1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * @(#)tcp_timer.c 8.1 (Berkeley) 6/10/93 34 * $Id: tcp_timer.c,v 1.3 1995/02/09 23:13:26 wollman Exp $ 35 */ 36 37 #ifndef TUBA_INCLUDE 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/malloc.h> 41 #include <sys/mbuf.h> 42 #include <sys/socket.h> 43 #include <sys/socketvar.h> 44 #include <sys/protosw.h> 45 #include <sys/errno.h> 46 47 #include <net/if.h> 48 #include <net/route.h> 49 50 #include <netinet/in.h> 51 #include <netinet/in_systm.h> 52 #include <netinet/ip.h> 53 #include <netinet/in_pcb.h> 54 #include <netinet/ip_var.h> 55 #include <netinet/tcp.h> 56 #include <netinet/tcp_fsm.h> 57 #include <netinet/tcp_seq.h> 58 #include <netinet/tcp_timer.h> 59 #include <netinet/tcp_var.h> 60 #include <netinet/tcpip.h> 61 62 int tcp_keepidle = TCPTV_KEEP_IDLE; 63 int tcp_keepintvl = TCPTV_KEEPINTVL; 64 int tcp_maxidle; 65 #endif /* TUBA_INCLUDE */ 66 /* 67 * Fast timeout routine for processing delayed acks 68 */ 69 void 70 tcp_fasttimo() 71 { 72 register struct inpcb *inp; 73 register struct tcpcb *tp; 74 int s = splnet(); 75 76 inp = tcb.inp_next; 77 if (inp) 78 for (; inp != &tcb; inp = inp->inp_next) 79 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 80 (tp->t_flags & TF_DELACK)) { 81 tp->t_flags &= ~TF_DELACK; 82 tp->t_flags |= TF_ACKNOW; 83 tcpstat.tcps_delack++; 84 (void) tcp_output(tp); 85 } 86 splx(s); 87 } 88 89 /* 90 * Tcp protocol timeout routine called every 500 ms. 91 * Updates the timers in all active tcb's and 92 * causes finite state machine actions if timers expire. 93 */ 94 void 95 tcp_slowtimo() 96 { 97 register struct inpcb *ip, *ipnxt; 98 register struct tcpcb *tp; 99 int s = splnet(); 100 register int i; 101 102 tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl; 103 /* 104 * Search through tcb's and update active timers. 105 */ 106 ip = tcb.inp_next; 107 if (ip == 0) { 108 splx(s); 109 return; 110 } 111 for (; ip != &tcb; ip = ipnxt) { 112 ipnxt = ip->inp_next; 113 tp = intotcpcb(ip); 114 if (tp == 0) 115 continue; 116 for (i = 0; i < TCPT_NTIMERS; i++) { 117 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 118 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 119 PRU_SLOWTIMO, (struct mbuf *)0, 120 (struct mbuf *)i, (struct mbuf *)0); 121 if (ipnxt->inp_prev != ip) 122 goto tpgone; 123 } 124 } 125 tp->t_idle++; 126 tp->t_duration++; 127 if (tp->t_rtt) 128 tp->t_rtt++; 129 tpgone: 130 ; 131 } 132 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 133 #ifdef TCP_COMPAT_42 134 if ((int)tcp_iss < 0) 135 tcp_iss = 0; /* XXX */ 136 #endif 137 tcp_now++; /* for timestamps */ 138 splx(s); 139 } 140 #ifndef TUBA_INCLUDE 141 142 /* 143 * Cancel all timers for TCP tp. 144 */ 145 void 146 tcp_canceltimers(tp) 147 struct tcpcb *tp; 148 { 149 register int i; 150 151 for (i = 0; i < TCPT_NTIMERS; i++) 152 tp->t_timer[i] = 0; 153 } 154 155 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 156 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 157 158 /* 159 * TCP timer processing. 160 */ 161 struct tcpcb * 162 tcp_timers(tp, timer) 163 register struct tcpcb *tp; 164 int timer; 165 { 166 register int rexmt; 167 168 switch (timer) { 169 170 /* 171 * 2 MSL timeout in shutdown went off. If we're closed but 172 * still waiting for peer to close and connection has been idle 173 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 174 * control block. Otherwise, check again in a bit. 175 */ 176 case TCPT_2MSL: 177 if (tp->t_state != TCPS_TIME_WAIT && 178 tp->t_idle <= tcp_maxidle) 179 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 180 else 181 tp = tcp_close(tp); 182 break; 183 184 /* 185 * Retransmission timer went off. Message has not 186 * been acked within retransmit interval. Back off 187 * to a longer retransmit interval and retransmit one segment. 188 */ 189 case TCPT_REXMT: 190 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 191 tp->t_rxtshift = TCP_MAXRXTSHIFT; 192 tcpstat.tcps_timeoutdrop++; 193 tp = tcp_drop(tp, tp->t_softerror ? 