Adding upstream version 7.0.14-dfsg.upstream/7.0.14-dfsg

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

79 files changed, 32664 insertions, 0 deletions

diff --git a/src/VBox/HostServices/.scm-settings b/src/VBox/HostServices/.scm-settings
new file mode 100644
index 00000000..afa97e72
--- /dev/null
+++ b/src/VBox/HostServices/.scm-settings
@@ -0,0 +1,29 @@
+# $Id: .scm-settings $
+## @file
+# Source code massager settings for the host HGCM services.
+#
+
+#
+# Copyright (C) 2019-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+/*.h: --guard-relative-to-dir .
+
diff --git a/src/VBox/HostServices/DragAndDrop/Makefile.kmk b/src/VBox/HostServices/DragAndDrop/Makefile.kmk
new file mode 100644
index 00000000..37b88830
--- /dev/null
+++ b/src/VBox/HostServices/DragAndDrop/Makefile.kmk
@@ -0,0 +1,65 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Guest Control Host Service.
+#
+
+#
+# Copyright (C) 2011-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+# Include sub-makefile(s).
+# include $(PATH_SUB_CURRENT)/testcase/Makefile.kmk
+
+#
+# The drag and drop service DLL.
+#
+DLLS += VBoxDragAndDropSvc
+VBoxDragAndDropSvc_TEMPLATE  = VBoxR3Dll
+VBoxDragAndDropSvc_NAME.os2  = VBoxDnD
+VBoxDragAndDropSvc_DEFS      = \
+	VBOX_WITH_HGCM \
+	$(if $(VBOX_WITH_DRAG_AND_DROP_GH),VBOX_WITH_DRAG_AND_DROP_GH,)
+VBoxDragAndDropSvc_INCS      = $(PATH_ROOT)/src/VBox/Main/include ./
+VBoxDragAndDropSvc_INCS.win  = \
+	$(VBOX_PATH_SDK)
+
+VBoxDragAndDropSvc_SOURCES = \
+	VBoxDragAndDropSvc.cpp \
+	dndmanager.cpp
+
+VBoxDragAndDropSvc_SOURCES += \
+	../common/client.cpp \
+	../common/message.cpp
+
+VBoxDragAndDropSvc_SOURCES.win = \
+	VBoxDragAndDropSvc.rc
+
+VBoxDragAndDropSvc_LIBS = \
+	$(LIB_RUNTIME) \
+	$(PATH_STAGE_LIB)/VBoxDnDHostR3Lib$(VBOX_SUFF_LIB)
+
+VBoxDragAndDropSvc_LDFLAGS.darwin = \
+	-install_name $(VBOX_DYLD_EXECUTABLE_PATH)/VBoxDragAndDropSvc.dylib
+
+include $(FILE_KBUILD_SUB_FOOTER)
diff --git a/src/VBox/HostServices/DragAndDrop/VBoxDragAndDropSvc.cpp b/src/VBox/HostServices/DragAndDrop/VBoxDragAndDropSvc.cpp
new file mode 100644
index 00000000..c9ac0119
--- /dev/null
+++ b/src/VBox/HostServices/DragAndDrop/VBoxDragAndDropSvc.cpp
@@ -0,0 +1,1352 @@
+/* $Id: VBoxDragAndDropSvc.cpp $ */
+/** @file
+ * Drag and Drop Service.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+/** @page pg_svc_dnd    Drag and drop HGCM Service
+ *
+ * @sa See src/VBox/Main/src-client/GuestDnDPrivate.cpp for more information.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_GUEST_DND
+#include <VBox/GuestHost/DragAndDrop.h>
+#include <VBox/GuestHost/DragAndDropDefs.h>
+#include <VBox/HostServices/Service.h>
+#include <VBox/HostServices/DragAndDropSvc.h>
+#include <VBox/AssertGuest.h>
+
+#include <VBox/err.h>
+
+#include <algorithm>
+#include <list>
+#include <map>
+
+#include "dndmanager.h"
+
+using namespace DragAndDropSvc;
+
+
+/*********************************************************************************************************************************
+*   Service class declaration                                                                                                    *
+*********************************************************************************************************************************/
+
+class DragAndDropClient : public HGCM::Client
+{
+public:
+
+    DragAndDropClient(uint32_t idClient)
+        : HGCM::Client(idClient)
+        , uProtocolVerDeprecated(0)
+        , fGuestFeatures0(VBOX_DND_GF_NONE)
+        , fGuestFeatures1(VBOX_DND_GF_NONE)
+    {
+        RT_ZERO(m_SvcCtx);
+    }
+
+    virtual ~DragAndDropClient(void)
+    {
+        disconnect();
+    }
+
+public:
+
+    void disconnect(void) RT_NOEXCEPT;
+
+public:
+
+    /** Protocol version used by this client.
+     *  Deprecated; only used for keeping backwards compatibility. */
+    uint32_t                uProtocolVerDeprecated;
+    /** Guest feature flags, VBOX_DND_GF_0_XXX. */
+    uint64_t                fGuestFeatures0;
+    /** Guest feature flags, VBOX_DND_GF_1_XXX. */
+    uint64_t                fGuestFeatures1;
+};
+
+/** Map holding pointers to drag and drop clients. Key is the (unique) HGCM client ID. */
+typedef std::map<uint32_t, DragAndDropClient*> DnDClientMap;
+
+/** Simple queue (list) which holds deferred (waiting) clients. */
+typedef std::list<uint32_t> DnDClientQueue;
+
+/**
+ * Specialized drag & drop service class.
+ */
+class DragAndDropService : public HGCM::AbstractService<DragAndDropService>
+{
+public:
+    explicit DragAndDropService(PVBOXHGCMSVCHELPERS pHelpers)
+        : HGCM::AbstractService<DragAndDropService>(pHelpers)
+        , m_pManager(NULL)
+        , m_u32Mode(VBOX_DRAG_AND_DROP_MODE_OFF)
+    {}
+
+protected:
+    int  init(VBOXHGCMSVCFNTABLE *pTable) RT_NOEXCEPT RT_OVERRIDE;
+    int  uninit(void) RT_NOEXCEPT RT_OVERRIDE;
+    int  clientConnect(uint32_t idClient, void *pvClient) RT_NOEXCEPT RT_OVERRIDE;
+    int  clientDisconnect(uint32_t idClient, void *pvClient) RT_NOEXCEPT RT_OVERRIDE;
+    int  clientQueryFeatures(uint32_t cParms, VBOXHGCMSVCPARM paParms[]) RT_NOEXCEPT;
+    int  clientReportFeatures(DragAndDropClient *pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[]) RT_NOEXCEPT;
+    void guestCall(VBOXHGCMCALLHANDLE callHandle, uint32_t idClient, void *pvClient, uint32_t u32Function,
+                   uint32_t cParms, VBOXHGCMSVCPARM paParms[]) RT_NOEXCEPT RT_OVERRIDE;
+    int  hostCall(uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[]) RT_NOEXCEPT RT_OVERRIDE;
+
+private:
+    int  modeSet(uint32_t u32Mode) RT_NOEXCEPT;
+    inline uint32_t modeGet(void) const RT_NOEXCEPT
+    { return m_u32Mode; };
+
+    static DECLCALLBACK(int) progressCallback(uint32_t uStatus, uint32_t uPercentage, int rc, void *pvUser);
+
+private:
+    /** Pointer to our DnD manager instance. */
+    DnDManager                        *m_pManager;
+    /** Map of all connected clients.
+     *  The primary key is the (unique) client ID, the secondary value
+     *  an allocated pointer to the DragAndDropClient class, managed
+     *  by this service class. */
+    DnDClientMap                       m_clientMap;
+    /** List of all clients which are queued up (deferred return) and ready
+     *  to process new commands. The key is the (unique) client ID. */
+    DnDClientQueue                     m_clientQueue;
+    /** Current drag and drop mode, VBOX_DRAG_AND_DROP_MODE_XXX. */
+    uint32_t                           m_u32Mode;
+    /** Host feature mask (VBOX_DND_HF_0_XXX) for DND_GUEST_REPORT_FEATURES
+     * and DND_GUEST_QUERY_FEATURES. */
+    uint64_t                           m_fHostFeatures0;
+};
+
+
+/*********************************************************************************************************************************
+*   Client implementation                                                                                                        *
+*********************************************************************************************************************************/
+
+/**
+ * Called when the HGCM client disconnected on the guest side.
+ *
+ * This function takes care of the client's data cleanup and also lets the host
+ * know that the client has been disconnected.
+ */
+void DragAndDropClient::disconnect(void) RT_NOEXCEPT
+{
+    LogFlowThisFunc(("uClient=%RU32, fDeferred=%RTbool\n", m_idClient, IsDeferred()));
+
+    /*
+     * If the client still is waiting for a message (i.e in deferred mode),
+     * complete the call with a VERR_CANCELED status so that the client (VBoxTray / VBoxClient) knows
+     * it should bail out.
+     */
+    if (IsDeferred())
+        CompleteDeferred(VERR_CANCELLED);
+
+    /*
+     * Let the host know.
+     */
+    VBOXDNDCBDISCONNECTMSGDATA data;
+    RT_ZERO(data);
+    /** @todo Magic needed? */
+    /** @todo Add context ID. */
+
+    if (m_SvcCtx.pfnHostCallback)
+    {
+        int rc2 = m_SvcCtx.pfnHostCallback(m_SvcCtx.pvHostData, GUEST_DND_FN_DISCONNECT, &data, sizeof(data));
+        if (RT_FAILURE(rc2))
+            LogFlowFunc(("Warning: Unable to notify host about client %RU32 disconnect, rc=%Rrc\n", m_idClient, rc2));
+        /* Not fatal. */
+    }
+}
+
+
+/*********************************************************************************************************************************
+*   Service class implementation                                                                                                 *
+*********************************************************************************************************************************/
+
+int DragAndDropService::init(VBOXHGCMSVCFNTABLE *pTable) RT_NOEXCEPT
+{
+    /* Legacy clients map to the root category. */
+    pTable->idxLegacyClientCategory = HGCM_CLIENT_CATEGORY_ROOT;
+
+    /* Limit to 255 clients (see also DragAndDropService::clientConnect). */
+    for (uintptr_t i = 0; i < RT_ELEMENTS(pTable->acMaxClients); i++)
+        pTable->acMaxClients[i] = UINT8_MAX;
+
+    /* Limit the number of concurrent calls to 256 (playing safe).  */
+    /** @todo Properly determin the max number of pending/concurrent calls for DnD. */
+    for (uintptr_t i = 0; i < RT_ELEMENTS(pTable->acMaxClients); i++)
+        pTable->acMaxCallsPerClient[i] = 256;
+
+    /* Register functions. */
+    pTable->pfnHostCall          = svcHostCall;
+    pTable->pfnSaveState         = NULL;  /* The service is stateless, so the normal */
+    pTable->pfnLoadState         = NULL;  /* construction done before restoring suffices */
+    pTable->pfnRegisterExtension = svcRegisterExtension;
+    pTable->pfnNotify            = NULL;
+
+    /* Drag'n drop mode is disabled by default. */
+    modeSet(VBOX_DRAG_AND_DROP_MODE_OFF);
+
+    /* Set host features. */
+    m_fHostFeatures0 = VBOX_DND_HF_NONE;
+
+    int rc = VINF_SUCCESS;
+
+    try
+    {
+        m_pManager = new DnDManager(&DragAndDropService::progressCallback, this);
+    }
+    catch (std::bad_alloc &)
+    {
+        rc = VERR_NO_MEMORY;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int DragAndDropService::uninit(void) RT_NOEXCEPT
+{
+    LogFlowFuncEnter();
+
+    if (m_pManager)
+    {
+        delete m_pManager;
+        m_pManager = NULL;
+    }
+
+    DnDClientMap::iterator itClient =  m_clientMap.begin();
+    while (itClient != m_clientMap.end())
+    {
+        delete itClient->second;
+        m_clientMap.erase(itClient);
+        itClient = m_clientMap.begin();
+    }
+
+    LogFlowFuncLeave();
+    return VINF_SUCCESS;
+}
+
+int DragAndDropService::clientConnect(uint32_t idClient, void *pvClient) RT_NOEXCEPT
+{
+    RT_NOREF1(pvClient);
+    if (m_clientMap.size() >= UINT8_MAX) /* Don't allow too much clients at the same time. */
+    {
+        AssertMsgFailed(("Maximum number of clients reached\n"));
+        return VERR_MAX_PROCS_REACHED;
+    }
+
+    /*
+     * Add client to our client map.
+     */
+    if (m_clientMap.find(idClient) != m_clientMap.end())
+    {
+        LogFunc(("Client %RU32 is already connected!\n", idClient));
+        return VERR_ALREADY_EXISTS;
+    }
+
+    try
+    {
+        DragAndDropClient *pClient = new DragAndDropClient(idClient);
+        pClient->SetSvcContext(m_SvcCtx);
+        m_clientMap[idClient] = pClient;
+    }
+    catch (std::bad_alloc &)
+    {
+        LogFunc(("Client %RU32 - VERR_NO_MEMORY!\n", idClient));
+        return VERR_NO_MEMORY;
+    }
+
+    LogFlowFunc(("Client %RU32 connected (VINF_SUCCESS)\n", idClient));
+    return VINF_SUCCESS;
+}
+
+int DragAndDropService::clientDisconnect(uint32_t idClient, void *pvClient) RT_NOEXCEPT
+{
+    RT_NOREF1(pvClient);
+
+    /* Client not found? Bail out early. */
+    DnDClientMap::iterator itClient =  m_clientMap.find(idClient);
+    if (itClient == m_clientMap.end())
+    {
+        LogFunc(("Client %RU32 not found!\n", idClient));
+        return VERR_NOT_FOUND;
+    }
+
+    /*
+     * Remove from waiters queue.
+     */
+    m_clientQueue.remove(idClient);
+
+    /*
+     * Remove from client map and deallocate.
+     */
+    AssertPtr(itClient->second);
+    delete itClient->second;
+
+    m_clientMap.erase(itClient);
+
+    LogFlowFunc(("Client %RU32 disconnected\n", idClient));
+    return VINF_SUCCESS;
+}
+
+/**
+ * Implements GUEST_DND_FN_REPORT_FEATURES.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success (we complete the message here).
+ * @retval  VERR_ACCESS_DENIED if not master
+ * @retval  VERR_INVALID_PARAMETER if bit 63 in the 2nd parameter isn't set.
+ * @retval  VERR_WRONG_PARAMETER_COUNT
+ *
+ * @param   pClient     The client state.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ */
+int DragAndDropService::clientReportFeatures(DragAndDropClient *pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[]) RT_NOEXCEPT
+{
+    RT_NOREF(pClient);
+
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_RETURN(cParms == 2, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint64_t const fFeatures0 = paParms[0].u.uint64;
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint64_t const fFeatures1 = paParms[1].u.uint64;
+    ASSERT_GUEST_RETURN(fFeatures1 & VBOX_DND_GF_1_MUST_BE_ONE, VERR_INVALID_PARAMETER);
+
+    /*
+     * Report back the host features.
+     */
+    paParms[0].u.uint64 = m_fHostFeatures0;
+    paParms[1].u.uint64 = 0;
+
+    pClient->fGuestFeatures0 = fFeatures0;
+    pClient->fGuestFeatures1 = fFeatures1;
+
+    Log(("[Client %RU32] features: %#RX64 %#RX64\n", pClient->GetClientID(), fFeatures0, fFeatures1));
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Implements GUEST_DND_FN_QUERY_FEATURES.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success (we complete the message here).
+ * @retval  VERR_WRONG_PARAMETER_COUNT
+ *
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ */
+int DragAndDropService::clientQueryFeatures(uint32_t cParms, VBOXHGCMSVCPARM paParms[]) RT_NOEXCEPT
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_RETURN(cParms == 2, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    ASSERT_GUEST(paParms[1].u.uint64 & RT_BIT_64(63));
+
+    /*
+     * Report back the host features.
+     */
+    paParms[0].u.uint64 = m_fHostFeatures0;
+    paParms[1].u.uint64 = 0;
+
+    return VINF_SUCCESS;
+}
+
+int DragAndDropService::modeSet(uint32_t u32Mode) RT_NOEXCEPT
+{
+#ifndef VBOX_WITH_DRAG_AND_DROP_GH
+    if (   u32Mode == VBOX_DRAG_AND_DROP_MODE_GUEST_TO_HOST
+        || u32Mode == VBOX_DRAG_AND_DROP_MODE_BIDIRECTIONAL)
+    {
+        m_u32Mode = VBOX_DRAG_AND_DROP_MODE_OFF;
+        return VERR_NOT_SUPPORTED;
+    }
+#endif
+
+    switch (u32Mode)
+    {
+        case VBOX_DRAG_AND_DROP_MODE_OFF:
+        case VBOX_DRAG_AND_DROP_MODE_HOST_TO_GUEST:
+        case VBOX_DRAG_AND_DROP_MODE_GUEST_TO_HOST:
+        case VBOX_DRAG_AND_DROP_MODE_BIDIRECTIONAL:
+            m_u32Mode = u32Mode;
+            break;
+
+        default:
+            m_u32Mode = VBOX_DRAG_AND_DROP_MODE_OFF;
+            break;
+    }
+
+    return VINF_SUCCESS;
+}
+
+void DragAndDropService::guestCall(VBOXHGCMCALLHANDLE callHandle, uint32_t idClient,
+                                   void *pvClient, uint32_t u32Function,
+                                   uint32_t cParms, VBOXHGCMSVCPARM paParms[]) RT_NOEXCEPT
+{
+    RT_NOREF1(pvClient);
+    LogFlowFunc(("idClient=%RU32, u32Function=%s (%#x), cParms=%RU32\n",
+                 idClient, DnDGuestMsgToStr(u32Function), u32Function, cParms));
+
+    /* Check if we've the right mode set. */
+    int rc = VERR_ACCESS_DENIED; /* Play safe. */
+    switch (u32Function)
+    {
+        case GUEST_DND_FN_GET_NEXT_HOST_MSG:
+        {
+            if (modeGet() != VBOX_DRAG_AND_DROP_MODE_OFF)
+                rc = VINF_SUCCESS;
+            else
+            {
+                LogRel(("DnD: Feature is disabled, ignoring request from guest\n"));
+                rc = VINF_HGCM_ASYNC_EXECUTE;
+            }
+            break;
+        }
+
+        /* New since protocol v2. */
+        case GUEST_DND_FN_CONNECT:
+            RT_FALL_THROUGH();
+        /* New since VBox 6.1.x. */
+        case GUEST_DND_FN_REPORT_FEATURES:
+            RT_FALL_THROUGH();
+        /* New since VBox 6.1.x. */
+        case GUEST_DND_FN_QUERY_FEATURES:
+        {
+            /*
+             * Never block these calls, as the clients issues those when
+             * initializing and might get stuck if drag and drop is set to "disabled" at
+             * that time.
+             */
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        /* New since VBOx 7.0.x. See define for details. */
+        case GUEST_DND_FN_EVT_ERROR:
+        {
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        case GUEST_DND_FN_HG_ACK_OP:
+        case GUEST_DND_FN_HG_REQ_DATA:
+        case GUEST_DND_FN_HG_EVT_PROGRESS:
+        {
+            if (   modeGet() == VBOX_DRAG_AND_DROP_MODE_BIDIRECTIONAL
+                || modeGet() == VBOX_DRAG_AND_DROP_MODE_HOST_TO_GUEST)
+                rc = VINF_SUCCESS;
+            else
+                LogRel(("DnD: Host -> Guest mode disabled, ignoring request from guest\n"));
+            break;
+        }
+
+        case GUEST_DND_FN_GH_ACK_PENDING:
+        case GUEST_DND_FN_GH_SND_DATA_HDR:
+        case GUEST_DND_FN_GH_SND_DATA:
+        case GUEST_DND_FN_GH_SND_DIR:
+        case GUEST_DND_FN_GH_SND_FILE_HDR:
+        case GUEST_DND_FN_GH_SND_FILE_DATA:
+        {
+#ifdef VBOX_WITH_DRAG_AND_DROP_GH
+            if (   modeGet() == VBOX_DRAG_AND_DROP_MODE_BIDIRECTIONAL
+                || modeGet() == VBOX_DRAG_AND_DROP_MODE_GUEST_TO_HOST)
+                rc = VINF_SUCCESS;
+            else
+#endif
+                LogRel(("DnD: Guest -> Host mode disabled, ignoring request from guest\n"));
+            break;
+        }
+
+        default:
+            /* Reach through to DnD manager. */
+            rc = VINF_SUCCESS;
+            break;
+    }
+
+#define DO_HOST_CALLBACK();                                                                   \
+    if (   RT_SUCCESS(rc)                                                                     \
+        && m_SvcCtx.pfnHostCallback)                                                          \
+    {                                                                                         \
+        rc = m_SvcCtx.pfnHostCallback(m_SvcCtx.pvHostData, u32Function, &data, sizeof(data)); \
+    }
+
+    /*
+     * Lookup client.
+     */
+    DragAndDropClient *pClient = NULL;
+
+    DnDClientMap::iterator itClient =  m_clientMap.find(idClient);
+    if (itClient != m_clientMap.end())
+    {
+        pClient = itClient->second;
+        AssertPtr(pClient);
+    }
+    else
+    {
+        LogFunc(("Client %RU32 was not found\n", idClient));
+        rc = VERR_NOT_FOUND;
+    }
+
+/* Verifies that an uint32 parameter has the expected buffer size set.
+ * Will set rc to VERR_INVALID_PARAMETER otherwise. See #9777. */
+#define VERIFY_BUFFER_SIZE_UINT32(a_ParmUInt32, a_SizeExpected) \
+do { \
+    uint32_t cbTemp = 0; \
+    rc = HGCMSvcGetU32(&a_ParmUInt32, &cbTemp); \
+    ASSERT_GUEST_BREAK(RT_SUCCESS(rc) && cbTemp == a_SizeExpected); \
+} while (0)
+
+/* Gets the context ID from the first parameter and store it into the data header.
+ * Then increments idxParm by one if more than one parameter is available. */
+#define GET_CONTEXT_ID_PARM0() \
+    if (fHasCtxID) \
+    { \
+        ASSERT_GUEST_BREAK(cParms >= 1); \
+        rc = HGCMSvcGetU32(&paParms[0], &data.hdr.uContextID); \
+        ASSERT_GUEST_BREAK(RT_SUCCESS(rc)); \
+        if (cParms > 1) \
+            idxParm++; \
+    }
+
+    if (rc == VINF_SUCCESS) /* Note: rc might be VINF_HGCM_ASYNC_EXECUTE! */
+    {
+        rc = VERR_INVALID_PARAMETER; /* Play safe by default. */
+
+        /* Whether the client's advertised protocol sends context IDs with commands. */
+        const bool fHasCtxID = pClient->uProtocolVerDeprecated >= 3;
+
+        /* Current parameter index to process. */
+        unsigned idxParm = 0;
+
+        switch (u32Function)
+        {
+            /*
+             * Note: Older VBox versions with enabled DnD guest->host support (< 5.0)
+             *       used the same message ID (300) for GUEST_DND_FN_GET_NEXT_HOST_MSG and
+             *       HOST_DND_FN_GH_REQ_PENDING, which led this service returning
+             *       VERR_INVALID_PARAMETER when the guest wanted to actually
+             *       handle HOST_DND_FN_GH_REQ_PENDING.
+             */
+            case GUEST_DND_FN_GET_NEXT_HOST_MSG:
+            {
+                if (cParms == 3)
+                {
+                    /* Make sure to increase the reference count so that the next message doesn't get removed between
+                     * the guest's GUEST_DND_FN_GET_NEXT_HOST_MSG call and the actual message retrieval call. */
+                    rc = m_pManager->GetNextMsgInfo(true /* fAddRef */,
+                                                    &paParms[0].u.uint32 /* uMsg */, &paParms[1].u.uint32 /* cParms */);
+                    if (RT_FAILURE(rc)) /* No queued messages available? */
+                    {
+                        if (m_SvcCtx.pfnHostCallback) /* Try asking the host. */
+                        {
+                            VBOXDNDCBHGGETNEXTHOSTMSG data;
+                            RT_ZERO(data);
+                            data.hdr.uMagic = CB_MAGIC_DND_HG_GET_NEXT_HOST_MSG;
+                            rc = m_SvcCtx.pfnHostCallback(m_SvcCtx.pvHostData, u32Function, &data, sizeof(data));
+                            if (RT_SUCCESS(rc))
+                            {
+                                paParms[0].u.uint32 = data.uMsg;   /* uMsg */
+                                paParms[1].u.uint32 = data.cParms; /* cParms */
+                                /* Note: paParms[2] was set by the guest as blocking flag. */
+                            }
+
+                            LogFlowFunc(("Host callback returned %Rrc\n", rc));
+                        }
+                        else /* No host callback in place, so drag and drop is not supported by the host. */
+                            rc = VERR_NOT_SUPPORTED;
+
+                        if (RT_FAILURE(rc))
+                            rc = m_pManager->GetNextMsg(u32Function, cParms, paParms);
+
+                        /* Some error occurred or no (new) messages available? */
+                        if (RT_FAILURE(rc))
+                        {
+                            uint32_t fFlags = 0;
+                            int rc2 = HGCMSvcGetU32(&paParms[2], &fFlags);
+                            if (   RT_SUCCESS(rc2)
+                                && fFlags) /* Blocking flag set? */
+                            {
+                                /* Defer client returning. */
+                                rc = VINF_HGCM_ASYNC_EXECUTE;
+                            }
+                            else
+                                rc = VERR_INVALID_PARAMETER;
+
+                            LogFlowFunc(("Message queue is empty, returning %Rrc to guest\n", rc));
+                        }
+                    }
+                }
+                break;
+            }
+            case GUEST_DND_FN_CONNECT:
+            {
+                ASSERT_GUEST_BREAK(cParms >= 2);
+
+                VBOXDNDCBCONNECTDATA data;
+                RT_ZERO(data);
+                data.hdr.uMagic = CB_MAGIC_DND_CONNECT;
+
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.hdr.uContextID); \
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.uProtocolVersion);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU32(&paParms[idxParm], &data.fFlags);
+                ASSERT_GUEST_RC_BREAK(rc);
+
+                unsigned uProtocolVer = 3; /* The protocol version we're going to use. */
+
+                /* Make sure we're only setting a protocl version we're supporting on the host. */
+                if (data.uProtocolVersion > uProtocolVer)
+                    data.uProtocolVersion = uProtocolVer;
+
+                pClient->uProtocolVerDeprecated = data.uProtocolVersion;
+
+                /* Return the highest protocol version we're supporting. */
+                AssertBreak(idxParm);
+                ASSERT_GUEST_BREAK(idxParm);
+                paParms[idxParm - 1].u.uint32 = data.uProtocolVersion;
+
+                LogFlowFunc(("Client %RU32 is now using protocol v%RU32\n",
+                             pClient->GetClientID(), pClient->uProtocolVerDeprecated));
+
+                DO_HOST_CALLBACK();
+                break;
+            }
+            case GUEST_DND_FN_REPORT_FEATURES:
+            {
+                rc = clientReportFeatures(pClient, cParms, paParms);
+                if (RT_SUCCESS(rc))
+                {
+                    VBOXDNDCBREPORTFEATURESDATA data;
+                    RT_ZERO(data);
+                    data.hdr.uMagic = CB_MAGIC_DND_REPORT_FEATURES;
+
+                    data.fGuestFeatures0 = pClient->fGuestFeatures0;
+                    /* fGuestFeatures1 is not used yet. */
+
+                    /* Don't touch initial rc. */
+                    int rc2 = m_SvcCtx.pfnHostCallback(m_SvcCtx.pvHostData, u32Function, &data, sizeof(data));
+                    AssertRC(rc2);
+                }
+                break;
+            }
+            case GUEST_DND_FN_QUERY_FEATURES:
+            {
+                rc = clientQueryFeatures(cParms, paParms);
+                break;
+            }
+            case GUEST_DND_FN_HG_ACK_OP:
+            {
+                ASSERT_GUEST_BREAK(cParms >= 2);
+
+                VBOXDNDCBHGACKOPDATA data;
+                RT_ZERO(data);
+                data.hdr.uMagic = CB_MAGIC_DND_HG_ACK_OP;
+
+                GET_CONTEXT_ID_PARM0();
+                rc = HGCMSvcGetU32(&paParms[idxParm], &data.uAction); /* Get drop action. */
+                ASSERT_GUEST_RC_BREAK(rc);
+
+                DO_HOST_CALLBACK();
+                break;
+            }
+            case GUEST_DND_FN_HG_REQ_DATA:
+            {
+                VBOXDNDCBHGREQDATADATA data;
+                RT_ZERO(data);
+                data.hdr.uMagic = CB_MAGIC_DND_HG_REQ_DATA;
+
+                switch (pClient->uProtocolVerDeprecated)
+                {
+                    case 3:
+                    {
+                        ASSERT_GUEST_BREAK(cParms == 3);
+                        GET_CONTEXT_ID_PARM0();
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void **)&data.pszFormat, &data.cbFormat);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm], data.cbFormat);
+                        break;
+                    }
+
+                    case 2:
+                        RT_FALL_THROUGH();
+                    default:
+                    {
+                        ASSERT_GUEST_BREAK(cParms == 1);
+                        rc = HGCMSvcGetPv(&paParms[idxParm], (void**)&data.pszFormat, &data.cbFormat);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        break;
+                    }
+                }
+
+                DO_HOST_CALLBACK();
+                break;
+            }
+            case GUEST_DND_FN_HG_EVT_PROGRESS:
+            {
+                ASSERT_GUEST_BREAK(cParms >= 3);
+
+                VBOXDNDCBHGEVTPROGRESSDATA data;
+                RT_ZERO(data);
+                data.hdr.uMagic = CB_MAGIC_DND_HG_EVT_PROGRESS;
+
+                GET_CONTEXT_ID_PARM0();
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.uStatus);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.uPercentage);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU32(&paParms[idxParm], &data.rc);
+                ASSERT_GUEST_RC_BREAK(rc);
+
+                DO_HOST_CALLBACK();
+                break;
+            }
+#ifdef VBOX_WITH_DRAG_AND_DROP_GH
+            case GUEST_DND_FN_GH_ACK_PENDING:
+            {
+                VBOXDNDCBGHACKPENDINGDATA data;
+                RT_ZERO(data);
+                data.hdr.uMagic = CB_MAGIC_DND_GH_ACK_PENDING;
+
+                switch (pClient->uProtocolVerDeprecated)
+                {
+                    case 3:
+                    {
+                        ASSERT_GUEST_BREAK(cParms == 5);
+                        GET_CONTEXT_ID_PARM0();
+                        rc = HGCMSvcGetU32(&paParms[idxParm++], &data.uDefAction);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        rc = HGCMSvcGetU32(&paParms[idxParm++], &data.uAllActions);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.pszFormat, &data.cbFormat);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm], data.cbFormat);
+                        break;
+                    }
+
+                    case 2:
+                    default:
+                    {
+                        ASSERT_GUEST_BREAK(cParms == 3);
+                        rc = HGCMSvcGetU32(&paParms[idxParm++], &data.uDefAction);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        rc = HGCMSvcGetU32(&paParms[idxParm++], &data.uAllActions);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        rc = HGCMSvcGetPv(&paParms[idxParm], (void**)&data.pszFormat, &data.cbFormat);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        break;
+                    }
+                }
+
+                DO_HOST_CALLBACK();
+                break;
+            }
+            /* New since protocol v3. */
+            case GUEST_DND_FN_GH_SND_DATA_HDR:
+            {
+                ASSERT_GUEST_BREAK(cParms == 12);
+
+                VBOXDNDCBSNDDATAHDRDATA data;
+                RT_ZERO(data);
+                data.hdr.uMagic = CB_MAGIC_DND_GH_SND_DATA_HDR;
+
+                GET_CONTEXT_ID_PARM0();
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.data.uFlags);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.data.uScreenId);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU64(&paParms[idxParm++], &data.data.cbTotal);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.data.cbMeta);
+                ASSERT_GUEST_RC_BREAK(rc);
+                ASSERT_GUEST_BREAK(data.data.cbMeta <= data.data.cbTotal);
+                rc = HGCMSvcGetPv(&paParms[idxParm++], &data.data.pvMetaFmt, &data.data.cbMetaFmt);
+                ASSERT_GUEST_RC_BREAK(rc);
+                VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm++], data.data.cbMetaFmt);
+                rc = HGCMSvcGetU64(&paParms[idxParm++], &data.data.cObjects);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.data.enmCompression);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU32(&paParms[idxParm++], (uint32_t *)&data.data.enmChecksumType);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetPv(&paParms[idxParm++], &data.data.pvChecksum, &data.data.cbChecksum);
+                ASSERT_GUEST_RC_BREAK(rc);
+                VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm], data.data.cbChecksum);
+
+                DO_HOST_CALLBACK();
+                break;
+            }
+            case GUEST_DND_FN_GH_SND_DATA:
+            {
+                switch (pClient->uProtocolVerDeprecated)
+                {
+                    case 3:
+                    {
+                        ASSERT_GUEST_BREAK(cParms == 5);
+
+                        VBOXDNDCBSNDDATADATA data;
+                        RT_ZERO(data);
+                        data.hdr.uMagic = CB_MAGIC_DND_GH_SND_DATA;
+
+                        GET_CONTEXT_ID_PARM0();
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.data.u.v3.pvData, &data.data.u.v3.cbData);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm++], data.data.u.v3.cbData);
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.data.u.v3.pvChecksum, &data.data.u.v3.cbChecksum);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm], data.data.u.v3.cbChecksum);
+
+                        DO_HOST_CALLBACK();
+                        break;
+                    }
+
+                    case 2:
+                        RT_FALL_THROUGH();
+                    default:
+                    {
+                        ASSERT_GUEST_BREAK(cParms == 2);
+
+                        VBOXDNDCBSNDDATADATA data;
+                        RT_ZERO(data);
+                        data.hdr.uMagic = CB_MAGIC_DND_GH_SND_DATA;
+
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.data.u.v1.pvData, &data.data.u.v1.cbData);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        rc = HGCMSvcGetU32(&paParms[idxParm], &data.data.u.v1.cbTotalSize);
+                        ASSERT_GUEST_RC_BREAK(rc);
+
+                        DO_HOST_CALLBACK();
+                        break;
+                    }
+                }
+                break;
+            }
+            case GUEST_DND_FN_GH_SND_DIR:
+            {
+                ASSERT_GUEST_BREAK(cParms >= 3);
+
+                VBOXDNDCBSNDDIRDATA data;
+                RT_ZERO(data);
+                data.hdr.uMagic = CB_MAGIC_DND_GH_SND_DIR;
+
+                GET_CONTEXT_ID_PARM0();
+                rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.pszPath, &data.cbPath);
+                ASSERT_GUEST_RC_BREAK(rc);
+                VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm++], data.cbPath);
+                rc = HGCMSvcGetU32(&paParms[idxParm], &data.fMode);
+                ASSERT_GUEST_RC_BREAK(rc);
+
+                DO_HOST_CALLBACK();
+                break;
+            }
+            /* New since protocol v2 (>= VBox 5.0). */
+            case GUEST_DND_FN_GH_SND_FILE_HDR:
+            {
+                ASSERT_GUEST_BREAK(cParms == 6);
+
+                VBOXDNDCBSNDFILEHDRDATA data;
+                RT_ZERO(data);
+                data.hdr.uMagic = CB_MAGIC_DND_GH_SND_FILE_HDR;
+
+                GET_CONTEXT_ID_PARM0();
+                rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.pszFilePath, &data.cbFilePath);
+                ASSERT_GUEST_RC_BREAK(rc);
+                VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm++], data.cbFilePath);
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.fFlags);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU32(&paParms[idxParm++], &data.fMode);
+                ASSERT_GUEST_RC_BREAK(rc);
+                rc = HGCMSvcGetU64(&paParms[idxParm], &data.cbSize);
+                ASSERT_GUEST_RC_BREAK(rc);
+
+                DO_HOST_CALLBACK();
+                break;
+            }
+            case GUEST_DND_FN_GH_SND_FILE_DATA:
+            {
+                switch (pClient->uProtocolVerDeprecated)
+                {
+                    /* Protocol v3 adds (optional) checksums. */
+                    case 3:
+                    {
+                        ASSERT_GUEST_BREAK(cParms == 5);
+
+                        VBOXDNDCBSNDFILEDATADATA data;
+                        RT_ZERO(data);
+                        data.hdr.uMagic = CB_MAGIC_DND_GH_SND_FILE_DATA;
+
+                        GET_CONTEXT_ID_PARM0();
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.pvData, &data.cbData);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm++], data.cbData);
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.u.v3.pvChecksum, &data.u.v3.cbChecksum);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm], data.u.v3.cbChecksum);
+
+                        DO_HOST_CALLBACK();
+                        break;
+                    }
+                    /* Protocol v2 only sends the next data chunks to reduce traffic. */
+                    case 2:
+                    {
+                        ASSERT_GUEST_BREAK(cParms == 3);
+
+                        VBOXDNDCBSNDFILEDATADATA data;
+                        RT_ZERO(data);
+                        data.hdr.uMagic = CB_MAGIC_DND_GH_SND_FILE_DATA;
+
+                        GET_CONTEXT_ID_PARM0();
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.pvData, &data.cbData);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm], data.cbData);
+
+                        DO_HOST_CALLBACK();
+                        break;
+                    }
+                    /* Protocol v1 sends the file path and attributes for every file chunk (!). */
+                    default:
+                    {
+                        ASSERT_GUEST_BREAK(cParms == 5);
+
+                        VBOXDNDCBSNDFILEDATADATA data;
+                        RT_ZERO(data);
+                        data.hdr.uMagic = CB_MAGIC_DND_GH_SND_FILE_DATA;
+
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.u.v1.pszFilePath, &data.u.v1.cbFilePath);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm++], data.u.v1.cbFilePath);
+                        rc = HGCMSvcGetPv(&paParms[idxParm++], (void**)&data.pvData, &data.cbData);
+                        ASSERT_GUEST_RC_BREAK(rc);
+                        VERIFY_BUFFER_SIZE_UINT32(paParms[idxParm++], data.cbData);
+                        rc = HGCMSvcGetU32(&paParms[idxParm], &data.u.v1.fMode);
+                        ASSERT_GUEST_RC_BREAK(rc);
+
+                        DO_HOST_CALLBACK();
+                        break;
+                    }
+                }
+                break;
+            }
+            case GUEST_DND_FN_EVT_ERROR:
+            {
+                ASSERT_GUEST_BREAK(cParms >= 1);
+
+                VBOXDNDCBEVTERRORDATA data;
+                RT_ZERO(data);
+                data.hdr.uMagic = CB_MAGIC_DND_EVT_ERROR;
+
+                GET_CONTEXT_ID_PARM0();
+                rc = HGCMSvcGetU32(&paParms[idxParm], (uint32_t *)&data.rc);
+                ASSERT_GUEST_RC_BREAK(rc);
+
+                DO_HOST_CALLBACK();
+                break;
+            }
+#endif /* VBOX_WITH_DRAG_AND_DROP_GH */
+
+            default:
+            {
+                LogFlowFunc(("u32Function=%s (%#x), cParms=%RU32\n", DnDHostMsgToStr(u32Function), u32Function, cParms));
+
+                /* All other messages are handled by the DnD manager. */
+                rc = m_pManager->GetNextMsg(u32Function, cParms, paParms);
+                if (rc == VERR_NO_DATA) /* Manager has no new messsages? Try asking the host. */
+                {
+                    if (m_SvcCtx.pfnHostCallback)
+                    {
+                        VBOXDNDCBHGGETNEXTHOSTMSGDATA data;
+                        RT_ZERO(data);
+
+                        data.hdr.uMagic = VBOX_DND_CB_MAGIC_MAKE(0 /* uFn */, 0 /* uVer */);
+
+                        data.uMsg    = u32Function;
+                        data.cParms  = cParms;
+                        data.paParms = paParms;
+
+                        rc = m_SvcCtx.pfnHostCallback(m_SvcCtx.pvHostData, u32Function, &data, sizeof(data));
+                        if (RT_SUCCESS(rc))
+                        {
+                            cParms  = data.cParms;
+                            paParms = data.paParms;
+                        }
+                        else
+                        {
+                            if (rc == VERR_CANCELLED)
+                            {
+                                /* Host indicated that the current operation was cancelled. Tell the guest. */
+                                LogFunc(("Host indicated that operation was cancelled\n"));
+                            }
+                            else
+                            {
+                                /*
+                                 * In case the guest is too fast asking for the next message
+                                 * and the host did not supply it yet, just defer the client's
+                                 * return until a response from the host available.
+                                 */
+                                LogFunc(("No new messages from the host (%Rrc), deferring request\n", rc));
+                                rc = VINF_HGCM_ASYNC_EXECUTE;
+                            }
+                        }
+                    }
+                    else /* No host callback in place, so drag and drop is not supported by the host. */
+                        rc = VERR_NOT_SUPPORTED;
+                }
+                break;
+            }
+        }
+    }
+
+#undef VERIFY_BUFFER_SIZE_UINT32
+
+    /*
+     * If async execution is requested, we didn't notify the guest yet about
+     * completion. The client is queued into the waiters list and will be
+     * notified as soon as a new event is available.
+     */
+    if (rc == VINF_HGCM_ASYNC_EXECUTE)
+    {
+        LogFunc(("Deferring client %RU32\n", idClient));
+
+        try
+        {
+            AssertPtr(pClient);
+            pClient->SetDeferred(callHandle, u32Function, cParms, paParms);
+            m_clientQueue.push_back(idClient);
+        }
+        catch (std::bad_alloc &)
+        {
+            rc = VERR_NO_MEMORY;
+            /* Don't report to guest. */
+        }
+    }
+    else if (pClient)
+    {
+        /* Complete the call on the guest side. */
+        pClient->Complete(callHandle, rc);
+    }
+    else
+    {
+        AssertMsgFailed(("Guest call failed with %Rrc\n", rc));
+        rc = VERR_NOT_IMPLEMENTED;
+    }
+
+    LogFunc(("Returning %Rrc to guest\n", rc));
+}
+
+int DragAndDropService::hostCall(uint32_t u32Function,
+                                 uint32_t cParms, VBOXHGCMSVCPARM paParms[]) RT_NOEXCEPT
+{
+    LogFlowFunc(("u32Function=%s (%#x), cParms=%RU32, cClients=%zu, cQueue=%zu\n",
+                 DnDHostMsgToStr(u32Function), u32Function, cParms, m_clientMap.size(), m_clientQueue.size()));
+
+    uint32_t const uMode = modeGet();
+
+    /* Check if we've the right mode set. */
+    int rc = VERR_ACCESS_DENIED; /* Play safe. */
+    switch (u32Function)
+    {
+        /*
+         * Host -> Guest mode
+         */
+        case HOST_DND_FN_HG_EVT_ENTER:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_HG_EVT_MOVE:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_HG_EVT_LEAVE:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_HG_EVT_DROPPED:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_HG_SND_DATA_HDR:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_HG_SND_DATA:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_HG_SND_MORE_DATA:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_HG_SND_DIR:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_HG_SND_FILE_DATA:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_HG_SND_FILE_HDR:
+        {
+            if (   uMode == VBOX_DRAG_AND_DROP_MODE_HOST_TO_GUEST
+                || uMode == VBOX_DRAG_AND_DROP_MODE_BIDIRECTIONAL)
+                rc = VINF_SUCCESS;
+            else
+            {
+                LogRel2(("DnD: Host to guest mode is disabled, ignoring request from host\n"));
+            }
+            break;
+        }
+
+        /*
+         * Guest -> Host mode
+         */
+        case HOST_DND_FN_GH_REQ_PENDING:
+            RT_FALL_THROUGH();
+        case HOST_DND_FN_GH_EVT_DROPPED:
+        {
+            if (   uMode == VBOX_DRAG_AND_DROP_MODE_GUEST_TO_HOST
+                || uMode == VBOX_DRAG_AND_DROP_MODE_BIDIRECTIONAL)
+                rc = VINF_SUCCESS;
+            else
+            {
+                LogRel2(("DnD: Guest to host mode is disabled, ignoring request from host\n"));
+            }
+            break;
+        }
+
+        /*
+         * Both modes
+         */
+        case HOST_DND_FN_CANCEL:
+            if (uMode != VBOX_DRAG_AND_DROP_MODE_OFF)
+                rc = VINF_SUCCESS;
+            break;
+
+        /*
+         * Functions that always work.
+         */
+        case HOST_DND_FN_SET_MODE:
+            rc = VINF_SUCCESS;
+            break;
+
+        /*
+         * Forbid everything else not explicitly allowed.
+         */
+        default:
+            break;
+    }
+
+    if (RT_FAILURE(rc))
+        return rc;
+
+    bool fSendToGuest = false; /* Whether to send the message down to the guest side or not. */
+
+    switch (u32Function)
+    {
+        case HOST_DND_FN_SET_MODE:
+        {
+            if (cParms != 1)
+                rc = VERR_INVALID_PARAMETER;
+            else if (paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT)
+                rc = VERR_INVALID_PARAMETER;
+            else
+                rc = modeSet(paParms[0].u.uint32);
+            break;
+        }
+
+        case HOST_DND_FN_CANCEL:
+        {
+            LogFlowFunc(("Cancelling all waiting clients ...\n"));
+
+            /* Forcefully reset the message queue, as the host has cancelled the current operation. */
+            m_pManager->Reset(true /* fForce */);
+
+            /*
+             * Wake up all deferred clients and tell them to process
+             * the cancelling message next.
+             */
+            DnDClientQueue::iterator itQueue = m_clientQueue.begin();
+            while (itQueue != m_clientQueue.end())
+            {
+                DnDClientMap::iterator itClient = m_clientMap.find(*itQueue);
+                Assert(itClient != m_clientMap.end());
+
+                DragAndDropClient *pClient = itClient->second;
+                AssertPtr(pClient);
+
+                int rc2 = pClient->SetDeferredMsgInfo(HOST_DND_FN_CANCEL,
+                                                      /* Protocol v3+ also contains the context ID. */
+                                                      pClient->uProtocolVerDeprecated >= 3 ? 1 : 0);
+                AssertRC(rc2);
+
+                /* Return VERR_CANCELLED when waking up the guest side. */
+                pClient->CompleteDeferred(VERR_CANCELLED);
+
+                m_clientQueue.erase(itQueue);
+                itQueue = m_clientQueue.begin();
+            }
+
+            Assert(m_clientQueue.empty());
+
+            /* Tell the host that everything went well. */
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        case HOST_DND_FN_HG_EVT_ENTER:
+        {
+            /* Reset the message queue as a new DnD operation just began. */
+            m_pManager->Reset(false /* fForce */);
+
+            fSendToGuest = true;
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        default:
+        {
+            fSendToGuest = true;
+            rc = VINF_SUCCESS;
+            break;
+        }
+    }
+
+    do /* goto avoidance break-loop. */
+    {
+        if (fSendToGuest)
+        {
+            if (m_clientMap.empty()) /* At least one client on the guest connected? */
+            {
+                /*
+                 * Tell the host that the guest does not support drag'n drop.
+                 * This might happen due to not installed Guest Additions or
+                 * not running VBoxTray/VBoxClient.
+                 */
+                rc = VERR_NOT_SUPPORTED;
+                break;
+            }
+
+            rc = m_pManager->AddMsg(u32Function, cParms, paParms, true /* fAppend */);
+            if (RT_FAILURE(rc))
+            {
+                AssertMsgFailed(("Adding new message of type=%RU32 failed with rc=%Rrc\n", u32Function, rc));
+                break;
+            }
+
+            /* Any clients in our queue ready for processing the next command? */
+            if (m_clientQueue.empty())
+            {
+                LogFlowFunc(("All clients (%zu) busy -- delaying execution\n", m_clientMap.size()));
+                break;
+            }
+
+            uint32_t uClientNext = m_clientQueue.front();
+            DnDClientMap::iterator itClientNext = m_clientMap.find(uClientNext);
+            Assert(itClientNext != m_clientMap.end());
+
+            DragAndDropClient *pClient = itClientNext->second;
+            AssertPtr(pClient);
+
+            /*
+             * Check if this was a request for getting the next host
+             * message. If so, return the message ID and the parameter
+             * count. The message itself has to be queued.
+             */
+            uint32_t uMsgClient = pClient->GetMsgType();
+
+            uint32_t uMsgNext   = 0;
+            uint32_t cParmsNext = 0;
+            /* Note: We only want to peek for the next message, hence fAddRef is false. */
+            int rcNext = m_pManager->GetNextMsgInfo(false /* fAddRef */, &uMsgNext, &cParmsNext);
+
+            LogFlowFunc(("uMsgClient=%s (%#x), uMsgNext=%s (%#x), cParmsNext=%RU32, rcNext=%Rrc\n",
+                         DnDGuestMsgToStr(uMsgClient), uMsgClient, DnDHostMsgToStr(uMsgNext), uMsgNext, cParmsNext, rcNext));
+
+            if (RT_SUCCESS(rcNext))
+            {
+                if (uMsgClient == GUEST_DND_FN_GET_NEXT_HOST_MSG)
+                {
+                    rc = pClient->SetDeferredMsgInfo(uMsgNext, cParmsNext);
+
+                    /* Note: Report the current rc back to the guest. */
+                    pClient->CompleteDeferred(rc);
+                }
+                /*
+                 * Does the message the client is waiting for match the message
+                 * next in the queue? Process it right away then.
+                 */
+                else if (uMsgClient == uMsgNext)
+                {
+                    rc = m_pManager->GetNextMsg(u32Function, cParms, paParms);
+
+                    /* Note: Report the current rc back to the guest. */
+                    pClient->CompleteDeferred(rc);
+                }
+                else /* Should not happen; cancel the operation on the guest. */
+                {
+                    LogFunc(("Client ID=%RU32 in wrong state with uMsg=%RU32 (next message in queue: %RU32), cancelling\n",
+                             pClient->GetClientID(), uMsgClient, uMsgNext));
+
+                    pClient->CompleteDeferred(VERR_CANCELLED);
+                }
+
+                m_clientQueue.pop_front();
+            }
+
+        } /* fSendToGuest */
+
+    } while (0); /* To use breaks. */
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+DECLCALLBACK(int) DragAndDropService::progressCallback(uint32_t uStatus, uint32_t uPercentage, int rc, void *pvUser)
+{
+    AssertPtrReturn(pvUser, VERR_INVALID_POINTER);
+
+    DragAndDropService *pSelf = static_cast<DragAndDropService *>(pvUser);
+    AssertPtr(pSelf);
+
+    if (pSelf->m_SvcCtx.pfnHostCallback)
+    {
+        LogFlowFunc(("GUEST_DND_FN_HG_EVT_PROGRESS: uStatus=%RU32, uPercentage=%RU32, rc=%Rrc\n",
+                     uStatus, uPercentage, rc));
+
+        VBOXDNDCBHGEVTPROGRESSDATA data;
+        data.hdr.uMagic = CB_MAGIC_DND_HG_EVT_PROGRESS;
+        data.uPercentage  = RT_MIN(uPercentage, 100);
+        data.uStatus      = uStatus;
+        data.rc           = rc; /** @todo uin32_t vs. int. */
+
+        return pSelf->m_SvcCtx.pfnHostCallback(pSelf->m_SvcCtx.pvHostData,
+                                               GUEST_DND_FN_HG_EVT_PROGRESS,
+                                               &data, sizeof(data));
+    }
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * @copydoc FNVBOXHGCMSVCLOAD
+ */
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad(VBOXHGCMSVCFNTABLE *pTable)
+{
+    return DragAndDropService::svcLoad(pTable);
+}
+
diff --git a/src/VBox/HostServices/DragAndDrop/VBoxDragAndDropSvc.rc b/src/VBox/HostServices/DragAndDrop/VBoxDragAndDropSvc.rc
new file mode 100644
index 00000000..27229180
--- /dev/null
+++ b/src/VBox/HostServices/DragAndDrop/VBoxDragAndDropSvc.rc
@@ -0,0 +1,61 @@
+/* $Id: VBoxDragAndDropSvc.rc $ */
+/** @file
+ * VBoxDragAndDropSvc - Resource file containing version info and icon.
+ */
+
+/*
+ * Copyright (C) 2015-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <windows.h>
+#include <VBox/version.h>
+
+LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION      VBOX_RC_FILE_VERSION
+  PRODUCTVERSION   VBOX_RC_FILE_VERSION
+  FILEFLAGSMASK    VS_FFI_FILEFLAGSMASK
+  FILEFLAGS        VBOX_RC_FILE_FLAGS
+  FILEOS           VBOX_RC_FILE_OS
+  FILETYPE         VBOX_RC_TYPE_DLL
+  FILESUBTYPE      VFT2_UNKNOWN
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904b0" // Lang=US English, CharSet=Unicode
+    BEGIN
+      VALUE "FileDescription",  "VirtualBox Drag and Drop Host Service\0"
+      VALUE "InternalName",     "VBoxDragAndDropSvc\0"
+      VALUE "OriginalFilename", "VBoxDragAndDropSvc.dll\0"
+      VALUE "CompanyName",      VBOX_RC_COMPANY_NAME
+      VALUE "FileVersion",      VBOX_RC_FILE_VERSION_STR
+      VALUE "LegalCopyright",   VBOX_RC_LEGAL_COPYRIGHT
+      VALUE "ProductName",      VBOX_RC_PRODUCT_NAME_STR
+      VALUE "ProductVersion",   VBOX_RC_PRODUCT_VERSION_STR
+      VBOX_RC_MORE_STRINGS
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x409, 1200
+  END
+END
diff --git a/src/VBox/HostServices/DragAndDrop/dndmanager.cpp b/src/VBox/HostServices/DragAndDrop/dndmanager.cpp
new file mode 100644
index 00000000..137df6cc
--- /dev/null
+++ b/src/VBox/HostServices/DragAndDrop/dndmanager.cpp
@@ -0,0 +1,233 @@
+/* $Id: dndmanager.cpp $ */
+/** @file
+ * Drag and Drop manager: Handling of DnD messages on the host side.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+
+#ifdef LOG_GROUP
+ #undef LOG_GROUP
+#endif
+#define LOG_GROUP LOG_GROUP_GUEST_DND
+
+#include "dndmanager.h"
+
+#include <VBox/log.h>
+#include <iprt/file.h>
+#include <iprt/dir.h>
+#include <iprt/path.h>
+#include <iprt/uri.h>
+
+
+/*********************************************************************************************************************************
+*   DnDManager                                                                                                                   *
+*********************************************************************************************************************************/
+
+/**
+ * Adds a DnD message to the manager's queue.
+ *
+ * @returns IPRT status code.
+ * @param   pMsg                Pointer to DnD message to add. The queue then owns the pointer.
+ * @param   fAppend             Whether to append or prepend the message to the queue.
+ */
+int DnDManager::AddMsg(DnDMessage *pMsg, bool fAppend /* = true */)
+{
+    AssertPtrReturn(pMsg, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("uMsg=%s (%#x), cParms=%RU32, fAppend=%RTbool\n",
+                 DnDHostMsgToStr(pMsg->GetType()), pMsg->GetType(), pMsg->GetParamCount(), fAppend));
+
+    if (fAppend)
+        m_queueMsg.append(pMsg);
+    else
+        m_queueMsg.prepend(pMsg);
+
+#ifdef DEBUG
+    DumpQueue();
+#endif
+
+    /** @todo Catch / handle OOM? */
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Adds a DnD message to the manager's queue.
+ *
+ * @returns IPRT status code.
+ * @param   uMsg                Type (function number) of message to add.
+ * @param   cParms              Number of parameters of message to add.
+ * @param   paParms             Array of parameters of message to add.
+ * @param   fAppend             Whether to append or prepend the message to the queue.
+ */
+int DnDManager::AddMsg(uint32_t uMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[], bool fAppend /* = true */)
+{
+    int rc;
+
+    try
+    {
+        DnDMessage *pMsg = new DnDGenericMessage(uMsg, cParms, paParms);
+        rc = AddMsg(pMsg, fAppend);
+    }
+    catch(std::bad_alloc &)
+    {
+        rc = VERR_NO_MEMORY;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+#ifdef DEBUG
+void DnDManager::DumpQueue(void)
+{
+    LogFunc(("Current queue (%zu items, FIFO) is: %s", m_queueMsg.size(), m_queueMsg.isEmpty() ? "<Empty>" : ""));
+    for (size_t i = 0; i < m_queueMsg.size(); ++i)
+    {
+        if (i > 0)
+            Log((" - "));
+        DnDMessage const *pMsg = m_queueMsg[i];
+        uint32_t const uType = pMsg->GetType();
+        Log(("%s (%d / %#x) cRefS=%RU32", DnDHostMsgToStr(uType), uType, uType, pMsg->RefCount()));
+    }
+    Log(("\n"));
+}
+#endif /* DEBUG */
+
+/**
+ * Retrieves information about the next message in the queue.
+ *
+ * @returns IPRT status code. VERR_NO_DATA if no next message is available.
+ * @param   fAddRef             Set to \c true to increase the message's reference count, or \c false if not.
+ * @param   puType              Where to store the message type.
+ * @param   pcParms             Where to store the message parameter count.
+ */
+int DnDManager::GetNextMsgInfo(bool fAddRef, uint32_t *puType, uint32_t *pcParms)
+{
+    AssertPtrReturn(puType, VERR_INVALID_POINTER);
+    AssertPtrReturn(pcParms, VERR_INVALID_POINTER);
+
+    int rc;
+
+    if (m_queueMsg.isEmpty())
+    {
+        rc = VERR_NO_DATA;
+    }
+    else
+    {
+        DnDMessage *pMsg = m_queueMsg.first();
+        AssertPtr(pMsg);
+
+        *puType  = pMsg->GetType();
+        *pcParms = pMsg->GetParamCount();
+
+        if (fAddRef)
+            pMsg->AddRef();
+
+        rc = VINF_SUCCESS;
+    }
+
+#ifdef DEBUG
+    DumpQueue();
+#endif
+
+    LogFlowFunc(("Returning uMsg=%s (%#x), cParms=%RU32, fAddRef=%RTbool, rc=%Rrc\n",
+                 DnDHostMsgToStr(*puType), *puType, *pcParms, fAddRef, rc));
+    return rc;
+}
+
+/**
+ * Retrieves the next queued up message and removes it from the queue on success.
+ *
+ * @returns VBox status code.
+ * @retval  VERR_NO_DATA if no next message is available.
+ * @param   uMsg                Message type to retrieve.
+ * @param   cParms              Number of parameters the \@a paParms array can store.
+ * @param   paParms             Where to store the message parameters.
+ */
+int DnDManager::GetNextMsg(uint32_t uMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    LogFlowFunc(("uMsg=%s (%#x), cParms=%RU32\n", DnDHostMsgToStr(uMsg), uMsg, cParms));
+
+    /* Check for pending messages in our queue. */
+    if (m_queueMsg.isEmpty())
+        return VERR_NO_DATA;
+
+#ifdef DEBUG
+    DumpQueue();
+#endif
+
+    /* Get the current message. */
+    DnDMessage *pMsg = m_queueMsg.first();
+    AssertPtr(pMsg);
+
+    if (pMsg->Release() == 0)     /* Not referenced by any client anymore? */
+        m_queueMsg.removeFirst(); /* Remove the current message from the queue. */
+
+    /* Fetch the current message info. */
+    int rc = pMsg->GetData(uMsg, cParms, paParms);
+
+    /*
+     * If there was an error handling the current message or the user has canceled
+     * the operation, we need to cleanup all pending events.
+     */
+    if (RT_FAILURE(rc))
+    {
+        /* Clear any pending messages. */
+        Reset(true /* fForce */);
+    }
+
+    LogFlowFunc(("Message processed with rc=%Rrc\n", rc));
+    return rc;
+}
+
+/**
+ * Resets the manager by clearing the message queue and internal state.
+ *
+ * @param   fForce              Set to \c true to forcefully also remove still referenced messages, or \c false to only
+ *                              remove non-referenced messages.
+ */
+void DnDManager::Reset(bool fForce)
+{
+    LogFlowFuncEnter();
+
+#ifdef DEBUG
+    DumpQueue();
+#endif
+
+    for (size_t i = 0; i < m_queueMsg.size(); i++)
+    {
+        if (   fForce
+            || m_queueMsg[i]->RefCount() == 0)
+        {
+            m_queueMsg.removeAt(i);
+            i = i > 0 ? i - 1 : 0;
+        }
+    }
+}
+
diff --git a/src/VBox/HostServices/DragAndDrop/dndmanager.h b/src/VBox/HostServices/DragAndDrop/dndmanager.h
new file mode 100644
index 00000000..2abb71b1
--- /dev/null
+++ b/src/VBox/HostServices/DragAndDrop/dndmanager.h
@@ -0,0 +1,136 @@
+/** @file
+ * Drag and Drop manager.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_DragAndDrop_dndmanager_h
+#define VBOX_INCLUDED_SRC_DragAndDrop_dndmanager_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <VBox/GuestHost/DragAndDrop.h>
+#include <VBox/HostServices/Service.h>
+#include <VBox/HostServices/DragAndDropSvc.h>
+
+#include <iprt/cpp/ministring.h>
+#include <iprt/cpp/list.h>
+
+typedef DECLCALLBACKTYPE(int, FNDNDPROGRESS,(uint32_t uState, uint32_t uPercentage, int rc, void *pvUser));
+typedef FNDNDPROGRESS *PFNDNDPROGRESS;
+
+/**
+ * DnD message class. This class forms the base of all other more specialized
+ * message classes.
+ */
+class DnDMessage : public HGCM::Message
+{
+public:
+
+    DnDMessage(void)
+        : m_cRefs(0) { }
+
+    DnDMessage(uint32_t uMsg, uint32_t cParms, VBOXHGCMSVCPARM aParms[])
+        : Message(uMsg, cParms, aParms)
+        , m_cRefs(0) { }
+
+    virtual ~DnDMessage(void) { }
+
+    uint32_t AddRef(void) { Assert(m_cRefs < 32); return ++m_cRefs; }
+    uint32_t Release(void) { if (m_cRefs) return --m_cRefs; return m_cRefs; }
+    uint32_t RefCount(void) const { return m_cRefs; }
+
+protected:
+
+    /** The message's current reference count. */
+    uint32_t m_cRefs;
+};
+
+/**
+ * DnD message class for generic messages which didn't need any special
+ * handling.
+ */
+class DnDGenericMessage: public DnDMessage
+{
+public:
+    DnDGenericMessage(uint32_t uMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+        : DnDMessage(uMsg, cParms, paParms) { }
+};
+
+/**
+ * DnD message class for informing the guest to cancel any current (and pending) activities.
+ */
+class DnDHGCancelMessage: public DnDMessage
+{
+public:
+
+    DnDHGCancelMessage(void)
+    {
+        int rc2 = initData(DragAndDropSvc::HOST_DND_FN_CANCEL,
+                           0 /* cParms */, 0 /* aParms */);
+        AssertRC(rc2);
+    }
+};
+
+/**
+ * DnD manager. Manage creation and queuing of messages for the various DnD
+ * messages types.
+ */
+class DnDManager
+{
+public:
+
+    DnDManager(PFNDNDPROGRESS pfnProgressCallback, void *pvProgressUser)
+        : m_pfnProgressCallback(pfnProgressCallback)
+        , m_pvProgressUser(pvProgressUser)
+    {}
+
+    virtual ~DnDManager(void)
+    {
+        Reset(true /* fForce */);
+    }
+
+    int AddMsg(DnDMessage *pMessage, bool fAppend = true);
+    int AddMsg(uint32_t uMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[], bool fAppend = true);
+
+#ifdef DEBUG
+    void DumpQueue();
+#endif
+
+    int GetNextMsgInfo(bool fAddRef, uint32_t *puType, uint32_t *pcParms);
+    int GetNextMsg(uint32_t uMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+
+    void Reset(bool fForce);
+
+protected:
+
+    /** DnD message queue (FIFO). */
+    RTCList<DnDMessage *> m_queueMsg;
+    /** Pointer to host progress callback. Optional, can be NULL. */
+    PFNDNDPROGRESS        m_pfnProgressCallback;
+    /** Pointer to progress callback user context. Can be NULL if not used. */
+    void                 *m_pvProgressUser;
+};
+#endif /* !VBOX_INCLUDED_SRC_DragAndDrop_dndmanager_h */
+
diff --git a/src/VBox/HostServices/GuestControl/Makefile.kmk b/src/VBox/HostServices/GuestControl/Makefile.kmk
new file mode 100644
index 00000000..88a37450
--- /dev/null
+++ b/src/VBox/HostServices/GuestControl/Makefile.kmk
@@ -0,0 +1,57 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Guest Control Host Service.
+#
+
+#
+# Copyright (C) 2011-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+# Include sub-makefile(s).
+include $(PATH_SUB_CURRENT)/testcase/Makefile.kmk
+
+#
+# The guest control service DLL.
+#
+DLLS += VBoxGuestControlSvc
+VBoxGuestControlSvc_TEMPLATE  = VBoxR3Dll
+VBoxGuestControlSvc_NAME.os2  = VBoxGCTL
+VBoxGuestControlSvc_DEFS      = VBOX_WITH_HGCM
+VBoxGuestControlSvc_INCS      = $(PATH_ROOT)/src/VBox/Main/include
+VBoxGuestControlSvc_INCS.win  = \
+	$(VBOX_PATH_SDK)
+
+VBoxGuestControlSvc_SOURCES = \
+	VBoxGuestControlSvc.cpp
+
+VBoxGuestControlSvc_SOURCES.win = \
+	VBoxGuestControlSvc.rc
+
+VBoxGuestControlSvc_LIBS = \
+	$(LIB_RUNTIME)
+
+VBoxGuestControlSvc_LDFLAGS.darwin = \
+	-install_name $(VBOX_DYLD_EXECUTABLE_PATH)/VBoxGuestControlSvc.dylib
+
+include $(FILE_KBUILD_SUB_FOOTER)
diff --git a/src/VBox/HostServices/GuestControl/VBoxGuestControlSvc.cpp b/src/VBox/HostServices/GuestControl/VBoxGuestControlSvc.cpp
new file mode 100644
index 00000000..c61f9919
--- /dev/null
+++ b/src/VBox/HostServices/GuestControl/VBoxGuestControlSvc.cpp
@@ -0,0 +1,2612 @@
+/* $Id: VBoxGuestControlSvc.cpp $ */
+/** @file
+ * Guest Control Service: Controlling the guest.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+/** @page pg_svc_guest_control   Guest Control HGCM Service
+ *
+ * This service acts as a proxy for handling and buffering host message requests
+ * and clients on the guest. It tries to be as transparent as possible to let
+ * the guest (client) and host side do their protocol handling as desired.
+ *
+ * The following terms are used:
+ * - Host:   A host process (e.g. VBoxManage or another tool utilizing the Main API)
+ *           which wants to control something on the guest.
+ * - Client: A client (e.g. VBoxService) running inside the guest OS waiting for
+ *           new host messages to perform. There can be multiple clients connected
+ *           to this service. A client is represented by its unique HGCM client ID.
+ * - Context ID: An (almost) unique ID automatically generated on the host (Main API)
+ *               to not only distinguish clients but individual requests. Because
+ *               the host does not know anything about connected clients it needs
+ *               an indicator which it can refer to later. This context ID gets
+ *               internally bound by the service to a client which actually processes
+ *               the message in order to have a relationship between client<->context ID(s).
+ *
+ * The host can trigger messages which get buffered by the service (with full HGCM
+ * parameter info). As soon as a client connects (or is ready to do some new work)
+ * it gets a buffered host message  to process it. This message then will be immediately
+ * removed from the message list. If there are ready clients but no new messages to be
+ * processed, these clients will be set into a deferred state (that is being blocked
+ * to return until a new host message is available).
+ *
+ * If a client needs to inform the host that something happened, it can send a
+ * message to a low level HGCM callback registered in Main. This callback contains
+ * the actual data as well as the context ID to let the host do the next necessary
+ * steps for this context. This context ID makes it possible to wait for an event
+ * inside the host's Main API function (like starting a process on the guest and
+ * wait for getting its PID returned by the client) as well as cancelling blocking
+ * host calls in order the client terminated/crashed (HGCM detects disconnected
+ * clients and reports it to this service's callback).
+ *
+ * Starting at VBox 4.2 the context ID itself consists of a session ID, an object
+ * ID (for example a process or file ID) and a count. This is necessary to not break
+ * compatibility between older hosts and to manage guest session on the host.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_GUEST_CONTROL
+#include <VBox/HostServices/GuestControlSvc.h>
+#include <VBox/GuestHost/GuestControl.h> /** @todo r=bird: Why two headers??? */
+
+#include <VBox/err.h>
+#include <VBox/log.h>
+#include <VBox/AssertGuest.h>
+#include <VBox/VMMDev.h>
+#include <VBox/vmm/ssm.h>
+#include <VBox/vmm/vmmr3vtable.h>
+#include <iprt/assert.h>
+#include <iprt/cpp/autores.h>
+#include <iprt/cpp/utils.h>
+#include <iprt/mem.h>
+#include <iprt/list.h>
+#include <iprt/req.h>
+#include <iprt/string.h>
+#include <iprt/thread.h>
+#include <iprt/time.h>
+
+#include <map>
+#include <new>      /* for std::nothrow*/
+
+
+using namespace guestControl;
+
+
+/**
+ * Structure for maintaining a request.
+ */
+typedef struct ClientRequest
+{
+    /** The call handle */
+    VBOXHGCMCALLHANDLE mHandle;
+    /** Number of parameters */
+    uint32_t mNumParms;
+    /** The call parameters */
+    VBOXHGCMSVCPARM *mParms;
+    /** The default constructor. */
+    ClientRequest(void)
+        : mHandle(0), mNumParms(0), mParms(NULL)
+    {}
+} ClientRequest;
+
+/**
+ * Structure for holding a buffered host message which has
+ * not been processed yet.
+ */
+typedef struct HostMsg
+{
+    /** Entry on the ClientState::m_HostMsgList list. */
+    RTLISTNODE      m_ListEntry;
+    union
+    {
+        /** The top two twomost bits are exploited for message destination.
+         * See VBOX_GUESTCTRL_DST_XXX.  */
+        uint64_t    m_idContextAndDst;
+        /** The context ID this message belongs to (extracted from the first parameter). */
+        uint32_t    m_idContext;
+    };
+    /** Dynamic structure for holding the HGCM parms */
+    uint32_t mType;
+    /** Number of HGCM parameters. */
+    uint32_t mParmCount;
+    /** Array of HGCM parameters. */
+    PVBOXHGCMSVCPARM mpParms;
+    /** Set if we detected the message skipping hack from r121400. */
+    bool m_f60BetaHackInPlay;
+
+    HostMsg()
+        : m_idContextAndDst(0)
+        , mType(UINT32_MAX)
+        , mParmCount(0)
+        , mpParms(NULL)
+        , m_f60BetaHackInPlay(false)
+    {
+        RTListInit(&m_ListEntry);
+    }
+
+    /**
+     * Releases the host message, properly deleting it if no further references.
+     */
+    void Delete(void)
+    {
+        LogFlowThisFunc(("[Msg %RU32 (%s)] destroying\n", mType, GstCtrlHostMsgtoStr((eHostMsg)mType)));
+        if (mpParms)
+        {
+            for (uint32_t i = 0; i < mParmCount; i++)
+                if (mpParms[i].type == VBOX_HGCM_SVC_PARM_PTR)
+                {
+                    RTMemFree(mpParms[i].u.pointer.addr);
+                    mpParms[i].u.pointer.addr = NULL;
+                }
+            RTMemFree(mpParms);
+            mpParms = NULL;
+        }
+        mParmCount = 0;
+        delete this;
+    }
+
+
+    /**
+     * Initializes the message.
+     *
+     * The specified parameters are copied and any buffers referenced by it
+     * duplicated as well.
+     *
+     * @returns VBox status code.
+     * @param   idMsg       The host message number, eHostMsg.
+     * @param   cParms      Number of parameters in the HGCM request.
+     * @param   paParms     Array of parameters.
+     */
+    int Init(uint32_t idMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+    {
+        LogFlowThisFunc(("[Msg %RU32 (%s)] Allocating cParms=%RU32, paParms=%p\n",
+                         idMsg, GstCtrlHostMsgtoStr((eHostMsg)idMsg), cParms, paParms));
+        Assert(mpParms == NULL);
+        Assert(mParmCount == 0);
+        Assert(RTListIsEmpty(&m_ListEntry));
+
+        /*
+         * Fend of bad stuff.
+         */
+        AssertReturn(cParms > 0, VERR_WRONG_PARAMETER_COUNT); /* At least one parameter (context ID) must be present. */
+        AssertReturn(cParms < VMMDEV_MAX_HGCM_PARMS, VERR_WRONG_PARAMETER_COUNT);
+        AssertPtrReturn(paParms, VERR_INVALID_POINTER);
+
+        /*
+         * The first parameter is the context ID and the message destination mask.
+         */
+        if (paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT)
+        {
+            m_idContextAndDst = paParms[0].u.uint64;
+            AssertReturn(m_idContextAndDst & VBOX_GUESTCTRL_DST_BOTH, VERR_INTERNAL_ERROR_3);
+        }
+        else if (paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT)
+        {
+            AssertMsgFailed(("idMsg=%u %s - caller must set dst!\n", idMsg, GstCtrlHostMsgtoStr((eHostMsg)idMsg)));
+            m_idContextAndDst = paParms[0].u.uint32 | VBOX_GUESTCTRL_DST_BOTH;
+        }
+        else
+            AssertFailedReturn(VERR_WRONG_PARAMETER_TYPE);
+
+        /*
+         * Just make a copy of the parameters and any buffers.
+         */
+        mType   = idMsg;
+        mParmCount = cParms;
+        mpParms    = (VBOXHGCMSVCPARM *)RTMemAllocZ(sizeof(VBOXHGCMSVCPARM) * mParmCount);
+        AssertReturn(mpParms, VERR_NO_MEMORY);
+
+        for (uint32_t i = 0; i < cParms; i++)
+        {
+            mpParms[i].type = paParms[i].type;
+            switch (paParms[i].type)
+            {
+                case VBOX_HGCM_SVC_PARM_32BIT:
+                    mpParms[i].u.uint32 = paParms[i].u.uint32;
+                    break;
+
+                case VBOX_HGCM_SVC_PARM_64BIT:
+                    mpParms[i].u.uint64 = paParms[i].u.uint64;
+                    break;
+
+                case VBOX_HGCM_SVC_PARM_PTR:
+                    mpParms[i].u.pointer.size = paParms[i].u.pointer.size;
+                    if (mpParms[i].u.pointer.size > 0)
+                    {
+                        mpParms[i].u.pointer.addr = RTMemDup(paParms[i].u.pointer.addr, mpParms[i].u.pointer.size);
+                        AssertReturn(mpParms[i].u.pointer.addr, VERR_NO_MEMORY);
+                    }
+                    /* else: structure is zeroed by allocator. */
+                    break;
+
+                default:
+                    AssertMsgFailedReturn(("idMsg=%u (%s) parameter #%u: type=%u\n",
+                                           idMsg, GstCtrlHostMsgtoStr((eHostMsg)idMsg), i, paParms[i].type),
+                                          VERR_WRONG_PARAMETER_TYPE);
+            }
+        }
+
+        /*
+         * Morph the first parameter back to 32-bit.
+         */
+        mpParms[0].type     = VBOX_HGCM_SVC_PARM_32BIT;
+        mpParms[0].u.uint32 = (uint32_t)paParms[0].u.uint64;
+
+        return VINF_SUCCESS;
+    }
+
+
+    /**
+     * Sets the GUEST_MSG_PEEK_WAIT GUEST_MSG_PEEK_NOWAIT return parameters.
+     *
+     * @param   paDstParms  The peek parameter vector.
+     * @param   cDstParms   The number of peek parameters (at least two).
+     * @remarks ASSUMES the parameters has been cleared by clientMsgPeek.
+     */
+    inline void setPeekReturn(PVBOXHGCMSVCPARM paDstParms, uint32_t cDstParms)
+    {
+        Assert(cDstParms >= 2);
+        if (paDstParms[0].type == VBOX_HGCM_SVC_PARM_32BIT)
+            paDstParms[0].u.uint32 = mType;
+        else
+            paDstParms[0].u.uint64 = mType;
+        paDstParms[1].u.uint32 = mParmCount;
+
+        uint32_t i = RT_MIN(cDstParms, mParmCount + 2);
+        while (i-- > 2)
+            switch (mpParms[i - 2].type)
+            {
+                case VBOX_HGCM_SVC_PARM_32BIT: paDstParms[i].u.uint32 = ~(uint32_t)sizeof(uint32_t); break;
+                case VBOX_HGCM_SVC_PARM_64BIT: paDstParms[i].u.uint32 = ~(uint32_t)sizeof(uint64_t); break;
+                case VBOX_HGCM_SVC_PARM_PTR:   paDstParms[i].u.uint32 = mpParms[i - 2].u.pointer.size; break;
+            }
+    }
+
+
+    /** @name Support for old-style (GUEST_MSG_WAIT) operation.
+     * @{
+     */
+
+    /**
+     * Worker for Assign() that opies data from the buffered HGCM request to the
+     * current HGCM request.
+     *
+     * @returns VBox status code.
+     * @param   paDstParms              Array of parameters of HGCM request to fill the data into.
+     * @param   cDstParms               Number of parameters the HGCM request can handle.
+     */
+    int CopyTo(VBOXHGCMSVCPARM paDstParms[], uint32_t cDstParms) const
+    {
+        LogFlowThisFunc(("[Msg %RU32] mParmCount=%RU32, m_idContext=%RU32 (Session %RU32)\n",
+                         mType, mParmCount, m_idContext, VBOX_GUESTCTRL_CONTEXTID_GET_SESSION(m_idContext)));
+
+        int rc = VINF_SUCCESS;
+        if (cDstParms != mParmCount)
+        {
+            LogFlowFunc(("Parameter count does not match (got %RU32, expected %RU32)\n",
+                         cDstParms, mParmCount));
+            rc = VERR_INVALID_PARAMETER;
+        }
+
+        if (RT_SUCCESS(rc))
+        {
+            for (uint32_t i = 0; i < mParmCount; i++)
+            {
+                if (paDstParms[i].type != mpParms[i].type)
+                {
+                    LogFunc(("Parameter %RU32 type mismatch (got %RU32, expected %RU32)\n", i, paDstParms[i].type, mpParms[i].type));
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    switch (mpParms[i].type)
+                    {
+                        case VBOX_HGCM_SVC_PARM_32BIT:
+#ifdef DEBUG_andy
+                            LogFlowFunc(("\tmpParms[%RU32] = %RU32 (uint32_t)\n",
+                                         i, mpParms[i].u.uint32));
+#endif
+                            paDstParms[i].u.uint32 = mpParms[i].u.uint32;
+                            break;
+
+                        case VBOX_HGCM_SVC_PARM_64BIT:
+#ifdef DEBUG_andy
+                            LogFlowFunc(("\tmpParms[%RU32] = %RU64 (uint64_t)\n",
+                                         i, mpParms[i].u.uint64));
+#endif
+                            paDstParms[i].u.uint64 = mpParms[i].u.uint64;
+                            break;
+
+                        case VBOX_HGCM_SVC_PARM_PTR:
+                        {
+#ifdef DEBUG_andy
+                            LogFlowFunc(("\tmpParms[%RU32] = %p (ptr), size = %RU32\n",
+                                         i, mpParms[i].u.pointer.addr, mpParms[i].u.pointer.size));
+#endif
+                            if (!mpParms[i].u.pointer.size)
+                                continue; /* Only copy buffer if there actually is something to copy. */
+
+                            if (!paDstParms[i].u.pointer.addr)
+                                rc = VERR_INVALID_PARAMETER;
+                            else if (paDstParms[i].u.pointer.size < mpParms[i].u.pointer.size)
+                                rc = VERR_BUFFER_OVERFLOW;
+                            else
+                                memcpy(paDstParms[i].u.pointer.addr,
+                                       mpParms[i].u.pointer.addr,
+                                       mpParms[i].u.pointer.size);
+                            break;
+                        }
+
+                        default:
+                            LogFunc(("Parameter %RU32 of type %RU32 is not supported yet\n", i, mpParms[i].type));
+                            rc = VERR_NOT_SUPPORTED;
+                            break;
+                    }
+                }
+
+                if (RT_FAILURE(rc))
+                {
+                    LogFunc(("Parameter %RU32 invalid (%Rrc), refusing\n", i, rc));
+                    break;
+                }
+            }
+        }
+
+        LogFlowFunc(("Returned with rc=%Rrc\n", rc));
+        return rc;
+    }
+
+    int Assign(const ClientRequest *pReq)
+    {
+        AssertPtrReturn(pReq, VERR_INVALID_POINTER);
+
+        int rc;
+
+        LogFlowThisFunc(("[Msg %RU32] mParmCount=%RU32, mpParms=%p\n", mType, mParmCount, mpParms));
+
+        /* Does the current host message need more parameter space which
+         * the client does not provide yet? */
+        if (mParmCount > pReq->mNumParms)
+        {
+            LogFlowThisFunc(("[Msg %RU32] Requires %RU32 parms, only got %RU32 from client\n",
+                             mType, mParmCount, pReq->mNumParms));
+            /*
+             * So this call apparently failed because the guest wanted to peek
+             * how much parameters it has to supply in order to successfully retrieve
+             * this message. Let's tell him so!
+             */
+            rc = VERR_TOO_MUCH_DATA;
+        }
+        else
+        {
+            rc = CopyTo(pReq->mParms, pReq->mNumParms);
+
+            /*
+             * Has there been enough parameter space but the wrong parameter types
+             * were submitted -- maybe the client was just asking for the next upcoming
+             * host message?
+             *
+             * Note: To keep this compatible to older clients we return VERR_TOO_MUCH_DATA
+             *       in every case.
+             */
+            if (RT_FAILURE(rc))
+                rc = VERR_TOO_MUCH_DATA;
+        }
+
+        return rc;
+    }
+
+    int Peek(const ClientRequest *pReq)
+    {
+        AssertPtrReturn(pReq, VERR_INVALID_POINTER);
+
+        LogFlowThisFunc(("[Msg %RU32] mParmCount=%RU32, mpParms=%p\n", mType, mParmCount, mpParms));
+
+        if (pReq->mNumParms >= 2)
+        {
+            HGCMSvcSetU32(&pReq->mParms[0], mType);   /* Message ID */
+            HGCMSvcSetU32(&pReq->mParms[1], mParmCount); /* Required parameters for message */
+        }
+        else
+            LogFlowThisFunc(("Warning: Client has not (yet) submitted enough parameters (%RU32, must be at least 2) to at least peak for the next message\n",
+                             pReq->mNumParms));
+
+        /*
+         * Always return VERR_TOO_MUCH_DATA data here to
+         * keep it compatible with older clients and to
+         * have correct accounting (mHostRc + mHostMsgTries).
+         */
+        return VERR_TOO_MUCH_DATA;
+    }
+
+    /** @} */
+} HostMsg;
+
+/**
+ * Per-client structure used for book keeping/state tracking a
+ * certain host message.
+ */
+typedef struct ClientContext
+{
+    /* Pointer to list node of this message. */
+    HostMsg *mpHostMsg;
+    /** The standard constructor. */
+    ClientContext(void) : mpHostMsg(NULL) {}
+    /** Internal constrcutor. */
+    ClientContext(HostMsg *pHostMsg) : mpHostMsg(pHostMsg) {}
+} ClientContext;
+typedef std::map< uint32_t, ClientContext > ClientContextMap;
+
+/**
+ * Structure for holding a connected guest client state.
+ */
+typedef struct ClientState
+{
+    PVBOXHGCMSVCHELPERS     m_pSvcHelpers;
+    /** Host message list to process (HostMsg). */
+    RTLISTANCHOR            m_HostMsgList;
+    /** The HGCM client ID. */
+    uint32_t                m_idClient;
+    /** The session ID for this client, UINT32_MAX if not set or master. */
+    uint32_t                m_idSession;
+    /** Set if master. */
+    bool                    m_fIsMaster;
+    /** Set if restored (needed for shutting legacy mode assert on non-masters). */
+    bool                    m_fRestored;
+
+    /** Set if we've got a pending wait cancel. */
+    bool                    m_fPendingCancel;
+    /** Pending client call (GUEST_MSG_PEEK_WAIT or GUEST_MSG_WAIT), zero if none pending.
+     *
+     * This means the client waits for a new host message to reply and won't return
+     * from the waiting call until a new host message is available. */
+    guestControl::eGuestMsg m_enmPendingMsg;
+    /** Pending peek/wait request details. */
+    ClientRequest           m_PendingReq;
+
+
+    ClientState(void)
+        : m_pSvcHelpers(NULL)
+        , m_idClient(0)
+        , m_idSession(UINT32_MAX)
+        , m_fIsMaster(false)
+        , m_fRestored(false)
+        , m_fPendingCancel(false)
+        , m_enmPendingMsg((guestControl::eGuestMsg)0)
+        , mHostMsgRc(VINF_SUCCESS)
+        , mHostMsgTries(0)
+        , mPeekCount(0)
+    {
+        RTListInit(&m_HostMsgList);
+    }
+
+    ClientState(PVBOXHGCMSVCHELPERS pSvcHelpers, uint32_t idClient)
+        : m_pSvcHelpers(pSvcHelpers)
+        , m_idClient(idClient)
+        , m_idSession(UINT32_MAX)
+        , m_fIsMaster(false)
+        , m_fRestored(false)
+        , m_fPendingCancel(false)
+        , m_enmPendingMsg((guestControl::eGuestMsg)0)
+        , mHostMsgRc(VINF_SUCCESS)
+        , mHostMsgTries(0)
+        , mPeekCount(0)
+    {
+        RTListInit(&m_HostMsgList);
+    }
+
+    /**
+     * Used by for Service::hostProcessMessage().
+     */
+    void EnqueueMessage(HostMsg *pHostMsg)
+    {
+        AssertPtr(pHostMsg);
+        RTListAppend(&m_HostMsgList, &pHostMsg->m_ListEntry);
+    }
+
+    /**
+     * Used by for Service::hostProcessMessage().
+     *
+     * @returns VBox status code.
+     * @retval  VINF_NO_CHANGE if the client has not been woken up.
+     *
+     * @note This wakes up both GUEST_MSG_WAIT and GUEST_MSG_PEEK_WAIT sleepers.
+     */
+    int Wakeup(void)
+    {
+        int rc = VINF_NO_CHANGE;
+
+        LogFlowFunc(("[Client %RU32] enmPendingMsg=%RU32, idSession=%RU32, fIsMaster=%RTbool, fRestored=%RTbool\n",
+                     m_idClient, m_enmPendingMsg, m_idSession, m_fIsMaster, m_fRestored));
+
+        if (m_enmPendingMsg != 0)
+        {
+            rc = VINF_SUCCESS;
+
+            HostMsg *pFirstMsg = RTListGetFirstCpp(&m_HostMsgList, HostMsg, m_ListEntry);
+            if (pFirstMsg)
+            {
+                LogFlowThisFunc(("[Client %RU32] Current host message is %RU32 (CID=%#RX32, cParms=%RU32)\n",
+                                 m_idClient, pFirstMsg->mType, pFirstMsg->m_idContext, pFirstMsg->mParmCount));
+
+                if (m_enmPendingMsg == GUEST_MSG_PEEK_WAIT)
+                {
+                    pFirstMsg->setPeekReturn(m_PendingReq.mParms, m_PendingReq.mNumParms);
+                    rc = m_pSvcHelpers->pfnCallComplete(m_PendingReq.mHandle, VINF_SUCCESS);
+
+                    m_PendingReq.mHandle    = NULL;
+                    m_PendingReq.mParms     = NULL;
+                    m_PendingReq.mNumParms  = 0;
+                    m_enmPendingMsg         = (guestControl::eGuestMsg)0;
+                }
+                else if (m_enmPendingMsg == GUEST_MSG_WAIT)
+                    rc = OldRun(&m_PendingReq, pFirstMsg);
+                else
+                    AssertMsgFailed(("m_enmIsPending=%d\n", m_enmPendingMsg));
+            }
+            else
+                AssertMsgFailed(("Waking up client ID=%RU32 with no host message in queue is a bad idea\n", m_idClient));
+        }
+
+        LogFlowFuncLeaveRC(rc);
+        return rc;
+    }
+
+    /**
+     * Used by Service::call() to handle GUEST_MSG_CANCEL.
+     *
+     * @note This cancels both GUEST_MSG_WAIT and GUEST_MSG_PEEK_WAIT sleepers.
+     */
+    int CancelWaiting()
+    {
+        LogFlowFunc(("[Client %RU32] Cancelling waiting thread, isPending=%d, pendingNumParms=%RU32, m_idSession=%x\n",
+                     m_idClient, m_enmPendingMsg, m_PendingReq.mNumParms, m_idSession));
+
+        /*
+         * The PEEK call is simple: At least two parameters, all set to zero before sleeping.
+         */
+        int rcComplete;
+        if (m_enmPendingMsg == GUEST_MSG_PEEK_WAIT)
+        {
+            HGCMSvcSetU32(&m_PendingReq.mParms[0], HOST_MSG_CANCEL_PENDING_WAITS);
+            rcComplete = VINF_TRY_AGAIN;
+        }
+        /*
+         * The GUEST_MSG_WAIT call is complicated, though we're generally here
+         * to wake up someone who is peeking and have two parameters.  If there
+         * aren't two parameters, fail the call.
+         */
+        else if (m_enmPendingMsg != 0)
+        {
+            Assert(m_enmPendingMsg == GUEST_MSG_WAIT);
+            if (m_PendingReq.mNumParms > 0)
+                HGCMSvcSetU32(&m_PendingReq.mParms[0], HOST_MSG_CANCEL_PENDING_WAITS);
+            if (m_PendingReq.mNumParms > 1)
+                HGCMSvcSetU32(&m_PendingReq.mParms[1], 0);
+            rcComplete = m_PendingReq.mNumParms == 2 ? VINF_SUCCESS : VERR_TRY_AGAIN;
+        }
+        /*
+         * If nobody is waiting, flag the next wait call as cancelled.
+         */
+        else
+        {
+            m_fPendingCancel = true;
+            return VINF_SUCCESS;
+        }
+
+        m_pSvcHelpers->pfnCallComplete(m_PendingReq.mHandle, rcComplete);
+
+        m_PendingReq.mHandle   = NULL;
+        m_PendingReq.mParms    = NULL;
+        m_PendingReq.mNumParms = 0;
+        m_enmPendingMsg            = (guestControl::eGuestMsg)0;
+        m_fPendingCancel      = false;
+        return VINF_SUCCESS;
+    }
+
+
+    /** @name The GUEST_MSG_WAIT state and helpers.
+     *
+     * @note Don't try understand this, it is certificable!
+     *
+     * @{
+     */
+
+    /** Last (most recent) rc after handling the host message. */
+    int mHostMsgRc;
+    /** How many GUEST_MSG_WAIT calls the client has issued to retrieve one message.
+     *
+     * This is used as a heuristic to remove a message that the client appears not
+     * to be able to successfully retrieve.  */
+    uint32_t mHostMsgTries;
+    /** Number of times we've peeked at a pending message.
+     *
+     * This is necessary for being compatible with older Guest Additions.  In case
+     * there are messages which only have two (2) parameters and therefore would fit
+     * into the GUEST_MSG_WAIT reply immediately, we now can make sure that the
+     * client first gets back the GUEST_MSG_WAIT results first.
+     */
+    uint32_t mPeekCount;
+
+    /**
+     * Ditches the first host message and crazy GUEST_MSG_WAIT state.
+     *
+     * @note Only used by GUEST_MSG_WAIT scenarios.
+     */
+    void OldDitchFirstHostMsg()
+    {
+        HostMsg *pFirstMsg = RTListGetFirstCpp(&m_HostMsgList, HostMsg, m_ListEntry);
+        Assert(pFirstMsg);
+        RTListNodeRemove(&pFirstMsg->m_ListEntry);
+        pFirstMsg->Delete();
+
+        /* Reset state else. */
+        mHostMsgRc    = VINF_SUCCESS;
+        mHostMsgTries = 0;
+        mPeekCount    = 0;
+    }
+
+    /**
+     * Used by Wakeup() and OldRunCurrent().
+     *
+     * @note Only used by GUEST_MSG_WAIT scenarios.
+     */
+    int OldRun(ClientRequest const *pReq, HostMsg *pHostMsg)
+    {
+        AssertPtrReturn(pReq, VERR_INVALID_POINTER);
+        AssertPtrReturn(pHostMsg, VERR_INVALID_POINTER);
+        Assert(RTListNodeIsFirst(&m_HostMsgList, &pHostMsg->m_ListEntry));
+
+        LogFlowFunc(("[Client %RU32] pReq=%p, mHostMsgRc=%Rrc, mHostMsgTries=%RU32, mPeekCount=%RU32\n",
+                      m_idClient, pReq, mHostMsgRc, mHostMsgTries, mPeekCount));
+
+        int rc = mHostMsgRc = OldSendReply(pReq, pHostMsg);
+
+        LogFlowThisFunc(("[Client %RU32] Processing host message %RU32 ended with rc=%Rrc\n",
+                         m_idClient, pHostMsg->mType, mHostMsgRc));
+
+        bool fRemove = false;
+        if (RT_FAILURE(rc))
+        {
+            mHostMsgTries++;
+
+            /*
+             * If the client understood the message but supplied too little buffer space
+             * don't send this message again and drop it after 6 unsuccessful attempts.
+             *
+             * Note: Due to legacy reasons this the retry counter has to be even because on
+             *       every peek there will be the actual message retrieval from the client side.
+             *       To not get the actual message if the client actually only wants to peek for
+             *       the next message, there needs to be two rounds per try, e.g. 3 rounds = 6 tries.
+             */
+            /** @todo Fix the mess stated above. GUEST_MSG_WAIT should be become GUEST_MSG_PEEK, *only*
+             *        (and every time) returning the next upcoming host message (if any, blocking). Then
+             *        it's up to the client what to do next, either peeking again or getting the actual
+             *        host message via an own GUEST_ type message.
+             */
+            if (   rc == VERR_TOO_MUCH_DATA
+                || rc == VERR_CANCELLED)
+            {
+                if (mHostMsgTries == 6)
+                    fRemove = true;
+            }
+            /* Client did not understand the message or something else weird happened. Try again one
+             * more time and drop it if it didn't get handled then. */
+            else if (mHostMsgTries > 1)
+                fRemove = true;
+        }
+        else
+            fRemove = true; /* Everything went fine, remove it. */
+
+        LogFlowThisFunc(("[Client %RU32] Tried host message %RU32 for %RU32 times, (last result=%Rrc, fRemove=%RTbool)\n",
+                         m_idClient, pHostMsg->mType, mHostMsgTries, rc, fRemove));
+
+        if (fRemove)
+        {
+            Assert(RTListNodeIsFirst(&m_HostMsgList, &pHostMsg->m_ListEntry));
+            OldDitchFirstHostMsg();
+        }
+
+        LogFlowFunc(("[Client %RU32] Returned with rc=%Rrc\n", m_idClient, rc));
+        return rc;
+    }
+
+    /**
+     * @note Only used by GUEST_MSG_WAIT scenarios.
+     */
+    int OldRunCurrent(const ClientRequest *pReq)
+    {
+        AssertPtrReturn(pReq, VERR_INVALID_POINTER);
+
+        /*
+         * If the host message list is empty, the request must wait for one to be posted.
+         */
+        HostMsg *pFirstMsg = RTListGetFirstCpp(&m_HostMsgList, HostMsg, m_ListEntry);
+        if (!pFirstMsg)
+        {
+            if (!m_fPendingCancel)
+            {
+                /* Go to sleep. */
+                ASSERT_GUEST_RETURN(m_enmPendingMsg == 0, VERR_WRONG_ORDER);
+                m_PendingReq = *pReq;
+                m_enmPendingMsg  = GUEST_MSG_WAIT;
+                LogFlowFunc(("[Client %RU32] Is now in pending mode\n", m_idClient));
+                return VINF_HGCM_ASYNC_EXECUTE;
+            }
+
+            /* Wait was cancelled. */
+            m_fPendingCancel = false;
+            if (pReq->mNumParms > 0)
+                HGCMSvcSetU32(&pReq->mParms[0], HOST_MSG_CANCEL_PENDING_WAITS);
+            if (pReq->mNumParms > 1)
+                HGCMSvcSetU32(&pReq->mParms[1], 0);
+            return pReq->mNumParms == 2 ? VINF_SUCCESS : VERR_TRY_AGAIN;
+        }
+
+        /*
+         * Return first host message.
+         */
+        return OldRun(pReq, pFirstMsg);
+    }
+
+    /**
+     * Internal worker for OldRun().
+     * @note Only used for GUEST_MSG_WAIT.
+     */
+    int OldSendReply(ClientRequest const *pReq,
+                     HostMsg         *pHostMsg)
+    {
+        AssertPtrReturn(pReq, VERR_INVALID_POINTER);
+        AssertPtrReturn(pHostMsg, VERR_INVALID_POINTER);
+
+        /* In case of VERR_CANCELLED. */
+        uint32_t const cSavedPeeks = mPeekCount;
+
+        int rc;
+        /* If the client is in pending mode, always send back
+         * the peek result first. */
+        if (m_enmPendingMsg)
+        {
+            Assert(m_enmPendingMsg == GUEST_MSG_WAIT);
+            rc = pHostMsg->Peek(pReq);
+            mPeekCount++;
+        }
+        else
+        {
+            /* If this is the very first peek, make sure to *always* give back the peeking answer
+             * instead of the actual message, even if this message would fit into the current
+             * connection buffer. */
+            if (!mPeekCount)
+            {
+                rc = pHostMsg->Peek(pReq);
+                mPeekCount++;
+            }
+            else
+            {
+                /* Try assigning the host message to the client and store the
+                 * result code for later use. */
+                rc = pHostMsg->Assign(pReq);
+                if (RT_FAILURE(rc)) /* If something failed, let the client peek (again). */
+                {
+                    rc = pHostMsg->Peek(pReq);
+                    mPeekCount++;
+                }
+                else
+                    mPeekCount = 0;
+            }
+        }
+
+        /* Reset pending status. */
+        m_enmPendingMsg = (guestControl::eGuestMsg)0;
+
+        /* In any case the client did something, so complete
+         * the pending call with the result we just got. */
+        AssertPtr(m_pSvcHelpers);
+        int rc2 = m_pSvcHelpers->pfnCallComplete(pReq->mHandle, rc);
+
+        /* Rollback in case the guest cancelled the call. */
+        if (rc2 == VERR_CANCELLED && RT_SUCCESS(rc))
+        {
+            mPeekCount = cSavedPeeks;
+            rc = VERR_CANCELLED;
+        }
+
+        LogFlowThisFunc(("[Client %RU32] Message %RU32 ended with %Rrc (mPeekCount=%RU32, pReq=%p)\n",
+                         m_idClient, pHostMsg->mType, rc, mPeekCount, pReq));
+        return rc;
+    }
+
+    /** @} */
+} ClientState;
+typedef std::map< uint32_t, ClientState *> ClientStateMap;
+
+/**
+ * Prepared session (GUEST_SESSION_PREPARE).
+ */
+typedef struct GstCtrlPreparedSession
+{
+    /** List entry. */
+    RTLISTNODE  ListEntry;
+    /** The session ID.   */
+    uint32_t    idSession;
+    /** The key size. */
+    uint32_t    cbKey;
+    /** The key bytes. */
+    RT_FLEXIBLE_ARRAY_EXTENSION
+    uint8_t     abKey[RT_FLEXIBLE_ARRAY];
+} GstCtrlPreparedSession;
+
+
+/**
+ * Class containing the shared information service functionality.
+ */
+class GstCtrlService : public RTCNonCopyable
+{
+
+private:
+
+    /** Type definition for use in callback functions. */
+    typedef GstCtrlService SELF;
+    /** HGCM helper functions. */
+    PVBOXHGCMSVCHELPERS     mpHelpers;
+    /** Callback function supplied by the host for notification of updates to properties. */
+    PFNHGCMSVCEXT           mpfnHostCallback;
+    /** User data pointer to be supplied to the host callback function. */
+    void                   *mpvHostData;
+    /** Map containing all connected clients, key is HGCM client ID. */
+    ClientStateMap          m_ClientStateMap;
+    /** Session ID -> client state. */
+    ClientStateMap          m_SessionIdMap;
+    /** The current master client, NULL if none. */
+    ClientState            *m_pMasterClient;
+    /** The master HGCM client ID, UINT32_MAX if none. */
+    uint32_t                m_idMasterClient;
+    /** Set if we're in legacy mode (pre 6.0). */
+    bool                    m_fLegacyMode;
+    /** Number of prepared sessions. */
+    uint32_t                m_cPreparedSessions;
+    /** List of prepared session (GstCtrlPreparedSession). */
+    RTLISTANCHOR            m_PreparedSessions;
+    /** Guest feature flags, VBOX_GUESTCTRL_GF_0_XXX. */
+    uint64_t                m_fGuestFeatures0;
+    /** Guest feature flags, VBOX_GUESTCTRL_GF_1_XXX. */
+    uint64_t                m_fGuestFeatures1;
+
+public:
+    explicit GstCtrlService(PVBOXHGCMSVCHELPERS pHelpers)
+        : mpHelpers(pHelpers)
+        , mpfnHostCallback(NULL)
+        , mpvHostData(NULL)
+        , m_pMasterClient(NULL)
+        , m_idMasterClient(UINT32_MAX)
+        , m_fLegacyMode(true)
+        , m_cPreparedSessions(0)
+        , m_fGuestFeatures0(0)
+        , m_fGuestFeatures1(0)
+    {
+        RTListInit(&m_PreparedSessions);
+    }
+
+    static DECLCALLBACK(int)  svcUnload(void *pvService);
+    static DECLCALLBACK(int)  svcConnect(void *pvService, uint32_t idClient, void *pvClient,
+                                         uint32_t fRequestor, bool fRestoring);
+    static DECLCALLBACK(int)  svcDisconnect(void *pvService, uint32_t idClient, void *pvClient);
+    static DECLCALLBACK(void) svcCall(void *pvService, VBOXHGCMCALLHANDLE hCall, uint32_t idClient, void *pvClient,
+                                      uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[], uint64_t tsArrival);
+    static DECLCALLBACK(int)  svcHostCall(void *pvService, uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    static DECLCALLBACK(int)  svcSaveState(void *pvService, uint32_t idClient, void *pvClient,
+                                           PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM);
+    static DECLCALLBACK(int)  svcLoadState(void *pvService, uint32_t idClient, void *pvClient,
+                                           PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion);
+    static DECLCALLBACK(int)  svcRegisterExtension(void *pvService, PFNHGCMSVCEXT pfnExtension, void *pvExtension);
+
+private:
+    int clientMakeMeMaster(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms);
+    int clientReportFeatures(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientQueryFeatures(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientMsgPeek(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[], bool fWait);
+    int clientMsgGet(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientMsgCancel(ClientState *pClient, uint32_t cParms);
+    int clientMsgSkip(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientSessionPrepare(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientSessionCancelPrepared(ClientState *pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientSessionAccept(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientSessionCloseOther(ClientState *pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientToMain(ClientState *pClient, uint32_t idMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+
+    int clientMsgOldGet(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientMsgOldFilterSet(ClientState *pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int clientMsgOldSkip(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms);
+
+    int hostCallback(uint32_t idMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int hostProcessMessage(uint32_t idMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+
+    DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(GstCtrlService);
+};
+
+
+/** Host feature mask for GUEST_MSG_REPORT_FEATURES/GUEST_MSG_QUERY_FEATURES. */
+static uint64_t const g_fGstCtrlHostFeatures0 = VBOX_GUESTCTRL_HF_0_NOTIFY_RDWR_OFFSET
+                                              | VBOX_GUESTCTRL_HF_0_PROCESS_ARGV0;
+
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnUnload,
+ *  Simply deletes the GstCtrlService object}
+ */
+/*static*/ DECLCALLBACK(int)
+GstCtrlService::svcUnload(void *pvService)
+{
+    AssertLogRelReturn(RT_VALID_PTR(pvService), VERR_INVALID_PARAMETER);
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertPtrReturn(pThis, VERR_INVALID_POINTER);
+
+    delete pThis;
+
+    return VINF_SUCCESS;
+}
+
+
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnConnect,
+ *  Initializes the state for a new client.}
+ */
+/*static*/ DECLCALLBACK(int)
+GstCtrlService::svcConnect(void *pvService, uint32_t idClient, void *pvClient, uint32_t fRequestor, bool fRestoring)
+{
+    LogFlowFunc(("[Client %RU32] Connected\n", idClient));
+
+    RT_NOREF(fRestoring, pvClient);
+    AssertLogRelReturn(RT_VALID_PTR(pvService), VERR_INVALID_PARAMETER);
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertPtrReturn(pThis, VERR_INVALID_POINTER);
+
+    AssertMsg(pThis->m_ClientStateMap.find(idClient) == pThis->m_ClientStateMap.end(),
+              ("Client with ID=%RU32 already connected when it should not\n", idClient));
+
+    /*
+     * Create client state.
+     */
+    ClientState *pClient = NULL;
+    try
+    {
+        pClient = new (pvClient) ClientState(pThis->mpHelpers, idClient);
+        pThis->m_ClientStateMap[idClient] = pClient;
+    }
+    catch (std::bad_alloc &)
+    {
+        if (pClient)
+            pClient->~ClientState();
+        return VERR_NO_MEMORY;
+    }
+
+    /*
+     * For legacy compatibility reasons we have to pick a master client at some
+     * point, so if the /dev/vboxguest requirements checks out we pick the first
+     * one through the door.
+     */
+/** @todo make picking the master more dynamic/flexible? */
+    if (   pThis->m_fLegacyMode
+        && pThis->m_idMasterClient == UINT32_MAX)
+    {
+        if (   fRequestor == VMMDEV_REQUESTOR_LEGACY
+            || !(fRequestor & VMMDEV_REQUESTOR_USER_DEVICE))
+        {
+            LogFunc(("Picking %u as master for now.\n", idClient));
+            pThis->m_pMasterClient  = pClient;
+            pThis->m_idMasterClient = idClient;
+            pClient->m_fIsMaster = true;
+        }
+    }
+
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnConnect,
+ *  Handles a client which disconnected.}
+ *
+ * This functiond does some internal cleanup as well as sends notifications to
+ * the host so that the host can do the same (if required).
+ */
+/*static*/ DECLCALLBACK(int)
+GstCtrlService::svcDisconnect(void *pvService, uint32_t idClient, void *pvClient)
+{
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertPtrReturn(pThis, VERR_INVALID_POINTER);
+    ClientState *pClient = reinterpret_cast<ClientState *>(pvClient);
+    AssertPtrReturn(pClient, VERR_INVALID_POINTER);
+    LogFlowFunc(("[Client %RU32] Disconnected (%zu clients total)\n", idClient, pThis->m_ClientStateMap.size()));
+
+    /*
+     * Cancel all pending host messages, replying with GUEST_DISCONNECTED if final recipient.
+     */
+    HostMsg *pCurMsg, *pNextMsg;
+    RTListForEachSafeCpp(&pClient->m_HostMsgList, pCurMsg, pNextMsg, HostMsg, m_ListEntry)
+    {
+        RTListNodeRemove(&pCurMsg->m_ListEntry);
+
+        VBOXHGCMSVCPARM Parm;
+        HGCMSvcSetU32(&Parm, pCurMsg->m_idContext);
+        int rc2 = pThis->hostCallback(GUEST_MSG_DISCONNECTED, 1, &Parm);
+        LogFlowFunc(("Cancelled host message %u (%s) with idContext=%#x -> %Rrc\n",
+                     pCurMsg->mType, GstCtrlHostMsgtoStr((eHostMsg)pCurMsg->mType), pCurMsg->m_idContext, rc2));
+        RT_NOREF(rc2);
+
+        pCurMsg->Delete();
+    }
+
+    /*
+     * If it's the master disconnecting, we need to reset related globals.
+     */
+    if (idClient == pThis->m_idMasterClient)
+    {
+        pThis->m_pMasterClient  = NULL;
+        pThis->m_idMasterClient = UINT32_MAX;
+
+        GstCtrlPreparedSession *pCur, *pNext;
+        RTListForEachSafe(&pThis->m_PreparedSessions, pCur, pNext, GstCtrlPreparedSession, ListEntry)
+        {
+            RTListNodeRemove(&pCur->ListEntry);
+            RTMemFree(pCur);
+        }
+        pThis->m_cPreparedSessions = 0;
+
+        /* Make sure that the host gets notified about still associated guest sessions going down.
+         *
+         * Some guest OSes (like OL8) do reboot / shut down quite abruptly so that
+         * VBoxService does not have the chance to do so instead.
+         *
+         * Note: We do this only when the master disconnects as a last meassure, as this otherwise
+         *       would overwrite formerly sent session statuses on the host.
+         */
+        ClientStateMap::const_iterator itClientState = pThis->m_SessionIdMap.begin();
+        while (itClientState != pThis->m_SessionIdMap.end())
+        {
+            VBOXHGCMSVCPARM aParms[4];
+            HGCMSvcSetU32(&aParms[0], VBOX_GUESTCTRL_CONTEXTID_MAKE(pCur->idSession, 0 /* uObject */, 0 /* uCount */));
+            HGCMSvcSetU32(&aParms[1], GUEST_SESSION_NOTIFYTYPE_DWN); /* type */
+            HGCMSvcSetU32(&aParms[2], VINF_SUCCESS);                 /* result */
+
+            int rc2 = pThis->hostCallback(GUEST_MSG_SESSION_NOTIFY, 3, aParms);
+            LogFlowFunc(("Notified host about session ID=%RU32 going down -> %Rrc\n", pClient->m_idSession, rc2));
+            RT_NOREF(rc2);
+
+            ++itClientState;
+            /* Note: Don't erase the client state -- this will be done when the actual client is disconnecting. */
+        }
+    }
+    else
+        Assert(pClient != pThis->m_pMasterClient);
+
+    /*
+     * Delete the client state.
+     */
+    pThis->m_ClientStateMap.erase(idClient);
+    if (pClient->m_idSession != UINT32_MAX)
+        pThis->m_SessionIdMap.erase(pClient->m_idSession);
+    pClient->~ClientState();
+
+    if (pThis->m_ClientStateMap.empty())
+        pThis->m_fLegacyMode = true;
+
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * A client asks for the next message to process.
+ *
+ * This either fills in a pending host message into the client's parameter space
+ * or defers the guest call until we have something from the host.
+ *
+ * @returns VBox status code.
+ * @param   pClient         The client state.
+ * @param   hCall           The client's call handle.
+ * @param   cParms          Number of parameters.
+ * @param   paParms         Array of parameters.
+ */
+int GstCtrlService::clientMsgOldGet(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    ASSERT_GUEST(pClient->m_idSession != UINT32_MAX || pClient->m_fIsMaster || pClient->m_fRestored);
+
+    /* Use the current (inbound) connection. */
+    ClientRequest thisCon;
+    thisCon.mHandle   = hCall;
+    thisCon.mNumParms = cParms;
+    thisCon.mParms    = paParms;
+
+    return pClient->OldRunCurrent(&thisCon);
+}
+
+
+/**
+ * Implements GUEST_MAKE_ME_MASTER.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success (we complete the message here).
+ * @retval  VERR_ACCESS_DENIED if not using main VBoxGuest device not
+ * @retval  VERR_RESOURCE_BUSY if there is already a master.
+ * @retval  VERR_VERSION_MISMATCH if VBoxGuest didn't supply requestor info.
+ * @retval  VERR_WRONG_PARAMETER_COUNT
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The client's call handle.
+ * @param   cParms      Number of parameters.
+ */
+int GstCtrlService::clientMakeMeMaster(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms)
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_RETURN(cParms == 0, VERR_WRONG_PARAMETER_COUNT);
+
+    uint32_t fRequestor = mpHelpers->pfnGetRequestor(hCall);
+    /* The next assertion triggers upgrading GAs on some linux guests. Problem is that VBoxService is
+       restarted after installation but the kernel module hasn't been reloaded, so things are out
+       of wack.  Just reboot. */
+    ASSERT_GUEST_LOGREL_MSG_RETURN(fRequestor != VMMDEV_REQUESTOR_LEGACY,
+                                   ("Guest is using outdated VBoxGuest w/o requestor support.\n"
+                                    "Please update guest additions (or restart guest if you just did)!\n"),
+                                   VERR_VERSION_MISMATCH);
+    ASSERT_GUEST_LOGREL_MSG_RETURN(!(fRequestor & VMMDEV_REQUESTOR_USER_DEVICE), ("fRequestor=%#x\n", fRequestor),
+                                   VERR_ACCESS_DENIED);
+
+    /*
+     * Do the work.
+     */
+    ASSERT_GUEST_MSG_RETURN(m_idMasterClient == pClient->m_idClient || m_idMasterClient == UINT32_MAX,
+                            ("Already have master session %RU32, refusing %RU32.\n", m_idMasterClient, pClient->m_idClient),
+                            VERR_RESOURCE_BUSY);
+    int rc = mpHelpers->pfnCallComplete(hCall, VINF_SUCCESS);
+    if (RT_SUCCESS(rc))
+    {
+        m_pMasterClient  = pClient;
+        m_idMasterClient = pClient->m_idClient;
+        m_fLegacyMode    = false;
+        pClient->m_fIsMaster = true;
+        Log(("[Client %RU32] is master.\n", pClient->m_idClient));
+    }
+    else
+        LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+
+    return VINF_HGCM_ASYNC_EXECUTE;
+}
+
+
+/**
+ * Implements GUEST_MSG_REPORT_FEATURES.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success (we complete the message here).
+ * @retval  VERR_ACCESS_DENIED if not master
+ * @retval  VERR_INVALID_PARAMETER if bit 63 in the 2nd parameter isn't set.
+ * @retval  VERR_WRONG_PARAMETER_COUNT
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The client's call handle.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ */
+int GstCtrlService::clientReportFeatures(ClientState *pClient, VBOXHGCMCALLHANDLE hCall,
+                                         uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_RETURN(cParms == 2, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint64_t const fFeatures0 = paParms[0].u.uint64;
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint64_t const fFeatures1 = paParms[1].u.uint64;
+    ASSERT_GUEST_RETURN(fFeatures1 & VBOX_GUESTCTRL_GF_1_MUST_BE_ONE, VERR_INVALID_PARAMETER);
+
+    ASSERT_GUEST_RETURN(pClient->m_fIsMaster, VERR_ACCESS_DENIED);
+
+    /*
+     * Do the work.
+     */
+    VBOXHGCMSVCPARM aCopyForMain[2] = { paParms[0], paParms[1] };
+
+    paParms[0].u.uint64 = g_fGstCtrlHostFeatures0;
+    paParms[1].u.uint64 = 0;
+
+    int rc = mpHelpers->pfnCallComplete(hCall, VINF_SUCCESS);
+    if (RT_SUCCESS(rc))
+    {
+        m_fGuestFeatures0 = fFeatures0;
+        m_fGuestFeatures1 = fFeatures1;
+        Log(("[Client %RU32] reported features: %#RX64 %#RX64\n", pClient->m_idClient, fFeatures0, fFeatures1));
+
+        /*
+         * Forward the info to main.
+         */
+        hostCallback(GUEST_MSG_REPORT_FEATURES, RT_ELEMENTS(aCopyForMain), aCopyForMain);
+    }
+    else
+        LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+
+    return VINF_HGCM_ASYNC_EXECUTE;
+}
+
+
+/**
+ * Implements GUEST_MSG_QUERY_FEATURES.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success (we complete the message here).
+ * @retval  VERR_WRONG_PARAMETER_COUNT
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The client's call handle.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ */
+int GstCtrlService::clientQueryFeatures(ClientState *pClient,
+                                        VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    RT_NOREF(pClient);
+
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_RETURN(cParms == 2, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    ASSERT_GUEST(paParms[1].u.uint64 & RT_BIT_64(63));
+
+    /*
+     * Do the work.
+     */
+    paParms[0].u.uint64 = g_fGstCtrlHostFeatures0;
+    paParms[1].u.uint64 = 0;
+    int rc = mpHelpers->pfnCallComplete(hCall, VINF_SUCCESS);
+    if (RT_SUCCESS(rc))
+    {
+        Log(("[Client %RU32] query features: %#RX64 0\n", pClient->m_idClient, g_fGstCtrlHostFeatures0));
+    }
+    else
+        LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+
+    return VINF_HGCM_ASYNC_EXECUTE;
+}
+
+
+/**
+ * Implements GUEST_MSG_PEEK_WAIT and GUEST_MSG_PEEK_NOWAIT.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_SUCCESS if a message was pending and is being returned.
+ * @retval  VERR_TRY_AGAIN if no message pending and not blocking.
+ * @retval  VERR_RESOURCE_BUSY if another read already made a waiting call.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE if message wait is pending.
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The client's call handle.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ * @param   fWait       Set if we should wait for a message, clear if to return
+ *                      immediately.
+ */
+int GstCtrlService::clientMsgPeek(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[], bool fWait)
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_MSG_RETURN(cParms >= 2, ("cParms=%u!\n", cParms), VERR_WRONG_PARAMETER_COUNT);
+
+    uint64_t idRestoreCheck = 0;
+    uint32_t i              = 0;
+    if (paParms[i].type == VBOX_HGCM_SVC_PARM_64BIT)
+    {
+        idRestoreCheck = paParms[0].u.uint64;
+        paParms[0].u.uint64 = 0;
+        i++;
+    }
+    for (; i < cParms; i++)
+    {
+        ASSERT_GUEST_MSG_RETURN(paParms[i].type == VBOX_HGCM_SVC_PARM_32BIT, ("#%u type=%u\n", i, paParms[i].type),
+                                VERR_WRONG_PARAMETER_TYPE);
+        paParms[i].u.uint32 = 0;
+    }
+
+    /*
+     * Check restore session ID.
+     */
+    if (idRestoreCheck != 0)
+    {
+        uint64_t idRestore = mpHelpers->pfnGetVMMDevSessionId(mpHelpers);
+        if (idRestoreCheck != idRestore)
+        {
+            paParms[0].u.uint64 = idRestore;
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_PEEK_XXXX -> VERR_VM_RESTORED (%#RX64 -> %#RX64)\n",
+                         pClient->m_idClient, idRestoreCheck, idRestore));
+            return VERR_VM_RESTORED;
+        }
+        Assert(!mpHelpers->pfnIsCallRestored(hCall));
+    }
+
+    /*
+     * Return information about the first message if one is pending in the list.
+     */
+    HostMsg *pFirstMsg = RTListGetFirstCpp(&pClient->m_HostMsgList, HostMsg, m_ListEntry);
+    if (pFirstMsg)
+    {
+        pFirstMsg->setPeekReturn(paParms, cParms);
+        LogFlowFunc(("[Client %RU32] GUEST_MSG_PEEK_XXXX -> VINF_SUCCESS (idMsg=%u (%s), cParms=%u)\n",
+                     pClient->m_idClient, pFirstMsg->mType, GstCtrlHostMsgtoStr((eHostMsg)pFirstMsg->mType), pFirstMsg->mParmCount));
+        return VINF_SUCCESS;
+    }
+
+    /*
+     * If we cannot wait, fail the call.
+     */
+    if (!fWait)
+    {
+        LogFlowFunc(("[Client %RU32] GUEST_MSG_PEEK_NOWAIT -> VERR_TRY_AGAIN\n", pClient->m_idClient));
+        return VERR_TRY_AGAIN;
+    }
+
+    /*
+     * Wait for the host to queue a message for this client.
+     */
+    ASSERT_GUEST_MSG_RETURN(pClient->m_enmPendingMsg == 0, ("Already pending! (idClient=%RU32)\n", pClient->m_idClient),
+                            VERR_RESOURCE_BUSY);
+    pClient->m_PendingReq.mHandle   = hCall;
+    pClient->m_PendingReq.mNumParms = cParms;
+    pClient->m_PendingReq.mParms    = paParms;
+    pClient->m_enmPendingMsg         = GUEST_MSG_PEEK_WAIT;
+    LogFlowFunc(("[Client %RU32] Is now in pending mode...\n", pClient->m_idClient));
+    return VINF_HGCM_ASYNC_EXECUTE;
+}
+
+/**
+ * Implements GUEST_MSG_GET.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_SUCCESS if message retrieved and removed from the pending queue.
+ * @retval  VERR_TRY_AGAIN if no message pending.
+ * @retval  VERR_BUFFER_OVERFLOW if a parmeter buffer is too small.  The buffer
+ *          size was updated to reflect the required size, though this isn't yet
+ *          forwarded to the guest.  (The guest is better of using peek with
+ *          parameter count + 2 parameters to get the sizes.)
+ * @retval  VERR_MISMATCH if the incoming message ID does not match the pending.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE if message was completed already.
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The client's call handle.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ */
+int GstCtrlService::clientMsgGet(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate the request.
+     *
+     * The weird first parameter logic is due to GUEST_MSG_WAIT compatibility
+     * (don't want to rewrite all the message structures).
+     */
+    uint32_t const idMsgExpected = cParms > 0 && paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT ? paParms[0].u.uint32
+                                 : cParms > 0 && paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT ? paParms[0].u.uint64
+                                 : UINT32_MAX;
+
+    /*
+     * Return information about the first message if one is pending in the list.
+     */
+    HostMsg *pFirstMsg = RTListGetFirstCpp(&pClient->m_HostMsgList, HostMsg, m_ListEntry);
+    if (pFirstMsg)
+    {
+
+        ASSERT_GUEST_MSG_RETURN(pFirstMsg->mType == idMsgExpected || idMsgExpected == UINT32_MAX,
+                                ("idMsg=%u (%s) cParms=%u, caller expected %u (%s) and %u\n",
+                                 pFirstMsg->mType, GstCtrlHostMsgtoStr((eHostMsg)pFirstMsg->mType), pFirstMsg->mParmCount,
+                                 idMsgExpected, GstCtrlHostMsgtoStr((eHostMsg)idMsgExpected), cParms),
+                                VERR_MISMATCH);
+        ASSERT_GUEST_MSG_RETURN(pFirstMsg->mParmCount == cParms,
+                                ("idMsg=%u (%s) cParms=%u, caller expected %u (%s) and %u\n",
+                                 pFirstMsg->mType, GstCtrlHostMsgtoStr((eHostMsg)pFirstMsg->mType), pFirstMsg->mParmCount,
+                                 idMsgExpected, GstCtrlHostMsgtoStr((eHostMsg)idMsgExpected), cParms),
+                                VERR_WRONG_PARAMETER_COUNT);
+
+        /* Check the parameter types. */
+        for (uint32_t i = 0; i < cParms; i++)
+            ASSERT_GUEST_MSG_RETURN(pFirstMsg->mpParms[i].type == paParms[i].type,
+                                    ("param #%u: type %u, caller expected %u (idMsg=%u %s)\n", i, pFirstMsg->mpParms[i].type,
+                                     paParms[i].type, pFirstMsg->mType, GstCtrlHostMsgtoStr((eHostMsg)pFirstMsg->mType)),
+                                    VERR_WRONG_PARAMETER_TYPE);
+
+        /*
+         * Copy out the parameters.
+         *
+         * No assertions on buffer overflows, and keep going till the end so we can
+         * communicate all the required buffer sizes.
+         */
+        int rc = VINF_SUCCESS;
+        for (uint32_t i = 0; i < cParms; i++)
+            switch (pFirstMsg->mpParms[i].type)
+            {
+                case VBOX_HGCM_SVC_PARM_32BIT:
+                    paParms[i].u.uint32 = pFirstMsg->mpParms[i].u.uint32;
+                    break;
+
+                case VBOX_HGCM_SVC_PARM_64BIT:
+                    paParms[i].u.uint64 = pFirstMsg->mpParms[i].u.uint64;
+                    break;
+
+                case VBOX_HGCM_SVC_PARM_PTR:
+                {
+                    uint32_t const cbSrc = pFirstMsg->mpParms[i].u.pointer.size;
+                    uint32_t const cbDst = paParms[i].u.pointer.size;
+                    paParms[i].u.pointer.size = cbSrc; /** @todo Check if this is safe in other layers...
+                                                        * Update: Safe, yes, but VMMDevHGCM doesn't pass it along. */
+                    if (cbSrc <= cbDst)
+                        memcpy(paParms[i].u.pointer.addr, pFirstMsg->mpParms[i].u.pointer.addr, cbSrc);
+                    else
+                        rc = VERR_BUFFER_OVERFLOW;
+                    break;
+                }
+
+                default:
+                    AssertMsgFailed(("#%u: %u\n", i, pFirstMsg->mpParms[i].type));
+                    rc = VERR_INTERNAL_ERROR;
+                    break;
+            }
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Complete the message and remove the pending message unless the
+             * guest raced us and cancelled this call in the meantime.
+             */
+            AssertPtr(mpHelpers);
+            rc = mpHelpers->pfnCallComplete(hCall, rc);
+            if (rc != VERR_CANCELLED)
+            {
+                RTListNodeRemove(&pFirstMsg->m_ListEntry);
+                pFirstMsg->Delete();
+            }
+            else
+                LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+            return VINF_HGCM_ASYNC_EXECUTE; /* The caller must not complete it. */
+        }
+        return rc;
+    }
+
+    paParms[0].u.uint32 = 0;
+    paParms[1].u.uint32 = 0;
+    LogFlowFunc(("[Client %RU32] GUEST_MSG_GET -> VERR_TRY_AGAIN\n", pClient->m_idClient));
+    return VERR_TRY_AGAIN;
+}
+
+/**
+ * Implements GUEST_MSG_CANCEL.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_SUCCESS if cancelled any calls.
+ * @retval  VWRN_NOT_FOUND if no callers.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE if message wait is pending.
+ *
+ * @param   pClient     The client state.
+ * @param   cParms      Number of parameters.
+ */
+int GstCtrlService::clientMsgCancel(ClientState *pClient, uint32_t cParms)
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_MSG_RETURN(cParms == 0, ("cParms=%u!\n", cParms), VERR_WRONG_PARAMETER_COUNT);
+
+    /*
+     * Execute.
+     */
+    if (pClient->m_enmPendingMsg != 0)
+    {
+        pClient->CancelWaiting();
+        return VINF_SUCCESS;
+    }
+    return VWRN_NOT_FOUND;
+}
+
+
+/**
+ * Implements GUEST_MSG_SKIP.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success as we complete the message.
+ * @retval  VERR_NOT_FOUND if no message pending.
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The call handle for completing it.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     The parameters.
+ */
+int GstCtrlService::clientMsgSkip(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate the call.
+     */
+    ASSERT_GUEST_RETURN(cParms <= 2, VERR_WRONG_PARAMETER_COUNT);
+
+    int32_t rcSkip = VERR_NOT_SUPPORTED;
+    if (cParms >= 1)
+    {
+        ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+        rcSkip = (int32_t)paParms[0].u.uint32;
+    }
+
+    uint32_t idMsg = UINT32_MAX;
+    if (cParms >= 2)
+    {
+        ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+        idMsg = paParms[1].u.uint32;
+    }
+
+    /*
+     * Do the job.
+     */
+    HostMsg *pFirstMsg = RTListGetFirstCpp(&pClient->m_HostMsgList, HostMsg, m_ListEntry);
+    if (pFirstMsg)
+    {
+        if (   pFirstMsg->mType == idMsg
+            || idMsg == UINT32_MAX)
+        {
+            int rc = mpHelpers->pfnCallComplete(hCall, VINF_SUCCESS);
+            if (RT_SUCCESS(rc))
+            {
+                /*
+                 * Remove the message from the queue.
+                 */
+                Assert(RTListNodeIsFirst(&pClient->m_HostMsgList, &pFirstMsg->m_ListEntry) );
+                RTListNodeRemove(&pFirstMsg->m_ListEntry);
+
+                /*
+                 * Compose a reply to the host service.
+                 */
+                VBOXHGCMSVCPARM aReplyParams[5];
+                HGCMSvcSetU32(&aReplyParams[0], pFirstMsg->m_idContext);
+                switch (pFirstMsg->mType)
+                {
+                    case HOST_MSG_EXEC_CMD:
+                        HGCMSvcSetU32(&aReplyParams[1], 0);              /* pid */
+                        HGCMSvcSetU32(&aReplyParams[2], PROC_STS_ERROR); /* status */
+                        HGCMSvcSetU32(&aReplyParams[3], rcSkip);         /* flags / whatever */
+                        HGCMSvcSetPv(&aReplyParams[4], NULL, 0);         /* data buffer */
+                        hostCallback(GUEST_MSG_EXEC_STATUS, 5, aReplyParams);
+                        break;
+
+                    case HOST_MSG_SESSION_CREATE:
+                        HGCMSvcSetU32(&aReplyParams[1], GUEST_SESSION_NOTIFYTYPE_ERROR);    /* type */
+                        HGCMSvcSetU32(&aReplyParams[2], rcSkip);                            /* result */
+                        hostCallback(GUEST_MSG_SESSION_NOTIFY, 3, aReplyParams);
+                        break;
+
+                    case HOST_MSG_EXEC_SET_INPUT:
+                        HGCMSvcSetU32(&aReplyParams[1], pFirstMsg->mParmCount >= 2 ? pFirstMsg->mpParms[1].u.uint32 : 0);
+                        HGCMSvcSetU32(&aReplyParams[2], INPUT_STS_ERROR);   /* status */
+                        HGCMSvcSetU32(&aReplyParams[3], rcSkip);            /* flags / whatever */
+                        HGCMSvcSetU32(&aReplyParams[4], 0);                 /* bytes consumed */
+                        hostCallback(GUEST_MSG_EXEC_INPUT_STATUS, 5, aReplyParams);
+                        break;
+
+                    case HOST_MSG_FILE_OPEN:
+                        HGCMSvcSetU32(&aReplyParams[1], GUEST_FILE_NOTIFYTYPE_OPEN); /* type*/
+                        HGCMSvcSetU32(&aReplyParams[2], rcSkip);                     /* rc */
+                        HGCMSvcSetU32(&aReplyParams[3], VBOX_GUESTCTRL_CONTEXTID_GET_OBJECT(pFirstMsg->m_idContext)); /* handle */
+                        hostCallback(GUEST_MSG_FILE_NOTIFY, 4, aReplyParams);
+                        break;
+                    case HOST_MSG_FILE_CLOSE:
+                        HGCMSvcSetU32(&aReplyParams[1], GUEST_FILE_NOTIFYTYPE_ERROR); /* type*/
+                        HGCMSvcSetU32(&aReplyParams[2], rcSkip);                      /* rc */
+                        hostCallback(GUEST_MSG_FILE_NOTIFY, 3, aReplyParams);
+                        break;
+                    case HOST_MSG_FILE_READ:
+                    case HOST_MSG_FILE_READ_AT:
+                        HGCMSvcSetU32(&aReplyParams[1], GUEST_FILE_NOTIFYTYPE_READ);  /* type */
+                        HGCMSvcSetU32(&aReplyParams[2], rcSkip);                      /* rc */
+                        HGCMSvcSetPv(&aReplyParams[3], NULL, 0);                      /* data buffer */
+                        hostCallback(GUEST_MSG_FILE_NOTIFY, 4, aReplyParams);
+                        break;
+                    case HOST_MSG_FILE_WRITE:
+                    case HOST_MSG_FILE_WRITE_AT:
+                        HGCMSvcSetU32(&aReplyParams[1], GUEST_FILE_NOTIFYTYPE_WRITE); /* type */
+                        HGCMSvcSetU32(&aReplyParams[2], rcSkip);                      /* rc */
+                        HGCMSvcSetU32(&aReplyParams[3], 0);                           /* bytes written */
+                        hostCallback(GUEST_MSG_FILE_NOTIFY, 4, aReplyParams);
+                        break;
+                    case HOST_MSG_FILE_SEEK:
+                        HGCMSvcSetU32(&aReplyParams[1], GUEST_FILE_NOTIFYTYPE_SEEK);  /* type */
+                        HGCMSvcSetU32(&aReplyParams[2], rcSkip);                      /* rc */
+                        HGCMSvcSetU64(&aReplyParams[3], 0);                           /* actual */
+                        hostCallback(GUEST_MSG_FILE_NOTIFY, 4, aReplyParams);
+                        break;
+                    case HOST_MSG_FILE_TELL:
+                        HGCMSvcSetU32(&aReplyParams[1], GUEST_FILE_NOTIFYTYPE_TELL);  /* type */
+                        HGCMSvcSetU32(&aReplyParams[2], rcSkip);                      /* rc */
+                        HGCMSvcSetU64(&aReplyParams[3], 0);                           /* actual */
+                        hostCallback(GUEST_MSG_FILE_NOTIFY, 4, aReplyParams);
+                        break;
+                    case HOST_MSG_FILE_SET_SIZE:
+                        HGCMSvcSetU32(&aReplyParams[1], GUEST_FILE_NOTIFYTYPE_SET_SIZE); /* type */
+                        HGCMSvcSetU32(&aReplyParams[2], rcSkip);                         /* rc */
+                        HGCMSvcSetU64(&aReplyParams[3], 0);                              /* actual */
+                        hostCallback(GUEST_MSG_FILE_NOTIFY, 4, aReplyParams);
+                        break;
+
+                    case HOST_MSG_EXEC_GET_OUTPUT: /** @todo This can't be right/work. */
+                    case HOST_MSG_EXEC_TERMINATE:  /** @todo This can't be right/work. */
+                    case HOST_MSG_EXEC_WAIT_FOR:   /** @todo This can't be right/work. */
+                    case HOST_MSG_PATH_USER_DOCUMENTS:
+                    case HOST_MSG_PATH_USER_HOME:
+                    case HOST_MSG_PATH_RENAME:
+                    case HOST_MSG_DIR_REMOVE:
+                    default:
+                        HGCMSvcSetU32(&aReplyParams[1], pFirstMsg->mType);
+                        HGCMSvcSetU32(&aReplyParams[2], (uint32_t)rcSkip);
+                        HGCMSvcSetPv(&aReplyParams[3], NULL, 0);
+                        hostCallback(GUEST_MSG_REPLY, 4, aReplyParams);
+                        break;
+                }
+
+                /*
+                 * Free the message.
+                 */
+                pFirstMsg->Delete();
+            }
+            else
+                LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+            return VINF_HGCM_ASYNC_EXECUTE; /* The caller must not complete it. */
+        }
+        LogFunc(("Warning: GUEST_MSG_SKIP mismatch! Found %u, caller expected %u!\n", pFirstMsg->mType, idMsg));
+        return VERR_MISMATCH;
+    }
+    return VERR_NOT_FOUND;
+}
+
+
+/**
+ * Implements GUEST_SESSION_PREPARE.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success as we complete the message.
+ * @retval  VERR_OUT_OF_RESOURCES if too many pending sessions hanging around.
+ * @retval  VERR_OUT_OF_RANGE if the session ID outside the allowed range.
+ * @retval  VERR_BUFFER_OVERFLOW if key too large.
+ * @retval  VERR_BUFFER_UNDERFLOW if key too small.
+ * @retval  VERR_ACCESS_DENIED if not master or in legacy mode.
+ * @retval  VERR_DUPLICATE if the session ID has been prepared already.
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The call handle for completing it.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     The parameters.
+ */
+int GstCtrlService::clientSessionPrepare(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate parameters.
+     */
+    ASSERT_GUEST_RETURN(cParms == 2, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const idSession = paParms[0].u.uint32;
+    ASSERT_GUEST_RETURN(idSession >= 1, VERR_OUT_OF_RANGE);
+    ASSERT_GUEST_RETURN(idSession <= 0xfff0, VERR_OUT_OF_RANGE);
+
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_PTR, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const cbKey = paParms[1].u.pointer.size;
+    void const    *pvKey = paParms[1].u.pointer.addr;
+    ASSERT_GUEST_RETURN(cbKey >= 64, VERR_BUFFER_UNDERFLOW);
+    ASSERT_GUEST_RETURN(cbKey <= _16K, VERR_BUFFER_OVERFLOW);
+
+    ASSERT_GUEST_RETURN(pClient->m_fIsMaster, VERR_ACCESS_DENIED);
+    ASSERT_GUEST_RETURN(!m_fLegacyMode, VERR_ACCESS_DENIED);
+    Assert(m_idMasterClient == pClient->m_idClient);
+    Assert(m_pMasterClient == pClient);
+
+    /* Now that we know it's the master, we can check for session ID duplicates. */
+    GstCtrlPreparedSession *pCur;
+    RTListForEach(&m_PreparedSessions, pCur, GstCtrlPreparedSession, ListEntry)
+    {
+        ASSERT_GUEST_RETURN(pCur->idSession != idSession, VERR_DUPLICATE);
+    }
+
+    /*
+     * Make a copy of the session ID and key.
+     */
+    ASSERT_GUEST_RETURN(m_cPreparedSessions < 128, VERR_OUT_OF_RESOURCES);
+
+    GstCtrlPreparedSession *pPrepped = (GstCtrlPreparedSession *)RTMemAlloc(RT_UOFFSETOF_DYN(GstCtrlPreparedSession, abKey[cbKey]));
+    AssertReturn(pPrepped, VERR_NO_MEMORY);
+    pPrepped->idSession = idSession;
+    pPrepped->cbKey     = cbKey;
+    memcpy(pPrepped->abKey, pvKey, cbKey);
+
+    RTListAppend(&m_PreparedSessions, &pPrepped->ListEntry);
+    m_cPreparedSessions++;
+
+    /*
+     * Try complete the message.
+     */
+    int rc = mpHelpers->pfnCallComplete(hCall, VINF_SUCCESS);
+    if (RT_SUCCESS(rc))
+        LogFlow(("Prepared %u with a %#x byte key (%u pending).\n", idSession, cbKey, m_cPreparedSessions));
+    else
+    {
+        LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+        RTListNodeRemove(&pPrepped->ListEntry);
+        RTMemFree(pPrepped);
+        m_cPreparedSessions--;
+    }
+    return VINF_HGCM_ASYNC_EXECUTE; /* The caller must not complete it. */
+}
+
+
+/**
+ * Implements GUEST_SESSION_CANCEL_PREPARED.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success as we complete the message.
+ * @retval  VWRN_NOT_FOUND if no session with the specified ID.
+ * @retval  VERR_ACCESS_DENIED if not master or in legacy mode.
+ *
+ * @param   pClient     The client state.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     The parameters.
+ */
+int GstCtrlService::clientSessionCancelPrepared(ClientState *pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate parameters.
+     */
+    ASSERT_GUEST_RETURN(cParms == 1, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const idSession = paParms[0].u.uint32;
+
+    ASSERT_GUEST_RETURN(pClient->m_fIsMaster, VERR_ACCESS_DENIED);
+    ASSERT_GUEST_RETURN(!m_fLegacyMode, VERR_ACCESS_DENIED);
+    Assert(m_idMasterClient == pClient->m_idClient);
+    Assert(m_pMasterClient == pClient);
+
+    /*
+     * Do the work.
+     */
+    int rc = VWRN_NOT_FOUND;
+    if (idSession == UINT32_MAX)
+    {
+        GstCtrlPreparedSession *pCur, *pNext;
+        RTListForEachSafe(&m_PreparedSessions, pCur, pNext, GstCtrlPreparedSession, ListEntry)
+        {
+            RTListNodeRemove(&pCur->ListEntry);
+            RTMemFree(pCur);
+            rc = VINF_SUCCESS;
+        }
+        m_cPreparedSessions = 0;
+    }
+    else
+    {
+        GstCtrlPreparedSession *pCur, *pNext;
+        RTListForEachSafe(&m_PreparedSessions, pCur, pNext, GstCtrlPreparedSession, ListEntry)
+        {
+            if (pCur->idSession == idSession)
+            {
+                RTListNodeRemove(&pCur->ListEntry);
+                RTMemFree(pCur);
+                m_cPreparedSessions -= 1;
+                rc = VINF_SUCCESS;
+                break;
+            }
+        }
+    }
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * Implements GUEST_SESSION_ACCEPT.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success as we complete the message.
+ * @retval  VERR_NOT_FOUND if the specified session ID wasn't found.
+ * @retval  VERR_MISMATCH if the key didn't match.
+ * @retval  VERR_ACCESS_DENIED if we're in legacy mode or is master.
+ * @retval  VERR_RESOURCE_BUSY if the client is already associated with a
+ *          session.
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The call handle for completing it.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     The parameters.
+ */
+int GstCtrlService::clientSessionAccept(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate parameters.
+     */
+    ASSERT_GUEST_RETURN(cParms == 2, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const idSession = paParms[0].u.uint32;
+    ASSERT_GUEST_RETURN(idSession >= 1, VERR_OUT_OF_RANGE);
+    ASSERT_GUEST_RETURN(idSession <= 0xfff0, VERR_OUT_OF_RANGE);
+
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_PTR, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const cbKey = paParms[1].u.pointer.size;
+    void const    *pvKey = paParms[1].u.pointer.addr;
+    ASSERT_GUEST_RETURN(cbKey >= 64, VERR_BUFFER_UNDERFLOW);
+    ASSERT_GUEST_RETURN(cbKey <= _16K, VERR_BUFFER_OVERFLOW);
+
+    ASSERT_GUEST_RETURN(!pClient->m_fIsMaster, VERR_ACCESS_DENIED);
+    ASSERT_GUEST_RETURN(!m_fLegacyMode, VERR_ACCESS_DENIED);
+    Assert(m_idMasterClient != pClient->m_idClient);
+    Assert(m_pMasterClient != pClient);
+    ASSERT_GUEST_RETURN(pClient->m_idSession == UINT32_MAX, VERR_RESOURCE_BUSY);
+
+    /*
+     * Look for the specified session and match the key to it.
+     */
+    GstCtrlPreparedSession *pCur;
+    RTListForEach(&m_PreparedSessions, pCur, GstCtrlPreparedSession, ListEntry)
+    {
+        if (pCur->idSession == idSession)
+        {
+            if (   pCur->cbKey == cbKey
+                && memcmp(pCur->abKey, pvKey, cbKey) == 0)
+            {
+                /*
+                 * We've got a match.
+                 * Try insert it into the sessio ID map and complete the request.
+                 */
+                try
+                {
+                    m_SessionIdMap[idSession] = pClient;
+                }
+                catch (std::bad_alloc &)
+                {
+                    LogFunc(("Out of memory!\n"));
+                    return VERR_NO_MEMORY;
+                }
+
+                int rc = mpHelpers->pfnCallComplete(hCall, VINF_SUCCESS);
+                if (RT_SUCCESS(rc))
+                {
+                    pClient->m_idSession = idSession;
+
+                    RTListNodeRemove(&pCur->ListEntry);
+                    RTMemFree(pCur);
+                    m_cPreparedSessions -= 1;
+                    Log(("[Client %RU32] accepted session id %u.\n", pClient->m_idClient, idSession));
+                }
+                else
+                {
+                    LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+                    m_SessionIdMap.erase(idSession);
+                }
+                return VINF_HGCM_ASYNC_EXECUTE; /* The caller must not complete it. */
+            }
+            LogFunc(("Key mismatch for %u!\n", pClient->m_idClient));
+            return VERR_MISMATCH;
+        }
+    }
+
+    LogFunc(("No client prepared for %u!\n", pClient->m_idClient));
+    return VERR_NOT_FOUND;
+}
+
+
+/**
+ * Client asks another client (guest) session to close.
+ *
+ * @returns VBox status code.
+ * @param   pClient         The client state.
+ * @param   cParms          Number of parameters.
+ * @param   paParms         Array of parameters.
+ */
+int GstCtrlService::clientSessionCloseOther(ClientState *pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate input.
+     */
+    ASSERT_GUEST_RETURN(cParms == 2, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const idContext = paParms[0].u.uint32;
+
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const fFlags = paParms[1].u.uint32;
+
+    ASSERT_GUEST_RETURN(pClient->m_fIsMaster || (m_fLegacyMode && pClient->m_idSession == UINT32_MAX), VERR_ACCESS_DENIED);
+
+    /*
+     * Forward the message to the destiation.
+     * Since we modify the first parameter, we must make a copy of the parameters.
+     */
+    VBOXHGCMSVCPARM aParms[2];
+    HGCMSvcSetU64(&aParms[0], idContext | VBOX_GUESTCTRL_DST_SESSION);
+    HGCMSvcSetU32(&aParms[1], fFlags);
+    int rc = hostProcessMessage(HOST_MSG_SESSION_CLOSE, RT_ELEMENTS(aParms), aParms);
+
+    LogFlowFunc(("Closing guest context ID=%RU32 (from client ID=%RU32) returned with rc=%Rrc\n", idContext, pClient->m_idClient, rc));
+    return rc;
+}
+
+
+/**
+ * For compatiblity with old additions only - filtering / set session ID.
+ *
+ * @return  VBox status code.
+ * @param   pClient     The client state.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ */
+int GstCtrlService::clientMsgOldFilterSet(ClientState *pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate input and access.
+     */
+    ASSERT_GUEST_RETURN(cParms == 4, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t uValue = paParms[0].u.uint32;
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t fMaskAdd = paParms[1].u.uint32;
+    ASSERT_GUEST_RETURN(paParms[2].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t fMaskRemove = paParms[2].u.uint32;
+    ASSERT_GUEST_RETURN(paParms[3].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE); /* flags, unused */
+
+    /*
+     * We have a bunch of expectations here:
+     *  - Never called in non-legacy mode.
+     *  - Only called once per session.
+     *  - Never called by the master session.
+     *  - Clients that doesn't wish for any messages passes all zeros.
+     *  - All other calls has a unique session ID.
+     */
+    ASSERT_GUEST_LOGREL_RETURN(m_fLegacyMode, VERR_WRONG_ORDER);
+    ASSERT_GUEST_LOGREL_MSG_RETURN(pClient->m_idSession == UINT32_MAX, ("m_idSession=%#x\n", pClient->m_idSession),
+                                   VERR_WRONG_ORDER);
+    ASSERT_GUEST_LOGREL_RETURN(!pClient->m_fIsMaster, VERR_WRONG_ORDER);
+
+    if (uValue == 0)
+    {
+        ASSERT_GUEST_LOGREL(fMaskAdd == 0);
+        ASSERT_GUEST_LOGREL(fMaskRemove == 0);
+        /* Nothing to do, already muted (UINT32_MAX). */
+    }
+    else
+    {
+        ASSERT_GUEST_LOGREL(fMaskAdd == UINT32_C(0xf8000000));
+        ASSERT_GUEST_LOGREL(fMaskRemove == 0);
+
+        uint32_t idSession = VBOX_GUESTCTRL_CONTEXTID_GET_SESSION(uValue);
+        ASSERT_GUEST_LOGREL_MSG_RETURN(idSession > 0, ("idSession=%u (%#x)\n", idSession, uValue), VERR_OUT_OF_RANGE);
+
+        ClientStateMap::iterator ItConflict = m_SessionIdMap.find(idSession);
+        ASSERT_GUEST_LOGREL_MSG_RETURN(ItConflict == m_SessionIdMap.end(),
+                                       ("idSession=%u uValue=%#x idClient=%u; conflicting with client %u\n",
+                                        idSession, uValue, pClient->m_idClient, ItConflict->second->m_idClient),
+                                       VERR_DUPLICATE);
+
+        /* Commit it. */
+        try
+        {
+            m_SessionIdMap[idSession] = pClient;
+        }
+        catch (std::bad_alloc &)
+        {
+            LogFunc(("Out of memory\n"));
+            return VERR_NO_MEMORY;
+        }
+        pClient->m_idSession = idSession;
+    }
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * For compatibility with old additions only - skip the current message w/o
+ * calling main code.
+ *
+ * Please note that we don't care if the caller cancelled the request, because
+ * old additions code didn't give damn about VERR_INTERRUPT.
+ *
+ * @return  VBox status code.
+ * @param   pClient     The client state.
+ * @param   hCall       The call handle for completing it.
+ * @param   cParms      Number of parameters.
+ */
+int GstCtrlService::clientMsgOldSkip(ClientState *pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms)
+{
+    /*
+     * Validate input and access.
+     */
+    ASSERT_GUEST_RETURN(cParms == 1, VERR_WRONG_PARAMETER_COUNT);
+
+    /*
+     * Execute the request.
+     *
+     * Note! As it turns out the old and new skip should be mostly the same.  The
+     *       pre-6.0 GAs (up to BETA3) has a hack which tries to issue a
+     *       VERR_NOT_SUPPORTED reply to unknown host requests, however the 5.2.x
+     *       and earlier GAs doesn't.  We need old skip behavior only for the 6.0
+     *       beta GAs, nothing else.
+     *       So, we have to track whether they issued a MSG_REPLY or not.  Wonderful.
+     */
+    HostMsg *pFirstMsg = RTListGetFirstCpp(&pClient->m_HostMsgList, HostMsg, m_ListEntry);
+    if (pFirstMsg)
+    {
+        uint32_t const idMsg             = pFirstMsg->mType;
+        bool const     f60BetaHackInPlay = pFirstMsg->m_f60BetaHackInPlay;
+        int            rc;
+        if (!f60BetaHackInPlay)
+            rc = clientMsgSkip(pClient, hCall, 0, NULL);
+        else
+        {
+            RTListNodeRemove(&pFirstMsg->m_ListEntry);
+            pFirstMsg->Delete();
+            rc = VINF_SUCCESS;
+        }
+
+        /* Reset legacy message wait/get state: */
+        if (RT_SUCCESS(rc))
+        {
+            pClient->mHostMsgRc    = VINF_SUCCESS;
+            pClient->mHostMsgTries = 0;
+            pClient->mPeekCount    = 0;
+        }
+
+        LogFlowFunc(("[Client %RU32] Legacy message skipping: Skipped %u (%s)%s!\n",
+                     pClient->m_idClient, idMsg, GstCtrlHostMsgtoStr((eHostMsg)idMsg), f60BetaHackInPlay ? " hack style" : ""));
+        NOREF(idMsg);
+        return rc;
+    }
+    LogFlowFunc(("[Client %RU32] Legacy message skipping: No messages pending!\n", pClient->m_idClient));
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * Forwards client call to the Main API.
+ *
+ * This is typically notifications and replys.
+ *
+ * @returns VBox status code.
+ * @param   pClient         The client state.
+ * @param   idMsg           Message ID that occured.
+ * @param   cParms          Number of parameters.
+ * @param   paParms         Array of parameters.
+ */
+int GstCtrlService::clientToMain(ClientState *pClient, uint32_t idMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Do input validation.  This class of messages all have a 32-bit context ID as
+     * the first parameter, so make sure it is there and appropriate for the caller.
+     */
+    ASSERT_GUEST_RETURN(cParms >= 1, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_COUNT);
+    uint32_t const idContext = paParms[0].u.uint32;
+    uint32_t const idSession = VBOX_GUESTCTRL_CONTEXTID_GET_SESSION(idContext);
+
+    ASSERT_GUEST_MSG_RETURN(   pClient->m_idSession == idSession
+                            || pClient->m_fIsMaster
+                            || (   m_fLegacyMode                                /* (see bugref:9313#c16) */
+                                && pClient->m_idSession == UINT32_MAX
+                                && (   idMsg == GUEST_MSG_EXEC_STATUS
+                                    || idMsg == GUEST_MSG_SESSION_NOTIFY)),
+                            ("idSession=%u (CID=%#x) m_idSession=%u idClient=%u idMsg=%u (%s)\n", idSession, idContext,
+                             pClient->m_idSession, pClient->m_idClient, idMsg, GstCtrlGuestMsgToStr((eGuestMsg)idMsg)),
+                            VERR_ACCESS_DENIED);
+
+    /*
+     * It seems okay, so make the call.
+     */
+    return hostCallback(idMsg, cParms, paParms);
+}
+
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnCall}
+ *
+ * @note    All functions which do not involve an unreasonable delay will be
+ *          handled synchronously.  If needed, we will add a request handler
+ *          thread in future for those which do.
+ * @thread  HGCM
+ */
+/*static*/ DECLCALLBACK(void)
+GstCtrlService::svcCall(void *pvService, VBOXHGCMCALLHANDLE hCall, uint32_t idClient, void *pvClient,
+                        uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[], uint64_t tsArrival)
+{
+    LogFlowFunc(("[Client %RU32] u32Function=%RU32 (%s), cParms=%RU32, paParms=0x%p\n",
+                 idClient, u32Function, GstCtrlGuestMsgToStr((eGuestMsg)u32Function), cParms, paParms));
+    RT_NOREF(tsArrival, idClient);
+
+    /*
+     * Convert opaque pointers to typed ones.
+     */
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertPtrReturnVoid(pThis);
+    ClientState *pClient = reinterpret_cast<ClientState *>(pvClient);
+    AssertReturnVoidStmt(pClient, pThis->mpHelpers->pfnCallComplete(hCall, VERR_INVALID_CLIENT_ID));
+    Assert(pClient->m_idClient == idClient);
+
+    /*
+     * Do the dispatching.
+     */
+    int rc;
+    switch (u32Function)
+    {
+        case GUEST_MSG_MAKE_ME_MASTER:
+            LogFlowFunc(("[Client %RU32] GUEST_MAKE_ME_MASTER\n", idClient));
+            rc = pThis->clientMakeMeMaster(pClient, hCall, cParms);
+            break;
+        case GUEST_MSG_REPORT_FEATURES:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_REPORT_FEATURES\n", idClient));
+            rc = pThis->clientReportFeatures(pClient, hCall, cParms, paParms);
+            break;
+        case GUEST_MSG_QUERY_FEATURES:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_QUERY_FEATURES\n", idClient));
+            rc = pThis->clientQueryFeatures(pClient, hCall, cParms, paParms);
+            break;
+        case GUEST_MSG_PEEK_NOWAIT:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_PEEK_NOWAIT\n", idClient));
+            rc = pThis->clientMsgPeek(pClient, hCall, cParms, paParms, false /*fWait*/);
+            break;
+        case GUEST_MSG_PEEK_WAIT:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_PEEK_WAIT\n", idClient));
+            rc = pThis->clientMsgPeek(pClient, hCall, cParms, paParms, true /*fWait*/);
+            break;
+        case GUEST_MSG_GET:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_GET\n", idClient));
+            rc = pThis->clientMsgGet(pClient, hCall, cParms, paParms);
+            break;
+        case GUEST_MSG_CANCEL:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_CANCEL\n", idClient));
+            rc = pThis->clientMsgCancel(pClient, cParms);
+            break;
+        case GUEST_MSG_SKIP:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_SKIP\n", idClient));
+            rc = pThis->clientMsgSkip(pClient, hCall, cParms, paParms);
+            break;
+        case GUEST_MSG_SESSION_PREPARE:
+            LogFlowFunc(("[Client %RU32] GUEST_SESSION_PREPARE\n", idClient));
+            rc = pThis->clientSessionPrepare(pClient, hCall, cParms, paParms);
+            break;
+        case GUEST_MSG_SESSION_CANCEL_PREPARED:
+            LogFlowFunc(("[Client %RU32] GUEST_SESSION_CANCEL_PREPARED\n", idClient));
+            rc = pThis->clientSessionCancelPrepared(pClient, cParms, paParms);
+            break;
+        case GUEST_MSG_SESSION_ACCEPT:
+            LogFlowFunc(("[Client %RU32] GUEST_SESSION_ACCEPT\n", idClient));
+            rc = pThis->clientSessionAccept(pClient, hCall, cParms, paParms);
+            break;
+        case GUEST_MSG_SESSION_CLOSE:
+            LogFlowFunc(("[Client %RU32] GUEST_SESSION_CLOSE\n", idClient));
+            rc = pThis->clientSessionCloseOther(pClient, cParms, paParms);
+            break;
+
+        /*
+         * Stuff the goes to various main objects:
+         */
+        case GUEST_MSG_REPLY:
+            if (cParms >= 3 && paParms[2].u.uint32 == (uint32_t)VERR_NOT_SUPPORTED)
+            {
+                HostMsg *pFirstMsg = RTListGetFirstCpp(&pClient->m_HostMsgList, HostMsg, m_ListEntry);
+                if (pFirstMsg && pFirstMsg->m_idContext == paParms[0].u.uint32)
+                    pFirstMsg->m_f60BetaHackInPlay = true;
+            }
+            RT_FALL_THROUGH();
+        case GUEST_MSG_PROGRESS_UPDATE:
+        case GUEST_MSG_SESSION_NOTIFY:
+        case GUEST_MSG_EXEC_OUTPUT:
+        case GUEST_MSG_EXEC_STATUS:
+        case GUEST_MSG_EXEC_INPUT_STATUS:
+        case GUEST_MSG_EXEC_IO_NOTIFY:
+        case GUEST_MSG_DIR_NOTIFY:
+        case GUEST_MSG_FILE_NOTIFY:
+            LogFlowFunc(("[Client %RU32] %s\n", idClient, GstCtrlGuestMsgToStr((eGuestMsg)u32Function)));
+            rc = pThis->clientToMain(pClient, u32Function /* Msg */, cParms, paParms);
+            Assert(rc != VINF_HGCM_ASYNC_EXECUTE);
+            break;
+
+        /*
+         * The remaining messages are here for compatibility with older Guest Additions:
+         */
+        case GUEST_MSG_WAIT:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_WAIT\n", idClient));
+            pThis->clientMsgOldGet(pClient, hCall, cParms, paParms);
+            rc = VINF_HGCM_ASYNC_EXECUTE;
+            break;
+
+        case GUEST_MSG_SKIP_OLD:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_SKIP_OLD\n", idClient));
+            rc = pThis->clientMsgOldSkip(pClient, hCall, cParms);
+            break;
+
+        case GUEST_MSG_FILTER_SET:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_FILTER_SET\n", idClient));
+            rc = pThis->clientMsgOldFilterSet(pClient, cParms, paParms);
+            break;
+
+        case GUEST_MSG_FILTER_UNSET:
+            LogFlowFunc(("[Client %RU32] GUEST_MSG_FILTER_UNSET\n", idClient));
+            rc = VERR_NOT_IMPLEMENTED;
+            break;
+
+        /*
+         * Anything else shall return invalid function.
+         * Note! We used to return VINF_SUCCESS for these.  See bugref:9313
+         *       and Guest::i_notifyCtrlDispatcher().
+         */
+        default:
+            ASSERT_GUEST_MSG_FAILED(("u32Function=%RU32 (%#x)\n", u32Function, u32Function));
+            rc = VERR_INVALID_FUNCTION;
+            break;
+    }
+
+    if (rc != VINF_HGCM_ASYNC_EXECUTE)
+    {
+        /* Tell the client that the call is complete (unblocks waiting). */
+        LogFlowFunc(("[Client %RU32] Calling pfnCallComplete w/ rc=%Rrc\n", idClient, rc));
+        AssertPtr(pThis->mpHelpers);
+        pThis->mpHelpers->pfnCallComplete(hCall, rc);
+    }
+}
+
+
+/**
+ * Notifies the host (using low-level HGCM callbacks) about an event
+ * which was sent from the client.
+ *
+ * @returns VBox status code.
+ * @param   u32Function     Message ID that occured.
+ * @param   cParms          Number of parameters.
+ * @param   paParms         Array of parameters.
+ */
+int GstCtrlService::hostCallback(uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    LogFlowFunc(("u32Function=%RU32 (%s), cParms=%ld, paParms=%p\n",
+                 u32Function, GstCtrlGuestMsgToStr((eGuestMsg)u32Function), cParms, paParms));
+
+    int rc;
+    if (mpfnHostCallback)
+    {
+        VBOXGUESTCTRLHOSTCALLBACK data = { cParms, paParms };
+        rc = mpfnHostCallback(mpvHostData, u32Function, &data, sizeof(data));
+    }
+    else
+        rc = VERR_NOT_SUPPORTED;
+
+    LogFlowFunc(("Returning rc=%Rrc\n", rc));
+    return rc;
+}
+
+
+/**
+ * Processes a message received from the host side and re-routes it to
+ * a connect client on the guest.
+ *
+ * @returns VBox status code.
+ * @param   idMsg   Message ID to process.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ */
+int GstCtrlService::hostProcessMessage(uint32_t idMsg, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * If no client is connected at all we don't buffer any host messages
+     * and immediately return an error to the host.  This avoids the host
+     * waiting for a response from the guest side in case VBoxService on
+     * the guest is not running/system is messed up somehow.
