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 1.7 2004/04/07 17:01:25 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() 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(tp) 156 struct tcpcb *tp; 157 { 158 callout_stop(tp->tt_2msl); 159 callout_stop(tp->tt_persist); 160 callout_stop(tp->tt_keep); 161 callout_stop(tp->tt_rexmt); 162 } 163 164 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 165 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 166 167 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 168 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 169 170 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 171 172 /* 173 * TCP timer processing. 174 */ 175 void 176 tcp_timer_delack(xtp) 177 void *xtp; 178 { 179 struct tcpcb *tp = xtp; 180 int s; 181 182 s = splnet(); 183 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { 184 splx(s); 185 return; 186 } 187 callout_deactivate(tp->tt_delack); 188 189 tp->t_flags |= TF_ACKNOW; 190 tcpstat.tcps_delack++; 191 (void) tcp_output(tp); 192 splx(s); 193 } 194 195 void 196 tcp_timer_2msl(xtp) 197 void *xtp; 198 { 199 struct tcpcb *tp = xtp; 200 int s; 201 #ifdef TCPDEBUG 202 int ostate; 203 204 ostate = tp->t_state; 205 #endif 206 s = splnet(); 207 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { 208 splx(s); 209 return; 210 } 211 callout_deactivate(tp->tt_2msl); 212 /* 213 * 2 MSL timeout in shutdown went off. If we're closed but 214 * still waiting for peer to close and connection has been idle 215 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 216 * control block. Otherwise, check again in a bit. 217 */ 218 if (tp->t_state != TCPS_TIME_WAIT && 219 (ticks - tp->t_rcvtime) <= tcp_maxidle) 220 callout_reset(tp->tt_2msl, tcp_keepintvl, 221 tcp_timer_2msl, tp); 222 else 223 tp = tcp_close(tp); 224 225 #ifdef TCPDEBUG 226 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 227 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 228 PRU_SLOWTIMO); 229 #endif 230 splx(s); 231 } 232 233 void 234 tcp_timer_keep(xtp) 235 void *xtp; 236 { 237 struct tcpcb *tp = xtp; 238 struct tcptemp *t_template; 239 int s; 240 #ifdef TCPDEBUG 241 int ostate; 242 243 ostate = tp->t_state; 244 #endif 245 s = splnet(); 246 if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) { 247 splx(s); 248 return; 249 } 250 callout_deactivate(tp->tt_keep); 251 /* 252 * Keep-alive timer went off; send something 253 * or drop connection if idle for too long. 254 */ 255 tcpstat.tcps_keeptimeo++; 256 if (tp->t_state < TCPS_ESTABLISHED) 257 goto dropit; 258 if ((always_keepalive || 259 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 260 tp->t_state <= TCPS_CLOSING) { 261 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 262 goto dropit; 263 /* 264 * Send a packet designed to force a response 265 * if the peer is up and reachable: 266 * either an ACK if the connection is still alive, 267 * or an RST if the peer has closed the connection 268 * due to timeout or reboot. 269 * Using sequence number tp->snd_una-1 270 * causes the transmitted zero-length segment 271 * to lie outside the receive window; 272 * by the protocol spec, this requires the 273 * correspondent TCP to respond. 274 */ 275 tcpstat.tcps_keepprobe++; 276 t_template = tcp_maketemplate(tp); 277 if (t_template) { 278 tcp_respond(tp, t_template->tt_ipgen, 279 &t_template->tt_t, (struct mbuf *)NULL, 280 tp->rcv_nxt, tp->snd_una - 1, 0); 281 (void) m_free(dtom(t_template)); 282 } 283 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 284 } else 285 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 286 287 #ifdef TCPDEBUG 288 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 289 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 290 PRU_SLOWTIMO); 291 #endif 292 splx(s); 293 return; 294 295 dropit: 296 tcpstat.tcps_keepdrops++; 297 tp = tcp_drop(tp, ETIMEDOUT); 298 299 #ifdef TCPDEBUG 300 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 301 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 302 PRU_SLOWTIMO); 303 #endif 304 splx(s); 305 } 306 307 void 308 tcp_timer_persist(xtp) 309 void *xtp; 310 { 311 struct tcpcb *tp = xtp; 312 int s; 313 #ifdef TCPDEBUG 314 int ostate; 315 316 ostate = tp->t_state; 317 #endif 318 s = splnet(); 319 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ 320 splx(s); 321 return; 322 } 323 callout_deactivate(tp->tt_persist); 324 /* 325 * Persistance timer into zero window. 326 * Force a byte to be output, if possible. 