If the Windows client is killed hard, the TAP adapter can be left in a connected media state. A retry should not resolve or connect to the relay while stale TAP state might still influence Windows routing. Select and open the intended TAP adapter before relay endpoint resolution, force its media state to disconnected, then proceed with the existing relay connect, route pin, TAP route protection, and bridge startup flow. This also makes missing or ambiguous TAP adapters fail before the client joins the relay room. The README and MVP test guide now show the new startup line and the early TAP preflight troubleshooting checks. Test Plan: All cargo commands used these environment variables: RUSTUP_HOME=/tmp/softlan-vpn-rustup CARGO_HOME=/tmp/softlan-vpn-cargo - cargo fmt --check - cargo test --workspace - cargo clippy --workspace --all-targets -- -D warnings - cargo check -p lanparty-client-tap --tests --target x86_64-pc-windows-gnu - cargo check -p lanparty-client-tap --tests --target x86_64-pc-windows-msvc - cargo check -p lanparty-client-route --tests --target x86_64-pc-windows-gnu - cargo check -p lanparty-client-route --tests --target x86_64-pc-windows-msvc - git diff --check Known limitation: full lanparty-client-win Windows cross-check is still blocked on this Linux host by the external ring toolchain setup. The default GNU target lacks x86_64-w64-mingw32-gcc, the default MSVC target lacks lib.exe, and the LLVM MSVC attempt gets as far as ring C compilation but lacks Windows CRT headers such as assert.h. Refs: PLAN.md route-protection startup requirement
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MVP Test Guide
This guide is for the manual end-to-end MVP proof:
Windows TAP client -> public QUIC relay -> Linux AF_PACKET gateway -> LAN
The MVP is intentionally manual. It does not include an installer, GUI, production certificates, auth, or end-to-end payload encryption.
Machines
- Relay: public Linux host reachable over UDP.
- Gateway: Linux machine plugged into the LAN party switch with wired Ethernet.
- Client: Windows 11 machine with TAP-Windows6 installed.
Use the same room code everywhere, for example ROOM1.
Build
On the relay or Linux build host:
cargo build --release -p lanparty-relay -p lanparty-gateway
On Windows, in an Administrator terminal:
cargo build --release -p lanparty-client-win
The Windows client must run elevated because it opens TAP and edits routes. The gateway usually needs root because it opens an AF_PACKET raw socket.
Start The Relay
Use a high UDP port first unless you already want to deal with privileged
443/udp binding:
./target/release/lanparty-relay \
--listen 0.0.0.0:8443 \
--dev-cert-der-out relay-cert.der
Open inbound UDP for the selected port on the relay host firewall.
Expected relay output:
lanparty-relay configured for 0.0.0.0:8443/udp ...
lanparty-relay listening on 0.0.0.0:8443
Copy relay-cert.der to the gateway and Windows client. The development
certificate is for lanparty-relay.local, so keep
--server-name lanparty-relay.local even when --relay is an IP address or
another DNS name.
Start The Gateway
On the LAN gateway machine:
sudo ./target/release/lanparty-gateway \
--relay relay.example.net:8443 \
--server-name lanparty-relay.local \
--relay-ca-cert ./relay-cert.der \
--room ROOM1 \
--iface eth0
Use the real wired LAN interface name for --iface. Do not use Wi-Fi.
Expected gateway output:
lanparty-gateway opening interface eth0 and connecting to relay ...
lanparty-gateway opened AF_PACKET socket on eth0 ...
lanparty-gateway connected as peer ...
lanparty-gateway bridging frames; press Ctrl-C to stop
Expected relay output:
accepted Gateway peer ... in room ROOM1 ...
