Check WinTime and XenTime for drift

Windows 10/Server 2016 changed how Windows maintains the accuracy of its
clock
This can allow reported time to drift away from host time, and Windows time
will need to be updated regularly in order to minimise the drift.

* Add a wrapper for SetXenTime to manage the critical section
* Remove SetXenTime from CheckSuspend and call it from the calling function
* Add a timeout to the WaitForMultipleObjectsEx, which calls SetXenTime
* Prevent SetXenTime from updating the time if its not changed (and avoid
  outputting the log lines)

Signed-off-by: Owen Smith <owen.smith@citrix.com>
Moved the call to get current time earlier in SetXenTime() and also made
it call GetSystemTime() if the RTC is in UTC. Also added missing
__fallthrough annotation for case WAIT_TIMEOUT in ServiceMainLoop().

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>

diff --git a/src/xenagent/service.cpp b/src/xenagent/service.cpp
index dfcf8a597bea099cd40aa31059c05b0656bd1583..a77ff2395a1cdbbfa09283a75f02b39cdc8e5525 100644 (file)
--- a/src/xenagent/service.cpp
+++ b/src/xenagent/service.cpp
@@ -239,6 +239,15 @@ bool CXenIfaceCreator::CheckShutdown()
     return false;
 }
 
+void CXenIfaceCreator::CheckXenTime()
+{
+    CCritSec crit(&m_crit);
+    if (m_device == NULL)
+        return;
+
+    SetXenTime();
+}
+
 void CXenIfaceCreator::CheckSuspend()
 {
     CCritSec crit(&m_crit);
@@ -268,7 +277,6 @@ void CXenIfaceCreator::CheckSuspend()
     if (m_agent.ConvDevicePresent())
         StartSlateModeWatch();
 
-    SetXenTime();
     m_count = count;
 }
 
@@ -420,12 +428,18 @@ void CXenIfaceCreator::AdjustXenTimeToUTC(FILETIME* now)
 
 void CXenIfaceCreator::SetXenTime()
 {
-    // Set VM's time to Xen's time (adjust for UTC setting)
+    bool IsUTC = IsRTCInUTC();
+
+    SYSTEMTIME cur = { 0 };
+    if (IsUTC)
+        GetSystemTime(&cur);
+    else
+        GetLocalTime(&cur);
+
     FILETIME now = { 0 };
     if (!m_device->SharedInfoGetTime(&now))
         return;
 
-    bool IsUTC = IsRTCInUTC();
     if (IsUTC)
         AdjustXenTimeToUTC(&now);
 
@@ -433,8 +447,8 @@ void CXenIfaceCreator::SetXenTime()
     if (!FileTimeToSystemTime(&now, &sys))
         return;
 
-    SYSTEMTIME cur = { 0 };
-    GetLocalTime(&cur);
+    if (memcmp(&cur, &sys, sizeof(SYSTEMTIME)) == 0)
+        return;
 
     CXenAgent::Log("RTC is in %s\n", IsUTC ? "UTC" : "local time");
     CXenAgent::Log("Time Now = %d/%d/%d %d:%02d:%02d.%d\n",
@@ -696,11 +710,12 @@ void CXenAgent::OnPowerEvent(DWORD evt, LPVOID data)
 
 bool CXenAgent::ServiceMainLoop()
 {
+    DWORD   timeout = 30 * 60 * 1000;
     HANDLE  events[] = { m_svc_stop,
                          m_xeniface.m_evt_shutdown,
                          m_xeniface.m_evt_suspend,
                          m_xeniface.m_evt_slate_mode };
-    DWORD   wait = WaitForMultipleObjectsEx(4, events, FALSE, INFINITE, TRUE);
+    DWORD   wait = WaitForMultipleObjectsEx(4, events, FALSE, timeout, TRUE);
 
     switch (wait) {
     case WAIT_OBJECT_0:
@@ -713,6 +728,7 @@ bool CXenAgent::ServiceMainLoop()
 
     case WAIT_OBJECT_0+2:
         ResetEvent(m_xeniface.m_evt_suspend);
+        m_xeniface.CheckXenTime();
         m_xeniface.CheckSuspend();
         return true; // continue loop
 
@@ -725,8 +741,10 @@ bool CXenAgent::ServiceMainLoop()
 
         return true; // continue loop
     }
-    case WAIT_IO_COMPLETION:
     case WAIT_TIMEOUT:
+        m_xeniface.CheckXenTime();
+        __fallthrough;
+    case WAIT_IO_COMPLETION:
         m_xeniface.CheckSuspend();
         return !m_xeniface.CheckShutdown();
 

diff --git a/src/xenagent/service.h b/src/xenagent/service.h
index 2f1bbd2544f4db19285cbb2d9497dd1cb88a346c..9547177e6b24aec9b15b183ad30d373c2d0134c4 100644 (file)
--- a/src/xenagent/service.h
+++ b/src/xenagent/service.h
@@ -69,6 +69,7 @@ public: // IDeviceCreator
 
 public:
     bool CheckShutdown();
+    void CheckXenTime();
     void CheckSuspend();
     bool CheckSlateMode(std::string *mode);