| 1 | /** $Id: VBoxServiceTimeSync.cpp 5999 2007-12-07 15:05:06Z 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 (GPL) as published by the Free Software
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| 13 | * Foundation, in version 2 as it comes in the "COPYING" file of the
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| 14 | * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
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| 15 | * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
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| 16 | */
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| 17 |
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| 18 |
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| 19 | /** @page pg_vboxservice_timesync The Time Sync Service
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| 20 | *
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| 21 | * The time sync service plays along with the Time Manager (TM) in the VMM
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| 22 | * to keep the guest time accurate using the host machine as reference.
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| 23 | * TM will try its best to make sure all timer ticks gets delivered so that
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| 24 | * there isn't normally any need to adjust the guest time.
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| 25 | *
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| 26 | * There are three normal (= acceptable) cases:
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| 27 | * -# When the service starts up. This is because ticks and such might
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| 28 | * be lost during VM and OS startup. (Need to figure out exactly why!)
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| 29 | * -# When the TM is unable to deliver all the ticks and swallows a
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| 30 | * backlog of ticks. The threshold for this is configurable with
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| 31 | * a default of 60 seconds.
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| 32 | * -# The time is adjusted on the host. This can be caused manually by
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| 33 | * the user or by some time sync daemon (NTP, LAN server, etc.).
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| 34 | *
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| 35 | * There are a number of very odd case where adjusting is needed. Here
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| 36 | * are some of them:
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| 37 | * -# Timer device emulation inaccurancies (like rounding).
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| 38 | * -# Inaccurancies in time source VirtualBox uses.
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| 39 | * -# The Guest and/or Host OS doesn't perform proper time keeping. This
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| 40 | * come about as a result of OS and/or hardware issues.
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| 41 | *
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| 42 | * The TM is our source for the host time and will make adjustments for
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| 43 | * current timer delivery lag. The simplistic approach taken by TM is to
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| 44 | * adjust the host time by the current guest timer delivery lag, meaning that
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| 45 | * if the guest is behind 1 second with PIT/RTC/++ ticks this should be reflected
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| 46 | * in the guest wall time as well.
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| 47 | *
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| 48 | * Now, there is any amount of trouble we can cause by changing the time.
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| 49 | * Most applications probably uses the wall time when they need to measure
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| 50 | * things. A walltime that is being juggled about every so often, even if just
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| 51 | * a little bit, could occationally upset these measurements by for instance
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| 52 | * yielding negative results.
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| 53 | *
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| 54 | * This bottom line here is that the time sync service isn't really supposed
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| 55 | * to do anything and will try avoid having to do anything when possible.
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| 56 | *
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| 57 | * The implementation uses the latency it takes to query host time as the
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| 58 | * absolute maximum precision to avoid messing up under timer tick catchup
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| 59 | * and/or heavy host/guest load. (Rational is that a *lot* of stuff may happen
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| 60 | * on our way back from ring-3 and TM/VMMDev since we're taking the route
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| 61 | * thru the inner EM loop with it's force action processing.)
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| 62 | *
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| 63 | * But this latency has to be measured from our perspective, which means it
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| 64 | * could just as easily come out as 0. (OS/2 and Windows guest only updates
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| 65 | * the current time when the timer ticks for instance.) The good thing is
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| 66 | * that this isn't really a problem since we won't ever do anything unless
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| 67 | * the drift is noticable.
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| 68 | *
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| 69 | * It now boils down to these three (configuration) factors:
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| 70 | * -# g_TimesyncMinAdjust - The minimum drift we will ever bother with.
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| 71 | * -# g_TimesyncLatencyFactor - The factor we multiply the latency by to
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| 72 | * calculate the dynamic minimum adjust factor.
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| 73 | * -# g_TimesyncMaxLatency - When to start discarding the data as utterly
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| 74 | * useless and take a rest (someone is too busy to give us good data).
