# Copyright (C) 2013 Canonical Ltd.
#
# Author: Scott Moser <scott.moser@canonical.com>
#
# This file is part of cloud-init. See LICENSE file for license information.

import base64
import contextlib
import crypt
from functools import partial
import os
import os.path
import re
from time import time
from time import sleep
from xml.dom import minidom
import xml.etree.ElementTree as ET
from enum import Enum

from cloudinit import dmi
from cloudinit import log as logging
from cloudinit import net
from cloudinit.event import EventType
from cloudinit.net import device_driver
from cloudinit.net.dhcp import EphemeralDHCPv4
from cloudinit import sources
from cloudinit.sources.helpers import netlink
from cloudinit import subp
from cloudinit.url_helper import UrlError, readurl, retry_on_url_exc
from cloudinit import util
from cloudinit.reporting import events

from cloudinit.sources.helpers.azure import (
    DEFAULT_REPORT_FAILURE_USER_VISIBLE_MESSAGE,
    azure_ds_reporter,
    azure_ds_telemetry_reporter,
    get_metadata_from_fabric,
    get_boot_telemetry,
    get_system_info,
    report_diagnostic_event,
    EphemeralDHCPv4WithReporting,
    is_byte_swapped,
    dhcp_log_cb,
    push_log_to_kvp,
    report_failure_to_fabric)

LOG = logging.getLogger(__name__)

DS_NAME = 'Azure'
DEFAULT_METADATA = {"instance-id": "iid-AZURE-NODE"}
AGENT_START = ['service', 'walinuxagent', 'start']
AGENT_START_BUILTIN = "__builtin__"
BOUNCE_COMMAND_IFUP = [
    'sh', '-xc',
    "i=$interface; x=0; ifdown $i || x=$?; ifup $i || x=$?; exit $x"
]
BOUNCE_COMMAND_FREEBSD = [
    'sh', '-xc',
    ("i=$interface; x=0; ifconfig down $i || x=$?; "
     "ifconfig up $i || x=$?; exit $x")
]

# azure systems will always have a resource disk, and 66-azure-ephemeral.rules
# ensures that it gets linked to this path.
RESOURCE_DISK_PATH = '/dev/disk/cloud/azure_resource'
DEFAULT_PRIMARY_NIC = 'eth0'
LEASE_FILE = '/var/lib/dhcp/dhclient.eth0.leases'
DEFAULT_FS = 'ext4'
# DMI chassis-asset-tag is set static for all azure instances
AZURE_CHASSIS_ASSET_TAG = '7783-7084-3265-9085-8269-3286-77'
REPROVISION_MARKER_FILE = "/var/lib/cloud/data/poll_imds"
REPROVISION_NIC_ATTACH_MARKER_FILE = "/var/lib/cloud/data/wait_for_nic_attach"
REPROVISION_NIC_DETACHED_MARKER_FILE = "/var/lib/cloud/data/nic_detached"
REPORTED_READY_MARKER_FILE = "/var/lib/cloud/data/reported_ready"
AGENT_SEED_DIR = '/var/lib/waagent'


# In the event where the IMDS primary server is not
# available, it takes 1s to fallback to the secondary one
IMDS_TIMEOUT_IN_SECONDS = 2
IMDS_URL = "http://169.254.169.254/metadata/"
IMDS_VER = "2019-06-01"
IMDS_VER_PARAM = "api-version={}".format(IMDS_VER)


class metadata_type(Enum):
    compute = "{}instance?{}".format(IMDS_URL, IMDS_VER_PARAM)
    network = "{}instance/network?{}".format(IMDS_URL,
                                             IMDS_VER_PARAM)
    reprovisiondata = "{}reprovisiondata?{}".format(IMDS_URL,
                                                    IMDS_VER_PARAM)


PLATFORM_ENTROPY_SOURCE = "/sys/firmware/acpi/tables/OEM0"

# List of static scripts and network config artifacts created by
# stock ubuntu suported images.
UBUNTU_EXTENDED_NETWORK_SCRIPTS = [
    '/etc/netplan/90-hotplug-azure.yaml',
    '/usr/local/sbin/ephemeral_eth.sh',
    '/etc/udev/rules.d/10-net-device-added.rules',
    '/run/network/interfaces.ephemeral.d',
]

# This list is used to blacklist devices that will be considered
# for renaming or fallback interfaces.
#
# On Azure network devices using these drivers are automatically
# configured by the platform and should not be configured by
# cloud-init's network configuration.
#
# Note:
# Azure Dv4 and Ev4 series VMs always have mlx5 hardware.
# https://docs.microsoft.com/en-us/azure/virtual-machines/dv4-dsv4-series
# https://docs.microsoft.com/en-us/azure/virtual-machines/ev4-esv4-series
# Earlier D and E series VMs (such as Dv2, Dv3, and Ev3 series VMs)
# can have either mlx4 or mlx5 hardware, with the older series VMs
# having a higher chance of coming with mlx4 hardware.
# https://docs.microsoft.com/en-us/azure/virtual-machines/dv2-dsv2-series
# https://docs.microsoft.com/en-us/azure/virtual-machines/dv3-dsv3-series
# https://docs.microsoft.com/en-us/azure/virtual-machines/ev3-esv3-series
BLACKLIST_DRIVERS = ['mlx4_core', 'mlx5_core']


def find_storvscid_from_sysctl_pnpinfo(sysctl_out, deviceid):
    # extract the 'X' from dev.storvsc.X. if deviceid matches
    """
    dev.storvsc.1.%pnpinfo:
        classid=32412632-86cb-44a2-9b5c-50d1417354f5
        deviceid=00000000-0001-8899-0000-000000000000
    """
    for line in sysctl_out.splitlines():
        if re.search(r"pnpinfo", line):
            fields = line.split()
            if len(fields) >= 3:
                columns = fields[2].split('=')
                if (len(columns) >= 2 and
                        columns[0] == "deviceid" and
                        columns[1].startswith(deviceid)):
                    comps = fields[0].split('.')
                    return comps[2]
    return None


def find_busdev_from_disk(camcontrol_out, disk_drv):
    # find the scbusX from 'camcontrol devlist -b' output
    # if disk_drv matches the specified disk driver, i.e. blkvsc1
    """
    scbus0 on ata0 bus 0
    scbus1 on ata1 bus 0
    scbus2 on blkvsc0 bus 0
    scbus3 on blkvsc1 bus 0
    scbus4 on storvsc2 bus 0
    scbus5 on storvsc3 bus 0
    scbus-1 on xpt0 bus 0
    """
    for line in camcontrol_out.splitlines():
        if re.search(disk_drv, line):
            items = line.split()
            return items[0]
    return None


def find_dev_from_busdev(camcontrol_out, busdev):
    # find the daX from 'camcontrol devlist' output
    # if busdev matches the specified value, i.e. 'scbus2'
    """
    <Msft Virtual CD/ROM 1.0>          at scbus1 target 0 lun 0 (cd0,pass0)
    <Msft Virtual Disk 1.0>            at scbus2 target 0 lun 0 (da0,pass1)
    <Msft Virtual Disk 1.0>            at scbus3 target 1 lun 0 (da1,pass2)
    """
    for line in camcontrol_out.splitlines():
        if re.search(busdev, line):
            items = line.split('(')
            if len(items) == 2:
                dev_pass = items[1].split(',')
                return dev_pass[0]
    return None


def execute_or_debug(cmd, fail_ret=None):
    try:
        return subp.subp(cmd)[0]
    except subp.ProcessExecutionError:
        LOG.debug("Failed to execute: %s", ' '.join(cmd))
        return fail_ret


def get_dev_storvsc_sysctl():
    return execute_or_debug(["sysctl", "dev.storvsc"], fail_ret="")


def get_camcontrol_dev_bus():
    return execute_or_debug(['camcontrol', 'devlist', '-b'])


def get_camcontrol_dev():
    return execute_or_debug(['camcontrol', 'devlist'])


def get_resource_disk_on_freebsd(port_id):
    g0 = "00000000"
    if port_id > 1:
        g0 = "00000001"
        port_id = port_id - 2
    g1 = "000" + str(port_id)
    g0g1 = "{0}-{1}".format(g0, g1)

    # search 'X' from
    #  'dev.storvsc.X.%pnpinfo:
    #      classid=32412632-86cb-44a2-9b5c-50d1417354f5
    #      deviceid=00000000-0001-8899-0000-000000000000'
    sysctl_out = get_dev_storvsc_sysctl()

    storvscid = find_storvscid_from_sysctl_pnpinfo(sysctl_out, g0g1)
    if not storvscid:
        LOG.debug("Fail to find storvsc id from sysctl")
        return None

    camcontrol_b_out = get_camcontrol_dev_bus()
    camcontrol_out = get_camcontrol_dev()
    # try to find /dev/XX from 'blkvsc' device
    blkvsc = "blkvsc{0}".format(storvscid)
    scbusx = find_busdev_from_disk(camcontrol_b_out, blkvsc)
    if scbusx:
        devname = find_dev_from_busdev(camcontrol_out, scbusx)
        if devname is None:
            LOG.debug("Fail to find /dev/daX")
            return None
        return devname
    # try to find /dev/XX from 'storvsc' device
    storvsc = "storvsc{0}".format(storvscid)
    scbusx = find_busdev_from_disk(camcontrol_b_out, storvsc)
    if scbusx:
        devname = find_dev_from_busdev(camcontrol_out, scbusx)
        if devname is None:
            LOG.debug("Fail to find /dev/daX")
            return None
        return devname
    return None


# update the FreeBSD specific information
if util.is_FreeBSD():
    DEFAULT_PRIMARY_NIC = 'hn0'
    LEASE_FILE = '/var/db/dhclient.leases.hn0'
    DEFAULT_FS = 'freebsd-ufs'
    res_disk = get_resource_disk_on_freebsd(1)
    if res_disk is not None:
        LOG.debug("resource disk is not None")
        RESOURCE_DISK_PATH = "/dev/" + res_disk
    else:
        LOG.debug("resource disk is None")
    # TODO Find where platform entropy data is surfaced
    PLATFORM_ENTROPY_SOURCE = None

