# Copyright (c) 2015 Red Hat Inc.
#
#    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.

import os
import queue
import sys
import threading

import httplib2
from oslo_config import cfg
from oslo_log import log as logging

from neutron._i18n import _
from neutron.agent.l3 import ha
from neutron.agent.linux import daemon
from neutron.agent.linux import ip_lib
from neutron.agent.linux import utils as agent_utils
from neutron.common import config
from neutron.common import utils as common_utils
from neutron.conf.agent import common as agent_config
from neutron.conf.agent.l3 import ha as ha_conf
from neutron.conf.agent.l3 import keepalived
from neutron import privileged


LOG = logging.getLogger(__name__)
INITIAL_STATE_READ_TIMEOUT = 10


class KeepalivedUnixDomainConnection(agent_utils.UnixDomainHTTPConnection):
    def __init__(self, *args, **kwargs):
        # Old style super initialization is required!
        agent_utils.UnixDomainHTTPConnection.__init__(
            self, *args, **kwargs)
        self.socket_path = (
            ha.L3AgentKeepalivedStateChangeServer.
            get_keepalived_state_change_socket_path(cfg.CONF))


class MonitorDaemon(daemon.Daemon):
    def __init__(self, pidfile, router_id, user, group, namespace, conf_dir,
                 interface, cidr, ha_conntrackd_enabled):
        self.router_id = router_id
        self.namespace = namespace
        self.conf_dir = conf_dir
        self.interface = interface
        self.cidr = cidr
        self.ha_conntrackd_enabled = ha_conntrackd_enabled
        self.monitor = None
        self.event_stop = threading.Event()
        self.event_started = threading.Event()
        self.queue = queue.Queue()
        self._initial_state = None
        super().__init__(pidfile, uuid=router_id,
                         user=user, group=group)

    @property
    def initial_state(self):
        return self._initial_state

    @initial_state.setter
    def initial_state(self, state):
        if not self._initial_state:
            LOG.debug('Initial status of router %s is %s', self.router_id,
                      state)
            self._initial_state = state

    def run(self):
        self._thread_initial_state = threading.Thread(
            target=self.handle_initial_state)
        self._thread_ip_monitor = threading.Thread(
            target=ip_lib.ip_monitor,
            args=(self.namespace, self.queue, self.event_stop,
                  self.event_started))
        self._thread_read_queue = threading.Thread(
            target=self.read_queue,
            args=(self.queue, self.event_stop, self.event_started))
        self._thread_initial_state.start()

        # NOTE(ralonsoh): if the initial status is not read in a defined
        # timeout, "backup" state is set.
        self._thread_initial_state.join(timeout=INITIAL_STATE_READ_TIMEOUT)
        if not self.initial_state:
            LOG.warning('Timeout reading the initial status of router %s, '
                        'state is set to "backup".', self.router_id)
            self.write_state_change('backup')
            if self.ha_conntrackd_enabled:
                self.sync_conntrack('backup')
            self.notify_agent('backup')

        # NOTE(gaudenz): Only starte these threads after the initial status is
        # set because otherwise the initial status thread sometimes hangs.
        self._thread_ip_monitor.start()
        self._thread_read_queue.start()
        self._thread_read_queue.join()

    def read_queue(self, _queue, event_stop, event_started):
        event_started.wait()
        while not event_stop.is_set():
            try:
                event = _queue.get(timeout=2)
            except queue.Empty:
                event = None
            if not event:
                continue

            if event['name'] == self.interface and event['cidr'] == self.cidr:
                if event['event'] == 'added':
                    new_state = 'primary'
                else:
                    new_state = 'backup'
                self.write_state_change(new_state)
                if self.ha_conntrackd_enabled:
                    self.sync_conntrack(new_state)
                self.notify_agent(new_state)

