GR-speak (semantics).

REST mass m_o is, h*fL*Sqrt{1 - (v^2/c^2)} / c^2 ..SI kilograms.

$$ GR-speak (semantics).
$$ A moving FOOTBALL is still a "football".
$$ A moving RESTmass is still a "RESTmass".
$$ And ..ANY moving RESTmass is a "PHOTON".

Where, PHOTON mass m_ph = m1 = m_o / Sqrt{1 - (v^2/c^2)} = h*fL/c^2.

$$ More exactly:
My PHOTON mass m_ph = REST mass m_o / Sqrt{1 - (v^2/c^2)} = h*fL/c^2.
PHOTON mass m_ph = REST mass m_o / Sqrt[1 - {G*m*M1/(n - 1)*rA/c^2}].

$$ Note the (n - 1) changes the SiGN ..and EVERYthing.

p.s. Hope this helps. End of POST.