1 /* $NetBSD: tcp_timer.c,v 1.17 1996/12/10 18:20:24 mycroft 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_maxidle; 66 #endif /* TUBA_INCLUDE */ 67 /* 68 * Fast timeout routine for processing delayed acks 69 */ 70 void 71 tcp_fasttimo() 72 { 73 register struct inpcb *inp; 74 register struct tcpcb *tp; 75 int s; 76 77 s = splsoftnet(); 78 inp = tcbtable.inpt_queue.cqh_first; 79 if (inp) /* XXX */ 80 for (; inp != (struct inpcb *)&tcbtable.inpt_queue; 81 inp = inp->inp_queue.cqe_next) { 82 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 83 (tp->t_flags & TF_DELACK)) { 84 tp->t_flags &= ~TF_DELACK; 85 tp->t_flags |= TF_ACKNOW; 86 tcpstat.tcps_delack++; 87 (void) tcp_output(tp); 88 } 89 } 90 splx(s); 91 } 92 93 /* 94 * Tcp protocol timeout routine called every 500 ms. 95 * Updates the timers in all active tcb's and 96 * causes finite state machine actions if timers expire. 97 */ 98 void 99 tcp_slowtimo() 100 { 101 register struct inpcb *inp, *ninp; 102 register struct tcpcb *tp; 103 int s; 104 register long i; 105 106 s = splsoftnet(); 107 tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl; 108 /* 109 * Search through tcb's and update active timers. 110 */ 111 inp = tcbtable.inpt_queue.cqh_first; 112 if (inp == (struct inpcb *)0) { /* XXX */ 113 splx(s); 114 return; 115 } 116 for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = ninp) { 117 ninp = inp->inp_queue.cqe_next; 118 tp = intotcpcb(inp); 119 if (tp == 0) 120 continue; 121 for (i = 0; i < TCPT_NTIMERS; i++) { 122 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 123 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 124 PRU_SLOWTIMO, (struct mbuf *)0, 125 (struct mbuf *)i, (struct mbuf *)0, 126 (struct proc *)0); 127 /* XXX NOT MP SAFE */ 128 if ((ninp == (void *)&tcbtable.inpt_queue && 129 tcbtable.inpt_queue.cqh_last != inp) || 130 ninp->inp_queue.cqe_prev != inp) 131 goto tpgone; 132 } 133 } 134 tp->t_idle++; 135 if (tp->t_rtt) 136 tp->t_rtt++; 137 tpgone: 138 ; 139 } 140 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 141 #ifdef TCP_COMPAT_42 142 if ((int)tcp_iss < 0) 143 tcp_iss = 0; /* XXX */ 144 #endif 145 tcp_now++; /* for timestamps */ 146 splx(s); 147 } 148 #ifndef TUBA_INCLUDE 149 150 /* 151 * Cancel all timers for TCP tp. 152 */ 153 void 154 tcp_canceltimers(tp) 155 struct tcpcb *tp; 156 { 157 register int i; 158 159 for (i = 0; i < TCPT_NTIMERS; i++) 160 tp->t_timer[i] = 0; 161 } 162 163 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 164 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 165 166 /* 167 * TCP timer processing. 168 */ 169 struct tcpcb * 170 tcp_timers(tp, timer) 171 register struct tcpcb *tp; 172 int timer; 173 { 174 175 switch (timer) { 176 177 /* 178 * 2 MSL timeout in shutdown went off. If we're closed but 179 * still waiting for peer to close and connection has been idle 180 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 181 * control block. Otherwise, check again in a bit. 182 */ 183 case TCPT_2MSL: 184 if (tp->t_state != TCPS_TIME_WAIT && 185 tp->t_idle <= tcp_maxidle) 186 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 187 else 188 tp = tcp_close(tp); 189 break; 190 191 /* 192 * Retransmission timer went off. Message has not 193 * been acked within retransmit interval. Back off 194 * to a longer retransmit interval and retransmit one segment. 195 */ 196 case TCPT_REXMT: 197 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 198 tp->t_rxtshift = TCP_MAXRXTSHIFT; 199 tcpstat.tcps_timeoutdrop++; 200 tp = tcp_drop(tp, tp->t_softerror ? 