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# This file is part of cloud-init. See LICENSE file for license information.
"""Module for ephemeral network context managers
"""
import contextlib
import logging
from functools import partial
from typing import Any, Callable, Dict, List, Optional
import cloudinit.net as net
from cloudinit.net.dhcp import (
IscDhclient,
NoDHCPLeaseError,
maybe_perform_dhcp_discovery,
)
from cloudinit.subp import ProcessExecutionError
LOG = logging.getLogger(__name__)
class EphemeralIPv4Network:
"""Context manager which sets up temporary static network configuration.
No operations are performed if the provided interface already has the
specified configuration.
This can be verified with the connectivity_url_data.
If unconnected, bring up the interface with valid ip, prefix and broadcast.
If router is provided setup a default route for that interface. Upon
context exit, clean up the interface leaving no configuration behind.
"""
def __init__(
self,
distro,
interface,
ip,
prefix_or_mask,
broadcast,
router=None,
connectivity_url_data: Optional[Dict[str, Any]] = None,
static_routes=None,
):
"""Setup context manager and validate call signature.
@param interface: Name of the network interface to bring up.
@param ip: IP address to assign to the interface.
@param prefix_or_mask: Either netmask of the format X.X.X.X or an int
prefix.
@param broadcast: Broadcast address for the IPv4 network.
@param router: Optionally the default gateway IP.
@param connectivity_url_data: Optionally, a URL to verify if a usable
connection already exists.
@param static_routes: Optionally a list of static routes from DHCP
"""
if not all([interface, ip, prefix_or_mask, broadcast]):
raise ValueError(
"Cannot init network on {0} with {1}/{2} and bcast {3}".format(
interface, ip, prefix_or_mask, broadcast
)
)
try:
self.prefix = net.ipv4_mask_to_net_prefix(prefix_or_mask)
except ValueError as e:
raise ValueError(
"Cannot setup network, invalid prefix or "
"netmask: {0}".format(e)
) from e
self.connectivity_url_data = connectivity_url_data
self.interface = interface
self.ip = ip
self.broadcast = broadcast
self.router = router
self.static_routes = static_routes
# List of commands to run to cleanup state.
self.cleanup_cmds: List[Callable] = []
self.distro = distro
def __enter__(self):
"""Perform ephemeral network setup if interface is not connected."""
if self.connectivity_url_data:
if net.has_url_connectivity(self.connectivity_url_data):
LOG.debug(
"Skip ephemeral network setup, instance has connectivity"
" to %s",
self.connectivity_url_data["url"],
)
return
try:
self._bringup_device()
# rfc3442 requires us to ignore the router config *if*
# classless static routes are provided.
#
# https://tools.ietf.org/html/rfc3442
#
# If the DHCP server returns both a Classless Static Routes
# option and a Router option, the DHCP client MUST ignore
# the Router option.
#
# Similarly, if the DHCP server returns both a Classless
# Static Routes option and a Static Routes option, the DHCP
# client MUST ignore the Static Routes option.
if self.static_routes:
self._bringup_static_routes()
elif self.router:
self._bringup_router()
except ProcessExecutionError:
self.__exit__(None, None, None)
raise
def __exit__(self, excp_type, excp_value, excp_traceback):
"""Teardown anything we set up."""
for cmd in self.cleanup_cmds:
cmd()
def _bringup_device(self):
"""Perform the ip comands to fully setup the device."""
cidr = "{0}/{1}".format(self.ip, self.prefix)
LOG.debug(
"Attempting setup of ephemeral network on %s with %s brd %s",
self.interface,
cidr,
self.broadcast,
)
try:
self.distro.net_ops.add_addr(self.interface, cidr, self.broadcast)
except ProcessExecutionError as e:
if "File exists" not in str(e.stderr):
raise
LOG.debug(
"Skip ephemeral network setup, %s already has address %s",
self.interface,
self.ip,
)
else:
# Address creation success, bring up device and queue cleanup
self.distro.net_ops.link_up(self.interface, family="inet")
self.cleanup_cmds.append(
partial(
self.distro.net_ops.link_down,
self.interface,
family="inet",
)
)
self.cleanup_cmds.append(
partial(self.distro.net_ops.del_addr, self.interface, cidr)
)
def _bringup_static_routes(self):
# static_routes = [("169.254.169.254/32", "130.56.248.255"),
# ("0.0.0.0/0", "130.56.240.1")]
for net_address, gateway in self.static_routes:
# Use "append" rather than "add" since the DHCP server may provide
# rfc3442 classless static routes with multiple routes to the same
# subnet via different routers or local interface addresses.
#
# In this scenario, `ip r add` fails.
#
# RHBZ: #2003231
self.distro.net_ops.append_route(
self.interface, net_address, gateway
)
self.cleanup_cmds.insert(
0,
partial(
self.distro.net_ops.del_route,
self.interface,
net_address,
gateway=gateway,
),
)
def _bringup_router(self):
"""Perform the ip commands to fully setup the router if needed."""
# Check if a default route exists and exit if it does
out = self.distro.net_ops.get_default_route()
if "default" in out:
LOG.debug(
"Skip ephemeral route setup. %s already has default route: %s",
self.interface,
out.strip(),
)
return
self.distro.net_ops.add_route(
self.interface, self.router, source_address=self.ip
)
self.cleanup_cmds.insert(
0,
partial(
self.distro.net_ops.del_route,
self.interface,
self.router,
source_address=self.ip,
),
)
self.distro.net_ops.add_route(
self.interface, "default", gateway=self.router
)
self.cleanup_cmds.insert(
0,
partial(self.distro.net_ops.del_route, self.interface, "default"),
)
class EphemeralIPv6Network:
"""Context manager which sets up a ipv6 link local address
The linux kernel assigns link local addresses on link-up, which is
sufficient for link-local communication.
