move win/gatuna-client to gatuna-win, rename project to gatuna

- Directory: win/gatuna-client/ -> gatuna-win/
- Project file: gatuna-client.csproj -> gatuna.csproj
- Assembly name: gatuna-client -> gatuna
- Root namespace: gatuna_client -> gatuna
- All .cs files: namespace gatuna_client -> gatuna
- app.manifest: assemblyIdentity name -> gatuna
- README: updated all paths and references

PROTOCOL.md

@@ -40,7 +40,7 @@ emitted in v1.
 | Type | Name        | Direction     | session_id | Payload                          |
 |------|-------------|---------------|------------|----------------------------------|
 | 0x01 | DISCOVER    | C → broadcast | 0          | empty                            |
-| 0x02 | MANIFEST    | S → C         | 0          | `id:1, proto:1, port:2` × N      |
+| 0x02 | MANIFEST    | S → C         | 0          | `hostname_len:1, hostname:N, entries...` |
 | 0x03 | OPEN        | C → S         | 0          | `upstream_id:1`                  |
 | 0x04 | OPEN_ACK    | S → C         | assigned   | `upstream_id:1`                  |
 | 0x05 | OPEN_NAK    | S → C         | 0          | `upstream_id:1, reason:1`        |
@@ -212,3 +212,26 @@ client                            server
   it emits `CLOSE` and exits.
 - The server's tunnel→socket path writes `DATA` payloads to the `TcpStream`
   with `write_all`. On error it emits `CLOSE` and drops the session.
+
+## Network test (PING/PONG)
+
+```
+client                            server
+  |                                 |
+  | PING { nonce }                  |
+  |-------------------------------->|
+  |                                 |
+  |        PONG { nonce }           |
+  |<--------------------------------|
+  |                                 |
+  | (repeated at random intervals)  |
+  |                                 |
+```
+
+- The client sends `PING` frames at random 10–100 ms intervals, each with a
+  unique `nonce`.
+- The server echoes the nonce verbatim in a `PONG` frame.
+- The client correlates `PONG` nonces with outstanding `PING` timestamps to
+  compute RTT, average latency, jitter (mean absolute delta of consecutive
+  RTTs), and drop rate (unanswered PINGs).
+- PING/PONG frames use `session_id = 0`; they are independent of TCP sessions.

README.md

@@ -16,32 +16,35 @@ pass unimpeded. See `wireguard-windows/tunnel/firewall/blocker.go:156`.
 
 ## Components
 
-- `gatunad` — Rust server. Runs on the peer (Linux) that owns the real
-  services. Announces upstreams and relays TCP between the tunnel and
+- **`gatunad`** — Rust server (`gatunad/`). Runs on the peer (Linux) that owns
+  the real services. Announces upstreams and relays TCP between the tunnel and
   `127.0.0.1:<port>`.
-- `gatuna` (planned) — .NET WinForms client. Runs on the killswitched Windows
-  box. Discovers the server, presents its upstreams as local loopback
-  listeners, and hauls bytes over the same L2 protocol.
-
-This repository builds `gatunad` first.
+- **`gatuna`** — .NET 8 WinForms client (`gatuna-win/`). Runs on the
+  killswitched Windows box. Discovers the server, presents its upstreams as
+  local loopback listeners, and hauls bytes over the same L2 protocol. Includes
+  a network test (PING/PONG) for measuring latency, jitter, and loss.
 
 ## Transport
 
 - **Medium:** raw Ethernet frames on a shared L2 segment.
 - **Ethertype:** `0x6969` (hardcoded).
-- **No IP stack involvement.** Frames carry only our 6-byte header + payload.
-- **BPF:** the server attaches a classic BPF filter `ether proto 0x6969` to its
-  `AF_PACKET` socket so it only wakes on our ethertype. No eBPF authoring.
+- **No IP stack involvement.** Frames carry only our 8-byte header + payload.
+- **BPF:** both sides filter on ethertype — the server via classic BPF on
+  `AF_PACKET` (`SO_ATTACH_FILTER`), the client via Npcap's compiled filter.
+  No eBPF authoring.
 
