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 7.5 (Berkeley) 06/06/87 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 int tcp_keeplen = 1; /* must be nonzero for 4.2 compat- XXX */ 119 120 /* 121 * TCP timer processing. 122 */ 123 struct tcpcb * 124 tcp_timers(tp, timer) 125 register struct tcpcb *tp; 126 int timer; 127 { 128 register int rexmt; 129 130 switch (timer) { 131 132 /* 133 * 2 MSL timeout in shutdown went off. If we're closed but 134 * still waiting for peer to close and connection has been idle 135 * too long, or if 2MSL time is up from TIME_WAIT, delete connection 136 * control block. Otherwise, check again in a bit. 137 */ 138 case TCPT_2MSL: 139 if (tp->t_state != TCPS_TIME_WAIT && 140 tp->t_idle <= TCPTV_MAXIDLE) 141 tp->t_timer[TCPT_2MSL] = TCPTV_KEEP; 142 else 143 tp = tcp_close(tp); 144 break; 145 146 /* 147 * Retransmission timer went off. Message has not 148 * been acked within retransmit interval. Back off 149 * to a longer retransmit interval and retransmit one segment. 150 */ 151 case TCPT_REXMT: 152 tp->t_rxtshift++; 153 if (tp->t_rxtshift > TCP_MAXRXTSHIFT) { 154 tcpstat.tcps_timeoutdrop++; 155 tp = tcp_drop(tp, ETIMEDOUT); 156 break; 157 } 158 tcpstat.tcps_rexmttimeo++; 159 if (tp->t_srtt == 0) 160 rexmt = tcp_beta * TCPTV_SRTTDFLT; 161 else 162 rexmt = (int)(tcp_beta * tp->t_srtt); 163 rexmt *= tcp_backoff[tp->t_rxtshift - 1]; 164 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], rexmt, 165 TCPTV_MIN, TCPTV_MAX); 166 /* 167 * If losing, let the lower level know 168 * and try for a better route. 169 */ 170 if (tp->t_rxtshift >= TCP_MAXRXTSHIFT / 4 || 171 rexmt >= 10 * PR_SLOWHZ) 172 in_losing(tp->t_inpcb); 173 tp->snd_nxt = tp->snd_una; 174 /* 175 * If timing a segment in this window, 176 * and we have already gotten some timing estimate, 177 * stop the timer. 178 */ 179 if (tp->t_rtt && tp->t_srtt) 180 tp->t_rtt = 0; 181 /* 182 * Close the congestion window down to one segment 183 * (we'll open it by one segment for each ack we get). 184 * Since we probably have a window's worth of unacked 185 * data accumulated, this "slow start" keeps us from 186 * dumping all that data as back-to-back packets (which 187 * might overwhelm an intermediate gateway). 188 */ 189 tp->snd_cwnd = tp->t_maxseg; 190 (void) tcp_output(tp); 191 break; 192 193 /* 194 * Persistance timer into zero window. 195 * Force a byte to be output, if possible. 196 */ 197 case TCPT_PERSIST: 198 tcpstat.tcps_persisttimeo++; 199 tcp_setpersist(tp); 200 tp->t_force = 1; 201 (void) tcp_output(tp); 202 tp->t_force = 0; 203 break; 204 205 /* 206 * Keep-alive timer went off; send something 207 * or drop connection if idle for too long. 208 */ 209 case TCPT_KEEP: 210 tcpstat.tcps_keeptimeo++; 211 if (tp->t_state < TCPS_ESTABLISHED) 212 goto dropit; 213 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 214 tp->t_state <= TCPS_CLOSE_WAIT) { 215 if (tp->t_idle >= TCPTV_MAXIDLE) 216 goto dropit; 217 /* 218 * Send a packet designed to force a response 219 * if the peer is up and reachable: 220 * either an ACK if the connection is still alive, 221 * or an RST if the peer has closed the connection 222 * due to timeout or reboot. 223 * Using sequence number tp->snd_una-1 224 * causes the transmitted zero-length segment 225 * to lie outside the receive window; 226 * by the protocol spec, this requires the 227 * correspondent TCP to respond. 228 */ 229 tcpstat.tcps_keepprobe++; 230 tcp_respond(tp, tp->t_template, 231 tp->rcv_nxt - tcp_keeplen, tp->snd_una - 1, 0); 232 } 233 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 234 break; 235 dropit: 236 tcpstat.tcps_keepdrops++; 237 tp = tcp_drop(tp, ETIMEDOUT); 238 break; 239 } 240 return (tp); 241 } 242