{"record":{"id":"0c9303503314e854","repo":"XTLS/Xray-core","slug":"padding-turn-d-combines-variants-with-generated-w","errorCode":null,"errorMessage":"padding turn %d combines variants with generated write chunks","messagePattern":"padding turn (.+?) combines variants with generated write chunks","errorType":"validation","errorClass":null,"httpStatus":null,"severity":"error","filePath":"transport/internet/finalmask/xmc/padding.go","lineNumber":98,"sourceCode":"\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}\n\t\tif i == 0 && minLength-firstTurnPrefixLength < 1 {\n\t\t\treturn fmt.Errorf(\"padding turn 0 is too short for %d prefix bytes\", firstTurnPrefixLength)\n\t\t}","sourceCodeStart":80,"sourceCodeEnd":116,"githubUrl":"https://github.com/XTLS/Xray-core/blob/7d214f8b094f75322fa3990f8aadad1c912f24f5/transport/internet/finalmask/xmc/padding.go#L80-L116","documentation":"validatePaddingSchedule rejected turn i because it defines both explicit variants (pre-shaped chunk lists) and a non-zero writeChunkLength (randomly generated chunks). A turn must choose one shaping mode: variant-based or generator-based; combining them is ambiguous.","triggerScenarios":"A hand-authored turn that copies a variant list and also sets writeChunkLength for tuning; merging two schedule profiles without clearing one field.","commonSituations":"Forks extending schedules; config formats where both fields are optional and both get filled; schedule merge/refactor mistakes.","solutions":["If using variants, leave writeChunkLength (and writeChunkMinLength) at 0","If using generated chunks, remove the variants list","Enforce mutual exclusion in the schedule builder so this cannot compile/configure its way into runtime"],"exampleFix":"// before\nturn := paddingTurn{variants: vs, writeChunkLength: 8 * 1024}\n\n// after\nturn := paddingTurn{variants: vs} // generated chunks disabled","handlingStrategy":"validation","validationCode":"func variantsExclusive(turn paddingTurn) bool {\n    return !(len(turn.variants) > 0 && turn.writeChunkLength != 0)\n}","typeGuard":null,"tryCatchPattern":null,"preventionTips":["Enforce variants-vs-generator mutual exclusion in the schedule builder","Clear writeChunkLength when copying variant-based turns"],"tags":["go","padding","validation","schedule"],"backgroundTag":null,"analyzedSha":"7d214f8b094f75322fa3990f8aadad1c912f24f5","analyzedAt":"2026-08-15T14:26:24.325Z","schemaVersion":2},"datasetVersion":"2026-08-15T22:17:37.221Z"}