+     */
+    if (m_ClientStateMap.empty())
+    {
+        LogFlow(("GstCtrlService::hostProcessMessage: VERR_NOT_FOUND!\n"));
+        return VERR_NOT_FOUND;
+    }
+
+    /*
+     * Create a host message for each destination.
+     * Note! There is currently only one scenario in which we send a host
+     *       message to two recipients.
+     */
+    HostMsg *pHostMsg = new (std::nothrow) HostMsg();
+    AssertReturn(pHostMsg, VERR_NO_MEMORY);
+    int rc = pHostMsg->Init(idMsg, cParms, paParms);
+    if (RT_SUCCESS(rc))
+    {
+        uint64_t const fDestinations = pHostMsg->m_idContextAndDst & VBOX_GUESTCTRL_DST_BOTH;
+        HostMsg       *pHostMsg2     = NULL;
+        if (fDestinations != VBOX_GUESTCTRL_DST_BOTH)
+        { /* likely */ }
+        else
+        {
+            pHostMsg2 = new (std::nothrow) HostMsg();
+            if (pHostMsg2)
+                rc = pHostMsg2->Init(idMsg, cParms, paParms);
+            else
+                rc = VERR_NO_MEMORY;
+        }
+        if (RT_SUCCESS(rc))
+        {
+            LogFlowFunc(("Handling host message m_idContextAndDst=%#RX64, idMsg=%RU32, cParms=%RU32, paParms=%p, cClients=%zu\n",
+                         pHostMsg->m_idContextAndDst, idMsg, cParms, paParms, m_ClientStateMap.size()));
+
+            /*
+             * Find the message destination and post it to the client.  If the
+             * session ID doesn't match any particular client it goes to the master.
+             */
+            AssertMsg(!m_ClientStateMap.empty(), ("Client state map is empty when it should not be!\n"));
+
+            /* Dispatch to the session. */
+            if (fDestinations & VBOX_GUESTCTRL_DST_SESSION)
+            {
+                uint32_t const idSession = VBOX_GUESTCTRL_CONTEXTID_GET_SESSION(pHostMsg->m_idContext);
+                ClientStateMap::iterator It = m_SessionIdMap.find(idSession);
+                if (It != m_SessionIdMap.end())
+                {
+                    ClientState *pClient = It->second;
+                    Assert(pClient->m_idSession == idSession);
+                    RTListAppend(&pClient->m_HostMsgList, &pHostMsg->m_ListEntry);
+                    pHostMsg  = pHostMsg2;
+                    pHostMsg2 = NULL;
+
+                    int rc2 = pClient->Wakeup();
+                    LogFlowFunc(("Woke up client ID=%RU32 -> rc=%Rrc\n", pClient->m_idClient, rc2));
+                    RT_NOREF(rc2);
+                    rc = VINF_SUCCESS;
+                }
+                else
+                {
+                    LogFunc(("No client with session ID %u was found! (idMsg=%d %s)\n",
+                             idSession, idMsg, GstCtrlHostMsgtoStr((eHostMsg)idMsg)));
+                    rc = !(fDestinations & VBOX_GUESTCTRL_DST_ROOT_SVC) ? VERR_NOT_FOUND : VWRN_NOT_FOUND;
+                }
+            }
+
+            /* Does the message go to the root service? */
+            if (   (fDestinations & VBOX_GUESTCTRL_DST_ROOT_SVC)
+                && RT_SUCCESS(rc))
+            {
+                Assert(pHostMsg);
+                if (m_pMasterClient)
+                {
+                    RTListAppend(&m_pMasterClient->m_HostMsgList, &pHostMsg->m_ListEntry);
+                    pHostMsg = NULL;
+
+                    int rc2 = m_pMasterClient->Wakeup();
+                    LogFlowFunc(("Woke up client ID=%RU32 (master) -> rc=%Rrc\n", m_pMasterClient->m_idClient, rc2));
+                    NOREF(rc2);
+                }
+                else
+                    rc = VERR_NOT_FOUND;
+            }
+        }
+
+        /* Drop unset messages. */
+        if (pHostMsg2)
+            pHostMsg2->Delete();
+    }
+    if (pHostMsg)
+        pHostMsg->Delete();
+
+    if (RT_FAILURE(rc))
+        LogFunc(("Failed %Rrc (idMsg=%u, cParms=%u)\n", rc, idMsg, cParms));
+    return rc;
+}
+
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnHostCall,
+ *  Wraps to the hostProcessMessage() member function.}
+ */
+/*static*/ DECLCALLBACK(int)
+GstCtrlService::svcHostCall(void *pvService, uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    AssertLogRelReturn(RT_VALID_PTR(pvService), VERR_INVALID_PARAMETER);
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertPtrReturn(pThis, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("u32Function=%RU32, cParms=%RU32, paParms=0x%p\n", u32Function, cParms, paParms));
+    AssertReturn(u32Function != HOST_MSG_CANCEL_PENDING_WAITS, VERR_INVALID_FUNCTION);
+    return pThis->hostProcessMessage(u32Function, cParms, paParms);
+}
+
+
+
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnSaveState}
+ */
+/*static*/ DECLCALLBACK(int)
+GstCtrlService::svcSaveState(void *pvService, uint32_t idClient, void *pvClient, PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM)
+{
+    RT_NOREF(pvClient);
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertPtrReturn(pThis, VERR_INVALID_POINTER);
+
+    /* Note! We don't need to save the idSession here because it's only used
+             for sessions and the sessions are not persistent across a state
+             save/restore.  The Main objects aren't there.  Clients shuts down.
+             Only the root service survives, so remember who that is and its mode. */
+
+    pVMM->pfnSSMR3PutU32(pSSM, 1);
+    pVMM->pfnSSMR3PutBool(pSSM, pThis->m_fLegacyMode);
+    return pVMM->pfnSSMR3PutBool(pSSM, idClient == pThis->m_idMasterClient);
+}
+
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnLoadState}
+ */
+/*static*/ DECLCALLBACK(int)
+GstCtrlService::svcLoadState(void *pvService, uint32_t idClient, void *pvClient,
+                             PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion)
+{
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertPtrReturn(pThis, VERR_INVALID_POINTER);
+    ClientState *pClient = reinterpret_cast<ClientState *>(pvClient);
+    AssertReturn(pClient, VERR_INVALID_CLIENT_ID);
+    Assert(pClient->m_idClient == idClient);
+
+    if (uVersion >= HGCM_SAVED_STATE_VERSION)
+    {
+        uint32_t uSubVersion;
+        int rc = pVMM->pfnSSMR3GetU32(pSSM, &uSubVersion);
+        AssertRCReturn(rc, rc);
+        if (uSubVersion != 1)
+            return pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_DATA_UNIT_FORMAT_CHANGED, RT_SRC_POS,
+                                     "sub version %u, expected 1\n", uSubVersion);
+        bool fLegacyMode;
+        rc = pVMM->pfnSSMR3GetBool(pSSM, &fLegacyMode);
+        AssertRCReturn(rc, rc);
+        pThis->m_fLegacyMode = fLegacyMode;
+
+        bool fIsMaster;
+        rc = pVMM->pfnSSMR3GetBool(pSSM, &fIsMaster);
+        AssertRCReturn(rc, rc);
+
+        pClient->m_fIsMaster = fIsMaster;
+        if (fIsMaster)
+        {
+            pThis->m_pMasterClient  = pClient;
+            pThis->m_idMasterClient = idClient;
+        }
+    }
+    else
+    {
+        /*
+         * For old saved states we have to guess at who should be the master.
+         * Given how HGCMService::CreateAndConnectClient and associates manage
+         * and saves the client, the first client connecting will be restored
+         * first.  The only time this might go wrong if the there are zombie
+         * VBoxService session processes in the restored guest, and I don't
+         * we need to care too much about that scenario.
+         *
+         * Given how HGCM first re-connects the clients before this function
+         * gets called, there isn't anything we need to do here it turns out. :-)
+         */
+    }
+    pClient->m_fRestored = true;
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnRegisterExtension,
+ *  Installs a host callback for notifications of property changes.}
+ */
+/*static*/ DECLCALLBACK(int) GstCtrlService::svcRegisterExtension(void *pvService, PFNHGCMSVCEXT pfnExtension, void *pvExtension)
+{
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertPtrReturn(pThis, VERR_INVALID_POINTER);
+    AssertPtrNullReturn(pfnExtension, VERR_INVALID_POINTER);
+
+    pThis->mpfnHostCallback = pfnExtension;
+    pThis->mpvHostData      = pvExtension;
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * @copydoc FNVBOXHGCMSVCLOAD
+ */
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad(VBOXHGCMSVCFNTABLE *pTable)
+{
+    int rc = VINF_SUCCESS;
+
+    LogFlowFunc(("pTable=%p\n", pTable));
+
+    if (!RT_VALID_PTR(pTable))
+        rc = VERR_INVALID_PARAMETER;
+    else
+    {
+        LogFlowFunc(("pTable->cbSize=%d, pTable->u32Version=0x%08X\n", pTable->cbSize, pTable->u32Version));
+
+        if (   pTable->cbSize != sizeof (VBOXHGCMSVCFNTABLE)
+            || pTable->u32Version != VBOX_HGCM_SVC_VERSION)
+        {
+            rc = VERR_VERSION_MISMATCH;
+        }
+        else
+        {
+            GstCtrlService *pService = NULL;
+            /* No exceptions may propagate outside. */
+            try
+            {
+                pService = new GstCtrlService(pTable->pHelpers);
+            }
+            catch (int rcThrown)
+            {
+                rc = rcThrown;
+            }
+            catch(std::bad_alloc &)
+            {
+                rc = VERR_NO_MEMORY;
+            }
+
+            if (RT_SUCCESS(rc))
+            {
+                /*
+                 * We don't need an additional client data area on the host,
+                 * because we're a class which can have members for that :-).
+                 */
+                pTable->cbClient = sizeof(ClientState);
+
+                /* Limit pending calls to 8 pending per connection (doubt we need more than
+                   one).  Map legacy clients to the root and limit kernel to 1.  Use defaults
+                   for root and user clients. */
+                for (uintptr_t i = 0; i < RT_ELEMENTS(pTable->acMaxClients); i++)
+                    pTable->acMaxCallsPerClient[i] = 8;
+
+                pTable->idxLegacyClientCategory = HGCM_CLIENT_CATEGORY_ROOT;
+                pTable->acMaxClients[HGCM_CLIENT_CATEGORY_KERNEL] = 1;
+
+                /* Register functions. */
+                pTable->pfnUnload               = GstCtrlService::svcUnload;
+                pTable->pfnConnect              = GstCtrlService::svcConnect;
+                pTable->pfnDisconnect           = GstCtrlService::svcDisconnect;
+                pTable->pfnCall                 = GstCtrlService::svcCall;
+                pTable->pfnHostCall             = GstCtrlService::svcHostCall;
+                pTable->pfnSaveState            = GstCtrlService::svcSaveState;
+                pTable->pfnLoadState            = GstCtrlService::svcLoadState;
+                pTable->pfnRegisterExtension    = GstCtrlService::svcRegisterExtension;
+                pTable->pfnNotify               = NULL;
+
+                /* Service specific initialization. */
+                pTable->pvService = pService;
+            }
+            else
+            {
+                if (pService)
+                {
+                    delete pService;
+                    pService = NULL;
+                }
+            }
+        }
+    }
+
+    LogFlowFunc(("Returning %Rrc\n", rc));
+    return rc;
+}
+
diff --git a/src/VBox/HostServices/GuestControl/VBoxGuestControlSvc.rc b/src/VBox/HostServices/GuestControl/VBoxGuestControlSvc.rc
new file mode 100644
index 00000000..a10c8803
--- /dev/null
+++ b/src/VBox/HostServices/GuestControl/VBoxGuestControlSvc.rc
@@ -0,0 +1,61 @@
+/* $Id: VBoxGuestControlSvc.rc $ */
+/** @file
+ * VBoxGuestControlSvc - Resource file containing version info and icon.
+ */
+
+/*
+ * Copyright (C) 2015-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <windows.h>
+#include <VBox/version.h>
+
+LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION      VBOX_RC_FILE_VERSION
+  PRODUCTVERSION   VBOX_RC_FILE_VERSION
+  FILEFLAGSMASK    VS_FFI_FILEFLAGSMASK
+  FILEFLAGS        VBOX_RC_FILE_FLAGS
+  FILEOS           VBOX_RC_FILE_OS
+  FILETYPE         VBOX_RC_TYPE_DLL
+  FILESUBTYPE      VFT2_UNKNOWN
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904b0" // Lang=US English, CharSet=Unicode
+    BEGIN
+      VALUE "FileDescription",  "VirtualBox Guest Control Host Service\0"
+      VALUE "InternalName",     "VBoxGuestControl\0"
+      VALUE "OriginalFilename", "VBoxGuestControl.dll\0"
+      VALUE "CompanyName",      VBOX_RC_COMPANY_NAME
+      VALUE "FileVersion",      VBOX_RC_FILE_VERSION_STR
+      VALUE "LegalCopyright",   VBOX_RC_LEGAL_COPYRIGHT
+      VALUE "ProductName",      VBOX_RC_PRODUCT_NAME_STR
+      VALUE "ProductVersion",   VBOX_RC_PRODUCT_VERSION_STR
+      VBOX_RC_MORE_STRINGS
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x409, 1200
+  END
+END
diff --git a/src/VBox/HostServices/GuestControl/testcase/Makefile.kmk b/src/VBox/HostServices/GuestControl/testcase/Makefile.kmk
new file mode 100644
index 00000000..1fa6a759
--- /dev/null
+++ b/src/VBox/HostServices/GuestControl/testcase/Makefile.kmk
@@ -0,0 +1,56 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Guest Control Host Service testcases.
+#
+
+#
+# Copyright (C) 2010-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+if defined(VBOX_WITH_TESTCASES) && !defined(VBOX_ONLY_ADDITIONS) && !defined(VBOX_ONLY_SDK)
+
+ # Set this in LocalConfig.kmk if you are working on the guest property
+ # service to automatically run the testcase at build time.
+ #    OTHERS += $(tstGuestControlSvc_0_OUTDIR)/tstGuestControlSvc.run
+ #
+
+ PROGRAMS += tstGuestControlSvc
+ TESTING  += $(tstGuestControlSvc_0_OUTDIR)/tstGuestControlSvc.run
+ tstGuestControlSvc_TEMPLATE = VBoxR3TstExe
+ # The second define here is to ensure that the testcase will run fast,
+ # without waiting for any thread synchronisation.
+ tstGuestControlSvc_DEFS     = VBOX_WITH_HGCM VBOX_GUEST_CONTROL_TEST_NOTHREAD
+ tstGuestControlSvc_SOURCES  = \
+ 	../VBoxGuestControlSvc.cpp \
+ 	tstGuestControlSvc.cpp
+ tstGuestControlSvc_LIBS     = $(LIB_RUNTIME)
+
+ $$(tstGuestControlSvc_0_OUTDIR)/tstGuestControlSvc.run: $$(tstGuestControlSvc_1_STAGE_TARGET)
+	export VBOX_LOG_DEST=nofile; $(tstGuestControlSvc_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+
+endif
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/HostServices/GuestControl/testcase/tstGuestControlSvc.cpp b/src/VBox/HostServices/GuestControl/testcase/tstGuestControlSvc.cpp
new file mode 100644
index 00000000..e00d4955
--- /dev/null
+++ b/src/VBox/HostServices/GuestControl/testcase/tstGuestControlSvc.cpp
@@ -0,0 +1,282 @@
+/* $Id: tstGuestControlSvc.cpp $ */
+/** @file
+ * Testcase for the guest control service.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#include <VBox/HostServices/GuestControlSvc.h>
+#include <iprt/initterm.h>
+#include <iprt/stream.h>
+#include <iprt/test.h>
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+static RTTEST g_hTest = NIL_RTTEST;
+
+using namespace guestControl;
+
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad(VBOXHGCMSVCFNTABLE *pTable);
+
+/** Simple call handle structure for the guest call completion callback */
+struct VBOXHGCMCALLHANDLE_TYPEDEF
+{
+    /** Where to store the result code. */
+    int32_t rc;
+};
+
+/** Call completion callback for guest calls. */
+static DECLCALLBACK(int) callComplete(VBOXHGCMCALLHANDLE callHandle, int32_t rc)
+{
+    callHandle->rc = rc;
+    return VINF_SUCCESS;
+}
+
+/**
+ * Initialise the HGCM service table as much as we need to start the
+ * service.
+ *
+ * @return IPRT status code.
+ * @param  pTable the table to initialise
+ */
+int initTable(VBOXHGCMSVCFNTABLE *pTable, VBOXHGCMSVCHELPERS *pHelpers)
+{
+    pTable->cbSize = sizeof (VBOXHGCMSVCFNTABLE);
+    pTable->u32Version = VBOX_HGCM_SVC_VERSION;
+    pHelpers->pfnCallComplete = callComplete;
+    pTable->pHelpers = pHelpers;
+
+    return VINF_SUCCESS;
+}
+
+typedef struct CMDHOST
+{
+    /** The HGCM command to execute. */
+    int cmd;
+    /** Number of parameters. */
+    int num_parms;
+    /** The actual parameters. */
+    const PVBOXHGCMSVCPARM parms;
+    /** Flag indicating whether we need a connected client for this command. */
+    bool fNeedsClient;
+    /** The desired return value from the host. */
+    int rc;
+} CMDHOST, *PCMDHOST;
+
+typedef struct CMDCLIENT
+{
+    /** The client's ID. */
+    int client_id;
+    /** The HGCM command to execute. */
+    int cmd;
+    /** Number of parameters. */
+    int num_parms;
+    /** The actual parameters. */
+    const PVBOXHGCMSVCPARM parms;
+    /** The desired return value from the host. */
+    int rc;
+} CMDCLIENT, *PCMDCLIENT;
+
+/**
+ * Tests the HOST_EXEC_CMD function.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static int testHostCmd(const VBOXHGCMSVCFNTABLE *pTable, const PCMDHOST pCmd, uint32_t uNumTests)
+{
+    int rc = VINF_SUCCESS;
+    if (!RT_VALID_PTR(pTable->pfnHostCall))
+    {
+        RTTestPrintf(g_hTest, RTTESTLVL_FAILURE, "Invalid pfnHostCall() pointer\n");
+        rc = VERR_INVALID_POINTER;
+    }
+    if (RT_SUCCESS(rc))
+    {
+        for (unsigned i = 0; (i < uNumTests) && RT_SUCCESS(rc); i++)
+        {
+            RTTestPrintf(g_hTest, RTTESTLVL_INFO, "Testing #%u (cmd: %d, num_parms: %d, parms: 0x%p\n",
+                         i, pCmd[i].cmd, pCmd[i].num_parms, pCmd[i].parms);
+
+            if (pCmd[i].fNeedsClient)
+            {
+                int client_rc = pTable->pfnConnect(pTable->pvService, 1000 /* Client ID */, NULL /* pvClient */, 0, false);
+                if (RT_FAILURE(client_rc))
+                    rc = client_rc;
+            }
+
+            if (RT_SUCCESS(rc))
+            {
+                int host_rc = pTable->pfnHostCall(pTable->pvService,
+                                                  pCmd[i].cmd,
+                                                  pCmd[i].num_parms,
+                                                  pCmd[i].parms);
+                if (host_rc != pCmd[i].rc)
+                {
+                    RTTestPrintf(g_hTest, RTTESTLVL_FAILURE, "Host call test #%u returned with rc=%Rrc instead of rc=%Rrc\n",
+                                 i, host_rc, pCmd[i].rc);
+                    rc = host_rc;
+                    if (RT_SUCCESS(rc))
+                        rc = VERR_INVALID_PARAMETER;
+                }
+
+                if (pCmd[i].fNeedsClient)
+                {
+                    int client_rc = pTable->pfnDisconnect(pTable->pvService, 1000 /* Client ID */, NULL /* pvClient */);
+                    if (RT_SUCCESS(rc))
+                        rc = client_rc;
+                }
+            }
+        }
+    }
+    return rc;
+}
+
+static int testHost(const VBOXHGCMSVCFNTABLE *pTable)
+{
+    RTTestSub(g_hTest, "Testing host commands ...");
+
+    VBOXHGCMSVCPARM aParms[1];
+    HGCMSvcSetU32(&aParms[0], 1000 /* Context ID */);
+
+    CMDHOST aCmdHostAll[] =
+    {
+#if 0
+        /** No client connected. */
+        { 1024 /* Not existing command */, 0, 0, false, VERR_NOT_FOUND },
+        { -1 /* Invalid command */, 0, 0, false, VERR_NOT_FOUND },
+        { HOST_CANCEL_PENDING_WAITS, 1024, 0, false, VERR_NOT_FOUND },
+        { HOST_CANCEL_PENDING_WAITS, 0, &aParms[0], false, VERR_NOT_FOUND },
+
+        /** No client connected, valid command. */
+        { HOST_CANCEL_PENDING_WAITS, 0, 0, false, VERR_NOT_FOUND },
+
+        /** Client connected, no parameters given. */
+        { HOST_EXEC_SET_INPUT, 0 /* No parameters given */, 0, true, VERR_INVALID_PARAMETER },
+        { 1024 /* Not existing command */, 0 /* No parameters given */, 0, true, VERR_INVALID_PARAMETER },
+        { -1 /* Invalid command */, 0 /* No parameters given */, 0, true, VERR_INVALID_PARAMETER },
+
+        /** Client connected, valid parameters given. */
+        { HOST_CANCEL_PENDING_WAITS, 0, 0, true, VINF_SUCCESS },
+        { HOST_CANCEL_PENDING_WAITS, 1024, &aParms[0], true, VINF_SUCCESS },
+        { HOST_CANCEL_PENDING_WAITS, 0, &aParms[0], true, VINF_SUCCESS},
+#endif
+
+        /** Client connected, invalid parameters given. */
+        { HOST_MSG_EXEC_CMD, 1024, 0, true, VERR_INVALID_POINTER },
+        { HOST_MSG_EXEC_CMD, 1, 0, true, VERR_INVALID_POINTER },
+        { HOST_MSG_EXEC_CMD, -1, 0, true, VERR_INVALID_POINTER },
+
+        /** Client connected, parameters given. */
+        { HOST_MSG_CANCEL_PENDING_WAITS, 1, &aParms[0], true, VINF_SUCCESS },
+        { HOST_MSG_EXEC_CMD, 1, &aParms[0], true, VINF_SUCCESS },
+        { HOST_MSG_EXEC_SET_INPUT, 1, &aParms[0], true, VINF_SUCCESS },
+        { HOST_MSG_EXEC_GET_OUTPUT, 1, &aParms[0], true, VINF_SUCCESS },
+
+        /** Client connected, unknown command + valid parameters given. */
+        { -1, 1, &aParms[0], true, VINF_SUCCESS }
+    };
+
+    int rc = testHostCmd(pTable, &aCmdHostAll[0], RT_ELEMENTS(aCmdHostAll));
+    RTTestSubDone(g_hTest);
+    return rc;
+}
+
+static int testClient(const VBOXHGCMSVCFNTABLE *pTable)
+{
+    RTTestSub(g_hTest, "Testing client commands ...");
+
+    int rc = pTable->pfnConnect(pTable->pvService, 1 /* Client ID */, NULL /* pvClient */, 0, false);
+    if (RT_SUCCESS(rc))
+    {
+        VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+
+        /* No commands from host yet. */
+        VBOXHGCMSVCPARM aParmsGuest[8];
+        HGCMSvcSetU32(&aParmsGuest[0], 0 /* Msg type */);
+        HGCMSvcSetU32(&aParmsGuest[1], 0 /* Parameters */);
+        pTable->pfnCall(pTable->pvService, &callHandle, 1 /* Client ID */, NULL /* pvClient */,
+                        GUEST_MSG_WAIT, 2, &aParmsGuest[0], 0);
+        RTTEST_CHECK_RC_RET(g_hTest, callHandle.rc, VINF_SUCCESS, callHandle.rc);
+
+        /* Host: Add a dummy command. */
+        VBOXHGCMSVCPARM aParmsHost[8];
+        HGCMSvcSetU32(&aParmsHost[0], 1000 /* Context ID */);
+        HGCMSvcSetStr(&aParmsHost[1], "foo.bar");
+        HGCMSvcSetStr(&aParmsHost[2], "baz");
+
+        rc = pTable->pfnHostCall(pTable->pvService, HOST_MSG_EXEC_CMD, 3, &aParmsHost[0]);
+        RTTEST_CHECK_RC_RET(g_hTest, rc, VINF_SUCCESS, rc);
+
+        /* Client: Disconnect again. */
+        int rc2 = pTable->pfnDisconnect(pTable->pvService, 1000 /* Client ID */, NULL /* pvClient */);
+        if (RT_SUCCESS(rc))
+            rc = rc2;
+    }
+
+    RTTestSubDone(g_hTest);
+    return rc;
+}
+
+/*
+ * Set environment variable "IPRT_TEST_MAX_LEVEL=all" to get more debug output!
+ */
+int main()
+{
+    RTEXITCODE rcExit  = RTTestInitAndCreate("tstGuestControlSvc", &g_hTest);
+    if (rcExit != RTEXITCODE_SUCCESS)
+        return rcExit;
+    RTTestBanner(g_hTest);
+
+    /* Some host info. */
+    RTTestIPrintf(RTTESTLVL_ALWAYS, "sizeof(void*)=%d\n", sizeof(void*));
+
+    /* Do the tests. */
+    VBOXHGCMSVCFNTABLE svcTable;
+    VBOXHGCMSVCHELPERS svcHelpers;
+    RTTEST_CHECK_RC_RET(g_hTest, initTable(&svcTable, &svcHelpers), VINF_SUCCESS, 1);
+
+    do
+    {
+        RTTESTI_CHECK_RC_BREAK(VBoxHGCMSvcLoad(&svcTable), VINF_SUCCESS);
+
+        RTTESTI_CHECK_RC_BREAK(testHost(&svcTable), VINF_SUCCESS);
+
+        RTTESTI_CHECK_RC_BREAK(svcTable.pfnUnload(svcTable.pvService), VINF_SUCCESS);
+
+        RTTESTI_CHECK_RC_BREAK(VBoxHGCMSvcLoad(&svcTable), VINF_SUCCESS);
+
+        RTTESTI_CHECK_RC_BREAK(testClient(&svcTable), VINF_SUCCESS);
+
+        RTTESTI_CHECK_RC_BREAK(svcTable.pfnUnload(svcTable.pvService), VINF_SUCCESS);
+
+    } while (0);
+
+    return RTTestSummaryAndDestroy(g_hTest);
+}
+
diff --git a/src/VBox/HostServices/GuestProperties/Makefile.kmk b/src/VBox/HostServices/GuestProperties/Makefile.kmk
new file mode 100644
index 00000000..80e5c63b
--- /dev/null
+++ b/src/VBox/HostServices/GuestProperties/Makefile.kmk
@@ -0,0 +1,58 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Shared Info Services Host Service.
+#
+
+#
+# Copyright (C) 2006-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+# Include sub-makefile(s).
+include $(PATH_SUB_CURRENT)/testcase/Makefile.kmk
+
+#
+# The shared folder service DLL.
+#
+DLLS += VBoxGuestPropSvc
+VBoxGuestPropSvc_TEMPLATE  = VBoxR3Dll
+VBoxGuestPropSvc_NAME.os2  = VBoxSIS
+VBoxGuestPropSvc_DEFS      = VBOX_WITH_HGCM
+VBoxGuestPropSvc_INCS      = $(PATH_ROOT)/src/VBox/Main/include
+VBoxGuestPropSvc_INCS.win  = \
+	$(VBOX_PATH_SDK)
+
+VBoxGuestPropSvc_SOURCES = \
+	VBoxGuestPropSvc.cpp
+
+VBoxGuestPropSvc_SOURCES.win = \
+	VBoxGuestPropSvc.rc
+
+VBoxGuestPropSvc_LIBS = \
+	$(LIB_RUNTIME)
+
+VBoxGuestPropSvc_LDFLAGS.darwin = \
+	-install_name $(VBOX_DYLD_EXECUTABLE_PATH)/VBoxGuestPropSvc.dylib
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/HostServices/GuestProperties/VBoxGuestPropSvc.cpp b/src/VBox/HostServices/GuestProperties/VBoxGuestPropSvc.cpp
new file mode 100644
index 00000000..0336999b
--- /dev/null
+++ b/src/VBox/HostServices/GuestProperties/VBoxGuestPropSvc.cpp
@@ -0,0 +1,1885 @@
+/* $Id: VBoxGuestPropSvc.cpp $ */
+/** @file
+ * Guest Property Service: Host service entry points.
+ */
+
+/*
+ * Copyright (C) 2008-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+/** @page pg_svc_guest_properties   Guest Property HGCM Service
+ *
+ * This HGCM service allows the guest to set and query values in a property
+ * store on the host.  The service proxies the guest requests to the service
+ * owner on the host using a request callback provided by the owner, and is
+ * notified of changes to properties made by the host.  It forwards these
+ * notifications to clients in the guest which have expressed interest and
+ * are waiting for notification.
+ *
+ * The service currently consists of two threads.  One of these is the main
+ * HGCM service thread which deals with requests from the guest and from the
+ * host.  The second thread sends the host asynchronous notifications of
+ * changes made by the guest and deals with notification timeouts.
+ *
+ * Guest requests to wait for notification are added to a list of open
+ * notification requests and completed when a corresponding guest property
+ * is changed or when the request times out.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_HGCM
+#include <VBox/HostServices/GuestPropertySvc.h>
+
+#include <VBox/log.h>
+#include <iprt/asm.h>
+#include <iprt/assert.h>
+#include <iprt/buildconfig.h>
+#include <iprt/cpp/autores.h>
+#include <iprt/cpp/utils.h>
+#include <iprt/cpp/ministring.h>
+#include <VBox/err.h>
+#include <VBox/hgcmsvc.h>
+#include <iprt/mem.h>
+#include <iprt/req.h>
+#include <iprt/string.h>
+#include <iprt/thread.h>
+#include <iprt/time.h>
+#include <VBox/vmm/dbgf.h>
+#include <VBox/version.h>
+#include <VBox/AssertGuest.h>
+
+#include <list>
+
+
+namespace guestProp {
+
+/**
+ * Structure for holding a property
+ */
+struct Property
+{
+    /** The string space core record. */
+    RTSTRSPACECORE mStrCore;
+    /** The name of the property */
+    RTCString mName;
+    /** The property value */
+    RTCString mValue;
+    /** The timestamp of the property */
+    uint64_t mTimestamp;
+    /** The property flags */
+    uint32_t mFlags;
+
+    /** Default constructor */
+    Property() : mTimestamp(0), mFlags(GUEST_PROP_F_NILFLAG)
+    {
+        RT_ZERO(mStrCore);
+    }
+    /** Constructor with const char * */
+    Property(const char *pcszName, const char *pcszValue, uint64_t nsTimestamp, uint32_t u32Flags)
+        : mName(pcszName)
+        , mValue(pcszValue)
+        , mTimestamp(nsTimestamp)
+        , mFlags(u32Flags)
+    {
+        RT_ZERO(mStrCore);
+        mStrCore.pszString = mName.c_str();
+    }
+    /** Constructor with std::string */
+    Property(RTCString const &rName, RTCString const &rValue, uint64_t nsTimestamp, uint32_t fFlags)
+        : mName(rName)
+        , mValue(rValue)
+        , mTimestamp(nsTimestamp)
+        , mFlags(fFlags)
+    {}
+
+    /** Does the property name match one of a set of patterns? */
+    bool Matches(const char *pszPatterns) const
+    {
+        return (   pszPatterns[0] == '\0'  /* match all */
+                || RTStrSimplePatternMultiMatch(pszPatterns, RTSTR_MAX,
+                                                mName.c_str(), RTSTR_MAX,
+                                                NULL)
+               );
+    }
+
+    /** Are two properties equal? */
+    bool operator==(const Property &prop)
+    {
+        if (mTimestamp != prop.mTimestamp)
+            return false;
+        if (mFlags != prop.mFlags)
+            return false;
+        if (mName != prop.mName)
+            return false;
+        if (mValue != prop.mValue)
+            return false;
+        return true;
+    }
+
+    /* Is the property nil? */
+    bool isNull()
+    {
+        return mName.isEmpty();
+    }
+};
+/** The properties list type */
+typedef std::list <Property> PropertyList;
+
+/**
+ * Structure for holding an uncompleted guest call
+ */
+struct GuestCall
+{
+    uint32_t u32ClientId;
+    /** The call handle */
+    VBOXHGCMCALLHANDLE mHandle;
+    /** The function that was requested */
+    uint32_t mFunction;
+    /** Number of call parameters. */
+    uint32_t mParmsCnt;
+    /** The call parameters */
+    VBOXHGCMSVCPARM *mParms;
+    /** The default return value, used for passing warnings */
+    int mRc;
+
+    /** The standard constructor */
+    GuestCall(void) : u32ClientId(0), mFunction(0), mParmsCnt(0) {}
+    /** The normal constructor */
+    GuestCall(uint32_t aClientId, VBOXHGCMCALLHANDLE aHandle, uint32_t aFunction,
+              uint32_t aParmsCnt, VBOXHGCMSVCPARM aParms[], int aRc)
+              : u32ClientId(aClientId), mHandle(aHandle), mFunction(aFunction),
+                mParmsCnt(aParmsCnt), mParms(aParms), mRc(aRc) {}
+};
+/** The guest call list type */
+typedef std::list <GuestCall> CallList;
+
+/**
+ * Class containing the shared information service functionality.
+ */
+class Service : public RTCNonCopyable
+{
+private:
+    /** Type definition for use in callback functions */
+    typedef Service SELF;
+    /** HGCM helper functions. */
+    PVBOXHGCMSVCHELPERS mpHelpers;
+    /** Global flags for the service */
+    uint32_t mfGlobalFlags;
+    /** The property string space handle. */
+    RTSTRSPACE mhProperties;
+    /** The number of properties. */
+    unsigned mcProperties;
+    /** The list of property changes for guest notifications;
+     *  only used for timestamp tracking in notifications at the moment */
+    PropertyList mGuestNotifications;
+    /** The list of outstanding guest notification calls */
+    CallList mGuestWaiters;
+    /** @todo we should have classes for thread and request handler thread */
+    /** Callback function supplied by the host for notification of updates
+     * to properties */
+    PFNHGCMSVCEXT mpfnHostCallback;
+    /** User data pointer to be supplied to the host callback function */
+    void *mpvHostData;
+    /** The previous timestamp.
+     * This is used by getCurrentTimestamp() to decrease the chance of
+     * generating duplicate timestamps.  */
+    uint64_t mPrevTimestamp;
+    /** The number of consecutive timestamp adjustments that we've made.
+     * Together with mPrevTimestamp, this defines a set of obsolete timestamp
+     * values: {(mPrevTimestamp - mcTimestampAdjustments), ..., mPrevTimestamp} */
+    uint64_t mcTimestampAdjustments;
+    /** For helping setting host version properties _after_ restoring VMs. */
+    bool m_fSetHostVersionProps;
+
+    /**
+     * Get the next property change notification from the queue of saved
+     * notification based on the timestamp of the last notification seen.
+     * Notifications will only be reported if the property name matches the
+     * pattern given.
+     *
+     * @returns iprt status value
+     * @returns VWRN_NOT_FOUND if the last notification was not found in the queue
+     * @param   pszPatterns   the patterns to match the property name against
+     * @param   nsTimestamp   the timestamp of the last notification
+     * @param   pProp         where to return the property found.  If none is
+     *                        found this will be set to nil.
+     * @throws  nothing
+     * @thread  HGCM
+     */
+    int getOldNotification(const char *pszPatterns, uint64_t nsTimestamp, Property *pProp)
+    {
+        AssertPtrReturn(pszPatterns, VERR_INVALID_POINTER);
+        /* Zero means wait for a new notification. */
+        AssertReturn(nsTimestamp != 0, VERR_INVALID_PARAMETER);
+        AssertPtrReturn(pProp, VERR_INVALID_POINTER);
+        int rc = getOldNotificationInternal(pszPatterns, nsTimestamp, pProp);
+
+#ifdef VBOX_STRICT
+        /*
+         * ENSURE that pProp is the first event in the notification queue that:
+         *  - Appears later than nsTimestamp
+         *  - Matches the pszPatterns
+         */
+        /** @todo r=bird: This incorrectly ASSUMES that mTimestamp is unique.
+         *  The timestamp resolution can be very coarse on windows for instance. */
+        PropertyList::const_iterator it = mGuestNotifications.begin();
+        for (;    it != mGuestNotifications.end()
+               && it->mTimestamp != nsTimestamp; ++it)
+        { /*nothing*/ }
+        if (it == mGuestNotifications.end())  /* Not found */
+            it = mGuestNotifications.begin();
+        else
+            ++it;  /* Next event */
+        for (;    it != mGuestNotifications.end()
+               && it->mTimestamp != pProp->mTimestamp; ++it)
+            Assert(!it->Matches(pszPatterns));
+        if (pProp->mTimestamp != 0)
+        {
+            Assert(*pProp == *it);
+            Assert(pProp->Matches(pszPatterns));
+        }
+#endif /* VBOX_STRICT */
+        return rc;
+    }
+
+    /**
+     * Check whether we have permission to change a property.
+     *
+     * @returns Strict VBox status code.
+     * @retval  VINF_SUCCESS if we do.
+     * @retval  VERR_PERMISSION_DENIED if the value is read-only for the requesting
+     *          side.
+     * @retval  VINF_PERMISSION_DENIED if the side is globally marked read-only.
+     *
+     * @param   fFlags   the flags on the property in question
+     * @param   isGuest  is the guest or the host trying to make the change?
+     */
+    int checkPermission(uint32_t fFlags, bool isGuest)
+    {
+        if (fFlags & (isGuest ? GUEST_PROP_F_RDONLYGUEST : GUEST_PROP_F_RDONLYHOST))
+            return VERR_PERMISSION_DENIED;
+        if (isGuest && (mfGlobalFlags & GUEST_PROP_F_RDONLYGUEST))
+            return VINF_PERMISSION_DENIED;
+        return VINF_SUCCESS;
+    }
+
+    /**
+     * Check whether the property name is reserved for host changes only.
+     *
+     * @returns Boolean true (host reserved) or false (available to guest).
+     *
+     * @param   pszName  The property name to check.
+     */
+    bool checkHostReserved(const char *pszName)
+    {
+        if (RTStrStartsWith(pszName, "/VirtualBox/GuestAdd/VBoxService/"))
+            return true;
+        if (RTStrStartsWith(pszName, "/VirtualBox/GuestAdd/PAM/"))
+            return true;
+        if (RTStrStartsWith(pszName, "/VirtualBox/GuestAdd/Greeter/"))
+            return true;
+        if (RTStrStartsWith(pszName, "/VirtualBox/GuestAdd/SharedFolders/"))
+            return true;
+        if (RTStrStartsWith(pszName, "/VirtualBox/HostInfo/"))
+            return true;
+        if (RTStrStartsWith(pszName, "/VirtualBox/VMInfo/"))
+            return true;
+        return false;
+    }
+
+    /**
+     * Gets a property.
+     *
+     * @returns Pointer to the property if found, NULL if not.
+     *
+     * @param   pszName     The name of the property to get.
+     */
+    Property *getPropertyInternal(const char *pszName)
+    {
+        return (Property *)RTStrSpaceGet(&mhProperties, pszName);
+    }
+
+public:
+    explicit Service(PVBOXHGCMSVCHELPERS pHelpers)
+        : mpHelpers(pHelpers)
+        , mfGlobalFlags(GUEST_PROP_F_NILFLAG)
+        , mhProperties(NULL)
+        , mcProperties(0)
+        , mpfnHostCallback(NULL)
+        , mpvHostData(NULL)
+        , mPrevTimestamp(0)
+        , mcTimestampAdjustments(0)
+        , m_fSetHostVersionProps(false)
+        , mhThreadNotifyHost(NIL_RTTHREAD)
+        , mhReqQNotifyHost(NIL_RTREQQUEUE)
+    { }
+
+    /**
+     * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnUnload}
+     * Simply deletes the service object
+     */
+    static DECLCALLBACK(int) svcUnload(void *pvService)
+    {
+        AssertLogRelReturn(RT_VALID_PTR(pvService), VERR_INVALID_PARAMETER);
+        SELF *pSelf = reinterpret_cast<SELF *>(pvService);
+        int rc = pSelf->uninit();
+        AssertRC(rc);
+        if (RT_SUCCESS(rc))
+            delete pSelf;
+        return rc;
+    }
+
+    /**
+     * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnConnect}
+     * Stub implementation of pfnConnect.
+     */
+    static DECLCALLBACK(int) svcConnect(void * /* pvService */,
+                                        uint32_t /* u32ClientID */,
+                                        void * /* pvClient */,
+                                        uint32_t /*fRequestor*/,
+                                        bool /*fRestoring*/)
+    {
+        return VINF_SUCCESS;
+    }
+
+    static DECLCALLBACK(int) svcDisconnect(void *pvService, uint32_t idClient, void *pvClient);
+
+    /**
+     * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnCall}
+     * Wraps to the call member function
+     */
+    static DECLCALLBACK(void) svcCall(void * pvService,
+                                      VBOXHGCMCALLHANDLE callHandle,
+                                      uint32_t u32ClientID,
+                                      void *pvClient,
+                                      uint32_t u32Function,
+                                      uint32_t cParms,
+                                      VBOXHGCMSVCPARM paParms[],
+                                      uint64_t tsArrival)
+    {
+        AssertLogRelReturnVoid(RT_VALID_PTR(pvService));
+        LogFlowFunc(("pvService=%p, callHandle=%p, u32ClientID=%u, pvClient=%p, u32Function=%u, cParms=%u, paParms=%p\n", pvService, callHandle, u32ClientID, pvClient, u32Function, cParms, paParms));
+        SELF *pSelf = reinterpret_cast<SELF *>(pvService);
+        pSelf->call(callHandle, u32ClientID, pvClient, u32Function, cParms, paParms);
+        LogFlowFunc(("returning\n"));
+        RT_NOREF_PV(tsArrival);
+    }
+
+    /**
+     * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnHostCall}
+     * Wraps to the hostCall member function
+     */
+    static DECLCALLBACK(int) svcHostCall(void *pvService,
+                                         uint32_t u32Function,
+                                         uint32_t cParms,
+                                         VBOXHGCMSVCPARM paParms[])
+    {
+        AssertLogRelReturn(RT_VALID_PTR(pvService), VERR_INVALID_PARAMETER);
+        LogFlowFunc(("pvService=%p, u32Function=%u, cParms=%u, paParms=%p\n", pvService, u32Function, cParms, paParms));
+        SELF *pSelf = reinterpret_cast<SELF *>(pvService);
+        int rc = pSelf->hostCall(u32Function, cParms, paParms);
+        LogFlowFunc(("rc=%Rrc\n", rc));
+        return rc;
+    }
+
+    /**
+     * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnRegisterExtension}
+     * Installs a host callback for notifications of property changes.
+     */
+    static DECLCALLBACK(int) svcRegisterExtension(void *pvService,
+                                                  PFNHGCMSVCEXT pfnExtension,
+                                                  void *pvExtension)
+    {
+        AssertLogRelReturn(RT_VALID_PTR(pvService), VERR_INVALID_PARAMETER);
+        SELF *pSelf = reinterpret_cast<SELF *>(pvService);
+        pSelf->mpfnHostCallback = pfnExtension;
+        pSelf->mpvHostData = pvExtension;
+        return VINF_SUCCESS;
+    }
+
+    int setHostVersionProps();
+    void incrementCounterProp(const char *pszName);
+    static DECLCALLBACK(void) svcNotify(void *pvService, HGCMNOTIFYEVENT enmEvent);
+
+    int initialize();
+
+private:
+    static DECLCALLBACK(int) reqThreadFn(RTTHREAD ThreadSelf, void *pvUser);
+    uint64_t getCurrentTimestamp(void);
+    int setPropertyBlock(uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int getProperty(uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int setProperty(uint32_t cParms, VBOXHGCMSVCPARM paParms[], bool isGuest);
+    int setPropertyInternal(const char *pcszName, const char *pcszValue, uint32_t fFlags, uint64_t nsTimestamp,
+                            bool fIsGuest = false);
+    int delProperty(uint32_t cParms, VBOXHGCMSVCPARM paParms[], bool isGuest);
+    int enumProps(uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int getNotification(uint32_t u32ClientId, VBOXHGCMCALLHANDLE callHandle, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int getOldNotificationInternal(const char *pszPattern, uint64_t nsTimestamp, Property *pProp);
+    int getNotificationWriteOut(uint32_t cParms, VBOXHGCMSVCPARM paParms[], Property const &prop, bool fWasDeleted);
+    int doNotifications(const char *pszProperty, uint64_t nsTimestamp);
+    int notifyHost(const char *pszName, const char *pszValue, uint64_t nsTimestamp, const char *pszFlags);
+
+    void call(VBOXHGCMCALLHANDLE callHandle, uint32_t u32ClientID,
+              void *pvClient, uint32_t eFunction, uint32_t cParms,
+              VBOXHGCMSVCPARM paParms[]);
+    int hostCall(uint32_t eFunction, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+    int uninit();
+    static DECLCALLBACK(void) dbgInfo(void *pvUser, PCDBGFINFOHLP pHlp, const char *pszArgs);
+
+    /* Thread for handling host notifications. */
+    RTTHREAD mhThreadNotifyHost;
+    /* Queue for handling requests for notifications. */
+    RTREQQUEUE mhReqQNotifyHost;
+    static DECLCALLBACK(int) threadNotifyHost(RTTHREAD self, void *pvUser);
+
+    DECLARE_CLS_COPY_CTOR_ASSIGN_NOOP(Service);
+};
+
+
+/**
+ * Gets the current timestamp.
+ *
+ * Since the RTTimeNow resolution can be very coarse, this method takes some
+ * simple steps to try avoid returning the same timestamp for two consecutive
+ * calls.  Code like getOldNotification() more or less assumes unique
+ * timestamps.
+ *
+ * @returns Nanosecond timestamp.
+ */
+uint64_t Service::getCurrentTimestamp(void)
+{
+    RTTIMESPEC time;
+    uint64_t u64NanoTS = RTTimeSpecGetNano(RTTimeNow(&time));
+    if (mPrevTimestamp - u64NanoTS > mcTimestampAdjustments)
+        mcTimestampAdjustments = 0;
+    else
+    {
+        mcTimestampAdjustments++;
+        u64NanoTS = mPrevTimestamp + 1;
+    }
+    this->mPrevTimestamp = u64NanoTS;
+    return u64NanoTS;
+}
+
+/**
+ * Set a block of properties in the property registry, checking the validity
+ * of the arguments passed.
+ *
+ * @returns iprt status value
+ * @param   cParms  the number of HGCM parameters supplied
+ * @param   paParms the array of HGCM parameters
+ * @thread  HGCM
+ */
+int Service::setPropertyBlock(uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    const char **papszNames;
+    const char **papszValues;
+    const char **papszFlags;
+    uint64_t    *paNsTimestamps;
+    uint32_t     cbDummy;
+    int          rc = VINF_SUCCESS;
+
+    /*
+     * Get and validate the parameters
+     */
+    if (   cParms != 4
+        || RT_FAILURE(HGCMSvcGetPv(&paParms[0], (void **)&papszNames, &cbDummy))
+        || RT_FAILURE(HGCMSvcGetPv(&paParms[1], (void **)&papszValues, &cbDummy))
+        || RT_FAILURE(HGCMSvcGetPv(&paParms[2], (void **)&paNsTimestamps, &cbDummy))
+        || RT_FAILURE(HGCMSvcGetPv(&paParms[3], (void **)&papszFlags, &cbDummy))
+        )
+        rc = VERR_INVALID_PARAMETER;
+    /** @todo validate the array sizes... */
+    else
+    {
+        for (unsigned i = 0; RT_SUCCESS(rc) && papszNames[i] != NULL; ++i)
+        {
+            if (   !RT_VALID_PTR(papszNames[i])
+                || !RT_VALID_PTR(papszValues[i])
+                || !RT_VALID_PTR(papszFlags[i])
+                )
+                rc = VERR_INVALID_POINTER;
+            else
+            {
+                uint32_t fFlagsIgn;
+                rc = GuestPropValidateFlags(papszFlags[i], &fFlagsIgn);
+            }
+        }
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Add the properties.  No way to roll back here.
+             */
+            for (unsigned i = 0; papszNames[i] != NULL; ++i)
+            {
+                uint32_t fFlags;
+                rc = GuestPropValidateFlags(papszFlags[i], &fFlags);
+                AssertRCBreak(rc);
+                /*
+                 * Handle names which are read-only for the guest.
+                 */
+                if (checkHostReserved(papszNames[i]))
+                    fFlags |= GUEST_PROP_F_RDONLYGUEST;
+
+                Property *pProp = getPropertyInternal(papszNames[i]);
+                if (pProp)
+                {
+                    /* Update existing property. */
+                    rc = pProp->mValue.assignNoThrow(papszValues[i]);
+                    AssertRCBreak(rc);
+                    pProp->mTimestamp = paNsTimestamps[i];
+                    pProp->mFlags     = fFlags;
+                }
+                else
+                {
+                    /* Create a new property */
+                    try
+                    {
+                        pProp = new Property(papszNames[i], papszValues[i], paNsTimestamps[i], fFlags);
+                    }
+                    catch (std::bad_alloc &)
+                    {
+                        return VERR_NO_MEMORY;
+                    }
+                    if (RTStrSpaceInsert(&mhProperties, &pProp->mStrCore))
+                        mcProperties++;
+                    else
+                    {
+                        delete pProp;
+                        rc = VERR_INTERNAL_ERROR_3;
+                        AssertFailedBreak();
+                    }
+                }
+            }
+        }
+    }
+
+    return rc;
+}
+
+/**
+ * Retrieve a value from the property registry by name, checking the validity
+ * of the arguments passed.  If the guest has not allocated enough buffer
+ * space for the value then we return VERR_OVERFLOW and set the size of the
+ * buffer needed in the "size" HGCM parameter.  If the name was not found at
+ * all, we return VERR_NOT_FOUND.
+ *
+ * @returns iprt status value
+ * @param   cParms  the number of HGCM parameters supplied
+ * @param   paParms the array of HGCM parameters
+ * @thread  HGCM
+ */
+int Service::getProperty(uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    int         rc;
+    const char *pcszName = NULL;        /* shut up gcc */
+    char       *pchBuf = NULL;          /* shut up MSC */
+    uint32_t    cbName;
+    uint32_t    cbBuf = 0;              /* shut up MSC */
+
+    /*
+     * Get and validate the parameters
+     */
+    LogFlowThisFunc(("\n"));
+    if (   cParms != 4  /* Hardcoded value as the next lines depend on it. */
+        || RT_FAILURE(HGCMSvcGetCStr(&paParms[0], &pcszName, &cbName))  /* name */
+        || RT_FAILURE(HGCMSvcGetBuf(&paParms[1], (void **)&pchBuf, &cbBuf))  /* buffer */
+       )
+        rc = VERR_INVALID_PARAMETER;
+    else
+        rc = GuestPropValidateName(pcszName, cbName);
+    if (RT_FAILURE(rc))
+    {
+        LogFlowThisFunc(("rc = %Rrc\n", rc));
+        return rc;
+    }
+
+    /*
+     * Read and set the values we will return
+     */
+
+    /* Get the property. */
+    Property *pProp = getPropertyInternal(pcszName);
+    if (pProp)
+    {
+        char szFlags[GUEST_PROP_MAX_FLAGS_LEN];
+        rc = GuestPropWriteFlags(pProp->mFlags, szFlags);
+        if (RT_SUCCESS(rc))
+        {
+            /* Check that the buffer is big enough */
+            size_t const cbFlags  = strlen(szFlags) + 1;
+            size_t const cbValue  = pProp->mValue.length() + 1;
+            size_t const cbNeeded = cbValue + cbFlags;
+            HGCMSvcSetU32(&paParms[3], (uint32_t)cbNeeded);
+            if (cbBuf >= cbNeeded)
+            {
+                /* Write the value, flags and timestamp */
+                memcpy(pchBuf, pProp->mValue.c_str(), cbValue);
+                memcpy(pchBuf + cbValue, szFlags, cbFlags);
+
+                HGCMSvcSetU64(&paParms[2], pProp->mTimestamp);
+
+                /*
+                 * Done!  Do exit logging and return.
+                 */
+                Log2(("Queried string %s, value=%s, timestamp=%lld, flags=%s\n",
+                      pcszName, pProp->mValue.c_str(), pProp->mTimestamp, szFlags));
+            }
+            else
+                rc = VERR_BUFFER_OVERFLOW;
+        }
+    }
+    else
+        rc = VERR_NOT_FOUND;
+
+    LogFlowThisFunc(("rc = %Rrc (%s)\n", rc, pcszName));
+    return rc;
+}
+
+/**
+ * Set a value in the property registry by name, checking the validity
+ * of the arguments passed.
+ *
+ * @returns iprt status value
+ * @param   cParms  the number of HGCM parameters supplied
+ * @param   paParms the array of HGCM parameters
+ * @param   isGuest is this call coming from the guest (or the host)?
+ * @throws  std::bad_alloc  if an out of memory condition occurs
+ * @thread  HGCM
+ */
+int Service::setProperty(uint32_t cParms, VBOXHGCMSVCPARM paParms[], bool isGuest)
+{
+    const char *pcszName = NULL;        /* shut up gcc */
+    const char *pcszValue = NULL;       /* ditto */
+    const char *pcszFlags = NULL;
+    uint32_t cbName = 0;                /* ditto */
+    uint32_t cbValue = 0;               /* ditto */
+    uint32_t cbFlags = 0;
+    uint32_t fFlags = GUEST_PROP_F_NILFLAG;
+    uint64_t u64TimeNano = getCurrentTimestamp();
+
+    LogFlowThisFunc(("\n"));
+
+    /*
+     * General parameter correctness checking.
+     */
+    int rc = VINF_SUCCESS;
+    if (   cParms < 2  /* Hardcoded value as the next lines depend on it these range checks. */
+        || cParms > 3
+        || RT_FAILURE(HGCMSvcGetCStr(&paParms[0], &pcszName, &cbName))  /* name */
+        || RT_FAILURE(HGCMSvcGetCStr(&paParms[1], &pcszValue, &cbValue))  /* value */
+        || (   cParms == 3
+            && RT_FAILURE(HGCMSvcGetCStr(&paParms[2], &pcszFlags, &cbFlags)) /* flags */
+           )
+       )
+        rc = VERR_INVALID_PARAMETER;
+
+    /*
+     * Check the values passed in the parameters for correctness.
+     */
+    if (RT_SUCCESS(rc))
+        rc = GuestPropValidateName(pcszName, cbName);
+    if (RT_SUCCESS(rc))
+        rc = GuestPropValidateValue(pcszValue, cbValue);
+    if (cParms == 3 && RT_SUCCESS(rc))
+        rc = GuestPropValidateFlags(pcszFlags, &fFlags);
+    if (RT_FAILURE(rc))
+    {
+        LogFlowThisFunc(("rc = %Rrc\n", rc));
+        return rc;
+    }
+
+    /*
+     * Hand it over to the internal setter method.
+     */
+    rc = setPropertyInternal(pcszName, pcszValue, fFlags, u64TimeNano, isGuest);
+
+    LogFlowThisFunc(("%s=%s, rc=%Rrc\n", pcszName, pcszValue, rc));
+    return rc;
+}
+
+/**
+ * Internal property setter.
+ *
+ * @returns VBox status code.
+ * @param   pcszName            The property name.
+ * @param   pcszValue           The new value.
+ * @param   fFlags              The flags.
+ * @param   nsTimestamp         The timestamp.
+ * @param   fIsGuest            Is it the guest calling.
+ * @throws  std::bad_alloc  if an out of memory condition occurs
+ * @thread  HGCM
+ */
+int Service::setPropertyInternal(const char *pcszName, const char *pcszValue, uint32_t fFlags, uint64_t nsTimestamp,
+                                 bool fIsGuest /*= false*/)
+{
+    /*
+     * If the property already exists, check its flags to see if we are allowed
+     * to change it.
+     */
+    Property *pProp = getPropertyInternal(pcszName);
+    int rc = checkPermission(pProp ? pProp->mFlags : GUEST_PROP_F_NILFLAG, fIsGuest);
+    /*
+     * Handle names which are read-only for the guest.
+     */
+    if (rc == VINF_SUCCESS && checkHostReserved(pcszName))
+    {
+        if (fIsGuest)
+            rc = VERR_PERMISSION_DENIED;
+        else
+            fFlags |= GUEST_PROP_F_RDONLYGUEST;
+    }
+    if (rc == VINF_SUCCESS)
+    {
+        /*
+         * Set the actual value
+         */
+        if (pProp)
+        {
+            rc = pProp->mValue.assignNoThrow(pcszValue);
+            if (RT_SUCCESS(rc))
+            {
+                pProp->mTimestamp = nsTimestamp;
+                pProp->mFlags = fFlags;
+            }
+        }
+        else if (mcProperties < GUEST_PROP_MAX_PROPS)
+        {
+            try
+            {
+                /* Create a new string space record. */
+                pProp = new Property(pcszName, pcszValue, nsTimestamp, fFlags);
+                AssertPtr(pProp);
+
+                if (RTStrSpaceInsert(&mhProperties, &pProp->mStrCore))
+                    mcProperties++;
+                else
+                {
+                    AssertFailed();
+                    delete pProp;
+
+                    rc = VERR_ALREADY_EXISTS;
+                }
+            }
+            catch (std::bad_alloc &)
+            {
+                rc = VERR_NO_MEMORY;
+            }
+        }
+        else
+            rc = VERR_TOO_MUCH_DATA;
+
+        /*
+         * Send a notification to the guest and host and return.
+         */
+        // if (fIsGuest) /* Notify the host even for properties that the host
+        //                * changed.  Less efficient, but ensures consistency. */
+        int rc2 = doNotifications(pcszName, nsTimestamp);
+        if (RT_SUCCESS(rc))
+            rc = rc2;
+    }
+
+    LogFlowThisFunc(("%s=%s, rc=%Rrc\n", pcszName, pcszValue, rc));
+    return rc;
+}
+
+
+/**
+ * Remove a value in the property registry by name, checking the validity
+ * of the arguments passed.
+ *
+ * @returns iprt status value
+ * @param   cParms  the number of HGCM parameters supplied
+ * @param   paParms the array of HGCM parameters
+ * @param   isGuest is this call coming from the guest (or the host)?
+ * @thread  HGCM
+ */
+int Service::delProperty(uint32_t cParms, VBOXHGCMSVCPARM paParms[], bool isGuest)
+{
+    int         rc;
+    const char *pcszName = NULL;        /* shut up gcc */
+    uint32_t    cbName;
+
+    LogFlowThisFunc(("\n"));
+
+    /*
+     * Check the user-supplied parameters.
+     */
+    if (   (cParms == 1)  /* Hardcoded value as the next lines depend on it. */
+        && RT_SUCCESS(HGCMSvcGetCStr(&paParms[0], &pcszName, &cbName))  /* name */
+       )
+        rc = GuestPropValidateName(pcszName, cbName);
+    else
+        rc = VERR_INVALID_PARAMETER;
+    if (RT_FAILURE(rc))
+    {
+        LogFlowThisFunc(("rc=%Rrc\n", rc));
+        return rc;
+    }
+
+    /*
+     * If the property exists, check its flags to see if we are allowed
+     * to change it.
+     */
+    Property *pProp = getPropertyInternal(pcszName);
+    if (pProp)
+        rc = checkPermission(pProp->mFlags, isGuest);
+
+    /*
+     * And delete the property if all is well.
+     */
+    if (rc == VINF_SUCCESS && pProp)
+    {
+        uint64_t nsTimestamp = getCurrentTimestamp();
+        PRTSTRSPACECORE pStrCore = RTStrSpaceRemove(&mhProperties, pProp->mStrCore.pszString);
+        AssertPtr(pStrCore); NOREF(pStrCore);
+        mcProperties--;
+        delete pProp;
+        // if (isGuest)  /* Notify the host even for properties that the host
+        //                * changed.  Less efficient, but ensures consistency. */
+        int rc2 = doNotifications(pcszName, nsTimestamp);
+        if (RT_SUCCESS(rc))
+            rc = rc2;
+    }
+
+    LogFlowThisFunc(("%s: rc=%Rrc\n", pcszName, rc));
+    return rc;
+}
+
+/**
+ * Enumeration data shared between enumPropsCallback and Service::enumProps.
+ */
+typedef struct ENUMDATA
+{
+    const char *pszPattern; /**< The pattern to match properties against. */
+    char       *pchCur;     /**< The current buffer postion. */
+    size_t      cbLeft;     /**< The amount of available buffer space. */
+    size_t      cbNeeded;   /**< The amount of needed buffer space. */
+} ENUMDATA;
+
+/**
+ * @callback_method_impl{FNRTSTRSPACECALLBACK}
+ */
+static DECLCALLBACK(int) enumPropsCallback(PRTSTRSPACECORE pStr, void *pvUser)
+{
+    Property *pProp = (Property *)pStr;
+    ENUMDATA *pEnum = (ENUMDATA *)pvUser;
+
+    /* Included in the enumeration? */
+    if (!pProp->Matches(pEnum->pszPattern))
+        return 0;
+
+    /* Convert the non-string members into strings. */
+    char            szTimestamp[256];
+    size_t const    cbTimestamp = RTStrFormatNumber(szTimestamp, pProp->mTimestamp, 10, 0, 0, 0) + 1;
+
+    char            szFlags[GUEST_PROP_MAX_FLAGS_LEN];
+    int rc = GuestPropWriteFlags(pProp->mFlags, szFlags);
+    if (RT_FAILURE(rc))
+        return rc;
+    size_t const    cbFlags = strlen(szFlags) + 1;
+
+    /* Calculate the buffer space requirements. */
+    size_t const    cbName     = pProp->mName.length() + 1;
+    size_t const    cbValue    = pProp->mValue.length() + 1;
+    size_t const    cbRequired = cbName + cbValue + cbTimestamp + cbFlags;
+    pEnum->cbNeeded += cbRequired;
+
+    /* Sufficient buffer space? */
+    if (cbRequired > pEnum->cbLeft)
+    {
+        pEnum->cbLeft = 0;
+        return 0; /* don't quit */
+    }
+    pEnum->cbLeft -= cbRequired;
+
+    /* Append the property to the buffer. */
+    char *pchCur = pEnum->pchCur;
+    pEnum->pchCur += cbRequired;
+
+    memcpy(pchCur, pProp->mName.c_str(), cbName);
+    pchCur += cbName;
+
+    memcpy(pchCur, pProp->mValue.c_str(), cbValue);
+    pchCur += cbValue;
+
+    memcpy(pchCur, szTimestamp, cbTimestamp);
+    pchCur += cbTimestamp;
+
+    memcpy(pchCur, szFlags, cbFlags);
+    pchCur += cbFlags;
+
+    Assert(pchCur == pEnum->pchCur);
+    return 0;
+}
+
+/**
+ * Enumerate guest properties by mask, checking the validity
+ * of the arguments passed.
+ *
+ * @returns iprt status value
+ * @param   cParms  the number of HGCM parameters supplied
+ * @param   paParms the array of HGCM parameters
+ * @thread  HGCM
+ */
+int Service::enumProps(uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    int rc = VINF_SUCCESS;
+
+    /*
+     * Get the HGCM function arguments.
+     */
+    char const *pchPatterns = NULL;
+    char *pchBuf = NULL;
+    uint32_t cbPatterns = 0;
+    uint32_t cbBuf = 0;
+    LogFlowThisFunc(("\n"));
+    if (   (cParms != 3)  /* Hardcoded value as the next lines depend on it. */
+        || RT_FAILURE(HGCMSvcGetCStr(&paParms[0], &pchPatterns, &cbPatterns))  /* patterns */
+        || RT_FAILURE(HGCMSvcGetBuf(&paParms[1], (void **)&pchBuf, &cbBuf))  /* return buffer */
+       )
+        rc = VERR_INVALID_PARAMETER;
+    if (RT_SUCCESS(rc) && cbPatterns > GUEST_PROP_MAX_PATTERN_LEN)
+        rc = VERR_TOO_MUCH_DATA;
+
+    /*
+     * First repack the patterns into the format expected by RTStrSimplePatternMatch()
+     */
+    char szPatterns[GUEST_PROP_MAX_PATTERN_LEN];
+    if (RT_SUCCESS(rc))
+    {
+        for (unsigned i = 0; i < cbPatterns - 1; ++i)
+        {
+            char ch = pchPatterns[i];
+            if (pchPatterns[i] != '\0')
+            { /* likely*/ }
+            else
+            {
+                /* Since the RTStrValidateEncodingEx call in HGCMSvcGetCStr stops at the
+                   first terminator, we have to validate all subsequent pattern strings. */
+                rc = RTStrValidateEncodingEx(&pchPatterns[i + 1], cbPatterns - i -1, RTSTR_VALIDATE_ENCODING_ZERO_TERMINATED);
+                ASSERT_GUEST_RC_BREAK(rc);
+                ch = '|';
+            }
+            szPatterns[i] = ch;
+        }
+        szPatterns[cbPatterns - 1] = '\0';
+    }
+
+    /*
+     * Next enumerate into the buffer.
+     */
+    if (RT_SUCCESS(rc))
+    {
+        ENUMDATA EnumData;
+        EnumData.pszPattern = szPatterns;
+        EnumData.pchCur     = pchBuf;
+        EnumData.cbLeft     = cbBuf;
+        EnumData.cbNeeded   = 0;
+        rc = RTStrSpaceEnumerate(&mhProperties, enumPropsCallback, &EnumData);
+        AssertRCSuccess(rc);
+        if (RT_SUCCESS(rc))
+        {
+            HGCMSvcSetU32(&paParms[2], (uint32_t)(EnumData.cbNeeded + 4));
+            if (EnumData.cbLeft >= 4)
+            {
+                /* The final terminators. */
+                EnumData.pchCur[0] = '\0';
+                EnumData.pchCur[1] = '\0';
+                EnumData.pchCur[2] = '\0';
+                EnumData.pchCur[3] = '\0';
+            }
+            else
+                rc = VERR_BUFFER_OVERFLOW;
+        }
+    }
+
+    return rc;
+}
+
+
+/** Helper query used by getOldNotification
+ * @throws  nothing
+ */
+int Service::getOldNotificationInternal(const char *pszPatterns, uint64_t nsTimestamp, Property *pProp)
+{
+    /* We count backwards, as the guest should normally be querying the
+     * most recent events. */
+    int rc = VWRN_NOT_FOUND;
+    PropertyList::reverse_iterator it = mGuestNotifications.rbegin();
+    for (; it != mGuestNotifications.rend(); ++it)
+        if (it->mTimestamp == nsTimestamp)
+        {
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+    /* Now look for an event matching the patterns supplied.  The base()
+     * member conveniently points to the following element. */
+    PropertyList::iterator base = it.base();
+    for (; base != mGuestNotifications.end(); ++base)
+        if (base->Matches(pszPatterns))
+        {
+            try
+            {
+                *pProp = *base;
+            }
+            catch (std::bad_alloc &)
+            {
+                rc = VERR_NO_MEMORY;
+            }
+            return rc;
+        }
+    *pProp = Property();
+    return rc;
+}
+
+
+/** Helper query used by getNotification */
+int Service::getNotificationWriteOut(uint32_t cParms, VBOXHGCMSVCPARM paParms[], Property const &rProp, bool fWasDeleted)
+{
+    AssertReturn(cParms == 4, VERR_INVALID_PARAMETER); /* Basic sanity checking. */
+
+    /* Format the data to write to the buffer. */
+    char    *pchBuf;
+    uint32_t cbBuf;
+    int rc = HGCMSvcGetBuf(&paParms[2], (void **)&pchBuf, &cbBuf);
+    if (RT_SUCCESS(rc))
+    {
+        char szFlags[GUEST_PROP_MAX_FLAGS_LEN];
+        rc = GuestPropWriteFlags(rProp.mFlags, szFlags);
+        if (RT_SUCCESS(rc))
+        {
+            HGCMSvcSetU64(&paParms[1], rProp.mTimestamp);
+
+            size_t const cbFlags      = strlen(szFlags) + 1;
+            size_t const cbName       = rProp.mName.length() + 1;
+            size_t const cbValue      = rProp.mValue.length() + 1;
+            size_t const cbWasDeleted = 2;
+            size_t const cbNeeded     = cbName + cbValue + cbFlags + cbWasDeleted;
+            HGCMSvcSetU32(&paParms[3], (uint32_t)cbNeeded);
+            if (cbNeeded <= cbBuf)
+            {
+                /* Buffer layout: Name\0Value\0Flags\0fWasDeleted\0. */
+                memcpy(pchBuf, rProp.mName.c_str(), cbName);
+                pchBuf += cbName;
+                memcpy(pchBuf, rProp.mValue.c_str(), cbValue);
+                pchBuf += cbValue;
+                memcpy(pchBuf, szFlags, cbFlags);
+                pchBuf += cbFlags;
+                *pchBuf++ = fWasDeleted ? '1' : '0';
+                *pchBuf++ = '\0';
+            }
+            else
+                rc = VERR_BUFFER_OVERFLOW;
+        }
+    }
+    return rc;
+}
+
+
+/**
+ * Get the next guest notification.
+ *
+ * @returns iprt status value
+ * @param   u32ClientId the client ID
+ * @param   callHandle  handle
+ * @param   cParms      the number of HGCM parameters supplied
+ * @param   paParms     the array of HGCM parameters
+ * @thread  HGCM
+ * @throws  nothing
+ */
+int Service::getNotification(uint32_t u32ClientId, VBOXHGCMCALLHANDLE callHandle,
+                             uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    int rc = VINF_SUCCESS;
+    char *pszPatterns = NULL;           /* shut up gcc */
+    char *pchBuf;
+    uint32_t cchPatterns = 0;
+    uint32_t cbBuf = 0;
+    uint64_t nsTimestamp;
+
+    /*
+     * Get the HGCM function arguments and perform basic verification.
+     */
+    LogFlowThisFunc(("\n"));
+    if (   cParms != 4  /* Hardcoded value as the next lines depend on it. */
+        || RT_FAILURE(HGCMSvcGetStr(&paParms[0], &pszPatterns, &cchPatterns))  /* patterns */
+        || RT_FAILURE(HGCMSvcGetU64(&paParms[1], &nsTimestamp))  /* timestamp */
+        || RT_FAILURE(HGCMSvcGetBuf(&paParms[2], (void **)&pchBuf, &cbBuf))  /* return buffer */
+       )
+        rc = VERR_INVALID_PARAMETER;
+    else
+    {
+        LogFlow(("pszPatterns=%s, nsTimestamp=%llu\n", pszPatterns, nsTimestamp));
+
+        /*
+         * If no timestamp was supplied or no notification was found in the queue
+         * of old notifications, enqueue the request in the waiting queue.
+         */
+        Property prop;
+        if (RT_SUCCESS(rc) && nsTimestamp != 0)
+            rc = getOldNotification(pszPatterns, nsTimestamp, &prop);
+        if (RT_SUCCESS(rc))
+        {
+            if (prop.isNull())
+            {
+                /*
+                 * Check if the client already had the same request.
+                 * Complete the old request with an error in this case.
+                 * Protection against clients, which cancel and resubmits requests.
+                 */
+                uint32_t cPendingWaits = 0;
+                CallList::iterator it = mGuestWaiters.begin();
+                while (it != mGuestWaiters.end())
+                {
+                    if (u32ClientId == it->u32ClientId)
+                    {
+                        const char *pszPatternsExisting;
+                        uint32_t    cchPatternsExisting;
+                        int rc3 = HGCMSvcGetCStr(&it->mParms[0], &pszPatternsExisting, &cchPatternsExisting);
+                        if (   RT_SUCCESS(rc3)
+                            && RTStrCmp(pszPatterns, pszPatternsExisting) == 0)
+                        {
+                            /* Complete the old request. */
+                            mpHelpers->pfnCallComplete(it->mHandle, VERR_INTERRUPTED);
+                            it = mGuestWaiters.erase(it);
+                        }
+                        else if (mpHelpers->pfnIsCallCancelled(it->mHandle))
+                        {
+                            /* Cleanup cancelled request. */
+                            mpHelpers->pfnCallComplete(it->mHandle, VERR_INTERRUPTED);
+                            it = mGuestWaiters.erase(it);
+                        }
+                        else
+                        {
+                            /** @todo check if cancelled. */
+                            cPendingWaits++;
+                            ++it;
+                        }
+                    }
+                    else
+                        ++it;
+                }
+
+                if (cPendingWaits < GUEST_PROP_MAX_GUEST_CONCURRENT_WAITS)
+                {
+                    try
+                    {
+                        mGuestWaiters.push_back(GuestCall(u32ClientId, callHandle, GUEST_PROP_FN_GET_NOTIFICATION,
+                                                          cParms, paParms, rc));
+                        rc = VINF_HGCM_ASYNC_EXECUTE;
+                    }
+                    catch (std::bad_alloc &)
+                    {
+                        rc = VERR_NO_MEMORY;
+                    }
+                }
+                else
+                {
+                    LogFunc(("Too many pending waits already!\n"));
+                    rc = VERR_OUT_OF_RESOURCES;
+                }
+            }
+            /*
+             * Otherwise reply at once with the enqueued notification we found.
+             */
+            else
+            {
+                int rc2 = getNotificationWriteOut(cParms, paParms, prop, !getPropertyInternal(prop.mName.c_str()));
+                if (RT_FAILURE(rc2))
+                    rc = rc2;
+            }
+        }
+    }
+
+    LogFlowThisFunc(("returning rc=%Rrc\n", rc));
+    return rc;
+}
+
+
+/**
+ * Notify the service owner and the guest that a property has been
+ * added/deleted/changed
+ *
+ * @param   pszProperty The name of the property which has changed.
+ * @param   nsTimestamp The time at which the change took place.
+ * @throws  nothing.
+ * @thread  HGCM service
+ */
+int Service::doNotifications(const char *pszProperty, uint64_t nsTimestamp)
+{
+    AssertPtrReturn(pszProperty, VERR_INVALID_POINTER);
+    LogFlowThisFunc(("pszProperty=%s, nsTimestamp=%llu\n", pszProperty, nsTimestamp));
+    /* Ensure that our timestamp is different to the last one. */
+    if (   !mGuestNotifications.empty()
+        && nsTimestamp == mGuestNotifications.back().mTimestamp)
+        ++nsTimestamp;
+
+    /*
+     * Don't keep too many changes around.
+     */
+    if (mGuestNotifications.size() >= GUEST_PROP_MAX_GUEST_NOTIFICATIONS)
+        mGuestNotifications.pop_front();
+
+    /*
+     * Try to find the property.  Create a change event if we find it and a
+     * delete event if we do not.
+     */
+    Property prop;
+    int rc = prop.mName.assignNoThrow(pszProperty);
+    AssertRCReturn(rc, rc);
+    prop.mTimestamp = nsTimestamp;
+    /* prop is currently a delete event for pszProperty */
+    Property const * const pProp = getPropertyInternal(pszProperty);
+    if (pProp)
+    {
+        /* Make prop into a change event. */
+        rc = prop.mValue.assignNoThrow(pProp->mValue);
+        AssertRCReturn(rc, rc);
+        prop.mFlags = pProp->mFlags;
+    }
+
+    /* Release guest waiters if applicable and add the event
+     * to the queue for guest notifications */
+    CallList::iterator it = mGuestWaiters.begin();
+    while (it != mGuestWaiters.end())
+    {
+        const char *pszPatterns = NULL;
+        uint32_t    cchPatterns;
+        int rc2;
+
+        rc2 = HGCMSvcGetCStr(&it->mParms[0], &pszPatterns, &cchPatterns);
+        if (RT_FAILURE(rc2))
+        {
+            LogRel(("doNotifications: failed to get match pattern for guest property notification request, rc=%Rrc\n", rc2));
+            mpHelpers->pfnCallComplete(it->mHandle, VERR_INVALID_PARAMETER);
+            it = mGuestWaiters.erase(it);
+        }
+        else if (prop.Matches(pszPatterns))
+        {
+            rc2 = getNotificationWriteOut(it->mParmsCnt, it->mParms, prop, !pProp);
+            if (RT_SUCCESS(rc2))
+                rc2 = it->mRc;
+            mpHelpers->pfnCallComplete(it->mHandle, rc2);
+            it = mGuestWaiters.erase(it);
+        }
+        else
+            ++it;
+    }
+
+    try
+    {
+        mGuestNotifications.push_back(prop);
+    }
+    catch (std::bad_alloc &)
+    {
+        rc = VERR_NO_MEMORY;
+    }
+
+    if (   RT_SUCCESS(rc)
+        && mpfnHostCallback)
+    {
+        /*
+         * Host notifications - first case: if the property exists then send its
+         * current value
+         */
+        if (pProp)
+        {
+            char szFlags[GUEST_PROP_MAX_FLAGS_LEN];
+            /* Send out a host notification */
+            const char *pszValue = prop.mValue.c_str();
+            rc = GuestPropWriteFlags(prop.mFlags, szFlags);
+            if (RT_SUCCESS(rc))
+                rc = notifyHost(pszProperty, pszValue, nsTimestamp, szFlags);
+        }
+        /*
+         * Host notifications - second case: if the property does not exist then
+         * send the host an empty value
+         */
+        else
+        {
+            /* Send out a host notification */
+            rc = notifyHost(pszProperty, NULL, nsTimestamp, "");
+        }
+    }
+
+    LogFlowThisFunc(("returning rc=%Rrc\n", rc));
+    return rc;
+}
+
+static DECLCALLBACK(void)
+notifyHostAsyncWorker(PFNHGCMSVCEXT pfnHostCallback, void *pvHostData, PGUESTPROPHOSTCALLBACKDATA pHostCallbackData)
+{
+    pfnHostCallback(pvHostData, 0 /*u32Function*/, (void *)pHostCallbackData, sizeof(GUESTPROPHOSTCALLBACKDATA));
+    RTMemFree(pHostCallbackData);
+}
+
+/**
+ * Notify the service owner that a property has been added/deleted/changed.
+ * @returns  IPRT status value
+ * @param    pszName       the property name
+ * @param    pszValue      the new value, or NULL if the property was deleted
+ * @param    nsTimestamp   the time of the change
+ * @param    pszFlags      the new flags string
+ */
+int Service::notifyHost(const char *pszName, const char *pszValue, uint64_t nsTimestamp, const char *pszFlags)
+{
+    LogFlowFunc(("pszName=%s, pszValue=%s, nsTimestamp=%llu, pszFlags=%s\n", pszName, pszValue, nsTimestamp, pszFlags));
+    int rc;
+
+    /* Allocate buffer for the callback data and strings. */
+    size_t cbName = pszName? strlen(pszName): 0;
+    size_t cbValue = pszValue? strlen(pszValue): 0;
+    size_t cbFlags = pszFlags? strlen(pszFlags): 0;
+    size_t cbAlloc = sizeof(GUESTPROPHOSTCALLBACKDATA) + cbName + cbValue + cbFlags + 3;
+    PGUESTPROPHOSTCALLBACKDATA pHostCallbackData = (PGUESTPROPHOSTCALLBACKDATA)RTMemAlloc(cbAlloc);
+    if (pHostCallbackData)
+    {
+        uint8_t *pu8 = (uint8_t *)pHostCallbackData;
+        pu8 += sizeof(GUESTPROPHOSTCALLBACKDATA);
+
+        pHostCallbackData->u32Magic     = GUESTPROPHOSTCALLBACKDATA_MAGIC;
+
+        pHostCallbackData->pcszName     = (const char *)pu8;
+        memcpy(pu8, pszName, cbName);
+        pu8 += cbName;
+        *pu8++ = 0;
+
+        /* NULL value means property was deleted. */
+        pHostCallbackData->pcszValue    = pszValue ? (const char *)pu8 : NULL;
+        memcpy(pu8, pszValue, cbValue);
+        pu8 += cbValue;
+        *pu8++ = 0;
+
+        pHostCallbackData->u64Timestamp = nsTimestamp;
+
+        pHostCallbackData->pcszFlags    = (const char *)pu8;
+        memcpy(pu8, pszFlags, cbFlags);
+        pu8 += cbFlags;
+        *pu8++ = 0;
+
+        rc = RTReqQueueCallEx(mhReqQNotifyHost, NULL, 0, RTREQFLAGS_VOID | RTREQFLAGS_NO_WAIT,
+                              (PFNRT)notifyHostAsyncWorker, 3,
+                              mpfnHostCallback, mpvHostData, pHostCallbackData);
+        if (RT_FAILURE(rc))
+        {
+            RTMemFree(pHostCallbackData);
+        }
+    }
+    else
+    {
+        rc = VERR_NO_MEMORY;
+    }
+    LogFlowFunc(("returning rc=%Rrc\n", rc));
+    return rc;
+}
+
+
+/**
+ * Handle an HGCM service call.
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnCall}
+ * @note    All functions which do not involve an unreasonable delay will be
+ *          handled synchronously.  If needed, we will add a request handler
+ *          thread in future for those which do.
+ *
+ * @thread  HGCM
+ */
+void Service::call (VBOXHGCMCALLHANDLE callHandle, uint32_t u32ClientID,
+                    void * /* pvClient */, uint32_t eFunction, uint32_t cParms,
+                    VBOXHGCMSVCPARM paParms[])
+{
+    int rc;
+    LogFlowFunc(("u32ClientID = %d, fn = %d, cParms = %d, pparms = %p\n",
+                 u32ClientID, eFunction, cParms, paParms));
+
+    switch (eFunction)
+    {
+        /* The guest wishes to read a property */
+        case GUEST_PROP_FN_GET_PROP:
+            LogFlowFunc(("GET_PROP\n"));
+            rc = getProperty(cParms, paParms);
+            break;
+
+        /* The guest wishes to set a property */
+        case GUEST_PROP_FN_SET_PROP:
+            LogFlowFunc(("SET_PROP\n"));
+            rc = setProperty(cParms, paParms, true);
+            break;
+
+        /* The guest wishes to set a property value */
+        case GUEST_PROP_FN_SET_PROP_VALUE:
+            LogFlowFunc(("SET_PROP_VALUE\n"));
+            rc = setProperty(cParms, paParms, true);
+            break;
+
+        /* The guest wishes to remove a configuration value */
+        case GUEST_PROP_FN_DEL_PROP:
+            LogFlowFunc(("DEL_PROP\n"));
+            rc = delProperty(cParms, paParms, true);
+            break;
+
+        /* The guest wishes to enumerate all properties */
+        case GUEST_PROP_FN_ENUM_PROPS:
+            LogFlowFunc(("ENUM_PROPS\n"));
+            rc = enumProps(cParms, paParms);
+            break;
+
+        /* The guest wishes to get the next property notification */
+        case GUEST_PROP_FN_GET_NOTIFICATION:
+            LogFlowFunc(("GET_NOTIFICATION\n"));
+            rc = getNotification(u32ClientID, callHandle, cParms, paParms);
+            break;
+
+        default:
+            rc = VERR_NOT_IMPLEMENTED;
+    }
+    LogFlowFunc(("rc = %Rrc\n", rc));
+    if (rc != VINF_HGCM_ASYNC_EXECUTE)
+        mpHelpers->pfnCallComplete(callHandle, rc);
+}
+
+/**
+ * Enumeration data shared between dbgInfoCallback and Service::dbgInfoShow.
+ */
+typedef struct ENUMDBGINFO
+{
+    PCDBGFINFOHLP pHlp;
+} ENUMDBGINFO;
+
+static DECLCALLBACK(int) dbgInfoCallback(PRTSTRSPACECORE pStr, void *pvUser)
+{
+    Property     *pProp = (Property *)pStr;
+    PCDBGFINFOHLP pHlp  = ((ENUMDBGINFO *)pvUser)->pHlp;
+
+    char szFlags[GUEST_PROP_MAX_FLAGS_LEN];
+    int rc = GuestPropWriteFlags(pProp->mFlags, szFlags);
+    if (RT_FAILURE(rc))
+        RTStrPrintf(szFlags, sizeof(szFlags), "???");
+
+    pHlp->pfnPrintf(pHlp, "%s: '%s', %RU64", pProp->mName.c_str(), pProp->mValue.c_str(), pProp->mTimestamp);
+    if (strlen(szFlags))
+        pHlp->pfnPrintf(pHlp, " (%s)", szFlags);
+    pHlp->pfnPrintf(pHlp, "\n");
+    return 0;
+}
+
+
+/**
+ * Handler for debug info.
+ *
+ * @param   pvUser      user pointer.
+ * @param   pHlp        The info helper functions.
+ * @param   pszArgs     Arguments, ignored.
+ */
+DECLCALLBACK(void) Service::dbgInfo(void *pvUser, PCDBGFINFOHLP pHlp, const char *pszArgs)
+{
+    RT_NOREF1(pszArgs);
+    SELF *pSelf = reinterpret_cast<SELF *>(pvUser);
+
+    ENUMDBGINFO EnumData = { pHlp };
+    RTStrSpaceEnumerate(&pSelf->mhProperties, dbgInfoCallback, &EnumData);
+}
+
+
+/**
+ * Service call handler for the host.
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnHostCall}
+ * @thread  hgcm
+ */
+int Service::hostCall (uint32_t eFunction, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    int rc;
+    LogFlowFunc(("fn = %d, cParms = %d, pparms = %p\n", eFunction, cParms, paParms));
+
+    switch (eFunction)
+    {
+        /* The host wishes to set a block of properties */
+        case GUEST_PROP_FN_HOST_SET_PROPS:
+            LogFlowFunc(("SET_PROPS_HOST\n"));
+            rc = setPropertyBlock(cParms, paParms);
+            break;
+
+        /* The host wishes to read a configuration value */
+        case GUEST_PROP_FN_HOST_GET_PROP:
+            LogFlowFunc(("GET_PROP_HOST\n"));
+            rc = getProperty(cParms, paParms);
+            break;
+
+        /* The host wishes to set a configuration value */
+        case GUEST_PROP_FN_HOST_SET_PROP:
+            LogFlowFunc(("SET_PROP_HOST\n"));
+            rc = setProperty(cParms, paParms, false);
+            break;
+
+        /* The host wishes to set a configuration value */
+        case GUEST_PROP_FN_HOST_SET_PROP_VALUE:
+            LogFlowFunc(("SET_PROP_VALUE_HOST\n"));
+            rc = setProperty(cParms, paParms, false);
+            break;
+
+        /* The host wishes to remove a configuration value */
+        case GUEST_PROP_FN_HOST_DEL_PROP:
+            LogFlowFunc(("DEL_PROP_HOST\n"));
+            rc = delProperty(cParms, paParms, false);
+            break;
+
+        /* The host wishes to enumerate all properties */
+        case GUEST_PROP_FN_HOST_ENUM_PROPS:
+            LogFlowFunc(("ENUM_PROPS\n"));
+            rc = enumProps(cParms, paParms);
+            break;
+
+        /* The host wishes to set global flags for the service */
+        case GUEST_PROP_FN_HOST_SET_GLOBAL_FLAGS:
+            LogFlowFunc(("SET_GLOBAL_FLAGS_HOST\n"));
+            if (cParms == 1)
+            {
+                uint32_t fFlags;
+                rc = HGCMSvcGetU32(&paParms[0], &fFlags);
+                if (RT_SUCCESS(rc))
+                    mfGlobalFlags = fFlags;
+            }
+            else
+                rc = VERR_INVALID_PARAMETER;
+            break;
+
+        default:
+            rc = VERR_NOT_SUPPORTED;
+            break;
+    }
+
+    LogFlowFunc(("rc = %Rrc\n", rc));
+    return rc;
+}
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnDisconnect}
+ */
+/*static*/ DECLCALLBACK(int) Service::svcDisconnect(void *pvService, uint32_t idClient, void *pvClient)
+{
+    RT_NOREF(pvClient);
+    LogFlowFunc(("idClient=%u\n", idClient));
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertLogRelReturn(pThis, VERR_INVALID_POINTER);
+
+    /*
+     * Complete all pending requests for this client.
+     */
+    for (CallList::iterator It = pThis->mGuestWaiters.begin(); It != pThis->mGuestWaiters.end();)
+    {
+        GuestCall &rCurCall = *It;
+        if (rCurCall.u32ClientId != idClient)
+            ++It;
+        else
+        {
+            LogFlowFunc(("Completing call %u (%p)...\n", rCurCall.mFunction, rCurCall.mHandle));
+            pThis->mpHelpers->pfnCallComplete(rCurCall.mHandle, VERR_INTERRUPTED);
+            It = pThis->mGuestWaiters.erase(It);
+        }
+    }
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Increments a counter property.
+ *
+ * It is assumed that this a transient property that is read-only to the guest.
+ *
+ * @param   pszName     The property name.
+ * @throws  std::bad_alloc  if an out of memory condition occurs
+ */
+void Service::incrementCounterProp(const char *pszName)
+{
+    /* Format the incremented value. */
+    char szValue[64];
+    Property *pProp = getPropertyInternal(pszName);
+    if (pProp)
+    {
+        uint64_t uValue = RTStrToUInt64(pProp->mValue.c_str());
+        RTStrFormatU64(szValue, sizeof(szValue), uValue + 1, 10, 0, 0, 0);
+    }
+    else
+    {
+        szValue[0] = '1';
+        szValue[1] = '\0';
+    }
+
+    /* Set it. */
+    setPropertyInternal(pszName, szValue, GUEST_PROP_F_TRANSIENT | GUEST_PROP_F_RDONLYGUEST, getCurrentTimestamp());
+}
+
+/**
+ * Sets the VBoxVer, VBoxVerExt and VBoxRev properties.
+ */
+int Service::setHostVersionProps()
+{
+    uint64_t nsTimestamp = getCurrentTimestamp();
+
+    /* Set the raw VBox version string as a guest property. Used for host/guest
+     * version comparison. */
+    int rc = setPropertyInternal("/VirtualBox/HostInfo/VBoxVer", VBOX_VERSION_STRING_RAW,
+                                 GUEST_PROP_F_TRANSIENT | GUEST_PROP_F_RDONLYGUEST, nsTimestamp);
+    AssertRCReturn(rc, rc);
+
+    /* Set the full VBox version string as a guest property. Can contain vendor-specific
+     * information/branding and/or pre-release tags. */
+    rc = setPropertyInternal("/VirtualBox/HostInfo/VBoxVerExt", VBOX_VERSION_STRING,
+                             GUEST_PROP_F_TRANSIENT | GUEST_PROP_F_RDONLYGUEST, nsTimestamp + 1);
+    AssertRCReturn(rc, rc);
+
+    /* Set the VBox SVN revision as a guest property */
+    rc = setPropertyInternal("/VirtualBox/HostInfo/VBoxRev", RTBldCfgRevisionStr(),
+                             GUEST_PROP_F_TRANSIENT | GUEST_PROP_F_RDONLYGUEST, nsTimestamp + 2);
+    AssertRCReturn(rc, rc);
+    return VINF_SUCCESS;
+}
+
+
+/**
+ * @interface_method_impl{VBOXHGCMSVCFNTABLE,pfnNotify}
+ */
+/*static*/ DECLCALLBACK(void) Service::svcNotify(void *pvService, HGCMNOTIFYEVENT enmEvent)
+{
+    SELF *pThis = reinterpret_cast<SELF *>(pvService);
+    AssertPtrReturnVoid(pThis);
+
+    /* Make sure the host version properties have been touched and are
+       up-to-date after a restore: */
+    if (   !pThis->m_fSetHostVersionProps
+        && (enmEvent == HGCMNOTIFYEVENT_RESUME || enmEvent == HGCMNOTIFYEVENT_POWER_ON))
+    {
+        pThis->setHostVersionProps();
+        pThis->m_fSetHostVersionProps = true;
+    }
+
+    if (enmEvent == HGCMNOTIFYEVENT_RESUME)
+        pThis->incrementCounterProp("/VirtualBox/VMInfo/ResumeCounter");
+
+    if (enmEvent == HGCMNOTIFYEVENT_RESET)
+        pThis->incrementCounterProp("/VirtualBox/VMInfo/ResetCounter");
+}
+
+
+/* static */
+DECLCALLBACK(int) Service::threadNotifyHost(RTTHREAD hThreadSelf, void *pvUser)
+{
+    RT_NOREF1(hThreadSelf);
+    Service *pThis = (Service *)pvUser;
+    int rc = VINF_SUCCESS;
+
+    LogFlowFunc(("ENTER: %p\n", pThis));
+
+    for (;;)
+    {
+        rc = RTReqQueueProcess(pThis->mhReqQNotifyHost, RT_INDEFINITE_WAIT);
+
+        AssertMsg(rc == VWRN_STATE_CHANGED,
+                  ("Left RTReqProcess and error code is not VWRN_STATE_CHANGED rc=%Rrc\n",
+                   rc));
+        if (rc == VWRN_STATE_CHANGED)
+        {
+            break;
+        }
+    }
+
+    LogFlowFunc(("LEAVE: %Rrc\n", rc));
+    return rc;
+}
+
+static DECLCALLBACK(int) wakeupNotifyHost(void)
+{
+    /* Returning a VWRN_* will cause RTReqQueueProcess return. */
+    return VWRN_STATE_CHANGED;
+}
+
+
+int Service::initialize()
+{
+    /*
+     * Insert standard host properties.
+     */
+    /* The host version will but updated again on power on or resume
+       (after restore), however we need the properties now for restored
+       guest notification/wait calls. */
+    int rc = setHostVersionProps();
+    AssertRCReturn(rc, rc);
+
+    uint64_t nsNow = getCurrentTimestamp(); /* Must increment this for each property to avoid asserting in getOldNotification. */
+
+    /* Resume and reset counters. */
+    rc = setPropertyInternal("/VirtualBox/VMInfo/ResetCounter",  "0", GUEST_PROP_F_TRANSIENT | GUEST_PROP_F_RDONLYGUEST, nsNow);
+    AssertRCReturn(rc, rc);
+    rc = setPropertyInternal("/VirtualBox/VMInfo/ResumeCounter", "0", GUEST_PROP_F_TRANSIENT | GUEST_PROP_F_RDONLYGUEST, ++nsNow);
+    AssertRCReturn(rc, rc);
+
+    /* Sysprep execution by VBoxService (host is allowed to change these). */
+    rc = setPropertyInternal("/VirtualBox/HostGuest/SysprepExec", "", GUEST_PROP_F_TRANSIENT | GUEST_PROP_F_RDONLYGUEST, ++nsNow);
+    AssertRCReturn(rc, rc);
+    rc = setPropertyInternal("/VirtualBox/HostGuest/SysprepArgs", "", GUEST_PROP_F_TRANSIENT | GUEST_PROP_F_RDONLYGUEST, ++nsNow);
+    AssertRCReturn(rc, rc);
+
+
+    /* The host notification thread and queue. */
+    rc = RTReqQueueCreate(&mhReqQNotifyHost);
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTThreadCreate(&mhThreadNotifyHost,
+                            threadNotifyHost,
+                            this,
+                            0 /* default stack size */,
+                            RTTHREADTYPE_DEFAULT,
+                            RTTHREADFLAGS_WAITABLE,
+                            "GstPropNtfy");
+        if (RT_SUCCESS(rc))
+        {
+            /* Finally debug stuff (ignore failures): */
+            HGCMSvcHlpInfoRegister(mpHelpers, "guestprops", "Display the guest properties", Service::dbgInfo, this);
+            return rc;
+        }
+
+        RTReqQueueDestroy(mhReqQNotifyHost);
+        mhReqQNotifyHost = NIL_RTREQQUEUE;
+    }
+    return rc;
+}
+
+/**
+ * @callback_method_impl{FNRTSTRSPACECALLBACK, Destroys Property.}
+ */
+static DECLCALLBACK(int) destroyProperty(PRTSTRSPACECORE pStr, void *pvUser)
+{
+    RT_NOREF(pvUser);
+    Property *pProp = RT_FROM_CPP_MEMBER(pStr, struct Property, mStrCore); /* clang objects to offsetof on non-POD.*/
+    delete pProp;
+    return 0;
+}
+
+
+int Service::uninit()
+{
+    if (mpHelpers)
+        HGCMSvcHlpInfoDeregister(mpHelpers, "guestprops");
+
+    if (mhReqQNotifyHost != NIL_RTREQQUEUE)
+    {
+        /* Stop the thread */
+        PRTREQ pReq;
+        int rc = RTReqQueueCall(mhReqQNotifyHost, &pReq, 10000, (PFNRT)wakeupNotifyHost, 0);
+        if (RT_SUCCESS(rc))
+            RTReqRelease(pReq);
+        rc = RTThreadWait(mhThreadNotifyHost, 10000, NULL);
+        AssertRC(rc);
+        rc = RTReqQueueDestroy(mhReqQNotifyHost);
+        AssertRC(rc);
+        mhReqQNotifyHost = NIL_RTREQQUEUE;
+        mhThreadNotifyHost = NIL_RTTHREAD;
+        RTStrSpaceDestroy(&mhProperties, destroyProperty, NULL);
+        mhProperties = NULL;
+    }
+    return VINF_SUCCESS;
+}
+
+} /* namespace guestProp */
+
+using guestProp::Service;
+
+/**
+ * @copydoc FNVBOXHGCMSVCLOAD
+ */
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad(VBOXHGCMSVCFNTABLE *ptable)
+{
+    int rc = VERR_IPE_UNINITIALIZED_STATUS;
+
+    LogFlowFunc(("ptable = %p\n", ptable));
+
+    if (!RT_VALID_PTR(ptable))
+        rc = VERR_INVALID_PARAMETER;
+    else
+    {
+        LogFlowFunc(("ptable->cbSize = %d, ptable->u32Version = 0x%08X\n", ptable->cbSize, ptable->u32Version));
+
+        if (   ptable->cbSize != sizeof(VBOXHGCMSVCFNTABLE)
+            || ptable->u32Version != VBOX_HGCM_SVC_VERSION)
+            rc = VERR_VERSION_MISMATCH;
+        else
+        {
+            Service *pService = NULL;
+            /* No exceptions may propagate outside. */
+            try
+            {
+                pService = new Service(ptable->pHelpers);
+                rc = VINF_SUCCESS;
+            }
+            catch (int rcThrown)
+            {
+                rc = rcThrown;
+            }
+            catch (...)
+            {
+                rc = VERR_UNEXPECTED_EXCEPTION;
+            }
+
+            if (RT_SUCCESS(rc))
+            {
+                /* We do not maintain connections, so no client data is needed. */
+                ptable->cbClient = 0;
+
+                /* Legacy clients map to the kernel category. */
+                ptable->idxLegacyClientCategory = HGCM_CLIENT_CATEGORY_KERNEL;
+
+                /* Go with default client limits, but we won't ever need more than
+                   16 pending calls per client I would think (1 should be enough). */
+                for (uintptr_t i = 0; i < RT_ELEMENTS(ptable->acMaxClients); i++)
+                    ptable->acMaxCallsPerClient[i] = 16;
+
+                ptable->pfnUnload             = Service::svcUnload;
+                ptable->pfnConnect            = Service::svcConnect;
+                ptable->pfnDisconnect         = Service::svcDisconnect;
+                ptable->pfnCall               = Service::svcCall;
+                ptable->pfnHostCall           = Service::svcHostCall;
+                ptable->pfnSaveState          = NULL;  /* The service is stateless, so the normal */
+                ptable->pfnLoadState          = NULL;  /* construction done before restoring suffices */
+                ptable->pfnRegisterExtension  = Service::svcRegisterExtension;
+                ptable->pfnNotify             = Service::svcNotify;
+                ptable->pvService             = pService;
+
+                /* Service specific initialization. */
+                rc = pService->initialize();
+                if (RT_FAILURE(rc))
+                {
+                    delete pService;
+                    pService = NULL;
+                }
+            }
+            else
+                Assert(!pService);
+        }
+    }
+
+    LogFlowFunc(("returning %Rrc\n", rc));
+    return rc;
+}
+
diff --git a/src/VBox/HostServices/GuestProperties/VBoxGuestPropSvc.rc b/src/VBox/HostServices/GuestProperties/VBoxGuestPropSvc.rc
new file mode 100644
index 00000000..da45d2e2
--- /dev/null
+++ b/src/VBox/HostServices/GuestProperties/VBoxGuestPropSvc.rc
@@ -0,0 +1,61 @@
+/* $Id: VBoxGuestPropSvc.rc $ */
+/** @file
+ * VBoxGuestPropSvc - Resource file containing version info and icon.
+ */
+
+/*
+ * Copyright (C) 2015-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <windows.h>
+#include <VBox/version.h>
+
+LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION      VBOX_RC_FILE_VERSION
+  PRODUCTVERSION   VBOX_RC_FILE_VERSION
+  FILEFLAGSMASK    VS_FFI_FILEFLAGSMASK
+  FILEFLAGS        VBOX_RC_FILE_FLAGS
+  FILEOS           VBOX_RC_FILE_OS
+  FILETYPE         VBOX_RC_TYPE_DLL
+  FILESUBTYPE      VFT2_UNKNOWN
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904b0" // Lang=US English, CharSet=Unicode
+    BEGIN
+      VALUE "FileDescription",  "VirtualBox Guest Properties Service\0"
+      VALUE "InternalName",     "VBoxGuestPropSvc\0"
+      VALUE "OriginalFilename", "VBoxGuestPropSvc.dll\0"
+      VALUE "CompanyName",      VBOX_RC_COMPANY_NAME
+      VALUE "FileVersion",      VBOX_RC_FILE_VERSION_STR
+      VALUE "LegalCopyright",   VBOX_RC_LEGAL_COPYRIGHT
+      VALUE "ProductName",      VBOX_RC_PRODUCT_NAME_STR
+      VALUE "ProductVersion",   VBOX_RC_PRODUCT_VERSION_STR
+      VBOX_RC_MORE_STRINGS
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x409, 1200
+  END
+END
diff --git a/src/VBox/HostServices/GuestProperties/testcase/Makefile.kmk b/src/VBox/HostServices/GuestProperties/testcase/Makefile.kmk
new file mode 100644
index 00000000..aac7a8c6
--- /dev/null
+++ b/src/VBox/HostServices/GuestProperties/testcase/Makefile.kmk
@@ -0,0 +1,56 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Guest Properties Host Service testcases.
+#
+
+#
+# Copyright (C) 2006-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+if defined(VBOX_WITH_TESTCASES) && !defined(VBOX_ONLY_ADDITIONS) && !defined(VBOX_ONLY_SDK)
+
+ # Set this in LocalConfig.kmk if you are working on the guest property
+ # service to automatically run the testcase at build time.
+ #    OTHERS += $(tstGuestPropSvc_0_OUTDIR)/tstGuestPropSvc.run
+ #
+
+ PROGRAMS += tstGuestPropSvc
+ TESTING  += $(tstGuestPropSvc_0_OUTDIR)/tstGuestPropSvc.run
+ tstGuestPropSvc_TEMPLATE = VBoxR3TstExe
+ # The second define here is to ensure that the testcase will run fast,
+ # without waiting for any thread synchronisation.
+ tstGuestPropSvc_DEFS     = VBOX_WITH_HGCM VBOX_GUEST_PROP_TEST_NOTHREAD
+ tstGuestPropSvc_SOURCES  = \
+ 	tstGuestPropSvc.cpp \
+ 	../VBoxGuestPropSvc.cpp
+ tstGuestPropSvc_LIBS     = $(LIB_RUNTIME)
+
+ $$(tstGuestPropSvc_0_OUTDIR)/tstGuestPropSvc.run: $$(tstGuestPropSvc_1_STAGE_TARGET)
+	export VBOX_LOG_DEST=nofile; $(tstGuestPropSvc_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+
+endif
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/HostServices/GuestProperties/testcase/tstGuestPropSvc.cpp b/src/VBox/HostServices/GuestProperties/testcase/tstGuestPropSvc.cpp
new file mode 100644
index 00000000..987cff43
--- /dev/null
+++ b/src/VBox/HostServices/GuestProperties/testcase/tstGuestPropSvc.cpp
@@ -0,0 +1,1206 @@
+/* $Id: tstGuestPropSvc.cpp $ */
+/** @file
+ *
+ * Testcase for the guest property service.
+ */
+
+/*
+ * Copyright (C) 2008-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#include <VBox/HostServices/GuestPropertySvc.h>
+#include <VBox/err.h>
+#include <VBox/hgcmsvc.h>
+#include <iprt/test.h>
+#include <iprt/time.h>
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+static RTTEST g_hTest = NIL_RTTEST;
+
+
+/*********************************************************************************************************************************
+*   Internal Functions                                                                                                           *
+*********************************************************************************************************************************/
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad (VBOXHGCMSVCFNTABLE *ptable);
+
+
+/** Simple call handle structure for the guest call completion callback */
+struct VBOXHGCMCALLHANDLE_TYPEDEF
+{
+    /** Where to store the result code */
+    int32_t rc;
+};
+
+/** Dummy helper callback. */
+static DECLCALLBACK(int) tstHlpInfoDeregister(void *pvInstance, const char *pszName)
+{
+    RT_NOREF(pvInstance, pszName);
+    return VINF_SUCCESS;
+}
+
+/** Dummy helper callback. */
+static DECLCALLBACK(int) tstHlpInfoRegister(void *pvInstance, const char *pszName, const char *pszDesc,
+                                            PFNDBGFHANDLEREXT pfnHandler, void *pvUser)
+{
+    RT_NOREF(pvInstance, pszName, pszDesc, pfnHandler, pvUser);
+    return VINF_SUCCESS;
+}
+
+/** Call completion callback for guest calls. */
+static DECLCALLBACK(int) callComplete(VBOXHGCMCALLHANDLE callHandle, int32_t rc)
+{
+    callHandle->rc = rc;
+    return VINF_SUCCESS;
+}
+
+/**
+ * Initialise the HGCM service table as much as we need to start the
+ * service
+ * @param  pTable the table to initialise
+ */
+void initTable(VBOXHGCMSVCFNTABLE *pTable, VBOXHGCMSVCHELPERS *pHelpers)
+{
+    RT_ZERO(*pHelpers);
+    pHelpers->pfnCallComplete   = callComplete;
+    pHelpers->pfnInfoRegister   = tstHlpInfoRegister;
+    pHelpers->pfnInfoDeregister = tstHlpInfoDeregister;
+
+    RT_ZERO(*pTable);
+    pTable->cbSize              = sizeof(VBOXHGCMSVCFNTABLE);
+    pTable->u32Version          = VBOX_HGCM_SVC_VERSION;
+    pTable->pHelpers            = pHelpers;
+}
+
+/**
+ * A list of valid flag strings for testConvertFlags.  The flag conversion
+ * functions should accept these and convert them from string to a flag type
+ * and back without errors.
+ */
+struct flagStrings
+{
+    /** Flag string in a format the functions should recognise */
+    const char *pcszIn;
+    /** How the functions should output the string again */
+    const char *pcszOut;
+}
+g_aValidFlagStrings[] =
+{
+    /* pcszIn,                                          pcszOut */
+    { "  ",                                             "" },
+    { "transient, ",                                    "TRANSIENT" },
+    { "  rdOnLyHOST, transIENT  ,     READONLY    ",    "TRANSIENT, READONLY" },
+    { " rdonlyguest",                                   "RDONLYGUEST" },
+    { "rdonlyhost     ",                                "RDONLYHOST" },
+    { "transient, transreset, rdonlyhost",              "TRANSIENT, RDONLYHOST, TRANSRESET" },
+    { "transient, transreset, rdonlyguest",             "TRANSIENT, RDONLYGUEST, TRANSRESET" },     /* max length */
+    { "rdonlyguest, rdonlyhost",                        "READONLY" },
+    { "transient,   transreset, ",                      "TRANSIENT, TRANSRESET" }, /* Don't combine them ... */
+    { "transreset, ",                                   "TRANSIENT, TRANSRESET" }, /* ... instead expand transreset for old adds. */
+};
+
+/**
+ * A list of invalid flag strings for testConvertFlags.  The flag conversion
+ * functions should reject these.
+ */
+const char *g_apszInvalidFlagStrings[] =
+{
+    "RDONLYHOST,,",
+    "  TRANSIENT READONLY"
+};
+
+/**
+ * Test the flag conversion functions.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static void testConvertFlags(void)
+{
+    int rc = VINF_SUCCESS;
+    char *pszFlagBuffer = (char *)RTTestGuardedAllocTail(g_hTest, GUEST_PROP_MAX_FLAGS_LEN);
+
+    RTTestISub("Conversion of valid flags strings");
+    for (unsigned i = 0; i < RT_ELEMENTS(g_aValidFlagStrings) && RT_SUCCESS(rc); ++i)
+    {
+        uint32_t fFlags;
+        rc = GuestPropValidateFlags(g_aValidFlagStrings[i].pcszIn, &fFlags);
+        if (RT_FAILURE(rc))
+            RTTestIFailed("Failed to validate flag string '%s'", g_aValidFlagStrings[i].pcszIn);
+        if (RT_SUCCESS(rc))
+        {
+            rc = GuestPropWriteFlags(fFlags, pszFlagBuffer);
+            if (RT_FAILURE(rc))
+                RTTestIFailed("Failed to convert flag string '%s' back to a string.",
+                              g_aValidFlagStrings[i].pcszIn);
+        }
+        if (RT_SUCCESS(rc) && (strlen(pszFlagBuffer) > GUEST_PROP_MAX_FLAGS_LEN - 1))
+        {
+            RTTestIFailed("String '%s' converts back to a flag string which is too long.\n",
+                          g_aValidFlagStrings[i].pcszIn);
+            rc = VERR_TOO_MUCH_DATA;
+        }
+        if (RT_SUCCESS(rc) && (strcmp(pszFlagBuffer, g_aValidFlagStrings[i].pcszOut) != 0))
+        {
+            RTTestIFailed("String '%s' converts back to '%s' instead of to '%s'\n",
+                          g_aValidFlagStrings[i].pcszIn, pszFlagBuffer,
+                          g_aValidFlagStrings[i].pcszOut);
+            rc = VERR_PARSE_ERROR;
+        }
+    }
+    if (RT_SUCCESS(rc))
+    {
+        RTTestISub("Rejection of invalid flags strings");
+        for (unsigned i = 0; i < RT_ELEMENTS(g_apszInvalidFlagStrings) && RT_SUCCESS(rc); ++i)
+        {
+            uint32_t fFlags;
+            /* This is required to fail. */
+            if (RT_SUCCESS(GuestPropValidateFlags(g_apszInvalidFlagStrings[i], &fFlags)))
+            {
+                RTTestIFailed("String '%s' was incorrectly accepted as a valid flag string.\n",
+                              g_apszInvalidFlagStrings[i]);
+                rc = VERR_PARSE_ERROR;
+            }
+        }
+    }
+    if (RT_SUCCESS(rc))
+    {
+        uint32_t u32BadFlags = GUEST_PROP_F_ALLFLAGS << 1;
+        RTTestISub("Rejection of an invalid flags field");
+        /* This is required to fail. */
+        if (RT_SUCCESS(GuestPropWriteFlags(u32BadFlags, pszFlagBuffer)))
+        {
+            RTTestIFailed("Flags 0x%x were incorrectly written out as '%.*s'\n",
+                          u32BadFlags, GUEST_PROP_MAX_FLAGS_LEN, pszFlagBuffer);
+            rc = VERR_PARSE_ERROR;
+        }
+    }
+
+    RTTestGuardedFree(g_hTest, pszFlagBuffer);
+}
+
+/**
+ * List of property names for testSetPropsHost.
+ */
+const char *g_apcszNameBlock[] =
+{
+    "test/name/",
+    "test name",
+    "TEST NAME",
+    "/test/name",
+    NULL
+};
+
+/**
+ * List of property values for testSetPropsHost.
+ */
+const char *g_apcszValueBlock[] =
+{
+    "test/value/",
+    "test value",
+    "TEST VALUE",
+    "/test/value",
+    NULL
+};
+
+/**
+ * List of property timestamps for testSetPropsHost.
+ */
+uint64_t g_au64TimestampBlock[] =
+{
+    0, 999, 999999, UINT64_C(999999999999), 0
+};
+
+/**
+ * List of property flags for testSetPropsHost.
+ */
+const char *g_apcszFlagsBlock[] =
+{
+    "",
+    "readonly, transient",
+    "RDONLYHOST",
+    "RdOnlyGuest",
+    NULL
+};
+
+/**
+ * Test the SET_PROPS_HOST function.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static void testSetPropsHost(VBOXHGCMSVCFNTABLE *ptable)
+{
+    RTTestISub("SET_PROPS_HOST");
+    RTTESTI_CHECK_RETV(RT_VALID_PTR(ptable->pfnHostCall));
+
+    VBOXHGCMSVCPARM aParms[4];
+    HGCMSvcSetPv(&aParms[0], (void *)g_apcszNameBlock, 0);
+    HGCMSvcSetPv(&aParms[1], (void *)g_apcszValueBlock, 0);
+    HGCMSvcSetPv(&aParms[2], (void *)g_au64TimestampBlock, 0);
+    HGCMSvcSetPv(&aParms[3], (void *)g_apcszFlagsBlock, 0);
+    RTTESTI_CHECK_RC(ptable->pfnHostCall(ptable->pvService, GUEST_PROP_FN_HOST_SET_PROPS, 4, &aParms[0]), VINF_SUCCESS);
+}
+
+#if 0
+/** Result strings for zeroth enumeration test */
+static const char *g_apchEnumResult0[] =
+{
+    "test/name/\0test/value/\0""0\0",
+    "test name\0test value\0""999\0TRANSIENT, READONLY",
+    "TEST NAME\0TEST VALUE\0""999999\0RDONLYHOST",
+    "/test/name\0/test/value\0""999999999999\0RDONLYGUEST",
+    NULL
+};
+
+/** Result string sizes for zeroth enumeration test */
+static const uint32_t g_acbEnumResult0[] =
+{
+    sizeof("test/name/\0test/value/\0""0\0"),
+    sizeof("test name\0test value\0""999\0TRANSIENT, READONLY"),
+    sizeof("TEST NAME\0TEST VALUE\0""999999\0RDONLYHOST"),
+    sizeof("/test/name\0/test/value\0""999999999999\0RDONLYGUEST"),
+    0
+};
+
+/**
+ * The size of the buffer returned by the zeroth enumeration test -
+ * the - 1 at the end is because of the hidden zero terminator
+ */
+static const uint32_t g_cbEnumBuffer0 =
+    sizeof("test/name/\0test/value/\0""0\0\0"
+           "test name\0test value\0""999\0TRANSIENT, READONLY\0"
+           "TEST NAME\0TEST VALUE\0""999999\0RDONLYHOST\0"
+           "/test/name\0/test/value\0""999999999999\0RDONLYGUEST\0\0\0\0\0") - 1;
+#endif
+
+/** Result strings for first and second enumeration test */
+static const char *g_apchEnumResult1[] =
+{
+    "TEST NAME\0TEST VALUE\0""999999\0RDONLYHOST",
+    "/test/name\0/test/value\0""999999999999\0RDONLYGUEST",
+    NULL
+};
+
+/** Result string sizes for first and second enumeration test */
+static const uint32_t g_acbEnumResult1[] =
+{
+    sizeof("TEST NAME\0TEST VALUE\0""999999\0RDONLYHOST"),
+    sizeof("/test/name\0/test/value\0""999999999999\0RDONLYGUEST"),
+    0
+};
+
+/**
+ * The size of the buffer returned by the first enumeration test -
+ * the - 1 at the end is because of the hidden zero terminator
+ */
+static const uint32_t g_cbEnumBuffer1 =
+    sizeof("TEST NAME\0TEST VALUE\0""999999\0RDONLYHOST\0"
+           "/test/name\0/test/value\0""999999999999\0RDONLYGUEST\0\0\0\0\0") - 1;
+
+static const struct enumStringStruct
+{
+    /** The enumeration pattern to test */
+    const char     *pszPatterns;
+    /** The size of the pattern string (including terminator) */
+    const uint32_t  cbPatterns;
+    /** The expected enumeration output strings */
+    const char    **papchResult;
+    /** The size of the output strings */
+    const uint32_t *pacchResult;
+    /** The size of the buffer needed for the enumeration */
+    const uint32_t  cbBuffer;
+}   g_aEnumStrings[] =
+{
+#if 0 /* unpredictable automatic variables set by the service now */
+    {
+        "", sizeof(""),
+        g_apchEnumResult0,
+        g_acbEnumResult0,
+        g_cbEnumBuffer0
+    },
+#endif
+    {
+        "/t*\0?E*", sizeof("/t*\0?E*"),
+        g_apchEnumResult1,
+        g_acbEnumResult1,
+        g_cbEnumBuffer1
+    },
+    {
+        "/t*|?E*", sizeof("/t*|?E*"),
+        g_apchEnumResult1,
+        g_acbEnumResult1,
+        g_cbEnumBuffer1
+    }
+};
+
+/**
+ * Test the ENUM_PROPS_HOST function.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static void testEnumPropsHost(VBOXHGCMSVCFNTABLE *ptable)
+{
+    RTTestISub("ENUM_PROPS_HOST");
+    RTTESTI_CHECK_RETV(RT_VALID_PTR(ptable->pfnHostCall));
+
+    for (unsigned i = 0; i < RT_ELEMENTS(g_aEnumStrings); ++i)
+    {
+        VBOXHGCMSVCPARM aParms[3];
+        char            abBuffer[2048];
+        RTTESTI_CHECK_RETV(g_aEnumStrings[i].cbBuffer < sizeof(abBuffer));
+
+        /* Check that we get buffer overflow with a too small buffer. */
+        HGCMSvcSetPv(&aParms[0], (void *)g_aEnumStrings[i].pszPatterns, g_aEnumStrings[i].cbPatterns);
+        HGCMSvcSetPv(&aParms[1], (void *)abBuffer, g_aEnumStrings[i].cbBuffer - 1);
+        memset(abBuffer, 0x55, sizeof(abBuffer));
+        int rc2 = ptable->pfnHostCall(ptable->pvService, GUEST_PROP_FN_HOST_ENUM_PROPS, 3, aParms);
+        if (rc2 == VERR_BUFFER_OVERFLOW)
+        {
+            uint32_t cbNeeded;
+            RTTESTI_CHECK_RC(rc2 = HGCMSvcGetU32(&aParms[2], &cbNeeded), VINF_SUCCESS);
+            if (RT_SUCCESS(rc2))
+                RTTESTI_CHECK_MSG(cbNeeded == g_aEnumStrings[i].cbBuffer,
+                                  ("expected %#x, got %#x, pattern %d\n", g_aEnumStrings[i].cbBuffer, cbNeeded, i));
+        }
+        else
+            RTTestIFailed("ENUM_PROPS_HOST returned %Rrc instead of VERR_BUFFER_OVERFLOW on too small buffer, pattern number %d.", rc2, i);
+
+        /* Make a successfull call. */
+        HGCMSvcSetPv(&aParms[0], (void *)g_aEnumStrings[i].pszPatterns, g_aEnumStrings[i].cbPatterns);
+        HGCMSvcSetPv(&aParms[1], (void *)abBuffer, g_aEnumStrings[i].cbBuffer);
+        memset(abBuffer, 0x55, sizeof(abBuffer));
+        rc2 = ptable->pfnHostCall(ptable->pvService, GUEST_PROP_FN_HOST_ENUM_PROPS, 3, aParms);
+        if (rc2 == VINF_SUCCESS)
+        {
+            /* Look for each of the result strings in the buffer which was returned */
+            for (unsigned j = 0; g_aEnumStrings[i].papchResult[j] != NULL; ++j)
+            {
+                bool found = false;
+                for (unsigned k = 0; !found && k < g_aEnumStrings[i].cbBuffer - g_aEnumStrings[i].pacchResult[j]; ++k)
+                    if (memcmp(abBuffer + k, g_aEnumStrings[i].papchResult[j], g_aEnumStrings[i].pacchResult[j]) == 0)
+                        found = true;
+                if (!found)
+                    RTTestIFailed("ENUM_PROPS_HOST did not produce the expected output for pattern %d.", i);
+            }
+        }
+        else
+            RTTestIFailed("ENUM_PROPS_HOST returned %Rrc instead of VINF_SUCCESS, pattern number %d.", rc2, i);
+    }
+}
+
+/**
+ * Set a property by calling the service
+ * @returns the status returned by the call to the service
+ *
+ * @param   pTable      the service instance handle
+ * @param   pcszName    the name of the property to set
+ * @param   pcszValue   the value to set the property to
+ * @param   pcszFlags   the flag string to set if one of the SET_PROP[_HOST]
+ *                      commands is used
+ * @param   isHost      whether the SET_PROP[_VALUE]_HOST commands should be
+ *                      used, rather than the guest ones
+ * @param   useSetProp  whether SET_PROP[_HOST] should be used rather than
+ *                      SET_PROP_VALUE[_HOST]
+ */
+int doSetProperty(VBOXHGCMSVCFNTABLE *pTable, const char *pcszName,
+                  const char *pcszValue, const char *pcszFlags, bool isHost,
+                  bool useSetProp)
+{
+    RTThreadSleep(1); /* stupid, stupid timestamp fudge to avoid asserting in getOldNotification() */
+
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+    int command = GUEST_PROP_FN_SET_PROP_VALUE;
+    if (isHost)
+    {
+        if (useSetProp)
+            command = GUEST_PROP_FN_HOST_SET_PROP;
+        else
+            command = GUEST_PROP_FN_HOST_SET_PROP_VALUE;
+    }
+    else if (useSetProp)
+        command = GUEST_PROP_FN_SET_PROP;
+    VBOXHGCMSVCPARM aParms[3];
+    /* Work around silly constant issues - we ought to allow passing
+     * constant strings in the hgcm parameters. */
+    char szName[GUEST_PROP_MAX_NAME_LEN];
+    char szValue[GUEST_PROP_MAX_VALUE_LEN];
+    char szFlags[GUEST_PROP_MAX_FLAGS_LEN];
+    RTStrPrintf(szName, sizeof(szName), "%s", pcszName);
+    RTStrPrintf(szValue, sizeof(szValue), "%s", pcszValue);
+    RTStrPrintf(szFlags, sizeof(szFlags), "%s", pcszFlags);
+    HGCMSvcSetStr(&aParms[0], szName);
+    HGCMSvcSetStr(&aParms[1], szValue);
+    HGCMSvcSetStr(&aParms[2], szFlags);
+    if (isHost)
+        callHandle.rc = pTable->pfnHostCall(pTable->pvService, command,
+                                            useSetProp ? 3 : 2, aParms);
+    else
+        pTable->pfnCall(pTable->pvService, &callHandle, 0, NULL, command,
+                        useSetProp ? 3 : 2, aParms, 0);
+    return callHandle.rc;
+}
+
+/**
+ * Test the SET_PROP, SET_PROP_VALUE, SET_PROP_HOST and SET_PROP_VALUE_HOST
+ * functions.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static void testSetProp(VBOXHGCMSVCFNTABLE *pTable)
+{
+    RTTestISub("SET_PROP, _VALUE, _HOST, _VALUE_HOST");
+
+    /** Array of properties for testing SET_PROP_HOST and _GUEST. */
+    static const struct
+    {
+        /** Property name */
+        const char *pcszName;
+        /** Property value */
+        const char *pcszValue;
+        /** Property flags */
+        const char *pcszFlags;
+        /** Should this be set as the host or the guest? */
+        bool isHost;
+        /** Should we use SET_PROP or SET_PROP_VALUE? */
+        bool useSetProp;
+        /** Should this succeed or be rejected with VERR_PERMISSION_DENIED? */
+        bool isAllowed;
+    }
+    s_aSetProperties[] =
+    {
+        { "Red", "Stop!", "transient", false, true, true },
+        { "Amber", "Caution!", "", false, false, true },
+        { "Green", "Go!", "readonly", true, true, true },
+        { "Blue", "What on earth...?", "", true, false, true },
+        { "/test/name", "test", "", false, true, false },
+        { "TEST NAME", "test", "", true, true, false },
+        { "Green", "gone out...", "", false, false, false },
+        { "Green", "gone out...", "", true, false, false },
+        { "/VirtualBox/GuestAdd/SharedFolders/MountDir", "test", "", false, true, false },
+        { "/VirtualBox/GuestAdd/SomethingElse", "test", "", false, true, true },
+        { "/VirtualBox/HostInfo/VRDP/Client/1/Name", "test", "", false, false, false },
+        { "/VirtualBox/GuestAdd/SharedFolders/MountDir", "test", "", true, true, true },
+        { "/VirtualBox/HostInfo/VRDP/Client/1/Name", "test", "TRANSRESET", true, true, true },
+    };
+
+    for (unsigned i = 0; i < RT_ELEMENTS(s_aSetProperties); ++i)
+    {
+        int rc = doSetProperty(pTable,
+                               s_aSetProperties[i].pcszName,
+                               s_aSetProperties[i].pcszValue,
+                               s_aSetProperties[i].pcszFlags,
+                               s_aSetProperties[i].isHost,
+                               s_aSetProperties[i].useSetProp);
+        if (s_aSetProperties[i].isAllowed && RT_FAILURE(rc))
+            RTTestIFailed("Setting property '%s' failed with rc=%Rrc.",
+                          s_aSetProperties[i].pcszName, rc);
+        else if (   !s_aSetProperties[i].isAllowed
+                 && rc != VERR_PERMISSION_DENIED)
+            RTTestIFailed("Setting property '%s' returned %Rrc instead of VERR_PERMISSION_DENIED.",
+                          s_aSetProperties[i].pcszName, rc);
+    }
+}
+
+/**
+ * Delete a property by calling the service
+ * @returns the status returned by the call to the service
+ *
+ * @param   pTable    the service instance handle
+ * @param   pcszName  the name of the property to delete
+ * @param   isHost    whether the DEL_PROP_HOST command should be used, rather
+ *                    than the guest one
+ */
+static int doDelProp(VBOXHGCMSVCFNTABLE *pTable, const char *pcszName, bool isHost)
+{
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+    int command = GUEST_PROP_FN_DEL_PROP;
+    if (isHost)
+        command = GUEST_PROP_FN_HOST_DEL_PROP;
+    VBOXHGCMSVCPARM aParms[1];
+    HGCMSvcSetStr(&aParms[0], pcszName);
+    if (isHost)
+        callHandle.rc = pTable->pfnHostCall(pTable->pvService, command, 1, aParms);
+    else
+        pTable->pfnCall(pTable->pvService, &callHandle, 0, NULL, command, 1, aParms, 0);
+    return callHandle.rc;
+}
+
+/**
+ * Test the DEL_PROP, and DEL_PROP_HOST functions.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static void testDelProp(VBOXHGCMSVCFNTABLE *pTable)
+{
+    RTTestISub("DEL_PROP, DEL_PROP_HOST");
+
+    /** Array of properties for testing DEL_PROP_HOST and _GUEST. */
+    static const struct
+    {
+        /** Property name */
+        const char *pcszName;
+        /** Should this be set as the host or the guest? */
+        bool isHost;
+        /** Should this succeed or be rejected with VERR_PERMISSION_DENIED? */
+        bool isAllowed;
+    } s_aDelProperties[] =
+    {
+        { "Red", false, true },
+        { "Amber", true, true },
+        { "Red2", false, true },
+        { "Amber2", true, true },
+        { "Green", false, false },
+        { "Green", true, false },
+        { "/test/name", false, false },
+        { "TEST NAME", true, false },
+    };
+
+    for (unsigned i = 0; i < RT_ELEMENTS(s_aDelProperties); ++i)
+    {
+        int rc = doDelProp(pTable, s_aDelProperties[i].pcszName, s_aDelProperties[i].isHost);
+        if (s_aDelProperties[i].isAllowed && RT_FAILURE(rc))
+            RTTestIFailed("Deleting property '%s' failed with rc=%Rrc.",
+                          s_aDelProperties[i].pcszName, rc);
+        else if (   !s_aDelProperties[i].isAllowed
+                 && rc != VERR_PERMISSION_DENIED )
+            RTTestIFailed("Deleting property '%s' returned %Rrc instead of VERR_PERMISSION_DENIED.",
+                          s_aDelProperties[i].pcszName, rc);
+    }
+}
+
+/**
+ * Test the GET_PROP_HOST function.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static void testGetProp(VBOXHGCMSVCFNTABLE *pTable)
+{
+    RTTestISub("GET_PROP_HOST");
+
+    /** Array of properties for testing GET_PROP_HOST. */
+    static const struct
+    {
+        /** Property name */
+        const char *pcszName;
+        /** What value/flags pattern do we expect back? */
+        const char *pchValue;
+        /** What size should the value/flags array be? */
+        uint32_t cchValue;
+        /** Should this property exist? */
+        bool exists;
+        /** Do we expect a particular timestamp? */
+        bool hasTimestamp;
+        /** What timestamp if any do ex expect? */
+        uint64_t u64Timestamp;
+    }
+    s_aGetProperties[] =
+    {
+        { "test/name/", "test/value/\0", sizeof("test/value/\0"), true, true, 0 },
+        { "test name", "test value\0TRANSIENT, READONLY",
+          sizeof("test value\0TRANSIENT, READONLY"), true, true, 999 },
+        { "TEST NAME", "TEST VALUE\0RDONLYHOST", sizeof("TEST VALUE\0RDONLYHOST"),
+          true, true, 999999 },
+        { "/test/name", "/test/value\0RDONLYGUEST",
+          sizeof("/test/value\0RDONLYGUEST"), true, true, UINT64_C(999999999999) },
+        { "Green", "Go!\0READONLY", sizeof("Go!\0READONLY"), true, false, 0 },
+        { "Blue", "What on earth...?\0", sizeof("What on earth...?\0"), true,
+          false, 0 },
+        { "Red", "", 0, false, false, 0 },
+    };
+
+    for (unsigned i = 0; i < RT_ELEMENTS(s_aGetProperties); ++i)
+    {
+        VBOXHGCMSVCPARM aParms[4];
+        /* Work around silly constant issues - we ought to allow passing
+         * constant strings in the hgcm parameters. */
+        char szBuffer[GUEST_PROP_MAX_VALUE_LEN + GUEST_PROP_MAX_FLAGS_LEN];
+        RTTESTI_CHECK_RETV(s_aGetProperties[i].cchValue < sizeof(szBuffer));
+
+        HGCMSvcSetStr(&aParms[0], s_aGetProperties[i].pcszName);
+        memset(szBuffer, 0x55, sizeof(szBuffer));
+        HGCMSvcSetPv(&aParms[1], szBuffer, sizeof(szBuffer));
+        int rc2 = pTable->pfnHostCall(pTable->pvService, GUEST_PROP_FN_HOST_GET_PROP, 4, aParms);
+
+        if (s_aGetProperties[i].exists && RT_FAILURE(rc2))
+        {
+            RTTestIFailed("Getting property '%s' failed with rc=%Rrc.",
+                          s_aGetProperties[i].pcszName, rc2);
+            continue;
+        }
+
+        if (!s_aGetProperties[i].exists && rc2 != VERR_NOT_FOUND)
+        {
+            RTTestIFailed("Getting property '%s' returned %Rrc instead of VERR_NOT_FOUND.",
+                          s_aGetProperties[i].pcszName, rc2);
+            continue;
+        }
+
+        if (s_aGetProperties[i].exists)
+        {
+            AssertRC(rc2);
+
+            uint32_t u32ValueLen = UINT32_MAX;
+            RTTESTI_CHECK_RC(rc2 = HGCMSvcGetU32(&aParms[3], &u32ValueLen), VINF_SUCCESS);
+            if (RT_SUCCESS(rc2))
+            {
+                RTTESTI_CHECK_MSG(u32ValueLen <= sizeof(szBuffer), ("u32ValueLen=%d", u32ValueLen));
+                if (memcmp(szBuffer, s_aGetProperties[i].pchValue, s_aGetProperties[i].cchValue) != 0)
+                    RTTestIFailed("Unexpected result '%.*s' for property '%s', expected '%.*s'.",
+                                  u32ValueLen, szBuffer, s_aGetProperties[i].pcszName,
+                                  s_aGetProperties[i].cchValue, s_aGetProperties[i].pchValue);
+            }
+
+            if (s_aGetProperties[i].hasTimestamp)
+            {
+                uint64_t u64Timestamp = UINT64_MAX;
+                RTTESTI_CHECK_RC(rc2 = HGCMSvcGetU64(&aParms[2], &u64Timestamp), VINF_SUCCESS);
+                if (u64Timestamp != s_aGetProperties[i].u64Timestamp)
+                    RTTestIFailed("Bad timestamp %llu for property '%s', expected %llu.",
+                                  u64Timestamp, s_aGetProperties[i].pcszName,
+                                  s_aGetProperties[i].u64Timestamp);
+            }
+        }
+    }
+}
+
+/** Array of properties for testing GET_PROP_HOST. */
+static const struct
+{
+    /** Buffer returned */
+    const char *pchBuffer;
+    /** What size should the buffer be? */
+    uint32_t cbBuffer;
+}
+g_aGetNotifications[] =
+{
+    // Name\0Value\0Flags\0fWasDeleted\0
+#define STR_AND_SIZE(a_sz) { a_sz, sizeof(a_sz) }
+    STR_AND_SIZE("Red\0Stop!\0TRANSIENT\0" "0"), /* first test is used by testAsyncNotification, - testGetNotification skips it. (mess) */
+    STR_AND_SIZE("Red\0Stop!\0TRANSIENT\0" "1"),
+    STR_AND_SIZE("Amber\0Caution!\0\0" "1"),
+    STR_AND_SIZE("Green\0Go!\0READONLY\0" "0"),
+    STR_AND_SIZE("Blue\0What on earth...?\0\0" "0"),
+    STR_AND_SIZE("/VirtualBox/GuestAdd/SomethingElse\0test\0\0" "0"),
+    STR_AND_SIZE("/VirtualBox/GuestAdd/SharedFolders/MountDir\0test\0RDONLYGUEST\0" "0"),
+    STR_AND_SIZE("/VirtualBox/HostInfo/VRDP/Client/1/Name\0test\0TRANSIENT, RDONLYGUEST, TRANSRESET\0" "0"),
+    STR_AND_SIZE("Red\0\0\0" "1"),
+    STR_AND_SIZE("Amber\0\0\0" "1"),
+#undef STR_AND_SIZE
+};
+
+/**
+ * Test the GET_NOTIFICATION function.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static void testGetNotification(VBOXHGCMSVCFNTABLE *pTable)
+{
+    RTTestISub("GET_NOTIFICATION");
+
+    /* Test "buffer too small" */
+    static char                 s_szPattern[] = "/VirtualBox/GuestAdd/*|/VirtualBox/HostInfo/VRDP/Client*|Red*|Amber*|Green*|Blue*";
+    VBOXHGCMCALLHANDLE_TYPEDEF  callHandle = { VINF_SUCCESS };
+    VBOXHGCMSVCPARM             aParms[4];
+    uint32_t                    cbRetNeeded = 0;
+
+    for (uint32_t cbBuf = 1;
+         cbBuf < g_aGetNotifications[1].cbBuffer - 1;
+         cbBuf++)
+    {
+        void *pvBuf = RTTestGuardedAllocTail(g_hTest, cbBuf);
+        RTTESTI_CHECK_BREAK(pvBuf);
+        memset(pvBuf, 0x55, cbBuf);
+
+        HGCMSvcSetStr(&aParms[0], s_szPattern);
+        HGCMSvcSetU64(&aParms[1], 1);
+        HGCMSvcSetPv(&aParms[2], pvBuf, cbBuf);
+        pTable->pfnCall(pTable->pvService, &callHandle, 0, NULL, GUEST_PROP_FN_GET_NOTIFICATION, 4, aParms, 0);
+
+        if (   callHandle.rc != VERR_BUFFER_OVERFLOW
+            || RT_FAILURE(HGCMSvcGetU32(&aParms[3], &cbRetNeeded))
+            || cbRetNeeded != g_aGetNotifications[1].cbBuffer
+           )
+            RTTestIFailed("Getting notification for property '%s' with a too small buffer did not fail correctly: rc=%Rrc, cbRetNeeded=%#x (expected %#x)",
+                          g_aGetNotifications[1].pchBuffer, callHandle.rc, cbRetNeeded, g_aGetNotifications[1].cbBuffer);
+        RTTestGuardedFree(g_hTest, pvBuf);
+    }
+
+    /* Test successful notification queries.  Start with an unknown timestamp
+     * to get the oldest available notification. */
+    uint64_t u64Timestamp = 1;
+    for (unsigned i = 1; i < RT_ELEMENTS(g_aGetNotifications); ++i)
+    {
+        uint32_t cbBuf = g_aGetNotifications[i].cbBuffer + _1K;
+        void *pvBuf = RTTestGuardedAllocTail(g_hTest, cbBuf);
+        RTTESTI_CHECK_BREAK(pvBuf);
+        memset(pvBuf, 0x55, cbBuf);
+
+        HGCMSvcSetStr(&aParms[0], s_szPattern);
+        HGCMSvcSetU64(&aParms[1], u64Timestamp);
+        HGCMSvcSetPv(&aParms[2], pvBuf, cbBuf);
+        pTable->pfnCall(pTable->pvService, &callHandle, 0, NULL, GUEST_PROP_FN_GET_NOTIFICATION, 4, aParms, 0);
+        if (   RT_FAILURE(callHandle.rc)
+            || (i == 0 && callHandle.rc != VWRN_NOT_FOUND)
+            || RT_FAILURE(HGCMSvcGetU64(&aParms[1], &u64Timestamp))
+            || RT_FAILURE(HGCMSvcGetU32(&aParms[3], &cbRetNeeded))
+            || cbRetNeeded != g_aGetNotifications[i].cbBuffer
+            || memcmp(pvBuf, g_aGetNotifications[i].pchBuffer, cbRetNeeded) != 0
+           )
+        {
+            RTTestIFailed("Failed to get notification for property '%s' (#%u): rc=%Rrc (expected %Rrc), cbRetNeeded=%#x (expected %#x)\n"
+                          "%.*Rhxd\n---expected:---\n%.*Rhxd",
+                          g_aGetNotifications[i].pchBuffer, i, callHandle.rc, i == 0 ? VWRN_NOT_FOUND : VINF_SUCCESS,
+                          cbRetNeeded, g_aGetNotifications[i].cbBuffer, RT_MIN(cbRetNeeded, cbBuf), pvBuf,
+                          g_aGetNotifications[i].cbBuffer, g_aGetNotifications[i].pchBuffer);
+        }
+        RTTestGuardedFree(g_hTest, pvBuf);
+    }
+}
+
+/** Parameters for the asynchronous guest notification call */
+struct asyncNotification_
+{
+    /** Call parameters */
+    VBOXHGCMSVCPARM aParms[4];
+    /** Result buffer */
+    char abBuffer[GUEST_PROP_MAX_NAME_LEN + GUEST_PROP_MAX_VALUE_LEN + GUEST_PROP_MAX_FLAGS_LEN];
+    /** Return value */
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle;
+} g_AsyncNotification;
+
+/**
+ * Set up the test for the asynchronous GET_NOTIFICATION function.
+ */
+static void setupAsyncNotification(VBOXHGCMSVCFNTABLE *pTable)
+{
+    RTTestISub("Async GET_NOTIFICATION without notifications");
+    static char s_szPattern[] = "";
+
+    HGCMSvcSetStr(&g_AsyncNotification.aParms[0], s_szPattern);
+    HGCMSvcSetU64(&g_AsyncNotification.aParms[1], 0);
+    HGCMSvcSetPv(&g_AsyncNotification.aParms[2], g_AsyncNotification.abBuffer, sizeof(g_AsyncNotification.abBuffer));
+    g_AsyncNotification.callHandle.rc = VINF_HGCM_ASYNC_EXECUTE;
+    pTable->pfnCall(pTable->pvService, &g_AsyncNotification.callHandle, 0, NULL,
+                    GUEST_PROP_FN_GET_NOTIFICATION, 4, g_AsyncNotification.aParms, 0);
+    if (RT_FAILURE(g_AsyncNotification.callHandle.rc))
+        RTTestIFailed("GET_NOTIFICATION call failed, rc=%Rrc.", g_AsyncNotification.callHandle.rc);
+    else if (g_AsyncNotification.callHandle.rc != VINF_HGCM_ASYNC_EXECUTE)
+        RTTestIFailed("GET_NOTIFICATION call completed when no new notifications should be available.");
+}
+
+/**
+ * Test the asynchronous GET_NOTIFICATION function.
+ */
+static void testAsyncNotification(VBOXHGCMSVCFNTABLE *pTable)
+{
+    RT_NOREF1(pTable);
+    uint64_t u64Timestamp;
+    uint32_t cb = 0;
+    if (   g_AsyncNotification.callHandle.rc != VINF_SUCCESS
+        || RT_FAILURE(HGCMSvcGetU64(&g_AsyncNotification.aParms[1], &u64Timestamp))
+        || RT_FAILURE(HGCMSvcGetU32(&g_AsyncNotification.aParms[3], &cb))
+        || cb != g_aGetNotifications[0].cbBuffer
+        || memcmp(g_AsyncNotification.abBuffer, g_aGetNotifications[0].pchBuffer, cb) != 0
+       )
+    {
+        RTTestIFailed("Asynchronous GET_NOTIFICATION call did not complete as expected: rc=%Rrc, cb=%#x (expected %#x)\n"
+                      "abBuffer=%.*Rhxs\n"
+                      "expected=%.*Rhxs",
+                      g_AsyncNotification.callHandle.rc, cb, g_aGetNotifications[0].cbBuffer,
+                      cb, g_AsyncNotification.abBuffer, g_aGetNotifications[0].cbBuffer, g_aGetNotifications[0].pchBuffer);
+    }
+}
+
+
+static void test2(void)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    initTable(&svcTable, &svcHelpers);
+
+    /* The function is inside the service, not HGCM. */
+    RTTESTI_CHECK_RC_OK_RETV(VBoxHGCMSvcLoad(&svcTable));
+
+    testSetPropsHost(&svcTable);
+    testEnumPropsHost(&svcTable);
+
+    /* Set up the asynchronous notification test */
+    setupAsyncNotification(&svcTable);
+    testSetProp(&svcTable);
+    RTTestISub("Async notification call data");
+    testAsyncNotification(&svcTable); /* Our previous notification call should have completed by now. */
+
+    testDelProp(&svcTable);
+    testGetProp(&svcTable);
+    testGetNotification(&svcTable);
+
+    /* Cleanup */
+    RTTESTI_CHECK_RC_OK(svcTable.pfnUnload(svcTable.pvService));
+}
+
+/**
+ * Set the global flags value by calling the service
+ * @returns the status returned by the call to the service
+ *
+ * @param   pTable  the service instance handle
+ * @param   fFlags  the flags to set
+ */
+static int doSetGlobalFlags(VBOXHGCMSVCFNTABLE *pTable, uint32_t fFlags)
+{
+    VBOXHGCMSVCPARM paParm;
+    HGCMSvcSetU32(&paParm, fFlags);
+    int rc = pTable->pfnHostCall(pTable->pvService, GUEST_PROP_FN_HOST_SET_GLOBAL_FLAGS, 1, &paParm);
+    if (RT_FAILURE(rc))
+    {
+        char szFlags[GUEST_PROP_MAX_FLAGS_LEN];
+        if (RT_FAILURE(GuestPropWriteFlags(fFlags, szFlags)))
+            RTTestIFailed("Failed to set the global flags.");
+        else
+            RTTestIFailed("Failed to set the global flags \"%s\".", szFlags);
+    }
+    return rc;
+}
+
+/**
+ * Test the SET_PROP, SET_PROP_VALUE, SET_PROP_HOST and SET_PROP_VALUE_HOST
+ * functions.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static void testSetPropROGuest(VBOXHGCMSVCFNTABLE *pTable)
+{
+    RTTestISub("global READONLYGUEST and SET_PROP*");
+
+    /** Array of properties for testing SET_PROP_HOST and _GUEST with the
+     * READONLYGUEST global flag set. */
+    static const struct
+    {
+        /** Property name */
+        const char *pcszName;
+        /** Property value */
+        const char *pcszValue;
+        /** Property flags */
+        const char *pcszFlags;
+        /** Should this be set as the host or the guest? */
+        bool isHost;
+        /** Should we use SET_PROP or SET_PROP_VALUE? */
+        bool useSetProp;
+        /** Should this succeed or be rejected with VERR_ (NOT VINF_!)
+         * PERMISSION_DENIED?  The global check is done after the property one. */
+        bool isAllowed;
+    }
+    s_aSetPropertiesROGuest[] =
+    {
+        { "Red", "Stop!", "transient", false, true, true },
+        { "Amber", "Caution!", "", false, false, true },
+        { "Green", "Go!", "readonly", true, true, true },
+        { "Blue", "What on earth...?", "", true, false, true },
+        { "/test/name", "test", "", false, true, true },
+        { "TEST NAME", "test", "", true, true, true },
+        { "Green", "gone out...", "", false, false, false },
+        { "Green", "gone out....", "", true, false, false },
+    };
+
+    RTTESTI_CHECK_RC_OK_RETV(VBoxHGCMSvcLoad(pTable));
+    int rc = doSetGlobalFlags(pTable, GUEST_PROP_F_RDONLYGUEST);
+    if (RT_SUCCESS(rc))
+    {
+        for (unsigned i = 0; i < RT_ELEMENTS(s_aSetPropertiesROGuest); ++i)
+        {
+            rc = doSetProperty(pTable, s_aSetPropertiesROGuest[i].pcszName,
+                               s_aSetPropertiesROGuest[i].pcszValue,
+                               s_aSetPropertiesROGuest[i].pcszFlags,
+                               s_aSetPropertiesROGuest[i].isHost,
+                               s_aSetPropertiesROGuest[i].useSetProp);
+            if (s_aSetPropertiesROGuest[i].isAllowed && RT_FAILURE(rc))
+                RTTestIFailed("Setting property '%s' to '%s' failed with rc=%Rrc.",
+                              s_aSetPropertiesROGuest[i].pcszName,
+                              s_aSetPropertiesROGuest[i].pcszValue, rc);
+            else if (   !s_aSetPropertiesROGuest[i].isAllowed
+                     && rc != VERR_PERMISSION_DENIED)
+                RTTestIFailed("Setting property '%s' to '%s' returned %Rrc instead of VERR_PERMISSION_DENIED.\n",
+                              s_aSetPropertiesROGuest[i].pcszName,
+                              s_aSetPropertiesROGuest[i].pcszValue, rc);
+            else if (   !s_aSetPropertiesROGuest[i].isHost
+                     && s_aSetPropertiesROGuest[i].isAllowed
+                     && rc != VINF_PERMISSION_DENIED)
+                RTTestIFailed("Setting property '%s' to '%s' returned %Rrc instead of VINF_PERMISSION_DENIED.\n",
+                              s_aSetPropertiesROGuest[i].pcszName,
+                              s_aSetPropertiesROGuest[i].pcszValue, rc);
+        }
+    }
+    RTTESTI_CHECK_RC_OK(pTable->pfnUnload(pTable->pvService));
+}
+
+/**
+ * Test the DEL_PROP, and DEL_PROP_HOST functions.
+ * @returns iprt status value to indicate whether the test went as expected.
+ * @note    prints its own diagnostic information to stdout.
+ */
+static void testDelPropROGuest(VBOXHGCMSVCFNTABLE *pTable)
+{
+    RTTestISub("global READONLYGUEST and DEL_PROP*");
+
+    /** Array of properties for testing DEL_PROP_HOST and _GUEST with
+     * READONLYGUEST set globally. */
+    static const struct
+    {
+        /** Property name */
+        const char *pcszName;
+        /** Should this be deleted as the host (or the guest)? */
+        bool isHost;
+        /** Should this property be created first?  (As host, obviously) */
+        bool shouldCreate;
+        /** And with what flags? */
+        const char *pcszFlags;
+        /** Should this succeed or be rejected with VERR_ (NOT VINF_!)
+         * PERMISSION_DENIED?  The global check is done after the property one. */
+        bool isAllowed;
+    }
+    s_aDelPropertiesROGuest[] =
+    {
+        { "Red", true, true, "", true },
+        { "Amber", false, true, "", true },
+        { "Red2", true, false, "", true },
+        { "Amber2", false, false, "", true },
+        { "Red3", true, true, "READONLY", false },
+        { "Amber3", false, true, "READONLY", false },
+        { "Red4", true, true, "RDONLYHOST", false },
+        { "Amber4", false, true, "RDONLYHOST", true },
+    };
+
+    RTTESTI_CHECK_RC_OK_RETV(VBoxHGCMSvcLoad(pTable));
+    int rc = doSetGlobalFlags(pTable, GUEST_PROP_F_RDONLYGUEST);
+    if (RT_SUCCESS(rc))
+    {
+        for (unsigned i = 0; i < RT_ELEMENTS(s_aDelPropertiesROGuest); ++i)
+        {
+            if (s_aDelPropertiesROGuest[i].shouldCreate)
+                rc = doSetProperty(pTable, s_aDelPropertiesROGuest[i].pcszName,
+                                   "none", s_aDelPropertiesROGuest[i].pcszFlags,
+                                   true, true);
+            rc = doDelProp(pTable, s_aDelPropertiesROGuest[i].pcszName,
+                           s_aDelPropertiesROGuest[i].isHost);
+            if (s_aDelPropertiesROGuest[i].isAllowed && RT_FAILURE(rc))
+                RTTestIFailed("Deleting property '%s' failed with rc=%Rrc.",
+                              s_aDelPropertiesROGuest[i].pcszName, rc);
+            else if (   !s_aDelPropertiesROGuest[i].isAllowed
+                     && rc != VERR_PERMISSION_DENIED)
+                RTTestIFailed("Deleting property '%s' returned %Rrc instead of VERR_PERMISSION_DENIED.",
+                              s_aDelPropertiesROGuest[i].pcszName, rc);
+            else if (   !s_aDelPropertiesROGuest[i].isHost
+                     && s_aDelPropertiesROGuest[i].shouldCreate
+                     && s_aDelPropertiesROGuest[i].isAllowed
+                     && rc != VINF_PERMISSION_DENIED)
+                RTTestIFailed("Deleting property '%s' as guest returned %Rrc instead of VINF_PERMISSION_DENIED.",
+                              s_aDelPropertiesROGuest[i].pcszName, rc);
+        }
+    }
+    RTTESTI_CHECK_RC_OK(pTable->pfnUnload(pTable->pvService));
+}
+
+static void test3(void)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    initTable(&svcTable, &svcHelpers);
+    testSetPropROGuest(&svcTable);
+    testDelPropROGuest(&svcTable);
+}
+
+static void test4(void)
+{
+    RTTestISub("GET_PROP_HOST buffer handling");
+
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    initTable(&svcTable, &svcHelpers);
+    RTTESTI_CHECK_RC_OK_RETV(VBoxHGCMSvcLoad(&svcTable));
+
+    /* Insert a property that we can mess around with. */
+    static char const s_szProp[]  = "/MyProperties/Sub/Sub/Sub/Sub/Sub/Sub/Sub/Property";
+    static char const s_szValue[] = "Property Value";
+    RTTESTI_CHECK_RC_OK(doSetProperty(&svcTable, s_szProp, s_szValue, "", true, true));
+
+
+    /* Get the value with buffer sizes up to 1K.  */
+    for (unsigned iVariation = 0; iVariation < 2; iVariation++)
+    {
+        for (uint32_t cbBuf = 0; cbBuf < _1K; cbBuf++)
+        {
+            void *pvBuf;
+            RTTESTI_CHECK_RC_BREAK(RTTestGuardedAlloc(g_hTest, cbBuf, 1, iVariation == 0, &pvBuf), VINF_SUCCESS);
+
+            VBOXHGCMSVCPARM aParms[4];
+            HGCMSvcSetStr(&aParms[0], s_szProp);
+            HGCMSvcSetPv(&aParms[1], pvBuf, cbBuf);
+            svcTable.pfnHostCall(svcTable.pvService, GUEST_PROP_FN_HOST_GET_PROP, RT_ELEMENTS(aParms), aParms);
+
+            RTTestGuardedFree(g_hTest, pvBuf);
+        }
+    }
+
+    /* Done. */
+    RTTESTI_CHECK_RC_OK(svcTable.pfnUnload(svcTable.pvService));
+}
+
+static void test5(void)
+{
+    RTTestISub("ENUM_PROPS_HOST buffer handling");
+
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    initTable(&svcTable, &svcHelpers);
+    RTTESTI_CHECK_RC_OK_RETV(VBoxHGCMSvcLoad(&svcTable));
+
+    /* Insert a few property that we can mess around with. */
+    RTTESTI_CHECK_RC_OK(doSetProperty(&svcTable, "/MyProperties/Sub/Sub/Sub/Sub/Sub/Sub/Sub/Property", "Property Value", "", true, true));
+    RTTESTI_CHECK_RC_OK(doSetProperty(&svcTable, "/MyProperties/12357",  "83848569", "", true, true));
+    RTTESTI_CHECK_RC_OK(doSetProperty(&svcTable, "/MyProperties/56678",  "abcdefghijklm", "", true, true));
+    RTTESTI_CHECK_RC_OK(doSetProperty(&svcTable, "/MyProperties/932769", "n", "", true, true));
+
+    /* Get the value with buffer sizes up to 1K.  */
+    for (unsigned iVariation = 0; iVariation < 2; iVariation++)
+    {
+        for (uint32_t cbBuf = 0; cbBuf < _1K; cbBuf++)
+        {
+            void *pvBuf;
+            RTTESTI_CHECK_RC_BREAK(RTTestGuardedAlloc(g_hTest, cbBuf, 1, iVariation == 0, &pvBuf), VINF_SUCCESS);
+
+            VBOXHGCMSVCPARM aParms[3];
+            HGCMSvcSetStr(&aParms[0], "*");
+            HGCMSvcSetPv(&aParms[1], pvBuf, cbBuf);
+            svcTable.pfnHostCall(svcTable.pvService, GUEST_PROP_FN_HOST_ENUM_PROPS, RT_ELEMENTS(aParms), aParms);
+
+            RTTestGuardedFree(g_hTest, pvBuf);
+        }
+    }
+
+    /* Done. */
+    RTTESTI_CHECK_RC_OK(svcTable.pfnUnload(svcTable.pvService));
+}
+
+static void test6(void)
+{
+    RTTestISub("Max properties");
+
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    initTable(&svcTable, &svcHelpers);
+    RTTESTI_CHECK_RC_OK_RETV(VBoxHGCMSvcLoad(&svcTable));
+
+    /* Insert the max number of properties. */
+    static char const   s_szPropFmt[] = "/MyProperties/Sub/Sub/Sub/Sub/Sub/Sub/Sub/PropertyNo#%u";
+    char                szProp[80];
+    unsigned            cProps = 0;
+    for (;;)
+    {
+        RTStrPrintf(szProp, sizeof(szProp), s_szPropFmt, cProps);
+        int rc = doSetProperty(&svcTable, szProp, "myvalue", "", true, true);
+        if (rc == VERR_TOO_MUCH_DATA)
+            break;
+        if (RT_FAILURE(rc))
+        {
+            RTTestIFailed("Unexpected error %Rrc setting property number %u", rc, cProps);
+            break;
+        }
+        cProps++;
+    }
+    RTTestIValue("Max Properties", cProps, RTTESTUNIT_OCCURRENCES);
+
+    /* Touch them all again. */
+    for (unsigned iProp = 0; iProp < cProps; iProp++)
+    {
+        RTStrPrintf(szProp, sizeof(szProp), s_szPropFmt, iProp);
+        int rc;
+        RTTESTI_CHECK_MSG((rc = doSetProperty(&svcTable, szProp, "myvalue", "", true, true)) == VINF_SUCCESS,
+                          ("%Rrc - #%u\n", rc, iProp));
+        RTTESTI_CHECK_MSG((rc = doSetProperty(&svcTable, szProp, "myvalue", "", true, false)) == VINF_SUCCESS,
+                          ("%Rrc - #%u\n", rc, iProp));
+        RTTESTI_CHECK_MSG((rc = doSetProperty(&svcTable, szProp, "myvalue", "", false, true)) == VINF_SUCCESS,
+                          ("%Rrc - #%u\n", rc, iProp));
+        RTTESTI_CHECK_MSG((rc = doSetProperty(&svcTable, szProp, "myvalue", "", false, false)) == VINF_SUCCESS,
+                          ("%Rrc - #%u\n", rc, iProp));
+    }
+
+    /* Benchmark. */
+    uint64_t cNsMax = 0;
+    uint64_t cNsMin = UINT64_MAX;
+    uint64_t cNsAvg = 0;
+    for (unsigned iProp = 0; iProp < cProps; iProp++)
+    {
+        size_t cchProp = RTStrPrintf(szProp, sizeof(szProp), s_szPropFmt, iProp);
+
+        uint64_t cNsElapsed = RTTimeNanoTS();
+        unsigned iCall;
+        for (iCall = 0; iCall < 1000; iCall++)
+        {
+            VBOXHGCMSVCPARM aParms[4];
+            char            szBuffer[256];
+            HGCMSvcSetPv(&aParms[0], szProp, (uint32_t)cchProp + 1);
+            HGCMSvcSetPv(&aParms[1], szBuffer, sizeof(szBuffer));
+            RTTESTI_CHECK_RC_BREAK(svcTable.pfnHostCall(svcTable.pvService, GUEST_PROP_FN_HOST_GET_PROP, 4, aParms), VINF_SUCCESS);
+        }
+        cNsElapsed = RTTimeNanoTS() - cNsElapsed;
+        if (iCall)
+        {
+            uint64_t cNsPerCall = cNsElapsed / iCall;
+            cNsAvg += cNsPerCall;
+            if (cNsPerCall < cNsMin)
+                cNsMin = cNsPerCall;
+            if (cNsPerCall > cNsMax)
+                cNsMax = cNsPerCall;
+        }
+    }
+    if (cProps)
+        cNsAvg /= cProps;
+    RTTestIValue("GET_PROP_HOST Min", cNsMin, RTTESTUNIT_NS_PER_CALL);
+    RTTestIValue("GET_PROP_HOST Avg", cNsAvg, RTTESTUNIT_NS_PER_CALL);
+    RTTestIValue("GET_PROP_HOST Max", cNsMax, RTTESTUNIT_NS_PER_CALL);
+
+    /* Done. */
+    RTTESTI_CHECK_RC_OK(svcTable.pfnUnload(svcTable.pvService));
+}
+
+
+
+
+int main()
+{
+    RTEXITCODE rcExit = RTTestInitAndCreate("tstGuestPropSvc", &g_hTest);
+    if (rcExit != RTEXITCODE_SUCCESS)
+        return rcExit;
+    RTTestBanner(g_hTest);
+
+    testConvertFlags();
+    test2();
+    test3();
+    test4();
+    test5();
+    test6();
+
+    return RTTestSummaryAndDestroy(g_hTest);
+}
diff --git a/src/VBox/HostServices/HostChannel/HostChannel.cpp b/src/VBox/HostServices/HostChannel/HostChannel.cpp
new file mode 100644
index 00000000..d52e50d5
--- /dev/null
+++ b/src/VBox/HostServices/HostChannel/HostChannel.cpp
@@ -0,0 +1,1030 @@
+/** @file
+ * Host channel.
