1 /* $NetBSD: tcp_timer.c,v 1.43 1998/09/10 10:47:00 mouse 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 <sys/param.h> 76 #include <sys/systm.h> 77 #include <sys/malloc.h> 78 #include <sys/mbuf.h> 79 #include <sys/socket.h> 80 #include <sys/socketvar.h> 81 #include <sys/protosw.h> 82 #include <sys/errno.h> 83 84 #include <net/if.h> 85 #include <net/route.h> 86 87 #include <netinet/in.h> 88 #include <netinet/in_systm.h> 89 #include <netinet/ip.h> 90 #include <netinet/in_pcb.h> 91 #include <netinet/ip_var.h> 92 #include <netinet/tcp.h> 93 #include <netinet/tcp_fsm.h> 94 #include <netinet/tcp_seq.h> 95 #include <netinet/tcp_timer.h> 96 #include <netinet/tcp_var.h> 97 #include <netinet/tcpip.h> 98 99 int tcp_keepidle = TCPTV_KEEP_IDLE; 100 int tcp_keepintvl = TCPTV_KEEPINTVL; 101 int tcp_keepcnt = TCPTV_KEEPCNT; /* max idle probes */ 102 int tcp_maxpersistidle = TCPTV_KEEP_IDLE; /* max idle time in persist */ 103 int tcp_maxidle; 104 105 struct tcp_delack_head tcp_delacks; 106 107 /* 108 * Fast timeout routine for processing delayed acks 109 */ 110 void 111 tcp_fasttimo() 112 { 113 register struct tcpcb *tp, *ntp; 114 int s; 115 116 s = splsoftnet(); 117 for (tp = tcp_delacks.lh_first; tp != NULL; tp = ntp) { 118 /* 119 * If tcp_output() can't transmit the ACK for whatever 120 * reason, it will remain on the queue for the next 121 * time the heartbeat ticks. 122 */ 123 ntp = tp->t_delack.le_next; 124 tp->t_flags |= TF_ACKNOW; 125 (void) tcp_output(tp); 126 } 127 splx(s); 128 } 129 130 /* 131 * Tcp protocol timeout routine called every 500 ms. 132 * Updates the timers in all active tcb's and 133 * causes finite state machine actions if timers expire. 134 */ 135 void 136 tcp_slowtimo() 137 { 138 register struct inpcb *inp, *ninp; 139 register struct tcpcb *tp; 140 int s; 141 register long i; 142 static int syn_cache_last = 0; 143 144 s = splsoftnet(); 145 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 146 /* 147 * Search through tcb's and update active timers. 148 */ 149 inp = tcbtable.inpt_queue.cqh_first; 150 if (inp == (struct inpcb *)0) { /* XXX */ 151 splx(s); 152 return; 153 } 154 for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = ninp) { 155 ninp = inp->inp_queue.cqe_next; 156 tp = intotcpcb(inp); 157 if (tp == 0 || tp->t_state == TCPS_LISTEN) 158 continue; 159 for (i = 0; i < TCPT_NTIMERS; i++) { 160 if (TCP_TIMER_ISEXPIRED(tp, i)) { 161 TCP_TIMER_DISARM(tp, i); 162 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 163 PRU_SLOWTIMO, (struct mbuf *)0, 164 (struct mbuf *)i, (struct mbuf *)0, 165 (struct proc *)0); 166 /* XXX NOT MP SAFE */ 167 if ((ninp == (void *)&tcbtable.inpt_queue && 168 tcbtable.inpt_queue.cqh_last != inp) || 169 ninp->inp_queue.cqe_prev != inp) 170 goto tpgone; 171 } 172 } 173 tp->t_idle++; 174 if (tp->t_rtt) 175 tp->t_rtt++; 176 tpgone: 177 ; 178 } 179 tcp_iss_seq += TCP_ISSINCR; /* increment iss */ 180 tcp_now++; /* for timestamps */ 181 if (++syn_cache_last >= tcp_syn_cache_interval) { 182 syn_cache_timer(); 183 syn_cache_last = 0; 184 } 185 splx(s); 186 } 187 188 /* 189 * Cancel all timers for TCP tp. 190 */ 191 void 192 tcp_canceltimers(tp) 193 struct tcpcb *tp; 194 { 195 register int i; 196 197 for (i = 0; i < TCPT_NTIMERS; i++) 198 TCP_TIMER_DISARM(tp, i); 199 } 200 201 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 202 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 203 204 int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 205 206 /* 207 * TCP timer processing. 