topology.py 文件源码

def get_path_to_netbox(netbox):
    """Returns a likely path from netbox to its apparent gateway/router.

    If any switches on the path, or the router itself is down,
    no current path exists and a False value is returned. However,
    if there is insufficient information for NAV to find a likely path,
    a True value is returned.

    """
    prefix = netbox.get_prefix()
    if not prefix:
        _logger.warning("couldn't find prefix for %s", netbox)
        return True

    router_ports = prefix.get_router_ports()
    if router_ports:
        router_port = router_ports[0]
    else:
        _logger.warning("couldn't find router ports for %s", prefix)
        return True

    router = router_port.interface.netbox
    _logger.debug("reachability check for %s on %s (router: %s)",
                  netbox, prefix, router)

    graph = get_graph_for_vlan(prefix.vlan)
    try:
        netbox.add_to_graph(graph)
    except AttributeError:
        pass

    # first, see if any path exists
    if not _path_exists(graph, netbox, router):
        _logger.warning("cannot find a path between %s and %s on VLAN %s",
                        netbox, router, prefix.vlan)
        return True

    # now, remove nodes that are down and see if a path still exists
    strip_down_nodes_from_graph(graph, keep=netbox)

    if netbox not in graph or router not in graph:
        if router.up == router.UP_UP:
            _logger.warning("%(netbox)s topology problem: router %(router)s "
                            "is up, but not in VLAN graph for %(prefix)r. "
                            "Defaulting to 'reachable' status.", locals())
            return True
        _logger.debug("%s not reachable, router or box not in graph: %r",
                      netbox, graph.edges())
        return False

    try:
        path = networkx.shortest_path(graph, netbox, router)
    except NetworkXException as error:
        _logger.debug("an internal networkx exception was raised in "
                      "shortest_path, assuming no path was found: %s", error)
        path = []
    else:
        _logger.debug("path to %s: %r", netbox, path)
    return path