{"record":{"id":"228254b11ce19614","repo":"XTLS/Xray-core","slug":"padding-turn-d-has-an-invalid-write-chunk-range","errorCode":null,"errorMessage":"padding turn %d has an invalid write chunk range: %d-%d","messagePattern":"padding turn (.+?) has an invalid write chunk range: (.+?)-(.+?)","errorType":"validation","errorClass":null,"httpStatus":null,"severity":"error","filePath":"transport/internet/finalmask/xmc/padding.go","lineNumber":95,"sourceCode":"\tif firstTurnPrefixLength < 0 {\n\t\treturn fmt.Errorf(\"negative first turn prefix length: %d\", firstTurnPrefixLength)\n\t}\n\tif firstTurnPrefixLength > 0 && schedule[0].direction != paddingClientToServer {\n\t\treturn fmt.Errorf(\"first prefixed padding turn is not client-to-server\")\n\t}\n\n\tfor i, turn := range schedule {\n\t\tif turn.direction != paddingClientToServer && turn.direction != paddingServerToClient {\n\t\t\treturn fmt.Errorf(\"padding turn %d has invalid direction: %d\", i, turn.direction)\n\t\t}\n\t\tif err := validatePaddingDelayRange(turn.startDelay); err != nil {\n\t\t\treturn fmt.Errorf(\"padding turn %d has an invalid start delay: %w\", i, err)\n\t\t}\n\t\tif err := validatePaddingDelayRange(turn.chunkDelay); err != nil {\n\t\t\treturn fmt.Errorf(\"padding turn %d has an invalid chunk delay: %w\", i, err)\n\t\t}\n\t\tif turn.writeChunkMinLength < 0 || turn.writeChunkLength < turn.writeChunkMinLength || turn.writeChunkLength > maxPaddingChunkLength {\n\t\t\treturn fmt.Errorf(\"padding turn %d has an invalid write chunk range: %d-%d\", i, turn.writeChunkMinLength, turn.writeChunkLength)\n\t\t}\n\t\tif len(turn.variants) > 0 && turn.writeChunkLength != 0 {\n\t\t\treturn fmt.Errorf(\"padding turn %d combines variants with generated write chunks\", i)\n\t\t}\n\n\t\tminLength, maxLength, err := paddingTurnBounds(turn)\n\t\tif err != nil {\n\t\t\treturn fmt.Errorf(\"padding turn %d: %w\", i, err)\n\t\t}\n\t\thasSendRange := turn.sendMinLength != 0 || turn.sendMaxLength != 0\n\t\tif hasSendRange {\n\t\t\tif len(turn.variants) > 0 {\n\t\t\t\treturn fmt.Errorf(\"padding turn %d combines variants with a send range\", i)\n\t\t\t}\n\t\t\tif turn.sendMinLength < minLength || turn.sendMaxLength < turn.sendMinLength || turn.sendMaxLength > maxLength {\n\t\t\t\treturn fmt.Errorf(\"padding turn %d has an invalid send range: %d-%d\", i, turn.sendMinLength, turn.sendMaxLength)\n\t\t\t}\n\t\t}","sourceCodeStart":77,"sourceCodeEnd":113,"githubUrl":"https://github.com/XTLS/Xray-core/blob/7d214f8b094f75322fa3990f8aadad1c912f24f5/transport/internet/finalmask/xmc/padding.go#L77-L113","documentation":"validatePaddingSchedule rejected turn i's generated write-chunk parameters: writeChunkMinLength is negative, writeChunkLength < writeChunkMinLength, or writeChunkLength exceeds maxPaddingChunkLength (48 KiB). These bound the random chunk sizes used when the turn writes padding without explicit variants.","triggerScenarios":"A turn with writeChunkMinLength < 0, a min greater than the fixed length, or a writeChunkLength above 49152; setting writeChunkLength without clamping to the 48 KiB cap.","commonSituations":"Forks tuning chunk sizes for different Minecraft versions; config values expressed in the wrong unit (bits vs bytes); off-by-one conversions at the 48 KiB boundary.","solutions":["Set 0 <= writeChunkMinLength <= writeChunkLength <= 48*1024","Leave both zero to use the default 16 KiB paddingBufferLength chunking","Clamp externally supplied chunk sizes to maxPaddingChunkLength before building the turn"],"exampleFix":"// before\nwriteChunkMinLength: 32 * 1024, writeChunkLength: 64 * 1024 // > 48 KiB cap\n\n// after\nwriteChunkMinLength: 32 * 1024, writeChunkLength: 48 * 1024","handlingStrategy":"validation","validationCode":"func validWriteChunkRange(minLen, length int) bool {\n    return minLen >= 0 && length >= minLen && length <= 48*1024\n}","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Clamp chunk sizes to the 48 KiB cap when they come from config","Leave both values zero to use the safe default chunking"],"tags":["go","padding","validation","chunking"],"backgroundTag":null,"analyzedSha":"7d214f8b094f75322fa3990f8aadad1c912f24f5","analyzedAt":"2026-08-15T14:26:24.325Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}