+ */
+
+/*
+ * Copyright (C) 2012-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <iprt/alloc.h>
+#include <iprt/string.h>
+#include <iprt/asm.h>
+#include <iprt/assert.h>
+
+#include "HostChannel.h"
+
+
+static DECLCALLBACK(void) HostChannelCallbackEvent(void *pvCallbacks, void *pvInstance,
+                                                   uint32_t u32Id, const void *pvEvent, uint32_t cbEvent);
+static DECLCALLBACK(void) HostChannelCallbackDeleted(void *pvCallbacks, void *pvChannel);
+
+
+/* A registered provider of channels. */
+typedef struct VBOXHOSTCHPROVIDER
+{
+    int32_t volatile cRefs;
+
+    RTLISTNODE nodeContext; /* Member of the list of providers in the service context. */
+
+    VBOXHOSTCHCTX *pCtx;
+
+    VBOXHOSTCHANNELINTERFACE iface;
+
+    char *pszName;
+
+    RTLISTANCHOR listChannels;
+} VBOXHOSTCHPROVIDER;
+
+/* An established channel. */
+typedef struct VBOXHOSTCHINSTANCE
+{
+    int32_t volatile cRefs;
+
+    RTLISTNODE nodeClient;    /* In the client, for cleanup when a client disconnects. */
+    RTLISTNODE nodeProvider;  /* In the provider, needed for cleanup when the provider is unregistered. */
+
+    VBOXHOSTCHCLIENT *pClient; /* The client which uses the channel. */
+    VBOXHOSTCHPROVIDER *pProvider; /* NULL if the provider was unregistered. */
+    void *pvChannel;               /* Provider's context of the channel. */
+    uint32_t u32Handle;        /* handle assigned to the channel by the service. */
+} VBOXHOSTCHINSTANCE;
+
+struct VBOXHOSTCHCTX
+{
+    bool fInitialized;
+
+    RTLISTANCHOR listProviders;
+};
+
+/* The channel callbacks context. The provider passes the pointer as a callback parameter.
+ * Created for the provider and deleted when the provider says so.
+ */
+typedef struct VBOXHOSTCHCALLBACKCTX
+{
+    RTLISTNODE nodeClient;     /* In the client, for cleanup when a client disconnects. */
+
+    VBOXHOSTCHCLIENT *pClient; /* The client which uses the channel, NULL when the client does not exist. */
+} VBOXHOSTCHCALLBACKCTX;
+
+/* Only one service instance is supported. */
+static VBOXHOSTCHCTX g_ctx = { false };
+
+static VBOXHOSTCHANNELCALLBACKS g_callbacks =
+{
+    HostChannelCallbackEvent,
+    HostChannelCallbackDeleted
+};
+
+
+/*
+ * Provider management.
+ */
+
+static void vhcProviderDestroy(VBOXHOSTCHPROVIDER *pProvider)
+{
+    RTStrFree(pProvider->pszName);
+}
+
+static int32_t vhcProviderAddRef(VBOXHOSTCHPROVIDER *pProvider)
+{
+    return ASMAtomicIncS32(&pProvider->cRefs);
+}
+
+static void vhcProviderRelease(VBOXHOSTCHPROVIDER *pProvider)
+{
+    int32_t c = ASMAtomicDecS32(&pProvider->cRefs);
+    Assert(c >= 0);
+    if (c == 0)
+    {
+        vhcProviderDestroy(pProvider);
+        RTMemFree(pProvider);
+    }
+}
+
+static VBOXHOSTCHPROVIDER *vhcProviderFind(VBOXHOSTCHCTX *pCtx, const char *pszName)
+{
+    VBOXHOSTCHPROVIDER *pProvider = NULL;
+
+    int rc = vboxHostChannelLock();
+
+    if (RT_SUCCESS(rc))
+    {
+        VBOXHOSTCHPROVIDER *pIter;
+        RTListForEach(&pCtx->listProviders, pIter, VBOXHOSTCHPROVIDER, nodeContext)
+        {
+            if (RTStrCmp(pIter->pszName, pszName) == 0)
+            {
+                pProvider = pIter;
+
+                vhcProviderAddRef(pProvider);
+
+                break;
+            }
+        }
+
+        vboxHostChannelUnlock();
+    }
+
+    return pProvider;
+}
+
+static int vhcProviderRegister(VBOXHOSTCHCTX *pCtx, VBOXHOSTCHPROVIDER *pProvider)
+{
+    int rc = vboxHostChannelLock();
+
+    if (RT_SUCCESS(rc))
+    {
+        /** @todo check a duplicate. */
+
+        RTListAppend(&pCtx->listProviders, &pProvider->nodeContext);
+
+        vboxHostChannelUnlock();
+    }
+
+    if (RT_FAILURE(rc))
+    {
+        vhcProviderRelease(pProvider);
+    }
+
+    return rc;
+}
+
+static int vhcProviderUnregister(VBOXHOSTCHPROVIDER *pProvider)
+{
+    int rc = vboxHostChannelLock();
+
+    if (RT_SUCCESS(rc))
+    {
+        /** @todo check that the provider is in the list. */
+        /** @todo mark the provider as invalid in each instance. also detach channels? */
+
+        RTListNodeRemove(&pProvider->nodeContext);
+
+        vboxHostChannelUnlock();
+
+        vhcProviderRelease(pProvider);
+    }
+
+    return rc;
+}
+
+
+/*
+ * Select an unique handle for the new channel.
+ * Works under the lock.
+ */
+static int vhcHandleCreate(VBOXHOSTCHCLIENT *pClient, uint32_t *pu32Handle)
+{
+    bool fOver = false;
+
+    for(;;)
+    {
+        uint32_t u32Handle = ASMAtomicIncU32(&pClient->u32HandleSrc);
+
+        if (u32Handle == 0)
+        {
+            if (fOver)
+            {
+                return VERR_NOT_SUPPORTED;
+            }
+
+            fOver = true;
+            continue;
+        }
+
+        VBOXHOSTCHINSTANCE *pDuplicate = NULL;
+        VBOXHOSTCHINSTANCE *pIter;
+        RTListForEach(&pClient->listChannels, pIter, VBOXHOSTCHINSTANCE, nodeClient)
+        {
+            if (pIter->u32Handle == u32Handle)
+            {
+                pDuplicate = pIter;
+                break;
+            }
+        }
+
+        if (pDuplicate == NULL)
+        {
+            *pu32Handle = u32Handle;
+            break;
+        }
+    }
+
+    return VINF_SUCCESS;
+}
+
+
+/*
+ * Channel instance management.
+ */
+
+static void vhcInstanceDestroy(VBOXHOSTCHINSTANCE *pInstance)
+{
+    RT_NOREF1(pInstance);
+    HOSTCHLOG(("HostChannel: destroy %p\n", pInstance));
+}
+
+static int32_t vhcInstanceAddRef(VBOXHOSTCHINSTANCE *pInstance)
+{
+    HOSTCHLOG(("INST: %p %d addref\n", pInstance, pInstance->cRefs));
+    return ASMAtomicIncS32(&pInstance->cRefs);
+}
+
+static void vhcInstanceRelease(VBOXHOSTCHINSTANCE *pInstance)
+{
+    int32_t c = ASMAtomicDecS32(&pInstance->cRefs);
+    HOSTCHLOG(("INST: %p %d release\n", pInstance, pInstance->cRefs));
+    Assert(c >= 0);
+    if (c == 0)
+    {
+        vhcInstanceDestroy(pInstance);
+        RTMemFree(pInstance);
+    }
+}
+
+static int vhcInstanceCreate(VBOXHOSTCHCLIENT *pClient, VBOXHOSTCHINSTANCE **ppInstance)
+{
+    int rc = VINF_SUCCESS;
+
+    VBOXHOSTCHINSTANCE *pInstance = (VBOXHOSTCHINSTANCE *)RTMemAllocZ(sizeof(VBOXHOSTCHINSTANCE));
+
+    if (pInstance)
+    {
+        rc = vboxHostChannelLock();
+
+        if (RT_SUCCESS(rc))
+        {
+            rc = vhcHandleCreate(pClient, &pInstance->u32Handle);
+
+            if (RT_SUCCESS(rc))
+            {
+                /* Used by the client, that is in the list of channels. */
+                vhcInstanceAddRef(pInstance);
+                /* Add to the list of created channel instances. It is inactive while pClient is 0. */
+                RTListAppend(&pClient->listChannels, &pInstance->nodeClient);
+
+                /* Return to the caller. */
+                vhcInstanceAddRef(pInstance);
+                *ppInstance = pInstance;
+            }
+
+            vboxHostChannelUnlock();
+        }
+
+        if (RT_FAILURE(rc))
+        {
+            RTMemFree(pInstance);
+        }
+    }
+    else
+    {
+        rc = VERR_NO_MEMORY;
+    }
+
+    return rc;
+}
+
+static VBOXHOSTCHINSTANCE *vhcInstanceFind(VBOXHOSTCHCLIENT *pClient, uint32_t u32Handle)
+{
+    VBOXHOSTCHINSTANCE *pInstance = NULL;
+
+    int rc = vboxHostChannelLock();
+
+    if (RT_SUCCESS(rc))
+    {
+        VBOXHOSTCHINSTANCE *pIter;
+        RTListForEach(&pClient->listChannels, pIter, VBOXHOSTCHINSTANCE, nodeClient)
+        {
+            if (   pIter->pClient
+                && pIter->u32Handle == u32Handle)
+            {
+                pInstance = pIter;
+
+                vhcInstanceAddRef(pInstance);
+
+                break;
+            }
+        }
+
+        vboxHostChannelUnlock();
+    }
+
+    return pInstance;
+}
+
+static VBOXHOSTCHINSTANCE *vhcInstanceFindByChannelPtr(VBOXHOSTCHCLIENT *pClient, void *pvChannel)
+{
+    VBOXHOSTCHINSTANCE *pInstance = NULL;
+
+    if (pvChannel == NULL)
+    {
+        return NULL;
+    }
+
+    int rc = vboxHostChannelLock();
+
+    if (RT_SUCCESS(rc))
+    {
+        VBOXHOSTCHINSTANCE *pIter;
+        RTListForEach(&pClient->listChannels, pIter, VBOXHOSTCHINSTANCE, nodeClient)
+        {
+            if (   pIter->pClient
+                && pIter->pvChannel == pvChannel)
+            {
+                pInstance = pIter;
+
+                vhcInstanceAddRef(pInstance);
+
+                break;
+            }
+        }
+
+        vboxHostChannelUnlock();
+    }
+
+    return pInstance;
+}
+
+static void vhcInstanceDetach(VBOXHOSTCHINSTANCE *pInstance)
+{
+    HOSTCHLOG(("HostChannel: detach %p\n", pInstance));
+
+    if (pInstance->pProvider)
+    {
+        pInstance->pProvider->iface.HostChannelDetach(pInstance->pvChannel);
+        RTListNodeRemove(&pInstance->nodeProvider);
+        vhcProviderRelease(pInstance->pProvider);
+        pInstance->pProvider = NULL;
+        vhcInstanceRelease(pInstance); /* Not in the provider's list anymore. */
+    }
+
+    int rc = vboxHostChannelLock();
+
+    if (RT_SUCCESS(rc))
+    {
+        RTListNodeRemove(&pInstance->nodeClient);
+
+        vboxHostChannelUnlock();
+
+        vhcInstanceRelease(pInstance); /* Not used by the client anymore. */
+    }
+}
+
+/*
+ * Channel callback contexts.
+ */
+static int vhcCallbackCtxCreate(VBOXHOSTCHCLIENT *pClient, VBOXHOSTCHCALLBACKCTX **ppCallbackCtx)
+{
+    int rc = VINF_SUCCESS;
+
+    VBOXHOSTCHCALLBACKCTX *pCallbackCtx = (VBOXHOSTCHCALLBACKCTX *)RTMemAllocZ(sizeof(VBOXHOSTCHCALLBACKCTX));
+
+    if (pCallbackCtx != NULL)
+    {
+        /* The callback context is accessed by the providers threads. */
+        rc = vboxHostChannelLock();
+        if (RT_SUCCESS(rc))
+        {
+            RTListAppend(&pClient->listContexts, &pCallbackCtx->nodeClient);
+            pCallbackCtx->pClient = pClient;
+
+            vboxHostChannelUnlock();
+        }
+        else
+        {
+            RTMemFree(pCallbackCtx);
+        }
+    }
+    else
+    {
+        rc = VERR_NO_MEMORY;
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        *ppCallbackCtx = pCallbackCtx;
+    }
+
+    return rc;
+}
+
+static int vhcCallbackCtxDelete(VBOXHOSTCHCALLBACKCTX *pCallbackCtx)
+{
+    int rc = vboxHostChannelLock();
+    if (RT_SUCCESS(rc))
+    {
+        VBOXHOSTCHCLIENT *pClient = pCallbackCtx->pClient;
+
+        if (pClient != NULL)
+        {
+            /* The callback is associated with a client.
+             * Check that the callback is in the list and remove it from the list.
+             */
+            bool fFound = false;
+
+            VBOXHOSTCHCALLBACKCTX *pIter;
+            RTListForEach(&pClient->listContexts, pIter, VBOXHOSTCHCALLBACKCTX, nodeClient)
+            {
+                if (pIter == pCallbackCtx)
+                {
+                    fFound = true;
+                    break;
+                }
+            }
+
+            if (fFound)
+            {
+                RTListNodeRemove(&pCallbackCtx->nodeClient);
+            }
+            else
+            {
+                AssertFailed();
+                rc = VERR_INVALID_PARAMETER;
+            }
+        }
+        else
+        {
+            /* It is not in the clients anymore. May be the client has been disconnected.
+             * Just free the memory.
+             */
+        }
+
+        vboxHostChannelUnlock();
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        RTMemFree(pCallbackCtx);
+    }
+
+    return rc;
+}
+
+/*
+ * Host channel service functions.
+ */
+
+int vboxHostChannelInit(void)
+{
+    VBOXHOSTCHCTX *pCtx = &g_ctx;
+
+    if (pCtx->fInitialized)
+    {
+        return VERR_NOT_SUPPORTED;
+    }
+
+    pCtx->fInitialized = true;
+    RTListInit(&pCtx->listProviders);
+
+    return VINF_SUCCESS;
+}
+
+void vboxHostChannelDestroy(void)
+{
+    VBOXHOSTCHCTX *pCtx = &g_ctx;
+
+    VBOXHOSTCHPROVIDER *pIter;
+    VBOXHOSTCHPROVIDER *pIterNext;
+    RTListForEachSafe(&pCtx->listProviders, pIter, pIterNext, VBOXHOSTCHPROVIDER, nodeContext)
+    {
+        vhcProviderUnregister(pIter);
+    }
+    pCtx->fInitialized = false;
+}
+
+int vboxHostChannelClientConnect(VBOXHOSTCHCLIENT *pClient)
+{
+    /* A guest client is connecting to the service.
+     * Later the client will use Attach calls to connect to channel providers.
+     * pClient is already zeroed.
+     */
+    pClient->pCtx = &g_ctx;
+
+    RTListInit(&pClient->listChannels);
+    RTListInit(&pClient->listEvents);
+    RTListInit(&pClient->listContexts);
+
+    return VINF_SUCCESS;
+}
+
+void vboxHostChannelClientDisconnect(VBOXHOSTCHCLIENT *pClient)
+{
+    /* Clear the list of contexts and prevent acceess to the client. */
+    int rc = vboxHostChannelLock();
+    if (RT_SUCCESS(rc))
+    {
+        VBOXHOSTCHCALLBACKCTX *pIter;
+        VBOXHOSTCHCALLBACKCTX *pNext;
+        RTListForEachSafe(&pClient->listContexts, pIter, pNext, VBOXHOSTCHCALLBACKCTX, nodeClient)
+        {
+            pIter->pClient = NULL;
+            RTListNodeRemove(&pIter->nodeClient);
+        }
+
+        vboxHostChannelUnlock();
+    }
+
+    /* If there are attached channels, detach them. */
+    VBOXHOSTCHINSTANCE *pIter;
+    VBOXHOSTCHINSTANCE *pIterNext;
+    RTListForEachSafe(&pClient->listChannels, pIter, pIterNext, VBOXHOSTCHINSTANCE, nodeClient)
+    {
+        vhcInstanceDetach(pIter);
+    }
+}
+
+int vboxHostChannelAttach(VBOXHOSTCHCLIENT *pClient,
+                          uint32_t *pu32Handle,
+                          const char *pszName,
+                          uint32_t u32Flags)
+{
+    int rc = VINF_SUCCESS;
+
+    HOSTCHLOG(("HostChannel: Attach: (%d) [%s] 0x%08X\n", pClient->u32ClientID, pszName, u32Flags));
+
+    /* Look if there is a provider. */
+    VBOXHOSTCHPROVIDER *pProvider = vhcProviderFind(pClient->pCtx, pszName);
+
+    if (pProvider)
+    {
+        VBOXHOSTCHINSTANCE *pInstance = NULL;
+
+        rc = vhcInstanceCreate(pClient, &pInstance);
+
+        if (RT_SUCCESS(rc))
+        {
+            VBOXHOSTCHCALLBACKCTX *pCallbackCtx = NULL;
+            rc = vhcCallbackCtxCreate(pClient, &pCallbackCtx);
+
+            if (RT_SUCCESS(rc))
+            {
+                void *pvChannel = NULL;
+                rc = pProvider->iface.HostChannelAttach(pProvider->iface.pvProvider,
+                                                        &pvChannel,
+                                                        u32Flags,
+                                                        &g_callbacks, pCallbackCtx);
+
+                if (RT_SUCCESS(rc))
+                {
+                    vhcProviderAddRef(pProvider);
+                    pInstance->pProvider = pProvider;
+
+                    pInstance->pClient = pClient;
+                    pInstance->pvChannel = pvChannel;
+
+                    /* It is already in the channels list of the client. */
+
+                    vhcInstanceAddRef(pInstance); /* Referenced by the list of provider's channels. */
+                    RTListAppend(&pProvider->listChannels, &pInstance->nodeProvider);
+
+                    *pu32Handle = pInstance->u32Handle;
+
+                    HOSTCHLOG(("HostChannel: Attach: (%d) handle %d\n", pClient->u32ClientID, pInstance->u32Handle));
+                }
+
+                if (RT_FAILURE(rc))
+                {
+                    vhcCallbackCtxDelete(pCallbackCtx);
+                }
+            }
+
+            if (RT_FAILURE(rc))
+            {
+                vhcInstanceDetach(pInstance);
+            }
+
+            vhcInstanceRelease(pInstance);
+        }
+
+        vhcProviderRelease(pProvider);
+    }
+    else
+    {
+        rc = VERR_NOT_SUPPORTED;
+    }
+
+    return rc;
+}
+
+int vboxHostChannelDetach(VBOXHOSTCHCLIENT *pClient,
+                          uint32_t u32Handle)
+{
+    HOSTCHLOG(("HostChannel: Detach: (%d) handle %d\n", pClient->u32ClientID, u32Handle));
+
+    int rc = VINF_SUCCESS;
+
+    VBOXHOSTCHINSTANCE *pInstance = vhcInstanceFind(pClient, u32Handle);
+
+    if (pInstance)
+    {
+        vhcInstanceDetach(pInstance);
+
+        vhcInstanceRelease(pInstance);
+    }
+    else
+    {
+        rc = VERR_NOT_SUPPORTED;
+    }
+
+    return rc;
+}
+
+int vboxHostChannelSend(VBOXHOSTCHCLIENT *pClient,
+                        uint32_t u32Handle,
+                        const void *pvData,
+                        uint32_t cbData)
+{
+    HOSTCHLOG(("HostChannel: Send: (%d) handle %d, %d bytes\n", pClient->u32ClientID, u32Handle, cbData));
+
+    int rc = VINF_SUCCESS;
+
+    VBOXHOSTCHINSTANCE *pInstance = vhcInstanceFind(pClient, u32Handle);
+
+    if (pInstance)
+    {
+        if (pInstance->pProvider)
+        {
+            pInstance->pProvider->iface.HostChannelSend(pInstance->pvChannel, pvData, cbData);
+        }
+
+        vhcInstanceRelease(pInstance);
+    }
+    else
+    {
+        rc = VERR_NOT_SUPPORTED;
+    }
+
+    return rc;
+}
+
+int vboxHostChannelRecv(VBOXHOSTCHCLIENT *pClient,
+                        uint32_t u32Handle,
+                        void *pvData,
+                        uint32_t cbData,
+                        uint32_t *pu32SizeReceived,
+                        uint32_t *pu32SizeRemaining)
+{
+    HOSTCHLOG(("HostChannel: Recv: (%d) handle %d, cbData %d\n", pClient->u32ClientID, u32Handle, cbData));
+
+    int rc = VINF_SUCCESS;
+
+    VBOXHOSTCHINSTANCE *pInstance = vhcInstanceFind(pClient, u32Handle);
+
+    if (pInstance)
+    {
+        if (pInstance->pProvider)
+        {
+            rc = pInstance->pProvider->iface.HostChannelRecv(pInstance->pvChannel, pvData, cbData,
+                                                             pu32SizeReceived, pu32SizeRemaining);
+
+            HOSTCHLOG(("HostChannel: Recv: (%d) handle %d, rc %Rrc, cbData %d, recv %d, rem %d\n",
+                       pClient->u32ClientID, u32Handle, rc, cbData, *pu32SizeReceived, *pu32SizeRemaining));
+        }
+
+        vhcInstanceRelease(pInstance);
+    }
+    else
+    {
+        rc = VERR_NOT_SUPPORTED;
+    }
+
+    return rc;
+}
+
+int vboxHostChannelControl(VBOXHOSTCHCLIENT *pClient,
+                           uint32_t u32Handle,
+                           uint32_t u32Code,
+                           void *pvParm,
+                           uint32_t cbParm,
+                           void *pvData,
+                           uint32_t cbData,
+                           uint32_t *pu32SizeDataReturned)
+{
+    HOSTCHLOG(("HostChannel: Control: (%d) handle %d, cbData %d\n", pClient->u32ClientID, u32Handle, cbData));
+
+    int rc = VINF_SUCCESS;
+
+    VBOXHOSTCHINSTANCE *pInstance = vhcInstanceFind(pClient, u32Handle);
+
+    if (pInstance)
+    {
+        if (pInstance->pProvider)
+        {
+            pInstance->pProvider->iface.HostChannelControl(pInstance->pvChannel, u32Code,
+                                                           pvParm, cbParm,
+                                                           pvData, cbData, pu32SizeDataReturned);
+        }
+
+        vhcInstanceRelease(pInstance);
+    }
+    else
+    {
+        rc = VERR_NOT_SUPPORTED;
+    }
+
+    return rc;
+}
+
+typedef struct VBOXHOSTCHANNELEVENT
+{
+    RTLISTNODE NodeEvent;
+
+    uint32_t u32ChannelHandle;
+
+    uint32_t u32Id;
+    void *pvEvent;
+    uint32_t cbEvent;
+} VBOXHOSTCHANNELEVENT;
+
+int vboxHostChannelEventWait(VBOXHOSTCHCLIENT *pClient,
+                             bool *pfEvent,
+                             VBOXHGCMCALLHANDLE callHandle,
+                             VBOXHGCMSVCPARM *paParms)
+{
+    int rc = vboxHostChannelLock();
+    if (RT_FAILURE(rc))
+    {
+        return rc;
+    }
+
+    if (pClient->fAsync)
+    {
+        /* If there is a wait request already, cancel it. */
+        vboxHostChannelReportAsync(pClient, 0, VBOX_HOST_CHANNEL_EVENT_CANCELLED, NULL, 0);
+        pClient->fAsync = false;
+    }
+
+    /* Check if there is something in the client's event queue. */
+    VBOXHOSTCHANNELEVENT *pEvent = RTListGetFirst(&pClient->listEvents, VBOXHOSTCHANNELEVENT, NodeEvent);
+
+    HOSTCHLOG(("HostChannel: QueryEvent: (%d), event %p\n", pClient->u32ClientID, pEvent));
+
+    if (pEvent)
+    {
+        /* Report the event. */
+        RTListNodeRemove(&pEvent->NodeEvent);
+
+        HOSTCHLOG(("HostChannel: QueryEvent: (%d), cbEvent %d\n",
+                   pClient->u32ClientID, pEvent->cbEvent));
+
+        vboxHostChannelEventParmsSet(paParms, pEvent->u32ChannelHandle,
+                                     pEvent->u32Id, pEvent->pvEvent, pEvent->cbEvent);
+
+        *pfEvent = true;
+
+        RTMemFree(pEvent);
+    }
+    else
+    {
+        /* No event available at the time. Process asynchronously. */
+        pClient->fAsync           = true;
+        pClient->async.callHandle = callHandle;
+        pClient->async.paParms    = paParms;
+
+        /* Tell the caller that there is no event. */
+        *pfEvent = false;
+    }
+
+    vboxHostChannelUnlock();
+    return rc;
+}
+
+int vboxHostChannelEventCancel(VBOXHOSTCHCLIENT *pClient)
+{
+    int rc = vboxHostChannelLock();
+
+    if (RT_SUCCESS(rc))
+    {
+        if (pClient->fAsync)
+        {
+            /* If there is a wait request alredy, cancel it. */
+            vboxHostChannelReportAsync(pClient, 0, VBOX_HOST_CHANNEL_EVENT_CANCELLED, NULL, 0);
+
+            pClient->fAsync = false;
+        }
+
+        vboxHostChannelUnlock();
+    }
+
+    return rc;
+}
+
+/* @thread provider */
+static DECLCALLBACK(void) HostChannelCallbackEvent(void *pvCallbacks, void *pvChannel,
+                                                   uint32_t u32Id, const void *pvEvent, uint32_t cbEvent)
+{
+    VBOXHOSTCHCALLBACKCTX *pCallbackCtx = (VBOXHOSTCHCALLBACKCTX *)pvCallbacks;
+
+    int rc = vboxHostChannelLock();
+    if (RT_FAILURE(rc))
+    {
+        return;
+    }
+
+    /* Check that the structure is still associated with a client.
+     * The client can disconnect and will be invalid.
+     */
+    VBOXHOSTCHCLIENT *pClient = pCallbackCtx->pClient;
+
+    if (pClient == NULL)
+    {
+        vboxHostChannelUnlock();
+
+        HOSTCHLOG(("HostChannel: CallbackEvent[%p]: client gone.\n", pvEvent));
+
+        /* The client does not exist anymore, skip the event. */
+        return;
+    }
+
+    bool fFound = false;
+
+    VBOXHOSTCHCALLBACKCTX *pIter;
+    RTListForEach(&pClient->listContexts, pIter, VBOXHOSTCHCALLBACKCTX, nodeClient)
+    {
+        if (pIter == pCallbackCtx)
+        {
+            fFound = true;
+            break;
+        }
+    }
+
+    if (!fFound)
+    {
+        AssertFailed();
+
+        vboxHostChannelUnlock();
+
+        HOSTCHLOG(("HostChannel: CallbackEvent[%p]: client does not have the context.\n", pvEvent));
+
+        /* The context is not in the list of contexts. Skip the event. */
+        return;
+    }
+
+    VBOXHOSTCHINSTANCE *pInstance = vhcInstanceFindByChannelPtr(pClient, pvChannel);
+
+    HOSTCHLOG(("HostChannel: CallbackEvent[%p]: (%d) instance %p\n",
+               pCallbackCtx, pClient->u32ClientID, pInstance));
+
+    if (!pInstance)
+    {
+        /* Instance was already detached. Skip the event. */
+        vboxHostChannelUnlock();
+
+        return;
+    }
+
+    uint32_t u32ChannelHandle = pInstance->u32Handle;
+
+    HOSTCHLOG(("HostChannel: CallbackEvent: (%d) handle %d, async %d, cbEvent %d\n",
+               pClient->u32ClientID, u32ChannelHandle, pClient->fAsync, cbEvent));
+
+    /* Check whether the event is waited. */
+    if (pClient->fAsync)
+    {
+        /* Report the event. */
+        vboxHostChannelReportAsync(pClient, u32ChannelHandle, u32Id, pvEvent, cbEvent);
+
+        pClient->fAsync = false;
+    }
+    else
+    {
+        /* Put it to the queue. */
+        VBOXHOSTCHANNELEVENT *pEvent = (VBOXHOSTCHANNELEVENT *)RTMemAlloc(sizeof(VBOXHOSTCHANNELEVENT) + cbEvent);
+
+        if (pEvent)
+        {
+            pEvent->u32ChannelHandle = u32ChannelHandle;
+            pEvent->u32Id = u32Id;
+
+            if (cbEvent)
+            {
+                pEvent->pvEvent = &pEvent[1];
+                memcpy(pEvent->pvEvent, pvEvent, cbEvent);
+            }
+            else
+            {
+                pEvent->pvEvent = NULL;
+            }
+
+            pEvent->cbEvent = cbEvent;
+
+            RTListAppend(&pClient->listEvents, &pEvent->NodeEvent);
+        }
+    }
+
+    vboxHostChannelUnlock();
+
+    vhcInstanceRelease(pInstance);
+}
+
+/* @thread provider */
+static DECLCALLBACK(void) HostChannelCallbackDeleted(void *pvCallbacks, void *pvChannel)
+{
+    RT_NOREF1(pvChannel);
+    vhcCallbackCtxDelete((VBOXHOSTCHCALLBACKCTX *)pvCallbacks);
+}
+
+int vboxHostChannelQuery(VBOXHOSTCHCLIENT *pClient,
+                         const char *pszName,
+                         uint32_t u32Code,
+                         void *pvParm,
+                         uint32_t cbParm,
+                         void *pvData,
+                         uint32_t cbData,
+                         uint32_t *pu32SizeDataReturned)
+{
+    HOSTCHLOG(("HostChannel: Query: (%d) name [%s], cbData %d\n", pClient->u32ClientID, pszName, cbData));
+
+    int rc = VINF_SUCCESS;
+
+    /* Look if there is a provider. */
+    VBOXHOSTCHPROVIDER *pProvider = vhcProviderFind(pClient->pCtx, pszName);
+
+    if (pProvider)
+    {
+        pProvider->iface.HostChannelControl(NULL, u32Code,
+                                            pvParm, cbParm,
+                                            pvData, cbData, pu32SizeDataReturned);
+
+        vhcProviderRelease(pProvider);
+    }
+    else
+    {
+        rc = VERR_NOT_SUPPORTED;
+    }
+
+    return rc;
+}
+
+int vboxHostChannelRegister(const char *pszName,
+                            const VBOXHOSTCHANNELINTERFACE *pInterface,
+                            uint32_t cbInterface)
+{
+    RT_NOREF1(cbInterface);
+    int rc = VINF_SUCCESS;
+
+    VBOXHOSTCHCTX *pCtx = &g_ctx;
+
+    VBOXHOSTCHPROVIDER *pProvider = (VBOXHOSTCHPROVIDER *)RTMemAllocZ(sizeof(VBOXHOSTCHPROVIDER));
+
+    if (pProvider)
+    {
+        pProvider->pCtx = pCtx;
+        pProvider->iface = *pInterface;
+
+        RTListInit(&pProvider->listChannels);
+
+        pProvider->pszName = RTStrDup(pszName);
+        if (pProvider->pszName)
+        {
+            vhcProviderAddRef(pProvider);
+            rc = vhcProviderRegister(pCtx, pProvider);
+        }
+        else
+        {
+            RTMemFree(pProvider);
+            rc = VERR_NO_MEMORY;
+        }
+    }
+    else
+    {
+        rc = VERR_NO_MEMORY;
+    }
+
+    return rc;
+}
+
+int vboxHostChannelUnregister(const char *pszName)
+{
+    int rc = VINF_SUCCESS;
+
+    VBOXHOSTCHCTX *pCtx = &g_ctx;
+
+    VBOXHOSTCHPROVIDER *pProvider = vhcProviderFind(pCtx, pszName);
+
+    if (pProvider)
+    {
+        rc = vhcProviderUnregister(pProvider);
+        vhcProviderRelease(pProvider);
+    }
+
+    return rc;
+}
diff --git a/src/VBox/HostServices/HostChannel/HostChannel.h b/src/VBox/HostServices/HostChannel/HostChannel.h
new file mode 100644
index 00000000..75cb0385
--- /dev/null
+++ b/src/VBox/HostServices/HostChannel/HostChannel.h
@@ -0,0 +1,147 @@
+/* @file
+ *
+ * Host Channel
+ */
+
+/*
+ * Copyright (C) 2012-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_HostChannel_HostChannel_h
+#define VBOX_INCLUDED_SRC_HostChannel_HostChannel_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <iprt/list.h>
+
+#define LOG_GROUP LOG_GROUP_HGCM
+#include <VBox/log.h>
+#include <VBox/HostServices/VBoxHostChannel.h>
+
+#define HOSTCHLOG Log
+
+#ifdef DEBUG_sunlover
+# undef HOSTCHLOG
+# define HOSTCHLOG LogRel
+#endif /* DEBUG_sunlover */
+
+struct VBOXHOSTCHCTX;
+typedef struct VBOXHOSTCHCTX VBOXHOSTCHCTX;
+
+typedef struct VBOXHOSTCHCLIENT
+{
+    RTLISTNODE nodeClient;
+
+    VBOXHOSTCHCTX *pCtx;
+
+    uint32_t u32ClientID;
+
+    RTLISTANCHOR listChannels;
+    uint32_t volatile u32HandleSrc;
+
+    RTLISTANCHOR listContexts; /* Callback contexts. */
+
+    RTLISTANCHOR listEvents;
+
+    bool fAsync;        /* Guest is waiting for a message. */
+
+    struct {
+        VBOXHGCMCALLHANDLE callHandle;
+        VBOXHGCMSVCPARM *paParms;
+    } async;
+
+} VBOXHOSTCHCLIENT;
+
+
+/*
+ * The service functions. Locking is between the service thread and the host channel provider thread.
+ */
+int vboxHostChannelLock(void);
+void vboxHostChannelUnlock(void);
+
+int vboxHostChannelInit(void);
+void vboxHostChannelDestroy(void);
+
+int vboxHostChannelClientConnect(VBOXHOSTCHCLIENT *pClient);
+void vboxHostChannelClientDisconnect(VBOXHOSTCHCLIENT *pClient);
+
+int vboxHostChannelAttach(VBOXHOSTCHCLIENT *pClient,
+                          uint32_t *pu32Handle,
+                          const char *pszName,
+                          uint32_t u32Flags);
+int vboxHostChannelDetach(VBOXHOSTCHCLIENT *pClient,
+                          uint32_t u32Handle);
+
+int vboxHostChannelSend(VBOXHOSTCHCLIENT *pClient,
+                        uint32_t u32Handle,
+                        const void *pvData,
+                        uint32_t cbData);
+int vboxHostChannelRecv(VBOXHOSTCHCLIENT *pClient,
+                        uint32_t u32Handle,
+                        void *pvData,
+                        uint32_t cbData,
+                        uint32_t *pu32DataReceived,
+                        uint32_t *pu32DataRemaining);
+int vboxHostChannelControl(VBOXHOSTCHCLIENT *pClient,
+                           uint32_t u32Handle,
+                           uint32_t u32Code,
+                           void *pvParm,
+                           uint32_t cbParm,
+                           void *pvData,
+                           uint32_t cbData,
+                           uint32_t *pu32SizeDataReturned);
+
+int vboxHostChannelEventWait(VBOXHOSTCHCLIENT *pClient,
+                             bool *pfEvent,
+                             VBOXHGCMCALLHANDLE callHandle,
+                             VBOXHGCMSVCPARM *paParms);
+
+int vboxHostChannelEventCancel(VBOXHOSTCHCLIENT *pClient);
+
+int vboxHostChannelQuery(VBOXHOSTCHCLIENT *pClient,
+                         const char *pszName,
+                         uint32_t u32Code,
+                         void *pvParm,
+                         uint32_t cbParm,
+                         void *pvData,
+                         uint32_t cbData,
+                         uint32_t *pu32SizeDataReturned);
+
+int vboxHostChannelRegister(const char *pszName,
+                            const VBOXHOSTCHANNELINTERFACE *pInterface,
+                            uint32_t cbInterface);
+int vboxHostChannelUnregister(const char *pszName);
+
+
+void vboxHostChannelEventParmsSet(VBOXHGCMSVCPARM *paParms,
+                                  uint32_t u32ChannelHandle,
+                                  uint32_t u32Id,
+                                  const void *pvEvent,
+                                  uint32_t cbEvent);
+
+void vboxHostChannelReportAsync(VBOXHOSTCHCLIENT *pClient,
+                                uint32_t u32ChannelHandle,
+                                uint32_t u32Id,
+                                const void *pvEvent,
+                                uint32_t cbEvent);
+
+#endif /* !VBOX_INCLUDED_SRC_HostChannel_HostChannel_h */
diff --git a/src/VBox/HostServices/HostChannel/Makefile.kmk b/src/VBox/HostServices/HostChannel/Makefile.kmk
new file mode 100644
index 00000000..377bd7e6
--- /dev/null
+++ b/src/VBox/HostServices/HostChannel/Makefile.kmk
@@ -0,0 +1,50 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Host Channel Service.
+#
+
+#
+# Copyright (C) 2012-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+#
+# The service DLL.
+#
+DLLS += VBoxHostChannel
+VBoxHostChannel_TEMPLATE  = VBoxR3Dll
+VBoxHostChannel_DEFS      = VBOX_WITH_HGCM
+VBoxHostChannel_INCS.win  = \
+	$(VBOX_PATH_SDK)
+
+VBoxHostChannel_SOURCES = \
+	VBoxHostChannelSvc.cpp \
+	HostChannel.cpp
+
+VBoxHostChannel_SOURCES.win = \
+	VBoxHostChannelSvc.rc
+
+VBoxHostChannel_LIBS = \
+	$(LIB_RUNTIME)
+
+include $(FILE_KBUILD_SUB_FOOTER)
diff --git a/src/VBox/HostServices/HostChannel/VBoxHostChannelSvc.cpp b/src/VBox/HostServices/HostChannel/VBoxHostChannelSvc.cpp
new file mode 100644
index 00000000..3df8b9d5
--- /dev/null
+++ b/src/VBox/HostServices/HostChannel/VBoxHostChannelSvc.cpp
@@ -0,0 +1,891 @@
+/* $Id: VBoxHostChannelSvc.cpp $ */
+/* @file
+ * Host Channel: Host service entry points.
+ */
+
+/*
+ * Copyright (C) 2012-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*
+ * The HostChannel host service provides a generic proxy between a host's
+ * channel provider and a client running in the guest.
+ *
+ * Host providers must register via a HostCall.
+ *
+ * A guest client can connect to a host provider and send/receive data.
+ *
+ * GuestCalls:
+ *    * Attach      - attach to a host channel
+ *    * Detach      - completely detach from a channel
+ *    * Send        - send data from the guest to the channel
+ *    * Recv        - non blocking read of available data from the channel
+ *    * Control     - generic channel specific command exchange
+ *    * EventWait   - wait for a host event
+ *    * EventCancel - make the blocking EventWait call to return
+ * HostCalls:
+ *    * Register    - register a host channel
+ *    * Unregister  - unregister it
+ *
+ * The guest HGCM client connects to the service. The client can attach multiple channels.
+ *
+ */
+
+#include <iprt/alloc.h>
+#include <iprt/string.h>
+#include <iprt/assert.h>
+#include <iprt/critsect.h>
+#include <VBox/vmm/ssm.h>
+
+#include "HostChannel.h"
+
+
+static void VBoxHGCMParmUInt32Set(VBOXHGCMSVCPARM *pParm, uint32_t u32)
+{
+    pParm->type = VBOX_HGCM_SVC_PARM_32BIT;
+    pParm->u.uint32 = u32;
+}
+
+static int VBoxHGCMParmUInt32Get(VBOXHGCMSVCPARM *pParm, uint32_t *pu32)
+{
+    if (pParm->type == VBOX_HGCM_SVC_PARM_32BIT)
+    {
+        *pu32 = pParm->u.uint32;
+        return VINF_SUCCESS;
+    }
+
+    AssertFailed();
+    return VERR_INVALID_PARAMETER;
+}
+
+#if 0 /* unused */
+static void VBoxHGCMParmPtrSet(VBOXHGCMSVCPARM *pParm, void *pv, uint32_t cb)
+{
+    pParm->type             = VBOX_HGCM_SVC_PARM_PTR;
+    pParm->u.pointer.size   = cb;
+    pParm->u.pointer.addr   = pv;
+}
+#endif
+
+static int VBoxHGCMParmPtrGet(VBOXHGCMSVCPARM *pParm, void **ppv, uint32_t *pcb)
+{
+    if (pParm->type == VBOX_HGCM_SVC_PARM_PTR)
+    {
+        *ppv = pParm->u.pointer.addr;
+        *pcb = pParm->u.pointer.size;
+        return VINF_SUCCESS;
+    }
+
+    AssertFailed();
+    return VERR_INVALID_PARAMETER;
+}
+
+
+static PVBOXHGCMSVCHELPERS g_pHelpers = NULL;
+
+static RTCRITSECT g_critsect;
+
+/*
+ * Helpers.
+ */
+
+int vboxHostChannelLock(void)
+{
+    return RTCritSectEnter(&g_critsect);
+}
+
+void vboxHostChannelUnlock(void)
+{
+    RTCritSectLeave(&g_critsect);
+}
+
+void vboxHostChannelEventParmsSet(VBOXHGCMSVCPARM *paParms,
+                                  uint32_t u32ChannelHandle,
+                                  uint32_t u32Id,
+                                  const void *pvEvent,
+                                  uint32_t cbEvent)
+{
+    if (cbEvent > 0)
+    {
+        void *pvParm = NULL;
+        uint32_t cbParm = 0;
+
+        VBoxHGCMParmPtrGet(&paParms[2], &pvParm, &cbParm);
+
+        uint32_t cbToCopy = RT_MIN(cbParm, cbEvent);
+        if (cbToCopy > 0)
+        {
+            Assert(pvParm);
+            memcpy(pvParm, pvEvent, cbToCopy);
+        }
+    }
+
+    VBoxHGCMParmUInt32Set(&paParms[0], u32ChannelHandle);
+    VBoxHGCMParmUInt32Set(&paParms[1], u32Id);
+    VBoxHGCMParmUInt32Set(&paParms[3], cbEvent);
+}
+
+/* This is called under the lock. */
+void vboxHostChannelReportAsync(VBOXHOSTCHCLIENT *pClient,
+                                uint32_t u32ChannelHandle,
+                                uint32_t u32Id,
+                                const void *pvEvent,
+                                uint32_t cbEvent)
+{
+    Assert(RTCritSectIsOwner(&g_critsect));
+
+    vboxHostChannelEventParmsSet(pClient->async.paParms,
+                                 u32ChannelHandle,
+                                 u32Id,
+                                 pvEvent,
+                                 cbEvent);
+
+    LogRelFlow(("svcCall: CallComplete for pending\n"));
+
+    g_pHelpers->pfnCallComplete (pClient->async.callHandle, VINF_SUCCESS);
+}
+
+
+/*
+ *  Service entry points.
+ */
+
+static DECLCALLBACK(int) svcUnload(void *pvService)
+{
+    NOREF(pvService);
+    vboxHostChannelDestroy();
+    RTCritSectDelete(&g_critsect);
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) svcDisconnect(void *pvService, uint32_t u32ClientID, void *pvClient)
+{
+    RT_NOREF2(pvService, u32ClientID);
+
+    VBOXHOSTCHCLIENT *pClient = (VBOXHOSTCHCLIENT *)pvClient;
+
+    vboxHostChannelClientDisconnect(pClient);
+
+    memset(pClient, 0, sizeof(VBOXHOSTCHCLIENT));
+
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) svcConnect(void *pvService, uint32_t u32ClientID, void *pvClient, uint32_t fRequestor, bool fRestoring)
+{
+    RT_NOREF(pvService, fRequestor, fRestoring);
+    VBOXHOSTCHCLIENT *pClient = (VBOXHOSTCHCLIENT *)pvClient;
+
+    /* Register the client. */
+    memset(pClient, 0, sizeof(VBOXHOSTCHCLIENT));
+
+    pClient->u32ClientID = u32ClientID;
+
+    int rc = vboxHostChannelClientConnect(pClient);
+
+    LogRel2(("svcConnect: rc = %Rrc\n", rc));
+
+    return rc;
+}
+
+static DECLCALLBACK(void) svcCall(void *pvService,
+                                  VBOXHGCMCALLHANDLE callHandle,
+                                  uint32_t u32ClientID,
+                                  void *pvClient,
+                                  uint32_t u32Function,
+                                  uint32_t cParms,
+                                  VBOXHGCMSVCPARM paParms[],
+                                  uint64_t tsArrival)
+{
+    RT_NOREF(pvService, tsArrival);
+
+    int rc = VINF_SUCCESS;
+
+    LogRel2(("svcCall: u32ClientID = %d, fn = %d, cParms = %d, pparms = %d\n",
+             u32ClientID, u32Function, cParms, paParms));
+
+    VBOXHOSTCHCLIENT *pClient = (VBOXHOSTCHCLIENT *)pvClient;
+
+    bool fAsynchronousProcessing = false;
+
+#ifdef DEBUG
+    uint32_t i;
+
+    for (i = 0; i < cParms; i++)
+    {
+        /** @todo parameters other than 32 bit */
+        LogRel2(("    pparms[%d]: type %d value %d\n", i, paParms[i].type, paParms[i].u.uint32));
+    }
+#endif
+
+    switch (u32Function)
+    {
+        case VBOX_HOST_CHANNEL_FN_ATTACH:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_FN_ATTACH\n"));
+
+            if (cParms != 3)
+                rc = VERR_INVALID_PARAMETER;
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_PTR     /* name */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_32BIT   /* flags */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_32BIT   /* handle */
+                    )
+                rc = VERR_INVALID_PARAMETER;
+            else
+            {
+                uint32_t u32Flags = 0; /* Shut up msvc*/
+                const char *pszName;
+                uint32_t cbName;
+
+                rc = VBoxHGCMParmPtrGet(&paParms[0], (void **)&pszName, &cbName);
+                if (   RT_SUCCESS(rc)
+                    && pszName[cbName - 1] != '\0')
+                    rc = VERR_INVALID_PARAMETER;
+                if (RT_SUCCESS(rc))
+                    rc = VBoxHGCMParmUInt32Get(&paParms[1], &u32Flags);
+                if (RT_SUCCESS(rc))
+                {
+                    uint32_t u32Handle = 0;
+                    rc = vboxHostChannelAttach(pClient, &u32Handle, pszName, u32Flags);
+                    if (RT_SUCCESS(rc))
+                        VBoxHGCMParmUInt32Set(&paParms[2], u32Handle);
+                }
+            }
+        } break;
+
+        case VBOX_HOST_CHANNEL_FN_DETACH:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_FN_DETACH\n"));
+
+            if (cParms != 1)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* handle */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                uint32_t u32Handle;
+
+                rc = VBoxHGCMParmUInt32Get(&paParms[0], &u32Handle);
+
+                if (RT_SUCCESS(rc))
+                {
+                    rc = vboxHostChannelDetach(pClient, u32Handle);
+                }
+            }
+        } break;
+
+        case VBOX_HOST_CHANNEL_FN_SEND:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_FN_SEND\n"));
+
+            if (cParms != 2)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* handle */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_PTR     /* data */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                uint32_t u32Handle;
+                void *pvData;
+                uint32_t cbData;
+
+                rc = VBoxHGCMParmUInt32Get (&paParms[0], &u32Handle);
+
+                if (RT_SUCCESS (rc))
+                {
+                    rc = VBoxHGCMParmPtrGet (&paParms[1], &pvData, &cbData);
+
+                    if (RT_SUCCESS (rc))
+                    {
+                        rc = vboxHostChannelSend(pClient, u32Handle, pvData, cbData);
+                    }
+                }
+            }
+        } break;
+
+        case VBOX_HOST_CHANNEL_FN_RECV:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_FN_RECV\n"));
+
+            if (cParms != 4)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* handle */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_PTR     /* data */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_32BIT   /* sizeReceived */
+                     || paParms[3].type != VBOX_HGCM_SVC_PARM_32BIT   /* sizeRemaining */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                uint32_t u32Handle;
+                void *pvData;
+                uint32_t cbData;
+
+                rc = VBoxHGCMParmUInt32Get (&paParms[0], &u32Handle);
+
+                if (RT_SUCCESS (rc))
+                {
+                    rc = VBoxHGCMParmPtrGet (&paParms[1], &pvData, &cbData);
+
+                    if (RT_SUCCESS (rc))
+                    {
+                        uint32_t u32SizeReceived = 0;
+                        uint32_t u32SizeRemaining = 0;
+
+                        rc = vboxHostChannelRecv(pClient, u32Handle,
+                                                 pvData, cbData,
+                                                 &u32SizeReceived, &u32SizeRemaining);
+
+                        if (RT_SUCCESS(rc))
+                        {
+                            VBoxHGCMParmUInt32Set(&paParms[2], u32SizeReceived);
+                            VBoxHGCMParmUInt32Set(&paParms[3], u32SizeRemaining);
+                        }
+                    }
+                }
+            }
+        } break;
+
+        case VBOX_HOST_CHANNEL_FN_CONTROL:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_FN_CONTROL\n"));
+
+            if (cParms != 5)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* handle */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_32BIT   /* code */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_PTR     /* parm */
+                     || paParms[3].type != VBOX_HGCM_SVC_PARM_PTR     /* data */
+                     || paParms[4].type != VBOX_HGCM_SVC_PARM_32BIT   /* sizeDataReturned */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                uint32_t u32Handle;
+                uint32_t u32Code;
+                void *pvParm;
+                uint32_t cbParm;
+                void *pvData;
+                uint32_t cbData;
+
+                rc = VBoxHGCMParmUInt32Get (&paParms[0], &u32Handle);
+
+                if (RT_SUCCESS (rc))
+                {
+                    rc = VBoxHGCMParmUInt32Get (&paParms[1], &u32Code);
+
+                    if (RT_SUCCESS (rc))
+                    {
+                        rc = VBoxHGCMParmPtrGet (&paParms[2], &pvParm, &cbParm);
+
+                        if (RT_SUCCESS (rc))
+                        {
+                            rc = VBoxHGCMParmPtrGet (&paParms[3], &pvData, &cbData);
+
+                            if (RT_SUCCESS (rc))
+                            {
+                                uint32_t u32SizeDataReturned = 0;
+
+                                rc = vboxHostChannelControl(pClient, u32Handle, u32Code,
+                                                            pvParm, cbParm,
+                                                            pvData, cbData, &u32SizeDataReturned);
+                                if (RT_SUCCESS(rc))
+                                {
+                                    VBoxHGCMParmUInt32Set(&paParms[4], u32SizeDataReturned);
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        } break;
+
+        case VBOX_HOST_CHANNEL_FN_EVENT_WAIT:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_FN_EVENT_WAIT\n"));
+
+            if (cParms != 4)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* handle */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_32BIT   /* id */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_PTR     /* parm */
+                     || paParms[3].type != VBOX_HGCM_SVC_PARM_32BIT   /* sizeReturned */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                bool fEvent = false;
+
+                rc = vboxHostChannelEventWait(pClient, &fEvent, callHandle, paParms);
+
+                if (RT_SUCCESS(rc))
+                {
+                    if (!fEvent)
+                    {
+                        /* No event available at the time. Process asynchronously. */
+                        fAsynchronousProcessing = true;
+
+                        LogRel2(("svcCall: async.\n"));
+                    }
+                }
+            }
+        } break;
+
+        case VBOX_HOST_CHANNEL_FN_EVENT_CANCEL:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_FN_EVENT_CANCEL\n"));
+
+            if (cParms != 0)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                rc = vboxHostChannelEventCancel(pClient);
+            }
+        } break;
+
+        case VBOX_HOST_CHANNEL_FN_QUERY:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_FN_QUERY\n"));
+
+            if (cParms != 5)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_PTR     /* channel name */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_32BIT   /* code */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_PTR     /* parm */
+                     || paParms[3].type != VBOX_HGCM_SVC_PARM_PTR     /* data */
+                     || paParms[4].type != VBOX_HGCM_SVC_PARM_32BIT   /* sizeDataReturned */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                const char *pszName;
+                uint32_t cbName;
+                uint32_t u32Code = 0; /* Shut up msvc*/
+                void *pvParm = NULL;  /* Shut up msvc*/
+                uint32_t cbParm = 0;  /* Shut up msvc*/
+                void *pvData = NULL;  /* Shut up msvc*/
+                uint32_t cbData = 0;  /* Shut up msvc*/
+
+                rc = VBoxHGCMParmPtrGet(&paParms[0], (void **)&pszName, &cbName);
+                if (   RT_SUCCESS(rc)
+                    && pszName[cbName - 1] != '\0')
+                    rc = VERR_INVALID_PARAMETER;
+
+                if (RT_SUCCESS(rc))
+                    rc = VBoxHGCMParmUInt32Get(&paParms[1], &u32Code);
+                if (RT_SUCCESS (rc))
+                    rc = VBoxHGCMParmPtrGet(&paParms[2], &pvParm, &cbParm);
+                if (RT_SUCCESS (rc))
+                    rc = VBoxHGCMParmPtrGet(&paParms[3], &pvData, &cbData);
+                if (RT_SUCCESS (rc))
+                {
+                    uint32_t u32SizeDataReturned = 0;
+                    rc = vboxHostChannelQuery(pClient, pszName, u32Code,
+                                              pvParm, cbParm,
+                                              pvData, cbData, &u32SizeDataReturned);
+                    if (RT_SUCCESS(rc))
+                        VBoxHGCMParmUInt32Set(&paParms[4], u32SizeDataReturned);
+                }
+            }
+        } break;
+
+        default:
+        {
+            rc = VERR_NOT_IMPLEMENTED;
+        }
+    }
+
+    LogRelFlow(("svcCall: rc = %Rrc, async %d\n", rc, fAsynchronousProcessing));
+
+    if (!fAsynchronousProcessing)
+    {
+        g_pHelpers->pfnCallComplete(callHandle, rc);
+    }
+}
+
+static DECLCALLBACK(int) svcHostCall(void *pvService,
+                                     uint32_t u32Function,
+                                     uint32_t cParms,
+                                     VBOXHGCMSVCPARM paParms[])
+{
+    NOREF(pvService);
+
+    int rc = VINF_SUCCESS;
+
+    LogRel2(("svcHostCall: fn = %d, cParms = %d, pparms = %d\n",
+             u32Function, cParms, paParms));
+
+    switch (u32Function)
+    {
+        case VBOX_HOST_CHANNEL_HOST_FN_REGISTER:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_HOST_FN_REGISTER\n"));
+
+            if (cParms != 2)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_PTR /* name */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_PTR /* iface */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                void *pvName;
+                uint32_t cbName;
+                void *pvInterface;
+                uint32_t cbInterface;
+
+                rc = VBoxHGCMParmPtrGet(&paParms[0], &pvName, &cbName);
+
+                if (RT_SUCCESS(rc))
+                {
+                    rc = VBoxHGCMParmPtrGet(&paParms[1], &pvInterface, &cbInterface);
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        rc = vboxHostChannelRegister((const char *)pvName,
+                                                     (VBOXHOSTCHANNELINTERFACE *)pvInterface, cbInterface);
+                    }
+                }
+            }
+        } break;
+
+        case VBOX_HOST_CHANNEL_HOST_FN_UNREGISTER:
+        {
+            LogRel2(("svcCall: VBOX_HOST_CHANNEL_HOST_FN_UNREGISTER\n"));
+
+            if (cParms != 1)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_PTR /* name */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                void *pvName;
+                uint32_t cbName;
+
+                rc = VBoxHGCMParmPtrGet(&paParms[0], &pvName, &cbName);
+
+                if (RT_SUCCESS(rc))
+                {
+                    rc = vboxHostChannelUnregister((const char *)pvName);
+                }
+            }
+        } break;
+
+        default:
+            break;
+    }
+
+    LogRelFlow(("svcHostCall: rc = %Rrc\n", rc));
+    return rc;
+}
+
+#if 0
+/** If the client in the guest is waiting for a read operation to complete
+ * then complete it, otherwise return.  See the protocol description in the
+ * shared clipboard module description. */
+void vboxSvcClipboardCompleteReadData(VBOXHOSTCHCLIENT *pClient, int rc, uint32_t cbActual)
+{
+    VBOXHGCMCALLHANDLE callHandle = NULL;
+    VBOXHGCMSVCPARM *paParms = NULL;
+    bool fReadPending = false;
+    if (vboxSvcClipboardLock())  /* if not can we do anything useful? */
+    {
+        callHandle   = pClient->asyncRead.callHandle;
+        paParms      = pClient->asyncRead.paParms;
+        fReadPending = pClient->fReadPending;
+        pClient->fReadPending = false;
+        vboxSvcClipboardUnlock();
+    }
+    if (fReadPending)
+    {
+        VBoxHGCMParmUInt32Set (&paParms[2], cbActual);
+        g_pHelpers->pfnCallComplete (callHandle, rc);
+    }
+}
+
+/**
+ * SSM descriptor table for the VBOXHOSTCHCLIENT structure.
+ */
+static SSMFIELD const g_aClipboardClientDataFields[] =
+{
+    SSMFIELD_ENTRY(VBOXHOSTCHCLIENT, u32ClientID),  /* for validation purposes */
+    SSMFIELD_ENTRY(VBOXHOSTCHCLIENT, fMsgQuit),
+    SSMFIELD_ENTRY(VBOXHOSTCHCLIENT, fMsgReadData),
+    SSMFIELD_ENTRY(VBOXHOSTCHCLIENT, fMsgFormats),
+    SSMFIELD_ENTRY(VBOXHOSTCHCLIENT, u32RequestedFormat),
+    SSMFIELD_ENTRY_TERM()
+};
+
+static DECLCALLBACK(int) svcSaveState(void *pvService, uint32_t u32ClientID, void *pvClient, PSSMHANDLE pSSM)
+{
+    NOREF(pvService);
+
+    /* If there are any pending requests, they must be completed here. Since
+     * the service is single threaded, there could be only requests
+     * which the service itself has postponed.
+     *
+     * HGCM knows that the state is being saved and that the pfnComplete
+     * calls are just clean ups. These requests are saved by the VMMDev.
+     *
+     * When the state will be restored, these requests will be reissued
+     * by VMMDev. The service therefore must save state as if there were no
+     * pending request.
+     */
+    LogRel2 (("svcSaveState: u32ClientID = %d\n", u32ClientID));
+
+    VBOXHOSTCHCLIENT *pClient = (VBOXHOSTCHCLIENT *)pvClient;
+
+    /* This field used to be the length. We're using it as a version field
+       with the high bit set. */
+    SSMR3PutU32 (pSSM, UINT32_C (0x80000002));
+    int rc = SSMR3PutStructEx (pSSM, pClient, sizeof(*pClient), 0 /*fFlags*/, &g_aClipboardClientDataFields[0], NULL);
+    AssertRCReturn (rc, rc);
+
+    if (pClient->fAsync)
+    {
+        g_pHelpers->pfnCallComplete (pClient->async.callHandle, VINF_SUCCESS /* error code is not important here. */);
+        pClient->fAsync = false;
+    }
+
+    vboxSvcClipboardCompleteReadData (pClient, VINF_SUCCESS, 0);
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * This structure corresponds to the original layout of the
+ * VBOXHOSTCHCLIENT structure.  As the structure was saved as a whole
+ * when saving state, we need to remember it forever in order to preserve
+ * compatibility.
+ *
+ * (Starting with 3.1 this is no longer used.)
+ *
+ * @remarks Putting this outside svcLoadState to avoid visibility warning caused
+ *          by -Wattributes.
+ */
+typedef struct CLIPSAVEDSTATEDATA
+{
+    struct CLIPSAVEDSTATEDATA *pNext;
+    struct CLIPSAVEDSTATEDATA *pPrev;
+
+    VBOXCLIPBOARDCONTEXT *pCtx;
+
+    uint32_t u32ClientID;
+
+    bool fAsync: 1; /* Guest is waiting for a message. */
+
+    bool fMsgQuit: 1;
+    bool fMsgReadData: 1;
+    bool fMsgFormats: 1;
+
+    struct {
+        VBOXHGCMCALLHANDLE callHandle;
+        VBOXHGCMSVCPARM *paParms;
+    } async;
+
+    struct {
+         void *pv;
+         uint32_t cb;
+         uint32_t u32Format;
+    } data;
+
+    uint32_t u32AvailableFormats;
+    uint32_t u32RequestedFormat;
+
+} CLIPSAVEDSTATEDATA;
+
+static DECLCALLBACK(int) svcLoadState(void *, uint32_t u32ClientID, void *pvClient, PSSMHANDLE pSSM)
+{
+    LogRel2 (("svcLoadState: u32ClientID = %d\n", u32ClientID));
+
+    VBOXHOSTCHCLIENT *pClient = (VBOXHOSTCHCLIENT *)pvClient;
+
+    /* Existing client can not be in async state yet. */
+    Assert (!pClient->fAsync);
+
+    /* Save the client ID for data validation. */
+    /** @todo isn't this the same as u32ClientID? Playing safe for now... */
+    uint32_t const u32ClientIDOld = pClient->u32ClientID;
+
+    /* Restore the client data. */
+    uint32_t lenOrVer;
+    int rc = SSMR3GetU32 (pSSM, &lenOrVer);
+    AssertRCReturn (rc, rc);
+    if (lenOrVer == UINT32_C (0x80000002))
+    {
+        rc = SSMR3GetStructEx (pSSM, pClient, sizeof(*pClient), 0 /*fFlags*/, &g_aClipboardClientDataFields[0], NULL);
+        AssertRCReturn (rc, rc);
+    }
+    else if (lenOrVer == (SSMR3HandleHostBits (pSSM) == 64 ? 72 : 48))
+    {
+        /**
+         * SSM descriptor table for the CLIPSAVEDSTATEDATA structure.
+         */
+        static SSMFIELD const s_aClipSavedStateDataFields30[] =
+        {
+            SSMFIELD_ENTRY_IGN_HCPTR(       CLIPSAVEDSTATEDATA, pNext),
+            SSMFIELD_ENTRY_IGN_HCPTR(       CLIPSAVEDSTATEDATA, pPrev),
+            SSMFIELD_ENTRY_IGN_HCPTR(       CLIPSAVEDSTATEDATA, pCtx),
+            SSMFIELD_ENTRY(                 CLIPSAVEDSTATEDATA, u32ClientID),
+            SSMFIELD_ENTRY_CUSTOM(fMsgQuit+fMsgReadData+fMsgFormats, RT_OFFSETOF(CLIPSAVEDSTATEDATA, u32ClientID) + 4, 4),
+            SSMFIELD_ENTRY_IGN_HCPTR(       CLIPSAVEDSTATEDATA, async.callHandle),
+            SSMFIELD_ENTRY_IGN_HCPTR(       CLIPSAVEDSTATEDATA, async.paParms),
+            SSMFIELD_ENTRY_IGNORE(          CLIPSAVEDSTATEDATA, data.pv),
+            SSMFIELD_ENTRY_IGNORE(          CLIPSAVEDSTATEDATA, data.cb),
+            SSMFIELD_ENTRY_IGNORE(          CLIPSAVEDSTATEDATA, data.u32Format),
+            SSMFIELD_ENTRY_IGNORE(          CLIPSAVEDSTATEDATA, u32AvailableFormats),
+            SSMFIELD_ENTRY(                 CLIPSAVEDSTATEDATA, u32RequestedFormat),
+            SSMFIELD_ENTRY_TERM()
+        };
+
+        CLIPSAVEDSTATEDATA savedState;
+        RT_ZERO (savedState);
+        rc = SSMR3GetStructEx (pSSM, &savedState, sizeof(savedState), SSMSTRUCT_FLAGS_MEM_BAND_AID,
+                               &s_aClipSavedStateDataFields30[0], NULL);
+        AssertRCReturn (rc, rc);
+
+        pClient->fMsgQuit           = savedState.fMsgQuit;
+        pClient->fMsgReadData       = savedState.fMsgReadData;
+        pClient->fMsgFormats        = savedState.fMsgFormats;
+        pClient->u32RequestedFormat = savedState.u32RequestedFormat;
+    }
+    else
+    {
+        LogRel (("Client data size mismatch: got %#x\n", lenOrVer));
+        return VERR_SSM_DATA_UNIT_FORMAT_CHANGED;
+    }
+
+    /* Verify the client ID. */
+    if (pClient->u32ClientID != u32ClientIDOld)
+    {
+        LogRel (("Client ID mismatch: expected %d, got %d\n", u32ClientIDOld, pClient->u32ClientID));
+        pClient->u32ClientID = u32ClientIDOld;
+        return VERR_SSM_DATA_UNIT_FORMAT_CHANGED;
+    }
+
+    /* Actual host data are to be reported to guest (SYNC). */
+    vboxClipboardSync (pClient);
+
+    return VINF_SUCCESS;
+}
+#endif
+
+static int svcInit(void)
+{
+    int rc = RTCritSectInit(&g_critsect);
+
+    if (RT_SUCCESS (rc))
+    {
+        rc = vboxHostChannelInit();
+
+        /* Clean up on failure, because 'svnUnload' will not be called
+         * if the 'svcInit' returns an error.
+         */
+        if (RT_FAILURE(rc))
+        {
+            RTCritSectDelete(&g_critsect);
+        }
+    }
+
+    return rc;
+}
+
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad(VBOXHGCMSVCFNTABLE *pTable)
+{
+    int rc = VINF_SUCCESS;
+
+    LogRelFlowFunc(("pTable = %p\n", pTable));
+
+    if (!pTable)
+    {
+        rc = VERR_INVALID_PARAMETER;
+    }
+    else
+    {
+        LogRel2(("VBoxHGCMSvcLoad: pTable->cbSize = %d, pTable->u32Version = 0x%08X\n",
+                  pTable->cbSize, pTable->u32Version));
+
+        if (   pTable->cbSize != sizeof (VBOXHGCMSVCFNTABLE)
+            || pTable->u32Version != VBOX_HGCM_SVC_VERSION)
+        {
+            rc = VERR_INVALID_PARAMETER;
+        }
+        else
+        {
+            g_pHelpers = pTable->pHelpers;
+
+            pTable->cbClient = sizeof(VBOXHOSTCHCLIENT);
+
+            pTable->pfnUnload     = svcUnload;
+            pTable->pfnConnect    = svcConnect;
+            pTable->pfnDisconnect = svcDisconnect;
+            pTable->pfnCall       = svcCall;
+            pTable->pfnHostCall   = svcHostCall;
+            pTable->pfnSaveState  = NULL; // svcSaveState;
+            pTable->pfnLoadState  = NULL; // svcLoadState;
+            pTable->pfnRegisterExtension  = NULL;
+            pTable->pvService     = NULL;
+
+            /* Service specific initialization. */
+            rc = svcInit();
+        }
+    }
+
+    return rc;
+}
diff --git a/src/VBox/HostServices/HostChannel/VBoxHostChannelSvc.rc b/src/VBox/HostServices/HostChannel/VBoxHostChannelSvc.rc
new file mode 100644
index 00000000..aabf0874
--- /dev/null
+++ b/src/VBox/HostServices/HostChannel/VBoxHostChannelSvc.rc
@@ -0,0 +1,61 @@
+/* $Id: VBoxHostChannelSvc.rc $ */
+/** @file
+ * VBoxHostChannel - Resource file containing version info and icon.
+ */
+
+/*
+ * Copyright (C) 2015-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <windows.h>
+#include <VBox/version.h>
+
+LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION      VBOX_RC_FILE_VERSION
+  PRODUCTVERSION   VBOX_RC_FILE_VERSION
+  FILEFLAGSMASK    VS_FFI_FILEFLAGSMASK
+  FILEFLAGS        VBOX_RC_FILE_FLAGS
+  FILEOS           VBOX_RC_FILE_OS
+  FILETYPE         VBOX_RC_TYPE_DLL
+  FILESUBTYPE      VFT2_UNKNOWN
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904b0" // Lang=US English, CharSet=Unicode
+    BEGIN
+      VALUE "FileDescription",  "VirtualBox Host Channel Service\0"
+      VALUE "InternalName",     "VBoxHostChannel\0"
+      VALUE "OriginalFilename", "VBoxHostChannel.dll\0"
+      VALUE "CompanyName",      VBOX_RC_COMPANY_NAME
+      VALUE "FileVersion",      VBOX_RC_FILE_VERSION_STR
+      VALUE "LegalCopyright",   VBOX_RC_LEGAL_COPYRIGHT
+      VALUE "ProductName",      VBOX_RC_PRODUCT_NAME_STR
+      VALUE "ProductVersion",   VBOX_RC_PRODUCT_VERSION_STR
+      VBOX_RC_MORE_STRINGS
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x409, 1200
+  END
+END
diff --git a/src/VBox/HostServices/Makefile.kmk b/src/VBox/HostServices/Makefile.kmk
new file mode 100644
index 00000000..fccaf42b
--- /dev/null
+++ b/src/VBox/HostServices/Makefile.kmk
@@ -0,0 +1,56 @@
+# $Id: Makefile.kmk $
+## @file
+# Top-level makefile for the VBox Host Services.
+#
+
+#
+# Copyright (C) 2006-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+# Include sub-makefiles.
+include $(PATH_SUB_CURRENT)/auth/Makefile.kmk
+ifdef VBOX_WITH_SHARED_FOLDERS
+ include $(PATH_SUB_CURRENT)/SharedFolders/Makefile.kmk
+endif
+if1of ($(KBUILD_TARGET), win linux solaris darwin freebsd)
+ ifdef VBOX_WITH_SHARED_CLIPBOARD
+  include $(PATH_SUB_CURRENT)/SharedClipboard/Makefile.kmk
+ endif
+endif
+ifdef VBOX_WITH_GUEST_PROPS
+ include $(PATH_SUB_CURRENT)/GuestProperties/Makefile.kmk
+endif
+ifdef VBOX_WITH_GUEST_CONTROL
+ include $(PATH_SUB_CURRENT)/GuestControl/Makefile.kmk
+endif
+ifdef VBOX_WITH_DRAG_AND_DROP
+ include $(PATH_SUB_CURRENT)/DragAndDrop/Makefile.kmk
+endif
+ifdef VBOX_WITH_HOST_CHANNEL
+ include $(PATH_SUB_CURRENT)/HostChannel/Makefile.kmk
+endif
+include $(PATH_SUB_CURRENT)/testcase/Makefile.kmk
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/HostServices/SharedClipboard/Makefile.kmk b/src/VBox/HostServices/SharedClipboard/Makefile.kmk
new file mode 100644
index 00000000..e8c9b7b6
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/Makefile.kmk
@@ -0,0 +1,121 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Shared Clipboard Host Service.
+#
+
+#
+# Copyright (C) 2006-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+# Include sub-makefile(s).
+include $(PATH_SUB_CURRENT)/testcase/Makefile.kmk
+
+#
+# The Shared Clipboard service DLL.
+#
+DLLS += VBoxSharedClipboard
+VBoxSharedClipboard_TEMPLATE  = VBoxR3Dll
+VBoxSharedClipboard_DEFS      = \
+	VBOX_WITH_HGCM \
+	$(if $(VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS),VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS,)
+VBoxSharedClipboard_INCS.win  = \
+	$(VBOX_PATH_SDK)
+
+VBoxSharedClipboard_SOURCES = \
+	VBoxSharedClipboardSvc.cpp \
+	$(PATH_ROOT)/src/VBox/HostServices/common/message.cpp \
+	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp
+VBoxSharedClipboard_SOURCES.win = \
+	VBoxSharedClipboardSvc-win.cpp \
+	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-win.cpp \
+	VBoxSharedClipboardSvc.rc
+VBoxSharedClipboard_SOURCES.darwin = \
+	VBoxSharedClipboardSvc-darwin.cpp \
+	darwin-pasteboard.cpp
+ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+ if1of ($(KBUILD_TARGET), linux)
+  VBoxSharedClipboard_DEFS    += VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS_HTTP
+  VBoxSharedClipboard_SOURCES += \
+  	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-transfers-http.cpp
+ endif
+ VBoxSharedClipboard_DEFS    += VBOX_WITH_SHARED_CLIPBOARD_HOST
+ VBoxSharedClipboard_SOURCES += \
+ 	VBoxSharedClipboardSvc-transfers.cpp \
+ 	VBoxSharedClipboardSvc-utils.cpp \
+ 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/ClipboardPath.cpp \
+ 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-transfers.cpp
+ VBoxSharedClipboard_SOURCES.win += \
+ 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/ClipboardDataObjectImpl-win.cpp \
+ 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/ClipboardEnumFormatEtcImpl-win.cpp \
+ 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/ClipboardStreamImpl-win.cpp
+endif
+if1of ($(KBUILD_TARGET), linux solaris freebsd) ## @todo X11
+ ifndef VBOX_HEADLESS
+  VBoxSharedClipboard_SOURCES += \
+  	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-x11.cpp \
+  	VBoxSharedClipboardSvc-x11.cpp
+ else
+  VBoxSharedClipboard_SOURCES += \
+  	VBoxSharedClipboardSvc-x11-stubs.cpp
+ endif
+endif
+
+VBoxSharedClipboard_LIBS = \
+	$(LIB_RUNTIME)
+if1of ($(KBUILD_TARGET), linux solaris freebsd)
+ ifndef VBOX_HEADLESS
+  VBoxSharedClipboard_LIBPATH = \
+  	$(VBOX_LIBPATH_X11)
+  VBoxSharedClipboard_LIBS += \
+  	Xt \
+  	X11
+ endif
+endif
+
+VBoxSharedClipboard_LDFLAGS.darwin = \
+	-framework ApplicationServices -install_name $(VBOX_DYLD_EXECUTABLE_PATH)/VBoxSharedClipboard.dylib
+
+if 0 ## Disabled for now; needs to be adapted to the new protocol first.
+ if defined(VBOX_WITH_TESTCASES) && !defined(VBOX_ONLY_ADDITIONS) && !defined(VBOX_ONLY_SDK)
+  if1of ($(KBUILD_TARGET), freebsd linux netbsd openbsd solaris)
+   #
+   # Set this in LocalConfig.kmk if you are working on the X11 clipboard service
+   # to automatically run the unit test at build time.
+   #       OTHERS += $(tstClipboardX11-2_0_OUTDIR)/tstClipboardX11-2.run
+   PROGRAMS += tstClipboardX11-2
+   TESTING += $(tstClipboardX11-2_0_OUTDIR)/tstClipboardX11-2.run
+   tstClipboardX11-2_TEMPLATE = VBoxR3TstExe
+   tstClipboardX11-2_DEFS   = VBOX_WITH_HGCM TESTCASE
+   tstClipboardX11-2_SOURCES = VBoxSharedClipboardSvc-x11.cpp
+   tstClipboardX11-2_LIBS   = $(LIB_RUNTIME)
+   tstClipboardX11-2_CLEAN  = $(tstClipboardX11-2_0_OUTDIR)/tstClipboardX11-2.run
+
+   $$(tstClipboardX11-2_0_OUTDIR)/tstClipboardX11-2.run: $$(tstClipboardX11-2_1_STAGE_TARGET)
+	export VBOX_LOG_DEST=nofile; $(tstClipboardX11-2_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+  endif # 1of ($(KBUILD_TARGET),freebsd linux netbsd openbsd solaris)
+ endif
+endif
+
+include $(FILE_KBUILD_SUB_FOOTER)
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-darwin.cpp b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-darwin.cpp
new file mode 100644
index 00000000..23e6cd8d
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-darwin.cpp
@@ -0,0 +1,346 @@
+/* $Id: VBoxSharedClipboardSvc-darwin.cpp $ */
+/** @file
+ * Shared Clipboard Service - Mac OS X host.
+ */
+
+/*
+ * Copyright (C) 2008-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+
+#include <iprt/assert.h>
+#include <iprt/asm.h>
+#include <iprt/process.h>
+#include <iprt/rand.h>
+#include <iprt/string.h>
+#include <iprt/thread.h>
+
+#include "VBoxSharedClipboardSvc-internal.h"
+#include "darwin-pasteboard.h"
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+/** Global clipboard context information */
+typedef struct SHCLCONTEXT
+{
+    /** We have a separate thread to poll for new clipboard content. */
+    RTTHREAD                hThread;
+    /** Termination indicator.   */
+    bool volatile           fTerminate;
+    /** The reference to the current pasteboard */
+    PasteboardRef           hPasteboard;
+    /** Shared clipboard client. */
+    PSHCLCLIENT             pClient;
+    /** Random 64-bit number embedded into szGuestOwnershipFlavor. */
+    uint64_t                idGuestOwnership;
+    /** Ownership flavor CFStringRef returned by takePasteboardOwnership().
+     * This is the same a szGuestOwnershipFlavor only in core foundation terms. */
+    void                   *hStrOwnershipFlavor;
+    /** The guest ownership flavor (type) string. */
+    char                    szGuestOwnershipFlavor[64];
+} SHCLCONTEXT;
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+/** Only one client is supported. There seems to be no need for more clients. */
+static SHCLCONTEXT g_ctx;
+
+
+/**
+ * Checks if something is present on the clipboard and calls shclSvcReportMsg.
+ *
+ * @returns IPRT status code (ignored).
+ * @param   pCtx    The context.
+ *
+ * @note    Call must own lock.
+ */
+static int vboxClipboardChanged(SHCLCONTEXT *pCtx)
+{
+    if (pCtx->pClient == NULL)
+        return VINF_SUCCESS;
+
+    /* Retrieve the formats currently in the clipboard and supported by vbox */
+    uint32_t fFormats = 0;
+    bool     fChanged = false;
+    int rc = queryNewPasteboardFormats(pCtx->hPasteboard, pCtx->idGuestOwnership, pCtx->hStrOwnershipFlavor,
+                                       &fFormats, &fChanged);
+    if (   RT_SUCCESS(rc)
+        && fChanged
+        && ShClSvcIsBackendActive())
+        rc = ShClSvcHostReportFormats(pCtx->pClient, fFormats);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * @callback_method_impl{FNRTTHREAD, The poller thread.
+ *
+ * This thread will check for the arrival of new data on the clipboard.}
+ */
+static DECLCALLBACK(int) vboxClipboardThread(RTTHREAD ThreadSelf, void *pvUser)
+{
+    SHCLCONTEXT *pCtx = (SHCLCONTEXT *)pvUser;
+    AssertPtr(pCtx);
+    LogFlowFuncEnter();
+
+    while (!pCtx->fTerminate)
+    {
+        /* call this behind the lock because we don't know if the api is
+           thread safe and in any case we're calling several methods. */
+        ShClSvcLock();
+        vboxClipboardChanged(pCtx);
+        ShClSvcUnlock();
+
+        /* Sleep for 200 msecs before next poll */
+        RTThreadUserWait(ThreadSelf, 200);
+    }
+
+    LogFlowFuncLeaveRC(VINF_SUCCESS);
+    return VINF_SUCCESS;
+}
+
+
+int ShClBackendInit(PSHCLBACKEND pBackend, VBOXHGCMSVCFNTABLE *pTable)
+{
+    RT_NOREF(pBackend, pTable);
+    g_ctx.fTerminate = false;
+
+    int rc = initPasteboard(&g_ctx.hPasteboard);
+    AssertRCReturn(rc, rc);
+
+    rc = RTThreadCreate(&g_ctx.hThread, vboxClipboardThread, &g_ctx, 0,
+                        RTTHREADTYPE_IO, RTTHREADFLAGS_WAITABLE, "SHCLIP");
+    if (RT_FAILURE(rc))
+    {
+        g_ctx.hThread = NIL_RTTHREAD;
+        destroyPasteboard(&g_ctx.hPasteboard);
+    }
+
+    return rc;
+}
+
+void ShClBackendDestroy(PSHCLBACKEND pBackend)
+{
+    RT_NOREF(pBackend);
+
+    /*
+     * Signal the termination of the polling thread and wait for it to respond.
+     */
+    ASMAtomicWriteBool(&g_ctx.fTerminate, true);
+    int rc = RTThreadUserSignal(g_ctx.hThread);
+    AssertRC(rc);
+    rc = RTThreadWait(g_ctx.hThread, RT_INDEFINITE_WAIT, NULL);
+    AssertRC(rc);
+
+    /*
+     * Destroy the hPasteboard and uninitialize the global context record.
+     */
+    destroyPasteboard(&g_ctx.hPasteboard);
+    g_ctx.hThread = NIL_RTTHREAD;
+    g_ctx.pClient = NULL;
+}
+
+int ShClBackendConnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, bool fHeadless)
+{
+    RT_NOREF(pBackend, fHeadless);
+
+    if (g_ctx.pClient != NULL)
+    {
+        /* One client only. */
+        return VERR_NOT_SUPPORTED;
+    }
+
+    ShClSvcLock();
+
+    pClient->State.pCtx = &g_ctx;
+    pClient->State.pCtx->pClient = pClient;
+
+    ShClSvcUnlock();
+
+    return VINF_SUCCESS;
+}
+
+int ShClBackendSync(PSHCLBACKEND pBackend, PSHCLCLIENT pClient)
+{
+    RT_NOREF(pBackend);
+
+    /* Sync the host clipboard content with the client. */
+    ShClSvcLock();
+
+    int rc = vboxClipboardChanged(pClient->State.pCtx);
+
+    ShClSvcUnlock();
+
+    return rc;
+}
+
+int ShClBackendDisconnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient)
+{
+    RT_NOREF(pBackend);
+
+    ShClSvcLock();
+
+    pClient->State.pCtx->pClient = NULL;
+
+    ShClSvcUnlock();
+
+    return VINF_SUCCESS;
+}
+
+int ShClBackendReportFormats(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, SHCLFORMATS fFormats)
+{
+    RT_NOREF(pBackend);
+
+    LogFlowFunc(("fFormats=%02X\n", fFormats));
+
+    /** @todo r=bird: BUGBUG: The following is probably a mistake. */
+    /** @todo r=andy: BUGBUG: Has been there since forever; needs investigation first before removing. */
+    if (fFormats == VBOX_SHCL_FMT_NONE)
+    {
+        /* This is just an automatism, not a genuine announcement */
+        return VINF_SUCCESS;
+    }
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    if (fFormats & VBOX_SHCL_FMT_URI_LIST) /* No transfer support yet. */
+        return VINF_SUCCESS;
+#endif
+
+    SHCLCONTEXT *pCtx = pClient->State.pCtx;
+    ShClSvcLock();
+
+    /*
+     * Generate a unique flavor string for this format announcement.
+     */
+    uint64_t idFlavor = RTRandU64();
+    pCtx->idGuestOwnership = idFlavor;
+    RTStrPrintf(pCtx->szGuestOwnershipFlavor, sizeof(pCtx->szGuestOwnershipFlavor),
+                "org.virtualbox.sharedclipboard.%RTproc.%RX64", RTProcSelf(), idFlavor);
+
+    /*
+     * Empty the pasteboard and put our ownership indicator flavor there
+     * with the stringified formats as value.
+     */
+    char szValue[32];
+    RTStrPrintf(szValue, sizeof(szValue), "%#x", fFormats);
+
+    takePasteboardOwnership(pCtx->hPasteboard, pCtx->idGuestOwnership, pCtx->szGuestOwnershipFlavor, szValue,
+                            &pCtx->hStrOwnershipFlavor);
+
+    ShClSvcUnlock();
+
+    /*
+     * Now, request the data from the guest.
+     */
+    return ShClSvcGuestDataRequest(pClient, fFormats, NULL /* pidEvent */);
+}
+
+int ShClBackendReadData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx, SHCLFORMAT fFormat,
+                        void *pvData, uint32_t cbData, uint32_t *pcbActual)
+{
+    AssertPtrReturn(pClient,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pCmdCtx,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pvData,    VERR_INVALID_POINTER);
+    AssertPtrReturn(pcbActual, VERR_INVALID_POINTER);
+
+    RT_NOREF(pBackend, pCmdCtx);
+
+    ShClSvcLock();
+
+    /* Default to no data available. */
+    *pcbActual = 0;
+
+    int rc = readFromPasteboard(pClient->State.pCtx->hPasteboard, fFormat, pvData, cbData, pcbActual);
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Error reading host clipboard data from macOS, rc=%Rrc\n", rc));
+
+    ShClSvcUnlock();
+
+    return rc;
+}
+
+int ShClBackendWriteData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx, SHCLFORMAT fFormat, void *pvData, uint32_t cbData)
+{
+    RT_NOREF(pBackend, pCmdCtx);
+
+    LogFlowFuncEnter();
+
+    ShClSvcLock();
+
+    writeToPasteboard(pClient->State.pCtx->hPasteboard, pClient->State.pCtx->idGuestOwnership, pvData, cbData, fFormat);
+
+    ShClSvcUnlock();
+
+    LogFlowFuncLeaveRC(VINF_SUCCESS);
+    return VINF_SUCCESS;
+}
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+
+int ShClBackendTransferReadDir(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLDIRDATA pDirData)
+{
+    RT_NOREF(pBackend, pClient, pDirData);
+    return VERR_NOT_IMPLEMENTED;
+}
+
+int ShClBackendTransferWriteDir(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLDIRDATA pDirData)
+{
+    RT_NOREF(pBackend, pClient, pDirData);
+    return VERR_NOT_IMPLEMENTED;
+}
+
+int ShClBackendTransferReadFileHdr(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLFILEHDR pFileHdr)
+{
+    RT_NOREF(pBackend, pClient, pFileHdr);
+    return VERR_NOT_IMPLEMENTED;
+}
+
+int ShClBackendTransferWriteFileHdr(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLFILEHDR pFileHdr)
+{
+    RT_NOREF(pBackend, pClient, pFileHdr);
+    return VERR_NOT_IMPLEMENTED;
+}
+
+int ShClBackendTransferReadFileData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLFILEDATA pFileData)
+{
+    RT_NOREF(pBackend, pClient, pFileData);
+    return VERR_NOT_IMPLEMENTED;
+}
+
+int ShClBackendTransferWriteFileData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLFILEDATA pFileData)
+{
+    RT_NOREF(pBackend, pClient, pFileData);
+    return VERR_NOT_IMPLEMENTED;
+}
+
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-internal.h b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-internal.h
new file mode 100644
index 00000000..add48a0c
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-internal.h
@@ -0,0 +1,531 @@
+/* $Id: VBoxSharedClipboardSvc-internal.h $ */
+/** @file
+ * Shared Clipboard Service - Internal header.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_SharedClipboard_VBoxSharedClipboardSvc_internal_h
+#define VBOX_INCLUDED_SRC_SharedClipboard_VBoxSharedClipboardSvc_internal_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <algorithm>
+#include <list>
+#include <map>
+
+#include <iprt/cpp/list.h> /* For RTCList. */
+#include <iprt/list.h>
+#include <iprt/semaphore.h>
+
+#include <VBox/hgcmsvc.h>
+#include <VBox/log.h>
+
+#include <VBox/HostServices/Service.h>
+#include <VBox/GuestHost/SharedClipboard.h>
+#include <VBox/GuestHost/SharedClipboard-transfers.h>
+
+using namespace HGCM;
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+struct SHCLCLIENTSTATE;
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
+/**
+ * A queued message for the guest.
+ */
+typedef struct _SHCLCLIENTMSG
+{
+    /** The queue list entry. */
+    RTLISTNODE          ListEntry;
+    /** Stored message ID (VBOX_SHCL_HOST_MSG_XXX). */
+    uint32_t            idMsg;
+    /** Context ID. */
+    uint64_t            idCtx;
+    /** Number of stored parameters in aParms. */
+    uint32_t            cParms;
+    /** HGCM parameters. */
+    RT_FLEXIBLE_ARRAY_EXTENSION
+    VBOXHGCMSVCPARM     aParms[RT_FLEXIBLE_ARRAY];
+} SHCLCLIENTMSG;
+/** Pointer to a queue message for the guest.   */
+typedef SHCLCLIENTMSG *PSHCLCLIENTMSG;
+
+typedef struct SHCLCLIENTTRANSFERSTATE
+{
+    /** Directory of the transfer to start. */
+    SHCLTRANSFERDIR enmTransferDir;
+} SHCLCLIENTTRANSFERSTATE, *PSHCLCLIENTTRANSFERSTATE;
+
+/**
+ * Structure for holding a single POD (plain old data) transfer.
+ *
+ * This mostly is plain text, but also can be stuff like bitmap (BMP) or other binary data.
+ */
+typedef struct SHCLCLIENTPODSTATE
+{
+    /** POD transfer direction. */
+    SHCLTRANSFERDIR         enmDir;
+    /** Format of the data to be read / written. */
+    SHCLFORMAT              uFormat;
+    /** How much data (in bytes) to read/write for the current operation. */
+    uint64_t                cbToReadWriteTotal;
+    /** How much data (in bytes) already has been read/written for the current operation. */
+    uint64_t                cbReadWritten;
+    /** Timestamp (in ms) of Last read/write operation. */
+    uint64_t                tsLastReadWrittenMs;
+} SHCLCLIENTPODSTATE, *PSHCLCLIENTPODSTATE;
+
+/** @name SHCLCLIENTSTATE_FLAGS_XXX
+ * @note Part of saved state!
+ * @{ */
+/** No Shared Clipboard client flags defined. */
+#define SHCLCLIENTSTATE_FLAGS_NONE              0
+/** Client has a guest read operation active. Currently unused. */
+#define SHCLCLIENTSTATE_FLAGS_READ_ACTIVE       RT_BIT(0)
+/** Client has a guest write operation active. Currently unused. */
+#define SHCLCLIENTSTATE_FLAGS_WRITE_ACTIVE      RT_BIT(1)
+/** @} */
+
+/**
+ * Structure needed to support backwards compatbility for old(er) Guest Additions (< 6.1),
+ * which did not know the context ID concept then.
+ */
+typedef struct SHCLCLIENTLEGACYCID
+{
+    /** List node. */
+    RTLISTNODE Node;
+    /** The actual context ID. */
+    uint64_t   uCID;
+    /** Not used yet; useful to have it in the saved state though. */
+    uint32_t   enmType;
+    /** @todo Add an union here as soon as we utilize \a enmType. */
+    SHCLFORMAT uFormat;
+} SHCLCLIENTLEGACYCID;
+/** Pointer to a SHCLCLIENTLEGACYCID struct. */
+typedef SHCLCLIENTLEGACYCID *PSHCLCLIENTLEGACYCID;
+
+/**
+ * Structure for keeping legacy state, required for keeping backwards compatibility
+ * to old(er) Guest Additions.
+ */
+typedef struct SHCLCLIENTLEGACYSTATE
+{
+    /** List of context IDs (of type SHCLCLIENTLEGACYCID) for older Guest Additions which (< 6.1)
+     *  which did not know the concept of context IDs. */
+    RTLISTANCHOR lstCID;
+    /** Number of context IDs currently in \a lstCID. */
+    uint16_t     cCID;
+} SHCLCLIENTLEGACYSTATE;
+
+/**
+ * Structure for keeping generic client state data within the Shared Clipboard host service.
+ * This structure needs to be serializable by SSM (must be a POD type).
+ */
+typedef struct SHCLCLIENTSTATE
+{
+    struct SHCLCLIENTSTATE *pNext;
+    struct SHCLCLIENTSTATE *pPrev;
+
+    /** Backend-dependent opaque context structure.
+     *  This contains data only known to a certain backend implementation.
+     *  Optional and can be NULL. */
+    SHCLCONTEXT            *pCtx;
+    /** The client's HGCM ID. Not related to the session ID below! */
+    uint32_t                uClientID;
+    /** The client's session ID. */
+    SHCLSESSIONID           uSessionID;
+    /** Guest feature flags, VBOX_SHCL_GF_0_XXX. */
+    uint64_t                fGuestFeatures0;
+    /** Guest feature flags, VBOX_SHCL_GF_1_XXX. */
+    uint64_t                fGuestFeatures1;
+    /** Chunk size to use for data transfers. */
+    uint32_t                cbChunkSize;
+    /** Where the transfer sources its data from. */
+    SHCLSOURCE              enmSource;
+    /** Client state flags of type SHCLCLIENTSTATE_FLAGS_. */
+    uint32_t                fFlags;
+    /** POD (plain old data) state. */
+    SHCLCLIENTPODSTATE      POD;
+    /** The client's transfers state. */
+    SHCLCLIENTTRANSFERSTATE Transfers;
+} SHCLCLIENTSTATE, *PSHCLCLIENTSTATE;
+
+typedef struct _SHCLCLIENTCMDCTX
+{
+    uint64_t uContextID;
+} SHCLCLIENTCMDCTX, *PSHCLCLIENTCMDCTX;
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+/**
+ * Structure for keeping transfer-related data per HGCM client.
+ */
+typedef struct _SHCLIENTTRANSFERS
+{
+    /** Transfer context. */
+    SHCLTRANSFERCTX             Ctx;
+} SHCLIENTTRANSFERS, *PSHCLIENTTRANSFERS;
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
+/** Prototypes for the Shared Clipboard backend. */
+struct SHCLBACKEND;
+typedef SHCLBACKEND *PSHCLBACKEND;
+
+/**
+ * Structure for keeping data per (connected) HGCM client.
+ */
+typedef struct _SHCLCLIENT
+{
+    /** Pointer to associated backend, if any.
+     *  Might be NULL if not being used. */
+    PSHCLBACKEND                pBackend;
+    /** General client state data. */
+    SHCLCLIENTSTATE             State;
+    /** The critical section protecting the queue, event source and whatnot.   */
+    RTCRITSECT                  CritSect;
+    /** The client's message queue (SHCLCLIENTMSG). */
+    RTLISTANCHOR                MsgQueue;
+    /** Number of allocated messages (updated atomically, not under critsect). */
+    uint32_t volatile           cMsgAllocated;
+    /** Legacy cruft we have to keep to support old(er) Guest Additions. */
+    SHCLCLIENTLEGACYSTATE       Legacy;
+    /** The client's own event source.
+     *  Needed for events which are not bound to a specific transfer. */
+    SHCLEVENTSOURCE             EventSrc;
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    SHCLIENTTRANSFERS           Transfers;
+#endif
+    /** Structure for keeping the client's pending (deferred return) state.
+     *  A client is in a deferred state when it asks for the next HGCM message,
+     *  but the service can't provide it yet. That way a client will block (on the guest side, does not return)
+     *  until the service can complete the call. */
+    struct
+    {
+        /** The client's HGCM call handle. Needed for completing a deferred call. */
+        VBOXHGCMCALLHANDLE      hHandle;
+        /** Message type (function number) to use when completing the deferred call.
+         *  A non-0 value means the client is in pending mode. */
+        uint32_t                uType;
+        /** Parameter count to use when completing the deferred call. */
+        uint32_t                cParms;
+        /** Parameters to use when completing the deferred call. */
+        PVBOXHGCMSVCPARM        paParms;
+    } Pending;
+} SHCLCLIENT, *PSHCLCLIENT;
+
+/**
+ * Structure for keeping a single event source map entry.
+ * Currently empty.
+ */
+typedef struct _SHCLEVENTSOURCEMAPENTRY
+{
+} SHCLEVENTSOURCEMAPENTRY;
+
+/** Map holding information about connected HGCM clients. Key is the (unique) HGCM client ID.
+ *  The value is a weak pointer to PSHCLCLIENT, which is owned by HGCM. */
+typedef std::map<uint32_t, PSHCLCLIENT> ClipboardClientMap;
+
+/** Map holding information about event sources. Key is the (unique) event source ID. */
+typedef std::map<SHCLEVENTSOURCEID, SHCLEVENTSOURCEMAPENTRY> ClipboardEventSourceMap;
+
+/** Simple queue (list) which holds deferred (waiting) clients. */
+typedef std::list<uint32_t> ClipboardClientQueue;
+
+/**
+ * Structure for keeping the Shared Clipboard service extension state.
+ *
+ * A service extension is optional, and can be installed by a host component
+ * to communicate with the Shared Clipboard host service.
+ */
+typedef struct _SHCLEXTSTATE
+{
+    /** Pointer to the actual service extension handle. */
+    PFNHGCMSVCEXT  pfnExtension;
+    /** Opaque pointer to extension-provided data. Don't touch. */
+    void          *pvExtension;
+    /** The HGCM client ID currently assigned to this service extension.
+     *  At the moment only one HGCM client can be assigned per extension. */
+    uint32_t       uClientID;
+    /** Whether the host service is reading clipboard data currently. */
+    bool           fReadingData;
+    /** Whether the service extension has sent the clipboard formats while
+     *  the the host service is reading clipboard data from it. */
+    bool           fDelayedAnnouncement;
+    /** The actual clipboard formats announced while the host service
+     *  is reading clipboard data from the extension. */
+    uint32_t       fDelayedFormats;
+} SHCLEXTSTATE, *PSHCLEXTSTATE;
+
+extern SHCLEXTSTATE g_ExtState;
+
+int shClSvcSetSource(PSHCLCLIENT pClient, SHCLSOURCE enmSource);
+
+void shClSvcMsgQueueReset(PSHCLCLIENT pClient);
+PSHCLCLIENTMSG shClSvcMsgAlloc(PSHCLCLIENT pClient, uint32_t uMsg, uint32_t cParms);
+void shClSvcMsgFree(PSHCLCLIENT pClient, PSHCLCLIENTMSG pMsg);
+void shClSvcMsgAdd(PSHCLCLIENT pClient, PSHCLCLIENTMSG pMsg, bool fAppend);
+int shClSvcMsgAddAndWakeupClient(PSHCLCLIENT pClient, PSHCLCLIENTMSG pMsg);
+
+int shClSvcClientInit(PSHCLCLIENT pClient, uint32_t uClientID);
+void shClSvcClientDestroy(PSHCLCLIENT pClient);
+void shClSvcClientLock(PSHCLCLIENT pClient);
+void shClSvcClientUnlock(PSHCLCLIENT pClient);
+void shClSvcClientReset(PSHCLCLIENT pClient);
+
+int shClSvcClientStateInit(PSHCLCLIENTSTATE pClientState, uint32_t uClientID);
+int shClSvcClientStateDestroy(PSHCLCLIENTSTATE pClientState);
+void shclSvcClientStateReset(PSHCLCLIENTSTATE pClientState);
+
+int shClSvcClientWakeup(PSHCLCLIENT pClient);
+
+# ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+int shClSvcTransferModeSet(uint32_t fMode);
+int shClSvcTransferStart(PSHCLCLIENT pClient, SHCLTRANSFERDIR enmDir, SHCLSOURCE enmSource, PSHCLTRANSFER *ppTransfer);
+int shClSvcTransferStop(PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer);
+bool shClSvcTransferMsgIsAllowed(uint32_t uMode, uint32_t uMsg);
+void shClSvcClientTransfersReset(PSHCLCLIENT pClient);
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
+/** @name Service functions, accessible by the backends.
+ * Locking is between the (host) service thread and the platform-dependent (window) thread.
+ * @{
+ */
+int ShClSvcGuestDataRequest(PSHCLCLIENT pClient, SHCLFORMATS fFormats, PSHCLEVENT *ppEvent);
+int ShClSvcGuestDataSignal(PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx, SHCLFORMAT uFormat, void *pvData, uint32_t cbData);
+int ShClSvcHostReportFormats(PSHCLCLIENT pClient, SHCLFORMATS fFormats);
+PSHCLBACKEND ShClSvcGetBackend(void);
+uint32_t ShClSvcGetMode(void);
+bool ShClSvcGetHeadless(void);
+bool ShClSvcLock(void);
+void ShClSvcUnlock(void);
+
+/**
+ * Checks if the backend is active (@c true), or if VRDE is in control of
+ * the host side.
+ */
+DECLINLINE(bool) ShClSvcIsBackendActive(void)
+{
+    return g_ExtState.pfnExtension == NULL;
+}
+/** @} */
+
+/** @name Platform-dependent implementations for the Shared Clipboard host service ("backends"),
+ *        called *only* by the host service.
+ * @{
+ */
+/**
+ * Structure for keeping Shared Clipboard backend instance data.
+ */
+typedef struct SHCLBACKEND
+{
+    /** Callback table to use.
+     *  Some callbacks might be optional and therefore NULL -- see the table for more details. */
+    SHCLCALLBACKS Callbacks;
+} SHCLBACKEND;
+/** Pointer to a Shared Clipboard backend. */
+typedef SHCLBACKEND *PSHCLBACKEND;
+
+/**
+ * Called on initialization.
+ *
+ * @param   pBackend    Shared Clipboard backend to initialize.
+ * @param   pTable      The HGCM service call and parameter table.  Mainly for
+ *                      adjusting the limits.
+ */
+int ShClBackendInit(PSHCLBACKEND pBackend, VBOXHGCMSVCFNTABLE *pTable);
+
+/**
+ * Called on destruction.
+ *
+ * @param   pBackend    Shared Clipboard backend to destroy.
+ */
+void ShClBackendDestroy(PSHCLBACKEND pBackend);
+
+/**
+ * Called when a new HGCM client connects.
+ *
+ * @param   pBackend            Shared Clipboard backend to set callbacks for.
+ * @param   pCallbacks          Backend callbacks to use.
+ *                              When NULL is specified, the backend's default callbacks are being used.
+ */
+void ShClBackendSetCallbacks(PSHCLBACKEND pBackend, PSHCLCALLBACKS pCallbacks);
+
+/**
+ * Called when a new HGCM client connects.
+ *
+ * @returns VBox status code.
+ * @param   pBackend            Shared Clipboard backend to connect to.
+ * @param   pClient             Shared Clipboard client context.
+ * @param   fHeadless           Whether this is a headless connection or not.
+ */
+int ShClBackendConnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, bool fHeadless);
+
+/**
+ * Called when a HGCM client disconnects.
+ *
+ * @returns VBox status code.
+ * @param   pBackend            Shared Clipboard backend to disconnect from.
+ * @param   pClient             Shared Clipboard client context.
+ */
+int ShClBackendDisconnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient);
+
+/**
+ * Called when the guest reports available clipboard formats to the host OS.
+ *
+ * @returns VBox status code.
+ * @param   pBackend            Shared Clipboard backend to announce formats to.
+ * @param   pClient             Shared Clipboard client context.
+ * @param   fFormats            The announced formats from the guest,
+ *                              VBOX_SHCL_FMT_XXX.
+ */
+int ShClBackendReportFormats(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, SHCLFORMATS fFormats);
+
+/**
+ * Called when the guest wants to read host clipboard data.
+ *
+ * @returns VBox status code.
+ * @param   pBackend            Shared Clipboard backend to read data from.
+ * @param   pClient             Shared Clipboard client context.
+ * @param   pCmdCtx             Shared Clipboard command context.
+ * @param   uFormat             Clipboard format to read.
+ * @param   pvData              Where to return the read clipboard data.
+ * @param   cbData              Size (in bytes) of buffer where to return the clipboard data.
+ * @param   pcbActual           Where to return the amount of bytes read.
+ *
+ * @todo    Document: Can return VINF_HGCM_ASYNC_EXECUTE to defer returning read
+ *          data
+ */
+int ShClBackendReadData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx, SHCLFORMAT uFormat,
+                        void *pvData, uint32_t cbData, uint32_t *pcbActual);
+
+/**
+ * Called when the guest writes clipboard data to the host.
+ *
+ * @returns VBox status code.
+ * @param   pBackend            Shared Clipboard backend to write data to.
+ * @param   pClient             Shared Clipboard client context.
+ * @param   pCmdCtx             Shared Clipboard command context.
+ * @param   uFormat             Clipboard format to write.
+ * @param   pvData              Clipboard data to write.
+ * @param   cbData              Size (in bytes) of buffer clipboard data to write.
+ */
+int ShClBackendWriteData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx, SHCLFORMAT uFormat, void *pvData, uint32_t cbData);
+
+/**
+ * Called when synchronization of the clipboard contents of the host clipboard with the guest is needed.
+ *
+ * @returns VBox status code.
+ * @param   pBackend            Shared Clipboard backend to synchronize.
+ * @param   pClient             Shared Clipboard client context.
+ */
+int ShClBackendSync(PSHCLBACKEND pBackend, PSHCLCLIENT pClient);
+/** @} */
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+/** @name Host implementations for Shared Clipboard transfers.
+ * @{
+ */
+/**
+ * Called after a transfer got created.
+ *
+ * @returns VBox status code.
+ * @param   pBackend            Shared Clipboard backend to use.
+ * @param   pClient             Shared Clipboard client context.
+ * @param   pTransfer           Shared Clipboard transfer created.
+ */
+int ShClBackendTransferCreate(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer);
+/**
+ * Called before a transfer gets destroyed.
+ *
+ * @returns VBox status code.
+ * @param   pBackend            Shared Clipboard backend to use.
+ * @param   pClient             Shared Clipboard client context.
+ * @param   pTransfer           Shared Clipboard transfer to destroy.
+ */
+int ShClBackendTransferDestroy(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer);
+/**
+ * Called when getting (determining) the transfer roots on the host side.
+ *
+ * @returns VBox status code.
+ * @param   pBackend            Shared Clipboard backend to use.
+ * @param   pClient             Shared Clipboard client context.
+ * @param   pTransfer           Shared Clipboard transfer to get roots for.
+ */
+int ShClBackendTransferGetRoots(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer);
+/** @} */
+#endif
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+/** @name Internal Shared Clipboard transfer host service functions.
+ * @{
+ */
+int shClSvcTransferHandler(PSHCLCLIENT pClient, VBOXHGCMCALLHANDLE callHandle, uint32_t u32Function,
+                           uint32_t cParms, VBOXHGCMSVCPARM paParms[], uint64_t tsArrival);
+int shClSvcTransferHostHandler(uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[]);
+/** @} */
+
+/** @name Shared Clipboard transfer interface implementations for the host service.
+ * @{
+ */
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS_HTTP
+
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS_HTTP */
+
+int shClSvcTransferIfaceGetRoots(PSHCLTXPROVIDERCTX pCtx, PSHCLROOTLIST *ppRootList);
+
+int shClSvcTransferIfaceListOpen(PSHCLTXPROVIDERCTX pCtx, PSHCLLISTOPENPARMS pOpenParms, PSHCLLISTHANDLE phList);
+int shClSvcTransferIfaceListClose(PSHCLTXPROVIDERCTX pCtx, SHCLLISTHANDLE hList);
+int shClSvcTransferIfaceListHdrRead(PSHCLTXPROVIDERCTX pCtx, SHCLLISTHANDLE hList, PSHCLLISTHDR pListHdr);
+int shClSvcTransferIfaceListHdrWrite(PSHCLTXPROVIDERCTX pCtx, SHCLLISTHANDLE hList, PSHCLLISTHDR pListHdr);
+int shClSvcTransferIfaceListEntryRead(PSHCLTXPROVIDERCTX pCtx, SHCLLISTHANDLE hList, PSHCLLISTENTRY pListEntry);
+int shClSvcTransferIfaceListEntryWrite(PSHCLTXPROVIDERCTX pCtx, SHCLLISTHANDLE hList, PSHCLLISTENTRY pListEntry);
+
+int shClSvcTransferIfaceObjOpen(PSHCLTXPROVIDERCTX pCtx, PSHCLOBJOPENCREATEPARMS pCreateParms,
+                                PSHCLOBJHANDLE phObj);
+int shClSvcTransferIfaceObjClose(PSHCLTXPROVIDERCTX pCtx, SHCLOBJHANDLE hObj);
+int shClSvcTransferIfaceObjRead(PSHCLTXPROVIDERCTX pCtx, SHCLOBJHANDLE hObj,
+                                void *pvData, uint32_t cbData, uint32_t fFlags, uint32_t *pcbRead);
+int shClSvcTransferIfaceObjWrite(PSHCLTXPROVIDERCTX pCtx, SHCLOBJHANDLE hObj,
+                                 void *pvData, uint32_t cbData, uint32_t fFlags, uint32_t *pcbWritten);
+/** @} */
+
+/** @name Shared Clipboard transfer callbacks for the host service.
+ * @{
+ */
+DECLCALLBACK(void) VBoxSvcClipboardTransferPrepareCallback(PSHCLTXPROVIDERCTX pCtx);
+DECLCALLBACK(void) VBoxSvcClipboardDataHeaderCompleteCallback(PSHCLTXPROVIDERCTX pCtx);
+DECLCALLBACK(void) VBoxSvcClipboardDataCompleteCallback(PSHCLTXPROVIDERCTX pCtx);
+DECLCALLBACK(void) VBoxSvcClipboardTransferCompleteCallback(PSHCLTXPROVIDERCTX pCtx, int rc);
+DECLCALLBACK(void) VBoxSvcClipboardTransferCanceledCallback(PSHCLTXPROVIDERCTX pCtx);
+DECLCALLBACK(void) VBoxSvcClipboardTransferErrorCallback(PSHCLTXPROVIDERCTX pCtx, int rc);
+/** @} */
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
+/* Host unit testing interface */
+#ifdef UNIT_TEST
+uint32_t TestClipSvcGetMode(void);
+#endif
+
+#endif /* !VBOX_INCLUDED_SRC_SharedClipboard_VBoxSharedClipboardSvc_internal_h */
+
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-transfers.cpp b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-transfers.cpp
new file mode 100644
index 00000000..3f36f170
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-transfers.cpp
@@ -0,0 +1,2067 @@
+/* $Id: VBoxSharedClipboardSvc-transfers.cpp $ */
+/** @file
+ * Shared Clipboard Service - Internal code for transfer (list) handling.
+ */
+
+/*
+ * Copyright (C) 2019-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/log.h>
+
+#include <VBox/err.h>
+
+#include <VBox/GuestHost/clipboard-helper.h>
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#include <VBox/HostServices/VBoxClipboardExt.h>
+
+#include <VBox/AssertGuest.h>
+#include <iprt/dir.h>
+#include <iprt/file.h>
+#include <iprt/path.h>
+
+#include "VBoxSharedClipboardSvc-internal.h"
+#include "VBoxSharedClipboardSvc-transfers.h"
+
+
+/*********************************************************************************************************************************
+*   Externals                                                                                                                    *
+*********************************************************************************************************************************/
+extern uint32_t             g_fTransferMode;
+extern SHCLEXTSTATE         g_ExtState;
+extern PVBOXHGCMSVCHELPERS  g_pHelpers;
+extern ClipboardClientMap   g_mapClients;
+extern ClipboardClientQueue g_listClientsDeferred;
+
+
+/*********************************************************************************************************************************
+*   Prototypes                                                                                                                   *
+*********************************************************************************************************************************/
+static int shClSvcTransferSetListOpen(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                      uint64_t idCtx, PSHCLLISTOPENPARMS pOpenParms);
+static int shClSvcTransferSetListClose(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                       uint64_t idCtx, SHCLLISTHANDLE hList);
+
+
+/*********************************************************************************************************************************
+*   Provider implementation                                                                                                      *
+*********************************************************************************************************************************/
+
+/**
+ * Resets all transfers of a Shared Clipboard client.
+ *
+ * @param   pClient             Client to reset transfers for.
+ */
+void shClSvcClientTransfersReset(PSHCLCLIENT pClient)
+{
+    if (!pClient)
+        return;
+
+    LogFlowFuncEnter();
+
+    /* Make sure to let the backend know that all transfers are getting destroyed. */
+    uint32_t      uIdx = 0;
+    PSHCLTRANSFER pTransfer;
+    while ((pTransfer = ShClTransferCtxGetTransferByIndex(&pClient->Transfers.Ctx, uIdx++)))
+        ShClBackendTransferDestroy(pClient->pBackend, pClient, pTransfer);
+
+    ShClTransferCtxDestroy(&pClient->Transfers.Ctx);
+}
+
+
+/*********************************************************************************************************************************
+*   Provider interface implementation                                                                                            *
+*********************************************************************************************************************************/
+
+DECLCALLBACK(int) shClSvcTransferIfaceGetRoots(PSHCLTXPROVIDERCTX pCtx, PSHCLROOTLIST *ppRootList)
+{
+    LogFlowFuncEnter();
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pCtx->pvUser;
+    AssertPtr(pClient);
+
+    int rc;
+
+    PSHCLCLIENTMSG pMsgHdr = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_ROOT_LIST_HDR_READ,
+                                             VBOX_SHCL_CPARMS_ROOT_LIST_HDR_READ_REQ);
+    if (pMsgHdr)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            HGCMSvcSetU64(&pMsgHdr->aParms[0], VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID,
+                                                                        pCtx->pTransfer->State.uID, pEvent->idEvent));
+            HGCMSvcSetU32(&pMsgHdr->aParms[1], 0 /* fRoots */);
+
+            shClSvcClientLock(pClient);
+
+            shClSvcMsgAdd(pClient, pMsgHdr, true /* fAppend */);
+            rc = shClSvcClientWakeup(pClient);
+
+            shClSvcClientUnlock(pClient);
+
+            if (RT_SUCCESS(rc))
+            {
+                PSHCLEVENTPAYLOAD pPayloadHdr;
+                rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayloadHdr);
+                if (RT_SUCCESS(rc))
+                {
+                    PSHCLROOTLISTHDR pSrcRootListHdr = (PSHCLROOTLISTHDR)pPayloadHdr->pvData;
+                    Assert(pPayloadHdr->cbData == sizeof(SHCLROOTLISTHDR));
+
+                    LogFlowFunc(("cRoots=%RU32, fRoots=0x%x\n", pSrcRootListHdr->cRoots, pSrcRootListHdr->fRoots));
+
+                    PSHCLROOTLIST pRootList = ShClTransferRootListAlloc();
+                    if (pRootList)
+                    {
+                        if (pSrcRootListHdr->cRoots)
+                        {
+                            pRootList->paEntries =
+                                (PSHCLROOTLISTENTRY)RTMemAllocZ(pSrcRootListHdr->cRoots * sizeof(SHCLROOTLISTENTRY));
+
+                            if (pRootList->paEntries)
+                            {
+                                for (uint32_t i = 0; i < pSrcRootListHdr->cRoots; i++)
+                                {
+                                    PSHCLCLIENTMSG pMsgEntry = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_ROOT_LIST_ENTRY_READ,
+                                                                               VBOX_SHCL_CPARMS_ROOT_LIST_ENTRY_READ_REQ);
+
+                                    PSHCLEVENT pEvRoot;
+                                    rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvRoot);
+                                    if (RT_SUCCESS(rc))
+                                    {
+                                        HGCMSvcSetU64(&pMsgEntry->aParms[0],
+                                                      VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uClientID,
+                                                                               pCtx->pTransfer->State.uID, pEvRoot->idEvent));
+                                        HGCMSvcSetU32(&pMsgEntry->aParms[1], 0 /* fRoots */);
+                                        HGCMSvcSetU32(&pMsgEntry->aParms[2], i /* uIndex */);
+
+                                        shClSvcClientLock(pClient);
+                                        shClSvcMsgAdd(pClient, pMsgEntry, true /* fAppend */);
+                                        shClSvcClientUnlock(pClient);
+
+                                        PSHCLEVENTPAYLOAD pPayloadEntry;
+                                        rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayloadEntry);
+                                        if (RT_FAILURE(rc))
+                                            break;
+
+                                        PSHCLROOTLISTENTRY pSrcRootListEntry = (PSHCLROOTLISTENTRY)pPayloadEntry->pvData;
+                                        Assert(pPayloadEntry->cbData == sizeof(SHCLROOTLISTENTRY));
+
+                                        rc = ShClTransferListEntryCopy(&pRootList->paEntries[i], pSrcRootListEntry);
+
+                                        ShClPayloadFree(pPayloadEntry);
+
+                                        ShClEventRelease(pEvRoot);
+                                        pEvRoot = NULL;
+                                    }
+                                    else
+                                        rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+
+                                    if (RT_FAILURE(rc))
+                                        break;
+                                }
+                            }
+                            else
+                                rc = VERR_NO_MEMORY;
+                        }
+
+                        if (RT_SUCCESS(rc))
+                        {
+                            pRootList->Hdr.cRoots = pSrcRootListHdr->cRoots;
+                            pRootList->Hdr.fRoots = 0; /** @todo Implement this. */
+
+                            *ppRootList = pRootList;
+                        }
+                        else
+                            ShClTransferRootListFree(pRootList);
+
+                        ShClPayloadFree(pPayloadHdr);
+                    }
+                    else
+                        rc = VERR_NO_MEMORY;
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+        else
+            rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeave();
+    return rc;
+}
+
+DECLCALLBACK(int) shClSvcTransferIfaceListOpen(PSHCLTXPROVIDERCTX pCtx,
+                                               PSHCLLISTOPENPARMS pOpenParms, PSHCLLISTHANDLE phList)
+{
+    LogFlowFuncEnter();
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pCtx->pvUser;
+    AssertPtr(pClient);
+
+    int rc;
+
+    PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_LIST_OPEN,
+                                          VBOX_SHCL_CPARMS_LIST_OPEN);
+    if (pMsg)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            pMsg->idCtx = VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID, pCtx->pTransfer->State.uID,
+                                                   pEvent->idEvent);
+
+            rc = shClSvcTransferSetListOpen(pMsg->cParms, pMsg->aParms, pMsg->idCtx, pOpenParms);
+            if (RT_SUCCESS(rc))
+            {
+                shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+
+                rc = shClSvcClientWakeup(pClient);
+                if (RT_SUCCESS(rc))
+                {
+                    PSHCLEVENTPAYLOAD pPayload;
+                    rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayload);
+                    if (RT_SUCCESS(rc))
+                    {
+                        Assert(pPayload->cbData == sizeof(SHCLREPLY));
+
+                        PSHCLREPLY pReply = (PSHCLREPLY)pPayload->pvData;
+                        AssertPtr(pReply);
+
+                        Assert(pReply->uType == VBOX_SHCL_REPLYMSGTYPE_LIST_OPEN);
+
+                        LogFlowFunc(("hList=%RU64\n", pReply->u.ListOpen.uHandle));
+
+                        *phList = pReply->u.ListOpen.uHandle;
+
+                        ShClPayloadFree(pPayload);
+                    }
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+        else
+            rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+DECLCALLBACK(int) shClSvcTransferIfaceListClose(PSHCLTXPROVIDERCTX pCtx, SHCLLISTHANDLE hList)
+{
+    LogFlowFuncEnter();
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pCtx->pvUser;
+    AssertPtr(pClient);
+
+    int rc;
+
+    PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_LIST_CLOSE,
+                                          VBOX_SHCL_CPARMS_LIST_CLOSE);
+    if (pMsg)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            pMsg->idCtx = VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID, pCtx->pTransfer->State.uID,
+                                                   pEvent->idEvent);
+
+            rc = shClSvcTransferSetListClose(pMsg->cParms, pMsg->aParms, pMsg->idCtx, hList);
+            if (RT_SUCCESS(rc))
+            {
+                shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+
+                rc = shClSvcClientWakeup(pClient);
+                if (RT_SUCCESS(rc))
+                {
+                    PSHCLEVENTPAYLOAD pPayload;
+                    rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayload);
+                    if (RT_SUCCESS(rc))
+                        ShClPayloadFree(pPayload);
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+        else
+            rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+DECLCALLBACK(int) shClSvcTransferIfaceListHdrRead(PSHCLTXPROVIDERCTX pCtx,
+                                                  SHCLLISTHANDLE hList, PSHCLLISTHDR pListHdr)
+{
+    LogFlowFuncEnter();
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pCtx->pvUser;
+    AssertPtr(pClient);
+
+    int rc;
+
+    PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_LIST_HDR_READ,
+                                          VBOX_SHCL_CPARMS_LIST_HDR_READ_REQ);
+    if (pMsg)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            HGCMSvcSetU64(&pMsg->aParms[0], VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID,
+                                                                     pCtx->pTransfer->State.uID, pEvent->idEvent));
+            HGCMSvcSetU64(&pMsg->aParms[1], hList);
+            HGCMSvcSetU32(&pMsg->aParms[2], 0 /* fFlags */);
+
+            shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+
+            rc = shClSvcClientWakeup(pClient);
+            if (RT_SUCCESS(rc))
+            {
+                PSHCLEVENTPAYLOAD pPayload;
+                rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayload);
+                if (RT_SUCCESS(rc))
+                {
+                    Assert(pPayload->cbData == sizeof(SHCLLISTHDR));
+
+                    *pListHdr = *(PSHCLLISTHDR)pPayload->pvData;
+
+                    ShClPayloadFree(pPayload);
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+        else
+            rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+DECLCALLBACK(int) shClSvcTransferIfaceListHdrWrite(PSHCLTXPROVIDERCTX pCtx,
+                                                   SHCLLISTHANDLE hList, PSHCLLISTHDR pListHdr)
+{
+    RT_NOREF(pCtx, hList, pListHdr);
+
+    LogFlowFuncEnter();
+
+    return VERR_NOT_IMPLEMENTED;
+}
+
+DECLCALLBACK(int) shClSvcTransferIfaceListEntryRead(PSHCLTXPROVIDERCTX pCtx,
+                                                    SHCLLISTHANDLE hList, PSHCLLISTENTRY pListEntry)
+{
+    LogFlowFuncEnter();
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pCtx->pvUser;
+    AssertPtr(pClient);
+
+    int rc;
+
+    PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_LIST_ENTRY_READ,
+                                          VBOX_SHCL_CPARMS_LIST_ENTRY_READ);
+    if (pMsg)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            HGCMSvcSetU64(&pMsg->aParms[0], VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID,
+                                                                     pCtx->pTransfer->State.uID, pEvent->idEvent));
+            HGCMSvcSetU64(&pMsg->aParms[1], hList);
+            HGCMSvcSetU32(&pMsg->aParms[2], 0 /* fInfo */);
+
+            shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+
+            rc = shClSvcClientWakeup(pClient);
+            if (RT_SUCCESS(rc))
+            {
+                PSHCLEVENTPAYLOAD pPayload;
+                rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayload);
+                if (RT_SUCCESS(rc))
+                {
+                    Assert(pPayload->cbData == sizeof(SHCLLISTENTRY));
+
+                    rc = ShClTransferListEntryCopy(pListEntry, (PSHCLLISTENTRY)pPayload->pvData);
+
+                    ShClPayloadFree(pPayload);
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+        else
+            rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+DECLCALLBACK(int) shClSvcTransferIfaceListEntryWrite(PSHCLTXPROVIDERCTX pCtx,
+                                                     SHCLLISTHANDLE hList, PSHCLLISTENTRY pListEntry)
+{
+    RT_NOREF(pCtx, hList, pListEntry);
+
+    LogFlowFuncEnter();
+
+    return VERR_NOT_IMPLEMENTED;
+}
+
+int shClSvcTransferIfaceObjOpen(PSHCLTXPROVIDERCTX pCtx, PSHCLOBJOPENCREATEPARMS pCreateParms,
+                                PSHCLOBJHANDLE phObj)
+{
+    LogFlowFuncEnter();
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pCtx->pvUser;
+    AssertPtr(pClient);
+
+    int rc;
+
+    PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_OBJ_OPEN,
+                                          VBOX_SHCL_CPARMS_OBJ_OPEN);
+    if (pMsg)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            LogFlowFunc(("pszPath=%s, fCreate=0x%x\n", pCreateParms->pszPath, pCreateParms->fCreate));
+
+            const uint32_t cbPath = (uint32_t)strlen(pCreateParms->pszPath) + 1; /* Include terminating zero */
+
+            HGCMSvcSetU64(&pMsg->aParms[0], VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID,
+                                                                     pCtx->pTransfer->State.uID, pEvent->idEvent));
+            HGCMSvcSetU64(&pMsg->aParms[1], 0); /* uHandle */
+            HGCMSvcSetU32(&pMsg->aParms[2], cbPath);
+            HGCMSvcSetPv (&pMsg->aParms[3], pCreateParms->pszPath, cbPath);
+            HGCMSvcSetU32(&pMsg->aParms[4], pCreateParms->fCreate);
+
+            shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+
+            rc = shClSvcClientWakeup(pClient);
+            if (RT_SUCCESS(rc))
+            {
+                PSHCLEVENTPAYLOAD pPayload;
+                rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayload);
+                if (RT_SUCCESS(rc))
+                {
+                    Assert(pPayload->cbData == sizeof(SHCLREPLY));
+
+                    PSHCLREPLY pReply = (PSHCLREPLY)pPayload->pvData;
+                    AssertPtr(pReply);
+
+                    Assert(pReply->uType == VBOX_SHCL_REPLYMSGTYPE_OBJ_OPEN);
+
+                    LogFlowFunc(("hObj=%RU64\n", pReply->u.ObjOpen.uHandle));
+
+                    *phObj = pReply->u.ObjOpen.uHandle;
+
+                    ShClPayloadFree(pPayload);
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+        else
+            rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int shClSvcTransferIfaceObjClose(PSHCLTXPROVIDERCTX pCtx, SHCLOBJHANDLE hObj)
+{
+    LogFlowFuncEnter();
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pCtx->pvUser;
+    AssertPtr(pClient);
+
+    int rc;
+
+    PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_OBJ_CLOSE,
+                                          VBOX_SHCL_CPARMS_OBJ_CLOSE);
+    if (pMsg)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            HGCMSvcSetU64(&pMsg->aParms[0], VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID,
+                                                                     pCtx->pTransfer->State.uID, pEvent->idEvent));
+            HGCMSvcSetU64(&pMsg->aParms[1], hObj);
+
+            shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+
+            rc = shClSvcClientWakeup(pClient);
+            if (RT_SUCCESS(rc))
+            {
+                PSHCLEVENTPAYLOAD pPayload;
+                rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayload);
+                if (RT_SUCCESS(rc))
+                {
+                    Assert(pPayload->cbData == sizeof(SHCLREPLY));
+#ifdef VBOX_STRICT
+                    PSHCLREPLY pReply = (PSHCLREPLY)pPayload->pvData;
+                    AssertPtr(pReply);
+
+                    Assert(pReply->uType == VBOX_SHCL_REPLYMSGTYPE_OBJ_CLOSE);
+
+                    LogFlowFunc(("hObj=%RU64\n", pReply->u.ObjClose.uHandle));
+#endif
+                    ShClPayloadFree(pPayload);
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+        else
+            rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int shClSvcTransferIfaceObjRead(PSHCLTXPROVIDERCTX pCtx, SHCLOBJHANDLE hObj,
+                                void *pvData, uint32_t cbData, uint32_t fFlags, uint32_t *pcbRead)
+{
+    LogFlowFuncEnter();
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pCtx->pvUser;
+    AssertPtr(pClient);
+
+    int rc;
+
+    PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_OBJ_READ,
+                                          VBOX_SHCL_CPARMS_OBJ_READ_REQ);
+    if (pMsg)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            HGCMSvcSetU64(&pMsg->aParms[0], VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID,
+                                                                     pCtx->pTransfer->State.uID, pEvent->idEvent));
+            HGCMSvcSetU64(&pMsg->aParms[1], hObj);
+            HGCMSvcSetU32(&pMsg->aParms[2], cbData);
+            HGCMSvcSetU32(&pMsg->aParms[3], fFlags);
+
+            shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+
+            rc = shClSvcClientWakeup(pClient);
+            if (RT_SUCCESS(rc))
+            {
+                PSHCLEVENTPAYLOAD pPayload;
+                rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayload);
+                if (RT_SUCCESS(rc))
+                {
+                    Assert(pPayload->cbData == sizeof(SHCLOBJDATACHUNK));
+
+                    PSHCLOBJDATACHUNK pDataChunk = (PSHCLOBJDATACHUNK)pPayload->pvData;
+                    AssertPtr(pDataChunk);
+
+                    const uint32_t cbRead = RT_MIN(cbData, pDataChunk->cbData);
+
+                    memcpy(pvData, pDataChunk->pvData, cbRead);
+
+                    if (pcbRead)
+                        *pcbRead = cbRead;
+
+                    ShClPayloadFree(pPayload);
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+        else
+            rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int shClSvcTransferIfaceObjWrite(PSHCLTXPROVIDERCTX pCtx, SHCLOBJHANDLE hObj,
+                                 void *pvData, uint32_t cbData, uint32_t fFlags, uint32_t *pcbWritten)
+{
+    LogFlowFuncEnter();
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pCtx->pvUser;
+    AssertPtr(pClient);
+
+    int rc;
+
+    PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_OBJ_WRITE,
+                                          VBOX_SHCL_CPARMS_OBJ_WRITE);
+    if (pMsg)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            HGCMSvcSetU64(&pMsg->aParms[0], VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID,
+                                                                     pCtx->pTransfer->State.uID, pEvent->idEvent));
+            HGCMSvcSetU64(&pMsg->aParms[1], hObj);
+            HGCMSvcSetU64(&pMsg->aParms[2], cbData);
+            HGCMSvcSetU64(&pMsg->aParms[3], fFlags);
+
+            shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+
+            rc = shClSvcClientWakeup(pClient);
+            if (RT_SUCCESS(rc))
+            {
+                PSHCLEVENTPAYLOAD pPayload;
+                rc = ShClEventWait(pEvent, pCtx->pTransfer->uTimeoutMs, &pPayload);
+                if (RT_SUCCESS(rc))
+                {
+                    const uint32_t cbRead = RT_MIN(cbData, pPayload->cbData);
+
+                    memcpy(pvData, pPayload->pvData, cbRead);
+
+                    if (pcbWritten)
+                        *pcbWritten = cbRead;
+
+                    ShClPayloadFree(pPayload);
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+        else
+            rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+
+/*********************************************************************************************************************************
+*   HGCM getters / setters                                                                                                       *
+*********************************************************************************************************************************/
+
+/**
+ * Returns whether a HGCM message is allowed in a certain service mode or not.
+ *
+ * @returns \c true if message is allowed, \c false if not.
+ * @param   uMode               Service mode to check allowance for.
+ * @param   uMsg                HGCM message to check allowance for.
+ */
+bool shClSvcTransferMsgIsAllowed(uint32_t uMode, uint32_t uMsg)
+{
+    const bool fHostToGuest =    uMode == VBOX_SHCL_MODE_HOST_TO_GUEST
+                              || uMode == VBOX_SHCL_MODE_BIDIRECTIONAL;
+
+    const bool fGuestToHost =    uMode == VBOX_SHCL_MODE_GUEST_TO_HOST
+                              || uMode == VBOX_SHCL_MODE_BIDIRECTIONAL;
+
+    bool fAllowed = false; /* If in doubt, don't allow. */
+
+    switch (uMsg)
+    {
+        case VBOX_SHCL_GUEST_FN_ROOT_LIST_HDR_WRITE:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_ROOT_LIST_ENTRY_WRITE:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_LIST_HDR_WRITE:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_LIST_ENTRY_WRITE:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_OBJ_WRITE:
+            fAllowed = fGuestToHost;
+            break;
+
+        case VBOX_SHCL_GUEST_FN_ROOT_LIST_HDR_READ:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_ROOT_LIST_ENTRY_READ:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_LIST_HDR_READ:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_LIST_ENTRY_READ:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_OBJ_READ:
+            fAllowed = fHostToGuest;
+            break;
+
+        case VBOX_SHCL_GUEST_FN_CONNECT:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_NEGOTIATE_CHUNK_SIZE:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_MSG_PEEK_WAIT:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_MSG_PEEK_NOWAIT:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_REPORT_FEATURES:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_QUERY_FEATURES:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_MSG_GET:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_REPLY:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_MSG_CANCEL:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_ERROR:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_LIST_OPEN:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_LIST_CLOSE:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_OBJ_OPEN:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_GUEST_FN_OBJ_CLOSE:
+            fAllowed = fHostToGuest || fGuestToHost;
+            break;
+
+        default:
+            break;
+    }
+
+    LogFlowFunc(("uMsg=%RU32 (%s), uMode=%RU32 -> fAllowed=%RTbool\n", uMsg, ShClGuestMsgToStr(uMsg), uMode, fAllowed));
+    return fAllowed;
+}
+
+/**
+ * Gets a transfer message reply from HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   pReply              Where to store the reply.
+ */
+static int shClSvcTransferGetReply(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                   PSHCLREPLY pReply)
+{
+    int rc;
+
+    if (cParms >= VBOX_SHCL_CPARMS_REPLY_MIN)
+    {
+        /* aParms[0] has the context ID. */
+        rc = HGCMSvcGetU32(&aParms[1], &pReply->uType);
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetU32(&aParms[2], &pReply->rc);
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetPv(&aParms[3], &pReply->pvPayload, &pReply->cbPayload);
+
+        if (RT_SUCCESS(rc))
+        {
+            rc = VERR_INVALID_PARAMETER; /* Play safe. */
+
+            const unsigned idxParm = VBOX_SHCL_CPARMS_REPLY_MIN;
+
+            switch (pReply->uType)
+            {
+                case VBOX_SHCL_REPLYMSGTYPE_TRANSFER_STATUS:
+                {
+                    if (cParms > idxParm)
+                        rc = HGCMSvcGetU32(&aParms[idxParm], &pReply->u.TransferStatus.uStatus);
+
+                    LogFlowFunc(("uTransferStatus=%RU32\n", pReply->u.TransferStatus.uStatus));
+                    break;
+                }
+
+                case VBOX_SHCL_REPLYMSGTYPE_LIST_OPEN:
+                {
+                    if (cParms > idxParm)
+                        rc = HGCMSvcGetU64(&aParms[idxParm], &pReply->u.ListOpen.uHandle);
+
+                    LogFlowFunc(("hListOpen=%RU64\n", pReply->u.ListOpen.uHandle));
+                    break;
+                }
+
+                case VBOX_SHCL_REPLYMSGTYPE_LIST_CLOSE:
+                {
+                    if (cParms > idxParm)
+                        rc = HGCMSvcGetU64(&aParms[idxParm], &pReply->u.ListClose.uHandle);
+
+                    LogFlowFunc(("hListClose=%RU64\n", pReply->u.ListClose.uHandle));
+                    break;
+                }
+
+                case VBOX_SHCL_REPLYMSGTYPE_OBJ_OPEN:
+                {
+                    if (cParms > idxParm)
+                        rc = HGCMSvcGetU64(&aParms[idxParm], &pReply->u.ObjOpen.uHandle);
+
+                    LogFlowFunc(("hObjOpen=%RU64\n", pReply->u.ObjOpen.uHandle));
+                    break;
+                }
+
+                case VBOX_SHCL_REPLYMSGTYPE_OBJ_CLOSE:
+                {
+                    if (cParms > idxParm)
+                        rc = HGCMSvcGetU64(&aParms[idxParm], &pReply->u.ObjClose.uHandle);
+
+                    LogFlowFunc(("hObjClose=%RU64\n", pReply->u.ObjClose.uHandle));
+                    break;
+                }
+
+                default:
+                    rc = VERR_NOT_SUPPORTED;
+                    break;
+            }
+        }
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Gets a transfer root list header from HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   pRootLstHdr         Where to store the transfer root list header on success.
+ */
+static int shClSvcTransferGetRootListHdr(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                         PSHCLROOTLISTHDR pRootLstHdr)
+{
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_ROOT_LIST_HDR_WRITE)
+    {
+        rc = HGCMSvcGetU32(&aParms[1], &pRootLstHdr->fRoots);
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetU32(&aParms[2], &pRootLstHdr->cRoots);
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Gets a transfer root list entry from HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   pListEntry          Where to store the root list entry.
+ */
+static int shClSvcTransferGetRootListEntry(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                           PSHCLROOTLISTENTRY pListEntry)
+{
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_ROOT_LIST_ENTRY_WRITE)
+    {
+        rc = HGCMSvcGetU32(&aParms[1], &pListEntry->fInfo);
+        /* Note: aParms[2] contains the entry index, currently being ignored. */
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetPv(&aParms[3], (void **)&pListEntry->pszName, &pListEntry->cbName);
+        if (RT_SUCCESS(rc))
+        {
+            uint32_t cbInfo;
+            rc = HGCMSvcGetU32(&aParms[4], &cbInfo);
+            if (RT_SUCCESS(rc))
+            {
+                rc = HGCMSvcGetPv(&aParms[5], &pListEntry->pvInfo, &pListEntry->cbInfo);
+                AssertReturn(cbInfo == pListEntry->cbInfo, VERR_INVALID_PARAMETER);
+            }
+        }
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Gets a transfer list open request from HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   pOpenParms          Where to store the open parameters of the request.
+ */
+static int shClSvcTransferGetListOpen(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                      PSHCLLISTOPENPARMS pOpenParms)
+{
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_LIST_OPEN)
+    {
+        rc = HGCMSvcGetU32(&aParms[1], &pOpenParms->fList);
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetStr(&aParms[2], &pOpenParms->pszFilter, &pOpenParms->cbFilter);
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetStr(&aParms[3], &pOpenParms->pszPath, &pOpenParms->cbPath);
+
+        /** @todo Some more validation. */
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Sets a transfer list open request to HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   idCtx               Context ID to use.
+ * @param   pOpenParms          List open parameters to set.
+ */
+static int shClSvcTransferSetListOpen(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                      uint64_t idCtx, PSHCLLISTOPENPARMS pOpenParms)
+{
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_LIST_OPEN)
+    {
+        HGCMSvcSetU64(&aParms[0], idCtx);
+        HGCMSvcSetU32(&aParms[1], pOpenParms->fList);
+        HGCMSvcSetPv (&aParms[2], pOpenParms->pszFilter, pOpenParms->cbFilter);
+        HGCMSvcSetPv (&aParms[3], pOpenParms->pszPath, pOpenParms->cbPath);
+        HGCMSvcSetU64(&aParms[4], 0); /* OUT: uHandle */
+
+        rc = VINF_SUCCESS;
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Sets a transfer list close request to HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   idCtx               Context ID to use.
+ * @param   hList               Handle of list to close.
+ */
+static int shClSvcTransferSetListClose(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                       uint64_t idCtx, SHCLLISTHANDLE hList)
+{
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_LIST_CLOSE)
+    {
+        HGCMSvcSetU64(&aParms[0], idCtx);
+        HGCMSvcSetU64(&aParms[1], hList);
+
+        rc = VINF_SUCCESS;
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Gets a transfer list header from HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   phList              Where to store the list handle.
+ * @param   pListHdr            Where to store the list header.
+ */
+static int shClSvcTransferGetListHdr(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                     PSHCLLISTHANDLE phList, PSHCLLISTHDR pListHdr)
+{
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_LIST_HDR)
+    {
+        rc = HGCMSvcGetU64(&aParms[1], phList);
+        /* Note: Flags (aParms[2]) not used here. */
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetU32(&aParms[3], &pListHdr->fFeatures);
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetU64(&aParms[4], &pListHdr->cTotalObjects);
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetU64(&aParms[5], &pListHdr->cbTotalSize);
+
+        if (RT_SUCCESS(rc))
+        {
+            /** @todo Validate pvMetaFmt + cbMetaFmt. */
+            /** @todo Validate header checksum. */
+        }
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Sets a transfer list header to HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   pListHdr            Pointer to list header to set.
+ */
+static int shClSvcTransferSetListHdr(uint32_t cParms, VBOXHGCMSVCPARM aParms[], PSHCLLISTHDR pListHdr)
+{
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_LIST_HDR)
+    {
+        /** @todo Set pvMetaFmt + cbMetaFmt. */
+        /** @todo Calculate header checksum. */
+
+        HGCMSvcSetU32(&aParms[3], pListHdr->fFeatures);
+        HGCMSvcSetU64(&aParms[4], pListHdr->cTotalObjects);
+        HGCMSvcSetU64(&aParms[5], pListHdr->cbTotalSize);
+
+        rc = VINF_SUCCESS;
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Gets a transfer list entry from HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   phList              Where to store the list handle.
+ * @param   pListEntry          Where to store the list entry.
+ */
+static int shClSvcTransferGetListEntry(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                       PSHCLLISTHANDLE phList, PSHCLLISTENTRY pListEntry)
+{
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_LIST_ENTRY)
+    {
+        rc = HGCMSvcGetU64(&aParms[1], phList);
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetU32(&aParms[2], &pListEntry->fInfo);
+        if (RT_SUCCESS(rc))
+            rc = HGCMSvcGetPv(&aParms[3], (void **)&pListEntry->pszName, &pListEntry->cbName);
+        if (RT_SUCCESS(rc))
+        {
+            uint32_t cbInfo;
+            rc = HGCMSvcGetU32(&aParms[4], &cbInfo);
+            if (RT_SUCCESS(rc))
+            {
+                rc = HGCMSvcGetPv(&aParms[5], &pListEntry->pvInfo, &pListEntry->cbInfo);
+                AssertReturn(cbInfo == pListEntry->cbInfo, VERR_INVALID_PARAMETER);
+            }
+        }
+
+        if (RT_SUCCESS(rc))
+        {
+            if (!ShClTransferListEntryIsValid(pListEntry))
+                rc = VERR_INVALID_PARAMETER;
+        }
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Sets a Shared Clipboard list entry to HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   pListEntry          Pointer list entry to set.
+ */
+static int shClSvcTransferSetListEntry(uint32_t cParms, VBOXHGCMSVCPARM aParms[],
+                                       PSHCLLISTENTRY pListEntry)
+{
+    int rc;
+
+    /* Sanity. */
+    AssertReturn(ShClTransferListEntryIsValid(pListEntry), VERR_INVALID_PARAMETER);
+
+    if (cParms == VBOX_SHCL_CPARMS_LIST_ENTRY)
+    {
+        HGCMSvcSetPv (&aParms[3], pListEntry->pszName, pListEntry->cbName);
+        HGCMSvcSetU32(&aParms[4], pListEntry->cbInfo);
+        HGCMSvcSetPv (&aParms[5], pListEntry->pvInfo, pListEntry->cbInfo);
+
+        rc = VINF_SUCCESS;
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Gets a transfer object data chunk from HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a aParms.
+ * @param   aParms              Array of HGCM parameters.
+ * @param   pDataChunk          Where to store the object data chunk data.
+ */
+static int shClSvcTransferGetObjDataChunk(uint32_t cParms, VBOXHGCMSVCPARM aParms[], PSHCLOBJDATACHUNK pDataChunk)
+{
+    AssertPtrReturn(aParms,    VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pDataChunk, VERR_INVALID_PARAMETER);
+
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_OBJ_WRITE)
+    {
+        rc = HGCMSvcGetU64(&aParms[1], &pDataChunk->uHandle);
+        if (RT_SUCCESS(rc))
+        {
+            uint32_t cbData;
+            rc = HGCMSvcGetU32(&aParms[2], &cbData);
+            if (RT_SUCCESS(rc))
+            {
+                rc = HGCMSvcGetPv(&aParms[3], &pDataChunk->pvData, &pDataChunk->cbData);
+                AssertReturn(cbData == pDataChunk->cbData, VERR_INVALID_PARAMETER);
+
+                /** @todo Implement checksum handling. */
+            }
+        }
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Handles a guest reply (VBOX_SHCL_GUEST_FN_REPLY) message.
+ *
+ * @returns VBox status code.
+ * @param   pClient             Pointer to associated client.
+ * @param   pTransfer           Pointer to transfer to handle guest reply for.
+ * @param   cParms              Number of function parameters supplied.
+ * @param   aParms              Array function parameters supplied.
+ */
+static int shClSvcTransferHandleReply(PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer,
+                                      uint32_t cParms, VBOXHGCMSVCPARM aParms[])
+{
+    RT_NOREF(pClient, pTransfer);
+
+    int rc;
+
+    uint32_t   cbReply = sizeof(SHCLREPLY);
+    PSHCLREPLY pReply  = (PSHCLREPLY)RTMemAlloc(cbReply);
+    if (pReply)
+    {
+        rc = shClSvcTransferGetReply(cParms, aParms, pReply);
+        if (RT_SUCCESS(rc))
+        {
+            PSHCLEVENTPAYLOAD pPayload
+                = (PSHCLEVENTPAYLOAD)RTMemAlloc(sizeof(SHCLEVENTPAYLOAD));
+            if (pPayload)
+            {
+                pPayload->pvData = pReply;
+                pPayload->cbData = cbReply;
+
+                switch (pReply->uType)
+                {
+                    case VBOX_SHCL_REPLYMSGTYPE_TRANSFER_STATUS:
+                        RT_FALL_THROUGH();
+                    case VBOX_SHCL_REPLYMSGTYPE_LIST_OPEN:
+                        RT_FALL_THROUGH();
+                    case VBOX_SHCL_REPLYMSGTYPE_LIST_CLOSE:
+                        RT_FALL_THROUGH();
+                    case VBOX_SHCL_REPLYMSGTYPE_OBJ_OPEN:
+                        RT_FALL_THROUGH();
+                    case VBOX_SHCL_REPLYMSGTYPE_OBJ_CLOSE:
+                    {
+                        uint64_t uCID;
+                        rc = HGCMSvcGetU64(&aParms[0], &uCID);
+                        if (RT_SUCCESS(rc))
+                        {
+                            const PSHCLEVENT pEvent
+                                = ShClEventSourceGetFromId(&pClient->EventSrc, VBOX_SHCL_CONTEXTID_GET_EVENT(uCID));
+                            if (pEvent)
+                            {
+                                LogFlowFunc(("uCID=%RU64 -> idEvent=%RU32\n", uCID, pEvent->idEvent));
+
+                                rc = ShClEventSignal(pEvent, pPayload);
+                            }
+                            /** @todo Silently skip? */
+                        }
+                        break;
+                    }
+
+                    default:
+                        rc = VERR_NOT_FOUND;
+                        break;
+                }
+
+                if (RT_FAILURE(rc))
+                {
+                    if (pPayload)
+                        RTMemFree(pPayload);
+                }
+            }
+            else
+                rc = VERR_NO_MEMORY;
+        }
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    if (RT_FAILURE(rc))
+    {
+        if (pReply)
+            RTMemFree(pReply);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Transfer client (guest) handler for the Shared Clipboard host service.
+ *
+ * @returns VBox status code, or VINF_HGCM_ASYNC_EXECUTE if returning to the client will be deferred.
+ * @param   pClient             Pointer to associated client.
+ * @param   callHandle          The client's call handle of this call.
+ * @param   u32Function         Function number being called.
+ * @param   cParms              Number of function parameters supplied.
+ * @param   aParms              Array function parameters supplied.
+ * @param   tsArrival           Timestamp of arrival.
+ */
+int shClSvcTransferHandler(PSHCLCLIENT pClient,
+                           VBOXHGCMCALLHANDLE callHandle,
+                           uint32_t u32Function,
+                           uint32_t cParms,
+                           VBOXHGCMSVCPARM aParms[],
+                           uint64_t tsArrival)
+{
+    RT_NOREF(callHandle, aParms, tsArrival);
+
+    LogFlowFunc(("uClient=%RU32, u32Function=%RU32 (%s), cParms=%RU32, g_ExtState.pfnExtension=%p\n",
+                 pClient->State.uClientID, u32Function, ShClGuestMsgToStr(u32Function), cParms, g_ExtState.pfnExtension));
+
+    /* Check if we've the right mode set. */
+    if (!shClSvcTransferMsgIsAllowed(ShClSvcGetMode(), u32Function))
+    {
+        LogFunc(("Wrong clipboard mode, denying access\n"));
+        return VERR_ACCESS_DENIED;
+    }
+
+    int rc = VERR_INVALID_PARAMETER; /* Play safe by default. */
+
+    /*
+     * Pre-check: For certain messages we need to make sure that a (right) transfer is present.
+     */
+    uint64_t      uCID      = 0; /* Context ID */
+    PSHCLTRANSFER pTransfer = NULL;
+
+    switch (u32Function)
+    {
+        default:
+        {
+            if (!ShClTransferCtxGetTotalTransfers(&pClient->Transfers.Ctx))
+            {
+                LogFunc(("No transfers found\n"));
+                rc = VERR_SHCLPB_TRANSFER_ID_NOT_FOUND;
+                break;
+            }
+
+            if (cParms < 1)
+                break;
+
+            rc = HGCMSvcGetU64(&aParms[0], &uCID);
+            if (RT_FAILURE(rc))
+                break;
+
+            const SHCLTRANSFERID uTransferID = VBOX_SHCL_CONTEXTID_GET_TRANSFER(uCID);
+
+            pTransfer = ShClTransferCtxGetTransferById(&pClient->Transfers.Ctx, uTransferID);
+            if (!pTransfer)
+            {
+                LogFunc(("Transfer with ID %RU16 not found\n", uTransferID));
+                rc = VERR_SHCLPB_TRANSFER_ID_NOT_FOUND;
+            }
+            break;
+        }
+    }
+
+    if (RT_FAILURE(rc))
+        return rc;
+
+    rc = VERR_INVALID_PARAMETER; /* Play safe. */
+
+    switch (u32Function)
+    {
+        case VBOX_SHCL_GUEST_FN_REPLY:
+        {
+            rc = shClSvcTransferHandleReply(pClient, pTransfer, cParms, aParms);
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_ROOT_LIST_HDR_READ:
+        {
+            if (cParms != VBOX_SHCL_CPARMS_ROOT_LIST_HDR_READ)
+                break;
+
+            if (   ShClTransferGetSource(pTransfer) == SHCLSOURCE_LOCAL
+                && ShClTransferGetDir(pTransfer)    == SHCLTRANSFERDIR_TO_REMOTE)
+            {
+                /* Get roots if this is a local write transfer (host -> guest). */
+                rc = ShClBackendTransferGetRoots(pClient->pBackend, pClient, pTransfer);
+            }
+            else
+            {
+                rc = VERR_INVALID_PARAMETER;
+                break;
+            }
+
+            SHCLROOTLISTHDR rootListHdr;
+            RT_ZERO(rootListHdr);
+
+            rootListHdr.cRoots = ShClTransferRootsCount(pTransfer);
+
+            HGCMSvcSetU64(&aParms[0], 0 /* Context ID */);
+            HGCMSvcSetU32(&aParms[1], rootListHdr.fRoots);
+            HGCMSvcSetU32(&aParms[2], rootListHdr.cRoots);
+
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_ROOT_LIST_HDR_WRITE:
+        {
+            SHCLROOTLISTHDR lstHdr;
+            rc = shClSvcTransferGetRootListHdr(cParms, aParms, &lstHdr);
+            if (RT_SUCCESS(rc))
+            {
+                void    *pvData = ShClTransferRootListHdrDup(&lstHdr);
+                uint32_t cbData = sizeof(SHCLROOTLISTHDR);
+
+                const PSHCLEVENT pEvent = ShClEventSourceGetFromId(&pClient->EventSrc, VBOX_SHCL_CONTEXTID_GET_EVENT(uCID));
+                if (pEvent)
+                {
+                    PSHCLEVENTPAYLOAD pPayload;
+                    rc = ShClPayloadAlloc(pEvent->idEvent, pvData, cbData, &pPayload);
+                    if (RT_SUCCESS(rc))
+                    {
+                        rc = ShClEventSignal(pEvent, pPayload);
+                        if (RT_FAILURE(rc))
+                            ShClPayloadFree(pPayload);
+                    }
+                }
+                else
+                    rc = VERR_SHCLPB_EVENT_ID_NOT_FOUND;
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_ROOT_LIST_ENTRY_READ:
+        {
+            if (cParms != VBOX_SHCL_CPARMS_ROOT_LIST_ENTRY_READ)
+                break;
+
+            /* aParms[1] contains fInfo flags, currently unused. */
+            uint32_t uIndex;
+            rc = HGCMSvcGetU32(&aParms[2], &uIndex);
+            if (RT_SUCCESS(rc))
+            {
+                SHCLROOTLISTENTRY rootListEntry;
+                rc = ShClTransferRootsEntry(pTransfer, uIndex, &rootListEntry);
+                if (RT_SUCCESS(rc))
+                {
+                    HGCMSvcSetPv (&aParms[3], rootListEntry.pszName, rootListEntry.cbName);
+                    HGCMSvcSetU32(&aParms[4], rootListEntry.cbInfo);
+                    HGCMSvcSetPv (&aParms[5], rootListEntry.pvInfo, rootListEntry.cbInfo);
+                }
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_ROOT_LIST_ENTRY_WRITE:
+        {
+            SHCLROOTLISTENTRY lstEntry;
+            rc = shClSvcTransferGetRootListEntry(cParms, aParms, &lstEntry);
+            if (RT_SUCCESS(rc))
+            {
+                void    *pvData = ShClTransferRootListEntryDup(&lstEntry);
+                uint32_t cbData = sizeof(SHCLROOTLISTENTRY);
+
+                const PSHCLEVENT pEvent = ShClEventSourceGetFromId(&pClient->EventSrc, VBOX_SHCL_CONTEXTID_GET_EVENT(uCID));
+                if (pEvent)
+                {
+                    PSHCLEVENTPAYLOAD pPayload;
+                    rc = ShClPayloadAlloc(pEvent->idEvent, pvData, cbData, &pPayload);
+                    if (RT_SUCCESS(rc))
+                    {
+                        rc = ShClEventSignal(pEvent, pPayload);
+                        if (RT_FAILURE(rc))
+                            ShClPayloadFree(pPayload);
+                    }
+                }
+                else
+                    rc = VERR_SHCLPB_EVENT_ID_NOT_FOUND;
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_LIST_OPEN:
+        {
+            SHCLLISTOPENPARMS listOpenParms;
+            rc = shClSvcTransferGetListOpen(cParms, aParms, &listOpenParms);
+            if (RT_SUCCESS(rc))
+            {
+                SHCLLISTHANDLE hList;
+                rc = ShClTransferListOpen(pTransfer, &listOpenParms, &hList);
+                if (RT_SUCCESS(rc))
+                {
+                    /* Return list handle. */
+                    HGCMSvcSetU64(&aParms[6], hList);
+                }
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_LIST_CLOSE:
+        {
+            if (cParms != VBOX_SHCL_CPARMS_LIST_CLOSE)
+                break;
+
+            SHCLLISTHANDLE hList;
+            rc = HGCMSvcGetU64(&aParms[1], &hList);
+            if (RT_SUCCESS(rc))
+            {
+                rc = ShClTransferListClose(pTransfer, hList);
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_LIST_HDR_READ:
+        {
+            if (cParms != VBOX_SHCL_CPARMS_LIST_HDR)
+                break;
+
+            SHCLLISTHANDLE hList;
+            rc = HGCMSvcGetU64(&aParms[1], &hList); /* Get list handle. */
+            if (RT_SUCCESS(rc))
+            {
+                SHCLLISTHDR hdrList;
+                rc = ShClTransferListGetHeader(pTransfer, hList, &hdrList);
+                if (RT_SUCCESS(rc))
+                    rc = shClSvcTransferSetListHdr(cParms, aParms, &hdrList);
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_LIST_HDR_WRITE:
+        {
+            SHCLLISTHDR hdrList;
+            rc = ShClTransferListHdrInit(&hdrList);
+            if (RT_SUCCESS(rc))
+            {
+                SHCLLISTHANDLE hList;
+                rc = shClSvcTransferGetListHdr(cParms, aParms, &hList, &hdrList);
+                if (RT_SUCCESS(rc))
+                {
+                    void    *pvData = ShClTransferListHdrDup(&hdrList);
+                    uint32_t cbData = sizeof(SHCLLISTHDR);
+
+                    const PSHCLEVENT pEvent = ShClEventSourceGetFromId(&pClient->EventSrc, VBOX_SHCL_CONTEXTID_GET_EVENT(uCID));
+                    if (pEvent)
+                    {
+                        PSHCLEVENTPAYLOAD pPayload;
+                        rc = ShClPayloadAlloc(pEvent->idEvent, pvData, cbData, &pPayload);
+                        if (RT_SUCCESS(rc))
+                        {
+                            rc = ShClEventSignal(pEvent, pPayload);
+                            if (RT_FAILURE(rc))
+                                ShClPayloadFree(pPayload);
+                        }
+                    }
+                    else
+                        rc = VERR_SHCLPB_EVENT_ID_NOT_FOUND;
+                }
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_LIST_ENTRY_READ:
+        {
+            if (cParms != VBOX_SHCL_CPARMS_LIST_ENTRY)
+                break;
+
+            SHCLLISTHANDLE hList;
+            rc = HGCMSvcGetU64(&aParms[1], &hList); /* Get list handle. */
+            if (RT_SUCCESS(rc))
+            {
+                SHCLLISTENTRY entryList;
+                rc = ShClTransferListEntryInit(&entryList);
+                if (RT_SUCCESS(rc))
+                {
+                    rc = ShClTransferListRead(pTransfer, hList, &entryList);
+                    if (RT_SUCCESS(rc))
+                        rc = shClSvcTransferSetListEntry(cParms, aParms, &entryList);
+                }
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_LIST_ENTRY_WRITE:
+        {
+            SHCLLISTENTRY entryList;
+            rc = ShClTransferListEntryInit(&entryList);
+            if (RT_SUCCESS(rc))
+            {
+                SHCLLISTHANDLE hList;
+                rc = shClSvcTransferGetListEntry(cParms, aParms, &hList, &entryList);
+                if (RT_SUCCESS(rc))
+                {
+                    void    *pvData = ShClTransferListEntryDup(&entryList);
+                    uint32_t cbData = sizeof(SHCLLISTENTRY);
+
+                    const PSHCLEVENT pEvent = ShClEventSourceGetFromId(&pClient->EventSrc, VBOX_SHCL_CONTEXTID_GET_EVENT(uCID));
+                    if (pEvent)
+                    {
+                        PSHCLEVENTPAYLOAD pPayload;
+                        rc = ShClPayloadAlloc(pEvent->idEvent, pvData, cbData, &pPayload);
+                        if (RT_SUCCESS(rc))
+                        {
+                            rc = ShClEventSignal(pEvent, pPayload);
+                            if (RT_FAILURE(rc))
+                                ShClPayloadFree(pPayload);
+                        }
+                    }
+                    else
+                        rc = VERR_SHCLPB_EVENT_ID_NOT_FOUND;
+                }
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_OBJ_OPEN:
+        {
+            ASSERT_GUEST_STMT_BREAK(cParms == VBOX_SHCL_CPARMS_OBJ_OPEN, VERR_WRONG_PARAMETER_COUNT);
+
+            SHCLOBJOPENCREATEPARMS openCreateParms;
+            RT_ZERO(openCreateParms);
+
+            /* aParms[1] will return the object handle on success; see below. */
+            rc = HGCMSvcGetStr(&aParms[2], &openCreateParms.pszPath, &openCreateParms.cbPath);
+            if (RT_SUCCESS(rc))
+                rc = HGCMSvcGetU32(&aParms[3], &openCreateParms.fCreate);
+
+            if (RT_SUCCESS(rc))
+            {
+                SHCLOBJHANDLE hObj;
+                rc = ShClTransferObjOpen(pTransfer, &openCreateParms, &hObj);
+                if (RT_SUCCESS(rc))
+                {
+                    LogFlowFunc(("hObj=%RU64\n", hObj));
+
+                    HGCMSvcSetU64(&aParms[1], hObj);
+                }
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_OBJ_CLOSE:
+        {
+            if (cParms != VBOX_SHCL_CPARMS_OBJ_CLOSE)
+                break;
+
+            SHCLOBJHANDLE hObj;
+            rc = HGCMSvcGetU64(&aParms[1], &hObj); /* Get object handle. */
+            if (RT_SUCCESS(rc))
+                rc = ShClTransferObjClose(pTransfer, hObj);
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_OBJ_READ:
+        {
+            if (cParms != VBOX_SHCL_CPARMS_OBJ_READ)
+                break;
+
+            SHCLOBJHANDLE hObj;
+            rc = HGCMSvcGetU64(&aParms[1], &hObj); /* Get object handle. */
+
+            uint32_t cbToRead = 0;
+            if (RT_SUCCESS(rc))
+                rc = HGCMSvcGetU32(&aParms[2], &cbToRead);
+
+            void    *pvBuf = NULL;
+            uint32_t cbBuf = 0;
+            if (RT_SUCCESS(rc))
+                rc = HGCMSvcGetPv(&aParms[3], &pvBuf, &cbBuf);
+
+            LogFlowFunc(("hObj=%RU64, cbBuf=%RU32, cbToRead=%RU32, rc=%Rrc\n", hObj, cbBuf, cbToRead, rc));
+
+            if (   RT_SUCCESS(rc)
+                && (   !cbBuf
+                    || !cbToRead
+                    ||  cbBuf < cbToRead
+                   )
+               )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+
+            if (RT_SUCCESS(rc))
+            {
+                uint32_t cbRead;
+                rc = ShClTransferObjRead(pTransfer, hObj, pvBuf, cbToRead, 0 /* fFlags */, &cbRead);
+                if (RT_SUCCESS(rc))
+                {
+                    HGCMSvcSetU32(&aParms[3], cbRead);
+
+                    /** @todo Implement checksum support. */
+                }
+            }
+            break;
+        }
+
+        case VBOX_SHCL_GUEST_FN_OBJ_WRITE:
+        {
+            SHCLOBJDATACHUNK dataChunk;
+            rc = shClSvcTransferGetObjDataChunk(cParms, aParms, &dataChunk);
+            if (RT_SUCCESS(rc))
+            {
+                void    *pvData = ShClTransferObjDataChunkDup(&dataChunk);
+                uint32_t cbData = sizeof(SHCLOBJDATACHUNK);
+
+                const PSHCLEVENT pEvent = ShClEventSourceGetFromId(&pClient->EventSrc, VBOX_SHCL_CONTEXTID_GET_EVENT(uCID));
+                if (pEvent)
+                {
+                    PSHCLEVENTPAYLOAD pPayload;
+                    rc = ShClPayloadAlloc(pEvent->idEvent, pvData, cbData, &pPayload);
+                    if (RT_SUCCESS(rc))
+                    {
+                        rc = ShClEventSignal(pEvent, pPayload);
+                        if (RT_FAILURE(rc))
+                            ShClPayloadFree(pPayload);
+                    }
+                }
+                else
+                    rc = VERR_SHCLPB_EVENT_ID_NOT_FOUND;
+            }
+
+            break;
+        }
+
+        default:
+            rc = VERR_NOT_IMPLEMENTED;
+            break;
+    }
+
+    LogFlowFunc(("[Client %RU32] Returning rc=%Rrc\n", pClient->State.uClientID, rc));
+    return rc;
+}
+
+/**
+ * Transfer host handler for the Shared Clipboard host service.
