341 lines
10 KiB
Python
341 lines
10 KiB
Python
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#!/usr/bin/env python
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# -*- coding: utf-8 -*-
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#
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""" A telnet server which negotiates"""
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from __future__ import (absolute_import, division, print_function,
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unicode_literals)
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import argparse
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import os
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import sys
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import logging
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try: # Python 2
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import SocketServer as socketserver
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except ImportError: # Python 3
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import socketserver
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log = logging.getLogger(__name__)
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HOST = "localhost"
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IDENT = "NTEL"
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# The strings that indicate the test framework is checking our aliveness
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VERIFIED_REQ = "verifiedserver"
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VERIFIED_RSP = "WE ROOLZ: {pid}"
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def telnetserver(options):
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"""
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Starts up a TCP server with a telnet handler and serves DICT requests
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forever.
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"""
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if options.pidfile:
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pid = os.getpid()
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with open(options.pidfile, "w") as f:
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f.write(str(pid))
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local_bind = (HOST, options.port)
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log.info("Listening on %s", local_bind)
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# Need to set the allow_reuse on the class, not on the instance.
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socketserver.TCPServer.allow_reuse_address = True
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server = socketserver.TCPServer(local_bind, NegotiatingTelnetHandler)
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server.serve_forever()
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return ScriptRC.SUCCESS
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class NegotiatingTelnetHandler(socketserver.BaseRequestHandler):
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"""Handler class for Telnet connections.
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"""
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def handle(self):
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"""
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Negotiates options before reading data.
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"""
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neg = Negotiator(self.request)
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try:
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# Send some initial negotiations.
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neg.send_do("NEW_ENVIRON")
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neg.send_will("NEW_ENVIRON")
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neg.send_dont("NAWS")
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neg.send_wont("NAWS")
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# Get the data passed through the negotiator
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data = neg.recv(1024)
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log.debug("Incoming data: %r", data)
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if VERIFIED_REQ.encode('ascii') in data:
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log.debug("Received verification request from test framework")
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response = VERIFIED_RSP.format(pid=os.getpid())
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response_data = response.encode('ascii')
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else:
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log.debug("Received normal request - echoing back")
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response_data = data.strip()
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if response_data:
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log.debug("Sending %r", response_data)
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self.request.sendall(response_data)
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except IOError:
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log.exception("IOError hit during request")
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class Negotiator(object):
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NO_NEG = 0
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START_NEG = 1
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WILL = 2
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WONT = 3
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DO = 4
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DONT = 5
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def __init__(self, tcp):
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self.tcp = tcp
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self.state = self.NO_NEG
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def recv(self, bytes):
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"""
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Read bytes from TCP, handling negotiation sequences
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:param bytes: Number of bytes to read
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:return: a buffer of bytes
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"""
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buffer = bytearray()
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# If we keep receiving negotiation sequences, we won't fill the buffer.
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# Keep looping while we can, and until we have something to give back
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# to the caller.
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while len(buffer) == 0:
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data = self.tcp.recv(bytes)
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if not data:
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# TCP failed to give us any data. Break out.
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break
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for byte_int in bytearray(data):
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if self.state == self.NO_NEG:
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self.no_neg(byte_int, buffer)
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elif self.state == self.START_NEG:
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self.start_neg(byte_int)
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elif self.state in [self.WILL, self.WONT, self.DO, self.DONT]:
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self.handle_option(byte_int)
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else:
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# Received an unexpected byte. Stop negotiations
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log.error("Unexpected byte %s in state %s",
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byte_int,
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self.state)
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self.state = self.NO_NEG
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return buffer
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def no_neg(self, byte_int, buffer):
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# Not negotiating anything thus far. Check to see if we
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# should.
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if byte_int == NegTokens.IAC:
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# Start negotiation
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log.debug("Starting negotiation (IAC)")
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self.state = self.START_NEG
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else:
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# Just append the incoming byte to the buffer
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buffer.append(byte_int)
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def start_neg(self, byte_int):
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# In a negotiation.
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log.debug("In negotiation (%s)",
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NegTokens.from_val(byte_int))
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if byte_int == NegTokens.WILL:
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# Client is confirming they are willing to do an option
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log.debug("Client is willing")
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self.state = self.WILL
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elif byte_int == NegTokens.WONT:
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# Client is confirming they are unwilling to do an
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# option
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log.debug("Client is unwilling")
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self.state = self.WONT
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elif byte_int == NegTokens.DO:
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# Client is indicating they can do an option
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log.debug("Client can do")
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self.state = self.DO
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elif byte_int == NegTokens.DONT:
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# Client is indicating they can't do an option
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log.debug("Client can't do")
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self.state = self.DONT
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else:
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# Received an unexpected byte. Stop negotiations
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log.error("Unexpected byte %s in state %s",
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byte_int,
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self.state)
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self.state = self.NO_NEG
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def handle_option(self, byte_int):
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if byte_int in [NegOptions.BINARY,
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NegOptions.CHARSET,
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NegOptions.SUPPRESS_GO_AHEAD,
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NegOptions.NAWS,
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NegOptions.NEW_ENVIRON]:
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log.debug("Option: %s", NegOptions.from_val(byte_int))
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# No further negotiation of this option needed. Reset the state.
