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 1.14 1996/03/11 15:13:35 davidg Exp $ 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 67 int tcp_keepidle = TCPTV_KEEP_IDLE; 68 SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, 69 CTLFLAG_RW, &tcp_keepidle , 0, ""); 70 71 static int tcp_keepintvl = TCPTV_KEEPINTVL; 72 SYSCTL_INT(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, 73 CTLFLAG_RW, &tcp_keepintvl , 0, ""); 74 75 static int always_keepalive = 0; 76 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, 77 CTLFLAG_RW, &always_keepalive , 0, ""); 78 79 static int tcp_keepcnt = TCPTV_KEEPCNT; 80 /* max idle probes */ 81 static int tcp_maxpersistidle = TCPTV_KEEP_IDLE; 82 /* max idle time in persist */ 83 int tcp_maxidle; 84 #else /* TUBA_INCLUDE */ 85 86 static int tcp_maxpersistidle; 87 #endif /* TUBA_INCLUDE */ 88 89 /* 90 * Fast timeout routine for processing delayed acks 91 */ 92 void 93 tcp_fasttimo() 94 { 95 register struct inpcb *inp; 96 register struct tcpcb *tp; 97 int s; 98 99 s = splnet(); 100 101 for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) { 102 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 103 (tp->t_flags & TF_DELACK)) { 104 tp->t_flags &= ~TF_DELACK; 105 tp->t_flags |= TF_ACKNOW; 106 tcpstat.tcps_delack++; 107 (void) tcp_output(tp); 108 } 109 } 110 splx(s); 111 } 112 113 /* 114 * Tcp protocol timeout routine called every 500 ms. 115 * Updates the timers in all active tcb's and 116 * causes finite state machine actions if timers expire. 117 */ 118 void 119 tcp_slowtimo() 120 { 121 register struct inpcb *ip, *ipnxt; 122 register struct tcpcb *tp; 123 register int i; 124 int s; 125 126 s = splnet(); 127 128 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 129 130 ip = tcb.lh_first; 131 if (ip == NULL) { 132 splx(s); 133 return; 134 } 135 /* 136 * Search through tcb's and update active timers. 137 */ 138 for (; ip != NULL; ip = ipnxt) { 139 ipnxt = ip->inp_list.le_next; 140 tp = intotcpcb(ip); 141 if (tp == 0 || tp->t_state == TCPS_LISTEN) 142 continue; 143 for (i = 0; i < TCPT_NTIMERS; i++) { 144 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 145 if (tcp_usrreq(tp->t_inpcb->inp_socket, 146 PRU_SLOWTIMO, (struct mbuf *)0, 147 (struct mbuf *)i, (struct mbuf *)0) == NULL) 148 goto tpgone; 149 } 150 } 151 tp->t_idle++; 152 tp->t_duration++; 153 if (tp->t_rtt) 154 tp->t_rtt++; 155 tpgone: 156 ; 157 } 158 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 159 #ifdef TCP_COMPAT_42 160 if ((int)tcp_iss < 0) 161 tcp_iss = TCP_ISSINCR; /* XXX */ 162 #endif 163 tcp_now++; /* for timestamps */ 164 splx(s); 165 } 166 #ifndef TUBA_INCLUDE 167 168 /* 169 * Cancel all timers for TCP tp. 170 */ 171 void 172 tcp_canceltimers(tp) 173 struct tcpcb *tp; 174 { 175 register int i; 176 177 for (i = 0; i < TCPT_NTIMERS; i++) 178 tp->t_timer[i] = 0; 179 } 180 181 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 182 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 183 184 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 185 186 /* 187 * TCP timer processing. 188 */ 189 struct tcpcb * 190 tcp_timers(tp, timer) 191 register struct tcpcb *tp; 192 int timer; 193 { 194 register int rexmt; 195 196 switch (timer) { 197 198 /* 199 * 2 MSL timeout in shutdown went off. If we're closed but 200 * still waiting for peer to close and connection has been idle 201 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 202 * control block. Otherwise, check again in a bit. 203 */ 204 case TCPT_2MSL: 205 if (tp->t_state != TCPS_TIME_WAIT && 206 tp->t_idle <= tcp_maxidle) 207 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 208 else 209 tp = tcp_close(tp); 210 break; 211 212 /* 213 * Retransmission timer went off. Message has not 214 * been acked within retransmit interval. Back off 215 * to a longer retransmit interval and retransmit one segment. 216 */ 217 case TCPT_REXMT: 218 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 219 tp->t_rxtshift = TCP_MAXRXTSHIFT; 220 tcpstat.tcps_timeoutdrop++; 221 tp = tcp_drop(tp, tp->t_softerror ? 