 161 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 162 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 163 164 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 165 166 /* 167 * TCP timer processing. 168 */ 169 170 void 171 tcp_timer_delack(xtp) 172 void *xtp; 173 { 174 struct tcpcb *tp = xtp; 175 int s; 176 struct inpcb *inp; 177 178 s = splnet(); 179 INP_INFO_RLOCK(&tcbinfo); 180 inp = tp->t_inpcb; 181 INP_LOCK(inp); 182 INP_INFO_RUNLOCK(&tcbinfo); 183 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { 184 INP_UNLOCK(inp); 185 splx(s); 186 return; 187 } 188 callout_deactivate(tp->tt_delack); 189 190 tp->t_flags |= TF_ACKNOW; 191 tcpstat.tcps_delack++; 192 (void) tcp_output(tp); 193 INP_UNLOCK(inp); 194 splx(s); 195 } 196 197 void 198 tcp_timer_2msl(xtp) 199 void *xtp; 200 { 201 struct tcpcb *tp = xtp; 202 int s; 203 struct inpcb *inp; 204 #ifdef TCPDEBUG 205 int ostate; 206 207 ostate = tp->t_state; 208 #endif 209 s = splnet(); 210 INP_INFO_WLOCK(&tcbinfo); 211 inp = tp->t_inpcb; 212 INP_LOCK(inp); 213 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { 214 INP_UNLOCK(tp->t_inpcb); 215 INP_INFO_WUNLOCK(&tcbinfo); 216 splx(s); 217 return; 218 } 219 callout_deactivate(tp->tt_2msl); 220 /* 221 * 2 MSL timeout in shutdown went off. If we're closed but 222 * still waiting for peer to close and connection has been idle 223 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 224 * control block. Otherwise, check again in a bit. 225 */ 226 if (tp->t_state != TCPS_TIME_WAIT && 227 (ticks - tp->t_rcvtime) <= tcp_maxidle) 228 callout_reset(tp->tt_2msl, tcp_keepintvl, 229 tcp_timer_2msl, tp); 230 else 231 tp = tcp_close(tp); 232 233 #ifdef TCPDEBUG 234 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 235 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 236 PRU_SLOWTIMO); 237 #endif 238 if (tp) 239 INP_UNLOCK(inp); 240 INP_INFO_WUNLOCK(&tcbinfo); 241 splx(s); 242 } 243 244 void 245 tcp_timer_keep(xtp) 246 void *xtp; 247 { 248 struct tcpcb *tp = xtp; 249 struct tcptemp *t_template; 250 int s; 251 struct inpcb *inp; 252 #ifdef TCPDEBUG 253 int ostate; 254 255 ostate = tp->t_state; 256 #endif 257 s = splnet(); 258 INP_INFO_WLOCK(&tcbinfo); 259 inp = tp->t_inpcb; 260 INP_LOCK(inp); 261 if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) { 262 INP_UNLOCK(inp); 263 INP_INFO_WUNLOCK(&tcbinfo); 264 splx(s); 265 return; 266 } 267 callout_deactivate(tp->tt_keep); 268 /* 269 * Keep-alive timer went off; send something 270 * or drop connection if idle for too long. 271 */ 272 tcpstat.tcps_keeptimeo++; 273 if (tp->t_state < TCPS_ESTABLISHED) 274 goto dropit; 275 if ((always_keepalive || 276 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 277 tp->t_state <= TCPS_CLOSING) { 278 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 279 goto dropit; 280 /* 281 * Send a packet designed to force a response 282 * if the peer is up and reachable: 283 * either an ACK if the connection is still alive, 284 * or an RST if the peer has closed the connection 285 * due to timeout or reboot. 286 * Using sequence number tp->snd_una-1 287 * causes the transmitted zero-length segment 288 * to lie outside the receive window; 289 * by the protocol spec, this requires the 290 * correspondent TCP to respond. 