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Windows MVP debugging needs more than aggregate drop counters when LAN traffic reaches the client but is kept out of the TAP adapter. A DHCP or discovery failure is much easier to diagnose when the client log says which relayed frame was filtered and why. Expose a client receive outcome that preserves the existing accepted-frame API while allowing the Windows frame pump to log filtered RelayToTap frames with the source peer and drop reason. Document the new log signal in the README and manual MVP test guide. Test Plan: - cargo fmt --check - cargo test -p lanparty-client-core connects_to_relay_control_stream_as_client - cargo test -p lanparty-client-win formats_client_frame_log_lines - cargo test -p lanparty-client-core - cargo test -p lanparty-client-win - cargo test --workspace - cargo clippy -p lanparty-client-core --all-targets -- -D warnings - cargo clippy -p lanparty-client-win --all-targets -- -D warnings - cargo clippy --workspace --all-targets -- -D warnings - git diff --check - git diff --cached --check Windows-target check attempted: - cargo check -p lanparty-client-win --target x86_64-pc-windows-msvc The Windows-target check is still blocked on this Linux host before compiling lanparty-client-win because ring cannot find the MSVC lib.exe tool. Refs: MVP client diagnostics
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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.
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.
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.
Quick Windows checks:
rustc -vV
where.exe cl
where.exe lib
rustc -vV should report a host containing x86_64-pc-windows-msvc.
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 \
--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
lanparty-client-win connected as peer ...; LAN gateway connected yes (peer ...)
relay event: LAN gateway 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
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
- 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*"
Use the non-link-local IPv4 address as <tap-ip> in the next step.
- 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.
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.
- Stop the gateway with Ctrl-C while the relay and client keep running.
Expected client output:
relay event: LAN gateway disconnected (peer ..., Normal)
gateway connected no
Waiting for LAN gateway
- Start the gateway again with the same relay, room, cert, and interface.
Expected client output:
relay event: LAN gateway connected as peer ...
gateway connected yes
Connected to LAN gateway
After the 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