75 lines
3.2 KiB
C
75 lines
3.2 KiB
C
/* $OpenBSD: ntpleaps.h,v 1.4 2007/11/25 16:40:04 jmc Exp $ */
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/*
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* Copyright (c) 2002 Thorsten Glaser. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* - Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* - Redistributions in binary form must reproduce the above
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* copyright notice, this list of conditions and the following
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* disclaimer in the documentation and/or other materials provided
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* with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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* CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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*
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*/
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/* Leap second support for SNTP clients
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* This header file and its corresponding C file provide generic
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* ability for NTP or SNTP clients to correctly handle leap seconds
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* by reading them from an always existing file and subtracting the
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* leap seconds from the NTP return value before setting the posix
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* clock. This is fairly portable between operating systems and may
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* be used for patching other ntp clients, too. The tzfile used is:
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* /usr/share/zoneinfo/right/UTC which is available on any unix-like
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* platform with the Olson tz library, which is necessary to get real
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* leap second zoneinfo files and userland support anyways.
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*/
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#ifndef _NTPLEAPS_H
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#define _NTPLEAPS_H
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/* Offset between struct timeval.tv_sec and a tai64_t */
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#define NTPLEAPS_OFFSET (4611686018427387914ULL)
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/* Hide this ugly value from programmes */
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#define SEC_TO_TAI64(s) (NTPLEAPS_OFFSET + (u_int64_t)(s))
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#define TAI64_TO_SEC(t) ((t) - NTPLEAPS_OFFSET)
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/* Initializes the leap second table. Does not need to be called
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* before usage of the subtract function, but calls ntpleaps_read.
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* returns 0 on success, -1 on error (displays a warning on stderr)
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*/
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int ntpleaps_init(void);
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/* Re-reads the leap second table, thus consuming quite much time.
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* Ought to be called from within daemons at least once a month to
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* ensure the in-memory table is always up-to-date.
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* returns 0 on success, -1 on error (leap seconds will not be available)
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*/
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int ntpleaps_read(void);
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/* Subtracts leap seconds from the given value (converts NTP time
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* to posix clock tick time.
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* returns 0 on success, -1 on error (time is unchanged), 1 on leap second
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*/
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typedef unsigned long long u_int64_t;
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int ntpleaps_sub(u_int64_t *);
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#endif
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