[tor-dev] Status report - Stream-RTT

Damian Johnson atagar at torproject.org
Sat Jul 27 02:41:45 UTC 2013

> There is now a single script called "rttprober"[0] that depends on a
> patched[1] Tor client running a certain configuration[2]. The goal is to
> measure RTTs of Tor circuits. It takes a few parameters as input: an
> authenticated Stem Tor controller for communication with the Tor client..

Hi ra, glad to see that you're using stem! If you have any questions,
suggestions, feature requests, or would like a code review then let me
know. Few things I spotted...

> # Stem does not do that yet.
> # See https://trac.torproject.org/projects/tor/ticket/7953
> if is_valid_fingerprint(fingerprint):
>   query = "ns/id/%s" % fingerprint
> else:
>   raise ValueError("Invalid fingerprint: %s." % fingerprint)
> desc = self._controller.get_info(query)
> return RouterStatusEntryV3(desc)

As of just four weeks ago the Controller started providing v3
responses, so you can replace this with


> circ.build_flags.count('IS_INTERNAL') == 0

This would more commonly be done as...

'IS_INTERNAL' not in circ.build_flags

> try:
>   controller.reset_conf("__DisablePredictedCircuits")
>   controller.reset_conf("__LeaveStreamsUnattached")
>   controller.close()
> except NameError:
>   pass

What raises a NameError?

> # close circuit, but ignore if it does not exist anymore
> try:
>   self._controller.get_circuit(self._cid)
>   self._controller.close_circuit(self._cid)
> except (ValueError, InvalidArguments):
>   pass

What is the purpose of the get_circuit() call? If it's not superfluous
then you can provide a default argument to prevent it from raising an
exception (just about every getter allows for one). Also, you can omit
exception types to catch everything (if you'd like to ignore all
errors). For instance, in this case...

self._controller.get_circuit(self._cid, None)


> try:
>   controller = Controller.from_port()
> except SocketError:
>   sys.stderr.write("ERROR: Couldn't connect to Tor.\n")
>   sys.exit(1)
> controller.authenticate()

This is certainly a fine way of doing it, but you might want to also
look at connection.connect_port()...


It is intended to be a quick and easy method of getting a Controller
for command-line applications. For instance, it will present a
password prompt if tor is configured to use password authentication.
Just realized I should have included it in a tutorial somewhere...

Your code looks great! If you wouldn't mind I'd love to reference it
on stem's examples page...


Shall I reference 'https://bitbucket.org/ra_/tor-rtt/' or do you
anticipate your project having a more permanent home? (this might be a
question for Mike as much as you)

Cheers! -Damian

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