| 1 | // Cgroups snapshot codec -- request, response view, builder, dispatch. |
| 2 | |
| 3 | package protocol |
| 4 | |
| 5 | import ( |
| 6 | "fmt" |
| 7 | ) |
| 8 | |
| 9 | const ( |
| 10 | cgroupsReqSize = 4 |
| 11 | cgroupsRespHdr = 24 |
| 12 | cgroupsDirEntry = 8 |
| 13 | cgroupsItemHdr = 32 |
| 14 | ) |
| 15 | |
| 16 | // --------------------------------------------------------------------------- |
| 17 | // Cgroups snapshot request (4 bytes) |
| 18 | // --------------------------------------------------------------------------- |
| 19 | |
| 20 | // CgroupsRequest is the cgroups snapshot request payload (4 bytes). |
| 21 | type CgroupsRequest struct { |
| 22 | LayoutVersion uint16 |
| 23 | Flags uint16 |
| 24 | } |
| 25 | |
| 26 | // Encode writes the request into buf. Returns 4 on success, 0 if buf is |
| 27 | // too small. |
| 28 | func (r *CgroupsRequest) Encode(buf []byte) int { |
| 29 | if len(buf) < cgroupsReqSize { |
| 30 | return 0 |
| 31 | } |
| 32 | ne.PutUint16(buf[0:2], r.LayoutVersion) |
| 33 | ne.PutUint16(buf[2:4], r.Flags) |
| 34 | return cgroupsReqSize |
| 35 | } |
| 36 | |
| 37 | // DecodeCgroupsRequest decodes a cgroups request from buf. Validates |
| 38 | // layout_version. |
| 39 | func DecodeCgroupsRequest(buf []byte) (CgroupsRequest, error) { |
| 40 | if len(buf) < cgroupsReqSize { |
| 41 | return CgroupsRequest{}, ErrTruncated |
| 42 | } |
| 43 | r := CgroupsRequest{ |
| 44 | LayoutVersion: ne.Uint16(buf[0:2]), |
| 45 | Flags: ne.Uint16(buf[2:4]), |
| 46 | } |
| 47 | if r.LayoutVersion != 1 { |
| 48 | return CgroupsRequest{}, ErrBadLayout |
| 49 | } |
| 50 | // flags must be zero (reserved for future use) |
| 51 | if r.Flags != 0 { |
| 52 | return CgroupsRequest{}, ErrBadLayout |
| 53 | } |
| 54 | return r, nil |
| 55 | } |
| 56 | |
| 57 | // --------------------------------------------------------------------------- |
| 58 | // CStringView - borrowed string view into payload buffer |
| 59 | // --------------------------------------------------------------------------- |
| 60 | |
| 61 | // CStringView is a borrowed, zero-copy string view into the payload buffer. |
| 62 | // It wraps a byte slice that includes the NUL terminator. The view is |
| 63 | // ephemeral and valid only while the underlying payload buffer lives. |
| 64 | // Copy immediately via String() if the data is needed later. |
| 65 | type CStringView struct { |
| 66 | data []byte // includes trailing NUL |
| 67 | len uint32 // length excluding NUL |
| 68 | } |
| 69 | |
| 70 | // NewCStringView creates a CStringView from a slice that includes the NUL |
| 71 | // terminator and the length excluding the NUL. |
| 72 | func NewCStringView(data []byte, length uint32) CStringView { |
| 73 | return CStringView{data: data, len: length} |
| 74 | } |
| 75 | |
| 76 | // Bytes returns the string content as a byte slice (without the NUL). |
| 77 | func (v CStringView) Bytes() []byte { |
| 78 | return v.data[:v.len] |
| 79 | } |
| 80 | |
| 81 | // Len returns the string length excluding the NUL terminator. |
| 82 | func (v CStringView) Len() uint32 { |
