XTLS/Xray-core · error

padding turn %d has an invalid chunk delay: %w

Error message

padding turn %d has an invalid chunk delay: %w

What it means

validatePaddingSchedule rejected turn i's chunkDelay range: min negative or max < min. Chunk delays space out individual padding chunk writes inside a turn and must satisfy 0 <= min <= max, same rule as start delays.

Source

Thrown at transport/internet/finalmask/xmc/padding.go:92

	if len(schedule) == 0 {
		return fmt.Errorf("empty padding schedule")
	}
	if firstTurnPrefixLength < 0 {
		return fmt.Errorf("negative first turn prefix length: %d", firstTurnPrefixLength)
	}
	if firstTurnPrefixLength > 0 && schedule[0].direction != paddingClientToServer {
		return fmt.Errorf("first prefixed padding turn is not client-to-server")
	}

	for i, turn := range schedule {
		if turn.direction != paddingClientToServer && turn.direction != paddingServerToClient {
			return fmt.Errorf("padding turn %d has invalid direction: %d", i, turn.direction)
		}
		if err := validatePaddingDelayRange(turn.startDelay); err != nil {
			return fmt.Errorf("padding turn %d has an invalid start delay: %w", i, err)
		}
		if err := validatePaddingDelayRange(turn.chunkDelay); err != nil {
			return fmt.Errorf("padding turn %d has an invalid chunk delay: %w", i, err)
		}
		if turn.writeChunkMinLength < 0 || turn.writeChunkLength < turn.writeChunkMinLength || turn.writeChunkLength > maxPaddingChunkLength {
			return fmt.Errorf("padding turn %d has an invalid write chunk range: %d-%d", i, turn.writeChunkMinLength, turn.writeChunkLength)
		}
		if len(turn.variants) > 0 && turn.writeChunkLength != 0 {
			return fmt.Errorf("padding turn %d combines variants with generated write chunks", i)
		}

		minLength, maxLength, err := paddingTurnBounds(turn)
		if err != nil {
			return fmt.Errorf("padding turn %d: %w", i, err)
		}
		hasSendRange := turn.sendMinLength != 0 || turn.sendMaxLength != 0
		if hasSendRange {
			if len(turn.variants) > 0 {
				return fmt.Errorf("padding turn %d combines variants with a send range", i)
			}
			if turn.sendMinLength < minLength || turn.sendMaxLength < turn.sendMinLength || turn.sendMaxLength > maxLength {

View on GitHub (pinned to 7d214f8b09)

Solutions

1. Fix the range so 0 <= chunkDelay.min <= chunkDelay.max
2. Validate delay ranges at config-load time when they are externally configurable
3. Add a helper that constructs paddingDelayRange and rejects inverted inputs

Example fix

// before
chunkDelay: paddingDelayRange{min: -time.Millisecond, max: time.Second}

// after
chunkDelay: paddingDelayRange{min: 0, max: time.Second}

func validChunkDelay(d paddingDelayRange) bool { return d.min >= 0 && d.max >= d.min }

When it happens

Trigger: A schedule turn with chunkDelay.min negative or fields ordered max-then-min swapped in a struct literal.

Common situations: Config-driven delays with signed values; copy-paste between startDelay and chunkDelay fields with wrong ordering; tests with sentinel durations.

Related errors

• padding turn %d has an invalid start delay: %w
• empty padding schedule
• negative first turn prefix length: %d
• first prefixed padding turn is not client-to-server
• padding turn %d has invalid direction: %d

AI-assisted analysis of XTLS/Xray-core@7d214f8b09 (2026-08-15). Data as JSON: /api/errors/94bfcdf7ced7374f. Report an issue: GitHub.