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#!/usr/bin/python3
#
# Copyright (C) 2016 Canonical, Ltd.
# Author: Martin Pitt <martin.pitt@ubuntu.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 command line'''

import argparse
import logging
import os
import sys
import re
import shutil
import subprocess
from glob import glob

import yaml

path_generate = os.environ.get('NETPLAN_GENERATE_PATH', '/lib/netplan/generate')

NM_SERVICE_NAME = 'NetworkManager.service'
NM_SNAP_SERVICE_NAME = 'snap.network-manager.networkmanager.service'


#
# helper functions
#

def parse_args():
    parser = argparse.ArgumentParser(description='netplan commands')
    parser.add_argument('--debug', action='store_true',
                        help='Enable debug messages')
    subparsers = parser.add_subparsers(title='Available commands (see "netplan <command> --help")',
                                       metavar='', dest='command')

    # command: generate
    p_generate = subparsers.add_parser('generate',
                                       help='Generate backend specific configuration files from /etc/netplan/*.yaml.')
    p_generate.add_argument('--root-dir',
                            help='Search for and generate configuration files in this root directory instead of /')

    # command: apply
    p_generate = subparsers.add_parser('apply',
                                       help='Apply current netplan config to running system (use with care!)')

    # command: ifupdown-migrate
    p_ifupdown = subparsers.add_parser('ifupdown-migrate',
                                       help='Try to convert /etc/network/interfaces to netplan. '
                                       'If successful, disable /etc/network/interfaces.')
    p_ifupdown.add_argument('--root-dir',
                            help='Search for and generate configuration files in this root directory instead of /')
    p_ifupdown.add_argument('--dry-run', action='store_true',
                            help='Print converted netplan configuration to stdout instead of writing/changing files')

    args = parser.parse_args()

    if not args.command:
        parser.error('You need to specify a command')
    return args


def is_nm_snap_enabled():  # pragma: nocover (covered in autopkgtest)
    return subprocess.call(['systemctl', '--quiet', 'is-enabled', NM_SNAP_SERVICE_NAME], stderr=subprocess.DEVNULL) == 0


def nmcli(args):  # pragma: nocover (covered in autopkgtest)
    binary_name = 'nmcli'

    if is_nm_snap_enabled():
        binary_name = 'network-manager.nmcli'

    subprocess.check_call([binary_name] + args, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)


def nm_running():  # pragma: nocover (covered in autopkgtest)
    '''Check if NetworkManager is running'''

    try:
        nmcli(['general'])
        return True
    except (OSError, subprocess.SubprocessError):
        return False


def systemctl_network_manager(action):  # pragma: nocover (covered in autopkgtest)
    service_name = NM_SERVICE_NAME

    # If the network-manager snap is installed use its service
    # name rather than the one of the deb packaged NetworkManager
    if is_nm_snap_enabled():
        service_name = NM_SNAP_SERVICE_NAME

    subprocess.check_call(['systemctl', action, '--no-block', service_name])


def replug(device):  # pragma: nocover (covered in autopkgtest)
    '''Unbind and rebind device if it is down'''

    devdir = os.path.join('/sys/class/net', device)

    try:
        with open(os.path.join(devdir, 'operstate')) as f:
            state = f.read().strip()
            if state != 'down':
                logging.debug('device %s operstate is %s, not replugging', device, state)
                return False
    except IOError as e:
        logging.error('Cannot determine operstate of %s: %s', device, str(e))
        return False

