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 1.11 1995/11/09 20:23:07 phk Exp $ 35 */ 36 37 #ifndef TUBA_INCLUDE 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/kernel.h> 41 #include <sys/sysctl.h> 42 #include <sys/malloc.h> 43 #include <sys/mbuf.h> 44 #include <sys/socket.h> 45 #include <sys/socketvar.h> 46 #include <sys/protosw.h> 47 #include <sys/errno.h> 48 #include <sys/queue.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 tcp_keepcnt = TCPTV_KEEPCNT; 76 /* max idle probes */ 77 static int tcp_maxpersistidle = TCPTV_KEEP_IDLE; 78 /* max idle time in persist */ 79 int tcp_maxidle; 80 #else /* TUBA_INCLUDE */ 81 82 static int tcp_maxpersistidle; 83 #endif /* TUBA_INCLUDE */ 84 85 /* 86 * Fast timeout routine for processing delayed acks 87 */ 88 void 89 tcp_fasttimo() 90 { 91 register struct inpcb *inp; 92 register struct tcpcb *tp; 93 int s; 94 95 s = splnet(); 96 97 for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) { 98 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 99 (tp->t_flags & TF_DELACK)) { 100 tp->t_flags &= ~TF_DELACK; 101 tp->t_flags |= TF_ACKNOW; 102 tcpstat.tcps_delack++; 103 (void) tcp_output(tp); 104 } 105 } 106 splx(s); 107 } 108 109 /* 110 * Tcp protocol timeout routine called every 500 ms. 111 * Updates the timers in all active tcb's and 112 * causes finite state machine actions if timers expire. 113 */ 114 void 115 tcp_slowtimo() 116 { 117 register struct inpcb *ip, *ipnxt; 118 register struct tcpcb *tp; 119 register int i; 120 int s; 121 122 s = splnet(); 123 124 tcp_maxidle = tcp_keepcnt * tcp_keepintvl; 125 126 ip = tcb.lh_first; 127 if (ip == NULL) { 128 splx(s); 129 return; 130 } 131 /* 132 * Search through tcb's and update active timers. 133 */ 134 for (; ip != NULL; ip = ipnxt) { 135 ipnxt = ip->inp_list.le_next; 136 tp = intotcpcb(ip); 137 if (tp == 0 || tp->t_state == TCPS_LISTEN) 138 continue; 139 for (i = 0; i < TCPT_NTIMERS; i++) { 140 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 141 if (tcp_usrreq(tp->t_inpcb->inp_socket, 142 PRU_SLOWTIMO, (struct mbuf *)0, 143 (struct mbuf *)i, (struct mbuf *)0) == NULL) 144 goto tpgone; 145 } 146 } 147 tp->t_idle++; 148 tp->t_duration++; 149 if (tp->t_rtt) 150 tp->t_rtt++; 151 tpgone: 152 ; 153 } 154 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 155 #ifdef TCP_COMPAT_42 156 if ((int)tcp_iss < 0) 157 tcp_iss = TCP_ISSINCR; /* XXX */ 158 #endif 159 tcp_now++; /* for timestamps */ 160 splx(s); 161 } 162 #ifndef TUBA_INCLUDE 163 164 /* 165 * Cancel all timers for TCP tp. 166 */ 167 void 168 tcp_canceltimers(tp) 169 struct tcpcb *tp; 170 { 171 register int i; 172 173 for (i = 0; i < TCPT_NTIMERS; i++) 174 tp->t_timer[i] = 0; 175 } 176 177 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 178 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 179 180 static int tcp_totbackoff = 511; /* sum of tcp_backoff[] */ 181 182 /* 183 * TCP timer processing. 184 */ 185 struct tcpcb * 186 tcp_timers(tp, timer) 187 register struct tcpcb *tp; 188 int timer; 189 { 190 register int rexmt; 191 192 switch (timer) { 193 194 /* 195 * 2 MSL timeout in shutdown went off. If we're closed but 196 * still waiting for peer to close and connection has been idle 197 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 198 * control block. Otherwise, check again in a bit. 199 */ 200 case TCPT_2MSL: 201 if (tp->t_state != TCPS_TIME_WAIT && 202 tp->t_idle <= tcp_maxidle) 203 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 204 else 205 tp = tcp_close(tp); 206 break; 207 208 /* 209 * Retransmission timer went off. Message has not 210 * been acked within retransmit interval. Back off 211 * to a longer retransmit interval and retransmit one segment. 212 */ 213 case TCPT_REXMT: 214 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 215 tp->t_rxtshift = TCP_MAXRXTSHIFT; 216 tcpstat.tcps_timeoutdrop++; 217 tp = tcp_drop(tp, tp->t_softerror ? 