# tor-relay-selection
Logic to select Tor relays for specific purposes
## Overview
The `tor-relay-selection` crate provides higher-level functions
in order to select Tor relays for specific purposes,
or check whether they are suitable for those purposes.
It wraps lower-level functionality from `tor-netdir`.
This crate is part of
[Arti](https://gitlab.torproject.org/tpo/core/arti/), a project to
implement [Tor](https://www.torproject.org/) in Rust.
## Design
Our main types are `RelayUsage`, `RelayExclusion`, `RelayRestriction`, and `RelaySelector`.
A `RelayUsage` answers the question "what is this relay for?"
A `RelayExclusion` excludes one or more relays
as having already been selected,
or as sharing families with already-selected relays.
A `RelayRestriction` imposes additional restrictions on a relay.
A `RelaySelector` is a collection of a usage, an exclusion, and any number of restrictions.
In a `RelaySelector`, usages and restrictions can be strict or flexible.
If we fail to pick a relay, and there are any flexible usages/restrictions,
then we remove those usages/restrictions to produce a _relaxed_ selector
and we try again.
License: MIT OR Apache-2.0