BUILTIN_DS_CONFIG = {
    'agent_command': AGENT_START_BUILTIN,
    'data_dir': AGENT_SEED_DIR,
    'set_hostname': True,
    'hostname_bounce': {
        'interface': DEFAULT_PRIMARY_NIC,
        'policy': True,
        'command': 'builtin',
        'hostname_command': 'hostname',
    },
    'disk_aliases': {'ephemeral0': RESOURCE_DISK_PATH},
    'dhclient_lease_file': LEASE_FILE,
    'apply_network_config': True,  # Use IMDS published network configuration
}
# RELEASE_BLOCKER: Xenial and earlier apply_network_config default is False

BUILTIN_CLOUD_EPHEMERAL_DISK_CONFIG = {
    'disk_setup': {
        'ephemeral0': {'table_type': 'gpt',
                       'layout': [100],
                       'overwrite': True},
    },
    'fs_setup': [{'filesystem': DEFAULT_FS,
                  'device': 'ephemeral0.1'}],
}

DS_CFG_PATH = ['datasource', DS_NAME]
DS_CFG_KEY_PRESERVE_NTFS = 'never_destroy_ntfs'
DEF_EPHEMERAL_LABEL = 'Temporary Storage'

# The redacted password fails to meet password complexity requirements
# so we can safely use this to mask/redact the password in the ovf-env.xml
DEF_PASSWD_REDACTION = 'REDACTED'


def get_hostname(hostname_command='hostname'):
    if not isinstance(hostname_command, (list, tuple)):
        hostname_command = (hostname_command,)
    return subp.subp(hostname_command, capture=True)[0].strip()


def set_hostname(hostname, hostname_command='hostname'):
    subp.subp([hostname_command, hostname])


@azure_ds_telemetry_reporter
@contextlib.contextmanager
def temporary_hostname(temp_hostname, cfg, hostname_command='hostname'):
    """
    Set a temporary hostname, restoring the previous hostname on exit.

    Will have the value of the previous hostname when used as a context
    manager, or None if the hostname was not changed.
    """
    policy = cfg['hostname_bounce']['policy']
    previous_hostname = get_hostname(hostname_command)
    if (not util.is_true(cfg.get('set_hostname')) or
       util.is_false(policy) or
       (previous_hostname == temp_hostname and policy != 'force')):
        yield None
        return
    try:
        set_hostname(temp_hostname, hostname_command)
    except Exception as e:
        report_diagnostic_event(
            'Failed setting temporary hostname: %s' % e,
            logger_func=LOG.warning)
        yield None
        return
    try:
        yield previous_hostname
    finally:
        set_hostname(previous_hostname, hostname_command)


class DataSourceAzure(sources.DataSource):

    dsname = 'Azure'
    _negotiated = False
    _metadata_imds = sources.UNSET

    def __init__(self, sys_cfg, distro, paths):
        sources.DataSource.__init__(self, sys_cfg, distro, paths)
        self.seed_dir = os.path.join(paths.seed_dir, 'azure')
        self.cfg = {}
        self.seed = None
        self.ds_cfg = util.mergemanydict([
            util.get_cfg_by_path(sys_cfg, DS_CFG_PATH, {}),
            BUILTIN_DS_CONFIG])
        self.dhclient_lease_file = self.ds_cfg.get('dhclient_lease_file')
        self._network_config = None
        # Regenerate network config new_instance boot and every boot
        self.update_events['network'].add(EventType.BOOT)
        self._ephemeral_dhcp_ctx = None

    def __str__(self):
        root = sources.DataSource.__str__(self)
        return "%s [seed=%s]" % (root, self.seed)

    @azure_ds_telemetry_reporter
    def bounce_network_with_azure_hostname(self):
        # When using cloud-init to provision, we have to set the hostname from
        # the metadata and "bounce" the network to force DDNS to update via
        # dhclient
        azure_hostname = self.metadata.get('local-hostname')
        LOG.debug("Hostname in metadata is %s", azure_hostname)
        hostname_command = self.ds_cfg['hostname_bounce']['hostname_command']

        with temporary_hostname(azure_hostname, self.ds_cfg,
                                hostname_command=hostname_command) \
                as previous_hn:
            if (previous_hn is not None and
                    util.is_true(self.ds_cfg.get('set_hostname'))):
                cfg = self.ds_cfg['hostname_bounce']

                # "Bouncing" the network
                try:
                    return perform_hostname_bounce(hostname=azure_hostname,
                                                   cfg=cfg,
                                                   prev_hostname=previous_hn)
                except Exception as e:
                    report_diagnostic_event(
                        "Failed publishing hostname: %s" % e,
                        logger_func=LOG.warning)
                    util.logexc(LOG, "handling set_hostname failed")
        return False

    @azure_ds_telemetry_reporter
    def get_metadata_from_agent(self):
        temp_hostname = self.metadata.get('local-hostname')
        agent_cmd = self.ds_cfg['agent_command']
        LOG.debug("Getting metadata via agent.  hostname=%s cmd=%s",
                  temp_hostname, agent_cmd)

        self.bounce_network_with_azure_hostname()

        try:
            invoke_agent(agent_cmd)
        except subp.ProcessExecutionError:
            # claim the datasource even if the command failed
            util.logexc(LOG, "agent command '%s' failed.",
                        self.ds_cfg['agent_command'])

        ddir = self.ds_cfg['data_dir']

        fp_files = []
        key_value = None
        for pk in self.cfg.get('_pubkeys', []):
            if pk.get('value', None):
                key_value = pk['value']
                LOG.debug("SSH authentication: using value from fabric")
            else:
                bname = str(pk['fingerprint'] + ".crt")
                fp_files += [os.path.join(ddir, bname)]
                LOG.debug("SSH authentication: "
                          "using fingerprint from fabric")

        with events.ReportEventStack(
                name="waiting-for-ssh-public-key",
                description="wait for agents to retrieve SSH keys",
                parent=azure_ds_reporter):
            # wait very long for public SSH keys to arrive
            # https://bugs.launchpad.net/cloud-init/+bug/1717611
            missing = util.log_time(logfunc=LOG.debug,
                                    msg="waiting for SSH public key files",
                                    func=util.wait_for_files,
                                    args=(fp_files, 900))
            if len(missing):
                LOG.warning("Did not find files, but going on: %s", missing)

        metadata = {}
        metadata['public-keys'] = key_value or pubkeys_from_crt_files(fp_files)
        return metadata

    def _get_subplatform(self):
        """Return the subplatform metadata source details."""
        if self.seed.startswith('/dev'):
            subplatform_type = 'config-disk'
        else:
            subplatform_type = 'seed-dir'
        return '%s (%s)' % (subplatform_type, self.seed)

    @azure_ds_telemetry_reporter
    def crawl_metadata(self):
        """Walk all instance metadata sources returning a dict on success.

        @return: A dictionary of any metadata content for this instance.
        @raise: InvalidMetaDataException when the expected metadata service is
            unavailable, broken or disabled.
        """
        crawled_data = {}
        # azure removes/ejects the cdrom containing the ovf-env.xml
        # file on reboot.  So, in order to successfully reboot we
        # need to look in the datadir and consider that valid
        ddir = self.ds_cfg['data_dir']

        # The order in which the candidates are inserted matters here, because
        # it determines the value of ret. More specifically, the first one in
        # the candidate list determines the path to take in order to get the
        # metadata we need.
        candidates = [self.seed_dir]
        if os.path.isfile(REPROVISION_MARKER_FILE):
            candidates.insert(0, "IMDS")
            report_diagnostic_event("Reprovision marker file already present "
                                    "before crawling Azure metadata: %s" %
                                    REPROVISION_MARKER_FILE,
                                    logger_func=LOG.debug)
        elif os.path.isfile(REPROVISION_NIC_ATTACH_MARKER_FILE):
            candidates.insert(0, "NIC_ATTACH_MARKER_PRESENT")
            report_diagnostic_event("Reprovision nic attach marker file "
                                    "already present before crawling Azure "
                                    "metadata: %s" %
                                    REPROVISION_NIC_ATTACH_MARKER_FILE,
                                    logger_func=LOG.debug)
        candidates.extend(list_possible_azure_ds_devs())
        if ddir:
            candidates.append(ddir)

        found = None
        reprovision = False
        reprovision_after_nic_attach = False
        for cdev in candidates:
            try:
                if cdev == "IMDS":
                    ret = None
                    reprovision = True
                elif cdev == "NIC_ATTACH_MARKER_PRESENT":
                    ret = None
                    reprovision_after_nic_attach = True
                elif cdev.startswith("/dev/"):
                    if util.is_FreeBSD():
                        ret = util.mount_cb(cdev, load_azure_ds_dir,
                                            mtype="udf")
                    else:
                        ret = util.mount_cb(cdev, load_azure_ds_dir)
                else:
                    ret = load_azure_ds_dir(cdev)

            except NonAzureDataSource:
                report_diagnostic_event(
                    "Did not find Azure data source in %s" % cdev,
                    logger_func=LOG.debug)
                continue
            except BrokenAzureDataSource as exc:
                msg = 'BrokenAzureDataSource: %s' % exc
                report_diagnostic_event(msg, logger_func=LOG.error)
                raise sources.InvalidMetaDataException(msg)
            except util.MountFailedError:
                report_diagnostic_event(
                    '%s was not mountable' % cdev, logger_func=LOG.warning)
                continue

            perform_reprovision = reprovision or self._should_reprovision(ret)
            perform_reprovision_after_nic_attach = (
                reprovision_after_nic_attach or
                self._should_reprovision_after_nic_attach(ret))

            if perform_reprovision or perform_reprovision_after_nic_attach:
                if util.is_FreeBSD():
                    msg = "Free BSD is not supported for PPS VMs"
                    report_diagnostic_event(msg, logger_func=LOG.error)
                    raise sources.InvalidMetaDataException(msg)
                if perform_reprovision_after_nic_attach:
                    self._wait_for_all_nics_ready()
                ret = self._reprovision()

