82 lines
No EOL
4.5 KiB
Markdown
82 lines
No EOL
4.5 KiB
Markdown
# Netcode revival (branch `netcode-revival`)
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Goal: revive Skate 3's **original** Xbox 360 multiplayer — the game's own
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RakNet-based peer-to-peer netcode — instead of only the ghost co-presence
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layer. `main` keeps the working ghost multiplayer + releases; this branch
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carries the netcode work and stays clearly separate.
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The transport is **RakNet over XNet/XSocket** (confirmed: rexglue's XNet
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comments reference RakNet, and the game's `socket → setsockopt → bind →
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sendto` sequence matches `RakPeer::Startup`). The game speaks its own
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protocol; we only need the **platform netcode layer to work** (implement
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rexglue's stubbed XNet session APIs + route the game's UDP through the
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relay). We do not decode the game protocol.
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## Architecture
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- **Virtual addressing**: each machine gets a stable `XNADDR` (virtual IP
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`10.80.0.x` + unique 6-byte `abEnet` → RakNet GUID). `XNetXnAddrToInAddr` /
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`XNetServerToInAddr` resolve those into the socket layer's address space.
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- **Relay = P2P stabilizer**: session UDP is forwarded outbound through the
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relay (tagged `game` vs `ghost`) to the destination member's real socket;
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on a LAN the transport can go direct. The server stabilizes NAT/remote
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play but is not required on a LAN.
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- **Session registry in the relay**: `XNetQosListen` advertises a session;
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`XNetQosLookup` returns discovered sessions; the lobby/room-code UI stays
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as the manual join path.
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- **Ghost layer is kept** as the guaranteed fallback (co-presence that works
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for everyone even if the netcode path fails).
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## Phase 0 — XNet session/address layer (done, rexglue `767bd6e`)
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Implemented in `rexglue-sdk/src/kernel/xam/xam_net.cpp`:
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- `XNetGetTitleXnAddr`: stable virtual identity (was loopback + `0xCC` MAC).
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- `XNetXnAddrToInAddr` / `XNetInAddrToXnAddr` / `XNetServerToInAddr` /
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`XNetXnAddrToMachineId` / `XNetInAddrToString`: resolve virtual addresses
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(were failure / `666.666.666.666`).
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- `XNetQosListen`: accept advertisement (was `X_ERROR_FUNCTION_FAILED`).
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- `XNetQosLookup`: success + empty `XNQOS` + completion signal (Phase 1
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fills it from the relay registry).
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- `XNetCreateKey` / `XNetRegisterKey` / `XNetUnregisterKey`: session keys.
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- `XNetConnect` / `XNetGetConnectStatus`: report established.
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- `getsockopt`: real basic reads off the native socket.
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- `XNetSetSystemLinkPort`: accept.
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## Phase 1 — relay game-transport + session registry (done, built)
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- v5 relay: `kTypeGame` (opaque game UDP, unicast or room-broadcast) +
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`kTypeSessionQuery`/`Reply` (discovery). JoinPayload carries the virtual IP.
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- rexglue `XNetTransport`: joins the same relay + room as the ghost client,
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routes `sendto` to `10.80.0.x` peers through the relay, injects inbound
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game datagrams into the game's sockets, and serves session discovery to
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`XNetQosLookup`.
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- Wire structs byte-verified against the game's proto (sizes 7/31/1410/25/801)
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with `static_assert`s on both sides.
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## Test recipe (two instances on one machine, local relay)
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1. Build: `cmake --build out/build/linux-relwithdebinfo --target ghost_relay skate3 -j$(nproc)`
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2. Start the local relay: `./out/build/linux-relwithdebinfo/ghost_relay --port 40001`
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3. Launch instance A: `./out/build/linux-relwithdebinfo/skate3`
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Launch instance B (same machine; the relay loops them via 127.0.0.1).
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4. In each instance's M menu: set `skate3_ghost_server = 127.0.0.1`, enable
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multiplayer, join the SAME room code. The relay then routes both the ghost
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poses and the game's own netcode traffic.
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5. Verify in the log (stdout): `xnet transport: connecting to relay ...`,
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`xnet transport: relay joined`, and on session search
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`xnet transport: session reply with N session(s)`. Enable the game's
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online flow (invite/join) and check whether RakNet establishes a session.
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6. Two instances bind the same UDP data port → the second may fail to bind.
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If so, the game's socket bind must become relay-aware (bind to an
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ephemeral port in relay mode) — a known Phase 3 item.
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## Phase 2 — invite UI
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- `XamShowGameInviteUI` / `XamShowFriendsUI` as ImGui `XamDialog`s backed by
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the relay lobby (real player list). Receive side (`XamNotifyCreateListener`
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/ `XamSessionRefObjByHandle`) already works.
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## Phase 3 — iterate to playable
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Whatever the game needs past discovery (RakNet handshake, ports, privilege
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fakes). Ghost stays as fallback throughout.
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## Notes
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- Testing is done with **two instances on one machine** (no second device);
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the relay loops them via `127.0.0.1`. A headless harness may be added.
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- Build: `clang-22` override, preset `linux-relwithdebinfo`, per
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`docs/build.md` — same as `main`. |