208 */ 209 struct tcpcb * 210 tcp_timers(tp, timer) 211 register struct tcpcb *tp; 212 int timer; 213 { 214 short rto; 215 216 switch (timer) { 217 218 /* 219 * 2 MSL timeout in shutdown went off. If we're closed but 220 * still waiting for peer to close and connection has been idle 221 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 222 * control block. Otherwise, check again in a bit. 223 */ 224 case TCPT_2MSL: 225 if (tp->t_state != TCPS_TIME_WAIT && 226 ((tcp_maxidle == 0) || (tp->t_idle <= tcp_maxidle))) 227 TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_keepintvl); 228 else 229 tp = tcp_close(tp); 230 break; 231 232 /* 233 * Retransmission timer went off. Message has not 234 * been acked within retransmit interval. Back off 235 * to a longer retransmit interval and retransmit one segment. 236 */ 237 case TCPT_REXMT: 238 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 239 tp->t_rxtshift = TCP_MAXRXTSHIFT; 240 tcpstat.tcps_timeoutdrop++; 241 tp = tcp_drop(tp, tp->t_softerror ? 242 tp->t_softerror : ETIMEDOUT); 243 break; 244 } 245 tcpstat.tcps_rexmttimeo++; 246 rto = TCP_REXMTVAL(tp); 247 if (rto < tp->t_rttmin) 248 rto = tp->t_rttmin; 249 TCPT_RANGESET(tp->t_rxtcur, rto * tcp_backoff[tp->t_rxtshift], 250 tp->t_rttmin, TCPTV_REXMTMAX); 251 TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); 252 #if 0 253 /* 254 * If we are losing and we are trying path MTU discovery, 255 * try turning it off. This will avoid black holes in 256 * the network which suppress or fail to send "packet 257 * too big" ICMP messages. We should ideally do 258 * lots more sophisticated searching to find the right 259 * value here... 260 */ 261 if (ip_mtudisc && tp->t_rxtshift > TCP_MAXRXTSHIFT / 6) { 262 struct inpcb *inp = tp->t_inpcb; 263 struct rtentry *rt = in_pcbrtentry(inp); 264 265 /* XXX: Black hole recovery code goes here */ 266 } 267 #endif 268 /* 269 * If losing, let the lower level know and try for 270 * a better route. Also, if we backed off this far, 271 * our srtt estimate is probably bogus. Clobber it 272 * so we'll take the next rtt measurement as our srtt; 273 * move the current srtt into rttvar to keep the current 274 * retransmit times until then. 275 */ 276 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 277 in_losing(tp->t_inpcb); 278 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 279 tp->t_srtt = 0; 280 } 281 tp->snd_nxt = tp->snd_una; 282 /* 283 * If timing a segment in this window, stop the timer. 284 */ 285 tp->t_rtt = 0; 286 /* 287 * Remember if we are retransmitting a SYN, because if 288 * we do, set the initial congestion window must be set 289 * to 1 segment. 290 */ 291 if (tp->t_state == TCPS_SYN_SENT) 292 tp->t_flags |= TF_SYN_REXMT; 293 /* 294 * Close the congestion window down to one segment 295 * (we'll open it by one segment for each ack we get). 296 * Since we probably have a window's worth of unacked 297 * data accumulated, this "slow start" keeps us from 298 * dumping all that data as back-to-back packets (which 299 * might overwhelm an intermediate gateway). 