201 tp->t_softerror : ETIMEDOUT); 202 break; 203 } 204 tcpstat.tcps_rexmttimeo++; 205 TCPT_RANGESET(tp->t_rxtcur, 206 TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift], 207 tp->t_rttmin, TCPTV_REXMTMAX); 208 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 209 /* 210 * If losing, let the lower level know and try for 211 * a better route. Also, if we backed off this far, 212 * our srtt estimate is probably bogus. Clobber it 213 * so we'll take the next rtt measurement as our srtt; 214 * move the current srtt into rttvar to keep the current 215 * retransmit times until then. 216 */ 217 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 218 in_losing(tp->t_inpcb); 219 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 220 tp->t_srtt = 0; 221 } 222 tp->snd_nxt = tp->snd_una; 223 /* 224 * If timing a segment in this window, stop the timer. 225 */ 226 tp->t_rtt = 0; 227 /* 228 * Close the congestion window down to one segment 229 * (we'll open it by one segment for each ack we get). 230 * Since we probably have a window's worth of unacked 231 * data accumulated, this "slow start" keeps us from 232 * dumping all that data as back-to-back packets (which 233 * might overwhelm an intermediate gateway). 234 * 235 * There are two phases to the opening: Initially we 236 * open by one mss on each ack. This makes the window 237 * size increase exponentially with time. If the 238 * window is larger than the path can handle, this 239 * exponential growth results in dropped packet(s) 240 * almost immediately. To get more time between 241 * drops but still "push" the network to take advantage 242 * of improving conditions, we switch from exponential 243 * to linear window opening at some threshhold size. 244 * For a threshhold, we use half the current window 245 * size, truncated to a multiple of the mss. 246 * 247 * (the minimum cwnd that will give us exponential 248 * growth is 2 mss. We don't allow the threshhold 249 * to go below this.) 250 */ 251 { 252 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 253 if (win < 2) 254 win = 2; 255 tp->snd_cwnd = tp->t_maxseg; 256 tp->snd_ssthresh = win * tp->t_maxseg; 257 tp->t_dupacks = 0; 258 } 259 (void) tcp_output(tp); 260 break; 261 262 /* 263 * Persistance timer into zero window. 264 * Force a byte to be output, if possible. 265 */ 266 case TCPT_PERSIST: 267 tcpstat.tcps_persisttimeo++; 268 tcp_setpersist(tp); 269 tp->t_force = 1; 270 (void) tcp_output(tp); 271 tp->t_force = 0; 272 break; 273 274 /* 275 * Keep-alive timer went off; send something 276 * or drop connection if idle for too long. 277 */ 278 case TCPT_KEEP: 279 tcpstat.tcps_keeptimeo++; 280 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 281 goto dropit; 282 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 283 tp->t_state <= TCPS_CLOSE_WAIT) { 284 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 285 goto dropit; 286 /* 287 * Send a packet designed to force a response 288 * if the peer is up and reachable: 289 * either an ACK if the connection is still alive, 290 * or an RST if the peer has closed the connection 291 * due to timeout or reboot. 292 * Using sequence number tp->snd_una-1 293 * causes the transmitted zero-length segment 294 * to lie outside the receive window; 295 * by the protocol spec, this requires the 296 * correspondent TCP to respond. 297 */ 298 tcpstat.tcps_keepprobe++; 299 #ifdef TCP_COMPAT_42 300 /* 301 * The keepalive packet must have nonzero length 302 * to get a 4.2 host to respond. 303 */ 304 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 305 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 306 #else 307 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 308 tp->rcv_nxt, tp->snd_una - 1, 0); 309 #endif 310 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 311 } else 312 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 313 break; 314 dropit: 315 tcpstat.tcps_keepdrops++; 316 tp = tcp_drop(tp, ETIMEDOUT); 317 break; 318 } 319 return (tp); 320 } 321 #endif /* TUBA_INCLUDE */ 322