tcp_timer.c revision 1.27
1 /* $NetBSD: tcp_timer.c,v 1.27 1997/12/31 03:31:27 thorpej Exp $ */ 2 3 /* 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)tcp_timer.c 8.1 (Berkeley) 6/10/93 36 */ 37 38 #ifndef TUBA_INCLUDE 39 #include <sys/param.h> 40 #include <sys/systm.h> 41 #include <sys/malloc.h> 42 #include <sys/mbuf.h> 43 #include <sys/socket.h> 44 #include <sys/socketvar.h> 45 #include <sys/protosw.h> 46 #include <sys/errno.h> 47 48 #include <net/if.h> 49 #include <net/route.h> 50 51 #include <netinet/in.h> 52 #include <netinet/in_systm.h> 53 #include <netinet/ip.h> 54 #include <netinet/in_pcb.h> 55 #include <netinet/ip_var.h> 56 #include <netinet/tcp.h> 57 #include <netinet/tcp_fsm.h> 58 #include <netinet/tcp_seq.h> 59 #include <netinet/tcp_timer.h> 60 #include <netinet/tcp_var.h> 61 #include <netinet/tcpip.h> 62 63 int tcp_keepidle = TCPTV_KEEP_IDLE; 64 int tcp_keepintvl = TCPTV_KEEPINTVL; 65 int tcp_keepcnt = TCPTV_KEEPCNT; /* max idle probes */ 66 int tcp_maxpersistidle = TCPTV_KEEP_IDLE; /* max idle time in persist */ 67 int tcp_maxidle; 68 #else /* TUBA_INCLUDE */ 69 70 extern int tcp_keepcnt; 71 extern int tcp_maxpersistidle; 72 #endif /* TUBA_INCLUDE */ 73 74 struct tcp_delack_head tcp_delacks; 75 76 /* 77 * Fast timeout routine for processing delayed acks 78 */ 79 void 80 tcp_fasttimo() 81 { 82 register struct tcpcb *tp, *ntp; 83 int s; 84 85 s = splsoftnet(); 86 for (tp = tcp_delacks.lh_first; tp != NULL; tp = ntp) { 87 /* 88 * If tcp_output() can't transmit the ACK for whatever 89 * reason, it will remain on the queue for the next 90 * time the heartbeat ticks. 91 */ 92 ntp = tp->t_delack.le_next; 93 tp->t_flags |= TF_ACKNOW; 94 (void) tcp_output(tp); 95 } 96 splx(s); 97 } 98 99 /* 100 * Tcp protocol timeout routine called every 500 ms. 101 * Updates the timers in all active tcb's and 102 * causes finite state machine actions if timers expire. 103 */ 104 void 105 tcp_slowtimo() 106 { 107 register struct inpcb *inp, *ninp; 108 register struct tcpcb *tp; 109 int s; 110 register long i; 111 static int syn_cache_last = 0; 112 113 s = splsoftnet(); 114 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 115 /* 116 * Search through tcb's and update active timers. 117 */ 118 inp = tcbtable.inpt_queue.cqh_first; 119 if (inp == (struct inpcb *)0) { /* XXX */ 120 splx(s); 121 return; 122 } 123 for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = ninp) { 124 ninp = inp->inp_queue.cqe_next; 125 tp = intotcpcb(inp); 126 if (tp == 0 || tp->t_state == TCPS_LISTEN) 127 continue; 128 for (i = 0; i < TCPT_NTIMERS; i++) { 129 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 130 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 131 PRU_SLOWTIMO, (struct mbuf *)0, 132 (struct mbuf *)i, (struct mbuf *)0, 133 (struct proc *)0); 134 /* XXX NOT MP SAFE */ 135 if ((ninp == (void *)&tcbtable.inpt_queue && 136 tcbtable.inpt_queue.cqh_last != inp) || 137 ninp->inp_queue.cqe_prev != inp) 138 goto tpgone; 139 } 140 } 141 tp->t_idle++; 142 if (tp->t_rtt) 143 tp->t_rtt++; 144 tpgone: 145 ; 146 } 147 #if NRND == 0 /* Do we need to do this when using random() ? */ 148 tcp_iss_seq += TCP_ISSINCR; /* increment iss */ 149 #ifdef TCP_COMPAT_42 150 if ((int)tcp_iss_seq < 0) 151 tcp_iss_seq = 0; /* XXX */ 152 #endif 153 #endif 154 tcp_now++; /* for timestamps */ 155 if (++syn_cache_last >= tcp_syn_cache_interval) { 156 syn_cache_timer(syn_cache_last); 157 syn_cache_last = 0; 158 } 159 splx(s); 160 } 161 #ifndef TUBA_INCLUDE 162 163 /* 164 * Cancel all timers for TCP tp. 165 */ 166 void 167 tcp_canceltimers(tp) 168 struct tcpcb *tp; 169 { 170 register int i; 171 172 for (i = 0; i < TCPT_NTIMERS; i++) 173 tp->t_timer[i] = 0; 174 } 175 176 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 177 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 178 179 int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 180 181 /* 182 * TCP timer processing. 183 */ 184 struct tcpcb * 185 tcp_timers(tp, timer) 186 register struct tcpcb *tp; 187 int timer; 188 { 189 190 switch (timer) { 191 192 /* 193 * 2 MSL timeout in shutdown went off. If we're closed but 194 * still waiting for peer to close and connection has been idle 195 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 196 * control block. Otherwise, check again in a bit. 197 */ 198 case TCPT_2MSL: 199 if (tp->t_state != TCPS_TIME_WAIT && 200 tp->t_idle <= tcp_maxidle) 201 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 202 else 203 tp = tcp_close(tp); 204 break; 205 206 /* 207 * Retransmission timer went off. Message has not 208 * been acked within retransmit interval. Back off 209 * to a longer retransmit interval and retransmit one segment. 