+ *
+ * @returns VBox status code.
+ * @param   u32Function         Function number being called.
+ * @param   cParms              Number of function parameters supplied.
+ * @param   aParms              Array function parameters supplied.
+ */
+int shClSvcTransferHostHandler(uint32_t u32Function,
+                               uint32_t cParms,
+                               VBOXHGCMSVCPARM aParms[])
+{
+    RT_NOREF(cParms, aParms);
+
+    int rc = VERR_NOT_IMPLEMENTED; /* Play safe. */
+
+    switch (u32Function)
+    {
+        case VBOX_SHCL_HOST_FN_CANCEL: /** @todo Implement this. */
+            break;
+
+        case VBOX_SHCL_HOST_FN_ERROR: /** @todo Implement this. */
+            break;
+
+        default:
+            break;
+
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int shClSvcTransferHostMsgHandler(PSHCLCLIENT pClient, PSHCLCLIENTMSG pMsg)
+{
+    RT_NOREF(pClient);
+
+    int rc;
+
+    switch (pMsg->idMsg)
+    {
+        default:
+            rc = VINF_SUCCESS;
+            break;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Reports a transfer status to the guest.
+ *
+ * @returns VBox status code.
+ * @param   pClient             Client that owns the transfer.
+ * @param   pTransfer           Transfer to report status for.
+ * @param   uStatus             Status to report.
+ * @param   rcTransfer          Result code to report. Optional and depending on status.
+ * @param   ppEvent             Where to return the wait event on success. Optional.
+ *                              Must be released by the caller with ShClEventRelease().
+ */
+int shClSvcTransferSendStatus(PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer, SHCLTRANSFERSTATUS uStatus,
+                              int rcTransfer, PSHCLEVENT *ppEvent)
+{
+    AssertPtrReturn(pClient,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pTransfer, VERR_INVALID_POINTER);
+    /* ppEvent is optional. */
+
+    PSHCLCLIENTMSG pMsgReadData = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_TRANSFER_STATUS,
+                                                  VBOX_SHCL_CPARMS_TRANSFER_STATUS);
+    if (!pMsgReadData)
+        return VERR_NO_MEMORY;
+
+    PSHCLEVENT pEvent;
+    int rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+    if (RT_SUCCESS(rc))
+    {
+        HGCMSvcSetU64(&pMsgReadData->aParms[0], VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID,
+                                                                         pTransfer->State.uID, pEvent->idEvent));
+        HGCMSvcSetU32(&pMsgReadData->aParms[1], pTransfer->State.enmDir);
+        HGCMSvcSetU32(&pMsgReadData->aParms[2], uStatus);
+        HGCMSvcSetU32(&pMsgReadData->aParms[3], (uint32_t)rcTransfer); /** @todo uint32_t vs. int. */
+        HGCMSvcSetU32(&pMsgReadData->aParms[4], 0 /* fFlags, unused */);
+
+        shClSvcMsgAdd(pClient, pMsgReadData, true /* fAppend */);
+
+        rc = shClSvcClientWakeup(pClient);
+        if (RT_SUCCESS(rc))
+        {
+            LogRel2(("Shared Clipboard: Reported status %s (rc=%Rrc) of transfer %RU32 to guest\n",
+                     ShClTransferStatusToStr(uStatus), rcTransfer, pTransfer->State.uID));
+
+            if (ppEvent)
+            {
+                *ppEvent = pEvent; /* Takes ownership. */
+            }
+            else /* If event is not consumed by the caller, release the event again. */
+                ShClEventRelease(pEvent);
+        }
+        else
+            ShClEventRelease(pEvent);
+    }
+    else
+        rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Starts a new transfer, waiting for acknowledgement by the guest side.
+ *
+ * @note Assumes that the client's critical section is taken.
+ *
+ * @returns VBox status code.
+ * @param   pClient             Client that owns the transfer.
+ * @param   enmDir              Transfer direction to start.
+ * @param   enmSource           Transfer source to start.
+ * @param   ppTransfer          Where to return the created transfer on success. Optional.
+ */
+int shClSvcTransferStart(PSHCLCLIENT pClient,
+                         SHCLTRANSFERDIR enmDir, SHCLSOURCE enmSource,
+                         PSHCLTRANSFER *ppTransfer)
+{
+    AssertPtrReturn(pClient, VERR_INVALID_POINTER);
+    /* ppTransfer is optional. */
+
+    LogFlowFuncEnter();
+
+    PSHCLTRANSFERCTX pTxCtx = &pClient->Transfers.Ctx;
+
+    ShClTransferCtxCleanup(pTxCtx);
+
+    int rc;
+
+    if (!ShClTransferCtxTransfersMaximumReached(pTxCtx))
+    {
+        LogRel2(("Shared Clipboard: Starting %s transfer ...\n", enmDir == SHCLTRANSFERDIR_FROM_REMOTE ? "read" : "write"));
+
+        PSHCLTRANSFER pTransfer;
+        rc = ShClTransferCreate(&pTransfer);
+        if (RT_SUCCESS(rc))
+        {
+            SHCLTXPROVIDERCREATIONCTX creationCtx;
+            RT_ZERO(creationCtx);
+
+            if (enmDir == SHCLTRANSFERDIR_FROM_REMOTE)
+            {
+                creationCtx.Interface.pfnRootsGet      = shClSvcTransferIfaceGetRoots;
+
+                creationCtx.Interface.pfnListOpen      = shClSvcTransferIfaceListOpen;
+                creationCtx.Interface.pfnListClose     = shClSvcTransferIfaceListClose;
+                creationCtx.Interface.pfnListHdrRead   = shClSvcTransferIfaceListHdrRead;
+                creationCtx.Interface.pfnListEntryRead = shClSvcTransferIfaceListEntryRead;
+
+                creationCtx.Interface.pfnObjOpen       = shClSvcTransferIfaceObjOpen;
+                creationCtx.Interface.pfnObjClose      = shClSvcTransferIfaceObjClose;
+                creationCtx.Interface.pfnObjRead       = shClSvcTransferIfaceObjRead;
+            }
+            else if (enmDir == SHCLTRANSFERDIR_TO_REMOTE)
+            {
+                creationCtx.Interface.pfnListHdrWrite   = shClSvcTransferIfaceListHdrWrite;
+                creationCtx.Interface.pfnListEntryWrite = shClSvcTransferIfaceListEntryWrite;
+                creationCtx.Interface.pfnObjWrite       = shClSvcTransferIfaceObjWrite;
+            }
+            else
+                AssertFailed();
+
+            creationCtx.enmSource = pClient->State.enmSource;
+            creationCtx.pvUser    = pClient;
+
+            rc = ShClTransferSetProviderIface(pTransfer, &creationCtx);
+            if (RT_SUCCESS(rc))
+            {
+                rc = ShClTransferInit(pTransfer, enmDir, enmSource);
+                if (RT_SUCCESS(rc))
+                {
+                    SHCLTRANSFERID uTransferID = 0;
+                    rc = ShClTransferCtxTransferRegister(pTxCtx, pTransfer, &uTransferID);
+                    if (RT_SUCCESS(rc))
+                    {
+                        rc = ShClBackendTransferCreate(pClient->pBackend, pClient, pTransfer);
+                        if (RT_SUCCESS(rc))
+                        {
+                            if (RT_SUCCESS(rc))
+                                rc = ShClTransferStart(pTransfer);
+
+                            if (RT_SUCCESS(rc))
+                            {
+                                PSHCLEVENT pEvent;
+                                rc = shClSvcTransferSendStatus(pClient, pTransfer,
+                                                               SHCLTRANSFERSTATUS_INITIALIZED, VINF_SUCCESS, &pEvent);
+                                if (RT_SUCCESS(rc))
+                                {
+                                    LogRel2(("Shared Clipboard: Waiting for start of transfer %RU32 on guest ...\n",
+                                             pTransfer->State.uID));
+
+                                    /* Leave the client's critical section before waiting. */
+                                    RTCritSectLeave(&pClient->CritSect);
+
+                                    PSHCLEVENTPAYLOAD pPayload = NULL;
+                                    rc = ShClEventWait(pEvent, pTransfer->uTimeoutMs, &pPayload);
+                                    if (RT_SUCCESS(rc))
+                                    {
+                                        Assert(pPayload->cbData == sizeof(SHCLREPLY));
+                                        PSHCLREPLY pReply = (PSHCLREPLY)pPayload->pvData;
+                                        AssertPtr(pReply);
+
+                                        Assert(pReply->uType == VBOX_SHCL_REPLYMSGTYPE_TRANSFER_STATUS);
+
+                                        if (pReply->u.TransferStatus.uStatus == SHCLTRANSFERSTATUS_STARTED)
+                                        {
+                                            LogRel2(("Shared Clipboard: Started transfer %RU32 on guest\n", pTransfer->State.uID));
+                                        }
+                                        else
+                                            LogRel(("Shared Clipboard: Guest reported status %s (error %Rrc) while starting transfer %RU32\n",
+                                                    ShClTransferStatusToStr(pReply->u.TransferStatus.uStatus),
+                                                    pReply->rc, pTransfer->State.uID));
+
+                                        rc = pReply->rc; /* Set guest rc. */
+                                    }
+                                    else
+                                       LogRel(("Shared Clipboard: Unable to start transfer %RU32 on guest, rc=%Rrc\n",
+                                               pTransfer->State.uID, rc));
+
+                                    ShClPayloadFree(pPayload);
+                                    ShClEventRelease(pEvent);
+
+                                    /* Re-enter the client's critical section again. */
+                                    RTCritSectEnter(&pClient->CritSect);
+                                }
+                            }
+                        }
+                    }
+
+                    if (RT_FAILURE(rc))
+                        ShClTransferCtxTransferUnregister(pTxCtx, uTransferID);
+                }
+            }
+
+            if (RT_FAILURE(rc))
+            {
+                ShClBackendTransferDestroy(pClient->pBackend, pClient, pTransfer);
+                ShClTransferDestroy(pTransfer);
+
+                RTMemFree(pTransfer);
+                pTransfer = NULL;
+            }
+            else
+            {
+                if (ppTransfer)
+                    *ppTransfer = pTransfer;
+            }
+        }
+
+        if (RT_FAILURE(rc))
+            LogRel(("Shared Clipboard: Starting transfer failed with %Rrc\n", rc));
+    }
+    else
+        rc = VERR_SHCLPB_MAX_TRANSFERS_REACHED;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Stops (and destroys) a transfer, communicating the status to the guest side.
+ *
+ * @returns VBox status code.
+ * @param   pClient             Client that owns the transfer.
+ * @param   pTransfer           Transfer to stop.
+ */
+int shClSvcTransferStop(PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer)
+{
+    PSHCLEVENT pEvent;
+    int rc = shClSvcTransferSendStatus(pClient, pTransfer,
+                                       SHCLTRANSFERSTATUS_STOPPED, VINF_SUCCESS, &pEvent);
+    if (RT_SUCCESS(rc))
+    {
+        LogRel2(("Shared Clipboard: Waiting for stop of transfer %RU32 on guest ...\n", pTransfer->State.uID));
+
+        rc = ShClEventWait(pEvent, pTransfer->uTimeoutMs, NULL /* ppPayload */);
+        if (RT_SUCCESS(rc))
+            LogRel2(("Shared Clipboard: Stopped transfer %RU32 on guest\n", pTransfer->State.uID));
+
+        ShClEventRelease(pEvent);
+    }
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Unable to stop transfer %RU32 on guest, rc=%Rrc\n",
+                pTransfer->State.uID, rc));
+
+    /* Regardless of whether the guest was able to report back and/or stop the transfer, remove the transfer on the host
+     * so that we don't risk of having stale transfers here. */
+    int rc2 = ShClTransferCtxTransferUnregister(&pClient->Transfers.Ctx, ShClTransferGetID(pTransfer));
+    if (RT_SUCCESS(rc2))
+    {
+        ShClBackendTransferDestroy(pClient->pBackend, pClient, pTransfer);
+        ShClTransferDestroy(pTransfer);
+        pTransfer = NULL;
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Sets the host service's (file) transfer mode.
+ *
+ * @returns VBox status code.
+ * @param   fMode               Transfer mode to set.
+ */
+int shClSvcTransferModeSet(uint32_t fMode)
+{
+    if (fMode & ~VBOX_SHCL_TRANSFER_MODE_VALID_MASK)
+        return VERR_INVALID_FLAGS;
+
+    g_fTransferMode = fMode;
+
+#ifdef DEBUG_andy
+g_fTransferMode = VBOX_SHCL_TRANSFER_MODE_ENABLED;
+#endif
+
+    LogRel2(("Shared Clipboard: File transfers are now %s\n",
+             g_fTransferMode != VBOX_SHCL_TRANSFER_MODE_DISABLED ? "enabled" : "disabled"));
+
+    /* If file transfers are being disabled, make sure to also reset (destroy) all pending transfers. */
+    if (g_fTransferMode == VBOX_SHCL_TRANSFER_MODE_DISABLED)
+    {
+        ClipboardClientMap::const_iterator itClient = g_mapClients.begin();
+        while (itClient != g_mapClients.end())
+        {
+            PSHCLCLIENT pClient = itClient->second;
+            AssertPtr(pClient);
+
+            shClSvcClientTransfersReset(pClient);
+
+            ++itClient;
+        }
+    }
+
+    LogFlowFuncLeaveRC(VINF_SUCCESS);
+    return VINF_SUCCESS;
+}
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-transfers.h b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-transfers.h
new file mode 100644
index 00000000..89968d40
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-transfers.h
@@ -0,0 +1,35 @@
+/* $Id: VBoxSharedClipboardSvc-transfers.h $ */
+/** @file
+ * Shared Clipboard Service - Internal header for transfer (list) handling.
+ */
+
+/*
+ * Copyright (C) 2019-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_SharedClipboard_VBoxSharedClipboardSvc_transfers_h
+#define VBOX_INCLUDED_SRC_SharedClipboard_VBoxSharedClipboardSvc_transfers_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#endif /* !VBOX_INCLUDED_SRC_SharedClipboard_VBoxSharedClipboardSvc_transfers_h */
+
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-utils.cpp b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-utils.cpp
new file mode 100644
index 00000000..b008b2a2
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-utils.cpp
@@ -0,0 +1,42 @@
+/* $Id: VBoxSharedClipboardSvc-utils.cpp $ */
+/** @file
+ * Shared Clipboard Service - Host service utility functions.
+ */
+
+/*
+ * Copyright (C) 2019-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/log.h>
+
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#include <VBox/HostServices/VBoxClipboardExt.h>
+
+#include <iprt/errcore.h>
+#include <iprt/path.h>
+
+#include "VBoxSharedClipboardSvc-internal.h"
+
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-win.cpp b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-win.cpp
new file mode 100644
index 00000000..2a8db65d
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-win.cpp
@@ -0,0 +1,890 @@
+/* $Id: VBoxSharedClipboardSvc-win.cpp $ */
+/** @file
+ * Shared Clipboard Service - Win32 host.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <iprt/win/windows.h>
+
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#include <VBox/GuestHost/clipboard-helper.h>
+#include <VBox/GuestHost/SharedClipboard-win.h>
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+# include <VBox/GuestHost/SharedClipboard-transfers.h>
+#endif
+
+#include <iprt/alloc.h>
+#include <iprt/string.h>
+#include <iprt/asm.h>
+#include <iprt/assert.h>
+#include <iprt/ldr.h>
+#include <iprt/semaphore.h>
+#include <iprt/thread.h>
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+# include <iprt/utf16.h>
+#endif
+
+#include <process.h>
+#include <iprt/win/shlobj.h> /* Needed for shell objects. */
+
+#include "VBoxSharedClipboardSvc-internal.h"
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+# include "VBoxSharedClipboardSvc-transfers.h"
+#endif
+
+
+/*********************************************************************************************************************************
+*   Internal Functions                                                                                                           *
+*********************************************************************************************************************************/
+static int vboxClipboardSvcWinSyncInternal(PSHCLCONTEXT pCtx);
+
+struct SHCLCONTEXT
+{
+    /** Handle for window message handling thread. */
+    RTTHREAD    hThread;
+    /** Structure for keeping and communicating with service client. */
+    PSHCLCLIENT pClient;
+    /** Windows-specific context data. */
+    SHCLWINCTX  Win;
+};
+
+
+/**
+ * Copy clipboard data into the guest buffer.
+ *
+ * At first attempt, guest will provide a buffer of default size.
+ * Usually 1K or 4K (see platform specific Guest Additions code around
+ * VbglR3ClipboardReadData calls). If this buffer is not big enough
+ * to fit host clipboard content, this function will return VINF_BUFFER_OVERFLOW
+ * and provide guest with host's clipboard buffer actual size. This will be a
+ * signal for the guest to re-read host clipboard data providing bigger buffer
+ * to store it.
+ *
+ * @returns IPRT status code.
+ * @returns VINF_BUFFER_OVERFLOW returned when guest buffer size if not big
+ *          enough to store host clipboard data. This is a signal to the guest
+ *          to re-issue host clipboard read request with bigger buffer size
+ *          (specified in @a pcbActualDst output parameter).
+ * @param   u32Format           VBox clipboard format (VBOX_SHCL_FMT_XXX) of copied data.
+ * @param   pvSrc               Pointer to host clipboard data.
+ * @param   cbSrc               Size (in bytes) of actual clipboard data to copy.
+ * @param   pvDst               Pointer to guest buffer to store clipboard data.
+ * @param   cbDst               Size (in bytes) of guest buffer.
+ * @param   pcbActualDst        Actual size (in bytes) of host clipboard data.
+ *                              Only set if guest buffer size if not big enough
+ *                              to store host clipboard content. When set,
+ *                              function returns VINF_BUFFER_OVERFLOW.
+ */
+static int vboxClipboardSvcWinDataGet(uint32_t u32Format, const void *pvSrc, uint32_t cbSrc,
+                                      void *pvDst, uint32_t cbDst, uint32_t *pcbActualDst)
+{
+    AssertPtrReturn(pvSrc,        VERR_INVALID_POINTER);
+    AssertReturn   (cbSrc,        VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pvDst,        VERR_INVALID_POINTER);
+    AssertReturn   (cbDst,        VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pcbActualDst, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("cbSrc = %d, cbDst = %d\n", cbSrc, cbDst));
+
+    if (   u32Format == VBOX_SHCL_FMT_HTML
+        && SharedClipboardWinIsCFHTML((const char *)pvSrc))
+    {
+        /** @todo r=bird: Why the double conversion? */
+        char *pszBuf = NULL;
+        uint32_t cbBuf = 0;
+        int rc = SharedClipboardWinConvertCFHTMLToMIME((const char *)pvSrc, cbSrc, &pszBuf, &cbBuf);
+        if (RT_SUCCESS(rc))
+        {
+            *pcbActualDst = cbBuf;
+            if (cbBuf > cbDst)
+            {
+                /* Do not copy data. The dst buffer is not enough. */
+                RTMemFree(pszBuf);
+                return VINF_BUFFER_OVERFLOW;
+            }
+            memcpy(pvDst, pszBuf, cbBuf);
+            RTMemFree(pszBuf);
+        }
+        else
+            *pcbActualDst = 0;
+    }
+    else
+    {
+        *pcbActualDst = cbSrc; /* Tell the caller how much space we need. */
+
+        if (cbSrc > cbDst)
+            return VINF_BUFFER_OVERFLOW;
+
+        memcpy(pvDst, pvSrc, cbSrc);
+    }
+
+#ifdef LOG_ENABLED
+    ShClDbgDumpData(pvDst, cbSrc, u32Format);
+#endif
+
+    return VINF_SUCCESS;
+}
+
+static int vboxClipboardSvcWinDataRead(PSHCLCONTEXT pCtx, UINT uFormat, void **ppvData, uint32_t *pcbData)
+{
+    SHCLFORMAT fFormat = SharedClipboardWinClipboardFormatToVBox(uFormat);
+    LogFlowFunc(("uFormat=%u -> uFmt=0x%x\n", uFormat, fFormat));
+
+    if (fFormat == VBOX_SHCL_FMT_NONE)
+    {
+        LogRel2(("Shared Clipboard: Windows format %u not supported, ignoring\n", uFormat));
+        return VERR_NOT_SUPPORTED;
+    }
+
+    PSHCLEVENT pEvent;
+    int rc = ShClSvcGuestDataRequest(pCtx->pClient, fFormat, &pEvent);
+    if (RT_SUCCESS(rc))
+    {
+        PSHCLEVENTPAYLOAD pPayload;
+        rc = ShClEventWait(pEvent, 30 * 1000, &pPayload);
+        if (RT_SUCCESS(rc))
+        {
+            *ppvData = pPayload ? pPayload->pvData : NULL;
+            *pcbData = pPayload ? pPayload->cbData : 0;
+        }
+
+        ShClEventRelease(pEvent);
+    }
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Reading guest clipboard data for Windows host failed with %Rrc\n", rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+static LRESULT CALLBACK vboxClipboardSvcWinWndProcMain(PSHCLCONTEXT pCtx,
+                                                       HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) RT_NOTHROW_DEF
+{
+    AssertPtr(pCtx);
+
+    LRESULT lresultRc = 0;
+
+    const PSHCLWINCTX pWinCtx = &pCtx->Win;
+
+    switch (uMsg)
+    {
+        case WM_CLIPBOARDUPDATE:
+        {
+            LogFunc(("WM_CLIPBOARDUPDATE\n"));
+
+            int rc = RTCritSectEnter(&pWinCtx->CritSect);
+            if (RT_SUCCESS(rc))
+            {
+                const HWND hWndClipboardOwner = GetClipboardOwner();
+
+                LogFunc(("WM_CLIPBOARDUPDATE: hWndClipboardOwnerUs=%p, hWndNewClipboardOwner=%p\n",
+                         pWinCtx->hWndClipboardOwnerUs, hWndClipboardOwner));
+
+                if (pWinCtx->hWndClipboardOwnerUs != hWndClipboardOwner)
+                {
+                    int rc2 = RTCritSectLeave(&pWinCtx->CritSect);
+                    AssertRC(rc2);
+
+                    /* Clipboard was updated by another application, retrieve formats and report back. */
+                    rc = vboxClipboardSvcWinSyncInternal(pCtx);
+                }
+                else
+                {
+                    int rc2 = RTCritSectLeave(&pWinCtx->CritSect);
+                    AssertRC(rc2);
+                }
+            }
+
+            if (RT_FAILURE(rc))
+                LogRel(("Shared Clipboard: WM_CLIPBOARDUPDATE failed with %Rrc\n", rc));
+
+            break;
+        }
+
+        case WM_CHANGECBCHAIN:
+        {
+            LogFunc(("WM_CHANGECBCHAIN\n"));
+            lresultRc = SharedClipboardWinHandleWMChangeCBChain(pWinCtx, hWnd, uMsg, wParam, lParam);
+            break;
+        }
+
+        case WM_DRAWCLIPBOARD:
+        {
+            LogFunc(("WM_DRAWCLIPBOARD\n"));
+
+            int rc = RTCritSectEnter(&pWinCtx->CritSect);
+            if (RT_SUCCESS(rc))
+            {
+                const HWND hWndClipboardOwner = GetClipboardOwner();
+
+                LogFunc(("WM_DRAWCLIPBOARD: hWndClipboardOwnerUs=%p, hWndNewClipboardOwner=%p\n",
+                         pWinCtx->hWndClipboardOwnerUs, hWndClipboardOwner));
+
+                if (pWinCtx->hWndClipboardOwnerUs != hWndClipboardOwner)
+                {
+                    int rc2 = RTCritSectLeave(&pWinCtx->CritSect);
+                    AssertRC(rc2);
+
+                    /* Clipboard was updated by another application, retrieve formats and report back. */
+                    rc = vboxClipboardSvcWinSyncInternal(pCtx);
+                }
+                else
+                {
+                    int rc2 = RTCritSectLeave(&pWinCtx->CritSect);
+                    AssertRC(rc2);
+                }
+            }
+
+            lresultRc = SharedClipboardWinChainPassToNext(pWinCtx, uMsg, wParam, lParam);
+            break;
+        }
+
+        case WM_TIMER:
+        {
+            int rc = SharedClipboardWinHandleWMTimer(pWinCtx);
+            AssertRC(rc);
+
+            break;
+        }
+
+        case WM_RENDERFORMAT:
+        {
+            LogFunc(("WM_RENDERFORMAT\n"));
+
+            /* Insert the requested clipboard format data into the clipboard. */
+            const UINT       uFormat = (UINT)wParam;
+            const SHCLFORMAT fFormat = SharedClipboardWinClipboardFormatToVBox(uFormat);
+            LogFunc(("WM_RENDERFORMAT: uFormat=%u -> fFormat=0x%x\n", uFormat, fFormat));
+
+            if (   fFormat       == VBOX_SHCL_FMT_NONE
+                || pCtx->pClient == NULL)
+            {
+                /* Unsupported clipboard format is requested. */
+                LogFunc(("WM_RENDERFORMAT unsupported format requested or client is not active\n"));
+                SharedClipboardWinClear();
+            }
+            else
+            {
+                void    *pvData = NULL;
+                uint32_t cbData = 0;
+                int rc = vboxClipboardSvcWinDataRead(pCtx, uFormat, &pvData, &cbData);
+                if (   RT_SUCCESS(rc)
+                    && pvData
+                    && cbData)
+                {
+                    /* Wrap HTML clipboard content info CF_HTML format if needed. */
+                    if (fFormat == VBOX_SHCL_FMT_HTML
+                        && !SharedClipboardWinIsCFHTML((char *)pvData))
+                    {
+                        char *pszWrapped = NULL;
+                        uint32_t cbWrapped = 0;
+                        rc = SharedClipboardWinConvertMIMEToCFHTML((char *)pvData, cbData, &pszWrapped, &cbWrapped);
+                        if (RT_SUCCESS(rc))
+                        {
+                            /* Replace buffer with wrapped data content. */
+                            RTMemFree(pvData);
+                            pvData = (void *)pszWrapped;
+                            cbData = cbWrapped;
+                        }
+                        else
+                            LogRel(("Shared Clipboard: cannot convert HTML clipboard into CF_HTML format, rc=%Rrc\n", rc));
+                    }
+
+                    rc = SharedClipboardWinDataWrite(uFormat, pvData, cbData);
+                    if (RT_FAILURE(rc))
+                        LogRel(("Shared Clipboard: Setting clipboard data for Windows host failed with %Rrc\n", rc));
+
+                    RTMemFree(pvData);
+                    cbData = 0;
+                }
+
+                if (RT_FAILURE(rc))
+                    SharedClipboardWinClear();
+            }
+
+            break;
+        }
+
+        case WM_RENDERALLFORMATS:
+        {
+            LogFunc(("WM_RENDERALLFORMATS\n"));
+
+            int rc = SharedClipboardWinHandleWMRenderAllFormats(pWinCtx, hWnd);
+            AssertRC(rc);
+
+            break;
+        }
+
+        case SHCL_WIN_WM_REPORT_FORMATS:
+        {
+            /* Announce available formats. Do not insert data -- will be inserted in WM_RENDERFORMAT (or via IDataObject). */
+            SHCLFORMATS fFormats = (uint32_t)lParam;
+            LogFunc(("SHCL_WIN_WM_REPORT_FORMATS: fFormats=%#xn", fFormats));
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+            if (fFormats & VBOX_SHCL_FMT_URI_LIST)
+            {
+                PSHCLTRANSFER pTransfer;
+                int rc = shClSvcTransferStart(pCtx->pClient,
+                                              SHCLTRANSFERDIR_FROM_REMOTE, SHCLSOURCE_REMOTE,
+                                              &pTransfer);
+                if (RT_SUCCESS(rc))
+                {
+                    /* Create the IDataObject implementation the host OS needs and assign
+                     * the newly created transfer to this object. */
+                    rc = SharedClipboardWinTransferCreate(&pCtx->Win, pTransfer);
+
+                    /*  Note: The actual requesting + retrieving of data will be done in the IDataObject implementation
+                              (ClipboardDataObjectImpl::GetData()). */
+                }
+                else
+                    LogRel(("Shared Clipboard: Initializing read transfer failed with %Rrc\n", rc));
+            }
+            else
+            {
+#endif
+                int rc = SharedClipboardWinClearAndAnnounceFormats(pWinCtx, fFormats, hWnd);
+                if (RT_FAILURE(rc))
+                    LogRel(("Shared Clipboard: Reporting clipboard formats %#x to Windows host failed with %Rrc\n", fFormats, rc));
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+            }
+#endif
+            LogFunc(("SHCL_WIN_WM_REPORT_FORMATS: lastErr=%ld\n", GetLastError()));
+            break;
+        }
+
+        case WM_DESTROY:
+        {
+            LogFunc(("WM_DESTROY\n"));
+
+            int rc = SharedClipboardWinHandleWMDestroy(pWinCtx);
+            AssertRC(rc);
+
+            PostQuitMessage(0);
+            break;
+        }
+
+        default:
+            lresultRc = DefWindowProc(hWnd, uMsg, wParam, lParam);
+            break;
+    }
+
+    LogFlowFunc(("LEAVE hWnd=%p, WM_ %u -> %#zx\n", hWnd, uMsg, lresultRc));
+    return lresultRc;
+}
+
+/**
+ * Static helper function for having a per-client proxy window instances.
+ */
+static LRESULT CALLBACK vboxClipboardSvcWinWndProcInstance(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) RT_NOTHROW_DEF
+{
+    LONG_PTR pUserData = GetWindowLongPtr(hWnd, GWLP_USERDATA);
+    AssertPtrReturn(pUserData, 0);
+
+    PSHCLCONTEXT pCtx = reinterpret_cast<PSHCLCONTEXT>(pUserData);
+    if (pCtx)
+        return vboxClipboardSvcWinWndProcMain(pCtx, hWnd, uMsg, wParam, lParam);
+
+    return 0;
+}
+
+/**
+ * Static helper function for routing Windows messages to a specific
+ * proxy window instance.
+ */
+static LRESULT CALLBACK vboxClipboardSvcWinWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam) RT_NOTHROW_DEF
+{
+    /* Note: WM_NCCREATE is not the first ever message which arrives, but
+     *       early enough for us. */
+    if (uMsg == WM_NCCREATE)
+    {
+        LogFlowFunc(("WM_NCCREATE\n"));
+
+        LPCREATESTRUCT pCS = (LPCREATESTRUCT)lParam;
+        AssertPtr(pCS);
+        SetWindowLongPtr(hWnd, GWLP_USERDATA, (LONG_PTR)pCS->lpCreateParams);
+        SetWindowLongPtr(hWnd, GWLP_WNDPROC, (LONG_PTR)vboxClipboardSvcWinWndProcInstance);
+
+        return vboxClipboardSvcWinWndProcInstance(hWnd, uMsg, wParam, lParam);
+    }
+
+    /* No window associated yet. */
+    return DefWindowProc(hWnd, uMsg, wParam, lParam);
+}
+
+DECLCALLBACK(int) vboxClipboardSvcWinThread(RTTHREAD hThreadSelf, void *pvUser)
+{
+    LogFlowFuncEnter();
+
+    bool fThreadSignalled = false;
+
+    const PSHCLCONTEXT pCtx    = (PSHCLCONTEXT)pvUser;
+    AssertPtr(pCtx);
+    const PSHCLWINCTX  pWinCtx = &pCtx->Win;
+
+    HINSTANCE hInstance = (HINSTANCE)GetModuleHandle(NULL);
+
+    /* Register the Window Class. */
+    WNDCLASS wc;
+    RT_ZERO(wc);
+
+    wc.style         = CS_NOCLOSE;
+    wc.lpfnWndProc   = vboxClipboardSvcWinWndProc;
+    wc.hInstance     = hInstance;
+    wc.hbrBackground = (HBRUSH)(COLOR_BACKGROUND + 1);
+
+    /* Register an unique wnd class name. */
+    char szWndClassName[32];
+    RTStrPrintf2(szWndClassName, sizeof(szWndClassName),
+                 "%s-%RU64", SHCL_WIN_WNDCLASS_NAME, RTThreadGetNative(hThreadSelf));
+    wc.lpszClassName = szWndClassName;
+
+    int rc;
+
+    ATOM atomWindowClass = RegisterClass(&wc);
+    if (atomWindowClass == 0)
+    {
+        LogFunc(("Failed to register window class\n"));
+        rc = VERR_NOT_SUPPORTED;
+    }
+    else
+    {
+        /* Create a window and make it a clipboard viewer. */
+        pWinCtx->hWnd = CreateWindowEx(WS_EX_TOOLWINDOW | WS_EX_TRANSPARENT | WS_EX_TOPMOST,
+                                       szWndClassName, szWndClassName,
+                                       WS_POPUPWINDOW,
+                                       -200, -200, 100, 100, NULL, NULL, hInstance, pCtx /* lpParam */);
+        if (pWinCtx->hWnd == NULL)
+        {
+            LogFunc(("Failed to create window\n"));
+            rc = VERR_NOT_SUPPORTED;
+        }
+        else
+        {
+            SetWindowPos(pWinCtx->hWnd, HWND_TOPMOST, -200, -200, 0, 0,
+                         SWP_NOACTIVATE | SWP_HIDEWINDOW | SWP_NOCOPYBITS | SWP_NOREDRAW | SWP_NOSIZE);
+
+            rc = SharedClipboardWinChainAdd(&pCtx->Win);
+            if (RT_SUCCESS(rc))
+            {
+                if (!SharedClipboardWinIsNewAPI(&pWinCtx->newAPI))
+                    pWinCtx->oldAPI.timerRefresh = SetTimer(pWinCtx->hWnd, 0, 10 * 1000, NULL);
+            }
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+            if (RT_SUCCESS(rc))
+            {
+                HRESULT hr = OleInitialize(NULL);
+                if (FAILED(hr))
+                {
+                    LogRel(("Shared Clipboard: Initializing window thread OLE failed (%Rhrc) -- file transfers unavailable\n", hr));
+                    /* Not critical, the rest of the clipboard might work. */
+                }
+                else
+                    LogRel(("Shared Clipboard: Initialized window thread OLE\n"));
+            }
+#endif
+            int rc2 = RTThreadUserSignal(hThreadSelf);
+            AssertRC(rc2);
+
+            fThreadSignalled = true;
+
+            MSG msg;
+            BOOL msgret = 0;
+            while ((msgret = GetMessage(&msg, NULL, 0, 0)) > 0)
+            {
+                TranslateMessage(&msg);
+                DispatchMessage(&msg);
+            }
+
+            /*
+             * Window procedure can return error, * but this is exceptional situation that should be
+             * identified in testing.
+             */
+            Assert(msgret >= 0);
+            LogFunc(("Message loop finished. GetMessage returned %d, message id: %d \n", msgret, msg.message));
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+            OleSetClipboard(NULL); /* Make sure to flush the clipboard on destruction. */
+            OleUninitialize();
+#endif
+        }
+    }
+
+    pWinCtx->hWnd = NULL;
+
+    if (atomWindowClass != 0)
+    {
+        UnregisterClass(szWndClassName, hInstance);
+        atomWindowClass = 0;
+    }
+
+    if (!fThreadSignalled)
+    {
+        int rc2 = RTThreadUserSignal(hThreadSelf);
+        AssertRC(rc2);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Synchronizes the host and the guest clipboard formats by sending all supported host clipboard
+ * formats to the guest.
+ *
+ * @returns VBox status code, VINF_NO_CHANGE if no synchronization was required.
+ * @param   pCtx                Clipboard context to synchronize.
+ */
+static int vboxClipboardSvcWinSyncInternal(PSHCLCONTEXT pCtx)
+{
+    AssertPtrReturn(pCtx, VERR_INVALID_POINTER);
+
+    LogFlowFuncEnter();
+
+    int rc;
+
+    if (pCtx->pClient)
+    {
+        SHCLFORMATS fFormats = 0;
+        rc = SharedClipboardWinGetFormats(&pCtx->Win, &fFormats);
+        if (   RT_SUCCESS(rc)
+            && fFormats != VBOX_SHCL_FMT_NONE /** @todo r=bird: BUGBUG: revisit this. */
+            && ShClSvcIsBackendActive())
+            rc = ShClSvcHostReportFormats(pCtx->pClient, fFormats);
+    }
+    else /* If we don't have any client data (yet), bail out. */
+        rc = VINF_NO_CHANGE;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/*
+ * Public platform dependent functions.
+ */
+
+int ShClBackendInit(PSHCLBACKEND pBackend, VBOXHGCMSVCFNTABLE *pTable)
+{
+    RT_NOREF(pBackend, pTable);
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    HRESULT hr = OleInitialize(NULL);
+    if (FAILED(hr))
+    {
+        LogRel(("Shared Clipboard: Initializing OLE failed (%Rhrc) -- file transfers unavailable\n", hr));
+        /* Not critical, the rest of the clipboard might work. */
+    }
+    else
+        LogRel(("Shared Clipboard: Initialized OLE\n"));
+#endif
+
+    return VINF_SUCCESS;
+}
+
+void ShClBackendDestroy(PSHCLBACKEND pBackend)
+{
+    RT_NOREF(pBackend);
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    OleSetClipboard(NULL); /* Make sure to flush the clipboard on destruction. */
+    OleUninitialize();
+#endif
+}
+
+int ShClBackendConnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, bool fHeadless)
+{
+    RT_NOREF(pBackend, fHeadless);
+
+    LogFlowFuncEnter();
+
+    int rc;
+
+    PSHCLCONTEXT pCtx = (PSHCLCONTEXT)RTMemAllocZ(sizeof(SHCLCONTEXT));
+    if (pCtx)
+    {
+        rc = SharedClipboardWinCtxInit(&pCtx->Win);
+        if (RT_SUCCESS(rc))
+        {
+            rc = RTThreadCreate(&pCtx->hThread, vboxClipboardSvcWinThread, pCtx /* pvUser */, _64K /* Stack size */,
+                                RTTHREADTYPE_IO, RTTHREADFLAGS_WAITABLE, "SHCLIP");
+            if (RT_SUCCESS(rc))
+            {
+                int rc2 = RTThreadUserWait(pCtx->hThread, 30 * 1000 /* Timeout in ms */);
+                AssertRC(rc2);
+            }
+        }
+
+        pClient->State.pCtx = pCtx;
+        pClient->State.pCtx->pClient = pClient;
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int ShClBackendSync(PSHCLBACKEND pBackend, PSHCLCLIENT pClient)
+{
+    RT_NOREF(pBackend);
+
+    /* Sync the host clipboard content with the client. */
+    return vboxClipboardSvcWinSyncInternal(pClient->State.pCtx);
+}
+
+int ShClBackendDisconnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient)
+{
+    RT_NOREF(pBackend);
+
+    AssertPtrReturn(pClient, VERR_INVALID_POINTER);
+
+    LogFlowFuncEnter();
+
+    int rc = VINF_SUCCESS;
+
+    PSHCLCONTEXT pCtx = pClient->State.pCtx;
+    if (pCtx)
+    {
+        if (pCtx->Win.hWnd)
+            PostMessage(pCtx->Win.hWnd, WM_DESTROY, 0 /* wParam */, 0 /* lParam */);
+
+        if (pCtx->hThread != NIL_RTTHREAD)
+        {
+            LogFunc(("Waiting for thread to terminate ...\n"));
+
+            /* Wait for the window thread to terminate. */
+            rc = RTThreadWait(pCtx->hThread, 30 * 1000 /* Timeout in ms */, NULL);
+            if (RT_FAILURE(rc))
+                LogRel(("Shared Clipboard: Waiting for window thread termination failed with rc=%Rrc\n", rc));
+
+            pCtx->hThread = NIL_RTTHREAD;
+        }
+
+        SharedClipboardWinCtxDestroy(&pCtx->Win);
+
+        if (RT_SUCCESS(rc))
+        {
+            RTMemFree(pCtx);
+            pCtx = NULL;
+
+            pClient->State.pCtx = NULL;
+        }
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int ShClBackendReportFormats(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, SHCLFORMATS fFormats)
+{
+    RT_NOREF(pBackend);
+
+    AssertPtrReturn(pClient, VERR_INVALID_POINTER);
+
+    PSHCLCONTEXT pCtx = pClient->State.pCtx;
+    AssertPtrReturn(pCtx, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("fFormats=0x%x, hWnd=%p\n", fFormats, pCtx->Win.hWnd));
+
+    /*
+     * The guest announced formats. Forward to the window thread.
+     */
+    PostMessage(pCtx->Win.hWnd, SHCL_WIN_WM_REPORT_FORMATS,
+                0 /* wParam */, fFormats /* lParam */);
+
+
+    LogFlowFuncLeaveRC(VINF_SUCCESS);
+    return VINF_SUCCESS;
+}
+
+int ShClBackendReadData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx,
+                        SHCLFORMAT uFmt, void *pvData, uint32_t cbData, uint32_t *pcbActual)
+{
+    AssertPtrReturn(pClient,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pCmdCtx,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pvData,    VERR_INVALID_POINTER);
+    AssertPtrReturn(pcbActual, VERR_INVALID_POINTER);
+
+    RT_NOREF(pBackend, pCmdCtx);
+
+    AssertPtrReturn(pClient->State.pCtx, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("uFmt=%#x\n", uFmt));
+
+    HANDLE hClip = NULL;
+
+    const PSHCLWINCTX pWinCtx = &pClient->State.pCtx->Win;
+
+    /*
+     * The guest wants to read data in the given format.
+     */
+    int rc = SharedClipboardWinOpen(pWinCtx->hWnd);
+    if (RT_SUCCESS(rc))
+    {
+        if (uFmt & VBOX_SHCL_FMT_BITMAP)
+        {
+            LogFunc(("CF_DIB\n"));
+            hClip = GetClipboardData(CF_DIB);
+            if (hClip != NULL)
+            {
+                LPVOID lp = GlobalLock(hClip);
+                if (lp != NULL)
+                {
+                    rc = vboxClipboardSvcWinDataGet(VBOX_SHCL_FMT_BITMAP, lp, GlobalSize(hClip),
+                                                    pvData, cbData, pcbActual);
+                    GlobalUnlock(hClip);
+                }
+                else
+                {
+                    hClip = NULL;
+                }
+            }
+        }
+        else if (uFmt & VBOX_SHCL_FMT_UNICODETEXT)
+        {
+            LogFunc(("CF_UNICODETEXT\n"));
+            hClip = GetClipboardData(CF_UNICODETEXT);
+            if (hClip != NULL)
+            {
+                LPWSTR uniString = (LPWSTR)GlobalLock(hClip);
+                if (uniString != NULL)
+                {
+                    rc = vboxClipboardSvcWinDataGet(VBOX_SHCL_FMT_UNICODETEXT, uniString, (lstrlenW(uniString) + 1) * 2,
+                                                    pvData, cbData, pcbActual);
+                    GlobalUnlock(hClip);
+                }
+                else
+                {
+                    hClip = NULL;
+                }
+            }
+        }
+        else if (uFmt & VBOX_SHCL_FMT_HTML)
+        {
+            LogFunc(("SHCL_WIN_REGFMT_HTML\n"));
+            UINT uRegFmt = RegisterClipboardFormat(SHCL_WIN_REGFMT_HTML);
+            if (uRegFmt != 0)
+            {
+                hClip = GetClipboardData(uRegFmt);
+                if (hClip != NULL)
+                {
+                    LPVOID lp = GlobalLock(hClip);
+                    if (lp != NULL)
+                    {
+                        rc = vboxClipboardSvcWinDataGet(VBOX_SHCL_FMT_HTML, lp, GlobalSize(hClip),
+                                                        pvData, cbData, pcbActual);
+#ifdef LOG_ENABLED
+                        if (RT_SUCCESS(rc))
+                        {
+                            LogFlowFunc(("Raw HTML clipboard data from host:\n"));
+                            ShClDbgDumpHtml((char *)pvData, cbData);
+                        }
+#endif
+                        GlobalUnlock(hClip);
+                    }
+                    else
+                    {
+                        hClip = NULL;
+                    }
+                }
+            }
+        }
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+        else if (uFmt & VBOX_SHCL_FMT_URI_LIST)
+        {
+            AssertFailed(); /** @todo */
+        }
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+        SharedClipboardWinClose();
+    }
+
+    if (hClip == NULL) /* Empty data is not fatal. */
+    {
+        /* Reply with empty data. */
+        vboxClipboardSvcWinDataGet(0, NULL, 0, pvData, cbData, pcbActual);
+    }
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Error reading host clipboard data in format %#x from Windows, rc=%Rrc\n", uFmt, rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int ShClBackendWriteData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx,
+                         SHCLFORMAT uFormat, void *pvData, uint32_t cbData)
+{
+    RT_NOREF(pBackend, pClient, pCmdCtx, uFormat, pvData, cbData);
+
+    LogFlowFuncEnter();
+
+    /* Nothing to do here yet. */
+
+    LogFlowFuncLeave();
+    return VINF_SUCCESS;
+}
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+int ShClBackendTransferCreate(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer)
+{
+    RT_NOREF(pBackend, pClient, pTransfer);
+
+    LogFlowFuncEnter();
+
+    return VINF_SUCCESS;
+}
+
+int ShClBackendTransferDestroy(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer)
+{
+    RT_NOREF(pBackend);
+
+    LogFlowFuncEnter();
+
+    SharedClipboardWinTransferDestroy(&pClient->State.pCtx->Win, pTransfer);
+
+    return VINF_SUCCESS;
+}
+
+int ShClBackendTransferGetRoots(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer)
+{
+    RT_NOREF(pBackend);
+
+    LogFlowFuncEnter();
+
+    const PSHCLWINCTX pWinCtx = &pClient->State.pCtx->Win;
+
+    int rc = SharedClipboardWinGetRoots(pWinCtx, pTransfer);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-x11-stubs.cpp b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-x11-stubs.cpp
new file mode 100644
index 00000000..13499bf3
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-x11-stubs.cpp
@@ -0,0 +1,123 @@
+/* $Id: VBoxSharedClipboardSvc-x11-stubs.cpp $*/
+/** @file
+ * Shared Clipboard Service - Linux host, a stub version with no functionality for use on headless hosts.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+
+#include <iprt/alloc.h>
+#include <iprt/asm.h>        /* For atomic operations */
+#include <iprt/assert.h>
+#include <iprt/mem.h>
+#include <iprt/string.h>
+#include <iprt/thread.h>
+#include <iprt/process.h>
+#include <iprt/semaphore.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdint.h>
+
+#include "VBoxSharedClipboardSvc-internal.h"
+
+
+/*
+ * Initialise the host side of the shared clipboard - called by the hgcm layer.
+ */
+int ShClBackendInit(PSHCLBACKEND pBackend, VBOXHGCMSVCFNTABLE *pTable)
+{
+    RT_NOREF(pTable);
+    LogFlowFunc(("called, returning VINF_SUCCESS\n"));
+    return VINF_SUCCESS;
+}
+
+/*
+ * Terminate the host side of the shared clipboard - called by the hgcm layer.
+ */
+void ShClBackendDestroy(PSHCLBACKEND pBackend)
+{
+    RT_NOREF(pBackend);
+    LogFlowFunc(("called, returning\n"));
+}
+
+int ShClBackendConnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, bool fHeadless)
+{
+    RT_NOREF(pBackend, pClient, fHeadless);
+    LogFlowFunc(("called, returning VINF_SUCCESS\n"));
+    return VINF_SUCCESS;
+}
+
+/*
+ * Synchronise the contents of the host clipboard with the guest, called by the HGCM layer
+ * after a save and restore of the guest.
+ */
+int ShClBackendSync(PSHCLBACKEND pBackend, PSHCLCLIENT pClient)
+{
+    RT_NOREF(pBackend, pClient);
+    LogFlowFunc(("called, returning VINF_SUCCESS\n"));
+    return VINF_SUCCESS;
+}
+
+int ShClBackendDisconnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient)
+{
+    RT_NOREF(pBackend, pClient);
+    return VINF_SUCCESS;
+}
+
+/*
+ * The guest is taking possession of the shared clipboard.
+ * Called by the HGCM clipboard subsystem.
+ */
+int ShClBackendReportFormats(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, SHCLFORMATS fFormats)
+{
+    RT_NOREF(pBackend, pClient, fFormats);
+    return VINF_SUCCESS;
+}
+
+/*
+ * Called by the HGCM clipboard subsystem when the guest wants to read the host clipboard.
+ */
+int ShClBackendReadData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx,
+                        SHCLFORMAT uFormat, void *pvData, uint32_t cbData, uint32_t *pcbActual)
+{
+    RT_NOREF(pBackend, pClient, pCmdCtx, uFormat, pvData, cbData);
+
+    /* No data available. */
+    *pcbActual = 0;
+
+    return VINF_SUCCESS;
+}
+
+int ShClBackendWriteData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx,
+                         SHCLFORMAT uFormat, void *pvData, uint32_t cbData)
+{
+    RT_NOREF(pBackend, pClient, pCmdCtx, uFormat, pvData, cbData);
+    return VERR_NOT_IMPLEMENTED;
+}
+
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-x11.cpp b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-x11.cpp
new file mode 100644
index 00000000..e4eacb07
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc-x11.cpp
@@ -0,0 +1,566 @@
+/* $Id: VBoxSharedClipboardSvc-x11.cpp $ */
+/** @file
+ * Shared Clipboard Service - Linux host.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <iprt/assert.h>
+#include <iprt/critsect.h>
+#include <iprt/env.h>
+#include <iprt/mem.h>
+#include <iprt/semaphore.h>
+#include <iprt/string.h>
+#include <iprt/asm.h>
+
+#include <VBox/GuestHost/SharedClipboard.h>
+#include <VBox/GuestHost/SharedClipboard-x11.h>
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#include <iprt/errcore.h>
+
+#include "VBoxSharedClipboardSvc-internal.h"
+
+/* Number of currently extablished connections. */
+static volatile uint32_t g_cShClConnections;
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+/**
+ * Global context information used by the host glue for the X11 clipboard backend.
+ */
+struct SHCLCONTEXT
+{
+    /** This mutex is grabbed during any critical operations on the clipboard
+     * which might clash with others. */
+    RTCRITSECT           CritSect;
+    /** X11 context data. */
+    SHCLX11CTX           X11;
+    /** Pointer to the VBox host client data structure. */
+    PSHCLCLIENT          pClient;
+    /** We set this when we start shutting down as a hint not to post any new
+     * requests. */
+    bool                 fShuttingDown;
+};
+
+
+/*********************************************************************************************************************************
+*   Prototypes                                                                                                                   *
+*********************************************************************************************************************************/
+static DECLCALLBACK(int) shClReportFormatsCallback(PSHCLCONTEXT pCtx, uint32_t fFormats, void *pvUser);
+static DECLCALLBACK(int) shClSendDataToDestCallback(PSHCLCONTEXT pCtx, void *pv, uint32_t cb, void *pvUser);
+static DECLCALLBACK(int) shClRequestDataFromSourceCallback(PSHCLCONTEXT pCtx, SHCLFORMAT uFmt, void **ppv, uint32_t *pcb, void *pvUser);
+
+
+int ShClBackendInit(PSHCLBACKEND pBackend, VBOXHGCMSVCFNTABLE *pTable)
+{
+    RT_NOREF(pBackend);
+
+    LogFlowFuncEnter();
+
+    /* Override the connection limit. */
+    for (uintptr_t i = 0; i < RT_ELEMENTS(pTable->acMaxClients); i++)
+        pTable->acMaxClients[i] = RT_MIN(VBOX_SHARED_CLIPBOARD_X11_CONNECTIONS_MAX, pTable->acMaxClients[i]);
+
+    RT_ZERO(pBackend->Callbacks);
+    /* Use internal callbacks by default. */
+    pBackend->Callbacks.pfnReportFormats           = shClReportFormatsCallback;
+    pBackend->Callbacks.pfnOnRequestDataFromSource = shClRequestDataFromSourceCallback;
+    pBackend->Callbacks.pfnOnSendDataToDest        = shClSendDataToDestCallback;
+
+    return VINF_SUCCESS;
+}
+
+void ShClBackendDestroy(PSHCLBACKEND pBackend)
+{
+    RT_NOREF(pBackend);
+
+    LogFlowFuncEnter();
+}
+
+void ShClBackendSetCallbacks(PSHCLBACKEND pBackend, PSHCLCALLBACKS pCallbacks)
+{
+#define SET_FN_IF_NOT_NULL(a_Fn) \
+    if (pCallbacks->pfn##a_Fn) \
+        pBackend->Callbacks.pfn##a_Fn = pCallbacks->pfn##a_Fn;
+
+    SET_FN_IF_NOT_NULL(ReportFormats);
+    SET_FN_IF_NOT_NULL(OnClipboardRead);
+    SET_FN_IF_NOT_NULL(OnClipboardWrite);
+    SET_FN_IF_NOT_NULL(OnRequestDataFromSource);
+    SET_FN_IF_NOT_NULL(OnSendDataToDest);
+
+#undef SET_FN_IF_NOT_NULL
+}
+
+/**
+ * @note  On the host, we assume that some other application already owns
+ *        the clipboard and leave ownership to X11.
+ */
+int ShClBackendConnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, bool fHeadless)
+{
+    int rc;
+
+    /* Check if maximum allowed connections count has reached. */
+    if (ASMAtomicIncU32(&g_cShClConnections) > VBOX_SHARED_CLIPBOARD_X11_CONNECTIONS_MAX)
+    {
+        ASMAtomicDecU32(&g_cShClConnections);
+        LogRel(("Shared Clipboard: maximum amount for client connections reached\n"));
+        return VERR_OUT_OF_RESOURCES;
+    }
+
+    PSHCLCONTEXT pCtx = (PSHCLCONTEXT)RTMemAllocZ(sizeof(SHCLCONTEXT));
+    if (pCtx)
+    {
+        rc = RTCritSectInit(&pCtx->CritSect);
+        if (RT_SUCCESS(rc))
+        {
+            rc = ShClX11Init(&pCtx->X11, &pBackend->Callbacks, pCtx, fHeadless);
+            if (RT_SUCCESS(rc))
+            {
+                pClient->State.pCtx = pCtx;
+                pCtx->pClient = pClient;
+
+                rc = ShClX11ThreadStart(&pCtx->X11, true /* grab shared clipboard */);
+                if (RT_FAILURE(rc))
+                    ShClX11Destroy(&pCtx->X11);
+            }
+
+            if (RT_FAILURE(rc))
+                RTCritSectDelete(&pCtx->CritSect);
+        }
+
+        if (RT_FAILURE(rc))
+        {
+            pClient->State.pCtx = NULL;
+            RTMemFree(pCtx);
+        }
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    if (RT_FAILURE(rc))
+    {
+        /* Restore active connections count. */
+        ASMAtomicDecU32(&g_cShClConnections);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int ShClBackendSync(PSHCLBACKEND pBackend, PSHCLCLIENT pClient)
+{
+    RT_NOREF(pBackend);
+
+    LogFlowFuncEnter();
+
+    /* Tell the guest we have no data in case X11 is not available.  If
+     * there is data in the host clipboard it will automatically be sent to
+     * the guest when the clipboard starts up. */
+    if (ShClSvcIsBackendActive())
+        return ShClSvcHostReportFormats(pClient, VBOX_SHCL_FMT_NONE);
+    return VINF_SUCCESS;
+}
+
+/*
+ * Shut down the shared clipboard service and "disconnect" the guest.
+ * Note!  Host glue code
+ */
+int ShClBackendDisconnect(PSHCLBACKEND pBackend, PSHCLCLIENT pClient)
+{
+    RT_NOREF(pBackend);
+
+    LogFlowFuncEnter();
+
+    PSHCLCONTEXT pCtx = pClient->State.pCtx;
+    AssertPtr(pCtx);
+
+    /* Drop the reference to the client, in case it is still there.  This
+     * will cause any outstanding clipboard data requests from X11 to fail
+     * immediately. */
+    pCtx->fShuttingDown = true;
+
+    int rc = ShClX11ThreadStop(&pCtx->X11);
+    /** @todo handle this slightly more reasonably, or be really sure
+     *        it won't go wrong. */
+    AssertRC(rc);
+
+    ShClX11Destroy(&pCtx->X11);
+    RTCritSectDelete(&pCtx->CritSect);
+
+    RTMemFree(pCtx);
+
+    /* Decrease active connections count. */
+    ASMAtomicDecU32(&g_cShClConnections);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int ShClBackendReportFormats(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, SHCLFORMATS fFormats)
+{
+    RT_NOREF(pBackend);
+
+    int rc = ShClX11ReportFormatsToX11(&pClient->State.pCtx->X11, fFormats);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/** Structure describing a request for clipoard data from the guest. */
+struct CLIPREADCBREQ
+{
+    /** User-supplied data pointer, based on the request type. */
+    void                *pv;
+    /** The size (in bytes) of the the user-supplied pointer in pv. */
+    uint32_t             cb;
+    /** The actual size of the data written. */
+    uint32_t            *pcbActual;
+    /** The request's event ID. */
+    SHCLEVENTID          idEvent;
+};
+
+/**
+ * @note   We always fail or complete asynchronously.
+ * @note   On success allocates a CLIPREADCBREQ structure which must be
+ *         freed in ClipCompleteDataRequestFromX11 when it is called back from
+ *         the backend code.
+ */
+int ShClBackendReadData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx, SHCLFORMAT uFormat,
+                        void *pvData, uint32_t cbData, uint32_t *pcbActual)
+{
+    RT_NOREF(pBackend);
+
+    AssertPtrReturn(pClient,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pCmdCtx,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pvData,    VERR_INVALID_POINTER);
+    AssertPtrReturn(pcbActual, VERR_INVALID_POINTER);
+
+    RT_NOREF(pCmdCtx);
+
+    LogFlowFunc(("pClient=%p, uFormat=%#x, pv=%p, cb=%RU32, pcbActual=%p\n",
+                 pClient, uFormat, pvData, cbData, pcbActual));
+
+    int rc;
+
+    CLIPREADCBREQ *pReq = (CLIPREADCBREQ *)RTMemAllocZ(sizeof(CLIPREADCBREQ));
+    if (pReq)
+    {
+        PSHCLEVENT pEvent;
+        rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            pReq->pv        = pvData;
+            pReq->cb        = cbData;
+            pReq->pcbActual = pcbActual;
+            pReq->idEvent   = pEvent->idEvent;
+
+            /* Note: ShClX11ReadDataFromX11() will consume pReq on success. */
+            rc = ShClX11ReadDataFromX11(&pClient->State.pCtx->X11, uFormat, pReq);
+            if (RT_SUCCESS(rc))
+            {
+                PSHCLEVENTPAYLOAD pPayload;
+                rc = ShClEventWait(pEvent, 30 * 1000, &pPayload);
+                if (RT_SUCCESS(rc))
+                {
+                    if (pPayload)
+                    {
+                        memcpy(pvData, pPayload->pvData, RT_MIN(cbData, pPayload->cbData));
+
+                        *pcbActual = (uint32_t)pPayload->cbData;
+
+                        ShClPayloadFree(pPayload);
+                    }
+                    else /* No payload given; could happen on invalid / not-expected formats. */
+                        *pcbActual = 0;
+                }
+            }
+
+            ShClEventRelease(pEvent);
+        }
+
+        if (RT_FAILURE(rc))
+            RTMemFree(pReq);
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Error reading host clipboard data from X11, rc=%Rrc\n", rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+int ShClBackendWriteData(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx, SHCLFORMAT uFormat, void *pvData, uint32_t cbData)
+{
+    RT_NOREF(pBackend, pClient, pCmdCtx, uFormat, pvData, cbData);
+
+    LogFlowFuncEnter();
+
+    /* Nothing to do here yet. */
+
+    LogFlowFuncLeave();
+    return VINF_SUCCESS;
+}
+
+/** @copydoc SHCLCALLBACKS::pfnReportFormats */
+static DECLCALLBACK(int) shClReportFormatsCallback(PSHCLCONTEXT pCtx, uint32_t fFormats, void *pvUser)
+{
+    RT_NOREF(pvUser);
+
+    LogFlowFunc(("pCtx=%p, fFormats=%#x\n", pCtx, fFormats));
+
+    int rc = VINF_SUCCESS;
+    PSHCLCLIENT pClient = pCtx->pClient;
+    AssertPtr(pClient);
+
+    rc = RTCritSectEnter(&pClient->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        if (ShClSvcIsBackendActive())
+        {
+            /** @todo r=bird: BUGBUG: Revisit this   */
+            if (fFormats != VBOX_SHCL_FMT_NONE) /* No formats to report? */
+            {
+                rc = ShClSvcHostReportFormats(pCtx->pClient, fFormats);
+            }
+        }
+
+        RTCritSectLeave(&pClient->CritSect);
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/** @copydoc SHCLCALLBACKS::pfnOnSendDataToDest */
+static DECLCALLBACK(int) shClSendDataToDestCallback(PSHCLCONTEXT pCtx, void *pv, uint32_t cb, void *pvUser)
+{
+    AssertPtrReturn(pCtx,   VERR_INVALID_POINTER);
+    AssertPtrReturn(pvUser, VERR_INVALID_POINTER);
+
+    PSHCLX11READDATAREQ pData = (PSHCLX11READDATAREQ)pvUser;
+    CLIPREADCBREQ      *pReq  = pData->pReq;
+
+    LogFlowFunc(("rcCompletion=%Rrc, pReq=%p, pv=%p, cb=%RU32, idEvent=%RU32\n",
+                 pData->rcCompletion, pReq, pv, cb, pReq->idEvent));
+
+    if (pReq->idEvent != NIL_SHCLEVENTID)
+    {
+        int rc2;
+
+        PSHCLEVENTPAYLOAD pPayload = NULL;
+        if (   RT_SUCCESS(pData->rcCompletion)
+            && pv
+            && cb)
+        {
+            rc2 = ShClPayloadAlloc(pReq->idEvent, pv, cb, &pPayload);
+            AssertRC(rc2);
+        }
+
+        rc2 = RTCritSectEnter(&pCtx->pClient->CritSect);
+        if (RT_SUCCESS(rc2))
+        {
+            const PSHCLEVENT pEvent = ShClEventSourceGetFromId(&pCtx->pClient->EventSrc, pReq->idEvent);
+            if (pEvent)
+                rc2 = ShClEventSignal(pEvent, pPayload);
+
+            RTCritSectLeave(&pCtx->pClient->CritSect);
+
+            if (RT_SUCCESS(rc2))
+                pPayload = NULL;
+        }
+
+        if (pPayload)
+            ShClPayloadFree(pPayload);
+    }
+
+    if (pReq)
+        RTMemFree(pReq);
+
+    LogRel2(("Shared Clipboard: Reading X11 clipboard data from host completed with %Rrc\n", pData->rcCompletion));
+
+    return VINF_SUCCESS;
+}
+
+/** @copydoc SHCLCALLBACKS::pfnOnRequestDataFromSource */
+static DECLCALLBACK(int) shClRequestDataFromSourceCallback(PSHCLCONTEXT pCtx, SHCLFORMAT uFmt, void **ppv, uint32_t *pcb, void *pvUser)
+{
+    RT_NOREF(pvUser);
+
+    LogFlowFunc(("pCtx=%p, uFmt=0x%x\n", pCtx, uFmt));
+
+    if (pCtx->fShuttingDown)
+    {
+        /* The shared clipboard is disconnecting. */
+        LogRel(("Shared Clipboard: Host requested guest clipboard data after guest had disconnected\n"));
+        return VERR_WRONG_ORDER;
+    }
+
+    PSHCLCLIENT pClient = pCtx->pClient;
+    AssertPtr(pClient);
+
+    RTCritSectEnter(&pClient->CritSect);
+
+    int rc = VINF_SUCCESS;
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    /*
+     * Note: We always return a generic URI list here.
+     *       As we don't know which Atom target format was requested by the caller, the X11 clipboard codes needs
+     *       to decide & transform the list into the actual clipboard Atom target format the caller wanted.
+     */
+    if (uFmt == VBOX_SHCL_FMT_URI_LIST)
+    {
+        PSHCLTRANSFER pTransfer;
+        rc = shClSvcTransferStart(pCtx->pClient,
+                                  SHCLTRANSFERDIR_FROM_REMOTE, SHCLSOURCE_REMOTE,
+                                  &pTransfer);
+        if (RT_SUCCESS(rc))
+        {
+
+        }
+        else
+            LogRel(("Shared Clipboard: Initializing read transfer from guest failed with %Rrc\n", rc));
+
+        *ppv = NULL;
+        *pcb = 0;
+
+        rc = VERR_NO_DATA;
+    }
+#endif
+
+    if (RT_SUCCESS(rc))
+    {
+        /* Request data from the guest. */
+        PSHCLEVENT pEvent;
+        rc = ShClSvcGuestDataRequest(pCtx->pClient, uFmt, &pEvent);
+        if (RT_SUCCESS(rc))
+        {
+            RTCritSectLeave(&pClient->CritSect);
+
+            PSHCLEVENTPAYLOAD pPayload;
+            rc = ShClEventWait(pEvent, 30 * 1000, &pPayload);
+            if (RT_SUCCESS(rc))
+            {
+                if (   !pPayload
+                    || !pPayload->cbData)
+                {
+                    rc = VERR_NO_DATA;
+                }
+                else
+                {
+                    *ppv = pPayload->pvData;
+                    *pcb = pPayload->cbData;
+                }
+            }
+
+            RTCritSectEnter(&pClient->CritSect);
+
+            ShClEventRelease(pEvent);
+        }
+    }
+
+    RTCritSectLeave(&pClient->CritSect);
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Requesting data in format %#x for X11 host failed with %Rrc\n", uFmt, rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+
+int ShClBackendTransferCreate(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer)
+{
+    RT_NOREF(pBackend);
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS_HTTP
+    return ShClHttpTransferRegister(&pClient->State.pCtx->X11.HttpCtx, pTransfer);
+#else
+    RT_NOREF(pClient, pTransfer);
+#endif
+    return VERR_NOT_IMPLEMENTED;
+}
+
+int ShClBackendTransferDestroy(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer)
+{
+    RT_NOREF(pBackend);
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS_HTTP
+    return ShClHttpTransferUnregister(&pClient->State.pCtx->X11.HttpCtx, pTransfer);
+#else
+    RT_NOREF(pClient, pTransfer);
+#endif
+
+    return VINF_SUCCESS;
+}
+
+int ShClBackendTransferGetRoots(PSHCLBACKEND pBackend, PSHCLCLIENT pClient, PSHCLTRANSFER pTransfer)
+{
+    RT_NOREF(pBackend);
+
+    LogFlowFuncEnter();
+
+    PSHCLEVENT pEvent;
+    int rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+    if (RT_SUCCESS(rc))
+    {
+        CLIPREADCBREQ *pReq = (CLIPREADCBREQ *)RTMemAllocZ(sizeof(CLIPREADCBREQ));
+        if (pReq)
+        {
+            pReq->idEvent = pEvent->idEvent;
+
+            rc = ShClX11ReadDataFromX11(&pClient->State.pCtx->X11, VBOX_SHCL_FMT_URI_LIST, pReq);
+            if (RT_SUCCESS(rc))
+            {
+                /* X supplies the data asynchronously, so we need to wait for data to arrive first. */
+                PSHCLEVENTPAYLOAD pPayload;
+                rc = ShClEventWait(pEvent, 30 * 1000, &pPayload);
+                if (RT_SUCCESS(rc))
+                {
+                    rc = ShClTransferRootsSet(pTransfer,
+                                              (char *)pPayload->pvData, pPayload->cbData + 1 /* Include termination */);
+                }
+            }
+        }
+        else
+            rc = VERR_NO_MEMORY;
+
+        ShClEventRelease(pEvent);
+    }
+    else
+        rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc.cpp b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc.cpp
new file mode 100644
index 00000000..571e47e8
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc.cpp
@@ -0,0 +1,2834 @@
+/* $Id: VBoxSharedClipboardSvc.cpp $ */
+/** @file
+ * Shared Clipboard Service - Host service entry points.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/** @page pg_hostclip       The Shared Clipboard Host Service
+ *
+ * The shared clipboard host service is the host half of the clibpoard proxying
+ * between the host and the guest.  The guest parts live in VBoxClient, VBoxTray
+ * and VBoxService depending on the OS, with code shared between host and guest
+ * under src/VBox/GuestHost/SharedClipboard/.
+ *
+ * The service is split into a platform-independent core and platform-specific
+ * backends.  The service defines two communication protocols - one to
+ * communicate with the clipboard service running on the guest, and one to
+ * communicate with the backend.  These will be described in a very skeletal
+ * fashion here.
+ *
+ * r=bird: The "two communication protocols" does not seems to be factual, there
+ * is only one protocol, the first one mentioned.  It cannot be backend
+ * specific, because the guest/host protocol is platform and backend agnostic in
+ * nature.  You may call it versions, but I take a great dislike to "protocol
+ * versions" here, as you've just extended the existing protocol with a feature
+ * that allows to transfer files and directories too.  See @bugref{9437#c39}.
+ *
+ *
+ * @section sec_hostclip_guest_proto  The guest communication protocol
+ *
+ * The guest clipboard service communicates with the host service over HGCM
+ * (the host is a HGCM service).  HGCM is connection based, so the guest side
+ * has to connect before anything else can be done.  (Windows hosts currently
+ * only support one simultaneous connection.)  Once it has connected, it can
+ * send messages to the host services, some of which will receive immediate
+ * replies from the host, others which will block till a reply becomes
+ * available.  The latter is because HGCM does't allow the host to initiate
+ * communication, it must be guest triggered.  The HGCM service is single
+ * threaded, so it doesn't matter if the guest tries to send lots of requests in
+ * parallel, the service will process them one at the time.
+ *
+ * There are currently four messages defined.  The first is
+ * VBOX_SHCL_GUEST_FN_MSG_GET / VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, which waits
+ * for a message from the host.  If a host message is sent while the guest is
+ * not waiting, it will be queued until the guest requests it.  The host code
+ * only supports a single simultaneous GET call from one client guest.
+ *
+ * The second guest message is VBOX_SHCL_GUEST_FN_REPORT_FORMATS, which tells
+ * the host that the guest has new clipboard data available.  The third is
+ * VBOX_SHCL_GUEST_FN_DATA_READ, which asks the host to send its clipboard data
+ * and waits until it arrives.  The host supports at most one simultaneous
+ * VBOX_SHCL_GUEST_FN_DATA_READ call from a guest - if a second call is made
+ * before the first has returned, the first will be aborted.
+ *
+ * The last guest message is VBOX_SHCL_GUEST_FN_DATA_WRITE, which is used to
+ * send the contents of the guest clipboard to the host.  This call should be
+ * used after the host has requested data from the guest.
+ *
+ *
+ * @section sec_hostclip_backend_proto  The communication protocol with the
+ *                                      platform-specific backend
+ *
+ * The initial protocol implementation (called protocol v0) was very simple,
+ * and could only handle simple data (like copied text and so on). It also
+ * was limited to two (2) fixed parameters at all times.
+ *
+ * Since VBox 6.1 a newer protocol (v1) has been established to also support
+ * file transfers. This protocol uses a (per-client) message queue instead
+ * (see VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT vs. VBOX_SHCL_GUEST_FN_GET_HOST_MSG).
+ *
+ * To distinguish the old (legacy) or new(er) protocol, the VBOX_SHCL_GUEST_FN_CONNECT
+ * message has been introduced. If an older guest does not send this message,
+ * an appropriate translation will be done to serve older Guest Additions (< 6.1).
+ *
+ * The protocol also support out-of-order messages by using so-called "context IDs",
+ * which are generated by the host. A context ID consists of a so-called "source event ID"
+ * and a so-called "event ID". Each HGCM client has an own, random, source event ID and
+ * generates non-deterministic event IDs so that the guest side does not known what
+ * comes next; the guest side has to reply with the same conext ID which was sent by
+ * the host request.
+ *
+ * Also see the protocol changelog at VBoxShClSvc.h.
+ *
+ *
+ * @section sec_uri_intro               Transferring files
+ *
+ * Since VBox x.x.x transferring files via Shared Clipboard is supported.
+ * See the VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS define for supported / enabled
+ * platforms. This is called "Shared Clipboard transfers".
+ *
+ * Copying files / directories from guest A to guest B requires the host
+ * service to act as a proxy and cache, as we don't allow direct VM-to-VM
+ * communication. Copying from / to the host also is taken into account.
+ *
+ * At the moment a transfer is a all-or-nothing operation, e.g. it either
+ * completes or fails completely. There might be callbacks in the future
+ * to e.g. skip failing entries.
+ *
+ * Known limitations:
+ *
+ * - Support for VRDE (VRDP) is not implemented yet (see #9498).
+ * - Unicode support on Windows hosts / guests is not enabled (yet).
+ * - Symbolic links / Windows junctions are not allowed.
+ * - Windows alternate data streams (ADS) are not allowed.
+ * - No support for ACLs yet.
+ * - No (maybe never) support for NT4.
+
+ * @section sec_transfer_structure        Transfer handling structure
+ *
+ * All structures / classes are designed for running on both, on the guest
+ * (via VBoxTray / VBoxClient) or on the host (host service) to avoid code
+ * duplication where applicable.
+ *
+ * Per HGCM client there is a so-called "transfer context", which in turn can
+ * have one or mulitple so-called "Shared Clipboard transfer" objects. At the
+ * moment we only support on concurrent Shared Clipboard transfer per transfer
+ * context. It's being used for reading from a source or writing to destination,
+ * depening on its direction. An Shared Clipboard transfer can have optional
+ * callbacks which might be needed by various implementations. Also, transfers
+ * optionally can run in an asynchronous thread to prevent blocking the UI while
+ * running.
+ *
+ * @section sec_transfer_providers        Transfer providers
+ *
+ * For certain implementations (for example on Windows guests / hosts, using
+ * IDataObject and IStream objects) a more flexible approach reqarding reading /
+ * writing is needed. For this so-called transfer providers abstract the way of how
+ * data is being read / written in the current context (host / guest), while
+ * the rest of the code stays the same.
+ *
+ * @section sec_transfer_protocol         Transfer protocol
+ *
+ * The host service issues commands which the guest has to respond with an own
+ * message to. The protocol itself is designed so that it has primitives to list
+ * directories and open/close/read/write file system objects.
+ *
+ * Note that this is different from the DnD approach, as Shared Clipboard transfers
+ * need to be deeper integrated within the host / guest OS (i.e. for progress UI),
+ * and this might require non-monolithic / random access APIs to achieve.
+ *
+ * As there can be multiple file system objects (fs objects) selected for transfer,
+ * a transfer can be queried for its root entries, which then contains the top-level
+ * elements. Based on these elements, (a) (recursive) listing(s) can be performed
+ * to (partially) walk down into directories and query fs object information. The
+ * provider provides appropriate interface for this, even if not all implementations
+ * might need this mechanism.
+ *
+ * An Shared Clipboard transfer has three stages:
+ *  - 1. Announcement: An Shared Clipboard transfer-compatible format (currently only one format available)
+ *          has been announced, the destination side creates a transfer object, which then,
+ *          depending on the actual implementation, can be used to tell the OS that
+ *          there is transfer (file) data available.
+ *          At this point this just acts as a (kind-of) promise to the OS that we
+ *          can provide (file) data at some later point in time.
+ *
+ *  - 2. Initialization: As soon as the OS requests the (file) data, mostly triggered
+ *          by the user starting a paste operation (CTRL + V), the transfer get initialized
+ *          on the destination side, which in turn lets the source know that a transfer
+ *          is going to happen.
+ *
+ *  - 3. Transfer: At this stage the actual transfer from source to the destination takes
+ *          place. How the actual transfer is structurized (e.g. which files / directories
+ *          are transferred in which order) depends on the destination implementation. This
+ *          is necessary in order to fulfill requirements on the destination side with
+ *          regards to ETA calculation or other dependencies.
+ *          Both sides can abort or cancel the transfer at any time.
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <VBox/log.h>
+#include <VBox/vmm/vmmr3vtable.h> /* must be included before hgcmsvc.h */
+
+#include <VBox/GuestHost/clipboard-helper.h>
+#include <VBox/HostServices/Service.h>
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#include <VBox/HostServices/VBoxClipboardExt.h>
+
+#include <VBox/AssertGuest.h>
+#include <VBox/err.h>
+#include <VBox/VMMDev.h>
+#include <VBox/vmm/ssm.h>
+
+#include <iprt/mem.h>
+#include <iprt/string.h>
+#include <iprt/assert.h>
+#include <iprt/critsect.h>
+#include <iprt/rand.h>
+
+#include "VBoxSharedClipboardSvc-internal.h"
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+# include "VBoxSharedClipboardSvc-transfers.h"
+#endif
+
+using namespace HGCM;
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+/** @name The saved state versions for the shared clipboard service.
+ *
+ * @note We set bit 31 because prior to version 0x80000002 there would be a
+ *       structure size rather than a version number.  Setting bit 31 dispells
+ *       any possible ambiguity.
+ *
+ * @{ */
+/** The current saved state version. */
+#define VBOX_SHCL_SAVED_STATE_VER_CURRENT   VBOX_SHCL_SAVED_STATE_LEGACY_CID
+/** Adds the legacy context ID list. */
+#define VBOX_SHCL_SAVED_STATE_LEGACY_CID    UINT32_C(0x80000005)
+/** Adds the client's POD state and client state flags.
+ * @since 6.1 RC1 */
+#define VBOX_SHCL_SAVED_STATE_VER_6_1RC1    UINT32_C(0x80000004)
+/** First attempt saving state during @bugref{9437} development.
+ * @since 6.1 BETA 2   */
+#define VBOX_SHCL_SAVED_STATE_VER_6_1B2     UINT32_C(0x80000003)
+/** First structured version.
+ * @since 3.1 / r53668 */
+#define VBOX_SHCL_SAVED_STATE_VER_3_1       UINT32_C(0x80000002)
+/** This was just a state memory dump, including pointers and everything.
+ * @note This is not supported any more. Sorry.  */
+#define VBOX_SHCL_SAVED_STATE_VER_NOT_SUPP  (ARCH_BITS == 64 ? UINT32_C(72) : UINT32_C(48))
+/** @} */
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+/** The backend instance data.
+ *  Only one backend at a time is supported currently. */
+SHCLBACKEND         g_ShClBackend;
+PVBOXHGCMSVCHELPERS g_pHelpers;
+
+static RTCRITSECT g_CritSect;               /** @todo r=andy Put this into some instance struct, avoid globals. */
+/** Global Shared Clipboard mode. */
+static uint32_t g_uMode  = VBOX_SHCL_MODE_OFF;
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+/** Global Shared Clipboard (file) transfer mode. */
+uint32_t g_fTransferMode = VBOX_SHCL_TRANSFER_MODE_DISABLED;
+#endif
+
+/** Is the clipboard running in headless mode? */
+static bool g_fHeadless = false;
+
+/** Holds the service extension state. */
+SHCLEXTSTATE g_ExtState = { 0 };
+
+/** Global map of all connected clients. */
+ClipboardClientMap g_mapClients;
+
+/** Global list of all clients which are queued up (deferred return) and ready
+ *  to process new commands. The key is the (unique) client ID. */
+ClipboardClientQueue g_listClientsDeferred;
+
+/** Host feature mask (VBOX_SHCL_HF_0_XXX) for VBOX_SHCL_GUEST_FN_REPORT_FEATURES
+ * and VBOX_SHCL_GUEST_FN_QUERY_FEATURES. */
+static uint64_t const g_fHostFeatures0 = VBOX_SHCL_HF_0_CONTEXT_ID
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+                                       | VBOX_SHCL_HF_0_TRANSFERS
+#endif
+                                       ;
+
+
+/**
+ * Returns the current Shared Clipboard service mode.
+ *
+ * @returns Current Shared Clipboard service mode.
+ */
+uint32_t ShClSvcGetMode(void)
+{
+    return g_uMode;
+}
+
+/**
+ * Returns the Shared Clipboard backend in use.
+ *
+ * @returns Pointer to backend instance.
+ */
+PSHCLBACKEND ShClSvcGetBackend(void)
+{
+    return &g_ShClBackend;
+}
+
+/**
+ * Getter for headless setting. Also needed by testcase.
+ *
+ * @returns Whether service currently running in headless mode or not.
+ */
+bool ShClSvcGetHeadless(void)
+{
+    return g_fHeadless;
+}
+
+static int shClSvcModeSet(uint32_t uMode)
+{
+    int rc = VERR_NOT_SUPPORTED;
+
+    switch (uMode)
+    {
+        case VBOX_SHCL_MODE_OFF:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_MODE_HOST_TO_GUEST:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_MODE_GUEST_TO_HOST:
+            RT_FALL_THROUGH();
+        case VBOX_SHCL_MODE_BIDIRECTIONAL:
+        {
+            g_uMode = uMode;
+
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        default:
+        {
+            g_uMode = VBOX_SHCL_MODE_OFF;
+            break;
+        }
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Takes the global Shared Clipboard service lock.
+ *
+ * @returns \c true if locking was successful, or \c false if not.
+ */
+bool ShClSvcLock(void)
+{
+    return RT_SUCCESS(RTCritSectEnter(&g_CritSect));
+}
+
+/**
+ * Unlocks the formerly locked global Shared Clipboard service lock.
+ */
+void ShClSvcUnlock(void)
+{
+    int rc2 = RTCritSectLeave(&g_CritSect);
+    AssertRC(rc2);
+}
+
+/**
+ * Resets a client's state message queue.
+ *
+ * @param   pClient             Pointer to the client data structure to reset message queue for.
+ * @note    Caller enters pClient->CritSect.
+ */
+void shClSvcMsgQueueReset(PSHCLCLIENT pClient)
+{
+    Assert(RTCritSectIsOwner(&pClient->CritSect));
+    LogFlowFuncEnter();
+
+    while (!RTListIsEmpty(&pClient->MsgQueue))
+    {
+        PSHCLCLIENTMSG pMsg = RTListRemoveFirst(&pClient->MsgQueue, SHCLCLIENTMSG, ListEntry);
+        shClSvcMsgFree(pClient, pMsg);
+    }
+    pClient->cMsgAllocated = 0;
+
+    while (!RTListIsEmpty(&pClient->Legacy.lstCID))
+    {
+        PSHCLCLIENTLEGACYCID pCID = RTListRemoveFirst(&pClient->Legacy.lstCID, SHCLCLIENTLEGACYCID, Node);
+        RTMemFree(pCID);
+    }
+    pClient->Legacy.cCID = 0;
+}
+
+/**
+ * Allocates a new clipboard message.
+ *
+ * @returns Allocated clipboard message, or NULL on failure.
+ * @param   pClient     The client which is target of this message.
+ * @param   idMsg       The message ID (VBOX_SHCL_HOST_MSG_XXX) to use
+ * @param   cParms      The number of parameters the message takes.
+ */
+PSHCLCLIENTMSG shClSvcMsgAlloc(PSHCLCLIENT pClient, uint32_t idMsg, uint32_t cParms)
+{
+    RT_NOREF(pClient);
+    PSHCLCLIENTMSG pMsg = (PSHCLCLIENTMSG)RTMemAllocZ(RT_UOFFSETOF_DYN(SHCLCLIENTMSG, aParms[cParms]));
+    if (pMsg)
+    {
+        uint32_t cAllocated = ASMAtomicIncU32(&pClient->cMsgAllocated);
+        if (cAllocated <= 4096)
+        {
+            RTListInit(&pMsg->ListEntry);
+            pMsg->cParms = cParms;
+            pMsg->idMsg  = idMsg;
+            return pMsg;
+        }
+        AssertMsgFailed(("Too many messages allocated for client %u! (%u)\n", pClient->State.uClientID, cAllocated));
+        ASMAtomicDecU32(&pClient->cMsgAllocated);
+        RTMemFree(pMsg);
+    }
+    return NULL;
+}
+
+/**
+ * Frees a formerly allocated clipboard message.
+ *
+ * @param   pClient     The client which was the target of this message.
+ * @param   pMsg        Clipboard message to free.
+ */
+void shClSvcMsgFree(PSHCLCLIENT pClient, PSHCLCLIENTMSG pMsg)
+{
+    RT_NOREF(pClient);
+    /** @todo r=bird: Do accounting. */
+    if (pMsg)
+    {
+        pMsg->idMsg = UINT32_C(0xdeadface);
+        RTMemFree(pMsg);
+
+        uint32_t cAllocated = ASMAtomicDecU32(&pClient->cMsgAllocated);
+        Assert(cAllocated < UINT32_MAX / 2);
+        RT_NOREF(cAllocated);
+    }
+}
+
+/**
+ * Sets the VBOX_SHCL_GUEST_FN_MSG_PEEK_WAIT and VBOX_SHCL_GUEST_FN_MSG_PEEK_NOWAIT
+ * return parameters.
+ *
+ * @param   pMsg        Message to set return parameters to.
+ * @param   paDstParms  The peek parameter vector.
+ * @param   cDstParms   The number of peek parameters (at least two).
+ * @remarks ASSUMES the parameters has been cleared by clientMsgPeek.
+ */
+static void shClSvcMsgSetPeekReturn(PSHCLCLIENTMSG pMsg, PVBOXHGCMSVCPARM paDstParms, uint32_t cDstParms)
+{
+    Assert(cDstParms >= 2);
+    if (paDstParms[0].type == VBOX_HGCM_SVC_PARM_32BIT)
+        paDstParms[0].u.uint32 = pMsg->idMsg;
+    else
+        paDstParms[0].u.uint64 = pMsg->idMsg;
+    paDstParms[1].u.uint32 = pMsg->cParms;
+
+    uint32_t i = RT_MIN(cDstParms, pMsg->cParms + 2);
+    while (i-- > 2)
+        switch (pMsg->aParms[i - 2].type)
+        {
+            case VBOX_HGCM_SVC_PARM_32BIT: paDstParms[i].u.uint32 = ~(uint32_t)sizeof(uint32_t); break;
+            case VBOX_HGCM_SVC_PARM_64BIT: paDstParms[i].u.uint32 = ~(uint32_t)sizeof(uint64_t); break;
+            case VBOX_HGCM_SVC_PARM_PTR:   paDstParms[i].u.uint32 = pMsg->aParms[i - 2].u.pointer.size; break;
+        }
+}
+
+/**
+ * Sets the VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT return parameters.
+ *
+ * @returns VBox status code.
+ * @param   pMsg        The message which parameters to return to the guest.
+ * @param   paDstParms  The peek parameter vector.
+ * @param   cDstParms   The number of peek parameters should be exactly two
+ */
+static int shClSvcMsgSetOldWaitReturn(PSHCLCLIENTMSG pMsg, PVBOXHGCMSVCPARM paDstParms, uint32_t cDstParms)
+{
+    /*
+     * Assert sanity.
+     */
+    AssertPtr(pMsg);
+    AssertPtrReturn(paDstParms, VERR_INVALID_POINTER);
+    AssertReturn(cDstParms >= 2, VERR_INVALID_PARAMETER);
+
+    Assert(pMsg->cParms == 2);
+    Assert(pMsg->aParms[0].u.uint32 == pMsg->idMsg);
+    switch (pMsg->idMsg)
+    {
+        case VBOX_SHCL_HOST_MSG_READ_DATA:
+        case VBOX_SHCL_HOST_MSG_FORMATS_REPORT:
+            break;
+        default:
+            AssertFailed();
+    }
+
+    /*
+     * Set the parameters.
+     */
+    if (pMsg->cParms > 0)
+        paDstParms[0] = pMsg->aParms[0];
+    if (pMsg->cParms > 1)
+        paDstParms[1] = pMsg->aParms[1];
+    return VINF_SUCCESS;
+}
+
+/**
+ * Adds a new message to a client'S message queue.
+ *
+ * @param   pClient             Pointer to the client data structure to add new message to.
+ * @param   pMsg                Pointer to message to add. The queue then owns the pointer.
+ * @param   fAppend             Whether to append or prepend the message to the queue.
+ *
+ * @note    Caller must enter critical section.
+ */
+void shClSvcMsgAdd(PSHCLCLIENT pClient, PSHCLCLIENTMSG pMsg, bool fAppend)
+{
+    Assert(RTCritSectIsOwner(&pClient->CritSect));
+    AssertPtr(pMsg);
+
+    LogFlowFunc(("idMsg=%s (%RU32) cParms=%RU32 fAppend=%RTbool\n",
+                 ShClHostMsgToStr(pMsg->idMsg), pMsg->idMsg, pMsg->cParms, fAppend));
+
+    if (fAppend)
+        RTListAppend(&pClient->MsgQueue, &pMsg->ListEntry);
+    else
+        RTListPrepend(&pClient->MsgQueue, &pMsg->ListEntry);
+}
+
+
+/**
+ * Appends a message to the client's queue and wake it up.
+ *
+ * @returns VBox status code, though the message is consumed regardless of what
+ *          is returned.
+ * @param   pClient             The client to queue the message on.
+ * @param   pMsg                The message to queue.  Ownership is always
+ *                              transfered to the queue.
+ *
+ * @note    Caller must enter critical section.
+ */
+int shClSvcMsgAddAndWakeupClient(PSHCLCLIENT pClient, PSHCLCLIENTMSG pMsg)
+{
+    Assert(RTCritSectIsOwner(&pClient->CritSect));
+    AssertPtr(pMsg);
+    AssertPtr(pClient);
+    LogFlowFunc(("idMsg=%s (%u) cParms=%u\n", ShClHostMsgToStr(pMsg->idMsg), pMsg->idMsg, pMsg->cParms));
+
+    RTListAppend(&pClient->MsgQueue, &pMsg->ListEntry);
+    return shClSvcClientWakeup(pClient);
+}
+
+/**
+ * Initializes a Shared Clipboard client.
+ *
+ * @param   pClient             Client to initialize.
+ * @param   uClientID           HGCM client ID to assign client to.
+ */
+int shClSvcClientInit(PSHCLCLIENT pClient, uint32_t uClientID)
+{
+    AssertPtrReturn(pClient, VERR_INVALID_POINTER);
+
+    /* Assign the client ID. */
+    pClient->State.uClientID = uClientID;
+
+    RTListInit(&pClient->MsgQueue);
+    pClient->cMsgAllocated = 0;
+
+    RTListInit(&pClient->Legacy.lstCID);
+    pClient->Legacy.cCID = 0;
+
+    LogFlowFunc(("[Client %RU32]\n", pClient->State.uClientID));
+
+    int rc = RTCritSectInit(&pClient->CritSect);
+    if (RT_SUCCESS(rc))
+    {
+        /* Create the client's own event source. */
+        rc = ShClEventSourceCreate(&pClient->EventSrc, 0 /* ID, ignored */);
+        if (RT_SUCCESS(rc))
+        {
+            LogFlowFunc(("[Client %RU32] Using event source %RU32\n", uClientID, pClient->EventSrc.uID));
+
+            /* Reset the client state. */
+            shclSvcClientStateReset(&pClient->State);
+
+            /* (Re-)initialize the client state. */
+            rc = shClSvcClientStateInit(&pClient->State, uClientID);
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+            if (RT_SUCCESS(rc))
+                rc = ShClTransferCtxInit(&pClient->Transfers.Ctx);
+#endif
+        }
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Destroys a Shared Clipboard client.
+ *
+ * @param   pClient             Client to destroy.
+ */
+void shClSvcClientDestroy(PSHCLCLIENT pClient)
+{
+    AssertPtrReturnVoid(pClient);
+
+    LogFlowFunc(("[Client %RU32]\n", pClient->State.uClientID));
+
+    /* Make sure to send a quit message to the guest so that it can terminate gracefully. */
+    RTCritSectEnter(&pClient->CritSect);
+    if (pClient->Pending.uType)
+    {
+        if (pClient->Pending.cParms > 1)
+            HGCMSvcSetU32(&pClient->Pending.paParms[0], VBOX_SHCL_HOST_MSG_QUIT);
+        if (pClient->Pending.cParms > 2)
+            HGCMSvcSetU32(&pClient->Pending.paParms[1], 0);
+        g_pHelpers->pfnCallComplete(pClient->Pending.hHandle, VINF_SUCCESS);
+        pClient->Pending.uType   = 0;
+        pClient->Pending.cParms  = 0;
+        pClient->Pending.hHandle = NULL;
+        pClient->Pending.paParms = NULL;
+    }
+    RTCritSectLeave(&pClient->CritSect);
+
+    ShClEventSourceDestroy(&pClient->EventSrc);
+
+    shClSvcClientStateDestroy(&pClient->State);
+
+    PSHCLCLIENTLEGACYCID pCidIter, pCidIterNext;
+    RTListForEachSafe(&pClient->Legacy.lstCID, pCidIter, pCidIterNext, SHCLCLIENTLEGACYCID, Node)
+    {
+        RTMemFree(pCidIter);
+    }
+
+    int rc2 = RTCritSectDelete(&pClient->CritSect);
+    AssertRC(rc2);
+
+    ClipboardClientMap::iterator itClient = g_mapClients.find(pClient->State.uClientID);
+    if (itClient != g_mapClients.end())
+        g_mapClients.erase(itClient);
+    else
+        AssertFailed();
+
+    LogFlowFuncLeave();
+}
+
+void shClSvcClientLock(PSHCLCLIENT pClient)
+{
+    int rc2 = RTCritSectEnter(&pClient->CritSect);
+    AssertRC(rc2);
+}
+
+void shClSvcClientUnlock(PSHCLCLIENT pClient)
+{
+    int rc2 = RTCritSectLeave(&pClient->CritSect);
+    AssertRC(rc2);
+}
+
+/**
+ * Resets a Shared Clipboard client.
+ *
+ * @param   pClient             Client to reset.
+ */
+void shClSvcClientReset(PSHCLCLIENT pClient)
+{
+    if (!pClient)
+        return;
+
+    LogFlowFunc(("[Client %RU32]\n", pClient->State.uClientID));
+    RTCritSectEnter(&pClient->CritSect);
+
+    /* Reset message queue. */
+    shClSvcMsgQueueReset(pClient);
+
+    /* Reset event source. */
+    ShClEventSourceReset(&pClient->EventSrc);
+
+    /* Reset pending state. */
+    RT_ZERO(pClient->Pending);
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    shClSvcClientTransfersReset(pClient);
+#endif
+
+    shclSvcClientStateReset(&pClient->State);
+
+    RTCritSectLeave(&pClient->CritSect);
+}
+
+static int shClSvcClientNegogiateChunkSize(PSHCLCLIENT pClient, VBOXHGCMCALLHANDLE hCall,
+                                           uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_RETURN(cParms == VBOX_SHCL_CPARMS_NEGOTIATE_CHUNK_SIZE, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const cbClientMaxChunkSize = paParms[0].u.uint32;
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const cbClientChunkSize    = paParms[1].u.uint32;
+
+    uint32_t const cbHostMaxChunkSize = VBOX_SHCL_MAX_CHUNK_SIZE; /** @todo Make this configurable. */
+
+    /*
+     * Do the work.
+     */
+    if (cbClientChunkSize == 0) /* Does the client want us to choose? */
+    {
+        paParms[0].u.uint32 = cbHostMaxChunkSize;                                     /* Maximum */
+        paParms[1].u.uint32 = RT_MIN(pClient->State.cbChunkSize, cbHostMaxChunkSize); /* Preferred */
+
+    }
+    else /* The client told us what it supports, so update and report back. */
+    {
+        paParms[0].u.uint32 = RT_MIN(cbClientMaxChunkSize, cbHostMaxChunkSize);         /* Maximum */
+        paParms[1].u.uint32 = RT_MIN(cbClientMaxChunkSize, pClient->State.cbChunkSize); /* Preferred */
+    }
+
+    int rc = g_pHelpers->pfnCallComplete(hCall, VINF_SUCCESS);
+    if (RT_SUCCESS(rc))
+    {
+        Log(("[Client %RU32] chunk size: %#RU32, max: %#RU32\n",
+             pClient->State.uClientID, paParms[1].u.uint32, paParms[0].u.uint32));
+    }
+    else
+        LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+
+    return VINF_HGCM_ASYNC_EXECUTE;
+}
+
+/**
+ * Implements VBOX_SHCL_GUEST_FN_REPORT_FEATURES.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success (we complete the message here).
+ * @retval  VERR_ACCESS_DENIED if not master
+ * @retval  VERR_INVALID_PARAMETER if bit 63 in the 2nd parameter isn't set.
+ * @retval  VERR_WRONG_PARAMETER_COUNT
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The client's call handle.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ */
+static int shClSvcClientReportFeatures(PSHCLCLIENT pClient, VBOXHGCMCALLHANDLE hCall,
+                                       uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_RETURN(cParms == 2, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint64_t const fFeatures0 = paParms[0].u.uint64;
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint64_t const fFeatures1 = paParms[1].u.uint64;
+    ASSERT_GUEST_RETURN(fFeatures1 & VBOX_SHCL_GF_1_MUST_BE_ONE, VERR_INVALID_PARAMETER);
+
+    /*
+     * Do the work.
+     */
+    paParms[0].u.uint64 = g_fHostFeatures0;
+    paParms[1].u.uint64 = 0;
+
+    int rc = g_pHelpers->pfnCallComplete(hCall, VINF_SUCCESS);
+    if (RT_SUCCESS(rc))
+    {
+        pClient->State.fGuestFeatures0 = fFeatures0;
+        pClient->State.fGuestFeatures1 = fFeatures1;
+        LogRel2(("Shared Clipboard: Guest reported the following features: %#RX64\n",
+                 pClient->State.fGuestFeatures0)); /* Note: fFeatures1 not used yet. */
+        if (pClient->State.fGuestFeatures0 & VBOX_SHCL_GF_0_TRANSFERS)
+            LogRel2(("Shared Clipboard: Guest supports file transfers\n"));
+    }
+    else
+        LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+
+    return VINF_HGCM_ASYNC_EXECUTE;
+}
+
+/**
+ * Implements VBOX_SHCL_GUEST_FN_QUERY_FEATURES.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE on success (we complete the message here).
+ * @retval  VERR_WRONG_PARAMETER_COUNT
+ *
+ * @param   hCall       The client's call handle.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ */
+static int shClSvcClientQueryFeatures(VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_RETURN(cParms == 2, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+    ASSERT_GUEST(paParms[1].u.uint64 & RT_BIT_64(63));
+
+    /*
+     * Do the work.
+     */
+    paParms[0].u.uint64 = g_fHostFeatures0;
+    paParms[1].u.uint64 = 0;
+    int rc = g_pHelpers->pfnCallComplete(hCall, VINF_SUCCESS);
+    if (RT_FAILURE(rc))
+        LogFunc(("pfnCallComplete -> %Rrc\n", rc));
+
+    return VINF_HGCM_ASYNC_EXECUTE;
+}
+
+/**
+ * Implements VBOX_SHCL_GUEST_FN_MSG_PEEK_WAIT and VBOX_SHCL_GUEST_FN_MSG_PEEK_NOWAIT.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_SUCCESS if a message was pending and is being returned.
+ * @retval  VERR_TRY_AGAIN if no message pending and not blocking.
+ * @retval  VERR_RESOURCE_BUSY if another read already made a waiting call.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE if message wait is pending.
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The client's call handle.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ * @param   fWait       Set if we should wait for a message, clear if to return
+ *                      immediately.
+ *
+ * @note    Caller takes and leave the client's critical section.
+ */
+static int shClSvcClientMsgPeek(PSHCLCLIENT pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[], bool fWait)
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_MSG_RETURN(cParms >= 2, ("cParms=%u!\n", cParms), VERR_WRONG_PARAMETER_COUNT);
+
+    uint64_t idRestoreCheck = 0;
+    uint32_t i              = 0;
+    if (paParms[i].type == VBOX_HGCM_SVC_PARM_64BIT)
+    {
+        idRestoreCheck = paParms[0].u.uint64;
+        paParms[0].u.uint64 = 0;
+        i++;
+    }
+    for (; i < cParms; i++)
+    {
+        ASSERT_GUEST_MSG_RETURN(paParms[i].type == VBOX_HGCM_SVC_PARM_32BIT, ("#%u type=%u\n", i, paParms[i].type),
+                                VERR_WRONG_PARAMETER_TYPE);
+        paParms[i].u.uint32 = 0;
+    }
+
+    /*
+     * Check restore session ID.
+     */
+    if (idRestoreCheck != 0)
+    {
+        uint64_t idRestore = g_pHelpers->pfnGetVMMDevSessionId(g_pHelpers);
+        if (idRestoreCheck != idRestore)
+        {
+            paParms[0].u.uint64 = idRestore;
+            LogFlowFunc(("[Client %RU32] VBOX_SHCL_GUEST_FN_MSG_PEEK_XXX -> VERR_VM_RESTORED (%#RX64 -> %#RX64)\n",
+                         pClient->State.uClientID, idRestoreCheck, idRestore));
+            return VERR_VM_RESTORED;
+        }
+        Assert(!g_pHelpers->pfnIsCallRestored(hCall));
+    }
+
+    /*
+     * Return information about the first message if one is pending in the list.
+     */
+    PSHCLCLIENTMSG pFirstMsg = RTListGetFirst(&pClient->MsgQueue, SHCLCLIENTMSG, ListEntry);
+    if (pFirstMsg)
+    {
+        shClSvcMsgSetPeekReturn(pFirstMsg, paParms, cParms);
+        LogFlowFunc(("[Client %RU32] VBOX_SHCL_GUEST_FN_MSG_PEEK_XXX -> VINF_SUCCESS (idMsg=%s (%u), cParms=%u)\n",
+                     pClient->State.uClientID, ShClHostMsgToStr(pFirstMsg->idMsg), pFirstMsg->idMsg, pFirstMsg->cParms));
+        return VINF_SUCCESS;
+    }
+
+    /*
+     * If we cannot wait, fail the call.
+     */
+    if (!fWait)
+    {
+        LogFlowFunc(("[Client %RU32] GUEST_MSG_PEEK_NOWAIT -> VERR_TRY_AGAIN\n", pClient->State.uClientID));
+        return VERR_TRY_AGAIN;
+    }
+
+    /*
+     * Wait for the host to queue a message for this client.
+     */
+    ASSERT_GUEST_MSG_RETURN(pClient->Pending.uType == 0, ("Already pending! (idClient=%RU32)\n",
+                                                           pClient->State.uClientID), VERR_RESOURCE_BUSY);
+    pClient->Pending.hHandle = hCall;
+    pClient->Pending.cParms  = cParms;
+    pClient->Pending.paParms = paParms;
+    pClient->Pending.uType   = VBOX_SHCL_GUEST_FN_MSG_PEEK_WAIT;
+    LogFlowFunc(("[Client %RU32] Is now in pending mode...\n", pClient->State.uClientID));
+    return VINF_HGCM_ASYNC_EXECUTE;
+}
+
+/**
+ * Implements VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_SUCCESS if a message was pending and is being returned.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE if message wait is pending.
+ *
+ * @param   pClient     The client state.
+ * @param   hCall       The client's call handle.
+ * @param   cParms      Number of parameters.
+ * @param   paParms     Array of parameters.
+ *
+ * @note    Caller takes and leave the client's critical section.
+ */
+static int shClSvcClientMsgOldGet(PSHCLCLIENT pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate input.
+     */
+    ASSERT_GUEST_RETURN(cParms == VBOX_SHCL_CPARMS_GET_HOST_MSG_OLD, VERR_WRONG_PARAMETER_COUNT);
+    ASSERT_GUEST_RETURN(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE); /* id32Msg */
+    ASSERT_GUEST_RETURN(paParms[1].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE); /* f32Formats */
+
+    paParms[0].u.uint32 = 0;
+    paParms[1].u.uint32 = 0;
+
+    /*
+     * If there is a message pending we can return immediately.
+     */
+    int rc;
+    PSHCLCLIENTMSG pFirstMsg = RTListGetFirst(&pClient->MsgQueue, SHCLCLIENTMSG, ListEntry);
+    if (pFirstMsg)
+    {
+        LogFlowFunc(("[Client %RU32] uMsg=%s (%RU32), cParms=%RU32\n", pClient->State.uClientID,
+                     ShClHostMsgToStr(pFirstMsg->idMsg), pFirstMsg->idMsg, pFirstMsg->cParms));
+
+        rc = shClSvcMsgSetOldWaitReturn(pFirstMsg, paParms, cParms);
+        AssertPtr(g_pHelpers);
+        rc = g_pHelpers->pfnCallComplete(hCall, rc);
+        if (rc != VERR_CANCELLED)
+        {
+            RTListNodeRemove(&pFirstMsg->ListEntry);
+            shClSvcMsgFree(pClient, pFirstMsg);
+
+            rc = VINF_HGCM_ASYNC_EXECUTE; /* The caller must not complete it. */
+        }
+    }
+    /*
+     * Otherwise we must wait.
+     */
+    else
+    {
+        ASSERT_GUEST_MSG_RETURN(pClient->Pending.uType == 0, ("Already pending! (idClient=%RU32)\n", pClient->State.uClientID),
+                                VERR_RESOURCE_BUSY);
+
+        pClient->Pending.hHandle = hCall;
+        pClient->Pending.cParms  = cParms;
+        pClient->Pending.paParms = paParms;
+        pClient->Pending.uType   = VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT;
+
+        rc = VINF_HGCM_ASYNC_EXECUTE; /* The caller must not complete it. */
+
+        LogFlowFunc(("[Client %RU32] Is now in pending mode...\n", pClient->State.uClientID));
+    }
+
+    LogFlowFunc(("[Client %RU32] rc=%Rrc\n", pClient->State.uClientID, rc));
+    return rc;
+}
+
+/**
+ * Implements VBOX_SHCL_GUEST_FN_MSG_GET.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_SUCCESS if message retrieved and removed from the pending queue.
+ * @retval  VERR_TRY_AGAIN if no message pending.
+ * @retval  VERR_BUFFER_OVERFLOW if a parmeter buffer is too small.  The buffer
+ *          size was updated to reflect the required size, though this isn't yet
+ *          forwarded to the guest.  (The guest is better of using peek with
+ *          parameter count + 2 parameters to get the sizes.)
+ * @retval  VERR_MISMATCH if the incoming message ID does not match the pending.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE if message was completed already.
+ *
+ * @param   pClient      The client state.
+ * @param   hCall        The client's call handle.
+ * @param   cParms       Number of parameters.
+ * @param   paParms      Array of parameters.
+ *
+ * @note    Called from within pClient->CritSect.
+ */
+static int shClSvcClientMsgGet(PSHCLCLIENT pClient, VBOXHGCMCALLHANDLE hCall, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Validate the request.
+     */
+    uint32_t const idMsgExpected = cParms > 0 && paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT ? paParms[0].u.uint32
+                                 : cParms > 0 && paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT ? paParms[0].u.uint64
+                                 : UINT32_MAX;
+
+    /*
+     * Return information about the first message if one is pending in the list.
+     */
+    PSHCLCLIENTMSG pFirstMsg = RTListGetFirst(&pClient->MsgQueue, SHCLCLIENTMSG, ListEntry);
+    if (pFirstMsg)
+    {
+        LogFlowFunc(("First message is: %s (%u), cParms=%RU32\n", ShClHostMsgToStr(pFirstMsg->idMsg), pFirstMsg->idMsg, pFirstMsg->cParms));
+
+        ASSERT_GUEST_MSG_RETURN(pFirstMsg->idMsg == idMsgExpected || idMsgExpected == UINT32_MAX,
+                                ("idMsg=%u (%s) cParms=%u, caller expected %u (%s) and %u\n",
+                                 pFirstMsg->idMsg, ShClHostMsgToStr(pFirstMsg->idMsg), pFirstMsg->cParms,
+                                 idMsgExpected, ShClHostMsgToStr(idMsgExpected), cParms),
+                                VERR_MISMATCH);
+        ASSERT_GUEST_MSG_RETURN(pFirstMsg->cParms == cParms,
+                                ("idMsg=%u (%s) cParms=%u, caller expected %u (%s) and %u\n",
+                                 pFirstMsg->idMsg, ShClHostMsgToStr(pFirstMsg->idMsg), pFirstMsg->cParms,
+                                 idMsgExpected, ShClHostMsgToStr(idMsgExpected), cParms),
+                                VERR_WRONG_PARAMETER_COUNT);
+
+        /* Check the parameter types. */
+        for (uint32_t i = 0; i < cParms; i++)
+            ASSERT_GUEST_MSG_RETURN(pFirstMsg->aParms[i].type == paParms[i].type,
+                                    ("param #%u: type %u, caller expected %u (idMsg=%u %s)\n", i, pFirstMsg->aParms[i].type,
+                                     paParms[i].type, pFirstMsg->idMsg, ShClHostMsgToStr(pFirstMsg->idMsg)),
+                                    VERR_WRONG_PARAMETER_TYPE);
+        /*
+         * Copy out the parameters.
+         *
+         * No assertions on buffer overflows, and keep going till the end so we can
+         * communicate all the required buffer sizes.
+         */
+        int rc = VINF_SUCCESS;
+        for (uint32_t i = 0; i < cParms; i++)
+            switch (pFirstMsg->aParms[i].type)
+            {
+                case VBOX_HGCM_SVC_PARM_32BIT:
+                    paParms[i].u.uint32 = pFirstMsg->aParms[i].u.uint32;
+                    break;
+
+                case VBOX_HGCM_SVC_PARM_64BIT:
+                    paParms[i].u.uint64 = pFirstMsg->aParms[i].u.uint64;
+                    break;
+
+                case VBOX_HGCM_SVC_PARM_PTR:
+                {
+                    uint32_t const cbSrc = pFirstMsg->aParms[i].u.pointer.size;
+                    uint32_t const cbDst = paParms[i].u.pointer.size;
+                    paParms[i].u.pointer.size = cbSrc; /** @todo Check if this is safe in other layers...
+                                                        * Update: Safe, yes, but VMMDevHGCM doesn't pass it along. */
+                    if (cbSrc <= cbDst)
+                        memcpy(paParms[i].u.pointer.addr, pFirstMsg->aParms[i].u.pointer.addr, cbSrc);
+                    else
+                    {
+                        AssertMsgFailed(("#%u: cbSrc=%RU32 is bigger than cbDst=%RU32\n", i, cbSrc, cbDst));
+                        rc = VERR_BUFFER_OVERFLOW;
+                    }
+                    break;
+                }
+
+                default:
+                    AssertMsgFailed(("#%u: %u\n", i, pFirstMsg->aParms[i].type));
+                    rc = VERR_INTERNAL_ERROR;
+                    break;
+            }
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Complete the message and remove the pending message unless the
+             * guest raced us and cancelled this call in the meantime.
+             */
+            AssertPtr(g_pHelpers);
+            rc = g_pHelpers->pfnCallComplete(hCall, rc);
+
+            LogFlowFunc(("[Client %RU32] pfnCallComplete -> %Rrc\n", pClient->State.uClientID, rc));
+
+            if (rc != VERR_CANCELLED)
+            {
+                RTListNodeRemove(&pFirstMsg->ListEntry);
+                shClSvcMsgFree(pClient, pFirstMsg);
+            }
+
+            return VINF_HGCM_ASYNC_EXECUTE; /* The caller must not complete it. */
+        }
+
+        LogFlowFunc(("[Client %RU32] Returning %Rrc\n", pClient->State.uClientID, rc));
+        return rc;
+    }
+
+    paParms[0].u.uint32 = 0;
+    paParms[1].u.uint32 = 0;
+    LogFlowFunc(("[Client %RU32] -> VERR_TRY_AGAIN\n", pClient->State.uClientID));
+    return VERR_TRY_AGAIN;
+}
+
+/**
+ * Implements VBOX_SHCL_GUEST_FN_MSG_GET.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_SUCCESS if message retrieved and removed from the pending queue.
+ * @retval  VERR_TRY_AGAIN if no message pending.
+ * @retval  VERR_MISMATCH if the incoming message ID does not match the pending.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE if message was completed already.
+ *
+ * @param   pClient      The client state.
+ * @param   cParms       Number of parameters.
+ *
+ * @note    Called from within pClient->CritSect.
+ */
+static int shClSvcClientMsgCancel(PSHCLCLIENT pClient, uint32_t cParms)
+{
+    /*
+     * Validate the request.
+     */
+    ASSERT_GUEST_MSG_RETURN(cParms == 0, ("cParms=%u!\n", cParms), VERR_WRONG_PARAMETER_COUNT);
+
+    /*
+     * Execute.
+     */
+    if (pClient->Pending.uType != 0)
+    {
+        LogFlowFunc(("[Client %RU32] Cancelling waiting thread, isPending=%d, pendingNumParms=%RU32, m_idSession=%x\n",
+                     pClient->State.uClientID, pClient->Pending.uType, pClient->Pending.cParms, pClient->State.uSessionID));
+
+        /*
+         * The PEEK call is simple: At least two parameters, all set to zero before sleeping.
+         */
+        int rcComplete;
+        if (pClient->Pending.uType == VBOX_SHCL_GUEST_FN_MSG_PEEK_WAIT)
+        {
+            Assert(pClient->Pending.cParms >= 2);
+            if (pClient->Pending.paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT)
+                HGCMSvcSetU64(&pClient->Pending.paParms[0], VBOX_SHCL_HOST_MSG_CANCELED);
+            else
+                HGCMSvcSetU32(&pClient->Pending.paParms[0], VBOX_SHCL_HOST_MSG_CANCELED);
+            rcComplete = VINF_TRY_AGAIN;
+        }
+        /*
+         * The MSG_OLD call is complicated, though we're
+         * generally here to wake up someone who is peeking and have two parameters.
+         * If there aren't two parameters, fail the call.
+         */
+        else
+        {
+            Assert(pClient->Pending.uType == VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT);
+            if (pClient->Pending.cParms > 0)
+                HGCMSvcSetU32(&pClient->Pending.paParms[0], VBOX_SHCL_HOST_MSG_CANCELED);
+            if (pClient->Pending.cParms > 1)
+                HGCMSvcSetU32(&pClient->Pending.paParms[1], 0);
+            rcComplete = pClient->Pending.cParms == 2 ? VINF_SUCCESS : VERR_TRY_AGAIN;
+        }
+
+        g_pHelpers->pfnCallComplete(pClient->Pending.hHandle, rcComplete);
+
+        pClient->Pending.hHandle    = NULL;
+        pClient->Pending.paParms    = NULL;
+        pClient->Pending.cParms     = 0;
+        pClient->Pending.uType      = 0;
+        return VINF_SUCCESS;
+    }
+    return VWRN_NOT_FOUND;
+}
+
+
+/**
+ * Wakes up a pending client (i.e. waiting for new messages).
+ *
+ * @returns VBox status code.
+ * @retval  VINF_NO_CHANGE if the client is not in pending mode.
+ *
+ * @param   pClient             Client to wake up.
+ * @note    Caller must enter pClient->CritSect.
+ */
+int shClSvcClientWakeup(PSHCLCLIENT pClient)
+{
+    Assert(RTCritSectIsOwner(&pClient->CritSect));
+    int rc = VINF_NO_CHANGE;
+
+    if (pClient->Pending.uType != 0)
+    {
+        LogFunc(("[Client %RU32] Waking up ...\n", pClient->State.uClientID));
+
+        PSHCLCLIENTMSG pFirstMsg = RTListGetFirst(&pClient->MsgQueue, SHCLCLIENTMSG, ListEntry);
+        AssertReturn(pFirstMsg, VERR_INTERNAL_ERROR);
+
+        LogFunc(("[Client %RU32] Current host message is %s (%RU32), cParms=%RU32\n",
+                 pClient->State.uClientID, ShClHostMsgToStr(pFirstMsg->idMsg), pFirstMsg->idMsg, pFirstMsg->cParms));
+
+        if (pClient->Pending.uType == VBOX_SHCL_GUEST_FN_MSG_PEEK_WAIT)
+            shClSvcMsgSetPeekReturn(pFirstMsg, pClient->Pending.paParms, pClient->Pending.cParms);
+        else if (pClient->Pending.uType == VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT) /* Legacy, Guest Additions < 6.1. */
+            shClSvcMsgSetOldWaitReturn(pFirstMsg, pClient->Pending.paParms, pClient->Pending.cParms);
+        else
+            AssertMsgFailedReturn(("pClient->Pending.uType=%u\n", pClient->Pending.uType), VERR_INTERNAL_ERROR_3);
+
+        rc = g_pHelpers->pfnCallComplete(pClient->Pending.hHandle, VINF_SUCCESS);
+
+        if (   rc != VERR_CANCELLED
+            && pClient->Pending.uType == VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT)
+        {
+            RTListNodeRemove(&pFirstMsg->ListEntry);
+            shClSvcMsgFree(pClient, pFirstMsg);
+        }
+
+        pClient->Pending.hHandle = NULL;
+        pClient->Pending.paParms = NULL;
+        pClient->Pending.cParms  = 0;
+        pClient->Pending.uType   = 0;
+    }
+    else
+        LogFunc(("[Client %RU32] Not in pending state, skipping wakeup\n", pClient->State.uClientID));
+
+    return rc;
+}
+
+/**
+ * Requests to read clipboard data from the guest.
+ *
+ * @returns VBox status code.
+ * @param   pClient             Client to request to read data form.
+ * @param   fFormats            The formats being requested, OR'ed together (VBOX_SHCL_FMT_XXX).
+ * @param   ppEvent             Where to return the event for waiting for new data on success. Optional.
+ *                              Must be released by the caller with ShClEventRelease().
+ */
+int ShClSvcGuestDataRequest(PSHCLCLIENT pClient, SHCLFORMATS fFormats, PSHCLEVENT *ppEvent)
+{
+    AssertPtrReturn(pClient, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("fFormats=%#x\n", fFormats));
+
+    int rc = VERR_NOT_SUPPORTED;
+
+    /* Generate a separate message for every (valid) format we support. */
+    while (fFormats)
+    {
+        /* Pick the next format to get from the mask: */
+        /** @todo Make format reporting precedence configurable? */
+        SHCLFORMAT fFormat;
+        if (fFormats & VBOX_SHCL_FMT_UNICODETEXT)
+            fFormat = VBOX_SHCL_FMT_UNICODETEXT;
+        else if (fFormats & VBOX_SHCL_FMT_BITMAP)
+            fFormat = VBOX_SHCL_FMT_BITMAP;
+        else if (fFormats & VBOX_SHCL_FMT_HTML)
+            fFormat = VBOX_SHCL_FMT_HTML;
+        else
+            AssertMsgFailedBreak(("%#x\n", fFormats));
+
+        /* Remove it from the mask. */
+        fFormats &= ~fFormat;
+
+#ifdef LOG_ENABLED
+        char *pszFmt = ShClFormatsToStrA(fFormat);
+        AssertPtrReturn(pszFmt, VERR_NO_MEMORY);
+        LogRel2(("Shared Clipboard: Requesting guest clipboard data in format '%s'\n", pszFmt));
+        RTStrFree(pszFmt);
+#endif
+        /*
+         * Allocate messages, one for each format.
+         */
+        PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient,
+                                              pClient->State.fGuestFeatures0 & VBOX_SHCL_GF_0_CONTEXT_ID
+                                              ? VBOX_SHCL_HOST_MSG_READ_DATA_CID : VBOX_SHCL_HOST_MSG_READ_DATA,
+                                              2);
+        if (pMsg)
+        {
+            /*
+             * Enter the critical section and generate an event.
+             */
+            RTCritSectEnter(&pClient->CritSect);
+
+            PSHCLEVENT pEvent;
+            rc = ShClEventSourceGenerateAndRegisterEvent(&pClient->EventSrc, &pEvent);
+            if (RT_SUCCESS(rc))
+            {
+                LogFlowFunc(("fFormats=%#x -> fFormat=%#x, idEvent=%#x\n", fFormats, fFormat, pEvent->idEvent));
+
+                const uint64_t uCID = VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID, pClient->EventSrc.uID, pEvent->idEvent);
+
+                rc = VINF_SUCCESS;
+
+                /* Save the context ID in our legacy cruft if we have to deal with old(er) Guest Additions (< 6.1). */
+                if (!(pClient->State.fGuestFeatures0 & VBOX_SHCL_GF_0_CONTEXT_ID))
+                {
+                    AssertStmt(pClient->Legacy.cCID < 4096, rc = VERR_TOO_MUCH_DATA);
+                    if (RT_SUCCESS(rc))
+                    {
+                        PSHCLCLIENTLEGACYCID pCID = (PSHCLCLIENTLEGACYCID)RTMemAlloc(sizeof(SHCLCLIENTLEGACYCID));
+                        if (pCID)
+                        {
+                            pCID->uCID    = uCID;
+                            pCID->enmType = 0; /* Not used yet. */
+                            pCID->uFormat = fFormat;
+                            RTListAppend(&pClient->Legacy.lstCID, &pCID->Node);
+                            pClient->Legacy.cCID++;
+                        }
+                        else
+                            rc = VERR_NO_MEMORY;
+                    }
+                }
+
+                if (RT_SUCCESS(rc))
+                {
+                    /*
+                     * Format the message.
+                     */
+                    if (pMsg->idMsg == VBOX_SHCL_HOST_MSG_READ_DATA_CID)
+                        HGCMSvcSetU64(&pMsg->aParms[0], uCID);
+                    else
+                        HGCMSvcSetU32(&pMsg->aParms[0], VBOX_SHCL_HOST_MSG_READ_DATA);
+                    HGCMSvcSetU32(&pMsg->aParms[1], fFormat);
+
+                    shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+
+                    /* Return event handle to the caller if requested. */
+                    if (ppEvent)
+                    {
+                        *ppEvent = pEvent;
+                    }
+
+                    shClSvcClientWakeup(pClient);
+                }
+
+                /* Remove event from list if caller did not request event handle or in case
+                 * of failure (in this case caller should not release event). */
+                if (   RT_FAILURE(rc)
+                    || !ppEvent)
+                {
+                    ShClEventRelease(pEvent);
+                }
+            }
+            else
+                rc = VERR_SHCLPB_MAX_EVENTS_REACHED;
+
+            RTCritSectLeave(&pClient->CritSect);
+
+            if (RT_FAILURE(rc))
+                shClSvcMsgFree(pClient, pMsg);
+        }
+        else
+            rc = VERR_NO_MEMORY;
+
+        if (RT_FAILURE(rc))
+            break;
+    }
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Requesting data in formats %#x from guest failed with %Rrc\n", fFormats, rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Signals the host that clipboard data from the guest has been received.
+ *
+ * @returns VBox status code. Returns VERR_NOT_FOUND when related event ID was not found.
+ * @param   pClient             Client the guest clipboard data was received from.
+ * @param   pCmdCtx             Client command context.
+ * @param   uFormat             Clipboard format of data received.
+ * @param   pvData              Pointer to clipboard data received.  This can be
+ *                              NULL if @a cbData is zero.
+ * @param   cbData              Size (in bytes) of clipboard data received.
+ *                              This can be zero.
+ */
+int ShClSvcGuestDataSignal(PSHCLCLIENT pClient, PSHCLCLIENTCMDCTX pCmdCtx, SHCLFORMAT uFormat, void *pvData, uint32_t cbData)
+{
+    LogFlowFuncEnter();
+    RT_NOREF(uFormat);
+
+    /*
+     * Validate input.
+     */
+    AssertPtrReturn(pClient, VERR_INVALID_POINTER);
+    AssertPtrReturn(pCmdCtx, VERR_INVALID_POINTER);
+    if (cbData > 0)
+        AssertPtrReturn(pvData, VERR_INVALID_POINTER);
+
+    const SHCLEVENTID idEvent = VBOX_SHCL_CONTEXTID_GET_EVENT(pCmdCtx->uContextID);
+    AssertMsgReturn(idEvent != NIL_SHCLEVENTID, ("NIL event in context ID %#RX64\n", pCmdCtx->uContextID), VERR_WRONG_ORDER);
+
+    PSHCLEVENT pEvent = ShClEventSourceGetFromId(&pClient->EventSrc, idEvent);
+    AssertMsgReturn(pEvent != NULL, ("Event %#x not found\n", idEvent), VERR_NOT_FOUND);
+
+    /*
+     * Make a copy of the data so we can attach it to the signal.
+     *
+     * Note! We still signal the waiter should we run out of memory,
+     *       because otherwise it will be stuck waiting.
+     */
+    int rc = VINF_SUCCESS;
+    PSHCLEVENTPAYLOAD pPayload = NULL;
+    if (cbData > 0)
+        rc = ShClPayloadAlloc(idEvent, pvData, cbData, &pPayload);
+
+    /*
+     * Signal the event.
+     */
+    int rc2 = ShClEventSignal(pEvent, pPayload);
+    if (RT_FAILURE(rc2))
+    {
+        rc = rc2;
+        ShClPayloadFree(pPayload);
+        LogRel(("Shared Clipboard: Signalling of guest clipboard data to the host failed: %Rrc\n", rc));
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Reports available VBox clipboard formats to the guest.
+ *
+ * @note    Host backend callers must check if it's active (use
+ *          ShClSvcIsBackendActive) before calling to prevent mixing up the
+ *          VRDE clipboard.
+ *
+ * @returns VBox status code.
+ * @param   pClient             Client to report clipboard formats to.
+ * @param   fFormats            The formats to report (VBOX_SHCL_FMT_XXX), zero
+ *                              is okay (empty the clipboard).
+ */
+int ShClSvcHostReportFormats(PSHCLCLIENT pClient, SHCLFORMATS fFormats)
+{
+    /*
+     * Check if the service mode allows this operation and whether the guest is
+     * supposed to be reading from the host. Otherwise, silently ignore reporting
+     * formats and return VINF_SUCCESS in order to do not trigger client
+     * termination in svcConnect().
+     */
+    uint32_t uMode = ShClSvcGetMode();
+    if (   uMode == VBOX_SHCL_MODE_BIDIRECTIONAL
+        || uMode == VBOX_SHCL_MODE_HOST_TO_GUEST)
+    { /* likely */ }
+    else
+        return VINF_SUCCESS;
+
+    AssertPtrReturn(pClient, VERR_INVALID_POINTER);
+
+    LogFlowFunc(("fFormats=%#x\n", fFormats));
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    /*
+     * If transfer mode is set to disabled, don't report the URI list format to the guest.
+     */
+    if (!(g_fTransferMode & VBOX_SHCL_TRANSFER_MODE_ENABLED))
+    {
+        fFormats &= ~VBOX_SHCL_FMT_URI_LIST;
+        LogRel2(("Shared Clipboard: File transfers are disabled, skipping reporting those to the guest\n"));
+    }
+#endif
+
+#ifdef LOG_ENABLED
+    char *pszFmts = ShClFormatsToStrA(fFormats);
+    AssertPtrReturn(pszFmts, VERR_NO_MEMORY);
+    LogRel2(("Shared Clipboard: Reporting formats '%s' to guest\n", pszFmts));
+    RTStrFree(pszFmts);
+#endif
+
+    /*
+     * Allocate a message, populate parameters and post it to the client.
+     */
+    int rc;
+    PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, VBOX_SHCL_HOST_MSG_FORMATS_REPORT, 2);
+    if (pMsg)
+    {
+        HGCMSvcSetU32(&pMsg->aParms[0], VBOX_SHCL_HOST_MSG_FORMATS_REPORT);
+        HGCMSvcSetU32(&pMsg->aParms[1], fFormats);
+
+        RTCritSectEnter(&pClient->CritSect);
+        shClSvcMsgAddAndWakeupClient(pClient, pMsg);
+        RTCritSectLeave(&pClient->CritSect);
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+        /* If we announce an URI list, create a transfer locally and also tell the guest to create
+         * a transfer on the guest side. */
+        if (fFormats & VBOX_SHCL_FMT_URI_LIST)
+        {
+            rc = shClSvcTransferStart(pClient, SHCLTRANSFERDIR_TO_REMOTE, SHCLSOURCE_LOCAL,
+                                      NULL /* pTransfer */);
+            if (RT_SUCCESS(rc))
+                rc = shClSvcSetSource(pClient, SHCLSOURCE_LOCAL);
+
+            if (RT_FAILURE(rc))
+                LogRel(("Shared Clipboard: Initializing host write transfer failed with %Rrc\n", rc));
+        }
+        else
+#endif
+        {
+            rc = VINF_SUCCESS;
+        }
+    }
+    else
+        rc = VERR_NO_MEMORY;
+
+    if (RT_FAILURE(rc))
+        LogRel(("Shared Clipboard: Reporting formats %#x to guest failed with %Rrc\n", fFormats, rc));
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+
+/**
+ * Handles the VBOX_SHCL_GUEST_FN_REPORT_FORMATS message from the guest.
+ */
+static int shClSvcClientReportFormats(PSHCLCLIENT pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    /*
+     * Check if the service mode allows this operation and whether the guest is
+     * supposed to be reading from the host.
+     */
+    uint32_t uMode = ShClSvcGetMode();
+    if (   uMode == VBOX_SHCL_MODE_BIDIRECTIONAL
+        || uMode == VBOX_SHCL_MODE_GUEST_TO_HOST)
+    { /* likely */ }
+    else
+        return VERR_ACCESS_DENIED;
+
+    /*
+     * Digest parameters.
+     */
+    ASSERT_GUEST_RETURN(   cParms == VBOX_SHCL_CPARMS_REPORT_FORMATS
+                        || (   cParms == VBOX_SHCL_CPARMS_REPORT_FORMATS_61B
+                            && (pClient->State.fGuestFeatures0 & VBOX_SHCL_GF_0_CONTEXT_ID)),
+                        VERR_WRONG_PARAMETER_COUNT);
+
+    uintptr_t iParm = 0;
+    if (cParms == VBOX_SHCL_CPARMS_REPORT_FORMATS_61B)
+    {
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+        /* no defined value, so just ignore it */
+        iParm++;
+    }
+    ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uint32_t const fFormats = paParms[iParm].u.uint32;
+    iParm++;
+    if (cParms == VBOX_SHCL_CPARMS_REPORT_FORMATS_61B)
+    {
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+        ASSERT_GUEST_RETURN(paParms[iParm].u.uint32 == 0, VERR_INVALID_FLAGS);
+        iParm++;
+    }
+    Assert(iParm == cParms);
+
+    /*
+     * Report the formats.
+     *
+     * We ignore empty reports if the guest isn't the clipboard owner, this
+     * prevents a freshly booted guest with an empty clibpoard from clearing
+     * the host clipboard on startup.  Likewise, when a guest shutdown it will
+     * typically issue an empty report in case it's the owner, we don't want
+     * that to clear host content either.
+     */
+    int rc;
+    if (!fFormats && pClient->State.enmSource != SHCLSOURCE_REMOTE)
+        rc = VINF_SUCCESS;
+    else
+    {
+        rc = shClSvcSetSource(pClient, SHCLSOURCE_REMOTE);
+        if (RT_SUCCESS(rc))
+        {
+            rc = RTCritSectEnter(&g_CritSect);
+            if (RT_SUCCESS(rc))
+            {
+                if (g_ExtState.pfnExtension)
+                {
+                    SHCLEXTPARMS parms;
+                    RT_ZERO(parms);
+                    parms.uFormat = fFormats;
+
+                    g_ExtState.pfnExtension(g_ExtState.pvExtension, VBOX_CLIPBOARD_EXT_FN_FORMAT_ANNOUNCE, &parms, sizeof(parms));
+                }
+                else
+                {
+#ifdef LOG_ENABLED
+                    char *pszFmts = ShClFormatsToStrA(fFormats);
+                    if (pszFmts)
+                    {
+                        LogRel2(("Shared Clipboard: Guest reported formats '%s' to host\n", pszFmts));
+                        RTStrFree(pszFmts);
+                    }
+#endif
+                    rc = ShClBackendReportFormats(&g_ShClBackend, pClient, fFormats);
+                    if (RT_FAILURE(rc))
+                        LogRel(("Shared Clipboard: Reporting guest clipboard formats to the host failed with %Rrc\n", rc));
+                }
+
+                RTCritSectLeave(&g_CritSect);
+            }
+            else
+                LogRel2(("Shared Clipboard: Unable to take internal lock while receiving guest clipboard announcement: %Rrc\n", rc));
+        }
+    }
+
+    return rc;
+}
+
+/**
+ * Called when the guest wants to read host clipboard data.
+ * Handles the VBOX_SHCL_GUEST_FN_DATA_READ message.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_BUFFER_OVERFLOW if the guest supplied a smaller buffer than needed in order to read the host clipboard data.
+ * @param   pClient             Client that wants to read host clipboard data.
+ * @param   cParms              Number of HGCM parameters supplied in \a paParms.
+ * @param   paParms             Array of HGCM parameters.
+ */
+static int shClSvcClientReadData(PSHCLCLIENT pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    LogFlowFuncEnter();
+
+    /*
+     * Check if the service mode allows this operation and whether the guest is
+     * supposed to be reading from the host.
+     */
+    uint32_t uMode = ShClSvcGetMode();
+    if (   uMode == VBOX_SHCL_MODE_BIDIRECTIONAL
+        || uMode == VBOX_SHCL_MODE_HOST_TO_GUEST)
+    { /* likely */ }
+    else
+        return VERR_ACCESS_DENIED;
+
+    /*
+     * Digest parameters.
+     *
+     * We are dragging some legacy here from the 6.1 dev cycle, a 5 parameter
+     * variant which prepends a 64-bit context ID (RAZ as meaning not defined),
+     * a 32-bit flag (MBZ, no defined meaning) and switches the last two parameters.
+     */
+    ASSERT_GUEST_RETURN(   cParms == VBOX_SHCL_CPARMS_DATA_READ
+                        || (    cParms == VBOX_SHCL_CPARMS_DATA_READ_61B
+                            &&  (pClient->State.fGuestFeatures0 & VBOX_SHCL_GF_0_CONTEXT_ID)),
+                        VERR_WRONG_PARAMETER_COUNT);
+
+    uintptr_t iParm = 0;
+    SHCLCLIENTCMDCTX cmdCtx;
+    RT_ZERO(cmdCtx);
+    if (cParms == VBOX_SHCL_CPARMS_DATA_READ_61B)
+    {
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+        /* This has no defined meaning and was never used, however the guest passed stuff, so ignore it and leave idContext=0. */
+        iParm++;
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+        ASSERT_GUEST_RETURN(paParms[iParm].u.uint32 == 0, VERR_INVALID_FLAGS);
+        iParm++;
+    }
+
+    SHCLFORMAT  uFormat = VBOX_SHCL_FMT_NONE;
+    uint32_t    cbData  = 0;
+    void       *pvData  = NULL;
+
+    ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+    uFormat = paParms[iParm].u.uint32;
+    iParm++;
+    if (cParms != VBOX_SHCL_CPARMS_DATA_READ_61B)
+    {
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_PTR, VERR_WRONG_PARAMETER_TYPE); /* Data buffer */
+        pvData = paParms[iParm].u.pointer.addr;
+        cbData = paParms[iParm].u.pointer.size;
+        iParm++;
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE); /*cbDataReturned*/
+        iParm++;
+    }
+    else
+    {
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE); /*cbDataReturned*/
+        iParm++;
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_PTR, VERR_WRONG_PARAMETER_TYPE); /* Data buffer */
+        pvData = paParms[iParm].u.pointer.addr;
+        cbData = paParms[iParm].u.pointer.size;
+        iParm++;
+    }
+    Assert(iParm == cParms);
+
+    /*
+     * For some reason we need to do this (makes absolutely no sense to bird).
+     */
+    /** @todo r=bird: I really don't get why you need the State.POD.uFormat
+     *        member.  I'm sure there is a reason.  Incomplete code? */
+    if (!(pClient->State.fGuestFeatures0 & VBOX_SHCL_GF_0_CONTEXT_ID))
+    {
+        if (pClient->State.POD.uFormat == VBOX_SHCL_FMT_NONE)
+            pClient->State.POD.uFormat = uFormat;
+    }
+
+#ifdef LOG_ENABLED
+    char *pszFmt = ShClFormatsToStrA(uFormat);
+    AssertPtrReturn(pszFmt, VERR_NO_MEMORY);
+    LogRel2(("Shared Clipboard: Guest wants to read %RU32 bytes host clipboard data in format '%s'\n", cbData, pszFmt));
+    RTStrFree(pszFmt);
+#endif
+
+    /*
+     * Do the reading.
+     */
+    uint32_t cbActual = 0;
+
+    int rc = RTCritSectEnter(&g_CritSect);
+    AssertRCReturn(rc, rc);
+
+    /* If there is a service extension active, try reading data from it first. */
+    if (g_ExtState.pfnExtension)
+    {
+        SHCLEXTPARMS parms;
+        RT_ZERO(parms);
+
+        parms.uFormat  = uFormat;
+        parms.u.pvData = pvData;
+        parms.cbData   = cbData;
+
+        g_ExtState.fReadingData = true;
+
+        /* Read clipboard data from the extension. */
+        rc = g_ExtState.pfnExtension(g_ExtState.pvExtension, VBOX_CLIPBOARD_EXT_FN_DATA_READ, &parms, sizeof(parms));
+
+        LogRel2(("Shared Clipboard: Read extension clipboard data (fDelayedAnnouncement=%RTbool, fDelayedFormats=%#x, max %RU32 bytes), got %RU32 bytes: rc=%Rrc\n",
+                 g_ExtState.fDelayedAnnouncement, g_ExtState.fDelayedFormats, cbData, parms.cbData, rc));
+
+        /* Did the extension send the clipboard formats yet?
+         * Otherwise, do this now. */
+        if (g_ExtState.fDelayedAnnouncement)
+        {
+            int rc2 = ShClSvcHostReportFormats(pClient, g_ExtState.fDelayedFormats);
+            AssertRC(rc2);
+
+            g_ExtState.fDelayedAnnouncement = false;
+            g_ExtState.fDelayedFormats = 0;
+        }
+
+        g_ExtState.fReadingData = false;
+
+        if (RT_SUCCESS(rc))
+            cbActual = parms.cbData;
+    }
+    else
+    {
+        rc = ShClBackendReadData(&g_ShClBackend, pClient, &cmdCtx, uFormat, pvData, cbData, &cbActual);
+        if (RT_SUCCESS(rc))
+            LogRel2(("Shared Clipboard: Read host clipboard data (max %RU32 bytes), got %RU32 bytes\n", cbData, cbActual));
+        else
+            LogRel(("Shared Clipboard: Reading host clipboard data failed with %Rrc\n", rc));
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        /* Return the actual size required to fullfil the request. */
+        if (cParms != VBOX_SHCL_CPARMS_DATA_READ_61B)
+            HGCMSvcSetU32(&paParms[2], cbActual);
+        else
+            HGCMSvcSetU32(&paParms[3], cbActual);
+
+        /* If the data to return exceeds the buffer the guest supplies, tell it (and let it try again). */
+        if (cbActual >= cbData)
+            rc = VINF_BUFFER_OVERFLOW;
+    }
+
+    RTCritSectLeave(&g_CritSect);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Called when the guest writes clipboard data to the host.
+ * Handles the VBOX_SHCL_GUEST_FN_DATA_WRITE message.
+ *
+ * @returns VBox status code.
+ * @param   pClient             Client that wants to read host clipboard data.
+ * @param   cParms              Number of HGCM parameters supplied in \a paParms.
+ * @param   paParms             Array of HGCM parameters.
+ */
+int shClSvcClientWriteData(PSHCLCLIENT pClient, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    LogFlowFuncEnter();
+
+    /*
+     * Check if the service mode allows this operation and whether the guest is
+     * supposed to be reading from the host.
+     */
+    uint32_t uMode = ShClSvcGetMode();
+    if (   uMode == VBOX_SHCL_MODE_BIDIRECTIONAL
+        || uMode == VBOX_SHCL_MODE_GUEST_TO_HOST)
+    { /* likely */ }
+    else
+        return VERR_ACCESS_DENIED;
+
+    const bool fReportsContextID = RT_BOOL(pClient->State.fGuestFeatures0 & VBOX_SHCL_GF_0_CONTEXT_ID);
+
+    /*
+     * Digest parameters.
+     *
+     * There are 3 different format here, formatunately no parameters have been
+     * switch around so it's plain sailing compared to the DATA_READ message.
+     */
+    ASSERT_GUEST_RETURN(fReportsContextID
+                        ? cParms == VBOX_SHCL_CPARMS_DATA_WRITE || cParms == VBOX_SHCL_CPARMS_DATA_WRITE_61B
+                        : cParms == VBOX_SHCL_CPARMS_DATA_WRITE_OLD,
+                        VERR_WRONG_PARAMETER_COUNT);
+
+    uintptr_t iParm = 0;
+    SHCLCLIENTCMDCTX cmdCtx;
+    RT_ZERO(cmdCtx);
+    if (cParms > VBOX_SHCL_CPARMS_DATA_WRITE_OLD)
+    {
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_WRONG_PARAMETER_TYPE);
+        cmdCtx.uContextID = paParms[iParm].u.uint64;
+        iParm++;
+    }
+    else
+    {
+        /* Older Guest Additions (< 6.1) did not supply a context ID.
+         * We dig it out from our saved context ID list then a bit down below. */
+    }
+
+    if (cParms == VBOX_SHCL_CPARMS_DATA_WRITE_61B)
+    {
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE);
+        ASSERT_GUEST_RETURN(paParms[iParm].u.uint32 == 0, VERR_INVALID_FLAGS);
+        iParm++;
+    }
+
+    SHCLFORMAT  uFormat = VBOX_SHCL_FMT_NONE;
+    uint32_t    cbData  = 0;
+    void       *pvData  = NULL;
+
+    ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE); /* Format bit. */
+    uFormat = paParms[iParm].u.uint32;
+    iParm++;
+    if (cParms == VBOX_SHCL_CPARMS_DATA_WRITE_61B)
+    {
+        ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_WRONG_PARAMETER_TYPE); /* "cbData" - duplicates buffer size. */
+        iParm++;
+    }
+    ASSERT_GUEST_RETURN(paParms[iParm].type == VBOX_HGCM_SVC_PARM_PTR, VERR_WRONG_PARAMETER_TYPE); /* Data buffer */
+    pvData = paParms[iParm].u.pointer.addr;
+    cbData = paParms[iParm].u.pointer.size;
+    iParm++;
+    Assert(iParm == cParms);
+
+    /*
+     * Handle / check context ID.
+     */
+    if (!fReportsContextID) /* Do we have to deal with old(er) GAs (< 6.1) which don't support context IDs? Dig out the context ID then. */
+    {
+        PSHCLCLIENTLEGACYCID pCID = NULL;
+        PSHCLCLIENTLEGACYCID pCIDIter;
+        RTListForEach(&pClient->Legacy.lstCID, pCIDIter, SHCLCLIENTLEGACYCID, Node) /* Slow, but does the job for now. */
+        {
+            if (pCIDIter->uFormat == uFormat)
+            {
+                pCID = pCIDIter;
+                break;
+            }
+        }
+
+        ASSERT_GUEST_MSG_RETURN(pCID != NULL, ("Context ID for format %#x not found\n", uFormat), VERR_INVALID_CONTEXT);
+        cmdCtx.uContextID = pCID->uCID;
+
+        /* Not needed anymore; clean up. */
+        Assert(pClient->Legacy.cCID);
+        pClient->Legacy.cCID--;
+        RTListNodeRemove(&pCID->Node);
+        RTMemFree(pCID);
+    }
+
+    uint64_t const idCtxExpected = VBOX_SHCL_CONTEXTID_MAKE(pClient->State.uSessionID, pClient->EventSrc.uID,
+                                                            VBOX_SHCL_CONTEXTID_GET_EVENT(cmdCtx.uContextID));
+    ASSERT_GUEST_MSG_RETURN(cmdCtx.uContextID == idCtxExpected,
+                            ("Wrong context ID: %#RX64, expected %#RX64\n", cmdCtx.uContextID, idCtxExpected),
+                            VERR_INVALID_CONTEXT);
+
+    /*
+     * For some reason we need to do this (makes absolutely no sense to bird).
+     */
+    /** @todo r=bird: I really don't get why you need the State.POD.uFormat
+     *        member.  I'm sure there is a reason.  Incomplete code? */
+    if (!(pClient->State.fGuestFeatures0 & VBOX_SHCL_GF_0_CONTEXT_ID))
+    {
+        if (pClient->State.POD.uFormat == VBOX_SHCL_FMT_NONE)
+            pClient->State.POD.uFormat = uFormat;
+    }
+
+#ifdef LOG_ENABLED
+    char *pszFmt = ShClFormatsToStrA(uFormat);
+    if (pszFmt)
+    {
+        LogRel2(("Shared Clipboard: Guest writes %RU32 bytes clipboard data in format '%s' to host\n", cbData, pszFmt));
+        RTStrFree(pszFmt);
+    }
+#endif
+
+    /*
+     * Write the data to the active host side clipboard.
+     */
+    int rc = RTCritSectEnter(&g_CritSect);
+    AssertRCReturn(rc, rc);
+
+    if (g_ExtState.pfnExtension)
+    {
+        SHCLEXTPARMS parms;
+        RT_ZERO(parms);
+        parms.uFormat   = uFormat;
+        parms.u.pvData  = pvData;
+        parms.cbData    = cbData;
+
+        g_ExtState.pfnExtension(g_ExtState.pvExtension, VBOX_CLIPBOARD_EXT_FN_DATA_WRITE, &parms, sizeof(parms));
+        rc = VINF_SUCCESS;
+    }
+    else
+    {
+        /* Let the backend implementation know. */
+        rc = ShClBackendWriteData(&g_ShClBackend, pClient, &cmdCtx, uFormat, pvData, cbData);
+        if (RT_FAILURE(rc))
+            LogRel(("Shared Clipboard: Writing guest clipboard data to the host failed with %Rrc\n", rc));
+
+        int rc2; /* Don't return internals back to the guest. */
+        rc2 = ShClSvcGuestDataSignal(pClient, &cmdCtx, uFormat, pvData, cbData); /* To complete pending events, if any. */
+        if (RT_FAILURE(rc2))
+            LogRel(("Shared Clipboard: Signalling host about guest clipboard data failed with %Rrc\n", rc2));
+        AssertRC(rc2);
+    }
+
+    RTCritSectLeave(&g_CritSect);
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Gets an error from HGCM service parameters.
+ *
+ * @returns VBox status code.
+ * @param   cParms              Number of HGCM parameters supplied in \a paParms.
+ * @param   paParms             Array of HGCM parameters.
+ * @param   pRc                 Where to store the received error code.
+ */
+static int shClSvcClientError(uint32_t cParms, VBOXHGCMSVCPARM paParms[], int *pRc)
+{
+    AssertPtrReturn(paParms, VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pRc,     VERR_INVALID_PARAMETER);
+
+    int rc;
+
+    if (cParms == VBOX_SHCL_CPARMS_ERROR)
+    {
+        rc = HGCMSvcGetU32(&paParms[1], (uint32_t *)pRc); /** @todo int vs. uint32_t !!! */
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+/**
+ * Sets the transfer source type of a Shared Clipboard client.
+ *
+ * @returns VBox status code.
+ * @param   pClient             Client to set transfer source type for.
+ * @param   enmSource           Source type to set.
+ */
+int shClSvcSetSource(PSHCLCLIENT pClient, SHCLSOURCE enmSource)
+{
+    if (!pClient) /* If no client connected (anymore), bail out. */
+        return VINF_SUCCESS;
+
+    int rc = VINF_SUCCESS;
+
+    if (ShClSvcLock())
+    {
+        pClient->State.enmSource = enmSource;
+
+        LogFlowFunc(("Source of client %RU32 is now %RU32\n", pClient->State.uClientID, pClient->State.enmSource));
+
+        ShClSvcUnlock();
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+static int svcInit(VBOXHGCMSVCFNTABLE *pTable)
+{
+    int rc = RTCritSectInit(&g_CritSect);
+
+    if (RT_SUCCESS(rc))
+    {
+        shClSvcModeSet(VBOX_SHCL_MODE_OFF);
+
+        rc = ShClBackendInit(ShClSvcGetBackend(), pTable);
+
+        /* Clean up on failure, because 'svnUnload' will not be called
+         * if the 'svcInit' returns an error.
+         */
+        if (RT_FAILURE(rc))
+        {
+            RTCritSectDelete(&g_CritSect);
+        }
+    }
+
+    return rc;
+}
+
+static DECLCALLBACK(int) svcUnload(void *)
+{
+    LogFlowFuncEnter();
+
+    ShClBackendDestroy(ShClSvcGetBackend());
+
+    RTCritSectDelete(&g_CritSect);
+
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) svcDisconnect(void *, uint32_t u32ClientID, void *pvClient)
+{
+    LogFunc(("u32ClientID=%RU32\n", u32ClientID));
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pvClient;
+    AssertPtr(pClient);
+
+    /* In order to communicate with guest service, HGCM VRDP clipboard extension
+     * needs to know its connection client ID. Currently, in svcConnect() we always
+     * cache ID of the first ever connected client. When client disconnects,
+     * we need to forget its ID and let svcConnect() to pick up the next ID when a new
+     * connection will be requested by guest service (see #10115). */
+    if (g_ExtState.uClientID == u32ClientID)
+    {
+        g_ExtState.uClientID = 0;
+    }
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    shClSvcClientTransfersReset(pClient);
+#endif
+
+    ShClBackendDisconnect(&g_ShClBackend, pClient);
+
+    shClSvcClientDestroy(pClient);
+
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) svcConnect(void *, uint32_t u32ClientID, void *pvClient, uint32_t fRequestor, bool fRestoring)
+{
+    RT_NOREF(fRequestor, fRestoring);
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pvClient;
+    AssertPtr(pvClient);
+
+    int rc = shClSvcClientInit(pClient, u32ClientID);
+    if (RT_SUCCESS(rc))
+    {
+        /* Assign weak pointer to client map. */
+        /** @todo r=bird: The g_mapClients is only there for looking up
+         *        g_ExtState.uClientID (unserialized btw), so why not use store the
+         *        pClient value directly in g_ExtState instead of the ID?  It cannot
+         *        crash any worse that racing map insertion/removal. */
+        g_mapClients[u32ClientID] = pClient; /** @todo Handle OOM / collisions? */
+        rc = ShClBackendConnect(&g_ShClBackend, pClient, ShClSvcGetHeadless());
+        if (RT_SUCCESS(rc))
+        {
+            /* Sync the host clipboard content with the client. */
+            rc = ShClBackendSync(&g_ShClBackend, pClient);
+            if (RT_SUCCESS(rc))
+            {
+                /* For now we ASSUME that the first client that connects is in charge for
+                   communicating with the service extension. */
+                /** @todo This isn't optimal, but only the guest really knows which client is in
+                 *        focus on the console. See @bugref{10115} for details. */
+                if (g_ExtState.uClientID == 0)
+                    g_ExtState.uClientID = u32ClientID;
+
+                /* The sync could return VINF_NO_CHANGE if nothing has changed on the host, but
+                   older Guest Additions didn't use RT_SUCCESS to but == VINF_SUCCESS to check for
+                   success.  So just return VINF_SUCCESS here to not break older Guest Additions. */
+                LogFunc(("Successfully connected client %#x%s\n",
+                         u32ClientID, g_ExtState.uClientID == u32ClientID ? " - Use by ExtState too" : ""));
+                return VINF_SUCCESS;
+            }
+
+            LogFunc(("ShClBackendSync failed: %Rrc\n", rc));
+            ShClBackendDisconnect(&g_ShClBackend, pClient);
+        }
+        else
+            LogFunc(("ShClBackendConnect failed: %Rrc\n", rc));
+        shClSvcClientDestroy(pClient);
+    }
+    else
+        LogFunc(("shClSvcClientInit failed: %Rrc\n", rc));
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+static DECLCALLBACK(void) svcCall(void *,
+                                  VBOXHGCMCALLHANDLE callHandle,
+                                  uint32_t u32ClientID,
+                                  void *pvClient,
+                                  uint32_t u32Function,
+                                  uint32_t cParms,
+                                  VBOXHGCMSVCPARM paParms[],
+                                  uint64_t tsArrival)
+{
+    RT_NOREF(u32ClientID, pvClient, tsArrival);
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pvClient;
+    AssertPtr(pClient);
+
+#ifdef LOG_ENABLED
+    Log2Func(("u32ClientID=%RU32, fn=%RU32 (%s), cParms=%RU32, paParms=%p\n",
+              u32ClientID, u32Function, ShClGuestMsgToStr(u32Function), cParms, paParms));
+    for (uint32_t i = 0; i < cParms; i++)
+    {
+        switch (paParms[i].type)
+        {
+            case VBOX_HGCM_SVC_PARM_32BIT:
+                Log3Func(("    paParms[%RU32]: type uint32_t - value %RU32\n", i, paParms[i].u.uint32));
+                break;
+            case VBOX_HGCM_SVC_PARM_64BIT:
+                Log3Func(("    paParms[%RU32]: type uint64_t - value %RU64\n", i, paParms[i].u.uint64));
+                break;
+            case VBOX_HGCM_SVC_PARM_PTR:
+                Log3Func(("    paParms[%RU32]: type ptr - value 0x%p (%RU32 bytes)\n",
+                          i, paParms[i].u.pointer.addr, paParms[i].u.pointer.size));
+                break;
+            case VBOX_HGCM_SVC_PARM_PAGES:
+                Log3Func(("    paParms[%RU32]: type pages - cb=%RU32, cPages=%RU16\n",
+                          i, paParms[i].u.Pages.cb, paParms[i].u.Pages.cPages));
+                break;
+            default:
+                AssertFailed();
+        }
+    }
+    Log2Func(("Client state: fFlags=0x%x, fGuestFeatures0=0x%x, fGuestFeatures1=0x%x\n",
+              pClient->State.fFlags, pClient->State.fGuestFeatures0, pClient->State.fGuestFeatures1));
+#endif
+
+    int rc;
+    switch (u32Function)
+    {
+        case VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT:
+            RTCritSectEnter(&pClient->CritSect);
+            rc = shClSvcClientMsgOldGet(pClient, callHandle, cParms, paParms);
+            RTCritSectLeave(&pClient->CritSect);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_CONNECT:
+            LogRel(("Shared Clipboard: 6.1.0 beta or rc Guest Additions detected. Please upgrade!\n"));
+            rc = VERR_NOT_IMPLEMENTED;
+            break;
+
+        case VBOX_SHCL_GUEST_FN_NEGOTIATE_CHUNK_SIZE:
+            rc = shClSvcClientNegogiateChunkSize(pClient, callHandle, cParms, paParms);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_REPORT_FEATURES:
+            rc = shClSvcClientReportFeatures(pClient, callHandle, cParms, paParms);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_QUERY_FEATURES:
+            rc = shClSvcClientQueryFeatures(callHandle, cParms, paParms);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_MSG_PEEK_NOWAIT:
+            RTCritSectEnter(&pClient->CritSect);
+            rc = shClSvcClientMsgPeek(pClient, callHandle, cParms, paParms, false /*fWait*/);
+            RTCritSectLeave(&pClient->CritSect);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_MSG_PEEK_WAIT:
+            RTCritSectEnter(&pClient->CritSect);
+            rc = shClSvcClientMsgPeek(pClient, callHandle, cParms, paParms, true /*fWait*/);
+            RTCritSectLeave(&pClient->CritSect);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_MSG_GET:
+            RTCritSectEnter(&pClient->CritSect);
+            rc = shClSvcClientMsgGet(pClient, callHandle, cParms, paParms);
+            RTCritSectLeave(&pClient->CritSect);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_MSG_CANCEL:
+            RTCritSectEnter(&pClient->CritSect);
+            rc = shClSvcClientMsgCancel(pClient, cParms);
+            RTCritSectLeave(&pClient->CritSect);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_REPORT_FORMATS:
+            rc = shClSvcClientReportFormats(pClient, cParms, paParms);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_DATA_READ:
+            rc = shClSvcClientReadData(pClient, cParms, paParms);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_DATA_WRITE:
+            rc = shClSvcClientWriteData(pClient, cParms, paParms);
+            break;
+
+        case VBOX_SHCL_GUEST_FN_ERROR:
+        {
+            int rcGuest;
+            rc = shClSvcClientError(cParms,paParms, &rcGuest);
+            if (RT_SUCCESS(rc))
+            {
+                LogRel(("Shared Clipboard: Error reported from guest side: %Rrc\n", rcGuest));
+
+                shClSvcClientLock(pClient);
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+                shClSvcClientTransfersReset(pClient);
+#endif
+                shClSvcClientUnlock(pClient);
+            }
+            break;
+        }
+
+        default:
+        {
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+            if (   u32Function <= VBOX_SHCL_GUEST_FN_LAST
+                && (pClient->State.fGuestFeatures0 &  VBOX_SHCL_GF_0_CONTEXT_ID) )
+            {
+                if (g_fTransferMode & VBOX_SHCL_TRANSFER_MODE_ENABLED)
+                    rc = shClSvcTransferHandler(pClient, callHandle, u32Function, cParms, paParms, tsArrival);
+                else
+                {
+                    LogRel2(("Shared Clipboard: File transfers are disabled for this VM\n"));
+                    rc = VERR_ACCESS_DENIED;
+                }
+            }
+            else
+#endif
+            {
+                LogRel2(("Shared Clipboard: Unknown guest function: %u (%#x)\n", u32Function, u32Function));
+                rc = VERR_NOT_IMPLEMENTED;
+            }
+            break;
+        }
+    }
+
+    LogFlowFunc(("[Client %RU32] rc=%Rrc\n", pClient->State.uClientID, rc));
+
+    if (rc != VINF_HGCM_ASYNC_EXECUTE)
+        g_pHelpers->pfnCallComplete(callHandle, rc);
+}
+
+/**
+ * Initializes a Shared Clipboard service's client state.
+ *
+ * @returns VBox status code.
+ * @param   pClientState        Client state to initialize.
+ * @param   uClientID           Client ID (HGCM) to use for this client state.
+ */
+int shClSvcClientStateInit(PSHCLCLIENTSTATE pClientState, uint32_t uClientID)
+{
+    LogFlowFuncEnter();
+
+    shclSvcClientStateReset(pClientState);
+
+    /* Register the client. */
+    pClientState->uClientID    = uClientID;
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Destroys a Shared Clipboard service's client state.
+ *
+ * @returns VBox status code.
+ * @param   pClientState        Client state to destroy.
+ */
+int shClSvcClientStateDestroy(PSHCLCLIENTSTATE pClientState)
+{
+    RT_NOREF(pClientState);
+
+    LogFlowFuncEnter();
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Resets a Shared Clipboard service's client state.
+ *
+ * @param   pClientState    Client state to reset.
+ */
+void shclSvcClientStateReset(PSHCLCLIENTSTATE pClientState)
+{
+    LogFlowFuncEnter();
+
+    pClientState->fGuestFeatures0 = VBOX_SHCL_GF_NONE;
+    pClientState->fGuestFeatures1 = VBOX_SHCL_GF_NONE;
+
+    pClientState->cbChunkSize     = VBOX_SHCL_DEFAULT_CHUNK_SIZE; /** @todo Make this configurable. */
+    pClientState->enmSource       = SHCLSOURCE_INVALID;
+    pClientState->fFlags          = SHCLCLIENTSTATE_FLAGS_NONE;
+
+    pClientState->POD.enmDir             = SHCLTRANSFERDIR_UNKNOWN;
+    pClientState->POD.uFormat            = VBOX_SHCL_FMT_NONE;
+    pClientState->POD.cbToReadWriteTotal = 0;
+    pClientState->POD.cbReadWritten      = 0;
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    pClientState->Transfers.enmTransferDir = SHCLTRANSFERDIR_UNKNOWN;
+#endif
+}
+
+/*
+ * We differentiate between a function handler for the guest and one for the host.
