| 1 | /** $Id: VBoxServiceTimeSync.cpp 3725 2007-07-19 19:01:52Z vboxsync $ */
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| 2 | /** @file
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| 3 | * VBoxService - Guest Additions TimeSync Service.
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| 4 | */
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| 5 |
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| 6 | /*
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| 7 | * Copyright (C) 2007 innotek GmbH
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| 8 | *
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| 9 | * This file is part of VirtualBox Open Source Edition (OSE), as
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| 10 | * available from http://www.virtualbox.org. This file is free software;
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| 11 | * you can redistribute it and/or modify it under the terms of the GNU
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| 12 | * General Public License as published by the Free Software Foundation,
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| 13 | * in version 2 as it comes in the "COPYING" file of the VirtualBox OSE
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| 14 | * distribution. VirtualBox OSE is distributed in the hope that it will
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| 15 | * be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | *
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| 17 | * If you received this file as part of a commercial VirtualBox
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| 18 | * distribution, then only the terms of your commercial VirtualBox
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| 19 | * license agreement apply instead of the previous paragraph.
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| 20 | */
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| 21 |
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| 22 |
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| 23 | /** @page pg_vboxservice_timesync The Time Sync Service
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| 24 | *
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| 25 | * The time sync service plays along with the Time Manager (TM) in the VMM
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| 26 | * to keep the guest time accurate using the host machine as reference.
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| 27 | * TM will try its best to make sure all timer ticks gets delivered so that
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| 28 | * there isn't normally any need to adjust the guest time.
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| 29 | *
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| 30 | * There are three normal (= acceptable) cases:
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| 31 | * -# When the service starts up. This is because ticks and such might
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| 32 | * be lost during VM and OS startup. (Need to figure out exactly why!)
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| 33 | * -# When the TM is unable to deliver all the ticks and swallows a
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| 34 | * backlog of ticks. The threshold for this is configurable with
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| 35 | * a default of 60 seconds.
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| 36 | * -# The time is adjusted on the host. This can be caused manually by
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| 37 | * the user or by some time sync daemon (NTP, LAN server, etc.).
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| 38 | *
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| 39 | * There are a number of very odd case where adjusting is needed. Here
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| 40 | * are some of them:
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| 41 | * -# Timer device emulation inaccurancies (like rounding).
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| 42 | * -# Inaccurancies in time source VirtualBox uses.
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| 43 | * -# The Guest and/or Host OS doesn't perform proper time keeping. This
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| 44 | * come about as a result of OS and/or hardware issues.
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| 45 | *
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| 46 | * The TM is our source for the host time and will make adjustments for
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| 47 | * current timer delivery lag. The simplistic approach taken by TM is to
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| 48 | * adjust the host time by the current guest timer delivery lag, meaning that
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| 49 | * if the guest is behind 1 second with PIT/RTC/++ ticks this should be reflected
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| 50 | * in the guest wall time as well.
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| 51 | *
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| 52 | * Now, there is any amount of trouble we can cause by changing the time.
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| 53 | * Most applications probably uses the wall time when they need to measure
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| 54 | * things. A walltime that is being juggled about every so often, even if just
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| 55 | * a little bit, could occationally upset these measurements by for instance
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| 56 | * yielding negative results.
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| 57 | *
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| 58 | * This bottom line here is that the time sync service isn't really supposed
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| 59 | * to do anything and will try avoid having to do anything when possible.
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| 60 | *
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| 61 | * The implementation uses the latency it takes to query host time as the
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| 62 | * absolute maximum precision to avoid messing up under timer tick catchup
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| 63 | * and/or heavy host/guest load. (Rational is that a *lot* of stuff may happen
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| 64 | * on our way back from ring-3 and TM/VMMDev since we're taking the route
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| 65 | * thru the inner EM loop with it's force action processing.)
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| 66 | *
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| 67 | * But this latency has to be measured from our perspective, which means it
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| 68 | * could just as easily come out as 0. (OS/2 and Windows guest only updates
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| 69 | * the current time when the timer ticks for instance.) The good thing is
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| 70 | * that this isn't really a problem since we won't ever do anything unless
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| 71 | * the drift is noticable.
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| 72 | *
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| 73 | * It now boils down to these three (configuration) factors:
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| 74 | * -# g_TimesyncMinAdjust - The minimum drift we will ever bother with.
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| 75 | * -# g_TimesyncLatencyFactor - The factor we multiply the latency by to
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| 76 | * calculate the dynamic minimum adjust factor.
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| 77 | * -# g_TimesyncMaxLatency - When to start discarding the data as utterly
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| 78 | * useless and take a rest (someone is too busy to give us good data).
