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

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

1 files changed, 1765 insertions, 0 deletions

diff --git a/include/VBox/vd-ifs.h b/include/VBox/vd-ifs.h
new file mode 100644
index 00000000..c347e2fb
--- /dev/null
+++ b/include/VBox/vd-ifs.h
@@ -0,0 +1,1765 @@
+/** @file
+ * VD Container API - interfaces.
+ */
+
+/*
+ * 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>.
+ *
+ * The contents of this file may alternatively be used under the terms
+ * of the Common Development and Distribution License Version 1.0
+ * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included
+ * in the VirtualBox distribution, in which case the provisions of the
+ * CDDL are applicable instead of those of the GPL.
+ *
+ * You may elect to license modified versions of this file under the
+ * terms and conditions of either the GPL or the CDDL or both.
+ *
+ * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0
+ */
+
+#ifndef VBOX_INCLUDED_vd_ifs_h
+#define VBOX_INCLUDED_vd_ifs_h
+#ifndef RT_WITHOUT_PRAGMA_ONCE
+# pragma once
+#endif
+
+#include <iprt/assert.h>
+#include <iprt/string.h>
+#include <iprt/mem.h>
+#include <iprt/file.h>
+#include <iprt/net.h>
+#include <iprt/sg.h>
+#include <VBox/cdefs.h>
+#include <VBox/types.h>
+#include <VBox/err.h>
+
+RT_C_DECLS_BEGIN
+
+/** @addtogroup grp_vd
+ * @{ */
+
+/** Interface header magic. */
+#define VDINTERFACE_MAGIC UINT32_C(0x19701015)
+
+/**
+ * Supported interface types.
+ */
+typedef enum VDINTERFACETYPE
+{
+    /** First valid interface. */
+    VDINTERFACETYPE_FIRST = 0,
+    /** Interface to pass error message to upper layers. Per-disk. */
+    VDINTERFACETYPE_ERROR = VDINTERFACETYPE_FIRST,
+    /** Interface for I/O operations. Per-image. */
+    VDINTERFACETYPE_IO,
+    /** Interface for progress notification. Per-operation. */
+    VDINTERFACETYPE_PROGRESS,
+    /** Interface for configuration information. Per-image. */
+    VDINTERFACETYPE_CONFIG,
+    /** Interface for TCP network stack. Per-image. */
+    VDINTERFACETYPE_TCPNET,
+    /** Interface for getting parent image state. Per-operation. */
+    VDINTERFACETYPE_PARENTSTATE,
+    /** Interface for synchronizing accesses from several threads. Per-disk. */
+    VDINTERFACETYPE_THREADSYNC,
+    /** Interface for I/O between the generic VBoxHDD code and the backend. Per-image (internal).
+     * This interface is completely internal and must not be used elsewhere. */
+    VDINTERFACETYPE_IOINT,
+    /** Interface to query the use of block ranges on the disk. Per-operation. */
+    VDINTERFACETYPE_QUERYRANGEUSE,
+    /** Interface for the metadata traverse callback. Per-operation. */
+    VDINTERFACETYPE_TRAVERSEMETADATA,
+    /** Interface for crypto operations. Per-filter. */
+    VDINTERFACETYPE_CRYPTO,
+    /** invalid interface. */
+    VDINTERFACETYPE_INVALID
+} VDINTERFACETYPE;
+
+/**
+ * Common structure for all interfaces and at the beginning of all types.
+ */
+typedef struct VDINTERFACE
+{
+    uint32_t            u32Magic;
+    /** Human readable interface name. */
+    const char         *pszInterfaceName;
+    /** Pointer to the next common interface structure. */
+    struct VDINTERFACE *pNext;
+    /** Interface type. */
+    VDINTERFACETYPE     enmInterface;
+    /** Size of the interface. */
+    size_t              cbSize;
+    /** Opaque user data which is passed on every call. */
+    void               *pvUser;
+} VDINTERFACE;
+/** Pointer to a VDINTERFACE. */
+typedef VDINTERFACE *PVDINTERFACE;
+/** Pointer to a const VDINTERFACE. */
+typedef const VDINTERFACE *PCVDINTERFACE;
+
+/**
+ * Helper functions to handle interface lists.
+ *
+ * @note These interface lists are used consistently to pass per-disk,
+ * per-image and/or per-operation callbacks. Those three purposes are strictly
+ * separate. See the individual interface declarations for what context they
+ * apply to. The caller is responsible for ensuring that the lifetime of the
+ * interface descriptors is appropriate for the category of interface.
+ */
+
+/**
+ * Get a specific interface from a list of interfaces specified by the type.
+ *
+ * @return  Pointer to the matching interface or NULL if none was found.
+ * @param   pVDIfs          Pointer to the VD interface list.
+ * @param   enmInterface    Interface to search for.
+ */
+DECLINLINE(PVDINTERFACE) VDInterfaceGet(PVDINTERFACE pVDIfs, VDINTERFACETYPE enmInterface)
+{
+    AssertMsgReturn(   enmInterface >= VDINTERFACETYPE_FIRST
+                    && enmInterface < VDINTERFACETYPE_INVALID,
+                    ("enmInterface=%u", enmInterface), NULL);
+
+    while (pVDIfs)
+    {
+        AssertMsgBreak(pVDIfs->u32Magic == VDINTERFACE_MAGIC,
+                       ("u32Magic=%#x\n", pVDIfs->u32Magic));
+
+        if (pVDIfs->enmInterface == enmInterface)
+            return pVDIfs;
+        pVDIfs = pVDIfs->pNext;
+    }
+
+    /* No matching interface was found. */
+    return NULL;
+}
+
+/**
+ * Add an interface to a list of interfaces.
+ *
+ * @return VBox status code.
+ * @param  pInterface   Pointer to an unitialized common interface structure.
+ * @param  pszName      Name of the interface.
+ * @param  enmInterface Type of the interface.
+ * @param  pvUser       Opaque user data passed on every function call.
+ * @param  cbInterface  The interface size.
+ * @param  ppVDIfs      Pointer to the VD interface list.
+ */
+DECLINLINE(int) VDInterfaceAdd(PVDINTERFACE pInterface, const char *pszName, VDINTERFACETYPE enmInterface, void *pvUser,
+                               size_t cbInterface, PVDINTERFACE *ppVDIfs)
+{
+    /* Argument checks. */
+    AssertMsgReturn(   enmInterface >= VDINTERFACETYPE_FIRST
+                    && enmInterface < VDINTERFACETYPE_INVALID,
+                    ("enmInterface=%u", enmInterface), VERR_INVALID_PARAMETER);
+
+    AssertPtrReturn(ppVDIfs, VERR_INVALID_PARAMETER);
+
+    /* Fill out interface descriptor. */
+    pInterface->u32Magic         = VDINTERFACE_MAGIC;
+    pInterface->cbSize           = cbInterface;
+    pInterface->pszInterfaceName = pszName;
+    pInterface->enmInterface     = enmInterface;
+    pInterface->pvUser           = pvUser;
+    pInterface->pNext            = *ppVDIfs;
+
+    /* Remember the new start of the list. */
+    *ppVDIfs = pInterface;
+
+    return VINF_SUCCESS;
+}
+
+/**
+ * Removes an interface from a list of interfaces.
+ *
+ * @return VBox status code
+ * @param  pInterface   Pointer to an initialized common interface structure to remove.
+ * @param  ppVDIfs      Pointer to the VD interface list to remove from.
+ */
+DECLINLINE(int) VDInterfaceRemove(PVDINTERFACE pInterface, PVDINTERFACE *ppVDIfs)
+{
+    int rc = VERR_NOT_FOUND;
+
+    /* Argument checks. */
+    AssertPtrReturn(pInterface, VERR_INVALID_PARAMETER);
+    AssertPtrReturn(ppVDIfs, VERR_INVALID_PARAMETER);
+
+    if (*ppVDIfs)
+    {
+        PVDINTERFACE pPrev = NULL;
+        PVDINTERFACE pCurr = *ppVDIfs;
+
+        while (   pCurr
+               && (pCurr != pInterface))
+        {
+            pPrev = pCurr;
+            pCurr = pCurr->pNext;
+        }
+
+        /* First interface */
+        if (!pPrev)
+        {
+            *ppVDIfs = pCurr->pNext;
+            rc = VINF_SUCCESS;
+        }
+        else if (pCurr)
+        {
+            Assert(pPrev->pNext == pCurr);
+            pPrev->pNext = pCurr->pNext;
+            rc = VINF_SUCCESS;
+        }
+    }
+
+    return rc;
+}
+
+/**
+ * Interface to deliver error messages (and also informational messages)
+ * to upper layers.