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self.state = self.NO_NEG
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else:
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# Received an unexpected byte. Stop negotiations
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log.error("Unexpected byte %s in state %s",
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byte_int,
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self.state)
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self.state = self.NO_NEG
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def send_message(self, message_ints):
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self.tcp.sendall(bytearray(message_ints))
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def send_iac(self, arr):
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message = [NegTokens.IAC]
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message.extend(arr)
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self.send_message(message)
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def send_do(self, option_str):
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log.debug("Sending DO %s", option_str)
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self.send_iac([NegTokens.DO, NegOptions.to_val(option_str)])
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def send_dont(self, option_str):
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log.debug("Sending DONT %s", option_str)
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self.send_iac([NegTokens.DONT, NegOptions.to_val(option_str)])
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def send_will(self, option_str):
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log.debug("Sending WILL %s", option_str)
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self.send_iac([NegTokens.WILL, NegOptions.to_val(option_str)])
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def send_wont(self, option_str):
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log.debug("Sending WONT %s", option_str)
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self.send_iac([NegTokens.WONT, NegOptions.to_val(option_str)])
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class NegBase(object):
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@classmethod
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def to_val(cls, name):
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return getattr(cls, name)
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@classmethod
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def from_val(cls, val):
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for k in cls.__dict__.keys():
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if getattr(cls, k) == val:
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return k
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return "<unknown>"
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class NegTokens(NegBase):
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# The start of a negotiation sequence
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IAC = 255
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# Confirm willingness to negotiate
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WILL = 251
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# Confirm unwillingness to negotiate
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WONT = 252
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# Indicate willingness to negotiate
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DO = 253
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# Indicate unwillingness to negotiate
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DONT = 254
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# The start of sub-negotiation options.
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SB = 250
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# The end of sub-negotiation options.
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SE = 240
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class NegOptions(NegBase):
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# Binary Transmission
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BINARY = 0
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# Suppress Go Ahead
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SUPPRESS_GO_AHEAD = 3
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# NAWS - width and height of client
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NAWS = 31
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# NEW-ENVIRON - environment variables on client
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NEW_ENVIRON = 39
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# Charset option
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CHARSET = 42
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def get_options():
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parser = argparse.ArgumentParser()
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parser.add_argument("--port", action="store", default=9019,
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type=int, help="port to listen on")
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parser.add_argument("--verbose", action="store", type=int, default=0,
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help="verbose output")
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parser.add_argument("--pidfile", action="store",
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help="file name for the PID")
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parser.add_argument("--logfile", action="store",
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help="file name for the log")
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parser.add_argument("--srcdir", action="store", help="test directory")
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parser.add_argument("--id", action="store", help="server ID")
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parser.add_argument("--ipv4", action="store_true", default=0,
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help="IPv4 flag")
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return parser.parse_args()
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def setup_logging(options):
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"""
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Set up logging from the command line options
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"""
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root_logger = logging.getLogger()
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add_stdout = False
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formatter = logging.Formatter("%(asctime)s %(levelname)-5.5s "
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"[{ident}] %(message)s"
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.format(ident=IDENT))
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# Write out to a logfile
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if options.logfile:
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handler = logging.FileHandler(options.logfile, mode="w")
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handler.setFormatter(formatter)
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handler.setLevel(logging.DEBUG)
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root_logger.addHandler(handler)
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else:
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# The logfile wasn't specified. Add a stdout logger.
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add_stdout = True
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if options.verbose:
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# Add a stdout logger as well in verbose mode
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root_logger.setLevel(logging.DEBUG)
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add_stdout = True
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else:
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root_logger.setLevel(logging.INFO)
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if add_stdout:
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stdout_handler = logging.StreamHandler(sys.stdout)
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stdout_handler.setFormatter(formatter)
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stdout_handler.setLevel(logging.DEBUG)
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root_logger.addHandler(stdout_handler)
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class ScriptRC(object):
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"""Enum for script return codes"""
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SUCCESS = 0
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FAILURE = 1
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EXCEPTION = 2
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class ScriptException(Exception):
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pass
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if __name__ == '__main__':
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# Get the options from the user.
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options = get_options()
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# Setup logging using the user options
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setup_logging(options)
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# Run main script.
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try:
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rc = telnetserver(options)
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except Exception as e:
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log.exception(e)
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rc = ScriptRC.EXCEPTION
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log.info("Returning %d", rc)
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sys.exit(rc)
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