118 lines
4.2 KiB
Python
118 lines
4.2 KiB
Python
import socket
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import typing
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import zlib
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import bidict
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from source import packets
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from source.utils.crypto.type import CipherType
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class CommunicationManager:
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"""
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Manage everything about communication
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"""
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def __init__(self, interface: str, broadcast_address: str = "ff02::1", port: int = 5555):
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self.broadcast_address = broadcast_address
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self.port = port
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# create an IPv6 UDP socket
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self.socket = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
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# enable broadcast messages
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self.socket.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, True)
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# use multicast on the selected interface
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self.socket.setsockopt(socket.IPPROTO_IPV6, socket.IPV6_MULTICAST_IF, socket.if_nametoindex(interface))
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# bind to listen for any message on this port
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self.socket.bind(("::", self.port))
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# create a dictionary to hold the types of packets and their headers.
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self.packet_types: bidict.bidict[bytes, typing.Type[packets.base.BasePacket]] = bidict.bidict()
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# the secret key used for AES communication
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self.secret_key: bytes = b"secret key!"
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def __del__(self):
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# close the socket
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self.socket.close()
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def register_packet_type(self, header: bytes, packet_type: typing.Type[packets.base.BasePacket]) -> None:
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"""
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Register a new kind of packet that can be sent or received.
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:param header: the binary header identifying the packet
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:param packet_type: the class of the packet
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"""
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if len(header) != 4:
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raise Exception("The header should be exactly 4 bytes long.")
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self.packet_types[header] = packet_type
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def packet_encode(self, packet: packets.base.BasePacket, cipher_type: CipherType) -> bytes:
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"""
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Encode a packet for diffusion
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:param packet: a packet to encode to be sent
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:param cipher_type: the type of cipher
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:return: an encoded packet
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"""
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# get the header identifier of the type of this packet
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header: typing.Optional[bytes] = self.packet_types.inverse.get(type(packet))
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if header is None:
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raise Exception(f"Unrecognised packet type: {type(packet)}. Has it been registered ?")
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# get the encoded packet data
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data = packet.pack()
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# calculate its checksum using CRC32
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checksum = zlib.crc32(data).to_bytes(4, byteorder='big')
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return checksum + header + data
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def packet_decode(self, payload: bytes) -> packets.base.BasePacket:
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"""
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Decode a payload into a packet
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:param payload: the data of the packet
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:return: the deserialized packet
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"""
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# split the header and data from the raw payload
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checksum: int = int.from_bytes(payload[:4], "big")
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header: bytes = payload[4:8]
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data: bytes = payload[8:]
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# verify the checksum for corruption
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if zlib.crc32(data) != checksum:
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raise ValueError("The checksum is invalid.")
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# get the type of the packet from its header
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packet_type: typing.Optional[typing.Type[packets.base.BasePacket]] = self.packet_types.get(header)
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if header is None:
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raise Exception(f"Unrecognised packet header: {header}. Has it been registered ?")
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# unpack the packet
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return packet_type.unpack(data)
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def broadcast(self, packet: packets.base.BasePacket, cipher_type: CipherType = None):
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"""
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Broadcast a message in the network
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:param cipher_type: the type of cipher
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:param packet: the message to broadcast
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"""
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# TODO(Faraphel): should encrypt the data if required, prepend encryption mode
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# TODO(Faraphel): use a channel system (OR ESTABLISH ANOTHER PORT ???)
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self.socket.sendto(self.packet_encode(packet, cipher_type), (self.broadcast_address, self.port))
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def receive(self) -> tuple[packets.base.BasePacket, tuple]:
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"""
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Receive a packet
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:return: the packet content alongside the address of the sender
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"""
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# receive a message
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payload, address = self.socket.recvfrom(65536)
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# decode the payload
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return self.packet_decode(payload), address
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# TODO(Faraphel): should decrypt the data
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