_modules/routers.py

import netaddr
import itertools


class Route(object):
    def __init__(self, interface, router, cidr, next_hop):
        self.interface = interface
        self.router = router
        self.cidr = cidr
        self.next_hop = next_hop

    def __str__(self):
        return "%s via %s dev %s src %s # router: %s" % (
            self.cidr,
            self.next_hop,
            self.interface.name,
            self.interface.cidr.ip,
            self.router.name)


class Interface(object):
    def __init__(self, name, cidr):
        self.name = name
        self.cidr = cidr

    def __str__(self):
        return self.name

    @staticmethod
    def from_dict(data, default_name=None):
        try:
            cidr = netaddr.IPNetwork("%(address)s/%(netmask)s" % data)
        except KeyError:
            cidr = None
        return Interface(
            name = data.get('name', default_name),
            cidr = cidr)


class Router(object):
    def __init__(self,
                 name,
                 addresses=None,
                 networks=None,
                 implicit_routes=True):
        self.name = name
        self.addresses = list(addresses or [])
        self.networks = list(networks or [])
        if implicit_routes:
            self.networks.extend(addr.cidr for addr in self.addresses)

        if any(addr.ip == addr.network for addr in self.addresses):
            raise ValueError("Invalid router address")
        if any(cidr.ip != cidr.network for cidr in self.networks):
            raise ValueError("Invalid destination CIDR")

    def __str__(self):
        return self.name

    @staticmethod
    def from_dict(data, default_name=None):
        options = data.get('options', {})
        return Router(
            name = data.get('name', default_name),
            addresses = [
                netaddr.IPNetwork(router_addr)
                for router_addr in data.get('addresses', [])
            ],
            networks = [
                netaddr.IPNetwork(dest_cidr).cidr
                for dest_cidr in data.get('networks', [])
            ],
            implicit_routes = options.get('implicit_routes', True)
        )

    def get_routes(self, interface):
        next_hops = [addr.ip for addr in self.addresses
                     if addr.ip in interface.cidr]

        return [
            Route(interface, self, dest_cidr, next_hop)
            for next_hop in next_hops
            for dest_cidr in self.networks if next_hop not in dest_cidr
        ]


def get_routes(interfaces, routers):
    def sort_key_cidr(route):
        return route.cidr.sort_key()

    def sort_key_ifname(route):
        return (route.interface.name, route.cidr.sort_key())

    interfaces = [Interface.from_dict(data, key)
                  for key, data in interfaces.items()]
    routers = [Router.from_dict(data, key)
               for key, data in routers.items()]
    routes = [route
              for interface in interfaces if interface.cidr
              for router in routers
              for route in router.get_routes(interface)]

    routes_by_cidr = {k: list(g) for k, g in itertools.groupby(
        sorted(routes, key=sort_key_cidr),
        lambda route: route.cidr)
    }

    for cidr, duplicates in routes_by_cidr.items():
        if len(duplicates) > 1:
            raise ValueError("Found multiple routes for %s: %s" % (cidr,
                ["[via %s dev %s]" % (route.next_hop, route.interface)
                 for route in duplicates]))

    routes_by_ifname = {k: list(g) for k, g in itertools.groupby(
        sorted(routes, key=sort_key_ifname),
        lambda route: route.interface.name)
    }

    return routes_by_ifname