path: root/cloudinit/net/sysconfig.py

# This file is part of cloud-init. See LICENSE file for license information.

import os
import re

import six

from cloudinit.distros.parsers import networkmanager_conf
from cloudinit.distros.parsers import resolv_conf
from cloudinit import log as logging
from cloudinit import util

from . import renderer
from .network_state import (
    is_ipv6_addr, net_prefix_to_ipv4_mask, subnet_is_ipv6)

LOG = logging.getLogger(__name__)


def _make_header(sep='#'):
    lines = [
        "Created by cloud-init on instance boot automatically, do not edit.",
        "",
    ]
    for i in range(0, len(lines)):
        if lines[i]:
            lines[i] = sep + " " + lines[i]
        else:
            lines[i] = sep
    return "\n".join(lines)


def _is_default_route(route):
    default_nets = ('::', '0.0.0.0')
    return route['prefix'] == 0 and route['network'] in default_nets


def _quote_value(value):
    if re.search(r"\s", value):
        # This doesn't handle complex cases...
        if value.startswith('"') and value.endswith('"'):
            return value
        else:
            return '"%s"' % value
    else:
        return value


class ConfigMap(object):
    """Sysconfig like dictionary object."""

    # Why does redhat prefer yes/no to true/false??
    _bool_map = {
        True: 'yes',
        False: 'no',
    }

    def __init__(self):
        self._conf = {}

    def __setitem__(self, key, value):
        self._conf[key] = value

    def __getitem__(self, key):
        return self._conf[key]

    def __contains__(self, key):
        return key in self._conf

    def drop(self, key):
        self._conf.pop(key, None)

    def __len__(self):
        return len(self._conf)

    def to_string(self):
        buf = six.StringIO()
        buf.write(_make_header())
        if self._conf:
            buf.write("\n")
        for key in sorted(self._conf.keys()):
            value = self._conf[key]
            if isinstance(value, bool):
                value = self._bool_map[value]
            if not isinstance(value, six.string_types):
                value = str(value)
            buf.write("%s=%s\n" % (key, _quote_value(value)))
        return buf.getvalue()


class Route(ConfigMap):
    """Represents a route configuration."""

    def __init__(self, route_name, base_sysconf_dir,
                 ipv4_tpl, ipv6_tpl):
        super(Route, self).__init__()
        self.last_idx = 1
        self.has_set_default_ipv4 = False
        self.has_set_default_ipv6 = False
        self._route_name = route_name
        self._base_sysconf_dir = base_sysconf_dir
        self.route_fn_tpl_ipv4 = ipv4_tpl
        self.route_fn_tpl_ipv6 = ipv6_tpl

    def copy(self):
        r = Route(self._route_name, self._base_sysconf_dir,
                  self.route_fn_tpl_ipv4, self.route_fn_tpl_ipv6)
        r._conf = self._conf.copy()
        r.last_idx = self.last_idx
        r.has_set_default_ipv4 = self.has_set_default_ipv4
        r.has_set_default_ipv6 = self.has_set_default_ipv6
        return r

    @property
    def path_ipv4(self):
        return self.route_fn_tpl_ipv4 % ({'base': self._base_sysconf_dir,
                                          'name': self._route_name})

    @property
    def path_ipv6(self):
        return self.route_fn_tpl_ipv6 % ({'base': self._base_sysconf_dir,
                                          'name': self._route_name})

