~lfaraone/+junk/configure-interfaces

#!/usr/bin/python

# -*- coding: utf-8 -*-

#

# Copyright © 2013 Zulip, Inc.

#

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# in the Software without restriction, including without limitation the rights

# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

# copies of the Software, and to permit persons to whom the Software is

# furnished to do so, subject to the following conditions:

#

# The above copyright notice and this permission notice shall be included in

# all copies or substantial portions of the Software.

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# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

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# Original author: Luke Faraone

'''Configure a host for EC2-VPC dynamically assigned network interfaces

Amazon VPC gives us a good deal of flexibility compared to classic EC2.

However there are limitations; you can assign multiple IPs to a host

yet only the first IP per interface will be DHCP assigned, and you are

limited in the total number of interfaces you have, so doing one-IP-per-

interface is also untenable.

This script grabs the metadata provided by AWS and uses it to correctly

configure all available network interfaces.

It is suitable to be hooked in to system boot and network

reconfiguration scripts.

Note that it currently does not handle the deconfiguration of

interfaces.

'''

import sys

import logging

import logging.handlers

import subprocess

import re

import boto.utils

import netifaces

def address_of(device_id):

    try:

        return netifaces.ifaddresses("eth%i" % device_id)[netifaces.AF_INET][0]['addr']

    except KeyError:

        return None

def guess_gateway(device_id):

    # This will not work if the default gateway isn't n.n.n.1.

    address = address_of(device_id).split('.')

    address[3] = '1'

    return '.'.join(address)

log = logging.getLogger('configure-cloud-interfaces')

log.setLevel(logging.DEBUG)

log.addHandler(logging.handlers.SysLogHandler(facility=logging.handlers.SysLogHandler.LOG_DAEMON))

log.addHandler(logging.StreamHandler())

log.info("Starting.")

macs = boto.utils.get_instance_metadata()["network"]["interfaces"]["macs"]

ids = [int(macdata['device-number']) for macdata in macs.values()]

ifaces = [iface for iface in netifaces.interfaces() if ":" not in iface and iface != "lo"]

# Number of IDs should equal number of interfaces

if len(ids) != len(ifaces):

    log.error("Metadata indicated %i interfaces but we have %i!" % (len(ids), len(ifaces)))

    sys.exit(1)

for device in macs.values():

    # There's an annoying API inconsistency here:

    #   If you have multiple IPs, local-ipv4s is a list.

    #   If you only have one, local-ipv4s is a string.

    # Who knew?

    if type(device['local-ipv4s']) is str:

        # Only do dhcp, don't try to assign addresses

        to_configure = [device['local-ipv4s']]

    else:

        to_configure = list(device['local-ipv4s'])

    device_number = int(device['device-number'])

    if address_of(device_number) is None:

        # If the device was not autoconfigured, do so now.

        log.info("Device eth%i not configured, starting dhcpd" % device_number)

        subprocess.check_call(['/sbin/dhcpcd', 'eth%i' % device_number])

        # Horrible hack to route return packets on the correct interface

        # See http://unix.stackexchange.com/a/4421/933

        subprocess.check_call(

                ['/sbin/ip', 'rule', 'add', 'fwmark', str(device_number), 'table', str(device_number)])

        subprocess.check_call(

                ['/sbin/ip', 'route', 'add', '0.0.0.0/0', 'table', str(device_number), 'dev',

                    'eth%i' % device_number, 'via', guess_gateway(device_number)])

        subprocess.check_call(

                ['/sbin/iptables', '-t', 'mangle', '-A', 'OUTPUT', '-m', 'conntrack', '--ctorigdst',

                    address_of(device_number), '-j', 'MARK', '--set-mark', str(device_number)])

    to_configure.remove(address_of(device_number))

    for (count, ip) in enumerate(to_configure):

        # Configure the IP via a virtual interface

        device = "eth%i:%i" % (device_number, count)

        log.info("Configuring %s with IP %s" % (device, ip))

        subprocess.check_call(['/sbin/ifconfig', device, ip])

        subprocess.check_call(

                ['/sbin/iptables', '-t', 'mangle', '-A', 'OUTPUT', '-m', 'conntrack', '--ctorigdst',

                    ip, '-j', 'MARK', '--set-mark', str(device_number)])

    for throwaway in range(2):

        # Don't freak out if this doens't work.

        subprocess.call(

            ['/sbin/ip', 'route', 'del', '10.0.0.0/8'])

log.info("Finished.")