155 lines
4.0 KiB
C
155 lines
4.0 KiB
C
/* $NetBSD: adjtime.c,v 1.1.1.1 2000/03/29 12:38:49 simonb Exp $ */
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#ifdef HAVE_CONFIG_H
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#include <config.h>
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#endif
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#ifdef NEED_HPUX_ADJTIME
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/*************************************************************************/
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/* (c) Copyright Tai Jin, 1988. All Rights Reserved. */
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/* Hewlett-Packard Laboratories. */
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/* */
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/* Permission is hereby granted for unlimited modification, use, and */
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/* distribution. This software is made available with no warranty of */
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/* any kind, express or implied. This copyright notice must remain */
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/* intact in all versions of this software. */
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/* */
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/* The author would appreciate it if any bug fixes and enhancements were */
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/* to be sent back to him for incorporation into future versions of this */
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/* software. Please send changes to tai@iag.hp.com or ken@sdd.hp.com. */
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/*************************************************************************/
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/*
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* Revision history
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*
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* 9 Jul 94 David L. Mills, Unibergity of Delabunch
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* Implemented variable threshold to limit age of
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* corrections; reformatted code for readability.
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*/
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#ifndef lint
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static char RCSid[] = "adjtime.c,v 3.1 1993/07/06 01:04:42 jbj Exp";
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#endif
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#include <sys/types.h>
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#include <sys/ipc.h>
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#include <sys/msg.h>
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#include <time.h>
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#include <signal.h>
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#include "adjtime.h"
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#define abs(x) ((x) < 0 ? -(x) : (x))
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/*
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* The following paramters are appropriate for an NTP adjustment
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* interval of one second.
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*/
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#define ADJ_THRESH 200 /* initial threshold */
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#define ADJ_DELTA 4 /* threshold decrement */
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static long adjthresh; /* adjustment threshold */
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static long saveup; /* corrections accumulator */
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/*
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* clear_adjtime - reset accumulator and threshold variables
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*/
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void
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_clear_adjtime(void)
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{
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saveup = 0;
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adjthresh = ADJ_THRESH;
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}
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/*
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* adjtime - hp-ux copout of the standard Unix adjtime() system call
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*/
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int
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adjtime(
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register struct timeval *delta,
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register struct timeval *olddelta
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)
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{
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struct timeval newdelta;
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/*
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* Corrections greater than one second are done immediately.
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*/
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if (delta->tv_sec) {
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adjthresh = ADJ_THRESH;
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saveup = 0;
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return(_adjtime(delta, olddelta));
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}
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/*
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* Corrections less than one second are accumulated until
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* tripping a threshold, which is initially set at ADJ_THESH and
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* reduced in ADJ_DELTA steps to zero. The idea here is to
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* introduce large corrections quickly, while making sure that
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* small corrections are introduced without excessive delay. The
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* idea comes from the ARPAnet routing update algorithm.
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*/
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saveup += delta->tv_usec;
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if (abs(saveup) >= adjthresh) {
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adjthresh = ADJ_THRESH;
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newdelta.tv_sec = 0;
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newdelta.tv_usec = saveup;
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saveup = 0;
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return(_adjtime(&newdelta, olddelta));
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} else {
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adjthresh -= ADJ_DELTA;
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}
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/*
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* While nobody uses it, return the residual before correction,
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* as per Unix convention.
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*/
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if (olddelta)
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olddelta->tv_sec = olddelta->tv_usec = 0;
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return(0);
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}
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/*
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* _adjtime - does the actual work
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*/
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int
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_adjtime(
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register struct timeval *delta,
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register struct timeval *olddelta
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)
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{
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register int mqid;
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MsgBuf msg;
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register MsgBuf *msgp = &msg;
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/*
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* Get the key to the adjtime message queue (note that we must
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* get it every time because the queue might have been removed
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* and recreated)
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*/
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if ((mqid = msgget(KEY, 0)) == -1)
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return (-1);
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msgp->msgb.mtype = CLIENT;
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msgp->msgb.tv = *delta;
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if (olddelta)
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msgp->msgb.code = DELTA2;
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else
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msgp->msgb.code = DELTA1;
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/*
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* Tickle adjtimed and snatch residual, if indicated. Lots of
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* fanatic error checking here.
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*/
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if (msgsnd(mqid, &msgp->msgp, MSGSIZE, 0) == -1)
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return (-1);
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if (olddelta) {
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if (msgrcv(mqid, &msgp->msgp, MSGSIZE, SERVER, 0) == -1)
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return (-1);
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*olddelta = msgp->msgb.tv;
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}
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return (0);
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}
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#else /* not NEED_HPUX_ADJTIME */
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int adjtime_bs;
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#endif /* not NEED_HPUX_ADJTIME */
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