Unload MsQuic after checking for QUIC support to free resources. (dot…

…net#74749)

* Unload MsQuic after checking for QUIC support to free resources.

* Unload MsQuic unconditionally

* Code review feedback

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

@@ -1,6 +1,7 @@
 // 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.Diagnostics.CodeAnalysis;
 using System.Runtime.InteropServices;
 using Microsoft.Quic;
@@ -47,7 +48,8 @@ private MsQuicApi(QUIC_API_TABLE* apiTable)
  }
  }
 
- internal static MsQuicApi Api { get; } = null!;
+ private static readonly Lazy<MsQuicApi> _api = new Lazy<MsQuicApi>(AllocateMsQuicApi);
+ internal static MsQuicApi Api => _api.Value;
 
  internal static bool IsQuicSupported { get; }
 
@@ -58,29 +60,21 @@ private MsQuicApi(QUIC_API_TABLE* apiTable)
 
  static MsQuicApi()
  {
- IntPtr msQuicHandle;
- if (!NativeLibrary.TryLoad($"{Interop.Libraries.MsQuic}.{MsQuicVersion.Major}", typeof(MsQuicApi).Assembly, DllImportSearchPath.AssemblyDirectory, out msQuicHandle) &&
- !NativeLibrary.TryLoad(Interop.Libraries.MsQuic, typeof(MsQuicApi).Assembly, DllImportSearchPath.AssemblyDirectory, out msQuicHandle))
+ if (!TryLoadMsQuic(out IntPtr msQuicHandle))
  {
  return;
  }
 
  try
  {
- if (!NativeLibrary.TryGetExport(msQuicHandle, "MsQuicOpenVersion", out IntPtr msQuicOpenVersionAddress))
- {
- return;
- }
-
- QUIC_API_TABLE* apiTable = null;
- delegate* unmanaged[Cdecl]<uint, QUIC_API_TABLE**, int> msQuicOpenVersion = (delegate* unmanaged[Cdecl]<uint, QUIC_API_TABLE**, int>)msQuicOpenVersionAddress;
- if (StatusFailed(msQuicOpenVersion((uint)MsQuicVersion.Major, &apiTable)))
+ if (!TryOpenMsQuic(msQuicHandle, out QUIC_API_TABLE* apiTable))
  {
  return;
  }
 
  try
  {
+ // Check version
  int arraySize = 4;
  uint* libVersion = stackalloc uint[arraySize];
  uint size = (uint)arraySize * sizeof(uint);
@@ -99,7 +93,7 @@ static MsQuicApi()
  return;
  }
 
- // Assume SChannel is being used on windows and query for the actual provider from the library
+ // Assume SChannel is being used on windows and query for the actual provider from the library if querying is supported
  QUIC_TLS_PROVIDER provider = OperatingSystem.IsWindows() ? QUIC_TLS_PROVIDER.SCHANNEL : QUIC_TLS_PROVIDER.OPENSSL;
  size = sizeof(QUIC_TLS_PROVIDER);
  apiTable->GetParam(null, QUIC_PARAM_GLOBAL_TLS_PROVIDER, &size, &provider);
@@ -122,26 +116,67 @@ static MsQuicApi()
  Tls13ClientMayBeDisabled = IsTls13Disabled(isServer: false);
  }
 
- Api = new MsQuicApi(apiTable);
  IsQuicSupported = true;
  }
  finally
  {
- if (!IsQuicSupported && NativeLibrary.TryGetExport(msQuicHandle, "MsQuicClose", out IntPtr msQuicClose))
- {
- // Gracefully close the API table
- ((delegate* unmanaged[Cdecl]<QUIC_API_TABLE*, void>)msQuicClose)(apiTable);
- }
+ // Gracefully close the API table to free resources. The API table will be allocated lazily again if needed
+ bool closed = TryCloseMsQuic(msQuicHandle, apiTable);
+ Debug.Assert(closed, "Failed to close MsQuic");
  }
-
  }
  finally
  {
- if (!IsQuicSupported)
- {
- NativeLibrary.Free(msQuicHandle);
- }
+ // Unload the library, we will load it again when we actually use QUIC
+ NativeLibrary.Free(msQuicHandle);
+ }
+ }
+
+ private static MsQuicApi AllocateMsQuicApi()
+ {
+ Debug.Assert(IsQuicSupported);
+
+ if (TryLoadMsQuic(out IntPtr msQuicHandle) &&
+ TryOpenMsQuic(msQuicHandle, out QUIC_API_TABLE* apiTable))
+ {
+ return new MsQuicApi(apiTable);
+ }
+
+ throw new Exception("Failed to create MsQuicApi instance");
+ }
+
+ private static bool TryLoadMsQuic(out IntPtr msQuicHandle) =>
+ NativeLibrary.TryLoad($"{Interop.Libraries.MsQuic}.{MsQuicVersion.Major}", typeof(MsQuicApi).Assembly, DllImportSearchPath.AssemblyDirectory, out msQuicHandle) ||
+ NativeLibrary.TryLoad(Interop.Libraries.MsQuic, typeof(MsQuicApi).Assembly, DllImportSearchPath.AssemblyDirectory, out msQuicHandle);
+
+ private static bool TryOpenMsQuic(IntPtr msQuicHandle, out QUIC_API_TABLE* apiTable)
+ {
+ apiTable = null;
+ if (!NativeLibrary.TryGetExport(msQuicHandle, "MsQuicOpenVersion", out IntPtr msQuicOpenVersionAddress))
+ {
+ return false;
+ }
+
+ QUIC_API_TABLE* table = null;
+ delegate* unmanaged[Cdecl]<uint, QUIC_API_TABLE**, int> msQuicOpenVersion = (delegate* unmanaged[Cdecl]<uint, QUIC_API_TABLE**, int>)msQuicOpenVersionAddress;
+ if (StatusFailed(msQuicOpenVersion((uint)MsQuicVersion.Major, &table)))
+ {
+ return false;
  }
+
+ apiTable = table;
+ return true;
+ }
+
+ private static bool TryCloseMsQuic(IntPtr msQuicHandle, QUIC_API_TABLE* apiTable)
+ {
+ if (NativeLibrary.TryGetExport(msQuicHandle, "MsQuicClose", out IntPtr msQuicClose))
+ {
+ ((delegate* unmanaged[Cdecl]<QUIC_API_TABLE*, void>)msQuicClose)(apiTable);
+ return true;
+ }
+
+ return false;
  }
 
  private static bool IsWindowsVersionSupported() => OperatingSystem.IsWindowsVersionAtLeast(MinWindowsVersion.Major,