Rewrite Tor in Rust

https://trac.torproject.org/projects/tor/ticket/11331

by Jonhoo • 10 years ago

94 27 10 years ago

trac.torproject.org

kibwen2• 10 years ago

The OP is likely nothing more than wishful thinking, but I can see why people are intrigued by the prospect. An important thing to note is that it's entirely possible to perform a slow, gradual integration of Rust code into a C/C++ codebase (such as Mozilla is doing with Firefox), but only if your codebase is sufficiently modular with well-defined interfaces for Rust-based libs to slot into. If all you've got is a big ball of mud, then your first step is to work on the modularization of your codebase (which, IMO, has a good chance of increasing your code quality regardless of whether you eventually decide to introduce any Rust).

alexnewman2• 10 years ago

You end up having to toss a layer of c around your c++ last time I checked. Does c++ even have an abi yet?

roblabla• 10 years ago

well, not a standard one. That's what extern "C" is for : if you want a standardized API, C always had one.

Manishearth2• 10 years ago

You can call into Rust directly from C++ (with a header file).

But yeah, the reverse requires a C layer. rust-bindgen has experimental C++ support which we use for spidermonkey but it isn't perfect.

pjmlp2• 10 years ago

C never had one standard ABI, not one that I can read in ANSI C document.

What happens is that C ABI == OS ABI, when the OS is written in C. This is not the case in the mainframe OSes that are still alive, for example.

So people have come to expect C ABI as being some kind of standard.

On an OS written in pure C++, the OS vendor C++ compiler would be the ABI.

Having said this, there are efforts to partially standardize the C++ ABI:

https://isocpp.org/blog/2014/05/n4028

Also many vendors use the Intel's C++ Itanium ABI as reference.

voiper1• 10 years ago

If all you've got is a big ball of mud, then your first step is to work on the modularization of your codebase (which, IMO, has a good chance of increasing your code quality regardless of whether you eventually decide to introduce any Rust).

I wanted to up-vote that bit.

MichaelGG• 10 years ago

Since Rust and C can agree on ABI and memory layout issues, you can move the code over function-by-function if you were so inclined, right? Declare the structs in the headers and auto-gen the Rust versions (is there a tool for the inverse?).

comex2• 10 years ago

You can, but idiomatic Rust code looks pretty different from idiomatic C code - to give a concrete example,

    int get_a_string(char **out) // returns error code

could be translated literally as

    fn get_a_string(out: *mut *mut c_char) -> c_int

but much preferable would be

    fn get_a_string() -> Result<String, Errcode>

[where Result and String are standard library types; Errcode would be a custom enum.]

I suppose you could go from the first to the second incrementally, then refactor to the third. But I'm not sure it'd work well.

kibwen2• 10 years ago

This presumes that functions are well-defined boundaries in your C codebase, which may not be true if one is leaning heavily on global state.

CoconutPilot• 10 years ago

Is there an anti-pattern for this kind of thing? Its a two line bug report suggesting years of development effort. There is a huge multiplication factor between the time invested by the bug reporter and the time required to do what he asks.

alexnewman2• 10 years ago

Only if your goal is to doom the existing tor project. Lots of great research projects start this way. Often times it influences the main project or merges.

ycombinatorMan• 10 years ago

what good would come of this, to be honest?

axman6• 10 years ago

As a side note, Galois have written an implementation of Tor which happily interacts with official tor, for use in HalVM based unikernels. So, if you want ephemeral tor nodes, HalVM is a pretty great way to get it working.

Edit: Video about it [2]

[1] https://github.com/GaloisInc/haskell-tor [2] https://www.youtube.com/watch?v=oHcHTFleNtg

erlend_sh• 10 years ago

The discussion is 10 months old and never went anywhere. What makes this relevant now?

roywiggins• 10 years ago

It would be a bit embarrassing to rewrite in Rust and then have the network penetrated because they screwed up the crypto during the rewrite...

Rewrite Tor in Rust

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