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 * $Id$ 35 */ 36 37 #ifndef TUBA_INCLUDE 38 #include <sys/param.h> 39 #include <sys/queue.h> 40 #include <sys/systm.h> 41 #include <sys/kernel.h> 42 #include <sys/sysctl.h> 43 #include <sys/malloc.h> 44 #include <sys/mbuf.h> 45 #include <sys/socket.h> 46 #include <sys/socketvar.h> 47 #include <sys/protosw.h> 48 #include <sys/errno.h> 49 50 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 51 52 #include <net/if.h> 53 #include <net/route.h> 54 55 #include <netinet/in.h> 56 #include <netinet/in_systm.h> 57 #include <netinet/ip.h> 58 #include <netinet/in_pcb.h> 59 #include <netinet/ip_var.h> 60 #include <netinet/tcp.h> 61 #include <netinet/tcp_fsm.h> 62 #include <netinet/tcp_seq.h> 63 #include <netinet/tcp_timer.h> 64 #include <netinet/tcp_var.h> 65 #include <netinet/tcpip.h> 66 #ifdef TCPDEBUG 67 #include <netinet/tcp_debug.h> 68 #endif 69 70 int tcp_keepinit = TCPTV_KEEP_INIT; 71 SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, 72 CTLFLAG_RW, &tcp_keepinit , 0, ""); 73 74 int tcp_keepidle = TCPTV_KEEP_IDLE; 75 SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, 76 CTLFLAG_RW, &tcp_keepidle , 0, ""); 77 78 static int tcp_keepintvl = TCPTV_KEEPINTVL; 79 SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, 80 CTLFLAG_RW, &tcp_keepintvl , 0, ""); 81 82 static int always_keepalive = 0; 83 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, 84 CTLFLAG_RW, &always_keepalive , 0, ""); 85 86 static int tcp_keepcnt = TCPTV_KEEPCNT; 87 /* max idle probes */ 88 static int tcp_maxpersistidle = TCPTV_KEEP_IDLE; 89 /* max idle time in persist */ 90 int tcp_maxidle; 91 #else /* TUBA_INCLUDE */ 92 93 static int tcp_maxpersistidle; 94 #endif /* TUBA_INCLUDE */ 95 96 /* 97 * Fast timeout routine for processing delayed acks 98 */ 99 void 100 tcp_fasttimo() 101 { 102 register struct inpcb *inp; 103 register struct tcpcb *tp; 104 int s; 105 106 s = splnet(); 107 108 for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) { 109 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 110 (tp->t_flags & TF_DELACK)) { 111 tp->t_flags &= ~TF_DELACK; 112 tp->t_flags |= TF_ACKNOW; 113 tcpstat.tcps_delack++; 114 (void) tcp_output(tp); 115 } 116 } 117 splx(s); 118 } 119 120 /* 121 * Tcp protocol timeout routine called every 500 ms. 122 * Updates the timers in all active tcb's and 123 * causes finite state machine actions if timers expire. 124 */ 125 void 126 tcp_slowtimo() 127 { 128 register struct inpcb *ip, *ipnxt; 129 register struct tcpcb *tp; 130 register int i; 131 int s; 132 #ifdef TCPDEBUG 133 int ostate; 134 #endif 135 136 s = splnet(); 137 138 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 139 140 ip = tcb.lh_first; 141 if (ip == NULL) { 142 splx(s); 143 return; 144 } 145 /* 146 * Search through tcb's and update active timers. 147 */ 148 for (; ip != NULL; ip = ipnxt) { 149 ipnxt = ip->inp_list.le_next; 150 tp = intotcpcb(ip); 151 if (tp == 0 || tp->t_state == TCPS_LISTEN) 152 continue; 153 for (i = 0; i < TCPT_NTIMERS; i++) { 154 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 155 #ifdef TCPDEBUG 156 ostate = tp->t_state; 157 #endif 158 tp = tcp_timers(tp, i); 159 if (tp == NULL) 160 goto tpgone; 161 #ifdef TCPDEBUG 162 if (tp->t_inpcb->inp_socket->so_options 163 & SO_DEBUG) 164 tcp_trace(TA_USER, ostate, tp, 165 (struct tcpiphdr *)0, 166 PRU_SLOWTIMO); 167 #endif 168 } 169 } 170 tp->t_idle++; 171 tp->t_duration++; 172 if (tp->t_rtt) 173 tp->t_rtt++; 174 tpgone: 175 ; 176 } 177 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 178 #ifdef TCP_COMPAT_42 179 if ((int)tcp_iss < 0) 180 tcp_iss = TCP_ISSINCR; /* XXX */ 181 #endif 182 tcp_now++; /* for timestamps */ 183 splx(s); 184 } 185 #ifndef TUBA_INCLUDE 186 187 /* 188 * Cancel all timers for TCP tp. 189 */ 190 void 191 tcp_canceltimers(tp) 192 struct tcpcb *tp; 193 { 194 register int i; 195 196 for (i = 0; i < TCPT_NTIMERS; i++) 197 tp->t_timer[i] = 0; 198 } 199 200 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 201 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 202 203 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 204 205 /* 206 * TCP timer processing. 207 */ 208 struct tcpcb * 209 tcp_timers(tp, timer) 210 register struct tcpcb *tp; 211 int timer; 212 { 213 register int rexmt; 214 215 switch (timer) { 216 217 /* 218 * 2 MSL timeout in shutdown went off. If we're closed but 219 * still waiting for peer to close and connection has been idle 220 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 221 * control block. Otherwise, check again in a bit. 222 */ 223 case TCPT_2MSL: 224 if (tp->t_state != TCPS_TIME_WAIT && 225 tp->t_idle <= tcp_maxidle) 226 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 227 else 228 tp = tcp_close(tp); 229 break; 230 231 /* 232 * Retransmission timer went off. Message has not 233 * been acked within retransmit interval. Back off 234 * to a longer retransmit interval and retransmit one segment. 