+ *
+ * Per-disk interface. Optional, but think twice if you want to miss the
+ * opportunity of reporting better human-readable error messages.
+ */
+typedef struct VDINTERFACEERROR
+{
+    /**
+     * Common interface header.
+     */
+    VDINTERFACE    Core;
+
+    /**
+     * Error message callback. Must be able to accept special IPRT format
+     * strings.
+     *
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   rc              The VBox error code.
+     * @param   SRC_POS         Use RT_SRC_POS.
+     * @param   pszFormat       Error message format string.
+     * @param   va              Error message arguments.
+     */
+    DECLR3CALLBACKMEMBER(void, pfnError, (void *pvUser, int rc, RT_SRC_POS_DECL,
+                                          const char *pszFormat, va_list va) RT_IPRT_FORMAT_ATTR(6, 0));
+
+    /**
+     * Informational message callback. May be NULL. Used e.g. in
+     * VDDumpImages(). Must be able to accept special IPRT format strings.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pszFormat       Message format string.
+     * @param   va              Message arguments.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnMessage, (void *pvUser, const char *pszFormat, va_list va) RT_IPRT_FORMAT_ATTR(2, 0));
+
+} VDINTERFACEERROR, *PVDINTERFACEERROR;
+
+/**
+ * Get error interface from interface list.
+ *
+ * @return Pointer to the first error interface in the list.
+ * @param  pVDIfs    Pointer to the interface list.
+ */
+DECLINLINE(PVDINTERFACEERROR) VDIfErrorGet(PVDINTERFACE pVDIfs)
+{
+    PVDINTERFACE pIf = VDInterfaceGet(pVDIfs, VDINTERFACETYPE_ERROR);
+
+    /* Check that the interface descriptor is a progress interface. */
+    AssertMsgReturn(   !pIf
+                    || (   (pIf->enmInterface == VDINTERFACETYPE_ERROR)
+                        && (pIf->cbSize == sizeof(VDINTERFACEERROR))),
+                    ("Not an error interface\n"), NULL);
+
+    return (PVDINTERFACEERROR)pIf;
+}
+
+/**
+ * Signal an error to the frontend.
+ *
+ * @returns VBox status code.
+ * @param   pIfError           The error interface.
+ * @param   rc                 The status code.
+ * @param   SRC_POS            The position in the source code.
+ * @param   pszFormat          The format string to pass.
+ * @param   ...                Arguments to the format string.
+ */
+DECLINLINE(int) RT_IPRT_FORMAT_ATTR(6, 7) vdIfError(PVDINTERFACEERROR pIfError, int rc, RT_SRC_POS_DECL,
+                                                    const char *pszFormat, ...)
+{
+    va_list va;
+    va_start(va, pszFormat);
+    if (pIfError)
+        pIfError->pfnError(pIfError->Core.pvUser, rc, RT_SRC_POS_ARGS, pszFormat, va);
+    va_end(va);
+
+#if defined(LOG_ENABLED) && defined(Log)
+    va_start(va, pszFormat);
+    Log(("vdIfError: %N\n", pszFormat, &va));
+    va_end(va);
+#endif
+    return rc;
+}
+
+/**
+ * Signal an informational message to the frontend.
+ *
+ * @returns VBox status code.
+ * @param   pIfError           The error interface.
+ * @param   pszFormat          The format string to pass.
+ * @param   ...                Arguments to the format string.
+ */
+DECLINLINE(int) RT_IPRT_FORMAT_ATTR(2, 3) vdIfErrorMessage(PVDINTERFACEERROR pIfError, const char *pszFormat, ...)
+{
+    int rc = VINF_SUCCESS;
+    va_list va;
+    va_start(va, pszFormat);
+    if (pIfError && pIfError->pfnMessage)
+        rc = pIfError->pfnMessage(pIfError->Core.pvUser, pszFormat, va);
+    va_end(va);
+
+#if defined(LOG_ENABLED) && defined(Log)
+    va_start(va, pszFormat);
+    Log(("vdIfErrorMessage: %N\n", pszFormat, &va));
+    va_end(va);
+#endif
+    return rc;
+}
+
+/**
+ * Completion callback which is called by the interface owner
+ * to inform the backend that a task finished.
+ *
+ * @return  VBox status code.
+ * @param   pvUser          Opaque user data which is passed on request submission.
+ * @param   rcReq           Status code of the completed request.
+ */
+typedef DECLCALLBACKTYPE(int, FNVDCOMPLETED,(void *pvUser, int rcReq));
+/** Pointer to FNVDCOMPLETED() */
+typedef FNVDCOMPLETED *PFNVDCOMPLETED;
+
+/**
+ * Support interface for I/O
+ *
+ * Per-image. Optional as input.
+ */
+typedef struct VDINTERFACEIO
+{
+    /**
+     * Common interface header.
+     */
+    VDINTERFACE    Core;
+
+    /**
+     * Open callback
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pszLocation     Name of the location to open.
+     * @param   fOpen           Flags for opening the backend.
+     *                          See RTFILE_O_* \#defines, inventing another set
+     *                          of open flags is not worth the mapping effort.
+     * @param   pfnCompleted    The callback which is called whenever a task
+     *                          completed. The backend has to pass the user data
+     *                          of the request initiator (ie the one who calls
+     *                          VDAsyncRead or VDAsyncWrite) in pvCompletion
+     *                          if this is NULL.
+     * @param   ppvStorage      Where to store the opaque storage handle.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnOpen, (void *pvUser, const char *pszLocation,
+                                        uint32_t fOpen,
+                                        PFNVDCOMPLETED pfnCompleted,
+                                        void **ppvStorage));
+
+    /**
+     * Close callback.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pvStorage       The opaque storage handle to close.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnClose, (void *pvUser, void *pvStorage));
+
+    /**
+     * Delete callback.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pcszFilename    Name of the file to delete.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnDelete, (void *pvUser, const char *pcszFilename));
+
+    /**
+     * Move callback.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pcszSrc         The path to the source file.
+     * @param   pcszDst         The path to the destination file.
+     *                          This file will be created.
+     * @param   fMove           A combination of the RTFILEMOVE_* flags.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnMove, (void *pvUser, const char *pcszSrc, const char *pcszDst, unsigned fMove));
+
+    /**
+     * Returns the free space on a disk.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pcszFilename    Name of a file to identify the disk.
+     * @param   pcbFreeSpace    Where to store the free space of the disk.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnGetFreeSpace, (void *pvUser, const char *pcszFilename, int64_t *pcbFreeSpace));
+
+    /**
+     * Returns the last modification timestamp of a file.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pcszFilename    Name of a file to identify the disk.
+     * @param   pModificationTime   Where to store the timestamp of the file.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnGetModificationTime, (void *pvUser, const char *pcszFilename, PRTTIMESPEC pModificationTime));
+
+    /**
+     * Returns the size of the opened storage backend.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pvStorage       The opaque storage handle to get the size from.
+     * @param   pcb             Where to store the size of the storage backend.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnGetSize, (void *pvUser, void *pvStorage, uint64_t *pcb));
+
+    /**
+     * Sets the size of the opened storage backend if possible.
+     *
+     * @return  VBox status code.
+     * @retval  VERR_NOT_SUPPORTED if the backend does not support this operation.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pvStorage       The opaque storage handle to set the size for.
+     * @param   cb              The new size of the image.
+     *
+     * @note Depending on the host the underlying storage (backing file, etc.)
+     *       might not have all required storage allocated (sparse file) which
+     *       can delay writes or fail with a not enough free space error if there
+     *       is not enough space on the storage medium when writing to the range for
+     *       the first time.
+     *       Use VDINTERFACEIO::pfnSetAllocationSize to make sure the storage is
+     *       really alloacted.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnSetSize, (void *pvUser, void *pvStorage, uint64_t cb));
+
+    /**
+     * Sets the size of the opened storage backend making sure the given size
+     * is really allocated.
+     *
+     * @return VBox status code.
+     * @retval VERR_NOT_SUPPORTED if the implementer of the interface doesn't support
+     *         this method.
