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/sysctl.h> 45 #include <sys/socket.h> 46 #include <sys/socketvar.h> 47 #include <sys/protosw.h> 48 49 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 50 51 #include <net/route.h> 52 53 #include <netinet/in.h> 54 #include <netinet/in_systm.h> 55 #include <netinet/in_pcb.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_seq.h> 63 #include <netinet/tcp_timer.h> 64 #include <netinet/tcp_var.h> 65 #include <netinet/tcpip.h> 66 #ifdef TCPDEBUG 67 #include <netinet/tcp_debug.h> 68 #endif 69 70 static int 71 sysctl_msec_to_ticks(SYSCTL_HANDLER_ARGS) 72 { 73 int error, s, tt; 74 75 tt = *(int *)oidp->oid_arg1; 76 s = tt * 1000 / hz; 77 78 error = sysctl_handle_int(oidp, &s, 0, req); 79 if (error || !req->newptr) 80 return (error); 81 82 tt = s * hz / 1000; 83 if (tt < 1) 84 return (EINVAL); 85 86 *(int *)oidp->oid_arg1 = tt; 87 return (0); 88 } 89 90 int tcp_keepinit; 91 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, CTLTYPE_INT|CTLFLAG_RW, 92 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", ""); 93 94 int tcp_keepidle; 95 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, CTLTYPE_INT|CTLFLAG_RW, 96 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", ""); 97 98 int tcp_keepintvl; 99 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, CTLTYPE_INT|CTLFLAG_RW, 100 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", ""); 101 102 int tcp_delacktime; 103 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, 104 CTLTYPE_INT|CTLFLAG_RW, &tcp_delacktime, 0, sysctl_msec_to_ticks, "I", 105 "Time before a delayed ACK is sent"); 106 107 int tcp_msl; 108 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW, 109 &tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime"); 110 111 static int always_keepalive = 0; 112 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, 113 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); 114 115 static int tcp_keepcnt = TCPTV_KEEPCNT; 116 /* max idle probes */ 117 int tcp_maxpersistidle; 118 /* max idle time in persist */ 119 int tcp_maxidle; 120 121 /* 122 * Tcp protocol timeout routine called every 500 ms. 123 * Updates timestamps used for TCP 124 * causes finite state machine actions if timers expire. 125 */ 126 void 127 tcp_slowtimo() 128 { 129 int s; 130 131 s = splnet(); 132 133 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 134 135 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 136 #ifdef TCP_COMPAT_42 137 if ((int)tcp_iss < 0) 138 tcp_iss = TCP_ISSINCR; /* XXX */ 139 #endif 140 splx(s); 141 } 142 143 /* 144 * Cancel all timers for TCP tp. 145 */ 146 void 147 tcp_canceltimers(tp) 148 struct tcpcb *tp; 149 { 150 callout_stop(tp->tt_2msl); 151 callout_stop(tp->tt_persist); 152 callout_stop(tp->tt_keep); 153 callout_stop(tp->tt_rexmt); 154 } 155 156 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 157 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 158 159 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 160 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 161 162 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 163 164 /* 165 * TCP timer processing. 166 */ 167 void 168 tcp_timer_delack(xtp) 169 void *xtp; 170 { 171 struct tcpcb *tp = xtp; 172 int s; 173 174 s = splnet(); 175 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { 176 splx(s); 177 return; 178 } 179 callout_deactivate(tp->tt_delack); 180 181 tp->t_flags |= TF_ACKNOW; 182 tcpstat.tcps_delack++; 183 (void) tcp_output(tp); 184 splx(s); 185 } 186 187 void 188 tcp_timer_2msl(xtp) 189 void *xtp; 190 { 191 struct tcpcb *tp = xtp; 192 int s; 193 #ifdef TCPDEBUG 194 int ostate; 195 196 ostate = tp->t_state; 197 #endif 198 s = splnet(); 199 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { 200 splx(s); 201 return; 202 } 203 callout_deactivate(tp->tt_2msl); 204 /* 205 * 2 MSL timeout in shutdown went off. If we're closed but 206 * still waiting for