222 lines
8.2 KiB
C
222 lines
8.2 KiB
C
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/*===
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Direct Network Protocl -- Frame format header file
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Evan Schrier 10/98
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*/
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/*
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Direct Network Protocol
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| MEDIA HEADER | Var Len DN Header | Client Data |
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There are two types of packets that may be exchanged between Direct Network
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endpoints:
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Data Packets (D Frame) User data transmission
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Control Packets (C Frame) Internal link-state packets with no user data
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*/
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/*
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COMMAND FIELD
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The command field is the first byte of all frames. The first BIT of the command frame is always
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the COMMAND FRAME vs DATA FRAME opcode. The seven high bits of the Command field are flags. We have
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a requirement that the command field of all protocol packets must never be all zeros. Therefore, when
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the opcode bit is zero (COMMAND FRAME) we must be sure that one flag bit is always set. The highest flag bit,
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the USER2 flag is not relevant to COMMAND frames so we will always set the most significant bit when the opcode
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bit is zero.
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The seven command field flag bits are defined as follows:
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RELIABLE - Data delivery of this frame is guarenteed
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SEQUENTIAL - Data in this frame must be delivered in the order it was sent, with respect to other SEQ frames
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POLL - Protocol requests an immediate acknowledgement to this frame
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NEW MESSAGE - This frame is the first or only frame in a message
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END MESSAGE - This frame is the last or only frame in a message
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USER1 - First flag controlled by the higher layer (direct play core)
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USER2 - Second flag controlled by core. These flags are specified in the send API and are delivered with the data
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DATA FRAMES
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Data frames are between 4 and 20 bytes in length. They should typically be only 4 bytes. Following the
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Command byte in all data frames in the Control byte. This byte contains a 3-bit retry counter and 5 additional
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flags. The Control byte flags are defined as follows:
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END OF STREAM - This frame is the last data frame the transmitting partner will send.
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SACK_MASK_ONE - The low 32-bit Selective Acknowledgment mask is present in this header
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SACK_MASK_TWO - The high 32-bit Selective Acknowledgment mask is present in this header
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SEND_MASK_ONE - The low 32-bit Cancel Send mask is present in this header
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SEND_MASK_TWO - The high 32-bit Cancel Send mask is present in this header
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After Control byte come two one byte values: Sequence number for this frame, and Next Receive sequence number
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expected by this partner. After these two bytes comes zero through four bitmasks as specified by the control flags.
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After the bitmasks, the rest of the frame is user data to be delivered to the direct play core.
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*/
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#ifndef _DNET_FRAMES_
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#define _DNET_FRAMES_
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/*
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Command FRAME Extended Opcodes
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A CFrame without an opcode is a vehicle for non-piggybacked acknowledgement
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information. The following sub-commands are defined at this time:
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SACK - Only Ack/Nack info present
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CONNECT - Initialize a reliable connection
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CONNECTED - Response to CONNECT request, or CONNECTED depending on which side of the handshake
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*/
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#define FRAME_EXOPCODE_CONNECT 1
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#define FRAME_EXOPCODE_CONNECTED 2
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#define FRAME_EXOPCODE_DISCONNECTED 4 // Used in DP8, but not anymore
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#define FRAME_EXOPCODE_SACK 6
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// These structures are used to decode network data and so need to be packed
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#pragma pack(push, 1)
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typedef UNALIGNED struct packetheader PacketHeader, *PPacketHeader;
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typedef UNALIGNED struct dataframe DFRAME, *PDFRAME;
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typedef UNALIGNED struct cframe CFRAME, *PCFRAME;
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typedef UNALIGNED struct sackframe8 SACKFRAME8, *PSACKFRAME8;
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typedef UNALIGNED struct sackframe_big8 SFBIG8, *PSFBIG8;
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typedef UNALIGNED struct dataframe_masks DFMASKS, *PDFMASKS;
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typedef UNALIGNED struct dataframe_big DFBIG, *PDFBIG;
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// Packet Header is common to all frame formats
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#define PACKET_COMMAND_DATA 0x01 // Frame contains user data
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#define PACKET_COMMAND_RELIABLE 0x02 // Frame should be delivered reliably
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#define PACKET_COMMAND_SEQUENTIAL 0x04 // Frame should be indicated sequentially
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#define PACKET_COMMAND_POLL 0x08 // Partner should acknowlege immediately
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#define PACKET_COMMAND_NEW_MSG 0x10 // Data frame is first in message
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#define PACKET_COMMAND_END_MSG 0x20 // Data frame is last in message
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#define PACKET_COMMAND_USER_1 0x40 // First user controlled flag
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#define PACKET_COMMAND_USER_2 0x80 // Second user controlled flag
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#define PACKET_COMMAND_CFRAME 0x80 // Set high-bit on command frames because first byte must never be zero
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#define PACKET_CONTROL_RETRY 0x01 // This flag designates this frame as a retry of a previously xmitted frame
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#define PACKET_CONTROL_CORRELATE 0x02 // Respond to this frame with a dedicated reply
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#define PACKET_CONTROL_RESPONSE 0x04 // THIS IS NOT CURRENTLY IMPLEMENTED - CORR RESPONSES WILL USE DEDICATED FRAMES
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#define PACKET_CONTROL_END_STREAM 0x08 // This packet serves as Disconnect frame.
