1 /* 2 * Copyright (c) 1982, 1986 Regents of the University of California. 3 * All rights reserved. The Berkeley software License Agreement 4 * specifies the terms and conditions for redistribution. 5 * 6 * @(#)tcp_timer.c 7.9 (Berkeley) 08/10/87 7 */ 8 9 #include "param.h" 10 #include "systm.h" 11 #include "mbuf.h" 12 #include "socket.h" 13 #include "socketvar.h" 14 #include "protosw.h" 15 #include "errno.h" 16 17 #include "../net/if.h" 18 #include "../net/route.h" 19 20 #include "in.h" 21 #include "in_pcb.h" 22 #include "in_systm.h" 23 #include "ip.h" 24 #include "ip_var.h" 25 #include "tcp.h" 26 #include "tcp_fsm.h" 27 #include "tcp_seq.h" 28 #include "tcp_timer.h" 29 #include "tcp_var.h" 30 #include "tcpip.h" 31 32 int tcpnodelack = 0; 33 /* 34 * Fast timeout routine for processing delayed acks 35 */ 36 tcp_fasttimo() 37 { 38 register struct inpcb *inp; 39 register struct tcpcb *tp; 40 int s = splnet(); 41 42 inp = tcb.inp_next; 43 if (inp) 44 for (; inp != &tcb; inp = inp->inp_next) 45 if ((tp = (struct tcpcb *)inp->inp_ppcb) && 46 (tp->t_flags & TF_DELACK)) { 47 tp->t_flags &= ~TF_DELACK; 48 tp->t_flags |= TF_ACKNOW; 49 tcpstat.tcps_delack++; 50 (void) tcp_output(tp); 51 } 52 splx(s); 53 } 54 55 /* 56 * Tcp protocol timeout routine called every 500 ms. 57 * Updates the timers in all active tcb's and 58 * causes finite state machine actions if timers expire. 59 */ 60 tcp_slowtimo() 61 { 62 register struct inpcb *ip, *ipnxt; 63 register struct tcpcb *tp; 64 int s = splnet(); 65 register int i; 66 67 /* 68 * Search through tcb's and update active timers. 69 */ 70 ip = tcb.inp_next; 71 if (ip == 0) { 72 splx(s); 73 return; 74 } 75 for (; ip != &tcb; ip = ipnxt) { 76 ipnxt = ip->inp_next; 77 tp = intotcpcb(ip); 78 if (tp == 0) 79 continue; 80 for (i = 0; i < TCPT_NTIMERS; i++) { 81 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 82 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 83 PRU_SLOWTIMO, (struct mbuf *)0, 84 (struct mbuf *)i, (struct mbuf *)0); 85 if (ipnxt->inp_prev != ip) 86 goto tpgone; 87 } 88 } 89 tp->t_idle++; 90 if (tp->t_rtt) 91 tp->t_rtt++; 92 tpgone: 93 ; 94 } 95 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 96 #ifdef TCP_COMPAT_42 97 if ((int)tcp_iss < 0) 98 tcp_iss = 0; /* XXX */ 99 #endif 100 splx(s); 101 } 102 103 /* 104 * Cancel all timers for TCP tp. 105 */ 106 tcp_canceltimers(tp) 107 struct tcpcb *tp; 108 { 109 register int i; 110 111 for (i = 0; i < TCPT_NTIMERS; i++) 112 tp->t_timer[i] = 0; 113 } 114 115 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 116 { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 117 118 /* 119 * TCP timer processing. 120 */ 121 struct tcpcb * 122 tcp_timers(tp, timer) 123 register struct tcpcb *tp; 124 int timer; 125 { 126 register int rexmt; 127 128 switch (timer) { 129 130 /* 131 * 2 MSL timeout in shutdown went off. If we're closed but 132 * still waiting for peer to close and connection has been idle 133 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 134 * control block. Otherwise, check again in a bit. 135 */ 136 case TCPT_2MSL: 137 if (tp->t_state != TCPS_TIME_WAIT && 138 tp->t_idle <= TCPTV_MAXIDLE) 139 tp->t_timer[TCPT_2MSL] = TCPTV_KEEP; 140 else 141 tp = tcp_close(tp); 142 break; 143 144 /* 145 * Retransmission timer went off. Message has not 146 * been acked within retransmit interval. Back off 147 * to a longer retransmit interval and retransmit one segment. 