1 /* $NetBSD: tcp_timer.c,v 1.32 1998/03/31 22:49:10 thorpej Exp $ */ 2 3 /*- 4 * Copyright (c) 1997, 1998 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation 9 * Facility, NASA Ames Research Center. 10 * 11 * Redistribution and use in source and binary forms, with or without 12 * modification, are permitted provided that the following conditions 13 * are met: 14 * 1. Redistributions of source code must retain the above copyright 15 * notice, this list of conditions and the following disclaimer. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 3. All advertising materials mentioning features or use of this software 20 * must display the following acknowledgement: 21 * This product includes software developed by the NetBSD 22 * Foundation, Inc. and its contributors. 23 * 4. Neither the name of The NetBSD Foundation nor the names of its 24 * contributors may be used to endorse or promote products derived 25 * from this software without specific prior written permission. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 28 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 29 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 30 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 31 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 32 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 33 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 36 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 37 * POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 /* 41 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 42 * The Regents of the University of California. All rights reserved. 43 * 44 * Redistribution and use in source and binary forms, with or without 45 * modification, are permitted provided that the following conditions 46 * are met: 47 * 1. Redistributions of source code must retain the above copyright 48 * notice, this list of conditions and the following disclaimer. 49 * 2. Redistributions in binary form must reproduce the above copyright 50 * notice, this list of conditions and the following disclaimer in the 51 * documentation and/or other materials provided with the distribution. 52 * 3. All advertising materials mentioning features or use of this software 53 * must display the following acknowledgement: 54 * This product includes software developed by the University of 55 * California, Berkeley and its contributors. 56 * 4. Neither the name of the University nor the names of its contributors 57 * may be used to endorse or promote products derived from this software 58 * without specific prior written permission. 59 * 60 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 61 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 62 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 63 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 64 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 65 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 66 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 67 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 68 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 69 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 70 * SUCH DAMAGE. 71 * 72 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95 73 */ 74 75 #include "opt_tcp_compat_42.h" 76 77 #ifndef TUBA_INCLUDE 78 #include <sys/param.h> 79 #include <sys/systm.h> 80 #include <sys/malloc.h> 81 #include <sys/mbuf.h> 82 #include <sys/socket.h> 83 #include <sys/socketvar.h> 84 #include <sys/protosw.h> 85 #include <sys/errno.h> 86 87 #include <net/if.h> 88 #include <net/route.h> 89 90 #include <netinet/in.h> 91 #include <netinet/in_systm.h> 92 #include <netinet/ip.h> 93 #include <netinet/in_pcb.h> 94 #include <netinet/ip_var.h> 95 #include <netinet/tcp.h> 96 #include <netinet/tcp_fsm.h> 97 #include <netinet/tcp_seq.h> 98 #include <netinet/tcp_timer.h> 99 #include <netinet/tcp_var.h> 100 #include <netinet/tcpip.h> 101 102 int tcp_keepidle = TCPTV_KEEP_IDLE; 103 int tcp_keepintvl = TCPTV_KEEPINTVL; 104 int tcp_keepcnt = TCPTV_KEEPCNT; /* max idle probes */ 105 int tcp_maxpersistidle = TCPTV_KEEP_IDLE; /* max idle time in persist */ 106 int tcp_maxidle; 107 #else /* TUBA_INCLUDE */ 108 109 extern int tcp_keepcnt; 110 extern int tcp_maxpersistidle; 111 #endif /* TUBA_INCLUDE */ 112 113 struct tcp_delack_head tcp_delacks; 114 115 /* 116 * Fast timeout routine for processing delayed acks 117 */ 118 void 119 tcp_fasttimo() 120 { 121 register struct tcpcb *tp, *ntp; 122 int s; 123 124 s = splsoftnet(); 125 for (tp = tcp_delacks.lh_first; tp != NULL; tp = ntp) { 126 /* 127 * If tcp_output() can't transmit the ACK for whatever 128 * reason, it will remain on the queue for the next 129 * time the heartbeat ticks. 