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pv_header.go
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/
pv_header.go
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package lvm
import (
"bytes"
"encoding/binary"
"fmt"
"io"
"log"
"github.com/Soulou/go-lvm/crc32"
"github.com/pkg/errors"
)
const (
LabelID = "LABELONE"
// Label can be in any of the first 4 sectors
LabelScanSectors = 4
LabelScanSize = LabelScanSectors * SectorSize
LabelHeaderSize = 32
PhysicalVolumeIDLength = 32
)
type LabelHeader struct {
ID [8]byte /* LABELONE */
Sector uint64 /* Sector number of this label */
CRC uint32 /* From next field to end of sector */
Offset uint32 /* Offset from start of struct to contents */
Typename [8]byte /* LVM2 001 */
}
func (h LabelHeader) String() string {
return fmt.Sprintf(
"LabelHeader[ID:%s Sector:%d CRC:%d Offset:%d Typename:%s]",
string(h.ID[:]), h.Sector, h.CRC, h.Offset, string(h.Typename[:]),
)
}
func (h LabelHeader) CheckCRC32(sector []byte) (uint32, bool) {
crc32checksum := crc32.Calc(InitialCRC, sector[20:SectorSize])
return crc32checksum, crc32checksum == h.CRC
}
type StaticPhysicalVolumeHeader struct {
UUID [PhysicalVolumeIDLength]byte
/* This size can be overridden if PV belongs to a VG */
DeviceSize uint64 /* Bytes */
}
type PhysicalVolumeHeader struct {
StaticPhysicalVolumeHeader
/* NULL-terminated list of data areas followed by */
/* NULL-terminated list of metadata area headers */
DiskAreas []DataAreaDescriptor
MetadataAreas []DataAreaDescriptor
}
func (h PhysicalVolumeHeader) UUIDToString() string {
buf := bytes.NewBuffer(make([]byte, 0, 38))
buf.Write(h.UUID[0:6])
buf.Write([]byte{'-'})
buf.Write(h.UUID[6:10])
buf.Write([]byte{'-'})
buf.Write(h.UUID[14:18])
buf.Write([]byte{'-'})
buf.Write(h.UUID[18:22])
buf.Write([]byte{'-'})
buf.Write(h.UUID[22:26])
buf.Write([]byte{'-'})
buf.Write(h.UUID[26:32])
return buf.String()
}
func (h PhysicalVolumeHeader) String() string {
return fmt.Sprintf(
"PVHeader[ID:%s Size:%d DiskAreas:%d MetadataAreas:%d]",
h.UUIDToString(), h.DeviceSize, len(h.DiskAreas), len(h.MetadataAreas),
)
}
type StaticPhysicalVolumeHeaderExtension struct {
Version uint32
Flags uint32
}
type PhysicalVolumeHeaderExtension struct {
StaticPhysicalVolumeHeaderExtension
/* NULL-terminated list of bootloader areas */
BooloaderAreas []DataAreaDescriptor
}
func (ext PhysicalVolumeHeaderExtension) String() string {
return fmt.Sprintf("Ext[Version:%d Flags:%d, BootloaderAreas:%d]", ext.Version, ext.Flags, len(ext.BooloaderAreas))
}
func (pv *PhysicalVolume) readHeaderExt(reader io.Reader) (PhysicalVolumeHeaderExtension, error) {
var ext PhysicalVolumeHeaderExtension
err := binary.Read(reader, binary.LittleEndian, &(ext.StaticPhysicalVolumeHeaderExtension))
if err != nil {
return ext, errors.Wrapf(err, "fail to parse pv header extension")
}
areas, err := readDataAreaDescriptorList(reader)
if err != nil {
return ext, errors.Wrapf(err, "fail to parse data area descriptors for bootloader areas")
}
ext.BooloaderAreas = areas
return ext, nil
}
func (pv *PhysicalVolume) readHeader(reader io.Reader) (PhysicalVolumeHeader, error) {
var header PhysicalVolumeHeader
err := binary.Read(reader, binary.LittleEndian, &(header.StaticPhysicalVolumeHeader))
if err != nil {
return header, errors.Wrapf(err, "fail to parse pv header")
}
areas, err := readDataAreaDescriptorList(reader)
if err != nil {
return header, errors.Wrapf(err, "fail to parse data area descriptors for disk areas")
}
header.DiskAreas = areas
areas, err = readDataAreaDescriptorList(reader)
if err != nil {
return header, errors.Wrapf(err, "fail to parse data area descriptors for metadata areas")
}
header.MetadataAreas = areas
return header, nil
}
// It is expected to get the first block (block n°0) of the device
func (pv *PhysicalVolume) readLabelHeader(reader io.Reader) (LabelHeader, error) {
var header LabelHeader
for sector := 0; sector < LabelScanSectors; sector++ {
err := binary.Read(reader, binary.LittleEndian, &header)
if err != nil {
log.Println("error reading error: ", err, "continuing..")
continue
}
if string(header.ID[:]) == LabelID {
if header.Sector != uint64(sector) {
return header, errors.Errorf("header sector does not match: (%v, expected: %v)", header.Sector, sector)
}
break
} else {
toNextSector := make([]byte, SectorSize-LabelHeaderSize)
_, err := reader.Read(toNextSector)
if err != nil {
return header, errors.Wrapf(err, "fail to read to next sector")
}
}
}
if header.Sector == 0 {
return header, errors.New("label header not found")
}
return header, nil
}