+     * @param  pvUser          The opaque data passed on container creation.
+     * @param  pvStorage       The storage handle.
+     * @param  cbSize          The new size of the image.
+     * @param  fFlags          Flags for controlling the allocation strategy.
+     *                         Reserved for future use, MBZ.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnSetAllocationSize, (void *pvUser, void *pvStorage,
+                                                     uint64_t cbSize, uint32_t fFlags));
+
+    /**
+     * Synchronous write callback.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pvStorage       The storage handle to use.
+     * @param   off             The offset to start from.
+     * @param   pvBuf           Pointer to the bits need to be written.
+     * @param   cbToWrite       How many bytes to write.
+     * @param   pcbWritten      Where to store how many bytes were actually written.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnWriteSync, (void *pvUser, void *pvStorage, uint64_t off,
+                                             const void *pvBuf, size_t cbToWrite, size_t *pcbWritten));
+
+    /**
+     * Synchronous read callback.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pvStorage       The storage handle to use.
+     * @param   off             The offset to start from.
+     * @param   pvBuf           Where to store the read bits.
+     * @param   cbToRead        How many bytes to read.
+     * @param   pcbRead         Where to store how many bytes were actually read.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnReadSync, (void *pvUser, void *pvStorage, uint64_t off,
+                                            void *pvBuf, size_t cbToRead, size_t *pcbRead));
+
+    /**
+     * Flush data to the storage backend.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pvStorage       The storage handle to flush.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnFlushSync, (void *pvUser, void *pvStorage));
+
+    /**
+     * Initiate an asynchronous read request.
+     *
+     * @return  VBox status code.
+     * @param   pvUser         The opaque user data passed on container creation.
+     * @param   pvStorage      The storage handle.
+     * @param   uOffset        The offset to start reading from.
+     * @param   paSegments     Scatter gather list to store the data in.
+     * @param   cSegments      Number of segments in the list.
+     * @param   cbRead         How many bytes to read.
+     * @param   pvCompletion   The opaque user data which is returned upon completion.
+     * @param   ppTask         Where to store the opaque task handle.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnReadAsync, (void *pvUser, void *pvStorage, uint64_t uOffset,
+                                             PCRTSGSEG paSegments, size_t cSegments,
+                                             size_t cbRead, void *pvCompletion,
+                                             void **ppTask));
+
+    /**
+     * Initiate an asynchronous write request.
+     *
+     * @return  VBox status code.
+     * @param   pvUser         The opaque user data passed on conatiner creation.
+     * @param   pvStorage      The storage handle.
+     * @param   uOffset        The offset to start writing to.
+     * @param   paSegments     Scatter gather list of the data to write
+     * @param   cSegments      Number of segments in the list.
+     * @param   cbWrite        How many bytes to write.
+     * @param   pvCompletion   The opaque user data which is returned upon completion.
+     * @param   ppTask         Where to store the opaque task handle.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnWriteAsync, (void *pvUser, void *pvStorage, uint64_t uOffset,
+                                              PCRTSGSEG paSegments, size_t cSegments,
+                                              size_t cbWrite, void *pvCompletion,
+                                              void **ppTask));
+
+    /**
+     * Initiates an async flush request.
+     *
+     * @return  VBox status code.
+     * @param   pvUser          The opaque data passed on container creation.
+     * @param   pvStorage       The storage handle to flush.
+     * @param   pvCompletion    The opaque user data which is returned upon completion.
+     * @param   ppTask          Where to store the opaque task handle.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnFlushAsync, (void *pvUser, void *pvStorage,
+                                              void *pvCompletion, void **ppTask));
+
+} VDINTERFACEIO, *PVDINTERFACEIO;
+
+/**
+ * Get I/O interface from interface list.
+ *
+ * @return Pointer to the first I/O interface in the list.
+ * @param  pVDIfs    Pointer to the interface list.
+ */
+DECLINLINE(PVDINTERFACEIO) VDIfIoGet(PVDINTERFACE pVDIfs)
+{
+    PVDINTERFACE pIf = VDInterfaceGet(pVDIfs, VDINTERFACETYPE_IO);
+
+    /* Check that the interface descriptor is a progress interface. */
+    AssertMsgReturn(   !pIf
+                    || (   (pIf->enmInterface == VDINTERFACETYPE_IO)
+                        && (pIf->cbSize == sizeof(VDINTERFACEIO))),
+                    ("Not a I/O interface"), NULL);
+
+    return (PVDINTERFACEIO)pIf;
+}
+
+DECLINLINE(int) vdIfIoFileOpen(PVDINTERFACEIO pIfIo, const char *pszFilename,
+                               uint32_t fOpen, PFNVDCOMPLETED pfnCompleted,
+                               void **ppStorage)
+{
+    return pIfIo->pfnOpen(pIfIo->Core.pvUser, pszFilename, fOpen, pfnCompleted, ppStorage);
+}
+
+DECLINLINE(int) vdIfIoFileClose(PVDINTERFACEIO pIfIo, void *pStorage)
+{
+    return pIfIo->pfnClose(pIfIo->Core.pvUser, pStorage);
+}
+
+DECLINLINE(int) vdIfIoFileDelete(PVDINTERFACEIO pIfIo, const char *pszFilename)
+{
+    return pIfIo->pfnDelete(pIfIo->Core.pvUser, pszFilename);
+}
+
+DECLINLINE(int) vdIfIoFileMove(PVDINTERFACEIO pIfIo, const char *pszSrc,
+                               const char *pszDst, unsigned fMove)
+{
+    return pIfIo->pfnMove(pIfIo->Core.pvUser, pszSrc, pszDst, fMove);
+}
+
+DECLINLINE(int) vdIfIoFileGetFreeSpace(PVDINTERFACEIO pIfIo, const char *pszFilename,
+                                       int64_t *pcbFree)
+{
+    return pIfIo->pfnGetFreeSpace(pIfIo->Core.pvUser, pszFilename, pcbFree);
+}
+
+DECLINLINE(int) vdIfIoFileGetModificationTime(PVDINTERFACEIO pIfIo, const char *pcszFilename,
+                                              PRTTIMESPEC pModificationTime)
+{
+    return pIfIo->pfnGetModificationTime(pIfIo->Core.pvUser, pcszFilename,
+                                         pModificationTime);
+}
+
+DECLINLINE(int) vdIfIoFileGetSize(PVDINTERFACEIO pIfIo, void *pStorage,
+                                  uint64_t *pcbSize)
+{
+    return pIfIo->pfnGetSize(pIfIo->Core.pvUser, pStorage, pcbSize);
+}
+
+DECLINLINE(int) vdIfIoFileSetSize(PVDINTERFACEIO pIfIo, void *pStorage,
+                                  uint64_t cbSize)
+{
+    return pIfIo->pfnSetSize(pIfIo->Core.pvUser, pStorage, cbSize);
+}
+
+DECLINLINE(int) vdIfIoFileWriteSync(PVDINTERFACEIO pIfIo, void *pStorage,
+                                    uint64_t uOffset, const void *pvBuffer, size_t cbBuffer,
+                                    size_t *pcbWritten)
+{
+    return pIfIo->pfnWriteSync(pIfIo->Core.pvUser, pStorage, uOffset,
+                               pvBuffer, cbBuffer, pcbWritten);
+}
+
+DECLINLINE(int) vdIfIoFileReadSync(PVDINTERFACEIO pIfIo, void *pStorage,
+                                   uint64_t uOffset, void *pvBuffer, size_t cbBuffer,
+                                   size_t *pcbRead)
+{
+    return pIfIo->pfnReadSync(pIfIo->Core.pvUser, pStorage, uOffset,
+                              pvBuffer, cbBuffer, pcbRead);
+}
+
+DECLINLINE(int) vdIfIoFileFlushSync(PVDINTERFACEIO pIfIo, void *pStorage)
+{
+    return pIfIo->pfnFlushSync(pIfIo->Core.pvUser, pStorage);
+}
+
+/**
+ * Create a VFS stream handle around a VD I/O interface.
+ *
+ * The I/O interface will not be closed or free by the stream, the caller will
+ * do so after it is done with the stream and has released the instances of the
+ * I/O stream object returned by this API.
+ *
+ * @return  VBox status code.
+ * @param   pVDIfsIo        Pointer to the VD I/O interface.
