1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 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 8.2 (Berkeley) 5/24/95 34 * $Id: tcp_timer.c,v 1.8 1995/07/29 18:48:43 davidg 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 #include <sys/queue.h> 47 48 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 49 50 #include <net/if.h> 51 #include <net/route.h> 52 53 #include <netinet/in.h> 54 #include <netinet/in_systm.h> 55 #include <netinet/ip.h> 56 #include <netinet/in_pcb.h> 57 #include <netinet/ip_var.h> 58 #include <netinet/tcp.h> 59 #include <netinet/tcp_fsm.h> 60 #include <netinet/tcp_seq.h> 61 #include <netinet/tcp_timer.h> 62 #include <netinet/tcp_var.h> 63 #include <netinet/tcpip.h> 64 65 int tcp_keepidle = TCPTV_KEEP_IDLE; 66 int tcp_keepintvl = TCPTV_KEEPINTVL; 67 int tcp_keepcnt = TCPTV_KEEPCNT; /* max idle probes */ 68 int tcp_maxpersistidle = TCPTV_KEEP_IDLE; /* max idle time in persist */ 69 int tcp_maxidle; 70 #else /* TUBA_INCLUDE */ 71 72 extern int tcp_maxpersistidle; 73 #endif /* TUBA_INCLUDE */ 74 75 /* 76 * Fast timeout routine for processing delayed acks 77 */ 78 void 79 tcp_fasttimo() 80 { 81 register struct inpcb *inp; 82 register struct tcpcb *tp; 83 int s; 84 85 s = splnet(); 86 87 for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) { 88 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 89 (tp->t_flags & TF_DELACK)) { 90 tp->t_flags &= ~TF_DELACK; 91 tp->t_flags |= TF_ACKNOW; 92 tcpstat.tcps_delack++; 93 (void) tcp_output(tp); 94 } 95 } 96 splx(s); 97 } 98 99 /* 100 * Tcp protocol timeout routine called every 500 ms. 101 * Updates the timers in all active tcb's and 102 * causes finite state machine actions if timers expire. 103 */ 104 void 105 tcp_slowtimo() 106 { 107 register struct inpcb *ip, *ipnxt; 108 register struct tcpcb *tp; 109 register int i; 110 int s; 111 112 s = splnet(); 113 114 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 115 116 ip = tcb.lh_first; 117 if (ip == NULL) { 118 splx(s); 119 return; 120 } 121 /* 122 * Search through tcb's and update active timers. 123 */ 124 for (; ip != NULL; ip = ipnxt) { 125 ipnxt = ip->inp_list.le_next; 126 tp = intotcpcb(ip); 127 if (tp == 0 || tp->t_state == TCPS_LISTEN) 128 continue; 129 for (i = 0; i < TCPT_NTIMERS; i++) { 130 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 131 if (tcp_usrreq(tp->t_inpcb->inp_socket, 132 PRU_SLOWTIMO, (struct mbuf *)0, 133 (struct mbuf *)i, (struct mbuf *)0) == NULL) 134 goto tpgone; 135 } 136 } 137 tp->t_idle++; 138 tp->t_duration++; 139 if (tp->t_rtt) 140 tp->t_rtt++; 141 tpgone: 142 ; 143 } 144 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 145 #ifdef TCP_COMPAT_42 146 if ((int)tcp_iss < 0) 147 tcp_iss = TCP_ISSINCR; /* XXX */ 148 #endif 149 tcp_now++; /* for timestamps */ 150 splx(s); 151 } 152 #ifndef TUBA_INCLUDE 153 154 /* 155 * Cancel all timers for TCP tp. 156 */ 157 void 158 tcp_canceltimers(tp) 159 struct tcpcb *tp; 160 { 161 register int i; 162 163 for (i = 0; i < TCPT_NTIMERS; i++) 164 tp->t_timer[i] = 0; 165 } 166 167 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 168 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 169 170 int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 171 172 /* 173 * TCP timer processing. 174 */ 175 struct tcpcb * 176 tcp_timers(tp, timer) 177 register struct tcpcb *tp; 178 int timer; 179 { 180 register int rexmt; 181 182 switch (timer) { 183 184 /* 185 * 2 MSL timeout in shutdown went off. If we're closed but 186 * still waiting for peer to close and connection has been idle 187 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 188 * control block. Otherwise, check again in a bit. 189 */ 190 case TCPT_2MSL: 191 if (tp->t_state != TCPS_TIME_WAIT && 192 tp->t_idle <= tcp_maxidle) 193 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 194 else 195 tp = tcp_close(tp); 196 break; 197 198 /* 199 * Retransmission timer went off. Message has not 200 * been acked within retransmit interval. Back off 201 * to a longer retransmit interval and retransmit one segment. 202 */ 203 case TCPT_REXMT: 204 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 205 tp->t_rxtshift = TCP_MAXRXTSHIFT; 206 tcpstat.tcps_timeoutdrop++; 207 tp = tcp_drop(tp, tp->t_softerror ? 