softlan-vpn/TESTING.md

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.

Fast Path

Run the test in this order:

1. Build the relay and gateway on Linux, and build the Windows client on Windows.
2. Start the relay and keep relay-cert.der.
3. Copy relay-cert.der to the gateway and Windows client.
4. Start the Linux gateway on the wired LAN interface.
5. Start the Windows client from an elevated terminal.
6. Verify DHCP, ping -S, switch MAC learning, and one LAN game.
7. Restart the gateway once while the client stays up.

MVP Pass Conditions

The MVP proof is successful when all of these are true:

• Relay shows one gateway peer and one Windows client peer in the same room.
• Windows client reports gateway connected yes.
• Windows TAP adapter gets a real LAN DHCP address, not only 169.254.x.x.
• A LAN host can be reached from the TAP address with ping -S.
• The physical switch learns the Windows client MAC on the Linux gateway port.
• A LAN game can discover or join a server through the TAP adapter.

Fill these in before starting so the commands below are just copy/edit/run:

relay host:     relay.example.net
relay UDP port: 8443
room code:      ROOM1
gateway iface:  eth0
LAN test host:  <lan-host-ip>

Keep these values from the logs as you go:

gateway peer id:
client peer id:
client virtual MAC:
Windows TAP IPv4:

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. Start order is relay first, gateway second, Windows client last.

Log Capture

Keep one log per process. They are the easiest way to diagnose a failed run.

On Linux:

./target/release/lanparty-relay ... 2>&1 | tee relay.log
sudo ./target/release/lanparty-gateway ... 2>&1 | tee gateway.log

On Windows PowerShell:

Start-Transcript .\client.log
.\target\release\lanparty-client-win.exe ...
Stop-Transcript

Build Prerequisites

On Windows, use the Rust MSVC toolchain and install Visual Studio Build Tools with the C++ build tools. The dependency stack includes native code, so tools such as cl.exe and lib.exe must be available in the build environment. TAP-Windows6 must be installed before running the client.

Use an elevated x64 Native Tools Command Prompt for VS or Developer PowerShell for VS for the Windows build and client run. If the commands below cannot find cl, lib, or link, install or repair Visual Studio Build Tools with the C++ build tools and Windows SDK, then reopen the developer shell.

Quick Windows checks:

rustc -vV
where.exe cl
where.exe lib
where.exe link

rustc -vV should report a host containing x86_64-pc-windows-msvc.

Local Preflight

Run these before moving to the hardware test:

cargo fmt --check
cargo test --workspace
cargo clippy --workspace --all-targets -- -D warnings
cargo build --release -p lanparty-relay -p lanparty-gateway
git diff --check

The workspace tests include real client/relay/gateway session coverage for DHCP-shaped traffic, ARP-shaped traffic, ICMPv4 ping-shaped traffic, UDP broadcast discovery traffic, and gateway restart lifecycle. They do not prove the Windows TAP driver, real LAN DHCP, physical switch MAC learning, or a real game. Those are the manual pass conditions below.

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

Then confirm the binary starts and can see TAP-Windows6:

.\target\release\lanparty-client-win.exe --help
.\target\release\lanparty-client-win.exe --list-tap-adapters

The adapter list should show at least one TAP-Windows6 adapter before the full tunnel run. If it does not, fix the TAP install first.

The binaries used below are:

Linux:   ./target/release/lanparty-relay
Linux:   ./target/release/lanparty-gateway
Windows: .\target\release\lanparty-client-win.exe

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 wrote development certificate to relay-cert.der
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 \
  --interface eth0

Use the real wired LAN interface name for --interface. --iface is accepted as a shorter alias. Do not use Wi-Fi. The gateway fails before joining the relay if sysfs reports no Ethernet carrier.

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 ...

Leave this running before starting the Windows client.

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 ... MAC ... configured and media disconnected before relay connect
relay route pinned before TAP ...
relay route verified before TAP activation ...
lanparty-client-win connecting virtual MAC ... to relay ... room ROOM1
lanparty-client-win connected as peer ...; LAN gateway connected yes (peer ...)
lanparty-client-win opened TAP adapter ...
TAP driver reports MAC ... and MTU ...
TAP interface index ... LUID ...
relay route verified after TAP activation ...
client diagnostics: relay reachable yes gateway connected yes route pinned yes ...
bridging TAP frames; relay route is pinned and TAP route policy is scoped ...
relay event: LAN gateway connected as peer ...

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. You may also see TAP IPv4/IPv6 MTU, metric, and default-route protection lines between the connect and TAP-open lines. Those are expected. The lifecycle event may appear after the bridge starts because event logging begins once TAP and route protection are ready.