    def is_ipv6_route(self, address):
        return ':' in address

    def to_string(self, proto="ipv4"):
        # only accept ipv4 and ipv6
        if proto not in ['ipv4', 'ipv6']:
            raise ValueError("Unknown protocol '%s'" % (str(proto)))
        buf = six.StringIO()
        buf.write(_make_header())
        if self._conf:
            buf.write("\n")
        # need to reindex IPv4 addresses
        # (because Route can contain a mix of IPv4 and IPv6)
        reindex = -1
        for key in sorted(self._conf.keys()):
            if 'ADDRESS' in key:
                index = key.replace('ADDRESS', '')
                address_value = str(self._conf[key])
                # only accept combinations:
                # if proto ipv6 only display ipv6 routes
                # if proto ipv4 only display ipv4 routes
                # do not add ipv6 routes if proto is ipv4
                # do not add ipv4 routes if proto is ipv6
                # (this array will contain a mix of ipv4 and ipv6)
                if proto == "ipv4" and not self.is_ipv6_route(address_value):
                    netmask_value = str(self._conf['NETMASK' + index])
                    gateway_value = str(self._conf['GATEWAY' + index])
                    # increase IPv4 index
                    reindex = reindex + 1
                    buf.write("%s=%s\n" % ('ADDRESS' + str(reindex),
                                           _quote_value(address_value)))
                    buf.write("%s=%s\n" % ('GATEWAY' + str(reindex),
                                           _quote_value(gateway_value)))
                    buf.write("%s=%s\n" % ('NETMASK' + str(reindex),
                                           _quote_value(netmask_value)))
                    metric_key = 'METRIC' + index
                    if metric_key in self._conf:
                        metric_value = str(self._conf['METRIC' + index])
                        buf.write("%s=%s\n" % ('METRIC' + str(reindex),
                                               _quote_value(metric_value)))
                elif proto == "ipv6" and self.is_ipv6_route(address_value):
                    netmask_value = str(self._conf['NETMASK' + index])
                    gateway_value = str(self._conf['GATEWAY' + index])
                    metric_value = (
                        'metric ' + str(self._conf['METRIC' + index])
                        if 'METRIC' + index in self._conf else '')
                    buf.write(
                        "%s/%s via %s %s dev %s\n" % (address_value,
                                                      netmask_value,
                                                      gateway_value,
                                                      metric_value,
                                                      self._route_name))

        return buf.getvalue()


class NetInterface(ConfigMap):
    """Represents a sysconfig/networking-script (and its config + children)."""

    iface_types = {
        'ethernet': 'Ethernet',
        'bond': 'Bond',
        'bridge': 'Bridge',
        'infiniband': 'InfiniBand',
    }

    def __init__(self, iface_name, base_sysconf_dir, templates,
                 kind='ethernet'):
        super(NetInterface, self).__init__()
        self.children = []
        self.templates = templates
        route_tpl = self.templates.get('route_templates')
        self.routes = Route(iface_name, base_sysconf_dir,
                            ipv4_tpl=route_tpl.get('ipv4'),
                            ipv6_tpl=route_tpl.get('ipv6'))
        self.iface_fn_tpl = self.templates.get('iface_templates')
        self.kind = kind

        self._iface_name = iface_name
        self._conf['DEVICE'] = iface_name
        self._base_sysconf_dir = base_sysconf_dir

    @property
    def name(self):
        return self._iface_name

    @name.setter
    def name(self, iface_name):
        self._iface_name = iface_name
        self._conf['DEVICE'] = iface_name

    @property
    def kind(self):
        return self._kind

    @kind.setter
    def kind(self, kind):
        if kind not in self.iface_types:
            raise ValueError(kind)
        self._kind = kind
        self._conf['TYPE'] = self.iface_types[kind]

    @property
    def path(self):
        return self.iface_fn_tpl % ({'base': self._base_sysconf_dir,
                                     'name': self.name})

    def copy(self, copy_children=False, copy_routes=False):
        c = NetInterface(self.name, self._base_sysconf_dir,
                         self.templates, kind=self._kind)
        c._conf = self._conf.copy()
        if copy_children:
            c.children = list(self.children)
        if copy_routes:
            c.routes = self.routes.copy()
        return c


class Renderer(renderer.Renderer):
    """Renders network information in a /etc/sysconfig format."""

    # See: https://access.redhat.com/documentation/en-US/\
    #      Red_Hat_Enterprise_Linux/6/html/Deployment_Guide/\
    #      s1-networkscripts-interfaces.html (or other docs for
    #                                         details about this)

    iface_defaults = tuple([
        ('ONBOOT', True),
        ('USERCTL', False),
        ('NM_CONTROLLED', False),
        ('BOOTPROTO', 'none'),
    ])

    # If these keys exist, then their values will be used to form
    # a BONDING_OPTS grouping; otherwise no grouping will be set.
    bond_tpl_opts = tuple([
        ('bond_mode', "mode=%s"),
        ('bond_xmit_hash_policy', "xmit_hash_policy=%s"),
        ('bond_miimon', "miimon=%s"),
    ])

    bridge_opts_keys = tuple([
        ('bridge_stp', 'STP'),
        ('bridge_ageing', 'AGEING'),
        ('bridge_bridgeprio', 'PRIO'),
    ])

    templates = {}

    def __init__(self, config=None):
        if not config:
            config = {}
        self.sysconf_dir = config.get('sysconf_dir', 'etc/sysconfig')
        self.netrules_path = config.get(
            'netrules_path', 'etc/udev/rules.d/70-persistent-net.rules')
        self.dns_path = config.get('dns_path', 'etc/resolv.conf')
        nm_conf_path = 'etc/NetworkManager/conf.d/99-cloud-init.conf'
        self.networkmanager_conf_path = config.get('networkmanager_conf_path',
                                                   nm_conf_path)
        self.templates = {
            'control': config.get('control'),
            'iface_templates': config.get('iface_templates'),
            'route_templates': config.get('route_templates'),
        }

