code-dumps/py/nextSubnetLambda.py

"""
To use this function in lambda, one needs to upload netaddr and this code as a package. here is how
pip3 install netaddr -t ./
zip -r ../acrolinxNextSubnet.zip .
"""
from netaddr import *
import boto3
import cfnresponse
import json
import os

def lambda_handler(event, context):
    my_vpc = {
        'eu-west-1': 'vpc-55a5a930',
        'us-west-2': 'vpc-7155ca14'
    }
    session = boto3.session.Session()
    my_region = session.region_name
    ec2 = session.resource('ec2')
    vpc = ec2.Vpc(my_vpc[my_region])
    subnets = []
    for subnet in vpc.subnets.all():
        subnets.append(IPNetwork(subnet.cidr_block))

    lastSubnet = sorted(subnets).pop()
    nextSubnet = str(lastSubnet.next())

    return {
       'region': my_region,
       'body': json.dumps(nextSubnet)
    }

#    response_data = {}
#    response_data = {"cidr": nextSubnet}
#    my_data = nextSubnet
#    cfnresponse.send(event,context,cfnresponse.SUCCESS, response_data, my_data)