niko
91 lines
5.1 KiB
Markdown
91 lines
5.1 KiB
Markdown
# Tachyon — voice server for an NGO/LiteNetLib client
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A clean-room, protocol-compatible **voice server** (project name **Tachyon**) for the Rec Room
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client's in-room proximity voice. Same clean-room posture as the sibling LuxonServer, but a
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different, unrelated protocol: compatibility logic is derived from public MIT sources (NGO, the
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community LiteNetLib transport, LiteNetLib itself) and from black-box observation of network
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traffic. The stack, bottom-up, is Dissonance over NGO over the RecRoom encrypt layer over LiteNetLib.
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Two real clients hear each other through it, in plaintext, with no client patch — and voice is
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scoped to rooms server-side.
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## Layout
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- `src/` + `CMakeLists.txt` — **Tachyon** (C++23). Dependency-light: the LiteNetLib transport comes
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from the `vendor/LiteNetLibPP` submodule, hashing from the official single-header xxHash in
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`third_party/`, and the recflare room lookup from libcurl.
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- `patches/` — `0001-tachyon-packet-layer-hook.patch`, applied to the LiteNetLibPP submodule at
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configure time (adds the datagram-layer hook the RecRoom `0x11` marker needs). See `patches/README.md`.
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- `docs/ngo-litenetlib-wire.md` — the wire specification. Read this first.
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- `docs/tachyon-findings.md` — client static-analysis findings (the full Tachyon stack).
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- `docs/client-agent-request-*.md` — questions to the client-side static-analysis agent.
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- `tools/decode_lnl.py` — decoder for hex-dump captures of LiteNetLib traffic.
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- `traffic.txt` — an early capture of the client failing to connect (see spec §7).
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- `vendor/litenetlib`, `vendor/ngo`, `vendor/mcc` — upstream reference clones, git-ignored and not
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built against; re-create if you need to re-check the spec:
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```sh
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mkdir -p vendor && cd vendor
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git clone --filter=blob:none https://github.com/Unity-Technologies/com.unity.netcode.gameobjects.git ngo
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git clone --filter=blob:none https://github.com/Unity-Technologies/multiplayer-community-contributions.git mcc
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git clone --filter=blob:none https://github.com/RevenantX/LiteNetLib.git litenetlib
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```
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(A C#/.NET reference implementation lived in `reference/` earlier and proved the protocol end to end;
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it has been removed now that the C++ server is the product. Old commits still have it.)
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## Build & run
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Needs CMake, a C++23 compiler, `libcurl-devel` (room lookup) and `openssl-devel` (blob decryption)
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— e.g. `sudo dnf install libcurl-devel openssl-devel`. `vendor/LiteNetLibPP` is a submodule, so
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clone with it:
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```sh
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git clone --recurse-submodules <repo> # or: git submodule update --init --recursive
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cmake -S . -B build -DCMAKE_BUILD_TYPE=Release
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cmake --build build -j
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./build/tachyon --config tachyon.conf # or all-flags; fork+dissonance+0x11+rooms are defaults
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```
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Settings load from a `key = value` config file (`--config`, see `tachyon.conf.example`); CLI flags
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override it. The RSA private key that decrypts the client's wire blobs (`AT`/`VB`/`CKA`/`CIA`/`CPK`)
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is set via `private_key` in the config or `--private-key <file>` — a `.NET RSAKeyValue` XML file.
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Offline self-test (no network): `./build/tachyon --selftest [batch.hex]` — checks packing, batch
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build↔parse + hashes (fork & stock), and Dissonance primitives; exit 0 = pass. An optional captured
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NGO batch (hex) is fed through the parser.
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Flags: `--no-fork` / `--no-dissonance` / `--no-encrypt` / `--no-rooms` / `--room-url <u>` /
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`--room-timeout <ms>` / `--ds-count-width N`, plus logging: `-v`/`--verbose` (debug: per-message +
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per-relay), `-q`/`--quiet` (warnings/errors only), `--log-level error|warn|info|debug`. The default
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is **info** — a startup banner plus connect/disconnect/handshake lifecycle and all warnings, quiet
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enough to run as a service. It logs to stdout (line-buffered) and shuts down cleanly on SIGINT/SIGTERM
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(exit 0), so a minimal systemd unit is just:
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```ini
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[Service]
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ExecStart=/path/to/tachyon --port 7777 --quiet
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Restart=on-failure
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```
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With `--verbose`, a connection walks through, in order: LiteNetLib connect accepted →
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`ConnectionRequest` parsed → `ConnectionApproved` sent → room resolved (`account=… -> room=…`) →
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Dissonance `HandshakeResponse` → `ClientState` roster relays → `[relay] … delivered=1/1` when
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same-room clients talk.
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## Current status
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Works end to end against the real client (build 20250718.01): LiteNetLib (ProtocolId 13) + RecRoom
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`0x11` marker + forked NGO batch + the Tachyon `"Carrot"` approval + the Dissonance session/relay,
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all plaintext. Same-room clients hear each other; cross-room is silent; room membership follows
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players live as they switch rooms (resolved per handshake from recflare).
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## Scope
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Connection handshake, time sync, the Dissonance session handshake, voice relay (ServerRelay unwrap +
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per-client fan-out), and **server-side room scoping**. Rooms come from recflare
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(`GET <room-url>?id=<AccountId>` → room instance id — there is no room id on the wire); each room
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gets its own Dissonance session, and the relay/roster are scoped to same-room peers, with a
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lookup-failure fail-safe that isolates the client. There is no object replication, no NetworkVariable
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sync and no scene management — the client build does not contain those message types.
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