peer to close and connection has been idle 207 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 208 * control block. Otherwise, check again in a bit. 209 */ 210 if (tp->t_state != TCPS_TIME_WAIT && 211 (ticks - tp->t_rcvtime) <= tcp_maxidle) 212 callout_reset(tp->tt_2msl, tcp_keepintvl, 213 tcp_timer_2msl, tp); 214 else 215 tp = tcp_close(tp); 216 217 #ifdef TCPDEBUG 218 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 219 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 220 PRU_SLOWTIMO); 221 #endif 222 splx(s); 223 } 224 225 void 226 tcp_timer_keep(xtp) 227 void *xtp; 228 { 229 struct tcpcb *tp = xtp; 230 int s; 231 #ifdef TCPDEBUG 232 int ostate; 233 234 ostate = tp->t_state; 235 #endif 236 s = splnet(); 237 if (callout_pending(tp->tt_keep) || !callout_active(tp->tt_keep)) { 238 splx(s); 239 return; 240 } 241 callout_deactivate(tp->tt_keep); 242 /* 243 * Keep-alive timer went off; send something 244 * or drop connection if idle for too long. 245 */ 246 tcpstat.tcps_keeptimeo++; 247 if (tp->t_state < TCPS_ESTABLISHED) 248 goto dropit; 249 if ((always_keepalive || 250 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 251 tp->t_state <= TCPS_CLOSING) { 252 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 253 goto dropit; 254 /* 255 * Send a packet designed to force a response 256 * if the peer is up and reachable: 257 * either an ACK if the connection is still alive, 258 * or an RST if the peer has closed the connection 259 * due to timeout or reboot. 260 * Using sequence number tp->snd_una-1 261 * causes the transmitted zero-length segment 262 * to lie outside the receive window; 263 * by the protocol spec, this requires the 264 * correspondent TCP to respond. 265 */ 266 tcpstat.tcps_keepprobe++; 267 #ifdef TCP_COMPAT_42 268 /* 269 * The keepalive packet must have nonzero length 270 * to get a 4.2 host to respond. 271 */ 272 tcp_respond(tp, tp->t_template->tt_ipgen, 273 &tp->t_template->tt_t, (struct mbuf *)NULL, 274 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 275 #else 276 tcp_respond(tp, tp->t_template->tt_ipgen, 277 &tp->t_template->tt_t, (struct mbuf *)NULL, 278 tp->rcv_nxt, tp->snd_una - 1, 0); 279 #endif 280 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 281 } else 282 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 283 284 #ifdef TCPDEBUG 285 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 286 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 287 PRU_SLOWTIMO); 288 #endif 289 splx(s); 290 return; 291 292 dropit: 293 tcpstat.tcps_keepdrops++; 294 tp = tcp_drop(tp, ETIMEDOUT); 295 296 #ifdef TCPDEBUG 297 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 298 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 299 PRU_SLOWTIMO); 300 #endif 301 splx(s); 302 } 303 304 void 305 tcp_timer_persist(xtp) 306 void *xtp; 307 { 308 struct tcpcb *tp = xtp; 309 int s; 310 #ifdef TCPDEBUG 311 int ostate; 312 313 ostate = tp->t_state; 314 #endif 315 s = splnet(); 316 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ 317 splx(s); 318 return; 319 } 320 callout_deactivate(tp->tt_persist); 321 /* 322 * Persistance timer into zero window. 323 * Force a byte to be output, if possible. 324 */ 325 tcpstat.tcps_persisttimeo++; 326 /* 327 * Hack: if the peer is dead/unreachable, we do not 328 * time out if the window is closed. After a full 329 * backoff, drop the connection if the idle time 330 * (no responses to probes) reaches the maximum 331 * backoff that we would use if retransmitting. 