+ * @param   pvStorage       The storage argument to pass to the interface
+ *                          methods.
+ * @param   fFlags          RTFILE_O_XXX, access mask requied.
+ * @param   phVfsIos        Where to return the VFS I/O stream handle on
+ *                          success.
+ */
+VBOXDDU_DECL(int) VDIfCreateVfsStream(PVDINTERFACEIO pVDIfsIo, void *pvStorage, uint32_t fFlags, PRTVFSIOSTREAM phVfsIos);
+
+struct VDINTERFACEIOINT;
+
+/**
+ * Create a VFS file handle around a VD I/O interface.
+ *
+ * The I/O interface will not be closed or free by the VFS file, the caller will
+ * do so after it is done with the VFS file and has released the instances of
+ * the VFS object returned by this API.
+ *
+ * @return  VBox status code.
+ * @param   pVDIfs          Pointer to the VD I/O interface.  If NULL, then @a
+ *                          pVDIfsInt must be specified.
+ * @param   pVDIfsInt       Pointer to the internal VD I/O interface.  If NULL,
+ *                          then @ pVDIfs must be specified.
+ * @param   pvStorage       The storage argument to pass to the interface
+ *                          methods.
+ * @param   fFlags          RTFILE_O_XXX, access mask requied.
+ * @param   phVfsFile       Where to return the VFS file handle on success.
+ */
+VBOXDDU_DECL(int) VDIfCreateVfsFile(PVDINTERFACEIO pVDIfs, struct VDINTERFACEIOINT *pVDIfsInt, void *pvStorage,
+                                    uint32_t fFlags, PRTVFSFILE phVfsFile);
+
+/**
+ * Creates an VD I/O interface wrapper around an IPRT VFS I/O stream.
+ *
+ * @return  VBox status code.
+ * @param   hVfsIos         The IPRT VFS I/O stream handle. The handle will be
+ *                          retained by the returned I/O interface (released on
+ *                          close or destruction).
+ * @param   fAccessMode     The access mode (RTFILE_O_ACCESS_MASK) to accept.
+ * @param   ppIoIf          Where to return the pointer to the VD I/O interface.
+ *                          This must be passed to VDIfDestroyFromVfsStream().
+ */
+VBOXDDU_DECL(int) VDIfCreateFromVfsStream(RTVFSIOSTREAM hVfsIos, uint32_t fAccessMode, PVDINTERFACEIO *ppIoIf);
+
+/**
+ * Destroys the VD I/O interface returned by VDIfCreateFromVfsStream.
+ *
+ * @returns VBox status code.
+ * @param   pIoIf           The I/O interface pointer returned by
+ *                          VDIfCreateFromVfsStream.  NULL will be quietly
+ *                          ignored.
+ */
+VBOXDDU_DECL(int) VDIfDestroyFromVfsStream(PVDINTERFACEIO pIoIf);
+
+
+/**
+ * Callback which provides progress information about a currently running
+ * lengthy operation.
+ *
+ * @return  VBox status code.
+ * @param   pvUser          The opaque user data associated with this interface.
+ * @param   uPercentage     Completion percentage.
+ */
+typedef DECLCALLBACKTYPE(int, FNVDPROGRESS,(void *pvUser, unsigned uPercentage));
+/** Pointer to FNVDPROGRESS() */
+typedef FNVDPROGRESS *PFNVDPROGRESS;
+
+/**
+ * Progress notification interface
+ *
+ * Per-operation. Optional.
+ */
+typedef struct VDINTERFACEPROGRESS
+{
+    /**
+     * Common interface header.
+     */
+    VDINTERFACE    Core;
+
+    /**
+     * Progress notification callbacks.
+     */
+    PFNVDPROGRESS pfnProgress;
+
+} VDINTERFACEPROGRESS, *PVDINTERFACEPROGRESS;
+
+/** Initializer for VDINTERFACEPROGRESS.  */
+#define VDINTERFACEPROGRESS_INITALIZER(a_pfnProgress) { { 0, NULL, NULL, VDINTERFACETYPE_INVALID, 0, NULL }, a_pfnProgress }
+
+/**
+ * Get progress interface from interface list.
+ *
+ * @return Pointer to the first progress interface in the list.
+ * @param  pVDIfs    Pointer to the interface list.
+ */
+DECLINLINE(PVDINTERFACEPROGRESS) VDIfProgressGet(PVDINTERFACE pVDIfs)
+{
+    PVDINTERFACE pIf = VDInterfaceGet(pVDIfs, VDINTERFACETYPE_PROGRESS);
+
+    /* Check that the interface descriptor is a progress interface. */
+    AssertMsgReturn(   !pIf
+                    || (   (pIf->enmInterface == VDINTERFACETYPE_PROGRESS)
+                        && (pIf->cbSize == sizeof(VDINTERFACEPROGRESS))),
+                    ("Not a progress interface"), NULL);
+
+    return (PVDINTERFACEPROGRESS)pIf;
+}
+
+/**
+ * Signal new progress information to the frontend.
+ *
+ * @returns VBox status code.
+ * @param   pIfProgress        The progress interface.
+ * @param   uPercentage        Completion percentage.
+ */
+DECLINLINE(int) vdIfProgress(PVDINTERFACEPROGRESS pIfProgress, unsigned uPercentage)
+{
+    if (pIfProgress)
+        return pIfProgress->pfnProgress(pIfProgress->Core.pvUser, uPercentage);
+    return VINF_SUCCESS;
+}
+
+/**
+ * Configuration information interface
+ *
+ * Per-image. Optional for most backends, but mandatory for images which do
+ * not operate on files (including standard block or character devices).
+ */
+typedef struct VDINTERFACECONFIG
+{
+    /**
+     * Common interface header.
+     */
+    VDINTERFACE    Core;
+
+    /**
+     * Validates that the keys are within a set of valid names.
+     *
+     * @return  true if all key names are found in pszzAllowed.
+     * @return  false if not.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pszzValid       List of valid key names separated by '\\0' and ending with
+     *                          a double '\\0'.
+     */
+    DECLR3CALLBACKMEMBER(bool, pfnAreKeysValid, (void *pvUser, const char *pszzValid));
+
+    /**
+     * Retrieves the length of the string value associated with a key (including
+     * the terminator, for compatibility with CFGMR3QuerySize).
+     *
+     * @return  VBox status code.
+     *          VERR_CFGM_VALUE_NOT_FOUND means that the key is not known.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pszName         Name of the key to query.
+     * @param   pcbValue        Where to store the value length. Non-NULL.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnQuerySize, (void *pvUser, const char *pszName, size_t *pcbValue));
+
+    /**
+     * Query the string value associated with a key.
+     *
+     * @return  VBox status code.
+     *          VERR_CFGM_VALUE_NOT_FOUND means that the key is not known.
+     *          VERR_CFGM_NOT_ENOUGH_SPACE means that the buffer is not big enough.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pszName         Name of the key to query.
+     * @param   pszValue        Pointer to buffer where to store value.
+     * @param   cchValue        Length of value buffer.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnQuery, (void *pvUser, const char *pszName, char *pszValue, size_t cchValue));
+
+    /**
+     * Query the bytes value associated with a key.
+     *
+     * @return  VBox status code.
+     *          VERR_CFGM_VALUE_NOT_FOUND means that the key is not known.
+     *          VERR_CFGM_NOT_ENOUGH_SPACE means that the buffer is not big enough.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pszName         Name of the key to query.
+     * @param   ppvData         Pointer to buffer where to store the data.
+     * @param   cbData          Length of data buffer.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnQueryBytes, (void *pvUser, const char *pszName, void *ppvData, size_t cbData));
+
+    /**
+     * Set a named property to a specified string value, optionally creating if it doesn't exist.
+     *
+     * @return  VBox status code.
+     *          VERR_CFGM_VALUE_NOT_FOUND means that the key is not known and fCreate flag was not set.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   fCreate         Create property if it doesn't exist (if property exists, it is not an error)
+     * @param   pszName         Name of the key to query.
+     * @param   pszValue        String value to set the name property to.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnUpdate, (void *pvUser, bool fCreate,
+            const char *pszName, const char *pszValue));
+
+} VDINTERFACECONFIG, *PVDINTERFACECONFIG;
+
+/**
+ * Get configuration information interface from interface list.
+ *
+ * @return Pointer to the first configuration information interface in the list.
