1 /* 2 * Copyright (c) 2003-2004 Jeffrey Hsu. All rights reserved. 3 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 4 * The Regents of the University of California. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 3. All advertising materials mentioning features or use of this software 15 * must display the following acknowledgement: 16 * This product includes software developed by the University of 17 * California, Berkeley and its contributors. 18 * 4. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95 35 * $FreeBSD: src/sys/netinet/tcp_timer.c,v 1.34.2.14 2003/02/03 02:33:41 hsu Exp $ 36 * $DragonFly: src/sys/netinet/tcp_timer.c,v 1.10 2004/06/04 04:32:23 dillon Exp $ 37 */ 38 39 #include "opt_compat.h" 40 #include "opt_inet6.h" 41 #include "opt_tcpdebug.h" 42 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/kernel.h> 46 #include <sys/mbuf.h> 47 #include <sys/sysctl.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/protosw.h> 51 #include <sys/thread.h> 52 #include <sys/globaldata.h> 53 54 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 55 56 #include <net/route.h> 57 58 #include <netinet/in.h> 59 #include <netinet/in_systm.h> 60 #include <netinet/in_pcb.h> 61 #ifdef INET6 62 #include <netinet6/in6_pcb.h> 63 #endif 64 #include <netinet/ip_var.h> 65 #include <netinet/tcp.h> 66 #include <netinet/tcp_fsm.h> 67 #include <netinet/tcp_seq.h> 68 #include <netinet/tcp_timer.h> 69 #include <netinet/tcp_var.h> 70 #include <netinet/tcpip.h> 71 #ifdef TCPDEBUG 72 #include <netinet/tcp_debug.h> 73 #endif 74 75 static int 76 sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS) 77 { 78 int error, s, tt; 79 80 tt = *(int *)oidp->oid_arg1; 81 s = (int)((int64_t)tt * 1000 / hz); 82 83 error = sysctl_handle_int(oidp, &s, 0, req); 84 if (error || !req->newptr) 85 return (error); 86 87 tt = (int)((int64_t)s * hz / 1000); 88 if (tt < 1) 89 return (EINVAL); 90 91 *(int *)oidp->oid_arg1 = tt; 92 return (0); 93 } 94 95 int tcp_keepinit; 96 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW, 97 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", ""); 98 99 int tcp_keepidle; 100 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW, 101 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", ""); 102 103 int tcp_keepintvl; 104 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW, 105 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", ""); 106 107 int tcp_delacktime; 108 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, 109 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I", 110 "Time before a delayed ACK is sent"); 111 112 int tcp_msl; 113 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW, 114 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime"); 115 116 int tcp_rexmit_min; 117 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW, 118 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout"); 119 120 int tcp_rexmit_slop; 121 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW, 122 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", "Retransmission Timer Slop"); 123 124 static int always_keepalive = 0; 125 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, 126 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); 127 128 static int tcp_keepcnt = TCPTV_KEEPCNT; 129 /* max idle probes */ 130 int tcp_maxpersistidle; 131 /* max idle time in persist */ 132 int tcp_maxidle; 133 134 /* 135 * Tcp protocol timeout routine called every 500 ms. 136 * Updates timestamps used for TCP 137 * causes finite state machine actions if timers expire. 138 */ 139 void 140 tcp_slowtimo(void) 141 { 142 int s; 143 144 s = splnet(); 145 146 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 147 148 splx(s); 149 } 150 151 /* 152 * Cancel all timers for TCP tp. 153 */ 154 void 155 tcp_canceltimers(struct tcpcb *tp) 156 { 157 callout_stop(tp->tt_2msl); 158 callout_stop(tp->tt_persist); 159 callout_stop(tp->tt_keep); 160 callout_stop(tp->tt_rexmt); 161 } 162 163 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 164 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 165 166 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 167 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 168 169 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 170 171 /* 172 * TCP timer processing. 