/// <summary>
/// Kicks off the handshake process. It doesn't propagate the result outside directly but rather stores it in a task available via <see cref="FinishHandshakeAsync"/>.
/// </summary>
/// <remarks>
/// The method is <c>async void</c> on purpose so it starts an operation but doesn't wait for the result from the caller's perspective.
/// It does await <see cref="QuicConnection.FinishHandshakeAsync"/> but that never gets propagated to the caller for which the method ends with the first asynchronously processed <c>await</c>.
/// Once the asynchronous processing finishes, the result is stored in the task field that gets exposed via <see cref="FinishHandshakeAsync"/>.
/// </remarks>
/// <param name="connection">The new connection.</param>
/// <param name="clientHello">The TLS ClientHello data.</param>
/// <param name="connectionOptionsCallback">The connection options selection callback.</param>
public async void StartHandshake(QuicConnection connection, SslClientHelloInfo clientHello, Func <QuicConnection, SslClientHelloInfo, CancellationToken, ValueTask <QuicServerConnectionOptions> > connectionOptionsCallback)
{
try
{
_cancellationTokenSource.CancelAfter(s_handshakeTimeout);
QuicServerConnectionOptions options = await connectionOptionsCallback(connection, clientHello, _cancellationTokenSource.Token).ConfigureAwait(false);
options.Validate(nameof(options)); // Validate and fill in defaults for the options.
await connection.FinishHandshakeAsync(options, clientHello.ServerName, _cancellationTokenSource.Token).ConfigureAwait(false);
_finishHandshakeTask.SetResult(connection);
}
catch (Exception ex)
{
// Handshake failed:
// 1. Connection cannot be handed out since it's useless --> return null, listener will wait for another one.
// 2. Shutdown the connection to send a transport error to the peer --> application error code doesn't matter here, use default.
if (NetEventSource.Log.IsEnabled())
{
NetEventSource.Error(connection, $"{connection} Connection handshake failed: {ex}");
}
await connection.CloseAsync(default).ConfigureAwait(false);