130 */ 131 ntp = tp->t_delack.le_next; 132 tp->t_flags |= TF_ACKNOW; 133 (void) tcp_output(tp); 134 } 135 splx(s); 136 } 137 138 /* 139 * Tcp protocol timeout routine called every 500 ms. 140 * Updates the timers in all active tcb's and 141 * causes finite state machine actions if timers expire. 142 */ 143 void 144 tcp_slowtimo() 145 { 146 register struct inpcb *inp, *ninp; 147 register struct tcpcb *tp; 148 int s; 149 register long i; 150 static int syn_cache_last = 0; 151 152 s = splsoftnet(); 153 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 154 /* 155 * Search through tcb's and update active timers. 156 */ 157 inp = tcbtable.inpt_queue.cqh_first; 158 if (inp == (struct inpcb *)0) { /* XXX */ 159 splx(s); 160 return; 161 } 162 for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = ninp) { 163 ninp = inp->inp_queue.cqe_next; 164 tp = intotcpcb(inp); 165 if (tp == 0 || tp->t_state == TCPS_LISTEN) 166 continue; 167 for (i = 0; i < TCPT_NTIMERS; i++) { 168 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 169 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 170 PRU_SLOWTIMO, (struct mbuf *)0, 171 (struct mbuf *)i, (struct mbuf *)0, 172 (struct proc *)0); 173 /* XXX NOT MP SAFE */ 174 if ((ninp == (void *)&tcbtable.inpt_queue && 175 tcbtable.inpt_queue.cqh_last != inp) || 176 ninp->inp_queue.cqe_prev != inp) 177 goto tpgone; 178 } 179 } 180 tp->t_idle++; 181 if (tp->t_rtt) 182 tp->t_rtt++; 183 tpgone: 184 ; 185 } 186 #if NRND == 0 /* Do we need to do this when using random() ? */ 187 tcp_iss_seq += TCP_ISSINCR; /* increment iss */ 188 #ifdef TCP_COMPAT_42 189 if ((int)tcp_iss_seq < 0) 190 tcp_iss_seq = 0; /* XXX */ 191 #endif 192 #endif 193 tcp_now++; /* for timestamps */ 194 if (++syn_cache_last >= tcp_syn_cache_interval) { 195 syn_cache_timer(syn_cache_last); 196 syn_cache_last = 0; 197 } 198 splx(s); 199 } 200 #ifndef TUBA_INCLUDE 201 202 /* 203 * Cancel all timers for TCP tp. 204 */ 205 void 206 tcp_canceltimers(tp) 207 struct tcpcb *tp; 208 { 209 register int i; 210 211 for (i = 0; i < TCPT_NTIMERS; i++) 212 tp->t_timer[i] = 0; 213 } 214 215 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 216 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 217 218 int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 219 220 /* 221 * TCP timer processing. 222 */ 223 struct tcpcb * 224 tcp_timers(tp, timer) 225 register struct tcpcb *tp; 226 int timer; 227 { 228 short rto; 229 230 switch (timer) { 231 232 /* 233 * 2 MSL timeout in shutdown went off. If we're closed but 234 * still waiting for peer to close and connection has been idle 235 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 236 * control block. Otherwise, check again in a bit. 237 */ 238 case TCPT_2MSL: 239 if (tp->t_state != TCPS_TIME_WAIT && 240 tp->t_idle <= tcp_maxidle) 241 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 242 else 243 tp = tcp_close(tp); 244 break; 245 246 /* 247 * Retransmission timer went off. Message has not 248 * been acked within retransmit interval. Back off 249 * to a longer retransmit interval and retransmit one segment. 250 */ 251 case TCPT_REXMT: 252 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 253 tp->t_rxtshift = TCP_MAXRXTSHIFT; 254 tcpstat.tcps_timeoutdrop++; 255 tp = tcp_drop(tp, tp->t_softerror ? 256 tp->t_softerror : ETIMEDOUT); 257 break; 258 } 259 tcpstat.tcps_rexmttimeo++; 260 rto = TCP_REXMTVAL(tp); 261 if (rto < tp->t_rttmin) 262 rto = tp->t_rttmin; 263 TCPT_RANGESET(tp->t_rxtcur, rto * tcp_backoff[tp->t_rxtshift], 264 tp->t_rttmin, TCPTV_REXMTMAX); 265 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 266 /* 267 * If losing, let the lower level know and try for 268 * a better route. Also, if we backed off this far, 269 * our srtt estimate is probably bogus. Clobber it 270 * so we'll take the next rtt measurement as our srtt; 271 * move the current srtt into rttvar to keep the current 272 * retransmit times until then. 273 */ 274 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 275 in_losing(tp->t_inpcb); 276 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 277 tp->t_srtt = 0; 278 } 279 tp->snd_nxt = tp->snd_una; 280 /* 281 * If timing a segment in this window, stop the timer. 