+ * @param  pVDIfs    Pointer to the interface list.
+ */
+DECLINLINE(PVDINTERFACECONFIG) VDIfConfigGet(PVDINTERFACE pVDIfs)
+{
+    PVDINTERFACE pIf = VDInterfaceGet(pVDIfs, VDINTERFACETYPE_CONFIG);
+
+    /* Check that the interface descriptor is a progress interface. */
+    AssertMsgReturn(   !pIf
+                    || (   (pIf->enmInterface == VDINTERFACETYPE_CONFIG)
+                        && (pIf->cbSize == sizeof(VDINTERFACECONFIG))),
+                    ("Not a config interface"), NULL);
+
+    return (PVDINTERFACECONFIG)pIf;
+}
+
+/**
+ * Query configuration, validates that the keys are within a set of valid names.
+ *
+ * @return  true if all key names are found in pszzAllowed.
+ * @return  false if not.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszzValid   List of valid names separated by '\\0' and ending with
+ *                      a double '\\0'.
+ */
+DECLINLINE(bool) VDCFGAreKeysValid(PVDINTERFACECONFIG pCfgIf, const char *pszzValid)
+{
+    return pCfgIf->pfnAreKeysValid(pCfgIf->Core.pvUser, pszzValid);
+}
+
+/**
+ * Checks whether a given key is existing.
+ *
+ * @return  true if the key exists.
+ * @return  false if the key does not exist.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszName     Name of the key.
+ */
+DECLINLINE(bool) VDCFGIsKeyExisting(PVDINTERFACECONFIG pCfgIf, const char *pszName)
+{
+    size_t cb = 0;
+    int rc = pCfgIf->pfnQuerySize(pCfgIf->Core.pvUser, pszName, &cb);
+    return rc == VERR_CFGM_VALUE_NOT_FOUND ? false : true;
+}
+
+/**
+ * Query configuration, unsigned 64-bit integer value with default.
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszName     Name of an integer value
+ * @param   pu64        Where to store the value. Set to default on failure.
+ * @param   u64Def      The default value.
+ */
+DECLINLINE(int) VDCFGQueryU64Def(PVDINTERFACECONFIG pCfgIf,
+                                 const char *pszName, uint64_t *pu64,
+                                 uint64_t u64Def)
+{
+    char aszBuf[32];
+    int rc = pCfgIf->pfnQuery(pCfgIf->Core.pvUser, pszName, aszBuf, sizeof(aszBuf));
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTStrToUInt64Full(aszBuf, 0, pu64);
+    }
+    else if (rc == VERR_CFGM_VALUE_NOT_FOUND)
+    {
+        rc = VINF_SUCCESS;
+        *pu64 = u64Def;
+    }
+    return rc;
+}
+
+/**
+ * Query configuration, unsigned 64-bit integer value.
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszName     Name of an integer value
+ * @param   pu64        Where to store the value.
+ */
+DECLINLINE(int) VDCFGQueryU64(PVDINTERFACECONFIG pCfgIf, const char *pszName,
+                              uint64_t *pu64)
+{
+    char aszBuf[32];
+    int rc = pCfgIf->pfnQuery(pCfgIf->Core.pvUser, pszName, aszBuf, sizeof(aszBuf));
+    if (RT_SUCCESS(rc))
+    {
+        rc = RTStrToUInt64Full(aszBuf, 0, pu64);
+    }
+
+    return rc;
+}
+
+/**
+ * Query configuration, unsigned 32-bit integer value with default.
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszName     Name of an integer value
+ * @param   pu32        Where to store the value. Set to default on failure.
+ * @param   u32Def      The default value.
+ */
+DECLINLINE(int) VDCFGQueryU32Def(PVDINTERFACECONFIG pCfgIf,
+                                 const char *pszName, uint32_t *pu32,
+                                 uint32_t u32Def)
+{
+    uint64_t u64;
+    int rc = VDCFGQueryU64Def(pCfgIf, pszName, &u64, u32Def);
+    if (RT_SUCCESS(rc))
+    {
+        if (!(u64 & UINT64_C(0xffffffff00000000)))
+            *pu32 = (uint32_t)u64;
+        else
+            rc = VERR_CFGM_INTEGER_TOO_BIG;
+    }
+    return rc;
+}
+
+/**
+ * Query configuration, bool value with default.
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszName     Name of an integer value
+ * @param   pf          Where to store the value. Set to default on failure.
+ * @param   fDef        The default value.
+ */
+DECLINLINE(int) VDCFGQueryBoolDef(PVDINTERFACECONFIG pCfgIf,
+                                  const char *pszName, bool *pf,
+                                  bool fDef)
+{
+    uint64_t u64;
+    int rc = VDCFGQueryU64Def(pCfgIf, pszName, &u64, fDef);
+    if (RT_SUCCESS(rc))
+        *pf = u64 ? true : false;
+    return rc;
+}
+
+/**
+ * Query configuration, bool value.
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszName     Name of an integer value
+ * @param   pf          Where to store the value.
+ */
+DECLINLINE(int) VDCFGQueryBool(PVDINTERFACECONFIG pCfgIf, const char *pszName,
+                               bool *pf)
+{
+    uint64_t u64;
+    int rc = VDCFGQueryU64(pCfgIf, pszName, &u64);
+    if (RT_SUCCESS(rc))
+        *pf = u64 ? true : false;
+    return rc;
+}
+
+/**
+ * Query configuration, dynamically allocated (RTMemAlloc) zero terminated
+ * character value.
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszName     Name of an zero terminated character value
+ * @param   ppszString  Where to store the string pointer. Not set on failure.
+ *                      Free this using RTMemFree().
+ */
+DECLINLINE(int) VDCFGQueryStringAlloc(PVDINTERFACECONFIG pCfgIf,
+                                      const char *pszName, char **ppszString)
+{
+    size_t cb;
+    int rc = pCfgIf->pfnQuerySize(pCfgIf->Core.pvUser, pszName, &cb);
+    if (RT_SUCCESS(rc))
+    {
+        char *pszString = (char *)RTMemAlloc(cb);
+        if (pszString)
+        {
+            rc = pCfgIf->pfnQuery(pCfgIf->Core.pvUser, pszName, pszString, cb);
+            if (RT_SUCCESS(rc))
+                *ppszString = pszString;
+            else
+                RTMemFree(pszString);
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+    return rc;
+}
+
+/**
+ * Query configuration, dynamically allocated (RTMemAlloc) zero terminated
+ * character value with default.
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszName     Name of an zero terminated character value
+ * @param   ppszString  Where to store the string pointer. Not set on failure.
+ *                      Free this using RTMemFree().
+ * @param   pszDef      The default value.
+ */
+DECLINLINE(int) VDCFGQueryStringAllocDef(PVDINTERFACECONFIG pCfgIf,
+                                         const char *pszName,
+                                         char **ppszString,
+                                         const char *pszDef)
+{
+    size_t cb;
+    int rc = pCfgIf->pfnQuerySize(pCfgIf->Core.pvUser, pszName, &cb);
+    if (rc == VERR_CFGM_VALUE_NOT_FOUND || rc == VERR_CFGM_NO_PARENT)
+    {
+        cb = strlen(pszDef) + 1;
+        rc = VINF_SUCCESS;
+    }
+    if (RT_SUCCESS(rc))
+    {
+        char *pszString = (char *)RTMemAlloc(cb);
+        if (pszString)
+        {
+            rc = pCfgIf->pfnQuery(pCfgIf->Core.pvUser, pszName, pszString, cb);
+            if (rc == VERR_CFGM_VALUE_NOT_FOUND || rc == VERR_CFGM_NO_PARENT)
+            {
+                memcpy(pszString, pszDef, cb);
+                rc = VINF_SUCCESS;
+            }
+            if (RT_SUCCESS(rc))
+                *ppszString = pszString;
+            else
+                RTMemFree(pszString);
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+    return rc;
+}
+
+/**
+ * Query configuration, dynamically allocated (RTMemAlloc) byte string value.
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   pszName     Name of an zero terminated character value
+ * @param   ppvData     Where to store the byte string pointer. Not set on failure.
+ *                      Free this using RTMemFree().
+ * @param   pcbData     Where to store the byte string length.