    # /sys/class/net/ens3/device -> ../../../virtio0
    # /sys/class/net/ens3/device/driver -> ../../../../bus/virtio/drivers/virtio_net
    try:
        devname = os.path.basename(os.readlink(os.path.join(devdir, 'device')))
    except IOError as e:
        logging.debug('Cannot replug %s: cannot read link %s/device: %s', device, devdir, str(e))
        return False

    try:
        # we must resolve symlinks here as the device dir will be gone after unbind
        subsystem = os.path.realpath(os.path.join(devdir, 'device', 'subsystem'))
        subsystem_name = os.path.basename(subsystem)
        driver = os.path.realpath(os.path.join(devdir, 'device', 'driver'))
        driver_name = os.path.basename(driver)
        if driver_name == 'mac80211_hwsim':
            logging.debug('replug %s: mac80211_hwsim does not support rebinding, ignoring', device)
            return False
        # workaround for https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1630285
        if driver_name == 'mwifiex_pcie':
            logging.debug('replug %s: mwifiex_pcie crashes on rebinding, ignoring', device)
            return False
        # workaround for https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1729573
        if subsystem_name == 'xen' and driver_name == 'vif':
            logging.debug('replug %s: xen:vif fails on rebinding, ignoring', device)
            return False
        # workaround for problem with ath9k_htc module: this driver is async and does not support
        # sequential unbind / rebind, one soon after the other
        if driver_name == 'ath9k_htc':
            logging.debug('replug %s: ath9k_htc does not support rebinding, ignoring', device)
            return False
        # workaround for brcmfmac, interface will be gone after unbind
        if 'brcmfmac' in driver_name:
            logging.debug('replug %s: brcmfmac drivers do not support rebinding, ignoring', device)
            return False
        # workaround for ath6kl_sdio, interface does not work after unbinding
        if 'ath6kl_sdio' in driver_name:
            logging.debug('replug %s: ath6kl_sdio driver does not support rebinding, ignoring', device)
            return False
        # workaround for qeth: driver does not recognize unbind command
        # https://bugs.launchpad.net/ubuntu/+source/netplan.io/+bug/1756322
        if driver_name == 'qeth':
            logging.debug('replug %s: qeth driver do not support rebinding, ignoring (LP: #1756322)', device)
            return False
        logging.debug('replug %s: unbinding %s from %s', device, devname, driver)
        with open(os.path.join(driver, 'unbind'), 'w') as f:
            f.write(devname)
        logging.debug('replug %s: rebinding %s to %s', device, devname, driver)
        with open(os.path.join(driver, 'bind'), 'w') as f:
            f.write(devname)
    except IOError as e:
        logging.error('Cannot replug %s: %s', device, str(e))
        return False

    return True


def _ifupdown_lines_from_file(rootdir, path):
    '''Return normalized lines from ifupdown config

    This resolves "source" and "source-directory" includes.
    '''
    def expand_source_arg(rootdir, curdir, line):
        arg = line.split()[1]
        if arg.startswith('/'):
            return rootdir + arg
        else:
            return curdir + '/' + arg

    lines = []
    rootdir_len = len(rootdir) + 1
    try:
        with open(rootdir + '/' + path) as f:
            logging.debug('reading %s', f.name)
            for line in f:
                # normalize, strip empty lines and comments
                line = line.strip()
                if not line or line.startswith('#'):
                    continue

                if line.startswith('source-directory '):
                    valid_re = re.compile('^[a-zA-Z0-9_-]+$')
                    d = expand_source_arg(rootdir, os.path.dirname(f.name), line)
                    for f in os.listdir(d):
                        if valid_re.match(f):
                            lines += _ifupdown_lines_from_file(rootdir, os.path.join(d[rootdir_len:], f))
                elif line.startswith('source '):
                    for f in glob(expand_source_arg(rootdir, os.path.dirname(f.name), line)):
                        lines += _ifupdown_lines_from_file(rootdir, f[rootdir_len:])
                else:
                    lines.append(line)
    except FileNotFoundError:
        logging.debug('%s/%s does not exist, ignoring', rootdir, path)
    return lines


def parse_ifupdown(rootdir='/'):
    '''Parse ifupdown configuration.