332 */ 333 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 334 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 335 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 336 tcpstat.tcps_persistdrop++; 337 tp = tcp_drop(tp, ETIMEDOUT); 338 goto out; 339 } 340 tcp_setpersist(tp); 341 tp->t_force = 1; 342 (void) tcp_output(tp); 343 tp->t_force = 0; 344 345 out: 346 #ifdef TCPDEBUG 347 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 348 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 349 PRU_SLOWTIMO); 350 #endif 351 splx(s); 352 } 353 354 void 355 tcp_timer_rexmt(xtp) 356 void *xtp; 357 { 358 struct tcpcb *tp = xtp; 359 int s; 360 int rexmt; 361 #ifdef TCPDEBUG 362 int ostate; 363 364 ostate = tp->t_state; 365 #endif 366 s = splnet(); 367 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { 368 splx(s); 369 return; 370 } 371 callout_deactivate(tp->tt_rexmt); 372 /* 373 * Retransmission timer went off. Message has not 374 * been acked within retransmit interval. Back off 375 * to a longer retransmit interval and retransmit one segment. 376 */ 377 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 378 tp->t_rxtshift = TCP_MAXRXTSHIFT; 379 tcpstat.tcps_timeoutdrop++; 380 tp = tcp_drop(tp, tp->t_softerror ? 381 tp->t_softerror : ETIMEDOUT); 382 goto out; 383 } 384 if (tp->t_rxtshift == 1) { 385 /* 386 * first retransmit; record ssthresh and cwnd so they can 387 * be recovered if this turns out to be a "bad" retransmit. 388 * A retransmit is considered "bad" if an ACK for this 389 * segment is received within RTT/2 interval; the assumption 390 * here is that the ACK was already in flight. See 391 * "On Estimating End-to-End Network Path Properties" by 392 * Allman and Paxson for more details. 393 */ 394 tp->snd_cwnd_prev = tp->snd_cwnd; 395 tp->snd_ssthresh_prev = tp->snd_ssthresh; 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 * If losing, let the lower level know and try for 407 * a better route. Also, if we backed off this far, 408 * our srtt estimate is probably bogus. Clobber it 409 * so we'll take the next rtt measurement as our srtt; 410 * move the current srtt into rttvar to keep the current 411 * retransmit times until then. 412 */ 413 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 414 #ifdef INET6 415 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 416 in6_losing(tp->t_inpcb); 417 else 418 #endif 419 in_losing(tp->t_inpcb); 420 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 421 tp->t_srtt = 0; 422 } 423 tp->snd_nxt = tp->snd_una; 424 /* 425 * Note: We overload snd_recover to function also as the 426 * snd_last variable described in RFC 2582 427 */ 428 tp->snd_recover = tp->snd_max; 429 /* 430 * Force a segment to be sent. 431 */ 432 tp->t_flags |= TF_ACKNOW; 433 /* 434 * If timing a segment in this window, stop the timer. 435 */ 436 tp->t_rtttime = 0; 437 /* 438 * Close the congestion window down to one segment 439 * (we'll open it by one segment for each ack we get). 440 * Since we probably have a window's worth of unacked 441 * data accumulated, this "slow start" keeps us from 442 * dumping all that data as back-to-back packets (which 443 * might overwhelm an intermediate gateway). 444 * 445 * There are two phases to the opening: Initially we 446 * open by one mss on each ack. This makes the window 447 * size increase exponentially with time. If the 448 * window is larger than the path can handle, this 449 * exponential growth results in dropped packet(s) 450 * almost immediately. To get more time between 451 * drops but still "push" the network to take advantage 452 * of improving conditions, we switch from exponential 453 * to linear window opening at some threshhold size. 454 * For a threshhold, we use half the current window 455 * size, truncated to a multiple of the mss. 456 * 457 * (the minimum cwnd that will give us exponential 458 * growth is 2 mss. We don't allow the threshhold 459 * to go below this.) 460 */ 461 { 462 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 463 if (win < 2) 464 win = 2; 465 tp->snd_cwnd = tp->t_maxseg; 466 tp->snd_ssthresh = win * tp->t_maxseg; 467 tp->t_dupacks = 0; 468 } 469 (void) tcp_output(tp); 470 471 out: 472 #ifdef TCPDEBUG 473 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 474 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 475 PRU_SLOWTIMO); 476 #endif 477 splx(s); 478 } 479