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/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 = tt * 1000 / hz; 78 79 error = sysctl_handle_int(oidp, &s, 0, req); 80 if (error || !req->newptr) 81 return (error); 82 83 tt = 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 static int always_keepalive = 1; 113 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW, 114 &always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections"); 115 116 static int tcp_keepcnt = TCPTV_KEEPCNT; 117 /* max idle probes */ 118 int tcp_maxpersistidle; 119 /* max idle time in persist */ 120 int tcp_maxidle; 121 122 /* 123 * Tcp protocol timeout routine called every 500 ms. 124 * Updates timestamps used for TCP 125 * causes finite state machine actions if timers expire. 126 */ 127 void 128 tcp_slowtimo() 129 { 130 int s; 131 132 s = splnet(); 133 134 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 135 136 splx(s); 137 } 138 139 /* 140 * Cancel all timers for TCP tp. 141 */ 142 void 143 tcp_canceltimers(tp) 144 struct tcpcb *tp; 145 { 146 callout_stop(tp->tt_2msl); 147 callout_stop(tp->tt_persist); 148 callout_stop(tp->tt_keep); 149 callout_stop(tp->tt_rexmt); 150 } 151 152 int tcp_syn_backoff[TCP_MAXRXTSHIFT + 1] = 153 { 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 64, 64 }; 154 155 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 156 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 157 158 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 159 160 /* 161 * TCP timer processing. 162 */ 163 void 164 tcp_timer_delack(xtp) 165 void *xtp; 166 { 167 struct tcpcb *tp = xtp; 168 int s; 169 170 s = splnet(); 171 if (callout_pending(tp->tt_delack) || !callout_active(tp->tt_delack)) { 172 splx(s); 173 return; 174 } 175 callout_deactivate(tp->tt_delack); 176 177 tp->t_flags |= TF_ACKNOW; 178 tcpstat.tcps_delack++; 179 (void) tcp_output(tp); 180 splx(s); 181 } 182 183 void 184 tcp_timer_2msl(xtp) 185 void *xtp; 186 { 187 struct tcpcb *tp = xtp; 188 int s; 189 #ifdef TCPDEBUG 190 int ostate; 191 192 ostate = tp->t_state; 193 #endif 194 s = splnet(); 195 if (callout_pending(tp->tt_2msl) || !callout_active(tp->tt_2msl)) { 196 splx(s); 197 return; 198 } 199 callout_deactivate(tp->tt_2msl); 200 /* 201 * 2 MSL timeout in shutdown went off. If we're closed but 202 * still waiting for peer to close and connection has been idle 203 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 204 * control block. Otherwise, check again in a bit. 205 */ 206 if (tp->t_state != TCPS_TIME_WAIT && 207 (ticks - tp->t_rcvtime) <= tcp_maxidle) 208 callout_reset(tp->tt_2msl, tcp_keepintvl, 209 tcp_timer_2msl, tp); 210 else 211 tp = tcp_close(tp); 212 213 #ifdef TCPDEBUG 214 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 215 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 216 PRU_SLOWTIMO); 217 #endif 218 splx(s); 219 } 220 221 void 222 tcp_timer_keep(xtp) 223 void *xtp; 224 { 225 struct tcpcb *tp = xtp; 226 struct tcptemp *t_template; 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) || !callout_active(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 t_template = tcp_maketemplate(tp); 265 if (t_template) { 266 tcp_respond(tp, t_template->tt_ipgen, 267 &t_template->tt_t, (struct mbuf *)NULL, 268 tp->rcv_nxt, tp->snd_una - 1, 0); 269 (void) m_free(dtom(t_template)); 270 } 271 callout_reset(tp->tt_keep, tcp_keepintvl, tcp_timer_keep, tp); 272 } else 273 callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); 274 275 #ifdef TCPDEBUG 276 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 277 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 278 PRU_SLOWTIMO); 279 #endif 280 