In order to generate multiple session keys from a Diffie Hellman key agreement protocol I'm trying to use the HKDF to generate this session keys. The HKDF algorithm uses an Extraction-Expand procedure. In the extraction proceduere it takes as an input a salt and a source key (in my case it will be the diffie hellman generated key). I know that the salt it is a random non-secret value, my question is: How do I establish this random salt value between two entities? Can I set this value by applying a hash function to my diffie hellman key i.e. salt=hash(diffie_hellman_key)?      

Thenks in advance.