 ## Protocol
 
 See [`PROTOCOL.md`](PROTOCOL.md) for the full wire format. Summary:
 
-- 6-byte header, big-endian: `[ version:1 ][ type:1 ][ session_id:4 ][ payload:N ]`.
-- `version` = `1`. No length field (frame length comes from the capture). No
-  CRC. Ethertype discriminates our frames from everything else.
-- Discovery: client broadcasts `DISCOVER`; server unicasts `MANIFEST` back.
+- 8-byte header, big-endian:
+  `[ version:1 ][ type:1 ][ session_id:4 ][ payload_len:2 ][ payload:N ]`.
+- `version` = `1`. `payload_len` lets the receiver ignore Ethernet padding
+  (frames under 60 bytes are zero-padded by the NIC).
+- Discovery: client broadcasts `DISCOVER`; server unicasts `MANIFEST` (with
+  hostname and upstream list) back.
 - Sessions: `OPEN` → `OPEN_ACK` (or `OPEN_NAK`) → `DATA`* ↔ `DATA`* → `CLOSE`.
+- Network test: `PING` (with 8-byte nonce) → `PONG` (nonce echoed).
 - v1 ships TCP only. UDP frame types are reserved but unimplemented.
 
 ## `gatunad` usage
@@ -62,17 +65,82 @@ sudo ./gatunad eth0 22 8800:site-a 8080:site-b
 Exposes upstreams `1→127.0.0.1:22`, `2→127.0.0.1:8800` (label `site-a`),
 `3→127.0.0.1:8080` (label `site-b`).
 
+## `gatuna` usage
+
+1. Launch `gatuna.exe` (UAC prompt expected — Npcap requires admin).
+2. Select the network adapter connected to the same L2 segment as the server.
+3. Click **Discover**. The server's hostname and MAC appear; the upstream list
+   populates.
+4. Check the upstreams you want to use. The **Mirror** column shows the local
+   loopback port to connect to.
+5. Connect your app to `127.0.0.1:<mirror_port>`.
+6. Click **Test** to run a PING/PONG network test (latency, jitter, loss).
+7. Minimize to tray; close to exit.
+
+### Mirror ports
+
+Mirror ports are deterministic: `port ^ (mac[0]<<8 | mac[5])`, clamped to
+≥1024. The same server + upstream always yields the same local port, so you
+know where to connect without checking the UI. If the computed port is already
+in use, the client falls back to an OS-assigned port.
+
+## Building from source
+
+### Prerequisites
+
+- **Server:** Rust toolchain (edition 2021, MSRV 1.70+), Linux with `AF_PACKET`
+  support.
+- **Client:** .NET 8 SDK with Windows Desktop workload, Npcap installed
+  (bundled with Wireshark or standalone from <https://npcap.com>).
+
+### Build the server (Linux)
+
+```sh
+cd gatunad
+cargo build --release
+```
+
+The binary is at `gatunad/target/release/gatunad`.
+
+### Build the client (Windows)
+
+```powershell
+cd gatuna-win
+dotnet build -c Release
+```
+
+Or run directly:
+```powershell
+dotnet run --project gatuna-win -c Release
+```
+
+### Npcap
+
+The client requires Npcap's `wpcap.dll` and `Packet.dll` in the system path.
+These are installed by the Npcap installer (also bundled with Wireshark). No
+additional NuGet packages or driver installs are needed — SharpPcap talks to
+the existing Npcap installation.
+
 ## Privileges
 
-`AF_PACKET` requires `CAP_NET_RAW`. Run as root, or grant the binary the
-capability once:
+**Server (Linux):** `AF_PACKET` requires `CAP_NET_RAW`. Run as root, or grant
+the binary the capability once:
 ```
 sudo setcap cap_net_raw+ep ./target/release/gatunad
 ```
 
+**Client (Windows):** Npcap requires admin by default (`AdminOnly=1` in
+`HKLM\SYSTEM\CurrentControlSet\Services\npcap\Parameters`). The client's
+`app.manifest` requests `requireAdministrator`, so a UAC prompt appears on
+launch. See the [Npcap docs](https://npcap.com/guide/npcap-dev-guide-1.html)
+for details on the `AdminOnly` flag if you want to change this.
+
 ## Logging
 
-Errors only, to stdout. Normal lifecycle (DISCOVER/OPEN/CLOSE) is silent.
+**Server:** errors only, to stdout. Normal lifecycle (DISCOVER/OPEN/CLOSE) is
+silent.
+
+**Client:** status line in the UI. Errors are not logged to disk.
 
