title: Error building/linking ns3 network simulator with OpenFlow
body: <p>I'm trying to build ns-3.24.1 on Fedora 22 inside a VirtualBox VM. I am running:</p>
  
  <p>./waf configure --enable-examples --enable-tests --with-openflow=/path/to/openflow --with-pybindgen=/path/to/pybindgen
  ./waf build</p>
  
  <p>I want to use OpenFlow, so I downloaded and configured/built the OFSID according to <a href="https://www.nsnam.org/docs/release/3.24/models/html/openflow-switch.html#building-ofsid" rel="nofollow">these instructions</a> before running the above configure command. The output from the configure step shows OpenFlow as 'enabled'.</p>
  
  <p>The ns-3.24.1 build proceeds normally until it gets to the following step and spits out the subsequent error:</p>
  
  <pre><code>[2291/2493] Linking build/src/openflow/examples/ns3.24.1-openflow-switch-debug
  ./libns3.24.1-openflow-debug.so: undefined reference to `update_checksums'
  collect2: error: ld returned 1 exit status
  ...
  </code></pre>
  
  <p>I.e., it appears to build everything correctly but then errors on the link step.</p>
  
  <p>Apparently <em>update_checksums</em> is in [...]/ns-3.24.1/src/openflow/model/openflow-interface.h; for some reason the link step doesn't know to look here for <em>openflow-interface.h</em>.</p>
  
  <p>What could be causing it and what can I try to fix it? FWIW I've re-downloaded both the ns-3 and OFSID sources several times to no avail.</p>