            imds_md = get_metadata_from_imds(
                self.fallback_interface, retries=10)
            (md, userdata_raw, cfg, files) = ret
            self.seed = cdev
            crawled_data.update({
                'cfg': cfg,
                'files': files,
                'metadata': util.mergemanydict(
                    [md, {'imds': imds_md}]),
                'userdata_raw': userdata_raw})
            found = cdev

            report_diagnostic_event(
                'found datasource in %s' % cdev, logger_func=LOG.debug)
            break

        if not found:
            msg = 'No Azure metadata found'
            report_diagnostic_event(msg, logger_func=LOG.error)
            raise sources.InvalidMetaDataException(msg)

        if found == ddir:
            report_diagnostic_event(
                "using files cached in %s" % ddir, logger_func=LOG.debug)

        seed = _get_random_seed()
        if seed:
            crawled_data['metadata']['random_seed'] = seed
        crawled_data['metadata']['instance-id'] = self._iid()

        if perform_reprovision or perform_reprovision_after_nic_attach:
            LOG.info("Reporting ready to Azure after getting ReprovisionData")
            use_cached_ephemeral = (
                self.distro.networking.is_up(self.fallback_interface) and
                getattr(self, '_ephemeral_dhcp_ctx', None))
            if use_cached_ephemeral:
                self._report_ready(lease=self._ephemeral_dhcp_ctx.lease)
                self._ephemeral_dhcp_ctx.clean_network()  # Teardown ephemeral
            else:
                try:
                    with EphemeralDHCPv4WithReporting(
                            azure_ds_reporter) as lease:
                        self._report_ready(lease=lease)
                except Exception as e:
                    report_diagnostic_event(
                        "exception while reporting ready: %s" % e,
                        logger_func=LOG.error)
                    raise
        return crawled_data

    def _is_platform_viable(self):
        """Check platform environment to report if this datasource may run."""
        return _is_platform_viable(self.seed_dir)

    def clear_cached_attrs(self, attr_defaults=()):
        """Reset any cached class attributes to defaults."""
        super(DataSourceAzure, self).clear_cached_attrs(attr_defaults)
        self._metadata_imds = sources.UNSET

    @azure_ds_telemetry_reporter
    def _get_data(self):
        """Crawl and process datasource metadata caching metadata as attrs.

        @return: True on success, False on error, invalid or disabled
            datasource.
        """
        if not self._is_platform_viable():
            return False
        try:
            get_boot_telemetry()
        except Exception as e:
            LOG.warning("Failed to get boot telemetry: %s", e)

        try:
            get_system_info()
        except Exception as e:
            LOG.warning("Failed to get system information: %s", e)

        self.distro.networking.blacklist_drivers = BLACKLIST_DRIVERS

        try:
            crawled_data = util.log_time(
                logfunc=LOG.debug, msg='Crawl of metadata service',
                func=self.crawl_metadata
            )
        except Exception as e:
            report_diagnostic_event(
                'Could not crawl Azure metadata: %s' % e,
                logger_func=LOG.error)
            self._report_failure(
                description=DEFAULT_REPORT_FAILURE_USER_VISIBLE_MESSAGE)
            return False

        if (self.distro and self.distro.name == 'ubuntu' and
                self.ds_cfg.get('apply_network_config')):
            maybe_remove_ubuntu_network_config_scripts()

        # Process crawled data and augment with various config defaults

        # Only merge in default cloud config related to the ephemeral disk
        # if the ephemeral disk exists
        devpath = RESOURCE_DISK_PATH
        if os.path.exists(devpath):
            report_diagnostic_event(
                "Ephemeral resource disk '%s' exists. "
                "Merging default Azure cloud ephemeral disk configs."
                % devpath,
                logger_func=LOG.debug)
            self.cfg = util.mergemanydict(
                [crawled_data['cfg'], BUILTIN_CLOUD_EPHEMERAL_DISK_CONFIG])
        else:
            report_diagnostic_event(
                "Ephemeral resource disk '%s' does not exist. "
                "Not merging default Azure cloud ephemeral disk configs."
                % devpath,
                logger_func=LOG.debug)
            self.cfg = crawled_data['cfg']

        self._metadata_imds = crawled_data['metadata']['imds']
        self.metadata = util.mergemanydict(
            [crawled_data['metadata'], DEFAULT_METADATA])
        self.userdata_raw = crawled_data['userdata_raw']

        user_ds_cfg = util.get_cfg_by_path(self.cfg, DS_CFG_PATH, {})
        self.ds_cfg = util.mergemanydict([user_ds_cfg, self.ds_cfg])

        # walinux agent writes files world readable, but expects
        # the directory to be protected.
        write_files(
            self.ds_cfg['data_dir'], crawled_data['files'], dirmode=0o700)
        return True

    def device_name_to_device(self, name):
        return self.ds_cfg['disk_aliases'].get(name)

    @azure_ds_telemetry_reporter
    def get_public_ssh_keys(self):
        """
        Try to get the ssh keys from IMDS first, and if that fails
        (i.e. IMDS is unavailable) then fallback to getting the ssh
        keys from OVF.

        The benefit to getting keys from IMDS is a large performance
        advantage, so this is a strong preference. But we must keep
        OVF as a second option for environments that don't have IMDS.
        """
        LOG.debug('Retrieving public SSH keys')
        ssh_keys = []
        try:
            raise KeyError(
                "Not using public SSH keys from IMDS"
            )
            # pylint:disable=unreachable
            ssh_keys = [
                public_key['keyData']
                for public_key
                in self.metadata['imds']['compute']['publicKeys']
            ]
            LOG.debug('Retrieved SSH keys from IMDS')
        except KeyError:
            log_msg = 'Unable to get keys from IMDS, falling back to OVF'
            report_diagnostic_event(log_msg, logger_func=LOG.debug)
            try:
                ssh_keys = self.metadata['public-keys']
                LOG.debug('Retrieved keys from OVF')
            except KeyError:
                log_msg = 'No keys available from OVF'
                report_diagnostic_event(log_msg, logger_func=LOG.debug)

        return ssh_keys

    def get_config_obj(self):
        return self.cfg

    def check_instance_id(self, sys_cfg):
        # quickly (local check only) if self.instance_id is still valid
        return sources.instance_id_matches_system_uuid(self.get_instance_id())

    def _iid(self, previous=None):
        prev_iid_path = os.path.join(
            self.paths.get_cpath('data'), 'instance-id')
        # Older kernels than 4.15 will have UPPERCASE product_uuid.
        # We don't want Azure to react to an UPPER/lower difference as a new
        # instance id as it rewrites SSH host keys.
        # LP: #1835584
        iid = dmi.read_dmi_data('system-uuid').lower()
        if os.path.exists(prev_iid_path):
            previous = util.load_file(prev_iid_path).strip()
            if previous.lower() == iid:
                # If uppercase/lowercase equivalent, return the previous value
                # to avoid new instance id.
                return previous
            if is_byte_swapped(previous.lower(), iid):
                return previous
        return iid

    @azure_ds_telemetry_reporter
    def setup(self, is_new_instance):
        if self._negotiated is False:
            LOG.debug("negotiating for %s (new_instance=%s)",
                      self.get_instance_id(), is_new_instance)
            fabric_data = self._negotiate()
            LOG.debug("negotiating returned %s", fabric_data)
            if fabric_data:
                self.metadata.update(fabric_data)
            self._negotiated = True
        else:
            LOG.debug("negotiating already done for %s",
                      self.get_instance_id())

    @azure_ds_telemetry_reporter
    def _wait_for_nic_detach(self, nl_sock):
        """Use the netlink socket provided to wait for nic detach event.
           NOTE: The function doesn't close the socket. The caller owns closing
           the socket and disposing it safely.
        """
        try:
            ifname = None

            # Preprovisioned VM will only have one NIC, and it gets
            # detached immediately after deployment.
            with events.ReportEventStack(
                    name="wait-for-nic-detach",
                    description=("wait for nic detach"),
                    parent=azure_ds_reporter):
                ifname = netlink.wait_for_nic_detach_event(nl_sock)
            if ifname is None:
                msg = ("Preprovisioned nic not detached as expected. "
                       "Proceeding without failing.")
                report_diagnostic_event(msg, logger_func=LOG.warning)
            else:
                report_diagnostic_event("The preprovisioned nic %s is detached"
                                        % ifname, logger_func=LOG.warning)
            path = REPROVISION_NIC_DETACHED_MARKER_FILE
            LOG.info("Creating a marker file for nic detached: %s", path)
            util.write_file(path, "{pid}: {time}\n".format(
                pid=os.getpid(), time=time()))
        except AssertionError as error:
            report_diagnostic_event(error, logger_func=LOG.error)
            raise

    @azure_ds_telemetry_reporter
    def wait_for_link_up(self, ifname):
        """In cases where the link state is still showing down after a nic is
           hot-attached, we can attempt to bring it up by forcing the hv_netvsc
           drivers to query the link state by unbinding and then binding the
           device. This function attempts infinitely until the link is up,
           because we cannot proceed further until we have a stable link."""

        if self.distro.networking.try_set_link_up(ifname):
            report_diagnostic_event("The link %s is already up." % ifname,
                                    logger_func=LOG.info)
            return

        LOG.info("Attempting to bring %s up", ifname)

        attempts = 0
        while True:

            LOG.info("Unbinding and binding the interface %s", ifname)
            devicename = net.read_sys_net(ifname,
                                          'device/device_id').strip('{}')
            util.write_file('/sys/bus/vmbus/drivers/hv_netvsc/unbind',
                            devicename)
            util.write_file('/sys/bus/vmbus/drivers/hv_netvsc/bind',
                            devicename)

            attempts = attempts + 1
            if self.distro.networking.try_set_link_up(ifname):
                msg = "The link %s is up after %s attempts" % (ifname,
                                                               attempts)
                report_diagnostic_event(msg, logger_func=LOG.info)
                return

            sleep_duration = 1
            msg = ("Link is not up after %d attempts with %d seconds sleep "
                   "between attempts." % (attempts, sleep_duration))

            if attempts % 10 == 0:
                report_diagnostic_event(msg, logger_func=LOG.info)
            else:
                LOG.info(msg)

            sleep(sleep_duration)