    Return (iface_name →  family → {method, options}, auto_ifaces: set) tuple
    on successful parsing, or a ValueError when encountering an invalid file or
    ifupdown features which are not supported (such as "mapping").

    options is itself a dictionary option_name → value.
    '''
    # expected number of fields for every possible keyword, excluding the keyword itself
    fieldlen = {'auto': 1, 'allow-auto': 1, 'allow-hotplug': 1, 'mapping': 1, 'no-scripts': 1, 'iface': 3}

    # read and normalize all lines from config, with resolving includes
    lines = _ifupdown_lines_from_file(rootdir, '/etc/network/interfaces')

    ifaces = {}
    auto = set()
    in_options = None  # interface name if parsing options lines after iface stanza
    in_family = None

    # we now have resolved all includes and normalized lines
    for line in lines:
        fields = line.split()

        try:
            # does the line start with a known stanza field?
            exp_len = fieldlen[fields[0]]
            logging.debug('line fields %s (expected length: %i)', fields, exp_len)
            in_options = None  # stop option line parsing of iface stanza
            in_family = None
        except KeyError:
            # no known stanza field, are we in an iface stanza and parsing options?
            if in_options:
                logging.debug('in_options %s, parsing as option: %s', in_options, line)
                ifaces[in_options][in_family]['options'][fields[0]] = line.split(maxsplit=1)[1]
                continue
            else:
                raise ValueError('Unknown stanza type %s' % fields[0])

        # do we have the expected #parameters?
        if len(fields) != exp_len + 1:
            raise ValueError('Expected %i fields for stanza type %s but got %i' %
                             (exp_len, fields[0], len(fields) - 1))

        # we have a valid stanza line now, handle them
        if fields[0] in ('auto', 'allow-auto', 'allow-hotplug'):
            auto.add(fields[1])
        elif fields[0] == 'mapping':
            raise ValueError('mapping stanza is not supported')
        elif fields[0] == 'no-scripts':
            pass  # ignore these
        elif fields[0] == 'iface':
            if fields[2] not in ('inet', 'inet6'):
                raise ValueError('Unknown address family %s' % fields[2])
            if fields[3] not in ('loopback', 'static', 'dhcp'):
                raise ValueError('Unsupported method %s' % fields[3])
            in_options = fields[1]
            in_family = fields[2]
            ifaces.setdefault(fields[1], {})[in_family] = {'method': fields[3], 'options': {}}
        else:
            raise NotImplementedError('stanza type %s is not implemented' % fields[0])  # pragma nocover

    logging.debug('final parsed interfaces: %s; auto ifaces: %s', ifaces, auto)
    return (ifaces, auto)


#
# implementation of the top-level commands
#

def command_generate():
    argv = [path_generate]
    if args.root_dir:
        argv += ['--root-dir', args.root_dir]
    logging.debug('command generate: running %s', argv)
    # FIXME: os.execv(argv[0], argv) would be better but fails coverage
    sys.exit(subprocess.call(argv))


def command_apply():  # pragma: nocover (covered in autopkgtest)
    # if we are inside a snap, then call dbus to run netplan apply instead
    if "SNAP" in os.environ:
        # TODO: maybe check if we are inside a classic snap and don't do
        # this if we are in a classic snap?
        busctl = shutil.which("busctl")
        if busctl is None:
            raise RuntimeError("missing busctl utility")
        res = subprocess.call([busctl, "call", "--quiet", "--system",
                               "io.netplan.Netplan",  # the service
                               "/io/netplan/Netplan",  # the object
                               "io.netplan.Netplan",  # the interface
                               "Apply",  # the method
                               ])
        if res != 0:
            if res == 130:
                raise PermissionError(
                    "failed to communicate with dbus service")
            elif res == 1:
                raise RuntimeError(
                    "failed to communicate with dbus service")
            sys.exit(res)
        else:
            return

    if subprocess.call([path_generate]) != 0:
        sys.exit(1)

    devices = os.listdir('/sys/class/net')

    restart_networkd = bool(glob('/run/systemd/network/*netplan-*'))
    restart_nm = bool(glob('/run/NetworkManager/system-connections/netplan-*'))

