Module that will
a. perform mac learning and forwarding
b. perform firewalling to block traffic between host h2=10.0.0.2 and h3=10.0.0.3
c. counts all packets in and out of h1=10.0.0.1
d. then does a then b, and c in parallel
Taken from https://github.com/frenetic-lang/pyretic/blob/tester/pyretic/tutorial/of_tutorial.py