    def handle_initial_state(self):
        try:
            state = 'backup'
            cidr = common_utils.ip_to_cidr(self.cidr)
            # NOTE(ralonsoh): "get_devices_with_ip" without passing an IP
            # address performs one single pyroute2 command. Because the number
            # of interfaces in the namespace is reduced, this is faster.
            for address in ip_lib.get_devices_with_ip(self.namespace):
                if (address['name'] == self.interface and
                        address['cidr'] == cidr):
                    state = 'primary'
                    break

            if not self.initial_state:
                self.write_state_change(state)
                if self.ha_conntrackd_enabled:
                    self.sync_conntrack(state)
                self.notify_agent(state)
        except Exception:
            if not self.initial_state:
                LOG.exception('Failed to get initial status of router %s',
                              self.router_id)

    def write_state_change(self, state):
        self.initial_state = state
        with open(os.path.join(
                self.conf_dir, 'state'), 'w') as state_file:
            state_file.write(state)
        LOG.debug('Wrote router %s state %s', self.router_id, state)

    def notify_agent(self, state):
        resp, content = httplib2.Http().request(
            # Note that the message is sent via a Unix domain socket so that
            # the URL doesn't matter.
            'http://127.0.0.1/',
            headers={'X-Neutron-Router-Id': self.router_id,
                     'X-Neutron-State': state,
                     'Connection': 'close'},
            connection_type=KeepalivedUnixDomainConnection)

        if resp.status != 200:
            raise Exception(_('Unexpected response: %s') % resp)

        LOG.debug('Notified agent router %s, state %s', self.router_id, state)

    def conntrackd(self, option):
        execute = ip_lib.IPWrapper(namespace=self.namespace).netns.execute
        cmd = ['conntrackd', '-C', f'{self.conf_dir}/conntrackd.conf', option]

        LOG.debug('Executing "%s" on router %s', ' '.join(cmd), self.router_id)
        execute(
            cmd,
            run_as_root=True,
            # Errors are still logged, but should not crash the daemon
            check_exit_code=False,
        )

    def sync_conntrack(self, state):
        if state == 'primary':
            self.sync_conntrack_primary()
        elif state == 'backup':
            self.sync_conntrack_backup()
        else:
            LOG.error(f'Unknown state "{state}".')

    def sync_conntrack_primary(self):

        # commit the external cache into the kernel table
        self.conntrackd('-c')

        # flush the internal and the external caches
        self.conntrackd('-f')

        # resynchronize my internal cache to the kernel table
        self.conntrackd('-R')

        # send a bulk update to backups
        self.conntrackd('-B')

        LOG.debug('Synced connection tracking state on primary for router %s',
                  self.router_id)

    def sync_conntrack_backup(self):
        # shorten kernel conntrack timers to remove the zombie entries.
        self.conntrackd('-t')

        # request resynchronization with primary firewall replica (if any)
        self.conntrackd('-n')

        LOG.debug('Synced connection tracking state on backup for router %s',
                  self.router_id)

    def handle_sigterm(self, signum, frame):
        self.event_stop.set()
        self._thread_read_queue.join(timeout=5)
        super().handle_sigterm(signum, frame)


def configure(conf):
    config.register_common_config_options()
    config.init(sys.argv[1:])
    conf.set_override('log_dir', cfg.CONF.conf_dir)
    conf.set_override('use_syslog', True)
    config.setup_logging()
    privileged.default.set_client_mode(False)


def main():
    keepalived.register_cli_l3_agent_keepalived_opts()
    keepalived.register_l3_agent_keepalived_opts()
    ha_conf.register_l3_agent_ha_opts()
    agent_config.register_root_helper()
    configure(cfg.CONF)
    MonitorDaemon(cfg.CONF.pid_file,
                  cfg.CONF.router_id,
                  cfg.CONF.user,
                  cfg.CONF.group,
                  cfg.CONF.namespace,
                  cfg.CONF.conf_dir,
                  cfg.CONF.monitor_interface,
                  cfg.CONF.monitor_cidr,
                  cfg.CONF.enable_conntrackd).start()
