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 7.2 (Berkeley) 02/19/87 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, 6, 8, 10, 15, 20, 30, 30, 30, 30, 30 }; 117 /* 118 * TCP timer processing. 119 */ 120 struct tcpcb * 121 tcp_timers(tp, timer) 122 register struct tcpcb *tp; 123 int timer; 124 { 125 register int rexmt; 126 127 switch (timer) { 128 129 /* 130 * 2 MSL timeout in shutdown went off. If we're closed but 131 * still waiting for peer to close and connection has been idle 132 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 133 * control block. Otherwise, check again in a bit. 134 */ 135 case TCPT_2MSL: 136 if (tp->t_state != TCPS_TIME_WAIT && 137 tp->t_idle <= TCPTV_MAXIDLE) 138 tp->t_timer[TCPT_2MSL] = TCPTV_KEEP; 139 else 140 tp = tcp_close(tp); 141 break; 142 143 /* 144 * Retransmission timer went off. Message has not 145 * been acked within retransmit interval. Back off 146 * to a longer retransmit interval and retransmit one segment. 147 */ 148 case TCPT_REXMT: 149 tp->t_rxtshift++; 150 if (tp->t_rxtshift > TCP_MAXRXTSHIFT) { 151 tcpstat.tcps_timeoutdrop++; 152 tp = tcp_drop(tp, ETIMEDOUT); 153 break; 154 } 155 tcpstat.tcps_rexmttimeo++; 156 if (tp->t_srtt == 0) 157 rexmt = tcp_beta * TCPTV_SRTTDFLT; 158 else 159 rexmt = (int)(tcp_beta * tp->t_srtt); 160 rexmt *= tcp_backoff[tp->t_rxtshift - 1]; 161 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], rexmt, 162 TCPTV_MIN, TCPTV_MAX); 163 /* 164 * If losing, let the lower level know 165 * and try for a better route. 166 */ 167 if (tp->t_rxtshift >= TCP_MAXRXTSHIFT / 4 || 168 rexmt >= 10 * PR_SLOWHZ) 169 in_losing(tp->t_inpcb); 170 tp->snd_nxt = tp->snd_una; 171 /* 172 * If timing a segment in this window, 173 * and we have already gotten some timing estimate, 174 * stop the timer. 175 */ 176 if (tp->t_rtt && tp->t_srtt) 177 tp->t_rtt = 0; 178 (void) tcp_output(tp); 179 break; 180 181 /* 182 * Persistance timer into zero window. 183 * Force a byte to be output, if possible. 184 */ 185 case TCPT_PERSIST: 186 tcpstat.tcps_persisttimeo++; 187 tcp_setpersist(tp); 188 tp->t_force = 1; 189 (void) tcp_output(tp); 190 tp->t_force = 0; 191 break; 192 193 /* 194 * Keep-alive timer went off; send something 195 * or drop connection if idle for too long. 196 */ 197 case TCPT_KEEP: 198 tcpstat.tcps_keeptimeo++; 199 if (tp->t_state < TCPS_ESTABLISHED) 200 goto dropit; 201 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 202 tp->t_state <= TCPS_CLOSE_WAIT) { 203 if (tp->t_idle >= TCPTV_MAXIDLE) 204 goto dropit; 205 /* 206 * Send a packet designed to force a response 207 * if the peer is up and reachable: 208 * either an ACK if the connection is still alive, 209 * or an RST if the peer has closed the connection 210 * due to timeout or reboot. 211 * Using sequence number tp->snd_una-1 212 * causes the transmitted zero-length segment 213 * to lie outside the receive window; 214 * by the protocol spec, this requires the 215 * correspondent TCP to respond. 216 */ 217 tcpstat.tcps_keepprobe++; 218 tcp_respond(tp, 219 tp->t_template, tp->rcv_nxt, tp->snd_una-1, 0); 220 } 221 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 222 break; 223 dropit: 224 tcpstat.tcps_keepdrops++; 225 tp = tcp_drop(tp, ETIMEDOUT); 226 break; 227 } 228 return (tp); 229 } 230