fix: prevent QUIC heartbeat stalls and isolate TCP retransmission counters [CI] [SKIP TESTS]

backend/shared/tests/MoShiro.Measurement.Tests/MsQuicConnectionTests.cs

@@ -0,0 +1,77 @@
+using System.Net;
+using System.Runtime.InteropServices;
+using System.Security.Cryptography;
+using System.Security.Cryptography.X509Certificates;
+using Fleet.Core;
+
+namespace MoShiro.Measurement.Tests;
+
+public sealed class MsQuicConnectionTests
+{
+    [Theory]
+    [InlineData(1200, true)]
+    [InlineData(1280, true)]
+    [InlineData(1472, false)]
+    public void DatagramState_UsesTheNativeUint16Alignment(int maximum, bool enabled)
+    {
+        nint nativeEvent = Marshal.AllocHGlobal(IntPtr.Size + 4);
+        try
+        {
+            Marshal.WriteByte(nativeEvent, IntPtr.Size, enabled ? (byte)1 : (byte)0);
+            Marshal.WriteByte(nativeEvent, IntPtr.Size + 1, 0xA5); // padding is not part of MaxSendLength
+            Marshal.WriteInt16(nativeEvent, IntPtr.Size + 2, (short)maximum);
+            Assert.Equal((enabled, maximum), MsQuicConnection.ReadDatagramState(nativeEvent));
+        }
+        finally
+        {
+            Marshal.FreeHGlobal(nativeEvent);
+        }
+    }
+
+    [Fact]
+    public async Task DatagramConnection_CanSendCloseAndReconnect_WithoutBlockingNativeWorkers()
+    {
+        using ECDsa key = ECDsa.Create(ECCurve.NamedCurves.nistP256);
+        var request = new CertificateRequest("CN=localhost", key, HashAlgorithmName.SHA256);
+        using X509Certificate2 certificate = request.CreateSelfSigned(DateTimeOffset.UnixEpoch, DateTimeOffset.UnixEpoch.AddYears(100));
+        await using var listener = new MsQuicListener(IPAddress.Loopback, [0], certificate,
+            (connection, data) => connection.Send(data), NullNodeLog.Instance, null);
+        listener.Start();
+
+        for (int attempt = 0; attempt < 3; attempt++)
+        {
+            var reply = new TaskCompletionSource<byte[]>(TaskCreationOptions.RunContinuationsAsynchronously);
+            using var timeout = new CancellationTokenSource(TimeSpan.FromSeconds(10));
+            MsQuicConnection client = await MsQuicConnection.ConnectAsync(IPAddress.Loopback, listener.BoundPorts[0], 0,
+                key.ExportSubjectPublicKeyInfo(), (_, data) => reply.TrySetResult(data.ToArray()), NullNodeLog.Instance, timeout.Token);
+            try
+            {
+                while (!client.IsReady)
+                {
+                    await Task.Delay(10, timeout.Token);
+                }
+
+                Assert.InRange(client.MaxDatagramBytes, 64, 1500);
+                byte[] payload = Enumerable.Range(0, 64).Select(i => (byte)i).ToArray();
+                // DATAGRAM is unreliable, and the peer can receive the first
+                // packet before its handshake-complete notification permits replies.
+                while (!reply.Task.IsCompleted)
+                {
+                    Assert.True(client.Send(payload));
+                    await Task.WhenAny(reply.Task, Task.Delay(20, timeout.Token));
+                    timeout.Token.ThrowIfCancellationRequested();
+                }
+                Assert.Equal(payload, await reply.Task.WaitAsync(timeout.Token));
+                Assert.NotNull(client.TransportSnapshot);
+            }
+            finally
+            {
+                // The old callback called RegistrationClose, deadlocking its own
+                // worker. A second connection then hung in SetParam/GetParam.
+                await client.DisposeAsync().AsTask().WaitAsync(TimeSpan.FromSeconds(3));
+                await client.WaitForShutdownAsync().WaitAsync(TimeSpan.FromSeconds(3));
+            }
+        }
+    }
+
+}