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 7.8 (Berkeley) 06/30/87 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] = 116 { 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 }; 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 if (tp->t_rxtshift >= TCP_MAXRXTSHIFT) { 153 tcpstat.tcps_timeoutdrop++; 154 tp = tcp_drop(tp, ETIMEDOUT); 155 break; 156 } 157 tcpstat.tcps_rexmttimeo++; 158 rexmt = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1; 159 rexmt *= tcp_backoff[tp->t_rxtshift]; 160 tp->t_rxtshift++; 161 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], rexmt, 162 TCPTV_MIN, TCPTV_REXMTMAX); 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, stop the timer. 173 */ 174 tp->t_rtt = 0; 175 /* 176 * Close the congestion window down to one segment 177 * (we'll open it by one segment for each ack we get). 178 * Since we probably have a window's worth of unacked 179 * data accumulated, this "slow start" keeps us from 180 * dumping all that data as back-to-back packets (which 181 * might overwhelm an intermediate gateway). 182 */ 183 tp->snd_cwnd = tp->t_maxseg; 184 (void) tcp_output(tp); 185 break; 186 187 /* 188 * Persistance timer into zero window. 189 * Force a byte to be output, if possible. 190 */ 191 case TCPT_PERSIST: 192 tcpstat.tcps_persisttimeo++; 193 tcp_setpersist(tp); 194 tp->t_force = 1; 195 (void) tcp_output(tp); 196 tp->t_force = 0; 197 break; 198 199 /* 200 * Keep-alive timer went off; send something 201 * or drop connection if idle for too long. 202 */ 203 case TCPT_KEEP: 204 tcpstat.tcps_keeptimeo++; 205 if (tp->t_state < TCPS_ESTABLISHED) 206 goto dropit; 207 if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE && 208 tp->t_state <= TCPS_CLOSE_WAIT) { 209 if (tp->t_idle >= TCPTV_MAXIDLE) 210 goto dropit; 211 /* 212 * Send a packet designed to force a response 213 * if the peer is up and reachable: 214 * either an ACK if the connection is still alive, 215 * or an RST if the peer has closed the connection 216 * due to timeout or reboot. 217 * Using sequence number tp->snd_una-1 218 * causes the transmitted zero-length segment 219 * to lie outside the receive window; 220 * by the protocol spec, this requires the 221 * correspondent TCP to respond. 222 */ 223 tcpstat.tcps_keepprobe++; 224 #ifdef TCP_COMPAT_42 225 /* 226 * The keepalive packet must have nonzero length 227 * to get a 4.2 host to respond. 228 */ 229 tcp_respond(tp, tp->t_template, 230 tp->rcv_nxt - 1, tp->snd_una - 1, 0); 231 #else 232 tcp_respond(tp, tp->t_template, 233 tp->rcv_nxt, tp->snd_una - 1, 0); 234 #endif 235 } 236 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 237 break; 238 dropit: 239 tcpstat.tcps_keepdrops++; 240 tp = tcp_drop(tp, ETIMEDOUT); 241 break; 242 } 243 return (tp); 244 } 245