1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California. 3 * 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 7.18 (Berkeley) 6/28/90 34 */ 35 36 #include "param.h" 37 #include "systm.h" 38 #include "malloc.h" 39 #include "mbuf.h" 40 #include "socket.h" 41 #include "socketvar.h" 42 #include "protosw.h" 43 #include "errno.h" 44 45 #include "../net/if.h" 46 #include "../net/route.h" 47 48 #include "in.h" 49 #include "in_systm.h" 50 #include "ip.h" 51 #include "in_pcb.h" 52 #include "ip_var.h" 53 #include "tcp.h" 54 #include "tcp_fsm.h" 55 #include "tcp_seq.h" 56 #include "tcp_timer.h" 57 #include "tcp_var.h" 58 #include "tcpip.h" 59 60 int tcp_keepidle = TCPTV_KEEP_IDLE; 61 int tcp_keepintvl = TCPTV_KEEPINTVL; 62 int tcp_maxidle; 63 /* 64 * Fast timeout routine for processing delayed acks 65 */ 66 tcp_fasttimo() 67 { 68 register struct inpcb *inp; 69 register struct tcpcb *tp; 70 int s = splnet(); 71 72 inp = tcb.inp_next; 73 if (inp) 74 for (; inp != &tcb; inp = inp->inp_next) 75 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 76 (tp->t_flags & TF_DELACK)) { 77 tp->t_flags &= ~TF_DELACK; 78 tp->t_flags |= TF_ACKNOW; 79 tcpstat.tcps_delack++; 80 (void) tcp_output(tp); 81 } 82 splx(s); 83 } 84 85 /* 86 * Tcp protocol timeout routine called every 500 ms. 87 * Updates the timers in all active tcb's and 88 * causes finite state machine actions if timers expire. 89 */ 90 tcp_slowtimo() 91 { 92 register struct inpcb *ip, *ipnxt; 93 register struct tcpcb *tp; 94 int s = splnet(); 95 register int i; 96 97 tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl; 98 /* 99 * Search through tcb's and update active timers. 100 */ 101 ip = tcb.inp_next; 102 if (ip == 0) { 103 splx(s); 104 return; 105 } 106 for (; ip != &tcb; ip = ipnxt) { 107 ipnxt = ip->inp_next; 108 tp = intotcpcb(ip); 109 if (tp == 0) 110 continue; 111 for (i = 0; i < TCPT_NTIMERS; i++) { 112 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 113 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 114 PRU_SLOWTIMO, (struct mbuf *)0, 115 (struct mbuf *)i, (struct mbuf *)0); 116 if (ipnxt->inp_prev != ip) 117 goto tpgone; 118 } 119 } 120 tp->t_idle++; 121 if (tp->t_rtt) 122 tp->t_rtt++; 123 tpgone: 124 ; 125 } 126 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 127 #ifdef TCP_COMPAT_42 128 if ((int)tcp_iss < 0) 129 tcp_iss = 0; /* XXX */ 130 #endif 131 splx(s); 132 } 133 134 /* 135 * Cancel all timers for TCP tp. 136 */ 137 tcp_canceltimers(tp) 138 struct tcpcb *tp; 139 { 140 register int i; 141 142 for (i = 0; i < TCPT_NTIMERS; i++) 143 tp->t_timer[i] = 0; 144 } 145 146 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 147 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 148 149 /* 150 * TCP timer processing. 151 */ 152 struct tcpcb * 153 tcp_timers(tp, timer) 154 register struct tcpcb *tp; 155 int timer; 156 { 157 register int rexmt; 158 159 switch (timer) { 160 161 /* 162 * 2 MSL timeout in shutdown went off. If we're closed but 163 * still waiting for peer to close and connection has been idle 164 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 165 * control block. Otherwise, check again in a bit. 166 */ 167 case TCPT_2MSL: 168 if (tp->t_state != TCPS_TIME_WAIT && 169 tp->t_idle <= tcp_maxidle) 170 tp->t_timer[TCPT_2MSL] = tcp_keepintvl; 171 else 172 tp = tcp_close(tp); 173 break; 174 175 /* 176 * Retransmission timer went off. Message has not 177 * been acked within retransmit interval. Back off 178 * to a longer retransmit interval and retransmit one segment. 179 */ 180 case TCPT_REXMT: 181 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 182 tp->t_rxtshift = TCP_MAXRXTSHIFT; 183 tcpstat.tcps_timeoutdrop++; 184 tp = tcp_drop(tp, tp->t_softerror ? 