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[wip] SCTP common header, common chunk header and data chunk parsing
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‎microschc/protocol/sctp.py

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"""
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SCTP header declarations
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Declarations for the SCTP protocol header as defined in RFC9260 [1].
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Note 1: Hop by Hop Options, Routing header parsing is not implemented yet.
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Note 2: Fragment header parsing is not implemented as fragmentation and reassembly
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are handled by SCHC-RF.
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Note 3: Authentication and Encapsulating Security payload parsing is not implemented yet.
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[1] "RFC9260: Stream Control Transmission Protocol, R. Stewart et al.
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"""
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from enum import Enum
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SCTP_HEADER_ID = 'SCTP'
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class SCTPFields(str, Enum):
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SOURCE_PORT_NUMBER = f'{SCTP_HEADER_ID}:Source Port Number'
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DESTINATION_PORT_NUMBER = f'{SCTP_HEADER_ID}:Destination Port Number'
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VERIFICATION_TAG = f'{SCTP_HEADER_ID}:Verification Tag'
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CHECKSUM = f'{SCTP_HEADER_ID}:Checksum'
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CHUNK_TYPE = f'{SCTP_HEADER_ID}:Chunk Type'
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CHUNK_FLAGS = f'{SCTP_HEADER_ID}:Chunk Flags'
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CHUNK_LENGTH = f'{SCTP_HEADER_ID}:Chunk Length'
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DATA_RES = f'{SCTP_HEADER_ID}:Data Res'
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DATA_I = f'{SCTP_HEADER_ID}:Data I'
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DATA_U = f'{SCTP_HEADER_ID}:Data U'
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DATA_B = f'{SCTP_HEADER_ID}:Data B'
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DATA_E = f'{SCTP_HEADER_ID}:Data E'
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DATA_LENGTH = f'{SCTP_HEADER_ID}:Data Length'
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DATA_TSN = f'{SCTP_HEADER_ID}:Data TSN'
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DATA_STREAM_IDENTIFIER = f'{SCTP_HEADER_ID}:Data Stream Identifier S'
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DATA_STREAM_SEQUENCE_NUMBER = f'{SCTP_HEADER_ID}:Data Stream Sequence Number n'
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DATA_PAYLOAD_PROTOCOL_IDENTIFIER = f'{SCTP_HEADER_ID}:Data Payload Protocol Identifier'
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INIT_CHUNK_FLAGS = f'{SCTP_HEADER_ID}:Chunk Flags'
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INIT_CHUNK_LENGTH = f'{SCTP_HEADER_ID}:Chunk Length'
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INIT_INITIATE_TAG = f'{SCTP_HEADER_ID}:Initiate Tag'
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INIT_ADVERTISED_RECEIVER_WINDOW_CREDIT = f'{SCTP_HEADER_ID}:Advertised Receiver Window Credit'
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INIT_NUMBER_OF_OUTBOUND_STREAMS = f'{SCTP_HEADER_ID}:Number of Outbound Streams'
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INIT_NUMBER_OF_INBOUND_STREAMS = f'{SCTP_HEADER_ID}:Number of Inbound Streams'
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INIT_INITIAL_TSN = f'{SCTP_HEADER_ID}:Initial TSN'
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INIT_ACK_CHUNK_FLAGS = f'{SCTP_HEADER_ID}:Chunk Flags'
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INIT_ACK_CHUNK_LENGTH = f'{SCTP_HEADER_ID}:Chunk Length'
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INIT_ACK_INITIATE_TAG = f'{SCTP_HEADER_ID}:Initiate Tag'
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INIT_ACK_ADVERTISED_RECEIVER_WINDOW_CREDIT = f'{SCTP_HEADER_ID}:Advertised Receiver Window Credit'
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INIT_ACK_NUMBER_OF_OUTBOUND_STREAMS = f'{SCTP_HEADER_ID}:Number of Outbound Streams'
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INIT_ACK_NUMBER_OF_INBOUND_STREAMS = f'{SCTP_HEADER_ID}:Number of Inbound Streams'
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INIT_ACK_INITIAL_TSN = f'{SCTP_HEADER_ID}:Initial TSN'
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from enum import Enum
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from typing import Dict, List, Tuple
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from microschc.binary.buffer import Buffer
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from microschc.parser import HeaderParser, ParserError
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from microschc.rfc8724 import FieldDescriptor, HeaderDescriptor
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SCTP_HEADER_ID = 'SCTP'
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class SCTPFields(str, Enum):
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SOURCE_PORT = f'{SCTP_HEADER_ID}:Source Port'
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DESTINATION_PORT = f'{SCTP_HEADER_ID}:Destination Port'
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VERIFICATION_TAG = f'{SCTP_HEADER_ID}:Verification Tag'
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CHECKSUM = f'{SCTP_HEADER_ID}:Checksum'
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CHUNK_TYPE = f'{SCTP_HEADER_ID}:Chunk Type'
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CHUNK_FLAGS = f'{SCTP_HEADER_ID}:Chunk Flags'
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CHUNK_LENGTH = f'{SCTP_HEADER_ID}:Chunk Length'
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CHUNK_VALUE = f'{SCTP_HEADER_ID}:Chunk Value'
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CHUNK_PADDING = f'{SCTP_HEADER_ID}:Chunk Padding'
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CHUNK_DATA_TSN = f'{SCTP_HEADER_ID}:Data TSN'
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CHUNK_DATA_STREAM_IDENTIFIER = f'{SCTP_HEADER_ID}:Data Stream Identifier S'
