GetXattr/ListXattr implementation

connection.go

@@ -434,6 +434,10 @@ func (c *Connection) shouldLogError(
 			return false
 		}
 
+	case *fuseops.GetXattrOp:
+		if err == syscall.ENODATA || err == syscall.ERANGE {
+			return false
+		}
 	case *unknownOp:
 		// Don't bother the user with methods we intentionally don't support.
 		if err == syscall.ENOSYS {
@@ -489,7 +493,7 @@ func (c *Connection) Reply(ctx context.Context, opErr error) {
 	if !noResponse {
 		err := c.writeMessage(outMsg.Bytes())
 		if err != nil && c.errorLogger != nil {
-			c.errorLogger.Printf("writeMessage: %v", err)
+			c.errorLogger.Printf("writeMessage: %v %v", err, outMsg.Bytes())
 		}
 	}
 }

conversions.go

@@ -433,6 +433,61 @@ func convertInMessage(
 			Name:  string(buf[:n-1]),
 		}
 
+	case fusekernel.OpGetxattr:
+		type input fusekernel.GetxattrIn
+		in := (*input)(inMsg.Consume(unsafe.Sizeof(input{})))
+		if in == nil {
+			err = errors.New("Corrupt OpGetxattr")
+			return
+		}
+
+		name := inMsg.ConsumeBytes(inMsg.Len())
+		i := bytes.IndexByte(name, '\x00')
+		if i < 0 {
+			err = errors.New("Corrupt OpGetxattr")
+			return
+		}
+		name = name[:i]
+
+		to := &fuseops.GetXattrOp{
+			Inode: fuseops.InodeID(inMsg.Header().Nodeid),
+			Name:  string(name),
+		}
+		o = to
+
+		readSize := int(in.Size)
+		p := outMsg.GrowNoZero(readSize)
+		if p == nil {
+			err = fmt.Errorf("Can't grow for %d-byte read", readSize)
+			return
+		}
+
+		sh := (*reflect.SliceHeader)(unsafe.Pointer(&to.Dst))
+		sh.Data = uintptr(p)
+		sh.Len = readSize
+		sh.Cap = readSize
+
+	case fusekernel.OpListxattr:
+		type input fusekernel.ListxattrIn
+		in := (*input)(inMsg.Consume(unsafe.Sizeof(input{})))
+		if in == nil {
+			err = errors.New("Corrupt OpListxattr")
+			return
+		}
+
+		o = &fuseops.ListXattrOp{
+			Inode: fuseops.InodeID(inMsg.Header().Nodeid),
+		}
+
+		readSize := int(in.Size)
+		if readSize != 0 {
+			p := outMsg.GrowNoZero(readSize)
+			if p == nil {
+				err = fmt.Errorf("Can't grow for %d-byte read", readSize)
+				return
+			}
+		}
+
 	default:
 		o = &unknownOp{
 			OpCode: inMsg.Header().Opcode,
@@ -472,6 +527,20 @@ func (c *Connection) kernelResponse(
 	// If the user returned the error, fill in the error field of the outgoing
 	// message header.
 	if opErr != nil {
+		handled := false
+
+		if opErr == syscall.ERANGE {
+			switch o := op.(type) {
+			case *fuseops.GetXattrOp:
+				writeXattrSize(m, uint32(o.BytesRead))
+				handled = true
+			case *fuseops.ListXattrOp:
+				writeXattrSize(m, uint32(o.BytesRead))
+				handled = true
+			}
+		}
+
+		if !handled {
 			m.OutHeader().Error = -int32(syscall.EIO)
 			if errno, ok := opErr.(syscall.Errno); ok {
 				m.OutHeader().Error = -int32(errno)
@@ -484,6 +553,7 @@ func (c *Connection) kernelResponse(
 			// header.
 			m.ShrinkTo(buffer.OutMessageHeaderSize)
 		}
+	}
 
 	// Otherwise, fill in the rest of the response.
 	if opErr == nil {
@@ -639,6 +709,23 @@ func (c *Connection) kernelResponseForOp(
 	case *fuseops.RemoveXattrOp:
 		// Empty response
 
