Drive Redirection (RDPDR)

API reference for the FreeRDP drive/file-system redirection channel (RDPDR), covering RdpdrServerContext, drive APIs, client-side device registration, and mounting options.

Drive redirection uses the [MS-RDPEFS] Device Redirection Virtual Channel Extension (rdpdr SVC). It exposes client-side file systems to the RDP server as virtual drives, and enables the server to perform file operations on them.

SVC channel name: rdpdr

Server header: <freerdp/server/rdpdr.h>
Client header: <freerdp/client/rdpdr.h>
Protocol types: <freerdp/channels/rdpdr.h>

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Client-Side: Mounting Drives

Drives are exposed to the server from the client command line or via the client RdpdrClientContext API.

Command-line options

# Redirect all drives (auto-mount)
xfreerdp /drives /v:server

# Redirect a specific path with a custom name
xfreerdp /drive:docs,/home/user/Documents /v:server

# Redirect the user's home directory
xfreerdp /home-drive /v:server

RdpdrClientContext (since version 3.16.0)

typedef struct s_rdpdr_client_context RdpdrClientContext

Obtained via the channel manager after the rdpdr channel loads.

RdpdrRegisterDevice · pcRdpdrRegisterDevice

typedef UINT (*pcRdpdrRegisterDevice)(RdpdrClientContext* context,
                                     const RDPDR_DEVICE* device,
                                     uint32_t* pid);

Registers a new device and announces it to the remote server. The RDPDR_DEVICE struct is copied internally. On success *pid receives a unique identifier for later use with RdpdrUnregisterDevice.

RdpdrUnregisterDevice · pcRdpdrUnregisterDevice

typedef UINT (*pcRdpdrUnregisterDevice)(RdpdrClientContext* context,
                                       size_t count, const uint32_t ids[]);

Removes one or more previously registered devices by their IDs and notifies the server.

RdpdrHotplugDevice · pcRdpdrHotplugDevice

typedef UINT (*pcRdpdrHotplugDevice)(RdpdrClientContext* context,
                                    RdpdrHotplugEventType type);

Triggers a hotplug scan. type is RDPDR_HOTPLUG_FIRST_CHECK on startup or RDPDR_HOTPLUG_CHECK_FOR_CHANGES on subsequent checks. Newly discovered devices are announced automatically.

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Server-Side: RdpdrServerContext

Lifecycle

RdpdrServerContext* rdpdr_server_context_new(HANDLE vcm);
void                rdpdr_server_context_free(RdpdrServerContext* context);

Key fields

data · void*

Server-defined private context pointer.

supported · UINT16

Bitmask of supported redirection types. Initially set to indicate what the server supports; updated after client capability exchange to reflect mutual support. Use RDPDR_DTYP_* flags:

Flag	Meaning
RDPDR_DTYP_SERIAL	Serial port
RDPDR_DTYP_PARALLEL	Parallel port
RDPDR_DTYP_PRINT	Printer
RDPDR_DTYP_FILESYSTEM	Drive / filesystem
RDPDR_DTYP_SMARTCARD	Smartcard

Channel control

Start · psRdpdrStart

typedef UINT (*psRdpdrStart)(RdpdrServerContext* context);

Starts the RDPDR channel worker. Must be called after setting callbacks and supported.

Stop · psRdpdrStop

Stops the worker and drains any pending messages.

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Intercept callbacks

ReceiveDeviceAnnounce · psRdpdrReceiveDeviceAnnounce

typedef UINT (*psRdpdrReceiveDeviceAnnounce)(RdpdrServerContext* context,
                                            const RdpdrDevice* device);

Called when the client announces a new device (before it is added to the internal device list). Inspect device->DeviceType to filter.

ReceiveDeviceRemove · psRdpdrReceiveDeviceRemove

typedef UINT (*psRdpdrReceiveDeviceRemove)(RdpdrServerContext* context,
                                          UINT32 deviceId,
                                          const RdpdrDevice* device);

Called when a device is being removed.

OnDriveCreate · psRdpdrOnDeviceCreate

typedef UINT (*psRdpdrOnDeviceCreate)(RdpdrServerContext* context,
                                     const RdpdrDevice* device);

Called for RDPDR_DTYP_FILESYSTEM devices after ReceiveDeviceAnnounce. Use to record the deviceId for subsequent drive operations.

