A network of LXC containers, managed through libvirt
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""" Container objects """
from . import settings
from . import util
from .jinja_template import JinjaTemplate
import libvirt
import tempfile
from pathlib import Path
import getpass
import weakref
class OverlayDirectory:
"""Allocates an overlayfs with a given lower dir and a temporary upper dir. The
overlayfs is destroyed when this object is deallocated"""
class DoesNotExist(Exception):
"""Raised if `lower` does not exist"""
def __init__(self, path):
self.path = path
def __str__(self):
return "Path {} does not exist".format(self.path)
def __init__(self, lower, name=None):
if not name:
name = ""
self.lower = Path(lower)
if not self.lower.exists():
raise self.DoesNotExist(self.lower)
root_temp_dir = Path(settings.OVERLAYFS_BASE_DIR)
if not root_temp_dir.exists():
root_temp_dir.mkdir()
self.overlay_temp_dir = tempfile.TemporaryDirectory(
prefix=name + ("_" if name else ""),
dir=root_temp_dir.resolve(),
)
self.temp_dir = Path(self.overlay_temp_dir.name)
self.temp_dir_cleaner = None
self.upper = self.temp_dir / "upper"
self.work = self.temp_dir / "work"
self.mount_point = self.temp_dir / "mount"
self.upper.mkdir()
self.work.mkdir()
self.mount_point.mkdir()
self.mounted = False
self._mount()
def _mount(self):
if self.mounted:
return
command = [
"sudo",
"mount",
"-t",
"overlay",
"overlay",
"-o",
"lowerdir={lower},upperdir={upper},workdir={work}".format(
lower=self.lower.resolve(),
upper=self.upper.resolve(),
work=self.work.resolve(),
),
self.mount_point,
]
util.run_cmd_retry(command)
self.mounted = True
self.temp_dir_cleaner = weakref.finalize(
self.overlay_temp_dir, self.cleanup_mount
)
def _umount(self):
if not self.mounted:
return
command = [
"sudo",
"umount",
self.mount_point,
]
util.run_cmd_retry(command)
self.mounted = False
def _set_perms_for_cleanup(self):
"""Sets the permissions to allow cleanup"""
if not self.temp_dir.exists():
return # Already deleted
# The overlayfs runs as root, so we need to allow our current user to delete
# the temp directory files
command_chown = [
"sudo",
"chown",
"-R",
getpass.getuser(),
self.temp_dir.resolve(),
]
util.run_cmd_retry(command_chown)
command_chmod = [
"sudo",
"chmod",
"-R",
"700",
self.temp_dir.resolve(),
]
util.run_cmd_retry(command_chmod)
def cleanup_mount(self):
self._umount()
self._set_perms_for_cleanup()
class Container(util.LibvirtObject):
class AlreadyExists(Exception):
def __str__(self):
return "This container is already instanciated"
def __init__(self, conn, networks, name=None, mem=int(1e6), enable_v4=True):
"""Parameters:
* conn: connection to libvirt,
* networks: iterable of Network instances this container is connected to,
* name: name of the container. Defaults to something id-based.
* mem: KiB of memory available to this container,
* enable_v4: is IPv4 enabled for this container? Defaults to True. If False,
this container won't be given an IPv4 address.
"""
super().__init__(conn)
self.name = f"{settings.PREFIX}_dom{self.id:02d}"
if name:
self.name += "_" + name
self.networks = networks
self.mem = mem
self.enable_v4 = enable_v4
self.overlay_root = None
self.lxc_container = None
@property
def up(self):
return self.lxc_container is not None
def get_jinja_networks(self):
"""Get a jinja2 environment-compatible network list"""
return [
{"mac": util.MACAddress(net.id, self.id), "name": net.name, "net": net}
for net in self.networks
]
def _create_network_files(self):
"""Creates systemd-networkd .network files to set IP addresses"""
if not self.overlay_root:
raise Exception("No root directory specified yet")
net_config_templ = JinjaTemplate("nic.network")
net_conf_dir = self.overlay_root.mount_point / "etc/systemd/network/"
for net in self.networks:
net_config = net_config_templ.inst(
mac=util.MACAddress(net.id, self.id),
ipv4=util.Addrv4(net.id, self.id)
if self.enable_v4 and net.enable_v4
else None,
ipv6=util.Addrv6(net.id, self.id),
)
net_config_path = net_conf_dir / "11-{link:02d}-{name}.network".format(
link=net.id, name=net.name
)
with open(net_config_path, "w") as handle:
handle.write(net_config)
def create(self):
if self.lxc_container:
raise self.AlreadyExists()
self.overlay_root = OverlayDirectory(settings.BASE_SYSTEM_ROOT, name=self.name)
self._create_network_files()
xml = JinjaTemplate("container.xml").inst(
name=self.name,
uuid=self.uuid,
mem=self.mem,
filesystem_root=self.overlay_root.mount_point,
networks=self.get_jinja_networks(),
)
self.lxc_container = self.conn.createXML(xml)
def notify_cleanup(self):
"""This method can be called before `cleanup` to notify the host that a
cleanup will be performed soon, speeding the process up."""
if self.lxc_container:
try:
self.lxc_container.shutdown()
except libvirt.libvirtError as exn:
if not str(exn).startswith("Domain not found:"):
raise exn
# Else, the machine was already stopped: everything is fine
def cleanup(self):
if self.lxc_container:
try:
self.lxc_container.destroy()
except libvirt.libvirtError as exn:
if not str(exn).startswith("Domain not found:"):
raise exn
# Else, the machine was already stopped: everything is fine
self.lxc_container = None
if self.overlay_root:
self.overlay_root.cleanup_mount()
self.overlay_root.overlay_temp_dir.cleanup()
self.overlay_root = None
def __enter__(self):
self.create()
return self
def __exit__(self, exc_type, exc_val, exc_tb):
self.cleanup()
def __del__(self):
self.cleanup()