300 * 301 * There are two phases to the opening: Initially we 302 * open by one mss on each ack. This makes the window 303 * size increase exponentially with time. If the 304 * window is larger than the path can handle, this 305 * exponential growth results in dropped packet(s) 306 * almost immediately. To get more time between 307 * drops but still "push" the network to take advantage 308 * of improving conditions, we switch from exponential 309 * to linear window opening at some threshhold size. 310 * For a threshhold, we use half the current window 311 * size, truncated to a multiple of the mss. 312 * 313 * (the minimum cwnd that will give us exponential 314 * growth is 2 mss. We don't allow the threshhold 315 * to go below this.) 316 */ 317 { 318 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz; 319 if (win < 2) 320 win = 2; 321 /* Loss Window MUST be one segment. */ 322 tp->snd_cwnd = tp->t_segsz; 323 tp->snd_ssthresh = win * tp->t_segsz; 324 tp->t_dupacks = 0; 325 } 326 (void) tcp_output(tp); 327 break; 328 329 /* 330 * Persistance timer into zero window. 331 * Force a byte to be output, if possible. 332 */ 333 case TCPT_PERSIST: 334 /* 335 * Hack: if the peer is dead/unreachable, we do not 336 * time out if the window is closed. After a full 337 * backoff, drop the connection if the idle time 338 * (no responses to probes) reaches the maximum 339 * backoff that we would use if retransmitting. 340 */ 341 rto = TCP_REXMTVAL(tp); 342 if (rto < tp->t_rttmin) 343 rto = tp->t_rttmin; 344 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 345 (tp->t_idle >= tcp_maxpersistidle || 346 tp->t_idle >= rto * tcp_totbackoff)) { 347 tcpstat.tcps_persistdrops++; 348 tp = tcp_drop(tp, ETIMEDOUT); 349 break; 350 } 351 tcpstat.tcps_persisttimeo++; 352 tcp_setpersist(tp); 353 tp->t_force = 1; 354 (void) tcp_output(tp); 355 tp->t_force = 0; 356 break; 357 358 /* 359 * Keep-alive timer went off; send something 360 * or drop connection if idle for too long. 361 */ 362 case TCPT_KEEP: 363 tcpstat.tcps_keeptimeo++; 364 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 365 goto dropit; 366 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 367 tp->t_state <= TCPS_CLOSE_WAIT) { 368 if ((tcp_maxidle > 0) && 369 (tp->t_idle >= tcp_keepidle + tcp_maxidle)) 370 goto dropit; 371 /* 372 * Send a packet designed to force a response 373 * if the peer is up and reachable: 374 * either an ACK if the connection is still alive, 375 * or an RST if the peer has closed the connection 376 * due to timeout or reboot. 377 * Using sequence number tp->snd_una-1 378 * causes the transmitted zero-length segment 379 * to lie outside the receive window; 380 * by the protocol spec, this requires the 381 * correspondent TCP to respond. 382 */ 383 tcpstat.tcps_keepprobe++; 384 if (tcp_compat_42) { 385 /* 386 * The keepalive packet must have nonzero 387 * length to get a 4.2 host to respond. 388 */ 389 (void)tcp_respond(tp, tp->t_template, 390 (struct mbuf *)NULL, tp->rcv_nxt - 1, 391 tp->snd_una - 1, 0); 392 } else { 393 (void)tcp_respond(tp, tp->t_template, 394 (struct mbuf *)NULL, tp->rcv_nxt, 395 tp->snd_una - 1, 0); 396 } 397 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepintvl); 398 } else 399 TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle); 400 break; 401 dropit: 402 tcpstat.tcps_keepdrops++; 403 tp = tcp_drop(tp, ETIMEDOUT); 404 break; 405 } 406 return (tp); 407 } 408