282 */ 283 tp->t_rtt = 0; 284 /* 285 * Remember if we are retransmitting a SYN, because if 286 * we do, set the initial congestion window must be set 287 * to 1 segment. 288 */ 289 if (tp->t_state == TCPS_SYN_SENT) 290 tp->t_flags |= TF_SYN_REXMT; 291 /* 292 * Close the congestion window down to the initial window 293 * (we'll open it by one segment for each ack we get). 294 * Since we probably have a window's worth of unacked 295 * data accumulated, this "slow start" keeps us from 296 * dumping all that data as back-to-back packets (which 297 * might overwhelm an intermediate gateway). 298 * 299 * There are two phases to the opening: Initially we 300 * open by one mss on each ack. This makes the window 301 * size increase exponentially with time. If the 302 * window is larger than the path can handle, this 303 * exponential growth results in dropped packet(s) 304 * almost immediately. To get more time between 305 * drops but still "push" the network to take advantage 306 * of improving conditions, we switch from exponential 307 * to linear window opening at some threshhold size. 308 * For a threshhold, we use half the current window 309 * size, truncated to a multiple of the mss. 310 * 311 * (the minimum cwnd that will give us exponential 312 * growth is 2 mss. We don't allow the threshhold 313 * to go below this.) 314 */ 315 { 316 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz; 317 if (win < 2) 318 win = 2; 319 tp->snd_cwnd = TCP_INITIAL_WINDOW(tcp_init_win, tp->t_segsz); 320 tp->snd_ssthresh = win * tp->t_segsz; 321 tp->t_dupacks = 0; 322 } 323 (void) tcp_output(tp); 324 break; 325 326 /* 327 * Persistance timer into zero window. 328 * Force a byte to be output, if possible. 329 */ 330 case TCPT_PERSIST: 331 /* 332 * Hack: if the peer is dead/unreachable, we do not 333 * time out if the window is closed. After a full 334 * backoff, drop the connection if the idle time 335 * (no responses to probes) reaches the maximum 336 * backoff that we would use if retransmitting. 337 */ 338 rto = TCP_REXMTVAL(tp); 339 if (rto < tp->t_rttmin) 340 rto = tp->t_rttmin; 341 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 342 (tp->t_idle >= tcp_maxpersistidle || 343 tp->t_idle >= rto * tcp_totbackoff)) { 344 tcpstat.tcps_persistdrops++; 345 tp = tcp_drop(tp, ETIMEDOUT); 346 break; 347 } 348 tcpstat.tcps_persisttimeo++; 349 tcp_setpersist(tp); 350 tp->t_force = 1; 351 (void) tcp_output(tp); 352 tp->t_force = 0; 353 break; 354 355 /* 356 * Keep-alive timer went off; send something 357 * or drop connection if idle for too long. 358 */ 359 case TCPT_KEEP: 360 tcpstat.tcps_keeptimeo++; 361 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 362 goto dropit; 363 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 364 tp->t_state <= TCPS_CLOSE_WAIT) { 365 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 366 goto dropit; 367 /* 368 * Send a packet designed to force a response 369 * if the peer is up and reachable: 370 * either an ACK if the connection is still alive, 371 * or an RST if the peer has closed the connection 372 * due to timeout or reboot. 373 * Using sequence number tp->snd_una-1 374 * causes the transmitted zero-length segment 375 * to lie outside the receive window; 376 * by the protocol spec, this requires the 377 * correspondent TCP to respond. 378 */ 379 tcpstat.tcps_keepprobe++; 380 #ifdef TCP_COMPAT_42 381 /* 382 * The keepalive packet must have nonzero length 383 * to get a 4.2 host to respond. 384 */ 385 (void)tcp_respond(tp, tp->t_template, 386 (struct mbuf *)NULL, tp->rcv_nxt - 1, 387 tp->snd_una - 1, 0); 388 #else 389 (void)tcp_respond(tp, tp->t_template, 390 (struct mbuf *)NULL, tp->rcv_nxt, 391 tp->snd_una - 1, 0); 392 #endif 393 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 394 } else 395 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 396 break; 397 dropit: 398 tcpstat.tcps_keepdrops++; 399 tp = tcp_drop(tp, ETIMEDOUT); 400 break; 401 } 402 return (tp); 403 } 404 #endif /* TUBA_INCLUDE */ 405