anti-censorship-team August 2021

anti-censorship-team@lists.torproject.org

3 participants
3 discussions

SCTP-Based Pluggable Transport Prototype
by Alexander Mages 18 Sep '21

18 Sep '21

Hello Anti-Censorship Team, I was advised by Cecylia to share my project with this mailing list for the wider community to see and critique. For the past couple of months, I have been doing research under the advisory of Prof. Eugene Vasserman (CC) at Kansas State University, and this project is the result. I intend to continue working on privacy and anonymity, so if this project has potential I would be happy to keep working on it, as well as exploring other ways to contribute. The concept for this transport was derived from this wiki page: https://gitlab.torproject.org/legacy/trac/-/wikis/doc/PluggableTransports/i… . The transport is functional but not yet tested with the Tor Browser. I prototyped this transport using Ncat for SCTP and Telnet for TCP. It is written in Python 3 and SCTP functionality was implemented using C/POSIX-like socket parameters, removing the necessity of a third-party library. A write-up attached to this email denotes functionality, dependencies, limitations, and instructions for running the transport. I look forward to hearing everyone's thoughts! Regards, Alex Mages

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ansible role - snowflake - updates
by Jacobo Nájera 27 Aug '21

27 Aug '21

Hello, I added new features to the ansible role of snowflake: - Support for: Debian Bullseye and Ubuntu Focal - Variable to update the standalone version of Snowflake If you are using the ansible role you can update snowflake via your playbook. First, upgrade ansible role ansible-galaxy install -f nvjacobo.snowflake Then add snowflake_update var: - hosts: all vars: snowflake_update: yes roles: - nvjacobo.snowflake Finally run your playbook. Documentation of ansible role snowflake: https://www.jacobo.org/en/ansible-for-snowflake-proxies-of-the-tor-network/ Thanks, Jacobo

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Improving Snowflake performance by adjusting smux parameters
by David Fifield 04 Aug '21

04 Aug '21

While experimenting with another tunnel built on KCP and smux, I discovered that performance could be greatly increased by increasing the size of smux buffers. It's likely that doing the same can also improve performance in Snowflake. There are two relevant parameters, MaxReceiveBuffer and MaxStreamBuffer. MaxStreamBuffer seems to be the most important one to increase. https://pkg.go.dev/github.com/xtaci/smux#Config // MaxReceiveBuffer is used to control the maximum // number of data in the buffer pool MaxReceiveBuffer int // MaxStreamBuffer is used to control the maximum // number of data per stream MaxStreamBuffer int The default values are 4 MB and 64 KB. https://github.com/xtaci/smux/blob/eba6ee1d2a14eb7f86f43f7b7cb3e44234e13c66… MaxReceiveBuffer: 4194304, MaxStreamBuffer: 65536, kcptun, a prominent KCP/smux tunnel, has defaults of 4 MB (--smuxbuf) and 2 MB (--streambuf) in both client and server: https://github.com/xtaci/kcptun/blob/9a5b31b4706aba4c67bcb6ebfe108fdb564a90… In my experiment, I changed the values to 4 MB / 1 MB on the client and 16 MB / 1 MB on the server. This change increased download speed by about a factor of 3: default buffers 477.4 KB/s enlarged buffers 1388.3 KB/2 Values of MaxStreamBuffer higher than 1 MB didn't seem to have much of an effect. 256 KB did not help as much. My guess, based on intuition, is that on the server we should set a large value of MaxReceiveBuffer, as it is a global limit shared among all clients, and a relatively smaller value of MaxStreamBuffer, because there are expected to be many simultaneous streams. On the client, don't set MaxReceiveBuffer too high, because it's on an end-user device, but go ahead and set MaxStreamBuffer high, because there's expected to be only one or two streams at a time. I discovered this initially by temporarily settings smux to protocol v1 instead of v2. My understanding is that v1 lacks some kind of receive window mechanism that v2 has, and by default is more willing to expend memory receiving data. See "Per-stream sliding window to control congestion.(protocol version 2+)": https://pkg.go.dev/github.com/xtaci/smux#readme-features Past performance ticket: "Reduce KCP bottlenecks for Snowflake" https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snow…

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anti-censorship-team August 2021