| 83 | return v.len |
| 84 | } |
| 85 | |
| 86 | // String returns a copy of the string content. This allocates. |
| 87 | func (v CStringView) String() string { |
| 88 | return string(v.data[:v.len]) |
| 89 | } |
| 90 | |
| 91 | // GoString implements fmt.GoStringer for debug output. |
| 92 | func (v CStringView) GoString() string { |
| 93 | return fmt.Sprintf("CStringView(%q)", v.data[:v.len]) |
| 94 | } |
| 95 | |
| 96 | // --------------------------------------------------------------------------- |
| 97 | // Cgroups snapshot response |
| 98 | // --------------------------------------------------------------------------- |
| 99 | |
| 100 | // CgroupsItemView is a per-item view -- ephemeral, borrows the payload |
| 101 | // buffer. Valid only while the payload buffer is alive. |
| 102 | type CgroupsItemView struct { |
| 103 | LayoutVersion uint16 |
| 104 | Flags uint16 |
| 105 | Hash uint32 |
| 106 | Options uint32 |
| 107 | Enabled uint32 |
| 108 | Name CStringView |
| 109 | Path CStringView |
| 110 | } |
| 111 | |
| 112 | // CgroupsResponseView is a full snapshot view -- ephemeral, borrows the |
| 113 | // payload buffer. Valid only during the current library call or callback. |
| 114 | // Copy immediately if the data is needed later. |
| 115 | type CgroupsResponseView struct { |
| 116 | LayoutVersion uint16 |
| 117 | Flags uint16 |
| 118 | ItemCount uint32 |
| 119 | SystemdEnabled uint32 |
| 120 | Generation uint64 |
| 121 | payload []byte // full payload for item access |
| 122 | } |
| 123 | |
| 124 | // DecodeCgroupsResponse decodes the snapshot response header and validates |
| 125 | // the item directory. On success, use Item() to access individual items. |
| 126 | func DecodeCgroupsResponse(buf []byte) (CgroupsResponseView, error) { |
| 127 | if len(buf) < cgroupsRespHdr { |
| 128 | return CgroupsResponseView{}, ErrTruncated |
| 129 | } |
| 130 | |
| 131 | layoutVersion := ne.Uint16(buf[0:2]) |
| 132 | flags := ne.Uint16(buf[2:4]) |
| 133 | itemCount := ne.Uint32(buf[4:8]) |
| 134 | systemdEnabled := ne.Uint32(buf[8:12]) |
| 135 | reserved := ne.Uint32(buf[12:16]) |
| 136 | generation := ne.Uint64(buf[16:24]) |
| 137 | |
| 138 | if layoutVersion != 1 { |
| 139 | return CgroupsResponseView{}, ErrBadLayout |
| 140 | } |
| 141 | |
| 142 | // flags must be zero |
| 143 | if flags != 0 { |
| 144 | return CgroupsResponseView{}, ErrBadLayout |
| 145 | } |
| 146 | |
| 147 | // reserved field must be zero |
| 148 | if reserved != 0 { |
| 149 | return CgroupsResponseView{}, ErrBadLayout |
| 150 | } |
| 151 | |
| 152 | dirSize64 := uint64(itemCount) * uint64(cgroupsDirEntry) |
| 153 | dirEnd64 := uint64(cgroupsRespHdr) + dirSize64 |
| 154 | dirEnd, ok := checkedInt(dirEnd64) |
| 155 | if !ok { |
| 156 | return CgroupsResponseView{}, ErrBadItemCount |
| 157 | } |
| 158 | if dirEnd > len(buf) { |
| 159 | return CgroupsResponseView{}, ErrTruncated |
| 160 | } |
| 161 | |
| 162 | packedAreaLen := len(buf) - dirEnd |
| 163 | |
| 164 | // Validate each directory entry. |
| 165 | dirSize, ok := checkedInt(dirSize64) |
