tcp_timer.c revision 1.4
1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California. 3 * 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 7.18 (Berkeley) 6/28/90 34 * $Id: tcp_timer.c,v 1.4 1993/12/18 00:42:09 mycroft Exp $ 35 */ 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/malloc.h> 40 #include <sys/mbuf.h> 41 #include <sys/socket.h> 42 #include <sys/socketvar.h> 43 #include <sys/protosw.h> 44 #include <sys/errno.h> 45 46 #include <net/if.h> 47 #include <net/route.h> 48 49 #include <netinet/in.h> 50 #include <netinet/in_systm.h> 51 #include <netinet/ip.h> 52 #include <netinet/in_pcb.h> 53 #include <netinet/ip_var.h> 54 #include <netinet/tcp.h> 55 #include <netinet/tcp_fsm.h> 56 #include <netinet/tcp_seq.h> 57 #include <netinet/tcp_timer.h> 58 #include <netinet/tcp_var.h> 59 #include <netinet/tcpip.h> 60 61 int tcp_keepidle = TCPTV_KEEP_IDLE; 62 int tcp_keepintvl = TCPTV_KEEPINTVL; 63 int tcp_maxidle; 64 /* 65 * Fast timeout routine for processing delayed acks 66 */ 67 tcp_fasttimo() 68 { 69 register struct inpcb *inp; 70 register struct tcpcb *tp; 71 int s = splnet(); 72 73 inp = tcb.inp_next; 74 if (inp) 75 for (; inp != &tcb; inp = inp->inp_next) 76 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 77 (tp->t_flags & TF_DELACK)) { 78 tp->t_flags &= ~TF_DELACK; 79 tp->t_flags |= TF_ACKNOW; 80 tcpstat.tcps_delack++; 81 (void) tcp_output(tp); 82 } 83 splx(s); 84 } 85 86 /* 87 * Tcp protocol timeout routine called every 500 ms. 88 * Updates the timers in all active tcb's and 89 * causes finite state machine actions if timers expire. 90 */ 91 tcp_slowtimo() 92 { 93 register struct inpcb *ip, *ipnxt; 94 register struct tcpcb *tp; 95 int s = splnet(); 96 register int i; 97 98 tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl; 99 /* 100 * Search through tcb's and update active timers. 101 */ 102 ip = tcb.inp_next; 103 if (ip == 0) { 104 splx(s); 105 return; 106 } 107 for (; ip != &tcb; ip = ipnxt) { 108 ipnxt = ip->inp_next; 109 tp = intotcpcb(ip); 110 if (tp == 0) 111 continue; 112 for (i = 0; i < TCPT_NTIMERS; i++) { 113 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 114 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 115 PRU_SLOWTIMO, (struct mbuf *)0, 116 (struct mbuf *)i, (struct mbuf *)0); 117 if (ipnxt->inp_prev != ip) 118 goto tpgone; 119 } 120 } 121 tp->t_idle++; 122 if (tp->t_rtt) 123 tp->t_rtt++; 124 tpgone: 125 ; 126 } 127 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 128 #ifdef TCP_COMPAT_42 129 if ((int)tcp_iss < 0) 130 tcp_iss = 0; /* XXX */ 131 #endif 132 splx(s); 133 } 134 135 /* 136 * Cancel all timers for TCP tp. 137 */ 138 tcp_canceltimers(tp) 139 struct tcpcb *tp; 140 { 141 register int i; 142 143 for (i = 0; i < TCPT_NTIMERS; i++) 144 tp->t_timer[i] = 0; 145 } 146 147 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 148 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 149 150 /* 151 * TCP timer processing. 152 */ 153 struct tcpcb * 154 tcp_timers(tp, timer) 155 register struct tcpcb *tp; 156 int timer; 157 { 158 register int rexmt; 159 160 switch (timer) { 161 162 /* 163 * 2 MSL timeout in shutdown went off. If we're closed but 164 * still waiting for peer to close and connection has been idle 165 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 166 * control block. Otherwise, check again in a bit. 167 */ 168 case TCPT_2MSL: 169 if (tp->t_state != TCPS_TIME_WAIT && 170 tp->t_idle <= tcp_maxidle) 171 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 172 else 173 tp = tcp_close(tp); 174 break; 175 176 /* 177 * Retransmission timer went off. Message has not 178 * been acked within retransmit interval. Back off 179 * to a longer retransmit interval and retransmit one segment. 180 */ 181 case TCPT_REXMT: 182 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 183 tp->t_rxtshift = TCP_MAXRXTSHIFT; 184 tcpstat.tcps_timeoutdrop++; 185 tp = tcp_drop(tp, tp->t_softerror ? 