tcp_timer.c revision 1.29
1 /* $NetBSD: tcp_timer.c,v 1.29 1998/01/12 03:00:43 scottr Exp $ */ 2 3 /* 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 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 8.2 (Berkeley) 5/24/95 36 */ 37 38 #include "opt_tcp_compat_42.h" 39 40 #ifndef TUBA_INCLUDE 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/malloc.h> 44 #include <sys/mbuf.h> 45 #include <sys/socket.h> 46 #include <sys/socketvar.h> 47 #include <sys/protosw.h> 48 #include <sys/errno.h> 49 50 #include <net/if.h> 51 #include <net/route.h> 52 53 #include <netinet/in.h> 54 #include <netinet/in_systm.h> 55 #include <netinet/ip.h> 56 #include <netinet/in_pcb.h> 57 #include <netinet/ip_var.h> 58 #include <netinet/tcp.h> 59 #include <netinet/tcp_fsm.h> 60 #include <netinet/tcp_seq.h> 61 #include <netinet/tcp_timer.h> 62 #include <netinet/tcp_var.h> 63 #include <netinet/tcpip.h> 64 65 int tcp_keepidle = TCPTV_KEEP_IDLE; 66 int tcp_keepintvl = TCPTV_KEEPINTVL; 67 int tcp_keepcnt = TCPTV_KEEPCNT; /* max idle probes */ 68 int tcp_maxpersistidle = TCPTV_KEEP_IDLE; /* max idle time in persist */ 69 int tcp_maxidle; 70 #else /* TUBA_INCLUDE */ 71 72 extern int tcp_keepcnt; 73 extern int tcp_maxpersistidle; 74 #endif /* TUBA_INCLUDE */ 75 76 struct tcp_delack_head tcp_delacks; 77 78 /* 79 * Fast timeout routine for processing delayed acks 80 */ 81 void 82 tcp_fasttimo() 83 { 84 register struct tcpcb *tp, *ntp; 85 int s; 86 87 s = splsoftnet(); 88 for (tp = tcp_delacks.lh_first; tp != NULL; tp = ntp) { 89 /* 90 * If tcp_output() can't transmit the ACK for whatever 91 * reason, it will remain on the queue for the next 92 * time the heartbeat ticks. 93 */ 94 ntp = tp->t_delack.le_next; 95 tp->t_flags |= TF_ACKNOW; 96 (void) tcp_output(tp); 97 } 98 splx(s); 99 } 100 101 /* 102 * Tcp protocol timeout routine called every 500 ms. 103 * Updates the timers in all active tcb's and 104 * causes finite state machine actions if timers expire. 105 */ 106 void 107 tcp_slowtimo() 108 { 109 register struct inpcb *inp, *ninp; 110 register struct tcpcb *tp; 111 int s; 112 register long i; 113 static int syn_cache_last = 0; 114 115 s = splsoftnet(); 116 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 117 /* 118 * Search through tcb's and update active timers. 119 */ 120 inp = tcbtable.inpt_queue.cqh_first; 121 if (inp == (struct inpcb *)0) { /* XXX */ 122 splx(s); 123 return; 124 } 125 for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = ninp) { 126 ninp = inp->inp_queue.cqe_next; 127 tp = intotcpcb(inp); 128 if (tp == 0 || tp->t_state == TCPS_LISTEN) 129 continue; 130 for (i = 0; i < TCPT_NTIMERS; i++) { 131 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 132 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 133 PRU_SLOWTIMO, (struct mbuf *)0, 134 (struct mbuf *)i, (struct mbuf *)0, 135 (struct proc *)0); 136 /* XXX NOT MP SAFE */ 137 if ((ninp == (void *)&tcbtable.inpt_queue && 138 tcbtable.inpt_queue.cqh_last != inp) || 139 ninp->inp_queue.cqe_prev != inp) 140 goto tpgone; 141 } 142 } 143 tp->t_idle++; 144 if (tp->t_rtt) 145 tp->t_rtt++; 146 tpgone: 147 ; 148 } 149 #if NRND == 0 /* Do we need to do this when using random() ? */ 150 tcp_iss_seq += TCP_ISSINCR; /* increment iss */ 151 #ifdef TCP_COMPAT_42 152 if ((int)tcp_iss_seq < 0) 153 tcp_iss_seq = 0; /* XXX */ 154 #endif 155 #endif 156 tcp_now++; /* for timestamps */ 157 if (++syn_cache_last >= tcp_syn_cache_interval) { 158 syn_cache_timer(syn_cache_last); 159 syn_cache_last = 0; 160 } 161 splx(s); 162 } 163 #ifndef TUBA_INCLUDE 164 165 /* 166 * Cancel all timers for TCP tp. 167 */ 168 void 169 tcp_canceltimers(tp) 170 struct tcpcb *tp; 171 { 172 register int i; 173 174 for (i = 0; i < TCPT_NTIMERS; i++) 175 tp->t_timer[i] = 0; 176 } 177 178 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 179 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 180 181 int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 182 183 /* 184 * TCP timer processing. 185 */ 186 struct tcpcb * 187 tcp_timers(tp, timer) 188 register struct tcpcb *tp; 189 int timer; 190 { 191 192 switch (timer) { 193 194 /* 195 * 2 MSL timeout in shutdown went off. If we're closed but 196 * still waiting for peer to close and connection has been idle 197 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 198 * control block. Otherwise, check again in a bit. 199 */ 200 case TCPT_2MSL: 201 if (tp->t_state != TCPS_TIME_WAIT && 202 tp->t_idle <= tcp_maxidle) 203 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 204 else 205 tp = tcp_close(tp); 206 break; 207 208 /* 209 * Retransmission timer went off. Message has not 210 * been acked within retransmit interval. Back off 211 * to a longer retransmit interval and retransmit one segment. 