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