Pox/Pyretic firewall

'''
    Coursera:
    - Software Defined Networking (SDN) course
    -- Module 6 Programming Assignment

    Professor: Nick Feamster
    Teaching Assistant: Muhammad Shahbaz
'''

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# The Pyretic Project                                                          #
# frenetic-lang.org/pyretic                                                    #
# author: Joshua Reich (jreich@cs.princeton.edu)                               #
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from pyretic.lib.corelib import *
from pyretic.lib.std import *

# insert the name of the module and policy you want to import
from pox.lib.addresses import EthAddr
import os
import csv
from pyretic.modules.mac_learner import mac_learner as act_like_switch

policy_file = "%s/pyretic/pyretic/examples/firewall-policies.csv" % os.environ[ 'HOME' ]


def main():
    # Copy the code you used to read firewall-policies.csv last week

    rules = []

    with open(policy_file, 'rb') as f:
        reader = csv.reader(f)
        header = f.readline()
        for row in reader:
            row.pop(0)
            rules.append(row)

    # start with a policy that doesn't match any packets
    not_allowed = none
    # and add traffic that isn't allowed
    for (src,dst) in rules:
        direction1 = match(srcmac=MAC(src), dstmac=MAC(dst))
        direction2 = match(srcmac=MAC(dst), dstmac=MAC(src))
        not_allowed = not_allowed + direction1 + direction2

    # express allowed traffic in terms of not_allowed - hint use '~'
    allowed = ~not_allowed

    # and only send allowed traffic to the mac learning (act_like_switch) logic
    return allowed >> act_like_switch()