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 1.24 1997/09/16 18:36:06 joerg Exp $ 35 */ 36 37 #include "opt_compat.h" 38 #include "opt_tcpdebug.h" 39 40 #ifndef TUBA_INCLUDE 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/kernel.h> 44 #include <sys/sysctl.h> 45 #include <sys/socket.h> 46 #include <sys/socketvar.h> 47 #include <sys/protosw.h> 48 49 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 50 51 #include <net/route.h> 52 53 #include <netinet/in.h> 54 #include <netinet/in_systm.h> 55 #include <netinet/in_pcb.h> 56 #include <netinet/ip_var.h> 57 #include <netinet/tcp.h> 58 #include <netinet/tcp_fsm.h> 59 #include <netinet/tcp_seq.h> 60 #include <netinet/tcp_timer.h> 61 #include <netinet/tcp_var.h> 62 #include <netinet/tcpip.h> 63 #ifdef TCPDEBUG 64 #include <netinet/tcp_debug.h> 65 #endif 66 67 int tcp_keepinit = TCPTV_KEEP_INIT; 68 SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, 69 CTLFLAG_RW, &tcp_keepinit , 0, ""); 70 71 int tcp_keepidle = TCPTV_KEEP_IDLE; 72 SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, 73 CTLFLAG_RW, &tcp_keepidle , 0, ""); 74 75 static int tcp_keepintvl = TCPTV_KEEPINTVL; 76 SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, 77 CTLFLAG_RW, &tcp_keepintvl , 0, ""); 78 79 static int always_keepalive = 0; 80 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, 81 CTLFLAG_RW, &always_keepalive , 0, ""); 82 83 static int tcp_keepcnt = TCPTV_KEEPCNT; 84 /* max idle probes */ 85 static int tcp_maxpersistidle = TCPTV_KEEP_IDLE; 86 /* max idle time in persist */ 87 int tcp_maxidle; 88 #else /* TUBA_INCLUDE */ 89 90 static int tcp_maxpersistidle; 91 #endif /* TUBA_INCLUDE */ 92 93 /* 94 * Fast timeout routine for processing delayed acks 95 */ 96 void 97 tcp_fasttimo() 98 { 99 register struct inpcb *inp; 100 register struct tcpcb *tp; 101 int s; 102 103 s = splnet(); 104 105 for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) { 106 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 107 (tp->t_flags & TF_DELACK)) { 108 tp->t_flags &= ~TF_DELACK; 109 tp->t_flags |= TF_ACKNOW; 110 tcpstat.tcps_delack++; 111 (void) tcp_output(tp); 112 } 113 } 114 splx(s); 115 } 116 117 /* 118 * Tcp protocol timeout routine called every 500 ms. 119 * Updates the timers in all active tcb's and 120 * causes finite state machine actions if timers expire. 121 */ 122 void 123 tcp_slowtimo() 124 { 125 register struct inpcb *ip, *ipnxt; 126 register struct tcpcb *tp; 127 register int i; 128 int s; 129 #ifdef TCPDEBUG 130 int ostate; 131 #endif 132 133 s = splnet(); 134 135 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 136 137 ip = tcb.lh_first; 138 if (ip == NULL) { 139 splx(s); 140 return; 141 } 142 /* 143 * Search through tcb's and update active timers. 144 */ 145 for (; ip != NULL; ip = ipnxt) { 146 ipnxt = ip->inp_list.le_next; 147 tp = intotcpcb(ip); 148 if (tp == 0 || tp->t_state == TCPS_LISTEN) 149 continue; 150 for (i = 0; i < TCPT_NTIMERS; i++) { 151 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 152 #ifdef TCPDEBUG 153 ostate = tp->t_state; 154 #endif 155 tp = tcp_timers(tp, i); 156 if (tp == NULL) 157 goto tpgone; 158 #ifdef TCPDEBUG 159 if (tp->t_inpcb->inp_socket->so_options 160 & SO_DEBUG) 161 tcp_trace(TA_USER, ostate, tp, 162 (struct tcpiphdr *)0, 163 PRU_SLOWTIMO); 164 #endif 165 } 166 } 167 tp->t_idle++; 168 tp->t_duration++; 169 if (tp->t_rtt) 170 tp->t_rtt++; 171 tpgone: 172 ; 173 } 174 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 175 #ifdef TCP_COMPAT_42 176 if ((int)tcp_iss < 0) 177 tcp_iss = TCP_ISSINCR; /* XXX */ 178 #endif 179 tcp_now++; /* for timestamps */ 180 splx(s); 181 } 182 #ifndef TUBA_INCLUDE 183 184 /* 185 * Cancel all timers for TCP tp. 186 */ 187 void 188 tcp_canceltimers(tp) 189 struct tcpcb *tp; 190 { 191 register int i; 192 193 for (i = 0; i < TCPT_NTIMERS; i++) 194 tp->t_timer[i] = 0; 195 } 196 197 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 198 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 199 200 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 201 202 /* 203 * TCP timer processing. 204 */ 205 struct tcpcb * 206 tcp_timers(tp, timer) 207 register struct tcpcb *tp; 208 int timer; 209 { 210 register int rexmt; 211 212 switch (timer) { 213 214 /* 215 * 2 MSL timeout in shutdown went off. If we're closed but 216 * still waiting for peer to close and connection has been idle 217 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 218 * control block. Otherwise, check again in a bit. 219 */ 220 case TCPT_2MSL: 221 if (tp->t_state != TCPS_TIME_WAIT && 222 tp->t_idle <= tcp_maxidle) 223 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 224 else 225 tp = tcp_close(tp); 226 break; 227 228 /* 229 * Retransmission timer went off. Message has not 230 * been acked within retransmit interval. Back off 231 * to a longer retransmit interval and retransmit one segment. 