    @classmethod
    def _render_iface_shared(cls, iface, iface_cfg):
        for k, v in cls.iface_defaults:
            iface_cfg[k] = v

        for (old_key, new_key) in [('mac_address', 'HWADDR'), ('mtu', 'MTU')]:
            old_value = iface.get(old_key)
            if old_value is not None:
                # only set HWADDR on physical interfaces
                if old_key == 'mac_address' and iface['type'] != 'physical':
                    continue
                iface_cfg[new_key] = old_value

    @classmethod
    def _render_subnets(cls, iface_cfg, subnets):
        # setting base values
        iface_cfg['BOOTPROTO'] = 'none'

        # modifying base values according to subnets
        for i, subnet in enumerate(subnets, start=len(iface_cfg.children)):
            mtu_key = 'MTU'
            subnet_type = subnet.get('type')
            if subnet_type == 'dhcp6':
                iface_cfg['IPV6INIT'] = True
                iface_cfg['DHCPV6C'] = True
            elif subnet_type in ['dhcp4', 'dhcp']:
                iface_cfg['BOOTPROTO'] = 'dhcp'
            elif subnet_type == 'static':
                # grep BOOTPROTO sysconfig.txt -A2 | head -3
                # BOOTPROTO=none|bootp|dhcp
                # 'bootp' or 'dhcp' cause a DHCP client
                # to run on the device. Any other
                # value causes any static configuration
                # in the file to be applied.
                # ==> the following should not be set to 'static'
                # but should remain 'none'
                # if iface_cfg['BOOTPROTO'] == 'none':
                #    iface_cfg['BOOTPROTO'] = 'static'
                if subnet_is_ipv6(subnet):
                    mtu_key = 'IPV6_MTU'
                    iface_cfg['IPV6INIT'] = True
                if 'mtu' in subnet:
                    mtu_mismatch = bool(mtu_key in iface_cfg and
                                        subnet['mtu'] != iface_cfg[mtu_key])
                    if mtu_mismatch:
                        LOG.warning(
                            'Network config: ignoring %s device-level mtu:%s'
                            ' because ipv4 subnet-level mtu:%s provided.',
                            iface_cfg.name, iface_cfg[mtu_key], subnet['mtu'])
                    iface_cfg[mtu_key] = subnet['mtu']
            elif subnet_type == 'manual':
                # If the subnet has an MTU setting, then ONBOOT=True
                # to apply the setting
                iface_cfg['ONBOOT'] = mtu_key in iface_cfg
            else:
                raise ValueError("Unknown subnet type '%s' found"
                                 " for interface '%s'" % (subnet_type,
                                                          iface_cfg.name))
            if subnet.get('control') == 'manual':
                iface_cfg['ONBOOT'] = False

        # set IPv4 and IPv6 static addresses
        ipv4_index = -1
        ipv6_index = -1
        for i, subnet in enumerate(subnets, start=len(iface_cfg.children)):
            subnet_type = subnet.get('type')
            if subnet_type == 'dhcp6':
                continue
            elif subnet_type in ['dhcp4', 'dhcp']:
                continue
            elif subnet_type == 'static':
                if subnet_is_ipv6(subnet):
                    ipv6_index = ipv6_index + 1
                    ipv6_cidr = "%s/%s" % (subnet['address'], subnet['prefix'])
                    if ipv6_index == 0:
                        iface_cfg['IPV6ADDR'] = ipv6_cidr
                    elif ipv6_index == 1:
                        iface_cfg['IPV6ADDR_SECONDARIES'] = ipv6_cidr
                    else:
                        iface_cfg['IPV6ADDR_SECONDARIES'] += " " + ipv6_cidr
                else:
                    ipv4_index = ipv4_index + 1
                    suff = "" if ipv4_index == 0 else str(ipv4_index)
                    iface_cfg['IPADDR' + suff] = subnet['address']
                    iface_cfg['NETMASK' + suff] = \
                        net_prefix_to_ipv4_mask(subnet['prefix'])

