softlan-vpn/README.md

# softlan-vpn

Monorepo for a Layer 2 over QUIC LAN party bridge.

## Workspace crates

- `lanparty-proto`: shared frame format, MAC validation, MTU helpers.
- `lanparty-ctrl`: control-plane messages (join/hello/role/version).
- `lanparty-obs`: shared diagnostics/logging event models.
- `lanparty-client-core`: platform-agnostic client session state.
- `lanparty-client-route`: Windows relay-route inspection.
- `lanparty-client-tap`: TAP-Windows6 adapter discovery and frame I/O.
- `lanparty-client-win`: Windows TAP + route/metric handling binary.
- `lanparty-gateway`: Linux AF_PACKET gateway binary.
- `lanparty-relay`: public QUIC relay binary.

### `lanparty-proto`

Transport-agnostic tunnel contract shared by all binaries:

- overlay datagram header encoding and decoding
- Ethernet frame header parsing
- MAC address parsing and identity validation
- QUIC datagram to TAP MTU budget helpers

### `lanparty-ctrl`

Reliable control-plane schema shared by the QUIC stream handlers:

- endpoint hello messages with role, room, MAC, and datagram budget
- server welcome, reject, peer lifecycle, stats, and disconnect messages
- room-code, role/MAC, peer-id, and effective-MTU validation
- length-prefixed JSON control frames for reliable QUIC streams

### `lanparty-obs`

Shared diagnostics and structured logging vocabulary:

- gateway/relay frame logs with MACs, ethertype, length, peer, and action
- tunnel counters shared by control messages and runtime diagnostics
- client connectivity/TAP diagnostics and user-facing status messages

### `lanparty-client-core`

Platform-neutral remote client relay session:

- relay QUIC connection with pinned relay certificate trust
- client hello with room, virtual MAC, and datagram budget
- welcome/reject handling with assigned peer id and effective TAP MTU
- Ethernet frame send/receive helpers over QUIC DATAGRAM

### `lanparty-client-route`

Windows route-table boundary:

- read-only best-route lookup for a relay destination IP
- selected source address, next hop, interface index/LUID, prefix, and metric
- non-Windows builds return a clear unsupported-platform error

### `lanparty-client-tap`

Windows TAP adapter boundary:

- TAP-Windows6 adapter discovery from the Windows network adapter registry
- `\\.\Global\{NetCfgInstanceId}.tap` device path construction
- blocking Ethernet frame reads/writes through the TAP device handle
- TAP driver IOCTL helpers for media status, adapter MAC, and MTU

### `lanparty-relay`

Public relay binary and relay-owned room state:

- QUIC endpoint binding and first-stream hello/welcome admission
- room admission for clients and gateways
- one gateway per room, duplicate client MAC rejection, and room limits
- stable effective room MTU chosen before Ethernet datagrams flow
- live Ethernet datagram forwarding with no ingress reflection
- L2 safety filters for jumbo, switch-control, DHCP-server, and IPv6-RA frames
- peer leave cleanup for room membership and MAC indexes

## Build

```bash
cargo check --workspace
```

## Relay

```bash
cargo run -p lanparty-relay -- --listen 443/udp --dev-cert-der-out relay-cert.der
```

`--listen` accepts either a socket address or a UDP port shorthand such as
`443/udp`. The relay binds a QUIC endpoint, accepts a control-stream `hello`,
replies with `welcome` or `reject`, and forwards live Ethernet QUIC datagrams
between accepted peers in the same room. It currently uses a generated
self-signed development certificate; `--dev-cert-der-out` writes that
certificate so the gateway and client can pin it in development. Production
certificate handling remains future work. Ethernet forwarding decisions are
logged with room, peer, MAC, ethertype, action, drop reason, and target count.

## Gateway

```bash
cargo run -p lanparty-gateway -- \
  --relay 203.0.113.10:443 \
  --server-name lanparty-relay.local \
  --relay-ca-cert relay-cert.der \
  --room ROOM1 \
  --interface eth0
```

The gateway connects to the relay as `role = gateway`, completes the
control-stream hello/welcome handshake, opens an AF_PACKET socket on the LAN
interface, and bridges Ethernet frames between the relay and wired LAN until
shutdown. It tracks remote-client source MACs seen from relay traffic and
periodically emits small CAM refresh frames so the physical switch keeps those
MACs associated with the gateway port.

## Windows Client

```bash
cargo run -p lanparty-client-win -- \
  --relay 203.0.113.10:443 \
  --server-name lanparty-relay.local \
  --relay-ca-cert relay-cert.der \
  --room ROOM1
```

The Windows client binary currently connects to the relay as `role = client`
with a generated locally administered virtual MAC persisted in
`lanparty-client-identity.json`, completes the control-stream hello/welcome
handshake, and then bridges Ethernet frames between the relay and the first
TAP-Windows6 adapter until shutdown. `--virtual-mac` can still override the
stored identity for manual testing. On Windows it marks the TAP media
connected and reports the driver MAC/MTU before forwarding frames. Route
pinning and automatic TAP MAC/MTU configuration are not wired yet.