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Auto-enable SO_REUSE_UNICASTPORT for ConnectEx #54903

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merged 5 commits into from
Jul 8, 2021
Merged

Auto-enable SO_REUSE_UNICASTPORT for ConnectEx #54903

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dbd65ac
auto-enable SO_REUSE_UNICASTPORT
antonfirsov Jun 29, 2021
ce3e4a0
always attempt enabling the port
antonfirsov Jul 2, 2021
3195abe
add ConnectAsync_Enables_ReuseUnicastPort
antonfirsov Jul 5, 2021
c5dd223
delete leftover code in comments
antonfirsov Jul 5, 2021
557de56
Revert "add ConnectAsync_Enables_ReuseUnicastPort"
antonfirsov Jul 6, 2021
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32 changes: 32 additions & 0 deletions src/libraries/System.Net.Sockets/src/System/Net/Sockets/Socket.Windows.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ namespace System.Net.Sockets
{
public partial class Socket
{
private static readonly bool s_osSupportsReuseUnicastPort = IsReuseUnicastPortSupported();
private static CachedSerializedEndPoint? s_cachedAnyEndPoint;
private static CachedSerializedEndPoint? s_cachedAnyV6EndPoint;
private static CachedSerializedEndPoint? s_cachedMappedAnyV6EndPoint;
Expand Down Expand Up @@ -235,6 +236,13 @@ partial void WildcardBindForConnectIfNecessary(AddressFamily addressFamily)

if (NetEventSource.Log.IsEnabled()) NetEventSource.Info(this, csep.IPEndPoint);

// By enabling SO_REUSE_UNICASTPORT, we defer actual port allocation until the ConnectEx call,
// enabling to bind to ports from the Windows auto-reuse port range, if configured by an admin.
if (_socketType == SocketType.Stream && _protocolType == ProtocolType.Tcp && s_osSupportsReuseUnicastPort)
{
SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.ReuseUnicastPort, true);
}

DoBind(csep.IPEndPoint, csep.SocketAddress);
}

Expand Down Expand Up @@ -412,5 +420,29 @@ internal ThreadPoolBoundHandle GetOrAllocateThreadPoolBoundHandleSlow()
bool trySkipCompletionPortOnSuccess = !(CompletionPortHelper.PlatformHasUdpIssue && _protocolType == ProtocolType.Udp);
return _handle.GetOrAllocateThreadPoolBoundHandle(trySkipCompletionPortOnSuccess);
}

private static bool IsReuseUnicastPortSupported()
{
Interop.Winsock.EnsureInitialized();

try
{
IntPtr socket = Interop.Winsock.WSASocketW(AddressFamily.InterNetwork, SocketType.Stream, 0, IntPtr.Zero, 0, (int)Interop.Winsock.SocketConstructorFlags.WSA_FLAG_NO_HANDLE_INHERIT);
using var handle = new SafeSocketHandle(socket, ownsHandle: true);
if (handle.IsInvalid)
return false;

int optionValue = 1;
SocketError error = Interop.Winsock.setsockopt(
handle,
SocketOptionLevel.Socket,
SocketOptionName.ReuseUnicastPort,
ref optionValue,
sizeof(int));
return error == SocketError.Success;
}
catch { }
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I used try-catch block because SocketProtocolSupportPal does the same:

runtime/src/libraries/Common/src/System/Net/SocketProtocolSupportPal.Windows.cs

Lines 18 to 38 in f3bad4f

private static bool IsSupported(AddressFamily af)
{
Interop.Winsock.EnsureInitialized();
IntPtr INVALID_SOCKET = (IntPtr)(-1);
IntPtr socket = INVALID_SOCKET;
try
{
socket = Interop.Winsock.WSASocketW(af, SocketType.Stream, 0, IntPtr.Zero, 0, (int)Interop.Winsock.SocketConstructorFlags.WSA_FLAG_NO_HANDLE_INHERIT);
return
socket != INVALID_SOCKET ||
(SocketError)Marshal.GetLastWin32Error() != SocketError.AddressFamilyNotSupported;
}
finally
{
if (socket != INVALID_SOCKET)
{
Interop.Winsock.closesocket(socket);
}
}
}

Don't know what can potentially throw here.

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For native calls like this, usually the only thing that can throw is ObjectDisposedException if the SafeHandle is disposed. Maybe if it's invalid too.

That should never be the case here, but there's no harm in the try/catch just in case.

return false;
}
}
}