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package mount
import (
"github.com/hanwen/go-fuse/v2/fuse"
sys "golang.org/x/sys/unix"
"runtime"
"strings"
"syscall"
)
const (
// https://man7.org/linux/man-pages/man7/xattr.7.html#:~:text=The%20VFS%20imposes%20limitations%20that,in%20listxattr(2)).
MAX_XATTR_NAME_SIZE = 255
MAX_XATTR_VALUE_SIZE = 65536
XATTR_PREFIX = "xattr-" // same as filer
)
// GetXAttr reads an extended attribute, and should return the
// number of bytes. If the buffer is too small, return ERANGE,
// with the required buffer size.
func (wfs *WFS) GetXAttr(cancel <-chan struct{}, header *fuse.InHeader, attr string, dest []byte) (size uint32, code fuse.Status) {
if wfs.option.DisableXAttr {
return 0, fuse.Status(syscall.ENOTSUP)
}
//validate attr name
if len(attr) > MAX_XATTR_NAME_SIZE {
if runtime.GOOS == "darwin" {
return 0, fuse.EPERM
} else {
return 0, fuse.ERANGE
}
}
if len(attr) == 0 {
return 0, fuse.EINVAL
}
_, _, entry, status := wfs.maybeReadEntry(header.NodeId)
if status != fuse.OK {
return 0, status
}
if entry == nil {
return 0, fuse.ENOENT
}
if entry.Extended == nil {
return 0, fuse.ENOATTR
}
data, found := entry.Extended[XATTR_PREFIX+attr]
if !found {
return 0, fuse.ENOATTR
}
if len(dest) < len(data) {
return uint32(len(data)), fuse.ERANGE
}
copy(dest, data)
return uint32(len(data)), fuse.OK
}
// SetXAttr writes an extended attribute.
// https://man7.org/linux/man-pages/man2/setxattr.2.html
//
// By default (i.e., flags is zero), the extended attribute will be
// created if it does not exist, or the value will be replaced if
// the attribute already exists. To modify these semantics, one of
// the following values can be specified in flags:
//
// XATTR_CREATE
// Perform a pure create, which fails if the named attribute
// exists already.
//
// XATTR_REPLACE
// Perform a pure replace operation, which fails if the named
// attribute does not already exist.
func (wfs *WFS) SetXAttr(cancel <-chan struct{}, input *fuse.SetXAttrIn, attr string, data []byte) fuse.Status {
if wfs.option.DisableXAttr {
return fuse.Status(syscall.ENOTSUP)
}
if wfs.IsOverQuota {
return fuse.Status(syscall.ENOSPC)
}
//validate attr name
if len(attr) > MAX_XATTR_NAME_SIZE {
if runtime.GOOS == "darwin" {
return fuse.EPERM
} else {
return fuse.ERANGE
}
}
if len(attr) == 0 {
return fuse.EINVAL
}
//validate attr value
if len(data) > MAX_XATTR_VALUE_SIZE {
if runtime.GOOS == "darwin" {
return fuse.Status(syscall.E2BIG)
} else {
return fuse.ERANGE
}
}
path, fh, entry, status := wfs.maybeReadEntry(input.NodeId)
if status != fuse.OK {
return status
}
if entry == nil {
return fuse.ENOENT
}
if fh != nil {
fh.entryLock.Lock()
defer fh.entryLock.Unlock()
}
if entry.Extended == nil {
entry.Extended = make(map[string][]byte)
}
oldData, _ := entry.Extended[XATTR_PREFIX+attr]
switch input.Flags {
case sys.XATTR_CREATE:
if len(oldData) > 0 {
break
}
fallthrough
case sys.XATTR_REPLACE:
fallthrough
default:
entry.Extended[XATTR_PREFIX+attr] = data
}
return wfs.saveEntry(path, entry)
}
// ListXAttr lists extended attributes as '\0' delimited byte
// slice, and return the number of bytes. If the buffer is too
// small, return ERANGE, with the required buffer size.
func (wfs *WFS) ListXAttr(cancel <-chan struct{}, header *fuse.InHeader, dest []byte) (n uint32, code fuse.Status) {
if wfs.option.DisableXAttr {
return 0, fuse.Status(syscall.ENOTSUP)
}
_, _, entry, status := wfs.maybeReadEntry(header.NodeId)
if status != fuse.OK {
return 0, status
}
if entry == nil {
return 0, fuse.ENOENT
}
if entry.Extended == nil {
return 0, fuse.OK
}
var data []byte
for k := range entry.Extended {
if strings.HasPrefix(k, XATTR_PREFIX) {
data = append(data, k[len(XATTR_PREFIX):]...)
data = append(data, 0)
}
}
if len(dest) < len(data) {
return uint32(len(data)), fuse.ERANGE
}
copy(dest, data)
return uint32(len(data)), fuse.OK
}
// RemoveXAttr removes an extended attribute.
func (wfs *WFS) RemoveXAttr(cancel <-chan struct{}, header *fuse.InHeader, attr string) fuse.Status {
if wfs.option.DisableXAttr {
return fuse.Status(syscall.ENOTSUP)
}
if len(attr) == 0 {
return fuse.EINVAL
}
path, fh, entry, status := wfs.maybeReadEntry(header.NodeId)
if status != fuse.OK {
return status
}
if entry == nil {
return fuse.OK
}
if fh != nil {
fh.entryLock.Lock()
defer fh.entryLock.Unlock()
}
if entry.Extended == nil {
return fuse.ENOATTR
}
_, found := entry.Extended[XATTR_PREFIX+attr]
if !found {
return fuse.ENOATTR
}
delete(entry.Extended, XATTR_PREFIX+attr)
return wfs.saveEntry(path, entry)
}
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