[tor-bugs] #11769 [Obfsproxy]: Unexpected `NoneType` in obfs3

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#11769: Unexpected `NoneType` in obfs3
-----------------------+---------------------
 Reporter:  asn        |          Owner:  asn
     Type:  defect     |         Status:  new
 Priority:  normal     |      Milestone:
Component:  Obfsproxy  |        Version:
 Keywords:             |  Actual Points:
Parent ID:             |         Points:
-----------------------+---------------------
 Since my obfs3 bridge has gotten more popular, I decided to enable logging
 and I noticed that I've been getting these errors:

 {{{
 2014-05-06 15:49:51,869 [ERROR] Unhandled error in Deferred:
 2014-05-06 15:49:51,870 [ERROR] Unhandled Error
 Traceback (most recent call last):
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/internet/base.py", line 1201, in mainLoop
     self.runUntilCurrent()
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/internet/base.py", line 797, in runUntilCurrent
     f(*a, **kw)
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/internet/defer.py", line 382, in callback
     self._startRunCallbacks(result)
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/internet/defer.py", line 490, in _startRunCallbacks
     self._runCallbacks()
 --- <exception caught here> ---
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/internet/defer.py", line 577, in _runCallbacks
     current.result = callback(current.result, *args, **kw)
   File "/usr/local/lib/python2.7/dist-
 packages/obfsproxy-0.2.9_1_g4c41868-py2.7.egg/obfsproxy/transports/obfs3.py",
 line 154, in _uniform_dh_errback
     self.circuit.close()
 exceptions.AttributeError: 'NoneType' object has no attribute 'close'
 }}}
 {{{
 2014-05-06 14:47:51,643 [ERROR] Unhandled Error
 Traceback (most recent call last):
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/python/log.py", line 88, in callWithLogger
     return callWithContext({"system": lp}, func, *args, **kw)
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/python/log.py", line 73, in callWithContext
     return context.call({ILogContext: newCtx}, func, *args, **kw)
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/python/context.py", line 118, in callWithContext
     return self.currentContext().callWithContext(ctx, func, *args, **kw)
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/python/context.py", line 81, in callWithContext
     return func(*args,**kw)
 --- <exception caught here> ---
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/internet/posixbase.py", line 614, in _doReadOrWrite
     why = selectable.doRead()
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/internet/tcp.py", line 215, in doRead
     return self._dataReceived(data)
   File "/usr/local/lib/python2.7/dist-packages/Twisted-13.2.0-py2.7-linux-
 x86_64.egg/twisted/internet/tcp.py", line 221, in _dataReceived
     rval = self.protocol.dataReceived(data)
   File "/usr/local/lib/python2.7/dist-
 packages/obfsproxy-0.2.9_1_g4c41868-py2.7.egg/obfsproxy/network/extended_orport.py",
 line 189, in dataReceived
     self.circuit.dataReceived(self.buffer, self)
   File "/usr/local/lib/python2.7/dist-
 packages/obfsproxy-0.2.9_1_g4c41868-py2.7.egg/obfsproxy/network/network.py",
 line 157, in dataReceived
     self.transport.receivedUpstream(data)
   File "/usr/local/lib/python2.7/dist-
 packages/obfsproxy-0.2.9_1_g4c41868-py2.7.egg/obfsproxy/transports/obfs3.py",
 line 102, in receivedUpstream
     self.circuit.downstream.write(message)
 exceptions.AttributeError: 'NoneType' object has no attribute 'downstream'
 }}}

 I get around 2-3 of them per day which means that it's not a very usual
 bug.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/11769>
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