| 166 | if !ok { |
| 167 | return CgroupsResponseView{}, ErrBadItemCount |
| 168 | } |
| 169 | for i := 0; i < dirSize; i += cgroupsDirEntry { |
| 170 | base := cgroupsRespHdr + i |
| 171 | off, err := checkedWireU32Int(buf, base) |
| 172 | if err != nil { |
| 173 | return CgroupsResponseView{}, err |
| 174 | } |
| 175 | length, err := checkedWireU32Int(buf, base+4) |
| 176 | if err != nil { |
| 177 | return CgroupsResponseView{}, err |
| 178 | } |
| 179 | |
| 180 | if off%Alignment != 0 { |
| 181 | return CgroupsResponseView{}, ErrBadAlignment |
| 182 | } |
| 183 | end, ok := checkedAddInt(off, length) |
| 184 | if !ok || end > packedAreaLen { |
| 185 | return CgroupsResponseView{}, ErrOutOfBounds |
| 186 | } |
| 187 | if length < cgroupsItemHdr { |
| 188 | return CgroupsResponseView{}, ErrTruncated |
| 189 | } |
| 190 | } |
| 191 | |
| 192 | return CgroupsResponseView{ |
| 193 | LayoutVersion: layoutVersion, |
| 194 | Flags: flags, |
| 195 | ItemCount: itemCount, |
| 196 | SystemdEnabled: systemdEnabled, |
| 197 | Generation: generation, |
| 198 | payload: buf, |
| 199 | }, nil |
| 200 | } |
| 201 | |
| 202 | // Item accesses the item at index from a decoded snapshot view. Returns an |
| 203 | // ephemeral item view. |
| 204 | func (v *CgroupsResponseView) Item(index uint32) (CgroupsItemView, error) { |
| 205 | if index >= v.ItemCount { |
| 206 | return CgroupsItemView{}, ErrOutOfBounds |
| 207 | } |
| 208 | |
| 209 | dirStart := cgroupsRespHdr |
| 210 | dirSize, ok := checkedInt(uint64(v.ItemCount) * uint64(cgroupsDirEntry)) |
| 211 | if !ok { |
| 212 | return CgroupsItemView{}, ErrBadItemCount |
| 213 | } |
| 214 | packedAreaStart, ok := checkedAddInt(dirStart, dirSize) |
| 215 | if !ok { |
| 216 | return CgroupsItemView{}, ErrOutOfBounds |
| 217 | } |
| 218 | |
| 219 | dirIndexOff, ok := checkedInt(uint64(index) * uint64(cgroupsDirEntry)) |
| 220 | if !ok { |
| 221 | return CgroupsItemView{}, ErrOutOfBounds |
| 222 | } |
| 223 | dirBase, ok := checkedAddInt(dirStart, dirIndexOff) |
| 224 | if !ok { |
| 225 | return CgroupsItemView{}, ErrOutOfBounds |
| 226 | } |
| 227 | itemOff, err := checkedWireU32Int(v.payload, dirBase) |
| 228 | if err != nil { |
| 229 | return CgroupsItemView{}, err |
| 230 | } |
| 231 | itemLen, err := checkedWireU32Int(v.payload, dirBase+4) |
| 232 | if err != nil { |
| 233 | return CgroupsItemView{}, err |
| 234 | } |
| 235 | |
| 236 | itemStart, ok := checkedAddInt(packedAreaStart, itemOff) |
| 237 | if !ok { |
| 238 | return CgroupsItemView{}, ErrOutOfBounds |
| 239 | } |
| 240 | itemEnd, ok := checkedAddInt(itemStart, itemLen) |
| 241 | if !ok || itemEnd > len(v.payload) { |
| 242 | return CgroupsItemView{}, ErrOutOfBounds |
| 243 | } |
| 244 | item := v.payload[itemStart:itemEnd] |
| 245 | |
| 246 | layoutVersion := ne.Uint16(item[0:2]) |
| 247 | flags := ne.Uint16(item[2:4]) |
| 248 | hash := ne.Uint32(item[4:8]) |
| 249 | options := ne.Uint32(item[8:12]) |
| 250 | enabled := ne.Uint32(item[12:16]) |
| 251 | |
| 252 | nameOff, err := checkedWireU32Int(item, 16) |
