1 /* $NetBSD: tcp_timer.c,v 1.19 1997/07/28 22:07:40 thorpej 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 static int syn_cache_last = 0; 106 107 s = splsoftnet(); 108 tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl; 109 /* 110 * Search through tcb's and update active timers. 111 */ 112 inp = tcbtable.inpt_queue.cqh_first; 113 if (inp == (struct inpcb *)0) { /* XXX */ 114 splx(s); 115 return; 116 } 117 for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = ninp) { 118 ninp = inp->inp_queue.cqe_next; 119 tp = intotcpcb(inp); 120 if (tp == 0) 121 continue; 122 for (i = 0; i < TCPT_NTIMERS; i++) { 123 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 124 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 125 PRU_SLOWTIMO, (struct mbuf *)0, 126 (struct mbuf *)i, (struct mbuf *)0, 127 (struct proc *)0); 128 /* XXX NOT MP SAFE */ 129 if ((ninp == (void *)&tcbtable.inpt_queue && 130 tcbtable.inpt_queue.cqh_last != inp) || 131 ninp->inp_queue.cqe_prev != inp) 132 goto tpgone; 133 } 134 } 135 tp->t_idle++; 136 if (tp->t_rtt) 137 tp->t_rtt++; 138 tpgone: 139 ; 140 } 141 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 142 #ifdef TCP_COMPAT_42 143 if ((int)tcp_iss < 0) 144 tcp_iss = 0; /* XXX */ 145 #endif 146 tcp_now++; /* for timestamps */ 147 if (++syn_cache_last >= tcp_syn_cache_interval) { 148 syn_cache_timer(syn_cache_last); 149 syn_cache_last = 0; 150 } 151 splx(s); 152 } 153 #ifndef TUBA_INCLUDE 154 155 /* 156 * Cancel all timers for TCP tp. 157 */ 158 void 159 tcp_canceltimers(tp) 160 struct tcpcb *tp; 161 { 162 register int i; 163 164 for (i = 0; i < TCPT_NTIMERS; i++) 165 tp->t_timer[i] = 0; 166 } 167 168 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 169 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 170 171 /* 172 * TCP timer processing. 173 */ 174 struct tcpcb * 175 tcp_timers(tp, timer) 176 register struct tcpcb *tp; 177 int timer; 178 { 179 180 switch (timer) { 181 182 /* 183 * 2 MSL timeout in shutdown went off. If we're closed but 184 * still waiting for peer to close and connection has been idle 185 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 186 * control block. Otherwise, check again in a bit. 187 */ 188 case TCPT_2MSL: 189 if (tp->t_state != TCPS_TIME_WAIT && 190 tp->t_idle <= tcp_maxidle) 191 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 192 else 193 tp = tcp_close(tp); 194 break; 195 196 /* 197 * Retransmission timer went off. Message has not 198 * been acked within retransmit interval. Back off 199 * to a longer retransmit interval and retransmit one segment. 200 */ 201 case TCPT_REXMT: 202 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 203 tp->t_rxtshift = TCP_MAXRXTSHIFT; 204 tcpstat.tcps_timeoutdrop++; 205 tp = tcp_drop(tp, tp->t_softerror ? 206 tp->t_softerror : ETIMEDOUT); 207 break; 208 } 209 tcpstat.tcps_rexmttimeo++; 210 TCPT_RANGESET(tp->t_rxtcur, 211 TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift], 212 tp->t_rttmin, TCPTV_REXMTMAX); 213 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 214 /* 215 * If losing, let the lower level know and try for 216 * a better route. Also, if we backed off this far, 217 * our srtt estimate is probably bogus. Clobber it 218 * so we'll take the next rtt measurement as our srtt; 219 * move the current srtt into rttvar to keep the current 220 * retransmit times until then. 221 */ 222 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 223 in_losing(tp->t_inpcb); 224 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 225 tp->t_srtt = 0; 226 } 227 tp->snd_nxt = tp->snd_una; 228 /* 229 * If timing a segment in this window, stop the timer. 230 */ 231 tp->t_rtt = 0; 232 /* 233 * Close the congestion window down to one segment 234 * (we'll open it by one segment for each ack we get). 235 * Since we probably have a window's worth of unacked 236 * data accumulated, this "slow start" keeps us from 237 * dumping all that data as back-to-back packets (which 238 * might overwhelm an intermediate gateway). 239 * 240 * There are two phases to the opening: Initially we 241 * open by one mss on each ack. This makes the window 242 * size increase exponentially with time. If the 243 * window is larger than the path can handle, this 244 * exponential growth results in dropped packet(s) 245 * almost immediately. To get more time between 246 * drops but still "push" the network to take advantage 247 * of improving conditions, we switch from exponential 248 * to linear window opening at some threshhold size. 249 * For a threshhold, we use half the current window 250 * size, truncated to a multiple of the mss. 251 * 252 * (the minimum cwnd that will give us exponential 253 * growth is 2 mss. We don't allow the threshhold 254 * to go below this.) 255 */ 256 { 257 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 258 if (win < 2) 259 win = 2; 260 tp->snd_cwnd = tp->t_maxseg; 261 tp->snd_ssthresh = win * tp->t_maxseg; 262 tp->t_dupacks = 0; 263 } 264 (void) tcp_output(tp); 265 break; 266 267 /* 268 * Persistance timer into zero window. 269 * Force a byte to be output, if possible. 270 */ 271 case TCPT_PERSIST: 272 tcpstat.tcps_persisttimeo++; 273 tcp_setpersist(tp); 274 tp->t_force = 1; 275 (void) tcp_output(tp); 276 tp->t_force = 0; 277 break; 278 279 /* 280 * Keep-alive timer went off; send something 281 * or drop connection if idle for too long. 282 */ 283 case TCPT_KEEP: 284 tcpstat.tcps_keeptimeo++; 285 if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) 286 goto dropit; 287 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 288 tp->t_state <= TCPS_CLOSE_WAIT) { 289 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 290 goto dropit; 291 /* 292 * Send a packet designed to force a response 293 * if the peer is up and reachable: 294 * either an ACK if the connection is still alive, 295 * or an RST if the peer has closed the connection 296 * due to timeout or reboot. 297 * Using sequence number tp->snd_una-1 298 * causes the transmitted zero-length segment 299 * to lie outside the receive window; 300 * by the protocol spec, this requires the 301 * correspondent TCP to respond. 302 */ 303 tcpstat.tcps_keepprobe++; 304 #ifdef TCP_COMPAT_42 305 /* 306 * The keepalive packet must have nonzero length 307 * to get a 4.2 host to respond. 308 */ 309 (void)tcp_respond(tp, tp->t_template, 310 (struct mbuf *)NULL, tp->rcv_nxt - 1, 311 tp->snd_una - 1, 0); 312 #else 313 (void)tcp_respond(tp, tp->t_template, 314 (struct mbuf *)NULL, tp->rcv_nxt, 315 tp->snd_una - 1, 0); 316 #endif 317 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 318 } else 319 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 320 break; 321 dropit: 322 tcpstat.tcps_keepdrops++; 323 tp = tcp_drop(tp, ETIMEDOUT); 324 break; 325 } 326 return (tp); 327 } 328 #endif /* TUBA_INCLUDE */ 329