    @azure_ds_telemetry_reporter
    def _create_report_ready_marker(self):
        path = REPORTED_READY_MARKER_FILE
        LOG.info(
            "Creating a marker file to report ready: %s", path)
        util.write_file(path, "{pid}: {time}\n".format(
            pid=os.getpid(), time=time()))
        report_diagnostic_event(
            'Successfully created reported ready marker file '
            'while in the preprovisioning pool.',
            logger_func=LOG.debug)

    @azure_ds_telemetry_reporter
    def _report_ready_if_needed(self):
        """Report ready to the platform if the marker file is not present,
        and create the marker file.
        """
        have_not_reported_ready = (
            not os.path.isfile(REPORTED_READY_MARKER_FILE))

        if have_not_reported_ready:
            report_diagnostic_event("Reporting ready before nic detach",
                                    logger_func=LOG.info)
            try:
                with EphemeralDHCPv4WithReporting(azure_ds_reporter) as lease:
                    self._report_ready(lease=lease)
            except Exception as e:
                report_diagnostic_event("Exception reporting ready during "
                                        "preprovisioning before nic detach: %s"
                                        % e, logger_func=LOG.error)
                raise
            self._create_report_ready_marker()
        else:
            report_diagnostic_event("Already reported ready before nic detach."
                                    " The marker file already exists: %s" %
                                    REPORTED_READY_MARKER_FILE,
                                    logger_func=LOG.error)

    @azure_ds_telemetry_reporter
    def _check_if_nic_is_primary(self, ifname):
        """Check if a given interface is the primary nic or not. If it is the
        primary nic, then we also get the expected total nic count from IMDS.
        IMDS will process the request and send a response only for primary NIC.
        """
        is_primary = False
        expected_nic_count = -1
        imds_md = None

        # For now, only a VM's primary NIC can contact IMDS and WireServer. If
        # DHCP fails for a NIC, we have no mechanism to determine if the NIC is
        # primary or secondary. In this case, the desired behavior is to fail
        # VM provisioning if there is any DHCP failure when trying to determine
        # the primary NIC.
        try:
            with events.ReportEventStack(
                    name="obtain-dhcp-lease",
                    description=("obtain dhcp lease for %s when attempting to "
                                 "determine primary NIC during reprovision of "
                                 "a pre-provisioned VM" % ifname),
                    parent=azure_ds_reporter):
                dhcp_ctx = EphemeralDHCPv4(
                    iface=ifname,
                    dhcp_log_func=dhcp_log_cb)
                dhcp_ctx.obtain_lease()
        except Exception as e:
            report_diagnostic_event("Giving up. Failed to obtain dhcp lease "
                                    "for %s when attempting to determine "
                                    "primary NIC during reprovision due to %s"
                                    % (ifname, e), logger_func=LOG.error)
            raise

        # Primary nic detection will be optimized in the future. The fact that
        # primary nic is being attached first helps here. Otherwise each nic
        # could add several seconds of delay.
        try:
            imds_md = get_metadata_from_imds(
                ifname,
                5,
                metadata_type.network)
        except Exception as e:
            LOG.warning(
                "Failed to get network metadata using nic %s. Attempt to "
                "contact IMDS failed with error %s. Assuming this is not the "
                "primary nic.", ifname, e)
        finally:
            # If we are not the primary nic, then clean the dhcp context.
            if imds_md is None:
                dhcp_ctx.clean_network()

        if imds_md is not None:
            # Only primary NIC will get a response from IMDS.
            LOG.info("%s is the primary nic", ifname)
            is_primary = True

            # If primary, set ephemeral dhcp ctx so we can report ready
            self._ephemeral_dhcp_ctx = dhcp_ctx

            # Set the expected nic count based on the response received.
            expected_nic_count = len(
                imds_md['interface'])
            report_diagnostic_event("Expected nic count: %d" %
                                    expected_nic_count, logger_func=LOG.info)

        return is_primary, expected_nic_count

    @azure_ds_telemetry_reporter
    def _wait_for_hot_attached_nics(self, nl_sock):
        """Wait until all the expected nics for the vm are hot-attached.
        The expected nic count is obtained by requesting the network metadata
        from IMDS.
        """
        LOG.info("Waiting for nics to be hot-attached")
        try:
            # Wait for nics to be attached one at a time, until we know for
            # sure that all nics have been attached.
            nics_found = []
            primary_nic_found = False
            expected_nic_count = -1

            # Wait for netlink nic attach events. After the first nic is
            # attached, we are already in the customer vm deployment path and
            # so eerything from then on should happen fast and avoid
            # unnecessary delays wherever possible.
            while True:
                ifname = None
                with events.ReportEventStack(
                        name="wait-for-nic-attach",
                        description=("wait for nic attach after %d nics have "
                                     "been attached" % len(nics_found)),
                        parent=azure_ds_reporter):
                    ifname = netlink.wait_for_nic_attach_event(nl_sock,
                                                               nics_found)

                # wait_for_nic_attach_event guarantees that ifname it not None
                nics_found.append(ifname)
                report_diagnostic_event("Detected nic %s attached." % ifname,
                                        logger_func=LOG.info)

                # Attempt to bring the interface's operating state to
                # UP in case it is not already.
                self.wait_for_link_up(ifname)

                # If primary nic is not found, check if this is it. The
                # platform will attach the primary nic first so we
                # won't be in primary_nic_found = false state for long.
                if not primary_nic_found:
                    LOG.info("Checking if %s is the primary nic",
                             ifname)
                    (primary_nic_found, expected_nic_count) = (
                        self._check_if_nic_is_primary(ifname))

                # Exit criteria: check if we've discovered all nics
                if (expected_nic_count != -1
                        and len(nics_found) >= expected_nic_count):
                    LOG.info("Found all the nics for this VM.")
                    break

        except AssertionError as error:
            report_diagnostic_event(error, logger_func=LOG.error)

    @azure_ds_telemetry_reporter
    def _wait_for_all_nics_ready(self):
        """Wait for nic(s) to be hot-attached. There may be multiple nics
           depending on the customer request.
           But only primary nic would be able to communicate with wireserver
           and IMDS. So we detect and save the primary nic to be used later.
        """

        nl_sock = None
        try:
            nl_sock = netlink.create_bound_netlink_socket()

            report_ready_marker_present = bool(
                os.path.isfile(REPORTED_READY_MARKER_FILE))

            # Report ready if the marker file is not already present.
            # The nic of the preprovisioned vm gets hot-detached as soon as
            # we report ready. So no need to save the dhcp context.
            self._report_ready_if_needed()

            has_nic_been_detached = bool(
                os.path.isfile(REPROVISION_NIC_DETACHED_MARKER_FILE))

            if not has_nic_been_detached:
                LOG.info("NIC has not been detached yet.")
                self._wait_for_nic_detach(nl_sock)

            # If we know that the preprovisioned nic has been detached, and we
            # still have a fallback nic, then it means the VM must have
            # rebooted as part of customer assignment, and all the nics have
            # already been attached by the Azure platform. So there is no need
            # to wait for nics to be hot-attached.
            if not self.fallback_interface:
                self._wait_for_hot_attached_nics(nl_sock)
            else:
                report_diagnostic_event("Skipping waiting for nic attach "
                                        "because we already have a fallback "
                                        "interface. Report Ready marker "
                                        "present before detaching nics: %s" %
                                        report_ready_marker_present,
                                        logger_func=LOG.info)
        except netlink.NetlinkCreateSocketError as e:
            report_diagnostic_event(e, logger_func=LOG.warning)
            raise
        finally:
            if nl_sock:
                nl_sock.close()

    @azure_ds_telemetry_reporter
    def _poll_imds(self):
        """Poll IMDS for the new provisioning data until we get a valid
        response. Then return the returned JSON object."""
        url = metadata_type.reprovisiondata.value
        headers = {"Metadata": "true"}
        nl_sock = None
        report_ready = bool(not os.path.isfile(REPORTED_READY_MARKER_FILE))
        self.imds_logging_threshold = 1
        self.imds_poll_counter = 1
        dhcp_attempts = 0
        vnet_switched = False
        return_val = None

        def exc_cb(msg, exception):
            if isinstance(exception, UrlError):
                if exception.code in (404, 410):
                    if self.imds_poll_counter == self.imds_logging_threshold:
                        # Reducing the logging frequency as we are polling IMDS
                        self.imds_logging_threshold *= 2
                        LOG.debug("Backing off logging threshold for the same "
                                  "exception to %d",
                                  self.imds_logging_threshold)
                        report_diagnostic_event("poll IMDS with %s failed. "
                                                "Exception: %s and code: %s" %
                                                (msg, exception.cause,
                                                 exception.code),
                                                logger_func=LOG.debug)
                    self.imds_poll_counter += 1
                    return True
                else:
                    # If we get an exception while trying to call IMDS, we call
                    # DHCP and setup the ephemeral network to acquire a new IP.
                    report_diagnostic_event("poll IMDS with %s failed. "
                                            "Exception: %s and code: %s" %
                                            (msg, exception.cause,
                                             exception.code),
                                            logger_func=LOG.warning)
                    return False

            report_diagnostic_event(
                "poll IMDS failed with an "
                "unexpected exception: %s" % exception,
                logger_func=LOG.warning)
            return False

