Ensure given VPC subnets have zero overlap.

cidr.py

#!/usr/bin/env python

import ipaddr

accounts = {
    'flood-beta': {
        'public': [
            '10.1.32.0/20',
            '10.1.96.0/20',
            '10.1.160.0/20'
        ],
        'private': [
            '10.1.0.0/19',
            '10.1.64.0/19',
            '10.1.128.0/19'
        ],
        'spare': [
            '10.1.48.0/20',
            '10.1.112.0/20',
            '10.1.176.0/20'
        ]
    },
    'flood-prod': {
        'public': [
            '10.2.32.0/20',
            '10.2.96.0/20',
            '10.2.160.0/20'
        ],
        'private': [
            '10.2.0.0/19',
            '10.2.64.0/19',
            '10.2.128.0/19'
        ],
        'spare': [
            '10.2.48.0/20',
            '10.2.112.0/20',
            '10.2.176.0/20'
        ]
    },
    'flood-master': {
        'public': [
            '10.0.1.0/24',
            '10.0.2.0/24',
            '10.0.3.0/24'
        ],
        'private': [
            '10.0.0.0/24',
            '10.0.4.0/24'
        ],
        'spare': []
    }
}


for account, blocks in accounts.iteritems():
    print account
    print '=========='
    for block, cidrs in blocks.iteritems():
        print block + ':'
        overlapped = False
        for cidr in cidrs:
            n1 = ipaddr.IPNetwork(cidr)
            print '===> ' + cidr
            for account2, blocks2 in accounts.iteritems():
                if account != account2:
                    for block2, cidrs2 in blocks2.iteritems():
                        for cidr2 in cidrs2:
                            n2 = ipaddr.IPNetwork(cidr2)
                            if n1.overlaps(n2):
                                overlapped = True
                                print '---> overlaps ' + cidr2 + ' in ' + account2
        if not overlapped:
            print 'all clear'
        print
    print