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# Copyright (C) 2017 Canonical Ltd.
#
# Author: Chad Smith <chad.smith@canonical.com>
#
# This file is part of cloud-init. See LICENSE file for license information.
import logging
import os
import re
from cloudinit.net import find_fallback_nic, get_devicelist
from cloudinit import temp_utils
from cloudinit import util
LOG = logging.getLogger(__name__)
class InvalidDHCPLeaseFileError(Exception):
"""Raised when parsing an empty or invalid dhcp.leases file.
Current uses are DataSourceAzure and DataSourceEc2 during ephemeral
boot to scrape metadata.
"""
pass
def maybe_perform_dhcp_discovery(nic=None):
"""Perform dhcp discovery if nic valid and dhclient command exists.
If the nic is invalid or undiscoverable or dhclient command is not found,
skip dhcp_discovery and return an empty dict.
@param nic: Name of the network interface we want to run dhclient on.
@return: A dict of dhcp options from the dhclient discovery if run,
otherwise an empty dict is returned.
"""
if nic is None:
nic = find_fallback_nic()
if nic is None:
LOG.debug(
'Skip dhcp_discovery: Unable to find fallback nic.')
return {}
elif nic not in get_devicelist():
LOG.debug(
'Skip dhcp_discovery: nic %s not found in get_devicelist.', nic)
return {}
dhclient_path = util.which('dhclient')
if not dhclient_path:
LOG.debug('Skip dhclient configuration: No dhclient command found.')
return {}
with temp_utils.tempdir(prefix='cloud-init-dhcp-') as tmpdir:
return dhcp_discovery(dhclient_path, nic, tmpdir)
def parse_dhcp_lease_file(lease_file):
"""Parse the given dhcp lease file for the most recent lease.
Return a dict of dhcp options as key value pairs for the most recent lease
block.
@raises: InvalidDHCPLeaseFileError on empty of unparseable leasefile
content.
"""
lease_regex = re.compile(r"lease {(?P<lease>[^}]*)}\n")
dhcp_leases = []
lease_content = util.load_file(lease_file)
if len(lease_content) == 0:
raise InvalidDHCPLeaseFileError(
'Cannot parse empty dhcp lease file {0}'.format(lease_file))
for lease in lease_regex.findall(lease_content):
lease_options = []
for line in lease.split(';'):
# Strip newlines, double-quotes and option prefix
line = line.strip().replace('"', '').replace('option ', '')
if not line:
continue
lease_options.append(line.split(' ', 1))
dhcp_leases.append(dict(lease_options))
if not dhcp_leases:
raise InvalidDHCPLeaseFileError(
'Cannot parse dhcp lease file {0}. No leases found'.format(
lease_file))
return dhcp_leases
def dhcp_discovery(dhclient_cmd_path, interface, cleandir):
"""Run dhclient on the interface without scripts or filesystem artifacts.
@param dhclient_cmd_path: Full path to the dhclient used.
@param interface: Name of the network inteface on which to dhclient.
@param cleandir: The directory from which to run dhclient as well as store
dhcp leases.
@return: A dict of dhcp options parsed from the dhcp.leases file or empty
dict.
"""
LOG.debug('Performing a dhcp discovery on %s', interface)
# XXX We copy dhclient out of /sbin/dhclient to avoid dealing with strict
# app armor profiles which disallow running dhclient -sf <our-script-file>.
# We want to avoid running /sbin/dhclient-script because of side-effects in
# /etc/resolv.conf any any other vendor specific scripts in
# /etc/dhcp/dhclient*hooks.d.
sandbox_dhclient_cmd = os.path.join(cleandir, 'dhclient')
util.copy(dhclient_cmd_path, sandbox_dhclient_cmd)
pid_file = os.path.join(cleandir, 'dhclient.pid')
lease_file = os.path.join(cleandir, 'dhcp.leases')
# ISC dhclient needs the interface up to send initial discovery packets.
# Generally dhclient relies on dhclient-script PREINIT action to bring the
# link up before attempting discovery. Since we are using -sf /bin/true,
# we need to do that "link up" ourselves first.
util.subp(['ip', 'link', 'set', 'dev', interface, 'up'], capture=True)
cmd = [sandbox_dhclient_cmd, '-1', '-v', '-lf', lease_file,
'-pf', pid_file, interface, '-sf', '/bin/true']
util.subp(cmd, capture=True)
return parse_dhcp_lease_file(lease_file)
# vi: ts=4 expandtab
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