    # stop backends
    if restart_networkd:
        logging.debug('netplan generated networkd configuration exists, restarting networkd')
        subprocess.check_call(['systemctl', 'stop', '--no-block', 'systemd-networkd.service', 'netplan-wpa@*.service'])
    else:
        logging.debug('no netplan generated networkd configuration exists')

    if restart_nm:
        logging.debug('netplan generated NM configuration exists, restarting NM')
        if nm_running():
            # restarting NM does not cause new config to be applied, need to shut down devices first
            for device in devices:
                # ignore failures here -- some/many devices might not be managed by NM
                try:
                    nmcli(['device', 'disconnect', device])
                except subprocess.CalledProcessError:
                    pass

            systemctl_network_manager('stop')
    else:
        logging.debug('no netplan generated NM configuration exists')

    # force-hotplug all "down" network interfaces to apply renames
    any_replug = False
    for device in devices:
        if not os.path.islink('/sys/class/net/' + device):
            continue
        if replug(device):
            any_replug = True
        else:
            # if the interface is up, we can still apply .link file changes
            logging.debug('netplan triggering .link rules for %s', device)
            with open(os.devnull, 'w') as fd:
                subprocess.check_call(['udevadm', 'test-builtin',
                                       'net_setup_link',
                                       '/sys/class/net/' + device],
                                      stdout=fd, stderr=fd)
    if any_replug:
        subprocess.check_call(['udevadm', 'settle'])

    # (re)start backends
    if restart_networkd:
        subprocess.check_call(['systemctl', 'start', '--no-block', 'systemd-networkd.service'] +
                              [os.path.basename(f) for f in glob('/run/systemd/system/*.wants/netplan-wpa@*.service')])
    if restart_nm:
        systemctl_network_manager('start')


def command_ifupdown_migrate():
    netplan_config = {}
    try:
        ifaces, auto_ifaces = parse_ifupdown(args.root_dir or '')
    except ValueError as e:
        logging.error(str(e))
        sys.exit(2)
    for iface, family_config in ifaces.items():
        for family, config in family_config.items():
            logging.debug('Converting %s family %s %s', iface, family, config)
            if iface not in auto_ifaces:
                logging.error('%s: non-automatic interfaces are not supported', iface)
                sys.exit(2)
            if config['method'] == 'loopback':
                # both systemd and modern ifupdown set up lo automatically
                logging.debug('Ignoring loopback interface %s', iface)
            elif config['method'] == 'dhcp':
                if config['options']:
                    logging.error('%s: options are not supported for dhcp method', iface)
                    sys.exit(2)
                c = netplan_config.setdefault('network', {}).setdefault('ethernets', {}).setdefault(iface, {})
                if family == 'inet':
                    c['dhcp4'] = True
                else:
                    assert family == 'inet6'
                    c['dhcp6'] = True
            else:
                logging.error('%s: method %s is not supported', iface, config['method'])
                sys.exit(2)

    if_config = os.path.join(args.root_dir or '/', 'etc/network/interfaces')

    if netplan_config:
        netplan_config['network']['version'] = 2
        netplan_yaml = yaml.dump(netplan_config)
        if args.dry_run:
            print(netplan_yaml)
        else:
            dest = os.path.join(args.root_dir or '/', 'etc/netplan/10-ifupdown.yaml')
            try:
                os.makedirs(os.path.dirname(dest))
            except FileExistsError:
                pass
            try:
                with open(dest, 'x') as f:
                    f.write(netplan_yaml)
            except FileExistsError:
                logging.error('%s already exists; remove it if you want to run the migration again', dest)
                sys.exit(3)
            logging.info('migration complete, wrote %s', dest)
    else:
        logging.info('ifupdown does not configure any interfaces, nothing to migrate')

    if not args.dry_run:
        logging.info('renaming %s to %s.netplan-converted', if_config, if_config)
        os.rename(if_config, if_config + '.netplan-converted')


#
# main
#

args = parse_args()

if args.debug:
    logging.basicConfig(level=logging.DEBUG, format='%(levelname)s:%(message)s')
    os.environ['G_MESSAGES_DEBUG'] = 'all'
else:
    logging.basicConfig(level=logging.INFO, format='%(message)s')

eval('command_' + args.command.replace('-', '_'))()