+ */
+DECLINLINE(int) VDCFGQueryBytesAlloc(PVDINTERFACECONFIG pCfgIf,
+                                     const char *pszName, void **ppvData, size_t *pcbData)
+{
+    size_t cb;
+    int rc = pCfgIf->pfnQuerySize(pCfgIf->Core.pvUser, pszName, &cb);
+    if (RT_SUCCESS(rc))
+    {
+        char *pbData;
+        Assert(cb);
+
+        pbData = (char *)RTMemAlloc(cb);
+        if (pbData)
+        {
+            if(pCfgIf->pfnQueryBytes)
+                rc = pCfgIf->pfnQueryBytes(pCfgIf->Core.pvUser, pszName, pbData, cb);
+            else
+                rc = pCfgIf->pfnQuery(pCfgIf->Core.pvUser, pszName, pbData, cb);
+
+            if (RT_SUCCESS(rc))
+            {
+                *ppvData = pbData;
+                /* Exclude terminator if the byte data was obtained using the string query callback. */
+                *pcbData = cb;
+                if (!pCfgIf->pfnQueryBytes)
+                    (*pcbData)--;
+            }
+            else
+                RTMemFree(pbData);
+        }
+        else
+            rc = VERR_NO_MEMORY;
+    }
+    return rc;
+}
+
+/**
+ * Set property value to string (optionally create if non-existent).
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   fCreate     Create the property if it doesn't exist
+ * @param   pszName     Name of property
+ * @param   pszValue    String value to assign to property
+ */
+DECLINLINE(int) VDCFGUpdate(PVDINTERFACECONFIG pCfgIf, bool fCreate, const char *pszName, const char *pszValue)
+{
+    int rc = pCfgIf->pfnUpdate(pCfgIf->Core.pvUser, fCreate, pszName, pszValue);
+    return rc;
+}
+
+/**
+ * Set property value to Unsigned Int 64-bit (optionally create if non-existent).
+ *
+ * @return  VBox status code.
+ * @param   pCfgIf      Pointer to configuration callback table.
+ * @param   fCreate     Create the property if it doesn't exist
+ * @param   pszName     Name of property
+ * @param   u64Value    64-bit unsigned value to save with property.
+ */
+
+DECLINLINE(int) VDCFGUpdateU64(PVDINTERFACECONFIG pCfgIf, bool fCreate, const char *pszName, uint64_t u64Value)
+{
+     int rc = 0;
+     char pszValue[21];
+     (void) RTStrPrintf(pszValue, sizeof(pszValue), "%RU64", u64Value);
+     rc = VDCFGUpdate(pCfgIf, fCreate, pszName, pszValue);
+     return rc;
+}
+
+
+
+/** Forward declaration of a VD socket. */
+typedef struct VDSOCKETINT *VDSOCKET;
+/** Pointer to a VD socket. */
+typedef VDSOCKET *PVDSOCKET;
+/** Nil socket handle. */
+#define NIL_VDSOCKET ((VDSOCKET)0)
+
+/** Connect flag to indicate that the backend wants to use the extended
+ * socket I/O multiplexing call. This might not be supported on all configurations
+ * (internal networking and iSCSI)
+ * and the backend needs to take appropriate action.
+ */
+#define VD_INTERFACETCPNET_CONNECT_EXTENDED_SELECT RT_BIT_32(0)
+
+/** @name Select events
+ * @{ */
+/** Readable without blocking. */
+#define VD_INTERFACETCPNET_EVT_READ         RT_BIT_32(0)
+/** Writable without blocking. */
+#define VD_INTERFACETCPNET_EVT_WRITE        RT_BIT_32(1)
+/** Error condition, hangup, exception or similar. */
+#define VD_INTERFACETCPNET_EVT_ERROR        RT_BIT_32(2)
+/** Hint for the select that getting interrupted while waiting is more likely.
+ * The interface implementation can optimize the waiting strategy based on this.
+ * It is assumed that it is more likely to get one of the above socket events
+ * instead of being interrupted if the flag is not set. */
+#define VD_INTERFACETCPNET_HINT_INTERRUPT   RT_BIT_32(3)
+/** Mask of the valid bits. */
+#define VD_INTERFACETCPNET_EVT_VALID_MASK   UINT32_C(0x0000000f)
+/** @} */
+
+/**
+ * TCP network stack interface
+ *
+ * Per-image. Mandatory for backends which have the VD_CAP_TCPNET bit set.
+ */
+typedef struct VDINTERFACETCPNET
+{
+    /**
+     * Common interface header.
+     */
+    VDINTERFACE    Core;
+
+    /**
+     * Creates a socket. The socket is not connected if this succeeds.
+     *
+     * @return  iprt status code.
+     * @retval  VERR_NOT_SUPPORTED if the combination of flags is not supported.
+     * @param   fFlags    Combination of the VD_INTERFACETCPNET_CONNECT_* \#defines.
+     * @param   phVdSock  Where to store the handle.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnSocketCreate, (uint32_t fFlags, PVDSOCKET phVdSock));
+
+    /**
+     * Destroys the socket.
+     *
+     * @return iprt status code.
+     * @param  hVdSock    Socket handle (/ pointer).
+     */
+    DECLR3CALLBACKMEMBER(int, pfnSocketDestroy, (VDSOCKET hVdSock));
+
+    /**
+     * Connect as a client to a TCP port.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock         Socket handle (/ pointer)..
+     * @param   pszAddress      The address to connect to.
+     * @param   uPort           The port to connect to.
+     * @param   cMillies        Number of milliseconds to wait for the connect attempt to complete.
+     *                          Use RT_INDEFINITE_WAIT to wait for ever.
+     *                          Use RT_SOCKETCONNECT_DEFAULT_WAIT to wait for the default time
+     *                          configured on the running system.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnClientConnect, (VDSOCKET hVdSock, const char *pszAddress, uint32_t uPort,
+                                                 RTMSINTERVAL cMillies));
+
+    /**
+     * Close a TCP connection.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock         Socket handle (/ pointer).
+     */
+    DECLR3CALLBACKMEMBER(int, pfnClientClose, (VDSOCKET hVdSock));
+
+    /**
+     * Returns whether the socket is currently connected to the client.
+     *
+     * @returns true if the socket is connected.
+     *          false otherwise.
+     * @param   hVdSock     Socket handle (/ pointer).
+     */
+    DECLR3CALLBACKMEMBER(bool, pfnIsClientConnected, (VDSOCKET hVdSock));
+
+    /**
+     * Socket I/O multiplexing.
+     * Checks if the socket is ready for reading.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   cMillies    Number of milliseconds to wait for the socket.
+     *                      Use RT_INDEFINITE_WAIT to wait for ever.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnSelectOne, (VDSOCKET hVdSock, RTMSINTERVAL cMillies));
+
+    /**
+     * Receive data from a socket.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   pvBuffer    Where to put the data we read.
+     * @param   cbBuffer    Read buffer size.
+     * @param   pcbRead     Number of bytes read.
+     *                      If NULL the entire buffer will be filled upon successful return.
+     *                      If not NULL a partial read can be done successfully.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnRead, (VDSOCKET hVdSock, void *pvBuffer, size_t cbBuffer, size_t *pcbRead));
+
+    /**
+     * Send data to a socket.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   pvBuffer    Buffer to write data to socket.
+     * @param   cbBuffer    How much to write.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnWrite, (VDSOCKET hVdSock, const void *pvBuffer, size_t cbBuffer));
+
+    /**
+     * Send data from scatter/gather buffer to a socket.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   pSgBuf      Scatter/gather buffer to write data to socket.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnSgWrite, (VDSOCKET hVdSock, PCRTSGBUF pSgBuf));
+
+    /**
+     * Receive data from a socket - not blocking.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   pvBuffer    Where to put the data we read.
+     * @param   cbBuffer    Read buffer size.
+     * @param   pcbRead     Number of bytes read.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnReadNB, (VDSOCKET hVdSock, void *pvBuffer, size_t cbBuffer, size_t *pcbRead));
+
+    /**
+     * Send data to a socket - not blocking.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   pvBuffer    Buffer to write data to socket.
+     * @param   cbBuffer    How much to write.
+     * @param   pcbWritten  Number of bytes written.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnWriteNB, (VDSOCKET hVdSock, const void *pvBuffer, size_t cbBuffer, size_t *pcbWritten));
+
+    /**
+     * Send data from scatter/gather buffer to a socket - not blocking.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   pSgBuf      Scatter/gather buffer to write data to socket.