291 */ 292 tcpstat.tcps_keepprobe++; 293 t_template = tcp_maketemplate(tp); 294 if (t_template) { 295 tcp_respond(tp, t_template->tt_ipgen, 296 &t_template->tt_t, (struct mbuf *)NULL, 297 tp->rcv_nxt, tp->snd_una - 1, 0); 298 (void) m_free(dtom(t_template)); 299 } 300 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 301 } else 302 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 303 304 #ifdef TCPDEBUG 305 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 306 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 307 PRU_SLOWTIMO); 308 #endif 309 INP_UNLOCK(inp); 310 INP_INFO_WUNLOCK(&tcbinfo); 311 splx(s); 312 return; 313 314 dropit: 315 tcpstat.tcps_keepdrops++; 316 tp = tcp_drop(tp, ETIMEDOUT); 317 318 #ifdef TCPDEBUG 319 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 320 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 321 PRU_SLOWTIMO); 322 #endif 323 if (tp) 324 INP_UNLOCK(tp->t_inpcb); 325 INP_INFO_WUNLOCK(&tcbinfo); 326 splx(s); 327 } 328 329 void 330 tcp_timer_persist(xtp) 331 void *xtp; 332 { 333 struct tcpcb *tp = xtp; 334 int s; 335 struct inpcb *inp; 336 #ifdef TCPDEBUG 337 int ostate; 338 339 ostate = tp->t_state; 340 #endif 341 s = splnet(); 342 INP_INFO_WLOCK(&tcbinfo); 343 inp = tp->t_inpcb; 344 INP_LOCK(inp); 345 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ 346 INP_UNLOCK(inp); 347 INP_INFO_WUNLOCK(&tcbinfo); 348 splx(s); 349 return; 350 } 351 callout_deactivate(tp->tt_persist); 352 /* 353 * Persistance timer into zero window. 354 * Force a byte to be output, if possible. 355 */ 356 tcpstat.tcps_persisttimeo++; 357 /* 358 * Hack: if the peer is dead/unreachable, we do not 359 * time out if the window is closed. After a full 360 * backoff, drop the connection if the idle time 361 * (no responses to probes) reaches the maximum 362 * backoff that we would use if retransmitting. 363 */ 364 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 365 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 366 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 367 tcpstat.tcps_persistdrop++; 368 tp = tcp_drop(tp, ETIMEDOUT); 369 goto out; 370 } 371 tcp_setpersist(tp); 372 tp->t_force = 1; 373 (void) tcp_output(tp); 374 tp->t_force = 0; 375 376 out: 377 #ifdef TCPDEBUG 378 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 379 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 380 PRU_SLOWTIMO); 381 #endif 382 if (tp) 383 INP_UNLOCK(inp); 384 INP_INFO_WUNLOCK(&tcbinfo); 385 splx(s); 386 } 387 388 void 389 tcp_timer_rexmt(xtp) 390 void *xtp; 391 { 392 struct tcpcb *tp = xtp; 393 int s; 394 int rexmt; 395 int headlocked; 396 struct inpcb *inp; 397 #ifdef TCPDEBUG 398 int ostate; 399 400 ostate = tp->t_state; 401 #endif 402 s = splnet(); 403 INP_INFO_WLOCK(&tcbinfo); 404 headlocked = 1; 405 inp = tp->t_inpcb; 406 INP_LOCK(inp); 407 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { 408 INP_UNLOCK(inp); 409 INP_INFO_WUNLOCK(&tcbinfo); 410 splx(s); 411 return; 412 } 413 callout_deactivate(tp->tt_rexmt); 414 /* 415 * Retransmission timer went off. Message has not 416 * been acked within retransmit interval. Back off 417 * to a longer retransmit interval and retransmit one segment. 418 */ 419 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 420 tp->t_rxtshift = TCP_MAXRXTSHIFT; 421 tcpstat.tcps_timeoutdrop++; 422 tp = tcp_drop(tp, tp->t_softerror ? 423 tp->t_softerror : ETIMEDOUT); 424 goto out; 425 } 426 INP_INFO_WUNLOCK(&tcbinfo); 427 headlocked = 0; 428 if (tp->t_rxtshift == 1) { 429 /* 430 * first retransmit; record ssthresh and cwnd so they can 431 * be recovered if this turns out to be a "bad" retransmit. 432 * A retransmit is considered "bad" if an ACK for this 433 * segment is received within RTT/2 interval; the assumption 434 * here is that the ACK was already in flight. See 435 * "On Estimating End-to-End Network Path Properties" by 436 * Allman and Paxson for more details. 