212 */ 213 case TCPT_REXMT: 214 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 215 tp->t_rxtshift = TCP_MAXRXTSHIFT; 216 tcpstat.tcps_timeoutdrop++; 217 tp = tcp_drop(tp, tp->t_softerror ? 218 tp->t_softerror : ETIMEDOUT); 219 break; 220 } 221 tcpstat.tcps_rexmttimeo++; 222 TCPT_RANGESET(tp->t_rxtcur, 223 TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift], 224 tp->t_rttmin, TCPTV_REXMTMAX); 225 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 226 /* 227 * If losing, let the lower level know and try for 228 * a better route. Also, if we backed off this far, 229 * our srtt estimate is probably bogus. Clobber it 230 * so we'll take the next rtt measurement as our srtt; 231 * move the current srtt into rttvar to keep the current 232 * retransmit times until then. 233 */ 234 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 235 in_losing(tp->t_inpcb); 236 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 237 tp->t_srtt = 0; 238 } 239 tp->snd_nxt = tp->snd_una; 240 /* 241 * If timing a segment in this window, stop the timer. 242 */ 243 tp->t_rtt = 0; 244 /* 245 * Close the congestion window down to the initial window 246 * (we'll open it by one segment for each ack we get). 247 * Since we probably have a window's worth of unacked 248 * data accumulated, this "slow start" keeps us from 249 * dumping all that data as back-to-back packets (which 250 * might overwhelm an intermediate gateway). 251 * 252 * There are two phases to the opening: Initially we 253 * open by one mss on each ack. This makes the window 254 * size increase exponentially with time. If the 255 * window is larger than the path can handle, this 256 * exponential growth results in dropped packet(s) 257 * almost immediately. To get more time between 258 * drops but still "push" the network to take advantage 259 * of improving conditions, we switch from exponential 260 * to linear window opening at some threshhold size. 261 * For a threshhold, we use half the current window 262 * size, truncated to a multiple of the mss. 263 * 264 * (the minimum cwnd that will give us exponential 265 * growth is 2 mss. We don't allow the threshhold 266 * to go below this.) 267 */ 268 { 269 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz; 270 if (win < 2) 271 win = 2; 272 tp->snd_cwnd = TCP_INITIAL_WINDOW(tp->t_segsz); 273 tp->snd_ssthresh = win * tp->t_segsz; 274 tp->t_dupacks = 0; 275 } 276 (void) tcp_output(tp); 277 break; 278 279 /* 280 * Persistance timer into zero window. 281 * Force a byte to be output, if possible. 282 */ 283 case TCPT_PERSIST: 284 /* 285 * Hack: if the peer is dead/unreachable, we do not 286 * time out if the window is closed. After a full 287 * backoff, drop the connection if the idle time 288 * (no responses to probes) reaches the maximum 289 * backoff that we would use if retransmitting. 290 */ 291 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 292 (tp->t_idle >= tcp_maxpersistidle || 293 tp->t_idle >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 294 tcpstat.tcps_persistdrops++; 295 tp = tcp_drop(tp, ETIMEDOUT); 296 break; 297 } 298 tcpstat.tcps_persisttimeo++; 299 tcp_setpersist(tp); 300 tp->t_force = 1; 301 (void) tcp_output(tp); 302 tp->t_force = 0; 303 break; 304 305 /* 306 * Keep-alive timer went off; send something 307 * or drop connection if idle for too long. 308 */ 309 case TCPT_KEEP: 310 tcpstat.tcps_keeptimeo++; 311 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 312 goto dropit; 313 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 314 tp->t_state <= TCPS_CLOSE_WAIT) { 315 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 316 goto dropit; 317 /* 318 * Send a packet designed to force a response 319 * if the peer is up and reachable: 320 * either an ACK if the connection is still alive, 321 * or an RST if the peer has closed the connection 322 * due to timeout or reboot. 323 * Using sequence number tp->snd_una-1 324 * causes the transmitted zero-length segment 325 * to lie outside the receive window; 326 * by the protocol spec, this requires the 327 * correspondent TCP to respond. 328 */ 329 tcpstat.tcps_keepprobe++; 330 #ifdef TCP_COMPAT_42 331 /* 332 * The keepalive packet must have nonzero length 333 * to get a 4.2 host to respond. 334 */ 335 (void)tcp_respond(tp, tp->t_template, 336 (struct mbuf *)NULL, tp->rcv_nxt - 1, 337 tp->snd_una - 1, 0); 338 #else 339 (void)tcp_respond(tp, tp->t_template, 340 (struct mbuf *)NULL, tp->rcv_nxt, 341 tp->snd_una - 1, 0); 342 #endif 343 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 344 } else 345 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 346 break; 347 dropit: 348 tcpstat.tcps_keepdrops++; 349 tp = tcp_drop(tp, ETIMEDOUT); 350 break; 351 } 352 return (tp); 353 } 354 #endif /* TUBA_INCLUDE */ 355
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