235 */ 236 case TCPT_REXMT: 237 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 238 tp->t_rxtshift = TCP_MAXRXTSHIFT; 239 tcpstat.tcps_timeoutdrop++; 240 tp = tcp_drop(tp, tp->t_softerror ? 241 tp->t_softerror : ETIMEDOUT); 242 break; 243 } 244 tcpstat.tcps_rexmttimeo++; 245 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 246 TCPT_RANGESET(tp->t_rxtcur, rexmt, 247 tp->t_rttmin, TCPTV_REXMTMAX); 248 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 249 /* 250 * If losing, let the lower level know and try for 251 * a better route. Also, if we backed off this far, 252 * our srtt estimate is probably bogus. Clobber it 253 * so we'll take the next rtt measurement as our srtt; 254 * move the current srtt into rttvar to keep the current 255 * retransmit times until then. 256 */ 257 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 258 in_losing(tp->t_inpcb); 259 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 260 tp->t_srtt = 0; 261 } 262 tp->snd_nxt = tp->snd_una; 263 /* 264 * Force a segment to be sent. 265 */ 266 tp->t_flags |= TF_ACKNOW; 267 /* 268 * If timing a segment in this window, stop the timer. 269 */ 270 tp->t_rtt = 0; 271 /* 272 * Close the congestion window down to one segment 273 * (we'll open it by one segment for each ack we get). 274 * Since we probably have a window's worth of unacked 275 * data accumulated, this "slow start" keeps us from 276 * dumping all that data as back-to-back packets (which 277 * might overwhelm an intermediate gateway). 278 * 279 * There are two phases to the opening: Initially we 280 * open by one mss on each ack. This makes the window 281 * size increase exponentially with time. If the 282 * window is larger than the path can handle, this 283 * exponential growth results in dropped packet(s) 284 * almost immediately. To get more time between 285 * drops but still "push" the network to take advantage 286 * of improving conditions, we switch from exponential 287 * to linear window opening at some threshhold size. 288 * For a threshhold, we use half the current window 289 * size, truncated to a multiple of the mss. 290 * 291 * (the minimum cwnd that will give us exponential 292 * growth is 2 mss. We don't allow the threshhold 293 * to go below this.) 294 */ 295 { 296 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 297 if (win < 2) 298 win = 2; 299 tp->snd_cwnd = tp->t_maxseg; 300 tp->snd_ssthresh = win * tp->t_maxseg; 301 tp->t_dupacks = 0; 302 } 303 (void) tcp_output(tp); 304 break; 305 306 /* 307 * Persistance timer into zero window. 308 * Force a byte to be output, if possible. 309 */ 310 case TCPT_PERSIST: 311 tcpstat.tcps_persisttimeo++; 312 /* 313 * Hack: if the peer is dead/unreachable, we do not 314 * time out if the window is closed. After a full 315 * backoff, drop the connection if the idle time 316 * (no responses to probes) reaches the maximum 317 * backoff that we would use if retransmitting. 318 */ 319 if (tp->t_rxtshift == TCP_MAXRXTSHIFT) { 320 u_long maxidle = TCP_REXMTVAL(tp); 321 if (maxidle < tp->t_rttmin) 322 maxidle = tp->t_rttmin; 323 maxidle *= tcp_totbackoff; 324 if (tp->t_idle >= tcp_maxpersistidle || 325 tp->t_idle >= maxidle) { 326 tcpstat.tcps_persistdrop++; 327 tp = tcp_drop(tp, ETIMEDOUT); 328 break; 329 } 330 } 331 tcp_setpersist(tp); 332 tp->t_force = 1; 333 (void) tcp_output(tp); 334 tp->t_force = 0; 335 break; 336 337 /* 338 * Keep-alive timer went off; send something 339 * or drop connection if idle for too long. 340 */ 341 case TCPT_KEEP: 342 tcpstat.tcps_keeptimeo++; 343 if (tp->t_state < TCPS_ESTABLISHED) 344 goto dropit; 345 if ((always_keepalive || 346 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 347 tp->t_state <= TCPS_CLOSING) { 348 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 349 goto dropit; 350 /* 351 * Send a packet designed to force a response 352 * if the peer is up and reachable: 353 * either an ACK if the connection is still alive, 354 * or an RST if the peer has closed the connection 355 * due to timeout or reboot. 356 * Using sequence number tp->snd_una-1 357 * causes the transmitted zero-length segment 358 * to lie outside the receive window; 359 * by the protocol spec, this requires the 360 * correspondent TCP to respond. 361 */ 362 tcpstat.tcps_keepprobe++; 363 #ifdef TCP_COMPAT_42 364 /* 365 * The keepalive packet must have nonzero length 366 * to get a 4.2 host to respond. 367 */ 368 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 369 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 370 #else 371 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 372 tp->rcv_nxt, tp->snd_una - 1, 0); 373 #endif 374 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 375 } else 376 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 377 break; 378 dropit: 379 tcpstat.tcps_keepdrops++; 380 tp = tcp_drop(tp, ETIMEDOUT); 381 break; 382 } 383 return (tp); 384 } 385 #endif /* TUBA_INCLUDE */ 386