Start The Windows Client
In an Administrator terminal on Windows:
.\target\release\lanparty-client-win.exe `
--relay relay.example.net:8443 `
--server-name lanparty-relay.local `
--relay-ca-cert .\relay-cert.der `
--room ROOM1
If the Windows machine has multiple TAP-Windows6 adapters, select the intended one explicitly:
.\target\release\lanparty-client-win.exe --list-tap-adapters
.\target\release\lanparty-client-win.exe `
--relay relay.example.net:8443 `
--server-name lanparty-relay.local `
--relay-ca-cert .\relay-cert.der `
--room ROOM1 `
--tap-instance-id "{InterfaceGuid-from-the-command-above}"
Expected client output:
prepared TAP adapter ... media disconnected before relay connect
lanparty-client-win connected as peer ...
relay route pinned before TAP ...
relay route verified after TAP activation ...
TAP driver reports MAC ... and MTU ...
client diagnostics: relay reachable yes gateway connected yes route pinned yes ...
The route pin line ends with (created) or (already existed). Either is OK.
already existed usually means a matching relay host route was already present,
for example after a previous crashed test run.
The first diagnostics line may show IP unknown. After DHCP succeeds, a later
line should show:
DHCP received: 10.x.x.x
What To Verify
- Relay sees both peers:
accepted Gateway peer ...
accepted Client peer ...
- Client sees the gateway:
gateway connected yes
Connected to LAN gateway
- Windows TAP gets an address from the LAN:
Get-NetIPAddress | ? InterfaceAlias -like "*TAP*"
- ARP and ping work from the TAP-side address:
arp -d *
ping -S <tap-ip> <lan-host-ip>
arp -a
- The LAN switch learns the remote client MAC on the gateway port.
Use the switch UI or CLI and look for the client MAC printed by the Windows client. It should appear on the physical port connected to the Linux gateway.
- A real LAN game discovers or joins a LAN server.
This is the practical MVP acceptance test.
Useful Log Signals
Relay frame forwarding:
relay frame room=ROOM1 ... action=Forwarded drop_reason=- targets=1
Gateway LAN traffic:
gateway frame interface=eth0 direction=LanToRemote ... action=Forwarded
gateway frame interface=eth0 direction=RemoteToLan ... action=Forwarded
Client health:
Relay RTT: 23 ms
Broadcast traffic flowing
Drops that can be normal during testing:
drop_reason=UnknownDestination
drop_reason=DatagramBudget
drop_reason=RateLimit
Drops that should be investigated if they dominate:
drop_reason=Malformed
drop_reason=UnauthorizedSourceMac
drop_reason=ControlPlaneEtherType
Troubleshooting
If the client says Waiting for LAN gateway, check that the gateway uses the
same room code and is connected to the same relay.
If startup fails before the relay connection while preparing the TAP adapter,
check that the terminal is elevated, TAP-Windows6 is installed, and
--tap-instance-id selects the intended adapter when more than one TAP adapter
exists.
If the client says Waiting for TAP IP, DHCP is not making the full round trip.
Check relay/gateway frame logs for broadcast traffic and check that the gateway
is on wired Ethernet.
If startup fails with a TAP MAC mismatch, disable/enable the TAP adapter or
reinstall TAP-Windows6 so Windows reloads the NetworkAddress value. Do not
continue with a mismatched MAC.
If startup says the relay route changed, stop. The client is refusing to run because Windows would route the relay connection through the tunnel.
If ping fails but DHCP worked, check Windows firewall, the target LAN host
firewall, and whether the LAN subnet conflicts with the client's home LAN.
Uncommon LAN subnets such as 10.73.42.0/24 are safer than 192.168.0.0/24.
Cleanup
Stop client, gateway, and relay with Ctrl-C. The Windows client removes the relay host route only when it created that route itself, restores the TAP route policy, and marks TAP media disconnected when it exits normally.
Keep lanparty-client-identity.json if you want the same virtual MAC on the
next run. Delete it only when you intentionally want a new client identity.
Report Back
For a useful test report, capture:
- relay command and relay logs
- gateway command and gateway logs
- client command and client logs
- Windows TAP MAC and IP
- ping result from
<tap-ip>to a LAN host - switch MAC-table entry for the Windows client MAC
- LAN game discovery or join result