1 /* $NetBSD: tcp_timer.c,v 1.9 1994/10/14 16:01:52 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 = splnet(); 76 77 inp = tcb.inp_next; 78 if (inp) 79 for (; inp != &tcb; inp = inp->inp_next) 80 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 81 (tp->t_flags & TF_DELACK)) { 82 tp->t_flags &= ~TF_DELACK; 83 tp->t_flags |= TF_ACKNOW; 84 tcpstat.tcps_delack++; 85 (void) tcp_output(tp); 86 } 87 splx(s); 88 } 89 90 /* 91 * Tcp protocol timeout routine called every 500 ms. 92 * Updates the timers in all active tcb's and 93 * causes finite state machine actions if timers expire. 94 */ 95 void 96 tcp_slowtimo() 97 { 98 register struct inpcb *ip, *ipnxt; 99 register struct tcpcb *tp; 100 int s = splnet(); 101 register int i; 102 103 tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl; 104 /* 105 * Search through tcb's and update active timers. 106 */ 107 ip = tcb.inp_next; 108 if (ip == 0) { 109 splx(s); 110 return; 111 } 112 for (; ip != &tcb; ip = ipnxt) { 113 ipnxt = ip->inp_next; 114 tp = intotcpcb(ip); 115 if (tp == 0) 116 continue; 117 for (i = 0; i < TCPT_NTIMERS; i++) { 118 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 119 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 120 PRU_SLOWTIMO, (struct mbuf *)0, 121 (struct mbuf *)i, (struct mbuf *)0); 122 if (ipnxt->inp_prev != ip) 123 goto tpgone; 124 } 125 } 126 tp->t_idle++; 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 * If timing a segment in this window, stop the timer. 218 */ 219 tp->t_rtt = 0; 220 /* 221 * Close the congestion window down to one segment 222 * (we'll open it by one segment for each ack we get). 223 * Since we probably have a window's worth of unacked 224 * data accumulated, this "slow start" keeps us from 225 * dumping all that data as back-to-back packets (which 226 * might overwhelm an intermediate gateway). 227 * 228 * There are two phases to the opening: Initially we 229 * open by one mss on each ack. This makes the window 230 * size increase exponentially with time. If the 231 * window is larger than the path can handle, this 232 * exponential growth results in dropped packet(s) 233 * almost immediately. To get more time between 234 * drops but still "push" the network to take advantage 235 * of improving conditions, we switch from exponential 236 * to linear window opening at some threshhold size. 237 * For a threshhold, we use half the current window 238 * size, truncated to a multiple of the mss. 239 * 240 * (the minimum cwnd that will give us exponential 241 * growth is 2 mss. We don't allow the threshhold 242 * to go below this.) 243 */ 244 { 245 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 246 if (win < 2) 247 win = 2; 248 tp->snd_cwnd = tp->t_maxseg; 249 tp->snd_ssthresh = win * tp->t_maxseg; 250 tp->t_dupacks = 0; 251 } 252 (void) tcp_output(tp); 253 break; 254 255 /* 256 * Persistance timer into zero window. 257 * Force a byte to be output, if possible. 258 */ 259 case TCPT_PERSIST: 260 tcpstat.tcps_persisttimeo++; 261 tcp_setpersist(tp); 262 tp->t_force = 1; 263 (void) tcp_output(tp); 264 tp->t_force = 0; 265 break; 266 267 /* 268 * Keep-alive timer went off; send something 269 * or drop connection if idle for too long. 270 */ 271 case TCPT_KEEP: 272 tcpstat.tcps_keeptimeo++; 273 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 274 goto dropit; 275 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 276 tp->t_state <= TCPS_CLOSE_WAIT) { 277 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 278 goto dropit; 279 /* 280 * Send a packet designed to force a response 281 * if the peer is up and reachable: 282 * either an ACK if the connection is still alive, 283 * or an RST if the peer has closed the connection 284 * due to timeout or reboot. 285 * Using sequence number tp->snd_una-1 286 * causes the transmitted zero-length segment 287 * to lie outside the receive window; 288 * by the protocol spec, this requires the 289 * correspondent TCP to respond. 290 */ 291 tcpstat.tcps_keepprobe++; 292 #ifdef TCP_COMPAT_42 293 /* 294 * The keepalive packet must have nonzero length 295 * to get a 4.2 host to respond. 296 */ 297 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 298 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 299 #else 300 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 301 tp->rcv_nxt, tp->snd_una - 1, 0); 302 #endif 303 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 304 } else 305 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 306 break; 307 dropit: 308 tcpstat.tcps_keepdrops++; 309 tp = tcp_drop(tp, ETIMEDOUT); 310 break; 311 } 312 return (tp); 313 } 314 #endif /* TUBA_INCLUDE */ 315