Avoid some defensive copies on readonly structs in System.Net.Quic (d…

…otnet#101133)

* Avoid some defensive copies on readonly structs in System.Net.Quic

* Keep readonly-ness of CacheKey

* Apply suggestions from code review

* Remove ReadOnlySpan property

* Update src/libraries/System.Net.Quic/src/System/Net/Quic/Internal/MsQuicConfiguration.Cache.cs

Co-authored-by: Marie Píchová <11718369+ManickaP@users.noreply.github.com>

* Code review feedback

* Implement IEquattable for QUIC_SETTINGS

* More code review feedback

* Code review feedback

---------

Co-authored-by: Marie Píchová <11718369+ManickaP@users.noreply.github.com>

src/libraries/System.Net.Quic/src/System/Net/Quic/Internal/MsQuicSafeHandle.cs

@@ -88,7 +88,7 @@ internal sealed class MsQuicContextSafeHandle : MsQuicSafeHandle
     /// Holds a weak reference to the managed instance.
     /// It allows delegating MsQuic events to the managed object while it still can be collected and finalized.
     /// </summary>
-    private readonly GCHandle _context;
+    private GCHandle _context;
 
     /// <summary>
     /// Optional parent safe handle, used to increment/decrement reference count with the lifetime of this instance.

src/libraries/System.Net.Quic/src/System/Net/Quic/Interop/QUIC_SETTINGS.IEquattable.cs

@@ -0,0 +1,94 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+
+namespace Microsoft.Quic;
+
+internal partial struct QUIC_SETTINGS : System.IEquatable<QUIC_SETTINGS>
+{
+    // Because QUIC_SETTINGS may contain gaps due to layout/alignment of individual
+    // fields, we implement IEquatable<QUIC_SETTINGS> manually. If a new field is added,
+    // then there is a unit test which should fail.
+
+    public readonly bool Equals(QUIC_SETTINGS other)
+    {
+        return Anonymous1.IsSetFlags == other.Anonymous1.IsSetFlags
+            && MaxBytesPerKey == other.MaxBytesPerKey
+            && HandshakeIdleTimeoutMs == other.HandshakeIdleTimeoutMs
+            && IdleTimeoutMs == other.IdleTimeoutMs
+            && MtuDiscoverySearchCompleteTimeoutUs == other.MtuDiscoverySearchCompleteTimeoutUs
+            && TlsClientMaxSendBuffer == other.TlsClientMaxSendBuffer
+            && TlsServerMaxSendBuffer == other.TlsServerMaxSendBuffer
+            && StreamRecvWindowDefault == other.StreamRecvWindowDefault
+            && StreamRecvBufferDefault == other.StreamRecvBufferDefault
+            && ConnFlowControlWindow == other.ConnFlowControlWindow
+            && MaxWorkerQueueDelayUs == other.MaxWorkerQueueDelayUs
+            && MaxStatelessOperations == other.MaxStatelessOperations
+            && InitialWindowPackets == other.InitialWindowPackets
+            && SendIdleTimeoutMs == other.SendIdleTimeoutMs
+            && InitialRttMs == other.InitialRttMs
+            && MaxAckDelayMs == other.MaxAckDelayMs
+            && DisconnectTimeoutMs == other.DisconnectTimeoutMs
+            && KeepAliveIntervalMs == other.KeepAliveIntervalMs
+            && CongestionControlAlgorithm == other.CongestionControlAlgorithm
+            && PeerBidiStreamCount == other.PeerBidiStreamCount
+            && PeerUnidiStreamCount == other.PeerUnidiStreamCount
+            && MaxBindingStatelessOperations == other.MaxBindingStatelessOperations
+            && StatelessOperationExpirationMs == other.StatelessOperationExpirationMs
+            && MinimumMtu == other.MinimumMtu
+            && MaximumMtu == other.MaximumMtu
+            && _bitfield == other._bitfield
+            && MaxOperationsPerDrain == other.MaxOperationsPerDrain
+            && MtuDiscoveryMissingProbeCount == other.MtuDiscoveryMissingProbeCount
+            && DestCidUpdateIdleTimeoutMs == other.DestCidUpdateIdleTimeoutMs
+            && Anonymous2.Flags == other.Anonymous2.Flags
+            && StreamRecvWindowBidiLocalDefault == other.StreamRecvWindowBidiLocalDefault
+            && StreamRecvWindowBidiRemoteDefault == other.StreamRecvWindowBidiRemoteDefault
+            && StreamRecvWindowUnidiDefault == other.StreamRecvWindowUnidiDefault;
+    }
+
+    public override readonly int GetHashCode()
+    {
+        HashCode hash = default;
+        hash.Add(Anonymous1.IsSetFlags);
+        hash.Add(MaxBytesPerKey);
+        hash.Add(HandshakeIdleTimeoutMs);
+        hash.Add(IdleTimeoutMs);
+        hash.Add(MtuDiscoverySearchCompleteTimeoutUs);
+        hash.Add(TlsClientMaxSendBuffer);
+        hash.Add(TlsServerMaxSendBuffer);
+        hash.Add(StreamRecvWindowDefault);
+        hash.Add(StreamRecvBufferDefault);
+        hash.Add(ConnFlowControlWindow);
+        hash.Add(MaxWorkerQueueDelayUs);
+        hash.Add(MaxStatelessOperations);
+        hash.Add(InitialWindowPackets);
+        hash.Add(SendIdleTimeoutMs);
+        hash.Add(InitialRttMs);
+        hash.Add(MaxAckDelayMs);
+        hash.Add(DisconnectTimeoutMs);
+        hash.Add(KeepAliveIntervalMs);
+        hash.Add(CongestionControlAlgorithm);
+        hash.Add(PeerBidiStreamCount);
+        hash.Add(PeerUnidiStreamCount);
+        hash.Add(MaxBindingStatelessOperations);
+        hash.Add(StatelessOperationExpirationMs);
+        hash.Add(MinimumMtu);
+        hash.Add(MaximumMtu);
+        hash.Add(_bitfield);
+        hash.Add(MaxOperationsPerDrain);
+        hash.Add(MtuDiscoveryMissingProbeCount);
+        hash.Add(DestCidUpdateIdleTimeoutMs);
+        hash.Add(Anonymous2.Flags);
+        hash.Add(StreamRecvWindowBidiLocalDefault);
+        hash.Add(StreamRecvWindowBidiRemoteDefault);
+        hash.Add(StreamRecvWindowUnidiDefault);
+        return hash.ToHashCode();
+    }
+
+    public override readonly bool Equals(object? obj)
+    {
+        return obj is QUIC_SETTINGS other && Equals(other);
+    }
+}