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| 79 | */
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| 80 |
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| 81 |
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| 82 |
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| 83 | /*******************************************************************************
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| 84 | * Header Files *
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| 85 | *******************************************************************************/
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| 86 | #include <unistd.h>
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| 87 | #include <errno.h>
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| 88 | #include <time.h>
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| 89 | #include <sys/time.h>
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| 90 |
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| 91 | #include <iprt/thread.h>
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| 92 | #include <iprt/string.h>
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| 93 | #include <iprt/semaphore.h>
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| 94 | #include <iprt/time.h>
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| 95 | #include <iprt/assert.h>
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| 96 | #include <VBox/VBoxGuest.h>
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| 97 | #include "VBoxServiceInternal.h"
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| 98 |
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| 99 |
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| 100 | /*******************************************************************************
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| 101 | * Global Variables *
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| 102 | *******************************************************************************/
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| 103 | /** The timesync interval (millseconds). */
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| 104 | uint32_t g_TimeSyncInterval = 0;
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| 105 | /**
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| 106 | * @see pg_vboxservice_timesync
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| 107 | *
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| 108 | * @remark OS/2: There is either a 1 second resolution on the DosSetDateTime
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| 109 | * API or a but in the settimeofday implementation. Thus, don't
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| 110 | * bother unless there is at least a 1 second drift.
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| 111 | */
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| 112 | #ifdef RT_OS_OS2
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| 113 | static uint32_t g_TimeSyncMinAdjust = 1000;
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| 114 | #else
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| 115 | static uint32_t g_TimeSyncMinAdjust = 100;
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| 116 | #endif
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| 117 | /** @see pg_vboxservice_timesync */
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| 118 | static uint32_t g_TimeSyncLatencyFactor = 8;
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| 119 | /** @see pg_vboxservice_timesync */
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| 120 | static uint32_t g_TimeSyncMaxLatency = 250;
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| 121 |
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| 122 | /** The semaphore we're blocking on. */
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| 123 | static RTSEMEVENTMULTI g_TimeSyncEvent = NIL_RTSEMEVENTMULTI;
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| 124 |
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| 125 |
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| 126 | /** @copydoc VBOXSERVICE::pfnPreInit */
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| 127 | static DECLCALLBACK(int) VBoxServiceTimeSyncPreInit(void)
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| 128 | {
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| 129 | return VINF_SUCCESS;
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| 130 | }
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| 131 |
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| 132 |
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| 133 | /** @copydoc VBOXSERVICE::pfnOption */
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| 134 | static DECLCALLBACK(int) VBoxServiceTimeSyncOption(const char **ppszShort, int argc, char **argv, int *pi)
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| 135 | {
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| 136 | int rc = -1;
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| 137 | if (ppszShort)
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| 138 | /* no short options */;
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| 139 | else if (!strcmp(argv[*pi], "--timesync-interval"))
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| 140 | rc = VBoxServiceArgUInt32(argc, argv, "", pi,
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| 141 | &g_TimeSyncInterval, 1, UINT32_MAX - 1);
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| 142 | else if (!strcmp(argv[*pi], "--timesync-min-adjust"))
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| 143 | rc = VBoxServiceArgUInt32(argc, argv, "", pi,
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| 144 | &g_TimeSyncMinAdjust, 0, 3600000);
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| 145 | else if (!strcmp(argv[*pi], "--timesync-latency-factor"))
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| 146 | rc = VBoxServiceArgUInt32(argc, argv, "", pi,
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| 147 | &g_TimeSyncLatencyFactor, 1, 1024);
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| 148 | else if (!strcmp(argv[*pi], "--timesync-max-latency"))
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| 149 | rc = VBoxServiceArgUInt32(argc, argv, "", pi,
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| 150 | &g_TimeSyncMaxLatency, 1, 3600000);
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| 151 | return rc;
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| 152 | }
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| 153 |
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| 154 |
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| 155 | /** @copydoc VBOXSERVICE::pfnInit */
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| 156 | static DECLCALLBACK(int) VBoxServiceTimeSyncInit(void)
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| 157 | {
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| 158 | /*
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| 159 | * If not specified, find the right interval default.
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| 160 | * Then create the event sem to block on.
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| 161 | */
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| 162 | if (!g_TimeSyncInterval)
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| 163 | g_TimeSyncInterval = g_DefaultInterval * 1000;
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| 164 | if (!g_TimeSyncInterval)
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| 165 | g_TimeSyncInterval = 10 * 1000;
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| 166 |
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| 167 | int rc = RTSemEventMultiCreate(&g_TimeSyncEvent);
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| 168 | AssertRC(rc);
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| 169 | return rc;
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| 170 | }
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| 171 |
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| 172 |
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| 173 | /** @copydoc VBOXSERVICE::pfnWorker */
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| 174 | DECLCALLBACK(int) VBoxServiceTimeSyncWorker(bool volatile *pfShutdown)
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| 175 | {
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| 176 | RTTIME Time;
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| 177 | char sz[64];
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| 178 | int rc;
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| 179 |
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| 180 | unsigned cErrors = 0;
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| 181 | for (;;)
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| 182 | {
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| 183 | /*
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| 184 | * Try get a reliable time reading.