        # When the interface is hot-attached, we would have already
        # done dhcp and set the dhcp context. In that case, skip
        # the attempt to do dhcp.
        is_ephemeral_ctx_present = self._ephemeral_dhcp_ctx is not None
        msg = ("Unexpected error. Dhcp context is not expected to be already "
               "set when we need to wait for vnet switch")
        if is_ephemeral_ctx_present and report_ready:
            report_diagnostic_event(msg, logger_func=LOG.error)
            raise RuntimeError(msg)

        while True:
            try:
                # Since is_ephemeral_ctx_present is set only once, this ensures
                # that with regular reprovisioning, dhcp is always done every
                # time the loop runs.
                if not is_ephemeral_ctx_present:
                    # Save our EphemeralDHCPv4 context to avoid repeated dhcp
                    # later when we report ready
                    with events.ReportEventStack(
                            name="obtain-dhcp-lease",
                            description="obtain dhcp lease",
                            parent=azure_ds_reporter):
                        self._ephemeral_dhcp_ctx = EphemeralDHCPv4(
                            dhcp_log_func=dhcp_log_cb)
                        lease = self._ephemeral_dhcp_ctx.obtain_lease()

                if vnet_switched:
                    dhcp_attempts += 1
                if report_ready:
                    try:
                        nl_sock = netlink.create_bound_netlink_socket()
                    except netlink.NetlinkCreateSocketError as e:
                        report_diagnostic_event(
                            'Failed to create bound netlink socket: %s' % e,
                            logger_func=LOG.warning)
                        self._ephemeral_dhcp_ctx.clean_network()
                        break

                    report_ready_succeeded = self._report_ready(lease=lease)
                    if not report_ready_succeeded:
                        msg = ('Failed reporting ready while in '
                               'the preprovisioning pool.')
                        report_diagnostic_event(msg, logger_func=LOG.error)
                        self._ephemeral_dhcp_ctx.clean_network()
                        raise sources.InvalidMetaDataException(msg)

                    self._create_report_ready_marker()
                    report_ready = False

                    LOG.debug("Wait for vnetswitch to happen")
                    with events.ReportEventStack(
                            name="wait-for-media-disconnect-connect",
                            description="wait for vnet switch",
                            parent=azure_ds_reporter):
                        try:
                            netlink.wait_for_media_disconnect_connect(
                                nl_sock, lease['interface'])
                        except AssertionError as e:
                            report_diagnostic_event(
                                'Error while waiting for vnet switch: %s' % e,
                                logger_func=LOG.error)
                            break

                    vnet_switched = True
                    self._ephemeral_dhcp_ctx.clean_network()
                else:
                    with events.ReportEventStack(
                            name="get-reprovision-data-from-imds",
                            description="get reprovision data from imds",
                            parent=azure_ds_reporter):
                        return_val = readurl(url,
                                             timeout=IMDS_TIMEOUT_IN_SECONDS,
                                             headers=headers,
                                             exception_cb=exc_cb,
                                             infinite=True,
                                             log_req_resp=False).contents
                    break
            except UrlError:
                # Teardown our EphemeralDHCPv4 context on failure as we retry
                self._ephemeral_dhcp_ctx.clean_network()
            finally:
                if nl_sock:
                    nl_sock.close()

        if vnet_switched:
            report_diagnostic_event("attempted dhcp %d times after reuse" %
                                    dhcp_attempts,
                                    logger_func=LOG.debug)
            report_diagnostic_event("polled imds %d times after reuse" %
                                    self.imds_poll_counter,
                                    logger_func=LOG.debug)

        return return_val

    @azure_ds_telemetry_reporter
    def _report_failure(self, description=None) -> bool:
        """Tells the Azure fabric that provisioning has failed.

        @param description: A description of the error encountered.
        @return: The success status of sending the failure signal.
        """
        unknown_245_key = 'unknown-245'

        try:
            if (self.distro.networking.is_up(self.fallback_interface) and
                    getattr(self, '_ephemeral_dhcp_ctx', None) and
                    getattr(self._ephemeral_dhcp_ctx, 'lease', None) and
                    unknown_245_key in self._ephemeral_dhcp_ctx.lease):
                report_diagnostic_event(
                    'Using cached ephemeral dhcp context '
                    'to report failure to Azure', logger_func=LOG.debug)
                report_failure_to_fabric(
                    dhcp_opts=self._ephemeral_dhcp_ctx.lease[unknown_245_key],
                    description=description)
                self._ephemeral_dhcp_ctx.clean_network()  # Teardown ephemeral
                return True
        except Exception as e:
            report_diagnostic_event(
                'Failed to report failure using '
                'cached ephemeral dhcp context: %s' % e,
                logger_func=LOG.error)

        try:
            report_diagnostic_event(
                'Using new ephemeral dhcp to report failure to Azure',
                logger_func=LOG.debug)
            with EphemeralDHCPv4WithReporting(azure_ds_reporter) as lease:
                report_failure_to_fabric(
                    dhcp_opts=lease[unknown_245_key],
                    description=description)
            return True
        except Exception as e:
            report_diagnostic_event(
                'Failed to report failure using new ephemeral dhcp: %s' % e,
                logger_func=LOG.debug)

        try:
            report_diagnostic_event(
                'Using fallback lease to report failure to Azure')
            report_failure_to_fabric(
                fallback_lease_file=self.dhclient_lease_file,
                description=description)
            return True
        except Exception as e:
            report_diagnostic_event(
                'Failed to report failure using fallback lease: %s' % e,
                logger_func=LOG.debug)

        return False

    def _report_ready(self, lease: dict) -> bool:
        """Tells the fabric provisioning has completed.

        @param lease: dhcp lease to use for sending the ready signal.
        @return: The success status of sending the ready signal.
        """
        try:
            get_metadata_from_fabric(None, lease['unknown-245'])
            return True
        except Exception as e:
            report_diagnostic_event(
                "Error communicating with Azure fabric; You may experience "
                "connectivity issues: %s" % e, logger_func=LOG.warning)
            return False

    def _should_reprovision_after_nic_attach(self, candidate_metadata) -> bool:
        """Whether or not we should wait for nic attach and then poll
        IMDS for reprovisioning data. Also sets a marker file to poll IMDS.

        The marker file is used for the following scenario: the VM boots into
        wait for nic attach, which we expect to be proceeding infinitely until
        the nic is attached. If for whatever reason the platform moves us to a
        new host (for instance a hardware issue), we need to keep waiting.
        However, since the VM reports ready to the Fabric, we will not attach
        the ISO, thus cloud-init needs to have a way of knowing that it should
        jump back into the waiting mode in order to retrieve the ovf_env.

        @param candidate_metadata: Metadata obtained from reading ovf-env.
        @return: Whether to reprovision after waiting for nics to be attached.
        """
        if not candidate_metadata:
            return False
        (_md, _userdata_raw, cfg, _files) = candidate_metadata
        path = REPROVISION_NIC_ATTACH_MARKER_FILE
        if (cfg.get('PreprovisionedVMType', None) == "Savable" or
                os.path.isfile(path)):
            if not os.path.isfile(path):
                LOG.info("Creating a marker file to wait for nic attach: %s",
                         path)
                util.write_file(path, "{pid}: {time}\n".format(
                    pid=os.getpid(), time=time()))
            return True
        return False

    def _should_reprovision(self, ret):
        """Whether or not we should poll IMDS for reprovisioning data.
        Also sets a marker file to poll IMDS.

        The marker file is used for the following scenario: the VM boots into
        this polling loop, which we expect to be proceeding infinitely until
        the VM is picked. If for whatever reason the platform moves us to a
        new host (for instance a hardware issue), we need to keep polling.
        However, since the VM reports ready to the Fabric, we will not attach
        the ISO, thus cloud-init needs to have a way of knowing that it should
        jump back into the polling loop in order to retrieve the ovf_env."""
        if not ret:
            return False
        (_md, _userdata_raw, cfg, _files) = ret
        path = REPROVISION_MARKER_FILE
        if (cfg.get('PreprovisionedVm') is True or
                cfg.get('PreprovisionedVMType', None) == 'Running' or
                os.path.isfile(path)):
            if not os.path.isfile(path):
                LOG.info("Creating a marker file to poll imds: %s",
                         path)
                util.write_file(path, "{pid}: {time}\n".format(
                    pid=os.getpid(), time=time()))
            return True
        return False

    def _reprovision(self):
        """Initiate the reprovisioning workflow."""
        contents = self._poll_imds()
        with events.ReportEventStack(
                name="reprovisioning-read-azure-ovf",
                description="read azure ovf during reprovisioning",
                parent=azure_ds_reporter):
            md, ud, cfg = read_azure_ovf(contents)
            return (md, ud, cfg, {'ovf-env.xml': contents})

    @azure_ds_telemetry_reporter
    def _negotiate(self):
        """Negotiate with fabric and return data from it.

           On success, returns a dictionary including 'public_keys'.
           On failure, returns False.
        """

        if self.ds_cfg['agent_command'] == AGENT_START_BUILTIN:
            self.bounce_network_with_azure_hostname()

            pubkey_info = None
            try:
                raise KeyError(
                    "Not using public SSH keys from IMDS"
                )
                # pylint:disable=unreachable
                public_keys = self.metadata['imds']['compute']['publicKeys']
                LOG.debug(
                    'Successfully retrieved %s key(s) from IMDS',
                    len(public_keys)
                    if public_keys is not None
                    else 0
                )
            except KeyError:
                LOG.debug(
                    'Unable to retrieve SSH keys from IMDS during '
                    'negotiation, falling back to OVF'
                )
                pubkey_info = self.cfg.get('_pubkeys', None)

            metadata_func = partial(get_metadata_from_fabric,
                                    fallback_lease_file=self.
                                    dhclient_lease_file,
                                    pubkey_info=pubkey_info)
        else:
            metadata_func = self.get_metadata_from_agent

        LOG.debug("negotiating with fabric via agent command %s",
                  self.ds_cfg['agent_command'])
        try:
            fabric_data = metadata_func()
        except Exception as e:
            report_diagnostic_event(
                "Error communicating with Azure fabric; You may experience "
                "connectivity issues: %s" % e, logger_func=LOG.warning)
            return False

        util.del_file(REPORTED_READY_MARKER_FILE)
        util.del_file(REPROVISION_MARKER_FILE)
        util.del_file(REPROVISION_NIC_ATTACH_MARKER_FILE)
        util.del_file(REPROVISION_NIC_DETACHED_MARKER_FILE)
        return fabric_data

    @azure_ds_telemetry_reporter
    def activate(self, cfg, is_new_instance):
        try:
            address_ephemeral_resize(is_new_instance=is_new_instance,
                                     preserve_ntfs=self.ds_cfg.get(
                                         DS_CFG_KEY_PRESERVE_NTFS, False))
        finally:
            push_log_to_kvp(self.sys_cfg['def_log_file'])
        return

    @property
    def availability_zone(self):
        return self.metadata.get(
            'imds', {}).get('compute', {}).get('platformFaultDomain')

    @property
    def network_config(self):
        """Generate a network config like net.generate_fallback_network() with
           the following exceptions.