splx(s); 281 return; 282 283 dropit: 284 tcpstat.tcps_keepdrops++; 285 tp = tcp_drop(tp, ETIMEDOUT); 286 287 #ifdef TCPDEBUG 288 if (tp && (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 } 294 295 void 296 tcp_timer_persist(xtp) 297 void *xtp; 298 { 299 struct tcpcb *tp = xtp; 300 int s; 301 #ifdef TCPDEBUG 302 int ostate; 303 304 ostate = tp->t_state; 305 #endif 306 s = splnet(); 307 if (callout_pending(tp->tt_persist) || !callout_active(tp->tt_persist)){ 308 splx(s); 309 return; 310 } 311 callout_deactivate(tp->tt_persist); 312 /* 313 * Persistance timer into zero window. 314 * Force a byte to be output, if possible. 315 */ 316 tcpstat.tcps_persisttimeo++; 317 /* 318 * Hack: if the peer is dead/unreachable, we do not 319 * time out if the window is closed. After a full 320 * backoff, drop the connection if the idle time 321 * (no responses to probes) reaches the maximum 322 * backoff that we would use if retransmitting. 323 */ 324 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 325 ((ticks - tp->t_rcvtime) >= tcp_maxpersistidle || 326 (ticks - tp->t_rcvtime) >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 327 tcpstat.tcps_persistdrop++; 328 tp = tcp_drop(tp, ETIMEDOUT); 329 goto out; 330 } 331 tcp_setpersist(tp); 332 tp->t_force = 1; 333 (void) tcp_output(tp); 334 tp->t_force = 0; 335 336 out: 337 #ifdef TCPDEBUG 338 if (tp && tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 339 tcp_trace(TA_USER, ostate, tp, (void *)0, (struct tcphdr *)0, 340 PRU_SLOWTIMO); 341 #endif 342 splx(s); 343 } 344 345 void 346 tcp_timer_rexmt(xtp) 347 void *xtp; 348 { 349 struct tcpcb *tp = xtp; 350 int s; 351 int rexmt; 352 #ifdef TCPDEBUG 353 int ostate; 354 355 ostate = tp->t_state; 356 #endif 357 s = splnet(); 358 if (callout_pending(tp->tt_rexmt) || !callout_active(tp->tt_rexmt)) { 359 splx(s); 360 return; 361 } 362 callout_deactivate(tp->tt_rexmt); 363 /* 364 * Retransmission timer went off. Message has not 365 * been acked within retransmit interval. Back off 366 * to a longer retransmit interval and retransmit one segment. 367 */ 368 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 369 tp->t_rxtshift = TCP_MAXRXTSHIFT; 370 tcpstat.tcps_timeoutdrop++; 371 tp = tcp_drop(tp, tp->t_softerror ? 372 tp->t_softerror : ETIMEDOUT); 373 goto out; 374 } 375 if (tp->t_rxtshift == 1) { 376 /* 377 * first retransmit; record ssthresh and cwnd so they can 378 * be recovered if this turns out to be a "bad" retransmit. 379 * A retransmit is considered "bad" if an ACK for this 380 * segment is received within RTT/2 interval; the assumption 381 * here is that the ACK was already in flight. See 382 * "On Estimating End-to-End Network Path Properties" by 383 * Allman and Paxson for more details. 384 */ 385 tp->snd_cwnd_prev = tp->snd_cwnd; 386 tp->snd_ssthresh_prev = tp->snd_ssthresh; 387 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 388 } 389 tcpstat.tcps_rexmttimeo++; 390 if (tp->t_state == TCPS_SYN_SENT) 391 rexmt = TCP_REXMTVAL(tp) * tcp_syn_backoff[tp->t_rxtshift]; 392 else 393 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 394 TCPT_RANGESET(tp->t_rxtcur, rexmt, 395 tp->t_rttmin, TCPTV_REXMTMAX); 396 /* 397 * Disable rfc1323 and rfc1644 if we havn't got any response to 398 * our third SYN to work-around some broken terminal servers 399 * (most of which have hopefully been retired) that have bad VJ 400 * header compression code which trashes TCP segments containing 401 * unknown-to-them TCP options. 402 */ 403 if ((tp->t_state == TCPS_SYN_SENT) && (tp->t_rxtshift == 3)) 404 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_REQ_CC); 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