194 tp->t_softerror : ETIMEDOUT); 195 break; 196 } 197 tcpstat.tcps_rexmttimeo++; 198 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 199 TCPT_RANGESET(tp->t_rxtcur, rexmt, 200 tp->t_rttmin, TCPTV_REXMTMAX); 201 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 202 /* 203 * If losing, let the lower level know and try for 204 * a better route. Also, if we backed off this far, 205 * our srtt estimate is probably bogus. Clobber it 206 * so we'll take the next rtt measurement as our srtt; 207 * move the current srtt into rttvar to keep the current 208 * retransmit times until then. 209 */ 210 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 211 in_losing(tp->t_inpcb); 212 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 213 tp->t_srtt = 0; 214 } 215 tp->snd_nxt = tp->snd_una; 216 /* 217 * Force a segment to be sent. 218 */ 219 tp->t_flags |= TF_ACKNOW; 220 /* 221 * If timing a segment in this window, stop the timer. 222 */ 223 tp->t_rtt = 0; 224 /* 225 * Close the congestion window down to one segment 226 * (we'll open it by one segment for each ack we get). 227 * Since we probably have a window's worth of unacked 228 * data accumulated, this "slow start" keeps us from 229 * dumping all that data as back-to-back packets (which 230 * might overwhelm an intermediate gateway). 231 * 232 * There are two phases to the opening: Initially we 233 * open by one mss on each ack. This makes the window 234 * size increase exponentially with time. If the 235 * window is larger than the path can handle, this 236 * exponential growth results in dropped packet(s) 237 * almost immediately. To get more time between 238 * drops but still "push" the network to take advantage 239 * of improving conditions, we switch from exponential 240 * to linear window opening at some threshhold size. 241 * For a threshhold, we use half the current window 242 * size, truncated to a multiple of the mss. 243 * 244 * (the minimum cwnd that will give us exponential 245 * growth is 2 mss. We don't allow the threshhold 246 * to go below this.) 247 */ 248 { 249 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 250 if (win < 2) 251 win = 2; 252 tp->snd_cwnd = tp->t_maxseg; 253 tp->snd_ssthresh = win * tp->t_maxseg; 254 tp->t_dupacks = 0; 255 } 256 (void) tcp_output(tp); 257 break; 258 259 /* 260 * Persistance timer into zero window. 261 * Force a byte to be output, if possible. 262 */ 263 case TCPT_PERSIST: 264 tcpstat.tcps_persisttimeo++; 265 tcp_setpersist(tp); 266 tp->t_force = 1; 267 (void) tcp_output(tp); 268 tp->t_force = 0; 269 break; 270 271 /* 272 * Keep-alive timer went off; send something 273 * or drop connection if idle for too long. 274 */ 275 case TCPT_KEEP: 276 tcpstat.tcps_keeptimeo++; 277 if (tp->t_state < TCPS_ESTABLISHED) 278 goto dropit; 279 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 280 tp->t_state <= TCPS_CLOSE_WAIT) { 281 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 282 goto dropit; 283 /* 284 * Send a packet designed to force a response 285 * if the peer is up and reachable: 286 * either an ACK if the connection is still alive, 287 * or an RST if the peer has closed the connection 288 * due to timeout or reboot. 289 * Using sequence number tp->snd_una-1 290 * causes the transmitted zero-length segment 291 * to lie outside the receive window; 292 * by the protocol spec, this requires the 293 * correspondent TCP to respond. 294 */ 295 tcpstat.tcps_keepprobe++; 296 #ifdef TCP_COMPAT_42 297 /* 298 * The keepalive packet must have nonzero length 299 * to get a 4.2 host to respond. 300 */ 301 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 302 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 303 #else 304 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 305 tp->rcv_nxt, tp->snd_una - 1, 0); 306 #endif 307 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 308 } else 309 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 310 break; 311 dropit: 312 tcpstat.tcps_keepdrops++; 313 tp = tcp_drop(tp, ETIMEDOUT); 314 break; 315 } 316 return (tp); 317 } 318 #endif /* TUBA_INCLUDE */ 319