#!/usr/bin/python
# Copyright 2018 Google Inc. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

"""Manage networking on a Google Compute Engine instance.

Run network setup to enable multiple network interfaces on startup.
Update IP forwarding when metadata changes.
"""

import logging.handlers
import optparse
import random

from google_compute_engine import config_manager
from google_compute_engine import constants
from google_compute_engine import file_utils
from google_compute_engine import logger
from google_compute_engine import metadata_watcher
from google_compute_engine import network_utils
from google_compute_engine.networking.ip_forwarding import ip_forwarding
from google_compute_engine.networking.network_setup import network_setup

LOCKFILE = constants.LOCALSTATEDIR + '/lock/google_networking.lock'


class NetworkDaemon(object):
  """Manage networking based on changes to network metadata."""

  network_interface_metadata_key = 'instance/network-interfaces'

  def __init__(
      self, ip_forwarding_enabled, proto_id, ip_aliases, target_instance_ips,
      dhclient_script, dhcp_command, network_setup_enabled, debug=False):
    """Constructor.

    Args:
      ip_forwarding_enabled: bool, True if ip forwarding is enabled.
      proto_id: string, the routing protocol identifier for Google IP changes.
      ip_aliases: bool, True if the guest should configure IP alias routes.
      target_instance_ips: bool, True supports internal IP load balancing.
      dhclient_script: string, the path to a dhclient script used by dhclient.
      dhcp_command: string, a command to enable Ethernet interfaces.
      network_setup_enabled: bool, True if network setup is enabled.
      debug: bool, True if debug output should write to the console.
    """
    facility = logging.handlers.SysLogHandler.LOG_DAEMON
    self.logger = logger.Logger(
        name='google-networking', debug=debug, facility=facility)
    self.ip_aliases = ip_aliases
    self.ip_forwarding_enabled = ip_forwarding_enabled
    self.network_setup_enabled = network_setup_enabled
    self.target_instance_ips = target_instance_ips

    self.ip_forwarding = ip_forwarding.IpForwarding(
        proto_id=proto_id, debug=debug)
    self.network_setup = network_setup.NetworkSetup(
        dhclient_script=dhclient_script, dhcp_command=dhcp_command, debug=debug)
    self.network_utils = network_utils.NetworkUtils(logger=self.logger)
    self.watcher = metadata_watcher.MetadataWatcher(logger=self.logger)

    try:
      with file_utils.LockFile(LOCKFILE):
        self.logger.info('Starting Google Networking daemon.')
        timeout = 60 + random.randint(0, 30)
        self.watcher.WatchMetadata(
            self.HandleNetworkInterfaces,
            metadata_key=self.network_interface_metadata_key, recursive=True,
            timeout=timeout)
    except (IOError, OSError) as e:
      self.logger.warning(str(e))

  def HandleNetworkInterfaces(self, result):
    """Called when network interface metadata changes.

    Args:
      result: dict, the metadata response with the network interfaces.
    """
    network_interfaces = self._ExtractInterfaceMetadata(result)

    if self.network_setup_enabled:
      self.network_setup.EnableNetworkInterfaces(
          [interface.name for interface in network_interfaces[1:]])

    for interface in network_interfaces:
      if self.ip_forwarding_enabled:
        self.ip_forwarding.HandleForwardedIps(
            interface.name, interface.forwarded_ips, interface.ip)

  def _ExtractInterfaceMetadata(self, metadata):
    """Extracts network interface metadata.

    Args:
      metadata: dict, the metadata response with the new network interfaces.

    Returns:
      list, a list of NetworkInterface objects.
    """
    interfaces = []
    for network_interface in metadata:
      mac_address = network_interface.get('mac')
      interface = self.network_utils.GetNetworkInterface(mac_address)
      ip_addresses = []
      if interface:
        ip_addresses.extend(network_interface.get('forwardedIps', []))
        if self.ip_aliases:
          ip_addresses.extend(network_interface.get('ipAliases', []))
        if self.target_instance_ips:
          ip_addresses.extend(network_interface.get('targetInstanceIps', []))
        interfaces.append(NetworkDaemon.NetworkInterface(
            interface, ip_addresses, network_interface.get('ip', [])))
      else:
        message = 'Network interface not found for MAC address: %s.'
        self.logger.warning(message, mac_address)
    return interfaces

  class NetworkInterface(object):
    """Network interface information extracted from metadata."""

    def __init__(self, name, forwarded_ips=None, ip=None):
      self.name = name
      self.forwarded_ips = forwarded_ips
      self.ip = ip


def main():
  parser = optparse.OptionParser()
  parser.add_option(
      '-d', '--debug', action='store_true', dest='debug',
      help='print debug output to the console.')
  (options, _) = parser.parse_args()
  debug = bool(options.debug)
  instance_config = config_manager.ConfigManager()
  ip_forwarding_daemon_enabled = instance_config.GetOptionBool(
      'Daemons', 'ip_forwarding_daemon')
  ip_forwarding_enabled = instance_config.GetOptionBool(
      'NetworkInterfaces', 'ip_forwarding') or ip_forwarding_daemon_enabled
  network_setup_enabled = instance_config.GetOptionBool(
      'NetworkInterfaces', 'setup')
  network_daemon_enabled = instance_config.GetOptionBool(
      'Daemons', 'network_daemon')
  proto_id = instance_config.GetOptionString(
      'IpForwarding', 'ethernet_proto_id')
  ip_aliases = instance_config.GetOptionBool(
      'IpForwarding', 'ip_aliases')
  target_instance_ips = instance_config.GetOptionBool(
      'IpForwarding', 'target_instance_ips')
  dhclient_script = instance_config.GetOptionString(
      'NetworkInterfaces', 'dhclient_script')
  dhcp_command = instance_config.GetOptionString(
      'NetworkInterfaces', 'dhcp_command')

  if network_daemon_enabled:
    NetworkDaemon(
        ip_forwarding_enabled=ip_forwarding_enabled,
        proto_id=proto_id,
        ip_aliases=ip_aliases,
        target_instance_ips=target_instance_ips,
        dhclient_script=dhclient_script,
        dhcp_command=dhcp_command,
        network_setup_enabled=network_setup_enabled,
        debug=debug)


if __name__ == '__main__':
  main()
