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

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

@@ -2,11 +2,13 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Collections.Generic;
 using System.Collections.Concurrent;
 using System.Collections.ObjectModel;
 using System.Security.Authentication;
 using System.Net.Security;
+using System.Runtime.InteropServices;
 using System.Security.Cryptography.X509Certificates;
 using System.Threading;
 using Microsoft.Quic;

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/Internal/ReceiveBuffers.cs

@@ -52,7 +52,7 @@ public int CopyFrom(ReadOnlySpan<QUIC_BUFFER> quicBuffers, int totalLength, bool
             int totalCopied = 0;
             for (int i = 0; i < quicBuffers.Length; ++i)
             {
-                Span<byte> quicBuffer = quicBuffers[i].Span;
+                ReadOnlySpan<byte> quicBuffer = quicBuffers[i].Span;
                 if (totalLength < quicBuffer.Length)
                 {
                     quicBuffer = quicBuffer.Slice(0, totalLength);

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

@@ -0,0 +1,91 @@
+// 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>
+    {
+        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 +1,78 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+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 readonly ITestOutputHelper _output;
+
+        public MsQuicInteropTests(ITestOutputHelper output)
+        {
+            _output = output;
+        }
+
+        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();
+
+            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.");
+            }
+        }
+    }
+}