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) { //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 { //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, _, entry, status := wfs.maybeReadEntry(input.NodeId) if status != fuse.OK { return status } 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) { _, _, 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 } 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 len(attr) == 0 { return fuse.EINVAL } path, _, entry, status := wfs.maybeReadEntry(header.NodeId) if status != fuse.OK { return status } 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) }