private async Task HandleConnectRequestAsync(Request request, Memory <byte> buffer, CancellationToken cancellationToken = default)
{
// Connect to remote endpoint.
EndpointSocket = ClientSocket.CreateNewOfSameType();
EndpointSocket.Bind(new IPEndPoint(EndpointInterface, 0 /* any */));
var error = null as SocketError?;
try
{
switch (request)
{
case IpRequest ipRequest:
EndpointSocket = await EndpointSocket.ConnectAsync(ipRequest.Address, ipRequest.Port);
break;
case DomainNameRequest domainRequest:
EndpointSocket = await EndpointSocket.ConnectAsync(domainRequest.DomainName, domainRequest.Port);
break;
default:
throw new Exception("Unknown request type.");
}
}
catch (SocketException e)
{
error = e.SocketErrorCode;
}
var localEndpoint = EndpointSocket?.LocalEndPoint as IPEndPoint ?? new IPEndPoint(0, 0);
var remoteEndpoint = EndpointSocket?.RemoteEndPoint as IPEndPoint ?? new IPEndPoint(0, 0);
// The bind address and port should be the server local values during a CONNECT.
var localAddress = localEndpoint.Address;
if (localAddress.IsIPv4MappedToIPv6)
{
localAddress = localAddress.MapToIPv4();
}
var(portHigh, portLow) = Helpers.GetBytesFromPort(localEndpoint.Port);
// Select the reply code based on any errors.
var replyField = Helpers.GetSocksReply(error);
// Send reply to client.
var replyLength = 0;
buffer.Span[0] = 0x05; // VERSION
buffer.Span[1] = replyField; // REPLY.
buffer.Span[2] = 0x00; // RESERVED.
if (localAddress.AddressFamily == AddressFamily.InterNetwork)
{
buffer.Span[3] = 0x01; // ADDRESS TYPE (IPv4).
localAddress.TryWriteBytes(buffer.Span.Slice(4, 4), out int written);
buffer.Span[8] = portHigh;
buffer.Span[9] = portLow;
replyLength = 10;
}
else if (localAddress.AddressFamily == AddressFamily.InterNetworkV6)
{
buffer.Span[3] = 0x04; // ADDRESS TYPE (IPv6).
localAddress.TryWriteBytes(buffer.Span.Slice(4, 16), out int written);
buffer.Span[20] = portHigh;
buffer.Span[21] = portLow;
replyLength = 22;
}
else
{
throw new Exception("Unknown server-local bind address type.");
}
// Send a response to client regardless of failure.
await ClientSocket.SendAsync(buffer.Slice(0, replyLength), cancellationToken);
var sock = new Socket(SocketType.Dgram, ProtocolType.Udp);
var buf = new byte[4096];
// In a failure scenario, ensure the SOCKS process does not continue.
if (error != null)
{
throw new SocksException($"The connection failed gracefully with `{error}`.");
}
}