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| 185 | */
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| 186 | int cTries = 3;
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| 187 | do
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| 188 | {
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| 189 | /* query it. */
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| 190 | RTTIMESPEC GuestNow0, GuestNow, HostNow;
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| 191 | RTTimeNow(&GuestNow0);
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| 192 | int rc2 = VbglR3GetHostTime(&HostNow);
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| 193 | if (RT_FAILURE(rc2))
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| 194 | {
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| 195 | if (cErrors++ < 10)
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| 196 | VBoxServiceError("VbglR3GetHostTime failed; rc2=%Rrc\n", rc2);
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| 197 | break;
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| 198 | }
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| 199 | RTTimeNow(&GuestNow);
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| 200 |
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| 201 | /* calc latency and check if it's ok. */
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| 202 | RTTIMESPEC GuestElapsed = GuestNow;
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| 203 | RTTimeSpecSub(&GuestElapsed, &GuestNow0);
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| 204 | if ((uint32_t)RTTimeSpecGetMilli(&GuestElapsed) < g_TimeSyncMaxLatency)
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| 205 | {
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| 206 | /*
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| 207 | * Calculate the adjustment threshold and the current drift.
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| 208 | */
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| 209 | uint32_t MinAdjust = RTTimeSpecGetMilli(&GuestElapsed) * g_TimeSyncLatencyFactor;
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| 210 | if (MinAdjust < g_TimeSyncMinAdjust)
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| 211 | MinAdjust = g_TimeSyncMinAdjust;
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| 212 |
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| 213 | RTTIMESPEC Drift = HostNow;
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| 214 | RTTimeSpecSub(&Drift, &GuestNow);
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| 215 | if (RTTimeSpecGetMilli(&Drift) < 0)
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| 216 | MinAdjust += g_TimeSyncMinAdjust; /* extra buffer against moving time backwards. */
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| 217 |
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| 218 | RTTIMESPEC AbsDrift = Drift;
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| 219 | RTTimeSpecAbsolute(&AbsDrift);
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| 220 | if (g_cVerbosity >= 3)
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| 221 | {
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| 222 | VBoxServiceVerbose(3, "Host: %s (MinAdjust: %RU32 ms)\n",
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| 223 | RTTimeToString(RTTimeExplode(&Time, &HostNow), sz, sizeof(sz)), MinAdjust);
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| 224 | VBoxServiceVerbose(3, "Guest: - %s => %RDtimespec drift\n",
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| 225 | RTTimeToString(RTTimeExplode(&Time, &GuestNow), sz, sizeof(sz)),
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| 226 | &Drift);
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| 227 | }
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| 228 | if (RTTimeSpecGetMilli(&AbsDrift) > MinAdjust)
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| 229 | {
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| 230 | /*
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| 231 | * The drift is to big, we have to make adjustments. :-/
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| 232 | * If we've got adjtime around, try that first - most
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| 233 | * *NIX systems have it. Fall back on settimeofday.
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| 234 | */
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| 235 | struct timeval tv;
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| 236 | #if !defined(RT_OS_OS2) /* PORTME */
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| 237 | RTTimeSpecGetTimeval(Drift, &tv);
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| 238 | if (adjtime(&tv, NULL) == 0)
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| 239 | {
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| 240 | if (g_cVerbosity >= 1)
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| 241 | VBoxServiceVerbose(1, "adjtime by %RDtimespec\n", &Drift);
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| 242 | cErrors = 0;
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| 243 | }
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| 244 | else
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| 245 | #endif
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| 246 | {
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| 247 | errno = 0;
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| 248 | if (!gettimeofday(&tv, NULL))
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| 249 | {
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| 250 | RTTIMESPEC Tmp;
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| 251 | RTTimeSpecAdd(RTTimeSpecSetTimeval(&Tmp, &tv), &Drift);
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| 252 | if (!settimeofday(RTTimeSpecGetTimeval(&Tmp, &tv), NULL))
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| 253 | {
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| 254 | if (g_cVerbosity >= 1)
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| 255 | VBoxServiceVerbose(1, "settimeofday to %s\n",
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| 256 | RTTimeToString(RTTimeExplode(&Time, &Tmp), sz, sizeof(sz)));
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| 257 | #ifdef DEBUG
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| 258 | if (g_cVerbosity >= 3)
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| 259 | VBoxServiceVerbose(2, " new time %s\n",
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| 260 | RTTimeToString(RTTimeExplode(&Time, RTTimeNow(&Tmp)), sz, sizeof(sz)));
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| 261 | #endif
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| 262 | cErrors = 0;
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| 263 | }
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| 264 | else if (cErrors++ < 10)
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| 265 | VBoxServiceError("settimeofday failed; errno=%d: %s\n", errno, strerror(errno));
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| 266 | }
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| 267 | else if (cErrors++ < 10)
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| 268 | VBoxServiceError("gettimeofday failed; errno=%d: %s\n", errno, strerror(errno));
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| 269 | }
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| 270 | }
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| 271 | break;
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| 272 | }
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| 273 | VBoxServiceVerbose(3, "%RDtimespec: latency too high (%RDtimespec) sleeping 1s\n", GuestElapsed);
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| 274 | RTThreadSleep(1000);
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| 275 | } while (--cTries > 0);
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| 276 |
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| 277 | /*
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| 278 | * Block for a while.