                if 'gateway' in subnet:
                    iface_cfg['DEFROUTE'] = True
                    if is_ipv6_addr(subnet['gateway']):
                        iface_cfg['IPV6_DEFAULTGW'] = subnet['gateway']
                    else:
                        iface_cfg['GATEWAY'] = subnet['gateway']

                if 'metric' in subnet:
                    iface_cfg['METRIC'] = subnet['metric']

                if 'dns_search' in subnet:
                    iface_cfg['DOMAIN'] = ' '.join(subnet['dns_search'])

                if 'dns_nameservers' in subnet:
                    if len(subnet['dns_nameservers']) > 3:
                        # per resolv.conf(5) MAXNS sets this to 3.
                        LOG.debug("%s has %d entries in dns_nameservers. "
                                  "Only 3 are used.", iface_cfg.name,
                                  len(subnet['dns_nameservers']))
                    for i, k in enumerate(subnet['dns_nameservers'][:3], 1):
                        iface_cfg['DNS' + str(i)] = k

    @classmethod
    def _render_subnet_routes(cls, iface_cfg, route_cfg, subnets):
        for _, subnet in enumerate(subnets, start=len(iface_cfg.children)):
            for route in subnet.get('routes', []):
                is_ipv6 = subnet.get('ipv6') or is_ipv6_addr(route['gateway'])

                if _is_default_route(route):
                    if (
                            (subnet.get('ipv4') and
                             route_cfg.has_set_default_ipv4) or
                            (subnet.get('ipv6') and
                             route_cfg.has_set_default_ipv6)
                    ):
                        raise ValueError("Duplicate declaration of default "
                                         "route found for interface '%s'"
                                         % (iface_cfg.name))
                    # NOTE(harlowja): ipv6 and ipv4 default gateways
                    gw_key = 'GATEWAY0'
                    nm_key = 'NETMASK0'
                    addr_key = 'ADDRESS0'
                    # The owning interface provides the default route.
                    #
                    # TODO(harlowja): add validation that no other iface has
                    # also provided the default route?
                    iface_cfg['DEFROUTE'] = True
                    if 'gateway' in route:
                        if is_ipv6 or is_ipv6_addr(route['gateway']):
                            iface_cfg['IPV6_DEFAULTGW'] = route['gateway']
                            route_cfg.has_set_default_ipv6 = True
                        else:
                            iface_cfg['GATEWAY'] = route['gateway']
                            route_cfg.has_set_default_ipv4 = True
                    if 'metric' in route:
                        iface_cfg['METRIC'] = route['metric']

                else:
                    gw_key = 'GATEWAY%s' % route_cfg.last_idx
                    nm_key = 'NETMASK%s' % route_cfg.last_idx
                    addr_key = 'ADDRESS%s' % route_cfg.last_idx
                    metric_key = 'METRIC%s' % route_cfg.last_idx
                    route_cfg.last_idx += 1
                    # add default routes only to ifcfg files, not
                    # to route-* or route6-*
                    for (old_key, new_key) in [('gateway', gw_key),
                                               ('metric', metric_key),
                                               ('netmask', nm_key),
                                               ('network', addr_key)]:
                        if old_key in route:
                            route_cfg[new_key] = route[old_key]

    @classmethod
    def _render_bonding_opts(cls, iface_cfg, iface):
        bond_opts = []
        for (bond_key, value_tpl) in cls.bond_tpl_opts:
            # Seems like either dash or underscore is possible?
            bond_keys = [bond_key, bond_key.replace("_", "-")]
            for bond_key in bond_keys:
                if bond_key in iface:
                    bond_value = iface[bond_key]
                    if isinstance(bond_value, (tuple, list)):
                        bond_value = " ".join(bond_value)
                    bond_opts.append(value_tpl % (bond_value))
                    break
        if bond_opts:
            iface_cfg['BONDING_OPTS'] = " ".join(bond_opts)

    @classmethod
    def _render_physical_interfaces(cls, network_state, iface_contents):
        physical_filter = renderer.filter_by_physical
        for iface in network_state.iter_interfaces(physical_filter):
            iface_name = iface['name']
            iface_subnets = iface.get("subnets", [])
            iface_cfg = iface_contents[iface_name]
            route_cfg = iface_cfg.routes

            cls._render_subnets(iface_cfg, iface_subnets)
            cls._render_subnet_routes(iface_cfg, route_cfg, iface_subnets)

