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 6.7 (Berkeley) 06/08/85 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 float tcp_backoff[TCP_MAXRXTSHIFT] = 111 { 1.0, 1.2, 1.4, 1.7, 2.0, 3.0, 5.0, 8.0, 16.0, 32.0 }; 112 int tcpexprexmtbackoff = 0; 113 /* 114 * TCP timer processing. 115 */ 116 struct tcpcb * 117 tcp_timers(tp, timer) 118 register struct tcpcb *tp; 119 int timer; 120 { 121 122 switch (timer) { 123 124 /* 125 * 2 MSL timeout in shutdown went off. Delete connection 126 * control block. 127 */ 128 case TCPT_2MSL: 129 tp = tcp_close(tp); 130 break; 131 132 /* 133 * Retransmission timer went off. Message has not 134 * been acked within retransmit interval. Back off 135 * to a longer retransmit interval and retransmit one segment. 136 */ 137 case TCPT_REXMT: 138 tp->t_rxtshift++; 139 if (tp->t_rxtshift > TCP_MAXRXTSHIFT) { 140 tp = tcp_drop(tp, ETIMEDOUT); 141 break; 142 } 143 /* 144 * If losing, let the lower level know 145 * and try for a better route. 146 */ 147 if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 2) 148 in_rtchange(tp->t_inpcb); 149 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 150 (int)tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 151 if (tcpexprexmtbackoff) { 152 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 153 tp->t_timer[TCPT_REXMT] << tp->t_rxtshift, 154 TCPTV_MIN, TCPTV_MAX); 155 } else { 156 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 157 tp->t_timer[TCPT_REXMT] * 158 tcp_backoff[tp->t_rxtshift - 1], 159 TCPTV_MIN, TCPTV_MAX); 160 } 161 tp->snd_nxt = tp->snd_una; 162 /* 163 * If timing a segment in this window, 164 * and we have already gotten some timing estimate, 165 * stop the timer. 166 */ 167 if (tp->t_rtt && tp->t_srtt) 168 tp->t_rtt = 0; 169 (void) tcp_output(tp); 170 break; 171 172 /* 173 * Persistance timer into zero window. 174 * Force a byte to be output, if possible. 175 */ 176 case TCPT_PERSIST: 177 tcp_setpersist(tp); 178 tp->t_force = 1; 179 (void) tcp_output(tp); 180 tp->t_force = 0; 181 break; 182 183 /* 184 * Keep-alive timer went off; send something 185 * or drop connection if idle for too long. 186 */ 187 case TCPT_KEEP: 188 if (tp->t_state < TCPS_ESTABLISHED) 189 goto dropit; 190 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) { 191 if (tp->t_idle >= TCPTV_MAXIDLE) 192 goto dropit; 193 /* 194 * Saying tp->rcv_nxt-1 lies about what 195 * we have received, and by the protocol spec 196 * requires the correspondent TCP to respond. 197 * Saying tp->snd_una-1 causes the transmitted 198 * byte to lie outside the receive window; this 199 * is important because we don't necessarily 200 * have a byte in the window to send (consider 201 * a one-way stream!) 202 */ 203 tcp_respond(tp, 204 tp->t_template, tp->rcv_nxt-1, tp->snd_una-1, 0); 205 } else 206 tp->t_idle = 0; 207 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 208 break; 209 dropit: 210 tp = tcp_drop(tp, ETIMEDOUT); 211 break; 212 } 213 return (tp); 214 } 215