+ */
+static DECLCALLBACK(int) svcHostCall(void *,
+                                     uint32_t u32Function,
+                                     uint32_t cParms,
+                                     VBOXHGCMSVCPARM paParms[])
+{
+    int rc = VINF_SUCCESS;
+
+    LogFlowFunc(("u32Function=%RU32 (%s), cParms=%RU32, paParms=%p\n",
+                 u32Function, ShClHostFunctionToStr(u32Function), cParms, paParms));
+
+    switch (u32Function)
+    {
+        case VBOX_SHCL_HOST_FN_SET_MODE:
+        {
+            if (cParms != 1)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                uint32_t u32Mode = VBOX_SHCL_MODE_OFF;
+
+                rc = HGCMSvcGetU32(&paParms[0], &u32Mode);
+                if (RT_SUCCESS(rc))
+                    rc = shClSvcModeSet(u32Mode);
+            }
+
+            break;
+        }
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+        case VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE:
+        {
+            if (cParms != 1)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                uint32_t fTransferMode;
+                rc = HGCMSvcGetU32(&paParms[0], &fTransferMode);
+                if (RT_SUCCESS(rc))
+                    rc = shClSvcTransferModeSet(fTransferMode);
+            }
+            break;
+        }
+#endif
+        case VBOX_SHCL_HOST_FN_SET_HEADLESS:
+        {
+            if (cParms != 1)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                uint32_t uHeadless;
+                rc = HGCMSvcGetU32(&paParms[0], &uHeadless);
+                if (RT_SUCCESS(rc))
+                {
+                    g_fHeadless = RT_BOOL(uHeadless);
+                    LogRel(("Shared Clipboard: Service running in %s mode\n", g_fHeadless ? "headless" : "normal"));
+                }
+            }
+            break;
+        }
+
+        default:
+        {
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+            rc = shClSvcTransferHostHandler(u32Function, cParms, paParms);
+#else
+            rc = VERR_NOT_IMPLEMENTED;
+#endif
+            break;
+        }
+    }
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+#ifndef UNIT_TEST
+
+/**
+ * SSM descriptor table for the SHCLCLIENTLEGACYCID structure.
+ *
+ * @note Saving the ListEntry attribute is not necessary, as this gets used on runtime only.
+ */
+static SSMFIELD const s_aShClSSMClientLegacyCID[] =
+{
+    SSMFIELD_ENTRY(SHCLCLIENTLEGACYCID, uCID),
+    SSMFIELD_ENTRY(SHCLCLIENTLEGACYCID, enmType),
+    SSMFIELD_ENTRY(SHCLCLIENTLEGACYCID, uFormat),
+    SSMFIELD_ENTRY_TERM()
+};
+
+/**
+ * SSM descriptor table for the SHCLCLIENTSTATE structure.
+ *
+ * @note Saving the session ID not necessary, as they're not persistent across
+ *       state save/restore.
+ */
+static SSMFIELD const s_aShClSSMClientState[] =
+{
+    SSMFIELD_ENTRY(SHCLCLIENTSTATE, fGuestFeatures0),
+    SSMFIELD_ENTRY(SHCLCLIENTSTATE, fGuestFeatures1),
+    SSMFIELD_ENTRY(SHCLCLIENTSTATE, cbChunkSize),
+    SSMFIELD_ENTRY(SHCLCLIENTSTATE, enmSource),
+    SSMFIELD_ENTRY(SHCLCLIENTSTATE, fFlags),
+    SSMFIELD_ENTRY_TERM()
+};
+
+/**
+ * VBox 6.1 Beta 1 version of s_aShClSSMClientState (no flags).
+ */
+static SSMFIELD const s_aShClSSMClientState61B1[] =
+{
+    SSMFIELD_ENTRY(SHCLCLIENTSTATE, fGuestFeatures0),
+    SSMFIELD_ENTRY(SHCLCLIENTSTATE, fGuestFeatures1),
+    SSMFIELD_ENTRY(SHCLCLIENTSTATE, cbChunkSize),
+    SSMFIELD_ENTRY(SHCLCLIENTSTATE, enmSource),
+    SSMFIELD_ENTRY_TERM()
+};
+
+/**
+ * SSM descriptor table for the SHCLCLIENTPODSTATE structure.
+ */
+static SSMFIELD const s_aShClSSMClientPODState[] =
+{
+    SSMFIELD_ENTRY(SHCLCLIENTPODSTATE, enmDir),
+    SSMFIELD_ENTRY(SHCLCLIENTPODSTATE, uFormat),
+    SSMFIELD_ENTRY(SHCLCLIENTPODSTATE, cbToReadWriteTotal),
+    SSMFIELD_ENTRY(SHCLCLIENTPODSTATE, cbReadWritten),
+    SSMFIELD_ENTRY(SHCLCLIENTPODSTATE, tsLastReadWrittenMs),
+    SSMFIELD_ENTRY_TERM()
+};
+
+/**
+ * SSM descriptor table for the SHCLCLIENTURISTATE structure.
+ */
+static SSMFIELD const s_aShClSSMClientTransferState[] =
+{
+    SSMFIELD_ENTRY(SHCLCLIENTTRANSFERSTATE, enmTransferDir),
+    SSMFIELD_ENTRY_TERM()
+};
+
+/**
+ * SSM descriptor table for the header of the SHCLCLIENTMSG structure.
+ * The actual message parameters will be serialized separately.
+ */
+static SSMFIELD const s_aShClSSMClientMsgHdr[] =
+{
+    SSMFIELD_ENTRY(SHCLCLIENTMSG, idMsg),
+    SSMFIELD_ENTRY(SHCLCLIENTMSG, cParms),
+    SSMFIELD_ENTRY_TERM()
+};
+
+/**
+ * SSM descriptor table for what used to be the VBOXSHCLMSGCTX structure but is
+ * now part of SHCLCLIENTMSG.
+ */
+static SSMFIELD const s_aShClSSMClientMsgCtx[] =
+{
+    SSMFIELD_ENTRY(SHCLCLIENTMSG, idCtx),
+    SSMFIELD_ENTRY_TERM()
+};
+#endif /* !UNIT_TEST */
+
+static DECLCALLBACK(int) svcSaveState(void *, uint32_t u32ClientID, void *pvClient, PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM)
+{
+    LogFlowFuncEnter();
+
+#ifndef UNIT_TEST
+    /*
+     * When the state will be restored, pending requests will be reissued
+     * by VMMDev. The service therefore must save state as if there were no
+     * pending request.
+     * Pending requests, if any, will be completed in svcDisconnect.
+     */
+    RT_NOREF(u32ClientID);
+    LogFunc(("u32ClientID=%RU32\n", u32ClientID));
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pvClient;
+    AssertPtr(pClient);
+
+    /* Write Shared Clipboard saved state version. */
+    pVMM->pfnSSMR3PutU32(pSSM, VBOX_SHCL_SAVED_STATE_VER_CURRENT);
+
+    int rc = pVMM->pfnSSMR3PutStructEx(pSSM, &pClient->State, sizeof(pClient->State), 0 /*fFlags*/, &s_aShClSSMClientState[0], NULL);
+    AssertRCReturn(rc, rc);
+
+    rc = pVMM->pfnSSMR3PutStructEx(pSSM, &pClient->State.POD, sizeof(pClient->State.POD), 0 /*fFlags*/, &s_aShClSSMClientPODState[0], NULL);
+    AssertRCReturn(rc, rc);
+
+    rc = pVMM->pfnSSMR3PutStructEx(pSSM, &pClient->State.Transfers, sizeof(pClient->State.Transfers), 0 /*fFlags*/, &s_aShClSSMClientTransferState[0], NULL);
+    AssertRCReturn(rc, rc);
+
+    /* Serialize the client's internal message queue. */
+    rc = pVMM->pfnSSMR3PutU64(pSSM, pClient->cMsgAllocated);
+    AssertRCReturn(rc, rc);
+
+    PSHCLCLIENTMSG pMsg;
+    RTListForEach(&pClient->MsgQueue, pMsg, SHCLCLIENTMSG, ListEntry)
+    {
+        pVMM->pfnSSMR3PutStructEx(pSSM, pMsg, sizeof(SHCLCLIENTMSG), 0 /*fFlags*/, &s_aShClSSMClientMsgHdr[0], NULL);
+        pVMM->pfnSSMR3PutStructEx(pSSM, pMsg, sizeof(SHCLCLIENTMSG), 0 /*fFlags*/, &s_aShClSSMClientMsgCtx[0], NULL);
+
+        for (uint32_t iParm = 0; iParm < pMsg->cParms; iParm++)
+            HGCMSvcSSMR3Put(&pMsg->aParms[iParm], pSSM, pVMM);
+    }
+
+    rc = pVMM->pfnSSMR3PutU64(pSSM, pClient->Legacy.cCID);
+    AssertRCReturn(rc, rc);
+
+    PSHCLCLIENTLEGACYCID pCID;
+    RTListForEach(&pClient->Legacy.lstCID, pCID, SHCLCLIENTLEGACYCID, Node)
+    {
+        rc = pVMM->pfnSSMR3PutStructEx(pSSM, pCID, sizeof(SHCLCLIENTLEGACYCID), 0 /*fFlags*/, &s_aShClSSMClientLegacyCID[0], NULL);
+        AssertRCReturn(rc, rc);
+    }
+#else  /* UNIT_TEST */
+    RT_NOREF(u32ClientID, pvClient, pSSM, pVMM);
+#endif /* UNIT_TEST */
+    return VINF_SUCCESS;
+}
+
+#ifndef UNIT_TEST
+static int svcLoadStateV0(uint32_t u32ClientID, void *pvClient, PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion)
+{
+    RT_NOREF(u32ClientID, pvClient, pSSM, uVersion);
+
+    uint32_t uMarker;
+    int rc = pVMM->pfnSSMR3GetU32(pSSM, &uMarker);   /* Begin marker. */
+    AssertRC(rc);
+    Assert(uMarker == UINT32_C(0x19200102)  /* SSMR3STRUCT_BEGIN */);
+
+    rc = pVMM->pfnSSMR3Skip(pSSM, sizeof(uint32_t)); /* Client ID */
+    AssertRCReturn(rc, rc);
+
+    bool fValue;
+    rc = pVMM->pfnSSMR3GetBool(pSSM, &fValue);       /* fHostMsgQuit */
+    AssertRCReturn(rc, rc);
+
+    rc = pVMM->pfnSSMR3GetBool(pSSM, &fValue);       /* fHostMsgReadData */
+    AssertRCReturn(rc, rc);
+
+    rc = pVMM->pfnSSMR3GetBool(pSSM, &fValue);       /* fHostMsgFormats */
+    AssertRCReturn(rc, rc);
+
+    uint32_t fFormats;
+    rc = pVMM->pfnSSMR3GetU32(pSSM, &fFormats);      /* u32RequestedFormat */
+    AssertRCReturn(rc, rc);
+
+    rc = pVMM->pfnSSMR3GetU32(pSSM, &uMarker);       /* End marker. */
+    AssertRCReturn(rc, rc);
+    Assert(uMarker == UINT32_C(0x19920406) /* SSMR3STRUCT_END */);
+
+    return VINF_SUCCESS;
+}
+#endif /* UNIT_TEST */
+
+static DECLCALLBACK(int) svcLoadState(void *, uint32_t u32ClientID, void *pvClient,
+                                      PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion)
+{
+    LogFlowFuncEnter();
+
+#ifndef UNIT_TEST
+
+    RT_NOREF(u32ClientID, uVersion);
+
+    PSHCLCLIENT pClient = (PSHCLCLIENT)pvClient;
+    AssertPtr(pClient);
+
+    /* Restore the client data. */
+    uint32_t lenOrVer;
+    int rc = pVMM->pfnSSMR3GetU32(pSSM, &lenOrVer);
+    AssertRCReturn(rc, rc);
+
+    LogFunc(("u32ClientID=%RU32, lenOrVer=%#RX64\n", u32ClientID, lenOrVer));
+
+    if (lenOrVer == VBOX_SHCL_SAVED_STATE_VER_3_1)
+        return svcLoadStateV0(u32ClientID, pvClient, pSSM, pVMM, uVersion);
+
+    if (   lenOrVer >= VBOX_SHCL_SAVED_STATE_VER_6_1B2
+        && lenOrVer <= VBOX_SHCL_SAVED_STATE_VER_CURRENT)
+    {
+        if (lenOrVer >= VBOX_SHCL_SAVED_STATE_VER_6_1RC1)
+        {
+            pVMM->pfnSSMR3GetStructEx(pSSM, &pClient->State, sizeof(pClient->State), 0 /* fFlags */,
+                                      &s_aShClSSMClientState[0], NULL);
+            pVMM->pfnSSMR3GetStructEx(pSSM, &pClient->State.POD, sizeof(pClient->State.POD), 0 /* fFlags */,
+                                      &s_aShClSSMClientPODState[0], NULL);
+        }
+        else
+            pVMM->pfnSSMR3GetStructEx(pSSM, &pClient->State, sizeof(pClient->State), 0 /* fFlags */,
+                                      &s_aShClSSMClientState61B1[0], NULL);
+        rc = pVMM->pfnSSMR3GetStructEx(pSSM, &pClient->State.Transfers, sizeof(pClient->State.Transfers), 0 /* fFlags */,
+                                       &s_aShClSSMClientTransferState[0], NULL);
+        AssertRCReturn(rc, rc);
+
+        /* Load the client's internal message queue. */
+        uint64_t cMsgs;
+        rc = pVMM->pfnSSMR3GetU64(pSSM, &cMsgs);
+        AssertRCReturn(rc, rc);
+        AssertLogRelMsgReturn(cMsgs < _16K, ("Too many messages: %u (%x)\n", cMsgs, cMsgs), VERR_SSM_DATA_UNIT_FORMAT_CHANGED);
+
+        for (uint64_t i = 0; i < cMsgs; i++)
+        {
+            union
+            {
+                SHCLCLIENTMSG Msg;
+                uint8_t abPadding[RT_UOFFSETOF(SHCLCLIENTMSG, aParms) + sizeof(VBOXHGCMSVCPARM) * 2];
+            } u;
+
+            pVMM->pfnSSMR3GetStructEx(pSSM, &u.Msg, RT_UOFFSETOF(SHCLCLIENTMSG, aParms), 0 /*fFlags*/,
+                                      &s_aShClSSMClientMsgHdr[0], NULL);
+            rc = pVMM->pfnSSMR3GetStructEx(pSSM, &u.Msg, RT_UOFFSETOF(SHCLCLIENTMSG, aParms), 0 /*fFlags*/,
+                                           &s_aShClSSMClientMsgCtx[0], NULL);
+            AssertRCReturn(rc, rc);
+
+            AssertLogRelMsgReturn(u.Msg.cParms <= VMMDEV_MAX_HGCM_PARMS,
+                                  ("Too many HGCM message parameters: %u (%#x)\n", u.Msg.cParms, u.Msg.cParms),
+                                  VERR_SSM_DATA_UNIT_FORMAT_CHANGED);
+
+            PSHCLCLIENTMSG pMsg = shClSvcMsgAlloc(pClient, u.Msg.idMsg, u.Msg.cParms);
+            AssertReturn(pMsg, VERR_NO_MEMORY);
+            pMsg->idCtx = u.Msg.idCtx;
+
+            for (uint32_t p = 0; p < pMsg->cParms; p++)
+            {
+                rc = HGCMSvcSSMR3Get(&pMsg->aParms[p], pSSM, pVMM);
+                AssertRCReturnStmt(rc, shClSvcMsgFree(pClient, pMsg), rc);
+            }
+
+            RTCritSectEnter(&pClient->CritSect);
+            shClSvcMsgAdd(pClient, pMsg, true /* fAppend */);
+            RTCritSectLeave(&pClient->CritSect);
+        }
+
+        if (lenOrVer >= VBOX_SHCL_SAVED_STATE_LEGACY_CID)
+        {
+            uint64_t cCID;
+            rc = pVMM->pfnSSMR3GetU64(pSSM, &cCID);
+            AssertRCReturn(rc, rc);
+            AssertLogRelMsgReturn(cCID < _16K, ("Too many context IDs: %u (%x)\n", cCID, cCID), VERR_SSM_DATA_UNIT_FORMAT_CHANGED);
+
+            for (uint64_t i = 0; i < cCID; i++)
+            {
+                PSHCLCLIENTLEGACYCID pCID = (PSHCLCLIENTLEGACYCID)RTMemAlloc(sizeof(SHCLCLIENTLEGACYCID));
+                AssertPtrReturn(pCID, VERR_NO_MEMORY);
+
+                pVMM->pfnSSMR3GetStructEx(pSSM, pCID, sizeof(SHCLCLIENTLEGACYCID), 0 /* fFlags */,
+                                          &s_aShClSSMClientLegacyCID[0], NULL);
+                RTListAppend(&pClient->Legacy.lstCID, &pCID->Node);
+            }
+        }
+    }
+    else
+    {
+        LogRel(("Shared Clipboard: Unsupported saved state version (%#x)\n", lenOrVer));
+        return VERR_SSM_DATA_UNIT_FORMAT_CHANGED;
+    }
+
+    /* Actual host data are to be reported to guest (SYNC). */
+    ShClBackendSync(&g_ShClBackend, pClient);
+
+#else  /* UNIT_TEST */
+    RT_NOREF(u32ClientID, pvClient, pSSM, pVMM, uVersion);
+#endif /* UNIT_TEST */
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) extCallback(uint32_t u32Function, uint32_t u32Format, void *pvData, uint32_t cbData)
+{
+    RT_NOREF(pvData, cbData);
+
+    LogFlowFunc(("u32Function=%RU32\n", u32Function));
+
+    int rc = VINF_SUCCESS;
+
+    /* Figure out if the client in charge for the service extension still is connected. */
+    ClipboardClientMap::const_iterator itClient = g_mapClients.find(g_ExtState.uClientID);
+    if (itClient != g_mapClients.end())
+    {
+        PSHCLCLIENT pClient = itClient->second;
+        AssertPtr(pClient);
+
+        switch (u32Function)
+        {
+            /* The service extension announces formats to the guest. */
+            case VBOX_CLIPBOARD_EXT_FN_FORMAT_ANNOUNCE:
+            {
+                LogFlowFunc(("VBOX_CLIPBOARD_EXT_FN_FORMAT_ANNOUNCE: g_ExtState.fReadingData=%RTbool\n", g_ExtState.fReadingData));
+                if (!g_ExtState.fReadingData)
+                    rc = ShClSvcHostReportFormats(pClient, u32Format);
+                else
+                {
+                    g_ExtState.fDelayedAnnouncement = true;
+                    g_ExtState.fDelayedFormats = u32Format;
+                    rc = VINF_SUCCESS;
+                }
+                break;
+            }
+
+            /* The service extension wants read data from the guest. */
+            case VBOX_CLIPBOARD_EXT_FN_DATA_READ:
+                rc = ShClSvcGuestDataRequest(pClient, u32Format, NULL /* pidEvent */);
+                break;
+
+            default:
+                /* Just skip other messages. */
+                break;
+        }
+    }
+    else
+        rc = VERR_NOT_FOUND;
+
+    LogFlowFuncLeaveRC(rc);
+    return rc;
+}
+
+static DECLCALLBACK(int) svcRegisterExtension(void *, PFNHGCMSVCEXT pfnExtension, void *pvExtension)
+{
+    LogFlowFunc(("pfnExtension=%p\n", pfnExtension));
+
+    SHCLEXTPARMS parms;
+    RT_ZERO(parms);
+
+    /*
+     * Reference counting for service extension registration is done a few
+     * layers up (in ConsoleVRDPServer::ClipboardCreate()).
+     */
+
+    int rc = RTCritSectEnter(&g_CritSect);
+    AssertLogRelRCReturn(rc, rc);
+
+    if (pfnExtension)
+    {
+        /* Install extension. */
+        g_ExtState.pfnExtension = pfnExtension;
+        g_ExtState.pvExtension  = pvExtension;
+
+        parms.u.pfnCallback = extCallback;
+        g_ExtState.pfnExtension(g_ExtState.pvExtension, VBOX_CLIPBOARD_EXT_FN_SET_CALLBACK, &parms, sizeof(parms));
+
+        LogRel2(("Shared Clipboard: registered service extension\n"));
+    }
+    else
+    {
+        if (g_ExtState.pfnExtension)
+            g_ExtState.pfnExtension(g_ExtState.pvExtension, VBOX_CLIPBOARD_EXT_FN_SET_CALLBACK, &parms, sizeof(parms));
+
+        /* Uninstall extension. */
+        g_ExtState.pvExtension  = NULL;
+        g_ExtState.pfnExtension = NULL;
+
+        LogRel2(("Shared Clipboard: de-registered service extension\n"));
+    }
+
+    RTCritSectLeave(&g_CritSect);
+
+    return VINF_SUCCESS;
+}
+
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad(VBOXHGCMSVCFNTABLE *pTable)
+{
+    int rc = VINF_SUCCESS;
+
+    LogFlowFunc(("pTable=%p\n", pTable));
+
+    if (!RT_VALID_PTR(pTable))
+    {
+        rc = VERR_INVALID_PARAMETER;
+    }
+    else
+    {
+        LogFunc(("pTable->cbSize = %d, ptable->u32Version = 0x%08X\n", pTable->cbSize, pTable->u32Version));
+
+        if (   pTable->cbSize     != sizeof (VBOXHGCMSVCFNTABLE)
+            || pTable->u32Version != VBOX_HGCM_SVC_VERSION)
+        {
+            rc = VERR_VERSION_MISMATCH;
+        }
+        else
+        {
+            g_pHelpers = pTable->pHelpers;
+
+            pTable->cbClient = sizeof(SHCLCLIENT);
+
+            /* Map legacy clients to root. */
+            pTable->idxLegacyClientCategory = HGCM_CLIENT_CATEGORY_ROOT;
+
+            /* Limit the number of clients to 128 in each category (should be enough),
+               but set kernel clients to 1. */
+            for (uintptr_t i = 0; i < RT_ELEMENTS(pTable->acMaxClients); i++)
+                pTable->acMaxClients[i] = 128;
+            pTable->acMaxClients[HGCM_CLIENT_CATEGORY_KERNEL] = 1;
+
+            /* Only 16 pending calls per client (1 should be enough). */
+            for (uintptr_t i = 0; i < RT_ELEMENTS(pTable->acMaxClients); i++)
+                pTable->acMaxCallsPerClient[i] = 16;
+
+            pTable->pfnUnload            = svcUnload;
+            pTable->pfnConnect           = svcConnect;
+            pTable->pfnDisconnect        = svcDisconnect;
+            pTable->pfnCall              = svcCall;
+            pTable->pfnHostCall          = svcHostCall;
+            pTable->pfnSaveState         = svcSaveState;
+            pTable->pfnLoadState         = svcLoadState;
+            pTable->pfnRegisterExtension = svcRegisterExtension;
+            pTable->pfnNotify            = NULL;
+            pTable->pvService            = NULL;
+
+            /* Service specific initialization. */
+            rc = svcInit(pTable);
+        }
+    }
+
+    LogFlowFunc(("Returning %Rrc\n", rc));
+    return rc;
+}
diff --git a/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc.rc b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc.rc
new file mode 100644
index 00000000..7e17a0b5
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/VBoxSharedClipboardSvc.rc
@@ -0,0 +1,61 @@
+/* $Id: VBoxSharedClipboardSvc.rc $ */
+/** @file
+ * Shared Clipboard Service - Resource file containing version info and icon.
+ */
+
+/*
+ * Copyright (C) 2015-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <windows.h>
+#include <VBox/version.h>
+
+LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION      VBOX_RC_FILE_VERSION
+  PRODUCTVERSION   VBOX_RC_FILE_VERSION
+  FILEFLAGSMASK    VS_FFI_FILEFLAGSMASK
+  FILEFLAGS        VBOX_RC_FILE_FLAGS
+  FILEOS           VBOX_RC_FILE_OS
+  FILETYPE         VBOX_RC_TYPE_DLL
+  FILESUBTYPE      VFT2_UNKNOWN
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904b0" // Lang=US English, CharSet=Unicode
+    BEGIN
+      VALUE "FileDescription",  "VirtualBox Shared Clipboard Host Service\0"
+      VALUE "InternalName",     "VBoxSharedClipboard\0"
+      VALUE "OriginalFilename", "VBoxSharedClipboard.dll\0"
+      VALUE "CompanyName",      VBOX_RC_COMPANY_NAME
+      VALUE "FileVersion",      VBOX_RC_FILE_VERSION_STR
+      VALUE "LegalCopyright",   VBOX_RC_LEGAL_COPYRIGHT
+      VALUE "ProductName",      VBOX_RC_PRODUCT_NAME_STR
+      VALUE "ProductVersion",   VBOX_RC_PRODUCT_VERSION_STR
+      VBOX_RC_MORE_STRINGS
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x409, 1200
+  END
+END
diff --git a/src/VBox/HostServices/SharedClipboard/darwin-pasteboard.cpp b/src/VBox/HostServices/SharedClipboard/darwin-pasteboard.cpp
new file mode 100644
index 00000000..290763be
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/darwin-pasteboard.cpp
@@ -0,0 +1,718 @@
+/* $Id: darwin-pasteboard.cpp $ */
+/** @file
+ * Shared Clipboard Service - Mac OS X host implementation.
+ */
+
+/*
+ * Includes contributions from François Revol
+ *
+ * Copyright (C) 2008-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_CLIPBOARD
+#include <Carbon/Carbon.h>
+
+#include <iprt/assert.h>
+#include <iprt/mem.h>
+#include <iprt/errcore.h>
+#include <iprt/utf16.h>
+
+#include <VBox/log.h>
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#include <VBox/GuestHost/SharedClipboard.h>
+#include <VBox/GuestHost/clipboard-helper.h>
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+#define WITH_HTML_H2G 1
+#define WITH_HTML_G2H 1
+
+/* For debugging */
+//#define SHOW_CLIPBOARD_CONTENT
+
+
+/**
+ * Initialize the global pasteboard and return a reference to it.
+ *
+ * @param pPasteboardRef Reference to the global pasteboard.
+ *
+ * @returns IPRT status code.
+ */
+int initPasteboard(PasteboardRef *pPasteboardRef)
+{
+    int rc = VINF_SUCCESS;
+
+    if (PasteboardCreate(kPasteboardClipboard, pPasteboardRef))
+        rc = VERR_NOT_SUPPORTED;
+
+    return rc;
+}
+
+/**
+ * Release the reference to the global pasteboard.
+ *
+ * @param pPasteboardRef Reference to the global pasteboard.
+ */
+void destroyPasteboard(PasteboardRef *pPasteboardRef)
+{
+    CFRelease(*pPasteboardRef);
+    *pPasteboardRef = NULL;
+}
+
+/**
+ * Inspect the global pasteboard for new content. Check if there is some type
+ * that is supported by vbox and return it.
+ *
+ * @param   hPasteboard         Reference to the global pasteboard.
+ * @param   idOwnership         Our ownership ID.
+ * @param   hStrOwnershipFlavor The ownership flavor string reference returned
+ *                              by takePasteboardOwnership().
+ * @param   pfFormats           Pointer for the bit combination of the
+ *                              supported types.
+ * @param   pfChanged           True if something has changed after the
+ *                              last call.
+ *
+ * @returns VINF_SUCCESS.
+ */
+int queryNewPasteboardFormats(PasteboardRef hPasteboard, uint64_t idOwnership, void *hStrOwnershipFlavor,
+                              uint32_t *pfFormats, bool *pfChanged)
+{
+    OSStatus orc;
+
+    *pfFormats = 0;
+    *pfChanged = true;
+
+    PasteboardSyncFlags syncFlags;
+    /* Make sure all is in sync */
+    syncFlags = PasteboardSynchronize(hPasteboard);
+    /* If nothing changed return */
+    if (!(syncFlags & kPasteboardModified))
+    {
+        *pfChanged = false;
+        Log2(("queryNewPasteboardFormats: no change\n"));
+        return VINF_SUCCESS;
+    }
+
+    /* Are some items in the pasteboard? */
+    ItemCount cItems = 0;
+    orc = PasteboardGetItemCount(hPasteboard, &cItems);
+    if (orc == 0)
+    {
+        if (cItems < 1)
+            Log(("queryNewPasteboardFormats: changed: No items on the pasteboard\n"));
+        else
+        {
+            /* The id of the first element in the pasteboard */
+            PasteboardItemID idItem = 0;
+            orc = PasteboardGetItemIdentifier(hPasteboard, 1, &idItem);
+            if (orc == 0)
+            {
+                /*
+                 * Retrieve all flavors on the pasteboard, maybe there
+                 * is something we can use.  Or maybe we're the owner.
+                 */
+                CFArrayRef hFlavors = 0;
+                orc = PasteboardCopyItemFlavors(hPasteboard, idItem, &hFlavors);
+                if (orc == 0)
+                {
+                    CFIndex cFlavors = CFArrayGetCount(hFlavors);
+                    for (CFIndex idxFlavor = 0; idxFlavor < cFlavors; idxFlavor++)
+                    {
+                        CFStringRef hStrFlavor = (CFStringRef)CFArrayGetValueAtIndex(hFlavors, idxFlavor);
+                        if (   idItem == (PasteboardItemID)idOwnership
+                            && hStrOwnershipFlavor
+                            && CFStringCompare(hStrFlavor, (CFStringRef)hStrOwnershipFlavor, 0) == kCFCompareEqualTo)
+                        {
+                            /* We made the changes ourselves. */
+                            Log2(("queryNewPasteboardFormats: no-changed: our clipboard!\n"));
+                            *pfChanged = false;
+                            *pfFormats = 0;
+                            break;
+                        }
+
+                        if (UTTypeConformsTo(hStrFlavor, kUTTypeBMP))
+                        {
+                            Log(("queryNewPasteboardFormats: BMP flavor detected.\n"));
+                            *pfFormats |= VBOX_SHCL_FMT_BITMAP;
+                        }
+                        else if (   UTTypeConformsTo(hStrFlavor, kUTTypeUTF8PlainText)
+                                 || UTTypeConformsTo(hStrFlavor, kUTTypeUTF16PlainText))
+                        {
+                            Log(("queryNewPasteboardFormats: Unicode flavor detected.\n"));
+                            *pfFormats |= VBOX_SHCL_FMT_UNICODETEXT;
+                        }
+#ifdef WITH_HTML_H2G
+                        else if (UTTypeConformsTo(hStrFlavor, kUTTypeHTML))
+                        {
+                            Log(("queryNewPasteboardFormats: HTML flavor detected.\n"));
+                            *pfFormats |= VBOX_SHCL_FMT_HTML;
+                        }
+#endif
+#ifdef LOG_ENABLED
+                        else if (LogIs2Enabled())
+                        {
+                            if (CFStringGetCharactersPtr(hStrFlavor))
+                                Log2(("queryNewPasteboardFormats: Unknown flavor: %ls.\n", CFStringGetCharactersPtr(hStrFlavor)));
+                            else if (CFStringGetCStringPtr(hStrFlavor, kCFStringEncodingUTF8))
+                                Log2(("queryNewPasteboardFormats: Unknown flavor: %s.\n",
+                                      CFStringGetCStringPtr(hStrFlavor, kCFStringEncodingUTF8)));
+                            else
+                                Log2(("queryNewPasteboardFormats: Unknown flavor: ???\n"));
+                        }
+#endif
+                    }
+
+                    CFRelease(hFlavors);
+                }
+                else
+                    Log(("queryNewPasteboardFormats: PasteboardCopyItemFlavors failed - %d (%#x)\n", orc, orc));
+            }
+            else
+                Log(("queryNewPasteboardFormats: PasteboardGetItemIdentifier failed - %d (%#x)\n", orc, orc));
+
+            if (*pfChanged)
+                Log(("queryNewPasteboardFormats: changed: *pfFormats=%#x\n", *pfFormats));
+        }
+    }
+    else
+        Log(("queryNewPasteboardFormats: PasteboardGetItemCount failed - %d (%#x)\n", orc, orc));
+    return VINF_SUCCESS;
+}
+
+/**
+ * Read content from the host clipboard and write it to the internal clipboard
+ * structure for further processing.
+ *
+ * @param   pPasteboard    Reference to the global pasteboard.
+ * @param   fFormat        The format type which should be read.
+ * @param   pv             The destination buffer.
+ * @param   cb             The size of the destination buffer.
+ * @param   pcbActual      The size which is needed to transfer the content.
+ *
+ * @returns IPRT status code.
+ */
+int readFromPasteboard(PasteboardRef pPasteboard, uint32_t fFormat, void *pv, uint32_t cb, uint32_t *pcbActual)
+{
+    Log(("readFromPasteboard: fFormat = %02X\n", fFormat));
+
+    /* Make sure all is in sync */
+    PasteboardSynchronize(pPasteboard);
+
+    /* Are some items in the pasteboard? */
+    ItemCount cItems;
+    OSStatus orc = PasteboardGetItemCount(pPasteboard, &cItems);
+    if (cItems < 1)
+        return VINF_SUCCESS;
+
+    /*
+     * Our default response...
+     */
+    int rc = VERR_NOT_SUPPORTED;
+
+    /*
+     * The id of the first element in the pasteboard
+     */
+    PasteboardItemID idItem;
+    orc = PasteboardGetItemIdentifier(pPasteboard, 1, &idItem);
+    if (orc == 0)
+    {
+        CFDataRef hDataCopy  = 0;
+        size_t    cbDataCopy = 0;
+
+        /*
+         * The guest request unicode
+         */
+        if (fFormat & VBOX_SHCL_FMT_UNICODETEXT)
+        {
+            PRTUTF16  pwszSrcFree = NULL;
+            PCRTUTF16 pwszSrc     = NULL;
+            size_t    cwcSrc      = 0;
+
+            /* First preference is plain UTF-16 text: */
+            orc = PasteboardCopyItemFlavorData(pPasteboard, idItem, kUTTypeUTF16PlainText, &hDataCopy);
+            if (orc == 0)
+            {
+                cbDataCopy = CFDataGetLength(hDataCopy);
+                Log(("Clipboard content is utf-16 (%zu bytes)\n", cbDataCopy));
+                pwszSrc = (PCRTUTF16)CFDataGetBytePtr(hDataCopy);
+                if (pwszSrc)
+                {
+                    cwcSrc = RTUtf16NLen(pwszSrc, cbDataCopy / sizeof(RTUTF16));
+                    if (cwcSrc >= cbDataCopy / sizeof(RTUTF16))
+                    {
+                        pwszSrcFree = RTUtf16Alloc((cwcSrc + 1) * sizeof(RTUTF16));
+                        if (pwszSrcFree)
+                        {
+                            memcpy(pwszSrcFree, pwszSrc, cwcSrc * sizeof(RTUTF16));
+                            pwszSrcFree[cwcSrc] = '\0';
+                            pwszSrc = pwszSrcFree;
+                        }
+                        else
+                        {
+                            rc = VERR_NO_UTF16_MEMORY;
+                            pwszSrc = NULL;
+                        }
+                    }
+                }
+                else
+                    rc = VERR_GENERAL_FAILURE;
+            }
+            /* Second preference is plain UTF-8 text: */
+            else
+            {
+                orc = PasteboardCopyItemFlavorData(pPasteboard, idItem, kUTTypeUTF8PlainText, &hDataCopy);
+                if (orc == 0)
+                {
+                    cbDataCopy = CFDataGetLength(hDataCopy);
+                    Log(("readFromPasteboard: clipboard content is utf-8 (%zu bytes)\n", cbDataCopy));
+                    const char *pszSrc = (const char *)CFDataGetBytePtr(hDataCopy);
+                    if (pszSrc)
+                    {
+                        size_t cchSrc = RTStrNLen(pszSrc, cbDataCopy);
+                        rc = RTStrToUtf16Ex(pszSrc, cchSrc, &pwszSrcFree, 0, &cwcSrc);
+                        if (RT_SUCCESS(rc))
+                            pwszSrc = pwszSrcFree;
+                    }
+                    else
+                        rc = VERR_GENERAL_FAILURE;
+                }
+            }
+            if (pwszSrc)
+            {
+                /*
+                 * Convert to windows UTF-16.
+                 */
+                Assert(cwcSrc == RTUtf16Len(pwszSrc));
+                size_t cwcDst = 0;
+                rc = ShClUtf16LFLenUtf8(pwszSrc, cwcSrc, &cwcDst);
+                if (RT_SUCCESS(rc))
+                {
+                    cwcDst++; /* Add space for terminator. */
+
+                    *pcbActual = cwcDst * sizeof(RTUTF16);
+                    if (*pcbActual <= cb)
+                    {
+                        rc = ShClConvUtf16LFToCRLF(pwszSrc, cwcSrc, (PRTUTF16)pv, cb / sizeof(RTUTF16));
+                        if (RT_SUCCESS(rc))
+                        {
+#ifdef SHOW_CLIPBOARD_CONTENT
+                            Log(("readFromPasteboard: clipboard content: %ls\n", (PCRTUTF16)pv));
+#endif
+                        }
+                        else
+                        {
+                            Log(("readFromPasteboard: ShClUtf16LinToWin failed - %Rrc!\n", rc));
+                            AssertRC(rc);
+                        }
+                    }
+                    else
+                    {
+                        Log(("readFromPasteboard: Insufficient (text) buffer space: %#zx, need %#zx\n", cb, *pcbActual));
+                        rc = VINF_SUCCESS;
+                    }
+                }
+                else
+                {
+                    Log(("readFromPasteboard: ShClUtf16GetWinSize failed - %Rrc!\n", rc));
+                    AssertRC(rc);
+                }
+                RTUtf16Free(pwszSrcFree);
+            }
+        }
+        /*
+         * The guest request BITMAP
+         */
+        else if (fFormat & VBOX_SHCL_FMT_BITMAP)
+        {
+            /* Get the BMP data from the pasteboard */
+            orc = PasteboardCopyItemFlavorData(pPasteboard, idItem, kUTTypeBMP, &hDataCopy);
+            if (orc == 0)
+            {
+                cbDataCopy = CFDataGetLength(hDataCopy);
+                Log(("Clipboard content is BMP (%zu bytes)\n", cbDataCopy));
+                const void *pvSrc = CFDataGetBytePtr(hDataCopy);
+                if (pvSrc)
+                {
+                    /*
+                     * Try get the device independent bitmap (DIB) bit from it.
+                     */
+                    const void *pvDib;
+                    size_t      cbDib;
+                    rc = ShClBmpGetDib(pvSrc, cbDataCopy, &pvDib, &cbDib);
+                    if (RT_SUCCESS(rc))
+                    {
+                        *pcbActual = cbDib;
+                        if (*pcbActual <= cb)
+                        {
+                            memcpy(pv, pvDib, cbDib);
+#ifdef SHOW_CLIPBOARD_CONTENT
+                            Log(("readFromPasteboard: clipboard content bitmap %zx bytes\n", cbDib));
+#endif
+                        }
+                        else
+                            Log(("readFromPasteboard: Insufficient (bitmap) buffer space: %#zx, need %#zx\n", cb, cbDib));
+                        rc = VINF_SUCCESS;
+                    }
+                    else
+                    {
+                        AssertRC(rc);
+                        Log(("readFromPasteboard: ShClBmpGetDib failed - %Rrc - unknown bitmap format??\n", rc));
+                        rc = VERR_NOT_SUPPORTED;
+                    }
+                }
+                else
+                    rc = VERR_GENERAL_FAILURE;
+            }
+            else
+                LogFlow(("readFromPasteboard: PasteboardCopyItemFlavorData/kUTTypeBMP -> %d (%#x)\n", orc, orc));
+        }
+#ifdef WITH_HTML_H2G
+        /*
+         * The guest request HTML.  It expects a UTF-8 reply and we assume
+         * that's what's on the pasteboard too.
+         */
+        else if (fFormat & VBOX_SHCL_FMT_HTML)
+        {
+            orc = PasteboardCopyItemFlavorData(pPasteboard, idItem, kUTTypeHTML, &hDataCopy);
+            if (orc == 0)
+            {
+                cbDataCopy = CFDataGetLength(hDataCopy);
+                Log(("Clipboard content is HTML (%zu bytes):\n", cbDataCopy));
+                const char *pszSrc = (const char *)CFDataGetBytePtr(hDataCopy);
+                if (pszSrc)
+                {
+                    Log3(("%.*Rhxd\n", cbDataCopy, pszSrc));
+                    rc = RTStrValidateEncodingEx(pszSrc, cbDataCopy, 0 /*fFlags*/);
+                    if (RT_SUCCESS(rc))
+                    {
+                        size_t cchSrc = RTStrNLen(pszSrc, cbDataCopy);
+                        *pcbActual = cchSrc;
+                        if (cchSrc <= cb)
+                            memcpy(pv, pszSrc, cchSrc);
+                        else
+                            Log(("readFromPasteboard: Insufficient (HTML) buffer space: %#zx, need %#zx\n", cb, cchSrc));
+                        rc = VINF_SUCCESS;
+                    }
+                    else
+                    {
+                        Log(("readFromPasteboard: Invalid UTF-8 encoding on pasteboard: %Rrc\n", rc));
+                        rc = VERR_NOT_SUPPORTED;
+                    }
+                }
+                else
+                    rc = VERR_GENERAL_FAILURE;
+            }
+            else
+                LogFlow(("readFromPasteboard: PasteboardCopyItemFlavorData/kUTTypeHTML -> %d (%#x)\n", orc, orc));
+        }
+#endif
+        else
+        {
+            Log2(("readFromPasteboard: Unsupported format: %#x\n", fFormat));
+            rc = VERR_NOT_SUPPORTED;
+        }
+
+        /*
+         * Release the data copy, if we got one.  There are no returns above!
+         */
+        if (hDataCopy)
+            CFRelease(hDataCopy);
+    }
+    else
+    {
+        Log(("readFromPasteboard: PasteboardGetItemIdentifier failed: %u (%#x)\n", orc, orc));
+        rc = VERR_NOT_SUPPORTED;
+    }
+
+    Log(("readFromPasteboard: rc=%Rrc *pcbActual=%#zx\n", rc, *pcbActual));
+    return rc;
+}
+
+/**
+ * Takes the ownership of the pasteboard.
+ *
+ * This is called when the other end reports available formats.
+ *
+ * @returns VBox status code.
+ * @param   hPasteboard             The pastboard handle (reference).
+ * @param   idOwnership             The ownership ID to use now.
+ * @param   pszOwnershipFlavor      The ownership indicator flavor
+ * @param   pszOwnershipValue       The ownership value (stringified format mask).
+ * @param   phStrOwnershipFlavor    Pointer to a CFStringRef variable holding
+ *                                  the current ownership flavor string.  This
+ *                                  will always be released, and set again on
+ *                                  success.
+ *
+ * @todo    Add fFormats so we can make promises about available formats at once
+ *          without needing to request any data first.  That might help on
+ *          flavor priority.
+ */
+int takePasteboardOwnership(PasteboardRef hPasteboard, uint64_t idOwnership, const char *pszOwnershipFlavor,
+                            const char *pszOwnershipValue, void **phStrOwnershipFlavor)
+{
+    /*
+     * Release the old string.
+     */
+    if (*phStrOwnershipFlavor)
+    {
+        CFStringRef hOldFlavor = (CFStringRef)*phStrOwnershipFlavor;
+        CFRelease(hOldFlavor);
+        *phStrOwnershipFlavor = NULL;
+    }
+
+    /*
+     * Clear the pasteboard and take ownership over it.
+     */
+    OSStatus orc = PasteboardClear(hPasteboard);
+    if (orc == 0)
+    {
+        /* For good measure. */
+        PasteboardSynchronize(hPasteboard);
+
+        /*
+         * Put the ownership flavor and value onto the clipboard.
+         */
+        CFDataRef hData = CFDataCreate(kCFAllocatorDefault, (const UInt8 *)pszOwnershipValue, strlen(pszOwnershipValue));
+        if (hData)
+        {
+            CFStringRef hFlavor = CFStringCreateWithCString(kCFAllocatorDefault, pszOwnershipFlavor, kCFStringEncodingUTF8);
+            if (hFlavor)
+            {
+                orc = PasteboardPutItemFlavor(hPasteboard, (PasteboardItemID)idOwnership,
+                                              hFlavor, hData, kPasteboardFlavorNoFlags);
+                if (orc == 0)
+                {
+                    *phStrOwnershipFlavor = (void *)hFlavor;
+                    Log(("takePasteboardOwnership: idOwnership=%RX64 flavor=%s value=%s\n",
+                         idOwnership, pszOwnershipFlavor, pszOwnershipValue));
+                }
+                else
+                {
+                    Log(("takePasteboardOwnership: PasteboardPutItemFlavor -> %d (%#x)!\n", orc, orc));
+                    CFRelease(hFlavor);
+                }
+            }
+            else
+                Log(("takePasteboardOwnership: CFStringCreateWithCString failed!\n"));
+            CFRelease(hData);
+        }
+        else
+            Log(("takePasteboardOwnership: CFDataCreate failed!\n"));
+    }
+    else
+        Log(("takePasteboardOwnership: PasteboardClear failed -> %d (%#x)\n", orc, orc));
+    return orc == 0 ? VINF_SUCCESS : VERR_GENERAL_FAILURE;
+}
+
+/**
+ * Write clipboard content to the host clipboard from the internal clipboard
+ * structure.
+ *
+ * @param   hPasteboard    Reference to the global pasteboard.
+ * @param   idOwnership    The ownership ID.
+ * @param   pv             The source buffer.
+ * @param   cb             The size of the source buffer.
+ * @param   fFormat        The format type which should be written.
+ *
+ * @returns IPRT status code.
+ */
+int writeToPasteboard(PasteboardRef hPasteboard, uint64_t idOwnership, const void *pv, uint32_t cb, uint32_t fFormat)
+{
+    int       rc;
+    OSStatus  orc;
+    CFDataRef hData;
+    Log(("writeToPasteboard: fFormat=%#x\n", fFormat));
+
+    /* Make sure all is in sync */
+    PasteboardSynchronize(hPasteboard);
+
+    /*
+     * Handle the unicode text
+     */
+    if (fFormat & VBOX_SHCL_FMT_UNICODETEXT)
+    {
+        PCRTUTF16 const pwszSrc = (PCRTUTF16)pv;
+        size_t const    cwcSrc  = cb / sizeof(RTUTF16);
+
+        /*
+         * If the other side is windows or OS/2, we may have to convert
+         * '\r\n' -> '\n' and the drop ending marker.
+         */
+
+        /* How long will the converted text be? */
+        size_t cwcDst = 0;
+        rc = ShClUtf16CRLFLenUtf8(pwszSrc, cwcSrc, &cwcDst);
+        AssertMsgRCReturn(rc, ("ShClUtf16GetLinSize failed: %Rrc\n", rc), rc);
+
+        /* Ignore empty strings? */ /** @todo r=andy Really? Why? */
+        if (cwcDst == 0)
+        {
+            Log(("writeToPasteboard: received empty string from the guest; ignoreing it.\n"));
+            return VINF_SUCCESS;
+        }
+
+        cwcDst++; /* Add space for terminator. */
+
+        /* Allocate the necessary memory and do the conversion. */
+        PRTUTF16 pwszDst = (PRTUTF16)RTMemAlloc(cwcDst * sizeof(RTUTF16));
+        AssertMsgReturn(pwszDst, ("cwcDst=%#zx\n", cwcDst), VERR_NO_UTF16_MEMORY);
+
+        rc = ShClConvUtf16CRLFToLF(pwszSrc, cwcSrc, pwszDst, cwcDst);
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Create an immutable CFData object that we can place on the clipboard.
+             */
+            hData = CFDataCreate(kCFAllocatorDefault, (const UInt8 *)pwszDst, cwcDst * sizeof(RTUTF16));
+            if (hData)
+            {
+                orc = PasteboardPutItemFlavor(hPasteboard, (PasteboardItemID)idOwnership,
+                                              kUTTypeUTF16PlainText, hData, kPasteboardFlavorNoFlags);
+                if (orc == 0)
+                    rc = VINF_SUCCESS;
+                else
+                {
+                    Log(("writeToPasteboard: PasteboardPutItemFlavor/kUTTypeUTF16PlainText failed: %d (%#x)\n", orc, orc));
+                    rc = VERR_GENERAL_FAILURE;
+                }
+                CFRelease(hData);
+            }
+            else
+            {
+                Log(("writeToPasteboard: CFDataCreate/UTF16 failed!\n"));
+                rc = VERR_NO_MEMORY;
+            }
+
+            /*
+             * Now for the UTF-8 version.
+             */
+            char *pszDst;
+            int rc2 = RTUtf16ToUtf8(pwszDst, &pszDst);
+            if (RT_SUCCESS(rc2))
+            {
+                hData = CFDataCreate(kCFAllocatorDefault, (const UInt8 *)pszDst, strlen(pszDst));
+                if (hData)
+                {
+                    orc = PasteboardPutItemFlavor(hPasteboard, (PasteboardItemID)idOwnership,
+                                                  kUTTypeUTF8PlainText, hData, kPasteboardFlavorNoFlags);
+                    if (orc != 0)
+                    {
+                        Log(("writeToPasteboard: PasteboardPutItemFlavor/kUTTypeUTF8PlainText failed: %d (%#x)\n", orc, orc));
+                        rc = VERR_GENERAL_FAILURE;
+                    }
+                    CFRelease(hData);
+                }
+                else
+                {
+                    Log(("writeToPasteboard: CFDataCreate/UTF8 failed!\n"));
+                    rc = VERR_NO_MEMORY;
+                }
+                RTStrFree(pszDst);
+            }
+            else
+                rc = rc2;
+        }
+        else
+            Log(("writeToPasteboard: clipboard conversion failed.  vboxClipboardUtf16WinToLin() returned %Rrc.  Abandoning.\n", rc));
+
+        RTMemFree(pwszDst);
+    }
+    /*
+     * Handle the bitmap.  We convert the DIB to a bitmap and put it on
+     * the pasteboard using the BMP flavor.
+     */
+    else if (fFormat & VBOX_SHCL_FMT_BITMAP)
+    {
+        /* Create a full BMP from it */
+        void  *pvBmp;
+        size_t cbBmp;
+        rc = ShClDibToBmp(pv, cb, &pvBmp, &cbBmp);
+        if (RT_SUCCESS(rc))
+        {
+            hData = CFDataCreate(kCFAllocatorDefault, (UInt8 const *)pvBmp, cbBmp);
+            if (hData)
+            {
+                orc = PasteboardPutItemFlavor(hPasteboard, (PasteboardItemID)idOwnership,
+                                              kUTTypeBMP, hData, kPasteboardFlavorNoFlags);
+                if (orc != 0)
+                {
+                    Log(("writeToPasteboard: PasteboardPutItemFlavor/kUTTypeBMP failed: %d (%#x)\n", orc, orc));
+                    rc = VERR_GENERAL_FAILURE;
+                }
+                CFRelease(hData);
+            }
+            else
+            {
+                Log(("writeToPasteboard: CFDataCreate/UTF8 failed!\n"));
+                rc = VERR_NO_MEMORY;
+            }
+            RTMemFree(pvBmp);
+        }
+    }
+#ifdef WITH_HTML_G2H
+    /*
+     * Handle HTML.  Expect UTF-8, ignore line endings and just put it
+     * straigh up on the pasteboard for now.
+     */
+    else if (fFormat & VBOX_SHCL_FMT_HTML)
+    {
+        const char   *pszSrc = (const char *)pv;
+        size_t const  cchSrc = RTStrNLen(pszSrc, cb);
+        rc = RTStrValidateEncodingEx(pszSrc, cchSrc, 0);
+        if (RT_SUCCESS(rc))
+        {
+            hData = CFDataCreate(kCFAllocatorDefault, (const UInt8 *)pszSrc, cchSrc);
+            if (hData)
+            {
+                orc = PasteboardPutItemFlavor(hPasteboard, (PasteboardItemID)idOwnership, kUTTypeHTML,
+                                              hData, kPasteboardFlavorNoFlags);
+                if (orc == 0)
+                    rc = VINF_SUCCESS;
+                else
+                {
+                    Log(("writeToPasteboard: PasteboardPutItemFlavor/kUTTypeHTML failed: %d (%#x)\n", orc, orc));
+                    rc = VERR_GENERAL_FAILURE;
+                }
+                CFRelease(hData);
+            }
+            else
+            {
+                Log(("writeToPasteboard: CFDataCreate/HTML failed!\n"));
+                rc = VERR_NO_MEMORY;
+            }
+        }
+        else
+            Log(("writeToPasteboard: HTML: Invalid UTF-8 encoding: %Rrc\n", rc));
+    }
+#endif
+    else
+        rc = VERR_NOT_IMPLEMENTED;
+
+    Log(("writeToPasteboard: rc=%Rrc\n", rc));
+    return rc;
+}
+
diff --git a/src/VBox/HostServices/SharedClipboard/darwin-pasteboard.h b/src/VBox/HostServices/SharedClipboard/darwin-pasteboard.h
new file mode 100644
index 00000000..38238d0c
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/darwin-pasteboard.h
@@ -0,0 +1,47 @@
+/* $Id: darwin-pasteboard.h $ */
+/** @file
+ * Shared Clipboard Service - Mac OS X host implementation.
+ */
+
+/*
+ * Copyright (C) 2008-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_SharedClipboard_darwin_pasteboard_h
+#define VBOX_INCLUDED_SRC_SharedClipboard_darwin_pasteboard_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+typedef struct OpaquePasteboardRef *PasteboardRef;
+
+int initPasteboard(PasteboardRef *pPasteboardRef);
+void destroyPasteboard(PasteboardRef *pPasteboardRef);
+
+int queryNewPasteboardFormats(PasteboardRef hPasteboard, uint64_t idOwnership, void *hStrOwnershipFlavor,
+                              uint32_t *pfFormats, bool *pfChanged);
+int readFromPasteboard(PasteboardRef pPasteboard, uint32_t fFormat, void *pv, uint32_t cb, uint32_t *pcbActual);
+int takePasteboardOwnership(PasteboardRef pPasteboard, uint64_t idOwnership, const char *pszOwnershipFlavor,
+                            const char *pszOwnershipValue, void **phStrOwnershipFlavor);
+int writeToPasteboard(PasteboardRef hPasteboard, uint64_t idOwnership, void const *pv, uint32_t cb, uint32_t fFormat);
+
+#endif /* !VBOX_INCLUDED_SRC_SharedClipboard_darwin_pasteboard_h */
+
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/.scm-settings b/src/VBox/HostServices/SharedClipboard/testcase/.scm-settings
new file mode 100644
index 00000000..9fe67d17
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/.scm-settings
@@ -0,0 +1,29 @@
+# $Id: .scm-settings $
+## @file
+# Source code massager settings for the host HGCM services.
+#
+
+#
+# Copyright (C) 2019-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+--filter-out-files *.txt
+/*.h: --guard-relative-to-dir .
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/Makefile.kmk b/src/VBox/HostServices/SharedClipboard/testcase/Makefile.kmk
new file mode 100644
index 00000000..66160a26
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/Makefile.kmk
@@ -0,0 +1,147 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Shared Clipboard Host Service testcases.
+#
+
+#
+# Copyright (C) 2011-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+if defined(VBOX_WITH_TESTCASES) && !defined(VBOX_ONLY_ADDITIONS) && !defined(VBOX_ONLY_SDK)
+
+ #
+ # Testcase which mocks HGCM to also test the VbglR3-side of Shared Clipboard.
+ #
+ # Goal is to use and test as much guest side code as possible as a self-contained
+ # binary on the host here.
+ #
+ # Note: No #ifdef TESTCASE hacks or similar allowed, has to run
+ #       without #ifdef modifications to the core code!
+ #
+ tstClipboardMockHGCM_TEMPLATE = VBoxR3TstExe
+ tstClipboardMockHGCM_DEFS    = VBOX_WITH_HGCM VBOX_WITH_SHARED_CLIPBOARD
+ tstClipboardMockHGCM_SOURCES = \
+ 	../VBoxSharedClipboardSvc.cpp \
+ 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp \
+ 	$(PATH_ROOT)/src/VBox/Additions/common/VBoxGuest/lib/VBoxGuestR3LibClipboard.cpp \
+ 	$(PATH_ROOT)/src/VBox/HostServices/common/message.cpp \
+ 	tstClipboardMockHGCM.cpp
+ tstClipboardMockHGCM_LIBS    = $(LIB_RUNTIME)
+
+ if1of ($(KBUILD_TARGET), linux solaris)
+  PROGRAMS += tstClipboardMockHGCM
+  tstClipboardMockHGCM_SOURCES += \
+  	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-x11.cpp \
+  	../VBoxSharedClipboardSvc-x11.cpp
+  tstClipboardMockHGCM_LIBPATH = \
+  	$(VBOX_LIBPATH_X11)
+  tstClipboardMockHGCM_LIBS   += \
+  	Xt \
+  	X11
+ endif
+ if1of ($(KBUILD_TARGET), win)
+  PROGRAMS += tstClipboardMockHGCM
+  tstClipboardMockHGCM_SOURCES += \
+  	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-win.cpp \
+  	../VBoxSharedClipboardSvc-win.cpp
+ endif
+
+ tstClipboardMockHGCM_CLEAN = $(tstClipboardMockHGCM_0_OUTDIR)/tstClipboardMockHGCM.run
+
+ if defined(VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS)
+  tstClipboardMockHGCM_DEFS   += VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+  tstClipboardMockHGCM_SOURCES += \
+  	../VBoxSharedClipboardSvc-transfers.cpp \
+  	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-transfers.cpp
+ endif
+
+ if 0 # Enable this if you want automatic runs after compilation.
+  $$(tstClipboardMockHGCM_0_OUTDIR)/tstClipboardMockHGCM.run: $$(tstClipboardMockHGCM_1_STAGE_TARGET)
+	export VBOX_LOG_DEST=nofile; $(tstClipboardMockHGCM_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+  OTHERS += $(tstClipboardMockHGCM_0_OUTDIR)/tstClipboardMockHGCM.run
+ endif
+
+ #
+ #
+ #
+ PROGRAMS += tstClipboardServiceHost
+ tstClipboardServiceHost_TEMPLATE = VBoxR3TstExe
+ tstClipboardServiceHost_DEFS     = VBOX_WITH_HGCM UNIT_TEST
+ tstClipboardServiceHost_SOURCES  = \
+ 	../VBoxSharedClipboardSvc.cpp \
+ 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp \
+ 	$(PATH_ROOT)/src/VBox/HostServices/common/message.cpp \
+ 	tstClipboardServiceHost.cpp
+ tstClipboardServiceHost_LIBS     = $(LIB_RUNTIME)
+ tstClipboardServiceHost_CLEAN    = $(tstClipboardServiceHost_0_OUTDIR)/tstClipboardServiceHost.run
+
+ if defined(VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS)
+  tstClipboardServiceHost_DEFS    += VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+  tstClipboardServiceHost_SOURCES += \
+  	../VBoxSharedClipboardSvc-transfers.cpp \
+  	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-transfers.cpp
+ endif
+
+ #
+ #
+ #
+ PROGRAMS += tstClipboardServiceImpl
+ tstClipboardServiceImpl_TEMPLATE = VBoxR3TstExe
+ tstClipboardServiceImpl_DEFS     = VBOX_WITH_HGCM UNIT_TEST
+ tstClipboardServiceImpl_SOURCES  = \
+ 	../VBoxSharedClipboardSvc.cpp \
+ 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp \
+ 	$(PATH_ROOT)/src/VBox/HostServices/common/message.cpp \
+ 	tstClipboardServiceImpl.cpp
+ tstClipboardServiceImpl_SOURCES.win = \
+ 	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-win.cpp
+ tstClipboardServiceImpl_LIBS     = $(LIB_RUNTIME)
+ tstClipboardServiceImpl_CLEAN    = $(tstClipboardServiceImpl_0_OUTDIR)/tstClipboardServiceImpl.run
+
+ if defined(VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS)
+  #
+  #
+  #
+  PROGRAMS += tstClipboardTransfers
+  tstClipboardTransfers_TEMPLATE = VBoxR3TstExe
+  tstClipboardTransfers_DEFS     = VBOX_WITH_HGCM UNIT_TEST VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+  tstClipboardTransfers_SOURCES  = \
+  	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-common.cpp \
+  	$(PATH_ROOT)/src/VBox/GuestHost/SharedClipboard/clipboard-transfers.cpp \
+  	tstClipboardTransfers.cpp
+ endif
+endif
+
+#
+# List of above testcases that will be included in the ValKit.
+#
+ifdef VBOX_WITH_VALIDATIONKIT_UNITTESTS_PACKING
+ if1of ($(KBUILD_TARGET), linux solaris win)
+  VALKIT_UNITTESTS_WHITELIST_GUEST_ADDITIONS += \
+  	tstClipboardMockHGCM
+ endif
+endif # VBOX_WITH_VALIDATIONKIT_UNITTESTS_PACKING
+
+include $(FILE_KBUILD_SUB_FOOTER)
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgCfHtml1.h b/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgCfHtml1.h
new file mode 100644
index 00000000..35791604
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgCfHtml1.h
@@ -0,0 +1,165 @@
+/* $Id: VBoxOrgCfHtml1.h $ */
+/** @file
+ * Shared Clipboard host service test case C data file of VBoxOrgCfHtml1.txt.
+ */
+
+/*
+ * Copyright (C) 2022-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_VBoxOrgCfHtml1_h
+#define VBOX_INCLUDED_SRC_VBoxOrgCfHtml1_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <iprt/cdefs.h>
+
+const unsigned char g_abVBoxOrgCfHtml1[] =
+{
+    0x56, 0x65, 0x72, 0x73, 0x69, 0x6f, 0x6e, 0x3a, 0x30, 0x2e, 0x39, 0x0d, 0x0a, 0x53, 0x74, 0x61, /* 0x00000000: Version:0.9..Sta */
+    0x72, 0x74, 0x48, 0x54, 0x4d, 0x4c, 0x3a, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x31, 0x34, /* 0x00000010: rtHTML:000000014 */
+    0x34, 0x0d, 0x0a, 0x45, 0x6e, 0x64, 0x48, 0x54, 0x4d, 0x4c, 0x3a, 0x30, 0x30, 0x30, 0x30, 0x30, /* 0x00000020: 4..EndHTML:00000 */
+    0x30, 0x31, 0x39, 0x36, 0x31, 0x0d, 0x0a, 0x53, 0x74, 0x61, 0x72, 0x74, 0x46, 0x72, 0x61, 0x67, /* 0x00000030: 01961..StartFrag */
+    0x6d, 0x65, 0x6e, 0x74, 0x3a, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x30, 0x31, 0x38, 0x30, 0x0d, /* 0x00000040: ment:0000000180. */
+    0x0a, 0x45, 0x6e, 0x64, 0x46, 0x72, 0x61, 0x67, 0x6d, 0x65, 0x6e, 0x74, 0x3a, 0x30, 0x30, 0x30, /* 0x00000050: .EndFragment:000 */
+    0x30, 0x30, 0x30, 0x31, 0x39, 0x32, 0x35, 0x0d, 0x0a, 0x53, 0x6f, 0x75, 0x72, 0x63, 0x65, 0x55, /* 0x00000060: 0001925..SourceU */
+    0x52, 0x4c, 0x3a, 0x68, 0x74, 0x74, 0x70, 0x73, 0x3a, 0x2f, 0x2f, 0x77, 0x77, 0x77, 0x2e, 0x76, /* 0x00000070: RL:https:..www.v */
+    0x69, 0x72, 0x74, 0x75, 0x61, 0x6c, 0x62, 0x6f, 0x78, 0x2e, 0x6f, 0x72, 0x67, 0x2f, 0x0d, 0x0a, /* 0x00000080: irtualbox.org... */
+    0x3c, 0x68, 0x74, 0x6d, 0x6c, 0x3e, 0x0d, 0x0a, 0x3c, 0x62, 0x6f, 0x64, 0x79, 0x3e, 0x0d, 0x0a, /* 0x00000090: <html>..<body>.. */
+    0x3c, 0x21, 0x2d, 0x2d, 0x53, 0x74, 0x61, 0x72, 0x74, 0x46, 0x72, 0x61, 0x67, 0x6d, 0x65, 0x6e, /* 0x000000a0: <!--StartFragmen */
+    0x74, 0x2d, 0x2d, 0x3e, 0x3c, 0x73, 0x70, 0x61, 0x6e, 0x20, 0x73, 0x74, 0x79, 0x6c, 0x65, 0x3d, /* 0x000000b0: t--><span style= */
+    0x22, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x72, 0x67, 0x62, 0x28, 0x30, 0x2c, 0x20, 0x30, /* 0x000000c0: "color: rgb(0, 0 */
+    0x2c, 0x20, 0x30, 0x29, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x66, 0x61, 0x6d, 0x69, 0x6c, /* 0x000000d0: , 0); font-famil */
+    0x79, 0x3a, 0x20, 0x56, 0x65, 0x72, 0x64, 0x61, 0x6e, 0x61, 0x2c, 0x20, 0x26, 0x71, 0x75, 0x6f, /* 0x000000e0: y: Verdana, &quo */
+    0x74, 0x3b, 0x42, 0x69, 0x74, 0x73, 0x74, 0x72, 0x65, 0x61, 0x6d, 0x20, 0x56, 0x65, 0x72, 0x61, /* 0x000000f0: t;Bitstream Vera */
+    0x20, 0x53, 0x61, 0x6e, 0x73, 0x26, 0x71, 0x75, 0x6f, 0x74, 0x3b, 0x2c, 0x20, 0x73, 0x61, 0x6e, /* 0x00000100:  Sans&quot;, san */
+    0x73, 0x2d, 0x73, 0x65, 0x72, 0x69, 0x66, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x73, 0x69, /* 0x00000110: s-serif; font-si */
+    0x7a, 0x65, 0x3a, 0x20, 0x31, 0x33, 0x70, 0x78, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x73, /* 0x00000120: ze: 13px; font-s */
+    0x74, 0x79, 0x6c, 0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, /* 0x00000130: tyle: normal; fo */
+    0x6e, 0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x6c, 0x69, 0x67, 0x61, 0x74, /* 0x00000140: nt-variant-ligat */
+    0x75, 0x72, 0x65, 0x73, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, /* 0x00000150: ures: normal; fo */
+    0x6e, 0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x63, 0x61, 0x70, 0x73, 0x3a, /* 0x00000160: nt-variant-caps: */
+    0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x77, 0x65, /* 0x00000170:  normal; font-we */
+    0x69, 0x67, 0x68, 0x74, 0x3a, 0x20, 0x34, 0x30, 0x30, 0x3b, 0x20, 0x6c, 0x65, 0x74, 0x74, 0x65, /* 0x00000180: ight: 400; lette */
+    0x72, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, /* 0x00000190: r-spacing: norma */
+    0x6c, 0x3b, 0x20, 0x6f, 0x72, 0x70, 0x68, 0x61, 0x6e, 0x73, 0x3a, 0x20, 0x32, 0x3b, 0x20, 0x74, /* 0x000001a0: l; orphans: 2; t */
+    0x65, 0x78, 0x74, 0x2d, 0x61, 0x6c, 0x69, 0x67, 0x6e, 0x3a, 0x20, 0x73, 0x74, 0x61, 0x72, 0x74, /* 0x000001b0: ext-align: start */
+    0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x69, 0x6e, 0x64, 0x65, 0x6e, 0x74, 0x3a, 0x20, 0x30, /* 0x000001c0: ; text-indent: 0 */
+    0x70, 0x78, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x74, 0x72, 0x61, 0x6e, 0x73, 0x66, 0x6f, /* 0x000001d0: px; text-transfo */
+    0x72, 0x6d, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x20, 0x77, 0x68, 0x69, 0x74, 0x65, 0x2d, /* 0x000001e0: rm: none; white- */
+    0x73, 0x70, 0x61, 0x63, 0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x77, /* 0x000001f0: space: normal; w */
+    0x69, 0x64, 0x6f, 0x77, 0x73, 0x3a, 0x20, 0x32, 0x3b, 0x20, 0x77, 0x6f, 0x72, 0x64, 0x2d, 0x73, /* 0x00000200: idows: 2; word-s */
+    0x70, 0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, 0x2d, 0x77, 0x65, /* 0x00000210: pacing: 0px; -we */
+    0x62, 0x6b, 0x69, 0x74, 0x2d, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x73, 0x74, 0x72, 0x6f, 0x6b, 0x65, /* 0x00000220: bkit-text-stroke */
+    0x2d, 0x77, 0x69, 0x64, 0x74, 0x68, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, 0x62, 0x61, 0x63, /* 0x00000230: -width: 0px; bac */
+    0x6b, 0x67, 0x72, 0x6f, 0x75, 0x6e, 0x64, 0x2d, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x72, /* 0x00000240: kground-color: r */
+    0x67, 0x62, 0x28, 0x32, 0x35, 0x35, 0x2c, 0x20, 0x32, 0x35, 0x35, 0x2c, 0x20, 0x32, 0x35, 0x35, /* 0x00000250: gb(255, 255, 255 */
+    0x29, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, /* 0x00000260: ); text-decorati */
+    0x6f, 0x6e, 0x2d, 0x74, 0x68, 0x69, 0x63, 0x6b, 0x6e, 0x65, 0x73, 0x73, 0x3a, 0x20, 0x69, 0x6e, /* 0x00000270: on-thickness: in */
+    0x69, 0x74, 0x69, 0x61, 0x6c, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, /* 0x00000280: itial; text-deco */
+    0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2d, 0x73, 0x74, 0x79, 0x6c, 0x65, 0x3a, 0x20, 0x69, 0x6e, /* 0x00000290: ration-style: in */
+    0x69, 0x74, 0x69, 0x61, 0x6c, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, /* 0x000002a0: itial; text-deco */
+    0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2d, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x69, 0x6e, /* 0x000002b0: ration-color: in */
+    0x69, 0x74, 0x69, 0x61, 0x6c, 0x3b, 0x20, 0x64, 0x69, 0x73, 0x70, 0x6c, 0x61, 0x79, 0x3a, 0x20, /* 0x000002c0: itial; display:  */
+    0x69, 0x6e, 0x6c, 0x69, 0x6e, 0x65, 0x20, 0x21, 0x69, 0x6d, 0x70, 0x6f, 0x72, 0x74, 0x61, 0x6e, /* 0x000002d0: inline !importan */
+    0x74, 0x3b, 0x20, 0x66, 0x6c, 0x6f, 0x61, 0x74, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x22, /* 0x000002e0: t; float: none;" */
+    0x3e, 0x53, 0x65, 0x65, 0x20, 0x22, 0x3c, 0x2f, 0x73, 0x70, 0x61, 0x6e, 0x3e, 0x3c, 0x61, 0x20, /* 0x000002f0: >See "<.span><a  */
+    0x63, 0x6c, 0x61, 0x73, 0x73, 0x3d, 0x22, 0x77, 0x69, 0x6b, 0x69, 0x22, 0x20, 0x68, 0x72, 0x65, /* 0x00000300: class="wiki" hre */
+    0x66, 0x3d, 0x22, 0x68, 0x74, 0x74, 0x70, 0x73, 0x3a, 0x2f, 0x2f, 0x77, 0x77, 0x77, 0x2e, 0x76, /* 0x00000310: f="https:..www.v */
+    0x69, 0x72, 0x74, 0x75, 0x61, 0x6c, 0x62, 0x6f, 0x78, 0x2e, 0x6f, 0x72, 0x67, 0x2f, 0x77, 0x69, /* 0x00000320: irtualbox.org.wi */
+    0x6b, 0x69, 0x2f, 0x56, 0x69, 0x72, 0x74, 0x75, 0x61, 0x6c, 0x42, 0x6f, 0x78, 0x22, 0x20, 0x73, /* 0x00000330: ki.VirtualBox" s */
+    0x74, 0x79, 0x6c, 0x65, 0x3d, 0x22, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, 0x72, /* 0x00000340: tyle="text-decor */
+    0x61, 0x74, 0x69, 0x6f, 0x6e, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x20, 0x63, 0x6f, 0x6c, /* 0x00000350: ation: none; col */
+    0x6f, 0x72, 0x3a, 0x20, 0x72, 0x67, 0x62, 0x28, 0x30, 0x2c, 0x20, 0x30, 0x2c, 0x20, 0x31, 0x39, /* 0x00000360: or: rgb(0, 0, 19 */
+    0x32, 0x29, 0x3b, 0x20, 0x62, 0x6f, 0x72, 0x64, 0x65, 0x72, 0x2d, 0x62, 0x6f, 0x74, 0x74, 0x6f, /* 0x00000370: 2); border-botto */
+    0x6d, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x66, 0x61, /* 0x00000380: m: none; font-fa */
+    0x6d, 0x69, 0x6c, 0x79, 0x3a, 0x20, 0x56, 0x65, 0x72, 0x64, 0x61, 0x6e, 0x61, 0x2c, 0x20, 0x26, /* 0x00000390: mily: Verdana, & */
+    0x71, 0x75, 0x6f, 0x74, 0x3b, 0x42, 0x69, 0x74, 0x73, 0x74, 0x72, 0x65, 0x61, 0x6d, 0x20, 0x56, /* 0x000003a0: quot;Bitstream V */
+    0x65, 0x72, 0x61, 0x20, 0x53, 0x61, 0x6e, 0x73, 0x26, 0x71, 0x75, 0x6f, 0x74, 0x3b, 0x2c, 0x20, /* 0x000003b0: era Sans&quot;,  */
+    0x73, 0x61, 0x6e, 0x73, 0x2d, 0x73, 0x65, 0x72, 0x69, 0x66, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, /* 0x000003c0: sans-serif; font */
+    0x2d, 0x73, 0x69, 0x7a, 0x65, 0x3a, 0x20, 0x31, 0x33, 0x70, 0x78, 0x3b, 0x20, 0x66, 0x6f, 0x6e, /* 0x000003d0: -size: 13px; fon */
+    0x74, 0x2d, 0x73, 0x74, 0x79, 0x6c, 0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, /* 0x000003e0: t-style: normal; */
+    0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x6c, 0x69, /* 0x000003f0:  font-variant-li */
+    0x67, 0x61, 0x74, 0x75, 0x72, 0x65, 0x73, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, /* 0x00000400: gatures: normal; */
+    0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x63, 0x61, /* 0x00000410:  font-variant-ca */
+    0x70, 0x73, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, /* 0x00000420: ps: normal; font */
+    0x2d, 0x77, 0x65, 0x69, 0x67, 0x68, 0x74, 0x3a, 0x20, 0x34, 0x30, 0x30, 0x3b, 0x20, 0x6c, 0x65, /* 0x00000430: -weight: 400; le */
+    0x74, 0x74, 0x65, 0x72, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x6e, 0x6f, /* 0x00000440: tter-spacing: no */
+    0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x6f, 0x72, 0x70, 0x68, 0x61, 0x6e, 0x73, 0x3a, 0x20, 0x32, /* 0x00000450: rmal; orphans: 2 */
+    0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x61, 0x6c, 0x69, 0x67, 0x6e, 0x3a, 0x20, 0x73, 0x74, /* 0x00000460: ; text-align: st */
+    0x61, 0x72, 0x74, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x69, 0x6e, 0x64, 0x65, 0x6e, 0x74, /* 0x00000470: art; text-indent */
+    0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x74, 0x72, 0x61, 0x6e, /* 0x00000480: : 0px; text-tran */
+    0x73, 0x66, 0x6f, 0x72, 0x6d, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x20, 0x77, 0x68, 0x69, /* 0x00000490: sform: none; whi */
+    0x74, 0x65, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, /* 0x000004a0: te-space: normal */
+    0x3b, 0x20, 0x77, 0x69, 0x64, 0x6f, 0x77, 0x73, 0x3a, 0x20, 0x32, 0x3b, 0x20, 0x77, 0x6f, 0x72, /* 0x000004b0: ; widows: 2; wor */
+    0x64, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, /* 0x000004c0: d-spacing: 0px;  */
+    0x2d, 0x77, 0x65, 0x62, 0x6b, 0x69, 0x74, 0x2d, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x73, 0x74, 0x72, /* 0x000004d0: -webkit-text-str */
+    0x6f, 0x6b, 0x65, 0x2d, 0x77, 0x69, 0x64, 0x74, 0x68, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, /* 0x000004e0: oke-width: 0px;  */
+    0x62, 0x61, 0x63, 0x6b, 0x67, 0x72, 0x6f, 0x75, 0x6e, 0x64, 0x2d, 0x63, 0x6f, 0x6c, 0x6f, 0x72, /* 0x000004f0: background-color */
+    0x3a, 0x20, 0x72, 0x67, 0x62, 0x28, 0x32, 0x35, 0x35, 0x2c, 0x20, 0x32, 0x35, 0x35, 0x2c, 0x20, /* 0x00000500: : rgb(255, 255,  */
+    0x32, 0x35, 0x35, 0x29, 0x3b, 0x22, 0x3e, 0x41, 0x62, 0x6f, 0x75, 0x74, 0x20, 0x56, 0x69, 0x72, /* 0x00000510: 255);">About Vir */
+    0x74, 0x75, 0x61, 0x6c, 0x42, 0x6f, 0x78, 0x3c, 0x2f, 0x61, 0x3e, 0x3c, 0x73, 0x70, 0x61, 0x6e, /* 0x00000520: tualBox<.a><span */
+    0x20, 0x73, 0x74, 0x79, 0x6c, 0x65, 0x3d, 0x22, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x72, /* 0x00000530:  style="color: r */
+    0x67, 0x62, 0x28, 0x30, 0x2c, 0x20, 0x30, 0x2c, 0x20, 0x30, 0x29, 0x3b, 0x20, 0x66, 0x6f, 0x6e, /* 0x00000540: gb(0, 0, 0); fon */
+    0x74, 0x2d, 0x66, 0x61, 0x6d, 0x69, 0x6c, 0x79, 0x3a, 0x20, 0x56, 0x65, 0x72, 0x64, 0x61, 0x6e, /* 0x00000550: t-family: Verdan */
+    0x61, 0x2c, 0x20, 0x26, 0x71, 0x75, 0x6f, 0x74, 0x3b, 0x42, 0x69, 0x74, 0x73, 0x74, 0x72, 0x65, /* 0x00000560: a, &quot;Bitstre */
+    0x61, 0x6d, 0x20, 0x56, 0x65, 0x72, 0x61, 0x20, 0x53, 0x61, 0x6e, 0x73, 0x26, 0x71, 0x75, 0x6f, /* 0x00000570: am Vera Sans&quo */
+    0x74, 0x3b, 0x2c, 0x20, 0x73, 0x61, 0x6e, 0x73, 0x2d, 0x73, 0x65, 0x72, 0x69, 0x66, 0x3b, 0x20, /* 0x00000580: t;, sans-serif;  */
+    0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x73, 0x69, 0x7a, 0x65, 0x3a, 0x20, 0x31, 0x33, 0x70, 0x78, 0x3b, /* 0x00000590: font-size: 13px; */
+    0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x73, 0x74, 0x79, 0x6c, 0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, /* 0x000005a0:  font-style: nor */
+    0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, /* 0x000005b0: mal; font-varian */
+    0x74, 0x2d, 0x6c, 0x69, 0x67, 0x61, 0x74, 0x75, 0x72, 0x65, 0x73, 0x3a, 0x20, 0x6e, 0x6f, 0x72, /* 0x000005c0: t-ligatures: nor */
+    0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, /* 0x000005d0: mal; font-varian */
+    0x74, 0x2d, 0x63, 0x61, 0x70, 0x73, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, /* 0x000005e0: t-caps: normal;  */
+    0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x77, 0x65, 0x69, 0x67, 0x68, 0x74, 0x3a, 0x20, 0x34, 0x30, 0x30, /* 0x000005f0: font-weight: 400 */
+    0x3b, 0x20, 0x6c, 0x65, 0x74, 0x74, 0x65, 0x72, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x69, 0x6e, 0x67, /* 0x00000600: ; letter-spacing */
+    0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x6f, 0x72, 0x70, 0x68, 0x61, 0x6e, /* 0x00000610: : normal; orphan */
+    0x73, 0x3a, 0x20, 0x32, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x61, 0x6c, 0x69, 0x67, 0x6e, /* 0x00000620: s: 2; text-align */
+    0x3a, 0x20, 0x73, 0x74, 0x61, 0x72, 0x74, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x69, 0x6e, /* 0x00000630: : start; text-in */
+    0x64, 0x65, 0x6e, 0x74, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, /* 0x00000640: dent: 0px; text- */
+    0x74, 0x72, 0x61, 0x6e, 0x73, 0x66, 0x6f, 0x72, 0x6d, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, /* 0x00000650: transform: none; */
+    0x20, 0x77, 0x68, 0x69, 0x74, 0x65, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x65, 0x3a, 0x20, 0x6e, 0x6f, /* 0x00000660:  white-space: no */
+    0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x77, 0x69, 0x64, 0x6f, 0x77, 0x73, 0x3a, 0x20, 0x32, 0x3b, /* 0x00000670: rmal; widows: 2; */
+    0x20, 0x77, 0x6f, 0x72, 0x64, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x30, /* 0x00000680:  word-spacing: 0 */
+    0x70, 0x78, 0x3b, 0x20, 0x2d, 0x77, 0x65, 0x62, 0x6b, 0x69, 0x74, 0x2d, 0x74, 0x65, 0x78, 0x74, /* 0x00000690: px; -webkit-text */
+    0x2d, 0x73, 0x74, 0x72, 0x6f, 0x6b, 0x65, 0x2d, 0x77, 0x69, 0x64, 0x74, 0x68, 0x3a, 0x20, 0x30, /* 0x000006a0: -stroke-width: 0 */
+    0x70, 0x78, 0x3b, 0x20, 0x62, 0x61, 0x63, 0x6b, 0x67, 0x72, 0x6f, 0x75, 0x6e, 0x64, 0x2d, 0x63, /* 0x000006b0: px; background-c */
+    0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x72, 0x67, 0x62, 0x28, 0x32, 0x35, 0x35, 0x2c, 0x20, 0x32, /* 0x000006c0: olor: rgb(255, 2 */
+    0x35, 0x35, 0x2c, 0x20, 0x32, 0x35, 0x35, 0x29, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, /* 0x000006d0: 55, 255); text-d */
+    0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2d, 0x74, 0x68, 0x69, 0x63, 0x6b, 0x6e, /* 0x000006e0: ecoration-thickn */
+    0x65, 0x73, 0x73, 0x3a, 0x20, 0x69, 0x6e, 0x69, 0x74, 0x69, 0x61, 0x6c, 0x3b, 0x20, 0x74, 0x65, /* 0x000006f0: ess: initial; te */
+    0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2d, 0x73, 0x74, /* 0x00000700: xt-decoration-st */
+    0x79, 0x6c, 0x65, 0x3a, 0x20, 0x69, 0x6e, 0x69, 0x74, 0x69, 0x61, 0x6c, 0x3b, 0x20, 0x74, 0x65, /* 0x00000710: yle: initial; te */
+    0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2d, 0x63, 0x6f, /* 0x00000720: xt-decoration-co */
+    0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x69, 0x6e, 0x69, 0x74, 0x69, 0x61, 0x6c, 0x3b, 0x20, 0x64, 0x69, /* 0x00000730: lor: initial; di */
+    0x73, 0x70, 0x6c, 0x61, 0x79, 0x3a, 0x20, 0x69, 0x6e, 0x6c, 0x69, 0x6e, 0x65, 0x20, 0x21, 0x69, /* 0x00000740: splay: inline !i */
+    0x6d, 0x70, 0x6f, 0x72, 0x74, 0x61, 0x6e, 0x74, 0x3b, 0x20, 0x66, 0x6c, 0x6f, 0x61, 0x74, 0x3a, /* 0x00000750: mportant; float: */
+    0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x22, 0x3e, 0x22, 0x20, 0x66, 0x6f, 0x72, 0x20, 0x61, 0x6e, /* 0x00000760:  none;">" for an */
+    0x20, 0x69, 0x6e, 0x74, 0x72, 0x6f, 0x64, 0x75, 0x63, 0x74, 0x69, 0x6f, 0x6e, 0x2e, 0x3c, 0x2f, /* 0x00000770:  introduction.<. */
+    0x73, 0x70, 0x61, 0x6e, 0x3e, 0x3c, 0x21, 0x2d, 0x2d, 0x45, 0x6e, 0x64, 0x46, 0x72, 0x61, 0x67, /* 0x00000780: span><!--EndFrag */
+    0x6d, 0x65, 0x6e, 0x74, 0x2d, 0x2d, 0x3e, 0x0d, 0x0a, 0x3c, 0x2f, 0x62, 0x6f, 0x64, 0x79, 0x3e, /* 0x00000790: ment-->..<.body> */
+    0x0d, 0x0a, 0x3c, 0x2f, 0x68, 0x74, 0x6d, 0x6c, 0x3e, 0x00,                                     /* 0x000007a0: ..<.html>.       */
+};
+
+const unsigned g_cbVBoxOrgCfHtml1 = sizeof(g_abVBoxOrgCfHtml1);
+
+#endif /* !VBOX_INCLUDED_SRC_VBoxOrgCfHtml1_h */
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgCfHtml1.txt b/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgCfHtml1.txt
new file mode 100644
index 00000000..39a83822
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgCfHtml1.txt
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgMimeHtml1.h b/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgMimeHtml1.h
new file mode 100644
index 00000000..a2a0fe41
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgMimeHtml1.h
@@ -0,0 +1,152 @@
+/* $Id: VBoxOrgMimeHtml1.h $ */
+/** @file
+ * Shared Clipboard host service test case C data file of VBoxOrgMimeHtml1.txt.
+ */
+
+/*
+ * Copyright (C) 2022-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_VBoxOrgMimeHtml1_h
+#define VBOX_INCLUDED_SRC_VBoxOrgMimeHtml1_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <iprt/cdefs.h>
+
+const unsigned char g_abVBoxOrgMimeHtml1[] =
+{
+    0x3c, 0x73, 0x70, 0x61, 0x6e, 0x20, 0x73, 0x74, 0x79, 0x6c, 0x65, 0x3d, 0x22, 0x63, 0x6f, 0x6c, /* 0x00000000: <span style="col */
+    0x6f, 0x72, 0x3a, 0x20, 0x72, 0x67, 0x62, 0x28, 0x30, 0x2c, 0x20, 0x30, 0x2c, 0x20, 0x30, 0x29, /* 0x00000010: or: rgb(0, 0, 0) */
+    0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x66, 0x61, 0x6d, 0x69, 0x6c, 0x79, 0x3a, 0x20, 0x56, /* 0x00000020: ; font-family: V */
+    0x65, 0x72, 0x64, 0x61, 0x6e, 0x61, 0x2c, 0x20, 0x26, 0x71, 0x75, 0x6f, 0x74, 0x3b, 0x42, 0x69, /* 0x00000030: erdana, &quot;Bi */
+    0x74, 0x73, 0x74, 0x72, 0x65, 0x61, 0x6d, 0x20, 0x56, 0x65, 0x72, 0x61, 0x20, 0x53, 0x61, 0x6e, /* 0x00000040: tstream Vera San */
+    0x73, 0x26, 0x71, 0x75, 0x6f, 0x74, 0x3b, 0x2c, 0x20, 0x73, 0x61, 0x6e, 0x73, 0x2d, 0x73, 0x65, /* 0x00000050: s&quot;, sans-se */
+    0x72, 0x69, 0x66, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x73, 0x69, 0x7a, 0x65, 0x3a, 0x20, /* 0x00000060: rif; font-size:  */
+    0x31, 0x33, 0x70, 0x78, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x73, 0x74, 0x79, 0x6c, 0x65, /* 0x00000070: 13px; font-style */
+    0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x76, /* 0x00000080: : normal; font-v */
+    0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x6c, 0x69, 0x67, 0x61, 0x74, 0x75, 0x72, 0x65, 0x73, /* 0x00000090: ariant-ligatures */
+    0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x76, /* 0x000000a0: : normal; font-v */
+    0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x63, 0x61, 0x70, 0x73, 0x3a, 0x20, 0x6e, 0x6f, 0x72, /* 0x000000b0: ariant-caps: nor */
+    0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x77, 0x65, 0x69, 0x67, 0x68, 0x74, /* 0x000000c0: mal; font-weight */
+    0x3a, 0x20, 0x34, 0x30, 0x30, 0x3b, 0x20, 0x6c, 0x65, 0x74, 0x74, 0x65, 0x72, 0x2d, 0x73, 0x70, /* 0x000000d0: : 400; letter-sp */
+    0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x6f, /* 0x000000e0: acing: normal; o */
+    0x72, 0x70, 0x68, 0x61, 0x6e, 0x73, 0x3a, 0x20, 0x32, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, /* 0x000000f0: rphans: 2; text- */
+    0x61, 0x6c, 0x69, 0x67, 0x6e, 0x3a, 0x20, 0x73, 0x74, 0x61, 0x72, 0x74, 0x3b, 0x20, 0x74, 0x65, /* 0x00000100: align: start; te */
+    0x78, 0x74, 0x2d, 0x69, 0x6e, 0x64, 0x65, 0x6e, 0x74, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, /* 0x00000110: xt-indent: 0px;  */
+    0x74, 0x65, 0x78, 0x74, 0x2d, 0x74, 0x72, 0x61, 0x6e, 0x73, 0x66, 0x6f, 0x72, 0x6d, 0x3a, 0x20, /* 0x00000120: text-transform:  */
+    0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x20, 0x77, 0x68, 0x69, 0x74, 0x65, 0x2d, 0x73, 0x70, 0x61, 0x63, /* 0x00000130: none; white-spac */
+    0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x77, 0x69, 0x64, 0x6f, 0x77, /* 0x00000140: e: normal; widow */
+    0x73, 0x3a, 0x20, 0x32, 0x3b, 0x20, 0x77, 0x6f, 0x72, 0x64, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x69, /* 0x00000150: s: 2; word-spaci */
+    0x6e, 0x67, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, 0x2d, 0x77, 0x65, 0x62, 0x6b, 0x69, 0x74, /* 0x00000160: ng: 0px; -webkit */
+    0x2d, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x73, 0x74, 0x72, 0x6f, 0x6b, 0x65, 0x2d, 0x77, 0x69, 0x64, /* 0x00000170: -text-stroke-wid */
+    0x74, 0x68, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, 0x62, 0x61, 0x63, 0x6b, 0x67, 0x72, 0x6f, /* 0x00000180: th: 0px; backgro */
+    0x75, 0x6e, 0x64, 0x2d, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x72, 0x67, 0x62, 0x28, 0x32, /* 0x00000190: und-color: rgb(2 */
+    0x35, 0x35, 0x2c, 0x20, 0x32, 0x35, 0x35, 0x2c, 0x20, 0x32, 0x35, 0x35, 0x29, 0x3b, 0x20, 0x74, /* 0x000001a0: 55, 255, 255); t */
+    0x65, 0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2d, 0x74, /* 0x000001b0: ext-decoration-t */
+    0x68, 0x69, 0x63, 0x6b, 0x6e, 0x65, 0x73, 0x73, 0x3a, 0x20, 0x69, 0x6e, 0x69, 0x74, 0x69, 0x61, /* 0x000001c0: hickness: initia */
+    0x6c, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, /* 0x000001d0: l; text-decorati */
+    0x6f, 0x6e, 0x2d, 0x73, 0x74, 0x79, 0x6c, 0x65, 0x3a, 0x20, 0x69, 0x6e, 0x69, 0x74, 0x69, 0x61, /* 0x000001e0: on-style: initia */
+    0x6c, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, /* 0x000001f0: l; text-decorati */
+    0x6f, 0x6e, 0x2d, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x69, 0x6e, 0x69, 0x74, 0x69, 0x61, /* 0x00000200: on-color: initia */
+    0x6c, 0x3b, 0x20, 0x64, 0x69, 0x73, 0x70, 0x6c, 0x61, 0x79, 0x3a, 0x20, 0x69, 0x6e, 0x6c, 0x69, /* 0x00000210: l; display: inli */
+    0x6e, 0x65, 0x20, 0x21, 0x69, 0x6d, 0x70, 0x6f, 0x72, 0x74, 0x61, 0x6e, 0x74, 0x3b, 0x20, 0x66, /* 0x00000220: ne !important; f */
+    0x6c, 0x6f, 0x61, 0x74, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x22, 0x3e, 0x53, 0x65, 0x65, /* 0x00000230: loat: none;">See */
+    0x20, 0x22, 0x3c, 0x2f, 0x73, 0x70, 0x61, 0x6e, 0x3e, 0x3c, 0x61, 0x20, 0x63, 0x6c, 0x61, 0x73, /* 0x00000240:  "<.span><a clas */
+    0x73, 0x3d, 0x22, 0x77, 0x69, 0x6b, 0x69, 0x22, 0x20, 0x68, 0x72, 0x65, 0x66, 0x3d, 0x22, 0x68, /* 0x00000250: s="wiki" href="h */
+    0x74, 0x74, 0x70, 0x73, 0x3a, 0x2f, 0x2f, 0x77, 0x77, 0x77, 0x2e, 0x76, 0x69, 0x72, 0x74, 0x75, /* 0x00000260: ttps:..www.virtu */
+    0x61, 0x6c, 0x62, 0x6f, 0x78, 0x2e, 0x6f, 0x72, 0x67, 0x2f, 0x77, 0x69, 0x6b, 0x69, 0x2f, 0x56, /* 0x00000270: albox.org.wiki.V */
+    0x69, 0x72, 0x74, 0x75, 0x61, 0x6c, 0x42, 0x6f, 0x78, 0x22, 0x20, 0x73, 0x74, 0x79, 0x6c, 0x65, /* 0x00000280: irtualBox" style */
+    0x3d, 0x22, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, 0x6f, /* 0x00000290: ="text-decoratio */
+    0x6e, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x20, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, /* 0x000002a0: n: none; color:  */
+    0x72, 0x67, 0x62, 0x28, 0x30, 0x2c, 0x20, 0x30, 0x2c, 0x20, 0x31, 0x39, 0x32, 0x29, 0x3b, 0x20, /* 0x000002b0: rgb(0, 0, 192);  */
+    0x62, 0x6f, 0x72, 0x64, 0x65, 0x72, 0x2d, 0x62, 0x6f, 0x74, 0x74, 0x6f, 0x6d, 0x3a, 0x20, 0x6e, /* 0x000002c0: border-bottom: n */
+    0x6f, 0x6e, 0x65, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x66, 0x61, 0x6d, 0x69, 0x6c, 0x79, /* 0x000002d0: one; font-family */
+    0x3a, 0x20, 0x56, 0x65, 0x72, 0x64, 0x61, 0x6e, 0x61, 0x2c, 0x20, 0x26, 0x71, 0x75, 0x6f, 0x74, /* 0x000002e0: : Verdana, &quot */
+    0x3b, 0x42, 0x69, 0x74, 0x73, 0x74, 0x72, 0x65, 0x61, 0x6d, 0x20, 0x56, 0x65, 0x72, 0x61, 0x20, /* 0x000002f0: ;Bitstream Vera  */
+    0x53, 0x61, 0x6e, 0x73, 0x26, 0x71, 0x75, 0x6f, 0x74, 0x3b, 0x2c, 0x20, 0x73, 0x61, 0x6e, 0x73, /* 0x00000300: Sans&quot;, sans */
+    0x2d, 0x73, 0x65, 0x72, 0x69, 0x66, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x73, 0x69, 0x7a, /* 0x00000310: -serif; font-siz */
+    0x65, 0x3a, 0x20, 0x31, 0x33, 0x70, 0x78, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x73, 0x74, /* 0x00000320: e: 13px; font-st */
+    0x79, 0x6c, 0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, /* 0x00000330: yle: normal; fon */
+    0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x6c, 0x69, 0x67, 0x61, 0x74, 0x75, /* 0x00000340: t-variant-ligatu */
+    0x72, 0x65, 0x73, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, /* 0x00000350: res: normal; fon */
+    0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x63, 0x61, 0x70, 0x73, 0x3a, 0x20, /* 0x00000360: t-variant-caps:  */
+    0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x77, 0x65, 0x69, /* 0x00000370: normal; font-wei */
+    0x67, 0x68, 0x74, 0x3a, 0x20, 0x34, 0x30, 0x30, 0x3b, 0x20, 0x6c, 0x65, 0x74, 0x74, 0x65, 0x72, /* 0x00000380: ght: 400; letter */
+    0x2d, 0x73, 0x70, 0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, /* 0x00000390: -spacing: normal */
+    0x3b, 0x20, 0x6f, 0x72, 0x70, 0x68, 0x61, 0x6e, 0x73, 0x3a, 0x20, 0x32, 0x3b, 0x20, 0x74, 0x65, /* 0x000003a0: ; orphans: 2; te */
+    0x78, 0x74, 0x2d, 0x61, 0x6c, 0x69, 0x67, 0x6e, 0x3a, 0x20, 0x73, 0x74, 0x61, 0x72, 0x74, 0x3b, /* 0x000003b0: xt-align: start; */
+    0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x69, 0x6e, 0x64, 0x65, 0x6e, 0x74, 0x3a, 0x20, 0x30, 0x70, /* 0x000003c0:  text-indent: 0p */
+    0x78, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x74, 0x72, 0x61, 0x6e, 0x73, 0x66, 0x6f, 0x72, /* 0x000003d0: x; text-transfor */
+    0x6d, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x20, 0x77, 0x68, 0x69, 0x74, 0x65, 0x2d, 0x73, /* 0x000003e0: m: none; white-s */
+    0x70, 0x61, 0x63, 0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x77, 0x69, /* 0x000003f0: pace: normal; wi */
+    0x64, 0x6f, 0x77, 0x73, 0x3a, 0x20, 0x32, 0x3b, 0x20, 0x77, 0x6f, 0x72, 0x64, 0x2d, 0x73, 0x70, /* 0x00000400: dows: 2; word-sp */
+    0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, 0x2d, 0x77, 0x65, 0x62, /* 0x00000410: acing: 0px; -web */
+    0x6b, 0x69, 0x74, 0x2d, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x73, 0x74, 0x72, 0x6f, 0x6b, 0x65, 0x2d, /* 0x00000420: kit-text-stroke- */
+    0x77, 0x69, 0x64, 0x74, 0x68, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, 0x62, 0x61, 0x63, 0x6b, /* 0x00000430: width: 0px; back */
+    0x67, 0x72, 0x6f, 0x75, 0x6e, 0x64, 0x2d, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x72, 0x67, /* 0x00000440: ground-color: rg */
+    0x62, 0x28, 0x32, 0x35, 0x35, 0x2c, 0x20, 0x32, 0x35, 0x35, 0x2c, 0x20, 0x32, 0x35, 0x35, 0x29, /* 0x00000450: b(255, 255, 255) */
+    0x3b, 0x22, 0x3e, 0x41, 0x62, 0x6f, 0x75, 0x74, 0x20, 0x56, 0x69, 0x72, 0x74, 0x75, 0x61, 0x6c, /* 0x00000460: ;">About Virtual */
+    0x42, 0x6f, 0x78, 0x3c, 0x2f, 0x61, 0x3e, 0x3c, 0x73, 0x70, 0x61, 0x6e, 0x20, 0x73, 0x74, 0x79, /* 0x00000470: Box<.a><span sty */
+    0x6c, 0x65, 0x3d, 0x22, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, 0x20, 0x72, 0x67, 0x62, 0x28, 0x30, /* 0x00000480: le="color: rgb(0 */
+    0x2c, 0x20, 0x30, 0x2c, 0x20, 0x30, 0x29, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x66, 0x61, /* 0x00000490: , 0, 0); font-fa */
+    0x6d, 0x69, 0x6c, 0x79, 0x3a, 0x20, 0x56, 0x65, 0x72, 0x64, 0x61, 0x6e, 0x61, 0x2c, 0x20, 0x26, /* 0x000004a0: mily: Verdana, & */
+    0x71, 0x75, 0x6f, 0x74, 0x3b, 0x42, 0x69, 0x74, 0x73, 0x74, 0x72, 0x65, 0x61, 0x6d, 0x20, 0x56, /* 0x000004b0: quot;Bitstream V */
+    0x65, 0x72, 0x61, 0x20, 0x53, 0x61, 0x6e, 0x73, 0x26, 0x71, 0x75, 0x6f, 0x74, 0x3b, 0x2c, 0x20, /* 0x000004c0: era Sans&quot;,  */
+    0x73, 0x61, 0x6e, 0x73, 0x2d, 0x73, 0x65, 0x72, 0x69, 0x66, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, /* 0x000004d0: sans-serif; font */
+    0x2d, 0x73, 0x69, 0x7a, 0x65, 0x3a, 0x20, 0x31, 0x33, 0x70, 0x78, 0x3b, 0x20, 0x66, 0x6f, 0x6e, /* 0x000004e0: -size: 13px; fon */
+    0x74, 0x2d, 0x73, 0x74, 0x79, 0x6c, 0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, /* 0x000004f0: t-style: normal; */
+    0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x6c, 0x69, /* 0x00000500:  font-variant-li */
+    0x67, 0x61, 0x74, 0x75, 0x72, 0x65, 0x73, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, /* 0x00000510: gatures: normal; */
+    0x20, 0x66, 0x6f, 0x6e, 0x74, 0x2d, 0x76, 0x61, 0x72, 0x69, 0x61, 0x6e, 0x74, 0x2d, 0x63, 0x61, /* 0x00000520:  font-variant-ca */
+    0x70, 0x73, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x66, 0x6f, 0x6e, 0x74, /* 0x00000530: ps: normal; font */
+    0x2d, 0x77, 0x65, 0x69, 0x67, 0x68, 0x74, 0x3a, 0x20, 0x34, 0x30, 0x30, 0x3b, 0x20, 0x6c, 0x65, /* 0x00000540: -weight: 400; le */
+    0x74, 0x74, 0x65, 0x72, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x6e, 0x6f, /* 0x00000550: tter-spacing: no */
+    0x72, 0x6d, 0x61, 0x6c, 0x3b, 0x20, 0x6f, 0x72, 0x70, 0x68, 0x61, 0x6e, 0x73, 0x3a, 0x20, 0x32, /* 0x00000560: rmal; orphans: 2 */
+    0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x61, 0x6c, 0x69, 0x67, 0x6e, 0x3a, 0x20, 0x73, 0x74, /* 0x00000570: ; text-align: st */
+    0x61, 0x72, 0x74, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x69, 0x6e, 0x64, 0x65, 0x6e, 0x74, /* 0x00000580: art; text-indent */
+    0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x74, 0x72, 0x61, 0x6e, /* 0x00000590: : 0px; text-tran */
+    0x73, 0x66, 0x6f, 0x72, 0x6d, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, 0x65, 0x3b, 0x20, 0x77, 0x68, 0x69, /* 0x000005a0: sform: none; whi */
+    0x74, 0x65, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x65, 0x3a, 0x20, 0x6e, 0x6f, 0x72, 0x6d, 0x61, 0x6c, /* 0x000005b0: te-space: normal */
+    0x3b, 0x20, 0x77, 0x69, 0x64, 0x6f, 0x77, 0x73, 0x3a, 0x20, 0x32, 0x3b, 0x20, 0x77, 0x6f, 0x72, /* 0x000005c0: ; widows: 2; wor */
+    0x64, 0x2d, 0x73, 0x70, 0x61, 0x63, 0x69, 0x6e, 0x67, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, /* 0x000005d0: d-spacing: 0px;  */
+    0x2d, 0x77, 0x65, 0x62, 0x6b, 0x69, 0x74, 0x2d, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x73, 0x74, 0x72, /* 0x000005e0: -webkit-text-str */
+    0x6f, 0x6b, 0x65, 0x2d, 0x77, 0x69, 0x64, 0x74, 0x68, 0x3a, 0x20, 0x30, 0x70, 0x78, 0x3b, 0x20, /* 0x000005f0: oke-width: 0px;  */
+    0x62, 0x61, 0x63, 0x6b, 0x67, 0x72, 0x6f, 0x75, 0x6e, 0x64, 0x2d, 0x63, 0x6f, 0x6c, 0x6f, 0x72, /* 0x00000600: background-color */
+    0x3a, 0x20, 0x72, 0x67, 0x62, 0x28, 0x32, 0x35, 0x35, 0x2c, 0x20, 0x32, 0x35, 0x35, 0x2c, 0x20, /* 0x00000610: : rgb(255, 255,  */
+    0x32, 0x35, 0x35, 0x29, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, 0x65, 0x63, 0x6f, 0x72, /* 0x00000620: 255); text-decor */
+    0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2d, 0x74, 0x68, 0x69, 0x63, 0x6b, 0x6e, 0x65, 0x73, 0x73, 0x3a, /* 0x00000630: ation-thickness: */
+    0x20, 0x69, 0x6e, 0x69, 0x74, 0x69, 0x61, 0x6c, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, /* 0x00000640:  initial; text-d */
+    0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2d, 0x73, 0x74, 0x79, 0x6c, 0x65, 0x3a, /* 0x00000650: ecoration-style: */
+    0x20, 0x69, 0x6e, 0x69, 0x74, 0x69, 0x61, 0x6c, 0x3b, 0x20, 0x74, 0x65, 0x78, 0x74, 0x2d, 0x64, /* 0x00000660:  initial; text-d */
+    0x65, 0x63, 0x6f, 0x72, 0x61, 0x74, 0x69, 0x6f, 0x6e, 0x2d, 0x63, 0x6f, 0x6c, 0x6f, 0x72, 0x3a, /* 0x00000670: ecoration-color: */
+    0x20, 0x69, 0x6e, 0x69, 0x74, 0x69, 0x61, 0x6c, 0x3b, 0x20, 0x64, 0x69, 0x73, 0x70, 0x6c, 0x61, /* 0x00000680:  initial; displa */
+    0x79, 0x3a, 0x20, 0x69, 0x6e, 0x6c, 0x69, 0x6e, 0x65, 0x20, 0x21, 0x69, 0x6d, 0x70, 0x6f, 0x72, /* 0x00000690: y: inline !impor */
+    0x74, 0x61, 0x6e, 0x74, 0x3b, 0x20, 0x66, 0x6c, 0x6f, 0x61, 0x74, 0x3a, 0x20, 0x6e, 0x6f, 0x6e, /* 0x000006a0: tant; float: non */
+    0x65, 0x3b, 0x22, 0x3e, 0x22, 0x20, 0x66, 0x6f, 0x72, 0x20, 0x61, 0x6e, 0x20, 0x69, 0x6e, 0x74, /* 0x000006b0: e;">" for an int */
+    0x72, 0x6f, 0x64, 0x75, 0x63, 0x74, 0x69, 0x6f, 0x6e, 0x2e, 0x3c, 0x2f, 0x73, 0x70, 0x61, 0x6e, /* 0x000006c0: roduction.<.span */
+    0x3e, 0x00                                                                                      /* 0x000006d0: >                */
+};
+
+const unsigned g_cbVBoxOrgMimeHtml1 = sizeof(g_abVBoxOrgMimeHtml1);
+
+#endif /* !VBOX_INCLUDED_SRC_VBoxOrgMimeHtml1_h */
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgMimeHtml1.txt b/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgMimeHtml1.txt
new file mode 100644
index 00000000..6d5b4901
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/VBoxOrgMimeHtml1.txt
@@ -0,0 +1 @@
+<span style="color: rgb(0, 0, 0); font-family: Verdana, &quot;Bitstream Vera Sans&quot;, sans-serif; font-size: 13px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">See "</span><a class="wiki" href="https://www.virtualbox.org/wiki/VirtualBox" style="text-decoration: none; color: rgb(0, 0, 192); border-bottom: none; font-family: Verdana, &quot;Bitstream Vera Sans&quot;, sans-serif; font-size: 13px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);">About VirtualBox</a><span style="color: rgb(0, 0, 0); font-family: Verdana, &quot;Bitstream Vera Sans&quot;, sans-serif; font-size: 13px; font-style: normal; font-variant-ligatures: normal; font-variant-caps: normal; font-weight: 400; letter-spacing: normal; orphans: 2; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255); text-decoration-thickness: initial; text-decoration-style: initial; text-decoration-color: initial; display: inline !important; float: none;">" for an introduction.</span>
\ No newline at end of file
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardMockHGCM.cpp b/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardMockHGCM.cpp
new file mode 100644
index 00000000..ec35905c
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardMockHGCM.cpp
@@ -0,0 +1,735 @@
+/* $Id: tstClipboardMockHGCM.cpp $ */
+/** @file
+ * Shared Clipboard host service test case.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "../VBoxSharedClipboardSvc-internal.h"
+
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#include <VBox/VBoxGuestLib.h>
+#ifdef RT_OS_LINUX
+# include <VBox/GuestHost/SharedClipboard-x11.h>
+#endif
+#ifdef RT_OS_WINDOWS
+# include <VBox/GuestHost/SharedClipboard-win.h>
+#endif
+
+#include <VBox/GuestHost/HGCMMock.h>
+#include <VBox/GuestHost/HGCMMockUtils.h>
+
+#include <iprt/assert.h>
+#include <iprt/initterm.h>
+#include <iprt/mem.h>
+#include <iprt/rand.h>
+#include <iprt/stream.h>
+#include <iprt/string.h>
+#include <iprt/test.h>
+#include <iprt/utf16.h>
+
+
+/*********************************************************************************************************************************
+*   Static globals                                                                                                               *
+*********************************************************************************************************************************/
+static RTTEST     g_hTest;
+
+
+/*********************************************************************************************************************************
+*   Shared Clipboard testing                                                                                                     *
+*********************************************************************************************************************************/
+struct CLIPBOARDTESTDESC;
+/** Pointer to a test description. */
+typedef CLIPBOARDTESTDESC *PTESTDESC;
+
+struct CLIPBOARDTESTCTX;
+/** Pointer to a test context. */
+typedef CLIPBOARDTESTCTX *PCLIPBOARDTESTCTX;
+
+/** Pointer a test descriptor. */
+typedef CLIPBOARDTESTDESC *PTESTDESC;
+
+typedef DECLCALLBACKTYPE(int, FNTESTSETUP,(PCLIPBOARDTESTCTX pTstCtx, void **ppvCtx));
+/** Pointer to a test setup callback. */
+typedef FNTESTSETUP *PFNTESTSETUP;
+
+typedef DECLCALLBACKTYPE(int, FNTESTEXEC,(PCLIPBOARDTESTCTX pTstCtx, void *pvCtx));
+/** Pointer to a test exec callback. */
+typedef FNTESTEXEC *PFNTESTEXEC;
+
+typedef DECLCALLBACKTYPE(int, FNTESTDESTROY,(PCLIPBOARDTESTCTX pTstCtx, void *pvCtx));
+/** Pointer to a test destroy callback. */
+typedef FNTESTDESTROY *PFNTESTDESTROY;
+
+
+/**
+ * Structure for keeping a clipboard test task.
+ */
+typedef struct CLIPBOARDTESTTASK
+{
+    SHCLFORMATS enmFmtHst;
+    SHCLFORMATS enmFmtGst;
+    /** For testing chunked reads / writes. */
+    size_t      cbChunk;
+    /** Data buffer to read / write for this task.
+     *  Can be NULL if not needed. */
+    void       *pvData;
+    /** Size (in bytes) of \a pvData. */
+    size_t      cbData;
+    /** Number of bytes read / written from / to \a pvData. */
+    size_t      cbProcessed;
+} CLIPBOARDTESTTASK;
+typedef CLIPBOARDTESTTASK *PCLIPBOARDTESTTASK;
+
+/**
+ * Structure for keeping a clipboard test context.
+ */
+typedef struct CLIPBOARDTESTCTX
+{
+    /** The HGCM Mock utils context. */
+    TSTHGCMUTILSCTX   HGCM;
+    /** Clipboard-specific task data. */
+    CLIPBOARDTESTTASK Task;
+    struct
+    {
+        /** The VbglR3 Shared Clipboard context to work on. */
+        VBGLR3SHCLCMDCTX CmdCtx;
+    } Guest;
+} CLIPBOARDTESTCTX;
+
+/** The one and only clipboard test context. One at a time. */
+CLIPBOARDTESTCTX g_TstCtx;
+
+/**
+ * Structure for keeping a clipboard test description.
+ */
+typedef struct CLIPBOARDTESTDESC
+{
+    /** The setup callback. */
+    PFNTESTSETUP         pfnSetup;
+    /** The exec callback. */
+    PFNTESTEXEC          pfnExec;
+    /** The destruction callback. */
+    PFNTESTDESTROY       pfnDestroy;
+} CLIPBOARDTESTDESC;
+
+typedef struct SHCLCONTEXT
+{
+} SHCLCONTEXT;
+
+
+static int tstSetModeRc(PTSTHGCMMOCKSVC pSvc, uint32_t uMode, int rcExpected)
+{
+    VBOXHGCMSVCPARM aParms[2];
+    HGCMSvcSetU32(&aParms[0], uMode);
+    int rc2 = TstHgcmMockSvcHostCall(pSvc, NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, aParms);
+    RTTESTI_CHECK_MSG_RET(rcExpected == rc2, ("Expected %Rrc, got %Rrc\n", rcExpected, rc2), rc2);
+    if (RT_SUCCESS(rcExpected))
+    {
+        uint32_t const uModeRet = ShClSvcGetMode();
+        RTTESTI_CHECK_MSG_RET(uMode == uModeRet, ("Expected mode %RU32, got %RU32\n", uMode, uModeRet), VERR_WRONG_TYPE);
+    }
+    return rc2;
+}
+
+static int tstClipboardSetMode(PTSTHGCMMOCKSVC pSvc, uint32_t uMode)
+{
+    return tstSetModeRc(pSvc, uMode, VINF_SUCCESS);
+}
+
+static bool tstClipboardGetMode(PTSTHGCMMOCKSVC pSvc, uint32_t uModeExpected)
+{
+    RT_NOREF(pSvc);
+    RTTESTI_CHECK_RET(ShClSvcGetMode() == uModeExpected, false);
+    return true;
+}
+
+static void tstOperationModes(void)
+{
+    struct VBOXHGCMSVCPARM parms[2];
+    uint32_t u32Mode;
+    int rc;
+
+    RTTestISub("Testing VBOX_SHCL_HOST_FN_SET_MODE");
+
+    PTSTHGCMMOCKSVC pSvc = TstHgcmMockSvcInst();
+
+    /* Reset global variable which doesn't reset itself. */
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_MODE_OFF);
+    rc = TstHgcmMockSvcHostCall(pSvc, NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    u32Mode = ShClSvcGetMode();
+    RTTESTI_CHECK_MSG(u32Mode == VBOX_SHCL_MODE_OFF, ("u32Mode=%u\n", (unsigned) u32Mode));
+
+    rc = TstHgcmMockSvcHostCall(pSvc, NULL, VBOX_SHCL_HOST_FN_SET_MODE, 0, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+
+    rc = TstHgcmMockSvcHostCall(pSvc, NULL, VBOX_SHCL_HOST_FN_SET_MODE, 2, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+
+    HGCMSvcSetU64(&parms[0], 99);
+    rc = TstHgcmMockSvcHostCall(pSvc, NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+
+    tstClipboardSetMode(pSvc, VBOX_SHCL_MODE_HOST_TO_GUEST);
+    tstSetModeRc(pSvc, 99, VERR_NOT_SUPPORTED);
+    tstClipboardGetMode(pSvc, VBOX_SHCL_MODE_OFF);
+}
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+static void testSetTransferMode(void)
+{
+    RTTestISub("Testing VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE");
+
+    PTSTHGCMMOCKSVC pSvc = TstHgcmMockSvcInst();
+
+    /* Invalid parameter. */
+    VBOXHGCMSVCPARM parms[2];
+    HGCMSvcSetU64(&parms[0], 99);
+    int rc = TstHgcmMockSvcHostCall(pSvc, NULL, VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+
+    /* Invalid mode. */
+    HGCMSvcSetU32(&parms[0], 99);
+    rc = TstHgcmMockSvcHostCall(pSvc, NULL, VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_FLAGS);
+
+    /* Enable transfers. */
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_TRANSFER_MODE_ENABLED);
+    rc = TstHgcmMockSvcHostCall(pSvc, NULL, VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VINF_SUCCESS);
+
+    /* Disable transfers again. */
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_TRANSFER_MODE_DISABLED);
+    rc = TstHgcmMockSvcHostCall(pSvc, NULL, VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VINF_SUCCESS);
+}
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
+static void testGuestSimple(void)
+{
+    RTTestISub("Testing client (guest) API - Simple");
+
+    PTSTHGCMMOCKSVC pSvc = TstHgcmMockSvcInst();
+
+    /* Preparations. */
+    VBGLR3SHCLCMDCTX Ctx;
+    RT_ZERO(Ctx);
+
+    /*
+     * Multiple connects / disconnects.
+     */
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardConnectEx(&Ctx, VBOX_SHCL_GF_0_CONTEXT_ID));
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardDisconnectEx(&Ctx));
+    /* Report bogus guest features while connecting. */
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardConnectEx(&Ctx, 0xdeadbeef));
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardDisconnectEx(&Ctx));
+
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardConnectEx(&Ctx, VBOX_SHCL_GF_0_CONTEXT_ID));
+
+    /*
+     * Feature tests.
+     */
+
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardReportFeatures(Ctx.idClient, 0x0,        NULL /* pfHostFeatures */));
+    /* Report bogus features to the host. */
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardReportFeatures(Ctx.idClient, 0xdeadb33f, NULL /* pfHostFeatures */));
+
+    /*
+     * Access denied tests.
+     */
+
+    /* Try reading data from host. */
+    uint8_t abData[32]; uint32_t cbIgnored;
+    RTTESTI_CHECK_RC(VbglR3ClipboardReadData(Ctx.idClient, VBOX_SHCL_FMT_UNICODETEXT,
+                                             abData, sizeof(abData), &cbIgnored), VERR_ACCESS_DENIED);
+    /* Try writing data without reporting formats before (legacy). */
+    RTTESTI_CHECK_RC(VbglR3ClipboardWriteData(Ctx.idClient, 0xdeadb33f, abData, sizeof(abData)), VERR_ACCESS_DENIED);
+    /* Try writing data without reporting formats before. */
+    RTTESTI_CHECK_RC(VbglR3ClipboardWriteDataEx(&Ctx, 0xdeadb33f, abData, sizeof(abData)), VERR_ACCESS_DENIED);
+    /* Report bogus formats to the host. */
+    RTTESTI_CHECK_RC(VbglR3ClipboardReportFormats(Ctx.idClient, 0xdeadb33f), VERR_ACCESS_DENIED);
+    /* Report supported formats to host. */
+    RTTESTI_CHECK_RC(VbglR3ClipboardReportFormats(Ctx.idClient,
+                                                  VBOX_SHCL_FMT_UNICODETEXT | VBOX_SHCL_FMT_BITMAP | VBOX_SHCL_FMT_HTML),
+                                                  VERR_ACCESS_DENIED);
+    /*
+     * Access allowed tests.
+     */
+    tstClipboardSetMode(pSvc, VBOX_SHCL_MODE_BIDIRECTIONAL);
+
+    /* Try writing data without reporting formats before. */
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardWriteDataEx(&Ctx, 0xdeadb33f, abData, sizeof(abData)));
+    /* Try reading data from host. */
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardReadData(Ctx.idClient, VBOX_SHCL_FMT_UNICODETEXT,
+                                                abData, sizeof(abData), &cbIgnored));
+    /* Report bogus formats to the host. */
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardReportFormats(Ctx.idClient, 0xdeadb33f));
+    /* Report supported formats to host. */
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardReportFormats(Ctx.idClient,
+                                                     VBOX_SHCL_FMT_UNICODETEXT | VBOX_SHCL_FMT_BITMAP | VBOX_SHCL_FMT_HTML));
+    /* Tear down. */
+    RTTESTI_CHECK_RC_OK(VbglR3ClipboardDisconnectEx(&Ctx));
+}
+
+static RTUTF16 tstGetRandUtf8(void)
+{
+    return RTRandU32Ex(0x20, 0x7A);
+}
+
+static char *tstGenerateUtf8StringA(uint32_t uCch)
+{
+    char * pszRand = (char *)RTMemAlloc(uCch + 1);
+    for (uint32_t i = 0; i < uCch; i++)
+        pszRand[i] = tstGetRandUtf8();
+    pszRand[uCch] = 0;
+    return pszRand;
+}
+
+#if defined(RT_OS_WINDOWS) || defined(RT_OS_OS2)
+static RTUTF16 tstGetRandUtf16(void)
+{
+    RTUTF16 wc;
+    do
+    {
+        wc = (RTUTF16)RTRandU32Ex(1, 0xfffd);
+    } while (wc >= 0xd800 && wc <= 0xdfff);
+    return wc;
+}
+
+static PRTUTF16 tstGenerateUtf16StringA(uint32_t uCch)
+{
+    PRTUTF16 pwszRand = (PRTUTF16)RTMemAlloc((uCch + 1) * sizeof(RTUTF16));
+    for (uint32_t i = 0; i < uCch; i++)
+        pwszRand[i] = tstGetRandUtf16();
+    pwszRand[uCch] = 0;
+    return pwszRand;
+}
+#endif /* RT_OS_WINDOWS) || RT_OS_OS2 */
+
+static void testSetHeadless(void)
+{
+    RTTestISub("Testing HOST_FN_SET_HEADLESS");
+
+    PTSTHGCMMOCKSVC pSvc = TstHgcmMockSvcInst();
+
+    VBOXHGCMSVCPARM parms[2];
+    HGCMSvcSetU32(&parms[0], false);
+    int rc = pSvc->fnTable.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS, 1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    bool fHeadless = ShClSvcGetHeadless();
+    RTTESTI_CHECK_MSG(fHeadless == false, ("fHeadless=%RTbool\n", fHeadless));
+    rc = pSvc->fnTable.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS, 0, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+    rc = pSvc->fnTable.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS, 2, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+    HGCMSvcSetU64(&parms[0], 99);
+    rc = pSvc->fnTable.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS, 1, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+    HGCMSvcSetU32(&parms[0], true);
+    rc = pSvc->fnTable.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS, 1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    fHeadless = ShClSvcGetHeadless();
+    RTTESTI_CHECK_MSG(fHeadless == true, ("fHeadless=%RTbool\n", fHeadless));
+    HGCMSvcSetU32(&parms[0], 99);
+    rc = pSvc->fnTable.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS, 1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    fHeadless = ShClSvcGetHeadless();
+    RTTESTI_CHECK_MSG(fHeadless == true, ("fHeadless=%RTbool\n", fHeadless));
+}
+
+static void testHostCall(void)
+{
+    tstOperationModes();
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    testSetTransferMode();
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+    testSetHeadless();
+}
+
+
+/*********************************************************************************************************************************
+ * Test: Guest reading from host                                                                                                 *
+ ********************************************************************************************************************************/
+#if defined (RT_OS_LINUX) || defined (RT_OS_SOLARIS)
+/* Called from SHCLX11 thread. */
+static DECLCALLBACK(int) tstTestReadFromHost_ReportFormatsCallback(PSHCLCONTEXT pCtx, uint32_t fFormats, void *pvUser)
+{
+    RT_NOREF(pCtx, fFormats, pvUser);
+
+    RTTestPrintf(g_hTest, RTTESTLVL_ALWAYS, "tstTestReadFromHost_SvcReportFormatsCallback: fFormats=%#x\n", fFormats);
+    return VINF_SUCCESS;
+}
+
+/* Called by the backend, e.g. for X11 in the SHCLX11 thread. */
+static DECLCALLBACK(int) tstTestReadFromHost_OnClipboardReadCallback(PSHCLCONTEXT pCtx,
+                                                                     SHCLFORMAT uFmt, void **ppv, size_t *pcb, void *pvUser)
+{
+    RT_NOREF(pCtx, uFmt, pvUser);
+
+    PCLIPBOARDTESTTASK pTask = (PCLIPBOARDTESTTASK)TstHGCMUtilsTaskGetCurrent(&g_TstCtx.HGCM)->pvUser;
+
+    void   *pvData = NULL;
+    size_t  cbData = pTask->cbData - pTask->cbProcessed;
+    if (cbData)
+    {
+        pvData = RTMemDup((uint8_t *)pTask->pvData + pTask->cbProcessed, cbData);
+        AssertPtr(pvData);
+    }
+
+    RTTestPrintf(g_hTest, RTTESTLVL_DEBUG, "Host reporting back %RU32 bytes of data\n", cbData);
+
+    *ppv = pvData;
+    *pcb = cbData;
+
+    return VINF_SUCCESS;
+}
+#endif /* (RT_OS_LINUX) || defined (RT_OS_SOLARIS) */
+
+typedef struct TSTUSERMOCK
+{
+#if defined(RT_OS_LINUX)
+    SHCLX11CTX   X11Ctx;
+#endif
+    PSHCLCONTEXT pCtx;
+} TSTUSERMOCK;
+typedef TSTUSERMOCK *PTSTUSERMOCK;
+
+static void tstTestReadFromHost_MockInit(PTSTUSERMOCK pUsrMock, const char *pszName)
+{
+#if defined(RT_OS_LINUX)
+    SHCLCALLBACKS Callbacks;
+    RT_ZERO(Callbacks);
+    Callbacks.pfnReportFormats   = tstTestReadFromHost_ReportFormatsCallback;
+    Callbacks.pfnOnClipboardRead = tstTestReadFromHost_OnClipboardReadCallback;
+
+    pUsrMock->pCtx = (PSHCLCONTEXT)RTMemAllocZ(sizeof(SHCLCONTEXT));
+    AssertPtrReturnVoid(pUsrMock->pCtx);
+
+    ShClX11Init(&pUsrMock->X11Ctx, &Callbacks, pUsrMock->pCtx, false);
+    ShClX11ThreadStartEx(&pUsrMock->X11Ctx, pszName, false /* fGrab */);
+    /* Give the clipboard time to synchronise. */
+    RTThreadSleep(500);
+#else
+    RT_NOREF(pUsrMock, pszName);
+#endif /* RT_OS_LINUX */
+}
+
+static void tstTestReadFromHost_MockDestroy(PTSTUSERMOCK pUsrMock)
+{
+#if defined(RT_OS_LINUX)
+    ShClX11ThreadStop(&pUsrMock->X11Ctx);
+    ShClX11Destroy(&pUsrMock->X11Ctx);
+    RTMemFree(pUsrMock->pCtx);
+#else
+    RT_NOREF(pUsrMock);
+#endif
+}
+
+static int tstTestReadFromHost_DoIt(PCLIPBOARDTESTCTX pCtx, PCLIPBOARDTESTTASK pTask)
+{
+    size_t   cbDst       = RT_MAX(_64K, pTask->cbData);
+    uint8_t *pabDst      = (uint8_t *)RTMemAllocZ(cbDst);
+    AssertPtrReturn(pabDst, VERR_NO_MEMORY);
+
+    AssertPtr(pTask->pvData);                /* Racing condition with host thread? */
+    Assert(pTask->cbChunk);                  /* Buggy test? */
+    Assert(pTask->cbChunk <= pTask->cbData); /* Ditto. */
+
+    size_t   cbToRead = pTask->cbData;
+    switch (pTask->enmFmtGst)
+    {
+        case VBOX_SHCL_FMT_UNICODETEXT:
+#ifndef RT_OS_WINDOWS /** @todo Not sure about OS/2. */
+            cbToRead *= sizeof(RTUTF16);
+#endif
+            break;
+
+        default:
+            break;
+    }
+
+    PVBGLR3SHCLCMDCTX pCmdCtx = &pCtx->Guest.CmdCtx;
+
+    /* Do random chunked reads. */
+    uint32_t const cChunkedReads = RTRandU32Ex(1, 16);
+    RTTestPrintf(g_hTest, RTTESTLVL_DEBUG, "%RU32 chunked reads\n", cChunkedReads);
+    for (uint32_t i = 0; i < cChunkedReads; i++)
+    {
+        /* Note! VbglR3ClipboardReadData() currently does not support chunked reads!
+          *      It in turn returns VINF_BUFFER_OVERFLOW when the supplied buffer was too small. */
+
+        uint32_t cbChunk    = RTRandU32Ex(1, (uint32_t)(pTask->cbData / cChunkedReads));
+        uint32_t cbRead     = 0;
+        RTTestPrintf(g_hTest, RTTESTLVL_ALWAYS, "Guest trying to read %RU32 bytes\n", cbChunk);
+        int vrc2 = VbglR3ClipboardReadData(pCmdCtx->idClient, pTask->enmFmtGst, pabDst, cbChunk, &cbRead);
+        if (   vrc2   == VINF_SUCCESS
+            && cbRead == 0) /* No data there yet? */
+        {
+            RTTestPrintf(g_hTest, RTTESTLVL_ALWAYS, "No data (yet) from host\n");
+            RTThreadSleep(10);
+            continue;
+        }
+        RTTestPrintf(g_hTest, RTTESTLVL_ALWAYS, "Trying reading host clipboard data with a %RU32 buffer -> %Rrc (%RU32)\n", cbChunk, vrc2, cbRead);
+        RTTEST_CHECK_MSG(g_hTest, vrc2 == VINF_BUFFER_OVERFLOW, (g_hTest, "Got %Rrc, expected VINF_BUFFER_OVERFLOW\n", vrc2));
+    }
+
+    /* Last read: Read the data with a buffer big enough. This must succeed. */
+    RTTestPrintf(g_hTest, RTTESTLVL_ALWAYS, "Reading full data (%zu)\n", pTask->cbData);
+    uint32_t cbRead = 0;
+    int vrc2 = VbglR3ClipboardReadData(pCmdCtx->idClient, pTask->enmFmtGst, pabDst, (uint32_t)cbDst, &cbRead);
+    RTTEST_CHECK_MSG(g_hTest, vrc2 == VINF_SUCCESS, (g_hTest, "Got %Rrc, expected VINF_SUCCESS\n", vrc2));
+    RTTEST_CHECK_MSG(g_hTest, cbRead == cbToRead, (g_hTest, "Read %RU32 bytes, expected %zu\n", cbRead, cbToRead));
+
+    if (pTask->enmFmtGst == VBOX_SHCL_FMT_UNICODETEXT)
+        RTTEST_CHECK_MSG(g_hTest, RTUtf16ValidateEncoding((PRTUTF16)pabDst) == VINF_SUCCESS, (g_hTest, "Read data is not valid UTF-16\n"));
+    if (cbRead == cbToRead)
+    {
+#ifndef RT_OS_WINDOWS /** @todo Not sure about OS/2. */
+        PRTUTF16 pwszSrc = NULL;
+        RTTEST_CHECK(g_hTest, RT_SUCCESS(RTStrToUtf16((const char *)pTask->pvData, &pwszSrc)));
+        RTTEST_CHECK_MSG(g_hTest, memcmp(pwszSrc, pabDst, cbRead) == 0, (g_hTest, "Read data does not match host data\n"));
+        RTUtf16Free(pwszSrc);
+#else
+        RTTEST_CHECK_MSG(g_hTest, memcmp(pTask->pvData, pabDst, cbRead) == 0, (g_hTest, "Read data does not match host data\n"));
+#endif
+    }
+
+    RTTestPrintf(g_hTest, RTTESTLVL_DEBUG, "Read data from host:\n%.*Rhxd\n", cbRead, pabDst);
+
+    RTMemFree(pabDst);
+
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) tstTestReadFromHost_ThreadGuest(PTSTHGCMUTILSCTX pCtx, void *pvCtx)
+{
+    RTThreadSleep(1000); /* Fudge; wait until the host has prepared the data for the clipboard. */
+
+    PCLIPBOARDTESTCTX  pTstCtx  = (PCLIPBOARDTESTCTX)pvCtx;
+    AssertPtr(pTstCtx);
+
+    RT_ZERO(pTstCtx->Guest.CmdCtx);
+    RTTEST_CHECK_RC_OK(g_hTest, VbglR3ClipboardConnectEx(&pTstCtx->Guest.CmdCtx, VBOX_SHCL_GF_0_CONTEXT_ID));
+
+    RTThreadSleep(1000); /* Fudge; wait until the host has prepared the data for the clipboard. */
+
+    PCLIPBOARDTESTTASK pTstTask = (PCLIPBOARDTESTTASK)pCtx->Task.pvUser;
+    AssertPtr(pTstTask);
+    tstTestReadFromHost_DoIt(pTstCtx, pTstTask);
+
+    /* Signal that the task ended. */
+    TstHGCMUtilsTaskSignal(&pCtx->Task, VINF_SUCCESS);
+
+    RTTEST_CHECK_RC_OK(g_hTest, VbglR3ClipboardDisconnectEx(&pTstCtx->Guest.CmdCtx));
+
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) tstTestReadFromHost_ClientConnectedCallback(PTSTHGCMUTILSCTX pCtx, PTSTHGCMMOCKCLIENT pClient,
+                                                                     void *pvUser)
+{
+    RT_NOREF(pCtx, pClient);
+
+    PCLIPBOARDTESTCTX pTstCtx = (PCLIPBOARDTESTCTX)pvUser;
+    AssertPtr(pTstCtx); RT_NOREF(pTstCtx);
+
+    RTTestPrintf(g_hTest, RTTESTLVL_DEBUG, "Client %RU32 connected\n", pClient->idClient);
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) tstTestReadFromHostSetup(PCLIPBOARDTESTCTX pTstCtx, void **ppvCtx)
+{
+    RT_NOREF(ppvCtx);
+
+    /* Set the right clipboard mode, so that the guest can read from the host. */
+    tstClipboardSetMode(TstHgcmMockSvcInst(), VBOX_SHCL_MODE_BIDIRECTIONAL);
+
+    /* Start the host thread first, so that the guest thread can connect to it later. */
+    TSTHGCMUTILSHOSTCALLBACKS HostCallbacks;
+    RT_ZERO(HostCallbacks);
+    HostCallbacks.pfnOnClientConnected = tstTestReadFromHost_ClientConnectedCallback;
+    TstHGCMUtilsHostThreadStart(&pTstCtx->HGCM, &HostCallbacks, pTstCtx /* pvUser */);
+
+    PCLIPBOARDTESTTASK pTask  = &pTstCtx->Task;
+    AssertPtr(pTask);
+    pTask->enmFmtGst   = VBOX_SHCL_FMT_UNICODETEXT;
+    pTask->enmFmtHst   = pTask->enmFmtGst;
+    pTask->cbChunk     = RTRandU32Ex(1, 512);
+    pTask->cbData      = RT_ALIGN_32(pTask->cbChunk * RTRandU32Ex(1, 16), 2);
+    Assert(pTask->cbData % sizeof(RTUTF16) == 0);
+#if !defined(RT_OS_WINDOWS) && !defined(RT_OS_OS2)
+    pTask->pvData      = tstGenerateUtf8StringA(pTask->cbData);
+    pTask->cbData++; /* Add terminating zero. */
+#else
+    pTask->pvData      = tstGenerateUtf16StringA((uint32_t)(pTask->cbData /* We use bytes == chars here */));
+    pTask->cbData     *= sizeof(RTUTF16);
+    pTask->cbData     += sizeof(RTUTF16); /* Add terminating zero. */
+#endif
+    pTask->cbProcessed = 0;
+
+    int rc = VINF_SUCCESS;
+
+#if defined (RT_OS_LINUX) || defined (RT_OS_SOLARIS)
+    /* Initialize the Shared Clipboard backend callbacks. */
+    PSHCLBACKEND pBackend = ShClSvcGetBackend();
+
+    SHCLCALLBACKS ShClCallbacks;
+    RT_ZERO(ShClCallbacks);
+    ShClCallbacks.pfnReportFormats   = tstTestReadFromHost_ReportFormatsCallback;
+    ShClCallbacks.pfnOnClipboardRead = tstTestReadFromHost_OnClipboardReadCallback;
+    ShClBackendSetCallbacks(pBackend, &ShClCallbacks);
+#elif defined (RT_OS_WINDOWS)
+    rc = SharedClipboardWinOpen(GetDesktopWindow());
+    if (RT_SUCCESS(rc))
+    {
+        rc = SharedClipboardWinDataWrite(CF_UNICODETEXT, pTask->pvData, (uint32_t)pTask->cbData);
+        SharedClipboardWinClose();
+    }
+#endif /* defined (RT_OS_LINUX) || defined (RT_OS_SOLARIS) */
+
+    RTTestPrintf(g_hTest, RTTESTLVL_DEBUG, "Host data (%RU32):\n%.*Rhxd\n", pTask->cbData, pTask->cbData, pTask->pvData);
+    return rc;
+}
+
+static DECLCALLBACK(int) tstTestReadFromHostExec(PCLIPBOARDTESTCTX pTstCtx, void *pvCtx)
+{
+    RT_NOREF(pvCtx);
+
+    TstHGCMUtilsGuestThreadStart(&pTstCtx->HGCM, tstTestReadFromHost_ThreadGuest, pTstCtx);
+
+    PTSTHGCMUTILSTASK pTask = (PTSTHGCMUTILSTASK)TstHGCMUtilsTaskGetCurrent(&pTstCtx->HGCM);
+
+    bool fUseMock = false;
+    TSTUSERMOCK UsrMock;
+    if (fUseMock)
+        tstTestReadFromHost_MockInit(&UsrMock, "tstX11Hst");
+
+    /* Wait until the task has been finished. */
+    TstHGCMUtilsTaskWait(pTask, RT_MS_30SEC);
+
+    if (fUseMock)
+        tstTestReadFromHost_MockDestroy(&UsrMock);
+
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) tstTestReadFromHostDestroy(PCLIPBOARDTESTCTX pTstCtx, void *pvCtx)
+{
+    RT_NOREF(pvCtx);
+
+    int vrc = TstHGCMUtilsGuestThreadStop(&pTstCtx->HGCM);
+    AssertRC(vrc);
+    vrc = TstHGCMUtilsHostThreadStop(&pTstCtx->HGCM);
+    AssertRC(vrc);
+
+    return vrc;
+}
+
+
+/*********************************************************************************************************************************
+ * Main                                                                                                                          *
+ ********************************************************************************************************************************/
+
+/** Test definition table. */
+CLIPBOARDTESTDESC g_aTests[] =
+{
+    /* Tests guest reading clipboard data from the host.  */
+    { tstTestReadFromHostSetup,       tstTestReadFromHostExec,      tstTestReadFromHostDestroy }
+};
+/** Number of tests defined. */
+unsigned g_cTests = RT_ELEMENTS(g_aTests);
+
+static int tstOne(PTESTDESC pTstDesc)
+{
+    PCLIPBOARDTESTCTX pTstCtx = &g_TstCtx;
+
+    void *pvCtx;
+    int rc = pTstDesc->pfnSetup(pTstCtx, &pvCtx);
+    if (RT_SUCCESS(rc))
+    {
+        rc = pTstDesc->pfnExec(pTstCtx, pvCtx);
+
+        int rc2 = pTstDesc->pfnDestroy(pTstCtx, pvCtx);
+        if (RT_SUCCESS(rc))
+            rc = rc2;
+    }
+
+    return rc;
+}
+
+int main(int argc, char *argv[])
+{
+    /*
+     * Init the runtime, test and say hello.
+     */
+    const char *pcszExecName;
+    NOREF(argc);
+    pcszExecName = strrchr(argv[0], '/');
+    pcszExecName = pcszExecName ? pcszExecName + 1 : argv[0];
+    RTEXITCODE rcExit = RTTestInitAndCreate(pcszExecName, &g_hTest);
+    if (rcExit != RTEXITCODE_SUCCESS)
+        return rcExit;
+    RTTestBanner(g_hTest);
+
+#ifndef DEBUG_andy
+    /* Don't let assertions in the host service panic (core dump) the test cases. */
+    RTAssertSetMayPanic(false);
+#endif
+
+    PTSTHGCMMOCKSVC const pSvc = TstHgcmMockSvcInst();
+    TstHgcmMockSvcCreate(pSvc, sizeof(SHCLCLIENT));
+    TstHgcmMockSvcStart(pSvc);
+
+    /*
+     * Run the tests.
+     */
+    if (0)
+    {
+        testGuestSimple();
+        testHostCall();
+    }
+
+    RT_ZERO(g_TstCtx);
+
+    PTSTHGCMUTILSCTX pCtx = &g_TstCtx.HGCM;
+    TstHGCMUtilsCtxInit(pCtx, pSvc);
+
+    PTSTHGCMUTILSTASK pTask = (PTSTHGCMUTILSTASK)TstHGCMUtilsTaskGetCurrent(pCtx);
+    TstHGCMUtilsTaskInit(pTask);
+    pTask->pvUser = &g_TstCtx.Task;
+
+    for (unsigned i = 0; i < RT_ELEMENTS(g_aTests); i++)
+        tstOne(&g_aTests[i]);
+
+    TstHGCMUtilsTaskDestroy(pTask);
+
+    TstHgcmMockSvcStop(pSvc);
+    TstHgcmMockSvcDestroy(pSvc);
+
+    /*
+     * Summary
+     */
+    return RTTestSummaryAndDestroy(g_hTest);
+}
+
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardServiceHost.cpp b/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardServiceHost.cpp
new file mode 100644
index 00000000..28130531
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardServiceHost.cpp
@@ -0,0 +1,336 @@
+/* $Id: tstClipboardServiceHost.cpp $ */
+/** @file
+ * Shared Clipboard host service test case.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "../VBoxSharedClipboardSvc-internal.h"
+
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+
+#include <iprt/assert.h>
+#include <iprt/string.h>
+#include <iprt/test.h>
+
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad (VBOXHGCMSVCFNTABLE *ptable);
+
+static SHCLCLIENT g_Client;
+static VBOXHGCMSVCHELPERS g_Helpers = { NULL };
+
+/** Simple call handle structure for the guest call completion callback */
+struct VBOXHGCMCALLHANDLE_TYPEDEF
+{
+    /** Where to store the result code */
+    int32_t rc;
+};
+
+/** Call completion callback for guest calls. */
+static DECLCALLBACK(int) callComplete(VBOXHGCMCALLHANDLE callHandle, int32_t rc)
+{
+    callHandle->rc = rc;
+    return VINF_SUCCESS;
+}
+
+static int setupTable(VBOXHGCMSVCFNTABLE *pTable)
+{
+    pTable->cbSize = sizeof(*pTable);
+    pTable->u32Version = VBOX_HGCM_SVC_VERSION;
+    g_Helpers.pfnCallComplete = callComplete;
+    pTable->pHelpers = &g_Helpers;
+    return VBoxHGCMSvcLoad(pTable);
+}
+
+static void testSetMode(void)
+{
+    struct VBOXHGCMSVCPARM parms[2];
+    VBOXHGCMSVCFNTABLE table;
+    uint32_t u32Mode;
+    int rc;
+
+    RTTestISub("Testing VBOX_SHCL_HOST_FN_SET_MODE");
+    rc = setupTable(&table);
+    RTTESTI_CHECK_MSG_RETV(RT_SUCCESS(rc), ("rc=%Rrc\n", rc));
+
+    /* Reset global variable which doesn't reset itself. */
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_MODE_OFF);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    u32Mode = ShClSvcGetMode();
+    RTTESTI_CHECK_MSG(u32Mode == VBOX_SHCL_MODE_OFF, ("u32Mode=%u\n", (unsigned) u32Mode));
+
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_MODE, 0, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_MODE, 2, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+
+    HGCMSvcSetU64(&parms[0], 99);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_MODE_HOST_TO_GUEST);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    u32Mode = ShClSvcGetMode();
+    RTTESTI_CHECK_MSG(u32Mode == VBOX_SHCL_MODE_HOST_TO_GUEST, ("u32Mode=%u\n", (unsigned) u32Mode));
+
+    HGCMSvcSetU32(&parms[0], 99);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VERR_NOT_SUPPORTED);
+
+    u32Mode = ShClSvcGetMode();
+    RTTESTI_CHECK_MSG(u32Mode == VBOX_SHCL_MODE_OFF, ("u32Mode=%u\n", (unsigned) u32Mode));
+    table.pfnUnload(NULL);
+}
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+static void testSetTransferMode(void)
+{
+    struct VBOXHGCMSVCPARM parms[2];
+    VBOXHGCMSVCFNTABLE table;
+
+    RTTestISub("Testing VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE");
+    int rc = setupTable(&table);
+    RTTESTI_CHECK_MSG_RETV(RT_SUCCESS(rc), ("rc=%Rrc\n", rc));
+
+    /* Invalid parameter. */
+    HGCMSvcSetU64(&parms[0], 99);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+
+    /* Invalid mode. */
+    HGCMSvcSetU32(&parms[0], 99);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_FLAGS);
+
+    /* Enable transfers. */
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_TRANSFER_MODE_ENABLED);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VINF_SUCCESS);
+
+    /* Disable transfers again. */
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_TRANSFER_MODE_DISABLED);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_TRANSFER_MODE, 1, parms);
+    RTTESTI_CHECK_RC(rc, VINF_SUCCESS);
+}
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
+/* Adds a host data read request message to the client's message queue. */
+static void testMsgAddReadData(PSHCLCLIENT pClient, SHCLFORMATS fFormats)
+{
+    int rc = ShClSvcGuestDataRequest(pClient, fFormats, NULL /* pidEvent */);
+    RTTESTI_CHECK_RC_OK(rc);
+}
+
+/* Does testing of VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, needed for providing compatibility to older Guest Additions clients. */
+static void testGetHostMsgOld(void)
+{
+    struct VBOXHGCMSVCPARM parms[2];
+    VBOXHGCMSVCFNTABLE table;
+    VBOXHGCMCALLHANDLE_TYPEDEF call;
+    int rc;
+
+    RTTestISub("Setting up VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT test");
+    rc = setupTable(&table);
+    RTTESTI_CHECK_MSG_RETV(RT_SUCCESS(rc), ("rc=%Rrc\n", rc));
+    /* Unless we are bidirectional the host message requests will be dropped. */
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_MODE_BIDIRECTIONAL);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+
+
+    RTTestISub("Testing one format, waiting guest call.");
+    RT_ZERO(g_Client);
+    HGCMSvcSetU32(&parms[0], 0);
+    HGCMSvcSetU32(&parms[1], 0);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnConnect(NULL, 1 /* clientId */, &g_Client, 0, 0);
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK_RC(call.rc, VERR_IPE_UNINITIALIZED_STATUS);  /* This should get updated only when the guest call completes. */
+    testMsgAddReadData(&g_Client, VBOX_SHCL_FMT_UNICODETEXT);
+    RTTESTI_CHECK(parms[0].u.uint32 == VBOX_SHCL_HOST_MSG_READ_DATA);
+    RTTESTI_CHECK(parms[1].u.uint32 == VBOX_SHCL_FMT_UNICODETEXT);
+    RTTESTI_CHECK_RC_OK(call.rc);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK_RC(call.rc, VERR_IPE_UNINITIALIZED_STATUS);  /* This call should not complete yet. */
+    table.pfnDisconnect(NULL, 1 /* clientId */, &g_Client);
+
+    RTTestISub("Testing one format, no waiting guest calls.");
+    RT_ZERO(g_Client);
+    table.pfnConnect(NULL, 1 /* clientId */, &g_Client, 0, 0);
+    testMsgAddReadData(&g_Client, VBOX_SHCL_FMT_HTML);
+    HGCMSvcSetU32(&parms[0], 0);
+    HGCMSvcSetU32(&parms[1], 0);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK(parms[0].u.uint32 == VBOX_SHCL_HOST_MSG_READ_DATA);
+    RTTESTI_CHECK(parms[1].u.uint32 == VBOX_SHCL_FMT_HTML);
+    RTTESTI_CHECK_RC_OK(call.rc);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK_RC(call.rc, VERR_IPE_UNINITIALIZED_STATUS);  /* This call should not complete yet. */
+    table.pfnDisconnect(NULL, 1 /* clientId */, &g_Client);
+
+    RTTestISub("Testing two formats, waiting guest call.");
+    RT_ZERO(g_Client);
+    table.pfnConnect(NULL, 1 /* clientId */, &g_Client, 0, 0);
+    HGCMSvcSetU32(&parms[0], 0);
+    HGCMSvcSetU32(&parms[1], 0);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK_RC(call.rc, VERR_IPE_UNINITIALIZED_STATUS);  /* This should get updated only when the guest call completes. */
+    testMsgAddReadData(&g_Client, VBOX_SHCL_FMT_UNICODETEXT | VBOX_SHCL_FMT_HTML);
+    RTTESTI_CHECK(parms[0].u.uint32 == VBOX_SHCL_HOST_MSG_READ_DATA);
+    RTTESTI_CHECK(parms[1].u.uint32 == VBOX_SHCL_FMT_UNICODETEXT);
+    RTTESTI_CHECK_RC_OK(call.rc);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK(parms[0].u.uint32 == VBOX_SHCL_HOST_MSG_READ_DATA);
+    RTTESTI_CHECK(parms[1].u.uint32 == VBOX_SHCL_FMT_HTML);
+    RTTESTI_CHECK_RC_OK(call.rc);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK_RC(call.rc, VERR_IPE_UNINITIALIZED_STATUS);  /* This call should not complete yet. */
+    table.pfnDisconnect(NULL, 1 /* clientId */, &g_Client);
+
+    RTTestISub("Testing two formats, no waiting guest calls.");
+    RT_ZERO(g_Client);
+    table.pfnConnect(NULL, 1 /* clientId */, &g_Client, 0, 0);
+    testMsgAddReadData(&g_Client, VBOX_SHCL_FMT_UNICODETEXT | VBOX_SHCL_FMT_HTML);
+    HGCMSvcSetU32(&parms[0], 0);
+    HGCMSvcSetU32(&parms[1], 0);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK(parms[0].u.uint32 == VBOX_SHCL_HOST_MSG_READ_DATA);
+    RTTESTI_CHECK(parms[1].u.uint32 == VBOX_SHCL_FMT_UNICODETEXT);
+    RTTESTI_CHECK_RC_OK(call.rc);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK(parms[0].u.uint32 == VBOX_SHCL_HOST_MSG_READ_DATA);
+    RTTESTI_CHECK(parms[1].u.uint32 == VBOX_SHCL_FMT_HTML);
+    RTTESTI_CHECK_RC_OK(call.rc);
+    call.rc = VERR_IPE_UNINITIALIZED_STATUS;
+    table.pfnCall(NULL, &call, 1 /* clientId */, &g_Client, VBOX_SHCL_GUEST_FN_MSG_OLD_GET_WAIT, 2, parms, 0);
+    RTTESTI_CHECK_RC(call.rc, VERR_IPE_UNINITIALIZED_STATUS);  /* This call should not complete yet. */
+    table.pfnDisconnect(NULL, 1 /* clientId */, &g_Client);
+    table.pfnUnload(NULL);
+}
+
+static void testSetHeadless(void)
+{
+    struct VBOXHGCMSVCPARM parms[2];
+    VBOXHGCMSVCFNTABLE table;
+    bool fHeadless;
+    int rc;
+
+    RTTestISub("Testing HOST_FN_SET_HEADLESS");
+    rc = setupTable(&table);
+    RTTESTI_CHECK_MSG_RETV(RT_SUCCESS(rc), ("rc=%Rrc\n", rc));
+    /* Reset global variable which doesn't reset itself. */
+    HGCMSvcSetU32(&parms[0], false);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS,
+                           1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    fHeadless = ShClSvcGetHeadless();
+    RTTESTI_CHECK_MSG(fHeadless == false, ("fHeadless=%RTbool\n", fHeadless));
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS,
+                           0, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS,
+                           2, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+    HGCMSvcSetU64(&parms[0], 99);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS,
+                           1, parms);
+    RTTESTI_CHECK_RC(rc, VERR_INVALID_PARAMETER);
+    HGCMSvcSetU32(&parms[0], true);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS,
+                           1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    fHeadless = ShClSvcGetHeadless();
+    RTTESTI_CHECK_MSG(fHeadless == true, ("fHeadless=%RTbool\n", fHeadless));
+    HGCMSvcSetU32(&parms[0], 99);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_HEADLESS,
+                           1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    fHeadless = ShClSvcGetHeadless();
+    RTTESTI_CHECK_MSG(fHeadless == true, ("fHeadless=%RTbool\n", fHeadless));
+    table.pfnUnload(NULL);
+}
+
+static void testHostCall(void)
+{
+    testSetMode();
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+    testSetTransferMode();
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+    testSetHeadless();
+}
+
+int main(int argc, char *argv[])
+{
+    /*
+     * Init the runtime, test and say hello.
+     */
+    const char *pcszExecName;
+    NOREF(argc);
+    pcszExecName = strrchr(argv[0], '/');
+    pcszExecName = pcszExecName ? pcszExecName + 1 : argv[0];
+    RTTEST hTest;
+    RTEXITCODE rcExit = RTTestInitAndCreate(pcszExecName, &hTest);
+    if (rcExit != RTEXITCODE_SUCCESS)
+        return rcExit;
+    RTTestBanner(hTest);
+
+    /* Don't let assertions in the host service panic (core dump) the test cases. */
+    RTAssertSetMayPanic(false);
+
+    /*
+     * Run the tests.
+     */
+    testHostCall();
+    testGetHostMsgOld();
+
+    /*
+     * Summary
+     */
+    return RTTestSummaryAndDestroy(hTest);
+}
+
+int ShClBackendInit(PSHCLBACKEND, VBOXHGCMSVCFNTABLE *) { return VINF_SUCCESS; }
+void ShClBackendDestroy(PSHCLBACKEND) { }
+int ShClBackendDisconnect(PSHCLBACKEND, PSHCLCLIENT) { return VINF_SUCCESS; }
+int ShClBackendConnect(PSHCLBACKEND, PSHCLCLIENT, bool) { return VINF_SUCCESS; }
+int ShClBackendReportFormats(PSHCLBACKEND, PSHCLCLIENT, SHCLFORMATS) { AssertFailed(); return VINF_SUCCESS; }
+int ShClBackendReadData(PSHCLBACKEND, PSHCLCLIENT, PSHCLCLIENTCMDCTX, SHCLFORMAT, void *, uint32_t, unsigned int *) { AssertFailed(); return VERR_WRONG_ORDER; }
+int ShClBackendWriteData(PSHCLBACKEND, PSHCLCLIENT, PSHCLCLIENTCMDCTX, SHCLFORMAT, void *, uint32_t) { AssertFailed(); return VINF_SUCCESS; }
+int ShClBackendSync(PSHCLBACKEND, PSHCLCLIENT) { return VINF_SUCCESS; }
+
+#ifdef VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS
+int ShClBackendTransferCreate(PSHCLBACKEND, PSHCLCLIENT, PSHCLTRANSFER) { return VINF_SUCCESS; }
+int ShClBackendTransferDestroy(PSHCLBACKEND, PSHCLCLIENT, PSHCLTRANSFER) { return VINF_SUCCESS; }
+int ShClBackendTransferGetRoots(PSHCLBACKEND, PSHCLCLIENT, PSHCLTRANSFER) { return VINF_SUCCESS; }
+#endif /* VBOX_WITH_SHARED_CLIPBOARD_TRANSFERS */
+
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardServiceImpl.cpp b/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardServiceImpl.cpp
new file mode 100644
index 00000000..cfb4b665
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardServiceImpl.cpp
@@ -0,0 +1,205 @@
+/* $Id: tstClipboardServiceImpl.cpp $ */
+/** @file
+ * Shared Clipboard host service implementation (backend) test case.
+ */
+
+/*
+ * Copyright (C) 2020-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "../VBoxSharedClipboardSvc-internal.h"
+
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+#ifdef RT_OS_WINDOWS
+# include <VBox/GuestHost/SharedClipboard-win.h>
+#endif
+
+#include <iprt/assert.h>
+#include <iprt/string.h>
+#include <iprt/test.h>
+
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad(VBOXHGCMSVCFNTABLE *ptable);
+
+static SHCLCLIENT g_Client;
+static VBOXHGCMSVCHELPERS g_Helpers = { NULL };
+
+/** Simple call handle structure for the guest call completion callback */
+struct VBOXHGCMCALLHANDLE_TYPEDEF
+{
+    /** Where to store the result code */
+    int32_t rc;
+};
+
+/** Call completion callback for guest calls. */
+static DECLCALLBACK(int) callComplete(VBOXHGCMCALLHANDLE callHandle, int32_t rc)
+{
+    callHandle->rc = rc;
+    return VINF_SUCCESS;
+}
+
+static int setupTable(VBOXHGCMSVCFNTABLE *pTable)
+{
+    pTable->cbSize = sizeof(*pTable);
+    pTable->u32Version = VBOX_HGCM_SVC_VERSION;
+    g_Helpers.pfnCallComplete = callComplete;
+    pTable->pHelpers = &g_Helpers;
+    return VBoxHGCMSvcLoad(pTable);
+}
+
+int ShClBackendInit(PSHCLBACKEND, VBOXHGCMSVCFNTABLE *) { return VINF_SUCCESS; }
+void ShClBackendDestroy(PSHCLBACKEND) { }
+int ShClBackendDisconnect(PSHCLBACKEND, PSHCLCLIENT) { return VINF_SUCCESS; }
+int ShClBackendConnect(PSHCLBACKEND, PSHCLCLIENT, bool) { return VINF_SUCCESS; }
+int ShClBackendReportFormats(PSHCLBACKEND, PSHCLCLIENT, SHCLFORMATS) { AssertFailed(); return VINF_SUCCESS; }
+int ShClBackendReadData(PSHCLBACKEND, PSHCLCLIENT, PSHCLCLIENTCMDCTX, SHCLFORMAT, void *, uint32_t, unsigned int *) { AssertFailed(); return VERR_WRONG_ORDER; }
+int ShClBackendWriteData(PSHCLBACKEND, PSHCLCLIENT, PSHCLCLIENTCMDCTX, SHCLFORMAT, void *, uint32_t) { AssertFailed(); return VINF_SUCCESS; }
+int ShClBackendSync(PSHCLBACKEND, PSHCLCLIENT) { return VINF_SUCCESS; }
+
+static void testAnnounceAndReadData(void)
+{
+    struct VBOXHGCMSVCPARM parms[2];
+    VBOXHGCMSVCFNTABLE table;
+    int rc;
+
+    RTTestISub("Setting up client ...");
+    RTTestIDisableAssertions();
+
+    rc = setupTable(&table);
+    RTTESTI_CHECK_MSG_RETV(RT_SUCCESS(rc), ("rc=%Rrc\n", rc));
+    /* Unless we are bidirectional the host message requests will be dropped. */
+    HGCMSvcSetU32(&parms[0], VBOX_SHCL_MODE_BIDIRECTIONAL);
+    rc = table.pfnHostCall(NULL, VBOX_SHCL_HOST_FN_SET_MODE, 1, parms);
+    RTTESTI_CHECK_RC_OK(rc);
+    rc = shClSvcClientInit(&g_Client, 1 /* clientId */);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    RTTestIRestoreAssertions();
+}
+
+#ifdef RT_OS_WINDOWS
+# include "VBoxOrgCfHtml1.h"    /* From chrome 97.0.4692.71 */
+# include "VBoxOrgMimeHtml1.h"
+
+static void testHtmlCf(void)
+{
+    RTTestISub("CF_HTML");
+
+    char    *pszOutput = NULL;
+    uint32_t cbOutput  = UINT32_MAX/2;
+    RTTestIDisableAssertions();
+    RTTESTI_CHECK_RC(SharedClipboardWinConvertCFHTMLToMIME("", 0, &pszOutput, &cbOutput), VERR_INVALID_PARAMETER);
+    RTTestIRestoreAssertions();
+
+    pszOutput = NULL;
+    cbOutput  = UINT32_MAX/2;
+    RTTESTI_CHECK_RC(SharedClipboardWinConvertCFHTMLToMIME((char *)&g_abVBoxOrgCfHtml1[0], g_cbVBoxOrgCfHtml1,
+                                                           &pszOutput, &cbOutput), VINF_SUCCESS);
+    RTTESTI_CHECK(cbOutput == g_cbVBoxOrgMimeHtml1);
+    RTTESTI_CHECK(memcmp(pszOutput, g_abVBoxOrgMimeHtml1, cbOutput) == 0);
+    RTMemFree(pszOutput);
+
+
+    static RTSTRTUPLE const s_aRoundTrips[] =
+    {
+        { RT_STR_TUPLE("") },
+        { RT_STR_TUPLE("1") },
+        { RT_STR_TUPLE("12") },
+        { RT_STR_TUPLE("123") },
+        { RT_STR_TUPLE("1234") },
+        { RT_STR_TUPLE("12345") },
+        { RT_STR_TUPLE("123456") },
+        { RT_STR_TUPLE("1234567") },
+        { RT_STR_TUPLE("12345678") },
+        { RT_STR_TUPLE("123456789") },
+        { RT_STR_TUPLE("1234567890") },
+        { RT_STR_TUPLE("<h2>asdfkjhasdflhj</h2>") },
+        { RT_STR_TUPLE("<h2>asdfkjhasdflhj</h2>\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0") },
+        { (const char *)g_abVBoxOrgMimeHtml1, sizeof(g_abVBoxOrgMimeHtml1) },
+    };
+
+    for (size_t i = 0; i < RT_ELEMENTS(s_aRoundTrips); i++)
+    {
+        int      rc;
+        char    *pszCfHtml = NULL;
+        uint32_t cbCfHtml  = UINT32_MAX/2;
+        rc = SharedClipboardWinConvertMIMEToCFHTML(s_aRoundTrips[i].psz, s_aRoundTrips[i].cch + 1, &pszCfHtml, &cbCfHtml);
+        if (rc == VINF_SUCCESS)
+        {
+            if (strlen(pszCfHtml) + 1 != cbCfHtml)
+                RTTestIFailed("#%u: SharedClipboardWinConvertMIMEToCFHTML(%s, %#zx,,) returned incorrect length: %#x, actual %#zx",
+                              i, s_aRoundTrips[i].psz, s_aRoundTrips[i].cch, cbCfHtml, strlen(pszCfHtml) + 1);
+
+            char     *pszHtml = NULL;
+            uint32_t  cbHtml  = UINT32_MAX/4;
+            rc = SharedClipboardWinConvertCFHTMLToMIME(pszCfHtml, (uint32_t)strlen(pszCfHtml), &pszHtml, &cbHtml);
+            if (rc == VINF_SUCCESS)
+            {
+                if (strlen(pszHtml) + 1 != cbHtml)
+                    RTTestIFailed("#%u: SharedClipboardWinConvertCFHTMLToMIME(%s, %#zx,,) returned incorrect length: %#x, actual %#zx",
+                                  i, pszHtml, strlen(pszHtml), cbHtml, strlen(pszHtml) + 1);
+                if (strcmp(pszHtml, s_aRoundTrips[i].psz) != 0)
+                    RTTestIFailed("#%u: roundtrip for '%s' LB %#zx failed, ended up with '%s'",
+                                  i, s_aRoundTrips[i].psz, s_aRoundTrips[i].cch, pszHtml);
+                RTMemFree(pszHtml);
+            }
+            else
+                RTTestIFailed("#%u: SharedClipboardWinConvertCFHTMLToMIME(%s, %#zx,,) returned %Rrc, expected VINF_SUCCESS",
+                              i, pszCfHtml, strlen(pszCfHtml), rc);
+            RTMemFree(pszCfHtml);
+        }
+        else
+            RTTestIFailed("#%u: SharedClipboardWinConvertMIMEToCFHTML(%s, %#zx,,) returned %Rrc, expected VINF_SUCCESS",
+                          i, s_aRoundTrips[i].psz, s_aRoundTrips[i].cch, rc);
+    }
+}
+
+#endif /* RT_OS_WINDOWS */
+
+
+int main(int argc, char *argv[])
+{
+    /*
+     * Init the runtime, test and say hello.
