remove redundent code

proxy/socks/protocol.go

@@ -139,34 +139,13 @@ func (s *ServerSession) Handshake(reader io.Reader, writer io.Writer) (*protocol
 		buffer.Clear()
 
 		request.Version = socks5Version
-		switch addrType {
-		case addrTypeIPv4:
-			if err := buffer.AppendSupplier(buf.ReadFullFrom(reader, 4)); err != nil {
-				return nil, err
-			}
-			request.Address = net.IPAddress(buffer.Bytes())
-		case addrTypeIPv6:
-			if err := buffer.AppendSupplier(buf.ReadFullFrom(reader, 16)); err != nil {
-				return nil, err
-			}
-			request.Address = net.IPAddress(buffer.Bytes())
-		case addrTypeDomain:
-			if err := buffer.AppendSupplier(buf.ReadFullFrom(reader, 1)); err != nil {
-				return nil, err
-			}
-			domainLength := int(buffer.Byte(0))
-			if err := buffer.AppendSupplier(buf.ReadFullFrom(reader, domainLength)); err != nil {
-				return nil, err
-			}
-			request.Address = net.ParseAddress(string(buffer.BytesFrom(-domainLength)))
-		default:
-			return nil, newError("Unknown address type: ", addrType)
-		}
 
-		if err := buffer.AppendSupplier(buf.ReadFullFrom(reader, 2)); err != nil {
-			return nil, err
+		addr, port, err := ReadAddress(buffer, addrType, reader)
+		if err != nil {
+			return nil, newError("failed to read address").Base(err)
 		}
-		request.Port = net.PortFromBytes(buffer.BytesFrom(-2))
+		request.Address = addr
+		request.Port = port
 
 		responseAddress := net.AnyIP
 		responsePort := net.Port(1717)