/* tcp_timer.c - TCP timer routines *//* Copyright 1984-1996 Wind River Systems, Inc. */#include "copyright_wrs.h"/* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 *	The Regents of the University of California.  All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright *    notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright *    notice, this list of conditions and the following disclaimer in the *    documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software *    must display the following acknowledgement: *	This product includes software developed by the University of *	California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors *    may be used to endorse or promote products derived from this software *    without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * *	@(#)tcp_timer.c	8.2 (Berkeley) 5/24/95 *//*modification history--------------------01c,08mar97,vin  added changes to accomodate changes in pcb structure.01b,30oct96,vin  changed calls to tcp_respond, mtod(tp->t_template ...).01a,03mar96,vin  created from BSD4.4 stuff,integrated with 02j.*//*DESCRIPTION*/#include "vxWorks.h"#include "net/systm.h"#include "net/mbuf.h"#include "sys/socket.h"#include "net/socketvar.h"#include "net/protosw.h"#include "errno.h"#include "net/if.h"#include "net/route.h"#include "netinet/in.h"#include "netinet/in_pcb.h"#include "netinet/in_systm.h"#include "netinet/ip.h"#include "netinet/ip_var.h"#include "netinet/tcp.h"#include "netinet/tcp_fsm.h"#include "netinet/tcp_seq.h"#include "netinet/tcp_timer.h"#include "netinet/tcp_debug.h"#include "netinet/tcp_var.h"#include "netinet/tcpip.h"/* globals */int     tcp_keepidle = TCPTV_KEEP_IDLE;int     tcp_keepintvl = TCPTV_KEEPINTVL;int	tcp_keepcnt = TCPTV_KEEPCNT;int	tcp_keepinit = TCPTV_KEEP_INIT;int	tcp_maxpersistidle = TCPTV_KEEP_IDLE;   /* max idle time in persist */int     tcp_maxidle;/* * Fast timeout routine for processing delayed acks */voidtcp_fasttimo(){	register struct inpcb *inp;	register struct tcpcb *tp;	int s;        s = splnet();        for (inp = tcb.lh_first; inp != NULL; inp = inp->inp_list.le_next) {		if ((tp = (struct tcpcb *)inp->inp_ppcb) &&		    (tp->t_flags & TF_DELACK)) {			tp->t_flags &= ~TF_DELACK;			tp->t_flags |= TF_ACKNOW;			tcpstat.tcps_delack++;			(void) tcp_output(tp);		}        }	splx(s);}/* * Tcp protocol timeout routine called every 500 ms. * Updates the timers in all active tcb's and * causes finite state machine actions if timers expire. */voidtcp_slowtimo(){	register struct inpcb *ip, *ipnxt;	register struct tcpcb *tp;	int s = splnet();#ifdef BSDDEBUG        int ostate;#endif	register int i;	tcp_maxidle = tcp_keepcnt * tcp_keepintvl;	/*	 * Search through tcb's and update active timers.	 */	ip = tcb.lh_first;	if (ip == 0) {		splx(s);		return;	}	for (; ip != NULL; ip = ipnxt) {		ipnxt = ip->inp_list.le_next;		tp = intotcpcb(ip);		if (tp == 0 || tp->t_state == TCPS_LISTEN)			continue;		for (i = 0; i < TCPT_NTIMERS; i++) {			if (tp->t_timer[i] && --tp->t_timer[i] == 0) {#ifdef BSDDEBUG                                ostate = tp->t_state;#endif                                tp = tcp_timers(tp, i);                                if (tp == NULL)                                        goto tpgone;#ifdef BSDDEBUG                                if (tp->t_inpcb->inp_socket->so_options                                    & SO_DEBUG)                                    (*tcpTraceRtn)(TA_USER, ostate, tp,                                                   (struct tcpiphdr *)0,                                                   PRU_SLOWTIMO);#endif			}		}		tp->t_idle++;		if (tp->t_rtt)			tp->t_rtt++;tpgone:		;	}	tcp_iss += TCP_ISSINCR/PR_SLOWHZ;		/* increment iss */#ifdef TCP_COMPAT_42	if ((int)tcp_iss < 0)		tcp_iss = TCP_ISSINCR;			/* XXX */#endif	tcp_now++;					/* for timestamps */	splx(s);}#ifndef TUBA_INCLUDE/* * Cancel all timers for TCP tp. */voidtcp_canceltimers(tp)	struct tcpcb *tp;{	register int i;	for (i = 0; i < TCPT_NTIMERS; i++)		tp->t_timer[i] = 0;}int	tcp_backoff[TCP_MAXRXTSHIFT + 1] =    { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };int tcp_totbackoff = 511;	/* sum of tcp_backoff[] *//* * TCP timer processing. */struct tcpcb *tcp_timers(tp, timer)	register struct tcpcb *tp;	int timer;{	register int rexmt;	switch (timer) {	/*	 * 2 MSL timeout in shutdown went off.  If we're closed but	 * still waiting for peer to close and connection has been idle	 * too long, or if 2MSL time is up from TIME_WAIT, delete connection	 * control block.  Otherwise, check again in a bit.	 */	case TCPT_2MSL:		if (tp->t_state != TCPS_TIME_WAIT &&		    tp->t_idle <= tcp_maxidle)			tp->t_timer[TCPT_2MSL] = tcp_keepintvl;		else			tp = tcp_close(tp);		break;	/*	 * Retransmission timer went off.  Message has not	 * been acked within retransmit interval.  Back off	 * to a longer retransmit interval and retransmit one segment.	 */	case TCPT_REXMT:		if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {			tp->t_rxtshift = TCP_MAXRXTSHIFT;			tcpstat.tcps_timeoutdrop++;			tp = tcp_drop(tp, tp->t_softerror ?			    tp->t_softerror : ETIMEDOUT);			break;		}		tcpstat.tcps_rexmttimeo++;		rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift];		TCPT_RANGESET(tp->t_rxtcur, rexmt,		    tp->t_rttmin, TCPTV_REXMTMAX);		tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;		/*		 * If losing, let the lower level know and try for		 * a better route.  Also, if we backed off this far,		 * our srtt estimate is probably bogus.  Clobber it		 * so we'll take the next rtt measurement as our srtt;		 * move the current srtt into rttvar to keep the current		 * retransmit times until then.		 */		if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {			in_losing(tp->t_inpcb);			tp->t_rttvar += (tp->t_srtt >> TCP_RTT_SHIFT);			tp->t_srtt = 0;		}		tp->snd_nxt = tp->snd_una;		/*		 * If timing a segment in this window, stop the timer.		 */		tp->t_rtt = 0;		/*		 * Close the congestion window down to one segment		 * (we'll open it by one segment for each ack we get).		 * Since we probably have a window's worth of unacked		 * data accumulated, this "slow start" keeps us from		 * dumping all that data as back-to-back packets (which		 * might overwhelm an intermediate gateway).		 *		 * There are two phases to the opening: Initially we		 * open by one mss on each ack.  This makes the window		 * size increase exponentially with time.  If the		 * window is larger than the path can handle, this		 * exponential growth results in dropped packet(s)		 * almost immediately.  To get more time between 		 * drops but still "push" the network to take advantage		 * of improving conditions, we switch from exponential		 * to linear window opening at some threshhold size.		 * For a threshhold, we use half the current window		 * size, truncated to a multiple of the mss.		 *		 * (the minimum cwnd that will give us exponential		 * growth is 2 mss.  We don't allow the threshhold		 * to go below this.)		 */		{		u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;		if (win < 2)			win = 2;		tp->snd_cwnd = tp->t_maxseg;		tp->snd_ssthresh = win * tp->t_maxseg;		tp->t_dupacks = 0;		}		(void) tcp_output(tp);		break;	/*	 * Persistance timer into zero window.	 * Force a byte to be output, if possible.	 */	case TCPT_PERSIST:		tcpstat.tcps_persisttimeo++;		/*		 * Hack: if the peer is dead/unreachable, we do not		 * time out if the window is closed.  After a full		 * backoff, drop the connection if the idle time		 * (no responses to probes) reaches the maximum		 * backoff that we would use if retransmitting.		 */		if (tp->t_rxtshift == TCP_MAXRXTSHIFT &&		    (tp->t_idle >= tcp_maxpersistidle ||		    tp->t_idle >= TCP_REXMTVAL(tp) * tcp_totbackoff)) {			tcpstat.tcps_persistdrop++;			tp = tcp_drop(tp, ETIMEDOUT);			break;		}		tcp_setpersist(tp);		tp->t_force = 1;		(void) tcp_output(tp);		tp->t_force = 0;		break;	/*	 * Keep-alive timer went off; send something	 * or drop connection if idle for too long.	 */	case TCPT_KEEP:		tcpstat.tcps_keeptimeo++;		if (tp->t_state < TCPS_ESTABLISHED)			goto dropit;		if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&		    tp->t_state <= TCPS_CLOSE_WAIT) {		    	if (tp->t_idle >= tcp_keepidle + tcp_maxidle)				goto dropit;			/*			 * Send a packet designed to force a response			 * if the peer is up and reachable:			 * either an ACK if the connection is still alive,			 * or an RST if the peer has closed the connection			 * due to timeout or reboot.			 * Using sequence number tp->snd_una-1			 * causes the transmitted zero-length segment			 * to lie outside the receive window;			 * by the protocol spec, this requires the			 * correspondent TCP to respond.			 */			tcpstat.tcps_keepprobe++;#ifdef TCP_COMPAT_42			/*			 * The keepalive packet must have nonzero length			 * to get a 4.2 host to respond.			 */			tcp_respond(tp, 				    mtod(tp->t_template, struct tcpiphdr *),				    (struct mbuf *)NULL,				    tp->rcv_nxt - 1, tp->snd_una - 1, 0);#else			tcp_respond(tp, 				    mtod(tp->t_template, struct tcpiphdr *),				    (struct mbuf *)NULL,				    tp->rcv_nxt, tp->snd_una - 1, 0);#endif			tp->t_timer[TCPT_KEEP] = tcp_keepintvl;		} else			tp->t_timer[TCPT_KEEP] = tcp_keepidle;		break;	dropit:		tcpstat.tcps_keepdrops++;		tp = tcp_drop(tp, ETIMEDOUT);		break;	}	return (tp);}#endif /* TUBA_INCLUDE */