| 253 | if err != nil { |
| 254 | return CgroupsItemView{}, err |
| 255 | } |
| 256 | nameLen, err := checkedWireU32Int(item, 20) |
| 257 | if err != nil { |
| 258 | return CgroupsItemView{}, err |
| 259 | } |
| 260 | nameLen32 := ne.Uint32(item[20:24]) |
| 261 | pathOff, err := checkedWireU32Int(item, 24) |
| 262 | if err != nil { |
| 263 | return CgroupsItemView{}, err |
| 264 | } |
| 265 | pathLen, err := checkedWireU32Int(item, 28) |
| 266 | if err != nil { |
| 267 | return CgroupsItemView{}, err |
| 268 | } |
| 269 | pathLen32 := ne.Uint32(item[28:32]) |
| 270 | |
| 271 | if layoutVersion != 1 { |
| 272 | return CgroupsItemView{}, ErrBadLayout |
| 273 | } |
| 274 | |
| 275 | // item flags must be zero |
| 276 | if flags != 0 { |
| 277 | return CgroupsItemView{}, ErrBadLayout |
| 278 | } |
| 279 | |
| 280 | // Validate name string. |
| 281 | if nameOff < cgroupsItemHdr { |
| 282 | return CgroupsItemView{}, ErrOutOfBounds |
| 283 | } |
| 284 | nameEnd, ok := checkedAddInt(nameOff, nameLen) |
| 285 | if !ok { |
| 286 | return CgroupsItemView{}, ErrOutOfBounds |
| 287 | } |
| 288 | nameNulEnd, ok := checkedAddInt(nameEnd, 1) |
| 289 | if !ok || nameNulEnd > itemLen { |
| 290 | return CgroupsItemView{}, ErrOutOfBounds |
| 291 | } |
| 292 | if item[nameEnd] != 0 { |
| 293 | return CgroupsItemView{}, ErrMissingNul |
| 294 | } |
| 295 | |
| 296 | // Validate path string. |
| 297 | if pathOff < cgroupsItemHdr { |
| 298 | return CgroupsItemView{}, ErrOutOfBounds |
| 299 | } |
| 300 | pathEnd, ok := checkedAddInt(pathOff, pathLen) |
| 301 | if !ok { |
| 302 | return CgroupsItemView{}, ErrOutOfBounds |
| 303 | } |
| 304 | pathNulEnd, ok := checkedAddInt(pathEnd, 1) |
| 305 | if !ok || pathNulEnd > itemLen { |
| 306 | return CgroupsItemView{}, ErrOutOfBounds |
| 307 | } |
| 308 | if item[pathEnd] != 0 { |
| 309 | return CgroupsItemView{}, ErrMissingNul |
| 310 | } |
| 311 | |
| 312 | // Reject overlapping name and path regions (including NUL) |
| 313 | { |
| 314 | if overlap(nameOff, nameNulEnd, pathOff, pathNulEnd) { |
| 315 | return CgroupsItemView{}, ErrBadLayout |
| 316 | } |
| 317 | } |
| 318 | |
| 319 | name := NewCStringView(item[nameOff:nameNulEnd], nameLen32) |
| 320 | path := NewCStringView(item[pathOff:pathNulEnd], pathLen32) |
| 321 | |
| 322 | return CgroupsItemView{ |
| 323 | LayoutVersion: layoutVersion, |
| 324 | Flags: flags, |
| 325 | Hash: hash, |
| 326 | Options: options, |
| 327 | Enabled: enabled, |
| 328 | Name: name, |
| 329 | Path: path, |
| 330 | }, nil |
| 331 | } |
| 332 | |
| 333 | // --------------------------------------------------------------------------- |
| 334 | // Cgroups snapshot response builder |
| 335 | // --------------------------------------------------------------------------- |
| 336 | |
| 337 | // CgroupsBuilder builds a cgroups snapshot response payload. |
| 338 | // |
| 339 | // Layout during building (maxItems directory slots reserved): |
| 340 | // |
| 341 | // [24-byte header space] [maxItems*8 directory] [packed items] |
| 342 | // |
| 343 | // Layout after Finish (compacted to actual itemCount): |
