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_backoff[TCP_MAXRXTSHIFT + 1] = 157 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 158 159 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 160 161 /* 162 * TCP timer processing. 163 */ 164 void 165 tcp_timer_delack(xtp) 166 void *xtp; 167 { 168 struct tcpcb *tp = xtp; 169 int s; 170 171 s = splnet(); 172 if (callout_pending(tp->tt_delack)) { 173 splx(s); 174 return; 175 } 176 callout_deactivate(tp->tt_delack); 177 178 tp->t_flags |= TF_ACKNOW; 179 tcpstat.tcps_delack++; 180 (void) tcp_output(tp); 181 splx(s); 182 } 183 184 void 185 tcp_timer_2msl(xtp) 186 void *xtp; 187 { 188 struct tcpcb *tp = xtp; 189 int s; 190 #ifdef TCPDEBUG 191 int ostate; 192 193 ostate = tp->t_state; 194 #endif 195 s = splnet(); 196 if (callout_pending(tp->tt_2msl)) { 197 splx(s); 198 return; 199 } 200 callout_deactivate(tp->tt_2msl); 201 /* 202 * 2 MSL timeout in shutdown went off. If we're closed but 203 * still waiting for peer to close and connection has been idle 204 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 205 * control block. Otherwise, check again in a bit. 206 */ 207 if (tp->t_state != TCPS_TIME_WAIT && 208 (ticks - tp->t_rcvtime) <= tcp_maxidle) 209 callout_reset(tp->tt_2msl, tcp_keepintvl, 210 tcp_timer_2msl, tp); 211 else 212 tp = tcp_close(tp); 213 214 #ifdef TCPDEBUG 215 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 216 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 217 PRU_SLOWTIMO); 218 #endif 219 splx(s); 220 } 221 222 void 223 tcp_timer_keep(xtp) 224 void *xtp; 225 { 226 struct tcpcb *tp = xtp; 227 int s; 228 #ifdef TCPDEBUG 229 int ostate; 230 231 ostate = tp->t_state; 232 #endif 233 s = splnet(); 234 if (callout_pending(tp->tt_keep)) { 235 splx(s); 236 return; 237 } 238 callout_deactivate(tp->tt_keep); 239 /* 240 * Keep-alive timer went off; send something 241 * or drop connection if idle for too long. 242 */ 243 tcpstat.tcps_keeptimeo++; 244 if (tp->t_state < TCPS_ESTABLISHED) 245 goto dropit; 246 if ((always_keepalive || 247 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 248 tp->t_state <= TCPS_CLOSING) { 249 if ((ticks - tp->t_rcvtime) >= tcp_keepidle + tcp_maxidle) 250 goto dropit; 251 /* 252 * Send a packet designed to force a response 253 * if the peer is up and reachable: 254 * either an ACK if the connection is still alive, 255 * or an RST if the peer has closed the connection 256 * due to timeout or reboot. 257 * Using sequence number tp->snd_una-1 258 * causes the transmitted zero-length segment 259 * to lie outside the receive window; 260 * by the protocol spec, this requires the 261 * correspondent TCP to respond. 262 */ 263 tcpstat.tcps_keepprobe++; 264 #ifdef TCP_COMPAT_42 265 /* 266 * The keepalive packet must have nonzero length 267 * to get a 4.2 host to respond. 268 */ 269 tcp_respond(tp, tp->t_template->tt_ipgen, 270 &tp->t_template->tt_t, (struct mbuf *)NULL, 271 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 272 #else 273 tcp_respond(tp, tp->t_template->tt_ipgen, 274 &tp->t_template->tt_t, (struct mbuf *)NULL, 275 tp->rcv_nxt, tp->snd_una - 1, 0); 276 #endif 277 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 278 } else 279 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 280 281 #ifdef TCPDEBUG 282 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 283 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 284 PRU_SLOWTIMO); 285 #endif 286 splx(s); 287 return; 288 289 dropit: 290 tcpstat.tcps_keepdrops++; 291 tp = tcp_drop(tp, ETIMEDOUT); 292 293 #ifdef TCPDEBUG 294 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 295 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 296 PRU_SLOWTIMO); 297 #endif 298 splx(s); 299 } 300 301 void 302 tcp_timer_persist(xtp) 303 void *xtp; 304 { 305 struct tcpcb *tp = xtp; 306 int s; 307 #ifdef TCPDEBUG 308 int ostate; 309 310 ostate = tp->t_state; 311 #endif 312 s = splnet(); 313 if (callout_pending(tp->tt_persist)) { 314 splx(s); 315 return; 316 } 317 callout_deactivate(tp->tt_persist); 318 /* 319 * Persistance timer into zero window. 320 * Force a byte to be output, if possible. 321 */ 322 tcpstat.tcps_persisttimeo++; 323 /* 324 * Hack: if the peer is dead/unreachable, we do not 325 * time out if the window is closed. After a full 326 * backoff, drop the connection if the idle time 327 * (no responses to probes) reaches the maximum 328 * backoff that we would use if retransmitting. 