208 tp->t_softerror : ETIMEDOUT); 209 break; 210 } 211 tcpstat.tcps_rexmttimeo++; 212 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 213 TCPT_RANGESET(tp->t_rxtcur, rexmt, 214 tp->t_rttmin, TCPTV_REXMTMAX); 215 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 216 /* 217 * If losing, let the lower level know and try for 218 * a better route. Also, if we backed off this far, 219 * our srtt estimate is probably bogus. Clobber it 220 * so we'll take the next rtt measurement as our srtt; 221 * move the current srtt into rttvar to keep the current 222 * retransmit times until then. 223 */ 224 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 225 in_losing(tp->t_inpcb); 226 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 227 tp->t_srtt = 0; 228 } 229 tp->snd_nxt = tp->snd_una; 230 /* 231 * Force a segment to be sent. 232 */ 233 tp->t_flags |= TF_ACKNOW; 234 /* 235 * If timing a segment in this window, stop the timer. 236 */ 237 tp->t_rtt = 0; 238 /* 239 * Close the congestion window down to one segment 240 * (we'll open it by one segment for each ack we get). 241 * Since we probably have a window's worth of unacked 242 * data accumulated, this "slow start" keeps us from 243 * dumping all that data as back-to-back packets (which 244 * might overwhelm an intermediate gateway). 245 * 246 * There are two phases to the opening: Initially we 247 * open by one mss on each ack. This makes the window 248 * size increase exponentially with time. If the 249 * window is larger than the path can handle, this 250 * exponential growth results in dropped packet(s) 251 * almost immediately. To get more time between 252 * drops but still "push" the network to take advantage 253 * of improving conditions, we switch from exponential 254 * to linear window opening at some threshhold size. 255 * For a threshhold, we use half the current window 256 * size, truncated to a multiple of the mss. 257 * 258 * (the minimum cwnd that will give us exponential 259 * growth is 2 mss. We don't allow the threshhold 260 * to go below this.) 261 */ 262 { 263 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 264 if (win < 2) 265 win = 2; 266 tp->snd_cwnd = tp->t_maxseg; 267 tp->snd_ssthresh = win * tp->t_maxseg; 268 tp->t_dupacks = 0; 269 } 270 (void) tcp_output(tp); 271 break; 272 273 /* 274 * Persistance timer into zero window. 275 * Force a byte to be output, if possible. 276 */ 277 case TCPT_PERSIST: 278 tcpstat.tcps_persisttimeo++; 279 /* 280 * Hack: if the peer is dead/unreachable, we do not 281 * time out if the window is closed. After a full 282 * backoff, drop the connection if the idle time 283 * (no responses to probes) reaches the maximum 284 * backoff that we would use if retransmitting. 285 */ 286 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 287 (tp->t_idle >= tcp_maxpersistidle || 288 tp->t_idle >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 289 tcpstat.tcps_persistdrop++; 290 tp = tcp_drop(tp, ETIMEDOUT); 291 break; 292 } 293 tcp_setpersist(tp); 294 tp->t_force = 1; 295 (void) tcp_output(tp); 296 tp->t_force = 0; 297 break; 298 299 /* 300 * Keep-alive timer went off; send something 301 * or drop connection if idle for too long. 302 */ 303 case TCPT_KEEP: 304 tcpstat.tcps_keeptimeo++; 305 if (tp->t_state < TCPS_ESTABLISHED) 306 goto dropit; 307 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 308 tp->t_state <= TCPS_CLOSE_WAIT) { 309 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 310 goto dropit; 311 /* 312 * Send a packet designed to force a response 313 * if the peer is up and reachable: 314 * either an ACK if the connection is still alive, 315 * or an RST if the peer has closed the connection 316 * due to timeout or reboot. 317 * Using sequence number tp->snd_una-1 318 * causes the transmitted zero-length segment 319 * to lie outside the receive window; 320 * by the protocol spec, this requires the 321 * correspondent TCP to respond. 322 */ 323 tcpstat.tcps_keepprobe++; 324 #ifdef TCP_COMPAT_42 325 /* 326 * The keepalive packet must have nonzero length 327 * to get a 4.2 host to respond. 328 */ 329 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 330 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 331 #else 332 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 333 tp->rcv_nxt, tp->snd_una - 1, 0); 334 #endif 335 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 336 } else 337 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 338 break; 339 dropit: 340 tcpstat.tcps_keepdrops++; 341 tp = tcp_drop(tp, ETIMEDOUT); 342 break; 343 } 344 return (tp); 345 } 346 #endif /* TUBA_INCLUDE */ 347