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| 75 | */
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| 76 |
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| 77 |
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| 78 |
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| 79 | /*******************************************************************************
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| 80 | * Header Files *
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| 81 | *******************************************************************************/
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| 82 | #include <unistd.h>
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| 83 | #include <errno.h>
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| 84 | #include <time.h>
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| 85 | #include <sys/time.h>
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| 86 |
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| 87 | #include <iprt/thread.h>
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| 88 | #include <iprt/string.h>
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| 89 | #include <iprt/semaphore.h>
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| 90 | #include <iprt/time.h>
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| 91 | #include <iprt/assert.h>
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| 92 | #include <VBox/VBoxGuest.h>
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| 93 | #include "VBoxServiceInternal.h"
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| 94 |
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| 95 |
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| 96 | /*******************************************************************************
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| 97 | * Global Variables *
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| 98 | *******************************************************************************/
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| 99 | /** The timesync interval (millseconds). */
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| 100 | uint32_t g_TimeSyncInterval = 0;
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| 101 | /**
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| 102 | * @see pg_vboxservice_timesync
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| 103 | *
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| 104 | * @remark OS/2: There is either a 1 second resolution on the DosSetDateTime
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| 105 | * API or a but in the settimeofday implementation. Thus, don't
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| 106 | * bother unless there is at least a 1 second drift.
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| 107 | */
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| 108 | #ifdef RT_OS_OS2
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| 109 | static uint32_t g_TimeSyncMinAdjust = 1000;
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| 110 | #else
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| 111 | static uint32_t g_TimeSyncMinAdjust = 100;
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| 112 | #endif
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| 113 | /** @see pg_vboxservice_timesync */
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| 114 | static uint32_t g_TimeSyncLatencyFactor = 8;
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| 115 | /** @see pg_vboxservice_timesync */
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| 116 | static uint32_t g_TimeSyncMaxLatency = 250;
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| 117 |
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| 118 | /** The semaphore we're blocking on. */
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| 119 | static RTSEMEVENTMULTI g_TimeSyncEvent = NIL_RTSEMEVENTMULTI;
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| 120 |
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| 121 |
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| 122 | /** @copydoc VBOXSERVICE::pfnPreInit */
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| 123 | static DECLCALLBACK(int) VBoxServiceTimeSyncPreInit(void)
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| 124 | {
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| 125 | return VINF_SUCCESS;
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| 126 | }
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| 127 |
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| 128 |
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| 129 | /** @copydoc VBOXSERVICE::pfnOption */
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| 130 | static DECLCALLBACK(int) VBoxServiceTimeSyncOption(const char **ppszShort, int argc, char **argv, int *pi)
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| 131 | {
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| 132 | int rc = -1;
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| 133 | if (ppszShort)
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| 134 | /* no short options */;
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| 135 | else if (!strcmp(argv[*pi], "--timesync-interval"))
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| 136 | rc = VBoxServiceArgUInt32(argc, argv, "", pi,
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| 137 | &g_TimeSyncInterval, 1, UINT32_MAX - 1);
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| 138 | else if (!strcmp(argv[*pi], "--timesync-min-adjust"))
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| 139 | rc = VBoxServiceArgUInt32(argc, argv, "", pi,
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| 140 | &g_TimeSyncMinAdjust, 0, 3600000);
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| 141 | else if (!strcmp(argv[*pi], "--timesync-latency-factor"))
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| 142 | rc = VBoxServiceArgUInt32(argc, argv, "", pi,
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| 143 | &g_TimeSyncLatencyFactor, 1, 1024);
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| 144 | else if (!strcmp(argv[*pi], "--timesync-max-latency"))
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| 145 | rc = VBoxServiceArgUInt32(argc, argv, "", pi,
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| 146 | &g_TimeSyncMaxLatency, 1, 3600000);
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| 147 | return rc;
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| 148 | }
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| 149 |
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| 150 |
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| 151 | /** @copydoc VBOXSERVICE::pfnInit */
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| 152 | static DECLCALLBACK(int) VBoxServiceTimeSyncInit(void)
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| 153 | {
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| 154 | /*
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| 155 | * If not specified, find the right interval default.
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| 156 | * Then create the event sem to block on.
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| 157 | */
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| 158 | if (!g_TimeSyncInterval)
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| 159 | g_TimeSyncInterval = g_DefaultInterval * 1000;
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| 160 | if (!g_TimeSyncInterval)
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| 161 | g_TimeSyncInterval = 10 * 1000;
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| 162 |
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| 163 | int rc = RTSemEventMultiCreate(&g_TimeSyncEvent);
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| 164 | AssertRC(rc);
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| 165 | return rc;
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| 166 | }
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| 167 |
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| 168 |
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| 169 | /** @copydoc VBOXSERVICE::pfnWorker */
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| 170 | DECLCALLBACK(int) VBoxServiceTimeSyncWorker(bool volatile *pfShutdown)
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| 171 | {
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| 172 | RTTIME Time;
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| 173 | char sz[64];
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| 174 | int rc;
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| 175 |
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| 176 | unsigned cErrors = 0;
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| 177 | for (;;)
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| 178 | {
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| 179 | /*
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| 180 | * Try get a reliable time reading.
