perf(tests): isolate network E2E and await QUIC cleanup

backend/tests/MoShiro.Backend.Tests/AgentDataPlaneTests.cs

@@ -0,0 +1,78 @@
+using System.Net;
+using System.Net.Sockets;
+using MoShiro.Measurement;
+using MoShiro.Protocol;
+using MoShiro.TestSupport;
+
+namespace MoShiro.Backend.Tests;
+
+/// <summary>数据面协议拒绝错误首帧、伪造包、重放包和垃圾数据。</summary>
+[Trait("Category", "Slow")]
+public sealed class AgentDataPlaneTests : IClassFixture<BackendFixture>
+{
+    private readonly BackendFixture _backend;
+
+    public AgentDataPlaneTests(BackendFixture backend)
+    {
+        _backend = backend;
+    }
+
+    private async Task<(AgentHarness Agent, ProbeSimulator Probe, LineTask Udp)> LineAsync()
+    {
+        AgentHarness agent = await AgentHarness.StartAsync(_backend);
+        await agent.OverrideLineTasksAsync(rateHz: 30);
+        ProbeSimulator probe = await agent.ConnectProbeAsync();
+        LineTaskSet set = await probe.WaitForTasksAsync(s => s.Tasks.Any(t => t.Kind == "udp_echo" && t.Port == agent.App.QuicPorts[0]));
+        return (agent, probe, set.Tasks.Single(t => t.Kind == "udp_echo"));
+    }
+
+    [Fact]
+    public async Task TcpDataPlane_ClosesConnectionsWithoutAValidFirstFrame()
+    {
+        (AgentHarness agent, ProbeSimulator probe, _) = await LineAsync();
+        await using (agent)
+        await using (probe)
+        {
+            using var client = new TcpClient();
+            await client.ConnectAsync(IPAddress.Loopback, agent.App.TcpPorts[0]);
+            await client.GetStream().WriteAsync(new byte[TcpWire.AuthBytes]); // 全零：magic 不对
+            byte[] buffer = new byte[16];
+            Assert.Equal(0, await ReadOrResetAsync(client.GetStream(), buffer)); // 连接被关闭：没有任何字节（Windows 上可能是 RST）
+            await BackendFixture.EventuallyAsync(() => Task.FromResult(agent.App.Counters.DroppedInvalid >= 1));
+        }
+    }
+
+    [Fact]
+    public async Task DataPlane_DropsForgedReplayedAndGarbagePackets_WithoutAnswering()
+    {
+        (AgentHarness agent, ProbeSimulator probe, LineTask udp) = await LineAsync();
+        await using (agent)
+        await using (probe)
+        {
+            long before = agent.App.Counters.DroppedInvalid;
+            await probe.SendRawUdpAsync([1, 2, 3]);
+            await probe.SendRawUdpAsync(new byte[64]);
+            await probe.SendForgedEchoAsync(udp, 1);
+            await BackendFixture.EventuallyAsync(() => Task.FromResult(agent.App.Counters.DroppedInvalid - before >= 3), because: "garbage and forged packets are counted");
+
+            // 重放：同一个序号发两次，只有第一次被接受
+            await probe.SendEchoAsync(udp, 500);
+            await BackendFixture.EventuallyAsync(() => Task.FromResult(agent.App.Counters.PacketsOut >= 1));
+            long dropped = agent.App.Counters.DroppedInvalid;
+            await probe.SendEchoAsync(udp, 500);
+            await BackendFixture.EventuallyAsync(() => Task.FromResult(agent.App.Counters.DroppedInvalid > dropped), because: "a replayed packet is dropped");
+        }
+    }
+
+    private static async Task<int> ReadOrResetAsync(Stream stream, byte[] buffer)
+    {
+        try
+        {
+            return await stream.ReadAsync(buffer).AsTask().WaitAsync(TimeSpan.FromSeconds(10));
+        }
+        catch (IOException)
+        {
+            return 0;
+        }
+    }
+}