title: What is the difference between linux/if.h and net/if.h?
body: <p>The comments say that <code>net/if.h</code> is part of the GNU C Library and <code>linux/if.h</code> says it is "An implementation of the TCP/IP protocol suite for the LINUX operating system."</p>
  
  <p>But why are there two of them and what is the use of each one?</p>