222 tp->t_softerror : ETIMEDOUT); 223 break; 224 } 225 tcpstat.tcps_rexmttimeo++; 226 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 227 TCPT_RANGESET(tp->t_rxtcur, rexmt, 228 tp->t_rttmin, TCPTV_REXMTMAX); 229 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 230 /* 231 * If losing, let the lower level know and try for 232 * a better route. Also, if we backed off this far, 233 * our srtt estimate is probably bogus. Clobber it 234 * so we'll take the next rtt measurement as our srtt; 235 * move the current srtt into rttvar to keep the current 236 * retransmit times until then. 237 */ 238 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 239 in_losing(tp->t_inpcb); 240 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 241 tp->t_srtt = 0; 242 } 243 tp->snd_nxt = tp->snd_una; 244 /* 245 * Force a segment to be sent. 246 */ 247 tp->t_flags |= TF_ACKNOW; 248 /* 249 * If timing a segment in this window, stop the timer. 250 */ 251 tp->t_rtt = 0; 252 /* 253 * Close the congestion window down to one segment 254 * (we'll open it by one segment for each ack we get). 255 * Since we probably have a window's worth of unacked 256 * data accumulated, this "slow start" keeps us from 257 * dumping all that data as back-to-back packets (which 258 * might overwhelm an intermediate gateway). 259 * 260 * There are two phases to the opening: Initially we 261 * open by one mss on each ack. This makes the window 262 * size increase exponentially with time. If the 263 * window is larger than the path can handle, this 264 * exponential growth results in dropped packet(s) 265 * almost immediately. To get more time between 266 * drops but still "push" the network to take advantage 267 * of improving conditions, we switch from exponential 268 * to linear window opening at some threshhold size. 269 * For a threshhold, we use half the current window 270 * size, truncated to a multiple of the mss. 271 * 272 * (the minimum cwnd that will give us exponential 273 * growth is 2 mss. We don't allow the threshhold 274 * to go below this.) 275 */ 276 { 277 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 278 if (win < 2) 279 win = 2; 280 tp->snd_cwnd = tp->t_maxseg; 281 tp->snd_ssthresh = win * tp->t_maxseg; 282 tp->t_dupacks = 0; 283 } 284 (void) tcp_output(tp); 285 break; 286 287 /* 288 * Persistance timer into zero window. 289 * Force a byte to be output, if possible. 290 */ 291 case TCPT_PERSIST: 292 tcpstat.tcps_persisttimeo++; 293 /* 294 * Hack: if the peer is dead/unreachable, we do not 295 * time out if the window is closed. After a full 296 * backoff, drop the connection if the idle time 297 * (no responses to probes) reaches the maximum 298 * backoff that we would use if retransmitting. 299 */ 300 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 301 (tp->t_idle >= tcp_maxpersistidle || 302 tp->t_idle >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 303 tcpstat.tcps_persistdrop++; 304 tp = tcp_drop(tp, ETIMEDOUT); 305 break; 306 } 307 tcp_setpersist(tp); 308 tp->t_force = 1; 309 (void) tcp_output(tp); 310 tp->t_force = 0; 311 break; 312 313 /* 314 * Keep-alive timer went off; send something 315 * or drop connection if idle for too long. 316 */ 317 case TCPT_KEEP: 318 tcpstat.tcps_keeptimeo++; 319 if (tp->t_state < TCPS_ESTABLISHED) 320 goto dropit; 321 if ((always_keepalive || 322 tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) && 323 tp->t_state <= TCPS_CLOSE_WAIT) { 324 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 325 goto dropit; 326 /* 327 * Send a packet designed to force a response 328 * if the peer is up and reachable: 329 * either an ACK if the connection is still alive, 330 * or an RST if the peer has closed the connection 331 * due to timeout or reboot. 332 * Using sequence number tp->snd_una-1 333 * causes the transmitted zero-length segment 334 * to lie outside the receive window; 335 * by the protocol spec, this requires the 336 * correspondent TCP to respond. 337 */ 338 tcpstat.tcps_keepprobe++; 339 #ifdef TCP_COMPAT_42 340 /* 341 * The keepalive packet must have nonzero length 342 * to get a 4.2 host to respond. 343 */ 344 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 345 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 346 #else 347 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 348 tp->rcv_nxt, tp->snd_una - 1, 0); 349 #endif 350 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 351 } else 352 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 353 break; 354 dropit: 355 tcpstat.tcps_keepdrops++; 356 tp = tcp_drop(tp, ETIMEDOUT); 357 break; 358 } 359 return (tp); 360 } 361 #endif /* TUBA_INCLUDE */ 362