232 */ 233 case TCPT_REXMT: 234 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 235 tp->t_rxtshift = TCP_MAXRXTSHIFT; 236 tcpstat.tcps_timeoutdrop++; 237 tp = tcp_drop(tp, tp->t_softerror ? 238 tp->t_softerror : ETIMEDOUT); 239 break; 240 } 241 tcpstat.tcps_rexmttimeo++; 242 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 243 TCPT_RANGESET(tp->t_rxtcur, rexmt, 244 tp->t_rttmin, TCPTV_REXMTMAX); 245 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 246 /* 247 * If losing, let the lower level know and try for 248 * a better route. Also, if we backed off this far, 249 * our srtt estimate is probably bogus. Clobber it 250 * so we'll take the next rtt measurement as our srtt; 251 * move the current srtt into rttvar to keep the current 252 * retransmit times until then. 253 */ 254 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 255 in_losing(tp->t_inpcb); 256 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 257 tp->t_srtt = 0; 258 } 259 tp->snd_nxt = tp->snd_una; 260 /* 261 * Force a segment to be sent. 262 */ 263 tp->t_flags |= TF_ACKNOW; 264 /* 265 * If timing a segment in this window, stop the timer. 266 */ 267 tp->t_rtt = 0; 268 /* 269 * Close the congestion window down to one segment 270 * (we'll open it by one segment for each ack we get). 271 * Since we probably have a window's worth of unacked 272 * data accumulated, this "slow start" keeps us from 273 * dumping all that data as back-to-back packets (which 274 * might overwhelm an intermediate gateway). 275 * 276 * There are two phases to the opening: Initially we 277 * open by one mss on each ack. This makes the window 278 * size increase exponentially with time. If the 279 * window is larger than the path can handle, this 280 * exponential growth results in dropped packet(s) 281 * almost immediately. To get more time between 282 * drops but still "push" the network to take advantage 283 * of improving conditions, we switch from exponential 284 * to linear window opening at some threshhold size. 285 * For a threshhold, we use half the current window 286 * size, truncated to a multiple of the mss. 287 * 288 * (the minimum cwnd that will give us exponential 289 * growth is 2 mss. We don't allow the threshhold 290 * to go below this.) 291 */ 292 { 293 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 294 if (win < 2) 295 win = 2; 296 tp->snd_cwnd = tp->t_maxseg; 297 tp->snd_ssthresh = win * tp->t_maxseg; 298 tp->t_dupacks = 0; 299 } 300 (void) tcp_output(tp); 301 break; 302 303 /* 304 * Persistance timer into zero window. 305 * Force a byte to be output, if possible. 306 */ 307 case TCPT_PERSIST: 308 tcpstat.tcps_persisttimeo++; 309 /* 310 * Hack: if the peer is dead/unreachable, we do not 311 * time out if the window is closed. After a full 312 * backoff, drop the connection if the idle time 313 * (no responses to probes) reaches the maximum 314 * backoff that we would use if retransmitting. 315 */ 316 if (tp->t_rxtshift == TCP_MAXRXTSHIFT) { 317 u_long maxidle = TCP_REXMTVAL(tp); 318 if (maxidle < tp->t_rttmin) 319 maxidle = tp->t_rttmin; 320 maxidle *= tcp_totbackoff; 321 if (tp->t_idle >= tcp_maxpersistidle || 322 tp->t_idle >= maxidle) { 323 tcpstat.tcps_persistdrop++; 324 tp = tcp_drop(tp, ETIMEDOUT); 325 break; 326 } 327 } 328 tcp_setpersist(tp); 329 tp->t_force = 1; 330 (void) tcp_output(tp); 331 tp->t_force = 0; 332 break; 333 334 /* 335 * Keep-alive timer went off; send something 336 * or drop connection if idle for too long. 337 */ 338 case TCPT_KEEP: 339 tcpstat.tcps_keeptimeo++; 340 if (tp->t_state < TCPS_ESTABLISHED) 341 goto dropit; 342 if ((always_keepalive || 343 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 344 tp->t_state <= TCPS_CLOSING) { 345 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 346 goto dropit; 347 /* 348 * Send a packet designed to force a response 349 * if the peer is up and reachable: 350 * either an ACK if the connection is still alive, 351 * or an RST if the peer has closed the connection 352 * due to timeout or reboot. 353 * Using sequence number tp->snd_una-1 354 * causes the transmitted zero-length segment 355 * to lie outside the receive window; 356 * by the protocol spec, this requires the 357 * correspondent TCP to respond. 358 */ 359 tcpstat.tcps_keepprobe++; 360 #ifdef TCP_COMPAT_42 361 /* 362 * The keepalive packet must have nonzero length 363 * to get a 4.2 host to respond. 364 */ 365 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 366 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 367 #else 368 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 369 tp->rcv_nxt, tp->snd_una - 1, 0); 370 #endif 371 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 372 } else 373 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 374 break; 375 dropit: 376 tcpstat.tcps_keepdrops++; 377 tp = tcp_drop(tp, ETIMEDOUT); 378 break; 379 } 380 return (tp); 381 } 382 #endif /* TUBA_INCLUDE */ 383