claude-timemachine
f823c05aa3
Standalone Go service that routes SVC client traffic to per-server
backend voice endpoints, configured via pg LISTEN/NOTIFY (same channel
mc-router subscribes to). Each pg `servers` row with both
`voice_address` and `voice_proxy_port` set spawns a Valve: a public
UDP listener that maintains per-client ephemeral bridges to the
backend's SVC port.
Pieces:
cmd/svc-proxy/main.go entry; wires config, log fan-out,
bridge.Manager, pgsync, httpsrv
internal/config/ DATABASE_URL + BIND_HOST +
BRIDGE_IDLE_TTL (default 1m) +
HTTP_ADDR (default :8081)
internal/pgsync/ LISTEN automc_routes_changed; diff
desired/actual routes; emit Apply()
internal/bridge/ Valve per public port; per-client
bridge with atomic up/down byte counters;
idle eviction every 15s against TTL
internal/httpsrv/ operator UI — embedded single-page HTML
with active-connections table polled
every 1s + SSE log stream
(last 500 lines backlog on connect)
Reverse-proxied behind server-manager at /infra/svc-proxy/* — bind
internal-only addresses for production; auth is the dashboard's
Basic gate.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
91 lines
4.3 KiB
Markdown
91 lines
4.3 KiB
Markdown
# svc-proxy
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Standalone UDP "valve" for [Simple Voice Chat](https://github.com/henkelmax/simple-voice-chat). Per-server public UDP port → backend voice address. Routes read from Postgres via `LISTEN`/`NOTIFY`, same pattern as `mc-router`.
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## What it does
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Each MC server in the automc fleet runs SVC on its own UDP port inside its container (default 24454). svc-proxy exposes a **public** UDP port per server and bridges client traffic to the backend. SVC's own `SecretPacket` is configured per backend to advertise the public proxy hostname + the assigned proxy port, so the client connects directly to the proxy — no MITM, no plugin-channel sniffing.
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```
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SVC client ──UDP──► svc-proxy.timemachine.center:24455
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│
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├── (per-server valve)
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│
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└──UDP──► mc-gtnh:24454 (backend SVC)
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```
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The proxy is **opaque** to the SVC payload — it can read the cleartext outer header (magic byte + player UUID) but the AES-GCM body stays end-to-end. Source-address bridges (one ephemeral upstream socket per client `SocketAddress`) survive NAT rebinds within the idle TTL.
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## pg schema
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Two new columns on `servers`:
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| Column | Type | Meaning |
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|---|---|---|
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| `voice_address` | text | Backend SVC address — `<host>:<port>` reachable from svc-proxy |
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| `voice_proxy_port` | int | Public UDP port svc-proxy binds for this server |
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Rows with both NULL are ignored. Owner of allocation: **server-manager** (assigns the next free port from a configured pool when the server is provisioned; clears on delete).
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## NOTIFY channel
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Reuses `automc_routes_changed` from `mc-router`. The trigger on `servers` already fires on UPDATE, so adding/clearing the voice columns refreshes svc-proxy's bindings without restart.
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## Environment
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| Env | Default | Effect |
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|---|---|---|
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| `DATABASE_URL` | (required) | pgx DSN |
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| `BIND_HOST` | `0.0.0.0` | host for the per-server UDP listeners |
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| `BRIDGE_IDLE_TTL` | `5m` | tear down per-client upstream sockets after this much silence |
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| `LOG_LEVEL` | `info` | `debug` / `info` / `warn` |
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## Operator UX
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```bash
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# Allocate voice ports for an existing server (server-manager does this normally)
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UPDATE servers
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SET voice_address = 'mc-gtnh:24454',
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voice_proxy_port = 24455
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WHERE name = 'gtnh';
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NOTIFY automc_routes_changed;
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```
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svc-proxy logs `valve open: :24455 → mc-gtnh:24454 (gtnh)` and is ready.
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To retire a server's voice routing:
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```bash
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UPDATE servers SET voice_address = NULL, voice_proxy_port = NULL WHERE name = 'gtnh';
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NOTIFY automc_routes_changed;
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```
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svc-proxy logs `valve close: :24455 (gtnh)`. In-flight bridges are torn down.
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## Backend-side configuration
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The SVC plugin on the backend must advertise the **public** proxy address to clients (not the backend's own LAN address). Set in the backend's SVC config (`config/voicechat-server.properties`):
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```properties
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voice_host=svc-proxy.timemachine.center:24455
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```
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…or via env if mc-wrapper templates it. SVC bakes this into `SecretPacket.voiceHost`, the client uses it verbatim.
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## Why not the SVC bundled proxy
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SVC ships proxy support for BungeeCord/Velocity (`common-proxy` module). It sniffs the MC `voicechat:secret` plugin message and rewrites the host on the fly, then NAT-bridges UDP. That requires the SVC proxy to live inside the MC proxy process. We run mc-router (Go) instead of a Java MC proxy on the edge, so the bundled approach doesn't apply.
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svc-proxy is the equivalent for the mc-router shape: pure UDP data plane, pg-driven config, no plugin hooks.
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## Limitations
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- No replay protection at the proxy layer (SVC's AES-GCM is the only freshness guarantee — same as upstream).
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- No client rate-limiting (SVC's plugin-channel rate limit covers TCP setup; UDP audio relies on Opus payload caps + the wrapper's `BRIDGE_IDLE_TTL` to bound per-source sockets).
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- Bridge ephemeral upstream sockets aren't pooled — one syscall per concurrent client. Fine up to a few thousand concurrent voice users on a single proxy host.
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## Related
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- [mc-router (Timemachine fork)](https://git.timemachine.center/Timemachine/mc-router) — same NOTIFY channel, same pg-driven route source.
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- [Simple Voice Chat](https://github.com/henkelmax/simple-voice-chat) — upstream mod whose wire protocol we pass through.
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