commit 068d521002e0858d91c2fc65d4c16b1c226d8a1b Author: Matt Traudt sirmatt@ksu.edu Date: Thu Jun 14 19:49:19 2018 -0400

Implement the "MaxAdvertisedBandwidth" hack ...

Use a relay's {,Relay}BandwidthRate/MaxAdvertisedBandwidth as an upper bound on the measurements we make for it. --- CHANGELOG.md | 5 +++++ sbws/core/scanner.py | 36 ++++++++++++++++++++++++++++++++++++ 2 files changed, 41 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md index 3a79c02..6ce42bd 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -7,6 +7,11 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.

## [Unreleased]

+### Added + +- Use a relay's {,Relay}BandwidthRate/MaxAdvertisedBandwidth as an upper bound + on the measurements we make for it. (GH#155) + ### Changed

- Change the path where the Bandwidth List files are generated: now they are diff --git a/sbws/core/scanner.py b/sbws/core/scanner.py index 6af1b0c..2a3aadc 100644 --- a/sbws/core/scanner.py +++ b/sbws/core/scanner.py @@ -165,6 +165,41 @@ def _pick_ideal_second_hop(relay, dest, rl, cont, is_exit): return chosen

+def _clamp_bw_results(relay, bw_results): + ''' + If a relay has MaxAdvertisedBandwidth set, they may be capable of some + large amount of bandwidth but prefer if they didn't receive it. We also + could have managed to measure them faster than their {,Relay}BandwidthRate + somehow. + + See https://github.com/pastly/simple-bw-scanner/issues/155 and + https://trac.torproject.org/projects/tor/ticket/8494 + ''' + upper_bound = relay.average_bandwidth + if upper_bound is None: + log.warning( + 'Could not get average bandwidth from %s's descriptor. Not ' + 'capping the results for it to some upper bound.', relay.nickname) + return bw_results + capped_count = 0 + new_results = [] + for result in bw_results: + rate = result['amount'] / result['duration'] + if rate > upper_bound: + capped_count += 1 + new_results.append({ + 'amount': int(upper_bound * result['duration']), + 'duration': result['duration']}) + else: + new_results.append(result) + assert len(new_results) == len(bw_results) + if capped_count > 0: + log.debug( + 'Capped %d results to %d for relay %s', capped_count, upper_bound, + relay.nickname) + return new_results + + def measure_relay(args, conf, destinations, cb, rl, relay): s = requests_utils.make_session( cb.controller, conf.getfloat('general', 'http_timeout')) @@ -246,6 +281,7 @@ def measure_relay(args, conf, destinations, cb, rl, relay): ResultErrorStream(relay, circ_fps, dest.url, our_nick, msg=msg), ] cb.close_circuit(circ_id) + bw_results = _clamp_bw_results(relay, bw_results) # Finally: store result return [ ResultSuccess(rtts, bw_results, relay, circ_fps, dest.url, our_nick),