97 lines
3.2 KiB
Python
97 lines
3.2 KiB
Python
from .multiselect_muxer_interface import IMultiselectMuxer
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from .multiselect_communicator import MultiselectCommunicator
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MULTISELECT_PROTOCOL_ID = "/multistream/1.0.0"
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PROTOCOL_NOT_FOUND_MSG = "na"
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class Multiselect(IMultiselectMuxer):
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"""
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Multiselect module that is responsible for responding to
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a multiselect client and deciding on
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a specific protocol and handler pair to use for communication
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"""
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def __init__(self):
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self.handlers = {}
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def add_handler(self, protocol, handler):
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"""
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Store the handler with the given protocol
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:param protocol: protocol name
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:param handler: handler function
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"""
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self.handlers[protocol] = handler
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async def negotiate(self, stream):
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"""
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Negotiate performs protocol selection
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:param stream: stream to negotiate on
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:return: selected protocol name, handler function
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:raise Exception: negotiation failed exception
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"""
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# Create a communicator to handle all communication across the stream
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communicator = MultiselectCommunicator(stream)
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# Perform handshake to ensure multiselect protocol IDs match
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await self.handshake(communicator)
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# Read and respond to commands until a valid protocol ID is sent
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while True:
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# Read message
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command = await communicator.read_stream_until_eof()
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# Command is ls or a protocol
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if command == "ls":
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# TODO: handle ls command
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pass
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else:
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protocol = command
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if protocol in self.handlers:
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# Tell counterparty we have decided on a protocol
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await communicator.write(protocol)
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# Return the decided on protocol
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return protocol, self.handlers[protocol]
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# Tell counterparty this protocol was not found
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await communicator.write(PROTOCOL_NOT_FOUND_MSG)
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async def handshake(self, communicator):
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"""
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Perform handshake to agree on multiselect protocol
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:param communicator: communicator to use
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:raise Exception: error in handshake
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"""
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# TODO: Use format used by go repo for messages
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# Send our MULTISELECT_PROTOCOL_ID to other party
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await communicator.write(MULTISELECT_PROTOCOL_ID)
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# Read in the protocol ID from other party
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handshake_contents = await communicator.read_stream_until_eof()
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# Confirm that the protocols are the same
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if not validate_handshake(handshake_contents):
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raise MultiselectError("multiselect protocol ID mismatch")
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# Handshake succeeded if this point is reached
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def validate_handshake(handshake_contents):
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"""
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Determine if handshake is valid and should be confirmed
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:param handshake_contents: contents of handshake message
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:return: true if handshake is complete, false otherwise
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"""
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# TODO: Modify this when format used by go repo for messages
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# is added
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return handshake_contents == MULTISELECT_PROTOCOL_ID
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class MultiselectError(ValueError):
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"""Raised when an error occurs in multiselect process"""
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