[tor-dev] Transport composition

Ximin Luo infinity0 at gmx.com
Tue Nov 19 21:27:54 UTC 2013

Hey Kevin, to get you updated on what we've discussed so far, you could try to build the diagrams from this repo:


The build-dependencies are short and listed in the Makefile. There is also a sketch at the bottom of #9744:


For simplicity, we are only considering the case where, for a compsition chain of PT[0]..PT[n], every element except PT[n] makes one single outgoing stream to an address specified by the previous element. This excludes a chain that e.g. contains flashproxy in the middle.

Our current preferred design would require minimal changes to the Tor PT spec. However, we haven't considered potential performance bottlenecks.


On 19/11/13 20:15, Kevin P Dyer wrote:
> Hi George,
> Maybe I'm missing something from the discussions that happened eight
> months ago at the dev meeting. (as per the initial comment in [1])
> However, I guess I'm a bit confused about the motivation.
> Just to be clear, the goal is to be able to combine multiple
> transports easily, right? For example, we may want a transport that
> has the DPI-resistance of obfsproxy, but the address diversity of
> flashproxy.
> My main concern is that a general composition framework is going to
> add uneeded complexity to the interface between Tor and the pluggable
> transports. I understand the long-term benefits to being able to
> compose pluggable transports, but my concern is that it won't work
> well in practice, will be a nightmare to manage/deploy/develop, and
> will have irreconcilable performance bottlenecks.
> I think pluggable transport composition will be a good topic to
> discuss at the PT standup on Friday. To get my head around the current
> design, it would be great if we could discuss a few use cases beyond
> obfsproxy+flashproxy.
> -Kevin
> [1] https://trac.torproject.org/projects/tor/ticket/7167
> On Sun, Nov 10, 2013 at 3:43 AM, George Kadianakis <desnacked at riseup.net> wrote:
>> Hello Kevin,
>> If you are interested in learning more about the transport combiner
>> idea we were recently discussing, check out trac tickets #10061, #9744
>> and #7167.
>> It would be awesome if you could comment with any ideas or criticisms
>> you have.
>> Cheers!
> _______________________________________________
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> tor-dev at lists.torproject.org
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