title: How to know the active slave interface in a bonding pair
body: <p>I am working under Linux, with two physical ethernet interfaces.
  I have grouped the two interfaces to a bonding interface for backup... and it works.</p>
  
  <p>I would like to know if there is any way to know, from my C user program, what is the active interface.</p>
  
  <p>Thanks</p>