1 /* $OpenBSD: ntpleaps.h,v 1.4 2007/11/25 16:40:04 jmc Exp $ */ 2 3 /* 4 * Copyright (c) 2002 Thorsten Glaser. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 10 * - Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * - Redistributions in binary form must reproduce the above 13 * copyright notice, this list of conditions and the following 14 * disclaimer in the documentation and/or other materials provided 15 * with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 18 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 19 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 20 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 21 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 23 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 24 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER 25 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 26 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN 27 * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 28 * POSSIBILITY OF SUCH DAMAGE. 29 * 30 */ 31 32 /* Leap second support for SNTP clients 33 * This header file and its corresponding C file provide generic 34 * ability for NTP or SNTP clients to correctly handle leap seconds 35 * by reading them from an always existing file and subtracting the 36 * leap seconds from the NTP return value before setting the posix 37 * clock. This is fairly portable between operating systems and may 38 * be used for patching other ntp clients, too. The tzfile used is: 39 * /usr/share/zoneinfo/right/UTC which is available on any unix-like 40 * platform with the Olson tz library, which is necessary to get real 41 * leap second zoneinfo files and userland support anyways. 42 */ 43 44 #ifndef _NTPLEAPS_H 45 #define _NTPLEAPS_H 46 47 /* Offset between struct timeval.tv_sec and a tai64_t */ 48 #define NTPLEAPS_OFFSET (4611686018427387914ULL) 49 50 /* Hide this ugly value from programmes */ 51 #define SEC_TO_TAI64(s) (NTPLEAPS_OFFSET + (u_int64_t)(s)) 52 #define TAI64_TO_SEC(t) ((t) - NTPLEAPS_OFFSET) 53 54 /* Initializes the leap second table. Does not need to be called 55 * before usage of the subtract function, but calls ntpleaps_read. 56 * returns 0 on success, -1 on error (displays a warning on stderr) 57 */ 58 int ntpleaps_init(void); 59 60 /* Re-reads the leap second table, thus consuming quite much time. 61 * Ought to be called from within daemons at least once a month to 62 * ensure the in-memory table is always up-to-date. 63 * returns 0 on success, -1 on error (leap seconds will not be available) 64 */ 65 int ntpleaps_read(void); 66 67 /* Subtracts leap seconds from the given value (converts NTP time 68 * to posix clock tick time. 69 * returns 0 on success, -1 on error (time is unchanged), 1 on leap second 70 */ 71 int ntpleaps_sub(u_int64_t *); 72 73 #endif 74