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#define PACKET_CONTROL_SACK_MASK1 0x10 // The low 32-bit SACK mask is included in this frame.
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#define PACKET_CONTROL_SACK_MASK2 0x20 // The high 32 bit SACK mask is present
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#define PACKET_CONTROL_SEND_MASK1 0x40 // The low 32-bit SEND mask is included in this frame
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#define PACKET_CONTROL_SEND_MASK2 0x80 // The high 32-bit SEND mask is included in this frame
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#define PACKET_CONTROL_VARIABLE_MASKS 0xF0 // All four mask bits above
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struct packetheader
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{
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BYTE bCommand;
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};
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/* NEW DATA FRAMES
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**
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** Here in the new unified world we have only two frame types! CommandFrames and DataFrames...
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**
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*/
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struct dataframe
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{
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BYTE bCommand;
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BYTE bControl;
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BYTE bSeq;
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BYTE bNRcv;
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};
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// Following the 4 byte dataframe header will be between zero and four 32-bit masks, as defined by the CONTROL flags,
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// representing either Specific Acks (SACK) or unreliable dropped sends (SEND MASK).
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struct dataframe_masks
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{
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ULONG rgMask[1]; // Zero to four 32-bit masks of either SACK info or SEND info
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};
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struct dataframe_big
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{
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BYTE bCommand;
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BYTE bControl;
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BYTE bSeq;
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BYTE bNRcv;
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ULONG rgMask[4];
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};
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/*
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** COMMAND FRAMES
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**
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** Command frames are everything that is not part of the reliable stream. This is most of the control traffic
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** although some control traffic is part of the stream (keep-alive, End-of-Stream)
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*/
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struct cframe
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{
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BYTE bCommand;
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BYTE bExtOpcode; // CFrame sub-command
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BYTE bMsgID; // Correlator in case ExtOpcode requires a response
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BYTE bRspID; // Correlator in case this is a response
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DWORD dwVersion; // Protocol version #
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DWORD dwSessID; // Session identifier
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DWORD tTimestamp; // local tick count
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};
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/*
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** Selective Acknowledgement packet format
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**
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** When a specific acknowledgement frame is sent there may be two additional pieces
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** of data included with the frame. One is a bitmask allowing selective acknowledgment
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** of non-sequential frames. The other is timing information about the last frame acked
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** by this ACK (NRcv - 1). Specifically, it includes the lowest Retry number that this
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** node received, and the ms delay between that packets arrival and the sending of this
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** Ack.
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*/
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#define SACK_FLAGS_RESPONSE 0x01 // indicates that Retry and Timestamp fields are valid
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#define SACK_FLAGS_SACK_MASK1 0x02
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#define SACK_FLAGS_SACK_MASK2 0x04
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#define SACK_FLAGS_SEND_MASK1 0x08
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#define SACK_FLAGS_SEND_MASK2 0x10
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// First format is used when DATAGRAM_INFO flag is clear
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struct sackframe8
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{
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BYTE bCommand; // As above
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BYTE bExtOpcode; // As above
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BYTE bFlags; // Additional flags for sack frame
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BYTE bRetry;
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BYTE bNSeq; // Since this frame has no sequence number, this is the next Seq we will send
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BYTE bNRcv; // As above
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BYTE bReserved1; // We shipped DX8 with bad packing, so these were actually there
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BYTE bReserved2; // We shipped DX8 with bad packing, so these were actually there
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DWORD tTimestamp; // Local timestamp when packet (NRcv - 1) arrived
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};
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struct sackframe_big8
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{
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BYTE bCommand; // As above
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BYTE bExtOpcode; // As above
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BYTE bFlags; // Additional flags for sack frame
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BYTE bRetry;
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BYTE bNSeq; // Since this frame has no sequence number, this is the next Seq we
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BYTE bNRcv; // As above
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BYTE bReserved1; // We shipped DX8 with bad packing, so these were actually there
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BYTE bReserved2; // We shipped DX8 with bad packing, so these were actually there
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DWORD tTimestamp; // Local stamp when packet arrived
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ULONG rgMask[4];
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};
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#pragma pack(pop)
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#endif
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