    @classmethod
    def _render_bond_interfaces(cls, network_state, iface_contents):
        bond_filter = renderer.filter_by_type('bond')
        slave_filter = renderer.filter_by_attr('bond-master')
        for iface in network_state.iter_interfaces(bond_filter):
            iface_name = iface['name']
            iface_cfg = iface_contents[iface_name]
            cls._render_bonding_opts(iface_cfg, iface)

            # Ensure that the master interface (and any of its children)
            # are actually marked as being bond types...
            master_cfgs = [iface_cfg]
            master_cfgs.extend(iface_cfg.children)
            for master_cfg in master_cfgs:
                master_cfg['BONDING_MASTER'] = True
                master_cfg.kind = 'bond'

            if iface.get('mac_address'):
                iface_cfg['MACADDR'] = iface.get('mac_address')

            iface_subnets = iface.get("subnets", [])
            route_cfg = iface_cfg.routes
            cls._render_subnets(iface_cfg, iface_subnets)
            cls._render_subnet_routes(iface_cfg, route_cfg, iface_subnets)

            # iter_interfaces on network-state is not sorted to produce
            # consistent numbers we need to sort.
            bond_slaves = sorted(
                [slave_iface['name'] for slave_iface in
                 network_state.iter_interfaces(slave_filter)
                 if slave_iface['bond-master'] == iface_name])

            for index, bond_slave in enumerate(bond_slaves):
                slavestr = 'BONDING_SLAVE%s' % index
                iface_cfg[slavestr] = bond_slave

                slave_cfg = iface_contents[bond_slave]
                slave_cfg['MASTER'] = iface_name
                slave_cfg['SLAVE'] = True

    @classmethod
    def _render_vlan_interfaces(cls, network_state, iface_contents):
        vlan_filter = renderer.filter_by_type('vlan')
        for iface in network_state.iter_interfaces(vlan_filter):
            iface_name = iface['name']
            iface_cfg = iface_contents[iface_name]
            iface_cfg['VLAN'] = True
            iface_cfg['PHYSDEV'] = iface_name[:iface_name.rfind('.')]

            iface_subnets = iface.get("subnets", [])
            route_cfg = iface_cfg.routes
            cls._render_subnets(iface_cfg, iface_subnets)
            cls._render_subnet_routes(iface_cfg, route_cfg, iface_subnets)

    @staticmethod
    def _render_dns(network_state, existing_dns_path=None):
        content = resolv_conf.ResolvConf("")
        if existing_dns_path and os.path.isfile(existing_dns_path):
            content = resolv_conf.ResolvConf(util.load_file(existing_dns_path))
        for nameserver in network_state.dns_nameservers:
            content.add_nameserver(nameserver)
        for searchdomain in network_state.dns_searchdomains:
            content.add_search_domain(searchdomain)
        header = _make_header(';')
        content_str = str(content)
        if not content_str.startswith(header):
            content_str = header + '\n' + content_str
        return content_str

    @staticmethod
    def _render_networkmanager_conf(network_state, templates=None):
        content = networkmanager_conf.NetworkManagerConf("")

        # If DNS server information is provided, configure
        # NetworkManager to not manage dns, so that /etc/resolv.conf
        # does not get clobbered.
        if network_state.dns_nameservers:
            content.set_section_keypair('main', 'dns', 'none')

        if len(content) == 0:
            return None
        out = "".join([_make_header(), "\n", "\n".join(content.write()), "\n"])
        return out

    @classmethod
    def _render_bridge_interfaces(cls, network_state, iface_contents):
        bridge_filter = renderer.filter_by_type('bridge')
        for iface in network_state.iter_interfaces(bridge_filter):
            iface_name = iface['name']
            iface_cfg = iface_contents[iface_name]
            iface_cfg.kind = 'bridge'
            for old_key, new_key in cls.bridge_opts_keys:
                if old_key in iface:
                    iface_cfg[new_key] = iface[old_key]

            if iface.get('mac_address'):
                iface_cfg['MACADDR'] = iface.get('mac_address')

            # Is this the right key to get all the connected interfaces?
            for bridged_iface_name in iface.get('bridge_ports', []):
                # Ensure all bridged interfaces are correctly tagged
                # as being bridged to this interface.
                bridged_cfg = iface_contents[bridged_iface_name]
                bridged_cfgs = [bridged_cfg]
                bridged_cfgs.extend(bridged_cfg.children)
                for bridge_cfg in bridged_cfgs:
                    bridge_cfg['BRIDGE'] = iface_name

            iface_subnets = iface.get("subnets", [])
            route_cfg = iface_cfg.routes
            cls._render_subnets(iface_cfg, iface_subnets)
            cls._render_subnet_routes(iface_cfg, route_cfg, iface_subnets)