+     * @param   pcbWritten  Number of bytes written.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnSgWriteNB, (VDSOCKET hVdSock, PRTSGBUF pSgBuf, size_t *pcbWritten));
+
+    /**
+     * Flush socket write buffers.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     */
+    DECLR3CALLBACKMEMBER(int, pfnFlush, (VDSOCKET hVdSock));
+
+    /**
+     * Enables or disables delaying sends to coalesce packets.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   fEnable     When set to true enables coalescing.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnSetSendCoalescing, (VDSOCKET hVdSock, bool fEnable));
+
+    /**
+     * Gets the address of the local side.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   pAddr       Where to store the local address on success.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnGetLocalAddress, (VDSOCKET hVdSock, PRTNETADDR pAddr));
+
+    /**
+     * Gets the address of the other party.
+     *
+     * @return  iprt status code.
+     * @param   hVdSock     Socket handle (/ pointer).
+     * @param   pAddr       Where to store the peer address on success.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnGetPeerAddress, (VDSOCKET hVdSock, PRTNETADDR pAddr));
+
+    /**
+     * Socket I/O multiplexing - extended version which can be woken up.
+     * Checks if the socket is ready for reading or writing.
+     *
+     * @return  iprt status code.
+     * @retval  VERR_INTERRUPTED if the thread was woken up by a pfnPoke call.
+     * @param   hVdSock     VD Socket handle(/pointer).
+     * @param   fEvents     Mask of events to wait for.
+     * @param   pfEvents    Where to store the received events.
+     * @param   cMillies    Number of milliseconds to wait for the socket.
+     *                      Use RT_INDEFINITE_WAIT to wait for ever.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnSelectOneEx, (VDSOCKET hVdSock, uint32_t fEvents,
+                                               uint32_t *pfEvents, RTMSINTERVAL cMillies));
+
+    /**
+     * Wakes up the thread waiting in pfnSelectOneEx.
+     *
+     * @return iprt status code.
+     * @param  hVdSock      VD Socket handle(/pointer).
+     */
+    DECLR3CALLBACKMEMBER(int, pfnPoke, (VDSOCKET hVdSock));
+
+} VDINTERFACETCPNET, *PVDINTERFACETCPNET;
+
+/**
+ * Get TCP network stack interface from interface list.
+ *
+ * @return Pointer to the first TCP network stack interface in the list.
+ * @param  pVDIfs    Pointer to the interface list.
+ */
+DECLINLINE(PVDINTERFACETCPNET) VDIfTcpNetGet(PVDINTERFACE pVDIfs)
+{
+    PVDINTERFACE pIf = VDInterfaceGet(pVDIfs, VDINTERFACETYPE_TCPNET);
+
+    /* Check that the interface descriptor is a progress interface. */
+    AssertMsgReturn(   !pIf
+                    || (   (pIf->enmInterface == VDINTERFACETYPE_TCPNET)
+                        && (pIf->cbSize == sizeof(VDINTERFACETCPNET))),
+                    ("Not a TCP net interface"), NULL);
+
+    return (PVDINTERFACETCPNET)pIf;
+}
+
+
+/**
+ * Interface to synchronize concurrent accesses by several threads.
+ *
+ * @note The scope of this interface is to manage concurrent accesses after
+ * the HDD container has been created, and they must stop before destroying the
+ * container. Opening or closing images is covered by the synchronization, but
+ * that does not mean it is safe to close images while a thread executes
+ * #VDMerge or #VDCopy operating on these images. Making them safe would require
+ * the lock to be held during the entire operation, which prevents other
+ * concurrent acitivities.
+ *
+ * @note Right now this is kept as simple as possible, and does not even
+ * attempt to provide enough information to allow e.g. concurrent write
+ * accesses to different areas of the disk. The reason is that it is very
+ * difficult to predict which area of a disk is affected by a write,
+ * especially when different image formats are mixed. Maybe later a more
+ * sophisticated interface will be provided which has the necessary information
+ * about worst case affected areas.
+ *
+ * Per-disk interface. Optional, needed if the disk is accessed concurrently
+ * by several threads, e.g. when merging diff images while a VM is running.
+ */
+typedef struct VDINTERFACETHREADSYNC
+{
+    /**
+     * Common interface header.
+     */
+    VDINTERFACE    Core;
+
+    /**
+     * Start a read operation.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnStartRead, (void *pvUser));
+
+    /**
+     * Finish a read operation.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnFinishRead, (void *pvUser));
+
+    /**
+     * Start a write operation.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnStartWrite, (void *pvUser));
+
+    /**
+     * Finish a write operation.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnFinishWrite, (void *pvUser));
+
+} VDINTERFACETHREADSYNC, *PVDINTERFACETHREADSYNC;
+
+/**
+ * Get thread synchronization interface from interface list.
+ *
+ * @return Pointer to the first thread synchronization interface in the list.
+ * @param  pVDIfs    Pointer to the interface list.
+ */
+DECLINLINE(PVDINTERFACETHREADSYNC) VDIfThreadSyncGet(PVDINTERFACE pVDIfs)
+{
+    PVDINTERFACE pIf = VDInterfaceGet(pVDIfs, VDINTERFACETYPE_THREADSYNC);
+
+    /* Check that the interface descriptor is a progress interface. */
+    AssertMsgReturn(   !pIf
+                    || (   (pIf->enmInterface == VDINTERFACETYPE_THREADSYNC)
+                        && (pIf->cbSize == sizeof(VDINTERFACETHREADSYNC))),
+                    ("Not a thread synchronization interface"), NULL);
+
+    return (PVDINTERFACETHREADSYNC)pIf;
+}
+
+/**
+ * Interface to query usage of disk ranges.
+ *
+ * Per-operation interface. Optional.
+ */
+typedef struct VDINTERFACEQUERYRANGEUSE
+{
+    /**
+     * Common interface header.
+     */
+    VDINTERFACE    Core;
+
+    /**
+     * Query use of a disk range.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnQueryRangeUse, (void *pvUser, uint64_t off, uint64_t cb,
+                                                 bool *pfUsed));
+
+} VDINTERFACEQUERYRANGEUSE, *PVDINTERFACEQUERYRANGEUSE;
+
+/**
+ * Get query range use interface from interface list.
+ *
+ * @return Pointer to the first thread synchronization interface in the list.
+ * @param  pVDIfs    Pointer to the interface list.
+ */
+DECLINLINE(PVDINTERFACEQUERYRANGEUSE) VDIfQueryRangeUseGet(PVDINTERFACE pVDIfs)
+{
+    PVDINTERFACE pIf = VDInterfaceGet(pVDIfs, VDINTERFACETYPE_QUERYRANGEUSE);
+
+    /* Check that the interface descriptor is a progress interface. */
+    AssertMsgReturn(   !pIf
+                    || (   (pIf->enmInterface == VDINTERFACETYPE_QUERYRANGEUSE)
+                        && (pIf->cbSize == sizeof(VDINTERFACEQUERYRANGEUSE))),
+                    ("Not a query range use interface"), NULL);
+
+    return (PVDINTERFACEQUERYRANGEUSE)pIf;
+}
+
+DECLINLINE(int) vdIfQueryRangeUse(PVDINTERFACEQUERYRANGEUSE pIfQueryRangeUse, uint64_t off, uint64_t cb,
+                                  bool *pfUsed)
+{
+    return pIfQueryRangeUse->pfnQueryRangeUse(pIfQueryRangeUse->Core.pvUser, off, cb, pfUsed);
+}
+
+
+/**
+ * Interface used to retrieve keys for cryptographic operations.
+ *
+ * Per-module interface. Optional but cryptographic modules might fail and
+ * return an error if this is not present.
+ */
+typedef struct VDINTERFACECRYPTO
+{
+    /**
+     * Common interface header.
+     */
+    VDINTERFACE    Core;
+
+    /**
+     * Retains a key identified by the ID. The caller will only hold a reference
+     * to the key and must not modify the key buffer in any way.
+     *
+     * @returns VBox status code.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pszId           The alias/id for the key to retrieve.
+     * @param   ppbKey          Where to store the pointer to the key buffer on success.
+     * @param   pcbKey          Where to store the size of the key in bytes on success.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnKeyRetain, (void *pvUser, const char *pszId, const uint8_t **ppbKey, size_t *pcbKey));
+
+    /**
+     * Releases one reference of the key identified by the given identifier.