173 */ 174 void 175 tcp_timer_delack(void *xtp) 176 { 177 struct tcpcb *tp = xtp; 178 int s; 179 180 s = splnet(); 181 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { 182 splx(s); 183 return; 184 } 185 callout_deactivate(tp->tt_delack); 186 187 tp->t_flags |= TF_ACKNOW; 188 tcpstat.tcps_delack++; 189 (void) tcp_output(tp); 190 splx(s); 191 } 192 193 void 194 tcp_timer_2msl(void *xtp) 195 { 196 struct tcpcb *tp = xtp; 197 int s; 198 #ifdef TCPDEBUG 199 int ostate; 200 201 ostate = tp->t_state; 202 #endif 203 s = splnet(); 204 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { 205 splx(s); 206 return; 207 } 208 callout_deactivate(tp->tt_2msl); 209 /* 210 * 2 MSL timeout in shutdown went off. If we're closed but 211 * still waiting for peer to close and connection has been idle 212 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 213 * control block. Otherwise, check again in a bit. 214 */ 215 if (tp->t_state != TCPS_TIME_WAIT && 216 (ticks - tp->t_rcvtime) <= tcp_maxidle) 217 callout_reset(tp->tt_2msl, tcp_keepintvl, 218 tcp_timer_2msl, tp); 219 else 220 tp = tcp_close(tp); 221 222 #ifdef TCPDEBUG 223 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 224 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 225 PRU_SLOWTIMO); 226 #endif 227 splx(s); 228 } 229 230 void 231 tcp_timer_keep(void *xtp) 232 { 233 struct tcpcb *tp = xtp; 234 struct tcptemp *t_template; 235 int s; 236 #ifdef TCPDEBUG 237 int ostate; 238 239 ostate = tp->t_state; 240 #endif 241 s = splnet(); 242 if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) { 243 splx(s); 244 return; 245 } 246 callout_deactivate(tp->tt_keep); 247 /* 248 * Keep-alive timer went off; send something 249 * or drop connection if idle for too long. 250 */ 251 tcpstat.tcps_keeptimeo++; 252 if (tp->t_state < TCPS_ESTABLISHED) 253 goto dropit; 254 if ((always_keepalive || 255 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 256 tp->t_state <= TCPS_CLOSING) { 257 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 258 goto dropit; 259 /* 260 * Send a packet designed to force a response 261 * if the peer is up and reachable: 262 * either an ACK if the connection is still alive, 263 * or an RST if the peer has closed the connection 264 * due to timeout or reboot. 265 * Using sequence number tp->snd_una-1 266 * causes the transmitted zero-length segment 267 * to lie outside the receive window; 268 * by the protocol spec, this requires the 269 * correspondent TCP to respond. 270 */ 271 tcpstat.tcps_keepprobe++; 272 t_template = tcp_maketemplate(tp); 273 if (t_template) { 274 tcp_respond(tp, t_template->tt_ipgen, 275 &t_template->tt_t, (struct mbuf *)NULL, 276 tp->rcv_nxt, tp->snd_una - 1, 0); 277 tcp_freetemplate(t_template); 278 } 279 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 280 } else 281 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 282 283 #ifdef TCPDEBUG 284 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 285 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 286 PRU_SLOWTIMO); 287 #endif 288 splx(s); 289 return; 290 291 dropit: 292 tcpstat.tcps_keepdrops++; 293 tp = tcp_drop(tp, ETIMEDOUT); 294 295 #ifdef TCPDEBUG 296 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 297 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 298 PRU_SLOWTIMO); 299 #endif 300 splx(s); 301 } 302 303 void 304 tcp_timer_persist(void *xtp) 305 { 306 struct tcpcb *tp = xtp; 307 int s; 308 #ifdef TCPDEBUG 309 int ostate; 310 311 ostate = tp->t_state; 312 #endif 313 s = splnet(); 314 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ 315 splx(s); 316 return; 317 } 318 callout_deactivate(tp->tt_persist); 319 /* 320 * Persistance timer into zero window. 321 * Force a byte to be output, if possible. 322 */ 323 tcpstat.tcps_persisttimeo++; 324 /* 325 * Hack: if the peer is dead/unreachable, we do not 326 * time out if the window is closed. After a full 327 * backoff, drop the connection if the idle time 328 * (no responses to probes) reaches the maximum 329 * backoff that we would use if retransmitting. 330 */ 331 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 332 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 333 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 334 tcpstat.tcps_persistdrop++; 335 tp = tcp_drop(tp, ETIMEDOUT); 336 goto out; 337 } 338 tcp_setpersist(tp); 339 tp->t_flags |= TF_FORCE; 340 (void) tcp_output(tp); 341 tp->t_flags &= ~TF_FORCE; 342 343 out: 344 #ifdef TCPDEBUG 345 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 346 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 347 PRU_SLOWTIMO); 348 #endif 349 splx(s); 350 } 351 352 void 353 tcp_save_congestion_state(struct tcpcb *tp) 354 { 355 tp->snd_cwnd_prev = tp->snd_cwnd; 356 tp->snd_ssthresh_prev = tp->snd_ssthresh; 357 tp->snd_recover_prev = tp->snd_recover; 358 if (IN_FASTRECOVERY(tp)) 359 tp->t_flags |= TF_WASFRECOVERY; 360 else 361 tp->t_flags &= ~TF_WASFRECOVERY; 362 if (tp->t_flags & TF_RCVD_TSTMP) { 363 tp->t_rexmtTS = ticks; 364 tp->t_flags |= TF_FIRSTACCACK; 365 } 366 } 367 368 void 369 tcp_revert_congestion_state(struct tcpcb *tp) 370 { 371 tp->snd_cwnd = tp->snd_cwnd_prev; 372 tp->snd_ssthresh = tp->snd_ssthresh_prev; 373 tp->snd_recover = tp->snd_recover_prev; 374 if (tp->t_flags & TF_WASFRECOVERY) 375 ENTER_FASTRECOVERY(tp); 376 if (tp->t_flags & TF_FASTREXMT) { 377 ++tcpstat.tcps_sndfastrexmitbad; 378 if (tp->t_flags & TF_EARLYREXMT) 379 ++tcpstat.tcps_sndearlyrexmitbad; 380 } else 381 ++tcpstat.tcps_sndrtobad; 382 tp->t_badrxtwin = 0; 383 tp->t_rxtshift = 0; 384 tp->snd_nxt = tp->snd_max; 385 } 386 387 void 388 tcp_timer_rexmt(void *xtp) 389 { 390 struct tcpcb *tp = xtp; 391 int s; 392 int rexmt; 393 #ifdef TCPDEBUG 394 int ostate; 395 396 ostate = tp->t_state; 397 #endif 398 s = splnet(); 399 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { 400 splx(s); 401 return; 402 } 403 callout_deactivate(tp->tt_rexmt); 404 /* 405 * Retransmission timer went off. Message has not 406 * been acked within retransmit interval. Back off 407 * to a longer retransmit interval and retransmit one segment. 408 */ 409 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 410 tp->t_rxtshift = TCP_MAXRXTSHIFT; 411 tcpstat.tcps_timeoutdrop++; 412 tp = tcp_drop(tp, tp->t_softerror ? 413 tp->t_softerror : ETIMEDOUT); 414 goto out; 415 } 416 if (tp->t_rxtshift == 1) { 417 /* 418 * first retransmit; record ssthresh and cwnd so they can 419 * be recovered if this turns out to be a "bad" retransmit. 420 * A retransmit is considered "bad" if an ACK for this 421 * segment is received within RTT/2 interval; the assumption 422 * here is that the ACK was already in flight. See 423 * "On Estimating End-to-End Network Path Properties" by 424 * Allman and Paxson for more details. 425 */ 426 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 427 tcp_save_congestion_state(tp); 428 tp->t_flags &= ~(TF_FASTREXMT | TF_EARLYREXMT); 429 } 430 tcpstat.tcps_rexmttimeo++; 431 if (tp->t_state == TCPS_SYN_SENT) 432 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; 433 else 434 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 435 TCPT_RANGESET(tp->t_rxtcur, rexmt, 436 tp->t_rttmin, TCPTV_REXMTMAX); 437 /* 438 * Disable rfc1323 and rfc1644 if we havn't got any response to 439 * our third SYN to work-around some broken terminal servers 440 * (most of which have hopefully been retired) that have bad VJ 441 * header compression code which trashes TCP segments containing 442 * unknown-to-them TCP options. 443 */ 444 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3)) 445 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC); 446 /* 447 * If losing, let the lower level know and try for 448 * a better route. Also, if we backed off this far, 449 * our srtt estimate is probably bogus. Clobber it 450 * so we'll take the next rtt measurement as our srtt; 451 * move the current srtt into rttvar to keep the current 452 * retransmit times until then. 453 */ 454 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 455 #ifdef INET6 456 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 457 in6_losing(tp->t_inpcb); 458 else 459 #endif 460 in_losing(tp->t_inpcb); 461 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 462 tp->t_srtt = 0; 463 } 464 tp->snd_nxt = tp->snd_una; 465 tp->snd_recover = tp->snd_max; 466 /* 467 * Force a segment to be sent. 468 */ 469 tp->t_flags |= TF_ACKNOW; 470 /* 471 * If timing a segment in this window, stop the timer. 472 */ 473 tp->t_rtttime = 0; 474 /* 475 * Close the congestion window down to one segment 476 * (we'll open it by one segment for each ack we get). 477 * Since we probably have a window's worth of unacked 478 * data accumulated, this "slow start" keeps us from 479 * dumping all that data as back-to-back packets (which 480 * might overwhelm an intermediate gateway). 481 * 482 * There are two phases to the opening: Initially we 483 * open by one mss on each ack. This makes the window 484 * size increase exponentially with time. If the 485 * window is larger than the path can handle, this 486 * exponential growth results in dropped packet(s) 487 * almost immediately. To get more time between 488 * drops but still "push" the network to take advantage 489 * of improving conditions, we switch from exponential 490 * to linear window opening at some threshhold size. 491 * For a threshhold, we use half the current window 492 * size, truncated to a multiple of the mss. 493 * 494 * (the minimum cwnd that will give us exponential 495 * growth is 2 mss. We don't allow the threshhold 496 * to go below this.) 497 */ 498 { 499 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 500 if (win < 2) 501 win = 2; 502 tp->snd_cwnd = tp->t_maxseg; 503 tp->snd_ssthresh = win * tp->t_maxseg; 504 tp->t_dupacks = 0; 505 } 506 EXIT_FASTRECOVERY(tp); 507 (void) tcp_output(tp); 508 509 out: 510 #ifdef TCPDEBUG 511 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 512 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 513 PRU_SLOWTIMO); 514 #endif 515 splx(s); 516 } 517