185 tp->t_softerror : ETIMEDOUT); 186 break; 187 } 188 tcpstat.tcps_rexmttimeo++; 189 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 190 TCPT_RANGESET(tp->t_rxtcur, rexmt, 191 tp->t_rttmin, TCPTV_REXMTMAX); 192 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 193 /* 194 * If losing, let the lower level know and try for 195 * a better route. Also, if we backed off this far, 196 * our srtt estimate is probably bogus. Clobber it 197 * so we'll take the next rtt measurement as our srtt; 198 * move the current srtt into rttvar to keep the current 199 * retransmit times until then. 200 */ 201 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 202 in_losing(tp->t_inpcb); 203 tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT); 204 tp->t_srtt = 0; 205 } 206 tp->snd_nxt = tp->snd_una; 207 /* 208 * If timing a segment in this window, stop the timer. 209 */ 210 tp->t_rtt = 0; 211 /* 212 * Close the congestion window down to one segment 213 * (we'll open it by one segment for each ack we get). 214 * Since we probably have a window's worth of unacked 215 * data accumulated, this "slow start" keeps us from 216 * dumping all that data as back-to-back packets (which 217 * might overwhelm an intermediate gateway). 218 * 219 * There are two phases to the opening: Initially we 220 * open by one mss on each ack. This makes the window 221 * size increase exponentially with time. If the 222 * window is larger than the path can handle, this 223 * exponential growth results in dropped packet(s) 224 * almost immediately. To get more time between 225 * drops but still "push" the network to take advantage 226 * of improving conditions, we switch from exponential 227 * to linear window opening at some threshhold size. 228 * For a threshhold, we use half the current window 229 * size, truncated to a multiple of the mss. 230 * 231 * (the minimum cwnd that will give us exponential 232 * growth is 2 mss. We don't allow the threshhold 233 * to go below this.) 234 */ 235 { 236 u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; 237 if (win < 2) 238 win = 2; 239 tp->snd_cwnd = tp->t_maxseg; 240 tp->snd_ssthresh = win * tp->t_maxseg; 241 tp->t_dupacks = 0; 242 } 243 (void) tcp_output(tp); 244 break; 245 246 /* 247 * Persistance timer into zero window. 248 * Force a byte to be output, if possible. 249 */ 250 case TCPT_PERSIST: 251 tcpstat.tcps_persisttimeo++; 252 tcp_setpersist(tp); 253 tp->t_force = 1; 254 (void) tcp_output(tp); 255 tp->t_force = 0; 256 break; 257 258 /* 259 * Keep-alive timer went off; send something 260 * or drop connection if idle for too long. 261 */ 262 case TCPT_KEEP: 263 tcpstat.tcps_keeptimeo++; 264 if (tp->t_state < TCPS_ESTABLISHED) 265 goto dropit; 266 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 267 tp->t_state <= TCPS_CLOSE_WAIT) { 268 if (tp->t_idle >= tcp_keepidle + tcp_maxidle) 269 goto dropit; 270 /* 271 * Send a packet designed to force a response 272 * if the peer is up and reachable: 273 * either an ACK if the connection is still alive, 274 * or an RST if the peer has closed the connection 275 * due to timeout or reboot. 276 * Using sequence number tp->snd_una-1 277 * causes the transmitted zero-length segment 278 * to lie outside the receive window; 279 * by the protocol spec, this requires the 280 * correspondent TCP to respond. 281 */ 282 tcpstat.tcps_keepprobe++; 283 #ifdef TCP_COMPAT_42 284 /* 285 * The keepalive packet must have nonzero length 286 * to get a 4.2 host to respond. 287 */ 288 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 289 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 290 #else 291 tcp_respond(tp, tp->t_template, (struct mbuf *)NULL, 292 tp->rcv_nxt, tp->snd_una - 1, 0); 293 #endif 294 tp->t_timer[TCPT_KEEP] = tcp_keepintvl; 295 } else 296 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 297 break; 298 dropit: 299 tcpstat.tcps_keepdrops++; 300 tp = tcp_drop(tp, ETIMEDOUT); 301 break; 302 } 303 return (tp); 304 } 305