    @classmethod
    def _render_ib_interfaces(cls, network_state, iface_contents):
        ib_filter = renderer.filter_by_type('infiniband')
        for iface in network_state.iter_interfaces(ib_filter):
            iface_name = iface['name']
            iface_cfg = iface_contents[iface_name]
            iface_cfg.kind = 'infiniband'
            iface_subnets = iface.get("subnets", [])
            route_cfg = iface_cfg.routes
            cls._render_subnets(iface_cfg, iface_subnets)
            cls._render_subnet_routes(iface_cfg, route_cfg, iface_subnets)

    @classmethod
    def _render_sysconfig(cls, base_sysconf_dir, network_state,
                          templates=None):
        '''Given state, return /etc/sysconfig files + contents'''
        if not templates:
            templates = cls.templates
        iface_contents = {}
        for iface in network_state.iter_interfaces():
            if iface['type'] == "loopback":
                continue
            iface_name = iface['name']
            iface_cfg = NetInterface(iface_name, base_sysconf_dir, templates)
            cls._render_iface_shared(iface, iface_cfg)
            iface_contents[iface_name] = iface_cfg
        cls._render_physical_interfaces(network_state, iface_contents)
        cls._render_bond_interfaces(network_state, iface_contents)
        cls._render_vlan_interfaces(network_state, iface_contents)
        cls._render_bridge_interfaces(network_state, iface_contents)
        cls._render_ib_interfaces(network_state, iface_contents)
        contents = {}
        for iface_name, iface_cfg in iface_contents.items():
            if iface_cfg or iface_cfg.children:
                contents[iface_cfg.path] = iface_cfg.to_string()
                for iface_cfg in iface_cfg.children:
                    if iface_cfg:
                        contents[iface_cfg.path] = iface_cfg.to_string()
            if iface_cfg.routes:
                for cpath, proto in zip([iface_cfg.routes.path_ipv4,
                                         iface_cfg.routes.path_ipv6],
                                        ["ipv4", "ipv6"]):
                    if cpath not in contents:
                        contents[cpath] = iface_cfg.routes.to_string(proto)
        return contents

    def render_network_state(self, network_state, templates=None, target=None):
        if not templates:
            templates = self.templates
        file_mode = 0o644
        base_sysconf_dir = util.target_path(target, self.sysconf_dir)
        for path, data in self._render_sysconfig(base_sysconf_dir,
                                                 network_state,
                                                 templates=templates).items():
            util.write_file(path, data, file_mode)
        if self.dns_path:
            dns_path = util.target_path(target, self.dns_path)
            resolv_content = self._render_dns(network_state,
                                              existing_dns_path=dns_path)
            util.write_file(dns_path, resolv_content, file_mode)
        if self.networkmanager_conf_path:
            nm_conf_path = util.target_path(target,
                                            self.networkmanager_conf_path)
            nm_conf_content = self._render_networkmanager_conf(network_state,
                                                               templates)
            if nm_conf_content:
                util.write_file(nm_conf_path, nm_conf_content, file_mode)
        if self.netrules_path:
            netrules_content = self._render_persistent_net(network_state)
            netrules_path = util.target_path(target, self.netrules_path)
            util.write_file(netrules_path, netrules_content, file_mode)

        sysconfig_path = util.target_path(target, templates.get('control'))
        # Distros configuring /etc/sysconfig/network as a file e.g. Centos
        if sysconfig_path.endswith('network'):
            util.ensure_dir(os.path.dirname(sysconfig_path))
            netcfg = [_make_header(), 'NETWORKING=yes']
            if network_state.use_ipv6:
                netcfg.append('NETWORKING_IPV6=yes')
                netcfg.append('IPV6_AUTOCONF=no')
            util.write_file(sysconfig_path,
                            "\n".join(netcfg) + "\n", file_mode)


def available(target=None):
    expected = ['ifup', 'ifdown']
    search = ['/sbin', '/usr/sbin']
    for p in expected:
        if not util.which(p, search=search, target=target):
            return False

    expected_paths = [
        'etc/sysconfig/network-scripts/network-functions',
        'etc/sysconfig/network-scripts/ifdown-eth']
    for p in expected_paths:
        if not os.path.isfile(util.target_path(target, p)):
            return False
    return True


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