XTLS/Xray-core · error

target length %d leaves an invalid record length %d

Error message

target length %d leaves an invalid record length %d

What it means

Error "target length %d leaves an invalid record length %d" thrown in XTLS/Xray-core.

Source

Thrown at transport/internet/finalmask/xmc/padding.go:154

	return writePaddingTurnWithBuffer(w, turn, prefixLength, sleep, nil)
}

func writePaddingTurnWithBuffer(w io.Writer, turn paddingTurn, prefixLength int, sleep func(time.Duration), reusableBuffer *[]byte) error {
	startDelay, err := randomPaddingDelay(turn.startDelay)
	if err != nil {
		return fmt.Errorf("select padding start delay: %w", err)
	}
	if startDelay > 0 {
		sleep(startDelay)
	}

	targetLength, chunks, delays, err := selectPaddingVariant(turn, prefixLength)
	if err != nil {
		return err
	}
	recordLength := targetLength - prefixLength
	if recordLength < 1 {
		return fmt.Errorf("target length %d leaves an invalid record length %d", targetLength, recordLength)
	}

	encodedLength := Varint(recordLength)
	var header bytes.Buffer
	if err = encodedLength.writeTo(&header); err != nil {
		return fmt.Errorf("write padding header: %w", err)
	}
	if len(chunks) == 0 {
		writeChunkLength := turn.writeChunkLength
		if writeChunkLength == 0 {
			writeChunkLength = paddingBufferLength
		} else if turn.writeChunkMinLength > 0 {
			writeChunkLength, err = randomPaddingTarget(turn.writeChunkMinLength, writeChunkLength)
			if err != nil {
				return fmt.Errorf("select padding write chunk length: %w", err)
			}
		}
		chunks = defaultPaddingChunks(recordLength, writeChunkLength)

View on GitHub (pinned to 7d214f8b09)

When it happens

Trigger: Thrown at transport/internet/finalmask/xmc/padding.go:154 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/5274023b0342d9b8. Report an issue: GitHub.