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CHUNK_DATA_STREAM_SEQUENCE_NUMBER = f'{SCTP_HEADER_ID}:Data Stream Sequence Number n'
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CHUNK_DATA_PAYLOAD_PROTOCOL_IDENTIFIER = f'{SCTP_HEADER_ID}:Data Payload Protocol Identifier'
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CHUNK_DATA_PAYLOAD = f'{SCTP_HEADER_ID}:Data Payload'
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class SCTPChunkTypes(int, Enum):
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# ID Value Chunk Type
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# ----- ----------
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# 0 - Payload Data (DATA)
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# 1 - Initiation (INIT)
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# 2 - Initiation Acknowledgement (INIT ACK)
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# 3 - Selective Acknowledgement (SACK)
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# 4 - Heartbeat Request (HEARTBEAT)
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# 5 - Heartbeat Acknowledgement (HEARTBEAT ACK)
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# 6 - Abort (ABORT)
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# 7 - Shutdown (SHUTDOWN)
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# 8 - Shutdown Acknowledgement (SHUTDOWN ACK)
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# 9 - Operation Error (ERROR)
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# 10 - State Cookie (COOKIE ECHO)
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# 11 - Cookie Acknowledgement (COOKIE ACK)
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# 12 - Reserved for Explicit Congestion Notification Echo (ECNE)
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# 13 - Reserved for Congestion Window Reduced (CWR)
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# 14 - Shutdown Complete (SHUTDOWN COMPLETE)
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# 15 to 62 - reserved by IETF
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# 63 - IETF-defined Chunk Extensions
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# 64 to 126 - reserved by IETF
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# 127 - IETF-defined Chunk Extensions
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# 128 to 190 - reserved by IETF
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# 191 - IETF-defined Chunk Extensions
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# 192 to 254 - reserved by IETF
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# 255 - IETF-defined Chunk Extensions
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DATA = 0
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INIT = 1
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INIT_ACK = 2
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SACK = 3
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HEARTBEAT = 4
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HEARTBEAT_ACK = 5
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ABORT = 6
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SHUTDOWN = 7
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SHUTDOWN_ACK = 8
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ERROR = 9
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COOKIE_ECHO = 10
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COOKIE_ACK = 11
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ECNE = 12
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CWR = 13
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SHUTDOWN_COMPLETE = 14
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class SCTPParser(HeaderParser):
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def __init__(self) -> None:
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super().__init__(name=SCTP_HEADER_ID)
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def match(self, buffer: Buffer) -> bool:
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return buffer.length >= 12 * 8 # SCTP header is at least 12 bytes
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def parse(self, buffer: Buffer) -> HeaderDescriptor:
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"""
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Source Port Number | Destination Port Number |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Verification Tag |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Checksum |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| |
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| Chunk #1 |
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| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| |
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| Chunk #2 |
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| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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"""
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if buffer.length < 12 * 8:
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raise ParserError(buffer=buffer, message=f'length too short: {buffer.length} < 96')
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# Source Port: 16 bits
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source_port: Buffer = buffer[0:16]
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# Destination Port: 16 bits
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destination_port: Buffer = buffer[16:32]
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# Verification Tag: 32 bits
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verification_tag: Buffer = buffer[32:64]
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# Checksum: 32 bits
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checksum: Buffer = buffer[64:96]
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header_fields: List[FieldDescriptor] = [
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FieldDescriptor(id=SCTPFields.SOURCE_PORT, position=0, value=source_port),
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FieldDescriptor(id=SCTPFields.DESTINATION_PORT, position=0, value=destination_port),
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FieldDescriptor(id=SCTPFields.VERIFICATION_TAG, position=0, value=verification_tag),
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FieldDescriptor(id=SCTPFields.CHECKSUM, position=0, value=checksum),
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]