148 */ 149 case TCPT_REXMT: 150 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) { 151 tp->t_rxtshift = TCP_MAXRXTSHIFT; 152 tcpstat.tcps_timeoutdrop++; 153 tp = tcp_drop(tp, ETIMEDOUT); 154 break; 155 } 156 tcpstat.tcps_rexmttimeo++; 157 rexmt = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 158 rexmt *= tcp_backoff[tp->t_rxtshift]; 159 TCPT_RANGESET(tp->t_rxtcur, rexmt, TCPTV_MIN, TCPTV_REXMTMAX); 160 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 161 /* 162 * If losing, let the lower level know and try for 163 * a better route. Also, if we backed off this far, 164 * our srtt estimate is probably bogus. Clobber it 165 * so we'll take the next rtt measurement as our srtt; 166 * move the current srtt into rttvar to keep the current 167 * retransmit times until then. 168 */ 169 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) { 170 in_losing(tp->t_inpcb); 171 tp->t_rttvar += (tp->t_srtt >> 2); 172 tp->t_srtt = 0; 173 } 174 tp->snd_nxt = tp->snd_una; 175 /* 176 * If timing a segment in this window, stop the timer. 177 */ 178 tp->t_rtt = 0; 179 /* 180 * Close the congestion window down to one segment 181 * (we'll open it by one segment for each ack we get). 182 * Since we probably have a window's worth of unacked 183 * data accumulated, this "slow start" keeps us from 184 * dumping all that data as back-to-back packets (which 185 * might overwhelm an intermediate gateway). 186 */ 187 tp->snd_cwnd = tp->t_maxseg; 188 (void) tcp_output(tp); 189 break; 190 191 /* 192 * Persistance timer into zero window. 193 * Force a byte to be output, if possible. 194 */ 195 case TCPT_PERSIST: 196 tcpstat.tcps_persisttimeo++; 197 tcp_setpersist(tp); 198 tp->t_force = 1; 199 (void) tcp_output(tp); 200 tp->t_force = 0; 201 break; 202 203 /* 204 * Keep-alive timer went off; send something 205 * or drop connection if idle for too long. 206 */ 207 case TCPT_KEEP: 208 tcpstat.tcps_keeptimeo++; 209 if (tp->t_state < TCPS_ESTABLISHED) 210 goto dropit; 211 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 212 tp->t_state <= TCPS_CLOSE_WAIT) { 213 if (tp->t_idle >= TCPTV_MAXIDLE) 214 goto dropit; 215 /* 216 * Send a packet designed to force a response 217 * if the peer is up and reachable: 218 * either an ACK if the connection is still alive, 219 * or an RST if the peer has closed the connection 220 * due to timeout or reboot. 221 * Using sequence number tp->snd_una-1 222 * causes the transmitted zero-length segment 223 * to lie outside the receive window; 224 * by the protocol spec, this requires the 225 * correspondent TCP to respond. 226 */ 227 tcpstat.tcps_keepprobe++; 228 #ifdef TCP_COMPAT_42 229 /* 230 * The keepalive packet must have nonzero length 231 * to get a 4.2 host to respond. 232 */ 233 tcp_respond(tp, tp->t_template, 234 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 235 #else 236 tcp_respond(tp, tp->t_template, 237 tp->rcv_nxt, tp->snd_una - 1, 0); 238 #endif 239 } 240 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 241 break; 242 dropit: 243 tcpstat.tcps_keepdrops++; 244 tp = tcp_drop(tp, ETIMEDOUT); 245 break; 246 } 247 return (tp); 248 } 249