I need a multientry visa if I'm going to have a connexion flight?

Hi there, I will be there for a conexion flight from Hanoi to Shanghai and I'm from Spain, I'am worried because I do not have so many experience and I do not want to have any problem, I arrive to Guangzhou to the international base and I will flight later in a domestic flight... It's difficult to arrive from one side to the other one? I need to pass a control passport? Thank you!