437 */ 438 tp->snd_cwnd_prev = tp->snd_cwnd; 439 tp->snd_ssthresh_prev = tp->snd_ssthresh; 440 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 441 } 442 tcpstat.tcps_rexmttimeo++; 443 if (tp->t_state == TCPS_SYN_SENT) 444 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; 445 else 446 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 447 TCPT_RANGESET(tp->t_rxtcur, rexmt, 448 tp->t_rttmin, TCPTV_REXMTMAX); 449 /* 450 * Disable rfc1323 and rfc1644 if we havn't got any response to 451 * our third SYN to work-around some broken terminal servers 452 * (most of which have hopefully been retired) that have bad VJ 453 * header compression code which trashes TCP segments containing 454 * unknown-to-them TCP options. 455 */ 456 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3)) 457 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC); 458 /* 459 * If losing, let the lower level know and try for 460 * a better route. Also, if we backed off this far, 461 * our srtt estimate is probably bogus. Clobber it 462 * so we'll take the next rtt measurement as our srtt; 463 * move the current srtt into rttvar to keep the current 464 * retransmit times until then. 465 */ 466 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 467 #ifdef INET6 468 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 469 in6_losing(tp->t_inpcb); 470 else 471 #endif 472 in_losing(tp->t_inpcb); 473 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 474 tp->t_srtt = 0; 475 } 476 tp->snd_nxt = tp->snd_una; 477 /* 478 * Note: We overload snd_recover to function also as the 479 * snd_last variable described in RFC 2582 480 */ 481 tp->snd_recover = tp->snd_max; 482 /* 483 * Force a segment to be sent. 484 */ 485 tp->t_flags |= TF_ACKNOW; 486 /* 487 * If timing a segment in this window, stop the timer. 488 */ 489 tp->t_rtttime = 0; 490 /* 491 * Close the congestion window down to one segment 492 * (we'll open it by one segment for each ack we get). 493 * Since we probably have a window's worth of unacked 494 * data accumulated, this "slow start" keeps us from 495 * dumping all that data as back-to-back packets (which 496 * might overwhelm an intermediate gateway). 497 * 498 * There are two phases to the opening: Initially we 499 * open by one mss on each ack. This makes the window 500 * size increase exponentially with time. If the 501 * window is larger than the path can handle, this 502 * exponential growth results in dropped packet(s) 503 * almost immediately. To get more time between 504 * drops but still "push" the network to take advantage 505 * of improving conditions, we switch from exponential 506 * to linear window opening at some threshhold size. 507 * For a threshhold, we use half the current window 508 * size, truncated to a multiple of the mss. 509 * 510 * (the minimum cwnd that will give us exponential 511 * growth is 2 mss. We don't allow the threshhold 512 * to go below this.) 513 */ 514 { 515 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 516 if (win < 2) 517 win = 2; 518 tp->snd_cwnd = tp->t_maxseg; 519 tp->snd_ssthresh = win * tp->t_maxseg; 520 tp->t_dupacks = 0; 521 } 522 (void) tcp_output(tp); 523 524 out: 525 #ifdef TCPDEBUG 526 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 527 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 528 PRU_SLOWTIMO); 529 #endif 530 if (tp) 531 INP_UNLOCK(inp); 532 if (headlocked) 533 INP_INFO_WUNLOCK(&tcbinfo); 534 splx(s); 535 } 536