+	case *fuseops.GetXattrOp:
+		// convertInMessage already set up the destination buffer to be at the end
+		// of the out message. We need only shrink to the right size based on how
+		// much the user read.
+		if o.BytesRead == 0 {
+			writeXattrSize(m, uint32(o.BytesRead))
+		} else {
+			m.ShrinkTo(buffer.OutMessageHeaderSize + o.BytesRead)
+		}
+
+	case *fuseops.ListXattrOp:
+		if o.BytesRead == 0 {
+			writeXattrSize(m, uint32(o.BytesRead))
+		} else {
+			m.ShrinkTo(buffer.OutMessageHeaderSize + o.BytesRead)
+		}
+
 	case *initOp:
 		out := (*fusekernel.InitOut)(m.Grow(int(unsafe.Sizeof(fusekernel.InitOut{}))))
 
@@ -760,3 +847,8 @@ func convertFileMode(unixMode uint32) os.FileMode {
 	}
 	return mode
 }
+
+func writeXattrSize(m *buffer.OutMessage, size uint32) {
+	out := (*fusekernel.GetxattrOut)(m.Grow(int(unsafe.Sizeof(fusekernel.GetxattrOut{}))))
+	out.Size = size
+}

debug.go

@@ -89,6 +89,12 @@ func describeRequest(op interface{}) (s string) {
 		addComponent("handle %d", typed.Handle)
 		addComponent("offset %d", typed.Offset)
 		addComponent("%d bytes", len(typed.Data))
+
+	case *fuseops.RemoveXattrOp:
+		addComponent("name %s", typed.Name)
+
+	case *fuseops.GetXattrOp:
+		addComponent("name %s", typed.Name)
 	}
 
 	// Use just the name if there is no extra info.

fuseops/ops.go

@@ -780,3 +780,38 @@ type RemoveXattrOp struct {
 	// The name of the extended attribute
 	Name string
 }
+
+// Get an extended attribute
+type GetXattrOp struct {
+	// The inode that we are reading
+	Inode InodeID
+
+	// The name of the extended attribute
+	Name string
+
+	// The destination buffer.  If the size is too small for the
+	// value, the ERANGE error should be sent.
+	Dst []byte
+
+	// Set by the file system: the number of bytes read into Dst, or
+	// the number of bytes that would have been read into Dst if Dst was
+	// big enough
+	BytesRead int
+}
+
+type ListXattrOp struct {
+	// The inode that we are reading
+	Inode InodeID
+
+	// The destination buffer.  If the size is too small for the
+	// value, the ERANGE error should be sent.
+	//
+	// The output data should consist of a sequence of NUL-terminated strings,
+	// one for each xattr
+	Dst []byte
+
+	// Set by the file system: the number of bytes read into Dst, or
+	// the number of bytes that would have been read into Dst if Dst was
+	// big enough
+	BytesRead int
+}

fuseutil/file_system.go

@@ -58,6 +58,8 @@ type FileSystem interface {
 	ReleaseFileHandle(context.Context, *fuseops.ReleaseFileHandleOp) error
 	ReadSymlink(context.Context, *fuseops.ReadSymlinkOp) error
 	RemoveXattr(context.Context, *fuseops.RemoveXattrOp) error
+	GetXattr(context.Context, *fuseops.GetXattrOp) error
+	ListXattr(context.Context, *fuseops.ListXattrOp) error
 
 	// Regard all inodes (including the root inode) as having their lookup counts
 	// decremented to zero, and clean up any resources associated with the file
@@ -190,6 +192,12 @@ func (s *fileSystemServer) handleOp(
 
 	case *fuseops.RemoveXattrOp:
 		err = s.fs.RemoveXattr(ctx, typed)
+
+	case *fuseops.GetXattrOp:
+		err = s.fs.GetXattr(ctx, typed)
+
+	case *fuseops.ListXattrOp:
+		err = s.fs.ListXattr(ctx, typed)
 	}
 
 	c.Reply(ctx, err)

fuseutil/not_implemented_file_system.go

@@ -190,5 +190,19 @@ func (fs *NotImplementedFileSystem) RemoveXattr(
 	return
 }
 
+func (fs *NotImplementedFileSystem) GetXattr(
+	ctx context.Context,
+	op *fuseops.GetXattrOp) (err error) {
+	err = fuse.ENOSYS
+	return
+}
+
+func (fs *NotImplementedFileSystem) ListXattr(
+	ctx context.Context,
+	op *fuseops.ListXattrOp) (err error) {
+	err = fuse.ENOSYS
+	return
+}
+
 func (fs *NotImplementedFileSystem) Destroy() {
 }

internal/fusekernel/fuse_kernel.go

@@ -660,6 +660,11 @@ type GetxattrOut struct {
 	Padding uint32
 }
 
+type ListxattrIn struct {
+	Size    uint32
+	Padding uint32
+}
+
 type LkIn struct {
 	Fh      uint64
 	Owner   uint64