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| 181 | */
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| 182 | int cTries = 3;
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| 183 | do
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| 184 | {
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| 185 | /* query it. */
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| 186 | RTTIMESPEC GuestNow0, GuestNow, HostNow;
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| 187 | RTTimeNow(&GuestNow0);
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| 188 | int rc2 = VbglR3GetHostTime(&HostNow);
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| 189 | if (RT_FAILURE(rc2))
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| 190 | {
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| 191 | if (cErrors++ < 10)
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| 192 | VBoxServiceError("VbglR3GetHostTime failed; rc2=%Rrc\n", rc2);
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| 193 | break;
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| 194 | }
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| 195 | RTTimeNow(&GuestNow);
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| 196 |
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| 197 | /* calc latency and check if it's ok. */
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| 198 | RTTIMESPEC GuestElapsed = GuestNow;
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| 199 | RTTimeSpecSub(&GuestElapsed, &GuestNow0);
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| 200 | if ((uint32_t)RTTimeSpecGetMilli(&GuestElapsed) < g_TimeSyncMaxLatency)
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| 201 | {
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| 202 | /*
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| 203 | * Calculate the adjustment threshold and the current drift.
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| 204 | */
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| 205 | uint32_t MinAdjust = RTTimeSpecGetMilli(&GuestElapsed) * g_TimeSyncLatencyFactor;
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| 206 | if (MinAdjust < g_TimeSyncMinAdjust)
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| 207 | MinAdjust = g_TimeSyncMinAdjust;
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| 208 |
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| 209 | RTTIMESPEC Drift = HostNow;
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| 210 | RTTimeSpecSub(&Drift, &GuestNow);
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| 211 | if (RTTimeSpecGetMilli(&Drift) < 0)
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| 212 | MinAdjust += g_TimeSyncMinAdjust; /* extra buffer against moving time backwards. */
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| 213 |
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| 214 | RTTIMESPEC AbsDrift = Drift;
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| 215 | RTTimeSpecAbsolute(&AbsDrift);
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| 216 | if (g_cVerbosity >= 3)
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| 217 | {
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| 218 | VBoxServiceVerbose(3, "Host: %s (MinAdjust: %RU32 ms)\n",
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| 219 | RTTimeToString(RTTimeExplode(&Time, &HostNow), sz, sizeof(sz)), MinAdjust);
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| 220 | VBoxServiceVerbose(3, "Guest: - %s => %RDtimespec drift\n",
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| 221 | RTTimeToString(RTTimeExplode(&Time, &GuestNow), sz, sizeof(sz)),
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| 222 | &Drift);
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| 223 | }
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| 224 | if (RTTimeSpecGetMilli(&AbsDrift) > MinAdjust)
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| 225 | {
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| 226 | /*
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| 227 | * The drift is to big, we have to make adjustments. :-/
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| 228 | * If we've got adjtime around, try that first - most
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| 229 | * *NIX systems have it. Fall back on settimeofday.
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| 230 | */
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| 231 | struct timeval tv;
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| 232 | #if !defined(RT_OS_OS2) /* PORTME */
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| 233 | RTTimeSpecGetTimeval(Drift, &tv);
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| 234 | if (adjtime(&tv, NULL) == 0)
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| 235 | {
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| 236 | if (g_cVerbosity >= 1)
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| 237 | VBoxServiceVerbose(1, "adjtime by %RDtimespec\n", &Drift);
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| 238 | cErrors = 0;
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| 239 | }
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| 240 | else
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| 241 | #endif
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| 242 | {
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| 243 | errno = 0;
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| 244 | if (!gettimeofday(&tv, NULL))
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| 245 | {
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| 246 | RTTIMESPEC Tmp;
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| 247 | RTTimeSpecAdd(RTTimeSpecSetTimeval(&Tmp, &tv), &Drift);
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| 248 | if (!settimeofday(RTTimeSpecGetTimeval(&Tmp, &tv), NULL))
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| 249 | {
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| 250 | if (g_cVerbosity >= 1)
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| 251 | VBoxServiceVerbose(1, "settimeofday to %s\n",
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| 252 | RTTimeToString(RTTimeExplode(&Time, &Tmp), sz, sizeof(sz)));
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| 253 | #ifdef DEBUG
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| 254 | if (g_cVerbosity >= 3)
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| 255 | VBoxServiceVerbose(2, " new time %s\n",
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| 256 | RTTimeToString(RTTimeExplode(&Time, RTTimeNow(&Tmp)), sz, sizeof(sz)));
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| 257 | #endif
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| 258 | cErrors = 0;
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| 259 | }
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| 260 | else if (cErrors++ < 10)
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| 261 | VBoxServiceError("settimeofday failed; errno=%d: %s\n", errno, strerror(errno));
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| 262 | }
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| 263 | else if (cErrors++ < 10)
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| 264 | VBoxServiceError("gettimeofday failed; errno=%d: %s\n", errno, strerror(errno));
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| 265 | }
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| 266 | }
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| 267 | break;
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| 268 | }
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| 269 | VBoxServiceVerbose(3, "%RDtimespec: latency too high (%RDtimespec) sleeping 1s\n", GuestElapsed);
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| 270 | RTThreadSleep(1000);
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| 271 | } while (--cTries > 0);
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| 272 |
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| 273 | /*
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| 274 | * Block for a while.