"""
def __init__(self, distro, interface):
"""Setup context manager and validate call signature.
@param interface: Name of the network interface to bring up.
@param ip: IP address to assign to the interface.
@param prefix: IPv6 uses prefixes, not netmasks
"""
if not interface:
raise ValueError("Cannot init network on {0}".format(interface))
self.interface = interface
self.distro = distro
def __enter__(self):
"""linux kernel does autoconfiguration even when autoconf=0
https://www.kernel.org/doc/html/latest/networking/ipv6.html
"""
if net.read_sys_net(self.interface, "operstate") != "up":
self.distro.net_ops.link_up(self.interface)
def __exit__(self, *_args):
"""No need to set the link to down state"""
class EphemeralDHCPv4:
def __init__(
self,
distro,
iface=None,
connectivity_url_data: Optional[Dict[str, Any]] = None,
dhcp_log_func=None,
):
self.iface = iface
self._ephipv4 = None
self.lease = None
self.dhcp_log_func = dhcp_log_func
self.connectivity_url_data = connectivity_url_data
self.distro = distro
def __enter__(self):
"""Setup sandboxed dhcp context, unless connectivity_url can already be
reached."""
if self.connectivity_url_data:
if net.has_url_connectivity(self.connectivity_url_data):
LOG.debug(
"Skip ephemeral DHCP setup, instance has connectivity"
" to %s",
self.connectivity_url_data,
)
return
return self.obtain_lease()
def __exit__(self, excp_type, excp_value, excp_traceback):
"""Teardown sandboxed dhcp context."""
self.clean_network()
def clean_network(self):
"""Exit _ephipv4 context to teardown of ip configuration performed."""
self.lease = None
if self._ephipv4:
self._ephipv4.__exit__(None, None, None)
def obtain_lease(self):
"""Perform dhcp discovery in a sandboxed environment if possible.
@return: A dict representing dhcp options on the most recent lease
obtained from the dhclient discovery if run, otherwise an error
is raised.
@raises: NoDHCPLeaseError if no leases could be obtained.
"""
if self.lease:
return self.lease
leases = maybe_perform_dhcp_discovery(
self.distro, self.iface, self.dhcp_log_func
)
if not leases:
raise NoDHCPLeaseError()
self.lease = leases[-1]
LOG.debug(
"Received dhcp lease on %s for %s/%s",
self.lease["interface"],
self.lease["fixed-address"],
self.lease["subnet-mask"],
)
nmap = {
"interface": "interface",
"ip": "fixed-address",
"prefix_or_mask": "subnet-mask",
"broadcast": "broadcast-address",
"static_routes": [
"rfc3442-classless-static-routes",
"classless-static-routes",
],
"router": "routers",
}
kwargs = self.extract_dhcp_options_mapping(nmap)
if not kwargs["broadcast"]:
kwargs["broadcast"] = net.mask_and_ipv4_to_bcast_addr(
kwargs["prefix_or_mask"], kwargs["ip"]
)
if kwargs["static_routes"]:
kwargs["static_routes"] = IscDhclient.parse_static_routes(
kwargs["static_routes"]
)
if self.connectivity_url_data:
kwargs["connectivity_url_data"] = self.connectivity_url_data
ephipv4 = EphemeralIPv4Network(self.distro, **kwargs)
ephipv4.__enter__()
self._ephipv4 = ephipv4
return self.lease
def extract_dhcp_options_mapping(self, nmap):
result = {}
for internal_reference, lease_option_names in nmap.items():
if isinstance(lease_option_names, list):
self.get_first_option_value(
internal_reference, lease_option_names, result
)
else:
result[internal_reference] = self.lease.get(lease_option_names)
return result
def get_first_option_value(
self, internal_mapping, lease_option_names, result
):
for different_names in lease_option_names:
if not result.get(internal_mapping):
result[internal_mapping] = self.lease.get(different_names)
class EphemeralIPNetwork:
"""Combined ephemeral context manager for IPv4 and IPv6
Either ipv4 or ipv6 ephemeral network may fail to initialize, but if either
succeeds, then this context manager will not raise exception. This allows
either ipv4 or ipv6 ephemeral network to succeed, but requires that error
handling for networks unavailable be done within the context.
"""
def __init__(
self,
distro,
interface,
ipv6: bool = False,
ipv4: bool = True,
):
self.interface = interface
self.ipv4 = ipv4
self.ipv6 = ipv6
self.stack = contextlib.ExitStack()
self.state_msg: str = ""
self.distro = distro
def __enter__(self):
if not (self.ipv4 or self.ipv6):
# no ephemeral network requested, but this object still needs to
# function as a context manager
return self
exceptions = []
ephemeral_obtained = False
if self.ipv4:
try:
self.stack.enter_context(
EphemeralDHCPv4(
self.distro,
self.interface,
)
)
ephemeral_obtained = True
except (ProcessExecutionError, NoDHCPLeaseError) as e:
LOG.info("Failed to bring up %s for ipv4.", self)
exceptions.append(e)
if self.ipv6:
try:
self.stack.enter_context(
EphemeralIPv6Network(
self.distro,
self.interface,
)
)
ephemeral_obtained = True
if exceptions or not self.ipv4:
self.state_msg = "using link-local ipv6"
except ProcessExecutionError as e:
LOG.info("Failed to bring up %s for ipv6.", self)
exceptions.append(e)
if not ephemeral_obtained:
# Ephemeral network setup failed in linkup for both ipv4 and
# ipv6. Raise only the first exception found.
LOG.error(
"Failed to bring up EphemeralIPNetwork. "
"Datasource setup cannot continue"
)
raise exceptions[0]
return self
def __exit__(self, *_args):
self.stack.close()