AES key schedule. Does it use a KDF to generate the round keys? So for each round in AES a different key is used, and as I saw the keys are created form a master key.

My question is how these round keys are generated. 

Are they created via a Key Derivation Function as the session keys, or its something else ?
No, it uses a specific type of algorithm called a key schedule. Unlike a KDF, it is not designed to be slow (in the case of a password-based KDF) or to be irreversible. The requirements of a key schedule are quite simple. Whereas a KDF might need to expand a key into a number of keys such that knowledge of any one key does not reveal knowledge of the master key or any other derived keys, that is not always true for a key schedule. If you have any round key for 128-bit AES, you can derive all other round keys.