+     * The caller must not access the key buffer after calling this operation.
+     *
+     * @returns VBox status code.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pszId           The alias/id for the key to release.
+     *
+     * @note  It is advised to release the key whenever it is not used anymore so
+     *        the entity storing the key can do anything to make retrieving the key
+     *        from memory more difficult like scrambling the memory buffer for
+     *        instance.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnKeyRelease, (void *pvUser, const char *pszId));
+
+    /**
+     * Gets a reference to the password identified by the given ID to open a key store supplied through the config interface.
+     *
+     * @returns VBox status code.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pszId           The alias/id for the password to retain.
+     * @param   ppszPassword    Where to store the password to unlock the key store on success.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnKeyStorePasswordRetain, (void *pvUser, const char *pszId, const char **ppszPassword));
+
+    /**
+     * Releases a reference of the password previously acquired with VDINTERFACECRYPTO::pfnKeyStorePasswordRetain()
+     * identified by the given ID.
+     *
+     * @returns VBox status code.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pszId           The alias/id for the password to release.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnKeyStorePasswordRelease, (void *pvUser, const char *pszId));
+
+    /**
+     * Saves a key store.
+     *
+     * @returns VBox status code.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pvKeyStore      The key store to save.
+     * @param   cbKeyStore      Size of the key store in bytes.
+     *
+     * @note The format is filter specific and should be treated as binary data.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnKeyStoreSave, (void *pvUser, const void *pvKeyStore, size_t cbKeyStore));
+
+    /**
+     * Returns the parameters after the key store was loaded successfully.
+     *
+     * @returns VBox status code.
+     * @param   pvUser          The opaque user data associated with this interface.
+     * @param   pszCipher       The cipher identifier the DEK is used for.
+     * @param   pbDek           The raw DEK which was contained in the key store loaded by
+     *                          VDINTERFACECRYPTO::pfnKeyStoreLoad().
+     * @param   cbDek           The size of the DEK.
+     *
+     * @note The provided pointer to the DEK is only valid until this call returns.
+     *       The content might change afterwards with out notice (when scrambling the key
+     *       for further protection for example) or might be even freed.
+     *
+     * @note This method is optional and can be NULL if the caller does not require the
+     *       parameters.
+     */
+    DECLR3CALLBACKMEMBER(int, pfnKeyStoreReturnParameters, (void *pvUser, const char *pszCipher,
+                                                            const uint8_t *pbDek, size_t cbDek));
+
+} VDINTERFACECRYPTO, *PVDINTERFACECRYPTO;
+
+
+/**
+ * Get error interface from interface list.
+ *
+ * @return Pointer to the first error interface in the list.
+ * @param  pVDIfs    Pointer to the interface list.
+ */
+DECLINLINE(PVDINTERFACECRYPTO) VDIfCryptoGet(PVDINTERFACE pVDIfs)
+{
+    PVDINTERFACE pIf = VDInterfaceGet(pVDIfs, VDINTERFACETYPE_CRYPTO);
+
+    /* Check that the interface descriptor is a crypto interface. */
+    AssertMsgReturn(   !pIf
+                    || (   (pIf->enmInterface == VDINTERFACETYPE_CRYPTO)
+                        && (pIf->cbSize == sizeof(VDINTERFACECRYPTO))),
+                    ("Not an crypto interface\n"), NULL);
+
+    return (PVDINTERFACECRYPTO)pIf;
+}
+
+/**
+ * Retains a key identified by the ID. The caller will only hold a reference
+ * to the key and must not modify the key buffer in any way.
+ *
+ * @returns VBox status code.
+ * @param   pIfCrypto       Pointer to the crypto interface.
+ * @param   pszId           The alias/id for the key to retrieve.
+ * @param   ppbKey          Where to store the pointer to the key buffer on success.
+ * @param   pcbKey          Where to store the size of the key in bytes on success.
+ */
+DECLINLINE(int) vdIfCryptoKeyRetain(PVDINTERFACECRYPTO pIfCrypto, const char *pszId, const uint8_t **ppbKey, size_t *pcbKey)
+{
+    return pIfCrypto->pfnKeyRetain(pIfCrypto->Core.pvUser, pszId, ppbKey, pcbKey);
+}
+
+/**
+ * Releases one reference of the key identified by the given identifier.
+ * The caller must not access the key buffer after calling this operation.
+ *
+ * @returns VBox status code.
+ * @param   pIfCrypto       Pointer to the crypto interface.
+ * @param   pszId           The alias/id for the key to release.
+ *
+ * @note  It is advised to release the key whenever it is not used anymore so
+ *        the entity storing the key can do anything to make retrieving the key
+ *        from memory more difficult like scrambling the memory buffer for
+ *        instance.
+ */
+DECLINLINE(int) vdIfCryptoKeyRelease(PVDINTERFACECRYPTO pIfCrypto, const char *pszId)
+{
+    return pIfCrypto->pfnKeyRelease(pIfCrypto->Core.pvUser, pszId);
+}
+
+/**
+ * Gets a reference to the password identified by the given ID to open a key store supplied through the config interface.
+ *
+ * @returns VBox status code.
+ * @param   pIfCrypto       Pointer to the crypto interface.
+ * @param   pszId           The alias/id for the password to retain.
+ * @param   ppszPassword    Where to store the password to unlock the key store on success.
+ */
+DECLINLINE(int) vdIfCryptoKeyStorePasswordRetain(PVDINTERFACECRYPTO pIfCrypto, const char *pszId, const char **ppszPassword)
+{
+    return pIfCrypto->pfnKeyStorePasswordRetain(pIfCrypto->Core.pvUser, pszId, ppszPassword);
+}
+
+/**
+ * Releases a reference of the password previously acquired with VDINTERFACECRYPTO::pfnKeyStorePasswordRetain()
+ * identified by the given ID.
+ *
+ * @returns VBox status code.
+ * @param   pIfCrypto       Pointer to the crypto interface.
+ * @param   pszId           The alias/id for the password to release.
+ */
+DECLINLINE(int) vdIfCryptoKeyStorePasswordRelease(PVDINTERFACECRYPTO pIfCrypto, const char *pszId)
+{
+    return pIfCrypto->pfnKeyStorePasswordRelease(pIfCrypto->Core.pvUser, pszId);
+}
+
+/**
+ * Saves a key store.
+ *
+ * @returns VBox status code.
+ * @param   pIfCrypto       Pointer to the crypto interface.
+ * @param   pvKeyStore      The key store to save.
+ * @param   cbKeyStore      Size of the key store in bytes.
+ *
+ * @note The format is filter specific and should be treated as binary data.
+ */
+DECLINLINE(int) vdIfCryptoKeyStoreSave(PVDINTERFACECRYPTO pIfCrypto, const void *pvKeyStore, size_t cbKeyStore)
+{
+    return pIfCrypto->pfnKeyStoreSave(pIfCrypto->Core.pvUser, pvKeyStore, cbKeyStore);
+}
+
+/**
+ * Returns the parameters after the key store was loaded successfully.
+ *
+ * @returns VBox status code.
+ * @param   pIfCrypto       Pointer to the crypto interface.
+ * @param   pszCipher       The cipher identifier the DEK is used for.
+ * @param   pbDek           The raw DEK which was contained in the key store loaded by
+ *                          VDINTERFACECRYPTO::pfnKeyStoreLoad().
+ * @param   cbDek           The size of the DEK.
+ *
+ * @note The provided pointer to the DEK is only valid until this call returns.
+ *       The content might change afterwards with out notice (when scrambling the key
+ *       for further protection for example) or might be even freed.
+ *
+ * @note This method is optional and can be NULL if the caller does not require the
+ *       parameters.
+ */
+DECLINLINE(int) vdIfCryptoKeyStoreReturnParameters(PVDINTERFACECRYPTO pIfCrypto, const char *pszCipher,
+                                                   const uint8_t *pbDek, size_t cbDek)
+{
+    if (pIfCrypto->pfnKeyStoreReturnParameters)
+        return pIfCrypto->pfnKeyStoreReturnParameters(pIfCrypto->Core.pvUser, pszCipher, pbDek, cbDek);
+
+    return VINF_SUCCESS;
+}
+
+
+RT_C_DECLS_END
+
+/** @} */
+
+#endif /* !VBOX_INCLUDED_vd_ifs_h */