It's confirmed. Microsoft inadvertently left out IOCTL_REDIR_QUERY_PATH from the Windows XP IFS Kit.

This IOCTL is needed by redirectors that support the Universal Naming Convention (you know - resolving names with a leading double backslash.) The definition has not changed from the Windows 2000 IFS Kit, so it can be used by simply using the older definition. Word is that Microsoft will fix this in the .NET version of the IFS Kit.

For your reference, the old definition is:

#define IOCTL_REDIR_QUERY_PATH CTL_CODE(FILE_DEVICE_NETWORK_FILE_SYSTEM,
99, METHOD_NEITHER, FILE_ANY_ACCESS)

The two data structures that go along with this IOCTL are:

typedef struct _QUERY_PATH_REQUEST { ULONG PathNameLength; PIO_SECURITY_CONTEXT SecurityContext; WCHAR FilePathName[1];
} QUERY_PATH_REQUEST, *PQUERY_PATH_REQUEST;

typedef struct _QUERY_PATH_RESPONSE { ULONG LengthAccepted;
} QUERY_PATH_RESPONSE, *PQUERY_PATH_RESPONSE;