// Set the special header to trigger the upgrade to WebSocket.
	wsReq := cfg.headers.Clone()
	if len(cfg.hostHeader) > 0 {
		echo.HostField.WriteForRequest(&outBuffer, requestID, hostHeader)
	}
	writeForwardedHeaders(&outBuffer, requestID, wsReq)
	common.SetWebSocketHeader(wsReq)

	if req.Message != "" {
		echo.ForwarderMessageField.WriteForRequest(&outBuffer, requestID, req.Message)
	}

	"istio.io/istio/pkg/test/echo/common"
	"istio.io/istio/pkg/test/echo/proto"
)

const (
	hostHeader = "Host"
)

var fwLog = log.RegisterScope("forwarder", "echo clientside")

func writeForwardedHeaders(out *bytes.Buffer, requestID int, header http.Header) {
	for key, values := range header {
		for _, v := range values {
			echo.ForwarderHeaderField.WriteKeyValueForRequest(out, requestID, key, v)
		}
	}
}

	httpReq.URL.Opaque = cfg.urlPath

	// Use the host header as the host.
	httpReq.Host = cfg.hostHeader

	// Copy the headers.
	httpReq.Header = cfg.headers.Clone()
	writeForwardedHeaders(&outBuffer, requestID, cfg.headers)

	// Propagate previous response cookies if any
	if cfg.PropagateResponse != nil {
		cfg.PropagateResponse(httpReq, cfg.previousResponse)
	}
	// Get the transport.