TCP Convergence Layer (TCPCL)¶

The tcpcl module provides tools for parsing and creating TCP Convergence Layer packets as defined in RFC 7242 and RFC 9174.

Constants¶

A byte string sentinel (b"dtn!") used to identify the start of a TCPCL packet in a byte stream.

A dictionary used to map a combination of TCPCL version and message type to its corresponding message class.

Type: dict[tuple[TCPCLVersion, int], type[TCPCLMessage]]

The TCPCL class encapsulates a TCPCL packet and handles version-based dispatch to specific message types. It extends dpkt.Packet.

version (TCPCLVersion | None): The version of the TCPCL packet.
message_type (int | None): The type identifier of the TCPCL message.
message (TCPCLMessage | None): The unpacked message object containing the actual payload and semantics.

__init__(*args, **kwargs): Initializes the TCPCL packet with optional version and message attributes.
unpack(buf: bytes): Unpacks raw bytes into a TCPCL packet. Validates the MAGIC sentinel, version, and length. Raises ValueError if the buffer is too short or the format is invalid.
__bytes__(): Serializes the TCPCL packet back into bytes. Performs a reverse lookup in MESSAGE_MAP to determine the message type. Raises AttributeError if the version or type cannot be determined.
__str__(): Returns a human-readable string representation of the packet.
__repr__(): Returns a developer-friendly string representation of the packet.

A helper class designed to extract TCPCL packets from a continuous byte stream, handling partial packets and split-packet recovery.

buffer (bytearray): An internal buffer that stores incoming data until a complete packet can be parsed.

feed(data: bytes) -> list[TCPCL]: Appends new data to the internal buffer and attempts to extract all complete TCPCL packets. It searches for the MAGIC sentinel and verifies the length header before attempting to unpack. Returns a list of successfully parsed TCPCL instances.