feat(quic): replace probe UDP data plane with QUIC datagrams

backend/shared/MoShiro.Measurement/Net/MsQuicRuntime.cs

@@ -0,0 +1,118 @@
+using System.Runtime.InteropServices;
+
+namespace MoShiro.Measurement;
+
+/// <summary>Loads the MsQuic v2 ABI used by the QUIC datagram transport.</summary>
+internal static class MsQuicRuntime
+{
+    private const uint ApiVersion = 2;
+    private static readonly object s_gate = new();
+    private static nint s_library;
+    private static nint s_api;
+    private static OpenVersionDelegate? s_open;
+    private static CloseDelegate? s_close;
+    private static readonly List<nint> s_supportLibraries = [];
+
+    public static nint Api
+    {
+        get
+        {
+            lock (s_gate)
+            {
+                if (s_api != 0)
+                {
+                    return s_api;
+                }
+
+                string[] candidates = OperatingSystem.IsWindows()
+                    ? ["msquic.dll"]
+                    : OperatingSystem.IsMacOS()
+                        ? ["libmsquic.dylib"]
+                        : ["libmsquic.so.2", "libmsquic.so"];
+                LoadBundledSupportLibraries();
+                string appDirectory = AppContext.BaseDirectory;
+                foreach (string candidate in candidates)
+                {
+                    if (NativeLibrary.TryLoad(Path.Combine(appDirectory, candidate), out s_library)
+                        || NativeLibrary.TryLoad(candidate, out s_library))
+                    {
+                        break;
+                    }
+                }
+
+                if (s_library == 0)
+                {
+                    throw new DllNotFoundException($"MsQuic runtime was not found. Expected one of: {string.Join(", ", candidates)}.");
+                }
+
+                s_open = Marshal.GetDelegateForFunctionPointer<OpenVersionDelegate>(NativeLibrary.GetExport(s_library, "MsQuicOpenVersion"));
+                s_close = Marshal.GetDelegateForFunctionPointer<CloseDelegate>(NativeLibrary.GetExport(s_library, "MsQuicClose"));
+                int status = s_open(ApiVersion, out s_api);
+                if (status != 0 || s_api == 0)
+                {
+                    NativeLibrary.Free(s_library);
+                    s_library = 0;
+                    s_api = 0;
+                    throw new InvalidOperationException($"MsQuic API v{ApiVersion} could not be opened (status {status}).");
+                }
+
+                return s_api;
+            }
+        }
+    }
+
+    public static void Close()
+    {
+        lock (s_gate)
+        {
+            if (s_api != 0)
+            {
+                s_close!(s_api);
+                s_api = 0;
+            }
+
+            if (s_library != 0)
+            {
+                NativeLibrary.Free(s_library);
+                s_library = 0;
+            }
+
+            for (int i = s_supportLibraries.Count - 1; i >= 0; i--)
+            {
+                NativeLibrary.Free(s_supportLibraries[i]);
+            }
+
+            s_supportLibraries.Clear();
+        }
+    }
+
+    private static void LoadBundledSupportLibraries()
+    {
+        if (OperatingSystem.IsLinux())
+        {
+            TryLoadSupport("libnuma.so.1");
+        }
+        else if (OperatingSystem.IsMacOS())
+        {
+            TryLoadSupport("libcrypto.3.dylib");
+            TryLoadSupport("libssl.3.dylib");
+        }
+    }
+
+    private static void TryLoadSupport(string library)
+    {
+        if (NativeLibrary.TryLoad(Path.Combine(AppContext.BaseDirectory, library), out nint handle))
+        {
+            s_supportLibraries.Add(handle);
+        }
+    }
+
+    public static T Function<T>(int index)
+        where T : Delegate => Marshal.GetDelegateForFunctionPointer<T>(Marshal.ReadIntPtr(Api, checked(index * IntPtr.Size)));
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate int OpenVersionDelegate(uint version, out nint api);
+
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    private delegate void CloseDelegate(nint api);
+}