title: Standard c macros to indicate length of MAC address?
body: <p>Are there standard (or semi-standard, widely deployed) C macros for:</p>
  
  <ol>
  <li>The length of a MAC address formatted as 00:11:22:33:44:55, i.e. 17 bytes.</li>
  <li>The length of a raw MAC, i.e. 6 bytes.</li>
  </ol>
  
  <p>I have seen these defined in proprietary header files at various times, but I see a lot of sample/tutorial code that otherwise uses "proper" macros and doesn't have anything for these -- the "6" is always hardcoded.</p>
  
  <p>FWIW I'm on linux.</p>
  
  <p>Obviously it's trivial to define my own, but I'd like to use a standard where possible.</p>