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| 279 | *
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| 280 | * The event semaphore takes care of ignoring interruptions and it
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| 281 | * allows us to implement service wakeup later.
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| 282 | */
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| 283 | if (*pfShutdown)
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| 284 | break;
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| 285 | int rc2 = RTSemEventMultiWait(g_TimeSyncEvent, g_TimeSyncInterval);
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| 286 | if (*pfShutdown)
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| 287 | break;
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| 288 | if (rc2 != VERR_TIMEOUT && RT_FAILURE(rc2))
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| 289 | {
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| 290 | VBoxServiceError("RTSemEventMultiWait failed; rc2=%Rrc\n", rc2);
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| 291 | rc = rc2;
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| 292 | break;
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| 293 | }
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| 294 | }
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| 295 |
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| 296 | RTSemEventMultiDestroy(g_TimeSyncEvent);
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| 297 | g_TimeSyncEvent = NIL_RTSEMEVENTMULTI;
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| 298 | return rc;
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| 299 | }
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| 300 |
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| 301 |
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| 302 | /** @copydoc VBOXSERVICE::pfnStop */
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| 303 | static DECLCALLBACK(void) VBoxServiceTimeSyncStop(void)
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| 304 | {
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| 305 | RTSemEventMultiSignal(g_TimeSyncEvent);
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| 306 | }
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| 307 |
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| 308 |
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| 309 | /** @copydoc VBOXSERVICE::pfnTerm */
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| 310 | static DECLCALLBACK(void) VBoxServiceTimeSyncTerm(void)
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| 311 | {
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| 312 | RTSemEventMultiDestroy(g_TimeSyncEvent);
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| 313 | g_TimeSyncEvent = NIL_RTSEMEVENTMULTI;
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| 314 | }
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| 315 |
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| 316 |
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| 317 | /**
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| 318 | * The 'timesync' service description.
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| 319 | */
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| 320 | VBOXSERVICE g_TimeSync =
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| 321 | {
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| 322 | /* pszName. */
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| 323 | "timesync",
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| 324 | /* pszDescription. */
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| 325 | "Time synchronization",
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| 326 | /* pszUsage. */
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| 327 | "[--timesync-interval <ms>] [--timesync-min-adjust <ms>] "
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| 328 | "[--timesync-latency-factor <x>] [--time-sync-max-latency <ms>]"
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| 329 | ,
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| 330 | /* pszOptions. */
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| 331 | " --timesync-interval Specifies the interval at which to synchronize the\n"
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| 332 | " time with the host. The default is 10000 ms.\n"
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| 333 | " --timesync-min-adjust The minimum absolute drift drift value measured\n"
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| 334 | " in milliseconds to make adjustments for.\n"
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| 335 | " The default is 1000 ms on OS/2 and 100 ms elsewhere.\n"
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| 336 | " --timesync-latency-factor The factor to multiply the time query latency\n"
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| 337 | " with to calculate the dynamic minimum adjust time.\n"
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| 338 | " The default is 8 times.\n"
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| 339 | " --timesync-max-latency The max host timer query latency to accpet.\n"
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| 340 | " The default is 250 ms.\n"
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| 341 | ,
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| 342 | /* methods */
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| 343 | VBoxServiceTimeSyncPreInit,
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| 344 | VBoxServiceTimeSyncOption,
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| 345 | VBoxServiceTimeSyncInit,
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| 346 | VBoxServiceTimeSyncWorker,
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| 347 | VBoxServiceTimeSyncStop,
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| 348 | VBoxServiceTimeSyncTerm
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| 349 | };
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| 350 |
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