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: src/sys/netinet/tcp_timer.c,v 1.34.2.14 2003/02/03 02:33:41 hsu Exp $ 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 = 0; 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 void 172 tcp_timer_delack(xtp) 173 void *xtp; 174 { 175 struct tcpcb *tp = xtp; 176 int s; 177 178 s = splnet(); 179 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { 180 splx(s); 181 return; 182 } 183 callout_deactivate(tp->tt_delack); 184 185 tp->t_flags |= TF_ACKNOW; 186 tcpstat.tcps_delack++; 187 (void) tcp_output(tp); 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 #ifdef TCPDEBUG 198 int ostate; 199 200 ostate = tp->t_state; 201 #endif 202 s = splnet(); 203 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { 204 splx(s); 205 return; 206 } 207 callout_deactivate(tp->tt_2msl); 208 /* 209 * 2 MSL timeout in shutdown went off. If we're closed but 210 * still waiting for peer to close and connection has been idle 211 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 212 * control block. Otherwise, check again in a bit. 213 */ 214 if (tp->t_state != TCPS_TIME_WAIT && 215 (ticks - tp->t_rcvtime) <= tcp_maxidle) 216 callout_reset(tp->tt_2msl, tcp_keepintvl, 217 tcp_timer_2msl, tp); 218 else 219 tp = tcp_close(tp); 220 221 #ifdef TCPDEBUG 222 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 223 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 224 PRU_SLOWTIMO); 225 #endif 226 splx(s); 227 } 228 229 void 230 tcp_timer_keep(xtp) 231 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 (void) m_free(dtom(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(xtp) 305 void *xtp; 306 { 307 struct tcpcb *tp = xtp; 308 int s; 309 #ifdef TCPDEBUG 310 int ostate; 311 312 ostate = tp->t_state; 313 #endif 314 s = splnet(); 315 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ 316 splx(s); 317 return; 318 } 319 callout_deactivate(tp->tt_persist); 320 /* 321 * Persistance timer into zero window. 322 * Force a byte to be output, if possible. 323 */ 324 tcpstat.tcps_persisttimeo++; 325 /* 326 * Hack: if the peer is dead/unreachable, we do not 327 * time out if the window is closed. After a full 328 * backoff, drop the connection if the idle time 329 * (no responses to probes) reaches the maximum 330 * backoff that we would use if retransmitting. 331 */ 332 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 333 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 334 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 335 tcpstat.tcps_persistdrop++; 336 tp = tcp_drop(tp, ETIMEDOUT); 337 goto out; 338 } 339 tcp_setpersist(tp); 340 tp->t_force = 1; 341 (void) tcp_output(tp); 342 tp->t_force = 0; 343 344 out: 345 #ifdef TCPDEBUG 346 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 347 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 348 PRU_SLOWTIMO); 349 #endif 350 splx(s); 351 } 352 353 void 354 tcp_timer_rexmt(xtp) 355 void *xtp; 356 { 357 struct tcpcb *tp = xtp; 358 int s; 359 int rexmt; 360 #ifdef TCPDEBUG 361 int ostate; 362 363 ostate = tp->t_state; 364 #endif 365 s = splnet(); 366 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { 367 splx(s); 368 return; 369 } 370 callout_deactivate(tp->tt_rexmt); 371 /* 372 * Retransmission timer went off. Message has not 373 * been acked within retransmit interval. Back off 374 * to a longer retransmit interval and retransmit one segment. 375 */ 376 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 377 tp->t_rxtshift = TCP_MAXRXTSHIFT; 378 tcpstat.tcps_timeoutdrop++; 379 tp = tcp_drop(tp, tp->t_softerror ? 380 tp->t_softerror : ETIMEDOUT); 381 goto out; 382 } 383 if (tp->t_rxtshift == 1) { 384 /* 385 * first retransmit; record ssthresh and cwnd so they can 386 * be recovered if this turns out to be a "bad" retransmit. 387 * A retransmit is considered "bad" if an ACK for this 388 * segment is received within RTT/2 interval; the assumption 389 * here is that the ACK was already in flight. See 390 * "On Estimating End-to-End Network Path Properties" by 391 * Allman and Paxson for more details. 392 */ 393 tp->snd_cwnd_prev = tp->snd_cwnd; 394 tp->snd_ssthresh_prev = tp->snd_ssthresh; 395 tp->snd_high_prev = tp->snd_high; 396 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 397 } 398 tcpstat.tcps_rexmttimeo++; 399 if (tp->t_state == TCPS_SYN_SENT) 400 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; 401 else 402 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 403 TCPT_RANGESET(tp->t_rxtcur, rexmt, 404 tp->t_rttmin, TCPTV_REXMTMAX); 405 /* 406 * Disable rfc1323 and rfc1644 if we havn't got any response to 407 * our third SYN to work-around some broken terminal servers 408 * (most of which have hopefully been retired) that have bad VJ 409 * header compression code which trashes TCP segments containing 410 * unknown-to-them TCP options. 411 */ 412 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3)) 413 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC); 414 /* 415 * If losing, let the lower level know and try for 416 * a better route. Also, if we backed off this far, 417 * our srtt estimate is probably bogus. Clobber it 418 * so we'll take the next rtt measurement as our srtt; 419 * move the current srtt into rttvar to keep the current 420 * retransmit times until then. 421 */ 422 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 423 #ifdef INET6 424 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 425 in6_losing(tp->t_inpcb); 426 else 427 #endif 428 in_losing(tp->t_inpcb); 429 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 430 tp->t_srtt = 0; 431 } 432 tp->snd_nxt = tp->snd_una; 433 tp->snd_high = tp->snd_max; 434 /* 435 * Force a segment to be sent. 436 */ 437 tp->t_flags |= TF_ACKNOW; 438 /* 439 * If timing a segment in this window, stop the timer. 440 */ 441 tp->t_rtttime = 0; 442 /* 443 * Close the congestion window down to one segment 444 * (we'll open it by one segment for each ack we get). 445 * Since we probably have a window's worth of unacked 446 * data accumulated, this "slow start" keeps us from 447 * dumping all that data as back-to-back packets (which 448 * might overwhelm an intermediate gateway). 449 * 450 * There are two phases to the opening: Initially we 451 * open by one mss on each ack. This makes the window 452 * size increase exponentially with time. If the 453 * window is larger than the path can handle, this 454 * exponential growth results in dropped packet(s) 455 * almost immediately. To get more time between 456 * drops but still "push" the network to take advantage 457 * of improving conditions, we switch from exponential 458 * to linear window opening at some threshhold size. 459 * For a threshhold, we use half the current window 460 * size, truncated to a multiple of the mss. 461 * 462 * (the minimum cwnd that will give us exponential 463 * growth is 2 mss. We don't allow the threshhold 464 * to go below this.) 465 */ 466 { 467 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 468 if (win < 2) 469 win = 2; 470 tp->snd_cwnd = tp->t_maxseg; 471 tp->snd_ssthresh = win * tp->t_maxseg; 472 tp->t_dupacks = 0; 473 } 474 (void) tcp_output(tp); 475 476 out: 477 #ifdef TCPDEBUG 478 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 479 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 480 PRU_SLOWTIMO); 481 #endif 482 splx(s); 483 } 484