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chunks: Buffer = buffer[96:]
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while chunks.length > 0:
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chunks_fields, chunks_bits_consumed = self._parse_chunk(chunks)
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chunks = chunks[chunks_bits_consumed:]
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header_fields.extend(chunks_fields)
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header_descriptor: HeaderDescriptor = HeaderDescriptor(
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id=SCTP_HEADER_ID,
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length=buffer.length,
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fields=header_fields
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)
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return header_descriptor
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def _parse_chunk(self, buffer: Buffer) -> tuple[List[FieldDescriptor], int]:
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fields: List[FieldDescriptor] = []
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# Chunk Type: 8 bits
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chunk_type: Buffer = buffer[0:8]
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fields.append(FieldDescriptor(id=SCTPFields.CHUNK_TYPE, position=0, value=chunk_type))
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# Chunk Flags: 8 bits
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chunk_flags: Buffer = buffer[8:16]
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fields.append(FieldDescriptor(id=SCTPFields.CHUNK_FLAGS, position=0, value=chunk_flags))
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# Chunk Length: 16 bits
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chunk_length: Buffer = buffer[16:32]
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fields.append(FieldDescriptor(id=SCTPFields.CHUNK_LENGTH, position=0, value=chunk_length))
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chunk_length_value: int = chunk_length.value(type='unsigned int') * 8
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# Chunk Value: variable length
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chunk_value_length = chunk_length_value - 32 # Length includes the 4 bytes of type, flags, and length
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if chunk_value_length > 0:
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chunk_type_value: int = chunk_type.value()
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chunk_value: Buffer = buffer[32: 32 + chunk_value_length]
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if chunk_type_value == SCTPChunkTypes.DATA:
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chunk_fields: List[FieldDescriptor] = self._parse_chunk_data(chunk_value)
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fields.extend(chunk_fields)
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else:
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fields.append(FieldDescriptor(id=SCTPFields.CHUNK_VALUE, position=0, value=chunk_value))
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chunk_padding_length: int = (32 - chunk_length_value%32)%32
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if chunk_padding_length > 0:
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chunk_padding: Buffer = buffer[chunk_length_value: chunk_length_value+chunk_padding_length]
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fields.append(FieldDescriptor(id=SCTPFields.CHUNK_PADDING, position=0, value=chunk_padding))
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bits_consumed = chunk_length_value + chunk_padding_length
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return fields, bits_consumed
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def _parse_chunk_data(self, buffer: Buffer) -> List[FieldDescriptor]:
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"""
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0 1 2 3
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0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Type = 0 | Reserved|U|B|E| Length |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| TSN |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Stream Identifier S | Stream Sequence Number n |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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| Payload Protocol Identifier |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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\ \
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/ User Data (seq n of Stream S) /
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\ \
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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"""
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fields: List[FieldDescriptor] = []
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tsn: Buffer = buffer[0:32]
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stream_identifier_s: Buffer = buffer[32:48]
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stream_sequence_number_n: Buffer = buffer[48:64]
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payload_protocol_identifier: Buffer = buffer[64:96]
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user_data: Buffer = buffer[96:]
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fields.extend(
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[
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FieldDescriptor(id=SCTPFields.CHUNK_DATA_TSN, value=tsn, position=0),
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FieldDescriptor(id=SCTPFields.CHUNK_DATA_STREAM_IDENTIFIER, value=stream_identifier_s, position=0),
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FieldDescriptor(id=SCTPFields.CHUNK_DATA_STREAM_SEQUENCE_NUMBER, value=stream_sequence_number_n, position=0),
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FieldDescriptor(id=SCTPFields.CHUNK_DATA_PAYLOAD_PROTOCOL_IDENTIFIER, value=payload_protocol_identifier, position=0),
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FieldDescriptor(id=SCTPFields.CHUNK_DATA_PAYLOAD, value=user_data, position=0)
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]
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)
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return fields
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