327 */ 328 tcpstat.tcps_persisttimeo++; 329 /* 330 * Hack: if the peer is dead/unreachable, we do not 331 * time out if the window is closed. After a full 332 * backoff, drop the connection if the idle time 333 * (no responses to probes) reaches the maximum 334 * backoff that we would use if retransmitting. 335 */ 336 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 337 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 338 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 339 tcpstat.tcps_persistdrop++; 340 tp = tcp_drop(tp, ETIMEDOUT); 341 goto out; 342 } 343 tcp_setpersist(tp); 344 tp->t_force = 1; 345 (void) tcp_output(tp); 346 tp->t_force = 0; 347 348 out: 349 #ifdef TCPDEBUG 350 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 351 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 352 PRU_SLOWTIMO); 353 #endif 354 splx(s); 355 } 356 357 void 358 tcp_save_congestion_state(struct tcpcb *tp) 359 { 360 tp->snd_cwnd_prev = tp->snd_cwnd; 361 tp->snd_ssthresh_prev = tp->snd_ssthresh; 362 tp->snd_recover_prev = tp->snd_recover; 363 if (IN_FASTRECOVERY(tp)) 364 tp->t_flags |= TF_WASFRECOVERY; 365 else 366 tp->t_flags &= ~TF_WASFRECOVERY; 367 if (tp->t_flags & TF_RCVD_TSTMP) { 368 tp->t_rexmtTS = ticks; 369 tp->t_flags |= TF_FIRSTACCACK; 370 } 371 } 372 373 void 374 tcp_revert_congestion_state(struct tcpcb *tp) 375 { 376 tp->snd_cwnd = tp->snd_cwnd_prev; 377 tp->snd_ssthresh = tp->snd_ssthresh_prev; 378 tp->snd_recover = tp->snd_recover_prev; 379 if (tp->t_flags & TF_WASFRECOVERY) 380 ENTER_FASTRECOVERY(tp); 381 if (tp->t_flags & TF_FASTREXMT) { 382 ++tcpstat.tcps_sndfastrexmitbad; 383 if (tp->t_flags & TF_EARLYREXMT) 384 ++tcpstat.tcps_sndearlyrexmitbad; 385 } else 386 ++tcpstat.tcps_sndrtobad; 387 tp->t_badrxtwin = 0; 388 tp->t_rxtshift = 0; 389 tp->snd_nxt = tp->snd_max; 390 } 391 392 void 393 tcp_timer_rexmt(xtp) 394 void *xtp; 395 { 396 struct tcpcb *tp = xtp; 397 int s; 398 int rexmt; 399 #ifdef TCPDEBUG 400 int ostate; 401 402 ostate = tp->t_state; 403 #endif 404 s = splnet(); 405 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { 406 splx(s); 407 return; 408 } 409 callout_deactivate(tp->tt_rexmt); 410 /* 411 * Retransmission timer went off. Message has not 412 * been acked within retransmit interval. Back off 413 * to a longer retransmit interval and retransmit one segment. 414 */ 415 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 416 tp->t_rxtshift = TCP_MAXRXTSHIFT; 417 tcpstat.tcps_timeoutdrop++; 418 tp = tcp_drop(tp, tp->t_softerror ? 419 tp->t_softerror : ETIMEDOUT); 420 goto out; 421 } 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->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 433 tcp_save_congestion_state(tp); 434 tp->t_flags &= ~(TF_FASTREXMT | TF_EARLYREXMT); 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 tp->snd_recover = tp->snd_max; 472 /* 473 * Force a segment to be sent. 474 */ 475 tp->t_flags |= TF_ACKNOW; 476 /* 477 * If timing a segment in this window, stop the timer. 478 */ 479 tp->t_rtttime = 0; 480 /* 481 * Close the congestion window down to one segment 482 * (we'll open it by one segment for each ack we get). 483 * Since we probably have a window's worth of unacked 484 * data accumulated, this "slow start" keeps us from 485 * dumping all that data as back-to-back packets (which 486 * might overwhelm an intermediate gateway). 487 * 488 * There are two phases to the opening: Initially we 489 * open by one mss on each ack. This makes the window 490 * size increase exponentially with time. If the 491 * window is larger than the path can handle, this 492 * exponential growth results in dropped packet(s) 493 * almost immediately. To get more time between 494 * drops but still "push" the network to take advantage 495 * of improving conditions, we switch from exponential 496 * to linear window opening at some threshhold size. 497 * For a threshhold, we use half the current window 498 * size, truncated to a multiple of the mss. 499 * 500 * (the minimum cwnd that will give us exponential 501 * growth is 2 mss. We don't allow the threshhold 502 * to go below this.) 503 */ 504 { 505 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 506 if (win < 2) 507 win = 2; 508 tp->snd_cwnd = tp->t_maxseg; 509 tp->snd_ssthresh = win * tp->t_maxseg; 510 tp->t_dupacks = 0; 511 } 512 EXIT_FASTRECOVERY(tp); 513 (void) tcp_output(tp); 514 515 out: 516 #ifdef TCPDEBUG 517 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 518 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 519 PRU_SLOWTIMO); 520 #endif 521 splx(s); 522 } 523