The first diagnostics line may show IP unknown. After DHCP succeeds, a later line should show:

DHCP received: 10.x.x.x

If Windows reports both a 169.254.x.x TAP address and a real LAN IPv4 address, the client diagnostics should prefer the real LAN address.

Verify The Tunnel

1. Relay sees both peers:

accepted Gateway peer ...
accepted Client peer ...

2. Client sees the gateway:

gateway connected yes
Connected to LAN gateway

3. Windows TAP gets an address from the LAN:

Get-NetIPAddress | ? InterfaceAlias -like "*TAP*"
Get-NetRoute | ? InterfaceAlias -like "*TAP*" | ft -AutoSize

Use the non-link-local IPv4 address as <tap-ip> in the next step.

4. ARP and ping work from the TAP-side address:

arp -d *
ping -S <tap-ip> <lan-host-ip>
arp -a

5. 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.

6. A real LAN game discovers or joins a LAN server.

This is the practical MVP acceptance test.

Lifecycle Sanity Check

Run this after the basic tunnel works. It verifies that the room lifecycle is visible to the Windows client and that a gateway restart does not leave stale status behind.

1. Stop the gateway with Ctrl-C while the relay and client keep running.

Expected client output:

relay event: LAN gateway disconnected (peer ..., Normal)
client diagnostics: relay reachable yes gateway connected no ...
Warning: Waiting for LAN gateway

2. Start the gateway again with the same relay, room, cert, and interface.

Expected client output:

relay event: LAN gateway connected as peer ...
client diagnostics: relay reachable yes gateway connected yes ...
Connected to LAN gateway

The diagnostics line is periodic, so it may appear up to one diagnostics interval after the lifecycle event. After reconnect, repeat one quick ping -S <tap-ip> <lan-host-ip>.

Useful Log Signals

Relay frame forwarding:

relay frame room=ROOM1 ... action=Forwarded drop_reason=- targets=1

Gateway LAN traffic:

gateway control event: client peer ... joined with MAC ...
gateway frame interface=eth0 direction=LanToRemote ... action=Forwarded
gateway frame interface=eth0 direction=RemoteToLan ... action=Forwarded
gateway CAM refresh interface=eth0 peer_id=... mac=... reason=peer_joined
gateway CAM refresh interface=eth0 peer_id=... mac=... reason=periodic

Client health:

Relay RTT: 23 ms
Broadcast traffic flowing
Broadcast sent toward LAN; waiting for LAN broadcast reply
LAN broadcast received
client frame direction=TapToRelay ... action=Forwarded drop_reason=-
client frame direction=RelayToTap ... action=Forwarded drop_reason=-
client frame direction=RelayToTap ... action=Filtered drop_reason=UnknownDestination

A filtered RelayToTap line means the client received a relay frame but kept it out of the TAP adapter. Occasional unrelated unicast can be normal; repeated filtered DHCP, broadcast, or LAN-game traffic is worth investigating with the drop reason.

Drops that can be normal during testing:

drop_reason=UnknownDestination
drop_reason=TapMtuExceeded
drop_reason=DatagramBudget
drop_reason=RateLimit

On gateway LanToRemote logs, UnknownDestination usually means the gateway captured unrelated LAN unicast and dropped it locally instead of sending it to the relay. TapMtuExceeded means a host emitted an Ethernet frame larger than the negotiated tunnel MTU; occasional drops can happen while testing software that does not honor the smaller adapter MTU yet.

Drops that should be investigated if they dominate:

drop_reason=Malformed
drop_reason=InvalidSourceMac
drop_reason=UnauthorizedSourceMac
drop_reason=ControlPlaneEtherType
drop_reason=VlanTaggedFrame
drop_reason=DhcpServerReply
drop_reason=Ipv6RouterAdvertisement
drop_reason=Ipv6Fragment

On gateway RemoteToLan logs, UnauthorizedSourceMac means the relayed peer id did not match the client MAC announced by lifecycle events. If it repeats, check relay lifecycle logs and duplicate-MAC rejection first.

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 the client stays on gateway connected yes after the gateway has stopped, capture the relay and client lifecycle logs. The client should clear this state from the gateway peer id it received during welcome or peer-join catch-up.

If the gateway fails with reports no carrier, plug the selected Ethernet interface into the LAN party switch, bring the interface up, and restart the gateway.

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 the client reports a TAP link-local address such as 169.254.x.x, treat it the same way: Windows has self-assigned an address, but LAN DHCP did not complete through the tunnel.

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.

If switch MAC learning does not show the Windows client MAC on the gateway port, look for gateway CAM refresh ... reason=peer_joined immediately after join and gateway CAM refresh ... reason=periodic about once per minute after that. If those lines are present but the switch still does not learn it, check the selected gateway interface and switch port first.

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
• lifecycle sanity-check result
• whether the relay route pin was (created) or (already existed)