_, ll := a.lenAndSpace()
			l += ll
		case *DefaultAddr:
			_, ll := a.lenAndSpace()
			l += ll
		}
	}
	return l
}

// marshalAddrs marshals as and returns a bitmap indicating which
// address is stored in b.
func marshalAddrs(b []byte, as []Addr) (uint, error) {
	var attrs uint
	for i, a := range as {
		switch a := a.(type) {
		case *LinkAddr:
			l, err := a.marshal(b)