Based on Eric and Dave's kernel code, here's a patch that adds CoDel to ns3.  This uses the same approximations as v8 of the kernel code, so it should behave very similarly in terms of which packets get dropped.  It may have some issues with headers if you haven't built ns3 before applying the patch, I will try to address that next.

The patch doesn't do anything with CoDel, but you can replace droptail on any point-to-point in any of the examples by doing something like this:

      bottleneckchannel.SetQueue ("ns3::CoDelQueue",
                                  "Interval", StringValue("100ms"),
                                  "Target", StringValue("5ms"),
                                  "MinBytes", UintegerValue(1500)
                                  );

Andrew McGregor