+     */
+    const char *pcszExecName;
+    NOREF(argc);
+    pcszExecName = strrchr(argv[0], '/');
+    pcszExecName = pcszExecName ? pcszExecName + 1 : argv[0];
+    RTTEST hTest;
+    RTEXITCODE rcExit = RTTestInitAndCreate(pcszExecName, &hTest);
+    if (rcExit != RTEXITCODE_SUCCESS)
+        return rcExit;
+    RTTestBanner(hTest);
+
+    /*
+     * Run the tests.
+     */
+    testAnnounceAndReadData();
+#ifdef RT_OS_WINDOWS
+    testHtmlCf();
+#endif
+
+    /*
+     * Summary
+     */
+    return RTTestSummaryAndDestroy(hTest);
+}
+
diff --git a/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardTransfers.cpp b/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardTransfers.cpp
new file mode 100644
index 00000000..dfe363ee
--- /dev/null
+++ b/src/VBox/HostServices/SharedClipboard/testcase/tstClipboardTransfers.cpp
@@ -0,0 +1,389 @@
+/* $Id: tstClipboardTransfers.cpp $ */
+/** @file
+ * Shared Clipboard transfers test case.
+ */
+
+/*
+ * Copyright (C) 2019-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include "../VBoxSharedClipboardSvc-internal.h"
+
+#include <VBox/HostServices/VBoxClipboardSvc.h>
+
+#include <iprt/assert.h>
+#include <iprt/dir.h>
+#include <iprt/file.h>
+#include <iprt/path.h>
+#include <iprt/string.h>
+#include <iprt/test.h>
+
+
+static int testCreateTempDir(RTTEST hTest, const char *pszTestcase, char *pszTempDir, size_t cbTempDir)
+{
+    char szTempDir[RTPATH_MAX];
+    int rc = RTPathTemp(szTempDir, sizeof(szTempDir));
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    rc = RTPathAppend(szTempDir, sizeof(szTempDir), "tstClipboardTransfers");
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    rc = RTDirCreate(szTempDir, 0700, 0);
+    if (rc == VERR_ALREADY_EXISTS)
+        rc = VINF_SUCCESS;
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    rc = RTPathAppend(szTempDir, sizeof(szTempDir), "XXXXX");
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    rc = RTDirCreateTemp(szTempDir, 0700);
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    rc = RTPathJoin(pszTempDir, cbTempDir, szTempDir, pszTestcase);
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    RTTestPrintf(hTest, RTTESTLVL_DEBUG, "Created temporary directory: %s\n", pszTempDir);
+
+    return rc;
+}
+
+static int testRemoveTempDir(RTTEST hTest)
+{
+    char szTempDir[RTPATH_MAX];
+    int rc = RTPathTemp(szTempDir, sizeof(szTempDir));
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    rc = RTPathAppend(szTempDir, sizeof(szTempDir), "tstClipboardTransfers");
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    rc = RTDirRemoveRecursive(szTempDir, RTDIRRMREC_F_CONTENT_AND_DIR);
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    RTTestPrintf(hTest, RTTESTLVL_DEBUG, "Removed temporary directory: %s\n", szTempDir);
+
+    return rc;
+}
+
+static int testCreateDir(RTTEST hTest, const char *pszPathToCreate)
+{
+    RTTestPrintf(hTest, RTTESTLVL_DEBUG, "Creating directory: %s\n", pszPathToCreate);
+
+    int rc = RTDirCreateFullPath(pszPathToCreate, 0700);
+    if (rc == VERR_ALREADY_EXISTS)
+        rc = VINF_SUCCESS;
+    RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+
+    return rc;
+}
+
+static int testCreateFile(RTTEST hTest, const char *pszTempDir, const char *pszFileName, uint32_t fOpen, size_t cbSize,
+                          char **ppszFilePathAbs)
+{
+    char szFilePath[RTPATH_MAX];
+
+    int rc = RTStrCopy(szFilePath, sizeof(szFilePath), pszTempDir);
+    RTTESTI_CHECK_RC_OK_RET(rc, rc);
+
+    rc = RTPathAppend(szFilePath, sizeof(szFilePath), pszFileName);
+    RTTESTI_CHECK_RC_OK_RET(rc, rc);
+
+    char *pszDirToCreate = RTStrDup(szFilePath);
+    RTTESTI_CHECK_RET(pszDirToCreate, VERR_NO_MEMORY);
+
+    RTPathStripFilename(pszDirToCreate);
+
+    rc = testCreateDir(hTest, pszDirToCreate);
+    RTTESTI_CHECK_RC_OK_RET(rc, rc);
+
+    RTStrFree(pszDirToCreate);
+    pszDirToCreate = NULL;
+
+    if (!fOpen)
+        fOpen = RTFILE_O_OPEN_CREATE | RTFILE_O_WRITE | RTFILE_O_DENY_NONE;
+
+    RTTestPrintf(hTest, RTTESTLVL_DEBUG, "Creating file: %s\n", szFilePath);
+
+    RTFILE hFile;
+    rc = RTFileOpen(&hFile, szFilePath, fOpen);
+    if (RT_SUCCESS(rc))
+    {
+        if (cbSize)
+        {
+            /** @todo Fill in some random stuff. */
+        }
+
+        rc = RTFileClose(hFile);
+        RTTESTI_CHECK_RC_RET(rc, VINF_SUCCESS, rc);
+    }
+
+    if (ppszFilePathAbs)
+        *ppszFilePathAbs = RTStrDup(szFilePath);
+
+    return rc;
+}
+
+typedef struct TESTTRANSFERROOTENTRY
+{
+    TESTTRANSFERROOTENTRY(const RTCString &a_strPath)
+        : strPath(a_strPath) { }
+
+    RTCString strPath;
+} TESTTRANSFERROOTENTRY;
+
+static int testAddRootEntry(RTTEST hTest, const char *pszTempDir,
+                            const TESTTRANSFERROOTENTRY &rootEntry, char **ppszRoots)
+{
+    char *pszRoots = NULL;
+
+    const char *pszPath = rootEntry.strPath.c_str();
+
+    char *pszPathAbs;
+    int rc = testCreateFile(hTest, pszTempDir, pszPath, 0, 0, &pszPathAbs);
+    RTTESTI_CHECK_RC_OK_RET(rc, rc);
+
+    rc = RTStrAAppend(&pszRoots, pszPathAbs);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    rc = RTStrAAppend(&pszRoots, "\r\n");
+    RTTESTI_CHECK_RC_OK(rc);
+
+    RTStrFree(pszPathAbs);
+
+    *ppszRoots = pszRoots;
+
+    return rc;
+}
+
+static int testAddRootEntries(RTTEST hTest, const char *pszTempDir,
+                              RTCList<TESTTRANSFERROOTENTRY> &lstBase, RTCList<TESTTRANSFERROOTENTRY> lstToExtend,
+                              char **ppszRoots)
+{
+    int rc = VINF_SUCCESS;
+
+    char *pszRoots = NULL;
+
+    for (size_t i = 0; i < lstBase.size(); ++i)
+    {
+        char *pszEntry = NULL;
+        rc = testAddRootEntry(hTest, pszTempDir, lstBase.at(i), &pszEntry);
+        RTTESTI_CHECK_RC_OK_BREAK(rc);
+        rc = RTStrAAppend(&pszRoots, pszEntry);
+        RTTESTI_CHECK_RC_OK_BREAK(rc);
+        RTStrFree(pszEntry);
+    }
+
+    for (size_t i = 0; i < lstToExtend.size(); ++i)
+    {
+        char *pszEntry = NULL;
+        rc = testAddRootEntry(hTest, pszTempDir, lstToExtend.at(i), &pszEntry);
+        RTTESTI_CHECK_RC_OK_BREAK(rc);
+        rc = RTStrAAppend(&pszRoots, pszEntry);
+        RTTESTI_CHECK_RC_OK_BREAK(rc);
+        RTStrFree(pszEntry);
+    }
+
+    if (RT_SUCCESS(rc))
+        *ppszRoots = pszRoots;
+
+    return rc;
+}
+
+static void testTransferRootsSetSingle(RTTEST hTest,
+                                       RTCList<TESTTRANSFERROOTENTRY> &lstBase, RTCList<TESTTRANSFERROOTENTRY> lstToExtend,
+                                       int rcExpected)
+{
+    PSHCLTRANSFER pTransfer;
+    int rc = ShClTransferCreate(&pTransfer);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    char szTestTransferRootsSetDir[RTPATH_MAX];
+    rc = testCreateTempDir(hTest, "testTransferRootsSet", szTestTransferRootsSetDir, sizeof(szTestTransferRootsSetDir));
+    RTTESTI_CHECK_RC_OK_RETV(rc);
+
+    /* This is the file we're trying to access (but not supposed to). */
+    rc = testCreateFile(hTest, szTestTransferRootsSetDir, "must-not-access-this", 0, 0, NULL);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    char *pszRoots;
+    rc = testAddRootEntries(hTest, szTestTransferRootsSetDir, lstBase, lstToExtend, &pszRoots);
+    RTTESTI_CHECK_RC_OK_RETV(rc);
+
+    rc = ShClTransferRootsSet(pTransfer, pszRoots, strlen(pszRoots) + 1);
+    RTTESTI_CHECK_RC(rc, rcExpected);
+
+    RTStrFree(pszRoots);
+
+    rc = ShClTransferDestroy(pTransfer);
+    RTTESTI_CHECK_RC_OK(rc);
+}
+
+static void testTransferObjOpenSingle(RTTEST hTest,
+                                      RTCList<TESTTRANSFERROOTENTRY> &lstRoots, const char *pszObjPath, int rcExpected)
+{
+    RT_NOREF(hTest);
+
+    PSHCLTRANSFER pTransfer;
+    int rc = ShClTransferCreate(&pTransfer);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    rc = ShClTransferInit(pTransfer, SHCLTRANSFERDIR_FROM_REMOTE, SHCLSOURCE_LOCAL);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    char szTestTransferObjOpenDir[RTPATH_MAX];
+    rc = testCreateTempDir(hTest, "testTransferObjOpen", szTestTransferObjOpenDir, sizeof(szTestTransferObjOpenDir));
+    RTTESTI_CHECK_RC_OK_RETV(rc);
+
+    /* This is the file we're trying to access (but not supposed to). */
+    rc = testCreateFile(hTest, szTestTransferObjOpenDir, "file1.txt", 0, 0, NULL);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    RTCList<TESTTRANSFERROOTENTRY> lstToExtendEmpty;
+
+    char *pszRoots;
+    rc = testAddRootEntries(hTest, szTestTransferObjOpenDir, lstRoots, lstToExtendEmpty, &pszRoots);
+    RTTESTI_CHECK_RC_OK_RETV(rc);
+
+    rc = ShClTransferRootsSet(pTransfer, pszRoots, strlen(pszRoots) + 1);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    RTStrFree(pszRoots);
+
+    SHCLOBJOPENCREATEPARMS openCreateParms;
+    rc = ShClTransferObjOpenParmsInit(&openCreateParms);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    rc = RTStrCopy(openCreateParms.pszPath, openCreateParms.cbPath, pszObjPath);
+    RTTESTI_CHECK_RC_OK(rc);
+
+    SHCLOBJHANDLE hObj;
+    rc = ShClTransferObjOpen(pTransfer, &openCreateParms, &hObj);
+    RTTESTI_CHECK_RC(rc, rcExpected);
+    if (RT_SUCCESS(rc))
+    {
+        rc = ShClTransferObjClose(pTransfer, hObj);
+        RTTESTI_CHECK_RC_OK(rc);
+    }
+
+    rc = ShClTransferDestroy(pTransfer);
+    RTTESTI_CHECK_RC_OK(rc);
+}
+
+static void testTransferBasics(RTTEST hTest)
+{
+    RT_NOREF(hTest);
+
+    RTTestISub("Testing transfer basics");
+
+    SHCLEVENTSOURCE Source;
+    int rc = ShClEventSourceCreate(&Source, 0);
+    RTTESTI_CHECK_RC_OK(rc);
+    rc = ShClEventSourceDestroy(&Source);
+    RTTESTI_CHECK_RC_OK(rc);
+    PSHCLTRANSFER pTransfer;
+    rc = ShClTransferCreate(&pTransfer);
+    RTTESTI_CHECK_RC_OK(rc);
+    rc = ShClTransferDestroy(pTransfer);
+    RTTESTI_CHECK_RC_OK(rc);
+}
+
+static void testTransferRootsSet(RTTEST hTest)
+{
+    RTTestISub("Testing setting transfer roots");
+
+    /* Define the (valid) transfer root set. */
+    RTCList<TESTTRANSFERROOTENTRY> lstBase;
+    lstBase.append(TESTTRANSFERROOTENTRY("my-transfer-1/file1.txt"));
+    lstBase.append(TESTTRANSFERROOTENTRY("my-transfer-1/dir1/file1.txt"));
+    lstBase.append(TESTTRANSFERROOTENTRY("my-transfer-1/dir1/sub1/file1.txt"));
+    lstBase.append(TESTTRANSFERROOTENTRY("my-transfer-1/dir2/file1.txt"));
+    lstBase.append(TESTTRANSFERROOTENTRY("my-transfer-1/dir2/sub1/file1.txt"));
+
+    RTCList<TESTTRANSFERROOTENTRY> lstBreakout;
+    testTransferRootsSetSingle(hTest, lstBase, lstBreakout, VINF_SUCCESS);
+
+    lstBreakout.clear();
+    lstBase.append(TESTTRANSFERROOTENTRY("../must-not-access-this"));
+    testTransferRootsSetSingle(hTest, lstBase, lstBreakout, VERR_INVALID_PARAMETER);
+
+    lstBreakout.clear();
+    lstBase.append(TESTTRANSFERROOTENTRY("does-not-exist/file1.txt"));
+    testTransferRootsSetSingle(hTest, lstBase, lstBreakout, VERR_INVALID_PARAMETER);
+
+    lstBreakout.clear();
+    lstBase.append(TESTTRANSFERROOTENTRY("my-transfer-1/../must-not-access-this"));
+    testTransferRootsSetSingle(hTest, lstBase, lstBreakout, VERR_INVALID_PARAMETER);
+
+    lstBreakout.clear();
+    lstBase.append(TESTTRANSFERROOTENTRY("my-transfer-1/./../must-not-access-this"));
+    testTransferRootsSetSingle(hTest, lstBase, lstBreakout, VERR_INVALID_PARAMETER);
+
+    lstBreakout.clear();
+    lstBase.append(TESTTRANSFERROOTENTRY("../does-not-exist"));
+    testTransferRootsSetSingle(hTest, lstBase, lstBreakout, VERR_INVALID_PARAMETER);
+}
+
+static void testTransferObjOpen(RTTEST hTest)
+{
+    RTTestISub("Testing setting transfer object open");
+
+    /* Define the (valid) transfer root set. */
+    RTCList<TESTTRANSFERROOTENTRY> lstRoots;
+    lstRoots.append(TESTTRANSFERROOTENTRY("my-transfer-1/file1.txt"));
+    lstRoots.append(TESTTRANSFERROOTENTRY("my-transfer-1/dir1/file1.txt"));
+    lstRoots.append(TESTTRANSFERROOTENTRY("my-transfer-1/dir1/sub1/file1.txt"));
+    lstRoots.append(TESTTRANSFERROOTENTRY("my-transfer-1/dir2/file1.txt"));
+    lstRoots.append(TESTTRANSFERROOTENTRY("my-transfer-1/dir2/sub1/file1.txt"));
+
+    testTransferObjOpenSingle(hTest, lstRoots, "file1.txt", VINF_SUCCESS);
+    testTransferObjOpenSingle(hTest, lstRoots, "does-not-exist.txt", VERR_PATH_NOT_FOUND);
+    testTransferObjOpenSingle(hTest, lstRoots, "dir1/does-not-exist.txt", VERR_PATH_NOT_FOUND);
+    testTransferObjOpenSingle(hTest, lstRoots, "../must-not-access-this.txt", VERR_INVALID_PARAMETER);
+    testTransferObjOpenSingle(hTest, lstRoots, "dir1/../../must-not-access-this.txt", VERR_INVALID_PARAMETER);
+}
+
+int main(int argc, char *argv[])
+{
+    /*
+     * Init the runtime, test and say hello.
+     */
+    const char *pcszExecName;
+    NOREF(argc);
+    pcszExecName = strrchr(argv[0], '/');
+    pcszExecName = pcszExecName ? pcszExecName + 1 : argv[0];
+    RTTEST hTest;
+    RTEXITCODE rcExit = RTTestInitAndCreate(pcszExecName, &hTest);
+    if (rcExit != RTEXITCODE_SUCCESS)
+        return rcExit;
+    RTTestBanner(hTest);
+
+    testTransferBasics(hTest);
+    testTransferRootsSet(hTest);
+    testTransferObjOpen(hTest);
+
+    int rc = testRemoveTempDir(hTest);
+    RTTESTI_CHECK_RC(rc, VINF_SUCCESS);
+
+    /*
+     * Summary
+     */
+    return RTTestSummaryAndDestroy(hTest);
+}
+
diff --git a/src/VBox/HostServices/SharedFolders/Makefile.kmk b/src/VBox/HostServices/SharedFolders/Makefile.kmk
new file mode 100644
index 00000000..fc0ff6c5
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/Makefile.kmk
@@ -0,0 +1,62 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Shared Folders Host Service.
+#
+
+#
+# Copyright (C) 2006-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+# Include sub-makefile(s).
+include $(PATH_SUB_CURRENT)/testcase/Makefile.kmk
+
+#
+# The shared folder service DLL.
+#
+DLLS += VBoxSharedFolders
+VBoxSharedFolders_TEMPLATE  = VBoxR3Dll
+VBoxSharedFolders_NAME.os2  = VBoxSFld
+VBoxSharedFolders_DEFS      = VBOX_WITH_HGCM RTSHFL
+VBoxSharedFolders_INCS.win  = \
+	$(VBOX_PATH_SDK)
+
+VBoxSharedFolders_LDFLAGS.darwin = \
+	-framework Carbon \
+	-install_name $(VBOX_DYLD_EXECUTABLE_PATH)/VBoxSharedFolders.dylib
+
+VBoxSharedFolders_SOURCES = \
+	VBoxSharedFoldersSvc.cpp \
+	shflhandle.cpp \
+	vbsf.cpp \
+	vbsfpath.cpp \
+	vbsfpathabs.cpp \
+	mappings.cpp
+VBoxSharedFolders_SOURCES.win = \
+	VBoxSharedFoldersSvc.rc
+
+VBoxSharedFolders_LIBS = \
+	$(LIB_RUNTIME)
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/HostServices/SharedFolders/VBoxSharedFoldersSvc.cpp b/src/VBox/HostServices/SharedFolders/VBoxSharedFoldersSvc.cpp
new file mode 100644
index 00000000..3486709d
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/VBoxSharedFoldersSvc.cpp
@@ -0,0 +1,1971 @@
+/* $Id: VBoxSharedFoldersSvc.cpp $ */
+/** @file
+ * Shared Folders - Host service entry points.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_FOLDERS
+#include <VBox/shflsvc.h>
+
+#include "shfl.h"
+#include "mappings.h"
+#include "shflhandle.h"
+#include "vbsf.h"
+#include <iprt/alloc.h>
+#include <iprt/string.h>
+#include <iprt/assert.h>
+#include <VBox/AssertGuest.h>
+#include <VBox/vmm/ssm.h>
+#include <VBox/vmm/pdmifs.h>
+#include <VBox/vmm/vmmr3vtable.h>
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+#define SHFL_SAVED_STATE_VERSION_FOLDERNAME_UTF16       2
+#define SHFL_SAVED_STATE_VERSION_PRE_AUTO_MOUNT_POINT   3
+#define SHFL_SAVED_STATE_VERSION_PRE_ERROR_STYLE        4
+#define SHFL_SAVED_STATE_VERSION                        5
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+PVBOXHGCMSVCHELPERS g_pHelpers;
+static PPDMLED      g_pStatusLed = NULL;
+
+/** @name Shared folder statistics.
+ * @{ */
+static STAMPROFILE g_StatQueryMappings;
+static STAMPROFILE g_StatQueryMappingsFail;
+static STAMPROFILE g_StatQueryMapName;
+static STAMPROFILE g_StatCreate;
+static STAMPROFILE g_StatCreateFail;
+static STAMPROFILE g_StatLookup;
+static STAMPROFILE g_StatLookupFail;
+static STAMPROFILE g_StatClose;
+static STAMPROFILE g_StatCloseFail;
+static STAMPROFILE g_StatRead;
+static STAMPROFILE g_StatReadFail;
+static STAMPROFILE g_StatWrite;
+static STAMPROFILE g_StatWriteFail;
+static STAMPROFILE g_StatLock;
+static STAMPROFILE g_StatLockFail;
+static STAMPROFILE g_StatList;
+static STAMPROFILE g_StatListFail;
+static STAMPROFILE g_StatReadLink;
+static STAMPROFILE g_StatReadLinkFail;
+static STAMPROFILE g_StatMapFolderOld;
+static STAMPROFILE g_StatMapFolder;
+static STAMPROFILE g_StatMapFolderFail;
+static STAMPROFILE g_StatUnmapFolder;
+static STAMPROFILE g_StatUnmapFolderFail;
+static STAMPROFILE g_StatInformationFail;
+static STAMPROFILE g_StatInformationSetFile;
+static STAMPROFILE g_StatInformationSetFileFail;
+static STAMPROFILE g_StatInformationSetSize;
+static STAMPROFILE g_StatInformationSetSizeFail;
+static STAMPROFILE g_StatInformationGetFile;
+static STAMPROFILE g_StatInformationGetFileFail;
+static STAMPROFILE g_StatInformationGetVolume;
+static STAMPROFILE g_StatInformationGetVolumeFail;
+static STAMPROFILE g_StatRemove;
+static STAMPROFILE g_StatRemoveFail;
+static STAMPROFILE g_StatCloseAndRemove;
+static STAMPROFILE g_StatCloseAndRemoveFail;
+static STAMPROFILE g_StatRename;
+static STAMPROFILE g_StatRenameFail;
+static STAMPROFILE g_StatFlush;
+static STAMPROFILE g_StatFlushFail;
+static STAMPROFILE g_StatSetErrorStyle;
+static STAMPROFILE g_StatSetUtf8;
+static STAMPROFILE g_StatSetFileSize;
+static STAMPROFILE g_StatSetFileSizeFail;
+static STAMPROFILE g_StatSymlink;
+static STAMPROFILE g_StatSymlinkFail;
+static STAMPROFILE g_StatSetSymlinks;
+static STAMPROFILE g_StatQueryMapInfo;
+static STAMPROFILE g_StatQueryFeatures;
+static STAMPROFILE g_StatCopyFile;
+static STAMPROFILE g_StatCopyFileFail;
+static STAMPROFILE g_StatCopyFilePart;
+static STAMPROFILE g_StatCopyFilePartFail;
+static STAMPROFILE g_StatWaitForMappingsChanges;
+static STAMPROFILE g_StatWaitForMappingsChangesFail;
+static STAMPROFILE g_StatCancelMappingsChangesWait;
+static STAMPROFILE g_StatUnknown;
+static STAMPROFILE g_StatMsgStage1;
+/** @} */
+
+
+/** @page pg_shfl_svc   Shared Folders Host Service
+ *
+ * Shared Folders map a host file system to guest logical filesystem.
+ * A mapping represents 'host name'<->'guest name' translation and a root
+ * identifier to be used to access this mapping.
+ * Examples: "C:\WINNT"<->"F:", "C:\WINNT\System32"<->"/mnt/host/system32".
+ *
+ * Therefore, host name and guest name are strings interpreted
+ * only by host service and guest client respectively. Host name is
+ * passed to guest only for informational purpose. Guest may for example
+ * display the string or construct volume label out of the string.
+ *
+ * Root identifiers are unique for whole guest life,
+ * that is until next guest reset/fresh start.
+ * 32 bit value incremented for each new mapping is used.
+ *
+ * Mapping strings are taken from VM XML configuration on VM startup.
+ * The service DLL takes mappings during initialization. There is
+ * also API for changing mappings at runtime.
+ *
+ * Current mappings and root identifiers are saved when VM is saved.
+ *
+ * Guest may use any of these mappings. Full path information
+ * about an object on a mapping consists of the root identifier and
+ * a full path of object.
+ *
+ * Guest IFS connects to the service and calls SHFL_FN_QUERY_MAP
+ * function which returns current mappings. For guest convenience,
+ * removed mappings also returned with REMOVED flag and new mappings
+ * are marked with NEW flag.
+ *
+ * To access host file system guest just forwards file system calls
+ * to the service, and specifies full paths or handles for objects.
+ *
+ *
+ */
+
+
+
+static DECLCALLBACK(int) svcUnload (void *)
+{
+    int rc = VINF_SUCCESS;
+
+    Log(("svcUnload\n"));
+    vbsfFreeHandleTable();
+
+    if (g_pHelpers)
+        HGCMSvcHlpStamDeregister(g_pHelpers, "/HGCM/VBoxSharedFolders/*");
+    return rc;
+}
+
+static DECLCALLBACK(int) svcConnect (void *, uint32_t u32ClientID, void *pvClient, uint32_t fRequestor, bool fRestoring)
+{
+    RT_NOREF(u32ClientID, fRequestor, fRestoring);
+    SHFLCLIENTDATA *pClient = (SHFLCLIENTDATA *)pvClient;
+    Log(("SharedFolders host service: connected, u32ClientID = %u\n", u32ClientID));
+
+    pClient->fHasMappingCounts = true;
+    pClient->enmErrorStyle = SHFLERRORSTYLE_NATIVE;
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) svcDisconnect (void *, uint32_t u32ClientID, void *pvClient)
+{
+    RT_NOREF1(u32ClientID);
+    SHFLCLIENTDATA *pClient = (SHFLCLIENTDATA *)pvClient;
+
+    /* When a client disconnects, make sure that outstanding change waits are being canceled.
+     *
+     * Usually this will be done actively by VBoxService on the guest side when shutting down,
+     * but the VM could be reset without having VBoxService the chance of cancelling those waits.
+     *
+     * This in turn will eat up the call completion handle restrictions on the HGCM host side, throwing assertions. */
+    int rc = vbsfMappingsCancelChangesWaits(pClient);
+
+    Log(("SharedFolders host service: disconnected, u32ClientID = %u, rc = %Rrc\n", u32ClientID, rc));
+
+    vbsfDisconnect(pClient);
+    return rc;
+}
+
+/** @note We only save as much state as required to access the shared folder again after restore.
+ *        All I/O requests pending at the time of saving will never be completed or result in errors.
+ *        (file handles no longer valid etc)
+ *        This works as designed at the moment. A full state save would be difficult and not always possible
+ *        as the contents of a shared folder might change in between save and restore.
+ */
+static DECLCALLBACK(int) svcSaveState(void *, uint32_t u32ClientID, void *pvClient, PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM)
+{
+#ifndef UNITTEST  /* Read this as not yet tested */
+    RT_NOREF1(u32ClientID);
+    SHFLCLIENTDATA *pClient = (SHFLCLIENTDATA *)pvClient;
+
+    Log(("SharedFolders host service: saving state, u32ClientID = %u\n", u32ClientID));
+
+    int rc = pVMM->pfnSSMR3PutU32(pSSM, SHFL_SAVED_STATE_VERSION);
+    AssertRCReturn(rc, rc);
+
+    rc = pVMM->pfnSSMR3PutU32(pSSM, SHFL_MAX_MAPPINGS);
+    AssertRCReturn(rc, rc);
+
+    /* Save client structure length & contents */
+    rc = pVMM->pfnSSMR3PutU32(pSSM, sizeof(*pClient));
+    AssertRCReturn(rc, rc);
+
+    rc = pVMM->pfnSSMR3PutMem(pSSM, pClient, sizeof(*pClient));
+    AssertRCReturn(rc, rc);
+
+    /* Save all the active mappings. */
+    for (int i=0;i<SHFL_MAX_MAPPINGS;i++)
+    {
+        /* Mapping are saved in the order of increasing root handle values. */
+        MAPPING *pFolderMapping = vbsfMappingGetByRoot(i);
+
+        rc = pVMM->pfnSSMR3PutU32(pSSM, pFolderMapping? pFolderMapping->cMappings: 0);
+        AssertRCReturn(rc, rc);
+
+        rc = pVMM->pfnSSMR3PutBool(pSSM, pFolderMapping? pFolderMapping->fValid: false);
+        AssertRCReturn(rc, rc);
+
+        if (pFolderMapping && pFolderMapping->fValid)
+        {
+            uint32_t len = (uint32_t)strlen(pFolderMapping->pszFolderName);
+            pVMM->pfnSSMR3PutU32(pSSM, len);
+            pVMM->pfnSSMR3PutStrZ(pSSM, pFolderMapping->pszFolderName);
+
+            len = ShflStringSizeOfBuffer(pFolderMapping->pMapName);
+            pVMM->pfnSSMR3PutU32(pSSM, len);
+            pVMM->pfnSSMR3PutMem(pSSM, pFolderMapping->pMapName, len);
+
+            pVMM->pfnSSMR3PutBool(pSSM, pFolderMapping->fHostCaseSensitive);
+
+            pVMM->pfnSSMR3PutBool(pSSM, pFolderMapping->fGuestCaseSensitive);
+
+            len = ShflStringSizeOfBuffer(pFolderMapping->pAutoMountPoint);
+            pVMM->pfnSSMR3PutU32(pSSM, len);
+            rc = pVMM->pfnSSMR3PutMem(pSSM, pFolderMapping->pAutoMountPoint, len);
+            AssertRCReturn(rc, rc);
+        }
+    }
+
+#else
+    RT_NOREF(u32ClientID, pvClient, pSSM, pVMM);
+#endif
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) svcLoadState(void *, uint32_t u32ClientID, void *pvClient,
+                                      PSSMHANDLE pSSM, PCVMMR3VTABLE pVMM, uint32_t uVersion)
+{
+#ifndef UNITTEST  /* Read this as not yet tested */
+    RT_NOREF(u32ClientID, uVersion);
+    uint32_t        nrMappings;
+    SHFLCLIENTDATA *pClient = (SHFLCLIENTDATA *)pvClient;
+    uint32_t        len;
+
+    Log(("SharedFolders host service: loading state, u32ClientID = %u\n", u32ClientID));
+
+    uint32_t uShfVersion = 0;
+    int rc = pVMM->pfnSSMR3GetU32(pSSM, &uShfVersion);
+    AssertRCReturn(rc, rc);
+
+    if (   uShfVersion > SHFL_SAVED_STATE_VERSION
+        || uShfVersion < SHFL_SAVED_STATE_VERSION_FOLDERNAME_UTF16)
+        return pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_UNSUPPORTED_DATA_UNIT_VERSION, RT_SRC_POS,
+                                          "Unknown shared folders state version %u!", uShfVersion);
+
+    rc = pVMM->pfnSSMR3GetU32(pSSM, &nrMappings);
+    AssertRCReturn(rc, rc);
+    if (nrMappings != SHFL_MAX_MAPPINGS)
+        return VERR_SSM_DATA_UNIT_FORMAT_CHANGED;
+
+    /* Restore the client data (flags + path delimiter + mapping counts (new) at the moment) */
+    rc = pVMM->pfnSSMR3GetU32(pSSM, &len);
+    AssertRCReturn(rc, rc);
+
+    if (len == RT_UOFFSETOF(SHFLCLIENTDATA, acMappings))
+        pClient->fHasMappingCounts = false;
+    else if (len != sizeof(*pClient))
+        return pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_DATA_UNIT_FORMAT_CHANGED, RT_SRC_POS,
+                                          "Saved SHFLCLIENTDATA size %u differs from current %u!", len, sizeof(*pClient));
+
+    rc = pVMM->pfnSSMR3GetMem(pSSM, pClient, len);
+    AssertRCReturn(rc, rc);
+
+    /* For older saved state, use the default native error style, otherwise
+       check that the restored value makes sense to us. */
+    if (uShfVersion <= SHFL_SAVED_STATE_VERSION_PRE_ERROR_STYLE)
+        pClient->enmErrorStyle = SHFLERRORSTYLE_NATIVE;
+    else if (   pClient->enmErrorStyle <= kShflErrorStyle_Invalid
+             || pClient->enmErrorStyle >= kShflErrorStyle_End)
+        return pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_DATA_UNIT_FORMAT_CHANGED, RT_SRC_POS,
+                                          "Saved SHFLCLIENTDATA enmErrorStyle value %d is not known/valid!", pClient->enmErrorStyle);
+
+    /* Drop the root IDs of all configured mappings before restoring: */
+    vbsfMappingLoadingStart();
+
+    /* We don't actually (fully) restore the state; we simply check if the current state is as we it expect it to be. */
+    for (SHFLROOT i = 0; i < SHFL_MAX_MAPPINGS; i++)
+    {
+        /* Load the saved mapping description and try to find it in the mappings. */
+        MAPPING mapping;
+        RT_ZERO(mapping);
+
+        /* restore the folder mapping counter. */
+        rc = pVMM->pfnSSMR3GetU32(pSSM, &mapping.cMappings);
+        AssertRCReturn(rc, rc);
+
+        rc = pVMM->pfnSSMR3GetBool(pSSM, &mapping.fValid);
+        AssertRCReturn(rc, rc);
+
+        if (mapping.fValid)
+        {
+            /* Load the host path name. */
+            uint32_t cb;
+            rc = pVMM->pfnSSMR3GetU32(pSSM, &cb);
+            AssertRCReturn(rc, rc);
+
+            char *pszFolderName;
+            if (uShfVersion == SHFL_SAVED_STATE_VERSION_FOLDERNAME_UTF16) /* (See version range check above.) */
+            {
+                AssertReturn(cb > SHFLSTRING_HEADER_SIZE && cb <= UINT16_MAX + SHFLSTRING_HEADER_SIZE && !(cb & 1),
+                             pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_DATA_UNIT_FORMAT_CHANGED, RT_SRC_POS,
+                                                        "Bad folder name size: %#x", cb));
+                PSHFLSTRING pFolderName = (PSHFLSTRING)RTMemAlloc(cb);
+                AssertReturn(pFolderName != NULL, VERR_NO_MEMORY);
+
+                rc = pVMM->pfnSSMR3GetMem(pSSM, pFolderName, cb);
+                AssertRCReturn(rc, rc);
+                AssertReturn(pFolderName->u16Size < cb && pFolderName->u16Length < pFolderName->u16Size,
+                             pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_DATA_UNIT_FORMAT_CHANGED, RT_SRC_POS,
+                                                        "Bad folder name string: %#x/%#x cb=%#x",
+                                                        pFolderName->u16Size, pFolderName->u16Length, cb));
+
+                rc = RTUtf16ToUtf8(pFolderName->String.ucs2, &pszFolderName);
+                RTMemFree(pFolderName);
+                AssertRCReturn(rc, rc);
+            }
+            else
+            {
+                pszFolderName = (char *)RTStrAlloc(cb + 1);
+                AssertReturn(pszFolderName, VERR_NO_MEMORY);
+
+                rc = pVMM->pfnSSMR3GetStrZ(pSSM, pszFolderName, cb + 1);
+                AssertRCReturn(rc, rc);
+                mapping.pszFolderName = pszFolderName;
+            }
+
+            /* Load the map name. */
+            rc = pVMM->pfnSSMR3GetU32(pSSM, &cb);
+            AssertRCReturn(rc, rc);
+            AssertReturn(cb > SHFLSTRING_HEADER_SIZE && cb <= UINT16_MAX + SHFLSTRING_HEADER_SIZE && !(cb & 1),
+                         pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_DATA_UNIT_FORMAT_CHANGED, RT_SRC_POS,
+                                                    "Bad map name size: %#x", cb));
+
+            PSHFLSTRING pMapName = (PSHFLSTRING)RTMemAlloc(cb);
+            AssertReturn(pMapName != NULL, VERR_NO_MEMORY);
+
+            rc = pVMM->pfnSSMR3GetMem(pSSM, pMapName, cb);
+            AssertRCReturn(rc, rc);
+            AssertReturn(pMapName->u16Size < cb && pMapName->u16Length < pMapName->u16Size,
+                         pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_DATA_UNIT_FORMAT_CHANGED, RT_SRC_POS,
+                                                    "Bad map name string: %#x/%#x cb=%#x",
+                                                    pMapName->u16Size, pMapName->u16Length, cb));
+
+            /* Load case sensitivity config. */
+            rc = pVMM->pfnSSMR3GetBool(pSSM, &mapping.fHostCaseSensitive);
+            AssertRCReturn(rc, rc);
+
+            rc = pVMM->pfnSSMR3GetBool(pSSM, &mapping.fGuestCaseSensitive);
+            AssertRCReturn(rc, rc);
+
+            /* Load the auto mount point. */
+            PSHFLSTRING pAutoMountPoint;
+            if (uShfVersion > SHFL_SAVED_STATE_VERSION_PRE_AUTO_MOUNT_POINT)
+            {
+                rc = pVMM->pfnSSMR3GetU32(pSSM, &cb);
+                AssertRCReturn(rc, rc);
+                AssertReturn(cb > SHFLSTRING_HEADER_SIZE && cb <= UINT16_MAX + SHFLSTRING_HEADER_SIZE && !(cb & 1),
+                             pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_DATA_UNIT_FORMAT_CHANGED, RT_SRC_POS,
+                                                        "Bad auto mount point size: %#x", cb));
+
+                pAutoMountPoint = (PSHFLSTRING)RTMemAlloc(cb);
+                AssertReturn(pAutoMountPoint != NULL, VERR_NO_MEMORY);
+
+                rc = pVMM->pfnSSMR3GetMem(pSSM, pAutoMountPoint, cb);
+                AssertRCReturn(rc, rc);
+                AssertReturn(pAutoMountPoint->u16Size < cb && pAutoMountPoint->u16Length < pAutoMountPoint->u16Size,
+                             pVMM->pfnSSMR3SetLoadError(pSSM, VERR_SSM_DATA_UNIT_FORMAT_CHANGED, RT_SRC_POS,
+                                                        "Bad auto mount point string: %#x/%#x cb=%#x",
+                                                        pAutoMountPoint->u16Size, pAutoMountPoint->u16Length, cb));
+
+            }
+            else
+            {
+                pAutoMountPoint = ShflStringDupUtf8("");
+                AssertReturn(pAutoMountPoint, VERR_NO_MEMORY);
+            }
+
+            mapping.pszFolderName = pszFolderName;
+            mapping.pMapName = pMapName;
+            mapping.pAutoMountPoint = pAutoMountPoint;
+
+            /* 'i' is the root handle of the saved mapping. */
+            rc = vbsfMappingLoaded(&mapping, i);
+            if (RT_FAILURE(rc))
+            {
+                LogRel(("SharedFolders host service: %Rrc loading %d [%ls] -> [%s]\n",
+                        rc, i, pMapName->String.ucs2, pszFolderName));
+            }
+
+            RTMemFree(pAutoMountPoint);
+            RTMemFree(pMapName);
+            RTStrFree(pszFolderName);
+
+            AssertRCReturn(rc, rc);
+        }
+    }
+
+    /* Make sure all mappings have root IDs (global folders changes, VM
+       config changes (paranoia)): */
+    vbsfMappingLoadingDone();
+
+    Log(("SharedFolders host service: successfully loaded state\n"));
+#else
+    RT_NOREF(u32ClientID, pvClient, pSSM, pVMM, uVersion);
+#endif
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(void) svcCall (void *, VBOXHGCMCALLHANDLE callHandle, uint32_t u32ClientID, void *pvClient,
+                                   uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[], uint64_t tsArrival)
+{
+    RT_NOREF(u32ClientID, tsArrival);
+#ifndef VBOX_WITHOUT_RELEASE_STATISTICS
+    uint64_t tsStart;
+    STAM_GET_TS(tsStart);
+    STAM_REL_PROFILE_ADD_PERIOD(&g_StatMsgStage1, tsStart - tsArrival);
+#endif
+    Log(("SharedFolders host service: svcCall: u32ClientID = %u, fn = %u, cParms = %u, pparms = %p\n", u32ClientID, u32Function, cParms, paParms));
+
+    SHFLCLIENTDATA *pClient = (SHFLCLIENTDATA *)pvClient;
+
+    bool fAsynchronousProcessing = false;
+
+#ifdef LOG_ENABLED
+    for (uint32_t i = 0; i < cParms; i++)
+    {
+        /** @todo parameters other than 32 bit */
+        Log(("    pparms[%d]: type %u, value %u\n", i, paParms[i].type, paParms[i].u.uint32));
+    }
+#endif
+
+    int rc = VINF_SUCCESS;
+    PSTAMPROFILE pStat, pStatFail;
+    switch (u32Function)
+    {
+        case SHFL_FN_QUERY_MAPPINGS:
+        {
+            pStat     = &g_StatQueryMappings;
+            pStatFail = &g_StatQueryMappingsFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_QUERY_MAPPINGS\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_QUERY_MAPPINGS)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* flags */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_32BIT   /* numberOfMappings */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_PTR     /* mappings */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                uint32_t fu32Flags     = paParms[0].u.uint32;
+                uint32_t cMappings     = paParms[1].u.uint32;
+                SHFLMAPPING *pMappings = (SHFLMAPPING *)paParms[2].u.pointer.addr;
+                uint32_t cbMappings    = paParms[2].u.pointer.size;
+
+                /* Verify parameters values. */
+                if (   (fu32Flags & ~SHFL_MF_MASK) != 0
+                    || cbMappings / sizeof (SHFLMAPPING) != cMappings
+                   )
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    /* Execute the function. */
+                    if (fu32Flags & SHFL_MF_UTF8)
+                        pClient->fu32Flags |= SHFL_CF_UTF8;
+                    /// @todo r=bird: Someone please explain this amusing code (r63916):
+                    //if (fu32Flags & SHFL_MF_AUTOMOUNT)
+                    //    pClient->fu32Flags |= SHFL_MF_AUTOMOUNT;
+                    //
+                    //rc = vbsfMappingsQuery(pClient, pMappings, &cMappings);
+
+                    rc = vbsfMappingsQuery(pClient, RT_BOOL(fu32Flags & SHFL_MF_AUTOMOUNT), pMappings, &cMappings);
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Report that there are more mappings to get if
+                         * handed in buffer is too small. */
+                        if (paParms[1].u.uint32 < cMappings)
+                            rc = VINF_BUFFER_OVERFLOW;
+
+                        /* Update parameters. */
+                        paParms[1].u.uint32 = cMappings;
+                    }
+                }
+            }
+
+
+        } break;
+
+        case SHFL_FN_QUERY_MAP_NAME:
+        {
+            pStatFail = pStat = &g_StatQueryMapName;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_QUERY_MAP_NAME\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_QUERY_MAP_NAME)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT /* Root. */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_PTR   /* Name. */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT  root         = (SHFLROOT)paParms[0].u.uint32;
+                SHFLSTRING *pString    = (SHFLSTRING *)paParms[1].u.pointer.addr;
+
+                /* Verify parameters values. */
+                if (!ShflStringIsValidOut(pString, paParms[1].u.pointer.size))
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    /* Execute the function. */
+                    rc = vbsfMappingsQueryName(pClient, root, pString);
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        ; /* None. */
+                    }
+                }
+            }
+
+        } break;
+
+        case SHFL_FN_CREATE:
+        {
+            pStat     = &g_StatCreate;
+            pStatFail = &g_StatCreateFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_CREATE\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_CREATE)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT /* root */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_PTR   /* path */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_PTR   /* parms */
+                    )
+            {
+                Log(("SharedFolders host service: Invalid parameters types\n"));
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT  root          = (SHFLROOT)paParms[0].u.uint32;
+                SHFLSTRING *pPath       = (SHFLSTRING *)paParms[1].u.pointer.addr;
+                uint32_t cbPath         = paParms[1].u.pointer.size;
+                SHFLCREATEPARMS *pParms = (SHFLCREATEPARMS *)paParms[2].u.pointer.addr;
+                uint32_t cbParms        = paParms[2].u.pointer.size;
+
+                /* Verify parameters values. */
+                if (   !ShflStringIsValidIn(pPath, cbPath, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8))
+                    || (cbParms != sizeof (SHFLCREATEPARMS))
+                   )
+                {
+                    AssertMsgFailed (("Invalid parameters cbPath or cbParms (%x, %x - expected >=%x, %x)\n",
+                                      cbPath, cbParms, sizeof(SHFLSTRING), sizeof (SHFLCREATEPARMS)));
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    if (pParms->CreateFlags & SHFL_CF_LOOKUP)
+                    {
+                        pStat     = &g_StatLookup;
+                        pStatFail = &g_StatLookupFail;
+                    }
+
+                    /* Execute the function. */
+                    rc = vbsfCreate (pClient, root, pPath, cbPath, pParms);
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        ; /* none */
+                    }
+                }
+            }
+            break;
+        }
+
+        case SHFL_FN_CLOSE:
+        {
+            pStat     = &g_StatClose;
+            pStatFail = &g_StatCloseFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_CLOSE\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_CLOSE)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_64BIT   /* handle */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT   root   = (SHFLROOT)paParms[0].u.uint32;
+                SHFLHANDLE Handle = paParms[1].u.uint64;
+
+                /* Verify parameters values. */
+                if (Handle == SHFL_HANDLE_ROOT)
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                if (Handle == SHFL_HANDLE_NIL)
+                {
+                    AssertMsgFailed(("Invalid handle!\n"));
+                    rc = VERR_INVALID_HANDLE;
+                }
+                else
+                {
+                    /* Execute the function. */
+                    rc = vbsfClose (pClient, root, Handle);
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        ; /* none */
+                    }
+                }
+            }
+            break;
+
+        }
+
+        /* Read object content. */
+        case SHFL_FN_READ:
+        {
+            pStat     = &g_StatRead;
+            pStatFail = &g_StatReadFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_READ\n"));
+            /* Verify parameter count and types. */
+            ASSERT_GUEST_STMT_BREAK(cParms == SHFL_CPARMS_READ, rc = VERR_WRONG_PARAMETER_COUNT);
+            ASSERT_GUEST_STMT_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* root */
+            ASSERT_GUEST_STMT_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* handle */
+            ASSERT_GUEST_STMT_BREAK(paParms[2].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* offset */
+            ASSERT_GUEST_STMT_BREAK(paParms[3].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* count */
+            ASSERT_GUEST_STMT_BREAK(   paParms[4].type == VBOX_HGCM_SVC_PARM_PTR
+                                    || paParms[4].type == VBOX_HGCM_SVC_PARM_PAGES, rc = VERR_WRONG_PARAMETER_TYPE); /* buffer */
+
+            /* Fetch parameters. */
+            SHFLROOT   const idRoot  = (SHFLROOT)paParms[0].u.uint32;
+            SHFLHANDLE const hFile   = paParms[1].u.uint64;
+            uint64_t   const offFile = paParms[2].u.uint64;
+            uint32_t         cbRead  = paParms[3].u.uint32;
+
+            /* Verify parameters values. */
+            ASSERT_GUEST_STMT_BREAK(hFile != SHFL_HANDLE_ROOT, rc = VERR_INVALID_PARAMETER);
+            ASSERT_GUEST_STMT_BREAK(hFile != SHFL_HANDLE_NIL,  rc = VERR_INVALID_HANDLE);
+            if (paParms[4].type == VBOX_HGCM_SVC_PARM_PTR)
+                ASSERT_GUEST_STMT_BREAK(cbRead <= paParms[4].u.pointer.size, rc = VERR_INVALID_HANDLE);
+            else
+                ASSERT_GUEST_STMT_BREAK(cbRead <= paParms[4].u.Pages.cb, rc = VERR_OUT_OF_RANGE);
+
+            /* Execute the function. */
+            if (g_pStatusLed)
+            {
+                Assert(g_pStatusLed->u32Magic == PDMLED_MAGIC);
+                g_pStatusLed->Asserted.s.fReading = g_pStatusLed->Actual.s.fReading = 1;
+            }
+
+            if (paParms[4].type == VBOX_HGCM_SVC_PARM_PTR)
+                rc = vbsfRead(pClient, idRoot, hFile, offFile, &cbRead, (uint8_t *)paParms[4].u.pointer.addr);
+            else
+                rc = vbsfReadPages(pClient, idRoot, hFile, offFile, &cbRead, &paParms[4].u.Pages);
+
+            if (g_pStatusLed)
+                g_pStatusLed->Actual.s.fReading = 0;
+
+            /* Update parameters.*/
+            paParms[3].u.uint32 = RT_SUCCESS(rc) ? cbRead : 0  /* nothing read */;
+            break;
+        }
+
+        /* Write new object content. */
+        case SHFL_FN_WRITE:
+         {
+            pStat     = &g_StatWrite;
+            pStatFail = &g_StatWriteFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_WRITE\n"));
+
+            /* Verify parameter count and types. */
+            ASSERT_GUEST_STMT_BREAK(cParms == SHFL_CPARMS_WRITE, rc = VERR_WRONG_PARAMETER_COUNT);
+            ASSERT_GUEST_STMT_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* root */
+            ASSERT_GUEST_STMT_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* handle */
+            ASSERT_GUEST_STMT_BREAK(paParms[2].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* offset */
+            ASSERT_GUEST_STMT_BREAK(paParms[3].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* count */
+            ASSERT_GUEST_STMT_BREAK(   paParms[4].type == VBOX_HGCM_SVC_PARM_PTR
+                                    || paParms[4].type == VBOX_HGCM_SVC_PARM_PAGES, rc = VERR_WRONG_PARAMETER_TYPE); /* buffer */
+            /* Fetch parameters. */
+            SHFLROOT   const idRoot   = (SHFLROOT)paParms[0].u.uint32;
+            SHFLHANDLE const hFile    = paParms[1].u.uint64;
+            uint64_t         offFile  = paParms[2].u.uint64;
+            uint32_t         cbWrite  = paParms[3].u.uint32;
+
+            /* Verify parameters values. */
+            ASSERT_GUEST_STMT_BREAK(hFile != SHFL_HANDLE_ROOT, rc = VERR_INVALID_PARAMETER);
+            ASSERT_GUEST_STMT_BREAK(hFile != SHFL_HANDLE_NIL,  rc = VERR_INVALID_HANDLE);
+            if (paParms[4].type == VBOX_HGCM_SVC_PARM_PTR)
+                ASSERT_GUEST_STMT_BREAK(cbWrite <= paParms[4].u.pointer.size, rc = VERR_INVALID_HANDLE);
+            else
+                ASSERT_GUEST_STMT_BREAK(cbWrite <= paParms[4].u.Pages.cb, rc = VERR_OUT_OF_RANGE);
+
+            /* Execute the function. */
+            if (g_pStatusLed)
+            {
+                Assert(g_pStatusLed->u32Magic == PDMLED_MAGIC);
+                g_pStatusLed->Asserted.s.fWriting = g_pStatusLed->Actual.s.fWriting = 1;
+            }
+
+            if (paParms[4].type == VBOX_HGCM_SVC_PARM_PTR)
+                rc = vbsfWrite(pClient, idRoot, hFile, &offFile, &cbWrite, (uint8_t *)paParms[4].u.pointer.addr);
+            else
+                rc = vbsfWritePages(pClient, idRoot, hFile, &offFile, &cbWrite, &paParms[4].u.Pages);
+
+            if (g_pStatusLed)
+                g_pStatusLed->Actual.s.fWriting = 0;
+
+            /* Update parameters.*/
+            if (RT_SUCCESS(rc))
+            {
+                paParms[3].u.uint32 = cbWrite;
+                paParms[2].u.uint64 = offFile;
+            }
+            else
+                paParms[3].u.uint32 = 0;
+            break;
+        }
+
+        /* Lock/unlock a range in the object. */
+        case SHFL_FN_LOCK:
+            pStat     = &g_StatLock;
+            pStatFail = &g_StatLockFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_LOCK\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_LOCK)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                || paParms[1].type != VBOX_HGCM_SVC_PARM_64BIT   /* handle */
+                || paParms[2].type != VBOX_HGCM_SVC_PARM_64BIT   /* offset */
+                || paParms[3].type != VBOX_HGCM_SVC_PARM_64BIT   /* length */
+                || paParms[4].type != VBOX_HGCM_SVC_PARM_32BIT   /* flags */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT  root     = (SHFLROOT)paParms[0].u.uint32;
+                SHFLHANDLE Handle  = paParms[1].u.uint64;
+                uint64_t   offset  = paParms[2].u.uint64;
+                uint64_t   length  = paParms[3].u.uint64;
+                uint32_t   flags   = paParms[4].u.uint32;
+
+                /* Verify parameters values. */
+                if (Handle == SHFL_HANDLE_ROOT)
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                if (Handle == SHFL_HANDLE_NIL)
+                {
+                    AssertMsgFailed(("Invalid handle!\n"));
+                    rc = VERR_INVALID_HANDLE;
+                }
+                else if (flags & SHFL_LOCK_WAIT)
+                {
+                    /** @todo This should be properly implemented by the shared folders service.
+                     *       The service thread must never block. If an operation requires
+                     *       blocking, it must be processed by another thread and when it is
+                     *       completed, the another thread must call
+                     *
+                     *           g_pHelpers->pfnCallComplete (callHandle, rc);
+                     *
+                     * The operation is async.
+                     * fAsynchronousProcessing = true;
+                     */
+
+                    /* Here the operation must be posted to another thread. At the moment it is not implemented.
+                     * Until it is implemented, try to perform the operation without waiting.
+                     */
+                    flags &= ~SHFL_LOCK_WAIT;
+
+                    /* Execute the function. */
+                    if ((flags & SHFL_LOCK_MODE_MASK) == SHFL_LOCK_CANCEL)
+                        rc = vbsfUnlock(pClient, root, Handle, offset, length, flags);
+                    else
+                        rc = vbsfLock(pClient, root, Handle, offset, length, flags);
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        /* none */
+                    }
+                }
+                else
+                {
+                    /* Execute the function. */
+                    if ((flags & SHFL_LOCK_MODE_MASK) == SHFL_LOCK_CANCEL)
+                        rc = vbsfUnlock(pClient, root, Handle, offset, length, flags);
+                    else
+                        rc = vbsfLock(pClient, root, Handle, offset, length, flags);
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        /* none */
+                    }
+                }
+            }
+            break;
+
+        /* List object content. */
+        case SHFL_FN_LIST:
+        {
+            pStat     = &g_StatList;
+            pStatFail = &g_StatListFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_LIST\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_LIST)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                || paParms[1].type != VBOX_HGCM_SVC_PARM_64BIT   /* handle */
+                || paParms[2].type != VBOX_HGCM_SVC_PARM_32BIT   /* flags */
+                || paParms[3].type != VBOX_HGCM_SVC_PARM_32BIT   /* cb */
+                || paParms[4].type != VBOX_HGCM_SVC_PARM_PTR     /* pPath */
+                || paParms[5].type != VBOX_HGCM_SVC_PARM_PTR     /* buffer */
+                || paParms[6].type != VBOX_HGCM_SVC_PARM_32BIT   /* resumePoint */
+                || paParms[7].type != VBOX_HGCM_SVC_PARM_32BIT   /* cFiles (out) */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT  root     = (SHFLROOT)paParms[0].u.uint32;
+                SHFLHANDLE Handle  = paParms[1].u.uint64;
+                uint32_t   flags   = paParms[2].u.uint32;
+                uint32_t   length  = paParms[3].u.uint32;
+                SHFLSTRING *pPath  = (paParms[4].u.pointer.size == 0) ? 0 : (SHFLSTRING *)paParms[4].u.pointer.addr;
+                uint8_t   *pBuffer = (uint8_t *)paParms[5].u.pointer.addr;
+                uint32_t   resumePoint = paParms[6].u.uint32;
+                uint32_t   cFiles = 0;
+
+                /* Verify parameters values. */
+                if (   (length < sizeof (SHFLDIRINFO))
+                    ||  length > paParms[5].u.pointer.size
+                    ||  !ShflStringIsValidOrNullIn(pPath, paParms[4].u.pointer.size, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8))
+                   )
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    if (g_pStatusLed)
+                    {
+                        Assert(g_pStatusLed->u32Magic == PDMLED_MAGIC);
+                        g_pStatusLed->Asserted.s.fReading = g_pStatusLed->Actual.s.fReading = 1;
+                    }
+
+                    /* Execute the function. */
+                    rc = vbsfDirList (pClient, root, Handle, pPath, flags, &length, pBuffer, &resumePoint, &cFiles);
+
+                    if (g_pStatusLed)
+                        g_pStatusLed->Actual.s.fReading = 0;
+
+                    if (rc == VERR_NO_MORE_FILES && cFiles != 0)
+                        rc = VINF_SUCCESS; /* Successfully return these files. */
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        paParms[3].u.uint32 = length;
+                        paParms[6].u.uint32 = resumePoint;
+                        paParms[7].u.uint32 = cFiles;
+                    }
+                    else
+                    {
+                        paParms[3].u.uint32 = 0;  /* nothing read */
+                        paParms[6].u.uint32 = 0;
+                        paParms[7].u.uint32 = cFiles;
+                    }
+                }
+            }
+            break;
+        }
+
+        /* Read symlink destination */
+        case SHFL_FN_READLINK:
+        {
+            pStat     = &g_StatReadLink;
+            pStatFail = &g_StatReadLinkFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_READLINK\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_READLINK)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                || paParms[1].type != VBOX_HGCM_SVC_PARM_PTR     /* path */
+                || paParms[2].type != VBOX_HGCM_SVC_PARM_PTR     /* buffer */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT  root     = (SHFLROOT)paParms[0].u.uint32;
+                SHFLSTRING *pPath  = (SHFLSTRING *)paParms[1].u.pointer.addr;
+                uint32_t cbPath    = paParms[1].u.pointer.size;
+                uint8_t   *pBuffer = (uint8_t *)paParms[2].u.pointer.addr;
+                uint32_t  cbBuffer = paParms[2].u.pointer.size;
+
+                /* Verify parameters values. */
+                if (!ShflStringIsValidOrNullIn(pPath, paParms[1].u.pointer.size, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8)))
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    /* Execute the function. */
+                    rc = vbsfReadLink (pClient, root, pPath, cbPath, pBuffer, cbBuffer);
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        ; /* none */
+                    }
+                }
+            }
+
+            break;
+        }
+
+        /* Legacy interface */
+        case SHFL_FN_MAP_FOLDER_OLD:
+        {
+            pStatFail = pStat = &g_StatMapFolderOld;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_MAP_FOLDER_OLD\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_MAP_FOLDER_OLD)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_PTR     /* path */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_32BIT   /* delimiter */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                PSHFLSTRING pszMapName = (PSHFLSTRING)paParms[0].u.pointer.addr;
+                SHFLROOT    root       = (SHFLROOT)paParms[1].u.uint32;
+                RTUTF16     delimiter  = (RTUTF16)paParms[2].u.uint32;
+
+                /* Verify parameters values. */
+                if (!ShflStringIsValidIn(pszMapName, paParms[0].u.pointer.size, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8)))
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    /* Execute the function. */
+                    rc = vbsfMapFolder (pClient, pszMapName, delimiter, false,  &root);
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        paParms[1].u.uint32 = root;
+                    }
+                }
+            }
+            break;
+        }
+
+        case SHFL_FN_MAP_FOLDER:
+        {
+            pStat     = &g_StatMapFolder;
+            pStatFail = &g_StatMapFolderFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_MAP_FOLDER\n"));
+            if (BIT_FLAG(pClient->fu32Flags, SHFL_CF_UTF8))
+                Log(("SharedFolders host service: request to map folder '%s'\n",
+                     ((PSHFLSTRING)paParms[0].u.pointer.addr)->String.utf8));
+            else
+                Log(("SharedFolders host service: request to map folder '%ls'\n",
+                     ((PSHFLSTRING)paParms[0].u.pointer.addr)->String.ucs2));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_MAP_FOLDER)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_PTR     /* path */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_32BIT   /* delimiter */
+                     || paParms[3].type != VBOX_HGCM_SVC_PARM_32BIT   /* fCaseSensitive */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                PSHFLSTRING pszMapName = (PSHFLSTRING)paParms[0].u.pointer.addr;
+                SHFLROOT    root       = (SHFLROOT)paParms[1].u.uint32;
+                RTUTF16     delimiter  = (RTUTF16)paParms[2].u.uint32;
+                bool        fCaseSensitive = !!paParms[3].u.uint32;
+
+                /* Verify parameters values. */
+                if (ShflStringIsValidIn(pszMapName, paParms[0].u.pointer.size, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8)))
+                {
+                    rc = VINF_SUCCESS;
+                }
+                else
+                {
+                    rc = VERR_INVALID_PARAMETER;
+
+                    /* Fudge for windows GAs getting the length wrong by one char. */
+                    if (   !(pClient->fu32Flags & SHFL_CF_UTF8)
+                        && paParms[0].u.pointer.size >= sizeof(SHFLSTRING)
+                        && pszMapName->u16Length >= 2
+                        && pszMapName->String.ucs2[pszMapName->u16Length / 2 - 1] == 0x0000)
+                    {
+                        pszMapName->u16Length -= 2;
+                        if (ShflStringIsValidIn(pszMapName, paParms[0].u.pointer.size, false /*fUtf8Not16*/))
+                            rc = VINF_SUCCESS;
+                        else
+                            pszMapName->u16Length += 2;
+                    }
+                }
+
+                /* Execute the function. */
+                if (RT_SUCCESS(rc))
+                    rc = vbsfMapFolder (pClient, pszMapName, delimiter, fCaseSensitive, &root);
+
+                if (RT_SUCCESS(rc))
+                {
+                    /* Update parameters.*/
+                    paParms[1].u.uint32 = root;
+                }
+            }
+            Log(("SharedFolders host service: map operation result %Rrc\n", rc));
+            if (RT_SUCCESS(rc))
+                Log(("SharedFolders host service: mapped to handle %d\n", paParms[1].u.uint32));
+            break;
+        }
+
+        case SHFL_FN_UNMAP_FOLDER:
+        {
+            pStat     = &g_StatUnmapFolder;
+            pStatFail = &g_StatUnmapFolderFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_UNMAP_FOLDER\n"));
+            Log(("SharedFolders host service: request to unmap folder handle %u\n",
+                 paParms[0].u.uint32));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_UNMAP_FOLDER)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if ( paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT    root       = (SHFLROOT)paParms[0].u.uint32;
+
+                /* Execute the function. */
+                rc = vbsfUnmapFolder (pClient, root);
+
+                if (RT_SUCCESS(rc))
+                {
+                    /* Update parameters.*/
+                    /* nothing */
+                }
+            }
+            Log(("SharedFolders host service: unmap operation result %Rrc\n", rc));
+            break;
+        }
+
+        /* Query/set object information. */
+        case SHFL_FN_INFORMATION:
+        {
+            pStatFail = pStat = &g_StatInformationFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_INFORMATION\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_INFORMATION)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                || paParms[1].type != VBOX_HGCM_SVC_PARM_64BIT   /* handle */
+                || paParms[2].type != VBOX_HGCM_SVC_PARM_32BIT   /* flags */
+                || paParms[3].type != VBOX_HGCM_SVC_PARM_32BIT   /* cb */
+                || paParms[4].type != VBOX_HGCM_SVC_PARM_PTR     /* buffer */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT  root     = (SHFLROOT)paParms[0].u.uint32;
+                SHFLHANDLE Handle  = paParms[1].u.uint64;
+                uint32_t   flags   = paParms[2].u.uint32;
+                uint32_t   length  = paParms[3].u.uint32;
+                uint8_t   *pBuffer = (uint8_t *)paParms[4].u.pointer.addr;
+
+                /* Verify parameters values. */
+                if (length > paParms[4].u.pointer.size)
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    /* Execute the function. */
+                    if (flags & SHFL_INFO_SET)
+                    {
+                        rc = vbsfSetFSInfo (pClient, root, Handle, flags, &length, pBuffer);
+
+                        if (flags & SHFL_INFO_FILE)
+                        {
+                            pStat     = &g_StatInformationSetFile;
+                            pStatFail = &g_StatInformationSetFileFail;
+                        }
+                        else if (flags & SHFL_INFO_SIZE)
+                        {
+                            pStat     = &g_StatInformationSetSize;
+                            pStatFail = &g_StatInformationSetSizeFail;
+                        }
+                    }
+                    else /* SHFL_INFO_GET */
+                    {
+                        rc = vbsfQueryFSInfo (pClient, root, Handle, flags, &length, pBuffer);
+
+                        if (flags & SHFL_INFO_FILE)
+                        {
+                            pStat     = &g_StatInformationGetFile;
+                            pStatFail = &g_StatInformationGetFileFail;
+                        }
+                        else if (flags & SHFL_INFO_VOLUME)
+                        {
+                            pStat     = &g_StatInformationGetVolume;
+                            pStatFail = &g_StatInformationGetVolumeFail;
+                        }
+                    }
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        paParms[3].u.uint32 = length;
+                    }
+                    else
+                    {
+                        paParms[3].u.uint32 = 0;  /* nothing read */
+                    }
+                }
+            }
+            break;
+        }
+
+        /* Remove or rename object */
+        case SHFL_FN_REMOVE:
+        {
+            pStat     = &g_StatRemove;
+            pStatFail = &g_StatRemoveFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_REMOVE\n"));
+
+            /* Verify parameter count and types. */
+            ASSERT_GUEST_STMT_BREAK(cParms == SHFL_CPARMS_REMOVE, rc = VERR_WRONG_PARAMETER_COUNT);
+            ASSERT_GUEST_STMT_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* root */
+            ASSERT_GUEST_STMT_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_PTR,   rc = VERR_WRONG_PARAMETER_TYPE); /* path */
+            PCSHFLSTRING pStrPath = (PCSHFLSTRING)paParms[1].u.pointer.addr;
+            ASSERT_GUEST_STMT_BREAK(ShflStringIsValidIn(pStrPath, paParms[1].u.pointer.size,
+                                                        RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8)),
+                                    rc = VERR_INVALID_PARAMETER);
+            ASSERT_GUEST_STMT_BREAK(paParms[2].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* flags */
+            uint32_t const fFlags = paParms[2].u.uint32;
+            ASSERT_GUEST_STMT_BREAK(!(fFlags & ~(SHFL_REMOVE_FILE | SHFL_REMOVE_DIR | SHFL_REMOVE_SYMLINK)),
+                                    rc = VERR_INVALID_FLAGS);
+
+            /* Execute the function. */
+            rc = vbsfRemove(pClient, paParms[0].u.uint32, pStrPath, paParms[1].u.pointer.size, fFlags, SHFL_HANDLE_NIL);
+            break;
+        }
+
+        case SHFL_FN_CLOSE_AND_REMOVE:
+        {
+            pStat     = &g_StatCloseAndRemove;
+            pStatFail = &g_StatCloseAndRemoveFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_CLOSE_AND_REMOVE\n"));
+
+            /* Verify parameter count and types. */
+            ASSERT_GUEST_STMT_BREAK(cParms == SHFL_CPARMS_CLOSE_AND_REMOVE, rc = VERR_WRONG_PARAMETER_COUNT);
+            ASSERT_GUEST_STMT_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* root */
+            ASSERT_GUEST_STMT_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_PTR,   rc = VERR_WRONG_PARAMETER_TYPE); /* path */
+            PCSHFLSTRING pStrPath = (PCSHFLSTRING)paParms[1].u.pointer.addr;
+            ASSERT_GUEST_STMT_BREAK(ShflStringIsValidIn(pStrPath, paParms[1].u.pointer.size,
+                                                        RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8)),
+                                    rc = VERR_INVALID_PARAMETER);
+            ASSERT_GUEST_STMT_BREAK(paParms[2].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* flags */
+            uint32_t const fFlags = paParms[2].u.uint32;
+            ASSERT_GUEST_STMT_BREAK(!(fFlags & ~(SHFL_REMOVE_FILE | SHFL_REMOVE_DIR | SHFL_REMOVE_SYMLINK)),
+                                    rc = VERR_INVALID_FLAGS);
+            SHFLHANDLE const hToClose = paParms[3].u.uint64;
+            ASSERT_GUEST_STMT_BREAK(hToClose != SHFL_HANDLE_ROOT, rc = VERR_INVALID_HANDLE);
+
+            /* Execute the function. */
+            rc = vbsfRemove(pClient, paParms[0].u.uint32, pStrPath, paParms[1].u.pointer.size, fFlags, hToClose);
+            break;
+        }
+
+        case SHFL_FN_RENAME:
+        {
+            pStat     = &g_StatRename;
+            pStatFail = &g_StatRenameFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_RENAME\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_RENAME)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_PTR   /* src */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_PTR   /* dest */
+                     || paParms[3].type != VBOX_HGCM_SVC_PARM_32BIT /* flags */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT    root        = (SHFLROOT)paParms[0].u.uint32;
+                SHFLSTRING *pSrc        = (SHFLSTRING *)paParms[1].u.pointer.addr;
+                SHFLSTRING *pDest       = (SHFLSTRING *)paParms[2].u.pointer.addr;
+                uint32_t    flags       = paParms[3].u.uint32;
+
+                /* Verify parameters values. */
+                if (    !ShflStringIsValidIn(pSrc, paParms[1].u.pointer.size, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8))
+                    ||  !ShflStringIsValidIn(pDest, paParms[2].u.pointer.size, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8))
+                   )
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    /* Execute the function. */
+                    rc = vbsfRename (pClient, root, pSrc, pDest, flags);
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        ; /* none */
+                    }
+                }
+            }
+            break;
+        }
+
+        case SHFL_FN_FLUSH:
+        {
+            pStat     = &g_StatFlush;
+            pStatFail = &g_StatFlushFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_FLUSH\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_FLUSH)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                || paParms[1].type != VBOX_HGCM_SVC_PARM_64BIT   /* handle */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT   root    = (SHFLROOT)paParms[0].u.uint32;
+                SHFLHANDLE Handle  = paParms[1].u.uint64;
+
+                /* Verify parameters values. */
+                if (Handle == SHFL_HANDLE_ROOT)
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                if (Handle == SHFL_HANDLE_NIL)
+                {
+                    AssertMsgFailed(("Invalid handle!\n"));
+                    rc = VERR_INVALID_HANDLE;
+                }
+                else
+                {
+                    /* Execute the function. */
+
+                    rc = vbsfFlush (pClient, root, Handle);
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Nothing to do */
+                    }
+                }
+            }
+        } break;
+
+        case SHFL_FN_SET_UTF8:
+        {
+            pStatFail = pStat = &g_StatSetUtf8;
+
+            pClient->fu32Flags |= SHFL_CF_UTF8;
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        case SHFL_FN_SYMLINK:
+        {
+            pStat     = &g_StatSymlink;
+            pStatFail = &g_StatSymlinkFail;
+            Log(("SharedFolders host service: svnCall: SHFL_FN_SYMLINK\n"));
+
+            /* Verify parameter count and types. */
+            if (cParms != SHFL_CPARMS_SYMLINK)
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_32BIT   /* root */
+                     || paParms[1].type != VBOX_HGCM_SVC_PARM_PTR     /* newPath */
+                     || paParms[2].type != VBOX_HGCM_SVC_PARM_PTR     /* oldPath */
+                     || paParms[3].type != VBOX_HGCM_SVC_PARM_PTR     /* info */
+                    )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Fetch parameters. */
+                SHFLROOT     root     = (SHFLROOT)paParms[0].u.uint32;
+                SHFLSTRING  *pNewPath = (SHFLSTRING *)paParms[1].u.pointer.addr;
+                SHFLSTRING  *pOldPath = (SHFLSTRING *)paParms[2].u.pointer.addr;
+                SHFLFSOBJINFO *pInfo  = (SHFLFSOBJINFO *)paParms[3].u.pointer.addr;
+                uint32_t     cbInfo   = paParms[3].u.pointer.size;
+
+                /* Verify parameters values. */
+                if (    !ShflStringIsValidIn(pNewPath, paParms[1].u.pointer.size, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8))
+                    ||  !ShflStringIsValidIn(pOldPath, paParms[2].u.pointer.size, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8))
+                    ||  (cbInfo != sizeof(SHFLFSOBJINFO))
+                   )
+                {
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    /* Execute the function. */
+                    rc = vbsfSymlink (pClient, root, pNewPath, pOldPath, pInfo);
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        ; /* none */
+                    }
+                }
+            }
+        }
+        break;
+
+        case SHFL_FN_SET_SYMLINKS:
+        {
+            pStatFail = pStat = &g_StatSetSymlinks;
+
+            pClient->fu32Flags |= SHFL_CF_SYMLINKS;
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        case SHFL_FN_QUERY_MAP_INFO:
+        {
+            pStatFail = pStat = &g_StatQueryMapInfo;
+            Log(("SharedFolders host service: svnCall: SHFL_FN_QUERY_MAP_INFO\n"));
+
+            /* Validate input: */
+            rc = VERR_INVALID_PARAMETER;
+            ASSERT_GUEST_BREAK(cParms == SHFL_CPARMS_QUERY_MAP_INFO);
+            ASSERT_GUEST_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT); /* root */
+            ASSERT_GUEST_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_PTR);   /* name */
+            PSHFLSTRING  pNameBuf  = (PSHFLSTRING)paParms[1].u.pointer.addr;
+            ASSERT_GUEST_BREAK(ShflStringIsValidOut(pNameBuf, paParms[1].u.pointer.size));
+            ASSERT_GUEST_BREAK(paParms[2].type == VBOX_HGCM_SVC_PARM_PTR);   /* mountPoint */
+            PSHFLSTRING  pMntPtBuf = (PSHFLSTRING)paParms[2].u.pointer.addr;
+            ASSERT_GUEST_BREAK(ShflStringIsValidOut(pMntPtBuf, paParms[2].u.pointer.size));
+            ASSERT_GUEST_BREAK(paParms[3].type == VBOX_HGCM_SVC_PARM_64BIT); /* flags */
+            ASSERT_GUEST_BREAK(!(paParms[3].u.uint64 & ~(SHFL_MIQF_DRIVE_LETTER | SHFL_MIQF_PATH))); /* flags */
+            ASSERT_GUEST_BREAK(paParms[4].type == VBOX_HGCM_SVC_PARM_32BIT); /* version */
+
+            /* Execute the function: */
+            rc = vbsfMappingsQueryInfo(pClient, paParms[0].u.uint32, pNameBuf, pMntPtBuf,
+                                       &paParms[3].u.uint64, &paParms[4].u.uint32);
+            break;
+        }
+
+        case SHFL_FN_WAIT_FOR_MAPPINGS_CHANGES:
+        {
+            pStat = &g_StatWaitForMappingsChanges;
+            pStatFail = &g_StatWaitForMappingsChangesFail;
+            Log(("SharedFolders host service: svnCall: SHFL_FN_WAIT_FOR_MAPPINGS_CHANGES\n"));
+
+            /* Validate input: */
+            rc = VERR_INVALID_PARAMETER;
+            ASSERT_GUEST_BREAK(cParms == SHFL_CPARMS_WAIT_FOR_MAPPINGS_CHANGES);
+            ASSERT_GUEST_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT); /* uFolderMappingsVersion */
+
+            /* Execute the function: */
+            rc = vbsfMappingsWaitForChanges(pClient, callHandle, paParms, g_pHelpers->pfnIsCallRestored(callHandle));
+            fAsynchronousProcessing = rc == VINF_HGCM_ASYNC_EXECUTE;
+            break;
+        }
+
+        case SHFL_FN_CANCEL_MAPPINGS_CHANGES_WAITS:
+        {
+            pStatFail = pStat = &g_StatCancelMappingsChangesWait;
+            Log(("SharedFolders host service: svnCall: SHFL_FN_CANCEL_WAIT_FOR_CHANGES\n"));
+
+            /* Validate input: */
+            rc = VERR_INVALID_PARAMETER;
+            ASSERT_GUEST_BREAK(cParms == SHFL_CPARMS_CANCEL_MAPPINGS_CHANGES_WAITS);
+
+            /* Execute the function: */
+            rc = vbsfMappingsCancelChangesWaits(pClient);
+            break;
+        }
+
+        case SHFL_FN_SET_FILE_SIZE:
+        {
+            pStat     = &g_StatSetFileSize;
+            pStatFail = &g_StatSetFileSizeFail;
+            Log(("SharedFolders host service: svcCall: SHFL_FN_SET_FILE_SIZE\n"));
+
+            /* Validate input: */
+            ASSERT_GUEST_STMT_BREAK(cParms == SHFL_CPARMS_SET_FILE_SIZE,         rc = VERR_WRONG_PARAMETER_COUNT);
+            ASSERT_GUEST_STMT_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* id32Root */
+            ASSERT_GUEST_STMT_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* u64Handle */
+            ASSERT_GUEST_STMT_BREAK(paParms[2].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* cb64NewSize */
+
+            /* Execute the function: */
+            rc = vbsfSetFileSize(pClient, paParms[0].u.uint32, paParms[1].u.uint64, paParms[2].u.uint64);
+            break;
+        }
+
+        case SHFL_FN_QUERY_FEATURES:
+        {
+            pStat = pStatFail = &g_StatQueryFeatures;
+
+            /* Validate input: */
+            ASSERT_GUEST_STMT_BREAK(cParms == SHFL_CPARMS_QUERY_FEATURES, rc = VERR_WRONG_PARAMETER_COUNT);
+            ASSERT_GUEST_STMT_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* f64Features */
+            ASSERT_GUEST_STMT_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* u32LastFunction */
+
+            /* Execute the function: */
+            paParms[0].u.uint64 = SHFL_FEATURE_WRITE_UPDATES_OFFSET;
+            paParms[1].u.uint32 = SHFL_FN_LAST;
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        case SHFL_FN_COPY_FILE:
+        {
+            pStat     = &g_StatCopyFile;
+            pStatFail = &g_StatCopyFileFail;
+
+            /* Validate input: */
+            ASSERT_GUEST_STMT_BREAK(cParms == SHFL_CPARMS_COPY_FILE, rc = VERR_WRONG_PARAMETER_COUNT);
+            ASSERT_GUEST_STMT_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* i32RootSrc  */
+            ASSERT_GUEST_STMT_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_PTR, rc = VERR_WRONG_PARAMETER_TYPE);   /* pStrPathSrc */
+            PCSHFLSTRING pStrPathSrc = (PCSHFLSTRING)paParms[1].u.pointer.addr;
+            ASSERT_GUEST_STMT_BREAK(ShflStringIsValidIn(pStrPathSrc, paParms[1].u.pointer.size,
+                                                        RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8)),
+                                    rc = VERR_INVALID_PARAMETER);
+            ASSERT_GUEST_STMT_BREAK(paParms[2].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* i32RootDst  */
+            ASSERT_GUEST_STMT_BREAK(paParms[3].type == VBOX_HGCM_SVC_PARM_PTR, rc = VERR_WRONG_PARAMETER_TYPE);   /* pStrPathDst */
+            PCSHFLSTRING pStrPathDst = (PCSHFLSTRING)paParms[3].u.pointer.addr;
+            ASSERT_GUEST_STMT_BREAK(ShflStringIsValidIn(pStrPathDst, paParms[3].u.pointer.size,
+                                                        RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8)),
+                                    rc = VERR_INVALID_PARAMETER);
+            ASSERT_GUEST_STMT_BREAK(paParms[4].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* f32Flags */
+            ASSERT_GUEST_STMT_BREAK(paParms[4].u.uint32 == 0, rc = VERR_INVALID_FLAGS);
+
+            /* Execute the function: */
+            rc = vbsfCopyFile(pClient, paParms[0].u.uint32, pStrPathSrc, paParms[2].u.uint64, pStrPathDst, paParms[3].u.uint32);
+            break;
+        }
+
+
+        case SHFL_FN_COPY_FILE_PART:
+        {
+            pStat     = &g_StatCopyFilePart;
+            pStatFail = &g_StatCopyFilePartFail;
+
+            /* Validate input: */
+            ASSERT_GUEST_STMT_BREAK(cParms == SHFL_CPARMS_COPY_FILE_PART, rc = VERR_WRONG_PARAMETER_COUNT);
+            ASSERT_GUEST_STMT_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* i32RootSrc  */
+            ASSERT_GUEST_STMT_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* u64HandleSrc */
+            ASSERT_GUEST_STMT_BREAK(paParms[2].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* off64Src */
+            ASSERT_GUEST_STMT_BREAK((int64_t)paParms[2].u.uint64 >= 0, rc = VERR_NEGATIVE_SEEK);
+            ASSERT_GUEST_STMT_BREAK(paParms[3].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* i32RootDst  */
+            ASSERT_GUEST_STMT_BREAK(paParms[4].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* u64HandleDst */
+            ASSERT_GUEST_STMT_BREAK(paParms[5].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* off64Dst */
+            ASSERT_GUEST_STMT_BREAK((int64_t)paParms[5].u.uint64 >= 0, rc = VERR_NEGATIVE_SEEK);
+            ASSERT_GUEST_STMT_BREAK(paParms[6].type == VBOX_HGCM_SVC_PARM_64BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* cb64ToCopy */
+            ASSERT_GUEST_STMT_BREAK(paParms[6].u.uint64 < _1E, rc = VERR_OUT_OF_RANGE);
+            ASSERT_GUEST_STMT_BREAK(paParms[7].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* f32Flags */
+            ASSERT_GUEST_STMT_BREAK(paParms[7].u.uint32 == 0, rc = VERR_INVALID_FLAGS);
+
+            /* Execute the function: */
+            rc = vbsfCopyFilePart(pClient,
+                                  paParms[0].u.uint32, paParms[1].u.uint64, paParms[2].u.uint64,
+                                  paParms[3].u.uint32, paParms[4].u.uint64, paParms[5].u.uint64,
+                                  &paParms[6].u.uint64, paParms[7].u.uint64);
+            break;
+        }
+
+        case SHFL_FN_SET_ERROR_STYLE:
+        {
+            pStatFail = pStat = &g_StatSetErrorStyle;
+
+            /* Validate input: */
+            ASSERT_GUEST_STMT_BREAK(cParms == SHFL_CPARMS_SET_ERROR_STYLE, rc = VERR_WRONG_PARAMETER_COUNT);
+            ASSERT_GUEST_STMT_BREAK(paParms[0].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* enm32Style  */
+            ASSERT_GUEST_STMT_BREAK(   paParms[0].u.uint32 > (uint32_t)kShflErrorStyle_Invalid
+                                    && paParms[0].u.uint32 < (uint32_t)kShflErrorStyle_End, rc = VERR_WRONG_PARAMETER_TYPE);
+            ASSERT_GUEST_STMT_BREAK(paParms[1].type == VBOX_HGCM_SVC_PARM_32BIT, rc = VERR_WRONG_PARAMETER_TYPE); /* u32Reserved */
+            ASSERT_GUEST_STMT_BREAK(paParms[1].u.uint32 == 0, rc = VERR_WRONG_PARAMETER_TYPE);
+
+            /* Do the work: */
+            pClient->enmErrorStyle = (uint8_t)paParms[0].u.uint32;
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        default:
+        {
+            pStatFail = pStat = &g_StatUnknown;
+            rc = VERR_NOT_IMPLEMENTED;
+            break;
+        }
+    }
+
+    LogFlow(("SharedFolders host service: svcCall: rc=%Rrc\n", rc));
+
+    if (   !fAsynchronousProcessing
+        || RT_FAILURE (rc))
+    {
+        /* Complete the operation if it was unsuccessful or
+         * it was processed synchronously.
+         */
+        g_pHelpers->pfnCallComplete (callHandle, rc);
+    }
+
+#ifndef VBOX_WITHOUT_RELEASE_STATISTICS
+    /* Statistics: */
+    uint64_t cTicks;
+    STAM_GET_TS(cTicks);
+    cTicks -= tsStart;
+    if (RT_SUCCESS(rc))
+        STAM_REL_PROFILE_ADD_PERIOD(pStat, cTicks);
+    else
+        STAM_REL_PROFILE_ADD_PERIOD(pStatFail, cTicks);
+#endif
+
+    LogFlow(("\n"));        /* Add a new line to differentiate between calls more easily. */
+}
+
+/*
+ * We differentiate between a function handler for the guest (svcCall) and one
+ * for the host. The guest is not allowed to add or remove mappings for obvious
+ * security reasons.
+ */
+static DECLCALLBACK(int) svcHostCall (void *, uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[])
+{
+    int rc = VINF_SUCCESS;
+
+    Log(("svcHostCall: fn = %d, cParms = %d, pparms = %d\n", u32Function, cParms, paParms));
+
+#ifdef DEBUG
+    uint32_t i;
+
+    for (i = 0; i < cParms; i++)
+    {
+        /** @todo parameters other than 32 bit */
+        Log(("    pparms[%d]: type %d value %d\n", i, paParms[i].type, paParms[i].u.uint32));
+    }
+#endif
+
+    switch (u32Function)
+    {
+    case SHFL_FN_ADD_MAPPING:
+    {
+        Log(("SharedFolders host service: svcCall: SHFL_FN_ADD_MAPPING\n"));
+        LogRel(("SharedFolders host service: Adding host mapping\n"));
+        /* Verify parameter count and types. */
+        if (   (cParms != SHFL_CPARMS_ADD_MAPPING)
+           )
+        {
+            rc = VERR_INVALID_PARAMETER;
+        }
+        else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_PTR     /* host folder path */
+                 || paParms[1].type != VBOX_HGCM_SVC_PARM_PTR     /* map name */
+                 || paParms[2].type != VBOX_HGCM_SVC_PARM_32BIT   /* fFlags */
+                 || paParms[3].type != VBOX_HGCM_SVC_PARM_PTR     /* auto mount point */
+                )
+        {
+            rc = VERR_INVALID_PARAMETER;
+        }
+        else
+        {
+            /* Fetch parameters. */
+            SHFLSTRING *pHostPath       = (SHFLSTRING *)paParms[0].u.pointer.addr;
+            SHFLSTRING *pMapName        = (SHFLSTRING *)paParms[1].u.pointer.addr;
+            uint32_t fFlags             = paParms[2].u.uint32;
+            SHFLSTRING *pAutoMountPoint = (SHFLSTRING *)paParms[3].u.pointer.addr;
+
+            /* Verify parameters values. */
+            if (    !ShflStringIsValidIn(pHostPath, paParms[0].u.pointer.size, false /*fUtf8Not16*/)
+                ||  !ShflStringIsValidIn(pMapName, paParms[1].u.pointer.size, false /*fUtf8Not16*/)
+                ||  !ShflStringIsValidIn(pAutoMountPoint, paParms[3].u.pointer.size, false /*fUtf8Not16*/)
+               )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                LogRel(("    Host path '%ls', map name '%ls', %s, automount=%s, automntpnt=%ls, create_symlinks=%s, missing=%s\n",
+                        pHostPath->String.utf16, pMapName->String.utf16,
+                        RT_BOOL(fFlags & SHFL_ADD_MAPPING_F_WRITABLE) ? "writable" : "read-only",
+                        RT_BOOL(fFlags & SHFL_ADD_MAPPING_F_AUTOMOUNT) ? "true" : "false",
+                        pAutoMountPoint->String.utf16,
+                        RT_BOOL(fFlags & SHFL_ADD_MAPPING_F_CREATE_SYMLINKS) ? "true" : "false",
+                        RT_BOOL(fFlags & SHFL_ADD_MAPPING_F_MISSING) ? "true" : "false"));
+
+                char *pszHostPath;
+                rc = RTUtf16ToUtf8(pHostPath->String.ucs2, &pszHostPath);
+                if (RT_SUCCESS(rc))
+                {
+                    /* Execute the function. */
+                    rc = vbsfMappingsAdd(pszHostPath, pMapName,
+                                         RT_BOOL(fFlags & SHFL_ADD_MAPPING_F_WRITABLE),
+                                         RT_BOOL(fFlags & SHFL_ADD_MAPPING_F_AUTOMOUNT),
+                                         pAutoMountPoint,
+                                         RT_BOOL(fFlags & SHFL_ADD_MAPPING_F_CREATE_SYMLINKS),
+                                         RT_BOOL(fFlags & SHFL_ADD_MAPPING_F_MISSING),
+                                         /* fPlaceholder = */ false);
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Update parameters.*/
+                        ; /* none */
+                    }
+                    RTStrFree(pszHostPath);
+                }
+            }
+        }
+        if (RT_FAILURE(rc))
+            LogRel(("SharedFolders host service: Adding host mapping failed with rc=%Rrc\n", rc));
+        break;
+    }
+
+    case SHFL_FN_REMOVE_MAPPING:
+    {
+        Log(("SharedFolders host service: svcCall: SHFL_FN_REMOVE_MAPPING\n"));
+        LogRel(("SharedFolders host service: Removing host mapping '%ls'\n",
+                ((SHFLSTRING *)paParms[0].u.pointer.addr)->String.ucs2));
+
+        /* Verify parameter count and types. */
+        if (cParms != SHFL_CPARMS_REMOVE_MAPPING)
+        {
+            rc = VERR_INVALID_PARAMETER;
+        }
+        else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_PTR     /* folder name */
+                )
+        {
+            rc = VERR_INVALID_PARAMETER;
+        }
+        else
+        {
+            /* Fetch parameters. */
+            SHFLSTRING *pString = (SHFLSTRING *)paParms[0].u.pointer.addr;
+
+            /* Verify parameters values. */
+            if (!ShflStringIsValidIn(pString, paParms[0].u.pointer.size, false /*fUtf8Not16*/))
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Execute the function. */
+                rc = vbsfMappingsRemove (pString);
+
+                if (RT_SUCCESS(rc))
+                {
+                    /* Update parameters.*/
+                    ; /* none */
+                }
+            }
+        }
+        if (RT_FAILURE(rc))
+            LogRel(("SharedFolders host service: Removing host mapping failed with rc=%Rrc\n", rc));
+        break;
+    }
+
+    case SHFL_FN_SET_STATUS_LED:
+    {
+        Log(("SharedFolders host service: svcCall: SHFL_FN_SET_STATUS_LED\n"));
+
+        /* Verify parameter count and types. */
+        if (cParms != SHFL_CPARMS_SET_STATUS_LED)
+        {
+            rc = VERR_INVALID_PARAMETER;
+        }
+        else if (   paParms[0].type != VBOX_HGCM_SVC_PARM_PTR     /* folder name */
+                )
+        {
+            rc = VERR_INVALID_PARAMETER;
+        }
+        else
+        {
+            /* Fetch parameters. */
+            PPDMLED  pLed     = (PPDMLED)paParms[0].u.pointer.addr;
+            uint32_t cbLed    = paParms[0].u.pointer.size;
+
+            /* Verify parameters values. */
+            if (   (cbLed != sizeof (PDMLED))
+               )
+            {
+                rc = VERR_INVALID_PARAMETER;
+            }
+            else
+            {
+                /* Execute the function. */
+                g_pStatusLed = pLed;
+                rc = VINF_SUCCESS;
+            }
+        }
+        break;
+    }
+
+    default:
+        rc = VERR_NOT_IMPLEMENTED;
+        break;
+    }
+
+    LogFlow(("SharedFolders host service: svcHostCall ended with rc=%Rrc\n", rc));
+    return rc;
+}
+
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad (VBOXHGCMSVCFNTABLE *ptable)
+{
+    int rc = VINF_SUCCESS;
+
+    Log(("SharedFolders host service: VBoxHGCMSvcLoad: ptable = %p\n", ptable));
+
+    if (!RT_VALID_PTR(ptable))
+    {
+        LogRelFunc(("SharedFolders host service: Bad value of ptable (%p)\n", ptable));
+        rc = VERR_INVALID_PARAMETER;
+    }
+    else
+    {
+        Log(("SharedFolders host service: VBoxHGCMSvcLoad: ptable->cbSize = %u, ptable->u32Version = 0x%08X\n",
+             ptable->cbSize, ptable->u32Version));
+
+        if (    ptable->cbSize != sizeof (VBOXHGCMSVCFNTABLE)
+            ||  ptable->u32Version != VBOX_HGCM_SVC_VERSION)
+        {
+            LogRelFunc(("SharedFolders host service: Version mismatch while loading: ptable->cbSize = %u (should be %u), ptable->u32Version = 0x%08X (should be 0x%08X)\n",
+                        ptable->cbSize, sizeof (VBOXHGCMSVCFNTABLE), ptable->u32Version, VBOX_HGCM_SVC_VERSION));
+            rc = VERR_VERSION_MISMATCH;
+        }
+        else
+        {
+            g_pHelpers = ptable->pHelpers;
+
+            ptable->cbClient = sizeof (SHFLCLIENTDATA);
+
+            /* Map legacy clients to the kernel category. */
+            ptable->idxLegacyClientCategory = HGCM_CLIENT_CATEGORY_KERNEL;
+
+            /* Only 64K pending calls per kernel client, root gets 16K and regular users 1K. */
+            ptable->acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_KERNEL] = _64K;
+            ptable->acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_ROOT]   = _16K;
+            ptable->acMaxCallsPerClient[HGCM_CLIENT_CATEGORY_USER]   = _1K;
+
+            /* Reduce the number of clients to SHFL_MAX_MAPPINGS + 2 in each category,
+               so the increased calls-per-client value causes less trouble.
+               ((64 + 2) * 3 * 65536 = 12 976 128) */
+            for (uintptr_t i = 0; i < RT_ELEMENTS(ptable->acMaxClients); i++)
+                ptable->acMaxClients[i] = SHFL_MAX_MAPPINGS + 2;
+
+            ptable->pfnUnload     = svcUnload;
+            ptable->pfnConnect    = svcConnect;
+            ptable->pfnDisconnect = svcDisconnect;
+            ptable->pfnCall       = svcCall;
+            ptable->pfnHostCall   = svcHostCall;
+            ptable->pfnSaveState  = svcSaveState;
+            ptable->pfnLoadState  = svcLoadState;
+            ptable->pfnNotify     = NULL;
+            ptable->pvService     = NULL;
+        }
+
+        /* Init handle table */
+        rc = vbsfInitHandleTable();
+        AssertRC(rc);
+
+        vbsfMappingInit();
+
+        /* Finally, register statistics if everything went well: */
+        if (RT_SUCCESS(rc))
+        {
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatQueryMappings,             STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_QUERY_MAPPINGS successes",          "/HGCM/VBoxSharedFolders/FnQueryMappings");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatQueryMappingsFail,         STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_QUERY_MAPPINGS failures",           "/HGCM/VBoxSharedFolders/FnQueryMappingsFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatQueryMapName,              STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_QUERY_MAP_NAME",                    "/HGCM/VBoxSharedFolders/FnQueryMapName");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCreate,                    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_CREATE/CREATE successes",           "/HGCM/VBoxSharedFolders/FnCreate");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCreateFail,                STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_CREATE/CREATE failures",            "/HGCM/VBoxSharedFolders/FnCreateFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatLookup,                    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_CREATE/LOOKUP successes",           "/HGCM/VBoxSharedFolders/FnLookup");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatLookupFail,                STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_CREATE/LOOKUP failures",            "/HGCM/VBoxSharedFolders/FnLookupFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatClose,                     STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_CLOSE successes",                   "/HGCM/VBoxSharedFolders/FnClose");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCloseFail,                 STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_CLOSE failures",                    "/HGCM/VBoxSharedFolders/FnCloseFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatRead,                      STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_READ successes",                    "/HGCM/VBoxSharedFolders/FnRead");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatReadFail,                  STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_READ failures",                     "/HGCM/VBoxSharedFolders/FnReadFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatWrite,                     STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_WRITE successes",                   "/HGCM/VBoxSharedFolders/FnWrite");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatWriteFail,                 STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_WRITE failures",                    "/HGCM/VBoxSharedFolders/FnWriteFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatLock,                      STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_LOCK successes",                    "/HGCM/VBoxSharedFolders/FnLock");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatLockFail,                  STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_LOCK failures",                     "/HGCM/VBoxSharedFolders/FnLockFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatList,                      STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_LIST successes",                    "/HGCM/VBoxSharedFolders/FnList");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatListFail,                  STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_LIST failures",                     "/HGCM/VBoxSharedFolders/FnListFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatReadLink,                  STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_READLINK successes",                "/HGCM/VBoxSharedFolders/FnReadLink");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatReadLinkFail,              STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_READLINK failures",                 "/HGCM/VBoxSharedFolders/FnReadLinkFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatMapFolderOld,              STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_MAP_FOLDER_OLD",                    "/HGCM/VBoxSharedFolders/FnMapFolderOld");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatMapFolder,                 STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_MAP_FOLDER successes",              "/HGCM/VBoxSharedFolders/FnMapFolder");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatMapFolderFail,             STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_MAP_FOLDER failures",               "/HGCM/VBoxSharedFolders/FnMapFolderFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatUnmapFolder,               STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_UNMAP_FOLDER successes",            "/HGCM/VBoxSharedFolders/FnUnmapFolder");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatUnmapFolderFail,           STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_UNMAP_FOLDER failures",             "/HGCM/VBoxSharedFolders/FnUnmapFolderFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatInformationFail,           STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_INFORMATION early failures",        "/HGCM/VBoxSharedFolders/FnInformationFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatInformationSetFile,        STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_INFORMATION/SET/FILE successes",    "/HGCM/VBoxSharedFolders/FnInformationSetFile");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatInformationSetFileFail,    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_INFORMATION/SET/FILE failures",     "/HGCM/VBoxSharedFolders/FnInformationSetFileFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatInformationSetSize,        STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_INFORMATION/SET/SIZE successes",    "/HGCM/VBoxSharedFolders/FnInformationSetSize");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatInformationSetSizeFail,    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_INFORMATION/SET/SIZE failures",     "/HGCM/VBoxSharedFolders/FnInformationSetSizeFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatInformationGetFile,        STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_INFORMATION/GET/FILE successes",    "/HGCM/VBoxSharedFolders/FnInformationGetFile");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatInformationGetFileFail,    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_INFORMATION/GET/FILE failures",     "/HGCM/VBoxSharedFolders/FnInformationGetFileFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatInformationGetVolume,      STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_INFORMATION/GET/VOLUME successes",  "/HGCM/VBoxSharedFolders/FnInformationGetVolume");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatInformationGetVolumeFail,  STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_INFORMATION/GET/VOLUME failures",   "/HGCM/VBoxSharedFolders/FnInformationGetVolumeFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatRemove,                    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_REMOVE successes",                  "/HGCM/VBoxSharedFolders/FnRemove");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatRemoveFail,                STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_REMOVE failures",                   "/HGCM/VBoxSharedFolders/FnRemoveFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCloseAndRemove,            STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_CLOSE_AND_REMOVE successes",        "/HGCM/VBoxSharedFolders/FnCloseAndRemove");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCloseAndRemoveFail,        STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_CLOSE_AND_REMOVE failures",         "/HGCM/VBoxSharedFolders/FnCloseAndRemoveFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatRename,                    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_RENAME successes",                  "/HGCM/VBoxSharedFolders/FnRename");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatRenameFail,                STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_RENAME failures",                   "/HGCM/VBoxSharedFolders/FnRenameFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatFlush,                     STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_FLUSH successes",                   "/HGCM/VBoxSharedFolders/FnFlush");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatFlushFail,                 STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_FLUSH failures",                    "/HGCM/VBoxSharedFolders/FnFlushFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatSetErrorStyle,             STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_SET_ERROR_STYLE",                   "/HGCM/VBoxSharedFolders/FnSetErrorStyle");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatSetUtf8,                   STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_SET_UTF8",                          "/HGCM/VBoxSharedFolders/FnSetUtf8");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatSymlink,                   STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_SYMLINK successes",                 "/HGCM/VBoxSharedFolders/FnSymlink");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatSymlinkFail,               STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_SYMLINK failures",                  "/HGCM/VBoxSharedFolders/FnSymlinkFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatSetSymlinks,               STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_SET_SYMLINKS",                      "/HGCM/VBoxSharedFolders/FnSetSymlink");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatQueryMapInfo,              STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_QUERY_MAP_INFO",                    "/HGCM/VBoxSharedFolders/FnQueryMapInfo");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatQueryFeatures,             STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_QUERY_FEATURES",                    "/HGCM/VBoxSharedFolders/FnQueryFeatures");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCopyFile,                  STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_COPY_FILE successes",               "/HGCM/VBoxSharedFolders/FnCopyFile");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCopyFileFail,              STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_COPY_FILE failures",                "/HGCM/VBoxSharedFolders/FnCopyFileFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCopyFilePart,              STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_COPY_FILE_PART successes",          "/HGCM/VBoxSharedFolders/FnCopyFilePart");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCopyFilePartFail,          STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_COPY_FILE_PART failures",           "/HGCM/VBoxSharedFolders/FnCopyFilePartFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatWaitForMappingsChanges,    STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_WAIT_FOR_MAPPINGS_CHANGES successes", "/HGCM/VBoxSharedFolders/FnWaitForMappingsChanges");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatWaitForMappingsChangesFail,STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_WAIT_FOR_MAPPINGS_CHANGES failures","/HGCM/VBoxSharedFolders/FnWaitForMappingsChangesFail");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatCancelMappingsChangesWait, STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_CANCEL_MAPPINGS_CHANGES_WAITS",     "/HGCM/VBoxSharedFolders/FnCancelMappingsChangesWaits");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatUnknown,                   STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "SHFL_FN_???",                               "/HGCM/VBoxSharedFolders/FnUnknown");
+            HGCMSvcHlpStamRegister(g_pHelpers, &g_StatMsgStage1,                 STAMTYPE_PROFILE, STAMVISIBILITY_ALWAYS, STAMUNIT_TICKS_PER_CALL, "Time from VMMDev arrival to worker thread.","/HGCM/VBoxSharedFolders/MsgStage1");
+        }
+    }
+
+    return rc;
+}
+
diff --git a/src/VBox/HostServices/SharedFolders/VBoxSharedFoldersSvc.rc b/src/VBox/HostServices/SharedFolders/VBoxSharedFoldersSvc.rc
new file mode 100644
index 00000000..05a89bc8
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/VBoxSharedFoldersSvc.rc
@@ -0,0 +1,61 @@
+/* $Id: VBoxSharedFoldersSvc.rc $ */
+/** @file
+ * VBoxSharedFolders - Resource file containing version info and icon.
+ */
+
+/*
+ * Copyright (C) 2015-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <windows.h>
+#include <VBox/version.h>
+
+LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION      VBOX_RC_FILE_VERSION
+  PRODUCTVERSION   VBOX_RC_FILE_VERSION
+  FILEFLAGSMASK    VS_FFI_FILEFLAGSMASK
+  FILEFLAGS        VBOX_RC_FILE_FLAGS
+  FILEOS           VBOX_RC_FILE_OS
+  FILETYPE         VBOX_RC_TYPE_DLL
+  FILESUBTYPE      VFT2_UNKNOWN
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904b0" // Lang=US English, CharSet=Unicode
+    BEGIN
+      VALUE "FileDescription",  "VirtualBox Shared Folders Host Service\0"
+      VALUE "InternalName",     "VBoxSharedFolders\0"
+      VALUE "OriginalFilename", "VBoxSharedFolders.dll\0"
+      VALUE "CompanyName",      VBOX_RC_COMPANY_NAME
+      VALUE "FileVersion",      VBOX_RC_FILE_VERSION_STR
+      VALUE "LegalCopyright",   VBOX_RC_LEGAL_COPYRIGHT
+      VALUE "ProductName",      VBOX_RC_PRODUCT_NAME_STR
+      VALUE "ProductVersion",   VBOX_RC_PRODUCT_VERSION_STR
+      VBOX_RC_MORE_STRINGS
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x409, 1200
+  END
+END
diff --git a/src/VBox/HostServices/SharedFolders/mappings.cpp b/src/VBox/HostServices/SharedFolders/mappings.cpp
new file mode 100644
index 00000000..6a5b80f0
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/mappings.cpp
@@ -0,0 +1,1024 @@
+/* $Id: mappings.cpp $ */
+/** @file
+ * Shared Folders Service - Mappings support.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_FOLDERS
+#ifdef UNITTEST
+# include "testcase/tstSharedFolderService.h"
+#endif
+
+#include "mappings.h"
+#include "vbsfpath.h"
+#include <iprt/alloc.h>
+#include <iprt/assert.h>
+#include <iprt/list.h>
+#include <iprt/path.h>
+#include <iprt/string.h>
+#include <VBox/AssertGuest.h>
+
+#ifdef UNITTEST
+# include "teststubs.h"
+#endif
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+extern PVBOXHGCMSVCHELPERS g_pHelpers; /* service.cpp */
+
+
+/* Shared folders order in the saved state and in the g_FolderMapping can differ.
+ * So a translation array of root handle is needed.
+ */
+
+static MAPPING g_FolderMapping[SHFL_MAX_MAPPINGS];
+static SHFLROOT g_aIndexFromRoot[SHFL_MAX_MAPPINGS];
+/**< Array running parallel to g_aIndexFromRoot and which entries are increased
+ * as an root handle is added or removed.
+ *
+ * This helps the guest figuring out that a mapping may have been reconfigured
+ * or that saved state has been restored.  Entry reuse is very likely given that
+ * vbsfRootHandleAdd() always starts searching at the start for an unused entry.
+ */
+static uint32_t g_auRootHandleVersions[SHFL_MAX_MAPPINGS];
+/** Version number that is increased for every change made.
+ * This is used by the automount guest service to wait for changes.
+ * @note This does not need saving, the guest should be woken up and refresh
+ *       its sate when restored. */
+static uint32_t volatile g_uFolderMappingsVersion = 0;
+
+
+/** For recording async vbsfMappingsWaitForChanges calls. */
+typedef struct SHFLMAPPINGSWAIT
+{
+    RTLISTNODE          ListEntry;  /**< List entry. */
+    PSHFLCLIENTDATA     pClient;    /**< The client that's waiting. */
+    VBOXHGCMCALLHANDLE  hCall;      /**< The call handle to signal completion with. */
+    PVBOXHGCMSVCPARM    pParm;      /**< The 32-bit unsigned parameter to stuff g_uFolderMappingsVersion into. */
+} SHFLMAPPINGSWAIT;
+/** Pointer to async mappings change wait. */
+typedef SHFLMAPPINGSWAIT *PSHFLMAPPINGSWAIT;
+/** List head for clients waiting on mapping changes (SHFLMAPPINGSWAIT). */
+static RTLISTANCHOR g_MappingsChangeWaiters;
+/** Number of clients waiting on mapping changes.
+ * We use this to limit the number of waiting calls the clients can make.  */
+static uint32_t     g_cMappingChangeWaiters = 0;
+static void vbsfMappingsWakeupAllWaiters(void);
+
+
+void vbsfMappingInit(void)
+{
+    unsigned root;
+
+    for (root = 0; root < RT_ELEMENTS(g_aIndexFromRoot); root++)
+    {
+        g_aIndexFromRoot[root] = SHFL_ROOT_NIL;
+    }
+
+    RTListInit(&g_MappingsChangeWaiters);
+}
+
+/**
+ * Called before loading mappings from saved state to drop the root IDs.
+ */
+void vbsfMappingLoadingStart(void)
+{
+    for (SHFLROOT idRoot = 0; idRoot < RT_ELEMENTS(g_aIndexFromRoot); idRoot++)
+        g_aIndexFromRoot[idRoot] = SHFL_ROOT_NIL;
+
+    for (SHFLROOT i = 0; i < RT_ELEMENTS(g_FolderMapping); i++)
+        g_FolderMapping[i].fLoadedRootId = false;
+}
+
+/**
+ * Called when a mapping is loaded to restore the root ID and make sure it
+ * exists.
+ *
+ * @returns VBox status code.
+ */
+int vbsfMappingLoaded(const MAPPING *pLoadedMapping, SHFLROOT root)
+{
+    /* Mapping loaded from the saved state with the 'root' index. Which means
+     * the guest uses the 'root' as root handle for this folder.
+     * Check whether there is the same mapping in g_FolderMapping and
+     * update the g_aIndexFromRoot.
+     *
+     * Also update the mapping properties, which were lost: cMappings.
+     */
+    if (root >= SHFL_MAX_MAPPINGS)
+    {
+        return VERR_INVALID_PARAMETER;
+    }
+
+    SHFLROOT i;
+    for (i = 0; i < RT_ELEMENTS(g_FolderMapping); i++)
+    {
+        MAPPING *pMapping = &g_FolderMapping[i];
+
+        /* Equal? */
+        if (   pLoadedMapping->fValid == pMapping->fValid
+            && ShflStringSizeOfBuffer(pLoadedMapping->pMapName) == ShflStringSizeOfBuffer(pMapping->pMapName)
+            && memcmp(pLoadedMapping->pMapName, pMapping->pMapName, ShflStringSizeOfBuffer(pMapping->pMapName)) == 0)
+        {
+            Log(("vbsfMappingLoaded: root=%u i=%u (was %u) (%ls)\n",
+                 root, i, g_aIndexFromRoot[root], pLoadedMapping->pMapName->String.utf16));
+
+            if (!pMapping->fLoadedRootId)
+            {
+                /* First encounter. */
+                pMapping->fLoadedRootId = true;
+
+                /* Update the mapping properties. */
+                pMapping->cMappings = pLoadedMapping->cMappings;
+            }
+            else
+            {
+                /* When pMapping->fLoadedRootId is already true it means that another HGCM client uses the same mapping. */
+                Assert(pMapping->cMappings > 1);
+            }
+
+            /* Actual index is i. Remember that when the guest uses 'root' it is actually 'i'. */
+            AssertLogRelMsg(g_aIndexFromRoot[root] == SHFL_ROOT_NIL,
+                            ("idRoot=%u: current %u ([%s]), new %u (%ls [%s])\n",
+                             root, g_aIndexFromRoot[root], g_FolderMapping[g_aIndexFromRoot[root]].pszFolderName,
+                             i, pLoadedMapping->pMapName->String.utf16, pLoadedMapping->pszFolderName));
+            g_aIndexFromRoot[root] = i;
+
+            /* The mapping is known to the host and is used by the guest.
+             * No need for a 'placeholder'.
+             */
+            return VINF_SUCCESS;
+        }
+    }
+
+    /* No corresponding mapping on the host but the guest still uses it.
+     * Add a 'placeholder' mapping.
+     */
+    LogRel2(("SharedFolders: mapping a placeholder for '%ls' -> '%s'\n",
+              pLoadedMapping->pMapName->String.ucs2, pLoadedMapping->pszFolderName));
+    return vbsfMappingsAdd(pLoadedMapping->pszFolderName, pLoadedMapping->pMapName,
+                           pLoadedMapping->fWritable, pLoadedMapping->fAutoMount, pLoadedMapping->pAutoMountPoint,
+                           pLoadedMapping->fSymlinksCreate, /* fMissing = */ true, /* fPlaceholder = */ true);
+}
+
+/**
+ * Called after loading mappings from saved state to make sure every mapping has
+ * a root ID.
+ */
+void vbsfMappingLoadingDone(void)
+{
+    for (SHFLROOT iMapping = 0; iMapping < RT_ELEMENTS(g_FolderMapping); iMapping++)
+        if (g_FolderMapping[iMapping].fValid)
+        {
+            AssertLogRel(g_FolderMapping[iMapping].pMapName);
+            AssertLogRel(g_FolderMapping[iMapping].pszFolderName);
+
+            SHFLROOT idRoot;
+            for (idRoot = 0; idRoot < RT_ELEMENTS(g_aIndexFromRoot); idRoot++)
+                if (g_aIndexFromRoot[idRoot] == iMapping)
+                    break;
+            if (idRoot >= RT_ELEMENTS(g_aIndexFromRoot))
+            {
+                for (idRoot = 0; idRoot < RT_ELEMENTS(g_aIndexFromRoot); idRoot++)
+                    if (g_aIndexFromRoot[idRoot] == SHFL_ROOT_NIL)
+                        break;
+                if (idRoot < RT_ELEMENTS(g_aIndexFromRoot))
+                    g_aIndexFromRoot[idRoot] = iMapping;
+                else
+                    LogRel(("SharedFolders: Warning! No free root ID entry for mapping #%u: %ls [%s]\n", iMapping,
+                            g_FolderMapping[iMapping].pMapName->String.ucs2, g_FolderMapping[iMapping].pszFolderName));
+            }
+        }
+
+    /* Log the root ID mappings: */
+    if (LogRelIs2Enabled())
+        for (SHFLROOT idRoot = 0; idRoot < RT_ELEMENTS(g_aIndexFromRoot); idRoot++)
+        {
+            SHFLROOT const iMapping = g_aIndexFromRoot[idRoot];
+            if (iMapping != SHFL_ROOT_NIL)
+                LogRel2(("SharedFolders: idRoot %u: iMapping #%u: %ls [%s]\n", idRoot, iMapping,
+                         g_FolderMapping[iMapping].pMapName->String.ucs2, g_FolderMapping[iMapping].pszFolderName));
+        }
+}
+
+
+MAPPING *vbsfMappingGetByRoot(SHFLROOT root)
+{
+    if (root < RT_ELEMENTS(g_aIndexFromRoot))
+    {
+        SHFLROOT iMapping = g_aIndexFromRoot[root];
+
+        if (   iMapping != SHFL_ROOT_NIL
+            && iMapping < RT_ELEMENTS(g_FolderMapping))
+        {
+            return &g_FolderMapping[iMapping];
+        }
+    }
+
+    return NULL;
+}
+
+static SHFLROOT vbsfMappingGetRootFromIndex(SHFLROOT iMapping)
+{
+    unsigned root;
+
+    for (root = 0; root < RT_ELEMENTS(g_aIndexFromRoot); root++)
+    {
+        if (iMapping == g_aIndexFromRoot[root])
+        {
+            return root;
+        }
+    }
+
+    return SHFL_ROOT_NIL;
+}
+
+static MAPPING *vbsfMappingGetByName(PRTUTF16 pwszName, SHFLROOT *pRoot)
+{
+    for (unsigned i = 0; i < SHFL_MAX_MAPPINGS; i++)
+    {
+        if (   g_FolderMapping[i].fValid
+            && !g_FolderMapping[i].fPlaceholder) /* Don't allow mapping placeholders. */
+        {
+            if (!RTUtf16LocaleICmp(g_FolderMapping[i].pMapName->String.ucs2, pwszName))
+            {
+                SHFLROOT root = vbsfMappingGetRootFromIndex(i);
+
+                if (root != SHFL_ROOT_NIL)
+                {
+                    if (pRoot)
+                    {
+                        *pRoot = root;
+                    }
+                    return &g_FolderMapping[i];
+                }
+                AssertFailed();
+            }
+        }
+    }
+    return NULL;
+}
+
+static void vbsfRootHandleAdd(SHFLROOT iMapping)
+{
+    for (unsigned root = 0; root < RT_ELEMENTS(g_aIndexFromRoot); root++)
+    {
+        if (g_aIndexFromRoot[root] == SHFL_ROOT_NIL)
+        {
+            g_aIndexFromRoot[root] = iMapping;
+            g_auRootHandleVersions[root] += 1;
+            return;
+        }
+    }
+
+    AssertFailed();
+}
+
+static void vbsfRootHandleRemove(SHFLROOT iMapping)
+{
+    unsigned cFound = 0;
+
+    for (unsigned root = 0; root < RT_ELEMENTS(g_aIndexFromRoot); root++)
+    {
+        if (g_aIndexFromRoot[root] == iMapping)
+        {
+            g_aIndexFromRoot[root] = SHFL_ROOT_NIL;
+            g_auRootHandleVersions[root] += 1;
+            Log(("vbsfRootHandleRemove: Removed root=%u (iMapping=%u)\n", root, iMapping));
+
+            /* Note! Do not stop here as g_aIndexFromRoot may (at least it could
+                     prior to the introduction of fLoadedRootId) contain
+                     duplicates after restoring save state. */
+            cFound++;
+        }
+    }
+
+    Assert(cFound > 0); RT_NOREF(cFound);
+}
+
+
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_ADD_MAPPING API.  Located here as a form of API
+ * documentation. */
+void testMappingsAdd(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testMappingsAddBadParameters(hTest);
+    /* Add tests as required... */
+}
+#endif
+/*
+ * We are always executed from one specific HGCM thread. So thread safe.
+ */
+int vbsfMappingsAdd(const char *pszFolderName, PSHFLSTRING pMapName, bool fWritable,
+                    bool fAutoMount, PSHFLSTRING pAutoMountPoint, bool fSymlinksCreate, bool fMissing, bool fPlaceholder)
+{
+    unsigned i;
+
+    Assert(pszFolderName && pMapName);
+
+    Log(("vbsfMappingsAdd %ls\n", pMapName->String.ucs2));
+
+    /* Check for duplicates, ignoring placeholders to give the GUI to change stuff at runtime. */
+    /** @todo bird: Not entirely sure about ignoring placeholders, but you cannot
+     *        trigger auto-umounting without ignoring them. */
+    if (!fPlaceholder)
+    {
+        for (i = 0; i < SHFL_MAX_MAPPINGS; i++)
+        {
+            if (   g_FolderMapping[i].fValid
+                && !g_FolderMapping[i].fPlaceholder)
+            {
+                if (!RTUtf16LocaleICmp(g_FolderMapping[i].pMapName->String.ucs2, pMapName->String.ucs2))
+                {
+                    AssertMsgFailed(("vbsfMappingsAdd: %ls mapping already exists!!\n", pMapName->String.ucs2));
+                    return VERR_ALREADY_EXISTS;
+                }
+            }
+        }
+    }
+
+    for (i = 0; i < SHFL_MAX_MAPPINGS; i++)
+    {
+        if (g_FolderMapping[i].fValid == false)
+        {
+            /* Make sure the folder name is an absolute path, otherwise we're
+               likely to get into trouble with buffer sizes in vbsfPathGuestToHost. */
+            char szAbsFolderName[RTPATH_MAX];
+            int rc = vbsfPathAbs(NULL, pszFolderName, szAbsFolderName, sizeof(szAbsFolderName));
+            AssertRCReturn(rc, rc);
+
+            g_FolderMapping[i].pszFolderName   = RTStrDup(szAbsFolderName);
+            g_FolderMapping[i].pMapName        = ShflStringDup(pMapName);
+            g_FolderMapping[i].pAutoMountPoint = ShflStringDup(pAutoMountPoint);
+            if (   !g_FolderMapping[i].pszFolderName
+                || !g_FolderMapping[i].pMapName
+                || !g_FolderMapping[i].pAutoMountPoint)
+            {
+                RTStrFree(g_FolderMapping[i].pszFolderName);
+                RTMemFree(g_FolderMapping[i].pMapName);
+                RTMemFree(g_FolderMapping[i].pAutoMountPoint);
+                return VERR_NO_MEMORY;
+            }
+
+            g_FolderMapping[i].fValid          = true;
+            g_FolderMapping[i].cMappings       = 0;
+            g_FolderMapping[i].fWritable       = fWritable;
+            g_FolderMapping[i].fAutoMount      = fAutoMount;
+            g_FolderMapping[i].fSymlinksCreate = fSymlinksCreate;
+            g_FolderMapping[i].fMissing        = fMissing;
+            g_FolderMapping[i].fPlaceholder    = fPlaceholder;
+            g_FolderMapping[i].fLoadedRootId   = false;
+
+            /* Check if the host file system is case sensitive */
+            RTFSPROPERTIES prop;
+            prop.fCaseSensitive = false; /* Shut up MSC. */
+            rc = RTFsQueryProperties(g_FolderMapping[i].pszFolderName, &prop);
+#ifndef DEBUG_bird /* very annoying */
+            AssertRC(rc);
+#endif
+            g_FolderMapping[i].fHostCaseSensitive = RT_SUCCESS(rc) ? prop.fCaseSensitive : false;
+            vbsfRootHandleAdd(i);
+            vbsfMappingsWakeupAllWaiters();
+            break;
+        }
+    }
+    if (i == SHFL_MAX_MAPPINGS)
+    {
+        AssertLogRelMsgFailed(("vbsfMappingsAdd: no more room to add mapping %s to %ls!!\n", pszFolderName, pMapName->String.ucs2));
+        return VERR_TOO_MUCH_DATA;
+    }
+
+    Log(("vbsfMappingsAdd: added mapping %s to %ls (slot %u, root %u)\n",
+         pszFolderName, pMapName->String.ucs2, i, vbsfMappingGetRootFromIndex(i)));
+    return VINF_SUCCESS;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_REMOVE_MAPPING API.  Located here as a form of API
+ * documentation. */
+void testMappingsRemove(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testMappingsRemoveBadParameters(hTest);
+    /* Add tests as required... */
+}
+#endif
+int vbsfMappingsRemove(PSHFLSTRING pMapName)
+{
+    Assert(pMapName);
+    Log(("vbsfMappingsRemove %ls\n", pMapName->String.ucs2));
+
+    /*
+     * We must iterate thru the whole table as may have 0+ placeholder entries
+     * and 0-1 regular entries with the same name.  Also, it is good to kick
+     * the guest automounter into action wrt to evicting placeholders.
+     */
+    int rc = VERR_FILE_NOT_FOUND;
+    for (unsigned i = 0; i < SHFL_MAX_MAPPINGS; i++)
+    {
+        if (g_FolderMapping[i].fValid == true)
+        {
+            if (!RTUtf16LocaleICmp(g_FolderMapping[i].pMapName->String.ucs2, pMapName->String.ucs2))
+            {
+                if (g_FolderMapping[i].cMappings != 0)
+                {
+                    LogRel2(("SharedFolders: removing '%ls' -> '%s'%s, which is still used by the guest\n", pMapName->String.ucs2,
+                             g_FolderMapping[i].pszFolderName, g_FolderMapping[i].fPlaceholder ? " (again)" : ""));
+                    g_FolderMapping[i].fMissing = true;
+                    g_FolderMapping[i].fPlaceholder = true;
+                    vbsfMappingsWakeupAllWaiters();
+                    rc = VINF_PERMISSION_DENIED;
+                }
+                else
+                {
+                    /* pMapName can be the same as g_FolderMapping[i].pMapName when
+                     * called from vbsfUnmapFolder, log it before deallocating the memory. */
+                    Log(("vbsfMappingsRemove: mapping %ls removed\n", pMapName->String.ucs2));
+                    bool fSame = g_FolderMapping[i].pMapName == pMapName;
+
+                    RTStrFree(g_FolderMapping[i].pszFolderName);
+                    RTMemFree(g_FolderMapping[i].pMapName);
+                    RTMemFree(g_FolderMapping[i].pAutoMountPoint);
+                    g_FolderMapping[i].pszFolderName   = NULL;
+                    g_FolderMapping[i].pMapName        = NULL;
+                    g_FolderMapping[i].pAutoMountPoint = NULL;
+                    g_FolderMapping[i].fValid          = false;
+                    vbsfRootHandleRemove(i);
+                    vbsfMappingsWakeupAllWaiters();
+                    if (rc == VERR_FILE_NOT_FOUND)
+                        rc = VINF_SUCCESS;
+                    if (fSame)
+                        break;
+                }
+            }
+        }
+    }
+
+    return rc;
+}
+
+const char* vbsfMappingsQueryHostRoot(SHFLROOT root)
+{
+    MAPPING *pFolderMapping = vbsfMappingGetByRoot(root);
+    AssertReturn(pFolderMapping, NULL);
+    if (pFolderMapping->fMissing)
+        return NULL;
+    return pFolderMapping->pszFolderName;
+}
+
+int vbsfMappingsQueryHostRootEx(SHFLROOT hRoot, const char **ppszRoot, uint32_t *pcbRootLen)
+{
+    MAPPING *pFolderMapping = vbsfMappingGetByRoot(hRoot);
+    AssertReturn(pFolderMapping, VERR_INVALID_PARAMETER);
+    if (pFolderMapping->fMissing)
+        return VERR_NOT_FOUND;
+    if (   pFolderMapping->pszFolderName == NULL
+        || pFolderMapping->pszFolderName[0] == 0)
+        return VERR_NOT_FOUND;
+    *ppszRoot = pFolderMapping->pszFolderName;
+    *pcbRootLen = (uint32_t)strlen(pFolderMapping->pszFolderName);
+    return VINF_SUCCESS;
+}
+
+bool vbsfIsGuestMappingCaseSensitive(SHFLROOT root)
+{
+    MAPPING *pFolderMapping = vbsfMappingGetByRoot(root);
+    AssertReturn(pFolderMapping, false);
+    return pFolderMapping->fGuestCaseSensitive;
+}
+
+bool vbsfIsHostMappingCaseSensitive(SHFLROOT root)
+{
+    MAPPING *pFolderMapping = vbsfMappingGetByRoot(root);
+    AssertReturn(pFolderMapping, false);
+    return pFolderMapping->fHostCaseSensitive;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_QUERY_MAPPINGS API.  Located here as a form of API
+ * documentation (or should it better be inline in include/VBox/shflsvc.h?) */
+void testMappingsQuery(RTTEST hTest)
+{
+    /* The API should return all mappings if we provide enough buffers. */
+    testMappingsQuerySimple(hTest);
+    /* If we provide too few buffers that should be signalled correctly. */
+    testMappingsQueryTooFewBuffers(hTest);
+    /* The SHFL_MF_AUTOMOUNT flag means return only auto-mounted mappings. */
+    testMappingsQueryAutoMount(hTest);
+    /* The mappings return array must have numberOfMappings entries. */
+    testMappingsQueryArrayWrongSize(hTest);
+}
+#endif
+/**
+ * @note If pMappings / *pcMappings is smaller than the actual amount of
+ *       mappings that *could* have been returned *pcMappings contains the
+ *       required buffer size so that the caller can retry the operation if
+ *       wanted.
+ */
+int vbsfMappingsQuery(PSHFLCLIENTDATA pClient, bool fOnlyAutoMounts, PSHFLMAPPING pMappings, uint32_t *pcMappings)
+{
+    LogFlow(("vbsfMappingsQuery: pClient = %p, pMappings = %p, pcMappings = %p, *pcMappings = %d\n",
+             pClient, pMappings, pcMappings, *pcMappings));
+
+    uint32_t const cMaxMappings = *pcMappings;
+    uint32_t       idx          = 0;
+    for (uint32_t i = 0; i < SHFL_MAX_MAPPINGS; i++)
+    {
+        MAPPING *pFolderMapping = vbsfMappingGetByRoot(i);
+        if (   pFolderMapping != NULL
+            && pFolderMapping->fValid
+            && (   !fOnlyAutoMounts
+                || (pFolderMapping->fAutoMount && !pFolderMapping->fPlaceholder)) )
+        {
+            if (idx < cMaxMappings)
+            {
+                pMappings[idx].u32Status = SHFL_MS_NEW;
+                pMappings[idx].root      = i;
+            }
+            idx++;
+        }
+    }
+
+    /* Return actual number of mappings, regardless whether the handed in
+     * mapping buffer was big enough. */
+    /** @todo r=bird: This is non-standard interface behaviour.  We return
+     *        VERR_BUFFER_OVERFLOW or at least a VINF_BUFFER_OVERFLOW here.
+     *
+     *        Guess this goes well along with ORing SHFL_MF_AUTOMOUNT into
+     *        pClient->fu32Flags rather than passing it as fOnlyAutoMounts...
+     *        Not amused by this. */
+    *pcMappings = idx;
+
+    RT_NOREF_PV(pClient);
+    LogFlow(("vbsfMappingsQuery: returns VINF_SUCCESS (idx=%u, cMaxMappings=%u)\n", idx, cMaxMappings));
+    return VINF_SUCCESS;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_QUERY_MAP_NAME API.  Located here as a form of API
+ * documentation. */
+void testMappingsQueryName(RTTEST hTest)
+{
+    /* If we query an valid mapping it should be returned. */
+    testMappingsQueryNameValid(hTest);
+    /* If we query an invalid mapping that should be signalled. */
+    testMappingsQueryNameInvalid(hTest);
+    /* If we pass in a bad string buffer that should be detected. */
+    testMappingsQueryNameBadBuffer(hTest);
+}
+#endif
+int vbsfMappingsQueryName(PSHFLCLIENTDATA pClient, SHFLROOT root, SHFLSTRING *pString)
+{
+    LogFlow(("vbsfMappingsQuery: pClient = %p, root = %d, *pString = %p\n", pClient, root, pString));
+
+    int rc;
+    MAPPING *pFolderMapping = vbsfMappingGetByRoot(root);
+    if (pFolderMapping)
+    {
+        if (pFolderMapping->fValid)
+        {
+            if (BIT_FLAG(pClient->fu32Flags, SHFL_CF_UTF8))
+                rc = ShflStringCopyUtf16BufAsUtf8(pString, pFolderMapping->pMapName);
+            else
+            {
+                /* Not using ShlfStringCopy here as behaviour shouldn't change... */
+                if (pString->u16Size < pFolderMapping->pMapName->u16Size)
+                {
+                    Log(("vbsfMappingsQuery: passed string too short (%d < %d bytes)!\n",
+                        pString->u16Size,  pFolderMapping->pMapName->u16Size));
+                    rc = VERR_INVALID_PARAMETER;
+                }
+                else
+                {
+                    pString->u16Length = pFolderMapping->pMapName->u16Length;
+                    memcpy(pString->String.ucs2, pFolderMapping->pMapName->String.ucs2,
+                           pFolderMapping->pMapName->u16Size);
+                    rc = VINF_SUCCESS;
+                }
+            }
+        }
+        else
+            rc = VERR_FILE_NOT_FOUND;
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+
+    LogFlow(("vbsfMappingsQuery:Name return rc = %Rrc\n", rc));
+    return rc;
+}
+
+/** Queries fWritable flag for the given root. Returns error if the root is not accessible.
+ */
+int vbsfMappingsQueryWritable(PSHFLCLIENTDATA pClient, SHFLROOT root, bool *fWritable)
+{
+    RT_NOREF1(pClient);
+    int rc = VINF_SUCCESS;
+
+    LogFlow(("vbsfMappingsQueryWritable: pClient = %p, root = %d\n", pClient, root));
+
+    MAPPING *pFolderMapping = vbsfMappingGetByRoot(root);
+    AssertReturn(pFolderMapping, VERR_INVALID_PARAMETER);
+
+    if (   pFolderMapping->fValid
+        && !pFolderMapping->fMissing)
+        *fWritable = pFolderMapping->fWritable;
+    else
+        rc = VERR_FILE_NOT_FOUND;
+
+    LogFlow(("vbsfMappingsQuery:Writable return rc = %Rrc\n", rc));
+
+    return rc;
+}
+
+int vbsfMappingsQueryAutoMount(PSHFLCLIENTDATA pClient, SHFLROOT root, bool *fAutoMount)
+{
+    RT_NOREF1(pClient);
+    int rc = VINF_SUCCESS;
+
+    LogFlow(("vbsfMappingsQueryAutoMount: pClient = %p, root = %d\n", pClient, root));
+
+    MAPPING *pFolderMapping = vbsfMappingGetByRoot(root);
+    AssertReturn(pFolderMapping, VERR_INVALID_PARAMETER);
+
+    if (pFolderMapping->fValid == true)
+        *fAutoMount = pFolderMapping->fAutoMount;
+    else
+        rc = VERR_FILE_NOT_FOUND;
+
+    LogFlow(("vbsfMappingsQueryAutoMount:Writable return rc = %Rrc\n", rc));
+
+    return rc;
+}
+
+int vbsfMappingsQuerySymlinksCreate(PSHFLCLIENTDATA pClient, SHFLROOT root, bool *fSymlinksCreate)
+{
+    RT_NOREF1(pClient);
+    int rc = VINF_SUCCESS;
+
+    LogFlow(("vbsfMappingsQueryAutoMount: pClient = %p, root = %d\n", pClient, root));
+
+    MAPPING *pFolderMapping = vbsfMappingGetByRoot(root);
+    AssertReturn(pFolderMapping, VERR_INVALID_PARAMETER);
+
+    if (pFolderMapping->fValid == true)
+        *fSymlinksCreate = pFolderMapping->fSymlinksCreate;
+    else
+        rc = VERR_FILE_NOT_FOUND;
+
+    LogFlow(("vbsfMappingsQueryAutoMount:SymlinksCreate return rc = %Rrc\n", rc));
+
+    return rc;
+}
+
+/**
+ * Implements SHFL_FN_QUERY_MAP_INFO.
+ * @since VBox 6.0
+ */
+int vbsfMappingsQueryInfo(PSHFLCLIENTDATA pClient, SHFLROOT root, PSHFLSTRING pNameBuf, PSHFLSTRING pMntPtBuf,
+                          uint64_t *pfFlags, uint32_t *puVersion)
+{
+    LogFlow(("vbsfMappingsQueryInfo: pClient=%p root=%d\n", pClient, root));
+
+    /* Resolve the root handle. */
+    int rc;
+    PMAPPING pFolderMapping = vbsfMappingGetByRoot(root);
+    if (pFolderMapping)
+    {
+        if (pFolderMapping->fValid)
+        {
+            /*
+             * Produce the output.
+             */
+            *puVersion = g_auRootHandleVersions[root];
+
+            *pfFlags = 0;
+            if (pFolderMapping->fWritable)
+                *pfFlags |= SHFL_MIF_WRITABLE;
+            if (pFolderMapping->fAutoMount)
+                *pfFlags |= SHFL_MIF_AUTO_MOUNT;
+            if (pFolderMapping->fHostCaseSensitive)
+                *pfFlags |= SHFL_MIF_HOST_ICASE;
+            if (pFolderMapping->fGuestCaseSensitive)
+                *pfFlags |= SHFL_MIF_GUEST_ICASE;
+            if (pFolderMapping->fSymlinksCreate)
+                *pfFlags |= SHFL_MIF_SYMLINK_CREATION;
+
+            int rc2;
+            if (pClient->fu32Flags & SHFL_CF_UTF8)
+            {
+                rc = ShflStringCopyUtf16BufAsUtf8(pNameBuf, pFolderMapping->pMapName);
+                rc2 = ShflStringCopyUtf16BufAsUtf8(pMntPtBuf, pFolderMapping->pAutoMountPoint);
+            }
+            else
+            {
+                rc = ShflStringCopy(pNameBuf, pFolderMapping->pMapName, sizeof(RTUTF16));
+                rc2 = ShflStringCopy(pMntPtBuf, pFolderMapping->pAutoMountPoint, sizeof(RTUTF16));
+            }
+            if (RT_SUCCESS(rc))
+                rc = rc2;
+        }
+        else
+            rc = VERR_FILE_NOT_FOUND;
+    }
+    else
+        rc = VERR_INVALID_PARAMETER;
+    LogFlow(("vbsfMappingsQueryInfo: returns %Rrc\n", rc));
+    return rc;
+}
+
+
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_MAP_FOLDER API.  Located here as a form of API
+ * documentation. */
+void testMapFolder(RTTEST hTest)
+{
+    /* If we try to map a valid name we should get the root. */
+    testMapFolderValid(hTest);
+    /* If we try to map a valid name we should get VERR_FILE_NOT_FOUND. */
+    testMapFolderInvalid(hTest);
+    /* If we map a folder twice we can unmap it twice.
+     * Currently unmapping too often is only asserted but not signalled. */
+    testMapFolderTwice(hTest);
+    /* The delimiter should be converted in e.g. file delete operations. */
+    testMapFolderDelimiter(hTest);
+    /* Test case sensitive mapping by opening a file with the wrong case. */
+    testMapFolderCaseSensitive(hTest);
+    /* Test case insensitive mapping by opening a file with the wrong case. */
+    testMapFolderCaseInsensitive(hTest);
+    /* If the number or types of parameters are wrong the API should fail. */
+    testMapFolderBadParameters(hTest);
+}
+#endif
+int vbsfMapFolder(PSHFLCLIENTDATA pClient, PSHFLSTRING pszMapName,
+                  RTUTF16 wcDelimiter, bool fCaseSensitive, SHFLROOT *pRoot)
+{
+    MAPPING *pFolderMapping = NULL;
+
+    if (BIT_FLAG(pClient->fu32Flags, SHFL_CF_UTF8))
+    {
+        Log(("vbsfMapFolder %s\n", pszMapName->String.utf8));
+    }
+    else
+    {
+        Log(("vbsfMapFolder %ls\n", pszMapName->String.ucs2));
+    }
+
+    AssertMsgReturn(wcDelimiter == '/' || wcDelimiter == '\\',
+                    ("Invalid path delimiter: %#x\n", wcDelimiter),
+                    VERR_INVALID_PARAMETER);
+    if (pClient->PathDelimiter == 0)
+    {
+        pClient->PathDelimiter = wcDelimiter;
+    }
+    else
+    {
+        AssertMsgReturn(wcDelimiter == pClient->PathDelimiter,
+                        ("wcDelimiter=%#x PathDelimiter=%#x", wcDelimiter, pClient->PathDelimiter),
+                        VERR_INVALID_PARAMETER);
+    }
+
+    SHFLROOT RootTmp;
+    if (!pRoot)
+        pRoot = &RootTmp;
+    if (BIT_FLAG(pClient->fu32Flags, SHFL_CF_UTF8))
+    {
+        int rc;
+        PRTUTF16 utf16Name;
+
+        rc = RTStrToUtf16((const char *) pszMapName->String.utf8, &utf16Name);
+        if (RT_FAILURE (rc))
+            return rc;
+
+        pFolderMapping = vbsfMappingGetByName(utf16Name, pRoot);
+        RTUtf16Free(utf16Name);
+    }
+    else
+    {
+        pFolderMapping = vbsfMappingGetByName(pszMapName->String.ucs2, pRoot);
+    }
+
+    if (!pFolderMapping)
+    {
+        return VERR_FILE_NOT_FOUND;
+    }
+
+    /*
+     * Check for reference count overflows and settings compatibility.
+     * For paranoid reasons, we don't allow modifying the case sensitivity
+     * setting while there are other mappings of a folder.
+     */
+    AssertLogRelReturn(*pRoot < RT_ELEMENTS(pClient->acMappings), VERR_INTERNAL_ERROR);
+    AssertLogRelReturn(!pClient->fHasMappingCounts || pClient->acMappings[*pRoot] < _32K, VERR_TOO_MANY_OPENS);
+    ASSERT_GUEST_LOGREL_MSG_RETURN(   pFolderMapping->cMappings == 0
+                                   || pFolderMapping->fGuestCaseSensitive == fCaseSensitive,
+                                   ("Incompatible case sensitivity setting: %s: %u mappings, %ssenitive, requested %ssenitive!\n",
+                                    pFolderMapping->pszFolderName, pFolderMapping->cMappings,
+                                    pFolderMapping->fGuestCaseSensitive ? "" : "in",  fCaseSensitive ? "" : "in"),
+                                   VERR_INCOMPATIBLE_CONFIG);
+
+    /*
+     * Go ahead and map it.
+     */
+    if (pClient->fHasMappingCounts)
+        pClient->acMappings[*pRoot] += 1;
+    pFolderMapping->cMappings++;
+    pFolderMapping->fGuestCaseSensitive = fCaseSensitive;
+    Log(("vbsfMmapFolder (cMappings=%u, acMappings[%u]=%u)\n", pFolderMapping->cMappings, *pRoot, pClient->acMappings[*pRoot]));
+    return VINF_SUCCESS;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_UNMAP_FOLDER API.  Located here as a form of API
+ * documentation. */
+void testUnmapFolder(RTTEST hTest)
+{
+    /* Unmapping a mapped folder should succeed.
+     * If the folder is not mapped this is only asserted, not signalled. */
+    testUnmapFolderValid(hTest);
+    /* Unmapping a non-existant root should fail. */
+    testUnmapFolderInvalid(hTest);
+    /* If the number or types of parameters are wrong the API should fail. */
+    testUnmapFolderBadParameters(hTest);
+}
+#endif
+int vbsfUnmapFolder(PSHFLCLIENTDATA pClient, SHFLROOT root)
+{
+    RT_NOREF1(pClient);
+    int rc = VINF_SUCCESS;
+
+    MAPPING *pFolderMapping = vbsfMappingGetByRoot(root);
+    if (pFolderMapping == NULL)
+    {
+        AssertFailed();
+        return VERR_FILE_NOT_FOUND;
+    }
+    Assert(pFolderMapping->fValid == true && pFolderMapping->cMappings > 0);
+
+    AssertLogRelReturn(root < RT_ELEMENTS(pClient->acMappings), VERR_INTERNAL_ERROR);
+    AssertLogRelReturn(!pClient->fHasMappingCounts || pClient->acMappings[root] > 0, VERR_INVALID_HANDLE);
+
+    if (pClient->fHasMappingCounts)
+        pClient->acMappings[root] -= 1;
+
+    if (pFolderMapping->cMappings > 0)
+        pFolderMapping->cMappings--;
+
+    uint32_t const cMappings = pFolderMapping->cMappings;
+    if (   cMappings == 0
+        && pFolderMapping->fPlaceholder)
+    {
+        /* Automatically remove, it is not used by the guest anymore. */
+        Assert(pFolderMapping->fMissing);
+        LogRel2(("SharedFolders: unmapping placeholder '%ls' -> '%s'\n",
+                pFolderMapping->pMapName->String.ucs2, pFolderMapping->pszFolderName));
+        vbsfMappingsRemove(pFolderMapping->pMapName);
+    }
+
+    Log(("vbsfUnmapFolder (cMappings=%u, acMappings[%u]=%u)\n", cMappings, root, pClient->acMappings[root]));
+    return rc;
+}
+
+/**
+ * SHFL_FN_WAIT_FOR_MAPPINGS_CHANGES implementation.
+ *
+ * @returns VBox status code.
+ * @retval  VINF_SUCCESS on change.
+ * @retval  VINF_TRY_AGAIN on resume.
+ * @retval  VINF_HGCM_ASYNC_EXECUTE if waiting.
+ * @retval  VERR_CANCELLED if cancelled.
+ * @retval  VERR_OUT_OF_RESOURCES if there are too many pending waits.
+ *
+ * @param   pClient     The calling client.
+ * @param   hCall       The call handle.
+ * @param   pParm       The parameter (32-bit).
+ * @param   fRestored   Set if this is a call restored & resubmitted from saved
+ *                      state.
+ * @since   VBox 6.0
+ */
+int vbsfMappingsWaitForChanges(PSHFLCLIENTDATA pClient, VBOXHGCMCALLHANDLE hCall, PVBOXHGCMSVCPARM pParm, bool fRestored)
+{
+    /*
+     * Return immediately if the fodler mappings have changed since last call
+     * or if we got restored from saved state (adding of global folders, etc).
+     */
+    uint32_t uCurVersion = g_uFolderMappingsVersion;
+    if (   pParm->u.uint32 != uCurVersion
+        || fRestored
+        || (pClient->fu32Flags & SHFL_CF_CANCEL_NEXT_WAIT) )
+    {
+        int rc = VINF_SUCCESS;
+        if (pClient->fu32Flags & SHFL_CF_CANCEL_NEXT_WAIT)
+        {
+            pClient->fu32Flags &= ~SHFL_CF_CANCEL_NEXT_WAIT;
+            rc = VERR_CANCELLED;
+        }
+        else if (fRestored)
+        {
+            rc = VINF_TRY_AGAIN;
+            if (pParm->u.uint32 == uCurVersion)
+                uCurVersion = uCurVersion != UINT32_C(0x55555555) ? UINT32_C(0x55555555) : UINT32_C(0x99999999);
+        }
+        Log(("vbsfMappingsWaitForChanges: Version %#x -> %#x, returning %Rrc immediately.\n", pParm->u.uint32, uCurVersion, rc));
+        pParm->u.uint32 = uCurVersion;
+        return rc;
+    }
+
+    /*
+     * Setup a wait if we can.
+     */
+    if (g_cMappingChangeWaiters < 64)
+    {
+        PSHFLMAPPINGSWAIT pWait = (PSHFLMAPPINGSWAIT)RTMemAlloc(sizeof(*pWait));
+        if (pWait)
+        {
+            pWait->pClient = pClient;
+            pWait->hCall   = hCall;
+            pWait->pParm   = pParm;
+
+            RTListAppend(&g_MappingsChangeWaiters, &pWait->ListEntry);
+            g_cMappingChangeWaiters += 1;
+            return VINF_HGCM_ASYNC_EXECUTE;
+        }
+        return VERR_NO_MEMORY;
+    }
+    LogRelMax(32, ("vbsfMappingsWaitForChanges: Too many threads waiting for changes!\n"));
+    return VERR_OUT_OF_RESOURCES;
+}
+
+/**
+ * SHFL_FN_CANCEL_MAPPINGS_CHANGES_WAITS implementation.
+ *
+ * @returns VINF_SUCCESS
+ * @param   pClient     The calling client to cancel all waits for.
+ * @since   VBox 6.0
+ */
+int vbsfMappingsCancelChangesWaits(PSHFLCLIENTDATA pClient)
+{
+    uint32_t const uCurVersion = g_uFolderMappingsVersion;
+
+    PSHFLMAPPINGSWAIT pCur, pNext;
+    RTListForEachSafe(&g_MappingsChangeWaiters, pCur, pNext, SHFLMAPPINGSWAIT, ListEntry)
+    {
+        if (pCur->pClient == pClient)
+        {
+            RTListNodeRemove(&pCur->ListEntry);
+            pCur->pParm->u.uint32 = uCurVersion;
+            g_pHelpers->pfnCallComplete(pCur->hCall, VERR_CANCELLED);
+            RTMemFree(pCur);
+        }
+    }
+
+    /* Set a flag to make sure the next SHFL_FN_WAIT_FOR_MAPPINGS_CHANGES doesn't block.
+       This should help deal with races between this call and a thread about to do a wait. */
+    pClient->fu32Flags |= SHFL_CF_CANCEL_NEXT_WAIT;
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Wakes up all clients waiting on
+ */
+static void vbsfMappingsWakeupAllWaiters(void)
+{
+    uint32_t const uCurVersion = ++g_uFolderMappingsVersion;
+
+    PSHFLMAPPINGSWAIT pCur, pNext;
+    RTListForEachSafe(&g_MappingsChangeWaiters, pCur, pNext, SHFLMAPPINGSWAIT, ListEntry)
+    {
+        RTListNodeRemove(&pCur->ListEntry);
+        pCur->pParm->u.uint32 = uCurVersion;
+        g_pHelpers->pfnCallComplete(pCur->hCall, VERR_CANCELLED);
+        RTMemFree(pCur);
+    }
+}
+
diff --git a/src/VBox/HostServices/SharedFolders/mappings.h b/src/VBox/HostServices/SharedFolders/mappings.h
new file mode 100644
index 00000000..abeafb35
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/mappings.h
@@ -0,0 +1,92 @@
+/* $Id: mappings.h $ */
+/** @file
+ * Shared folders service - Mappings header.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_SharedFolders_mappings_h
+#define VBOX_INCLUDED_SRC_SharedFolders_mappings_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include "shfl.h"
+#include <VBox/shflsvc.h>
+
+typedef struct
+{
+    char       *pszFolderName;          /**< Directory at the host to share with the guest. */
+    PSHFLSTRING pMapName;               /**< Share name for the guest. */
+    uint32_t    cMappings;              /**< Number of mappings. */
+    bool        fValid;                 /**< Mapping entry is used/valid. */
+    bool        fHostCaseSensitive;     /**< Host file name space is case-sensitive. */
+    bool        fGuestCaseSensitive;    /**< Guest file name space is case-sensitive. */
+    bool        fWritable;              /**< Folder is writable for the guest. */
+    PSHFLSTRING pAutoMountPoint;        /**< Where the guest should try auto-mount the folder. */
+    bool        fAutoMount;             /**< Folder will be auto-mounted by the guest. */
+    bool        fSymlinksCreate;        /**< Guest is able to create symlinks. */
+    bool        fMissing;               /**< Mapping not invalid but host path does not exist.
+                                             Any guest operation on such a folder fails! */
+    bool        fPlaceholder;           /**< Mapping does not exist in the VM settings but the guest
+                                             still has. fMissing is always true for this mapping. */
+    bool        fLoadedRootId;          /**< Set if vbsfMappingLoaded has found this mapping already. */
+} MAPPING;
+/** Pointer to a MAPPING structure. */
+typedef MAPPING *PMAPPING;
+
+void vbsfMappingInit(void);
+
+bool vbsfMappingQuery(uint32_t iMapping, PMAPPING *pMapping);
+
+int vbsfMappingsAdd(const char *pszFolderName, PSHFLSTRING pMapName, bool fWritable,
+                    bool fAutoMount, PSHFLSTRING pAutoMountPoint, bool fCreateSymlinks, bool fMissing, bool fPlaceholder);
+int vbsfMappingsRemove(PSHFLSTRING pMapName);
+
+int vbsfMappingsQuery(PSHFLCLIENTDATA pClient, bool fOnlyAutoMounts, PSHFLMAPPING pMappings, uint32_t *pcMappings);
+int vbsfMappingsQueryName(PSHFLCLIENTDATA pClient, SHFLROOT root, SHFLSTRING *pString);
+int vbsfMappingsQueryWritable(PSHFLCLIENTDATA pClient, SHFLROOT root, bool *fWritable);
+int vbsfMappingsQueryAutoMount(PSHFLCLIENTDATA pClient, SHFLROOT root, bool *fAutoMount);
+int vbsfMappingsQuerySymlinksCreate(PSHFLCLIENTDATA pClient, SHFLROOT root, bool *fSymlinksCreate);
+int vbsfMappingsQueryInfo(PSHFLCLIENTDATA pClient, SHFLROOT root, PSHFLSTRING pNameBuf, PSHFLSTRING pMntPtBuf,
+                          uint64_t *pfFlags, uint32_t *puVersion);
+
+int vbsfMapFolder(PSHFLCLIENTDATA pClient, PSHFLSTRING pszMapName, RTUTF16 delimiter,
+                  bool fCaseSensitive, SHFLROOT *pRoot);
+int vbsfUnmapFolder(PSHFLCLIENTDATA pClient, SHFLROOT root);
+
+int vbsfMappingsWaitForChanges(PSHFLCLIENTDATA pClient, VBOXHGCMCALLHANDLE hCall, PVBOXHGCMSVCPARM pParm, bool fRestored);
+int vbsfMappingsCancelChangesWaits(PSHFLCLIENTDATA pClient);
+
+const char* vbsfMappingsQueryHostRoot(SHFLROOT root);
+int vbsfMappingsQueryHostRootEx(SHFLROOT hRoot, const char **ppszRoot, uint32_t *pcbRootLen);
+bool vbsfIsGuestMappingCaseSensitive(SHFLROOT root);
+bool vbsfIsHostMappingCaseSensitive(SHFLROOT root);
+
+void vbsfMappingLoadingStart(void);
+int  vbsfMappingLoaded(MAPPING const *pLoadedMapping, SHFLROOT root);
+void vbsfMappingLoadingDone(void);
+PMAPPING vbsfMappingGetByRoot(SHFLROOT root);
+
+#endif /* !VBOX_INCLUDED_SRC_SharedFolders_mappings_h */
+
diff --git a/src/VBox/HostServices/SharedFolders/shfl.h b/src/VBox/HostServices/SharedFolders/shfl.h
new file mode 100644
index 00000000..04f83eb4
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/shfl.h
@@ -0,0 +1,89 @@
+/** @file
+ * Shared Folders: Main header - Common data and function prototypes definitions.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_SharedFolders_shfl_h
+#define VBOX_INCLUDED_SRC_SharedFolders_shfl_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <VBox/err.h>
+#include <VBox/hgcmsvc.h>
+#include <VBox/shflsvc.h>
+
+#include <VBox/log.h>
+
+/** Shared Folders client flags.
+ * @{
+ */
+/** Client has queried mappings at least once and, therefore, the service can
+ * process its other requests too. */
+#define SHFL_CF_MAPPINGS_QUERIED (0x00000001)
+/** Mappings have been changed since last query. */
+#define SHFL_CF_MAPPINGS_CHANGED (0x00000002)
+/** Client uses UTF8 encoding, if not set then unicode 16 bit (UCS2) is used. */
+#define SHFL_CF_UTF8             (0x00000004)
+/** Client both supports and wants to use symlinks. */
+#define SHFL_CF_SYMLINKS         (0x00000008)
+/** The call to SHFL_FN_WAIT_FOR_MAPPINGS_CHANGES will return immediately
+ *  because of a SHFL_FN_CANCEL_MAPPINGS_CHANGES_WAITS call. */
+#define SHFL_CF_CANCEL_NEXT_WAIT (0x00000010)
+/** @} */
+
+/**
+ * @note This structure is dumped directly into the saved state, so care must be
+ *       taken when extending it!
+ */
+typedef struct SHFLCLIENTDATA
+{
+    /** Client flags */
+    uint32_t fu32Flags;
+    /** Path delimiter. */
+    RTUTF16  PathDelimiter;
+    /** The error style, SHFLERRORSTYLE. */
+    uint8_t  enmErrorStyle;
+    /** Set if the client has mapping usage counts.
+     * This is for helping with saved state. */
+    uint8_t  fHasMappingCounts;
+    /** Mapping counts for each root ID so we can unmap the folders when the
+     *  session disconnects or the VM resets. */
+    uint16_t acMappings[SHFL_MAX_MAPPINGS];
+} SHFLCLIENTDATA;
+/** Pointer to a SHFLCLIENTDATA structure. */
+typedef SHFLCLIENTDATA *PSHFLCLIENTDATA;
+
+
+/** @def SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX
+ * Whether to make windows error style adjustments on a posix host.
+ * This always returns false on windows hosts. */
+#ifdef RT_OS_WINDOWS
+# define SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(a_pClient) (false)
+#else
+# define SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(a_pClient) ((a_pClient)->enmErrorStyle == kShflErrorStyle_Windows)
+#endif
+
+#endif /* !VBOX_INCLUDED_SRC_SharedFolders_shfl_h */
+
diff --git a/src/VBox/HostServices/SharedFolders/shflhandle.cpp b/src/VBox/HostServices/SharedFolders/shflhandle.cpp
new file mode 100644
index 00000000..abf734dc
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/shflhandle.cpp
@@ -0,0 +1,236 @@
+/* $Id: shflhandle.cpp $ */
+/** @file
+ * Shared Folders Service - Handles helper functions.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_FOLDERS
+#include "shflhandle.h"
+#include <iprt/alloc.h>
+#include <iprt/assert.h>
+#include <iprt/critsect.h>
+
+
+/*********************************************************************************************************************************
+*   Structures and Typedefs                                                                                                      *
+*********************************************************************************************************************************/
+/**
+ * Very basic and primitive handle management. Should be sufficient for our needs.
+ * Handle allocation can be rather slow, but at least lookup is fast.
