2.2.30 SMB2 CANCEL Request
The SMB2 CANCEL Request packet is sent by the client to cancel a previously sent message on the same SMB2 transport connection. The MessageId of the request to be canceled MUST be set in the SMB2 header of the request. This request is composed of an SMB2 header, as specified in section 2.2.1, followed by this request structure:
StructureSize (2 bytes): The client MUST set this field to 4, indicating the size of the request structure, not including the header.
Reserved (2 bytes): This field MUST NOT be used and MUST be reserved. The client MUST set this field to 0, and the server MUST ignore it on receipt.