           1. Probe the drivers of the net-devices present and inject them in
              the network configuration under params: driver: <driver> value
           2. Generate a fallback network config that does not include any of
              the blacklisted devices.
        """
        if not self._network_config or self._network_config == sources.UNSET:
            if self.ds_cfg.get('apply_network_config'):
                nc_src = self._metadata_imds
            else:
                nc_src = None
            self._network_config = parse_network_config(nc_src)
        return self._network_config

    @property
    def region(self):
        return self.metadata.get('imds', {}).get('compute', {}).get('location')


def _partitions_on_device(devpath, maxnum=16):
    # return a list of tuples (ptnum, path) for each part on devpath
    for suff in ("-part", "p", ""):
        found = []
        for pnum in range(1, maxnum):
            ppath = devpath + suff + str(pnum)
            if os.path.exists(ppath):
                found.append((pnum, os.path.realpath(ppath)))
        if found:
            return found
    return []


@azure_ds_telemetry_reporter
def _has_ntfs_filesystem(devpath):
    ntfs_devices = util.find_devs_with("TYPE=ntfs", no_cache=True)
    LOG.debug('ntfs_devices found = %s', ntfs_devices)
    return os.path.realpath(devpath) in ntfs_devices


@azure_ds_telemetry_reporter
def can_dev_be_reformatted(devpath, preserve_ntfs):
    """Determine if the ephemeral drive at devpath should be reformatted.

    A fresh ephemeral disk is formatted by Azure and will:
      a.) have a partition table (dos or gpt)
      b.) have 1 partition that is ntfs formatted, or
          have 2 partitions with the second partition ntfs formatted.
          (larger instances with >2TB ephemeral disk have gpt, and will
           have a microsoft reserved partition as part 1.  LP: #1686514)
      c.) the ntfs partition will have no files other than possibly
          'dataloss_warning_readme.txt'

    User can indicate that NTFS should never be destroyed by setting
    DS_CFG_KEY_PRESERVE_NTFS in dscfg.
    If data is found on NTFS, user is warned to set DS_CFG_KEY_PRESERVE_NTFS
    to make sure cloud-init does not accidentally wipe their data.
    If cloud-init cannot mount the disk to check for data, destruction
    will be allowed, unless the dscfg key is set."""
    if preserve_ntfs:
        msg = ('config says to never destroy NTFS (%s.%s), skipping checks' %
               (".".join(DS_CFG_PATH), DS_CFG_KEY_PRESERVE_NTFS))
        return False, msg

    if not os.path.exists(devpath):
        return False, 'device %s does not exist' % devpath

    LOG.debug('Resolving realpath of %s -> %s', devpath,
              os.path.realpath(devpath))

    # devpath of /dev/sd[a-z] or /dev/disk/cloud/azure_resource
    # where partitions are "<devpath>1" or "<devpath>-part1" or "<devpath>p1"
    partitions = _partitions_on_device(devpath)
    if len(partitions) == 0:
        return False, 'device %s was not partitioned' % devpath
    elif len(partitions) > 2:
        msg = ('device %s had 3 or more partitions: %s' %
               (devpath, ' '.join([p[1] for p in partitions])))
        return False, msg
    elif len(partitions) == 2:
        cand_part, cand_path = partitions[1]
    else:
        cand_part, cand_path = partitions[0]

    if not _has_ntfs_filesystem(cand_path):
        msg = ('partition %s (%s) on device %s was not ntfs formatted' %
               (cand_part, cand_path, devpath))
        return False, msg

    @azure_ds_telemetry_reporter
    def count_files(mp):
        ignored = set(['dataloss_warning_readme.txt'])
        return len([f for f in os.listdir(mp) if f.lower() not in ignored])

    bmsg = ('partition %s (%s) on device %s was ntfs formatted' %
            (cand_part, cand_path, devpath))

    with events.ReportEventStack(
        name="mount-ntfs-and-count",
        description="mount-ntfs-and-count",
        parent=azure_ds_reporter
    ) as evt:
        try:
            file_count = util.mount_cb(cand_path, count_files, mtype="ntfs",
                                       update_env_for_mount={'LANG': 'C'})
        except util.MountFailedError as e:
            evt.description = "cannot mount ntfs"
            if "unknown filesystem type 'ntfs'" in str(e):
                return True, (bmsg + ' but this system cannot mount NTFS,'
                              ' assuming there are no important files.'
                              ' Formatting allowed.')
            return False, bmsg + ' but mount of %s failed: %s' % (cand_part, e)

        if file_count != 0:
            evt.description = "mounted and counted %d files" % file_count
            LOG.warning("it looks like you're using NTFS on the ephemeral"
                        " disk, to ensure that filesystem does not get wiped,"
                        " set %s.%s in config", '.'.join(DS_CFG_PATH),
                        DS_CFG_KEY_PRESERVE_NTFS)
            return False, bmsg + ' but had %d files on it.' % file_count

    return True, bmsg + ' and had no important files. Safe for reformatting.'


@azure_ds_telemetry_reporter
def address_ephemeral_resize(devpath=RESOURCE_DISK_PATH,
                             is_new_instance=False, preserve_ntfs=False):
    if not os.path.exists(devpath):
        report_diagnostic_event(
            "Ephemeral resource disk '%s' does not exist." % devpath,
            logger_func=LOG.debug)
        return
    else:
        report_diagnostic_event(
            "Ephemeral resource disk '%s' exists." % devpath,
            logger_func=LOG.debug)

    result = False
    msg = None
    if is_new_instance:
        result, msg = (True, "First instance boot.")
    else:
        result, msg = can_dev_be_reformatted(devpath, preserve_ntfs)

    LOG.debug("reformattable=%s: %s", result, msg)
    if not result:
        return

    for mod in ['disk_setup', 'mounts']:
        sempath = '/var/lib/cloud/instance/sem/config_' + mod
        bmsg = 'Marker "%s" for module "%s"' % (sempath, mod)
        if os.path.exists(sempath):
            try:
                os.unlink(sempath)
                LOG.debug('%s removed.', bmsg)
            except Exception as e:
                # python3 throws FileNotFoundError, python2 throws OSError
                LOG.warning('%s: remove failed! (%s)', bmsg, e)
        else:
            LOG.debug('%s did not exist.', bmsg)
    return


@azure_ds_telemetry_reporter
def perform_hostname_bounce(hostname, cfg, prev_hostname):
    # set the hostname to 'hostname' if it is not already set to that.
    # then, if policy is not off, bounce the interface using command
    # Returns True if the network was bounced, False otherwise.
    command = cfg['command']
    interface = cfg['interface']
    policy = cfg['policy']

    msg = ("hostname=%s policy=%s interface=%s" %
           (hostname, policy, interface))
    env = os.environ.copy()
    env['interface'] = interface
    env['hostname'] = hostname
    env['old_hostname'] = prev_hostname

    if command == "builtin":
        if util.is_FreeBSD():
            command = BOUNCE_COMMAND_FREEBSD
        elif subp.which('ifup'):
            command = BOUNCE_COMMAND_IFUP
        else:
            LOG.debug(
                "Skipping network bounce: ifupdown utils aren't present.")
            # Don't bounce as networkd handles hostname DDNS updates
            return False
    LOG.debug("pubhname: publishing hostname [%s]", msg)
    shell = not isinstance(command, (list, tuple))
    # capture=False, see comments in bug 1202758 and bug 1206164.
    util.log_time(logfunc=LOG.debug, msg="publishing hostname",
                  get_uptime=True, func=subp.subp,
                  kwargs={'args': command, 'shell': shell, 'capture': False,
                          'env': env})
    return True


@azure_ds_telemetry_reporter
def crtfile_to_pubkey(fname, data=None):
    pipeline = ('openssl x509 -noout -pubkey < "$0" |'
                'ssh-keygen -i -m PKCS8 -f /dev/stdin')
    (out, _err) = subp.subp(['sh', '-c', pipeline, fname],
                            capture=True, data=data)
    return out.rstrip()


@azure_ds_telemetry_reporter
def pubkeys_from_crt_files(flist):
    pubkeys = []
    errors = []
    for fname in flist:
        try:
            pubkeys.append(crtfile_to_pubkey(fname))
        except subp.ProcessExecutionError:
            errors.append(fname)

    if errors:
        report_diagnostic_event(
            "failed to convert the crt files to pubkey: %s" % errors,
            logger_func=LOG.warning)

    return pubkeys


@azure_ds_telemetry_reporter
def write_files(datadir, files, dirmode=None):

    def _redact_password(cnt, fname):
        """Azure provides the UserPassword in plain text. So we redact it"""
        try:
            root = ET.fromstring(cnt)
            for elem in root.iter():
                if ('UserPassword' in elem.tag and
                   elem.text != DEF_PASSWD_REDACTION):
                    elem.text = DEF_PASSWD_REDACTION
            return ET.tostring(root)
        except Exception:
            LOG.critical("failed to redact userpassword in %s", fname)
            return cnt

    if not datadir:
        return
    if not files:
        files = {}
    util.ensure_dir(datadir, dirmode)
    for (name, content) in files.items():
        fname = os.path.join(datadir, name)
        if 'ovf-env.xml' in name:
            content = _redact_password(content, fname)
        util.write_file(filename=fname, content=content, mode=0o600)


