nfs/internal/nfs4server/xattr.go

// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

// The handlers of the extended attribute family, RFC 8276. A backend
// without the XattrFS half answers NOT_SUPP to all of them.

package nfs4server

import (
	"sourcedock.dev/petrbalvin/nfs/internal/nfs4"
	"sourcedock.dev/petrbalvin/nfs/internal/nfsfs"
	"sourcedock.dev/petrbalvin/nfs/internal/xdr"
)

// xattrFS resolves the backend's xattr half, or nil when it has none.
func (h *Handler) xattrFS() nfsfs.XattrFS {
	x, _ := h.FS.(nfsfs.XattrFS)
	return x
}

// getXattrOp serves GETXATTR: one named value of the current object.
// The argument is the name alone, RFC 8276.
func (h *Handler) getXattrOp(d *xdr.Decoder, reg *fhreg) ([]byte, uint32, error) {
	name, err := d.String()
	if err != nil {
		return nil, 0, err
	}
	if !reg.haveCur {
		return nil, nfs4.ErrNoFileHandle, nil
	}
	x := h.xattrFS()
	if x == nil {
		return nil, nfs4.ErrNotSupp, nil
	}
	value, xerr := x.GetXattr(reg.cur, name, 0)
	if xerr == nfsfs.ErrNoXattr {
		return nil, nfs4.ErrNoXattr, nil
	}
	if xerr == nfsfs.ErrXattrNotSupp {
		return nil, nfs4.ErrNotSupp, nil
	}
	if xerr != nil {
		return nil, mapErr(xerr), nil
	}
	return nfs4.AppendGetXattrRes(nil, value), nfs4.ErrOK, nil
}

// setXattrOp serves SETXATTR: it writes or creates or replaces one named
// value of the current object. The argument order is the mode, the key
// and the value, RFC 8276.
func (h *Handler) setXattrOp(d *xdr.Decoder, reg *fhreg) ([]byte, uint32, error) {
	mode, err := d.Uint32()
	if err != nil {
		return nil, 0, err
	}
	name, err := d.String()
	if err != nil {
		return nil, 0, err
	}
	value, err := d.VarOpaque()
	if err != nil {
		return nil, 0, err
	}
	if !reg.haveCur {
		return nil, nfs4.ErrNoFileHandle, nil
	}
	x := h.xattrFS()
	if x == nil {
		return nil, nfs4.ErrNotSupp, nil
	}
	if err := x.SetXattr(reg.cur, name, value, mode); err != nil {
		if err == nfsfs.ErrXattrNotSupp {
			return nil, nfs4.ErrNotSupp, nil
		}
		return nil, mapErr(err), nil
	}
	return nil, nfs4.ErrOK, nil
}

// listXattrOp serves LISTXATTR: the names of the current object's
// attributes, one page bounded by the budget. The whole list answers in
// one page with the end of list flag set, so a resume cookie never
// names a remaining entry: cookie zero answers everything and any other
// cookie answers an empty final page, RFC 8276 section 5.
func (h *Handler) listXattrOp(d *xdr.Decoder, reg *fhreg) ([]byte, uint32, error) {
	cookie, err := d.Uint64()
	if err != nil {
		return nil, 0, err
	}
	maxcount, err := d.Uint32()
	if err != nil {
		return nil, 0, err
	}
	if maxcount > 1<<20 {
		maxcount = 1 << 20
	}
	if !reg.haveCur {
		return nil, nfs4.ErrNoFileHandle, nil
	}
	x := h.xattrFS()
	if x == nil {
		return nil, nfs4.ErrNotSupp, nil
	}
	names := []string{}
	if cookie == 0 {
		names, err = x.ListXattr(reg.cur, int(maxcount))
		if err == nfsfs.ErrXattrNotSupp {
			return nil, nfs4.ErrNotSupp, nil
		}
		if err != nil {
			return nil, mapErr(err), nil
		}
	}
	return nfs4.AppendListXattrRes(nil, cookie, names, true), nfs4.ErrOK, nil
}

// removeXattrOp serves REMOVEXATTR: it deletes one named value of the
// current object.
func (h *Handler) removeXattrOp(d *xdr.Decoder, reg *fhreg) ([]byte, uint32, error) {
	name, err := d.String()
	if err != nil {
		return nil, 0, err
	}
	if !reg.haveCur {
		return nil, nfs4.ErrNoFileHandle, nil
	}
	x := h.xattrFS()
	if x == nil {
		return nil, nfs4.ErrNotSupp, nil
	}
	if err := x.RemoveXattr(reg.cur, name); err != nil {
		if err == nfsfs.ErrNoXattr {
			return nil, nfs4.ErrNoXattr, nil
		}
		if err == nfsfs.ErrXattrNotSupp {
			return nil, nfs4.ErrNotSupp, nil
		}
		return nil, mapErr(err), nil
	}
	return nil, nfs4.ErrOK, nil
}