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Filename : try_command.py
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#!/usr/bin/python3
#
# Copyright (C) 2018 Canonical, Ltd.
# Author: Mathieu Trudel-Lapierre <mathieu.trudel-lapierre@canonical.com>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; version 3.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

'''netplan try command line'''

import os
import time
import signal
import sys
import logging
import subprocess

from netplan.configmanager import ConfigManager
import netplan.cli.utils as utils
from netplan.cli.commands.apply import NetplanApply
import netplan.terminal

# Keep a timeout long enough to allow the network to converge, 60 seconds may
# be slightly short given some complex configs, i.e. if STP must reconverge.
DEFAULT_INPUT_TIMEOUT = 120


class NetplanTry(utils.NetplanCommand):

    def __init__(self):
        super().__init__(command_id='try',
                         description='Try to apply a new netplan config to running '
                                     'system, with automatic rollback',
                         leaf=True)
        self.configuration_changed = False
        self.new_interfaces = None
        self._config_manager = None
        self.t_settings = None
        self.t = None

    @property
    def config_manager(self):  # pragma: nocover (called by later commands)
        if not self._config_manager:
            self._config_manager = ConfigManager()
        return self._config_manager

    def run(self):  # pragma: nocover (requires user input)
        self.parser.add_argument('--config-file',
                                 help='Apply the config file in argument in addition to current configuration.')
        self.parser.add_argument('--timeout',
                                 type=int, default=DEFAULT_INPUT_TIMEOUT,
                                 help="Maximum number of seconds to wait for the user's confirmation")

        self.func = self.command_try

        self.parse_args()
        self.run_command()

    def command_try(self):  # pragma: nocover (requires user input)
        if not self.is_revertable():
            sys.exit(os.EX_CONFIG)

        try:
            fd = sys.stdin.fileno()
            self.t = netplan.terminal.Terminal(fd)
            self.t.save(self.t_settings)

            # we really don't want to be interrupted while doing backup/revert operations
            signal.signal(signal.SIGINT, self._signal_handler)

            self.backup()
            self.setup()

            NetplanApply.command_apply(run_generate=True, sync=True, exit_on_error=False)

            self.t.get_confirmation_input(timeout=self.timeout)
        except netplan.terminal.InputRejected:
            print("\nReverting.")
            self.revert()
        except netplan.terminal.InputAccepted:
            print("\nConfiguration accepted.")
        except Exception as e:
            print("\nAn error occurred: %s" % e)
            print("\nReverting.")
            self.revert()
        finally:
            if self.t:
                self.t.reset(self.t_settings)
            self.cleanup()

    def backup(self):  # pragma: nocover (requires user input)
        backup_config_dir = False
        if self.config_file:
            backup_config_dir = True
        self.config_manager.backup(backup_config_dir=backup_config_dir)

    def setup(self):  # pragma: nocover (requires user input)
        if self.config_file:
            dest_dir = os.path.join("/", "etc", "netplan")
            dest_name = os.path.basename(self.config_file).rstrip('.yaml')
            dest_suffix = time.time()
            dest_path = os.path.join(dest_dir, "{}.{}.yaml".format(dest_name, dest_suffix))
            self.config_manager.add({self.config_file: dest_path})
        self.configuration_changed = True

    def revert(self):  # pragma: nocover (requires user input)
        self.config_manager.revert()
        NetplanApply.command_apply(run_generate=False, sync=True, exit_on_error=False)
        for ifname in self.new_interfaces:
            if ifname not in self.config_manager.bonds and \
               ifname not in self.config_manager.bridges and \
               ifname not in self.config_manager.vlans:
                logging.debug("{} will not be removed: not a virtual interface".format(ifname))
                continue
            try:
                cmd = ['ip', 'link', 'del', ifname]
                subprocess.check_call(cmd)
            except subprocess.CalledProcessError:
                logging.warn("Could not revert (remove) new interface '{}'".format(ifname))

    def cleanup(self):  # pragma: nocover (requires user input)
        self.config_manager.cleanup()

    def is_revertable(self):  # pragma: nocover (requires user input)
        '''
        Check if the configuration is revertable, if it doesn't contain bits
        that we know are likely to render the system unstable if we apply it,
        or if we revert.

        Returns True if the parsed config is "revertable", meaning that we
        can actually rely on backends to re-apply /all/ of the relevant
        configuration to interfaces when their config changes.

        Returns False if the parsed config contains options that are known
        to not cleanly revert via the backend.
        '''

        # Parse; including any new config file passed on the command-line:
        # new config might include things we can't revert.
        extra_config = []
        if self.config_file:
            extra_config.append(self.config_file)
        self.config_manager.parse(extra_config=extra_config)
        self.new_interfaces = self.config_manager.new_interfaces

        logging.debug("New interfaces: {}".format(self.new_interfaces))

        revert_unsupported = []

        # Bridges and bonds are special. They typically include (or could include)
        # more than one device in them, and they can be set with special parameters
        # to tweak their behavior, which are really hard to "revert", especially
        # as systemd-networkd doesn't necessarily touch them when config changes.
        multi_iface = {}
        multi_iface.update(self.config_manager.bridges)
        multi_iface.update(self.config_manager.bonds)
        for ifname, settings in multi_iface.items():
            if settings and 'parameters' in settings:
                reason = "reverting custom parameters for bridges and bonds is not supported"
                revert_unsupported.append((ifname, reason))

        if revert_unsupported:
            for ifname, reason in revert_unsupported:
                print("{}: {}".format(ifname, reason))
            print("\nPlease carefully review the configuration and use 'netplan apply' directly.")
            return False
        return True

    def _signal_handler(self, signal, frame):  # pragma: nocover (requires user input)
        if self.configuration_changed:
            raise netplan.terminal.InputRejected()