@azure_ds_telemetry_reporter
def invoke_agent(cmd):
    # this is a function itself to simplify patching it for test
    if cmd:
        LOG.debug("invoking agent: %s", cmd)
        subp.subp(cmd, shell=(not isinstance(cmd, list)))
    else:
        LOG.debug("not invoking agent")


def find_child(node, filter_func):
    ret = []
    if not node.hasChildNodes():
        return ret
    for child in node.childNodes:
        if filter_func(child):
            ret.append(child)
    return ret


@azure_ds_telemetry_reporter
def load_azure_ovf_pubkeys(sshnode):
    # This parses a 'SSH' node formatted like below, and returns
    # an array of dicts.
    #  [{'fingerprint': '6BE7A7C3C8A8F4B123CCA5D0C2F1BE4CA7B63ED7',
    #    'path': '/where/to/go'}]
    #
    # <SSH><PublicKeys>
    #   <PublicKey><Fingerprint>ABC</FingerPrint><Path>/x/y/z</Path>
    #   ...
    # </PublicKeys></SSH>
    # Under some circumstances, there may be a <Value> element along with the
    # Fingerprint and Path. Pass those along if they appear.
    results = find_child(sshnode, lambda n: n.localName == "PublicKeys")
    if len(results) == 0:
        return []
    if len(results) > 1:
        raise BrokenAzureDataSource("Multiple 'PublicKeys'(%s) in SSH node" %
                                    len(results))

    pubkeys_node = results[0]
    pubkeys = find_child(pubkeys_node, lambda n: n.localName == "PublicKey")

    if len(pubkeys) == 0:
        return []

    found = []
    text_node = minidom.Document.TEXT_NODE

    for pk_node in pubkeys:
        if not pk_node.hasChildNodes():
            continue

        cur = {'fingerprint': "", 'path': "", 'value': ""}
        for child in pk_node.childNodes:
            if child.nodeType == text_node or not child.localName:
                continue

            name = child.localName.lower()

            if name not in cur.keys():
                continue

            if (len(child.childNodes) != 1 or
                    child.childNodes[0].nodeType != text_node):
                continue

            cur[name] = child.childNodes[0].wholeText.strip()
        found.append(cur)

    return found


@azure_ds_telemetry_reporter
def read_azure_ovf(contents):
    try:
        dom = minidom.parseString(contents)
    except Exception as e:
        error_str = "Invalid ovf-env.xml: %s" % e
        report_diagnostic_event(error_str, logger_func=LOG.warning)
        raise BrokenAzureDataSource(error_str) from e

    results = find_child(dom.documentElement,
                         lambda n: n.localName == "ProvisioningSection")

    if len(results) == 0:
        raise NonAzureDataSource("No ProvisioningSection")
    if len(results) > 1:
        raise BrokenAzureDataSource("found '%d' ProvisioningSection items" %
                                    len(results))
    provSection = results[0]

    lpcs_nodes = find_child(provSection,
                            lambda n:
                            n.localName == "LinuxProvisioningConfigurationSet")

    if len(lpcs_nodes) == 0:
        raise NonAzureDataSource("No LinuxProvisioningConfigurationSet")
    if len(lpcs_nodes) > 1:
        raise BrokenAzureDataSource("found '%d' %ss" %
                                    (len(lpcs_nodes),
                                     "LinuxProvisioningConfigurationSet"))
    lpcs = lpcs_nodes[0]

    if not lpcs.hasChildNodes():
        raise BrokenAzureDataSource("no child nodes of configuration set")

    md_props = 'seedfrom'
    md = {'azure_data': {}}
    cfg = {}
    ud = ""
    password = None
    username = None

    for child in lpcs.childNodes:
        if child.nodeType == dom.TEXT_NODE or not child.localName:
            continue

        name = child.localName.lower()

        simple = False
        value = ""
        if (len(child.childNodes) == 1 and
                child.childNodes[0].nodeType == dom.TEXT_NODE):
            simple = True
            value = child.childNodes[0].wholeText

        attrs = dict([(k, v) for k, v in child.attributes.items()])

        # we accept either UserData or CustomData.  If both are present
        # then behavior is undefined.
        if name == "userdata" or name == "customdata":
            if attrs.get('encoding') in (None, "base64"):
                ud = base64.b64decode(''.join(value.split()))
            else:
                ud = value
        elif name == "username":
            username = value
        elif name == "userpassword":
            password = value
        elif name == "hostname":
            md['local-hostname'] = value
        elif name == "dscfg":
            if attrs.get('encoding') in (None, "base64"):
                dscfg = base64.b64decode(''.join(value.split()))
            else:
                dscfg = value
            cfg['datasource'] = {DS_NAME: util.load_yaml(dscfg, default={})}
        elif name == "ssh":
            cfg['_pubkeys'] = load_azure_ovf_pubkeys(child)
        elif name == "disablesshpasswordauthentication":
            cfg['ssh_pwauth'] = util.is_false(value)
        elif simple:
            if name in md_props:
                md[name] = value
            else:
                md['azure_data'][name] = value

    defuser = {}
    if username:
        defuser['name'] = username
    if password:
        defuser['lock_passwd'] = False
        if DEF_PASSWD_REDACTION != password:
            defuser['passwd'] = cfg['password'] = encrypt_pass(password)

    if defuser:
        cfg['system_info'] = {'default_user': defuser}

    if 'ssh_pwauth' not in cfg and password:
        cfg['ssh_pwauth'] = True

    preprovisioning_cfg = _get_preprovisioning_cfgs(dom)
    cfg = util.mergemanydict([cfg, preprovisioning_cfg])

    return (md, ud, cfg)


@azure_ds_telemetry_reporter
def _get_preprovisioning_cfgs(dom):
    """Read the preprovisioning related flags from ovf and populates a dict
    with the info.

    Two flags are in use today: PreprovisionedVm bool and
    PreprovisionedVMType enum. In the long term, the PreprovisionedVm bool
    will be deprecated in favor of PreprovisionedVMType string/enum.

    Only these combinations of values are possible today:
        - PreprovisionedVm=True and PreprovisionedVMType=Running
        - PreprovisionedVm=False and PreprovisionedVMType=Savable
        - PreprovisionedVm is missing and PreprovisionedVMType=Running/Savable
        - PreprovisionedVm=False and PreprovisionedVMType is missing

    More specifically, this will never happen:
        - PreprovisionedVm=True and PreprovisionedVMType=Savable
    """
    cfg = {
        "PreprovisionedVm": False,
        "PreprovisionedVMType": None
    }

    platform_settings_section = find_child(
        dom.documentElement,
        lambda n: n.localName == "PlatformSettingsSection")
    if not platform_settings_section or len(platform_settings_section) == 0:
        LOG.debug("PlatformSettingsSection not found")
        return cfg
    platform_settings = find_child(
        platform_settings_section[0],
        lambda n: n.localName == "PlatformSettings")
    if not platform_settings or len(platform_settings) == 0:
        LOG.debug("PlatformSettings not found")
        return cfg

    # Read the PreprovisionedVm bool flag. This should be deprecated when the
    # platform has removed PreprovisionedVm and only surfaces
    # PreprovisionedVMType.
    cfg["PreprovisionedVm"] = _get_preprovisionedvm_cfg_value(
        platform_settings)

    cfg["PreprovisionedVMType"] = _get_preprovisionedvmtype_cfg_value(
        platform_settings)
    return cfg


@azure_ds_telemetry_reporter
def _get_preprovisionedvm_cfg_value(platform_settings):
    preprovisionedVm = False

    # Read the PreprovisionedVm bool flag. This should be deprecated when the
    # platform has removed PreprovisionedVm and only surfaces
    # PreprovisionedVMType.
    preprovisionedVmVal = find_child(
        platform_settings[0],
        lambda n: n.localName == "PreprovisionedVm")
    if not preprovisionedVmVal or len(preprovisionedVmVal) == 0:
        LOG.debug("PreprovisionedVm not found")
        return preprovisionedVm
    preprovisionedVm = util.translate_bool(
        preprovisionedVmVal[0].firstChild.nodeValue)

    report_diagnostic_event(
        "PreprovisionedVm: %s" % preprovisionedVm, logger_func=LOG.info)

    return preprovisionedVm


@azure_ds_telemetry_reporter
def _get_preprovisionedvmtype_cfg_value(platform_settings):
    preprovisionedVMType = None

    # Read the PreprovisionedVMType value from the ovf. It can be
    # 'Running' or 'Savable' or not exist. This enum value is intended to
    # replace PreprovisionedVm bool flag in the long term.
    # A Running VM is the same as preprovisioned VMs of today. This is
    # equivalent to having PreprovisionedVm=True.
    # A Savable VM is one whose nic is hot-detached immediately after it
    # reports ready the first time to free up the network resources.
    # Once assigned to customer, the customer-requested nics are
    # hot-attached to it and reprovision happens like today.
    preprovisionedVMTypeVal = find_child(
        platform_settings[0],
        lambda n: n.localName == "PreprovisionedVMType")
    if (not preprovisionedVMTypeVal or len(preprovisionedVMTypeVal) == 0 or
            preprovisionedVMTypeVal[0].firstChild is None):
        LOG.debug("PreprovisionedVMType not found")
        return preprovisionedVMType

    preprovisionedVMType = preprovisionedVMTypeVal[0].firstChild.nodeValue

    report_diagnostic_event(
        "PreprovisionedVMType: %s" % preprovisionedVMType,
        logger_func=LOG.info)

    return preprovisionedVMType


def encrypt_pass(password, salt_id="$6$"):
    return crypt.crypt(password, salt_id + util.rand_str(strlen=16))


@azure_ds_telemetry_reporter
def _check_freebsd_cdrom(cdrom_dev):
    """Return boolean indicating path to cdrom device has content."""
    try:
        with open(cdrom_dev) as fp:
            fp.read(1024)
            return True
    except IOError:
        LOG.debug("cdrom (%s) is not configured", cdrom_dev)
    return False


