TeslaRel410/emulator/NET-NOTES.md

# Networking subsystem — recon & bring-up plan

Goal: bring the pod network up under the emulator so a pod boots the
production way (`netnub -f BTL4OPT`, mission egg delivered **over the
wire**) instead of the `-egg test.egg` dev bypass. This is also the
substrate the ops-console port will plug into.

## What the pod network actually is (recon 2026-07-04)

The stack, bottom to top:

1. **Ethernet NIC + Novell ODI** (AUTOEXEC.BAT): `lsl` (Link Support
   Layer) → `lnepci` (Lance/PCnet PCI ODI driver) → **`odipkt`** (Dan
   Lanciani's ODI→Packet-Driver shim). The ODI/Netware login side
   (IPXODI/VLM/NET LOGIN in STARTNET.BAT) is for file-server access; the
   game itself only needs the **packet-driver interface** odipkt exposes.
   `NET.CFG`: LNEPCI, FRAME Ethernet_II + 802.2.
2. **WATTCP** — the TCP/IP stack. Confirmed by `WATTCP.CFG` in
   `REL410/BT`, `REL410/RP`, and per-pod `VGL_LABS/THISPOD`:
   ```
   my_ip = 200.0.0.113   netmask = 255.255.255.0
   gateway = 200.0.0.1   nameserver = 200.0.0.1
   ```
   So each pod is a static host on an isolated **200.0.0.0/24** LAN; the
   ops console is almost certainly **200.0.0.1**.
3. **NetNub** (`netnub.exe`, real-mode) — launches the game as a child
   (`netnub -f BTL4OPT`) and is the network server for the
   protected-mode game. Interface (`NetNub/NETNUB.HPP`): a shared `Netcom`
   struct (version 11, 64KB buffer) + a software interrupt. The game sets
   a Function code (TCP_OPEN=3, TCP_LISTEN=4, TCP_CLOSE=5,
   RESOLVE_ADDRESS=6, CHECK_SOCKET=7, UDP_*, plus remote file
   OPEN/READ/WRITE/SEEK/CLOSE 12-19), copies the marked fields to real
   mode, INTs, copies back. `tcp_Socket` is ~4300 bytes = classic WATTCP.
4. **L4NetworkManager** (`L4NET.HPP/.TCP`) — the game's net brick. The
   **console is master and connects to the pods**; the pod receives
   `ReceiveEggFileMessage` (the mission egg), replies
   `AcknowledgeEggFileMessage` ("connected, ready, send the next host"),
   and tracks `HostConnected/HostDisconnected`. If the console drops, the
   pod is built to auto-start anyway.

Topology to replicate:
```
   [ops console 200.0.0.1] --TCP--> [pod 200.0.0.113]  (+ more pods .114..)
        (master, egg source)          (listens, ACKs, runs mission)
```

## Emulator enablers (already in the fork)

- **NE2000** ISA NIC emulated (`hardware/ne2000.cpp`, Bochs-derived);
  config `[ne2000] ne2000=true, nicbase=, nicirq=, macaddr=, backend=`.
- **Two Ethernet backends** built: `misc/ethernet_pcap.cpp` (bridge to a
  host NIC via npcap) and `misc/ethernet_slirp.cpp` (user-mode virtual
  net / NAT). Plus `ethernet_nothing`.

Key simplification: the emulated card is an **NE2000, not a PCI Lance**, so
`lnepci` won't bind. We don't need the Novell ODI chain at all — WATTCP
finds a packet driver by scanning INT 0x60-0x80 for the `PKT DRVR`
signature, so we load a generic **NE2000 packet driver** (Crynwr
`NE2000.COM`) directly against the emulated card's base/IRQ. That drops
lsl/lnepci/odipkt/VLM entirely and hands NetNub/WATTCP the packet
interface they expect.

## Bring-up plan

**Backend choice.** Two viable paths:
- *pcap + host-only adapter (recommended, matches real topology):* bridge
  the NE2000 to a host virtual switch; run the pod at 200.0.0.113 and the
  stand-in console at 200.0.0.1 on that segment. WATTCP's static IP + LAN
  assumptions hold exactly; the console connects inbound to the pod with
  no NAT. Cost: npcap + a host-only/loopback adapter + admin.
- *slirp (fallback, self-contained):* no host NIC/admin, but it's NAT and
  defaults to 10.0.2.0/24 — the pod LISTENS, so inbound needs slirp
  host-forwarding and a guest-network/IP reconciliation with WATTCP's
  hard-coded 200.0.0.113. Investigate whether DOSBox-X slirp allows the
  custom net + static guest IP + inbound forward cleanly.

**Milestones**
1. **NIC up**: `[ne2000]` on, NE2000.COM packet driver loaded, WATTCP/
   NetNub start clean; pod boots via `netnub -f BTL4OPT` (no `-egg`) and
   sits waiting for the console. Verify NetNub reports net address
   200.0.0.113 and a TCP_LISTEN is queued. (New scratch conf, mirror the
   RIO/sound conf pattern.)
2. **L3/L4 reachability**: from the host segment, confirm the pod answers
   ARP/ping at 200.0.0.113 and a raw TCP connect to its listen port
   completes (proves NE2000↔backend↔host path end-to-end).
3. **Decode the console→pod egg protocol**: `NetworkPacketHeader` +
   message framing from `network.hpp`/`hostmgr.hpp` + the
   ReceiveEggFileMessage layout, cross-checked with a live capture of the
   pod's listen/ACK. (Pin the listen port here — not yet found in source;
   grep NETNUB.EXE strings / capture.)
4. **Eggs over the wire**: a minimal host-side **stand-in console**
   (Python) connects to the pod, pushes a mission egg, handles the ACK →
   pod runs the mission with no `-egg` bypass. **This is the headline
   goal.**
5. *(later, joins the console-port workstream):* replace the stand-in
   with the ported/emulated Mac ops console; multi-pod coordination
   (HostConnected/Disconnected, mission review, camera ship).

## Open questions / notes
- Exact TCP listen port(s) — not in the source grep; get from NETNUB.EXE
  or a capture at milestone 3.
- Does WATTCP need a real ARP peer for the gateway at boot, or does it
  proceed with a static IP and only ARP on connect? Affects whether the
  stand-in console must answer ARP for 200.0.0.1.
- `NETCLIENT=PNW` (PARAMETR.bat) selects Personal NetWare — file-server
  side, not the game's TCP path; likely irrelevant to egg delivery and
  can stay unloaded under emulation.
- RP uses the identical MUNGA net brick + its own WATTCP.CFG — everything
  here carries over to Red Planet.