OnDriveDelete · psRdpdrOnDeviceDelete

typedef UINT (*psRdpdrOnDeviceDelete)(RdpdrServerContext* context, UINT32 deviceId);

Called when a filesystem device is removed.

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Drive file operations

The server can perform file operations on redirected drives. Each function takes a callbackData pointer that is echoed back in the completion callback.

DriveOpenFile · psRdpdrDriveOpenFile

typedef UINT (*psRdpdrDriveOpenFile)(RdpdrServerContext* context,
                                    void* callbackData,
                                    UINT32 deviceId, const char* path,
                                    UINT32 desiredAccess,
                                    UINT32 createDisposition);

desiredAccess and createDisposition use Win32 semantics (GENERIC_READ, OPEN_EXISTING, etc.).

DriveReadFile · psRdpdrDriveReadFile

typedef UINT (*psRdpdrDriveReadFile)(RdpdrServerContext* context,
                                    void* callbackData,
                                    UINT32 deviceId, UINT32 fileId,
                                    UINT32 length, UINT32 offset);

Reads length bytes at offset from an open file. Result delivered via OnDriveReadFileComplete.

DriveWriteFile · psRdpdrDriveWriteFile

typedef UINT (*psRdpdrDriveWriteFile)(RdpdrServerContext* context,
                                     void* callbackData,
                                     UINT32 deviceId, UINT32 fileId,
                                     const char* buffer, UINT32 length,
                                     UINT32 offset);

DriveCloseFile · psRdpdrDriveCloseFile

typedef UINT (*psRdpdrDriveCloseFile)(RdpdrServerContext* context,
                                     void* callbackData,
                                     UINT32 deviceId, UINT32 fileId);

DriveDeleteFile · psRdpdrDriveDeleteFile

typedef UINT (*psRdpdrDriveDeleteFile)(RdpdrServerContext* context,
                                      void* callbackData,
                                      UINT32 deviceId, const char* path);

DriveQueryDirectory · psRdpdrDriveQueryDirectory

typedef UINT (*psRdpdrDriveQueryDirectory)(RdpdrServerContext* context,
                                          void* callbackData,
                                          UINT32 deviceId, const char* path);

Enumerates directory entries. Results arrive via OnDriveQueryDirectoryComplete as FILE_DIRECTORY_INFORMATION structs.

DriveRenameFile · psRdpdrDriveRenameFile

typedef UINT (*psRdpdrDriveRenameFile)(RdpdrServerContext* context,
                                      void* callbackData,
                                      UINT32 deviceId,
                                      const char* oldPath,
                                      const char* newPath);

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Completion callbacks

All drive operations are asynchronous. Results arrive via corresponding OnDrive*Complete callbacks:

Operation	Completion callback	Extra result
DriveOpenFile	OnDriveOpenFileComplete	fileId
DriveReadFile	OnDriveReadFileComplete	buffer, length
DriveWriteFile	OnDriveWriteFileComplete	bytesWritten
DriveCloseFile	OnDriveCloseFileComplete	—
DriveDeleteFile	OnDriveDeleteFileComplete	—
DriveQueryDirectory	OnDriveQueryDirectoryComplete	FILE_DIRECTORY_INFORMATION*
DriveCreateDirectory	OnDriveCreateDirectoryComplete	—
DriveDeleteDirectory	OnDriveDeleteDirectoryComplete	—
DriveRenameFile	OnDriveRenameFileComplete	—

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How the Virtual Filesystem Works

1. Client device announcement

   On connection, the RDPDR client sends a PAKID_CORE_DEVICELIST_ANNOUNCE PDU listing each redirected drive. Each entry carries a DeviceType of RDPDR_DTYP_FILESYSTEM, a DeviceId, and a display name.

2. Server records devices

   OnDriveCreate is called for each filesystem device. Store the deviceId to address subsequent operations.

3. File I/O via IRP

   The server issues I/O Request Packets (IRPs) by calling DriveOpenFile, DriveReadFile, etc. Each IRP is forwarded to the client, which performs the actual file operation using its local OS.

4. Completion

   The client sends an IRP Response. The RDPDR layer parses it and calls the corresponding OnDrive*Complete callback with status and result data.

The drive client channel plugin (channels/drive/client/) implements the client-side IRP handling using POSIX file I/O on Linux/macOS and Win32 APIs on Windows.