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| 275 | *
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| 276 | * The event semaphore takes care of ignoring interruptions and it
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| 277 | * allows us to implement service wakeup later.
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| 278 | */
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| 279 | if (*pfShutdown)
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| 280 | break;
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| 281 | int rc2 = RTSemEventMultiWait(g_TimeSyncEvent, g_TimeSyncInterval);
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| 282 | if (*pfShutdown)
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| 283 | break;
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| 284 | if (rc2 != VERR_TIMEOUT && RT_FAILURE(rc2))
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| 285 | {
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| 286 | VBoxServiceError("RTSemEventMultiWait failed; rc2=%Rrc\n", rc2);
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| 287 | rc = rc2;
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| 288 | break;
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| 289 | }
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| 290 | }
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| 291 |
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| 292 | RTSemEventMultiDestroy(g_TimeSyncEvent);
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| 293 | g_TimeSyncEvent = NIL_RTSEMEVENTMULTI;
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| 294 | return rc;
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| 295 | }
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| 296 |
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| 297 |
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| 298 | /** @copydoc VBOXSERVICE::pfnStop */
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| 299 | static DECLCALLBACK(void) VBoxServiceTimeSyncStop(void)
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| 300 | {
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| 301 | RTSemEventMultiSignal(g_TimeSyncEvent);
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| 302 | }
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| 303 |
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| 304 |
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| 305 | /** @copydoc VBOXSERVICE::pfnTerm */
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| 306 | static DECLCALLBACK(void) VBoxServiceTimeSyncTerm(void)
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| 307 | {
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| 308 | RTSemEventMultiDestroy(g_TimeSyncEvent);
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| 309 | g_TimeSyncEvent = NIL_RTSEMEVENTMULTI;
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| 310 | }
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| 311 |
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| 312 |
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| 313 | /**
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| 314 | * The 'timesync' service description.
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| 315 | */
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| 316 | VBOXSERVICE g_TimeSync =
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| 317 | {
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| 318 | /* pszName. */
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| 319 | "timesync",
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| 320 | /* pszDescription. */
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| 321 | "Time synchronization",
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| 322 | /* pszUsage. */
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| 323 | "[--timesync-interval <ms>] [--timesync-min-adjust <ms>] "
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| 324 | "[--timesync-latency-factor <x>] [--time-sync-max-latency <ms>]"
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| 325 | ,
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| 326 | /* pszOptions. */
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| 327 | " --timesync-interval Specifies the interval at which to synchronize the\n"
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| 328 | " time with the host. The default is 10000 ms.\n"
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| 329 | " --timesync-min-adjust The minimum absolute drift drift value measured\n"
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| 330 | " in milliseconds to make adjustments for.\n"
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| 331 | " The default is 1000 ms on OS/2 and 100 ms elsewhere.\n"
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| 332 | " --timesync-latency-factor The factor to multiply the time query latency\n"
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| 333 | " with to calculate the dynamic minimum adjust time.\n"
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| 334 | " The default is 8 times.\n"
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| 335 | " --timesync-max-latency The max host timer query latency to accpet.\n"
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| 336 | " The default is 250 ms.\n"
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| 337 | ,
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| 338 | /* methods */
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| 339 | VBoxServiceTimeSyncPreInit,
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| 340 | VBoxServiceTimeSyncOption,
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| 341 | VBoxServiceTimeSyncInit,
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| 342 | VBoxServiceTimeSyncWorker,
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| 343 | VBoxServiceTimeSyncStop,
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| 344 | VBoxServiceTimeSyncTerm
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| 345 | };
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| 346 |
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