210 */ 211 case TCPT_REXMT: 212 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 213 tp->t_rxtshift = TCP_MAXRXTSHIFT; 214 tcpstat.tcps_timeoutdrop++; 215 tp = tcp_drop(tp, tp->t_softerror ? 216 tp->t_softerror : ETIMEDOUT); 217 break; 218 } 219 tcpstat.tcps_rexmttimeo++; 220 TCPT_RANGESET(tp->t_rxtcur, 221 TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift], 222 tp->t_rttmin, TCPTV_REXMTMAX); 223 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 224 /* 225 * If losing, let the lower level know and try for 226 * a better route. Also, if we backed off this far, 227 * our srtt estimate is probably bogus. Clobber it 228 * so we'll take the next rtt measurement as our srtt; 229 * move the current srtt into rttvar to keep the current 230 * retransmit times until then. 231 */ 232 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 233 in_losing(tp->t_inpcb); 234 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 235 tp->t_srtt = 0; 236 } 237 tp->snd_nxt = tp->snd_una; 238 /* 239 * If timing a segment in this window, stop the timer. 240 */ 241 tp->t_rtt = 0; 242 /* 243 * Close the congestion window down to the initial window 244 * (we'll open it by one segment for each ack we get). 245 * Since we probably have a window's worth of unacked 246 * data accumulated, this "slow start" keeps us from 247 * dumping all that data as back-to-back packets (which 248 * might overwhelm an intermediate gateway). 249 * 250 * There are two phases to the opening: Initially we 251 * open by one mss on each ack. This makes the window 252 * size increase exponentially with time. If the 253 * window is larger than the path can handle, this 254 * exponential growth results in dropped packet(s) 255 * almost immediately. To get more time between 256 * drops but still "push" the network to take advantage 257 * of improving conditions, we switch from exponential 258 * to linear window opening at some threshhold size. 259 * For a threshhold, we use half the current window 260 * size, truncated to a multiple of the mss. 261 * 262 * (the minimum cwnd that will give us exponential 263 * growth is 2 mss. We don't allow the threshhold 264 * to go below this.) 265 */ 266 { 267 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz; 268 if (win < 2) 269 win = 2; 270 tp->snd_cwnd = TCP_INITIAL_WINDOW(tp->t_segsz); 271 tp->snd_ssthresh = win * tp->t_segsz; 272 tp->t_dupacks = 0; 273 } 274 (void) tcp_output(tp); 275 break; 276 277 /* 278 * Persistance timer into zero window. 279 * Force a byte to be output, if possible. 280 */ 281 case TCPT_PERSIST: 282 /* 283 * Hack: if the peer is dead/unreachable, we do not 284 * time out if the window is closed. After a full 285 * backoff, drop the connection if the idle time 286 * (no responses to probes) reaches the maximum 287 * backoff that we would use if retransmitting. 288 */ 289 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 290 (tp->t_idle >= tcp_maxpersistidle || 291 tp->t_idle >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 292 tcpstat.tcps_persistdrops++; 293 tp = tcp_drop(tp, ETIMEDOUT); 294 break; 295 } 296 tcpstat.tcps_persisttimeo++; 297 tcp_setpersist(tp); 298 tp->t_force = 1; 299 (void) tcp_output(tp); 300 tp->t_force = 0; 301 break; 302 303 /* 304 * Keep-alive timer went off; send something 305 * or drop connection if idle for too long. 306 */ 307 case TCPT_KEEP: 308 tcpstat.tcps_keeptimeo++; 309 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 310 goto dropit; 311 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 312 tp->t_state <= TCPS_CLOSE_WAIT) { 313 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 314 goto dropit; 315 /* 316 * Send a packet designed to force a response 317 * if the peer is up and reachable: 318 * either an ACK if the connection is still alive, 319 * or an RST if the peer has closed the connection 320 * due to timeout or reboot. 321 * Using sequence number tp->snd_una-1 322 * causes the transmitted zero-length segment 323 * to lie outside the receive window; 324 * by the protocol spec, this requires the 325 * correspondent TCP to respond. 326 */ 327 tcpstat.tcps_keepprobe++; 328 #ifdef TCP_COMPAT_42 329 /* 330 * The keepalive packet must have nonzero length 331 * to get a 4.2 host to respond. 332 */ 333 (void)tcp_respond(tp, tp->t_template, 334 (struct mbuf *)NULL, tp->rcv_nxt - 1, 335 tp->snd_una - 1, 0); 336 #else 337 (void)tcp_respond(tp, tp->t_template, 338 (struct mbuf *)NULL, tp->rcv_nxt, 339 tp->snd_una - 1, 0); 340 #endif 341 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 342 } else 343 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 344 break; 345 dropit: 346 tcpstat.tcps_keepdrops++; 347 tp = tcp_drop(tp, ETIMEDOUT); 348 break; 349 } 350 return (tp); 351 } 352 #endif /* TUBA_INCLUDE */ 353
Indexes created Mon Sep 22 13:09:51 GMT 2025