+ */
+typedef struct
+{
+    uint32_t         uFlags;
+    uintptr_t        pvUserData;
+    PSHFLCLIENTDATA  pClient;
+} SHFLINTHANDLE, *PSHFLINTHANDLE;
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+static SHFLINTHANDLE *g_pHandles = NULL;
+static int32_t        gLastHandleIndex = 0;
+static RTCRITSECT     gLock;
+
+
+int vbsfInitHandleTable()
+{
+    g_pHandles = (SHFLINTHANDLE *)RTMemAllocZ (sizeof (SHFLINTHANDLE) * SHFLHANDLE_MAX);
+    if (!g_pHandles)
+    {
+        AssertFailed();
+        return VERR_NO_MEMORY;
+    }
+
+    /* Never return handle 0 */
+    g_pHandles[0].uFlags = SHFL_HF_TYPE_DONTUSE;
+    gLastHandleIndex     = 1;
+
+    return RTCritSectInit(&gLock);
+}
+
+int vbsfFreeHandleTable()
+{
+    if (g_pHandles)
+        RTMemFree(g_pHandles);
+
+    g_pHandles = NULL;
+
+    if (RTCritSectIsInitialized(&gLock))
+        RTCritSectDelete(&gLock);
+
+    return VINF_SUCCESS;
+}
+
+SHFLHANDLE  vbsfAllocHandle(PSHFLCLIENTDATA pClient, uint32_t uType,
+                            uintptr_t pvUserData)
+{
+    SHFLHANDLE handle;
+
+    Assert((uType & SHFL_HF_TYPE_MASK) != 0 && pvUserData);
+
+    RTCritSectEnter(&gLock);
+
+    /* Find next free handle */
+    if (gLastHandleIndex >= SHFLHANDLE_MAX-1)
+        gLastHandleIndex = 1;
+
+    /* Nice linear search */
+    for(handle=gLastHandleIndex;handle<SHFLHANDLE_MAX;handle++)
+    {
+        if (g_pHandles[handle].pvUserData == 0)
+        {
+            gLastHandleIndex = handle;
+            break;
+        }
+    }
+
+    if (handle == SHFLHANDLE_MAX)
+    {
+        /* Try once more from the start */
+        for(handle=1;handle<SHFLHANDLE_MAX;handle++)
+        {
+            if (g_pHandles[handle].pvUserData == 0)
+            {
+                gLastHandleIndex = handle;
+                break;
+            }
+        }
+        if (handle == SHFLHANDLE_MAX)
+        {
+            /* Out of handles */
+            RTCritSectLeave(&gLock);
+            AssertFailed();
+            return SHFL_HANDLE_NIL;
+        }
+    }
+    g_pHandles[handle].uFlags     = (uType & SHFL_HF_TYPE_MASK) | SHFL_HF_VALID;
+    g_pHandles[handle].pvUserData = pvUserData;
+    g_pHandles[handle].pClient    = pClient;
+
+    gLastHandleIndex++;
+
+    RTCritSectLeave(&gLock);
+
+    return handle;
+}
+
+static int vbsfFreeHandle(PSHFLCLIENTDATA pClient, SHFLHANDLE handle)
+{
+    if (   handle < SHFLHANDLE_MAX
+        && (g_pHandles[handle].uFlags & SHFL_HF_VALID)
+        && g_pHandles[handle].pClient == pClient)
+    {
+        g_pHandles[handle].uFlags     = 0;
+        g_pHandles[handle].pvUserData = 0;
+        g_pHandles[handle].pClient    = 0;
+        return VINF_SUCCESS;
+    }
+    return VERR_INVALID_HANDLE;
+}
+
+uintptr_t vbsfQueryHandle(PSHFLCLIENTDATA pClient, SHFLHANDLE handle,
+                          uint32_t uType)
+{
+    if (   handle < SHFLHANDLE_MAX
+        && (g_pHandles[handle].uFlags & SHFL_HF_VALID)
+        && g_pHandles[handle].pClient == pClient)
+    {
+        Assert((uType & SHFL_HF_TYPE_MASK) != 0);
+
+        if (g_pHandles[handle].uFlags & uType)
+            return g_pHandles[handle].pvUserData;
+    }
+    return 0;
+}
+
+SHFLFILEHANDLE *vbsfQueryFileHandle(PSHFLCLIENTDATA pClient, SHFLHANDLE handle)
+{
+    return (SHFLFILEHANDLE *)vbsfQueryHandle(pClient, handle,
+                                             SHFL_HF_TYPE_FILE);
+}
+
+SHFLFILEHANDLE *vbsfQueryDirHandle(PSHFLCLIENTDATA pClient, SHFLHANDLE handle)
+{
+    return (SHFLFILEHANDLE *)vbsfQueryHandle(pClient, handle,
+                                             SHFL_HF_TYPE_DIR);
+}
+
+uint32_t vbsfQueryHandleType(PSHFLCLIENTDATA pClient, SHFLHANDLE handle)
+{
+    if (   handle < SHFLHANDLE_MAX
+        && (g_pHandles[handle].uFlags & SHFL_HF_VALID)
+        && g_pHandles[handle].pClient == pClient)
+        return g_pHandles[handle].uFlags & SHFL_HF_TYPE_MASK;
+
+    return 0;
+}
+
+SHFLHANDLE vbsfAllocDirHandle(PSHFLCLIENTDATA pClient)
+{
+    SHFLFILEHANDLE *pHandle = (SHFLFILEHANDLE *)RTMemAllocZ (sizeof (SHFLFILEHANDLE));
+
+    if (pHandle)
+    {
+        pHandle->Header.u32Flags = SHFL_HF_TYPE_DIR;
+        return vbsfAllocHandle(pClient, pHandle->Header.u32Flags,
+                               (uintptr_t)pHandle);
+    }
+
+    return SHFL_HANDLE_NIL;
+}
+
+SHFLHANDLE vbsfAllocFileHandle(PSHFLCLIENTDATA pClient)
+{
+    SHFLFILEHANDLE *pHandle = (SHFLFILEHANDLE *)RTMemAllocZ (sizeof (SHFLFILEHANDLE));
+
+    if (pHandle)
+    {
+        pHandle->Header.u32Flags = SHFL_HF_TYPE_FILE;
+        return vbsfAllocHandle(pClient, pHandle->Header.u32Flags,
+                               (uintptr_t)pHandle);
+    }
+
+    return SHFL_HANDLE_NIL;
+}
+
+void vbsfFreeFileHandle(PSHFLCLIENTDATA pClient, SHFLHANDLE hHandle)
+{
+    SHFLFILEHANDLE *pHandle = (SHFLFILEHANDLE *)vbsfQueryHandle(pClient,
+               hHandle, SHFL_HF_TYPE_DIR|SHFL_HF_TYPE_FILE);
+
+    if (pHandle)
+    {
+        vbsfFreeHandle(pClient, hHandle);
+        RTMemFree (pHandle);
+    }
+    else
+        AssertFailed();
+}
+
diff --git a/src/VBox/HostServices/SharedFolders/shflhandle.h b/src/VBox/HostServices/SharedFolders/shflhandle.h
new file mode 100644
index 00000000..c4a50fbf
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/shflhandle.h
@@ -0,0 +1,91 @@
+/* $Id: shflhandle.h $ */
+/** @file
+ * Shared Folders Host Service - Handles helper functions header.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_SharedFolders_shflhandle_h
+#define VBOX_INCLUDED_SRC_SharedFolders_shflhandle_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include "shfl.h"
+#include <VBox/shflsvc.h>
+#include <iprt/dir.h>
+
+#define SHFL_HF_TYPE_MASK       (0x000000FF)
+#define SHFL_HF_TYPE_DIR        (0x00000001)
+#define SHFL_HF_TYPE_FILE       (0x00000002)
+#define SHFL_HF_TYPE_VOLUME     (0x00000004)
+#define SHFL_HF_TYPE_DONTUSE    (0x00000080)
+
+#define SHFL_HF_VALID           (0x80000000)
+
+#define SHFLHANDLE_MAX          (4096)
+
+typedef struct _SHFLHANDLEHDR
+{
+    uint32_t u32Flags;
+} SHFLHANDLEHDR;
+
+#define ShflHandleType(__Handle) BIT_FLAG(((SHFLHANDLEHDR *)(__Handle))->u32Flags, SHFL_HF_TYPE_MASK)
+
+typedef struct _SHFLFILEHANDLE
+{
+    SHFLHANDLEHDR Header;
+    SHFLROOT root; /* Where the handle has been opened. */
+    union
+    {
+        struct
+        {
+            RTFILE        Handle;
+            uint64_t      fOpenFlags;       /**< RTFILE_O_XXX. */
+        } file;
+        struct
+        {
+            RTDIR         Handle;
+            RTDIR         SearchHandle;
+            PRTDIRENTRYEX pLastValidEntry;  /**< last found file in a directory search */
+        } dir;
+    };
+} SHFLFILEHANDLE;
+
+
+SHFLHANDLE      vbsfAllocDirHandle(PSHFLCLIENTDATA pClient);
+SHFLHANDLE      vbsfAllocFileHandle(PSHFLCLIENTDATA pClient);
+void            vbsfFreeFileHandle (PSHFLCLIENTDATA pClient, SHFLHANDLE hHandle);
+
+
+int         vbsfInitHandleTable();
+int         vbsfFreeHandleTable();
+SHFLHANDLE  vbsfAllocHandle(PSHFLCLIENTDATA pClient, uint32_t uType,
+                            uintptr_t pvUserData);
+SHFLFILEHANDLE *vbsfQueryFileHandle(PSHFLCLIENTDATA pClient,
+                                    SHFLHANDLE handle);
+SHFLFILEHANDLE *vbsfQueryDirHandle(PSHFLCLIENTDATA pClient, SHFLHANDLE handle);
+uint32_t        vbsfQueryHandleType(PSHFLCLIENTDATA pClient,
+                                    SHFLHANDLE handle);
+
+#endif /* !VBOX_INCLUDED_SRC_SharedFolders_shflhandle_h */
diff --git a/src/VBox/HostServices/SharedFolders/testcase/Makefile.kmk b/src/VBox/HostServices/SharedFolders/testcase/Makefile.kmk
new file mode 100644
index 00000000..c451d7a1
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/testcase/Makefile.kmk
@@ -0,0 +1,104 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the Shared Folders Host Service testcases.
+#
+
+#
+# Copyright (C) 2006-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+#
+# Structure size testcase.
+#
+PROGRAMS += tstShflSizes
+TESTING  += $(tstShflSizes_0_OUTDIR)/tstShflSizes.run
+ifndef VBOX_ONLY_SDK
+ ifeq ($(KBUILD_TARGET),$(KBUILD_HOST))
+  if1of ($(KBUILD_TARGET_ARCH).$(KBUILD_HOST_ARCH), x86.x86 amd64.amd64 x86.amd64)
+   OTHERS  += $(tstShflSizes_0_OUTDIR)/tstShflSizes.run
+  endif
+ endif
+endif
+tstShflSizes_TEMPLATE = VBoxR3AutoTest
+tstShflSizes_DEFS     = VBOX_WITH_HGCM
+tstShflSizes_SOURCES  = tstShflSizes.cpp
+tstShflSizes_CLEAN    = $(tstShflSizes_0_OUTDIR)/tstShflSizes.run
+
+$$(tstShflSizes_0_OUTDIR)/tstShflSizes.run: $$(tstShflSizes_1_STAGE_TARGET)
+	$(tstShflSizes_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+
+
+ifdef VBOX_WITH_TESTCASES
+ #
+ # Case conversion testcase.
+ #
+ PROGRAMS += tstShflCase
+ tstShflCase_TEMPLATE = VBoxR3TstExe
+ tstShflCase_DEFS    = VBOX_WITH_HGCM
+ tstShflCase_SOURCES = tstShflCase.cpp
+ tstShflCase_LIBS    = $(LIB_RUNTIME)
+
+ #
+ # HGCM service testcase.
+ #
+
+ PROGRAMS += tstSharedFolderService
+ tstSharedFolderService_TEMPLATE = VBoxR3TstExe
+ tstSharedFolderService_DEFS    = VBOX_WITH_HGCM UNITTEST
+ tstSharedFolderService_INCS    = ..
+ tstSharedFolderService_SOURCES = \
+ 	tstSharedFolderService.cpp \
+ 	../mappings.cpp \
+ 	../VBoxSharedFoldersSvc.cpp \
+ 	../shflhandle.cpp \
+ 	../vbsfpathabs.cpp \
+ 	../vbsfpath.cpp \
+ 	../vbsf.cpp
+ tstSharedFolderService_LDFLAGS.darwin = \
+ 	-framework Carbon
+ tstSharedFolderService_LIBS    = $(LIB_RUNTIME)
+
+ if 0 # Cannot define two RT_OS_XXX macros!
+  # As there are differences between the Windows build of the service and others,
+  # we do an additional build with RT_OS_WINDOWS defined on non-Windows targets.
+  PROGRAMS += \
+  	tstSharedFolderService \
+  	$(if $(eq $(KBUILD_TARGET),win),,tstSharedFolderService-win)
+  tstSharedFolderService-win_TEMPLATE = $(tstSharedFolderService_TEMPLATE)
+  tstSharedFolderService-win_DEFS   = \
+  	$(tstSharedFolderService_DEFS) \
+  	RT_OS_WINDOWS
+  tstSharedFolderService-win_INCS   = $(tstSharedFolderService_INCS)
+  tstSharedFolderService-win_SOURCES = $(tstSharedFolderService_SOURCES)
+  tstSharedFolderService-win_LDFLAGS.darwin = \
+  	$(tstSharedFolderService_LDFLAGS.darwin)
+  tstSharedFolderService-win_LIBS   = $(tstSharedFolderService_LIBS)
+ endif
+
+endif # VBOX_WITH_TESTCASES
+
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/HostServices/SharedFolders/testcase/tstSharedFolderService.cpp b/src/VBox/HostServices/SharedFolders/testcase/tstSharedFolderService.cpp
new file mode 100644
index 00000000..3f105284
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/testcase/tstSharedFolderService.cpp
@@ -0,0 +1,1368 @@
+/* $Id: tstSharedFolderService.cpp $ */
+/** @file
+ * Testcase for the shared folder service vbsf API.
+ *
+ * Note that this is still very threadbare (there is an awful lot which should
+ * really be tested, but it already took too long to produce this much).  The
+ * idea is that anyone who makes changes to the shared folders service and who
+ * cares about unit testing them should add tests to the skeleton framework to
+ * exercise the bits they change before and after changing them.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+
+#include "tstSharedFolderService.h"
+#include "vbsf.h"
+
+#include <iprt/fs.h>
+#include <iprt/dir.h>
+#include <iprt/file.h>
+#include <iprt/path.h>
+#include <iprt/symlink.h>
+#include <iprt/stream.h>
+#include <iprt/test.h>
+#include <iprt/string.h>
+#include <iprt/utf16.h>
+
+#include "teststubs.h"
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+static RTTEST g_hTest = NIL_RTTEST;
+
+
+/*********************************************************************************************************************************
+*   Declarations                                                                                                                 *
+*********************************************************************************************************************************/
+extern "C" DECLCALLBACK(DECLEXPORT(int)) VBoxHGCMSvcLoad (VBOXHGCMSVCFNTABLE *ptable);
+
+
+/*********************************************************************************************************************************
+*   Helpers                                                                                                                      *
+*********************************************************************************************************************************/
+
+/** Simple call handle structure for the guest call completion callback */
+struct VBOXHGCMCALLHANDLE_TYPEDEF
+{
+    /** Where to store the result code */
+    int32_t rc;
+};
+
+/** Call completion callback for guest calls. */
+static DECLCALLBACK(int) callComplete(VBOXHGCMCALLHANDLE callHandle, int32_t rc)
+{
+    callHandle->rc = rc;
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) stamRegisterV(void *pvInstance, void *pvSample, STAMTYPE enmType, STAMVISIBILITY enmVisibility,
+                                       STAMUNIT enmUnit, const char *pszDesc, const char *pszName, va_list va)
+{
+    RT_NOREF(pvInstance, pvSample, enmType, enmVisibility, enmUnit, pszDesc, pszName, va);
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) stamDeregisterV(void *pvInstance, const char *pszPatFmt, va_list va)
+{
+    RT_NOREF(pvInstance, pszPatFmt, va);
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) infoRegister(void *pvInstance, const char *pszName, const char *pszDesc,
+                                      PFNDBGFHANDLEREXT pfnHandler, void *pvUser)
+{
+    RT_NOREF(pvInstance, pszName, pszDesc, pfnHandler, pvUser);
+    return VINF_SUCCESS;
+}
+
+static DECLCALLBACK(int) infoDeregister(void *pvInstance, const char *pszName)
+{
+    RT_NOREF(pvInstance, pszName);
+    return VINF_SUCCESS;
+}
+
+/**
+ * Initialise the HGCM service table as much as we need to start the
+ * service
+ * @param  pTable the table to initialise
+ */
+void initTable(VBOXHGCMSVCFNTABLE *pTable, VBOXHGCMSVCHELPERS *pHelpers)
+{
+    pTable->cbSize               = sizeof (VBOXHGCMSVCFNTABLE);
+    pTable->u32Version           = VBOX_HGCM_SVC_VERSION;
+    pHelpers->pfnCallComplete    = callComplete;
+    pHelpers->pfnStamRegisterV   = stamRegisterV;
+    pHelpers->pfnStamDeregisterV = stamDeregisterV;
+    pHelpers->pfnInfoRegister    = infoRegister;
+    pHelpers->pfnInfoDeregister  = infoDeregister;
+    pTable->pHelpers             = pHelpers;
+}
+
+#define LLUIFY(a) ((unsigned long long)(a))
+
+static void bufferFromPath(char *pszDst, size_t cbDst, const char *pcszSrc)
+{
+    RTStrCopy(pszDst, cbDst, pcszSrc);
+    uintptr_t const uDstEnd = (uintptr_t)&pszDst[cbDst];
+    for (char *psz = pszDst; psz && (uintptr_t)psz < uDstEnd; ++psz)
+        if (*psz == '\\')
+            *psz = '/';
+}
+
+#define ARRAY_FROM_PATH(a, b) \
+    do { \
+        char *p = (a); NOREF(p); \
+        Assert((a) == p); /* Constant parameter */ \
+        Assert(sizeof((a)) > 0); \
+        bufferFromPath(a, sizeof(a), b); \
+    } while (0)
+
+
+/*********************************************************************************************************************************
+*   Stub functions and data                                                                                                      *
+*********************************************************************************************************************************/
+static bool g_fFailIfNotLowercase = false;
+
+static RTDIR g_testRTDirClose_hDir = NIL_RTDIR;
+
+extern int testRTDirClose(RTDIR hDir)
+{
+ /* RTPrintf("%s: hDir=%p\n", __PRETTY_FUNCTION__, hDir); */
+    g_testRTDirClose_hDir = hDir;
+    return VINF_SUCCESS;
+}
+
+static char g_testRTDirCreate_szPath[256];
+//static RTFMODE testRTDirCreateMode; - unused
+
+extern int testRTDirCreate(const char *pszPath, RTFMODE fMode, uint32_t fCreate)
+{
+    RT_NOREF2(fMode, fCreate);
+ /* RTPrintf("%s: pszPath=%s, fMode=0x%llx\n", __PRETTY_FUNCTION__, pszPath,
+             LLUIFY(fMode)); */
+    if (g_fFailIfNotLowercase && !RTStrIsLowerCased(strpbrk(pszPath, "/\\")))
+        return VERR_FILE_NOT_FOUND;
+    ARRAY_FROM_PATH(g_testRTDirCreate_szPath, pszPath);
+    return 0;
+}
+
+static char g_testRTDirOpen_szName[256];
+static struct TESTDIRHANDLE
+{
+    int iEntry;
+    int iDir;
+} g_aTestDirHandles[4];
+static int g_iNextDirHandle = 0;
+static RTDIR g_testRTDirOpen_hDir;
+
+extern int testRTDirOpen(RTDIR *phDir, const char *pszPath)
+{
+ /* RTPrintf("%s: pszPath=%s\n", __PRETTY_FUNCTION__, pszPath); */
+    if (g_fFailIfNotLowercase && !RTStrIsLowerCased(strpbrk(pszPath, "/\\")))
+        return VERR_FILE_NOT_FOUND;
+    ARRAY_FROM_PATH(g_testRTDirOpen_szName, pszPath);
+    *phDir = g_testRTDirOpen_hDir;
+    g_testRTDirOpen_hDir = NIL_RTDIR;
+    if (!*phDir && g_fFailIfNotLowercase)
+        *phDir = (RTDIR)&g_aTestDirHandles[g_iNextDirHandle++ % RT_ELEMENTS(g_aTestDirHandles)];
+    if (*phDir)
+    {
+        struct TESTDIRHANDLE *pRealDir = (struct TESTDIRHANDLE *)*phDir;
+        pRealDir->iEntry = 0;
+        pRealDir->iDir   = 0;
+        const char *pszSlash = pszPath - 1;
+        while ((pszSlash = strpbrk(pszSlash + 1, "\\/")) != NULL)
+            pRealDir->iDir += 1;
+        /*RTPrintf("opendir %s = %d \n", pszPath, pRealDir->iDir);*/
+    }
+    return VINF_SUCCESS;
+}
+
+/** @todo Do something useful with the last two arguments. */
+extern int testRTDirOpenFiltered(RTDIR *phDir, const char *pszPath, RTDIRFILTER, uint32_t)
+{
+ /* RTPrintf("%s: pszPath=%s\n", __PRETTY_FUNCTION__, pszPath); */
+    if (g_fFailIfNotLowercase && !RTStrIsLowerCased(strpbrk(pszPath, "/\\")))
+        return VERR_FILE_NOT_FOUND;
+    ARRAY_FROM_PATH(g_testRTDirOpen_szName, pszPath);
+    *phDir = g_testRTDirOpen_hDir;
+    g_testRTDirOpen_hDir = NIL_RTDIR;
+    if (!*phDir && g_fFailIfNotLowercase)
+        *phDir = (RTDIR)&g_aTestDirHandles[g_iNextDirHandle++ % RT_ELEMENTS(g_aTestDirHandles)];
+    if (*phDir)
+    {
+        struct TESTDIRHANDLE *pRealDir = (struct TESTDIRHANDLE *)*phDir;
+        pRealDir->iEntry = 0;
+        pRealDir->iDir   = 0;
+        const char *pszSlash = pszPath - 1;
+        while ((pszSlash = strpbrk(pszSlash + 1, "\\/")) != NULL)
+            pRealDir->iDir += 1;
+        pRealDir->iDir -= 1;
+        /*RTPrintf("openfiltered %s = %d\n", pszPath, pRealDir->iDir);*/
+    }
+    return VINF_SUCCESS;
+}
+
+static RTDIR g_testRTDirQueryInfo_hDir;
+static RTTIMESPEC g_testRTDirQueryInfo_ATime;
+
+extern int testRTDirQueryInfo(RTDIR hDir, PRTFSOBJINFO pObjInfo, RTFSOBJATTRADD enmAdditionalAttribs)
+{
+    RT_NOREF1(enmAdditionalAttribs);
+ /* RTPrintf("%s: hDir=%p, enmAdditionalAttribs=0x%llx\n", __PRETTY_FUNCTION__,
+             hDir, LLUIFY(enmAdditionalAttribs)); */
+    g_testRTDirQueryInfo_hDir = hDir;
+    RT_ZERO(*pObjInfo);
+    pObjInfo->AccessTime = g_testRTDirQueryInfo_ATime;
+    RT_ZERO(g_testRTDirQueryInfo_ATime);
+    return VINF_SUCCESS;
+}
+
+extern int testRTDirRemove(const char *pszPath)
+{
+    if (g_fFailIfNotLowercase && !RTStrIsLowerCased(strpbrk(pszPath, "/\\")))
+        return VERR_FILE_NOT_FOUND;
+    RTPrintf("%s\n", __PRETTY_FUNCTION__);
+    return 0;
+}
+
+static RTDIR g_testRTDirReadEx_hDir;
+
+extern int testRTDirReadEx(RTDIR hDir, PRTDIRENTRYEX pDirEntry, size_t *pcbDirEntry,
+                           RTFSOBJATTRADD enmAdditionalAttribs, uint32_t fFlags)
+{
+    RT_NOREF4(pDirEntry, pcbDirEntry, enmAdditionalAttribs, fFlags);
+ /* RTPrintf("%s: hDir=%p, pcbDirEntry=%d, enmAdditionalAttribs=%llu, fFlags=0x%llx\n",
+             __PRETTY_FUNCTION__, hDir, pcbDirEntry ? (int) *pcbDirEntry : -1,
+             LLUIFY(enmAdditionalAttribs), LLUIFY(fFlags)); */
+    g_testRTDirReadEx_hDir = hDir;
+    if (g_fFailIfNotLowercase && hDir != NIL_RTDIR)
+    {
+        struct TESTDIRHANDLE *pRealDir = (struct TESTDIRHANDLE *)hDir;
+        if (pRealDir->iDir == 2) /* /test/mapping/ */
+        {
+            if (pRealDir->iEntry == 0)
+            {
+                pRealDir->iEntry++;
+                RT_ZERO(*pDirEntry);
+                pDirEntry->Info.Attr.fMode = RTFS_TYPE_DIRECTORY | RTFS_DOS_DIRECTORY | RTFS_UNIX_IROTH | RTFS_UNIX_IXOTH;
+                pDirEntry->cbName = 4;
+                pDirEntry->cwcShortName = 4;
+                strcpy(pDirEntry->szName, "test");
+                RTUtf16CopyAscii(pDirEntry->wszShortName, RT_ELEMENTS(pDirEntry->wszShortName), "test");
+                /*RTPrintf("readdir: 'test'\n");*/
+                return VINF_SUCCESS;
+            }
+        }
+        else if (pRealDir->iDir == 3) /* /test/mapping/test/ */
+        {
+            if (pRealDir->iEntry == 0)
+            {
+                pRealDir->iEntry++;
+                RT_ZERO(*pDirEntry);
+                pDirEntry->Info.Attr.fMode = RTFS_TYPE_FILE | RTFS_DOS_NT_NORMAL | RTFS_UNIX_IROTH | RTFS_UNIX_IXOTH;
+                pDirEntry->cbName = 4;
+                pDirEntry->cwcShortName = 4;
+                strcpy(pDirEntry->szName, "file");
+                RTUtf16CopyAscii(pDirEntry->wszShortName, RT_ELEMENTS(pDirEntry->wszShortName), "file");
+                /*RTPrintf("readdir: 'file'\n");*/
+                return VINF_SUCCESS;
+            }
+        }
+        /*else RTPrintf("%s: iDir=%d\n", pRealDir->iDir);*/
+    }
+    return VERR_NO_MORE_FILES;
+}
+
+static uint64_t g_testRTDirSetMode_fMode;
+
+extern int testRTDirSetMode(RTDIR hDir, RTFMODE fMode)
+{
+    RT_NOREF1(hDir);
+ /* RTPrintf("%s: fMode=%llu\n", __PRETTY_FUNCTION__, LLUIFY(fMode)); */
+    g_testRTDirSetMode_fMode = fMode;
+    return VINF_SUCCESS;
+}
+
+static RTTIMESPEC g_testRTDirSetTimes_ATime;
+
+extern int testRTDirSetTimes(RTDIR hDir, PCRTTIMESPEC pAccessTime, PCRTTIMESPEC pModificationTime,
+                             PCRTTIMESPEC pChangeTime, PCRTTIMESPEC pBirthTime)
+{
+    RT_NOREF4(hDir, pModificationTime, pChangeTime, pBirthTime);
+ /* RTPrintf("%s: hDir=%p, *pAccessTime=%lli, *pModificationTime=%lli, *pChangeTime=%lli, *pBirthTime=%lli\n",
+             __PRETTY_FUNCTION__, hDir,
+             pAccessTime ? (long long)RTTimeSpecGetNano(pAccessTime) : -1,
+               pModificationTime
+             ? (long long)RTTimeSpecGetNano(pModificationTime) : -1,
+             pChangeTime ? (long long)RTTimeSpecGetNano(pChangeTime) : -1,
+             pBirthTime ? (long long)RTTimeSpecGetNano(pBirthTime) : -1); */
+    if (pAccessTime)
+        g_testRTDirSetTimes_ATime = *pAccessTime;
+    else
+        RT_ZERO(g_testRTDirSetTimes_ATime);
+    return VINF_SUCCESS;
+}
+
+static RTFILE g_testRTFileClose_hFile;
+
+extern int  testRTFileClose(RTFILE File)
+{
+ /* RTPrintf("%s: File=%p\n", __PRETTY_FUNCTION__, File); */
+    g_testRTFileClose_hFile = File;
+    return 0;
+}
+
+extern int  testRTFileDelete(const char *pszFilename)
+{
+    if (g_fFailIfNotLowercase && !RTStrIsLowerCased(strpbrk(pszFilename, "/\\")))
+        return VERR_FILE_NOT_FOUND;
+    RTPrintf("%s\n", __PRETTY_FUNCTION__);
+    return 0;
+}
+
+static RTFILE g_testRTFileFlush_hFile;
+
+extern int  testRTFileFlush(RTFILE File)
+{
+ /* RTPrintf("%s: File=%p\n", __PRETTY_FUNCTION__, File); */
+    g_testRTFileFlush_hFile = File;
+    return VINF_SUCCESS;
+}
+
+static RTFILE g_testRTFileLock_hFile;
+static unsigned g_testRTFileLock_fLock;
+static int64_t g_testRTFileLock_offLock;
+static uint64_t g_testRTFileLock_cbLock;
+
+extern int  testRTFileLock(RTFILE hFile, unsigned fLock, int64_t offLock, uint64_t cbLock)
+{
+ /* RTPrintf("%s: hFile=%p, fLock=%u, offLock=%lli, cbLock=%llu\n",
+             __PRETTY_FUNCTION__, hFile, fLock, (long long) offLock,
+             LLUIFY(cbLock)); */
+    g_testRTFileLock_hFile = hFile;
+    g_testRTFileLock_fLock = fLock;
+    g_testRTFileLock_offLock = offLock;
+    g_testRTFileLock_cbLock = cbLock;
+    return VINF_SUCCESS;
+}
+
+static char g_testRTFileOpen_szName[256];
+static uint64_t g_testRTFileOpen_fOpen;
+static RTFILE g_testRTFileOpen_hFile;
+
+extern int  testRTFileOpenEx(const char *pszFilename, uint64_t fOpen, PRTFILE phFile, PRTFILEACTION penmActionTaken)
+{
+ /* RTPrintf("%s, pszFilename=%s, fOpen=0x%llx\n", __PRETTY_FUNCTION__,
+             pszFilename, LLUIFY(fOpen)); */
+    ARRAY_FROM_PATH(g_testRTFileOpen_szName, pszFilename);
+    g_testRTFileOpen_fOpen = fOpen;
+    if (g_fFailIfNotLowercase && !RTStrIsLowerCased(strpbrk(pszFilename, "/\\")))
+        return VERR_FILE_NOT_FOUND;
+    *phFile = g_testRTFileOpen_hFile;
+    *penmActionTaken = RTFILEACTION_CREATED;
+    g_testRTFileOpen_hFile = 0;
+    return VINF_SUCCESS;
+}
+
+static RTFILE g_testRTFileQueryInfo_hFile;
+static RTTIMESPEC g_testRTFileQueryInfo_ATime;
+static uint32_t g_testRTFileQueryInfo_fMode;
+
+extern int  testRTFileQueryInfo(RTFILE hFile, PRTFSOBJINFO pObjInfo, RTFSOBJATTRADD enmAdditionalAttribs)
+{
+    RT_NOREF1(enmAdditionalAttribs);
+ /* RTPrintf("%s, hFile=%p, enmAdditionalAttribs=0x%llx\n",
+             __PRETTY_FUNCTION__, hFile, LLUIFY(enmAdditionalAttribs)); */
+    g_testRTFileQueryInfo_hFile = hFile;
+    RT_ZERO(*pObjInfo);
+    pObjInfo->AccessTime = g_testRTFileQueryInfo_ATime;
+    RT_ZERO(g_testRTDirQueryInfo_ATime);
+    pObjInfo->Attr.fMode = g_testRTFileQueryInfo_fMode;
+    g_testRTFileQueryInfo_fMode = 0;
+    return VINF_SUCCESS;
+}
+
+static const char *g_testRTFileRead_pszData;
+
+extern int  testRTFileRead(RTFILE File, void *pvBuf, size_t cbToRead, size_t *pcbRead)
+{
+    RT_NOREF1(File);
+ /* RTPrintf("%s : File=%p, cbToRead=%llu\n", __PRETTY_FUNCTION__, File,
+             LLUIFY(cbToRead)); */
+    bufferFromPath((char *)pvBuf, cbToRead, g_testRTFileRead_pszData);
+    if (pcbRead)
+        *pcbRead = RT_MIN(cbToRead, strlen(g_testRTFileRead_pszData) + 1);
+    g_testRTFileRead_pszData = 0;
+    return VINF_SUCCESS;
+}
+
+extern int  testRTFileReadAt(RTFILE hFile, uint64_t offFile, void *pvBuf, size_t cbToRead, size_t *pcbRead)
+{
+    RT_NOREF1(hFile);
+    RT_NOREF(offFile);
+ /* RTPrintf("%s : File=%p, cbToRead=%llu\n", __PRETTY_FUNCTION__, File,
+             LLUIFY(cbToRead)); */
+    bufferFromPath((char *)pvBuf, cbToRead, g_testRTFileRead_pszData);
+    if (pcbRead)
+        *pcbRead = RT_MIN(cbToRead, strlen(g_testRTFileRead_pszData) + 1);
+    g_testRTFileRead_pszData = 0;
+    return VINF_SUCCESS;
+}
+
+extern int testRTFileSeek(RTFILE hFile, int64_t offSeek, unsigned uMethod, uint64_t *poffActual)
+{
+    RT_NOREF3(hFile, offSeek, uMethod);
+ /* RTPrintf("%s : hFile=%p, offSeek=%llu, uMethod=%u\n", __PRETTY_FUNCTION__,
+             hFile, LLUIFY(offSeek), uMethod); */
+    if (poffActual)
+        *poffActual = 0;
+    return VINF_SUCCESS;
+}
+
+static uint64_t g_testRTFileSet_fMode;
+
+extern int testRTFileSetMode(RTFILE File, RTFMODE fMode)
+{
+    RT_NOREF1(File);
+ /* RTPrintf("%s: fMode=%llu\n", __PRETTY_FUNCTION__, LLUIFY(fMode)); */
+    g_testRTFileSet_fMode = fMode;
+    return VINF_SUCCESS;
+}
+
+static RTFILE g_testRTFileSetSize_hFile;
+static RTFOFF g_testRTFileSetSize_cbSize;
+
+extern int  testRTFileSetSize(RTFILE File, uint64_t cbSize)
+{
+ /* RTPrintf("%s: File=%llu, cbSize=%llu\n", __PRETTY_FUNCTION__, LLUIFY(File),
+             LLUIFY(cbSize)); */
+    g_testRTFileSetSize_hFile = File;
+    g_testRTFileSetSize_cbSize = (RTFOFF) cbSize; /* Why was this signed before? */
+    return VINF_SUCCESS;
+}
+
+static RTTIMESPEC g_testRTFileSetTimes_ATime;
+
+extern int testRTFileSetTimes(RTFILE File, PCRTTIMESPEC pAccessTime, PCRTTIMESPEC pModificationTime,
+                              PCRTTIMESPEC pChangeTime, PCRTTIMESPEC pBirthTime)
+{
+    RT_NOREF4(File, pModificationTime, pChangeTime, pBirthTime);
+ /* RTPrintf("%s: pFile=%p, *pAccessTime=%lli, *pModificationTime=%lli, *pChangeTime=%lli, *pBirthTime=%lli\n",
+             __PRETTY_FUNCTION__,
+             pAccessTime ? (long long)RTTimeSpecGetNano(pAccessTime) : -1,
+               pModificationTime
+             ? (long long)RTTimeSpecGetNano(pModificationTime) : -1,
+             pChangeTime ? (long long)RTTimeSpecGetNano(pChangeTime) : -1,
+             pBirthTime ? (long long)RTTimeSpecGetNano(pBirthTime) : -1); */
+    if (pAccessTime)
+        g_testRTFileSetTimes_ATime = *pAccessTime;
+    else
+        RT_ZERO(g_testRTFileSetTimes_ATime);
+    return VINF_SUCCESS;
+}
+
+static RTFILE g_testRTFileUnlock_hFile;
+static int64_t g_testRTFileUnlock_offLock;
+static uint64_t g_testRTFileUnlock_cbLock;
+
+extern int  testRTFileUnlock(RTFILE File, int64_t offLock, uint64_t cbLock)
+{
+ /* RTPrintf("%s: hFile=%p, ofLock=%lli, cbLock=%llu\n", __PRETTY_FUNCTION__,
+             File, (long long) offLock, LLUIFY(cbLock)); */
+    g_testRTFileUnlock_hFile = File;
+    g_testRTFileUnlock_offLock = offLock;
+    g_testRTFileUnlock_cbLock = cbLock;
+    return VINF_SUCCESS;
+}
+
+static char g_testRTFileWrite_szData[256];
+
+extern int  testRTFileWrite(RTFILE File, const void *pvBuf, size_t cbToWrite, size_t *pcbWritten)
+{
+    RT_NOREF2(File, cbToWrite);
+ /* RTPrintf("%s: File=%p, pvBuf=%.*s, cbToWrite=%llu\n", __PRETTY_FUNCTION__,
+             File, cbToWrite, (const char *)pvBuf, LLUIFY(cbToWrite)); */
+    ARRAY_FROM_PATH(g_testRTFileWrite_szData, (const char *)pvBuf);
+    if (pcbWritten)
+        *pcbWritten = strlen(g_testRTFileWrite_szData) + 1;
+    return VINF_SUCCESS;
+}
+
+extern int  testRTFileWriteAt(RTFILE File, uint64_t offFile, const void *pvBuf, size_t cbToWrite, size_t *pcbWritten)
+{
+    RT_NOREF3(File, cbToWrite, offFile);
+ /* RTPrintf("%s: File=%p, pvBuf=%.*s, cbToWrite=%llu\n", __PRETTY_FUNCTION__,
+             File, cbToWrite, (const char *)pvBuf, LLUIFY(cbToWrite)); */
+    ARRAY_FROM_PATH(g_testRTFileWrite_szData, (const char *)pvBuf);
+    if (pcbWritten)
+        *pcbWritten = strlen(g_testRTFileWrite_szData) + 1;
+    return VINF_SUCCESS;
+}
+
+extern int testRTFsQueryProperties(const char *pszFsPath, PRTFSPROPERTIES pProperties)
+{
+    RT_NOREF1(pszFsPath);
+ /* RTPrintf("%s, pszFsPath=%s\n", __PRETTY_FUNCTION__, pszFsPath);
+    RT_ZERO(*pProperties); */
+    pProperties->cbMaxComponent = 256;
+    pProperties->fCaseSensitive = true;
+    return VINF_SUCCESS;
+}
+
+extern int testRTFsQuerySerial(const char *pszFsPath, uint32_t *pu32Serial)
+{
+    RT_NOREF2(pszFsPath, pu32Serial);
+    RTPrintf("%s\n", __PRETTY_FUNCTION__);
+    return 0;
+}
+extern int testRTFsQuerySizes(const char *pszFsPath, PRTFOFF pcbTotal, RTFOFF *pcbFree, uint32_t *pcbBlock, uint32_t *pcbSector)
+{
+    RT_NOREF5(pszFsPath, pcbTotal, pcbFree, pcbBlock, pcbSector);
+    RTPrintf("%s\n", __PRETTY_FUNCTION__);
+    return 0;
+}
+
+extern int testRTPathQueryInfoEx(const char *pszPath, PRTFSOBJINFO pObjInfo, RTFSOBJATTRADD enmAdditionalAttribs, uint32_t fFlags)
+{
+    RT_NOREF2(enmAdditionalAttribs, fFlags);
+ /* RTPrintf("%s: pszPath=%s, enmAdditionalAttribs=0x%x, fFlags=0x%x\n",
+             __PRETTY_FUNCTION__, pszPath, (unsigned) enmAdditionalAttribs,
+             (unsigned) fFlags); */
+    if (g_fFailIfNotLowercase && !RTStrIsLowerCased(strpbrk(pszPath, "/\\")))
+        return VERR_FILE_NOT_FOUND;
+    RT_ZERO(*pObjInfo);
+    return VINF_SUCCESS;
+}
+
+extern int testRTSymlinkDelete(const char *pszSymlink, uint32_t fDelete)
+{
+    RT_NOREF2(pszSymlink, fDelete);
+    if (g_fFailIfNotLowercase && !RTStrIsLowerCased(strpbrk(pszSymlink, "/\\")))
+        return VERR_FILE_NOT_FOUND;
+    RTPrintf("%s\n", __PRETTY_FUNCTION__);
+    return 0;
+}
+
+extern int testRTSymlinkRead(const char *pszSymlink, char *pszTarget, size_t cbTarget, uint32_t fRead)
+{
+    if (g_fFailIfNotLowercase && !RTStrIsLowerCased(strpbrk(pszSymlink, "/\\")))
+        return VERR_FILE_NOT_FOUND;
+    RT_NOREF4(pszSymlink, pszTarget, cbTarget, fRead);
+    RTPrintf("%s\n", __PRETTY_FUNCTION__);
+    return 0;
+}
+
+
+/*********************************************************************************************************************************
+*   Tests                                                                                                                        *
+*********************************************************************************************************************************/
+
+/* Sub-tests for testMappingsQuery(). */
+void testMappingsQuerySimple(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMappingsQueryTooFewBuffers(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMappingsQueryAutoMount(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMappingsQueryArrayWrongSize(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testMappingsQueryName(). */
+void testMappingsQueryNameValid(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMappingsQueryNameInvalid(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMappingsQueryNameBadBuffer(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testMapFolder(). */
+void testMapFolderValid(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMapFolderInvalid(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMapFolderTwice(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMapFolderDelimiter(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMapFolderCaseSensitive(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMapFolderCaseInsensitive(RTTEST hTest) { RT_NOREF1(hTest); }
+void testMapFolderBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testUnmapFolder(). */
+void testUnmapFolderValid(RTTEST hTest) { RT_NOREF1(hTest); }
+void testUnmapFolderInvalid(RTTEST hTest) { RT_NOREF1(hTest); }
+void testUnmapFolderBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testCreate(). */
+void testCreateBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testClose(). */
+void testCloseBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testRead(). */
+void testReadBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testWrite(). */
+void testWriteBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testLock(). */
+void testLockBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testFlush(). */
+void testFlushBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testDirList(). */
+void testDirListBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testReadLink(). */
+void testReadLinkBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testFSInfo(). */
+void testFSInfoBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testRemove(). */
+void testRemoveBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testRename(). */
+void testRenameBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testSymlink(). */
+void testSymlinkBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testMappingsAdd(). */
+void testMappingsAddBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+/* Sub-tests for testMappingsRemove(). */
+void testMappingsRemoveBadParameters(RTTEST hTest) { RT_NOREF1(hTest); }
+
+union TESTSHFLSTRING
+{
+    SHFLSTRING string;
+    char acData[256];
+};
+
+static void fillTestShflString(union TESTSHFLSTRING *pDest,
+                               const char *pcszSource)
+{
+    const size_t cchSource = strlen(pcszSource);
+    AssertRelease(  cchSource * 2 + 2
+                  < sizeof(*pDest) - RT_UOFFSETOF(SHFLSTRING, String));
+    pDest->string.u16Length = (uint16_t)(cchSource * sizeof(RTUTF16));
+    pDest->string.u16Size   = pDest->string.u16Length + sizeof(RTUTF16);
+    /* Copy pcszSource ASCIIZ, including the trailing 0, to the UTF16 pDest->string.String.ucs2. */
+    for (unsigned i = 0; i <= cchSource; ++i)
+        pDest->string.String.ucs2[i] = (uint16_t)pcszSource[i];
+}
+
+static SHFLROOT initWithWritableMapping(RTTEST hTest,
+                                        VBOXHGCMSVCFNTABLE *psvcTable,
+                                        VBOXHGCMSVCHELPERS *psvcHelpers,
+                                        const char *pcszFolderName,
+                                        const char *pcszMapping,
+                                        bool fCaseSensitive = true)
+{
+    VBOXHGCMSVCPARM aParms[RT_MAX(SHFL_CPARMS_ADD_MAPPING,
+                                  SHFL_CPARMS_MAP_FOLDER)];
+    union TESTSHFLSTRING FolderName;
+    union TESTSHFLSTRING Mapping;
+    union TESTSHFLSTRING AutoMountPoint;
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+    int rc;
+
+    initTable(psvcTable, psvcHelpers);
+    AssertReleaseRC(VBoxHGCMSvcLoad(psvcTable));
+    AssertRelease(  psvcTable->pvService
+                  = RTTestGuardedAllocTail(hTest, psvcTable->cbClient));
+    RT_BZERO(psvcTable->pvService, psvcTable->cbClient);
+    fillTestShflString(&FolderName, pcszFolderName);
+    fillTestShflString(&Mapping, pcszMapping);
+    fillTestShflString(&AutoMountPoint, "");
+    HGCMSvcSetPv(&aParms[0], &FolderName,   RT_UOFFSETOF(SHFLSTRING, String)
+                                      + FolderName.string.u16Size);
+    HGCMSvcSetPv(&aParms[1], &Mapping,   RT_UOFFSETOF(SHFLSTRING, String)
+                                   + Mapping.string.u16Size);
+    HGCMSvcSetU32(&aParms[2], 1);
+    HGCMSvcSetPv(&aParms[3], &AutoMountPoint, SHFLSTRING_HEADER_SIZE + AutoMountPoint.string.u16Size);
+    rc = psvcTable->pfnHostCall(psvcTable->pvService, SHFL_FN_ADD_MAPPING,
+                                SHFL_CPARMS_ADD_MAPPING, aParms);
+    AssertReleaseRC(rc);
+    HGCMSvcSetPv(&aParms[0], &Mapping,   RT_UOFFSETOF(SHFLSTRING, String)
+                                   + Mapping.string.u16Size);
+    HGCMSvcSetU32(&aParms[1], 0);  /* root */
+    HGCMSvcSetU32(&aParms[2], '/');  /* delimiter */
+    HGCMSvcSetU32(&aParms[3], fCaseSensitive);
+    psvcTable->pfnCall(psvcTable->pvService, &callHandle, 0,
+                       psvcTable->pvService, SHFL_FN_MAP_FOLDER,
+                       SHFL_CPARMS_MAP_FOLDER, aParms, 0);
+    AssertReleaseRC(callHandle.rc);
+    return aParms[1].u.uint32;
+}
+
+/** @todo Mappings should be automatically removed by unloading the service,
+ *        but unloading is currently a no-op! */
+static void unmapAndRemoveMapping(RTTEST hTest, VBOXHGCMSVCFNTABLE *psvcTable,
+                                  SHFLROOT root, const char *pcszFolderName)
+{
+    RT_NOREF1(hTest);
+    VBOXHGCMSVCPARM aParms[RT_MAX(SHFL_CPARMS_UNMAP_FOLDER,
+                                  SHFL_CPARMS_REMOVE_MAPPING)];
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+    union TESTSHFLSTRING FolderName;
+    int rc;
+
+    HGCMSvcSetU32(&aParms[0], root);
+    psvcTable->pfnCall(psvcTable->pvService, &callHandle, 0,
+                       psvcTable->pvService, SHFL_FN_UNMAP_FOLDER,
+                       SHFL_CPARMS_UNMAP_FOLDER, aParms, 0);
+    AssertReleaseRC(callHandle.rc);
+    fillTestShflString(&FolderName, pcszFolderName);
+    HGCMSvcSetPv(&aParms[0], &FolderName,   RT_UOFFSETOF(SHFLSTRING, String)
+                                      + FolderName.string.u16Size);
+    rc = psvcTable->pfnHostCall(psvcTable->pvService, SHFL_FN_REMOVE_MAPPING,
+                                SHFL_CPARMS_REMOVE_MAPPING, aParms);
+    AssertReleaseRC(rc);
+}
+
+static int createFile(VBOXHGCMSVCFNTABLE *psvcTable, SHFLROOT Root,
+                      const char *pcszFilename, uint32_t fCreateFlags,
+                      SHFLHANDLE *pHandle, SHFLCREATERESULT *pResult)
+{
+    VBOXHGCMSVCPARM aParms[SHFL_CPARMS_CREATE];
+    union TESTSHFLSTRING Path;
+    SHFLCREATEPARMS CreateParms;
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+
+    fillTestShflString(&Path, pcszFilename);
+    RT_ZERO(CreateParms);
+    CreateParms.CreateFlags = fCreateFlags;
+    HGCMSvcSetU32(&aParms[0], Root);
+    HGCMSvcSetPv(&aParms[1], &Path,   RT_UOFFSETOF(SHFLSTRING, String)
+                                + Path.string.u16Size);
+    HGCMSvcSetPv(&aParms[2], &CreateParms, sizeof(CreateParms));
+    psvcTable->pfnCall(psvcTable->pvService, &callHandle, 0,
+                       psvcTable->pvService, SHFL_FN_CREATE,
+                       RT_ELEMENTS(aParms), aParms, 0);
+    if (RT_FAILURE(callHandle.rc))
+        return callHandle.rc;
+    if (pHandle)
+        *pHandle = CreateParms.Handle;
+    if (pResult)
+        *pResult = CreateParms.Result;
+    return VINF_SUCCESS;
+}
+
+static int readFile(VBOXHGCMSVCFNTABLE *psvcTable, SHFLROOT Root,
+                    SHFLHANDLE hFile, uint64_t offSeek, uint32_t cbRead,
+                    uint32_t *pcbRead, void *pvBuf, uint32_t cbBuf)
+{
+    VBOXHGCMSVCPARM aParms[SHFL_CPARMS_READ];
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+
+    HGCMSvcSetU32(&aParms[0], Root);
+    HGCMSvcSetU64(&aParms[1], (uint64_t) hFile);
+    HGCMSvcSetU64(&aParms[2], offSeek);
+    HGCMSvcSetU32(&aParms[3], cbRead);
+    HGCMSvcSetPv(&aParms[4], pvBuf, cbBuf);
+    psvcTable->pfnCall(psvcTable->pvService, &callHandle, 0,
+                       psvcTable->pvService, SHFL_FN_READ,
+                       RT_ELEMENTS(aParms), aParms, 0);
+    if (pcbRead)
+        *pcbRead = aParms[3].u.uint32;
+    return callHandle.rc;
+}
+
+static int writeFile(VBOXHGCMSVCFNTABLE *psvcTable, SHFLROOT Root,
+                     SHFLHANDLE hFile, uint64_t offSeek, uint32_t cbWrite,
+                     uint32_t *pcbWritten, const void *pvBuf, uint32_t cbBuf)
+{
+    VBOXHGCMSVCPARM aParms[SHFL_CPARMS_WRITE];
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+
+    HGCMSvcSetU32(&aParms[0], Root);
+    HGCMSvcSetU64(&aParms[1], (uint64_t) hFile);
+    HGCMSvcSetU64(&aParms[2], offSeek);
+    HGCMSvcSetU32(&aParms[3], cbWrite);
+    HGCMSvcSetPv(&aParms[4], (void *)pvBuf, cbBuf);
+    psvcTable->pfnCall(psvcTable->pvService, &callHandle, 0,
+                       psvcTable->pvService, SHFL_FN_WRITE,
+                       RT_ELEMENTS(aParms), aParms, 0);
+    if (pcbWritten)
+        *pcbWritten = aParms[3].u.uint32;
+    return callHandle.rc;
+}
+
+static int flushFile(VBOXHGCMSVCFNTABLE *psvcTable, SHFLROOT root,
+                     SHFLHANDLE handle)
+{
+    VBOXHGCMSVCPARM aParms[SHFL_CPARMS_FLUSH];
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+
+    HGCMSvcSetU32(&aParms[0], root);
+    HGCMSvcSetU64(&aParms[1], handle);
+    psvcTable->pfnCall(psvcTable->pvService, &callHandle, 0,
+                       psvcTable->pvService, SHFL_FN_FLUSH,
+                       SHFL_CPARMS_FLUSH, aParms, 0);
+    return callHandle.rc;
+}
+
+static int listDir(VBOXHGCMSVCFNTABLE *psvcTable, SHFLROOT root,
+                   SHFLHANDLE handle, uint32_t fFlags,
+                   const char *pcszPath, void *pvBuf, uint32_t cbBuf,
+                   uint32_t resumePoint, uint32_t *pcFiles)
+{
+    VBOXHGCMSVCPARM aParms[SHFL_CPARMS_LIST];
+    union TESTSHFLSTRING Path;
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+
+    HGCMSvcSetU32(&aParms[0], root);
+    HGCMSvcSetU64(&aParms[1], handle);
+    HGCMSvcSetU32(&aParms[2], fFlags);
+    HGCMSvcSetU32(&aParms[3], cbBuf);
+    if (pcszPath)
+    {
+        fillTestShflString(&Path, pcszPath);
+        HGCMSvcSetPv(&aParms[4], &Path,   RT_UOFFSETOF(SHFLSTRING, String)
+                                    + Path.string.u16Size);
+    }
+    else
+        HGCMSvcSetPv(&aParms[4], NULL, 0);
+    HGCMSvcSetPv(&aParms[5], pvBuf, cbBuf);
+    HGCMSvcSetU32(&aParms[6], resumePoint);
+    HGCMSvcSetU32(&aParms[7], 0);
+    psvcTable->pfnCall(psvcTable->pvService, &callHandle, 0,
+                       psvcTable->pvService, SHFL_FN_LIST,
+                       RT_ELEMENTS(aParms), aParms, 0);
+    if (pcFiles)
+        *pcFiles = aParms[7].u.uint32;
+    return callHandle.rc;
+}
+
+static int sfInformation(VBOXHGCMSVCFNTABLE *psvcTable, SHFLROOT root,
+                         SHFLHANDLE handle, uint32_t fFlags, uint32_t cb,
+                         SHFLFSOBJINFO *pInfo)
+{
+    VBOXHGCMSVCPARM aParms[SHFL_CPARMS_INFORMATION];
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+
+    HGCMSvcSetU32(&aParms[0], root);
+    HGCMSvcSetU64(&aParms[1], handle);
+    HGCMSvcSetU32(&aParms[2], fFlags);
+    HGCMSvcSetU32(&aParms[3], cb);
+    HGCMSvcSetPv(&aParms[4], pInfo, cb);
+    psvcTable->pfnCall(psvcTable->pvService, &callHandle, 0,
+                       psvcTable->pvService, SHFL_FN_INFORMATION,
+                       RT_ELEMENTS(aParms), aParms, 0);
+    return callHandle.rc;
+}
+
+static int lockFile(VBOXHGCMSVCFNTABLE *psvcTable, SHFLROOT root,
+                    SHFLHANDLE handle, int64_t offLock, uint64_t cbLock,
+                    uint32_t fFlags)
+{
+    VBOXHGCMSVCPARM aParms[SHFL_CPARMS_LOCK];
+    VBOXHGCMCALLHANDLE_TYPEDEF callHandle = { VINF_SUCCESS };
+
+    HGCMSvcSetU32(&aParms[0], root);
+    HGCMSvcSetU64(&aParms[1], handle);
+    HGCMSvcSetU64(&aParms[2], offLock);
+    HGCMSvcSetU64(&aParms[3], cbLock);
+    HGCMSvcSetU32(&aParms[4], fFlags);
+    psvcTable->pfnCall(psvcTable->pvService, &callHandle, 0,
+                       psvcTable->pvService, SHFL_FN_LOCK,
+                       RT_ELEMENTS(aParms), aParms, 0);
+    return callHandle.rc;
+}
+
+void testCreateFileSimple(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTFILE hFile = (RTFILE) 0x10000;
+    SHFLCREATERESULT Result;
+    int rc;
+
+    RTTestSub(hTest, "Create file simple");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTFileOpen_hFile = hFile;
+    rc = createFile(&svcTable, Root, "/test/file", SHFL_CF_ACCESS_READ, NULL,
+                    &Result);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest,
+                     !strcmp(&g_testRTFileOpen_szName[RTPATH_STYLE == RTPATH_STR_F_STYLE_DOS ? 2 : 0],
+                             "/test/mapping/test/file"),
+                     (hTest, "pszFilename=%s\n", &g_testRTFileOpen_szName[RTPATH_STYLE == RTPATH_STR_F_STYLE_DOS ? 2 : 0]));
+    RTTEST_CHECK_MSG(hTest, g_testRTFileOpen_fOpen == 0x181,
+                     (hTest, "fOpen=%llu\n", LLUIFY(g_testRTFileOpen_fOpen)));
+    RTTEST_CHECK_MSG(hTest, Result == SHFL_FILE_CREATED,
+                     (hTest, "Result=%d\n", (int) Result));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileClose_hFile == hFile,
+                     (hTest, "File=%u\n", (uintptr_t)g_testRTFileClose_hFile));
+}
+
+void testCreateFileSimpleCaseInsensitive(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTFILE hFile = (RTFILE) 0x10000;
+    SHFLCREATERESULT Result;
+    int rc;
+
+    g_fFailIfNotLowercase = true;
+
+    RTTestSub(hTest, "Create file case insensitive");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname", false /*fCaseSensitive*/);
+    g_testRTFileOpen_hFile = hFile;
+    rc = createFile(&svcTable, Root, "/TesT/FilE", SHFL_CF_ACCESS_READ, NULL,
+                    &Result);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+
+    RTTEST_CHECK_MSG(hTest,
+                     !strcmp(&g_testRTFileOpen_szName[RTPATH_STYLE == RTPATH_STR_F_STYLE_DOS ? 2 : 0],
+                             "/test/mapping/test/file"),
+                     (hTest, "pszFilename=%s\n", &g_testRTFileOpen_szName[RTPATH_STYLE == RTPATH_STR_F_STYLE_DOS ? 2 : 0]));
+    RTTEST_CHECK_MSG(hTest, g_testRTFileOpen_fOpen == 0x181,
+                     (hTest, "fOpen=%llu\n", LLUIFY(g_testRTFileOpen_fOpen)));
+    RTTEST_CHECK_MSG(hTest, Result == SHFL_FILE_CREATED,
+                     (hTest, "Result=%d\n", (int) Result));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileClose_hFile == hFile,
+                     (hTest, "File=%u\n", (uintptr_t)g_testRTFileClose_hFile));
+
+    g_fFailIfNotLowercase = false;
+}
+
+void testCreateDirSimple(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    RTDIR hDir = (RTDIR)&g_aTestDirHandles[g_iNextDirHandle++ % RT_ELEMENTS(g_aTestDirHandles)];
+    SHFLCREATERESULT Result;
+    int rc;
+
+    RTTestSub(hTest, "Create directory simple");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTDirOpen_hDir = hDir;
+    rc = createFile(&svcTable, Root, "test/dir",
+                    SHFL_CF_DIRECTORY | SHFL_CF_ACCESS_READ, NULL, &Result);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest,
+                     !strcmp(&g_testRTDirCreate_szPath[RTPATH_STYLE == RTPATH_STR_F_STYLE_DOS ? 2 : 0],
+                             "/test/mapping/test/dir"),
+                     (hTest, "pszPath=%s\n", &g_testRTDirCreate_szPath[RTPATH_STYLE == RTPATH_STR_F_STYLE_DOS ? 2 : 0]));
+    RTTEST_CHECK_MSG(hTest,
+                     !strcmp(&g_testRTDirOpen_szName[RTPATH_STYLE == RTPATH_STR_F_STYLE_DOS ? 2 : 0],
+                             "/test/mapping/test/dir"),
+                     (hTest, "pszFilename=%s\n", &g_testRTDirOpen_szName[RTPATH_STYLE == RTPATH_STR_F_STYLE_DOS ? 2 : 0]));
+    RTTEST_CHECK_MSG(hTest, Result == SHFL_FILE_CREATED,
+                     (hTest, "Result=%d\n", (int) Result));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTDirClose_hDir == hDir, (hTest, "hDir=%p\n", g_testRTDirClose_hDir));
+}
+
+void testReadFileSimple(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTFILE hFile = (RTFILE) 0x10000;
+    SHFLHANDLE Handle;
+    const char *pcszReadData = "Data to read";
+    char achBuf[sizeof(pcszReadData) + 10];
+    uint32_t cbRead;
+    int rc;
+
+    RTTestSub(hTest, "Read file simple");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTFileOpen_hFile = hFile;
+    rc = createFile(&svcTable, Root, "/test/file", SHFL_CF_ACCESS_READ,
+                    &Handle, NULL);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    g_testRTFileRead_pszData = pcszReadData;
+    memset(achBuf, 'f', sizeof(achBuf));
+    rc = readFile(&svcTable, Root, Handle, 0, (uint32_t)strlen(pcszReadData) + 1,
+                  &cbRead, achBuf, (uint32_t)sizeof(achBuf));
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest,
+                     !strncmp(achBuf, pcszReadData, sizeof(achBuf)),
+                     (hTest, "pvBuf=%.*s Handle=%#RX64\n", sizeof(achBuf), achBuf, Handle));
+    RTTEST_CHECK_MSG(hTest, cbRead == strlen(pcszReadData) + 1,
+                     (hTest, "cbRead=%llu\n", LLUIFY(cbRead)));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    RTTEST_CHECK_MSG(hTest, g_testRTFileClose_hFile == hFile, (hTest, "File=%u\n", g_testRTFileClose_hFile));
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+}
+
+void testWriteFileSimple(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTFILE hFile = (RTFILE) 0x10000;
+    SHFLHANDLE Handle;
+    const char *pcszWrittenData = "Data to write";
+    uint32_t cbToWrite = (uint32_t)strlen(pcszWrittenData) + 1;
+    uint32_t cbWritten;
+    int rc;
+
+    RTTestSub(hTest, "Write file simple");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTFileOpen_hFile = hFile;
+    rc = createFile(&svcTable, Root, "/test/file", SHFL_CF_ACCESS_READ,
+                    &Handle, NULL);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    rc = writeFile(&svcTable, Root, Handle, 0, cbToWrite, &cbWritten,
+                   pcszWrittenData, cbToWrite);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest,
+                     !strcmp(g_testRTFileWrite_szData, pcszWrittenData),
+                     (hTest, "pvBuf=%s\n", g_testRTFileWrite_szData));
+    RTTEST_CHECK_MSG(hTest, cbWritten == cbToWrite,
+                     (hTest, "cbWritten=%llu\n", LLUIFY(cbWritten)));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    RTTEST_CHECK_MSG(hTest, g_testRTFileClose_hFile == hFile, (hTest, "File=%u\n", g_testRTFileClose_hFile));
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+}
+
+void testFlushFileSimple(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTFILE hFile = (RTFILE) 0x10000;
+    SHFLHANDLE Handle;
+    int rc;
+
+    RTTestSub(hTest, "Flush file simple");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTFileOpen_hFile = hFile;
+    rc = createFile(&svcTable, Root, "/test/file", SHFL_CF_ACCESS_READ,
+                    &Handle, NULL);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    rc = flushFile(&svcTable, Root, Handle);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileFlush_hFile == hFile, (hTest, "File=%u\n", g_testRTFileFlush_hFile));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileClose_hFile == hFile, (hTest, "File=%u\n", g_testRTFileClose_hFile));
+}
+
+void testDirListEmpty(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    RTDIR hDir = (RTDIR)&g_aTestDirHandles[g_iNextDirHandle++ % RT_ELEMENTS(g_aTestDirHandles)];
+    SHFLHANDLE Handle;
+    union
+    {
+        SHFLDIRINFO DirInfo;
+        uint8_t     abBuffer[sizeof(SHFLDIRINFO) + 2 * sizeof(RTUTF16)];
+    } Buf;
+    uint32_t cFiles;
+    int rc;
+
+    RTTestSub(hTest, "List empty directory");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTDirOpen_hDir = hDir;
+    rc = createFile(&svcTable, Root, "test/dir",
+                    SHFL_CF_DIRECTORY | SHFL_CF_ACCESS_READ, &Handle, NULL);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    rc = listDir(&svcTable, Root, Handle, 0, NULL, &Buf.DirInfo, sizeof(Buf), 0, &cFiles);
+    RTTEST_CHECK_RC(hTest, rc, VERR_NO_MORE_FILES);
+    RTTEST_CHECK_MSG(hTest, g_testRTDirReadEx_hDir == hDir, (hTest, "Dir=%p\n", g_testRTDirReadEx_hDir));
+    RTTEST_CHECK_MSG(hTest, cFiles == 0,
+                     (hTest, "cFiles=%llu\n", LLUIFY(cFiles)));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTDirClose_hDir == hDir, (hTest, "hDir=%p\n", g_testRTDirClose_hDir));
+}
+
+void testFSInfoQuerySetFMode(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTFILE hFile = (RTFILE) 0x10000;
+    const uint32_t fMode = 0660;
+    SHFLFSOBJINFO Info;
+    int rc;
+
+    RTTestSub(hTest, "Query and set file size");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    SHFLHANDLE Handle = SHFL_HANDLE_NIL;
+    g_testRTFileOpen_hFile = hFile;
+    rc = createFile(&svcTable, Root, "/test/file", SHFL_CF_ACCESS_READ,
+                    &Handle, NULL);
+    RTTEST_CHECK_RC_OK_RETV(hTest, rc);
+
+    RT_ZERO(Info);
+    g_testRTFileQueryInfo_fMode = fMode;
+    rc = sfInformation(&svcTable, Root, Handle, SHFL_INFO_FILE, sizeof(Info),
+                       &Info);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileQueryInfo_hFile == hFile, (hTest, "File=%u\n", g_testRTFileQueryInfo_hFile));
+    RTTEST_CHECK_MSG(hTest, Info.Attr.fMode == fMode,
+                     (hTest, "cbObject=%llu\n", LLUIFY(Info.cbObject)));
+    RT_ZERO(Info);
+    Info.Attr.fMode = fMode;
+    rc = sfInformation(&svcTable, Root, Handle, SHFL_INFO_SET | SHFL_INFO_FILE,
+                       sizeof(Info), &Info);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileSet_fMode == fMode,
+                     (hTest, "Size=%llu\n", LLUIFY(g_testRTFileSet_fMode)));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileClose_hFile == hFile, (hTest, "File=%u\n", g_testRTFileClose_hFile));
+}
+
+void testFSInfoQuerySetDirATime(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTDIR hDir = (RTDIR)&g_aTestDirHandles[g_iNextDirHandle++ % RT_ELEMENTS(g_aTestDirHandles)];
+    const int64_t ccAtimeNano = 100000;
+    SHFLFSOBJINFO Info;
+    SHFLHANDLE Handle;
+    int rc;
+
+    RTTestSub(hTest, "Query and set directory atime");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTDirOpen_hDir = hDir;
+    rc = createFile(&svcTable, Root, "test/dir",
+                    SHFL_CF_DIRECTORY | SHFL_CF_ACCESS_READ, &Handle, NULL);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RT_ZERO(Info);
+    RTTimeSpecSetNano(&g_testRTDirQueryInfo_ATime, ccAtimeNano);
+    rc = sfInformation(&svcTable, Root, Handle, SHFL_INFO_FILE, sizeof(Info),
+                       &Info);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest, g_testRTDirQueryInfo_hDir == hDir, (hTest, "Dir=%p\n", g_testRTDirQueryInfo_hDir));
+    RTTEST_CHECK_MSG(hTest, RTTimeSpecGetNano(&Info.AccessTime) == ccAtimeNano,
+                     (hTest, "ATime=%llu\n",
+                      LLUIFY(RTTimeSpecGetNano(&Info.AccessTime))));
+    RT_ZERO(Info);
+    RTTimeSpecSetNano(&Info.AccessTime, ccAtimeNano);
+    rc = sfInformation(&svcTable, Root, Handle, SHFL_INFO_SET | SHFL_INFO_FILE,
+                       sizeof(Info), &Info);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest,    RTTimeSpecGetNano(&g_testRTDirSetTimes_ATime)
+                            == ccAtimeNano,
+                     (hTest, "ATime=%llu\n",
+                      LLUIFY(RTTimeSpecGetNano(&g_testRTDirSetTimes_ATime))));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTDirClose_hDir == hDir, (hTest, "hDir=%p\n", g_testRTDirClose_hDir));
+}
+
+void testFSInfoQuerySetFileATime(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTFILE hFile = (RTFILE) 0x10000;
+    const int64_t ccAtimeNano = 100000;
+    SHFLFSOBJINFO Info;
+    SHFLHANDLE Handle;
+    int rc;
+
+    RTTestSub(hTest, "Query and set file atime");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTFileOpen_hFile = hFile;
+    rc = createFile(&svcTable, Root, "/test/file", SHFL_CF_ACCESS_READ,
+                    &Handle, NULL);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RT_ZERO(Info);
+    RTTimeSpecSetNano(&g_testRTFileQueryInfo_ATime, ccAtimeNano);
+    rc = sfInformation(&svcTable, Root, Handle, SHFL_INFO_FILE, sizeof(Info),
+                       &Info);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileQueryInfo_hFile == hFile, (hTest, "File=%u\n", g_testRTFileQueryInfo_hFile));
+    RTTEST_CHECK_MSG(hTest, RTTimeSpecGetNano(&Info.AccessTime) == ccAtimeNano,
+                     (hTest, "ATime=%llu\n",
+                      LLUIFY(RTTimeSpecGetNano(&Info.AccessTime))));
+    RT_ZERO(Info);
+    RTTimeSpecSetNano(&Info.AccessTime, ccAtimeNano);
+    rc = sfInformation(&svcTable, Root, Handle, SHFL_INFO_SET | SHFL_INFO_FILE,
+                       sizeof(Info), &Info);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest,    RTTimeSpecGetNano(&g_testRTFileSetTimes_ATime)
+                            == ccAtimeNano,
+                     (hTest, "ATime=%llu\n",
+                      LLUIFY(RTTimeSpecGetNano(&g_testRTFileSetTimes_ATime))));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileClose_hFile == hFile, (hTest, "File=%u\n", g_testRTFileClose_hFile));
+}
+
+void testFSInfoQuerySetEndOfFile(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTFILE hFile = (RTFILE) 0x10000;
+    const RTFOFF cbNew = 50000;
+    SHFLFSOBJINFO Info;
+    SHFLHANDLE Handle;
+    int rc;
+
+    RTTestSub(hTest, "Set end of file position");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTFileOpen_hFile = hFile;
+    rc = createFile(&svcTable, Root, "/test/file", SHFL_CF_ACCESS_READ,
+                    &Handle, NULL);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RT_ZERO(Info);
+    Info.cbObject = cbNew;
+    rc = sfInformation(&svcTable, Root, Handle, SHFL_INFO_SET | SHFL_INFO_SIZE,
+                       sizeof(Info), &Info);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileSetSize_hFile == hFile, (hTest, "File=%u\n", g_testRTFileSetSize_hFile));
+    RTTEST_CHECK_MSG(hTest, g_testRTFileSetSize_cbSize == cbNew,
+                     (hTest, "Size=%llu\n", LLUIFY(g_testRTFileSetSize_cbSize)));
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileClose_hFile == hFile, (hTest, "File=%u\n", g_testRTFileClose_hFile));
+}
+
+void testLockFileSimple(RTTEST hTest)
+{
+    VBOXHGCMSVCFNTABLE  svcTable;
+    VBOXHGCMSVCHELPERS  svcHelpers;
+    SHFLROOT Root;
+    const RTFILE hFile = (RTFILE) 0x10000;
+    const int64_t offLock = 50000;
+    const uint64_t cbLock = 4000;
+    SHFLHANDLE Handle;
+    int rc;
+
+    RTTestSub(hTest, "Simple file lock and unlock");
+    Root = initWithWritableMapping(hTest, &svcTable, &svcHelpers,
+                                   "/test/mapping", "testname");
+    g_testRTFileOpen_hFile = hFile;
+    rc = createFile(&svcTable, Root, "/test/file", SHFL_CF_ACCESS_READ,
+                    &Handle, NULL);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+    rc = lockFile(&svcTable, Root, Handle, offLock, cbLock, SHFL_LOCK_SHARED);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+#ifdef RT_OS_WINDOWS  /* Locking is a no-op elsewhere. */
+    RTTEST_CHECK_MSG(hTest, g_testRTFileLock_hFile == hFile, (hTest, "File=%u\n", g_testRTFileLock_hFile));
+    RTTEST_CHECK_MSG(hTest, g_testRTFileLock_fLock == 0,
+                     (hTest, "fLock=%u\n", g_testRTFileLock_fLock));
+    RTTEST_CHECK_MSG(hTest, g_testRTFileLock_offLock == offLock,
+                     (hTest, "Offs=%llu\n", (long long) g_testRTFileLock_offLock));
+    RTTEST_CHECK_MSG(hTest, g_testRTFileLock_cbLock == cbLock,
+                     (hTest, "Size=%llu\n", LLUIFY(g_testRTFileLock_cbLock)));
+#endif
+    rc = lockFile(&svcTable, Root, Handle, offLock, cbLock, SHFL_LOCK_CANCEL);
+    RTTEST_CHECK_RC_OK(hTest, rc);
+#ifdef RT_OS_WINDOWS
+    RTTEST_CHECK_MSG(hTest, g_testRTFileUnlock_hFile == hFile, (hTest, "File=%u\n", g_testRTFileUnlock_hFile));
+    RTTEST_CHECK_MSG(hTest, g_testRTFileUnlock_offLock == offLock,
+                     (hTest, "Offs=%llu\n",
+                      (long long) g_testRTFileUnlock_offLock));
+    RTTEST_CHECK_MSG(hTest, g_testRTFileUnlock_cbLock == cbLock,
+                     (hTest, "Size=%llu\n", LLUIFY(g_testRTFileUnlock_cbLock)));
+#endif
+    unmapAndRemoveMapping(hTest, &svcTable, Root, "testname");
+    AssertReleaseRC(svcTable.pfnDisconnect(NULL, 0, svcTable.pvService));
+    AssertReleaseRC(svcTable.pfnUnload(NULL));
+    RTTestGuardedFree(hTest, svcTable.pvService);
+    RTTEST_CHECK_MSG(hTest, g_testRTFileClose_hFile == hFile, (hTest, "File=%u\n", g_testRTFileClose_hFile));
+}
+
+
+/*********************************************************************************************************************************
+*   Main code                                                                                                                    *
+*********************************************************************************************************************************/
+
+static void testAPI(RTTEST hTest)
+{
+    testMappingsQuery(hTest);
+    testMappingsQueryName(hTest);
+    testMapFolder(hTest);
+    testUnmapFolder(hTest);
+    testCreate(hTest);
+    testClose(hTest);
+    testRead(hTest);
+    testWrite(hTest);
+    testLock(hTest);
+    testFlush(hTest);
+    testDirList(hTest);
+    testReadLink(hTest);
+    testFSInfo(hTest);
+    testRemove(hTest);
+    testRename(hTest);
+    testSymlink(hTest);
+    testMappingsAdd(hTest);
+    testMappingsRemove(hTest);
+    /* testSetStatusLed(hTest); */
+}
+
+int main(int argc, char **argv)
+{
+    RT_NOREF1(argc);
+    RTEXITCODE rcExit = RTTestInitAndCreate(RTPathFilename(argv[0]), &g_hTest);
+    if (rcExit != RTEXITCODE_SUCCESS)
+        return rcExit;
+    RTTestBanner(g_hTest);
+    testAPI(g_hTest);
+    return RTTestSummaryAndDestroy(g_hTest);
+}
diff --git a/src/VBox/HostServices/SharedFolders/testcase/tstSharedFolderService.h b/src/VBox/HostServices/SharedFolders/testcase/tstSharedFolderService.h
new file mode 100644
index 00000000..3be50c23
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/testcase/tstSharedFolderService.h
@@ -0,0 +1,140 @@
+/** @file
+ * VBox Shared Folders testcase stub redefinitions.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_SharedFolders_testcase_tstSharedFolderService_h
+#define VBOX_INCLUDED_SRC_SharedFolders_testcase_tstSharedFolderService_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+/* Grumble... if the coding style let us use the anonymous "struct RTTESTINT *"
+ * instead of "PRTTEST" here we wouldn't need to unnecessarily include this. */
+#include <iprt/test.h>
+
+void testMappingsQuery(RTTEST hTest);
+/* Sub-tests for testMappingsQuery(). */
+void testMappingsQuerySimple(RTTEST hTest);
+void testMappingsQueryTooFewBuffers(RTTEST hTest);
+void testMappingsQueryAutoMount(RTTEST hTest);
+void testMappingsQueryArrayWrongSize(RTTEST hTest);
+
+void testMappingsQueryName(RTTEST hTest);
+/* Sub-tests for testMappingsQueryName(). */
+void testMappingsQueryNameValid(RTTEST hTest);
+void testMappingsQueryNameInvalid(RTTEST hTest);
+void testMappingsQueryNameBadBuffer(RTTEST hTest);
+
+void testMapFolder(RTTEST hTest);
+/* Sub-tests for testMapFolder(). */
+void testMapFolderValid(RTTEST hTest);
+void testMapFolderInvalid(RTTEST hTest);
+void testMapFolderTwice(RTTEST hTest);
+void testMapFolderDelimiter(RTTEST hTest);
+void testMapFolderCaseSensitive(RTTEST hTest);
+void testMapFolderCaseInsensitive(RTTEST hTest);
+void testMapFolderBadParameters(RTTEST hTest);
+
+void testUnmapFolder(RTTEST hTest);
+/* Sub-tests for testUnmapFolder(). */
+void testUnmapFolderValid(RTTEST hTest);
+void testUnmapFolderInvalid(RTTEST hTest);
+void testUnmapFolderBadParameters(RTTEST hTest);
+
+void testCreate(RTTEST hTest);
+/* Sub-tests for testCreate(). */
+void testCreateFileSimple(RTTEST hTest);
+void testCreateFileSimpleCaseInsensitive(RTTEST hTest);
+void testCreateDirSimple(RTTEST hTest);
+void testCreateBadParameters(RTTEST hTest);
+
+void testClose(RTTEST hTest);
+/* Sub-tests for testClose(). */
+void testCloseBadParameters(RTTEST hTest);
+
+void testRead(RTTEST hTest);
+/* Sub-tests for testRead(). */
+void testReadBadParameters(RTTEST hTest);
+void testReadFileSimple(RTTEST hTest);
+
+void testWrite(RTTEST hTest);
+/* Sub-tests for testWrite(). */
+void testWriteBadParameters(RTTEST hTest);
+void testWriteFileSimple(RTTEST hTest);
+
+void testLock(RTTEST hTest);
+/* Sub-tests for testLock(). */
+void testLockBadParameters(RTTEST hTest);
+void testLockFileSimple(RTTEST hTest);
+
+void testFlush(RTTEST hTest);
+/* Sub-tests for testFlush(). */
+void testFlushBadParameters(RTTEST hTest);
+void testFlushFileSimple(RTTEST hTest);
+
+void testDirList(RTTEST hTest);
+/* Sub-tests for testDirList(). */
+void testDirListBadParameters(RTTEST hTest);
+void testDirListEmpty(RTTEST hTest);
+
+void testReadLink(RTTEST hTest);
+/* Sub-tests for testReadLink(). */
+void testReadLinkBadParameters(RTTEST hTest);
+
+void testFSInfo(RTTEST hTest);
+/* Sub-tests for testFSInfo(). */
+void testFSInfoBadParameters(RTTEST hTest);
+void testFSInfoQuerySetFMode(RTTEST hTest);
+void testFSInfoQuerySetDirATime(RTTEST hTest);
+void testFSInfoQuerySetFileATime(RTTEST hTest);
+void testFSInfoQuerySetEndOfFile(RTTEST hTest);
+
+void testRemove(RTTEST hTest);
+/* Sub-tests for testRemove(). */
+void testRemoveBadParameters(RTTEST hTest);
+
+void testRename(RTTEST hTest);
+/* Sub-tests for testRename(). */
+void testRenameBadParameters(RTTEST hTest);
+
+void testSymlink(RTTEST hTest);
+/* Sub-tests for testSymlink(). */
+void testSymlinkBadParameters(RTTEST hTest);
+
+void testMappingsAdd(RTTEST hTest);
+/* Sub-tests for testMappingsAdd(). */
+void testMappingsAddBadParameters(RTTEST hTest);
+
+void testMappingsRemove(RTTEST hTest);
+/* Sub-tests for testMappingsRemove(). */
+void testMappingsRemoveBadParameters(RTTEST hTest);
+
+#if 0  /* Where should this go? */
+void testSetStatusLed(RTTEST hTest);
+/* Sub-tests for testStatusLed(). */
+void testSetStatusLedBadParameters(RTTEST hTest);
+#endif
+
+#endif /* !VBOX_INCLUDED_SRC_SharedFolders_testcase_tstSharedFolderService_h */
diff --git a/src/VBox/HostServices/SharedFolders/testcase/tstShflCase.cpp b/src/VBox/HostServices/SharedFolders/testcase/tstShflCase.cpp
new file mode 100644
index 00000000..052b80d7
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/testcase/tstShflCase.cpp
@@ -0,0 +1,452 @@
+/** @file
+ * Testcase for shared folder case conversion code.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_MISC
+#define LOG_ENABLED
+#include <VBox/shflsvc.h>
+#include <VBox/log.h>
+#include <iprt/assert.h>
+#include <iprt/err.h>
+#include <iprt/file.h>
+#include <iprt/fs.h>
+#include <iprt/dir.h>
+#include <iprt/initterm.h>
+#include <iprt/mem.h>
+#include <iprt/path.h>
+#include <iprt/string.h>
+#include <iprt/uni.h>
+#include <stdio.h>
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+/* Override slash for non-windows hosts. */
+#undef RTPATH_DELIMITER
+#define RTPATH_DELIMITER       '\\'
+
+/* Use our own RTPath and RTDir methods. */
+#define RTPathQueryInfo     rtPathQueryInfo
+#define RTDirOpenFiltered   rtDirOpenFiltered
+#define RTDirClose          rtDirClose
+#define RTDirReadEx         rtDirReadEx
+
+
+/*********************************************************************************************************************************
+*   Global Variables                                                                                                             *
+*********************************************************************************************************************************/
+static int iDirList = 0;
+static int iDirFile = 0;
+
+static const char *g_apszDirs[] =
+{
+    "c:",
+    "c:\\test dir",
+    "c:\\test dir\\SUBDIR",
+};
+
+static const char *g_apszDirsC[] =
+{
+    ".",
+    "..",
+    "test dir"
+};
+
+static const char *g_apszTestdirEntries[] =
+{
+    ".",
+    "..",
+    "SUBDIR",
+    "a.bat",
+    "aTestJe.bat",
+    "aTestje.bat",
+    "b.bat",
+    "c.bat",
+    "d.bat",
+    "e.bat",
+    "f.bat",
+    "g.bat",
+    "h.bat",
+    "x.bat",
+    "z.bat",
+};
+
+static const char *g_apszSUBDIREntries[] =
+{
+    ".",
+    "..",
+    "a.bat",
+    "aTestJe.bat",
+    "aTestje.bat",
+    "b.bat",
+    "c.bat",
+    "d.bat",
+    "e.bat",
+    "f.bat",
+    "g.bat",
+    "h.bat",
+    "x.bat",
+    "z.bat",
+};
+
+int rtDirOpenFiltered(RTDIR *phDir, const char *pszPath, RTDIRFILTER enmFilter, uint32_t fFlags)
+{
+    RT_NOREF2(enmFilter, fFlags);
+    if (!strcmp(pszPath, "c:\\*"))
+        iDirList = 1;
+    else if (!strcmp(pszPath, "c:\\test dir\\*"))
+        iDirList = 2;
+    else if (!strcmp(pszPath, "c:\\test dir\\SUBDIR\\*"))
+        iDirList = 3;
+    else
+        AssertFailed();
+
+    *phDir = (RTDIR)1;
+    return VINF_SUCCESS;
+}
+
+int rtDirClose(RTDIR hDir)
+{
+    RT_NOREF1(hDir);
+    iDirFile = 0;
+    return VINF_SUCCESS;
+}
+
+int rtDirReadEx(RTDIR hDir, PRTDIRENTRYEX pDirEntry, size_t *pcbDirEntry, RTFSOBJATTRADD enmAdditionalAttribs, uint32_t fFlags)
+{
+    RT_NOREF4(hDir, pcbDirEntry, enmAdditionalAttribs, fFlags);
+    switch (iDirList)
+    {
+        case 1:
+            if (iDirFile == RT_ELEMENTS(g_apszDirsC))
+                return VERR_NO_MORE_FILES;
+            pDirEntry->cbName = (uint16_t)strlen(g_apszDirsC[iDirFile]);
+            strcpy(pDirEntry->szName, g_apszDirsC[iDirFile++]);
+            break;
+        case 2:
+            if (iDirFile == RT_ELEMENTS(g_apszTestdirEntries))
+                return VERR_NO_MORE_FILES;
+            pDirEntry->cbName = (uint16_t)strlen(g_apszTestdirEntries[iDirFile]);
+            strcpy(pDirEntry->szName, g_apszTestdirEntries[iDirFile++]);
+            break;
+        case 3:
+            if (iDirFile == RT_ELEMENTS(g_apszSUBDIREntries))
+                return VERR_NO_MORE_FILES;
+            pDirEntry->cbName = (uint16_t)strlen(g_apszSUBDIREntries[iDirFile]);
+            strcpy(pDirEntry->szName, g_apszSUBDIREntries[iDirFile++]);
+            break;
+    }
+    return VINF_SUCCESS;
+}
+
+int rtPathQueryInfo(const char *pszPath, PRTFSOBJINFO pObjInfo, RTFSOBJATTRADD enmAdditionalAttribs)
+{
+    RT_NOREF2(pObjInfo, enmAdditionalAttribs);
+    int cMax;
+
+    /* first try g_apszDirs */
+    for (unsigned int i=0;i<RT_ELEMENTS(g_apszDirs);i++)
+    {
+        if(!strcmp(pszPath, g_apszDirs[i]))
+            return VINF_SUCCESS;
+    }
+
+    const char **papszDirList;
+    switch (iDirList)
+    {
+        case 1:
+            cMax = RT_ELEMENTS(g_apszDirsC);
+            papszDirList = g_apszDirsC;
+            break;
+        case 2:
+            cMax = RT_ELEMENTS(g_apszTestdirEntries);
+            papszDirList = g_apszTestdirEntries;
+            break;
+        case 3:
+            cMax = RT_ELEMENTS(g_apszSUBDIREntries);
+            papszDirList = g_apszSUBDIREntries;
+            break;
+        default:
+            return VERR_FILE_NOT_FOUND;
+    }
+    for (int i = 0; i < cMax; i++)
+    {
+        if (!strcmp(pszPath, papszDirList[i]))
+            return VINF_SUCCESS;
+    }
+    return VERR_FILE_NOT_FOUND;
+}
+
+static int vbsfCorrectCasing(char *pszFullPath, char *pszStartComponent)
+{
+    PRTDIRENTRYEX  pDirEntry = NULL;
+    uint32_t       cbDirEntry;
+    size_t         cbComponent;
+    int            rc = VERR_FILE_NOT_FOUND;
+    RTDIR          hSearch = NIL_RTDIR;
+    char           szWildCard[4];
+
+    Log2(("vbsfCorrectCasing: %s %s\n", pszFullPath, pszStartComponent));
+
+    cbComponent = strlen(pszStartComponent);
+
+    cbDirEntry = 4096;
+    pDirEntry  = (PRTDIRENTRYEX)RTMemAlloc(cbDirEntry);
+    if (pDirEntry == 0)
+    {
+        AssertFailed();
+        return VERR_NO_MEMORY;
+    }
+
+    /** @todo this is quite inefficient, especially for directories with many files */
+    Assert(pszFullPath < pszStartComponent-1);
+    Assert(*(pszStartComponent-1) == RTPATH_DELIMITER);
+    *(pszStartComponent-1) = 0;
+    strcpy(pDirEntry->szName, pszFullPath);
+    szWildCard[0] = RTPATH_DELIMITER;
+    szWildCard[1] = '*';
+    szWildCard[2] = 0;
+    strcat(pDirEntry->szName, szWildCard);
+
+    rc = RTDirOpenFiltered(&hSearch, pDirEntry->szName, RTDIRFILTER_WINNT, 0 /*fFlags*/);
+    *(pszStartComponent-1) = RTPATH_DELIMITER;
+    if (RT_FAILURE(rc))
+        goto end;
+
+    for(;;)
+    {
+        size_t cbDirEntrySize = cbDirEntry;
+
+        rc = RTDirReadEx(hSearch, pDirEntry, &cbDirEntrySize, RTFSOBJATTRADD_NOTHING, RTPATH_F_FOLLOW_LINK);
+        if (rc == VERR_NO_MORE_FILES)
+            break;
+
+        if (VINF_SUCCESS != rc && rc != VWRN_NO_DIRENT_INFO)
+        {
+            AssertFailed();
+            if (rc != VERR_NO_TRANSLATION)
+                break;
+            else
+                continue;
+        }
+
+        Log2(("vbsfCorrectCasing: found %s\n", &pDirEntry->szName[0]));
+        if (    pDirEntry->cbName == cbComponent
+            &&  !RTStrICmp(pszStartComponent, &pDirEntry->szName[0]))
+        {
+            Log(("Found original name %s (%s)\n", &pDirEntry->szName[0], pszStartComponent));
+            strcpy(pszStartComponent, &pDirEntry->szName[0]);
+            rc = VINF_SUCCESS;
+            break;
+        }
+    }
+    if (RT_FAILURE(rc))
+        Log(("vbsfCorrectCasing %s failed with %d\n", pszStartComponent, rc));
+
+end:
+    if (pDirEntry)
+        RTMemFree(pDirEntry);
+
+    if (hSearch)
+        RTDirClose(hSearch);
+    return rc;
+}
+
+
+
+int testCase(char *pszFullPath, bool fWildCard = false)
+{
+    int rc;
+    RTFSOBJINFO info;
+    char *pszWildCardComponent = NULL;
+
+    if (fWildCard)
+    {
+        /* strip off the last path component, that contains the wildcard(s) */
+        size_t   len = strlen(pszFullPath);
+        char    *src = pszFullPath + len - 1;
+
+        while(src > pszFullPath)
+        {
+            if (*src == RTPATH_DELIMITER)
+                break;
+            src--;
+        }
+        if (*src == RTPATH_DELIMITER)
+        {
+            bool fHaveWildcards = false;
+            char *temp = src;
+
+            while(*temp)
+            {
+                char uc = *temp;
+                /** @todo should depend on the guest OS */
+                if (uc == '*' || uc == '?' || uc == '>' || uc == '<' || uc == '"')
+                {
+                    fHaveWildcards = true;
+                    break;
+                }
+                temp++;
+            }
+
+            if (fHaveWildcards)
+            {
+                pszWildCardComponent = src;
+                *pszWildCardComponent = 0;
+            }
+        }
+    }
+
+    rc = RTPathQueryInfo(pszFullPath, &info, RTFSOBJATTRADD_NOTHING);
+    if (rc == VERR_FILE_NOT_FOUND || rc == VERR_PATH_NOT_FOUND)
+    {
+        size_t   len = strlen(pszFullPath);
+        char    *src = pszFullPath + len - 1;
+
+        Log(("Handle case insensitive guest fs on top of host case sensitive fs for %s\n", pszFullPath));
+
+        /* Find partial path that's valid */
+        while(src > pszFullPath)
+        {
+            if (*src == RTPATH_DELIMITER)
+            {
+                *src = 0;
+                rc = RTPathQueryInfo (pszFullPath, &info, RTFSOBJATTRADD_NOTHING);
+                *src = RTPATH_DELIMITER;
+                if (rc == VINF_SUCCESS)
+                {
+#ifdef DEBUG
+                    *src = 0;
+                    Log(("Found valid partial path %s\n", pszFullPath));
+                    *src = RTPATH_DELIMITER;
+#endif
+                    break;
+                }
+            }
+
+            src--;
+        }
+        Assert(*src == RTPATH_DELIMITER && RT_SUCCESS(rc));
+        if (    *src == RTPATH_DELIMITER
+            &&  RT_SUCCESS(rc))
+        {
+            src++;
+            for(;;)
+            {
+                char *end = src;
+                bool fEndOfString = true;
+
+                while(*end)
+                {
+                    if (*end == RTPATH_DELIMITER)
+                        break;
+                    end++;
+                }
+
+                if (*end == RTPATH_DELIMITER)
+                {
+                    fEndOfString = false;
+                    *end = 0;
+                    rc = RTPathQueryInfo(src, &info, RTFSOBJATTRADD_NOTHING);
+                    Assert(rc == VINF_SUCCESS || rc == VERR_FILE_NOT_FOUND || rc == VERR_PATH_NOT_FOUND);
+                }
+                else
+                if (end == src)
+                    rc = VINF_SUCCESS;  /* trailing delimiter */
+                else
+                    rc = VERR_FILE_NOT_FOUND;
+
+                if (rc == VERR_FILE_NOT_FOUND || rc == VERR_PATH_NOT_FOUND)
+                {
+                    /* path component is invalid; try to correct the casing */
+                    rc = vbsfCorrectCasing(pszFullPath, src);
+                    if (RT_FAILURE(rc))
+                    {
+                        if (!fEndOfString)
+                              *end = RTPATH_DELIMITER;
+                        break;
+                    }
+                }
+
+                if (fEndOfString)
+                    break;
+
+                *end = RTPATH_DELIMITER;
+                src = end + 1;
+            }
+            if (RT_FAILURE(rc))
+                Log(("Unable to find suitable component rc=%d\n", rc));
+        }
+        else
+            rc = VERR_FILE_NOT_FOUND;
+
+    }
+    if (pszWildCardComponent)
+        *pszWildCardComponent = RTPATH_DELIMITER;
+
+    if (RT_SUCCESS(rc))
+        Log(("New valid path %s\n", pszFullPath));
+    else
+        Log(("Old invalid path %s\n", pszFullPath));
+    return rc;
+}
+
+
+int main()
+{
+    char szTest[128];
+
+    RTR3InitExeNoArguments(0);
+    RTLogFlush(NULL);
+    RTLogDestinations(NULL, "stdout");
+    RTLogGroupSettings(NULL, "misc=~0");
+    RTLogFlags(NULL, "unbuffered");
+
+    strcpy(szTest, "c:\\test Dir\\z.bAt");
+    testCase(szTest);
+    strcpy(szTest, "c:\\test dir\\z.bAt");
+    testCase(szTest);
+    strcpy(szTest, "c:\\test dir\\SUBDIR\\z.bAt");
+    testCase(szTest);
+    strcpy(szTest, "c:\\test dir\\SUBDiR\\atestje.bat");
+    testCase(szTest);
+    strcpy(szTest, "c:\\TEST dir\\subDiR\\aTestje.baT");
+    testCase(szTest);
+    strcpy(szTest, "c:\\TEST dir\\subDiR\\*");
+    testCase(szTest, true);
+    strcpy(szTest, "c:\\TEST dir\\subDiR\\");
+    testCase(szTest ,true);
+    strcpy(szTest, "c:\\test dir\\SUBDIR\\");
+    testCase(szTest);
+    strcpy(szTest, "c:\\test dir\\invalid\\SUBDIR\\test.bat");
+    testCase(szTest);
+    return 0;
+}
+
diff --git a/src/VBox/HostServices/SharedFolders/testcase/tstShflSizes.cpp b/src/VBox/HostServices/SharedFolders/testcase/tstShflSizes.cpp
new file mode 100644
index 00000000..c9832493
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/testcase/tstShflSizes.cpp
@@ -0,0 +1,144 @@
+/** @file
+ * tstShflSize - Testcase for shared folder structure sizes.
+ * Run this on Linux and Windows, then compare.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#include <VBox/shflsvc.h>
+#include <iprt/string.h>
+#include <iprt/stream.h>
+
+#define STRUCT(t, size)   \
+    do { \
+        if (fPrintChecks) \
+            RTPrintf("    STRUCT(" #t ", %d);\n", (int)sizeof(t)); \
+        else if ((size) != sizeof(t)) \
+        { \
+            RTPrintf("%30s: %d expected %d!\n", #t, (int)sizeof(t), (size)); \
+            cErrors++; \
+        } \
+        else if (!fQuiet)\
+            RTPrintf("%30s: %d\n", #t, (int)sizeof(t)); \
+    } while (0)
+
+
+int main(int argc, char **argv)
+{
+    unsigned cErrors = 0;
+
+    /*
+     * Prints the code below if any argument was giving.
+     */
+    bool fQuiet = argc == 2 && !strcmp(argv[1], "quiet");
+    bool fPrintChecks = !fQuiet && argc != 1;
+
+    RTPrintf("tstShflSizes: TESTING\n");
+
+    /*
+     * The checks.
+     */
+    STRUCT(SHFLROOT, 4);
+    STRUCT(SHFLHANDLE, 8);
+    STRUCT(SHFLSTRING, 6);
+    STRUCT(SHFLCREATERESULT, 4);
+    STRUCT(SHFLCREATEPARMS, 108);
+    STRUCT(SHFLMAPPING, 8);
+    STRUCT(SHFLDIRINFO, 128);
+    STRUCT(SHFLVOLINFO, 40);
+    STRUCT(SHFLFSOBJATTR, 44);
+    STRUCT(SHFLFSOBJINFO, 92);
+#ifdef VBOX_WITH_64_BITS_GUESTS
+/* The size of the guest structures depends on the current architecture bit count (ARCH_BITS)
+ * because the HGCMFunctionParameter structure differs in 32 and 64 bit guests.
+ * The host VMMDev device takes care about this.
+ *
+ * Therefore this testcase verifies whether structure sizes are correct for the current ARCH_BITS.
+ */
+# if ARCH_BITS == 64
+    STRUCT(VBoxSFQueryMappings, 88);
+    STRUCT(VBoxSFQueryMapName, 72);
+    STRUCT(VBoxSFMapFolder_Old, 88);
+    STRUCT(VBoxSFMapFolder, 104);
+    STRUCT(VBoxSFUnmapFolder, 56);
+    STRUCT(VBoxSFCreate, 88);
+    STRUCT(VBoxSFClose, 72);
+    STRUCT(VBoxSFRead, 120);
+    STRUCT(VBoxSFWrite, 120);
+    STRUCT(VBoxSFLock, 120);
+    STRUCT(VBoxSFFlush, 72);
+    STRUCT(VBoxSFList, 168);
+    STRUCT(VBoxSFInformation, 120);
+    STRUCT(VBoxSFRemove, 88);
+    STRUCT(VBoxSFRename, 104);
+# elif ARCH_BITS == 32
+    STRUCT(VBoxSFQueryMappings, 24+52);
+    STRUCT(VBoxSFQueryMapName, 24+40); /* this was changed from 52 in 21976 after VBox-1.4. */
+    STRUCT(VBoxSFMapFolder_Old, 24+52);
+    STRUCT(VBoxSFMapFolder, 24+64);
+    STRUCT(VBoxSFUnmapFolder, 24+28);
+    STRUCT(VBoxSFCreate, 24+52);
+    STRUCT(VBoxSFClose, 24+40);
+    STRUCT(VBoxSFRead, 24+76);
+    STRUCT(VBoxSFWrite, 24+76);
+    STRUCT(VBoxSFLock, 24+76);
+    STRUCT(VBoxSFFlush, 24+40);
+    STRUCT(VBoxSFList, 24+112);
+    STRUCT(VBoxSFInformation, 24+76);
+    STRUCT(VBoxSFRemove, 24+52);
+    STRUCT(VBoxSFRename, 24+64);
+# else
+#  error "Unsupported ARCH_BITS"
+# endif /* ARCH_BITS */
+#else
+    STRUCT(VBoxSFQueryMappings, 24+52);
+    STRUCT(VBoxSFQueryMapName, 24+40); /* this was changed from 52 in 21976 after VBox-1.4. */
+    STRUCT(VBoxSFMapFolder_Old, 24+52);
+    STRUCT(VBoxSFMapFolder, 24+64);
+    STRUCT(VBoxSFUnmapFolder, 24+28);
+    STRUCT(VBoxSFCreate, 24+52);
+    STRUCT(VBoxSFClose, 24+40);
+    STRUCT(VBoxSFRead, 24+76);
+    STRUCT(VBoxSFWrite, 24+76);
+    STRUCT(VBoxSFLock, 24+76);
+    STRUCT(VBoxSFFlush, 24+40);
+    STRUCT(VBoxSFList, 24+112);
+    STRUCT(VBoxSFInformation, 24+76);
+    STRUCT(VBoxSFRemove, 24+52);
+    STRUCT(VBoxSFRename, 24+64);
+#endif /* VBOX_WITH_64_BITS_GUESTS */
+
+    /*
+     * The summary.
+     */
+    if (!cErrors)
+        RTPrintf("tstShflSizes: SUCCESS\n");
+    else
+        RTPrintf("tstShflSizes: FAILURE - %d errors\n", cErrors);
+    return !!cErrors;
+}
+
diff --git a/src/VBox/HostServices/SharedFolders/teststubs.h b/src/VBox/HostServices/SharedFolders/teststubs.h
new file mode 100644
index 00000000..c7478621
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/teststubs.h
@@ -0,0 +1,104 @@
+/** @file
+ * VBox Shared Folders testcase stub redefinitions.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+/**
+ * Macros for renaming iprt file operations to redirect them to testcase
+ * stub functions (mocks).  The religiously correct way to do this would be
+ * to make the service use a file operations structure with function pointers
+ * but I'm not sure that would be universally appreciated. */
+
+#ifndef VBOX_INCLUDED_SRC_SharedFolders_teststubs_h
+#define VBOX_INCLUDED_SRC_SharedFolders_teststubs_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <iprt/dir.h>
+#include <iprt/file.h>
+#include <iprt/time.h>
+
+#define RTDirClose           testRTDirClose
+extern int testRTDirClose(RTDIR hDir);
+#define RTDirCreate          testRTDirCreate
+extern int testRTDirCreate(const char *pszPath, RTFMODE fMode, uint32_t fCreate);
+#define RTDirOpen            testRTDirOpen
+extern int testRTDirOpen(RTDIR *phDir, const char *pszPath);
+#define RTDirOpenFiltered    testRTDirOpenFiltered
+extern int testRTDirOpenFiltered(RTDIR *phDir, const char *pszPath, RTDIRFILTER enmFilter, uint32_t fFlags);
+#define RTDirQueryInfo       testRTDirQueryInfo
+extern int testRTDirQueryInfo(RTDIR hDir, PRTFSOBJINFO pObjInfo, RTFSOBJATTRADD enmAdditionalAttribs);
+#define RTDirRemove          testRTDirRemove
+extern int testRTDirRemove(const char *pszPath);
+#define RTDirReadEx          testRTDirReadEx
+extern int testRTDirReadEx(RTDIR hDir, PRTDIRENTRYEX pDirEntry, size_t *pcbDirEntry, RTFSOBJATTRADD enmAdditionalAttribs, uint32_t fFlags);
+#define RTDirSetMode         testRTDirSetMode
+extern int testRTDirSetMode(RTDIR hDir, RTFMODE fMode);
+#define RTDirSetTimes        testRTDirSetTimes
+extern int testRTDirSetTimes(RTDIR hDir, PCRTTIMESPEC pAccessTime, PCRTTIMESPEC pModificationTime, PCRTTIMESPEC pChangeTime, PCRTTIMESPEC pBirthTime);
+#define RTFileClose          testRTFileClose
+extern int testRTFileClose(RTFILE hFile);
+#define RTFileDelete         testRTFileDelete
+extern int testRTFileDelete(const char *pszFilename);
+#define RTFileFlush          testRTFileFlush
+extern int testRTFileFlush(RTFILE hFile);
+#define RTFileLock           testRTFileLock
+extern int testRTFileLock(RTFILE hFile, unsigned fLock, int64_t offLock, uint64_t cbLock);
+#define RTFileOpenEx         testRTFileOpenEx
+extern int testRTFileOpenEx(const char *pszFilename, uint64_t fOpen, PRTFILE phFile, PRTFILEACTION penmActionTaken);
+#define RTFileQueryInfo      testRTFileQueryInfo
+extern int testRTFileQueryInfo(RTFILE hFile, PRTFSOBJINFO pObjInfo, RTFSOBJATTRADD enmAdditionalAttribs);
+#define RTFileRead           testRTFileRead
+extern int testRTFileRead(RTFILE hFile, void *pvBuf, size_t cbToRead, size_t *pcbRead);
+#define RTFileReadAt         testRTFileReadAt
+extern int testRTFileReadAt(RTFILE hFile, uint64_t offFile, void *pvBuf, size_t cbToRead, size_t *pcbRead);
+#define RTFileSetMode        testRTFileSetMode
+extern int testRTFileSetMode(RTFILE hFile, RTFMODE fMode);
+#define RTFileSetSize        testRTFileSetSize
+extern int testRTFileSetSize(RTFILE hFile, uint64_t cbSize);
+#define RTFileSetTimes       testRTFileSetTimes
+extern int testRTFileSetTimes(RTFILE hFile, PCRTTIMESPEC pAccessTime, PCRTTIMESPEC pModificationTime, PCRTTIMESPEC pChangeTime, PCRTTIMESPEC pBirthTime);
+#define RTFileSeek           testRTFileSeek
+extern int testRTFileSeek(RTFILE hFile, int64_t offSeek, unsigned uMethod, uint64_t *poffActual);
+#define RTFileUnlock         testRTFileUnlock
+extern int testRTFileUnlock(RTFILE hFile, int64_t offLock, uint64_t cbLock);
+#define RTFileWrite          testRTFileWrite
+extern int testRTFileWrite(RTFILE hFile, const void *pvBuf, size_t cbToWrite, size_t *pcbWritten);
+#define RTFileWriteAt        testRTFileWriteAt
+extern int testRTFileWriteAt(RTFILE hFile, uint64_t offFile, const void *pvBuf, size_t cbToWrite, size_t *pcbWritten);
+#define RTFsQueryProperties  testRTFsQueryProperties
+extern int testRTFsQueryProperties(const char *pszFsPath, PRTFSPROPERTIES pProperties);
+#define RTFsQuerySerial      testRTFsQuerySerial
+extern int testRTFsQuerySerial(const char *pszFsPath, uint32_t *pu32Serial);
+#define RTFsQuerySizes       testRTFsQuerySizes
+extern int testRTFsQuerySizes(const char *pszFsPath, RTFOFF *pcbTotal, RTFOFF *pcbFree, uint32_t *pcbBlock, uint32_t *pcbSector);
+#define RTPathQueryInfoEx    testRTPathQueryInfoEx
+extern int testRTPathQueryInfoEx(const char *pszPath, PRTFSOBJINFO pObjInfo, RTFSOBJATTRADD enmAdditionalAttribs, uint32_t fFlags);
+#define RTSymlinkDelete      testRTSymlinkDelete
+extern int testRTSymlinkDelete(const char *pszSymlink, uint32_t fDelete);
+#define RTSymlinkRead        testRTSymlinkRead
+extern int testRTSymlinkRead(const char *pszSymlink, char *pszTarget, size_t cbTarget, uint32_t fRead);
+
+#endif /* !VBOX_INCLUDED_SRC_SharedFolders_teststubs_h */
diff --git a/src/VBox/HostServices/SharedFolders/vbsf.cpp b/src/VBox/HostServices/SharedFolders/vbsf.cpp
new file mode 100644
index 00000000..59907584
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/vbsf.cpp
@@ -0,0 +1,2690 @@
+/* $Id: vbsf.cpp $ */
+/** @file
+ * Shared Folders - VBox Shared Folders.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_FOLDERS
+#ifdef UNITTEST
+# include "testcase/tstSharedFolderService.h"
+#endif
+
+#include "vbsfpath.h"
+#include "mappings.h"
+#include "vbsf.h"
+#include "shflhandle.h"
+
+#include <VBox/AssertGuest.h>
+#include <VBox/param.h>
+#include <iprt/alloc.h>
+#include <iprt/assert.h>
+#include <iprt/asm.h>
+#include <iprt/fs.h>
+#include <iprt/dir.h>
+#include <iprt/file.h>
+#include <iprt/path.h>
+#include <iprt/string.h>
+#include <iprt/symlink.h>
+#include <iprt/uni.h>
+#include <iprt/stream.h>
+#ifdef RT_OS_DARWIN
+# include <Carbon/Carbon.h>
+#endif
+
+#ifdef UNITTEST
+# include "teststubs.h"
+#endif
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+#define SHFL_RT_LINK(pClient) ((pClient)->fu32Flags & SHFL_CF_SYMLINKS ? RTPATH_F_ON_LINK : RTPATH_F_FOLLOW_LINK)
+
+/**
+ * @todo find a better solution for supporting the execute bit for non-windows
+ * guests on windows host. Search for "0111" to find all the relevant places.
+ */
+
+
+#ifndef RT_OS_WINDOWS
+
+/**
+ * Helps to check if pszPath deserves a VERR_PATH_NOT_FOUND status when catering
+ * to windows guests.
+ */
+static bool vbsfErrorStyleIsWindowsPathNotFound(char *pszPath)
+{
+    /*
+     * Check if the parent directory actually exists.  We temporarily modify the path here.
+     */
+    size_t cchParent = RTPathParentLength(pszPath);
+    char chSaved = pszPath[cchParent];
+    pszPath[cchParent] = '\0';
+    RTFSOBJINFO ObjInfo;
+    int vrc = RTPathQueryInfoEx(pszPath, &ObjInfo, RTFSOBJATTRADD_NOTHING, RTPATH_F_FOLLOW_LINK);
+    pszPath[cchParent] = chSaved;
+    if (RT_SUCCESS(vrc))
+    {
+        if (RTFS_IS_DIRECTORY(ObjInfo.Attr.fMode))
+            return false;
+        return true;
+    }
+    if (vrc == VERR_FILE_NOT_FOUND || vrc == VERR_PATH_NOT_FOUND)
+        return true;
+    return false;
+}
+
+/**
+ * Helps to check if pszPath deserves a VERR_PATH_NOT_FOUND status when catering
+ * to windows guests.
+ */
+static bool vbsfErrorStyleIsWindowsPathNotFound2(char *pszSrcPath, char *pszDstPath)
+{
+    /*
+     * Do the source parent first.
+     */
+    size_t cchParent = RTPathParentLength(pszSrcPath);
+    char chSaved = pszSrcPath[cchParent];
+    pszSrcPath[cchParent] = '\0';
+    RTFSOBJINFO ObjInfo;
+    int vrc = RTPathQueryInfoEx(pszSrcPath, &ObjInfo, RTFSOBJATTRADD_NOTHING, RTPATH_F_FOLLOW_LINK);
+    pszSrcPath[cchParent] = chSaved;
+    if (   (RT_SUCCESS(vrc) && !RTFS_IS_DIRECTORY(ObjInfo.Attr.fMode))
+        || vrc == VERR_FILE_NOT_FOUND
+        || vrc == VERR_PATH_NOT_FOUND)
+        return true;
+    if (RT_FAILURE(vrc))
+        return false;
+
+    /*
+     * The source itself.
+     */
+    vrc = RTPathQueryInfoEx(pszSrcPath, &ObjInfo, RTFSOBJATTRADD_NOTHING, RTPATH_F_FOLLOW_LINK);
+    if (RT_SUCCESS(vrc))
+    {
+        /*
+         * The source is fine, continue with the destination.
+         */
+        cchParent = RTPathParentLength(pszDstPath);
+        chSaved = pszDstPath[cchParent];
+        pszDstPath[cchParent] = '\0';
+        vrc = RTPathQueryInfoEx(pszDstPath, &ObjInfo, RTFSOBJATTRADD_NOTHING, RTPATH_F_FOLLOW_LINK);
+        pszDstPath[cchParent] = chSaved;
+        if (   (RT_SUCCESS(vrc) && !RTFS_IS_DIRECTORY(ObjInfo.Attr.fMode))
+            || vrc == VERR_FILE_NOT_FOUND
+            || vrc == VERR_PATH_NOT_FOUND)
+            return true;
+    }
+    return false;
+}
+
+/**
+ * Helps checking if the specified path happens to exist but not be a directory.
+ */
+static bool vbsfErrorStyleIsWindowsNotADirectory(const char *pszPath)
+{
+    RTFSOBJINFO ObjInfo;
+    int vrc = RTPathQueryInfoEx(pszPath, &ObjInfo, RTFSOBJATTRADD_NOTHING, RTPATH_F_FOLLOW_LINK);
+    if (RT_SUCCESS(vrc))
+    {
+        if (RTFS_IS_DIRECTORY(ObjInfo.Attr.fMode))
+            return false;
+        return true;
+    }
+    return false;
+}
+
+/**
+ * Helps to check if pszPath deserves a VERR_INVALID_NAME status when catering
+ * to windows guests.
+ */
+static bool vbsfErrorStyleIsWindowsInvalidNameForNonDir(char *pszPath)
+{
+    /*
+     * This only applies to paths with trailing slashes.
+     */
+    size_t const cchPath = strlen(pszPath);
+    if (cchPath > 0 && RTPATH_IS_SLASH(pszPath[cchPath - 1]))
+    {
+        /*
+         * However it doesn't if an earlier path component is missing or not a file.
+         */
+        size_t cchParent = RTPathParentLength(pszPath);
+        char chSaved = pszPath[cchParent];
+        pszPath[cchParent] = '\0';
+        RTFSOBJINFO ObjInfo;
+        int vrc = RTPathQueryInfoEx(pszPath, &ObjInfo, RTFSOBJATTRADD_NOTHING, RTPATH_F_FOLLOW_LINK);
+        pszPath[cchParent] = chSaved;
+        if (RT_SUCCESS(vrc) && RTFS_IS_DIRECTORY(ObjInfo.Attr.fMode))
+            return true;
+    }
+    return false;
+}
+
+#endif /* RT_OS_WINDOWS */
+
+void vbsfStripLastComponent(char *pszFullPath, uint32_t cbFullPathRoot)
+{
+    RTUNICP cp;
+
+    /* Do not strip root. */
+    char *s = pszFullPath + cbFullPathRoot;
+    char *delimSecondLast = NULL;
+    char *delimLast = NULL;
+
+    LogFlowFunc(("%s -> %s\n", pszFullPath, s));
+
+    for (;;)
+    {
+        cp = RTStrGetCp(s);
+
+        if (cp == RTUNICP_INVALID || cp == 0)
+        {
+            break;
+        }
+
+        if (cp == RTPATH_DELIMITER)
+        {
+            if (delimLast != NULL)
+            {
+                delimSecondLast = delimLast;
+            }
+
+            delimLast = s;
+        }
+
+        s = RTStrNextCp(s);
+    }
+
+    if (cp == 0)
+    {
+        if (delimLast + 1 == s)
+        {
+            if (delimSecondLast)
+            {
+                *delimSecondLast = 0;
+            }
+            else if (delimLast)
+            {
+                *delimLast = 0;
+            }
+        }
+        else
+        {
+            if (delimLast)
+            {
+                *delimLast = 0;
+            }
+        }
+    }
+
+    LogFlowFunc(("%s, %s, %s\n", pszFullPath, delimLast, delimSecondLast));
+}
+
+static int vbsfBuildFullPath(SHFLCLIENTDATA *pClient, SHFLROOT root, PCSHFLSTRING pPath,
+                             uint32_t cbPath, char **ppszFullPath, uint32_t *pcbFullPathRoot,
+                             bool fWildCard = false, bool fPreserveLastComponent = false)
+{
+    char *pszHostPath = NULL;
+    uint32_t fu32PathFlags = 0;
+    uint32_t fu32Options =   VBSF_O_PATH_CHECK_ROOT_ESCAPE
+                           | (fWildCard? VBSF_O_PATH_WILDCARD: 0)
+                           | (fPreserveLastComponent? VBSF_O_PATH_PRESERVE_LAST_COMPONENT: 0);
+
+    int rc = vbsfPathGuestToHost(pClient, root, pPath, cbPath,
+                                 &pszHostPath, pcbFullPathRoot, fu32Options, &fu32PathFlags);
+    if (BIT_FLAG(pClient->fu32Flags, SHFL_CF_UTF8))
+    {
+        LogRel2(("SharedFolders: GuestToHost 0x%RX32 [%.*s]->[%s] %Rrc\n", fu32PathFlags, pPath->u16Length, &pPath->String.utf8[0], pszHostPath, rc));
+    }
+    else
+    {
+        LogRel2(("SharedFolders: GuestToHost 0x%RX32 [%.*ls]->[%s] %Rrc\n", fu32PathFlags, pPath->u16Length / 2, &pPath->String.ucs2[0], pszHostPath, rc));
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        if (ppszFullPath)
+            *ppszFullPath = pszHostPath;
+    }
+    return rc;
+}
+
+static void vbsfFreeFullPath(char *pszFullPath)
+{
+    vbsfFreeHostPath(pszFullPath);
+}
+
+typedef enum VBSFCHECKACCESS
+{
+    VBSF_CHECK_ACCESS_READ = 0,
+    VBSF_CHECK_ACCESS_WRITE = 1
+} VBSFCHECKACCESS;
+
+/**
+ * Check if the handle data is valid and the operation is allowed on the shared folder.
+ *
+ * @returns IPRT status code
+ * @param  pClient               Data structure describing the client accessing the shared folder
+ * @param  root                  The index of the shared folder in the table of mappings.
+ * @param  pHandle               Information about the file or directory object.
+ * @param  enmCheckAccess        Whether the operation needs read only or write access.
+ */
+static int vbsfCheckHandleAccess(SHFLCLIENTDATA *pClient, SHFLROOT root,
+                                 SHFLFILEHANDLE *pHandle, VBSFCHECKACCESS enmCheckAccess)
+{
+    /* Handle from the same 'root' index? */
+    if (RT_LIKELY(RT_VALID_PTR(pHandle) && root == pHandle->root))
+    { /* likely */ }
+    else
+        return VERR_INVALID_HANDLE;
+
+    /* Check if the guest is still allowed to access this share.
+     * vbsfMappingsQueryWritable returns error if the shared folder has been removed from the VM settings.
+     */
+    bool fWritable;
+    int rc = vbsfMappingsQueryWritable(pClient, root, &fWritable);
+    if (RT_SUCCESS(rc))
+    { /* likely */ }
+    else
+        return VERR_ACCESS_DENIED;
+
+    if (enmCheckAccess == VBSF_CHECK_ACCESS_WRITE)
+    {
+        /* Operation requires write access. Check if the shared folder is writable too. */
+        if (RT_LIKELY(fWritable))
+        { /* likely */ }
+        else
+            return VERR_WRITE_PROTECT;
+    }
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Convert shared folder create flags (see include/iprt/shflsvc.h) into iprt create flags.
+ *
+ * @returns iprt status code
+ * @param  fWritable  whether the shared folder is writable
+ * @param  fShflFlags shared folder create flags
+ * @param  fMode      file attributes
+ * @param  handleInitial initial handle
+ * @param  pfOpen     Where to return iprt create flags
+ */
+static int vbsfConvertFileOpenFlags(bool fWritable, unsigned fShflFlags, RTFMODE fMode, SHFLHANDLE handleInitial, uint64_t *pfOpen)
+{
+    uint64_t fOpen = 0;
+    int rc = VINF_SUCCESS;
+
+    if (   (fMode & RTFS_DOS_MASK) != 0
+        && (fMode & RTFS_UNIX_MASK) == 0)
+    {
+        /* A DOS/Windows guest, make RTFS_UNIX_* from RTFS_DOS_*.
+         * @todo this is based on rtFsModeNormalize/rtFsModeFromDos.
+         *       May be better to use RTFsModeNormalize here.
+         */
+        fMode |= RTFS_UNIX_IRUSR | RTFS_UNIX_IRGRP | RTFS_UNIX_IROTH;
+        /* x for directories. */
+        if (fMode & RTFS_DOS_DIRECTORY)
+            fMode |= RTFS_TYPE_DIRECTORY | RTFS_UNIX_IXUSR | RTFS_UNIX_IXGRP | RTFS_UNIX_IXOTH;
+        /* writable? */
+        if (!(fMode & RTFS_DOS_READONLY))
+            fMode |= RTFS_UNIX_IWUSR | RTFS_UNIX_IWGRP | RTFS_UNIX_IWOTH;
+
+        /* Set the requested mode using only allowed bits. */
+        fOpen |= ((fMode & RTFS_UNIX_MASK) << RTFILE_O_CREATE_MODE_SHIFT) & RTFILE_O_CREATE_MODE_MASK;
+    }
+    else
+    {
+        /* Old linux and solaris additions did not initialize the Info.Attr.fMode field
+         * and it contained random bits from stack. Detect this using the handle field value
+         * passed from the guest: old additions set it (incorrectly) to 0, new additions
+         * set it to SHFL_HANDLE_NIL(~0).
+         */
+        if (handleInitial == 0)
+        {
+            /* Old additions. Do nothing, use default mode. */
+        }
+        else
+        {
+            /* New additions or Windows additions. Set the requested mode using only allowed bits.
+             * Note: Windows guest set RTFS_UNIX_MASK bits to 0, which means a default mode
+             *       will be set in fOpen.
+             */
+            fOpen |= ((fMode & RTFS_UNIX_MASK) << RTFILE_O_CREATE_MODE_SHIFT) & RTFILE_O_CREATE_MODE_MASK;
+        }
+    }
+
+    switch (BIT_FLAG(fShflFlags, SHFL_CF_ACCESS_MASK_RW))
+    {
+        default:
+        case SHFL_CF_ACCESS_NONE:
+        {
+#ifdef RT_OS_WINDOWS
+            if (BIT_FLAG(fShflFlags, SHFL_CF_ACCESS_MASK_ATTR) != SHFL_CF_ACCESS_ATTR_NONE)
+                fOpen |= RTFILE_O_ATTR_ONLY;
+            else
+#endif
+                fOpen |= RTFILE_O_READ;
+            Log(("FLAG: SHFL_CF_ACCESS_NONE\n"));
+            break;
+        }
+
+        case SHFL_CF_ACCESS_READ:
+        {
+            fOpen |= RTFILE_O_READ;
+            Log(("FLAG: SHFL_CF_ACCESS_READ\n"));
+            break;
+        }
+
+        case SHFL_CF_ACCESS_WRITE:
+        {
+            fOpen |= RTFILE_O_WRITE;
+            Log(("FLAG: SHFL_CF_ACCESS_WRITE\n"));
+            break;
+        }
+
+        case SHFL_CF_ACCESS_READWRITE:
+        {
+            fOpen |= RTFILE_O_READWRITE;
+            Log(("FLAG: SHFL_CF_ACCESS_READWRITE\n"));
+            break;
+        }
+    }
+
+    if (fShflFlags & SHFL_CF_ACCESS_APPEND)
+    {
+        fOpen |= RTFILE_O_APPEND;
+    }
+
+    switch (BIT_FLAG(fShflFlags, SHFL_CF_ACCESS_MASK_ATTR))
+    {
+        default:
+        case SHFL_CF_ACCESS_ATTR_NONE:
+        {
+            fOpen |= RTFILE_O_ACCESS_ATTR_DEFAULT;
+            Log(("FLAG: SHFL_CF_ACCESS_ATTR_NONE\n"));
+            break;
+        }
+
+        case SHFL_CF_ACCESS_ATTR_READ:
+        {
+            fOpen |= RTFILE_O_ACCESS_ATTR_READ;
+            Log(("FLAG: SHFL_CF_ACCESS_ATTR_READ\n"));
+            break;
+        }
+
+        case SHFL_CF_ACCESS_ATTR_WRITE:
+        {
+            fOpen |= RTFILE_O_ACCESS_ATTR_WRITE;
+            Log(("FLAG: SHFL_CF_ACCESS_ATTR_WRITE\n"));
+            break;
+        }
+
+        case SHFL_CF_ACCESS_ATTR_READWRITE:
+        {
+            fOpen |= RTFILE_O_ACCESS_ATTR_READWRITE;
+            Log(("FLAG: SHFL_CF_ACCESS_ATTR_READWRITE\n"));
+            break;
+        }
+    }
+
+    /* Sharing mask */
+    switch (BIT_FLAG(fShflFlags, SHFL_CF_ACCESS_MASK_DENY))
+    {
+        default:
+        case SHFL_CF_ACCESS_DENYNONE:
+            fOpen |= RTFILE_O_DENY_NONE;
+            Log(("FLAG: SHFL_CF_ACCESS_DENYNONE\n"));
+            break;
+
+        case SHFL_CF_ACCESS_DENYREAD:
+            fOpen |= RTFILE_O_DENY_READ;
+            Log(("FLAG: SHFL_CF_ACCESS_DENYREAD\n"));
+            break;
+
+        case SHFL_CF_ACCESS_DENYWRITE:
+            fOpen |= RTFILE_O_DENY_WRITE;
+            Log(("FLAG: SHFL_CF_ACCESS_DENYWRITE\n"));
+            break;
+
+        case SHFL_CF_ACCESS_DENYALL:
+            fOpen |= RTFILE_O_DENY_ALL;
+            Log(("FLAG: SHFL_CF_ACCESS_DENYALL\n"));
+            break;
+    }
+
+    /* Open/Create action mask */
+    switch (BIT_FLAG(fShflFlags, SHFL_CF_ACT_MASK_IF_EXISTS))
+    {
+        case SHFL_CF_ACT_OPEN_IF_EXISTS:
+            if (SHFL_CF_ACT_CREATE_IF_NEW == BIT_FLAG(fShflFlags, SHFL_CF_ACT_MASK_IF_NEW))
+            {
+                fOpen |= RTFILE_O_OPEN_CREATE;
+                Log(("FLAGS: SHFL_CF_ACT_OPEN_IF_EXISTS and SHFL_CF_ACT_CREATE_IF_NEW\n"));
+            }
+            else if (SHFL_CF_ACT_FAIL_IF_NEW == BIT_FLAG(fShflFlags, SHFL_CF_ACT_MASK_IF_NEW))
+            {
+                fOpen |= RTFILE_O_OPEN;
+                Log(("FLAGS: SHFL_CF_ACT_OPEN_IF_EXISTS and SHFL_CF_ACT_FAIL_IF_NEW\n"));
+            }
+            else
+            {
+                Log(("FLAGS: invalid open/create action combination\n"));
+                rc = VERR_INVALID_PARAMETER;
+            }
+            break;
+        case SHFL_CF_ACT_FAIL_IF_EXISTS:
+            if (SHFL_CF_ACT_CREATE_IF_NEW == BIT_FLAG(fShflFlags, SHFL_CF_ACT_MASK_IF_NEW))
+            {
+                fOpen |= RTFILE_O_CREATE;
+                Log(("FLAGS: SHFL_CF_ACT_FAIL_IF_EXISTS and SHFL_CF_ACT_CREATE_IF_NEW\n"));
+            }
+            else
+            {
+                Log(("FLAGS: invalid open/create action combination\n"));
+                rc = VERR_INVALID_PARAMETER;
+            }
+            break;
+        case SHFL_CF_ACT_REPLACE_IF_EXISTS:
+            if (SHFL_CF_ACT_CREATE_IF_NEW == BIT_FLAG(fShflFlags, SHFL_CF_ACT_MASK_IF_NEW))
+            {
+                fOpen |= RTFILE_O_CREATE_REPLACE;
+                Log(("FLAGS: SHFL_CF_ACT_REPLACE_IF_EXISTS and SHFL_CF_ACT_CREATE_IF_NEW\n"));
+            }
+            else if (SHFL_CF_ACT_FAIL_IF_NEW == BIT_FLAG(fShflFlags, SHFL_CF_ACT_MASK_IF_NEW))
+            {
+                fOpen |= RTFILE_O_OPEN | RTFILE_O_TRUNCATE;
+                Log(("FLAGS: SHFL_CF_ACT_REPLACE_IF_EXISTS and SHFL_CF_ACT_FAIL_IF_NEW\n"));
+            }
+            else
+            {
+                Log(("FLAGS: invalid open/create action combination\n"));
+                rc = VERR_INVALID_PARAMETER;
+            }
+            break;
+        case SHFL_CF_ACT_OVERWRITE_IF_EXISTS:
+            if (SHFL_CF_ACT_CREATE_IF_NEW == BIT_FLAG(fShflFlags, SHFL_CF_ACT_MASK_IF_NEW))
+            {
+                fOpen |= RTFILE_O_CREATE_REPLACE;
+                Log(("FLAGS: SHFL_CF_ACT_OVERWRITE_IF_EXISTS and SHFL_CF_ACT_CREATE_IF_NEW\n"));
+            }
+            else if (SHFL_CF_ACT_FAIL_IF_NEW == BIT_FLAG(fShflFlags, SHFL_CF_ACT_MASK_IF_NEW))
+            {
+                fOpen |= RTFILE_O_OPEN | RTFILE_O_TRUNCATE;
+                Log(("FLAGS: SHFL_CF_ACT_OVERWRITE_IF_EXISTS and SHFL_CF_ACT_FAIL_IF_NEW\n"));
+            }
+            else
+            {
+                Log(("FLAGS: invalid open/create action combination\n"));
+                rc = VERR_INVALID_PARAMETER;
+            }
+            break;
+        default:
+            rc = VERR_INVALID_PARAMETER;
+            Log(("FLAG: SHFL_CF_ACT_MASK_IF_EXISTS - invalid parameter\n"));
+    }
+
+    if (RT_SUCCESS(rc))
+    {
+        if (!fWritable)
+            fOpen &= ~RTFILE_O_WRITE;
+
+        *pfOpen = fOpen;
+    }
+    return rc;
+}
+
+/**
+ * Open a file or create and open a new one.
+ *
+ * @returns IPRT status code
+ * @param  pClient  Data structure describing the client accessing the shared folder
+ * @param  root     The index of the shared folder in the table of mappings.
+ * @param  pszPath  Path to the file or folder on the host.
+ * @param  pParms   Input:
+ *                    - @a CreateFlags: Creation or open parameters, see include/VBox/shflsvc.h
+ *                    - @a Info:        When a new file is created this specifies the initial parameters.
+ *                                      When a file is created or overwritten, it also specifies the
+ *                                      initial size.
+ *                  Output:
+ *                    - @a Result:      Shared folder status code, see include/VBox/shflsvc.h
+ *                    - @a Handle:      On success the (shared folder) handle of the file opened or
+ *                                      created
+ *                    - @a Info:        On success the parameters of the file opened or created
+ */
+static int vbsfOpenFile(SHFLCLIENTDATA *pClient, SHFLROOT root, char *pszPath, SHFLCREATEPARMS *pParms)
+{
+    LogFlow(("vbsfOpenFile: pszPath = %s, pParms = %p\n", pszPath, pParms));
+    Log(("SHFL create flags %08x\n", pParms->CreateFlags));
+
+    RTFILEACTION    enmActionTaken = RTFILEACTION_INVALID;
+    SHFLHANDLE      handle         = SHFL_HANDLE_NIL;
+    SHFLFILEHANDLE *pHandle        = NULL;
+
+    /* is the guest allowed to write to this share? */
+    bool fWritable;
+    int rc = vbsfMappingsQueryWritable(pClient, root, &fWritable);
+    if (RT_FAILURE(rc))
+        fWritable = false;
+
+    uint64_t fOpen = 0;
+    rc = vbsfConvertFileOpenFlags(fWritable, pParms->CreateFlags, pParms->Info.Attr.fMode, pParms->Handle, &fOpen);
+    if (RT_SUCCESS(rc))
+    {
+        rc = VERR_NO_MEMORY;  /* Default error. */
+        handle  = vbsfAllocFileHandle(pClient);
+        if (handle != SHFL_HANDLE_NIL)
+        {
+            pHandle = vbsfQueryFileHandle(pClient, handle);
+            if (pHandle)
+            {
+                pHandle->root = root;
+                pHandle->file.fOpenFlags = fOpen;
+                rc = RTFileOpenEx(pszPath, fOpen, &pHandle->file.Handle, &enmActionTaken);
+            }
+        }
+    }
+    bool fNoError = false;
+    if (RT_FAILURE(rc))
+    {
+        switch (rc)
+        {
+            case VERR_FILE_NOT_FOUND:
+                pParms->Result = SHFL_FILE_NOT_FOUND;
+#ifndef RT_OS_WINDOWS
+                if (   SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(pClient)
+                    && vbsfErrorStyleIsWindowsPathNotFound(pszPath))
+                    pParms->Result = SHFL_PATH_NOT_FOUND;
+#endif
+                /* This actually isn't an error, so correct the rc before return later,
+                   because the driver (VBoxSF.sys) expects rc = VINF_SUCCESS and checks the result code. */
+                fNoError = true;
+                break;
+
+            case VERR_PATH_NOT_FOUND:
+#ifndef RT_OS_WINDOWS
+                if (   SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(pClient)
+                    && vbsfErrorStyleIsWindowsInvalidNameForNonDir(pszPath))
+                {
+                    rc = VERR_INVALID_NAME;
+                    pParms->Result = SHFL_NO_RESULT;
+                    break;
+                }
+#endif
+                pParms->Result = SHFL_PATH_NOT_FOUND;
+                fNoError = true; /* Not an error either (see above). */
+                break;
+
+            case VERR_ALREADY_EXISTS:
+            {
+                RTFSOBJINFO info;
+
+                /** @todo Possible race left here. */
+                if (RT_SUCCESS(RTPathQueryInfoEx(pszPath, &info, RTFSOBJATTRADD_NOTHING, SHFL_RT_LINK(pClient))))
+                {
+#ifdef RT_OS_WINDOWS
+                    info.Attr.fMode |= 0111;
+#endif
+                    vbfsCopyFsObjInfoFromIprt(&pParms->Info, &info);
+                }
+                pParms->Result = SHFL_FILE_EXISTS;
+
+                /* This actually isn't an error, so correct the rc before return later,
+                   because the driver (VBoxSF.sys) expects rc = VINF_SUCCESS and checks the result code. */
+                fNoError = true;
+                break;
+            }
+
+            case VERR_TOO_MANY_OPEN_FILES:
+            {
+                static int s_cErrors;
+                if (s_cErrors < 32)
+                {
+                    LogRel(("SharedFolders host service: Cannot open '%s' -- too many open files.\n", pszPath));
+#if defined RT_OS_LINUX || defined(RT_OS_SOLARIS)
+                    if (s_cErrors < 1)
+                        LogRel(("SharedFolders host service: Try to increase the limit for open files (ulimit -n)\n"));
+#endif
+                    s_cErrors++;
+                }
+                pParms->Result = SHFL_NO_RESULT;
+                break;
+            }
+
+            default:
+                pParms->Result = SHFL_NO_RESULT;
+        }
+    }
+    else
+    {
+        switch (enmActionTaken)
+        {
+            default:
+                AssertFailed();
+                RT_FALL_THRU();
+            case RTFILEACTION_OPENED:
+                pParms->Result = SHFL_FILE_EXISTS;
+                break;
+            case RTFILEACTION_CREATED:
+                pParms->Result = SHFL_FILE_CREATED;
+                break;
+            case RTFILEACTION_REPLACED:
+            case RTFILEACTION_TRUNCATED: /* not quite right */
+                pParms->Result = SHFL_FILE_REPLACED;
+                break;
+        }
+
+        if (   (pParms->CreateFlags & SHFL_CF_ACT_MASK_IF_EXISTS) == SHFL_CF_ACT_REPLACE_IF_EXISTS
+            || (pParms->CreateFlags & SHFL_CF_ACT_MASK_IF_EXISTS) == SHFL_CF_ACT_OVERWRITE_IF_EXISTS)
+        {
+            /* For now, we do not treat a failure here as fatal. */
+            /** @todo Also set the size for SHFL_CF_ACT_CREATE_IF_NEW if SHFL_CF_ACT_FAIL_IF_EXISTS is set. */
+            /** @todo r=bird: Exactly document cbObject usage and see what we can get
+             *        away with here.  I suspect it is only needed for windows and only
+             *        with SHFL_FILE_CREATED and SHFL_FILE_REPLACED, and only if
+             *        cbObject is non-zero. */
+            RTFileSetSize(pHandle->file.Handle, pParms->Info.cbObject);
+        }
+#if 0
+        /** @todo */
+        /* Set new attributes. */
+        if (   (   SHFL_CF_ACT_REPLACE_IF_EXISTS
+                == BIT_FLAG(pParms->CreateFlags, SHFL_CF_ACT_MASK_IF_EXISTS))
+            || (   SHFL_CF_ACT_CREATE_IF_NEW
+                == BIT_FLAG(pParms->CreateFlags, SHFL_CF_ACT_MASK_IF_NEW)))
+        {
+            RTFileSetTimes(pHandle->file.Handle,
+                          &pParms->Info.AccessTime,
+                          &pParms->Info.ModificationTime,
+                          &pParms->Info.ChangeTime,
+                          &pParms->Info.BirthTime
+                          );
+
+            RTFileSetMode (pHandle->file.Handle, pParms->Info.Attr.fMode);
+        }
+#endif
+        RTFSOBJINFO info;
+
+        /* Get file information */
+        rc = RTFileQueryInfo(pHandle->file.Handle, &info, RTFSOBJATTRADD_NOTHING);
+        if (RT_SUCCESS(rc))
+        {
+#ifdef RT_OS_WINDOWS
+            info.Attr.fMode |= 0111;
+#endif
+            vbfsCopyFsObjInfoFromIprt(&pParms->Info, &info);
+        }
+    }
+    /* Free resources if any part of the function has failed. */
+    if (RT_FAILURE(rc))
+    {
+        if (   (0 != pHandle)
+            && (NIL_RTFILE != pHandle->file.Handle)
+            && (0 != pHandle->file.Handle))
+        {
+            RTFileClose(pHandle->file.Handle);
+            pHandle->file.Handle = NIL_RTFILE;
+        }
+        if (SHFL_HANDLE_NIL != handle)
+        {
+            vbsfFreeFileHandle(pClient, handle);
+        }
+        pParms->Handle = SHFL_HANDLE_NIL;
+    }
+    else
+    {
+        pParms->Handle = handle;
+    }
+
+    /* Report the driver that all is okay, we're done here */
+    if (fNoError)
+        rc = VINF_SUCCESS;
+
+    LogFlow(("vbsfOpenFile: rc = %Rrc\n", rc));
+    return rc;
+}
+
+/**
+ * Open a folder or create and open a new one.
+ *
+ * @returns IPRT status code
+ * @param  pClient  Data structure describing the client accessing the shared
+ *                  folder
+ * @param  root     The index of the shared folder in the table of mappings.
+ * @param  pszPath  Path to the file or folder on the host.
+ * @param  pParms   Input: @a CreateFlags Creation or open parameters, see
+ *                  include/VBox/shflsvc.h
+ *                  Output:
+ *                    - @a Result: Shared folder status code, see include/VBox/shflsvc.h
+ *                    - @a Handle: On success the (shared folder) handle of the folder opened or
+ *                                 created
+ *                    - @a Info:   On success the parameters of the folder opened or created
+ *
+ * @note folders are created with fMode = 0777
+ */
+static int vbsfOpenDir(SHFLCLIENTDATA *pClient, SHFLROOT root, char *pszPath,
+                       SHFLCREATEPARMS *pParms)
+{
+    LogFlow(("vbsfOpenDir: pszPath = %s, pParms = %p\n", pszPath, pParms));
+    Log(("SHFL create flags %08x\n", pParms->CreateFlags));
+
+    int rc = VERR_NO_MEMORY;
+    SHFLHANDLE      handle = vbsfAllocDirHandle(pClient);
+    SHFLFILEHANDLE *pHandle = vbsfQueryDirHandle(pClient, handle);
+    if (0 != pHandle)
+    {
+        pHandle->root = root;
+        pParms->Result = SHFL_FILE_EXISTS;  /* May be overwritten with SHFL_FILE_CREATED. */
+        /** @todo Can anyone think of a sensible, race-less way to do this?  Although
+                  I suspect that the race is inherent, due to the API available... */
+        /* Try to create the folder first if "create if new" is specified.  If this
+           fails, and "open if exists" is specified, then we ignore the failure and try
+           to open the folder anyway. */
+        if (   SHFL_CF_ACT_CREATE_IF_NEW
+            == BIT_FLAG(pParms->CreateFlags, SHFL_CF_ACT_MASK_IF_NEW))
+        {
+            /** @todo render supplied attributes.
+            * bird: The guest should specify this. For windows guests RTFS_DOS_DIRECTORY should suffice. */
+            RTFMODE fMode = 0777;
+
+            pParms->Result = SHFL_FILE_CREATED;
+            rc = RTDirCreate(pszPath, fMode, 0);
+            if (RT_FAILURE(rc))
+            {
+                /** @todo we still return 'rc' as failure here, so this is mostly pointless.  */
+                switch (rc)
+                {
+                    case VERR_ALREADY_EXISTS:
+                        pParms->Result = SHFL_FILE_EXISTS;
+                        break;
+                    case VERR_PATH_NOT_FOUND:
+                        pParms->Result = SHFL_PATH_NOT_FOUND;
+                        break;
+                    case VERR_FILE_NOT_FOUND: /* may happen on posix */
+                        pParms->Result = SHFL_FILE_NOT_FOUND;
+#ifndef RT_OS_WINDOWS
+                        if (   SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(pClient)
+                            && vbsfErrorStyleIsWindowsPathNotFound(pszPath))
+                        {
+                            pParms->Result = SHFL_PATH_NOT_FOUND;
+                            rc = VERR_PATH_NOT_FOUND;
+                        }
+#endif
+                        break;
+                    default:
+                        pParms->Result = SHFL_NO_RESULT;
+                }
+            }
+        }
+        else
+            rc = VINF_SUCCESS;
+        if (   RT_SUCCESS(rc)
+            || (SHFL_CF_ACT_OPEN_IF_EXISTS == BIT_FLAG(pParms->CreateFlags, SHFL_CF_ACT_MASK_IF_EXISTS)))
+        {
+            /* Open the directory now */
+            rc = RTDirOpenFiltered(&pHandle->dir.Handle, pszPath, RTDIRFILTER_NONE, 0 /*fFlags*/);
+            if (RT_SUCCESS(rc))
+            {
+                RTFSOBJINFO info;
+
+                rc = RTDirQueryInfo(pHandle->dir.Handle, &info, RTFSOBJATTRADD_NOTHING);
+                if (RT_SUCCESS(rc))
+                {
+                    vbfsCopyFsObjInfoFromIprt(&pParms->Info, &info);
+                }
+            }
+            else
+            {
+                /** @todo we still return 'rc' as failure here, so this is mostly pointless.  */
+                switch (rc)
+                {
+                    case VERR_FILE_NOT_FOUND:
+                        pParms->Result = SHFL_FILE_NOT_FOUND;
+#ifndef RT_OS_WINDOWS
+                        if (   SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(pClient)
+                            && vbsfErrorStyleIsWindowsPathNotFound(pszPath))
+                        {
+                            pParms->Result = SHFL_PATH_NOT_FOUND;
+                            rc = VERR_PATH_NOT_FOUND;
+                        }
+#endif
+                        break;
+                    case VERR_PATH_NOT_FOUND:
+                        pParms->Result = SHFL_PATH_NOT_FOUND;
+#ifndef RT_OS_WINDOWS
+                        if (   SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(pClient)
+                            && vbsfErrorStyleIsWindowsNotADirectory(pszPath))
+                        {
+                            pParms->Result = SHFL_FILE_EXISTS;
+                            rc = VERR_NOT_A_DIRECTORY;
+                            break;
+                        }
+#endif
+                        break;
+                    case VERR_ACCESS_DENIED:
+                        pParms->Result = SHFL_FILE_EXISTS;
+                        break;
+                    default:
+                        pParms->Result = SHFL_NO_RESULT;
+                }
+            }
+        }
+    }
+    if (RT_FAILURE(rc))
+    {
+        if (   (0 != pHandle)
+            && (0 != pHandle->dir.Handle))
+        {
+            RTDirClose(pHandle->dir.Handle);
+            pHandle->dir.Handle = 0;
+        }
+        if (SHFL_HANDLE_NIL != handle)
+        {
+            vbsfFreeFileHandle(pClient, handle);
+        }
+        pParms->Handle = SHFL_HANDLE_NIL;
+    }
+    else
+    {
+        pParms->Handle = handle;
+    }
+    LogFlow(("vbsfOpenDir: rc = %Rrc\n", rc));
+    return rc;
+}
+
+static int vbsfCloseDir(SHFLFILEHANDLE *pHandle)
+{
+    int rc = VINF_SUCCESS;
+
+    LogFlow(("vbsfCloseDir: Handle = %08X Search Handle = %08X\n",
+             pHandle->dir.Handle, pHandle->dir.SearchHandle));
+
+    RTDirClose(pHandle->dir.Handle);
+
+    if (pHandle->dir.SearchHandle)
+        RTDirClose(pHandle->dir.SearchHandle);
+
+    if (pHandle->dir.pLastValidEntry)
+    {
+        RTMemFree(pHandle->dir.pLastValidEntry);
+        pHandle->dir.pLastValidEntry = NULL;
+    }
+
+    LogFlow(("vbsfCloseDir: rc = %d\n", rc));
+
+    return rc;
+}
+
+
+static int vbsfCloseFile(SHFLFILEHANDLE *pHandle)
+{
+    int rc = VINF_SUCCESS;
+
+    LogFlow(("vbsfCloseFile: Handle = %08X\n",
+             pHandle->file.Handle));
+
+    rc = RTFileClose(pHandle->file.Handle);
+
+    LogFlow(("vbsfCloseFile: rc = %d\n", rc));
+
+    return rc;
+}
+
+/**
+ * Look up file or folder information by host path.
+ *
+ * @returns iprt status code (currently VINF_SUCCESS)
+ * @param   pClient    client data
+ * @param   pszPath    The path of the file to be looked up
+ * @param   pParms     Output:
+ *                      - @a Result: Status of the operation (success or error)
+ *                      - @a Info:   On success, information returned about the
+ *                                   file
+ */
+static int vbsfLookupFile(SHFLCLIENTDATA *pClient, char *pszPath, SHFLCREATEPARMS *pParms)
+{
+    RTFSOBJINFO info;
+    int rc;
+
+    rc = RTPathQueryInfoEx(pszPath, &info, RTFSOBJATTRADD_NOTHING, SHFL_RT_LINK(pClient));
+    LogFlow(("SHFL_CF_LOOKUP\n"));
+    /* Client just wants to know if the object exists. */
+    switch (rc)
+    {
+        case VINF_SUCCESS:
+        {
+#ifdef RT_OS_WINDOWS
+            info.Attr.fMode |= 0111;
+#endif
+            vbfsCopyFsObjInfoFromIprt(&pParms->Info, &info);
+            pParms->Result = SHFL_FILE_EXISTS;
+            break;
+        }
+
+        case VERR_FILE_NOT_FOUND:
+        {
+            pParms->Result = SHFL_FILE_NOT_FOUND;
+            rc = VINF_SUCCESS;
+            break;
+        }
+
+        case VERR_PATH_NOT_FOUND:
+        {
+            pParms->Result = SHFL_PATH_NOT_FOUND;
+            rc = VINF_SUCCESS;
+            break;
+        }
+    }
+    pParms->Handle = SHFL_HANDLE_NIL;
+    return rc;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_CREATE API.  Located here as a form of API
+ * documentation. */
+void testCreate(RTTEST hTest)
+{
+    /* Simple opening of an existing file. */
+    testCreateFileSimple(hTest);
+    testCreateFileSimpleCaseInsensitive(hTest);
+    /* Simple opening of an existing directory. */
+    /** @todo How do wildcards in the path name work? */
+    testCreateDirSimple(hTest);
+    /* If the number or types of parameters are wrong the API should fail. */
+    testCreateBadParameters(hTest);
+    /* Add tests as required... */
+}
+#endif
+
+/**
+ * Create or open a file or folder.  Perform character set and case
+ * conversion on the file name if necessary.
+ *
+ * @returns IPRT status code, but see note below
+ * @param   pClient     Data structure describing the client accessing the
+ *                      shared folder
+ * @param   root        The index of the shared folder in the table of mappings.
+ *                      The host path of the shared folder is found using this.
+ * @param   pPath       The path of the file or folder relative to the host path
+ *                      indexed by root.
+ * @param   cbPath      Presumably the length of the path in pPath. Actually
+ *                      ignored, as pPath contains a length parameter.
+ * @param   pParms      Input: If a new file is created or an old one
+ *                      overwritten, set the @a Info attribute.
+ *
+ *                      Output:
+ *                        - @a Result Shared folder result code, see include/VBox/shflsvc.h
+ *                        - @a Handle Shared folder handle to the newly opened file
+ *                        - @a Info Attributes of the file or folder opened
+ *
+ * @note This function returns success if a "non-exceptional" error occurred,
+ *       such as "no such file".  In this case, the caller should check the
+ *       pParms->Result return value and whether pParms->Handle is valid.
+ */
+int vbsfCreate(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLSTRING *pPath, uint32_t cbPath, SHFLCREATEPARMS *pParms)
+{
+    int rc = VINF_SUCCESS;
+
+    LogFlow(("vbsfCreate: pClient = %p, pPath = %p, cbPath = %d, pParms = %p CreateFlags=%x\n",
+             pClient, pPath, cbPath, pParms, pParms->CreateFlags));
+
+    /* Check the client access rights to the root. */
+    /** @todo */
+
+    /* Build a host full path for the given path, handle file name case issues (if the guest
+     * expects case-insensitive paths but the host is case-sensitive) and convert ucs2 to utf8 if
+     * necessary.
+     */
+    char *pszFullPath = NULL;
+    uint32_t cbFullPathRoot = 0;
+
+    rc = vbsfBuildFullPath(pClient, root, pPath, cbPath, &pszFullPath, &cbFullPathRoot);
+    if (RT_SUCCESS(rc))
+    {
+        /* Reset return value in case client forgot to do so.
+         * pParms->Handle must not be reset here, as it is used
+         * in vbsfOpenFile to detect old additions.
+         */
+        pParms->Result = SHFL_NO_RESULT;
+
+        if (BIT_FLAG(pParms->CreateFlags, SHFL_CF_LOOKUP))
+        {
+            rc = vbsfLookupFile(pClient, pszFullPath, pParms);
+        }
+        else
+        {
+            /* Query path information. */
+            RTFSOBJINFO info;
+
+            rc = RTPathQueryInfoEx(pszFullPath, &info, RTFSOBJATTRADD_NOTHING, SHFL_RT_LINK(pClient));
+            LogFlow(("RTPathQueryInfoEx returned %Rrc\n", rc));
+
+            if (RT_SUCCESS(rc))
+            {
+                /* Mark it as a directory in case the caller didn't. */
+                /**
+                  * @todo I left this in in order not to change the behaviour of the
+                  *       function too much.  Is it really needed, and should it really be
+                  *       here?
+                  */
+                if (BIT_FLAG(info.Attr.fMode, RTFS_DOS_DIRECTORY))
+                {
+                    pParms->CreateFlags |= SHFL_CF_DIRECTORY;
+                }
+
+                /**
+                  * @todo This should be in the Windows Guest Additions, as no-one else
+                  *       needs it.
+                  */
+                if (BIT_FLAG(pParms->CreateFlags, SHFL_CF_OPEN_TARGET_DIRECTORY))
+                {
+                    vbsfStripLastComponent(pszFullPath, cbFullPathRoot);
+                    pParms->CreateFlags &= ~SHFL_CF_ACT_MASK_IF_EXISTS;
+                    pParms->CreateFlags &= ~SHFL_CF_ACT_MASK_IF_NEW;
+                    pParms->CreateFlags |= SHFL_CF_DIRECTORY;
+                    pParms->CreateFlags |= SHFL_CF_ACT_OPEN_IF_EXISTS;
+                    pParms->CreateFlags |= SHFL_CF_ACT_FAIL_IF_NEW;
+                }
+            }
+
+            rc = VINF_SUCCESS;
+
+            /* Note: do not check the SHFL_CF_ACCESS_WRITE here, only check if the open operation
+             * will cause changes.
+             *
+             * Actual operations (write, set attr, etc), which can write to a shared folder, have
+             * the check and will return VERR_WRITE_PROTECT if the folder is not writable.
+             */
+            if (   (pParms->CreateFlags & SHFL_CF_ACT_MASK_IF_EXISTS) == SHFL_CF_ACT_REPLACE_IF_EXISTS
+                || (pParms->CreateFlags & SHFL_CF_ACT_MASK_IF_EXISTS) == SHFL_CF_ACT_OVERWRITE_IF_EXISTS
+                || (pParms->CreateFlags & SHFL_CF_ACT_MASK_IF_NEW) == SHFL_CF_ACT_CREATE_IF_NEW
+               )
+            {
+                /* is the guest allowed to write to this share? */
+                bool fWritable;
+                rc = vbsfMappingsQueryWritable(pClient, root, &fWritable);
+                if (RT_FAILURE(rc) || !fWritable)
+                    rc = VERR_WRITE_PROTECT;
+            }
+
+            if (RT_SUCCESS(rc))
+            {
+                if (BIT_FLAG(pParms->CreateFlags, SHFL_CF_DIRECTORY))
+                {
+                    rc = vbsfOpenDir(pClient, root, pszFullPath, pParms);
+                }
+                else
+                {
+                    rc = vbsfOpenFile(pClient, root, pszFullPath, pParms);
+                }
+            }
+            else
+            {
+                pParms->Handle = SHFL_HANDLE_NIL;
+            }
+        }
+
+        /* free the path string */
+        vbsfFreeFullPath(pszFullPath);
+    }
+
+    Log(("vbsfCreate: handle = %RX64 rc = %Rrc result=%x\n", (uint64_t)pParms->Handle, rc, pParms->Result));
+
+    return rc;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_CLOSE API.  Located here as a form of API
+ * documentation. */
+void testClose(RTTEST hTest)
+{
+    /* If the API parameters are invalid the API should fail. */
+    testCloseBadParameters(hTest);
+    /* Add tests as required... */
+}
+#endif
+
+int vbsfClose(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle)
+{
+    LogFunc(("pClient = %p, root 0x%RX32, Handle = 0x%RX64\n",
+             pClient, root, Handle));
+
+    int rc = VERR_INVALID_HANDLE;
+    uint32_t type = vbsfQueryHandleType(pClient, Handle);
+    Assert((type & ~(SHFL_HF_TYPE_DIR | SHFL_HF_TYPE_FILE)) == 0);
+    switch (type & (SHFL_HF_TYPE_DIR | SHFL_HF_TYPE_FILE))
+    {
+        case SHFL_HF_TYPE_DIR:
+        {
+            SHFLFILEHANDLE *pHandle = vbsfQueryDirHandle(pClient, Handle);
+            if (RT_LIKELY(pHandle && root == pHandle->root))
+            {
+                rc = vbsfCloseDir(pHandle);
+                vbsfFreeFileHandle(pClient, Handle);
+            }
+            break;
+        }
+        case SHFL_HF_TYPE_FILE:
+        {
+            SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, Handle);
+            if (RT_LIKELY(pHandle && root == pHandle->root))
+            {
+                rc = vbsfCloseFile(pHandle);
+                vbsfFreeFileHandle(pClient, Handle);
+            }
+            break;
+        }
+        default:
+            break;
+    }
+
+    LogFunc(("rc = %Rrc\n", rc));
+    return rc;
+}
+
+/**
+ * Helper for vbsfReadPages and vbsfWritePages that creates a S/G buffer from a
+ * pages parameter.
+ */
+static int vbsfPagesToSgBuf(VBOXHGCMSVCPARMPAGES const *pPages, uint32_t cbLeft, PRTSGBUF pSgBuf)
+{
+    PRTSGSEG paSegs = (PRTSGSEG)RTMemTmpAlloc(sizeof(paSegs[0]) * pPages->cPages);
+    if (paSegs)
+    {
+        /*
+         * Convert the pages to segments.
+         */
+        uint32_t iSeg  = 0;
+        uint32_t iPage = 0;
+        for (;;)
+        {
+            Assert(iSeg < pPages->cPages);
+            Assert(iPage < pPages->cPages);
+
+            /* Current page. */
+            void *pvSeg;
+            paSegs[iSeg].pvSeg = pvSeg = pPages->papvPages[iPage];
+            uint32_t cbSeg = PAGE_SIZE - (uint32_t)((uintptr_t)pvSeg & PAGE_OFFSET_MASK);
+            iPage++;
+
+            /* Adjacent to the next page? */
+            while (   iPage < pPages->cPages
+                   && (uintptr_t)pvSeg + cbSeg == (uintptr_t)pPages->papvPages[iPage])
+            {
+                iPage++;
+                cbSeg += PAGE_SIZE;
+            }
+
+            /* Adjust for max size. */
+            if (cbLeft <= cbSeg)
+            {
+                paSegs[iSeg++].cbSeg = cbLeft;
+                break;
+            }
+            paSegs[iSeg++].cbSeg = cbSeg;
+            cbLeft -= cbSeg;
+        }
+
+        /*
+         * Initialize the s/g buffer and execute the read.
+         */
+        RTSgBufInit(pSgBuf, paSegs, iSeg);
+        return VINF_SUCCESS;
+    }
+    pSgBuf->paSegs = NULL;
+    return VERR_NO_TMP_MEMORY;
+}
+
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_READ API.  Located here as a form of API
+ * documentation. */
+void testRead(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testReadBadParameters(hTest);
+    /* Basic reading from a file. */
+    testReadFileSimple(hTest);
+    /* Add tests as required... */
+}
+#endif
+int vbsfRead(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint64_t offset, uint32_t *pcbBuffer, uint8_t *pBuffer)
+{
+    LogFunc(("pClient %p, root 0x%RX32, Handle 0x%RX64, offset 0x%RX64, bytes 0x%RX32\n",
+             pClient, root, Handle, offset, pcbBuffer? *pcbBuffer: 0));
+
+    AssertPtrReturn(pClient, VERR_INVALID_PARAMETER);
+
+    SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, Handle);
+    int rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_READ);
+    if (RT_SUCCESS(rc))
+    {
+        size_t const cbToRead = *pcbBuffer;
+        if (RT_LIKELY(cbToRead > 0))
+        {
+            size_t cbActual = 0;
+            rc = RTFileReadAt(pHandle->file.Handle, offset, pBuffer, cbToRead, &cbActual);
+            *pcbBuffer = (uint32_t)cbActual;
+        }
+        else
+        {
+            /* Reading zero bytes always succeeds. */
+            rc = VINF_SUCCESS;
+        }
+    }
+    else
+        *pcbBuffer = 0;
+
+    LogFunc(("%Rrc bytes read 0x%RX32\n", rc, *pcbBuffer));
+    return rc;
+}
+
+/**
+ * SHFL_FN_READ w/o bounce buffering.
+ */
+int vbsfReadPages(SHFLCLIENTDATA *pClient, SHFLROOT idRoot, SHFLHANDLE hFile, uint64_t offFile,
+                  uint32_t *pcbRead, PVBOXHGCMSVCPARMPAGES pPages)
+{
+    LogFunc(("pClient %p, idRoot %#RX32, hFile %#RX64, offFile %#RX64, cbRead %#RX32, cPages %#x\n",
+             pClient, idRoot, hFile, offFile, *pcbRead, pPages->cPages));
+
+    AssertPtrReturn(pClient, VERR_INVALID_PARAMETER);
+
+    size_t          cbTotal = 0;
+    SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, hFile);
+    int rc = vbsfCheckHandleAccess(pClient, idRoot, pHandle, VBSF_CHECK_ACCESS_READ);
+    if (RT_SUCCESS(rc))
+    {
+        uint32_t const cbToRead = *pcbRead;
+        if (cbToRead > 0)
+        {
+            ASSERT_GUEST_RETURN(pPages->cPages > 0, VERR_INTERNAL_ERROR_3);
+
+            /*
+             * Convert to a scatter-gather buffer.
+             *
+             * We need not do any platform specific code here as the RTSGBUF
+             * segment array maps directly onto the posix iovec structure.
+             * Windows does currently benefit much from this conversion, but
+             * so be it.
+             */
+            RTSGBUF SgBuf;
+            rc = vbsfPagesToSgBuf(pPages, cbToRead, &SgBuf);
+            if (RT_SUCCESS(rc))
+            {
+                rc = RTFileSgReadAt(pHandle->file.Handle, offFile, &SgBuf, cbToRead, &cbTotal);
+                while (rc == VERR_INTERRUPTED)
+                {
+                    RTSgBufReset(&SgBuf);
+                    rc = RTFileSgReadAt(pHandle->file.Handle, offFile, &SgBuf, cbToRead, &cbTotal);
+                }
+
+                RTMemTmpFree((void *)SgBuf.paSegs);
+            }
+            else
+                rc = VERR_NO_TMP_MEMORY;
+
+            *pcbRead = (uint32_t)cbTotal;
+        }
+        else
+        {
+            /* Reading zero bytes always succeeds. */
+            rc = VINF_SUCCESS;
+        }
+    }
+    else
+        *pcbRead = 0;
+
+    LogFunc(("%Rrc bytes read %#zx\n", rc, cbTotal));
+    return rc;
+}
+
+/**
+ * Helps with writes to RTFILE_O_APPEND files.
+ */
+static uint64_t vbsfWriteCalcPostAppendFilePosition(RTFILE hFile, uint64_t offGuessed)
+{
+    RTFSOBJINFO ObjInfo;
+    int rc2 = RTFileQueryInfo(hFile, &ObjInfo, RTFSOBJATTRADD_NOTHING);
+    if (RT_SUCCESS(rc2) && (uint64_t)ObjInfo.cbObject >= offGuessed)
+        return ObjInfo.cbObject;
+    return offGuessed;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_WRITE API.  Located here as a form of API
+ * documentation. */
+void testWrite(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testWriteBadParameters(hTest);
+    /* Simple test of writing to a file. */
+    testWriteFileSimple(hTest);
+    /* Add tests as required... */
+}
+#endif
+int vbsfWrite(SHFLCLIENTDATA *pClient, SHFLROOT idRoot, SHFLHANDLE hFile, uint64_t *poffFile,
+              uint32_t *pcbBuffer, uint8_t *pBuffer)
+{
+    uint64_t offFile = *poffFile;
+    LogFunc(("pClient %p, root 0x%RX32, Handle 0x%RX64, offFile 0x%RX64, bytes 0x%RX32\n",
+             pClient, idRoot, hFile, offFile, *pcbBuffer));
+
+    AssertPtrReturn(pClient, VERR_INVALID_PARAMETER);
+
+    SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, hFile);
+    int rc = vbsfCheckHandleAccess(pClient, idRoot, pHandle, VBSF_CHECK_ACCESS_WRITE);
+    if (RT_SUCCESS(rc))
+    {
+        size_t const cbToWrite = *pcbBuffer;
+        if (RT_LIKELY(cbToWrite != 0))
+        {
+            size_t cbWritten = 0;
+            if (!(pHandle->file.fOpenFlags & RTFILE_O_APPEND))
+                rc = RTFileWriteAt(pHandle->file.Handle, offFile, pBuffer, cbToWrite, &cbWritten);
+            else
+            {
+                rc = RTFileSeek(pHandle->file.Handle, offFile, RTFILE_SEEK_BEGIN, NULL);
+                AssertRC(rc);
+                if (RT_SUCCESS(rc))
+                {
+                    rc = RTFileWrite(pHandle->file.Handle, pBuffer, cbToWrite, &cbWritten);
+                    *pcbBuffer = (uint32_t)cbWritten;
+                }
+            }
+
+            /* Update the file offset (mainly for RTFILE_O_APPEND), */
+            if (RT_SUCCESS(rc))
+            {
+                offFile += cbWritten;
+                if (!(pHandle->file.fOpenFlags & RTFILE_O_APPEND))
+                    *poffFile = offFile;
+                else
+                    *poffFile = vbsfWriteCalcPostAppendFilePosition(pHandle->file.Handle, offFile);
+            }
+        }
+        else
+        {
+            /** @todo What writing zero bytes should do? */
+            rc = VINF_SUCCESS;
+        }
+    }
+    else
+        *pcbBuffer = 0;
+    LogFunc(("%Rrc bytes written 0x%RX32\n", rc, *pcbBuffer));
+    return rc;
+}
+
+/**
+ * SHFL_FN_WRITE w/o bounce buffering.
