Actually, if you read Javed , Jamil's post #78, it pretty much confirms that a photon has no rest mass. From a quantum standpoint, that defines why it travels at the speed of light. It has energy so it must be moving but without mass it can only travel at an infinite velocity (the
velocity of an object is proportional to its energy and inversely proportional to its mass). The speed of light is infinite from the perspective of anything traveling at that speed.

There is no need for special consideration for the photon. When a zero rest mass is assumed, it behaves exactly as it should. Incidentally, a rest mass less than Planck's constant is identical to zero.

If a photon had mass, most of physics would have to be rewritten.

As for the wave-particle duality, that applies to everything. Electron, protons, neutrinos, mesons, etc. all have that dual nature. This is a
basic part of quantum mechanics. In reality, they are neither wave nor particle. We just use these analogues to help us understand them,
because they do appear to behave like waves and particles depending on the experiment.