93 lines
3.3 KiB
Python
93 lines
3.3 KiB
Python
# This file is a part of sedbgmux, an open source DebugMux client.
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# Copyright (c) 2022 Vadim Yanitskiy <axilirator@gmail.com>
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#
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# SPDX-License-Identifier: GPL-3.0-or-later
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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import logging as log
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from typing import Any
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from construct import Const, Container, Int16ul
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from transport import Transport
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from proto import DbgMuxFrame
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class DbgMuxPeer:
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def __init__(self, io: Transport):
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self.tx_count: int = 0
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self.rx_count: int = 0
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self.io = io
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def send(self, msg_type: DbgMuxFrame.MsgType, msg: Any = b'') -> None:
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# Encode the inner message first
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msg_data = DbgMuxFrame.Msg.build(msg, MsgType=msg_type)
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c = Container({
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'TxCount': (self.tx_count + 1) % 256,
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'RxCount': self.rx_count % 256,
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'MsgType': msg_type,
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'MsgData': msg_data,
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'FCS': 0 # Calculated below
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})
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# ACK is a bit special
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if msg_type == DbgMuxFrame.MsgType.Ack:
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c['TxCount'] = 0xf1
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# There is a Checksum construct, but it requires all checksummed fields
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# to be wrapped into an additional RawCopy construct. This is ugly and
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# inconvinient from the API point of view, so we calculate the FCS manually:
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frame = DbgMuxFrame.Frame.build(c)[:-2] # strip b'\x00\x00'
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c['FCS'] = DbgMuxFrame.fcs_func(frame)
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log.debug('Tx frame (Ns=%03u, Nr=%03u, fcs=0x%04x) %s %s',
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c['TxCount'], c['RxCount'], c['FCS'],
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c['MsgType'], c['MsgData'].hex())
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self.io.write(frame + Int16ul.build(c['FCS']))
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# ACK is not getting accounted
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if msg_type != DbgMuxFrame.MsgType.Ack:
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self.tx_count += 1
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def recv(self) -> Container:
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frame: bytes = b''
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frame += self.io.read(2) # Magic
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Const(b'\x42\x42').parse(frame[:2])
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frame += self.io.read(2) # Length
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length: int = Int16ul.parse(frame[2:])
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frame += self.io.read(length) # Rest
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c = DbgMuxFrame.Frame.parse(frame)
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log.debug('Rx frame (Ns=%03u, Nr=%03u, fcs=0x%04x) %s %s',
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c['TxCount'], c['RxCount'], c['FCS'],
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c['MsgType'], c['MsgData'].hex())
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# Re-calculate and check the FCS
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fcs = DbgMuxFrame.fcs_func(frame[:-2])
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if fcs != c['FCS']:
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log.error('Rx frame (Ns=%03u, Nr=%03u) with bad FCS: '
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'indicated 0x%04x != calculated 0x%04x',
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c['TxCount'], c['RxCount'], c['FCS'], fcs)
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# TODO: NACK this frame?
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# Parse the inner message
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c['Msg'] = DbgMuxFrame.Msg.parse(c['MsgData'], MsgType=c['MsgType'])
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self.rx_count += 1
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return c
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