+ */
+int vbsfWritePages(SHFLCLIENTDATA *pClient, SHFLROOT idRoot, SHFLHANDLE hFile, uint64_t *poffFile,
+                   uint32_t *pcbWrite, PVBOXHGCMSVCPARMPAGES pPages)
+{
+    uint64_t offFile = *poffFile;
+    LogFunc(("pClient %p, idRoot %#RX32, hFile %#RX64, offFile %#RX64, cbWrite %#RX32, cPages %#x\n",
+             pClient, idRoot, hFile, offFile, *pcbWrite, pPages->cPages));
+
+    AssertPtrReturn(pClient, VERR_INVALID_PARAMETER);
+
+    size_t          cbTotal = 0;
+    SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, hFile);
+    int rc = vbsfCheckHandleAccess(pClient, idRoot, pHandle, VBSF_CHECK_ACCESS_WRITE);
+    if (RT_SUCCESS(rc))
+    {
+        uint32_t const cbToWrite = *pcbWrite;
+        if (cbToWrite > 0)
+        {
+            ASSERT_GUEST_RETURN(pPages->cPages > 0, VERR_INTERNAL_ERROR_3);
+
+            /*
+             * Convert to a scatter-gather buffer.
+             *
+             * We need not do any platform specific code here as the RTSGBUF
+             * segment array maps directly onto the posix iovec structure.
+             * Windows does currently benefit much from this conversion, but
+             * so be it.
+             */
+            RTSGBUF SgBuf;
+            rc = vbsfPagesToSgBuf(pPages, cbToWrite, &SgBuf);
+            if (RT_SUCCESS(rc))
+            {
+#ifndef RT_OS_LINUX
+                /* Cannot use RTFileSgWriteAt or RTFileWriteAt when opened with
+                   RTFILE_O_APPEND, except for on linux where the offset is
+                   then ignored by the low level kernel API. */
+                if (pHandle->file.fOpenFlags & RTFILE_O_APPEND)
+                {
+                    /* paranoia */
+                    RTFileSeek(pHandle->file.Handle, 0, RTFILE_SEEK_END, NULL);
+
+                    for (size_t iSeg = 0; iSeg < SgBuf.cSegs; iSeg++)
+                    {
+                        size_t cbWrittenNow = 0;
+                        do
+                            rc = RTFileWrite(pHandle->file.Handle, SgBuf.paSegs[iSeg].pvSeg,
+                                             SgBuf.paSegs[iSeg].cbSeg, &cbWrittenNow);
+                        while (rc == VERR_INTERRUPTED);
+                        if (RT_SUCCESS(rc))
+                        {
+                            cbTotal += cbWrittenNow;
+                            if (cbWrittenNow < SgBuf.paSegs[iSeg].cbSeg)
+                                break;
+                        }
+                        else
+                        {
+                            if (cbTotal > 0)
+                                rc = VINF_SUCCESS;
+                            break;
+                        }
+                    }
+                }
+                else
+#endif
+                {
+                    rc = RTFileSgWriteAt(pHandle->file.Handle, offFile, &SgBuf, cbToWrite, &cbTotal);
+                    while (rc == VERR_INTERRUPTED)
+                    {
+                        RTSgBufReset(&SgBuf);
+                        rc = RTFileSgWriteAt(pHandle->file.Handle, offFile, &SgBuf, cbToWrite, &cbTotal);
+                    }
+                }
+
+                RTMemTmpFree((void *)SgBuf.paSegs);
+
+                /* Update the file offset (mainly for RTFILE_O_APPEND), */
+                if (RT_SUCCESS(rc))
+                {
+                    offFile += cbTotal;
+                    if (!(pHandle->file.fOpenFlags & RTFILE_O_APPEND))
+                        *poffFile = offFile;
+                    else
+                        *poffFile = vbsfWriteCalcPostAppendFilePosition(pHandle->file.Handle, offFile);
+                }
+            }
+            else
+                rc = VERR_NO_TMP_MEMORY;
+
+            *pcbWrite = (uint32_t)cbTotal;
+        }
+        else
+        {
+            /* Writing zero bytes always succeeds. */
+            rc = VINF_SUCCESS;
+        }
+    }
+    else
+        *pcbWrite = 0;
+
+    LogFunc(("%Rrc bytes written %#zx\n", rc, cbTotal));
+    return rc;
+}
+
+/**
+ * Implements SHFL_FN_COPY_FILE_PART (wrapping RTFileCopyPart).
+ */
+int vbsfCopyFilePart(SHFLCLIENTDATA *pClient, SHFLROOT idRootSrc, SHFLHANDLE hFileSrc, uint64_t offSrc,
+                     SHFLROOT idRootDst, SHFLHANDLE hFileDst, uint64_t offDst, uint64_t *pcbToCopy, uint32_t fFlags)
+{
+    /*
+     * Validate and translates handles.
+     */
+    uint64_t const cbToCopy = *pcbToCopy;
+    *pcbToCopy = 0;
+    LogFunc(("pClient %p, idRootSrc %#RX32, hFileSrc %#RX64, offSrc %#RX64, idRootSrc %#RX32, hFileSrc %#RX64, offSrc %#RX64, cbToCopy %#RX64, fFlags %#x\n",
+             pClient, idRootSrc, hFileSrc, offSrc, idRootDst, hFileDst, offDst, cbToCopy, fFlags));
+
+    AssertPtrReturn(pClient, VERR_INVALID_PARAMETER);
+
+    uint64_t cbTotal = 0;
+
+    SHFLFILEHANDLE *pHandleSrc = vbsfQueryFileHandle(pClient, hFileSrc);
+    int rc = vbsfCheckHandleAccess(pClient, idRootSrc, pHandleSrc, VBSF_CHECK_ACCESS_READ);
+    if (RT_SUCCESS(rc))
+    {
+        SHFLFILEHANDLE *pHandleDst = vbsfQueryFileHandle(pClient, hFileDst);
+        rc = vbsfCheckHandleAccess(pClient, idRootDst, pHandleDst, VBSF_CHECK_ACCESS_WRITE);
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Do the job.
+             */
+            rc = RTFileCopyPart(pHandleSrc->file.Handle, offSrc, pHandleDst->file.Handle, offDst, cbToCopy, 0, &cbTotal);
+            *pcbToCopy = cbTotal;
+        }
+    }
+
+    RT_NOREF(fFlags);
+    LogFunc(("%Rrc bytes written %#zx\n", rc, cbTotal));
+    return rc;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_FLUSH API.  Located here as a form of API
+ * documentation. */
+void testFlush(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testFlushBadParameters(hTest);
+    /* Simple opening and flushing of a file. */
+    testFlushFileSimple(hTest);
+    /* Add tests as required... */
+}
+#endif
+
+int vbsfFlush(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle)
+{
+    LogFunc(("pClient %p, root 0x%RX32, Handle 0x%RX64\n",
+             pClient, root, Handle));
+
+    AssertPtrReturn(pClient, VERR_INVALID_PARAMETER);
+
+    SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, Handle);
+    int rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_WRITE);
+    if (RT_SUCCESS(rc))
+    { /* likely */ }
+    else
+        return rc;
+
+    rc = RTFileFlush(pHandle->file.Handle);
+
+    LogFunc(("%Rrc\n", rc));
+    return rc;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_LIST API.  Located here as a form of API
+ * documentation. */
+void testDirList(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testDirListBadParameters(hTest);
+    /* Test listing an empty directory (simple edge case). */
+    testDirListEmpty(hTest);
+    /* Add tests as required... */
+}
+#endif
+int vbsfDirList(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, SHFLSTRING *pPath, uint32_t flags,
+                uint32_t *pcbBuffer, uint8_t *pBuffer, uint32_t *pIndex, uint32_t *pcFiles)
+{
+    PRTDIRENTRYEX  pDirEntry = 0, pDirEntryOrg;
+    uint32_t       cbDirEntry, cbBufferOrg;
+    PSHFLDIRINFO   pSFDEntry;
+    PRTUTF16       pwszString;
+    RTDIR          hDir;
+    const bool     fUtf8 = BIT_FLAG(pClient->fu32Flags, SHFL_CF_UTF8) != 0;
+
+    AssertPtrReturn(pClient, VERR_INVALID_PARAMETER);
+
+    SHFLFILEHANDLE *pHandle = vbsfQueryDirHandle(pClient, Handle);
+    int rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_READ);
+    if (RT_SUCCESS(rc))
+    { /* likely */ }
+    else
+        return rc;
+
+    Assert(*pIndex == 0);
+
+    cbDirEntry = 4096;
+    pDirEntryOrg = pDirEntry  = (PRTDIRENTRYEX)RTMemAlloc(cbDirEntry);
+    if (pDirEntry == 0)
+    {
+        AssertFailed();
+        return VERR_NO_MEMORY;
+    }
+
+    cbBufferOrg = *pcbBuffer;
+    *pcbBuffer  = 0;
+    pSFDEntry   = (PSHFLDIRINFO)pBuffer;
+
+    *pIndex = 1; /* not yet complete */
+    *pcFiles = 0;
+
+    if (!pPath)
+        hDir = pHandle->dir.Handle;
+    else
+    {
+        if (pHandle->dir.SearchHandle == 0)
+        {
+            /* Build a host full path for the given path
+             * and convert ucs2 to utf8 if necessary.
+             */
+            char *pszFullPath = NULL;
+
+            Assert(pHandle->dir.pLastValidEntry == 0);
+
+            rc = vbsfBuildFullPath(pClient, root, pPath, pPath->u16Size + SHFLSTRING_HEADER_SIZE, &pszFullPath, NULL, true);
+
+            if (RT_SUCCESS(rc))
+            {
+                rc = RTDirOpenFiltered(&pHandle->dir.SearchHandle, pszFullPath, RTDIRFILTER_WINNT, 0 /*fFlags*/);
+
+                /* free the path string */
+                vbsfFreeFullPath(pszFullPath);
+
+                if (RT_FAILURE(rc))
+                    goto end;
+            }
+            else
+                goto end;
+            flags &= ~SHFL_LIST_RESTART;
+        }
+        Assert(pHandle->dir.SearchHandle);
+        hDir = pHandle->dir.SearchHandle;
+    }
+
+    if (flags & SHFL_LIST_RESTART)
+    {
+        rc = RTDirRewind(hDir);
+        if (RT_FAILURE(rc))
+            goto end;
+    }
+
+    while (cbBufferOrg)
+    {
+        size_t cbDirEntrySize = cbDirEntry;
+        uint32_t cbNeeded;
+
+        /* Do we still have a valid last entry for the active search? If so, then return it here */
+        if (pHandle->dir.pLastValidEntry)
+        {
+            pDirEntry = pHandle->dir.pLastValidEntry;
+        }
+        else
+        {
+            pDirEntry = pDirEntryOrg;
+
+            rc = RTDirReadEx(hDir, pDirEntry, &cbDirEntrySize, RTFSOBJATTRADD_NOTHING, SHFL_RT_LINK(pClient));
+            if (rc == VERR_NO_MORE_FILES)
+            {
+                *pIndex = 0; /* listing completed */
+                break;
+            }
+
+            if (   rc != VINF_SUCCESS
+                && rc != VWRN_NO_DIRENT_INFO)
+            {
+                //AssertFailed();
+                if (   rc == VERR_NO_TRANSLATION
+                    || rc == VERR_INVALID_UTF8_ENCODING)
+                    continue;
+                break;
+            }
+        }
+
+        cbNeeded = RT_OFFSETOF(SHFLDIRINFO, name.String);
+        if (fUtf8)
+            cbNeeded += pDirEntry->cbName + 1;
+        else
+            /* Overestimating, but that's ok */
+            cbNeeded += (pDirEntry->cbName + 1) * 2;
+
+        if (cbBufferOrg < cbNeeded)
+        {
+            /* No room, so save this directory entry, or else it's lost forever */
+            pHandle->dir.pLastValidEntry = pDirEntry;
+
+            if (*pcFiles == 0)
+            {
+                AssertFailed();
+                return VINF_BUFFER_OVERFLOW;    /* Return directly and don't free pDirEntry */
+            }
+            return VINF_SUCCESS;    /* Return directly and don't free pDirEntry */
+        }
+
+#ifdef RT_OS_WINDOWS
+        pDirEntry->Info.Attr.fMode |= 0111;
+#endif
+        vbfsCopyFsObjInfoFromIprt(&pSFDEntry->Info, &pDirEntry->Info);
+
+        /* The shortname (only used by OS/2 atm): */
+        Assert(pDirEntry->cwcShortName < RT_ELEMENTS(pSFDEntry->uszShortName));
+        Assert(pDirEntry->wszShortName[pDirEntry->cwcShortName] == '\0');
+        pSFDEntry->cucShortName = pDirEntry->cwcShortName;
+        if (pDirEntry->cwcShortName)
+            memcpy(pSFDEntry->uszShortName, pDirEntry->wszShortName, sizeof(pSFDEntry->uszShortName));
+
+        /* The name: */
+        if (fUtf8)
+        {
+            void *src, *dst;
+
+            src = &pDirEntry->szName[0];
+            dst = &pSFDEntry->name.String.utf8[0];
+
+            memcpy(dst, src, pDirEntry->cbName + 1);
+
+            pSFDEntry->name.u16Size = pDirEntry->cbName + 1;
+            pSFDEntry->name.u16Length = pDirEntry->cbName;
+        }
+        else
+        {
+            pSFDEntry->name.String.ucs2[0] = 0;
+            pwszString = pSFDEntry->name.String.ucs2;
+            int rc2 = RTStrToUtf16Ex(pDirEntry->szName, RTSTR_MAX, &pwszString, pDirEntry->cbName+1, NULL);
+            AssertRC(rc2);
+
+#ifdef RT_OS_DARWIN
+/** @todo This belongs in rtPathToNative or in the windows shared folder file system driver...
+ * The question is simply whether the NFD normalization is actually applied on a (virtual) file
+ * system level in darwin, or just by the user mode application libs. */
+            {
+                // Convert to
+                // Normalization Form C (composed Unicode). We need this because
+                // Mac OS X file system uses NFD (Normalization Form D :decomposed Unicode)
+                // while most other OS', server-side programs usually expect NFC.
+                uint16_t ucs2Length;
+                CFRange rangeCharacters;
+                CFMutableStringRef inStr = ::CFStringCreateMutable(NULL, 0);
+
+                ::CFStringAppendCharacters(inStr, (UniChar *)pwszString, RTUtf16Len(pwszString));
+                ::CFStringNormalize(inStr, kCFStringNormalizationFormC);
+                ucs2Length = ::CFStringGetLength(inStr);
+
+                rangeCharacters.location = 0;
+                rangeCharacters.length = ucs2Length;
+                ::CFStringGetCharacters(inStr, rangeCharacters, pwszString);
+                pwszString[ucs2Length] = 0x0000; // NULL terminated
+
+                CFRelease(inStr);
+            }
+#endif
+            pSFDEntry->name.u16Length = (uint32_t)RTUtf16Len(pSFDEntry->name.String.ucs2) * 2;
+            pSFDEntry->name.u16Size = pSFDEntry->name.u16Length + 2;
+
+            Log(("SHFL: File name size %d\n", pSFDEntry->name.u16Size));
+            Log(("SHFL: File name %ls\n", &pSFDEntry->name.String.ucs2));
+
+            // adjust cbNeeded (it was overestimated before)
+            cbNeeded = RT_OFFSETOF(SHFLDIRINFO, name.String) + pSFDEntry->name.u16Size;
+        }
+
+        /* Advance */
+        pSFDEntry   = (PSHFLDIRINFO)((uintptr_t)pSFDEntry + cbNeeded);
+        *pcbBuffer += cbNeeded;
+        cbBufferOrg-= cbNeeded;
+
+        *pcFiles   += 1;
+
+        /* Free the saved last entry, that we've just returned */
+        if (pHandle->dir.pLastValidEntry)
+        {
+            RTMemFree(pHandle->dir.pLastValidEntry);
+            pHandle->dir.pLastValidEntry = NULL;
+
+            /* And use the newly allocated buffer from now. */
+            pDirEntry = pDirEntryOrg;
+        }
+
+        if (flags & SHFL_LIST_RETURN_ONE)
+            break; /* we're done */
+    }
+    Assert(rc != VINF_SUCCESS || *pcbBuffer > 0);
+
+end:
+    if (pDirEntry)
+        RTMemFree(pDirEntry);
+
+    return rc;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_READLINK API.  Located here as a form of API
+ * documentation. */
+void testReadLink(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testReadLinkBadParameters(hTest);
+    /* Add tests as required... */
+}
+#endif
+int vbsfReadLink(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLSTRING *pPath, uint32_t cbPath, uint8_t *pBuffer, uint32_t cbBuffer)
+{
+    int rc = VINF_SUCCESS;
+
+    if (pPath == 0 || pBuffer == 0)
+    {
+        AssertFailed();
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Build a host full path for the given path, handle file name case issues
+     * (if the guest expects case-insensitive paths but the host is
+     * case-sensitive) and convert ucs2 to utf8 if necessary.
+     */
+    char *pszFullPath = NULL;
+    uint32_t cbFullPathRoot = 0;
+
+    rc = vbsfBuildFullPath(pClient, root, pPath, cbPath, &pszFullPath, &cbFullPathRoot);
+
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTSymlinkRead(pszFullPath, (char *) pBuffer, cbBuffer, 0);
+        if (RT_SUCCESS(rc))
+        {
+            /* Convert the slashes in the link target to the guest path separator characters. */
+            /** @todo r=bird: for some messed up reason, we return UTF-8 here rather than
+             * the character set selected by the client.  We also don't return the
+             * length, so the clients are paranoid about the zero termination behavior. */
+            char ch;
+            char *psz = (char *)pBuffer;
+            while ((ch = *psz) != '\0')
+            {
+                if (RTPATH_IS_SLASH(ch))
+                    *psz = pClient->PathDelimiter;
+                psz++;
+            }
+        }
+
+        /* free the path string */
+        vbsfFreeFullPath(pszFullPath);
+    }
+
+    return rc;
+}
+
+int vbsfQueryFileInfo(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint32_t flags,
+                      uint32_t *pcbBuffer, uint8_t *pBuffer)
+{
+    RT_NOREF1(flags);
+    uint32_t type = vbsfQueryHandleType(pClient, Handle);
+    int            rc = VINF_SUCCESS;
+    SHFLFSOBJINFO   *pObjInfo = (SHFLFSOBJINFO *)pBuffer;
+    RTFSOBJINFO    fileinfo;
+
+
+    AssertReturn(type == SHFL_HF_TYPE_DIR || type == SHFL_HF_TYPE_FILE, VERR_INVALID_PARAMETER);
+    AssertReturn(pcbBuffer != NULL, VERR_INVALID_PARAMETER);
+    AssertReturn(pObjInfo != NULL, VERR_INVALID_PARAMETER);
+    AssertReturn(*pcbBuffer >= sizeof(SHFLFSOBJINFO), VERR_INVALID_PARAMETER);
+
+    /** @todo other options */
+    Assert(flags == (SHFL_INFO_GET|SHFL_INFO_FILE));
+
+    *pcbBuffer  = 0;
+
+    if (type == SHFL_HF_TYPE_DIR)
+    {
+        SHFLFILEHANDLE *pHandle = vbsfQueryDirHandle(pClient, Handle);
+        rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_READ);
+        if (RT_SUCCESS(rc))
+            rc = RTDirQueryInfo(pHandle->dir.Handle, &fileinfo, RTFSOBJATTRADD_NOTHING);
+    }
+    else
+    {
+        SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, Handle);
+        rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_READ);
+        if (RT_SUCCESS(rc))
+            rc = RTFileQueryInfo(pHandle->file.Handle, &fileinfo, RTFSOBJATTRADD_NOTHING);
+#ifdef RT_OS_WINDOWS
+        if (RT_SUCCESS(rc) && RTFS_IS_FILE(pObjInfo->Attr.fMode))
+            pObjInfo->Attr.fMode |= 0111;
+#endif
+    }
+    if (rc == VINF_SUCCESS)
+    {
+        vbfsCopyFsObjInfoFromIprt(pObjInfo, &fileinfo);
+        *pcbBuffer = sizeof(SHFLFSOBJINFO);
+    }
+    else
+        AssertFailed();
+
+    return rc;
+}
+
+static int vbsfSetFileInfo(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint32_t flags,
+                           uint32_t *pcbBuffer, uint8_t *pBuffer)
+{
+    RT_NOREF1(flags);
+    uint32_t type = vbsfQueryHandleType(pClient, Handle);
+    int             rc = VINF_SUCCESS;
+    SHFLFSOBJINFO  *pSFDEntry;
+
+    if (   !(type == SHFL_HF_TYPE_DIR || type == SHFL_HF_TYPE_FILE)
+        || pcbBuffer == 0
+        || pBuffer == 0
+        || *pcbBuffer < sizeof(SHFLFSOBJINFO))
+    {
+        AssertFailed();
+        return VERR_INVALID_PARAMETER;
+    }
+
+    *pcbBuffer  = 0;
+    pSFDEntry   = (SHFLFSOBJINFO *)pBuffer;
+
+    Assert(flags == (SHFL_INFO_SET | SHFL_INFO_FILE));
+
+    /*
+     * Get the handle.
+     */
+    SHFLFILEHANDLE *pHandle;
+    if (type == SHFL_HF_TYPE_FILE)
+    {
+        pHandle = vbsfQueryFileHandle(pClient, Handle);
+        rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_WRITE);
+    }
+    else
+    {
+        Assert(type == SHFL_HF_TYPE_DIR);
+        pHandle = vbsfQueryDirHandle(pClient, Handle);
+        rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_WRITE);
+    }
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Any times to set?
+         */
+        if (   RTTimeSpecGetNano(&pSFDEntry->AccessTime)
+            || RTTimeSpecGetNano(&pSFDEntry->ModificationTime)
+            || RTTimeSpecGetNano(&pSFDEntry->ChangeTime)
+            || RTTimeSpecGetNano(&pSFDEntry->BirthTime))
+        {
+
+            /* Change only the time values that are not zero */
+            if (type == SHFL_HF_TYPE_FILE)
+                rc = RTFileSetTimes(pHandle->file.Handle,
+                                    RTTimeSpecGetNano(&pSFDEntry->AccessTime)       ? &pSFDEntry->AccessTime         : NULL,
+                                    RTTimeSpecGetNano(&pSFDEntry->ModificationTime) ? &pSFDEntry->ModificationTime   : NULL,
+                                    RTTimeSpecGetNano(&pSFDEntry->ChangeTime)       ? &pSFDEntry->ChangeTime         : NULL,
+                                    RTTimeSpecGetNano(&pSFDEntry->BirthTime)        ? &pSFDEntry->BirthTime          : NULL);
+            else
+                rc = RTDirSetTimes( pHandle->dir.Handle,
+                                    RTTimeSpecGetNano(&pSFDEntry->AccessTime)       ? &pSFDEntry->AccessTime         : NULL,
+                                    RTTimeSpecGetNano(&pSFDEntry->ModificationTime) ? &pSFDEntry->ModificationTime   : NULL,
+                                    RTTimeSpecGetNano(&pSFDEntry->ChangeTime)       ? &pSFDEntry->ChangeTime         : NULL,
+                                    RTTimeSpecGetNano(&pSFDEntry->BirthTime)        ? &pSFDEntry->BirthTime          : NULL);
+            if (RT_FAILURE(rc))
+            {
+                Log(("RT%sSetTimes failed with %Rrc\n", type == SHFL_HF_TYPE_FILE ? "File" : "Dir", rc));
+                Log(("AccessTime       %#RX64\n", RTTimeSpecGetNano(&pSFDEntry->AccessTime)));
+                Log(("ModificationTime %#RX64\n", RTTimeSpecGetNano(&pSFDEntry->ModificationTime)));
+                Log(("ChangeTime       %#RX64\n", RTTimeSpecGetNano(&pSFDEntry->ChangeTime)));
+                Log(("BirthTime        %#RX64\n", RTTimeSpecGetNano(&pSFDEntry->BirthTime)));
+                /* "temporary" hack */
+                rc = VINF_SUCCESS;
+            }
+        }
+
+        /*
+         * Any mode changes?
+         */
+        if (pSFDEntry->Attr.fMode)
+        {
+            RTFMODE fMode = pSFDEntry->Attr.fMode;
+
+            if (type == SHFL_HF_TYPE_FILE)
+            {
+#ifndef RT_OS_WINDOWS
+                /* Don't allow the guest to clear the read own bit, otherwise the guest wouldn't
+                 * be able to access this file anymore. Only for guests, which set the UNIX mode.
+                 * Also, clear bits which we don't pass through for security reasons. */
+                if (fMode & RTFS_UNIX_MASK)
+                {
+                    fMode |= RTFS_UNIX_IRUSR;
+                    fMode &= ~(RTFS_UNIX_ISUID | RTFS_UNIX_ISGID | RTFS_UNIX_ISTXT);
+                }
+#endif
+                rc = RTFileSetMode(pHandle->file.Handle, fMode);
+            }
+            else
+            {
+#ifndef RT_OS_WINDOWS
+                /* Don't allow the guest to clear the read+execute own bits, otherwise the guest
+                 * wouldn't be able to access this directory anymore.  Only for guests, which set
+                 * the UNIX mode.  Also, clear bits which we don't pass through for security reasons. */
+                if (fMode & RTFS_UNIX_MASK)
+                {
+                    fMode |= RTFS_UNIX_IRUSR | RTFS_UNIX_IXUSR;
+                    fMode &= ~(RTFS_UNIX_ISUID | RTFS_UNIX_ISGID | RTFS_UNIX_ISTXT /*?*/);
+                }
+#endif
+                rc = RTDirSetMode(pHandle->dir.Handle, fMode);
+            }
+            if (RT_FAILURE(rc))
+            {
+                Log(("RT%sSetMode %#x (%#x) failed with %Rrc\n", type == SHFL_HF_TYPE_FILE ? "File" : "Dir",
+                     fMode, pSFDEntry->Attr.fMode, rc));
+                /* silent failure, because this tends to fail with e.g. windows guest & linux host */
+                rc = VINF_SUCCESS;
+            }
+        }
+
+        /*
+         * Return the current file info on success.
+         */
+        if (RT_SUCCESS(rc))
+        {
+            uint32_t bufsize = sizeof(*pSFDEntry);
+            rc = vbsfQueryFileInfo(pClient, root, Handle, SHFL_INFO_GET | SHFL_INFO_FILE, &bufsize, (uint8_t *)pSFDEntry);
+            if (RT_SUCCESS(rc))
+                *pcbBuffer = sizeof(SHFLFSOBJINFO);
+            else
+                AssertFailed();
+        }
+    }
+    return rc;
+}
+
+
+/**
+ * Handles SHFL_FN_SET_FILE_SIZE.
+ */
+int vbsfSetFileSize(SHFLCLIENTDATA *pClient, SHFLROOT idRoot, SHFLHANDLE hHandle, uint64_t cbNewSize)
+{
+    /*
+     * Resolve handle and validate write access.
+     */
+    SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, hHandle);
+    ASSERT_GUEST_RETURN(pHandle, VERR_INVALID_HANDLE);
+
+    int rc = vbsfCheckHandleAccess(pClient, idRoot, pHandle, VBSF_CHECK_ACCESS_WRITE);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Execute the request.
+         */
+        rc = RTFileSetSize(pHandle->file.Handle, cbNewSize);
+    }
+    return rc;
+}
+
+
+static int vbsfSetEndOfFile(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint32_t flags,
+                            uint32_t *pcbBuffer, uint8_t *pBuffer)
+{
+    RT_NOREF1(flags);
+    SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, Handle);
+    SHFLFSOBJINFO  *pSFDEntry;
+
+    if (pHandle == 0 || pcbBuffer == 0 || pBuffer == 0 || *pcbBuffer < sizeof(SHFLFSOBJINFO))
+    {
+        AssertFailed();
+        return VERR_INVALID_PARAMETER;
+    }
+
+    int rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_WRITE);
+    if (RT_SUCCESS(rc))
+    { /* likely */ }
+    else
+        return rc;
+
+    *pcbBuffer  = 0;
+    pSFDEntry   = (SHFLFSOBJINFO *)pBuffer;
+
+    if (flags & SHFL_INFO_SIZE)
+    {
+        rc = RTFileSetSize(pHandle->file.Handle, pSFDEntry->cbObject);
+        if (rc != VINF_SUCCESS)
+            AssertFailed();
+    }
+    else
+        AssertFailed();
+
+    if (rc == VINF_SUCCESS)
+    {
+        RTFSOBJINFO fileinfo;
+
+        /* Query the new object info and return it */
+        rc = RTFileQueryInfo(pHandle->file.Handle, &fileinfo, RTFSOBJATTRADD_NOTHING);
+        if (rc == VINF_SUCCESS)
+        {
+#ifdef RT_OS_WINDOWS
+            fileinfo.Attr.fMode |= 0111;
+#endif
+            vbfsCopyFsObjInfoFromIprt(pSFDEntry, &fileinfo);
+            *pcbBuffer = sizeof(SHFLFSOBJINFO);
+        }
+        else
+            AssertFailed();
+    }
+
+    return rc;
+}
+
+int vbsfQueryVolumeInfo(SHFLCLIENTDATA *pClient, SHFLROOT root, uint32_t flags, uint32_t *pcbBuffer, uint8_t *pBuffer)
+{
+    RT_NOREF2(root, flags);
+    int            rc = VINF_SUCCESS;
+    SHFLVOLINFO   *pSFDEntry;
+    char          *pszFullPath = NULL;
+    union
+    {
+        SHFLSTRING  Dummy;
+        uint8_t     abDummy[SHFLSTRING_HEADER_SIZE + sizeof(RTUTF16)];
+    } Buf;
+
+    if (pcbBuffer == 0 || pBuffer == 0 || *pcbBuffer < sizeof(SHFLVOLINFO))
+    {
+        AssertFailed();
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /** @todo other options */
+    Assert(flags == (SHFL_INFO_GET|SHFL_INFO_VOLUME));
+
+    *pcbBuffer  = 0;
+    pSFDEntry   = (PSHFLVOLINFO)pBuffer;
+
+    ShflStringInitBuffer(&Buf.Dummy, sizeof(Buf));
+    Buf.Dummy.String.ucs2[0] = '\0';
+    rc = vbsfBuildFullPath(pClient, root, &Buf.Dummy, sizeof(Buf), &pszFullPath, NULL);
+
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTFsQuerySizes(pszFullPath, &pSFDEntry->ullTotalAllocationBytes, &pSFDEntry->ullAvailableAllocationBytes, &pSFDEntry->ulBytesPerAllocationUnit, &pSFDEntry->ulBytesPerSector);
+        if (rc != VINF_SUCCESS)
+            goto exit;
+
+        rc = RTFsQuerySerial(pszFullPath, &pSFDEntry->ulSerial);
+        if (rc != VINF_SUCCESS)
+            goto exit;
+
+        RTFSPROPERTIES FsProperties;
+        rc = RTFsQueryProperties(pszFullPath, &FsProperties);
+        if (rc != VINF_SUCCESS)
+            goto exit;
+        vbfsCopyFsPropertiesFromIprt(&pSFDEntry->fsProperties, &FsProperties);
+
+        *pcbBuffer = sizeof(SHFLVOLINFO);
+    }
+    else AssertFailed();
+
+exit:
+    AssertMsg(rc == VINF_SUCCESS, ("failure: rc = %Rrc\n", rc));
+    /* free the path string */
+    vbsfFreeFullPath(pszFullPath);
+    return rc;
+}
+
+int vbsfQueryFSInfo(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint32_t flags, uint32_t *pcbBuffer, uint8_t *pBuffer)
+{
+    if (pcbBuffer == 0 || pBuffer == 0)
+    {
+        AssertFailed();
+        return VERR_INVALID_PARAMETER;
+    }
+
+    if (flags & SHFL_INFO_FILE)
+        return vbsfQueryFileInfo(pClient, root, Handle, flags, pcbBuffer, pBuffer);
+
+    if (flags & SHFL_INFO_VOLUME)
+        return vbsfQueryVolumeInfo(pClient, root, flags, pcbBuffer, pBuffer);
+
+    AssertFailed();
+    return VERR_INVALID_PARAMETER;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_INFORMATION API.  Located here as a form of API
+ * documentation. */
+void testFSInfo(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testFSInfoBadParameters(hTest);
+    /* Basic get and set file size test. */
+    testFSInfoQuerySetFMode(hTest);
+    /* Basic get and set dir atime test. */
+    testFSInfoQuerySetDirATime(hTest);
+    /* Basic get and set file atime test. */
+    testFSInfoQuerySetFileATime(hTest);
+    /* Basic set end of file. */
+    testFSInfoQuerySetEndOfFile(hTest);
+    /* Add tests as required... */
+}
+#endif
+int vbsfSetFSInfo(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint32_t flags, uint32_t *pcbBuffer, uint8_t *pBuffer)
+{
+    uint32_t type =   vbsfQueryHandleType(pClient, Handle)
+                    & (SHFL_HF_TYPE_DIR|SHFL_HF_TYPE_FILE|SHFL_HF_TYPE_VOLUME);
+
+    if (type == 0 || pcbBuffer == 0 || pBuffer == 0)
+    {
+        AssertFailed();
+        return VERR_INVALID_PARAMETER;
+    }
+
+    if (flags & SHFL_INFO_FILE)
+        return vbsfSetFileInfo(pClient, root, Handle, flags, pcbBuffer, pBuffer);
+
+    if (flags & SHFL_INFO_SIZE)
+        return vbsfSetEndOfFile(pClient, root, Handle, flags, pcbBuffer, pBuffer);
+
+//    if (flags & SHFL_INFO_VOLUME)
+//        return vbsfVolumeInfo(pClient, root, Handle, flags, pcbBuffer, pBuffer);
+    AssertFailed();
+    return VERR_INVALID_PARAMETER;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_LOCK API.  Located here as a form of API
+ * documentation. */
+void testLock(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testLockBadParameters(hTest);
+    /* Simple file locking and unlocking test. */
+    testLockFileSimple(hTest);
+    /* Add tests as required... */
+}
+#endif
+
+int vbsfLock(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint64_t offset, uint64_t length, uint32_t flags)
+{
+    SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, Handle);
+    uint32_t        fRTLock = 0;
+
+    Assert((flags & SHFL_LOCK_MODE_MASK) != SHFL_LOCK_CANCEL);
+
+    int rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_READ);
+    if (RT_SUCCESS(rc))
+    { /* likely */ }
+    else
+        return rc;
+
+    if (   ((flags & SHFL_LOCK_MODE_MASK) == SHFL_LOCK_CANCEL)
+        || (flags & SHFL_LOCK_ENTIRE)
+       )
+    {
+        AssertFailed();
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Lock type */
+    switch(flags & SHFL_LOCK_MODE_MASK)
+    {
+    case SHFL_LOCK_SHARED:
+        fRTLock = RTFILE_LOCK_READ;
+        break;
+
+    case SHFL_LOCK_EXCLUSIVE:
+        fRTLock = RTFILE_LOCK_READ | RTFILE_LOCK_WRITE;
+        break;
+
+    default:
+        AssertFailed();
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Lock wait type */
+    if (flags & SHFL_LOCK_WAIT)
+        fRTLock |= RTFILE_LOCK_WAIT;
+    else
+        fRTLock |= RTFILE_LOCK_IMMEDIATELY;
+
+#ifdef RT_OS_WINDOWS
+    rc = RTFileLock(pHandle->file.Handle, fRTLock, offset, length);
+    if (rc != VINF_SUCCESS)
+        Log(("RTFileLock %RTfile %RX64 %RX64 failed with %Rrc\n", pHandle->file.Handle, offset, length, rc));
+#else
+    Log(("vbsfLock: Pretend success handle=%x\n", Handle));
+    rc = VINF_SUCCESS;
+    RT_NOREF2(offset,  length);
+#endif
+    return rc;
+}
+
+int vbsfUnlock(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint64_t offset, uint64_t length, uint32_t flags)
+{
+    SHFLFILEHANDLE *pHandle = vbsfQueryFileHandle(pClient, Handle);
+
+    Assert((flags & SHFL_LOCK_MODE_MASK) == SHFL_LOCK_CANCEL);
+
+    int rc = vbsfCheckHandleAccess(pClient, root, pHandle, VBSF_CHECK_ACCESS_READ);
+    if (RT_SUCCESS(rc))
+    { /* likely */ }
+    else
+        return rc;
+
+    if (   ((flags & SHFL_LOCK_MODE_MASK) != SHFL_LOCK_CANCEL)
+        || (flags & SHFL_LOCK_ENTIRE)
+       )
+    {
+       return VERR_INVALID_PARAMETER;
+    }
+
+#ifdef RT_OS_WINDOWS
+    rc = RTFileUnlock(pHandle->file.Handle, offset, length);
+    if (rc != VINF_SUCCESS)
+        Log(("RTFileUnlock %RTfile %RX64 %RTX64 failed with %Rrc\n", pHandle->file.Handle, offset, length, rc));
+#else
+    Log(("vbsfUnlock: Pretend success handle=%x\n", Handle));
+    rc = VINF_SUCCESS;
+    RT_NOREF2(offset,  length);
+#endif
+
+    return rc;
+}
+
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_REMOVE API.  Located here as a form of API
+ * documentation. */
+void testRemove(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testRemoveBadParameters(hTest);
+    /* Add tests as required... */
+}
+#endif
+int vbsfRemove(SHFLCLIENTDATA *pClient, SHFLROOT root, PCSHFLSTRING pPath, uint32_t cbPath, uint32_t flags, SHFLHANDLE hToClose)
+{
+
+    /* Validate input */
+    Assert(pPath);
+    AssertReturn(pPath->u16Size > 0, VERR_INVALID_PARAMETER);
+
+    /*
+     * Close the handle if specified.
+     */
+    int rc = VINF_SUCCESS;
+    if (hToClose != SHFL_HANDLE_NIL)
+        rc = vbsfClose(pClient, root, hToClose);
+    if (RT_SUCCESS(rc))
+    {
+        /*
+         * Build a host full path for the given path and convert ucs2 to utf8 if necessary.
+         */
+        char *pszFullPath = NULL;
+        rc = vbsfBuildFullPath(pClient, root, pPath, cbPath, &pszFullPath, NULL);
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Is the guest allowed to write to this share?
+             */
+            bool fWritable;
+            rc = vbsfMappingsQueryWritable(pClient, root, &fWritable);
+            if (RT_SUCCESS(rc) && fWritable)
+            {
+                /*
+                 * Do the removal/deletion according to the type flags.
+                 */
+                if (flags & SHFL_REMOVE_SYMLINK)
+                    rc = RTSymlinkDelete(pszFullPath, 0);
+                else if (flags & SHFL_REMOVE_FILE)
+                    rc = RTFileDelete(pszFullPath);
+                else
+                    rc = RTDirRemove(pszFullPath);
+
+#if 0 //ndef RT_OS_WINDOWS
+                /* There are a few adjustments to be made here: */
+                if (   rc == VERR_FILE_NOT_FOUND
+                    && SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(pClient)
+                    && vbsfErrorStyleIsWindowsPathNotFound(pszFullPath))
+                    rc = VERR_PATH_NOT_FOUND;
+                else if (   rc == VERR_PATH_NOT_FOUND
+                         && SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(pClient))
+                {
+                    if (flags & (SHFL_REMOVE_FILE | SHFL_REMOVE_SYMLINK))
+                    {
+                        size_t cchFullPath = strlen(pszFullPath);
+                        if (cchFullPath > 0 && RTPATH_IS_SLASH(pszFullPath[cchFullPath - 1]))
+                            rc = VERR_INVALID_NAME;
+                    }
+                    else if (vbsfErrorStyleIsWindowsNotADirectory(pszFullPath))
+                        rc = VERR_NOT_A_DIRECTORY;
+                }
+#endif
+            }
+            else
+                rc = VERR_WRITE_PROTECT;
+
+            /* free the path string */
+            vbsfFreeFullPath(pszFullPath);
+        }
+    }
+    return rc;
+}
+
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_RENAME API.  Located here as a form of API
+ * documentation. */
+void testRename(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testRenameBadParameters(hTest);
+    /* Add tests as required... */
+}
+#endif
+int vbsfRename(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLSTRING *pSrc, SHFLSTRING *pDest, uint32_t flags)
+{
+    int rc = VINF_SUCCESS;
+
+    /* Validate input */
+    if (   flags & ~(SHFL_RENAME_FILE|SHFL_RENAME_DIR|SHFL_RENAME_REPLACE_IF_EXISTS)
+        || pSrc == 0
+        || pDest == 0)
+    {
+        AssertFailed();
+        return VERR_INVALID_PARAMETER;
+    }
+
+    /* Build a host full path for the given path
+     * and convert ucs2 to utf8 if necessary.
+     */
+    char *pszFullPathSrc = NULL;
+    char *pszFullPathDest = NULL;
+
+    rc = vbsfBuildFullPath(pClient, root, pSrc, pSrc->u16Size + SHFLSTRING_HEADER_SIZE, &pszFullPathSrc, NULL);
+    if (rc != VINF_SUCCESS)
+        return rc;
+
+    rc = vbsfBuildFullPath(pClient, root, pDest, pDest->u16Size + SHFLSTRING_HEADER_SIZE, &pszFullPathDest, NULL, false, true);
+    if (RT_SUCCESS (rc))
+    {
+        Log(("Rename %s to %s\n", pszFullPathSrc, pszFullPathDest));
+
+        /* is the guest allowed to write to this share? */
+        bool fWritable;
+        rc = vbsfMappingsQueryWritable(pClient, root, &fWritable);
+        if (RT_FAILURE(rc) || !fWritable)
+            rc = VERR_WRITE_PROTECT;
+
+        if (RT_SUCCESS(rc))
+        {
+            if ((flags & (SHFL_RENAME_FILE | SHFL_RENAME_DIR)) == (SHFL_RENAME_FILE | SHFL_RENAME_DIR))
+            {
+                rc = RTPathRename(pszFullPathSrc, pszFullPathDest,
+                                  flags & SHFL_RENAME_REPLACE_IF_EXISTS ? RTPATHRENAME_FLAGS_REPLACE : 0);
+            }
+            else if (flags & SHFL_RENAME_FILE)
+            {
+                rc = RTFileMove(pszFullPathSrc, pszFullPathDest,
+                                ((flags & SHFL_RENAME_REPLACE_IF_EXISTS) ? RTFILEMOVE_FLAGS_REPLACE : 0));
+            }
+            else
+            {
+                /* NT ignores the REPLACE flag and simply return and already exists error. */
+                rc = RTDirRename(pszFullPathSrc, pszFullPathDest,
+                                 ((flags & SHFL_RENAME_REPLACE_IF_EXISTS) ? RTPATHRENAME_FLAGS_REPLACE : 0));
+            }
+#ifndef RT_OS_WINDOWS
+            if (   rc == VERR_FILE_NOT_FOUND
+                && SHFL_CLIENT_NEED_WINDOWS_ERROR_STYLE_ADJUST_ON_POSIX(pClient)
+                && vbsfErrorStyleIsWindowsPathNotFound2(pszFullPathSrc, pszFullPathDest))
+                rc = VERR_PATH_NOT_FOUND;
+#endif
+        }
+
+        /* free the path string */
+        vbsfFreeFullPath(pszFullPathDest);
+    }
+    /* free the path string */
+    vbsfFreeFullPath(pszFullPathSrc);
+    return rc;
+}
+
+/**
+ * Implements SHFL_FN_COPY_FILE (wrapping RTFileCopy).
+ */
+int vbsfCopyFile(SHFLCLIENTDATA *pClient, SHFLROOT idRootSrc, PCSHFLSTRING pStrPathSrc,
+                 SHFLROOT idRootDst, PCSHFLSTRING pStrPathDst, uint32_t fFlags)
+{
+    AssertPtrReturn(pClient, VERR_INVALID_PARAMETER);
+    if (pClient->fu32Flags & SHFL_CF_UTF8)
+        LogFunc(("pClient %p, idRootSrc %#RX32, '%.*s', idRootSrc %#RX32, '%.*s', fFlags %#x\n", pClient, idRootSrc,
+                 pStrPathSrc->u16Length, pStrPathSrc->String.ach, idRootDst, pStrPathDst->u16Length, pStrPathDst->String.ach, fFlags));
+    else
+        LogFunc(("pClient %p, idRootSrc %#RX32, '%.*ls', idRootSrc %#RX32, '%.*ls', fFlags %#x\n", pClient,
+                 idRootSrc, pStrPathSrc->u16Length / sizeof(RTUTF16), pStrPathSrc->String.ach,
+                 idRootDst, pStrPathDst->u16Length / sizeof(RTUTF16), pStrPathDst->String.ach, fFlags));
+
+    /*
+     * Build host paths.
+     */
+    char *pszPathSrc = NULL;
+    int rc = vbsfBuildFullPath(pClient, idRootSrc, pStrPathSrc, pStrPathSrc->u16Size + SHFLSTRING_HEADER_SIZE, &pszPathSrc, NULL);
+    if (RT_SUCCESS(rc))
+    {
+        char *pszPathDst = NULL;
+        rc = vbsfBuildFullPath(pClient, idRootDst, pStrPathDst, pStrPathDst->u16Size + SHFLSTRING_HEADER_SIZE, &pszPathDst, NULL);
+        if (RT_SUCCESS(rc))
+        {
+            /*
+             * Do the job.
+             */
+            rc = RTFileCopy(pszPathSrc, pszPathDst);
+
+            vbsfFreeFullPath(pszPathDst);
+        }
+        vbsfFreeFullPath(pszPathSrc);
+    }
+
+    RT_NOREF(fFlags);
+    LogFunc(("returns %Rrc\n", rc));
+    return rc;
+}
+
+#ifdef UNITTEST
+/** Unit test the SHFL_FN_SYMLINK API.  Located here as a form of API
+ * documentation. */
+void testSymlink(RTTEST hTest)
+{
+    /* If the number or types of parameters are wrong the API should fail. */
+    testSymlinkBadParameters(hTest);
+    /* Add tests as required... */
+}
+#endif
+int vbsfSymlink(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLSTRING *pNewPath, SHFLSTRING *pOldPath, SHFLFSOBJINFO *pInfo)
+{
+    int rc = VINF_SUCCESS;
+
+    char *pszFullNewPath = NULL;
+    char *pszFullOldPath = NULL;
+
+    /* XXX: no support for UCS2 at the moment. */
+    if (!BIT_FLAG(pClient->fu32Flags, SHFL_CF_UTF8))
+        return VERR_NOT_IMPLEMENTED;
+
+    bool fSymlinksCreate;
+    rc = vbsfMappingsQuerySymlinksCreate(pClient, root, &fSymlinksCreate);
+    AssertRCReturn(rc, rc);
+    if (!fSymlinksCreate)
+        return VERR_WRITE_PROTECT; /* XXX or VERR_TOO_MANY_SYMLINKS? */
+
+    rc = vbsfBuildFullPath(pClient, root, pNewPath, pNewPath->u16Size + SHFLSTRING_HEADER_SIZE, &pszFullNewPath, NULL);
+    AssertRCReturn(rc, rc);
+
+    /* Verify that the link target can be a valid host path, i.e. does not contain invalid characters. */
+    uint32_t fu32PathFlags = 0;
+    uint32_t fu32Options = 0;
+    rc = vbsfPathGuestToHost(pClient, root, pOldPath, pOldPath->u16Size + SHFLSTRING_HEADER_SIZE,
+                             &pszFullOldPath, NULL, fu32Options, &fu32PathFlags);
+    if (RT_FAILURE(rc))
+    {
+        vbsfFreeFullPath(pszFullNewPath);
+        return rc;
+    }
+
+    /** @todo r=bird: We _must_ perform slash conversion on the target (what this
+     *        code calls 'pOldPath' for some peculiar reason)! */
+
+    rc = RTSymlinkCreate(pszFullNewPath, (const char *)pOldPath->String.utf8,
+                         RTSYMLINKTYPE_UNKNOWN, 0);
+    if (RT_SUCCESS(rc))
+    {
+        RTFSOBJINFO info;
+        rc = RTPathQueryInfoEx(pszFullNewPath, &info, RTFSOBJATTRADD_NOTHING, RTPATH_F_ON_LINK);
+        if (RT_SUCCESS(rc))
+            vbfsCopyFsObjInfoFromIprt(pInfo, &info);
+    }
+
+    vbsfFreeFullPath(pszFullOldPath);
+    vbsfFreeFullPath(pszFullNewPath);
+
+    return rc;
+}
+
+/*
+ * Clean up our mess by freeing all handles that are still valid.
+ *
+ */
+int vbsfDisconnect(SHFLCLIENTDATA *pClient)
+{
+    for (int i = 0; i < SHFLHANDLE_MAX; ++i)
+    {
+        SHFLFILEHANDLE *pHandle = NULL;
+        SHFLHANDLE Handle = (SHFLHANDLE)i;
+
+        uint32_t type = vbsfQueryHandleType(pClient, Handle);
+        switch (type & (SHFL_HF_TYPE_DIR | SHFL_HF_TYPE_FILE))
+        {
+            case SHFL_HF_TYPE_DIR:
+            {
+                pHandle = vbsfQueryDirHandle(pClient, Handle);
+                break;
+            }
+            case SHFL_HF_TYPE_FILE:
+            {
+                pHandle = vbsfQueryFileHandle(pClient, Handle);
+                break;
+            }
+            default:
+                break;
+        }
+
+        if (pHandle)
+        {
+            LogFunc(("Opened handle 0x%08x\n", i));
+            vbsfClose(pClient, pHandle->root, Handle);
+        }
+    }
+
+    for (uint32_t i = 0; i < RT_ELEMENTS(pClient->acMappings); i++)
+        if (pClient->acMappings[i])
+        {
+            uint16_t cMappings = pClient->acMappings[i];
+            while (cMappings-- > 0)
+                vbsfUnmapFolder(pClient, i);
+        }
+
+    return VINF_SUCCESS;
+}
+
diff --git a/src/VBox/HostServices/SharedFolders/vbsf.h b/src/VBox/HostServices/SharedFolders/vbsf.h
new file mode 100644
index 00000000..04ef280a
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/vbsf.h
@@ -0,0 +1,68 @@
+/* $Id: vbsf.h $ */
+/** @file
+ * VBox Shared Folders header.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_SharedFolders_vbsf_h
+#define VBOX_INCLUDED_SRC_SharedFolders_vbsf_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include "shfl.h"
+#include <VBox/shflsvc.h>
+
+int vbsfCreate(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLSTRING *pPath, uint32_t cbPath, SHFLCREATEPARMS *pParms);
+
+int vbsfClose(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle);
+
+int vbsfRead(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint64_t offset, uint32_t *pcbBuffer, uint8_t *pBuffer);
+int vbsfReadPages(SHFLCLIENTDATA *pClient, SHFLROOT idRoot, SHFLHANDLE hFile, uint64_t offFile,
+                  uint32_t *pcbBuffer, PVBOXHGCMSVCPARMPAGES pPages);
+int vbsfWrite(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint64_t *poffFile, uint32_t *pcbBuffer, uint8_t *pBuffer);
+int vbsfWritePages(SHFLCLIENTDATA *pClient, SHFLROOT idRoot, SHFLHANDLE hFile, uint64_t *poffFile,
+                   uint32_t *pcbBuffer, PVBOXHGCMSVCPARMPAGES pPages);
+int vbsfCopyFilePart(SHFLCLIENTDATA *pClient, SHFLROOT idRootSrc, SHFLHANDLE hFileSrc, uint64_t offSrc,
+                     SHFLROOT idRootDst, SHFLHANDLE hFileDst, uint64_t offDst, uint64_t *pcbToCopy, uint32_t fFlags);
+
+int vbsfLock(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint64_t offset, uint64_t length, uint32_t flags);
+int vbsfUnlock(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint64_t offset, uint64_t length, uint32_t flags);
+int vbsfRemove(SHFLCLIENTDATA *pClient, SHFLROOT root, PCSHFLSTRING pPath, uint32_t cbPath, uint32_t flags, SHFLHANDLE hToClose);
+int vbsfRename(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLSTRING *pSrc, SHFLSTRING *pDest, uint32_t flags);
+int vbsfCopyFile(SHFLCLIENTDATA *pClient, SHFLROOT idRootSrc, PCSHFLSTRING pStrPathSrc,
+                 SHFLROOT idRootDst, PCSHFLSTRING pStrPathDst, uint32_t fFlags);
+int vbsfDirList(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, SHFLSTRING *pPath, uint32_t flags, uint32_t *pcbBuffer, uint8_t *pBuffer, uint32_t *pIndex, uint32_t *pcFiles);
+int vbsfFileInfo(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint32_t flags, uint32_t *pcbBuffer, uint8_t *pBuffer);
+int vbsfSetFileSize(SHFLCLIENTDATA *pClient, SHFLROOT idRoot, SHFLHANDLE hHandle, uint64_t cbNewSize);
+int vbsfQueryFSInfo(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint32_t flags, uint32_t *pcbBuffer, uint8_t *pBuffer);
+int vbsfSetFSInfo(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint32_t flags, uint32_t *pcbBuffer, uint8_t *pBuffer);
+int vbsfFlush(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle);
+int vbsfDisconnect(SHFLCLIENTDATA *pClient);
+int vbsfQueryFileInfo(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLHANDLE Handle, uint32_t flags, uint32_t *pcbBuffer, uint8_t *pBuffer);
+int vbsfReadLink(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLSTRING *pPath, uint32_t cbPath, uint8_t *pBuffer, uint32_t cbBuffer);
+int vbsfSymlink(SHFLCLIENTDATA *pClient, SHFLROOT root, SHFLSTRING *pNewPath, SHFLSTRING *pOldPath, SHFLFSOBJINFO *pInfo);
+
+#endif /* !VBOX_INCLUDED_SRC_SharedFolders_vbsf_h */
+
diff --git a/src/VBox/HostServices/SharedFolders/vbsfpath.cpp b/src/VBox/HostServices/SharedFolders/vbsfpath.cpp
new file mode 100644
index 00000000..afd13c4d
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/vbsfpath.cpp
@@ -0,0 +1,709 @@
+/* $Id: vbsfpath.cpp $ */
+/** @file
+ * Shared Folders Service - guest/host path convertion and verification.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_FOLDERS
+#ifdef UNITTEST
+# include "testcase/tstSharedFolderService.h"
+#endif
+
+#include "vbsfpath.h"
+#include "mappings.h"
+#include "vbsf.h"
+#include "shflhandle.h"
+
+#include <iprt/alloc.h>
+#include <iprt/asm.h>
+#include <iprt/assert.h>
+#include <iprt/fs.h>
+#include <iprt/dir.h>
+#include <iprt/file.h>
+#include <iprt/path.h>
+#include <iprt/string.h>
+#include <iprt/symlink.h>
+#include <iprt/uni.h>
+#include <iprt/stream.h>
+#ifdef RT_OS_DARWIN
+# include <Carbon/Carbon.h>
+#endif
+
+#ifdef UNITTEST
+# include "teststubs.h"
+#endif
+
+
+/*********************************************************************************************************************************
+*   Defined Constants And Macros                                                                                                 *
+*********************************************************************************************************************************/
+#define SHFL_RT_LINK(pClient) ((pClient)->fu32Flags & SHFL_CF_SYMLINKS ? RTPATH_F_ON_LINK : RTPATH_F_FOLLOW_LINK)
+
+
+/**
+ * @todo find a better solution for supporting the execute bit for non-windows
+ * guests on windows host. Search for "0111" to find all the relevant places.
+ */
+
+/**
+ * Corrects the casing of the final component
+ *
+ * @returns
+ * @param   pClient             .
+ * @param   pszFullPath         .
+ * @param   pszStartComponent   .
+ */
+static int vbsfCorrectCasing(SHFLCLIENTDATA *pClient, char *pszFullPath, char *pszStartComponent)
+{
+    Log2(("vbsfCorrectCasing: %s %s\n", pszFullPath, pszStartComponent));
+
+    AssertReturn((uintptr_t)pszFullPath < (uintptr_t)pszStartComponent - 1U, VERR_INTERNAL_ERROR_2);
+    AssertReturn(pszStartComponent[-1] == RTPATH_DELIMITER, VERR_INTERNAL_ERROR_5);
+
+    /*
+     * Allocate a buffer that can hold really long file name entries as well as
+     * the initial search pattern.
+     */
+    size_t cchComponent = strlen(pszStartComponent);
+    size_t cchParentDir = pszStartComponent - pszFullPath;
+    size_t cchFullPath  = cchParentDir + cchComponent;
+    Assert(strlen(pszFullPath) == cchFullPath);
+
+    size_t cbDirEntry   = 4096;
+    if (cchFullPath + 4 > cbDirEntry - RT_OFFSETOF(RTDIRENTRYEX, szName))
+        cbDirEntry = RT_OFFSETOF(RTDIRENTRYEX, szName) + cchFullPath + 4;
+
+    PRTDIRENTRYEX pDirEntry = (PRTDIRENTRYEX)RTMemAlloc(cbDirEntry);
+    if (pDirEntry == NULL)
+        return VERR_NO_MEMORY;
+
+    /*
+     * Construct the search criteria in the szName member of pDirEntry.
+     */
+    /** @todo This is quite inefficient, especially for directories with many
+     *        files.  If any of the typically case sensitive host systems start
+     *        supporting opendir wildcard filters, it would make sense to build
+     *        one here with '?' for case foldable charaters. */
+    /** @todo Use RTDirOpen here and drop the whole uncessary path copying? */
+    int rc = RTPathJoinEx(pDirEntry->szName, cbDirEntry - RT_OFFSETOF(RTDIRENTRYEX, szName),
+                          pszFullPath, cchParentDir,
+                          RT_STR_TUPLE("*"), RTPATH_STR_F_STYLE_HOST);
+    AssertRC(rc);
+    if (RT_SUCCESS(rc))
+    {
+        RTDIR hSearch = NULL;
+        rc = RTDirOpenFiltered(&hSearch, pDirEntry->szName, RTDIRFILTER_WINNT, 0 /*fFlags*/);
+        if (RT_SUCCESS(rc))
+        {
+            for (;;)
+            {
+                size_t cbDirEntrySize = cbDirEntry;
+
+                rc = RTDirReadEx(hSearch, pDirEntry, &cbDirEntrySize, RTFSOBJATTRADD_NOTHING, SHFL_RT_LINK(pClient));
+                if (rc == VERR_NO_MORE_FILES)
+                    break;
+
+                if (   rc != VINF_SUCCESS
+                    && rc != VWRN_NO_DIRENT_INFO)
+                {
+                    if (   rc == VERR_NO_TRANSLATION
+                        || rc == VERR_INVALID_UTF8_ENCODING)
+                        continue;
+                    AssertMsgFailed(("%Rrc\n", rc));
+                    break;
+                }
+
+                Log2(("vbsfCorrectCasing: found %s\n", &pDirEntry->szName[0]));
+                if (    pDirEntry->cbName == cchComponent
+                    &&  !RTStrICmp(pszStartComponent, &pDirEntry->szName[0]))
+                {
+                    Log(("Found original name %s (%s)\n", &pDirEntry->szName[0], pszStartComponent));
+                    strcpy(pszStartComponent, &pDirEntry->szName[0]);
+                    rc = VINF_SUCCESS;
+                    break;
+                }
+            }
+
+            RTDirClose(hSearch);
+        }
+    }
+
+    if (RT_FAILURE(rc))
+        Log(("vbsfCorrectCasing %s failed with %Rrc\n", pszStartComponent, rc));
+
+    RTMemFree(pDirEntry);
+
+    return rc;
+}
+
+/* Temporary stand-in for RTPathExistEx. */
+static int vbsfQueryExistsEx(const char *pszPath, uint32_t fFlags)
+{
+#if 0 /** @todo Fix the symlink issue on windows! */
+    return RTPathExistsEx(pszPath, fFlags);
+#else
+    RTFSOBJINFO IgnInfo;
+    return RTPathQueryInfoEx(pszPath, &IgnInfo, RTFSOBJATTRADD_NOTHING, fFlags);
+#endif
+}
+
+/**
+ * Helper for vbsfBuildFullPath that performs case corrections on the path
+ * that's being build.
+ *
+ * @returns VINF_SUCCESS at the moment.
+ * @param   pClient                 The client data.
+ * @param   pszFullPath             Pointer to the full path.  This is the path
+ *                                  which may need case corrections.  The
+ *                                  corrections will be applied in place.
+ * @param   cchFullPath             The length of the full path.
+ * @param   fWildCard               Whether the last component may contain
+ *                                  wildcards and thus might require exclusion
+ *                                  from the case correction.
+ * @param   fPreserveLastComponent  Always exclude the last component from case
+ *                                  correction if set.
+ */
+static int vbsfCorrectPathCasing(SHFLCLIENTDATA *pClient, char *pszFullPath, size_t cchFullPath,
+                                 bool fWildCard, bool fPreserveLastComponent)
+{
+    /*
+     * Hide the last path component if it needs preserving.  This is required
+     * in the following cases:
+     *    - Contains the wildcard(s).
+     *    - Is a 'rename' target.
+     */
+    char *pszLastComponent = NULL;
+    if (fWildCard || fPreserveLastComponent)
+    {
+        char *pszSrc = pszFullPath + cchFullPath - 1;
+        Assert(strchr(pszFullPath, '\0') == pszSrc + 1);
+        while ((uintptr_t)pszSrc > (uintptr_t)pszFullPath)
+        {
+            if (*pszSrc == RTPATH_DELIMITER)
+                break;
+            pszSrc--;
+        }
+        if (*pszSrc == RTPATH_DELIMITER)
+        {
+            if (   fPreserveLastComponent
+                /* Or does it really have wildcards? */
+                || strchr(pszSrc + 1, '*') != NULL
+                || strchr(pszSrc + 1, '?') != NULL
+                || strchr(pszSrc + 1, '>') != NULL
+                || strchr(pszSrc + 1, '<') != NULL
+                || strchr(pszSrc + 1, '"') != NULL )
+            {
+                pszLastComponent = pszSrc;
+                *pszLastComponent = '\0';
+            }
+        }
+    }
+
+    /*
+     * If the path/file doesn't exist, we need to attempt case correcting it.
+     */
+    /** @todo Don't check when creating files or directories; waste of time. */
+    int rc = vbsfQueryExistsEx(pszFullPath, SHFL_RT_LINK(pClient));
+    if (rc == VERR_FILE_NOT_FOUND || rc == VERR_PATH_NOT_FOUND)
+    {
+        Log(("Handle case insensitive guest fs on top of host case sensitive fs for %s\n", pszFullPath));
+
+        /*
+         * Work from the end of the path to find a partial path that's valid.
+         */
+        char *pszSrc = pszLastComponent ? pszLastComponent - 1 : pszFullPath + cchFullPath - 1;
+        Assert(strchr(pszFullPath, '\0') == pszSrc + 1);
+
+        while ((uintptr_t)pszSrc > (uintptr_t)pszFullPath)
+        {
+            if (*pszSrc == RTPATH_DELIMITER)
+            {
+                *pszSrc = '\0';
+                rc = vbsfQueryExistsEx(pszFullPath, SHFL_RT_LINK(pClient));
+                *pszSrc = RTPATH_DELIMITER;
+                if (RT_SUCCESS(rc))
+                {
+#ifdef DEBUG
+                    *pszSrc = '\0';
+                    Log(("Found valid partial path %s\n", pszFullPath));
+                    *pszSrc = RTPATH_DELIMITER;
+#endif
+                    break;
+                }
+            }
+
+            pszSrc--;
+        }
+        Assert(*pszSrc == RTPATH_DELIMITER && RT_SUCCESS(rc));
+        if (   *pszSrc == RTPATH_DELIMITER
+            && RT_SUCCESS(rc))
+        {
+            /*
+             * Turn around and work the other way case correcting the components.
+             */
+            pszSrc++;
+            for (;;)
+            {
+                bool fEndOfString = true;
+
+                /* Find the end of the component. */
+                char *pszEnd = pszSrc;
+                while (*pszEnd)
+                {
+                    if (*pszEnd == RTPATH_DELIMITER)
+                        break;
+                    pszEnd++;
+                }
+
+                if (*pszEnd == RTPATH_DELIMITER)
+                {
+                    fEndOfString = false;
+                    *pszEnd = '\0';
+#if 0 /** @todo Please, double check this. The original code is in the #if 0, what I hold as correct is in the #else. */
+                    rc = RTPathQueryInfoEx(pszSrc, &info, RTFSOBJATTRADD_NOTHING, SHFL_RT_LINK(pClient));
+#else
+                    rc = vbsfQueryExistsEx(pszFullPath, SHFL_RT_LINK(pClient));
+#endif
+                    Assert(rc == VINF_SUCCESS || rc == VERR_FILE_NOT_FOUND || rc == VERR_PATH_NOT_FOUND);
+                }
+                else if (pszEnd == pszSrc)
+                    rc = VINF_SUCCESS;  /* trailing delimiter */
+                else
+                    rc = VERR_FILE_NOT_FOUND;
+
+                if (rc == VERR_FILE_NOT_FOUND || rc == VERR_PATH_NOT_FOUND)
+                {
+                    /* Path component is invalid; try to correct the casing. */
+                    rc = vbsfCorrectCasing(pClient, pszFullPath, pszSrc);
+                    if (RT_FAILURE(rc))
+                    {
+                        /* Failed, so don't bother trying any further components. */
+                        if (!fEndOfString)
+                            *pszEnd = RTPATH_DELIMITER; /* Restore the original full path. */
+                        break;
+                    }
+                }
+
+                /* Next (if any). */
+                if (fEndOfString)
+                    break;
+
+                *pszEnd = RTPATH_DELIMITER;
+                pszSrc = pszEnd + 1;
+            }
+            if (RT_FAILURE(rc))
+                Log(("Unable to find suitable component rc=%d\n", rc));
+        }
+        else
+            rc = VERR_FILE_NOT_FOUND;
+
+    }
+
+    /* Restore the final component if it was dropped. */
+    if (pszLastComponent)
+        *pszLastComponent = RTPATH_DELIMITER;
+
+    /* might be a new file so don't fail here! */
+    return VINF_SUCCESS;
+}
+
+
+#ifdef RT_OS_DARWIN
+/* Misplaced hack! See todo! */
+
+/** Normalize the string using kCFStringNormalizationFormD.
+ *
+ * @param pwszSrc  The input UTF-16 string.
+ * @param cwcSrc   Length of the input string in characters.
+ * @param ppwszDst Where to store the pointer to the resulting normalized string.
+ * @param pcwcDst  Where to store length of the normalized string in characters (without the trailing nul).
+ */
+static int vbsfNormalizeStringDarwin(PCRTUTF16 pwszSrc, uint32_t cwcSrc, PRTUTF16 *ppwszDst, uint32_t *pcwcDst)
+{
+    /** @todo This belongs in rtPathToNative or in the windows shared folder file system driver...
+     * The question is simply whether the NFD normalization is actually applied on a (virtual) file
+     * system level in darwin, or just by the user mode application libs. */
+
+    PRTUTF16 pwszNFD;
+    uint32_t cwcNFD;
+
+    CFMutableStringRef inStr = ::CFStringCreateMutable(NULL, 0);
+
+    /* Is 8 times length enough for decomposed in worst case...? */
+    size_t cbNFDAlloc = cwcSrc * 8 + 2;
+    pwszNFD = (PRTUTF16)RTMemAllocZ(cbNFDAlloc);
+    if (!pwszNFD)
+    {
+        return VERR_NO_MEMORY;
+    }
+
+    ::CFStringAppendCharacters(inStr, (UniChar*)pwszSrc, cwcSrc);
+    ::CFStringNormalize(inStr, kCFStringNormalizationFormD);
+    cwcNFD = ::CFStringGetLength(inStr);
+
+    CFRange rangeCharacters;
+    rangeCharacters.location = 0;
+    rangeCharacters.length = cwcNFD;
+    ::CFStringGetCharacters(inStr, rangeCharacters, pwszNFD);
+
+    pwszNFD[cwcNFD] = 0x0000; /* NULL terminated */
+
+    CFRelease(inStr);
+
+    *ppwszDst = pwszNFD;
+    *pcwcDst = cwcNFD;
+    return VINF_SUCCESS;
+}
+#endif
+
+
+#if defined(RT_OS_WINDOWS) || defined(RT_OS_OS2)
+/* See MSDN "Naming Files, Paths, and Namespaces".
+ * '<', '>' and '"' are allowed as possible wildcards (see ANSI_DOS_STAR, etc in ntifs.h)
+ */
+static const char sachCharBlackList[] = ":/\\|";
+#else
+/* Something else. */
+static const char sachCharBlackList[] = "/";
+#endif
+
+/** Verify if the character can be used in a host file name.
+ * Wildcard characters ('?', '*') are allowed.
+ *
+ * @param c Character to verify.
+ */
+static bool vbsfPathIsValidNameChar(unsigned char c)
+{
+    /* Character 0 is not allowed too. */
+    if (c == 0 || strchr(sachCharBlackList, c))
+    {
+        return false;
+    }
+
+#if defined(RT_OS_WINDOWS) || defined(RT_OS_OS2)
+    /* Characters less than 32 are not allowed. */
+    if (c < 32)
+    {
+        return false;
+    }
+#endif
+
+    return true;
+}
+
+/** Verify if the character is a wildcard.
+ *
+ * @param c Character to verify.
+ */
+static bool vbsfPathIsWildcardChar(char c)
+{
+    if (   c == '*'
+        || c == '?'
+#ifdef RT_OS_WINDOWS /* See ntifs.h */
+        || c == '<' /* ANSI_DOS_STAR */
+        || c == '>' /* ANSI_DOS_QM */
+        || c == '"' /* ANSI_DOS_DOT */
+#endif
+       )
+    {
+        return true;
+    }
+
+    return false;
+}
+
+int vbsfPathGuestToHost(SHFLCLIENTDATA *pClient, SHFLROOT hRoot,
+                        PCSHFLSTRING pGuestString, uint32_t cbGuestString,
+                        char **ppszHostPath, uint32_t *pcbHostPathRoot,
+                        uint32_t fu32Options,
+                        uint32_t *pfu32PathFlags)
+{
+#ifdef VBOX_STRICT
+    /*
+     * Check that the pGuestPath has correct size and encoding.
+     */
+    if (ShflStringIsValidIn(pGuestString, cbGuestString, RT_BOOL(pClient->fu32Flags & SHFL_CF_UTF8)) == false)
+    {
+        LogFunc(("Invalid input string\n"));
+        return VERR_INTERNAL_ERROR;
+    }
+#else
+    NOREF(cbGuestString);
+#endif
+
+    /*
+     * Resolve the root handle into a string.
+     */
+    uint32_t cbRootLen = 0;
+    const char *pszRoot = NULL;
+    int rc = vbsfMappingsQueryHostRootEx(hRoot, &pszRoot, &cbRootLen);
+    if (RT_FAILURE(rc))
+    {
+        LogFunc(("invalid root\n"));
+        return rc;
+    }
+
+    AssertReturn(cbRootLen > 0, VERR_INTERNAL_ERROR_2); /* vbsfMappingsQueryHostRootEx ensures this. */
+
+    /*
+     * Get the UTF8 string with the relative path provided by the guest.
+     * If guest uses UTF-16 then convert it to UTF-8.
+     */
+    uint32_t    cbGuestPath = 0;        /* Shut up MSC */
+    const char *pchGuestPath = NULL;    /* Ditto. */
+    char *pchGuestPathAllocated = NULL; /* Converted from UTF-16. */
+    if (BIT_FLAG(pClient->fu32Flags, SHFL_CF_UTF8))
+    {
+        /* UTF-8 */
+        cbGuestPath = pGuestString->u16Length;
+        pchGuestPath = pGuestString->String.ach;
+    }
+    else
+    {
+        /* UTF-16 */
+
+#ifdef RT_OS_DARWIN /* Misplaced hack! See todo! */
+        uint32_t cwcSrc  = 0;
+        PRTUTF16 pwszSrc = NULL;
+        rc = vbsfNormalizeStringDarwin(&pGuestString->String.ucs2[0],
+                                       pGuestString->u16Length / sizeof(RTUTF16),
+                                       &pwszSrc, &cwcSrc);
+#else
+        uint32_t  const cwcSrc  = pGuestString->u16Length / sizeof(RTUTF16);
+        PCRTUTF16 const pwszSrc = &pGuestString->String.ucs2[0];
+#endif
+
+        if (RT_SUCCESS(rc))
+        {
+            size_t cbPathAsUtf8 = RTUtf16CalcUtf8Len(pwszSrc);
+            if (cbPathAsUtf8 >= cwcSrc)
+            {
+                /* Allocate buffer that will be able to contain the converted UTF-8 string. */
+                pchGuestPathAllocated = (char *)RTMemAlloc(cbPathAsUtf8 + 1);
+                if (RT_LIKELY(pchGuestPathAllocated != NULL))
+                {
+                    if (RT_LIKELY(cbPathAsUtf8))
+                    {
+                        size_t cchActual;
+                        char *pszDst = pchGuestPathAllocated;
+                        rc = RTUtf16ToUtf8Ex(pwszSrc, cwcSrc, &pszDst, cbPathAsUtf8 + 1, &cchActual);
+                        AssertRC(rc);
+                        AssertStmt(RT_FAILURE(rc) || cchActual == cbPathAsUtf8, rc = VERR_INTERNAL_ERROR_4);
+                        Assert(strlen(pszDst) == cbPathAsUtf8);
+                    }
+
+                    if (RT_SUCCESS(rc))
+                    {
+                        /* Terminate the string. */
+                        pchGuestPathAllocated[cbPathAsUtf8] = '\0';
+
+                        cbGuestPath = (uint32_t)cbPathAsUtf8; Assert(cbGuestPath == cbPathAsUtf8);
+                        pchGuestPath = pchGuestPathAllocated;
+                    }
+                }
+                else
+                {
+                    rc = VERR_NO_MEMORY;
+                }
+            }
+            else
+            {
+                AssertFailed();
+                rc = VERR_INTERNAL_ERROR_3;
+            }
+
+#ifdef RT_OS_DARWIN
+            RTMemFree(pwszSrc);
+#endif
+        }
+    }
+
+    char *pszFullPath = NULL;
+
+    if (RT_SUCCESS(rc))
+    {
+        LogFlowFunc(("Root %s path %.*s\n", pszRoot, cbGuestPath, pchGuestPath));
+
+        /*
+         * Allocate enough memory to build the host full path from the root and the relative path.
+         */
+        const uint32_t cbFullPathAlloc = cbRootLen + 1 + cbGuestPath + 1; /* root + possible_slash + relative + 0 */
+        pszFullPath = (char *)RTMemAlloc(cbFullPathAlloc);
+        if (RT_LIKELY(pszFullPath != NULL))
+        {
+            /* Buffer for the verified guest path. */
+            char *pchVerifiedPath = (char *)RTMemAlloc(cbGuestPath + 1);
+            if (RT_LIKELY(pchVerifiedPath != NULL))
+            {
+                /* Init the pointer for the guest relative path. */
+                uint32_t cbSrc = cbGuestPath;
+                const char *pchSrc = pchGuestPath;
+
+                /* Strip leading delimiters from the path the guest specified. */
+                while (   cbSrc > 0
+                       && *pchSrc == pClient->PathDelimiter)
+                {
+                    ++pchSrc;
+                    --cbSrc;
+                }
+
+                /*
+                 * Iterate the guest path components, verify each of them replacing delimiters with the host slash.
+                 */
+                char *pchDst = pchVerifiedPath;
+                bool fLastComponentHasWildcard = false;
+                for (; cbSrc > 0; --cbSrc, ++pchSrc)
+                {
+                    if (RT_LIKELY(*pchSrc != pClient->PathDelimiter))
+                    {
+                        if (RT_LIKELY(vbsfPathIsValidNameChar(*pchSrc)))
+                        {
+                            if (pfu32PathFlags && vbsfPathIsWildcardChar(*pchSrc))
+                            {
+                                fLastComponentHasWildcard = true;
+                            }
+
+                            *pchDst++ = *pchSrc;
+                        }
+                        else
+                        {
+                            rc = VERR_INVALID_NAME;
+                            break;
+                        }
+                    }
+                    else
+                    {
+                        /* Replace with the host slash. */
+                        *pchDst++ = RTPATH_SLASH;
+
+                        if (pfu32PathFlags && fLastComponentHasWildcard && cbSrc > 1)
+                        {
+                            /* Processed component has a wildcard and there are more characters in the path. */
+                            *pfu32PathFlags |= VBSF_F_PATH_HAS_WILDCARD_IN_PREFIX;
+                        }
+                        fLastComponentHasWildcard = false;
+                    }
+                }
+
+                if (RT_SUCCESS(rc))
+                {
+                    *pchDst++ = 0;
+
+                    /* Construct the full host path removing '.' and '..'. */
+                    rc = vbsfPathAbs(pszRoot, pchVerifiedPath, pszFullPath, cbFullPathAlloc);
+                    if (RT_SUCCESS(rc))
+                    {
+                        if (pfu32PathFlags && fLastComponentHasWildcard)
+                        {
+                            *pfu32PathFlags |= VBSF_F_PATH_HAS_WILDCARD_IN_LAST;
+                        }
+
+                        /* Check if the full path is still within the shared folder. */
+                        if (fu32Options & VBSF_O_PATH_CHECK_ROOT_ESCAPE)
+                        {
+                            if (!RTPathStartsWith(pszFullPath, pszRoot))
+                            {
+                                rc = VERR_INVALID_NAME;
+                            }
+                        }
+
+                        if (RT_SUCCESS(rc))
+                        {
+                            /*
+                             * If the host file system is case sensitive and the guest expects
+                             * a case insensitive fs, then correct the path components casing.
+                             */
+                            if (    vbsfIsHostMappingCaseSensitive(hRoot)
+                                && !vbsfIsGuestMappingCaseSensitive(hRoot))
+                            {
+                                const bool fWildCard = RT_BOOL(fu32Options & VBSF_O_PATH_WILDCARD);
+                                const bool fPreserveLastComponent = RT_BOOL(fu32Options & VBSF_O_PATH_PRESERVE_LAST_COMPONENT);
+                                rc = vbsfCorrectPathCasing(pClient, pszFullPath, strlen(pszFullPath),
+                                                           fWildCard, fPreserveLastComponent);
+                            }
+
+                            if (RT_SUCCESS(rc))
+                            {
+                               LogFlowFunc(("%s\n", pszFullPath));
+
+                               /* Return the full host path. */
+                               *ppszHostPath = pszFullPath;
+
+                               if (pcbHostPathRoot)
+                               {
+                                   /* Return the length of the root path without the trailing slash. */
+                                   *pcbHostPathRoot = RTPATH_IS_SLASH(pszFullPath[cbRootLen - 1]) ?
+                                                          cbRootLen - 1 : /* pszRoot already had the trailing slash. */
+                                                          cbRootLen; /* pszRoot did not have the trailing slash. */
+                               }
+                            }
+                        }
+                    }
+                    else
+                    {
+                        LogFunc(("vbsfPathAbs %Rrc\n", rc));
+                    }
+                }
+
+                RTMemFree(pchVerifiedPath);
+            }
+            else
+            {
+                rc = VERR_NO_MEMORY;
+            }
+        }
+        else
+        {
+            rc = VERR_NO_MEMORY;
+        }
+    }
+
+    /*
+     * Cleanup.
+     */
+    RTMemFree(pchGuestPathAllocated);
+
+    if (RT_SUCCESS(rc))
+    {
+        return rc;
+    }
+
+    /*
+     * Cleanup on failure.
+     */
+    RTMemFree(pszFullPath);
+
+    LogFunc(("%Rrc\n", rc));
+    return rc;
+}
+
+void vbsfFreeHostPath(char *pszHostPath)
+{
+    RTMemFree(pszHostPath);
+}
+
diff --git a/src/VBox/HostServices/SharedFolders/vbsfpath.h b/src/VBox/HostServices/SharedFolders/vbsfpath.h
new file mode 100644
index 00000000..f2b4e1a6
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/vbsfpath.h
@@ -0,0 +1,80 @@
+/* $Id: vbsfpath.h $ */
+/** @file
+ * Shared Folders Service - Guest/host path convertion and verification.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#ifndef VBOX_INCLUDED_SRC_SharedFolders_vbsfpath_h
+#define VBOX_INCLUDED_SRC_SharedFolders_vbsfpath_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include "shfl.h"
+#include <VBox/shflsvc.h>
+
+#define VBSF_O_PATH_WILDCARD                UINT32_C(0x00000001)
+#define VBSF_O_PATH_PRESERVE_LAST_COMPONENT UINT32_C(0x00000002)
+#define VBSF_O_PATH_CHECK_ROOT_ESCAPE       UINT32_C(0x00000004)
+
+#define VBSF_F_PATH_HAS_WILDCARD_IN_PREFIX UINT32_C(0x00000001) /* A component before the last one contains a wildcard. */
+#define VBSF_F_PATH_HAS_WILDCARD_IN_LAST   UINT32_C(0x00000002) /* The last component contains a wildcard. */
+
+/**
+ *
+ * @param pClient                Shared folder client.
+ * @param hRoot                  Root handle.
+ * @param pGuestString           Guest want to access the path.
+ * @param cbGuestString          Size of pGuestString memory buffer.
+ * @param ppszHostPath           Returned full host path: root prefix + guest path.
+ * @param pcbHostPathRoot        Length of the root prefix in bytes. Optional, can be NULL.
+ * @param fu32Options            Options.
+ * @param pfu32PathFlags         VBSF_F_PATH_* flags. Optional, can be NULL.
+ */
+int vbsfPathGuestToHost(SHFLCLIENTDATA *pClient, SHFLROOT hRoot,
+                        PCSHFLSTRING pGuestString, uint32_t cbGuestString,
+                        char **ppszHostPath, uint32_t *pcbHostPathRoot,
+                        uint32_t fu32Options, uint32_t *pfu32PathFlags);
+
+/** Free the host path returned by vbsfPathGuestToHost.
+ *
+ * @param pszHostPath Host path string.
+ */
+void vbsfFreeHostPath(char *pszHostPath);
+
+/**
+ * Build the absolute path by combining an absolute pszRoot and a relative pszPath.
+ * The resulting path does not contain '.' and '..' components.
+ * Similar to RTPathAbsEx but with support for Windows extended-length paths ("\\?\" prefix).
+ * Uses RTPathAbsEx for regular paths and on non-Windows hosts.
+ *
+ * @param pszRoot The absolute prefix. It is copied to the pszAbsPath without any processing.
+ *                If NULL then the pszPath must be converted to the absolute path.
+ * @param pszPath The relative path to be appended to pszRoot. Already has correct delimiters (RTPATH_SLASH).
+ * @param pszAbsPath Where to store the resulting absolute path.
+ * @param cbAbsPath Size of pszAbsBuffer in bytes.
+ */
+int vbsfPathAbs(const char *pszRoot, const char *pszPath, char *pszAbsPath, size_t cbAbsPath);
+
+#endif /* !VBOX_INCLUDED_SRC_SharedFolders_vbsfpath_h */
diff --git a/src/VBox/HostServices/SharedFolders/vbsfpathabs.cpp b/src/VBox/HostServices/SharedFolders/vbsfpathabs.cpp
new file mode 100644
index 00000000..ce6f9391
--- /dev/null
+++ b/src/VBox/HostServices/SharedFolders/vbsfpathabs.cpp
@@ -0,0 +1,200 @@
+/* $Id: vbsfpathabs.cpp $ */
+/** @file
+ * Shared Folders Service - guest/host path convertion and verification.
+ */
+
+/*
+ * Copyright (C) 2017-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#define LOG_GROUP LOG_GROUP_SHARED_FOLDERS
+#include <iprt/err.h>
+#include <iprt/path.h>
+#include <iprt/string.h>
+
+
+#if defined(RT_OS_WINDOWS)
+static void vbsfPathResolveRelative(char *pszPathBegin)
+{
+    char *pszCur = pszPathBegin;
+    char * const pszTop = pszCur;
+
+    /*
+     * Get rid of double dot path components by evaluating them.
+     */
+    for (;;)
+    {
+        char const chFirst = pszCur[0];
+        if (   chFirst == '.'
+            && pszCur[1] == '.'
+            && (!pszCur[2] || pszCur[2] == RTPATH_SLASH))
+        {
+            /* rewind to the previous component if any */
+            char *pszPrev = pszCur;
+            if ((uintptr_t)pszPrev > (uintptr_t)pszTop)
+            {
+                pszPrev--;
+                while (   (uintptr_t)pszPrev > (uintptr_t)pszTop
+                       && pszPrev[-1] != RTPATH_SLASH)
+                    pszPrev--;
+            }
+            if (!pszCur[2])
+            {
+                if (pszPrev != pszTop)
+                    pszPrev[-1] = '\0';
+                else
+                    *pszPrev = '\0';
+                break;
+            }
+            Assert(pszPrev[-1] == RTPATH_SLASH);
+            memmove(pszPrev, pszCur + 3, strlen(pszCur + 3) + 1);
+            pszCur = pszPrev - 1;
+        }
+        else if (   chFirst == '.'
+                 && (!pszCur[1] || pszCur[1] == RTPATH_SLASH))
+        {
+            /* remove unnecessary '.' */
+            if (!pszCur[1])
+            {
+                if (pszCur != pszTop)
+                    pszCur[-1] = '\0';
+                else
+                    *pszCur = '\0';
+                break;
+            }
+            memmove(pszCur, pszCur + 2, strlen(pszCur + 2) + 1);
+            continue;
+        }
+        else
+        {
+            /* advance to end of component. */
+            while (*pszCur && *pszCur != RTPATH_SLASH)
+                pszCur++;
+        }
+
+        if (!*pszCur)
+            break;
+
+        /* skip the slash */
+        ++pszCur;
+    }
+}
+#endif /* RT_OS_WINDOWS */
+
+int vbsfPathAbs(const char *pszRoot, const char *pszPath, char *pszAbsPath, size_t cbAbsPath)
+{
+#if defined(RT_OS_WINDOWS)
+    /** @todo This code is not needed in 6.0 and later as IPRT translates paths
+     *        to //./ (inverted slashes for doxygen) format if they're too long.  */
+    const char *pszPathStart = pszRoot? pszRoot: pszPath;
+
+    /* Windows extended-length paths. */
+    if (   RTPATH_IS_SLASH(pszPathStart[0])
+        && RTPATH_IS_SLASH(pszPathStart[1])
+        && pszPathStart[2] == '?'
+        && RTPATH_IS_SLASH(pszPathStart[3])
+       )
+    {
+        /* Maximum total path length of 32,767 characters. */
+        if (cbAbsPath > _32K)
+            cbAbsPath = _32K;
+
+        /* Copy the root to pszAbsPath buffer. */
+        size_t cchRoot = pszRoot? strlen(pszRoot): 0;
+        if (cchRoot >= cbAbsPath)
+            return VERR_FILENAME_TOO_LONG;
+
+        if (pszRoot)
+        {
+            /* Caller must ensure that the path is relative, without the leading path separator. */
+            if (RTPATH_IS_SLASH(pszPath[0]))
+                return VERR_INVALID_PARAMETER;
+
+            if (cchRoot)
+               memcpy(pszAbsPath, pszRoot, cchRoot);
+
+            if (cchRoot == 0 || !RTPATH_IS_SLASH(pszAbsPath[cchRoot - 1]))
+            {
+                /* Append path separator after the root. */
+                ++cchRoot;
+                if (cchRoot >= cbAbsPath)
+                    return VERR_FILENAME_TOO_LONG;
+
+                pszAbsPath[cchRoot - 1] = RTPATH_SLASH;
+            }
+        }
+
+        /* Append the path to the pszAbsPath buffer. */
+        const size_t cchPath = strlen(pszPath);
+        if (cchRoot + cchPath >= cbAbsPath)
+            return VERR_FILENAME_TOO_LONG;
+
+        memcpy(&pszAbsPath[cchRoot], pszPath, cchPath + 1); /* Including trailing 0. */
+
+        /* Find out where the actual path begins, i.e. skip the root spec. */
+        char *pszPathBegin = &pszAbsPath[4]; /* Skip the extended-length path prefix "\\?\" */
+        if (   pszPathBegin[0]
+            && RTPATH_IS_VOLSEP(pszPathBegin[1])
+            && pszPathBegin[2] == RTPATH_SLASH)
+        {
+            /* "\\?\C:\" */
+            pszPathBegin += 3;
+        }
+        else if (   pszPathBegin[0] == 'U'
+                 && pszPathBegin[1] == 'N'
+                 && pszPathBegin[2] == 'C'
+                 && pszPathBegin[3] == RTPATH_SLASH)
+        {
+            /* "\\?\UNC\server\share" */
+            pszPathBegin += 4;
+
+            /* Skip "server\share" too. */
+            while (*pszPathBegin != RTPATH_SLASH && *pszPathBegin)
+                ++pszPathBegin;
+            if (*pszPathBegin == RTPATH_SLASH)
+            {
+                ++pszPathBegin;
+                while (*pszPathBegin != RTPATH_SLASH && *pszPathBegin)
+                    ++pszPathBegin;
+                if (*pszPathBegin == RTPATH_SLASH)
+                    ++pszPathBegin;
+            }
+        }
+        else
+            return VERR_INVALID_NAME;
+
+        /* Process pszAbsPath in place. */
+        vbsfPathResolveRelative(pszPathBegin);
+
+        return VINF_SUCCESS;
+    }
+#endif /* RT_OS_WINDOWS */
+
+    /* Fallback for the common paths. */
+
+    if (*pszPath != '\0')
+        return RTPathAbsEx(pszRoot, pszPath, RTPATH_STR_F_STYLE_HOST, pszAbsPath, &cbAbsPath);
+    return RTPathAbsEx(NULL, pszRoot, RTPATH_STR_F_STYLE_HOST, pszAbsPath, &cbAbsPath);
+}
diff --git a/src/VBox/HostServices/auth/Makefile.kmk b/src/VBox/HostServices/auth/Makefile.kmk
new file mode 100644
index 00000000..93fc8eea
--- /dev/null
+++ b/src/VBox/HostServices/auth/Makefile.kmk
@@ -0,0 +1,76 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the VBox RDP authentication plugins.
+#
+
+#
+# Copyright (C) 2006-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+# The plugin.
+ifndef VBOX_ONLY_SDK
+ if ("$(KBUILD_TARGET)" != "linux" && "$(KBUILD_TARGET)" != "solaris") || defined(VBOX_WITH_PAM)
+  DLLS += VBoxAuth
+ endif
+endif
+VBoxAuth_TEMPLATE = VBoxR3Dll
+VBoxAuth_SOURCES.linux = pam/VBoxAuthPAM.c
+VBoxAuth_SOURCES.solaris = pam/VBoxAuthPAM.c
+VBoxAuth_SOURCES.freebsd = pam/VBoxAuthPAM.c
+VBoxAuth_SOURCES.win = winlogon/winlogon.cpp winlogon/VBoxAuth.rc
+VBoxAuth_SOURCES.darwin = directoryservice/directoryservice.cpp
+VBoxAuth_CXXFLAGS.darwin = -Wno-deprecated-declarations
+VBoxAuth_LIBS.linux = $(LIB_RUNTIME) dl
+VBoxAuth_LIBS.solaris = $(LIB_RUNTIME) dl
+VBoxAuth_LIBS.freebsd = $(LIB_RUNTIME)
+VBoxAuth_LIBS.darwin = $(LIB_RUNTIME)
+VBoxAuth_LDFLAGS.darwin = -framework DirectoryService
+
+# The simple plugin.
+ifndef VBOX_ONLY_SDK
+ if defined(VBOX_WITH_MAIN)
+  DLLS += VBoxAuthSimple
+ endif
+endif
+VBoxAuthSimple_TEMPLATE = VBoxMainClientDll
+VBoxAuthSimple_SOURCES = simple/VBoxAuthSimple.cpp
+VBoxAuthSimple_SOURCES.win = simple/VBoxAuthSimple.rc
+
+# Install the SDK samples.
+INSTALLS += VBoxAuth-samples
+VBoxAuth-samples_INST = $(INST_SDK)bindings/auth/
+VBoxAuth-samples_MODE = a+r,u+w
+VBoxAuth-samples_SOURCES = simple/VBoxAuthSimple.cpp
+VBoxAuth-samples_SOURCES.linux = pam/VBoxAuthPAM.c
+VBoxAuth-samples_SOURCES.win = winlogon/winlogon.cpp
+
+# Install the SDK header.
+INSTALLS += VBoxAuth-sdkhdr
+VBoxAuth-sdkhdr_INST = $(INST_SDK)bindings/auth/include/
+VBoxAuth-sdkhdr_MODE = a+r,u+w
+VBoxAuth-sdkhdr_SOURCES = $(PATH_ROOT)/include/VBox/VBoxAuth.h=>VBoxAuth.h
+
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/HostServices/auth/directoryservice/Makefile.kup b/src/VBox/HostServices/auth/directoryservice/Makefile.kup
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/src/VBox/HostServices/auth/directoryservice/Makefile.kup
diff --git a/src/VBox/HostServices/auth/directoryservice/directoryservice.cpp b/src/VBox/HostServices/auth/directoryservice/directoryservice.cpp
new file mode 100644
index 00000000..ea245961
--- /dev/null
+++ b/src/VBox/HostServices/auth/directoryservice/directoryservice.cpp
@@ -0,0 +1,338 @@
+/** @file
+ *
+ * VirtualBox External Authentication Library:
+ * Mac OS X Authentication. This is based on
+ * http://developer.apple.com/mac/library/samplecode/CryptNoMore/
+ */
+
+/*
+ * Copyright (C) 2009-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <iprt/cdefs.h>
+#include <iprt/assert.h>
+
+#include <VBox/VBoxAuth.h>
+
+#include <DirectoryService/DirectoryService.h>
+
+/* Globals */
+static const size_t s_cBufferSize = 32 * 1024;
+
+tDirStatus defaultSearchNodePath(tDirReference pDirRef, tDataListPtr *pdsNodePath)
+{
+    tDirStatus dsErr = eDSNoErr;
+    /* Create a buffer for the resulting nodes */
+    tDataBufferPtr pTmpBuf = NULL;
+    pTmpBuf = dsDataBufferAllocate(pDirRef, s_cBufferSize);
+    if (pTmpBuf)
+    {
+        /* Try to find the default search node for local names */
+        UInt32 cNodes;
+        tContextData hCtx = 0;
+        dsErr = dsFindDirNodes(pDirRef, pTmpBuf, NULL, eDSLocalNodeNames, &cNodes, &hCtx);
+        /* Any nodes found? */
+        if (   dsErr == eDSNoErr
+            && cNodes >= 1)
+            /* The first path of the node list is what we looking for. */
+            dsErr = dsGetDirNodeName(pDirRef, pTmpBuf, 1, pdsNodePath);
+        else
+            dsErr = eDSNodeNotFound;
+
+        if (hCtx) /* (DSoNodeConfig.m from DSTools-162 does exactly the same free if not-zero-regardless-of-return-code.) */
+            dsReleaseContinueData(pDirRef, hCtx);
+        dsDataBufferDeAllocate(pDirRef, pTmpBuf);
+    }
+    else
+        dsErr = eDSAllocationFailed;
+
+    return dsErr;
+}
+
+tDirStatus userAuthInfo(tDirReference pDirRef, tDirNodeReference pNodeRef, const char *pszUsername, tDataListPtr *ppAuthNodeListOut)
+{
+    tDirStatus dsErr = eDSNoErr;
+    tDirStatus dsCleanErr = eDSNoErr;
+    /* Create a buffer for the resulting authentication info */
+    tDataBufferPtr pTmpBuf = dsDataBufferAllocate(pDirRef, s_cBufferSize);
+    if (pTmpBuf)
+    {
+        /* Create the necessary lists for kDSNAttrMetaNodeLocation and kDSNAttrRecordName. */
+        tDataListPtr pRecordType = dsBuildListFromStrings(pDirRef, kDSStdRecordTypeUsers, NULL);
+        tDataListPtr pRecordName = dsBuildListFromStrings(pDirRef, pszUsername, NULL);
+        tDataListPtr pRequestedAttributes = dsBuildListFromStrings(pDirRef, kDSNAttrMetaNodeLocation, kDSNAttrRecordName, NULL);
+        if (!(   pRecordType == NULL
+              || pRecordName == NULL
+              || pRequestedAttributes == NULL))
+        {
+            /* Now search for the first matching record */
+            UInt32 cRecords = 1;
+            tContextData hCtx = 0;
+            dsErr = dsGetRecordList(pNodeRef,
+                                    pTmpBuf,
+                                    pRecordName,
+                                    eDSExact,
+                                    pRecordType,
+                                    pRequestedAttributes,
+                                    false,
+                                    &cRecords,
+                                    &hCtx);
+            if (   dsErr == eDSNoErr
+                && cRecords >= 1)
+            {
+                /* Process the first found record. Look at any attribute one by one. */
+                tAttributeListRef hRecAttrListRef = 0;
+                tRecordEntryPtr pRecEntry = NULL;
+                tDataListPtr pAuthNodeList = NULL;
+                dsErr = dsGetRecordEntry(pNodeRef, pTmpBuf, 1, &hRecAttrListRef, &pRecEntry);
+                if (dsErr == eDSNoErr)
+                {
+                    for (size_t i = 1; i <= pRecEntry->fRecordAttributeCount; ++i)
+                    {
+                        tAttributeValueListRef hAttrValueListRef = 0;
+                        tAttributeEntryPtr pAttrEntry = NULL;
+                        /* Get the information for this attribute. */
+                        dsErr = dsGetAttributeEntry(pNodeRef, pTmpBuf, hRecAttrListRef, i,
+                                                    &hAttrValueListRef, &pAttrEntry);
+                        if (dsErr == eDSNoErr)
+                        {
+                            tAttributeValueEntryPtr pValueEntry = NULL;
+                            /* Has any value? */
+                            if (pAttrEntry->fAttributeValueCount > 0)
+                            {
+                                dsErr = dsGetAttributeValue(pNodeRef, pTmpBuf, 1, hAttrValueListRef, &pValueEntry);
+                                if (dsErr == eDSNoErr)
+                                {
+                                    /* Check for kDSNAttrMetaNodeLocation */
+                                    if (strcmp(pAttrEntry->fAttributeSignature.fBufferData, kDSNAttrMetaNodeLocation) == 0)
+                                    {
+                                        /* Convert the meta location attribute to a path node list */
+                                        pAuthNodeList = dsBuildFromPath(pDirRef,
+                                                                        pValueEntry->fAttributeValueData.fBufferData,
+                                                                        "/");
+                                        if (pAuthNodeList == NULL)
+                                            dsErr = eDSAllocationFailed;
+                                    }
+                                }
+                            }
+
+                            if (pValueEntry != NULL)
+                                dsDeallocAttributeValueEntry(pDirRef, pValueEntry);
+                            if (hAttrValueListRef)
+                                dsCloseAttributeValueList(hAttrValueListRef);
+                            if (pAttrEntry != NULL)
+                                dsDeallocAttributeEntry(pDirRef, pAttrEntry);
+
+                            if (dsErr != eDSNoErr)
+                                break;
+                        }
+                    }
+                }
+                /* Copy the results */
+                if (dsErr == eDSNoErr)
+                {
+                    if (pAuthNodeList != NULL)
+                    {
+                        /* Copy out results. */
+                        *ppAuthNodeListOut = pAuthNodeList;
+                        pAuthNodeList = NULL;
+                    }
+                    else
+                        dsErr = eDSAttributeNotFound;
+                }
+
+                if (pAuthNodeList != NULL)
+                {
+                    dsCleanErr = dsDataListDeallocate(pDirRef, pAuthNodeList);
+                    if (dsCleanErr == eDSNoErr)
+                        free(pAuthNodeList);
+                }
+                if (hRecAttrListRef)
+                    dsCloseAttributeList(hRecAttrListRef);
+                if (pRecEntry != NULL)
+                    dsDeallocRecordEntry(pDirRef, pRecEntry);
+            }
+            else
+                dsErr = eDSRecordNotFound;
+            if (hCtx)
+                dsReleaseContinueData(pDirRef, hCtx);
+        }
+        else
+            dsErr = eDSAllocationFailed;
+        if (pRequestedAttributes != NULL)
+        {
+            dsCleanErr = dsDataListDeallocate(pDirRef, pRequestedAttributes);
+            if (dsCleanErr == eDSNoErr)
+                free(pRequestedAttributes);
+        }
+        if (pRecordName != NULL)
+        {
+            dsCleanErr = dsDataListDeallocate(pDirRef, pRecordName);
+            if (dsCleanErr == eDSNoErr)
+                free(pRecordName);
+        }
+        if (pRecordType != NULL)
+        {
+            dsCleanErr = dsDataListDeallocate(pDirRef, pRecordType);
+            if (dsCleanErr == eDSNoErr)
+                free(pRecordType);
+        }
+        dsDataBufferDeAllocate(pDirRef, pTmpBuf);
+    }
+    else
+        dsErr = eDSAllocationFailed;
+
+    return dsErr;
+}
+
+tDirStatus authWithNode(tDirReference pDirRef, tDataListPtr pAuthNodeList, const char *pszUsername, const char *pszPassword)
+{
+    tDirStatus dsErr = eDSNoErr;
+    /* Open the authentication node. */
+    tDirNodeReference hAuthNodeRef = 0;
+    dsErr = dsOpenDirNode(pDirRef, pAuthNodeList, &hAuthNodeRef);
+    if (dsErr == eDSNoErr)
+    {
+        /* How like we to authenticate! */
+        tDataNodePtr pAuthMethod = dsDataNodeAllocateString(pDirRef, kDSStdAuthNodeNativeClearTextOK);
+        if (pAuthMethod)
+        {
+            /* Create the memory holding the authentication data. The data
+             * structure consists of 4 byte length of the username + zero byte,
+             * the username itself, a 4 byte length of the password & the
+             * password itself + zero byte. */
+            tDataBufferPtr pAuthOutBuf = dsDataBufferAllocate(pDirRef, s_cBufferSize);
+            if (pAuthOutBuf)
+            {
+                size_t cUserName = strlen(pszUsername) + 1;
+                size_t cPassword = strlen(pszPassword) + 1;
+                unsigned long cLen = 0;
+                tDataBufferPtr pAuthInBuf = dsDataBufferAllocate(pDirRef, sizeof(cLen) + cUserName + sizeof(cLen) + cPassword);
+                if (pAuthInBuf)
+                {
+                    /* Move the data into the buffer. */
+                    pAuthInBuf->fBufferLength = 0;
+                    /* Length of the username */
+                    cLen = cUserName;
+                    memcpy(&pAuthInBuf->fBufferData[pAuthInBuf->fBufferLength], &cLen, sizeof(cLen));
+                    pAuthInBuf->fBufferLength += sizeof(cLen);
+                    /* The username itself */
+                    memcpy(&pAuthInBuf->fBufferData[pAuthInBuf->fBufferLength], pszUsername, cUserName);
+                    pAuthInBuf->fBufferLength += cUserName;
+                    /* Length of the password */
+                    cLen = cPassword;
+                    memcpy(&pAuthInBuf->fBufferData[pAuthInBuf->fBufferLength], &cLen, sizeof(cLen));
+                    pAuthInBuf->fBufferLength += sizeof(cLen);
+                    /* The password itself */
+                    memcpy(&pAuthInBuf->fBufferData[pAuthInBuf->fBufferLength], pszPassword, cPassword);
+                    pAuthInBuf->fBufferLength += cPassword;
+                    /* Now authenticate */
+                    dsErr = dsDoDirNodeAuth(hAuthNodeRef, pAuthMethod, true, pAuthInBuf, pAuthOutBuf, NULL);
+                    /* Clean up. */
+                    dsDataBufferDeAllocate(pDirRef, pAuthInBuf);
+                }
+                else
+                    dsErr = eDSAllocationFailed;
+                dsDataBufferDeAllocate(pDirRef, pAuthOutBuf);
+            }
+            else
+                dsErr = eDSAllocationFailed;
+            dsDataNodeDeAllocate(pDirRef, pAuthMethod);
+        }
+        else
+            dsErr = eDSAllocationFailed;
+        dsCloseDirNode(hAuthNodeRef);
+    }
+
+    return dsErr;
+}
+
+RT_C_DECLS_BEGIN
+DECLEXPORT(FNAUTHENTRY3) AuthEntry;
+RT_C_DECLS_END
+
+DECLEXPORT(AuthResult) AUTHCALL AuthEntry(const char *pszCaller,
+                                          PAUTHUUID pUuid,
+                                          AuthGuestJudgement guestJudgement,
+                                          const char *pszUser,
+                                          const char *pszPassword,
+                                          const char *pszDomain,
+                                          int fLogon,
+                                          unsigned clientId)
+{
+    RT_NOREF(pszCaller, pUuid, guestJudgement, pszDomain, clientId);
+
+    /* Validate input */
+    AssertPtrReturn(pszUser, AuthResultAccessDenied);
+    AssertPtrReturn(pszPassword, AuthResultAccessDenied);
+
+    /* Result to a default value */
+    AuthResult result = AuthResultAccessDenied;
+
+    /* Only process logon requests. */
+    if (!fLogon)
+        return result; /* Return value is ignored by the caller. */
+
+    tDirStatus dsErr = eDSNoErr;
+    tDirStatus dsCleanErr = eDSNoErr;
+    tDirReference hDirRef = 0;
+    /* Connect to the Directory Service. */
+    dsErr = dsOpenDirService(&hDirRef);
+    if (dsErr == eDSNoErr)
+    {
+        /* Fetch the default search node */
+        tDataListPtr pSearchNodeList = NULL;
+        dsErr = defaultSearchNodePath(hDirRef, &pSearchNodeList);
+        if (dsErr == eDSNoErr)
+        {
+            /* Open the default search node */
+            tDirNodeReference hSearchNodeRef = 0;
+            dsErr = dsOpenDirNode(hDirRef, pSearchNodeList, &hSearchNodeRef);
+            if (dsErr == eDSNoErr)
+            {
+                /* Search for the user info, fetch the authentication node &
+                 * the authentication user name. This allows the client to
+                 * specify a long user name even if the name which is used to
+                 * authenticate has the short form. */
+                tDataListPtr pAuthNodeList = NULL;
+                dsErr = userAuthInfo(hDirRef, hSearchNodeRef, pszUser, &pAuthNodeList);
+                if (dsErr == eDSNoErr)
+                {
+                    /* Open the authentication node and do the authentication. */
+                    dsErr = authWithNode(hDirRef, pAuthNodeList, pszUser, pszPassword);
+                    if (dsErr == eDSNoErr)
+                        result = AuthResultAccessGranted;
+                    dsCleanErr = dsDataListDeallocate(hDirRef, pAuthNodeList);
+                    if (dsCleanErr == eDSNoErr)
+                        free(pAuthNodeList);
+                }
+                dsCloseDirNode(hSearchNodeRef);
+            }
+            dsCleanErr = dsDataListDeallocate(hDirRef, pSearchNodeList);
+            if (dsCleanErr == eDSNoErr)
+                free(pSearchNodeList);
+        }
+        dsCloseDirService(hDirRef);
+    }
+
+    return result;
+}
+
diff --git a/src/VBox/HostServices/auth/pam/Makefile.kup b/src/VBox/HostServices/auth/pam/Makefile.kup
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/src/VBox/HostServices/auth/pam/Makefile.kup
diff --git a/src/VBox/HostServices/auth/pam/VBoxAuthPAM.c b/src/VBox/HostServices/auth/pam/VBoxAuthPAM.c
new file mode 100644
index 00000000..5b7f14a3
--- /dev/null
+++ b/src/VBox/HostServices/auth/pam/VBoxAuthPAM.c
@@ -0,0 +1,417 @@
+/** @file
+ *
+ * VirtualBox External Authentication Library:
+ * Linux PAM Authentication.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/* The PAM service name.
+ *
+ * The service name is the name of a file in the /etc/pam.d which contains
+ * authentication rules. It is possible to use an existing service
+ * name, like "login" for example. But if different set of rules
+ * is required, one can create a new file /etc/pam.d/vrdpauth
+ * specially for VRDP authentication. Note that the name of the
+ * service must be lowercase. See PAM documentation for details.
+ *
+ * The Auth module takes the PAM service name from the
+ * environment variable VBOX_AUTH_PAM_SERVICE. If the variable
+ * is not specified, then the 'login' PAM service is used.
+ */
+#define VBOX_AUTH_PAM_SERVICE_NAME_ENV_OLD "VRDP_AUTH_PAM_SERVICE"
+#define VBOX_AUTH_PAM_SERVICE_NAME_ENV "VBOX_AUTH_PAM_SERVICE"
+#define VBOX_AUTH_PAM_DEFAULT_SERVICE_NAME "login"
+
+
+/* The debug log file name.
+ *
+ * If defined, debug messages will be written to the file specified in the
+ * VBOX_AUTH_DEBUG_FILENAME (or deprecated VRDP_AUTH_DEBUG_FILENAME) environment
+ * variable:
+ *
+ * export VBOX_AUTH_DEBUG_FILENAME=pam.log
+ *
+ * The above will cause writing to the pam.log.
+ */
+#define VBOX_AUTH_DEBUG_FILENAME_ENV_OLD "VRDP_AUTH_DEBUG_FILENAME"
+#define VBOX_AUTH_DEBUG_FILENAME_ENV "VBOX_AUTH_DEBUG_FILENAME"
+
+
+/* Dynamic loading of the PAM library.
+ *
+ * If defined, the libpam.so is loaded dynamically.
+ * Enabled by default since it is often required,
+ * and does not harm.
+ */
+#define VBOX_AUTH_USE_PAM_DLLOAD
+
+
+#ifdef VBOX_AUTH_USE_PAM_DLLOAD
+/* The name of the PAM library */
+# ifdef RT_OS_SOLARIS
+#  define PAM_LIB_NAME "libpam.so.1"
+# elif defined(RT_OS_FREEBSD)
+#  define PAM_LIB_NAME "libpam.so"
+# else
+#  define PAM_LIB_NAME "libpam.so.0"
+# endif
+#endif /* VBOX_AUTH_USE_PAM_DLLOAD */
+
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdarg.h>
+#include <string.h>
+#ifndef RT_OS_FREEBSD
+# include <malloc.h>
+#endif
+
+#include <security/pam_appl.h>
+
+#include <VBox/VBoxAuth.h>
+
+#ifdef VBOX_AUTH_USE_PAM_DLLOAD
+#include <dlfcn.h>
+
+static int (*fn_pam_start)(const char *service_name,
+                           const char *user,
+                           const struct pam_conv *pam_conversation,
+                           pam_handle_t **pamh);
+static int (*fn_pam_authenticate)(pam_handle_t *pamh, int flags);
+static int (*fn_pam_acct_mgmt)(pam_handle_t *pamh, int flags);
+static int (*fn_pam_end)(pam_handle_t *pamh, int pam_status);
+static const char * (*fn_pam_strerror)(pam_handle_t *pamh, int errnum);
+#else
+#define fn_pam_start        pam_start
+#define fn_pam_authenticate pam_authenticate
+#define fn_pam_acct_mgmt    pam_acct_mgmt
+#define fn_pam_end          pam_end
+#define fn_pam_strerror     pam_strerror
+#endif /* VBOX_AUTH_USE_PAM_DLLOAD */
+
+static void debug_printf(const char *fmt, ...)
+{
+#if defined(VBOX_AUTH_DEBUG_FILENAME_ENV) || defined(VBOX_AUTH_DEBUG_FILENAME_ENV_OLD)
+    va_list va;
+
+    char buffer[1024];
+
+    const char *filename = NULL;
+
+    va_start(va, fmt);
+
+#if defined(VBOX_AUTH_DEBUG_FILENAME_ENV)
+    filename = getenv (VBOX_AUTH_DEBUG_FILENAME_ENV);
+#endif /* VBOX_AUTH_DEBUG_FILENAME_ENV */
+
+#if defined(VBOX_AUTH_DEBUG_FILENAME_ENV_OLD)
+    if (filename == NULL)
+    {
+        filename = getenv (VBOX_AUTH_DEBUG_FILENAME_ENV_OLD);
+    }
+#endif /* VBOX_AUTH_DEBUG_FILENAME_ENV_OLD */
+
+    if (filename)
+    {
+       FILE *f;
+
+       vsnprintf (buffer, sizeof (buffer), fmt, va);
+
+       f = fopen (filename, "ab");
+       if (f != NULL)
+       {
+          fprintf (f, "%s", buffer);
+          fclose (f);
+       }
+    }
+
+    va_end (va);
+#endif /* VBOX_AUTH_DEBUG_FILENAME_ENV || VBOX_AUTH_DEBUG_FILENAME_ENV_OLD */
+}
+
+#ifdef VBOX_AUTH_USE_PAM_DLLOAD
+
+static void *gpvLibPam = NULL;
+
+typedef struct _SymMap
+{
+    void **ppfn;
+    const char *pszName;
+} SymMap;
+
+static SymMap symmap[] =
+{
+    { (void **)&fn_pam_start,        "pam_start" },
+    { (void **)&fn_pam_authenticate, "pam_authenticate" },
+    { (void **)&fn_pam_acct_mgmt,    "pam_acct_mgmt" },
+    { (void **)&fn_pam_end,          "pam_end" },
+    { (void **)&fn_pam_strerror,     "pam_strerror" },
+    { NULL,                          NULL }
+};
+
+static int auth_pam_init(void)
+{
+    SymMap *iter;
+
+    gpvLibPam = dlopen(PAM_LIB_NAME, RTLD_LAZY | RTLD_GLOBAL);
+
+    if (!gpvLibPam)
+    {
+        debug_printf("auth_pam_init: dlopen %s failed\n", PAM_LIB_NAME);
+        return PAM_SYSTEM_ERR;
+    }
+
+    iter = &symmap[0];
+
+    while (iter->pszName != NULL)
+    {
+        void *pv = dlsym (gpvLibPam, iter->pszName);
+
+        if (pv == NULL)
+        {
+            debug_printf("auth_pam_init: dlsym %s failed\n", iter->pszName);
+
+            dlclose(gpvLibPam);
+            gpvLibPam = NULL;
+
+            return PAM_SYSTEM_ERR;
+        }
+
+        *iter->ppfn = pv;
+
+        iter++;
+    }
+
+    return PAM_SUCCESS;
+}
+
+static void auth_pam_close(void)
+{
+    if (gpvLibPam)
+    {
+        dlclose(gpvLibPam);
+        gpvLibPam = NULL;
+    }
+
+    return;
+}
+#else
+static int auth_pam_init(void)
+{
+    return PAM_SUCCESS;
+}
+
+static void auth_pam_close(void)
+{
+    return;
+}
+#endif /* VBOX_AUTH_USE_PAM_DLLOAD */
+
+static const char *auth_get_pam_service (void)
+{
+    const char *service = getenv (VBOX_AUTH_PAM_SERVICE_NAME_ENV);
+
+    if (service == NULL)
+    {
+        service = getenv (VBOX_AUTH_PAM_SERVICE_NAME_ENV_OLD);
+
+        if (service == NULL)
+        {
+            service = VBOX_AUTH_PAM_DEFAULT_SERVICE_NAME;
+        }
+    }
+
+    debug_printf ("Using PAM service: %s\n", service);
+
+    return service;
+}
+
+typedef struct _PamContext
+{
+    char *pszUser;
+    char *pszPassword;
+} PamContext;
+
+#if defined(RT_OS_SOLARIS)
+static int conv (int num_msg, struct pam_message **msg,
+                 struct pam_response **resp, void *appdata_ptr)
+#else
+static int conv (int num_msg, const struct pam_message **msg,
+                 struct pam_response **resp, void *appdata_ptr)
+#endif
+{
+    int i;
+    struct pam_response *r;
+
+    PamContext *ctx = (PamContext *)appdata_ptr;
+
+    if (ctx == NULL)
+    {
+        debug_printf("conv: ctx is NULL\n");
+        return PAM_CONV_ERR;
+    }
+
+    debug_printf("conv: num %d u[%s] p[%d]\n", num_msg, ctx->pszUser, ctx->pszPassword? strlen (ctx->pszPassword): 0);
+
+    r = (struct pam_response *) calloc (num_msg, sizeof (struct pam_response));
+
+    if (r == NULL)
+    {
+        return PAM_CONV_ERR;
+    }
+
+    for (i = 0; i < num_msg; i++)
+    {
+        r[i].resp_retcode = 0;
+
+        if (msg[i]->msg_style == PAM_PROMPT_ECHO_OFF)
+        {
+            r[i].resp = strdup (ctx->pszPassword);
+            debug_printf("conv: %d returning password [%d]\n", i, r[i].resp? strlen (r[i].resp): 0);
+        }
+        else if (msg[i]->msg_style == PAM_PROMPT_ECHO_ON)
+        {
+            r[i].resp = strdup (ctx->pszUser);
+            debug_printf("conv: %d returning name [%s]\n", i, r[i].resp);
+        }
+        else
+        {
+            debug_printf("conv: %d style %d: [%s]\n", i, msg[i]->msg_style, msg[i]->msg? msg[i]->msg: "(null)");
+            r[i].resp = NULL;
+        }
+    }
+
+    *resp = r;
+    return PAM_SUCCESS;
+}
+
+/* The entry point must be visible. */
+#if defined(_MSC_VER) || defined(__OS2__)
+# define DECLEXPORT(type)       __declspec(dllexport) type
+#else
+# ifdef VBOX_HAVE_VISIBILITY_HIDDEN
+#  define DECLEXPORT(type)      __attribute__((visibility("default"))) type
+# else
+#  define DECLEXPORT(type)      type
+# endif
+#endif
+
+/* prototype to prevent gcc warning */
+DECLEXPORT(AUTHENTRY3) AuthEntry;
+
+DECLEXPORT(AuthResult) AUTHCALL AuthEntry(const char *pszCaller,
+                                          PAUTHUUID pUuid,
+                                          AuthGuestJudgement guestJudgement,
+                                          const char *pszUser,
+                                          const char *pszPassword,
+                                          const char *pszDomain,
+                                          int fLogon,
+                                          unsigned clientId)
+{
+    AuthResult result = AuthResultAccessDenied;
+    int rc;
+    PamContext ctx;
+    struct pam_conv pam_conversation;
+    pam_handle_t *pam_handle = NULL;
+
+    (void)pszCaller;
+    (void)pUuid;
+    (void)guestJudgement;
+    (void)clientId;
+
+    /* Only process logon requests. */
+    if (!fLogon)
+        return result; /* Return value is ignored by the caller. */
+
+    debug_printf("u[%s], d[%s], p[%d]\n", pszUser, pszDomain, pszPassword ? strlen(pszPassword) : 0);
+
+    ctx.pszUser     = (char *)pszUser;
+    ctx.pszPassword = (char *)pszPassword;
+
+    pam_conversation.conv        = conv;
+    pam_conversation.appdata_ptr = &ctx;
+
+    rc = auth_pam_init ();
+
+    if (rc == PAM_SUCCESS)
+    {
+        debug_printf("init ok\n");
+
+        rc = fn_pam_start(auth_get_pam_service (), pszUser, &pam_conversation, &pam_handle);
+
+        if (rc == PAM_SUCCESS)
+        {
+            debug_printf("start ok\n");
+
+            rc = fn_pam_authenticate(pam_handle, 0);
+
+            if (rc == PAM_SUCCESS)
+            {
+                debug_printf("auth ok\n");
+
+                rc = fn_pam_acct_mgmt(pam_handle, 0);
+                if (rc == PAM_AUTHINFO_UNAVAIL
+                    &&
+                    getenv("VBOX_PAM_ALLOW_INACTIVE") != NULL)
+                {
+                    debug_printf("PAM_AUTHINFO_UNAVAIL\n");
+                    rc = PAM_SUCCESS;
+                }
+
+                if (rc == PAM_SUCCESS)
+                {
+                    debug_printf("access granted\n");
+
+                    result = AuthResultAccessGranted;
+                }
+                else
+                {
+                    debug_printf("pam_acct_mgmt failed %d. %s\n", rc, fn_pam_strerror (pam_handle, rc));
+                }
+            }
+            else
+            {
+                debug_printf("pam_authenticate failed %d. %s\n", rc, fn_pam_strerror (pam_handle, rc));
+            }
+
+            fn_pam_end(pam_handle, rc);
+        }
+        else
+        {
+            debug_printf("pam_start failed %d\n", rc);
+        }
+
+        auth_pam_close ();
+
+        debug_printf("auth_pam_close completed\n");
+    }
+    else
+    {
+        debug_printf("auth_pam_init failed %d\n", rc);
+    }
+
+    return result;
+}
+
diff --git a/src/VBox/HostServices/auth/simple/Makefile.kup b/src/VBox/HostServices/auth/simple/Makefile.kup
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/src/VBox/HostServices/auth/simple/Makefile.kup
diff --git a/src/VBox/HostServices/auth/simple/VBoxAuthSimple.cpp b/src/VBox/HostServices/auth/simple/VBoxAuthSimple.cpp
new file mode 100644
index 00000000..671f2f00
--- /dev/null
+++ b/src/VBox/HostServices/auth/simple/VBoxAuthSimple.cpp
@@ -0,0 +1,147 @@
+/* $Id: VBoxAuthSimple.cpp $ */
+/** @file
+ * VirtualBox External Authentication Library - Simple Authentication.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <iprt/cdefs.h>
+#include <iprt/uuid.h>
+#include <iprt/sha.h>
+
+#include <VBox/VBoxAuth.h>
+
+#include <VBox/com/com.h>
+#include <VBox/com/string.h>
+#include <VBox/com/Guid.h>
+#include <VBox/com/VirtualBox.h>
+
+using namespace com;
+
+/* If defined, debug messages will be written to the specified file. */
+//#define AUTH_DEBUG_FILE_NAME "/tmp/VBoxAuth.log"
+
+
+static void dprintf(const char *pszFormat, ...)
+{
+#ifdef AUTH_DEBUG_FILE_NAME
+    FILE *f = fopen(AUTH_DEBUG_FILE_NAME, "ab");
+    if (f)
+    {
+        va_list va;
+        va_start(va, pszFormat);
+        vfprintf(f, pszFormat, va);
+        va_end(va);
+        fclose(f);
+    }
+#else
+    RT_NOREF(pszFormat);
+#endif
+}
+
+RT_C_DECLS_BEGIN
+DECLEXPORT(FNAUTHENTRY3) AuthEntry;
+RT_C_DECLS_END
+
+DECLEXPORT(AuthResult) AUTHCALL AuthEntry(const char *pszCaller,
+                                          PAUTHUUID pUuid,
+                                          AuthGuestJudgement guestJudgement,
+                                          const char *pszUser,
+                                          const char *pszPassword,
+                                          const char *pszDomain,
+                                          int fLogon,
+                                          unsigned clientId)
+{
+    RT_NOREF(pszCaller, guestJudgement, pszDomain, clientId);
+
+    /* default is failed */
+    AuthResult result = AuthResultAccessDenied;
+
+    /* only interested in logon */
+    if (!fLogon)
+        /* return value ignored */
+        return result;
+
+    char uuid[RTUUID_STR_LENGTH] = {0};
+    if (pUuid)
+        RTUuidToStr((PCRTUUID)pUuid, (char*)uuid, RTUUID_STR_LENGTH);
+
+    /* the user might contain a domain name, split it */
+    const char *user = strchr(pszUser, '\\');
+    if (user)
+        user++;
+    else
+        user = (char*)pszUser;
+
+    dprintf("VBoxAuth: uuid: %s, user: %s, pszPassword: %s\n", uuid, user, pszPassword);
+
+    ComPtr<IVirtualBoxClient> virtualBoxClient;
+    ComPtr<IVirtualBox> virtualBox;
+    HRESULT rc;
+
+    rc = virtualBoxClient.createInprocObject(CLSID_VirtualBoxClient);
+    if (SUCCEEDED(rc))
+    {
+        rc = virtualBoxClient->COMGETTER(VirtualBox)(virtualBox.asOutParam());
+        if (SUCCEEDED(rc))
+        {
+            Bstr key = BstrFmt("VBoxAuthSimple/users/%s", user);
+            Bstr password;
+
+            /* lookup in VM's extra data? */
+            if (pUuid)
+            {
+                ComPtr<IMachine> machine;
+                virtualBox->FindMachine(Bstr(uuid).raw(), machine.asOutParam());
+                if (machine)
+                    machine->GetExtraData(key.raw(), password.asOutParam());
+            }
+            else
+                /* lookup global extra data */
+                virtualBox->GetExtraData(key.raw(), password.asOutParam());
+
+            if (!password.isEmpty())
+            {
+                /* calculate hash */
+                uint8_t abDigest[RTSHA256_HASH_SIZE];
+                RTSha256(pszPassword, strlen(pszPassword), abDigest);
+                char pszDigest[RTSHA256_DIGEST_LEN + 1];
+                RTSha256ToString(abDigest, pszDigest, sizeof(pszDigest));
+
+                if (password == pszDigest)
+                    result = AuthResultAccessGranted;
+            }
+        }
+        else
+            dprintf("VBoxAuth: failed to get VirtualBox object reference: %#x\n", rc);
+    }
+    else
+        dprintf("VBoxAuth: failed to get VirtualBoxClient object reference: %#x\n", rc);
+
+    return result;
+}
+
diff --git a/src/VBox/HostServices/auth/simple/VBoxAuthSimple.rc b/src/VBox/HostServices/auth/simple/VBoxAuthSimple.rc
new file mode 100644
index 00000000..9f466a46
--- /dev/null
+++ b/src/VBox/HostServices/auth/simple/VBoxAuthSimple.rc
@@ -0,0 +1,61 @@
+/* $Id: VBoxAuthSimple.rc $ */
+/** @file
+ * VBoxAuthSimple - Resource file containing version info and icon.
+ */
+
+/*
+ * Copyright (C) 2015-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <windows.h>
+#include <VBox/version.h>
+
+LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION      VBOX_RC_FILE_VERSION
+  PRODUCTVERSION   VBOX_RC_FILE_VERSION
+  FILEFLAGSMASK    VS_FFI_FILEFLAGSMASK
+  FILEFLAGS        VBOX_RC_FILE_FLAGS
+  FILEOS           VBOX_RC_FILE_OS
+  FILETYPE         VBOX_RC_TYPE_DLL
+  FILESUBTYPE      VFT2_UNKNOWN
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904b0" // Lang=US English, CharSet=Unicode
+    BEGIN
+      VALUE "FileDescription",  "VirtualBox Simple Authentication Host Service\0"
+      VALUE "InternalName",     "VBoxAuthSimple\0"
+      VALUE "OriginalFilename", "VBoxAuthSimple.dll\0"
+      VALUE "CompanyName",      VBOX_RC_COMPANY_NAME
+      VALUE "FileVersion",      VBOX_RC_FILE_VERSION_STR
+      VALUE "LegalCopyright",   VBOX_RC_LEGAL_COPYRIGHT
+      VALUE "ProductName",      VBOX_RC_PRODUCT_NAME_STR
+      VALUE "ProductVersion",   VBOX_RC_PRODUCT_VERSION_STR
+      VBOX_RC_MORE_STRINGS
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x409, 1200
+  END
+END
diff --git a/src/VBox/HostServices/auth/winlogon/Makefile.kup b/src/VBox/HostServices/auth/winlogon/Makefile.kup
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/src/VBox/HostServices/auth/winlogon/Makefile.kup
diff --git a/src/VBox/HostServices/auth/winlogon/VBoxAuth.rc b/src/VBox/HostServices/auth/winlogon/VBoxAuth.rc
new file mode 100644
index 00000000..800733f7
--- /dev/null
+++ b/src/VBox/HostServices/auth/winlogon/VBoxAuth.rc
@@ -0,0 +1,61 @@
+/* $Id: VBoxAuth.rc $ */
+/** @file
+ * VBoxAuth - Resource file containing version info and icon.
+ */
+
+/*
+ * Copyright (C) 2015-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <windows.h>
+#include <VBox/version.h>
+
+LANGUAGE LANG_ENGLISH, SUBLANG_ENGLISH_US
+
+VS_VERSION_INFO VERSIONINFO
+  FILEVERSION      VBOX_RC_FILE_VERSION
+  PRODUCTVERSION   VBOX_RC_FILE_VERSION
+  FILEFLAGSMASK    VS_FFI_FILEFLAGSMASK
+  FILEFLAGS        VBOX_RC_FILE_FLAGS
+  FILEOS           VBOX_RC_FILE_OS
+  FILETYPE         VBOX_RC_TYPE_DLL
+  FILESUBTYPE      VFT2_UNKNOWN
+BEGIN
+  BLOCK "StringFileInfo"
+  BEGIN
+    BLOCK "040904b0" // Lang=US English, CharSet=Unicode
+    BEGIN
+      VALUE "FileDescription",  "VirtualBox Authentication Host Service\0"
+      VALUE "InternalName",     "VBoxAuth\0"
+      VALUE "OriginalFilename", "VBoxAuth.dll\0"
+      VALUE "CompanyName",      VBOX_RC_COMPANY_NAME
+      VALUE "FileVersion",      VBOX_RC_FILE_VERSION_STR
+      VALUE "LegalCopyright",   VBOX_RC_LEGAL_COPYRIGHT
+      VALUE "ProductName",      VBOX_RC_PRODUCT_NAME_STR
+      VALUE "ProductVersion",   VBOX_RC_PRODUCT_VERSION_STR
+      VBOX_RC_MORE_STRINGS
+    END
+  END
+  BLOCK "VarFileInfo"
+  BEGIN
+    VALUE "Translation", 0x409, 1200
+  END
+END
diff --git a/src/VBox/HostServices/auth/winlogon/winlogon.cpp b/src/VBox/HostServices/auth/winlogon/winlogon.cpp
new file mode 100644
index 00000000..63277194
--- /dev/null
+++ b/src/VBox/HostServices/auth/winlogon/winlogon.cpp
@@ -0,0 +1,181 @@
+/* $Id: winlogon.cpp $ */
+/** @file
+ * VirtualBox External Authentication Library - Windows Logon Authentication.
+ */
+
+/*
+ * Copyright (C) 2006-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+/* If defined, debug messages will be written to the debugger. */
+// #define AUTH_DEBUG
+
+#include <iprt/win/windows.h>
+#include <VBox/VBoxAuth.h>
+#include <iprt/cdefs.h>
+
+#ifdef AUTH_DEBUG
+# include <stdio.h>
+
+static void dprintfw(const WCHAR *fmt, ...)
+{
+   va_list va;
+   va_start(va, fmt);
+
+   WCHAR buffer[1024];
+
+   _vsnwprintf(buffer, sizeof (buffer), fmt, va);
+
+   OutputDebugStringW(buffer);
+
+   va_end(va);
+}
+# define DBGAUTH(a) dprintfw a
+#else
+# define DBGAUTH(a)
+#endif
+
+static WCHAR g_wszEmpty[] = { L"" };
+
+static void freeWideChar(WCHAR *pwszString)
+{
+    if (pwszString && pwszString != &g_wszEmpty[0])
+    {
+        size_t cb = (wcslen(pwszString) + 1) * sizeof(WCHAR);
+        SecureZeroMemory(pwszString, cb);
+        free(pwszString);
+    }
+}
+
+static WCHAR *utf8ToWideChar(const char *pszString)
+{
+    /*
+     * Shortcut for empty strings.
+     */
+    if (!pszString || *pszString == 0)
+        return &g_wszEmpty[0];
+
+    /*
+     * Return NULL on errors.
+     */
+    WCHAR *pwszString = NULL;
+
+    /*
+     * First calc result string length.
+     */
+    const DWORD dwFlags = MB_ERR_INVALID_CHARS;
+    int cwc = MultiByteToWideChar(CP_UTF8, dwFlags, pszString, -1, NULL, 0);
+    if (cwc > 0)
+    {
+        /*
+         * Alloc space for result buffer.
+         */
+        pwszString = (WCHAR *)malloc(cwc * sizeof(WCHAR));
+        if (pwszString)
+        {
+            /*
+             * Do the translation.
+             */
+            if (MultiByteToWideChar(CP_UTF8, dwFlags, pszString, -1, pwszString, cwc) <= 0)
+            {
+                /* translation error */
+                free(pwszString);
+                pwszString = NULL;
+            }
+        }
+    }
+
+    return pwszString;
+}
+
+/* Prototype it to make sure we've got the right prototype. */
+#if defined(_MSC_VER)
+extern "C" __declspec(dllexport) FNAUTHENTRY3 AuthEntry;
+#else
+extern "C" FNAUTHENTRY3 AuthEntry;
+#endif
+
+/**
+ * @callback_method_impl{FNAUTHENTRY3}
+ */
+extern "C" DECLEXPORT(AuthResult) AUTHCALL
+AuthEntry(const char *pszCaller,
+          PAUTHUUID pUuid,
+          AuthGuestJudgement guestJudgement,
+          const char *pszUser,
+          const char *pszPassword,
+          const char *pszDomain,
+          int fLogon,
+          unsigned clientId)
+{
+    RT_NOREF4(pszCaller, pUuid, guestJudgement, clientId);
+    if (!fLogon)
+    {
+        /* Nothing to cleanup. The return code does not matter. */
+        return AuthResultAccessDenied;
+    }
+
+    LPWSTR pwszUsername = utf8ToWideChar(pszUser);
+    LPWSTR pwszDomain   = utf8ToWideChar(pszDomain);
+    LPWSTR pwszPassword = utf8ToWideChar(pszPassword);
+
+    DBGAUTH((L"u[%ls], d[%ls], p[%ls]\n", lpwszUsername, lpwszDomain, lpwszPassword));
+
+    AuthResult result = AuthResultAccessDenied;
+
+    if (pwszUsername && pwszDomain && pwszPassword)
+    {
+        /* LOGON32_LOGON_INTERACTIVE is intended for users who will be interactively using the computer,
+         * such as a user being logged on by a terminal server, remote shell, or similar process.
+         */
+        DWORD dwLogonType     = LOGON32_LOGON_INTERACTIVE;
+        DWORD dwLogonProvider = LOGON32_PROVIDER_DEFAULT;
+
+        HANDLE hToken;
+
+        BOOL fSuccess = LogonUserW(pwszUsername,
+                                   pwszDomain,
+                                   pwszPassword,
+                                   dwLogonType,
+                                   dwLogonProvider,
+                                   &hToken);
+
+        if (fSuccess)
+        {
+            DBGAUTH((L"LogonUser success. hToken = %p\n", hToken));
+
+            result = AuthResultAccessGranted;
+
+            CloseHandle(hToken);
+        }
+        else
+        {
+            DBGAUTH((L"LogonUser failed %08X\n", GetLastError()));
+        }
+    }
+
+    freeWideChar(pwszUsername);
+    freeWideChar(pwszDomain);
+    freeWideChar(pwszPassword);
+
+    return result;
+}
+
diff --git a/src/VBox/HostServices/common/client.cpp b/src/VBox/HostServices/common/client.cpp
new file mode 100644
index 00000000..67a03b8f
--- /dev/null
+++ b/src/VBox/HostServices/common/client.cpp
@@ -0,0 +1,241 @@
+/* $Id: client.cpp $ */
+/** @file
+ * Base class for a host-guest service.
+ */
+
+/*
+ * Copyright (C) 2011-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <VBox/log.h>
+#include <VBox/hgcmsvc.h>
+
+#include <iprt/assert.h>
+#include <iprt/alloc.h>
+#include <iprt/cpp/utils.h>
+
+#include <VBox/HostServices/Service.h>
+
+using namespace HGCM;
+
+Client::Client(uint32_t idClient)
+    : m_idClient(idClient)
+    , m_fDeferred(false)
+{
+    RT_ZERO(m_Deferred);
+    RT_ZERO(m_SvcCtx);
+}
+
+Client::~Client(void)
+{
+
+}
+
+/**
+ * Completes a guest call by returning the control back to the guest side,
+ * together with a status code, internal version.
+ *
+ * @returns IPRT status code.
+ * @param   hHandle             Call handle to complete guest call for.
+ * @param   rcOp                Return code to return to the guest side.
+ */
+int Client::completeInternal(VBOXHGCMCALLHANDLE hHandle, int rcOp) RT_NOEXCEPT
+{
+    LogFlowThisFunc(("idClient=%RU32\n", m_idClient));
+
+    if (   m_SvcCtx.pHelpers
+        && m_SvcCtx.pHelpers->pfnCallComplete)
+    {
+        m_SvcCtx.pHelpers->pfnCallComplete(hHandle, rcOp);
+
+        reset();
+        return VINF_SUCCESS;
+    }
+
+    return VERR_NOT_AVAILABLE;
+}
+
+/**
+ * Resets the client's internal state.
+ */
+void Client::reset(void) RT_NOEXCEPT
+{
+   m_fDeferred = false;
+
+   RT_ZERO(m_Deferred);
+}
+
+/**
+ * Completes a guest call by returning the control back to the guest side,
+ * together with a status code.
+ *
+ * @returns IPRT status code.
+ * @param   hHandle             Call handle to complete guest call for.
+ * @param   rcOp                Return code to return to the guest side.
+ */
+int Client::Complete(VBOXHGCMCALLHANDLE hHandle, int rcOp /* = VINF_SUCCESS */) RT_NOEXCEPT
+{
+    return completeInternal(hHandle, rcOp);
+}
+
+/**
+ * Completes a deferred guest call by returning the control back to the guest side,
+ * together with a status code.
+ *
+ * @returns IPRT status code. VERR_INVALID_STATE if the client is not in deferred mode.
+ * @param   rcOp                Return code to return to the guest side.
+ */
+int Client::CompleteDeferred(int rcOp) RT_NOEXCEPT
+{
+    if (m_fDeferred)
+    {
+        Assert(m_Deferred.hHandle != NULL);
+
+        int rc = completeInternal(m_Deferred.hHandle, rcOp);
+        if (RT_SUCCESS(rc))
+            m_fDeferred = false;
+
+        return rc;
+    }
+
+    AssertMsg(m_fDeferred, ("Client %RU32 is not in deferred mode\n", m_idClient));
+    return VERR_INVALID_STATE;
+}
+
+/**
+ * Returns the HGCM call handle of the client.
+ *
+ * @returns HGCM handle.
+ */
+VBOXHGCMCALLHANDLE Client::GetHandle(void) const RT_NOEXCEPT
+{
+    return m_Deferred.hHandle;
+}
+
+/**
+ * Returns the HGCM call handle of the client.
+ *
+ * @returns HGCM handle.
+ */
+uint32_t Client::GetMsgType(void) const RT_NOEXCEPT
+{
+    return m_Deferred.uType;
+}
+
+uint32_t Client::GetMsgParamCount(void) const RT_NOEXCEPT
+{
+    return m_Deferred.cParms;
+}
+
+/**
+ * Returns the client's (HGCM) ID.
+ *
+ * @returns The client's (HGCM) ID.
+ */
+uint32_t Client::GetClientID(void) const RT_NOEXCEPT
+{
+    return m_idClient;
+}
+
+/**
+ * Returns whether the client currently is in deferred mode or not.
+ *
+ * @returns \c True if in deferred mode, \c False if not.
+ */
+bool Client::IsDeferred(void) const RT_NOEXCEPT
+{
+    return m_fDeferred;
+}
+
+/**
+ * Set the client's status to deferred, meaning that it does not return to the caller
+ * until CompleteDeferred() has been called.
+ *
+ * @returns VBox status code.
+ * @param   hHandle             Call handle to save.
+ * @param   u32Function         Function number to save.
+ * @param   cParms              Number of HGCM parameters to save.
+ * @param   paParms             HGCM parameters to save.
+ */
+void Client::SetDeferred(VBOXHGCMCALLHANDLE hHandle, uint32_t u32Function, uint32_t cParms, VBOXHGCMSVCPARM paParms[]) RT_NOEXCEPT
+{
+    LogFlowThisFunc(("uClient=%RU32\n", m_idClient));
+
+    m_fDeferred = true;
+
+    m_Deferred.hHandle = hHandle;
+    m_Deferred.uType   = u32Function;
+    m_Deferred.cParms  = cParms;
+    m_Deferred.paParms = paParms;
+}
+
+/**
+ * Sets the HGCM service context.
+ *
+ * @param   SvcCtx              Service context to set.
+ */
+void Client::SetSvcContext(const VBOXHGCMSVCTX &SvcCtx) RT_NOEXCEPT
+{
+    m_SvcCtx = SvcCtx;
+}
+
+/**
+ * Sets the deferred parameters to a specific message type and
+ * required parameters. That way the client can re-request that message with
+ * the right amount of parameters from the service.
+ *
+ * @returns IPRT status code.
+ * @param   uMsg                Message type (number) to set.
+ * @param   cParms              Number of parameters the message needs.
+ */
+int Client::SetDeferredMsgInfo(uint32_t uMsg, uint32_t cParms) RT_NOEXCEPT
+{
+    if (m_fDeferred)
+    {
+        if (m_Deferred.cParms < 2)
+            return VERR_INVALID_PARAMETER;
+
+        AssertPtrReturn(m_Deferred.paParms, VERR_BUFFER_OVERFLOW);
+
+        HGCMSvcSetU32(&m_Deferred.paParms[0], uMsg);
+        HGCMSvcSetU32(&m_Deferred.paParms[1], cParms);
+
+        return VINF_SUCCESS;
+    }
+
+    AssertFailed();
+    return VERR_INVALID_STATE;
+}
+
+/**
+ * Sets the deferred parameters to a specific message type and
+ * required parameters. That way the client can re-request that message with
+ * the right amount of parameters from the service.
+ *
+ * @returns IPRT status code.
+ * @param   pMessage            Message to get message type and required parameters from.
+ */
+int Client::SetDeferredMsgInfo(const Message *pMessage) RT_NOEXCEPT
+{
+    AssertPtrReturn(pMessage, VERR_INVALID_POINTER);
+    return SetDeferredMsgInfo(pMessage->GetType(), pMessage->GetParamCount());
+}
+
diff --git a/src/VBox/HostServices/common/message.cpp b/src/VBox/HostServices/common/message.cpp
new file mode 100644
index 00000000..cb295563
--- /dev/null
+++ b/src/VBox/HostServices/common/message.cpp
@@ -0,0 +1,301 @@
+/* $Id: message.cpp $ */
+/** @file
+ * Base class for wrapping HCGM messages.
+ */
+
+/*
+ * Copyright (C) 2018-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+#include <VBox/HostServices/Service.h>
+#include <VBox/VMMDev.h> /* For VMMDEV_MAX_HGCM_PARMS. */
+
+using namespace HGCM;
+
+Message::Message(void)
+    : m_uMsg(0)
+    , m_cParms(0)
+    , m_paParms(NULL)
+{
+}
+
+Message::Message(uint32_t uMsg, uint32_t cParms, VBOXHGCMSVCPARM aParms[])
+    : m_uMsg(0)
+    , m_cParms(0)
+    , m_paParms(NULL)
+{
+    initData(uMsg, cParms, aParms);
+}
+
+Message::~Message(void)
+{
+    reset();
+}
+
+/**
+ * Resets the message by free'ing all allocated parameters and resetting the rest.
+ */
+void Message::reset(void) RT_NOEXCEPT
+{
+    if (m_paParms)
+    {
+        for (uint32_t i = 0; i < m_cParms; ++i)
+        {
+            switch (m_paParms[i].type)
+            {
+                case VBOX_HGCM_SVC_PARM_PTR:
+                    if (m_paParms[i].u.pointer.size)
+                        RTMemFree(m_paParms[i].u.pointer.addr);
+                    break;
+            }
+        }
+        RTMemFree(m_paParms);
+        m_paParms = 0;
+    }
+    m_cParms = 0;
+    m_uMsg = 0;
+}
+
+/**
+ * Returns the parameter count of this message.
+ *
+ * @returns Parameter count.
+ */
+uint32_t Message::GetParamCount(void) const RT_NOEXCEPT
+{
+    return m_cParms;
+}
+
+/**
+ * Retrieves the raw HGCM parameter data
+ *
+ * @returns IPRT status code.
+ * @param   uMsg            Message type to retrieve the parameter data for. Needed for sanity.
+ * @param   cParms          Size (in parameters) of @a aParms array.
+ * @param   aParms          Where to store the HGCM parameter data.
+ */
+int Message::GetData(uint32_t uMsg, uint32_t cParms, VBOXHGCMSVCPARM aParms[]) const RT_NOEXCEPT
+{
+    if (m_uMsg != uMsg)
+    {
+        LogFlowFunc(("Stored message type (%RU32) does not match request (%RU32)\n", m_uMsg, uMsg));
+        return VERR_INVALID_PARAMETER;
+    }
+
+    if (m_cParms == 0) /* Nothing to copy, take a shortcut. */
+        return VINF_SUCCESS;
+
+    if (m_cParms > cParms)
+    {
+        LogFlowFunc(("Stored parameter count (%RU32) exceeds request buffer (%RU32)\n", m_cParms, cParms));
+        return VERR_INVALID_PARAMETER;
+    }
+
+    return Message::CopyParms(&aParms[0], cParms, m_paParms, m_cParms, false /* fDeepCopy */);
+}
+
+/**
+ * Retrieves a specific parameter value as uint32_t.
+ *
+ * @returns IPRT status code.
+ * @param   uParm           Index of parameter to retrieve.
+ * @param   pu32Info        Where to store the parameter value.
+ */
+int Message::GetParmU32(uint32_t uParm, uint32_t *pu32Info) const RT_NOEXCEPT
+{
+    AssertPtrReturn(pu32Info, VERR_INVALID_PARAMETER);
+    AssertReturn(uParm < m_cParms, VERR_INVALID_PARAMETER);
+    AssertReturn(m_paParms[uParm].type == VBOX_HGCM_SVC_PARM_32BIT, VERR_INVALID_PARAMETER);
+
+    *pu32Info = m_paParms[uParm].u.uint32;
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Retrieves a specific parameter value as uint64_t.
+ *
+ * @returns IPRT status code.
+ * @param   uParm           Index of parameter to retrieve.
+ * @param   pu64Info        Where to store the parameter value.
+ */
+int Message::GetParmU64(uint32_t uParm, uint64_t *pu64Info) const RT_NOEXCEPT
+{
+    AssertPtrReturn(pu64Info, VERR_INVALID_PARAMETER);
+    AssertReturn(uParm < m_cParms, VERR_INVALID_PARAMETER);
+    AssertReturn(m_paParms[uParm].type == VBOX_HGCM_SVC_PARM_64BIT, VERR_INVALID_PARAMETER);
+
+    *pu64Info = m_paParms[uParm].u.uint64;
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Retrieves a specific parameter value as a data address + size.
+ *
+ * @returns IPRT status code.
+ * @param   uParm           Index of parameter to retrieve.
+ * @param   ppvAddr         Where to store the data address.
+ * @param   pcbSize         Where to store the data size (in bytes).
+ *
+ * @remarks Does not copy (store) the actual content of the pointer (deep copy).
+ */
+int Message::GetParmPtr(uint32_t uParm, void **ppvAddr, uint32_t *pcbSize) const RT_NOEXCEPT
+{
+    AssertPtrReturn(ppvAddr, VERR_INVALID_PARAMETER);
+    AssertPtrReturn(pcbSize, VERR_INVALID_PARAMETER);
+    AssertReturn(uParm < m_cParms, VERR_INVALID_PARAMETER);
+    AssertReturn(m_paParms[uParm].type == VBOX_HGCM_SVC_PARM_PTR, VERR_INVALID_PARAMETER);
+
+    *ppvAddr = m_paParms[uParm].u.pointer.addr;
+    *pcbSize = m_paParms[uParm].u.pointer.size;
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Returns the type of this message.
+ *
+ * @returns Message type.
+ */
+uint32_t Message::GetType(void) const RT_NOEXCEPT
+{
+    return m_uMsg;
+}
+
+/**
+ * Copies HGCM parameters from source to destination.
+ *
+ * @returns IPRT status code.
+ * @param   paParmsDst      Destination array to copy parameters to.
+ * @param   cParmsDst       Size (in parameters) of destination array.
+ * @param   paParmsSrc      Source array to copy parameters from.
+ * @param   cParmsSrc       Size (in parameters) of source array.
+ * @param   fDeepCopy       Whether to perform a deep copy of pointer parameters or not.
+ *
+ * @remark Static convenience function.
+ */
+/* static */
+int Message::CopyParms(PVBOXHGCMSVCPARM paParmsDst, uint32_t cParmsDst,
+                       PVBOXHGCMSVCPARM paParmsSrc, uint32_t cParmsSrc,
+                       bool fDeepCopy) RT_NOEXCEPT
+{
+    AssertPtrReturn(paParmsSrc, VERR_INVALID_POINTER);
+    AssertPtrReturn(paParmsDst, VERR_INVALID_POINTER);
+
+    if (cParmsSrc > cParmsDst)
+        return VERR_BUFFER_OVERFLOW;
+
+    for (uint32_t i = 0; i < cParmsSrc; i++)
+    {
+        paParmsDst[i].type = paParmsSrc[i].type;
+        switch (paParmsSrc[i].type)
+        {
+            case VBOX_HGCM_SVC_PARM_32BIT:
+            {
+                paParmsDst[i].u.uint32 = paParmsSrc[i].u.uint32;
+                break;
+            }
+            case VBOX_HGCM_SVC_PARM_64BIT:
+            {
+                paParmsDst[i].u.uint64 = paParmsSrc[i].u.uint64;
+                break;
+            }
+            case VBOX_HGCM_SVC_PARM_PTR:
+            {
+                /* Do we have to perform a deep copy? */
+                if (fDeepCopy)
+                {
+                    /* Yes, do so. */
+                    paParmsDst[i].u.pointer.size = paParmsSrc[i].u.pointer.size;
+                    if (paParmsDst[i].u.pointer.size > 0)
+                    {
+                        paParmsDst[i].u.pointer.addr = RTMemAlloc(paParmsDst[i].u.pointer.size);
+                        if (!paParmsDst[i].u.pointer.addr)
+                            return VERR_NO_MEMORY;
+                    }
+                }
+                else
+                {
+                    /* No, but we have to check if there is enough room. */
+                    if (paParmsDst[i].u.pointer.size < paParmsSrc[i].u.pointer.size)
+                        return VERR_BUFFER_OVERFLOW;
+                }
+
+                if (paParmsSrc[i].u.pointer.size)
+                {
+                    if (   paParmsDst[i].u.pointer.addr
+                        && paParmsDst[i].u.pointer.size)
+                        memcpy(paParmsDst[i].u.pointer.addr,
+                               paParmsSrc[i].u.pointer.addr,
+                               RT_MIN(paParmsDst[i].u.pointer.size, paParmsSrc[i].u.pointer.size));
+                    else
+                        return VERR_INVALID_POINTER;
+                }
+                break;
+            }
+            default:
+            {
+                AssertMsgFailed(("Unknown HGCM type %u\n", paParmsSrc[i].type));
+                return VERR_INVALID_PARAMETER;
+            }
+        }
+    }
+    return VINF_SUCCESS;
+}
+
+/**
+ * Initializes the message with a message type and parameters.
+ *
+ * @returns IPRT status code.
+ * @param   uMsg            Message type to set.
+ * @param   cParms          Number of parameters to set.
+ * @param   aParms          Array of parameters to set.
+ */
+int Message::initData(uint32_t uMsg, uint32_t cParms, VBOXHGCMSVCPARM aParms[]) RT_NOEXCEPT
+{
+    AssertReturn(cParms < VMMDEV_MAX_HGCM_PARMS, VERR_INVALID_PARAMETER);
+    AssertReturn(cParms == 0 || aParms != NULL, VERR_INVALID_POINTER);
+
+    /* Cleanup any eventual old stuff. */
+    reset();
+
+    m_uMsg   = uMsg;
+    m_cParms = cParms;
+
+    int rc = VINF_SUCCESS;
+
+    if (cParms)
+    {
+        m_paParms = (VBOXHGCMSVCPARM*)RTMemAllocZ(sizeof(VBOXHGCMSVCPARM) * m_cParms);
+        if (m_paParms)
+        {
+            rc = Message::CopyParms(m_paParms, m_cParms, &aParms[0], cParms, true /* fDeepCopy */);
+            if (RT_FAILURE(rc))
+                reset();
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+
+    return rc;
+}
+
diff --git a/src/VBox/HostServices/testcase/Makefile.kmk b/src/VBox/HostServices/testcase/Makefile.kmk
new file mode 100644
index 00000000..a6b63610
--- /dev/null
+++ b/src/VBox/HostServices/testcase/Makefile.kmk
@@ -0,0 +1,52 @@
+# $Id: Makefile.kmk $
+## @file
+# Sub-Makefile for the HGCM service testcase.
+#
+
+#
+# Copyright (C) 2009-2023 Oracle and/or its affiliates.
+#
+# This file is part of VirtualBox base platform packages, as
+# available from https://www.virtualbox.org.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License
+# as published by the Free Software Foundation, in version 3 of the
+# License.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, see <https://www.gnu.org/licenses>.
+#
+# SPDX-License-Identifier: GPL-3.0-only
+#
+
+SUB_DEPTH = ../../../..
+include $(KBUILD_PATH)/subheader.kmk
+
+if defined(VBOX_WITH_TESTCASES) && !defined(VBOX_ONLY_ADDITIONS) && !defined(VBOX_ONLY_SDK)
+
+ #
+ # Set this in LocalConfig.kmk if you are working on HGCM service internals
+ # to automatically run the unit test at build time:
+ #    OTHERS += $(tstHGCMSvc_0_OUTDIR)/tstHGCMSvc.run
+ #
+ PROGRAMS  += tstHGCMSvc
+ TESTING   += $(tstHGCMSvc_0_OUTDIR)/tstHGCMSvc.run
+ tstHGCMSvc_TEMPLATE  = VBoxR3TstExe
+ tstHGCMSvc_DEFS      = VBOX_WITH_HGCM VBOX_TEST_HGCM_PARMS
+ tstHGCMSvc_SOURCES   = tstHGCMSvc.cpp
+ tstHGCMSvc_CLEAN     = $(tstHGCMSvc_0_OUTDIR)/tstHGCMSvc.run
+
+ $$(tstHGCMSvc_0_OUTDIR)/tstHGCMSvc.run: $$(tstHGCMSvc_1_STAGE_TARGET)
+	export VBOX_LOG_DEST=nofile; $(tstHGCMSvc_1_STAGE_TARGET) quiet
+	$(QUIET)$(APPEND) -t "$@" "done"
+
+endif # VBOX_WITH_TESTCASES
+
+include $(FILE_KBUILD_SUB_FOOTER)
+
diff --git a/src/VBox/HostServices/testcase/tstHGCMSvc.cpp b/src/VBox/HostServices/testcase/tstHGCMSvc.cpp
new file mode 100644
index 00000000..9c2ee782
--- /dev/null
+++ b/src/VBox/HostServices/testcase/tstHGCMSvc.cpp
@@ -0,0 +1,119 @@
+/* $Id: tstHGCMSvc.cpp $ */
+/** @file
+ * HGCM Service Testcase.
+ */
+
+/*
+ * Copyright (C) 2009-2023 Oracle and/or its affiliates.
+ *
+ * This file is part of VirtualBox base platform packages, as
+ * available from https://www.virtualbox.org.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, in version 3 of the
+ * License.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <https://www.gnu.org/licenses>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only
+ */
+
+
+/*********************************************************************************************************************************
+*   Header Files                                                                                                                 *
+*********************************************************************************************************************************/
+#include <VBox/hgcmsvc.h>
+#include <iprt/initterm.h>
+#include <iprt/test.h>
+
+/** Test the getString member function.  Indirectly tests the getPointer
+ * and getBuffer APIs.
+ * @param  hTest  an running IPRT test
+ * @param  type  the type that the parameter should be set to before
+ *                calling getString
+ * @param  pcch   the value that the parameter should be set to before
+ *                calling getString, and also the address (!) which we
+ *                expect getString to return.  Stricter than needed of
+ *                course, but I was feeling lazy.
+ * @param  cb     the size that the parameter should be set to before
+ *                calling getString, and also the size which we expect
+ *                getString to return.
+ * @param  rcExp  the expected return value of the call to getString.
+ */
+void doTestGetString(VBOXHGCMSVCPARM *pParm, RTTEST hTest, uint32_t type,
+                     const char *pcch, uint32_t cb, int rcExp)
+{
+    /* An RTTest API like this, which would print out an additional line
+     * of context if a test failed, would be nice.  This is because the
+     * line number alone doesn't help much here, given that this is a
+     * subroutine called many times. */
+    /*
+    RTTestContextF(hTest,
+                   ("doTestGetString, type=%u, pcch=%p, acp=%u, rcExp=%Rrc",
+                    type, pcch, acp, rcExp));
+     */
+    HGCMSvcSetPv(pParm, (void *)pcch, cb);
+    pParm->type = type;  /* in case we don't want VBOX_HGCM_SVC_PARM_PTR */
+    const char *pcch2 = NULL;
+    uint32_t cb2 = 0;
+    int rc = HGCMSvcGetCStr(pParm, &pcch2, &cb2);
+    RTTEST_CHECK_RC(hTest, rc, rcExp);
+    if (RT_SUCCESS(rcExp))
+    {
+        RTTEST_CHECK_MSG_RETV(hTest, (pcch2 == pcch),
+                              (hTest, "expected %p, got %p", pcch, pcch2));
+        RTTEST_CHECK_MSG_RETV(hTest, (cb2 == cb),
+                              (hTest, "expected %u, got %u", cb, cb2));
+    }
+}
+
+/** Run some unit tests on the getString method and indirectly test
+ * getPointer and getBuffer as well. */
+void testGetString(VBOXHGCMSVCPARM *pParm, RTTEST hTest)
+{
+    RTTestSub(hTest, "HGCM string parameter handling");
+    doTestGetString(pParm, hTest, VBOX_HGCM_SVC_PARM_32BIT, "test", 3,
+                    VERR_INVALID_PARAMETER);
+    doTestGetString(pParm, hTest, VBOX_HGCM_SVC_PARM_PTR, "test", 5,
+                    VINF_SUCCESS);
+    doTestGetString(pParm, hTest, VBOX_HGCM_SVC_PARM_PTR, "test", 3,
+                    VERR_BUFFER_OVERFLOW);
+    doTestGetString(pParm, hTest, VBOX_HGCM_SVC_PARM_PTR, "test\xf0", 6,
+                    VERR_INVALID_UTF8_ENCODING);
+    doTestGetString(pParm, hTest, VBOX_HGCM_SVC_PARM_PTR, "test", 0,
+                    VERR_INVALID_PARAMETER);
+    doTestGetString(pParm, hTest, VBOX_HGCM_SVC_PARM_PTR, (const char *)0x1, 5,
+                    VERR_INVALID_PARAMETER);
+    RTTestSubDone(hTest);
+}
+
+int main()
+{
+    /*
+     * Init the runtime, test and say hello.
+     */
+    RTTEST hTest;
+    int rc = RTTestInitAndCreate("tstHGCMSvc", &hTest);
+    if (rc)
+        return rc;
+    RTTestBanner(hTest);
+
+    /*
+     * Run the test.
+     */
+    VBOXHGCMSVCPARM parm;
+    testGetString(&parm, hTest);
+
+    /*
+     * Summary
+     */
+    return RTTestSummaryAndDestroy(hTest);
+}
+