| 344 | // |
| 345 | // [24-byte header] [itemCount*8 directory] [packed items] |
| 346 | type CgroupsBuilder struct { |
| 347 | buf []byte |
| 348 | systemdEnabled uint32 |
| 349 | generation uint64 |
| 350 | itemCount uint32 |
| 351 | maxItems uint32 |
| 352 | dataOffset int // current write position (absolute in buf) |
| 353 | } |
| 354 | |
| 355 | // NewCgroupsBuilder initializes a cgroups response builder. buf must be |
| 356 | // caller-owned and large enough for the expected snapshot. |
| 357 | func NewCgroupsBuilder(buf []byte, maxItems uint32, systemdEnabled uint32, generation uint64) *CgroupsBuilder { |
| 358 | minRequired, ok := CgroupsBuilderMinBytes(maxItems) |
| 359 | if !ok || len(buf) < minRequired { |
| 360 | panic(fmt.Sprintf("CgroupsBuilder buffer too small: need at least %d bytes, got %d", |
| 361 | minRequired, len(buf))) |
| 362 | } |
| 363 | dataOffset := minRequired |
| 364 | return &CgroupsBuilder{ |
| 365 | buf: buf, |
| 366 | systemdEnabled: systemdEnabled, |
| 367 | generation: generation, |
| 368 | maxItems: maxItems, |
| 369 | dataOffset: dataOffset, |
| 370 | } |
| 371 | } |
| 372 | |
| 373 | // CgroupsBuilderMinBytes returns the minimum response buffer required to |
| 374 | // reserve directory slots for maxItems before packed item data is appended. |
| 375 | func CgroupsBuilderMinBytes(maxItems uint32) (int, bool) { |
| 376 | minRequired := uint64(cgroupsRespHdr) + uint64(maxItems)*uint64(cgroupsDirEntry) |
| 377 | return checkedInt(minRequired) |
| 378 | } |
| 379 | |
| 380 | // SetHeader updates the response header fields written by Finish(). |
| 381 | func (b *CgroupsBuilder) SetHeader(systemdEnabled uint32, generation uint64) { |
| 382 | b.systemdEnabled = systemdEnabled |
| 383 | b.generation = generation |
| 384 | } |
| 385 | |
| 386 | // EstimateCgroupsMaxItems returns a safe upper bound for the number of |
| 387 | // cgroup items that can fit in a response buffer of size bufSize. |
| 388 | // |
| 389 | // This is an upper bound for builder reservation, not a promise that all of |
| 390 | // those items will fit with arbitrary string lengths. |
| 391 | func EstimateCgroupsMaxItems(bufSize int) uint32 { |
| 392 | if bufSize <= cgroupsRespHdr { |
| 393 | return 0 |
| 394 | } |
| 395 | |
| 396 | minAlignedItem := Align8(cgroupsItemHdr + 2) |
| 397 | items := (bufSize - cgroupsRespHdr) / (cgroupsDirEntry + minAlignedItem) |
| 398 | items32, ok := checkedU32Int(items) |
| 399 | if !ok { |
| 400 | return ^uint32(0) |
| 401 | } |
| 402 | return items32 |
| 403 | } |
| 404 | |
| 405 | // Add adds one cgroup item. Handles offset bookkeeping, NUL termination, |
| 406 | // and alignment. |
| 407 | func (b *CgroupsBuilder) Add(hash, options, enabled uint32, name, path []byte) error { |
| 408 | if b.itemCount >= b.maxItems { |
| 409 | return ErrOverflow |
| 410 | } |
| 411 | |
| 412 | itemStart, ok := checkedAlign8(b.dataOffset) |
| 413 | if !ok { |
| 414 | return ErrOverflow |
| 415 | } |
| 416 | |
| 417 | nameSize, ok := checkedAddInt(len(name), 1) |
| 418 | if !ok { |
