Function verifyServerExtensions

dial.go:285–317

(copts *compressionOptions, h http.Header)

}

func verifyServerExtensions(copts *compressionOptions, h http.Header) (*compressionOptions, error) {
	exts := websocketExtensions(h)
	if len(exts) == 0 {
		return nil, nil
	}

	ext := exts[0]
	if ext.name != "permessage-deflate" || len(exts) > 1 || copts == nil {
		return nil, fmt.Errorf("WebSocket protcol violation: unsupported extensions from server: %+v", exts[1:])
	}

	_copts := *copts
	copts = &_copts

	for _, p := range ext.params {
		switch p {
		case "client_no_context_takeover":
			copts.clientNoContextTakeover = true
			continue
		case "server_no_context_takeover":
			copts.serverNoContextTakeover = true
			continue
		}
		if strings.HasPrefix(p, "server_max_window_bits=") {
			// We can't adjust the deflate window, but decoding with a larger window is acceptable.
			continue
		}

		return nil, fmt.Errorf("unsupported permessage-deflate parameter: %q", p)
	}

	return copts, nil
}

var bufioReaderPool sync.Pool