218 tp->t_softerror : ETIMEDOUT); 219 break; 220 } 221 tcpstat.tcps_rexmttimeo++; 222 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 223 TCPT_RANGESET(tp->t_rxtcur, rexmt, 224 tp->t_rttmin, TCPTV_REXMTMAX); 225 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 226 /* 227 * If losing, let the lower level know and try for 228 * a better route. Also, if we backed off this far, 229 * our srtt estimate is probably bogus. Clobber it 230 * so we'll take the next rtt measurement as our srtt; 231 * move the current srtt into rttvar to keep the current 232 * retransmit times until then. 233 */ 234 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 235 in_losing(tp->t_inpcb); 236 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 237 tp->t_srtt = 0; 238 } 239 tp->snd_nxt = tp->snd_una; 240 /* 241 * If timing a segment in this window, stop the timer. 242 */ 243 tp->t_rtt = 0; 244 /* 245 * Close the congestion window down to one segment 246 * (we'll open it by one segment for each ack we get). 247 * Since we probably have a window's worth of unacked 248 * data accumulated, this "slow start" keeps us from 249 * dumping all that data as back-to-back packets (which 250 * might overwhelm an intermediate gateway). 251 * 252 * There are two phases to the opening: Initially we 253 * open by one mss on each ack. This makes the window 254 * size increase exponentially with time. If the 255 * window is larger than the path can handle, this 256 * exponential growth results in dropped packet(s) 257 * almost immediately. To get more time between 258 * drops but still "push" the network to take advantage 259 * of improving conditions, we switch from exponential 260 * to linear window opening at some threshhold size. 261 * For a threshhold, we use half the current window 262 * size, truncated to a multiple of the mss. 263 * 264 * (the minimum cwnd that will give us exponential 265 * growth is 2 mss. We don't allow the threshhold 266 * to go below this.) 267 */ 268 { 269 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 270 if (win < 2) 271 win = 2; 272 tp->snd_cwnd = tp->t_maxseg; 273 tp->snd_ssthresh = win * tp->t_maxseg; 274 tp->t_dupacks = 0; 275 } 276 (void) tcp_output(tp); 277 break; 278 279 /* 280 * Persistance timer into zero window. 281 * Force a byte to be output, if possible. 282 */ 283 case TCPT_PERSIST: 284 tcpstat.tcps_persisttimeo++; 285 /* 286 * Hack: if the peer is dead/unreachable, we do not 287 * time out if the window is closed. After a full 288 * backoff, drop the connection if the idle time 289 * (no responses to probes) reaches the maximum 290 * backoff that we would use if retransmitting. 291 */ 292 if (tp->t_rxtshift == TCP_MAXRXTSHIFT && 293 (tp->t_idle >= tcp_maxpersistidle || 294 tp->t_idle >= TCP_REXMTVAL(tp) * tcp_totbackoff)) { 295 tcpstat.tcps_persistdrop++; 296 tp = tcp_drop(tp, ETIMEDOUT); 297 break; 298 } 299 tcp_setpersist(tp); 300 tp->t_force = 1; 301 (void) tcp_output(tp); 302 tp->t_force = 0; 303 break; 304 305 /* 306 * Keep-alive timer went off; send something 307 * or drop connection if idle for too long. 308 */ 309 case TCPT_KEEP: 310 tcpstat.tcps_keeptimeo++; 311 if (tp->t_state < TCPS_ESTABLISHED) 312 goto dropit; 313 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 314 tp->t_state <= TCPS_CLOSE_WAIT) { 315 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 316 goto dropit; 317 /* 318 * Send a packet designed to force a response 319 * if the peer is up and reachable: 320 * either an ACK if the connection is still alive, 321 * or an RST if the peer has closed the connection 322 * due to timeout or reboot. 323 * Using sequence number tp->snd_una-1 324 * causes the transmitted zero-length segment 325 * to lie outside the receive window; 326 * by the protocol spec, this requires the 327 * correspondent TCP to respond. 328 */ 329 tcpstat.tcps_keepprobe++; 330 #ifdef TCP_COMPAT_42 331 /* 332 * The keepalive packet must have nonzero length 333 * to get a 4.2 host to respond. 334 */ 335 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 336 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 337 #else 338 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 339 tp->rcv_nxt, tp->snd_una - 1, 0); 340 #endif 341 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 342 } else 343 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 344 break; 345 dropit: 346 tcpstat.tcps_keepdrops++; 347 tp = tcp_drop(tp, ETIMEDOUT); 348 break; 349 } 350 return (tp); 351 } 352 #endif /* TUBA_INCLUDE */ 353