1 /* 2 * Copyright (c) 1982 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 6.10 (Berkeley) 01/13/86 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 (void) tcp_output(tp); 50 } 51 splx(s); 52 } 53 54 /* 55 * Tcp protocol timeout routine called every 500 ms. 56 * Updates the timers in all active tcb's and 57 * causes finite state machine actions if timers expire. 58 */ 59 tcp_slowtimo() 60 { 61 register struct inpcb *ip, *ipnxt; 62 register struct tcpcb *tp; 63 int s = splnet(); 64 register int i; 65 66 /* 67 * Search through tcb's and update active timers. 68 */ 69 ip = tcb.inp_next; 70 if (ip == 0) { 71 splx(s); 72 return; 73 } 74 for (; ip != &tcb; ip = ipnxt) { 75 ipnxt = ip->inp_next; 76 tp = intotcpcb(ip); 77 if (tp == 0) 78 continue; 79 for (i = 0; i < TCPT_NTIMERS; i++) { 80 if (tp->t_timer[i] && --tp->t_timer[i] == 0) { 81 (void) tcp_usrreq(tp->t_inpcb->inp_socket, 82 PRU_SLOWTIMO, (struct mbuf *)0, 83 (struct mbuf *)i, (struct mbuf *)0); 84 if (ipnxt->inp_prev != ip) 85 goto tpgone; 86 } 87 } 88 tp->t_idle++; 89 if (tp->t_rtt) 90 tp->t_rtt++; 91 tpgone: 92 ; 93 } 94 tcp_iss += TCP_ISSINCR/PR_SLOWHZ; /* increment iss */ 95 splx(s); 96 } 97 98 /* 99 * Cancel all timers for TCP tp. 100 */ 101 tcp_canceltimers(tp) 102 struct tcpcb *tp; 103 { 104 register int i; 105 106 for (i = 0; i < TCPT_NTIMERS; i++) 107 tp->t_timer[i] = 0; 108 } 109 110 int tcp_backoff[TCP_MAXRXTSHIFT+1] = 111 { 1, 2, 4, 6, 8, 10, 15, 20, 30, 30, 30, 30, 30 }; 112 /* 113 * TCP timer processing. 114 */ 115 struct tcpcb * 116 tcp_timers(tp, timer) 117 register struct tcpcb *tp; 118 int timer; 119 { 120 register int rexmt; 121 122 switch (timer) { 123 124 /* 125 * 2 MSL timeout in shutdown went off. If we're closed but 126 * still waiting for peer to close and connection has been idle 127 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 128 * control block. Otherwise, check again in a bit. 129 */ 130 case TCPT_2MSL: 131 if (tp->t_state != TCPS_TIME_WAIT && 132 tp->t_idle <= TCPTV_MAXIDLE) 133 tp->t_timer[TCPT_2MSL] = TCPTV_KEEP; 134 else 135 tp = tcp_close(tp); 136 break; 137 138 /* 139 * Retransmission timer went off. Message has not 140 * been acked within retransmit interval. Back off 141 * to a longer retransmit interval and retransmit one segment. 142 */ 143 case TCPT_REXMT: 144 tp->t_rxtshift++; 145 if (tp->t_rxtshift > TCP_MAXRXTSHIFT) { 146 tp = tcp_drop(tp, ETIMEDOUT); 147 break; 148 } 149 /* 150 * If losing, let the lower level know 151 * and try for a better route. 152 */ 153 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 3) 154 in_losing(tp->t_inpcb); 155 if (tp->t_srtt == 0) 156 rexmt = tcp_beta * TCPTV_SRTTDFLT; 157 else 158 rexmt = (int)(tcp_beta * tp->t_srtt); 159 rexmt *= tcp_backoff[tp->t_rxtshift - 1]; 160 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], rexmt, 161 TCPTV_MIN, TCPTV_MAX); 162 tp->snd_nxt = tp->snd_una; 163 /* 164 * If timing a segment in this window, 165 * and we have already gotten some timing estimate, 166 * stop the timer. 167 */ 168 if (tp->t_rtt && tp->t_srtt) 169 tp->t_rtt = 0; 170 (void) tcp_output(tp); 171 break; 172 173 /* 174 * Persistance timer into zero window. 175 * Force a byte to be output, if possible. 176 */ 177 case TCPT_PERSIST: 178 tcp_setpersist(tp); 179 tp->t_force = 1; 180 (void) tcp_output(tp); 181 tp->t_force = 0; 182 break; 183 184 /* 185 * Keep-alive timer went off; send something 186 * or drop connection if idle for too long. 187 */ 188 case TCPT_KEEP: 189 if (tp->t_state < TCPS_ESTABLISHED) 190 goto dropit; 191 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) { 192 if (tp->t_idle >= TCPTV_MAXIDLE) 193 goto dropit; 194 /* 195 * Saying tp->rcv_nxt-1 lies about what 196 * we have received, and by the protocol spec 197 * requires the correspondent TCP to respond. 198 * Saying tp->snd_una-1 causes the transmitted 199 * byte to lie outside the receive window; this 200 * is important because we don't necessarily 201 * have a byte in the window to send (consider 202 * a one-way stream!) 203 */ 204 tcp_respond(tp, 205 tp->t_template, tp->rcv_nxt-1, tp->snd_una-1, 0); 206 } else 207 tp->t_idle = 0; 208 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 209 break; 210 dropit: 211 tp = tcp_drop(tp, ETIMEDOUT); 212 break; 213 } 214 return (tp); 215 } 216