| 419 | return ErrOverflow |
| 420 | } |
| 421 | pathSize, ok := checkedAddInt(len(path), 1) |
| 422 | if !ok { |
| 423 | return ErrOverflow |
| 424 | } |
| 425 | itemSize, ok := checkedAddInt(cgroupsItemHdr, nameSize) |
| 426 | if !ok { |
| 427 | return ErrOverflow |
| 428 | } |
| 429 | itemSize, ok = checkedAddInt(itemSize, pathSize) |
| 430 | if !ok { |
| 431 | return ErrOverflow |
| 432 | } |
| 433 | |
| 434 | itemEnd, ok := checkedAddInt(itemStart, itemSize) |
| 435 | if !ok || itemEnd > len(b.buf) { |
| 436 | return ErrOverflow |
| 437 | } |
| 438 | |
| 439 | // Zero alignment padding. |
| 440 | if itemStart > b.dataOffset { |
| 441 | clear(b.buf[b.dataOffset:itemStart]) |
| 442 | } |
| 443 | |
| 444 | nameLen32, ok := checkedU32Int(len(name)) |
| 445 | if !ok { |
| 446 | return ErrOverflow |
| 447 | } |
| 448 | pathLen32, ok := checkedU32Int(len(path)) |
| 449 | if !ok { |
| 450 | return ErrOverflow |
| 451 | } |
| 452 | nameOffset32 := uint32(cgroupsItemHdr) |
| 453 | pathOffset, ok := checkedAddInt(cgroupsItemHdr, nameSize) |
| 454 | if !ok { |
| 455 | return ErrOverflow |
| 456 | } |
| 457 | pathOffset32, ok := checkedU32Int(pathOffset) |
| 458 | if !ok { |
| 459 | return ErrOverflow |
| 460 | } |
| 461 | itemStart32, ok := checkedU32Int(itemStart) |
| 462 | if !ok { |
| 463 | return ErrOverflow |
| 464 | } |
| 465 | itemSize32, ok := checkedU32Int(itemSize) |
| 466 | if !ok { |
| 467 | return ErrOverflow |
| 468 | } |
| 469 | |
| 470 | // Write item header. |
| 471 | p := itemStart |
| 472 | ne.PutUint16(b.buf[p:p+2], 1) // layout_version |
| 473 | ne.PutUint16(b.buf[p+2:p+4], 0) // flags |
| 474 | ne.PutUint32(b.buf[p+4:p+8], hash) |
| 475 | ne.PutUint32(b.buf[p+8:p+12], options) |
| 476 | ne.PutUint32(b.buf[p+12:p+16], enabled) |
| 477 | ne.PutUint32(b.buf[p+16:p+20], nameOffset32) |
| 478 | ne.PutUint32(b.buf[p+20:p+24], nameLen32) |
| 479 | ne.PutUint32(b.buf[p+24:p+28], pathOffset32) |
| 480 | ne.PutUint32(b.buf[p+28:p+32], pathLen32) |
| 481 | |
| 482 | // Write strings with NUL terminators. |
| 483 | ns := p + cgroupsItemHdr |
| 484 | copy(b.buf[ns:], name) |
| 485 | b.buf[ns+len(name)] = 0 |
| 486 | |
| 487 | ps := p + pathOffset |
| 488 | copy(b.buf[ps:], path) |
| 489 | b.buf[ps+len(path)] = 0 |
| 490 | |
| 491 | // Write directory entry (absolute offset stored temporarily). |
| 492 | dirEntryOff, ok := checkedInt(uint64(b.itemCount) * uint64(cgroupsDirEntry)) |
| 493 | if !ok { |
| 494 | return ErrOverflow |
| 495 | } |
| 496 | dirEntry, ok := checkedAddInt(cgroupsRespHdr, dirEntryOff) |
| 497 | if !ok { |
| 498 | return ErrOverflow |
| 499 | } |
| 500 | ne.PutUint32(b.buf[dirEntry:dirEntry+4], itemStart32) |
| 501 | ne.PutUint32(b.buf[dirEntry+4:dirEntry+8], itemSize32) |
| 502 | |
| 503 | b.dataOffset = itemEnd |
| 504 | b.itemCount++ |
| 505 | return nil |
| 506 | } |
| 507 | |
| 508 | // Finish finalizes the builder. Returns the total payload size. The buffer |
| 509 | // now contains a complete, decodable cgroups snapshot response payload. |
| 510 | func (b *CgroupsBuilder) Finish() int { |
