2.2.4.46.1 Request

The SMB_COM_TRANSACTION2 request format is similar to that of the SMB_COM_TRANSACTION request except for the Name field. The differences are in the subcommands supported, and in the purposes and usages of some of the fields.

 SMB_Parameters
   {
   UCHAR  WordCount;
   Words
     {
     USHORT TotalParameterCount;
     USHORT TotalDataCount;
     USHORT MaxParameterCount;
     USHORT MaxDataCount;
     UCHAR  MaxSetupCount;
     UCHAR  Reserved1;
     USHORT Flags;
     ULONG  Timeout;
     USHORT Reserved2;
     USHORT ParameterCount;
     USHORT ParameterOffset;
     USHORT DataCount;
     USHORT DataOffset;
     UCHAR  SetupCount;
     UCHAR  Reserved3;
     USHORT Setup[SetupCount];
     }
   } 
 SMB_Data
   {
   USHORT ByteCount;
   Bytes
     {
     UCHAR Name;
     UCHAR Pad1[];
     UCHAR Trans2_Parameters[ParameterCount];
     UCHAR Pad2[];
     UCHAR Trans2_Data[DataCount];
     }
   }
  

SMB_Header:

The Command for the initial request and for all responses MUST be SMB_COM_TRANSACTION2 (0x32). The Command for secondary request messages that are part of the same transaction MUST be SMB_COM_TRANSACTION2_SECONDARY (0x33). The PID, MID, TID, and UID MUST be the same for all requests and responses that are part of the same transaction.

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SMB_Parameters (variable)
...

SMB_Parameters (variable):

The SMB_Parameters section of the SMB_COM_TRANSACTION2 request contains the information used to manage the transaction itself. It also contains flags and setup information that provide context for the execution of the operation on the server side.

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WordCount								Words (variable)
...
SMB_Data (variable)
...

WordCount (1 byte): The value of Words.SetupCount plus 14 (0x0E). This value represents the total number of SMB parameter words and MUST be greater than or equal to 14 (0x0E).

Words (variable):

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TotalParameterCount																TotalDataCount
MaxParameterCount																MaxDataCount
MaxSetupCount								Reserved1								Flags
Timeout
Reserved2																ParameterCount
ParameterOffset																DataCount
DataOffset																SetupCount								Reserved3
Setup (variable)
...

TotalParameterCount (2 bytes): The total number of SMB_COM_TRANSACTION2 parameter bytes to be sent in this transaction request. This value MAY be reduced in any or all subsequent SMB_COM_TRANSACTION2_SECONDARY requests that are part of the same transaction. This value represents transaction parameter bytes, not SMB parameter words. Transaction parameter bytes are carried in the SMB_Data block of the SMB_COM_TRANSACTION2 request.

TotalDataCount (2 bytes): The total number of SMB_COM_TRANSACTION2 data bytes to be sent in this transaction request. This value MAY be reduced in any or all subsequent SMB_COM_TRANSACTION2_SECONDARY requests that are part of the same transaction. This value represents transaction data bytes, not SMB data bytes.

MaxParameterCount (2 bytes): The maximum number of parameter bytes that the client will accept in the transaction reply. The server MUST NOT return more than this number of parameter bytes.

MaxDataCount (2 bytes): The maximum number of data bytes that the client will accept in the transaction reply. The server MUST NOT return more than this number of data bytes.

MaxSetupCount (1 byte): The maximum number of setup bytes that the client will accept in the transaction reply. The server MUST NOT return more than this number of setup bytes.

Reserved1 (1 byte): A padding byte. This field MUST be zero. Existing CIFS implementations MAY combine this field with MaxSetupCount to form a USHORT. If MaxSetupCount is defined as a USHORT, the high order byte MUST be 0x00.

Flags (2 bytes): A set of bit flags that alter the behavior of the requested operation. Unused bit fields MUST be set to zero by the client sending the request, and MUST be ignored by the server receiving the request. The client MAY set either or both of the following bit flags:

Name and bitmask	Meaning
DISCONNECT_TID 0x0001	If set, following the completion of the operation the server MUST disconnect the tree connect associated with the tree identifier (TID) field received in the SMB Header (section 2.2.3.1) of this request. The client SHOULD NOT send a subsequent SMB_COM_TREE_DISCONNECT for this tree connect.
NO_RESPONSE 0x0002	This is a one-way transaction. The server MUST attempt to complete the transaction, but SHOULD NOT send a response to the client.<65>

Timeout (4 bytes): The number of milliseconds that the server waits for completion of the transaction before generating a time-out. A value of 0x00000000 indicates that the operation is not blocked.<66>

Reserved2 (2 bytes): Reserved. This field MUST be 0x0000 in the client request. The server MUST ignore the contents of this field.

