XTLS/Xray-core · error

padding turn length %d is not an allowed variant

Error message

padding turn length %d is not an allowed variant

What it means

Error "padding turn length %d is not an allowed variant" thrown in XTLS/Xray-core.

Source

Thrown at transport/internet/finalmask/xmc/padding.go:237

	if written != recordLength {
		return fmt.Errorf("padding chunks total %d, want %d", written, recordLength)
	}
	return nil
}

func readPaddingTurn(r io.Reader, turn paddingTurn, prefixLength int) error {
	encodedLength, headerLength, err := readVarintWithLength(r)
	if err != nil {
		return fmt.Errorf("read padding header: %w", err)
	}
	recordLength := int(encodedLength)
	if recordLength < headerLength || recordLength > maxPaddingTurnLength {
		return fmt.Errorf("invalid padding record length: %d", recordLength)
	}
	totalLength := prefixLength + recordLength
	if !paddingTurnAcceptsLength(turn, totalLength) {
		if len(turn.variants) > 0 {
			return fmt.Errorf("padding turn length %d is not an allowed variant", totalLength)
		}
		return fmt.Errorf("padding turn length %d is outside %d-%d", totalLength, turn.minLength, turn.maxLength)
	}

	var buffer [paddingBufferLength]byte
	remaining := recordLength - headerLength
	for remaining > 0 {
		chunkLength := min(remaining, len(buffer))
		if _, err := io.ReadFull(r, buffer[:chunkLength]); err != nil {
			return fmt.Errorf("read padding body: %w", err)
		}
		remaining -= chunkLength
	}
	return nil
}

func selectPaddingVariant(turn paddingTurn, prefixLength int) (int, []int, []paddingDelayRange, error) {
	if len(turn.variants) == 0 {

View on GitHub (pinned to 7d214f8b09)

When it happens

Trigger: Thrown at transport/internet/finalmask/xmc/padding.go:237 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/f1bfdbc52cefeff7. Report an issue: GitHub.