| 511 | p := b.buf |
| 512 | |
| 513 | if b.itemCount == 0 { |
| 514 | ne.PutUint16(p[0:2], 1) |
| 515 | ne.PutUint16(p[2:4], 0) |
| 516 | ne.PutUint32(p[4:8], 0) |
| 517 | ne.PutUint32(p[8:12], b.systemdEnabled) |
| 518 | ne.PutUint32(p[12:16], 0) |
| 519 | ne.PutUint64(p[16:24], b.generation) |
| 520 | return cgroupsRespHdr |
| 521 | } |
| 522 | |
| 523 | dirSize, ok := checkedInt(uint64(b.itemCount) * uint64(cgroupsDirEntry)) |
| 524 | if !ok { |
| 525 | return 0 |
| 526 | } |
| 527 | finalPackedStart, ok := checkedAddInt(cgroupsRespHdr, dirSize) |
| 528 | if !ok { |
| 529 | return 0 |
| 530 | } |
| 531 | |
| 532 | // Read the first directory entry to find where packed data begins. |
| 533 | firstItemAbs32 := ne.Uint32(p[cgroupsRespHdr : cgroupsRespHdr+4]) |
| 534 | firstItemAbs, ok := checkedInt(uint64(firstItemAbs32)) |
| 535 | if !ok { |
| 536 | return 0 |
| 537 | } |
| 538 | |
| 539 | packedDataLen := b.dataOffset - firstItemAbs |
| 540 | |
| 541 | if finalPackedStart < firstItemAbs { |
| 542 | packedDataEnd, ok := checkedAddInt(firstItemAbs, packedDataLen) |
| 543 | if !ok { |
| 544 | return 0 |
| 545 | } |
| 546 | // Shift packed data left. |
| 547 | copy(p[finalPackedStart:], p[firstItemAbs:packedDataEnd]) |
| 548 | } |
| 549 | |
| 550 | // Convert directory entries from absolute to relative offsets. |
| 551 | dirBase := cgroupsRespHdr |
| 552 | for i := uint32(0); i < b.itemCount; i++ { |
| 553 | entryOff, ok := checkedInt(uint64(i) * uint64(cgroupsDirEntry)) |
| 554 | if !ok { |
| 555 | return 0 |
| 556 | } |
| 557 | entry, ok := checkedAddInt(dirBase, entryOff) |
| 558 | if !ok { |
| 559 | return 0 |
| 560 | } |
| 561 | absOff := ne.Uint32(p[entry : entry+4]) |
| 562 | if absOff < firstItemAbs32 { |
| 563 | return 0 |
| 564 | } |
| 565 | relOff := absOff - firstItemAbs32 |
| 566 | ne.PutUint32(p[entry:entry+4], relOff) |
| 567 | // length stays the same. |
| 568 | } |
| 569 | |
| 570 | // Write snapshot header. |
| 571 | ne.PutUint16(p[0:2], 1) |
| 572 | ne.PutUint16(p[2:4], 0) |
| 573 | ne.PutUint32(p[4:8], b.itemCount) |
| 574 | ne.PutUint32(p[8:12], b.systemdEnabled) |
| 575 | ne.PutUint32(p[12:16], 0) |
| 576 | ne.PutUint64(p[16:24], b.generation) |
| 577 | |
| 578 | total, ok := checkedAddInt(finalPackedStart, packedDataLen) |
| 579 | if !ok { |
| 580 | return 0 |
| 581 | } |
| 582 | return total |
| 583 | } |
| 584 | |
| 585 | // DispatchCgroupsSnapshot decodes request, builds response via handler. |
| 586 | func DispatchCgroupsSnapshot(req []byte, resp []byte, maxItems uint32, |
| 587 | handler func(*CgroupsRequest, *CgroupsBuilder) bool) (int, bool) { |
| 588 | request, err := DecodeCgroupsRequest(req) |
| 589 | if err != nil { |
| 590 | return 0, false |
| 591 | } |
| 592 | minRequired, ok := CgroupsBuilderMinBytes(maxItems) |
| 593 | if !ok || len(resp) < minRequired { |
| 594 | return 0, false |
| 595 | } |
| 596 | builder := NewCgroupsBuilder(resp, maxItems, 0, 0) |
| 597 | if !handler(&request, builder) { |
| 598 | return 0, false |
| 599 | } |
| 600 | return builder.Finish(), true |
| 601 | } |