src/libraries/System.Net.Quic/src/System/Net/Quic/Interop/msquic.cs

@@ -20,7 +20,7 @@ namespace Microsoft.Quic
 {
     internal unsafe partial struct QUIC_BUFFER
     {
-        public Span<byte> Span => new(Buffer, (int)Length);
+        public readonly Span<byte> Span => new(Buffer, (int)Length);
     }
 
     internal partial class MsQuic

src/libraries/System.Net.Quic/tests/FunctionalTests/MsQuicInteropTests.cs

@@ -0,0 +1,74 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Diagnostics;
+using System.Net.Security;
+using System.Threading.Tasks;
+using System.Runtime.InteropServices;
+using System.Reflection;
+using System.Linq;
+using Xunit;
+using Xunit.Abstractions;
+
+using Microsoft.Quic;
+
+namespace System.Net.Quic.Tests
+{
+    public class MsQuicInteropTests
+    {
+        private static MemberInfo[] GetMembers<T>()
+        {
+            var members = typeof(T).FindMembers(MemberTypes.Field | MemberTypes.Property, BindingFlags.NonPublic | BindingFlags.Instance | BindingFlags.Public, (mi, _) =>
+            {
+                if (mi is PropertyInfo property && property.GetSetMethod() == null)
+                {
+                    return false;
+                }
+
+                return true;
+            }, null);
+
+            Assert.NotEmpty(members);
+
+            return members;
+        }
+
+        private static void ResetMember(MemberInfo member, object instance)
+        {
+            switch (member)
+            {
+                case FieldInfo field:
+                    field.SetValue(instance, Activator.CreateInstance(field.FieldType));
+                    break;
+                case PropertyInfo property:
+                    property.SetValue(instance, Activator.CreateInstance(property.PropertyType));
+                    break;
+                default:
+                    throw new InvalidOperationException($"Unexpected member type: {member.MemberType}");
+            }
+        }
+
+        [Fact]
+        public void QuicSettings_Equals_RespectsAllMembers()
+        {
+            QUIC_SETTINGS settings = new QUIC_SETTINGS();
+
+            // make sure the extension definition is included in compilation
+            Assert.Contains(typeof(IEquatable<QUIC_SETTINGS>), typeof(QUIC_SETTINGS).GetInterfaces());
+
+            var settingsSpan = MemoryMarshal.AsBytes(new Span<QUIC_SETTINGS>(ref settings));
+
+            // Fill the memory with 1s,we will try to zero out each member and compare
+            settingsSpan.Fill(0xFF);
+
+            foreach (MemberInfo member in GetMembers<QUIC_SETTINGS>())
+            {
+                // copy and box the instance because reflection methods take a reference type arg
+                object boxed = settings;
+                ResetMember(member, boxed);
+                Assert.False(settings.Equals((QUIC_SETTINGS)boxed), $"Member {member.Name} is not compared.");
+            }
+        }
+    }
+}