 ## v1 limitations
 
@@ -82,6 +150,34 @@ Errors only, to stdout. Normal lifecycle (DISCOVER/OPEN/CLOSE) is silent.
   on a healthy switched link.
 - No auth/crypto. Anyone on the same L2 segment can `DISCOVER` and `OPEN`.
 - Single server instance per interface.
+- One outstanding `OPEN` at a time on the client (serialized via queue).
+
+## Repository layout
+
+```
+gatuna/
+├── README.md
+├── PROTOCOL.md
+├── LICENSE                  # CC0 1.0 Universal
+├── .gitignore
+├── gatunad/                 # Rust server
+│   ├── Cargo.toml
+│   └── src/
+│       ├── main.rs          # cmdline, rx dispatch, tx task
+│       ├── link.rs          # AF_PACKET, classic BPF, raw Ethernet I/O
+│       ├── frame.rs         # wire protocol encode/decode
+│       ├── upstream.rs      # cmdline parsing, hostname, upstream table
+│       └── session.rs       # session store, socket→tunnel pump
+└── gatuna-win/              # .NET 8 WinForms client
+    ├── gatuna.csproj
+    ├── app.manifest         # requireAdministrator
+    ├── Program.cs           # tray icon, entry point
+    ├── MainForm.cs          # UI: adapter picker, discover, test, upstream list
+    ├── TunnelLink.cs        # SharpPcap wrapper, raw Ethernet send/recv
+    ├── Frame.cs             # wire protocol encode/decode (mirrors Rust frame.rs)
+    ├── SessionManager.cs    # session lifecycle, listeners, OPEN serialization
+    └── PingTest.cs          # PING/PONG network test with stats
+```
 
 ## License
 

gatuna-win/Frame.cs

@@ -1,4 +1,4 @@
-namespace gatuna_client;
+namespace gatuna;
 
 using System.Text;
 

gatuna-win/MainForm.cs

@@ -1,6 +1,6 @@
 using SharpPcap.LibPcap;
 
-namespace gatuna_client;
+namespace gatuna;
 
 public partial class MainForm : Form
 {
@@ -20,6 +20,8 @@ public partial class MainForm : Form
         Text = "gatuna";
         Width = 520;
         Height = 420;
+        FormBorderStyle = FormBorderStyle.FixedSingle;
+        MaximizeBox = false;
         StartPosition = FormStartPosition.CenterScreen;
         Icon = SystemIcons.GetStockIcon(StockIconId.NetworkConnect, 32);
         InitializeComponents();

gatuna-win/PingTest.cs

@@ -1,6 +1,6 @@
 using System.Collections.Concurrent;
 
-namespace gatuna_client;
+namespace gatuna;
 
 sealed class PingTest
 {

gatuna-win/Program.cs

@@ -1,4 +1,4 @@
-namespace gatuna_client;
+namespace gatuna;
 
 static class Program
 {

gatuna-win/SessionManager.cs

@@ -3,7 +3,7 @@ using System.Net;
 using System.Net.Sockets;
 using System.Threading.Channels;
 
-namespace gatuna_client;
+namespace gatuna;
 
 sealed class SessionManager : IDisposable
 {

gatuna-win/TunnelLink.cs

@@ -1,7 +1,7 @@
 using SharpPcap;
 using SharpPcap.LibPcap;
 
-namespace gatuna_client;
+namespace gatuna;
 
 sealed class TunnelLink : IDisposable
 {

gatuna-win/app.manifest

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <assembly manifestVersion="1.0" xmlns="urn:schemas-microsoft-com:asm.v1">
-  <assemblyIdentity version="0.1.0.0" name="gatuna-client" />
+  <assemblyIdentity version="0.1.0.0" name="gatuna" />
   <trustInfo xmlns="urn:schemas-microsoft-com:asm.v2">
     <security>
       <requestedPrivileges xmlns="urn:schemas-microsoft-com:asm.v3">

gatuna-win/gatuna.csproj

@@ -3,7 +3,8 @@
   <PropertyGroup>
     <OutputType>WinExe</OutputType>
     <TargetFramework>net8.0-windows</TargetFramework>
-    <RootNamespace>gatuna_client</RootNamespace>
+    <AssemblyName>gatuna</AssemblyName>
+    <RootNamespace>gatuna</RootNamespace>
     <Nullable>enable</Nullable>
     <UseWindowsForms>true</UseWindowsForms>
     <ImplicitUsings>enable</ImplicitUsings>