96875ea208
Because we want to work more on ensuring that our semver stability story is solid, we are _not_ bumping arti-client to 1.0.0 right now. Here are the bumps we _are_ doing. Crates with "minor" bumps have had API breaks; crates with "patch" bumps have had new APIs added. Note that `tor-congestion` is not bumped here: it's a new crate, and hasn't been published before. ``` tor-basic-utils minor fs-mistrust minor tor-config minor tor-rtcompat minor tor-rtmock minor tor-llcrypto patch tor-bytes patch tor-linkspec minor tor-cell minor tor-proto minor tor-netdoc patch tor-netdir minor tor-persist patch tor-chanmgr minor tor-guardmgr minor tor-circmgr minor tor-dirmgr minor arti-client minor arti-hyper minor arti major arti-bench minor arti-testing minor ``` |
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README.md
tor-cell
Coding and decoding for the cell types that make up Tor's protocol
Overview
Tor's primary network protocol is oriented around a set of messages called "Cells". They exist at two primary layers of the protocol: the channel-cell layer, and the relay-cell layer.
Channel cells are sent between relays, or between a client and a relay, over a TLS connection. Each of them encodes a single Channel Message. Channel messages can affect the channel itself (such as those used to negotiate and authenticate the channel), but more frequently are used with respect to a given multi-hop circuit.
Channel message that refer to a circuit do so with a channel-local identifier called a Circuit ID. These messages include CREATE2 (used to extend a circuit to a first hop) and DESTROY (used to tear down a circuit). But the most frequently used channel message is RELAY, which is used to send a message to a given hop along a circuit.
Each RELAY cell is encrypted and decrypted (according to protocols not implemented in this crate) until it reaches its target. When it does, it is decoded into a single Relay Message. Some of these relay messages are used to manipulate circuits (e.g., by extending the circuit to a new hop); others are used to manipulate anonymous data-streams (by creating them, ending them, or sending data); and still others are used for protocol-specific purposes (like negotiating with an onion service.)
For a list of most of the cell types used in Tor, see tor-spec.txt. Other cell types are defined in rend-spec-v3.txt (for onion services) and padding-spec.txt (for padding negotiation).
This crate is part of Arti, a project to implement Tor in Rust.
Futureproofing note
There are two pending proposals to remove the one-to-one correspondence between relay cells and relay messages.
Proposal 319 would add a "RELAY_FRAGMENT" command that would allow larger relay messages to span multiple RELAY cells.
Proposal 325, on the other hand, would allow multiple relay messages to be packed into a single RELAY cell.
The distinction between RelayCell and RelayMsg is meant in part to future-proof arti against these proposals if they are adopted.
License: MIT OR Apache-2.0