tcp_timer.c revision 1.7
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 * from: @(#)tcp_timer.c 8.1 (Berkeley) 6/10/93 34 * $Id: tcp_timer.c,v 1.7 1994/05/13 06:06:46 mycroft 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 if (tp->t_rtt) 127 tp->t_rtt++; 128 tpgone: 129 ; 130 } 131 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 132 #ifdef TCP_COMPAT_42 133 if ((int)tcp_iss < 0) 134 tcp_iss = 0; /* XXX */ 135 #endif 136 tcp_now++; /* for timestamps */ 137 splx(s); 138 } 139 #ifndef TUBA_INCLUDE 140 141 /* 142 * Cancel all timers for TCP tp. 143 */ 144 void 145 tcp_canceltimers(tp) 146 struct tcpcb *tp; 147 { 148 register int i; 149 150 for (i = 0; i < TCPT_NTIMERS; i++) 151 tp->t_timer[i] = 0; 152 } 153 154 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 155 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 156 157 /* 158 * TCP timer processing. 159 */ 160 struct tcpcb * 161 tcp_timers(tp, timer) 162 register struct tcpcb *tp; 163 int timer; 164 { 165 register int rexmt; 166 167 switch (timer) { 168 169 /* 170 * 2 MSL timeout in shutdown went off. If we're closed but 171 * still waiting for peer to close and connection has been idle 172 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 173 * control block. Otherwise, check again in a bit. 174 */ 175 case TCPT_2MSL: 176 if (tp->t_state != TCPS_TIME_WAIT && 177 tp->t_idle <= tcp_maxidle) 178 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 179 else 180 tp = tcp_close(tp); 181 break; 182 183 /* 184 * Retransmission timer went off. Message has not 185 * been acked within retransmit interval. Back off 186 * to a longer retransmit interval and retransmit one segment. 187 */ 188 case TCPT_REXMT: 189 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 190 tp->t_rxtshift = TCP_MAXRXTSHIFT; 191 tcpstat.tcps_timeoutdrop++; 192 tp = tcp_drop(tp, tp->t_softerror ? 193 tp->t_softerror : ETIMEDOUT); 194 break; 195 } 196 tcpstat.tcps_rexmttimeo++; 197 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 198 TCPT_RANGESET(tp->t_rxtcur, rexmt, 199 tp->t_rttmin, TCPTV_REXMTMAX); 200 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 201 /* 202 * If losing, let the lower level know and try for 203 * a better route. Also, if we backed off this far, 204 * our srtt estimate is probably bogus. Clobber it 205 * so we'll take the next rtt measurement as our srtt; 206 * move the current srtt into rttvar to keep the current 207 * retransmit times until then. 208 */ 209 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 210 in_losing(tp->t_inpcb); 211 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 212 tp->t_srtt = 0; 213 } 214 tp->snd_nxt = tp->snd_una; 215 /* 216 * If timing a segment in this window, stop the timer. 217 */ 218 tp->t_rtt = 0; 219 /* 220 * Close the congestion window down to one segment 221 * (we'll open it by one segment for each ack we get). 222 * Since we probably have a window's worth of unacked 223 * data accumulated, this "slow start" keeps us from 224 * dumping all that data as back-to-back packets (which 225 * might overwhelm an intermediate gateway). 226 * 227 * There are two phases to the opening: Initially we 228 * open by one mss on each ack. This makes the window 229 * size increase exponentially with time. If the 230 * window is larger than the path can handle, this 231 * exponential growth results in dropped packet(s) 232 * almost immediately. To get more time between 233 * drops but still "push" the network to take advantage 234 * of improving conditions, we switch from exponential 235 * to linear window opening at some threshhold size. 236 * For a threshhold, we use half the current window 237 * size, truncated to a multiple of the mss. 238 * 239 * (the minimum cwnd that will give us exponential 240 * growth is 2 mss. We don't allow the threshhold 241 * to go below this.) 242 */ 243 { 244 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 245 if (win < 2) 246 win = 2; 247 tp->snd_cwnd = tp->t_maxseg; 248 tp->snd_ssthresh = win * tp->t_maxseg; 249 tp->t_dupacks = 0; 250 } 251 (void) tcp_output(tp); 252 break; 253 254 /* 255 * Persistance timer into zero window. 256 * Force a byte to be output, if possible. 257 */ 258 case TCPT_PERSIST: 259 tcpstat.tcps_persisttimeo++; 260 tcp_setpersist(tp); 261 tp->t_force = 1; 262 (void) tcp_output(tp); 263 tp->t_force = 0; 264 break; 265 266 /* 267 * Keep-alive timer went off; send something 268 * or drop connection if idle for too long. 269 */ 270 case TCPT_KEEP: 271 tcpstat.tcps_keeptimeo++; 272 if (tp->t_state < TCPS_ESTABLISHED) 273 goto dropit; 274 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 275 tp->t_state <= TCPS_CLOSE_WAIT) { 276 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 277 goto dropit; 278 /* 279 * Send a packet designed to force a response 280 * if the peer is up and reachable: 281 * either an ACK if the connection is still alive, 282 * or an RST if the peer has closed the connection 283 * due to timeout or reboot. 284 * Using sequence number tp->snd_una-1 285 * causes the transmitted zero-length segment 286 * to lie outside the receive window; 287 * by the protocol spec, this requires the 288 * correspondent TCP to respond. 289 */ 290 tcpstat.tcps_keepprobe++; 291 #ifdef TCP_COMPAT_42 292 /* 293 * The keepalive packet must have nonzero length 294 * to get a 4.2 host to respond. 295 */ 296 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 297 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 298 #else 299 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 300 tp->rcv_nxt, tp->snd_una - 1, 0); 301 #endif 302 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 303 } else 304 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 305 break; 306 dropit: 307 tcpstat.tcps_keepdrops++; 308 tp = tcp_drop(tp, ETIMEDOUT); 309 break; 310 } 311 return (tp); 312 } 313 #endif /* TUBA_INCLUDE */ 314
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