ParameterCount (2 bytes): The number of transaction parameter bytes being sent in this SMB message. If the transaction fits within a single SMB_COM_TRANSACTION2 request, then this value MUST be equal to TotalParameterCount. Otherwise, the sum of the ParameterCount values in the primary and secondary transaction request messages MUST be equal to the smallest TotalParameterCount value reported to the server. If the value of this field is less than the value of TotalParameterCount, then at least one SMB_COM_TRANSACTION2_SECONDARY message MUST be used to transfer the remaining parameter bytes. The ParameterCount field MUST be used to determine the number of transaction parameter bytes contained within the SMB_COM_TRANSACTION2 message.

ParameterOffset (2 bytes): The offset, in bytes, from the start of the SMB_Header to the transaction parameter bytes. This MUST be the number of bytes from the start of the SMB message to the start of the SMB_Data.Bytes.Parameters field. Server implementations MUST use this value to locate the transaction parameter block within the SMB message. If ParameterCount is zero, the client/server MAY set this field to zero.<67>

DataCount (2 bytes): The number of transaction data bytes being sent in this SMB message. If the transaction fits within a single SMB_COM_TRANSACTION2 request, then this value MUST be equal to TotalDataCount. Otherwise, the sum of the DataCount values in the primary and secondary transaction request messages MUST be equal to the smallest TotalDataCount value reported to the server. If the value of this field is less than the value of TotalDataCount, then at least one SMB_COM_TRANSACTION2_SECONDARY message MUST be used to transfer the remaining data bytes.

DataOffset (2 bytes): The offset, in bytes, from the start of the SMB Header (section 2.2.3.1) to the transaction data bytes. This MUST be the number of bytes from the start of the SMB message to the start of the SMB_Data.Bytes.Data field. Server implementations MUST use this value to locate the transaction data block within the SMB message. If DataCount is zero, the client/server MAY set this field to zero.<68>

SetupCount (1 byte): The number of setup words that are included in the transaction request.

Reserved3 (1 byte): A padding byte. This field MUST be 0x00. Existing CIFS implementations MAY combine this field with SetupCount to form a USHORT. If SetupCount is defined as a USHORT, the high order byte MUST be0x00.

Setup (variable): An array of two-byte words that provide transaction context to the server. The size and content of the array are specific to individual subcommands.SMB_COM_TRANSACTION2 messages MAY exceed the maximum size of a single SMB message (as determined by the value of the MaxBufferSize session parameter). If this is the case, then the client MUST use one or more SMB_COM_TRANSACTION2_SECONDARY messages to transfer transaction Data and Parameter bytes that did not fit in the initial message.

SMB_Data (variable):

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ByteCount																Bytes (variable)
...

ByteCount (2 bytes): The number of bytes in the SMB_Data.Bytes array.

Bytes (variable): The Name field MUST be the first field in this section. The locations and sizes of all other fields, including the padding, are determined by the values of ParameterOffset, ParameterCount, DataOffset, and DataCount. The server SHOULD be able to read the Parameters and Data regardless of their locations within the SMB_Data section of the message.

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Name								Pad1 (variable)
...
Trans2_Parameters (variable)
...
Pad2 (variable)
...
Trans2_Data (variable)
...

Name (1 byte): This field is not used in SMB_COM_TRANSACTION2 requests. This field MUST be set to zero, and the server MUST ignore it on receipt.

Pad1 (variable): This field MUST be used as an array of padding bytes to align the following field to a 4-byte boundary relative to the start of the SMB Header (section 2.2.3.1). This constraint can cause this field to be a zero-length field. This field SHOULD be set to zero by the client/server and MUST be ignored by the server/client.

Trans2_Parameters (variable): Transaction parameter bytes. See the individual SMB_COM_TRANSACTION2 subcommand descriptions for information on parameters sent for each subcommand.

Pad2 (variable): This field MUST be used as an array of padding bytes to align the following field to a 4-byte boundary relative to the start of the SMB Header. This constraint can cause this field to be a zero-length field. This field SHOULD be set to zero by the client/server and MUST be ignored by the server/client.

Trans2_Data (variable): Transaction data bytes. See the individual SMB_COM_TRANSACTION2 subcommand descriptions for information on data sent for each subcommand.