329 */ 330 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 331 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 332 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 333 tcpstat.tcps_persistdrop++; 334 tp = tcp_drop(tp, ETIMEDOUT); 335 goto out; 336 } 337 tcp_setpersist(tp); 338 tp->t_force = 1; 339 (void) tcp_output(tp); 340 tp->t_force = 0; 341 342 out: 343 #ifdef TCPDEBUG 344 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 345 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 346 PRU_SLOWTIMO); 347 #endif 348 splx(s); 349 } 350 351 void 352 tcp_timer_rexmt(xtp) 353 void *xtp; 354 { 355 struct tcpcb *tp = xtp; 356 int s; 357 int rexmt; 358 #ifdef TCPDEBUG 359 int ostate; 360 361 ostate = tp->t_state; 362 #endif 363 s = splnet(); 364 if (callout_pending(tp->tt_rexmt)) { 365 splx(s); 366 return; 367 } 368 callout_deactivate(tp->tt_rexmt); 369 /* 370 * Retransmission timer went off. Message has not 371 * been acked within retransmit interval. Back off 372 * to a longer retransmit interval and retransmit one segment. 373 */ 374 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 375 tp->t_rxtshift = TCP_MAXRXTSHIFT; 376 tcpstat.tcps_timeoutdrop++; 377 tp = tcp_drop(tp, tp->t_softerror ? 378 tp->t_softerror : ETIMEDOUT); 379 goto out; 380 } 381 if (tp->t_rxtshift == 1) { 382 /* 383 * first retransmit; record ssthresh and cwnd so they can 384 * be recovered if this turns out to be a "bad" retransmit. 385 * A retransmit is considered "bad" if an ACK for this 386 * segment is received within RTT/2 interval; the assumption 387 * here is that the ACK was already in flight. See 388 * "On Estimating End-to-End Network Path Properties" by 389 * Allman and Paxson for more details. 390 */ 391 tp->snd_cwnd_prev = tp->snd_cwnd; 392 tp->snd_ssthresh_prev = tp->snd_ssthresh; 393 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 394 } 395 tcpstat.tcps_rexmttimeo++; 396 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 397 TCPT_RANGESET(tp->t_rxtcur, rexmt, 398 tp->t_rttmin, TCPTV_REXMTMAX); 399 /* 400 * If losing, let the lower level know and try for 401 * a better route. Also, if we backed off this far, 402 * our srtt estimate is probably bogus. Clobber it 403 * so we'll take the next rtt measurement as our srtt; 404 * move the current srtt into rttvar to keep the current 405 * retransmit times until then. 406 */ 407 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 408 #ifdef INET6 409 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 410 in6_losing(tp->t_inpcb); 411 else 412 #endif 413 in_losing(tp->t_inpcb); 414 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 415 tp->t_srtt = 0; 416 } 417 tp->snd_nxt = tp->snd_una; 418 /* 419 * Force a segment to be sent. 420 */ 421 tp->t_flags |= TF_ACKNOW; 422 /* 423 * If timing a segment in this window, stop the timer. 424 */ 425 tp->t_rtttime = 0; 426 /* 427 * Close the congestion window down to one segment 428 * (we'll open it by one segment for each ack we get). 429 * Since we probably have a window's worth of unacked 430 * data accumulated, this "slow start" keeps us from 431 * dumping all that data as back-to-back packets (which 432 * might overwhelm an intermediate gateway). 433 * 434 * There are two phases to the opening: Initially we 435 * open by one mss on each ack. This makes the window 436 * size increase exponentially with time. If the 437 * window is larger than the path can handle, this 438 * exponential growth results in dropped packet(s) 439 * almost immediately. To get more time between 440 * drops but still "push" the network to take advantage 441 * of improving conditions, we switch from exponential 442 * to linear window opening at some threshhold size. 443 * For a threshhold, we use half the current window 444 * size, truncated to a multiple of the mss. 445 * 446 * (the minimum cwnd that will give us exponential 447 * growth is 2 mss. We don't allow the threshhold 448 * to go below this.) 449 */ 450 { 451 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 452 if (win < 2) 453 win = 2; 454 tp->snd_cwnd = tp->t_maxseg; 455 tp->snd_ssthresh = win * tp->t_maxseg; 456 tp->t_dupacks = 0; 457 } 458 (void) tcp_output(tp); 459 460 out: 461 #ifdef TCPDEBUG 462 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 463 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 464 PRU_SLOWTIMO); 465 #endif 466 splx(s); 467 } 468