186 tp->t_softerror : ETIMEDOUT); 187 break; 188 } 189 tcpstat.tcps_rexmttimeo++; 190 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 191 TCPT_RANGESET(tp->t_rxtcur, rexmt, 192 tp->t_rttmin, TCPTV_REXMTMAX); 193 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 194 /* 195 * If losing, let the lower level know and try for 196 * a better route. Also, if we backed off this far, 197 * our srtt estimate is probably bogus. Clobber it 198 * so we'll take the next rtt measurement as our srtt; 199 * move the current srtt into rttvar to keep the current 200 * retransmit times until then. 201 */ 202 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 203 in_losing(tp->t_inpcb); 204 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 205 tp->t_srtt = 0; 206 } 207 tp->snd_nxt = tp->snd_una; 208 /* 209 * If timing a segment in this window, stop the timer. 210 */ 211 tp->t_rtt = 0; 212 /* 213 * Close the congestion window down to one segment 214 * (we'll open it by one segment for each ack we get). 215 * Since we probably have a window's worth of unacked 216 * data accumulated, this "slow start" keeps us from 217 * dumping all that data as back-to-back packets (which 218 * might overwhelm an intermediate gateway). 219 * 220 * There are two phases to the opening: Initially we 221 * open by one mss on each ack. This makes the window 222 * size increase exponentially with time. If the 223 * window is larger than the path can handle, this 224 * exponential growth results in dropped packet(s) 225 * almost immediately. To get more time between 226 * drops but still "push" the network to take advantage 227 * of improving conditions, we switch from exponential 228 * to linear window opening at some threshhold size. 229 * For a threshhold, we use half the current window 230 * size, truncated to a multiple of the mss. 231 * 232 * (the minimum cwnd that will give us exponential 233 * growth is 2 mss. We don't allow the threshhold 234 * to go below this.) 235 */ 236 { 237 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 238 if (win < 2) 239 win = 2; 240 tp->snd_cwnd = tp->t_maxseg; 241 tp->snd_ssthresh = win * tp->t_maxseg; 242 tp->t_dupacks = 0; 243 } 244 (void) tcp_output(tp); 245 break; 246 247 /* 248 * Persistance timer into zero window. 249 * Force a byte to be output, if possible. 250 */ 251 case TCPT_PERSIST: 252 tcpstat.tcps_persisttimeo++; 253 tcp_setpersist(tp); 254 tp->t_force = 1; 255 (void) tcp_output(tp); 256 tp->t_force = 0; 257 break; 258 259 /* 260 * Keep-alive timer went off; send something 261 * or drop connection if idle for too long. 262 */ 263 case TCPT_KEEP: 264 tcpstat.tcps_keeptimeo++; 265 if (tp->t_state < TCPS_ESTABLISHED) 266 goto dropit; 267 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 268 tp->t_state <= TCPS_CLOSE_WAIT) { 269 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 270 goto dropit; 271 /* 272 * Send a packet designed to force a response 273 * if the peer is up and reachable: 274 * either an ACK if the connection is still alive, 275 * or an RST if the peer has closed the connection 276 * due to timeout or reboot. 277 * Using sequence number tp->snd_una-1 278 * causes the transmitted zero-length segment 279 * to lie outside the receive window; 280 * by the protocol spec, this requires the 281 * correspondent TCP to respond. 282 */ 283 tcpstat.tcps_keepprobe++; 284 #ifdef TCP_COMPAT_42 285 /* 286 * The keepalive packet must have nonzero length 287 * to get a 4.2 host to respond. 288 */ 289 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 290 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 291 #else 292 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 293 tp->rcv_nxt, tp->snd_una - 1, 0); 294 #endif 295 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 296 } else 297 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 298 break; 299 dropit: 300 tcpstat.tcps_keepdrops++; 301 tp = tcp_drop(tp, ETIMEDOUT); 302 break; 303 } 304 return (tp); 305 } 306
Indexes created Mon Sep 22 05:09:51 GMT 2025