@azure_ds_telemetry_reporter
def _get_random_seed(source=PLATFORM_ENTROPY_SOURCE):
    """Return content random seed file if available, otherwise,
       return None."""
    # azure / hyper-v provides random data here
    # now update ds_cfg to reflect contents pass in config
    if source is None:
        return None
    seed = util.load_file(source, quiet=True, decode=False)

    # The seed generally contains non-Unicode characters. load_file puts
    # them into a str (in python 2) or bytes (in python 3). In python 2,
    # bad octets in a str cause util.json_dumps() to throw an exception. In
    # python 3, bytes is a non-serializable type, and the handler load_file
    # uses applies b64 encoding *again* to handle it. The simplest solution
    # is to just b64encode the data and then decode it to a serializable
    # string. Same number of bits of entropy, just with 25% more zeroes.
    # There's no need to undo this base64-encoding when the random seed is
    # actually used in cc_seed_random.py.
    seed = base64.b64encode(seed).decode()

    return seed


@azure_ds_telemetry_reporter
def list_possible_azure_ds_devs():
    devlist = []
    if util.is_FreeBSD():
        cdrom_dev = "/dev/cd0"
        if _check_freebsd_cdrom(cdrom_dev):
            return [cdrom_dev]
    else:
        for fstype in ("iso9660", "udf"):
            devlist.extend(util.find_devs_with("TYPE=%s" % fstype))

    devlist.sort(reverse=True)
    return devlist


@azure_ds_telemetry_reporter
def load_azure_ds_dir(source_dir):
    ovf_file = os.path.join(source_dir, "ovf-env.xml")

    if not os.path.isfile(ovf_file):
        raise NonAzureDataSource("No ovf-env file found")

    with open(ovf_file, "rb") as fp:
        contents = fp.read()

    md, ud, cfg = read_azure_ovf(contents)
    return (md, ud, cfg, {'ovf-env.xml': contents})


@azure_ds_telemetry_reporter
def parse_network_config(imds_metadata) -> dict:
    """Convert imds_metadata dictionary to network v2 configuration.
    Parses network configuration from imds metadata if present or generate
    fallback network config excluding mlx4_core devices.

    @param: imds_metadata: Dict of content read from IMDS network service.
    @return: Dictionary containing network version 2 standard configuration.
    """
    if imds_metadata != sources.UNSET and imds_metadata:
        try:
            return _generate_network_config_from_imds_metadata(imds_metadata)
        except Exception as e:
            LOG.error(
                'Failed generating network config '
                'from IMDS network metadata: %s', str(e))
    try:
        return _generate_network_config_from_fallback_config()
    except Exception as e:
        LOG.error('Failed generating fallback network config: %s', str(e))
    return {}


@azure_ds_telemetry_reporter
def _generate_network_config_from_imds_metadata(imds_metadata) -> dict:
    """Convert imds_metadata dictionary to network v2 configuration.
    Parses network configuration from imds metadata.

    @param: imds_metadata: Dict of content read from IMDS network service.
    @return: Dictionary containing network version 2 standard configuration.
    """
    netconfig = {'version': 2, 'ethernets': {}}
    network_metadata = imds_metadata['network']
    for idx, intf in enumerate(network_metadata['interface']):
        has_ip_address = False
        # First IPv4 and/or IPv6 address will be obtained via DHCP.
        # Any additional IPs of each type will be set as static
        # addresses.
        nicname = 'eth{idx}'.format(idx=idx)
        dhcp_override = {'route-metric': (idx + 1) * 100}
        dev_config = {'dhcp4': True, 'dhcp4-overrides': dhcp_override,
                      'dhcp6': False}
        for addr_type in ('ipv4', 'ipv6'):
            addresses = intf.get(addr_type, {}).get('ipAddress', [])
            # If there are no available IP addresses, then we don't
            # want to add this interface to the generated config.
            if not addresses:
                continue
            has_ip_address = True
            if addr_type == 'ipv4':
                default_prefix = '24'
            else:
                default_prefix = '128'
                if addresses:
                    dev_config['dhcp6'] = True
                    # non-primary interfaces should have a higher
                    # route-metric (cost) so default routes prefer
                    # primary nic due to lower route-metric value
                    dev_config['dhcp6-overrides'] = dhcp_override
            for addr in addresses[1:]:
                # Append static address config for ip > 1
                netPrefix = intf[addr_type]['subnet'][0].get(
                    'prefix', default_prefix)
                privateIp = addr['privateIpAddress']
                if not dev_config.get('addresses'):
                    dev_config['addresses'] = []
                dev_config['addresses'].append(
                    '{ip}/{prefix}'.format(
                        ip=privateIp, prefix=netPrefix))
        if dev_config and has_ip_address:
            mac = ':'.join(re.findall(r'..', intf['macAddress']))
            dev_config.update({
                'match': {'macaddress': mac.lower()},
                'set-name': nicname
            })
            # With netvsc, we can get two interfaces that
            # share the same MAC, so we need to make sure
            # our match condition also contains the driver
            driver = device_driver(nicname)
            if driver and driver == 'hv_netvsc':
                dev_config['match']['driver'] = driver
            netconfig['ethernets'][nicname] = dev_config
    return netconfig


@azure_ds_telemetry_reporter
def _generate_network_config_from_fallback_config() -> dict:
    """Generate fallback network config excluding blacklisted devices.

    @return: Dictionary containing network version 2 standard configuration.
    """
    return net.generate_fallback_config(
        blacklist_drivers=BLACKLIST_DRIVERS, config_driver=True)


@azure_ds_telemetry_reporter
def get_metadata_from_imds(fallback_nic,
                           retries,
                           md_type=metadata_type.compute):
    """Query Azure's instance metadata service, returning a dictionary.

    If network is not up, setup ephemeral dhcp on fallback_nic to talk to the
    IMDS. For more info on IMDS:
        https://docs.microsoft.com/en-us/azure/virtual-machines/windows/instance-metadata-service

    @param fallback_nic: String. The name of the nic which requires active
        network in order to query IMDS.
    @param retries: The number of retries of the IMDS_URL.

    @return: A dict of instance metadata containing compute and network
        info.
    """
    kwargs = {'logfunc': LOG.debug,
              'msg': 'Crawl of Azure Instance Metadata Service (IMDS)',
              'func': _get_metadata_from_imds, 'args': (retries, md_type,)}
    if net.is_up(fallback_nic):
        return util.log_time(**kwargs)
    else:
        try:
            with EphemeralDHCPv4WithReporting(
                    azure_ds_reporter, fallback_nic):
                return util.log_time(**kwargs)
        except Exception as e:
            report_diagnostic_event(
                "exception while getting metadata: %s" % e,
                logger_func=LOG.warning)
            raise


@azure_ds_telemetry_reporter
def _get_metadata_from_imds(retries, md_type=metadata_type.compute):

    url = md_type.value
    headers = {"Metadata": "true"}
    try:
        response = readurl(
            url, timeout=IMDS_TIMEOUT_IN_SECONDS, headers=headers,
            retries=retries, exception_cb=retry_on_url_exc)
    except Exception as e:
        report_diagnostic_event(
            'Ignoring IMDS instance metadata. '
            'Get metadata from IMDS failed: %s' % e,
            logger_func=LOG.warning)
        return {}
    try:
        from json.decoder import JSONDecodeError
        json_decode_error = JSONDecodeError
    except ImportError:
        json_decode_error = ValueError

    try:
        return util.load_json(str(response))
    except json_decode_error as e:
        report_diagnostic_event(
            'Ignoring non-json IMDS instance metadata response: %s. '
            'Loading non-json IMDS response failed: %s' % (str(response), e),
            logger_func=LOG.warning)
    return {}


@azure_ds_telemetry_reporter
def maybe_remove_ubuntu_network_config_scripts(paths=None):
    """Remove Azure-specific ubuntu network config for non-primary nics.

    @param paths: List of networking scripts or directories to remove when
        present.

    In certain supported ubuntu images, static udev rules or netplan yaml
    config is delivered in the base ubuntu image to support dhcp on any
    additional interfaces which get attached by a customer at some point
    after initial boot. Since the Azure datasource can now regenerate
    network configuration as metadata reports these new devices, we no longer
    want the udev rules or netplan's 90-hotplug-azure.yaml to configure
    networking on eth1 or greater as it might collide with cloud-init's
    configuration.

    Remove the any existing extended network scripts if the datasource is
    enabled to write network per-boot.
    """
    if not paths:
        paths = UBUNTU_EXTENDED_NETWORK_SCRIPTS
    logged = False
    for path in paths:
        if os.path.exists(path):
            if not logged:
                LOG.info(
                    'Removing Ubuntu extended network scripts because'
                    ' cloud-init updates Azure network configuration on the'
                    ' following event: %s.',
                    EventType.BOOT)
                logged = True
            if os.path.isdir(path):
                util.del_dir(path)
            else:
                util.del_file(path)


def _is_platform_viable(seed_dir):
    """Check platform environment to report if this datasource may run."""
    with events.ReportEventStack(
        name="check-platform-viability",
        description="found azure asset tag",
        parent=azure_ds_reporter
    ) as evt:
        asset_tag = dmi.read_dmi_data('chassis-asset-tag')
        if asset_tag == AZURE_CHASSIS_ASSET_TAG:
            return True
        msg = "Non-Azure DMI asset tag '%s' discovered." % asset_tag
        evt.description = msg
        report_diagnostic_event(msg, logger_func=LOG.debug)
        if os.path.exists(os.path.join(seed_dir, 'ovf-env.xml')):
            return True
        return False


class BrokenAzureDataSource(Exception):
    pass


class NonAzureDataSource(Exception):
    pass


# Legacy: Must be present in case we load an old pkl object
DataSourceAzureNet = DataSourceAzure

# Used to match classes to dependencies
datasources = [
    (DataSourceAzure, (sources.DEP_FILESYSTEM, )),
]


# Return a list of data sources that match this set of dependencies
def get_datasource_list(depends):
    return sources.list_from_depends(depends, datasources)

# vi: ts=4 expandtab
