webvirtcloud/vrtManager/connection.py

import libvirt
import threading
import socket
import re
from vrtManager import util
from vrtManager.rwlock import ReadWriteLock
from django.conf import settings
from libvirt import libvirtError

CONN_SOCKET = 4
CONN_TLS = 3
CONN_SSH = 2
CONN_TCP = 1
TLS_PORT = 16514
SSH_PORT = 22
TCP_PORT = 16509


class wvmEventLoop(threading.Thread):
    """ Event Loop Class"""
    def __init__(self, group=None, target=None, name=None, args=(), kwargs={}):
        # register the default event implementation
        # of libvirt, as we do not have an existing
        # event loop.
        libvirt.virEventRegisterDefaultImpl()

        if name is None:
            name = 'libvirt event loop'

        super(wvmEventLoop, self).__init__(group, target, name, args, kwargs)

        # we run this thread in deamon mode, so it does
        # not block shutdown of the server
        self.daemon = True

    def run(self):
        while True:
            # if this method will fail it raises libvirtError
            # we do not catch the exception here so it will show up
            # in the logs. Not sure when this call will ever fail
            libvirt.virEventRunDefaultImpl()


class wvmConnection(object):
    """
    class representing a single connection stored in the Connection Manager
    # to-do: may also need some locking to ensure to not connect simultaniously in 2 threads
    """
    def __init__(self, host, login, passwd, conn):
        """
        Sets all class attributes and tries to open the connection
        """
        # connection lock is used to lock all changes to the connection state attributes
        # (connection and last_error)
        self.connection_state_lock = threading.Lock()
        self.connection = None
        self.last_error = None

        # credentials
        self.host = host
        self.login = login
        self.passwd = passwd
        self.type = conn

        # connect
        self.connect()

    def connect(self):
        self.connection_state_lock.acquire()
        try:
            # recheck if we have a connection (it may have been
            if not self.connected:
                if self.type == CONN_TCP:
                    self.__connect_tcp()
                elif self.type == CONN_SSH:
                    self.__connect_ssh()
                elif self.type == CONN_TLS:
                    self.__connect_tls()
                elif self.type == CONN_SOCKET:
                    self.__connect_socket()
                else:
                    raise ValueError(f'"{self.type}" is not a valid connection type')

                if self.connected:
                    # do some preprocessing of the connection:
                    #     * set keep alive interval
                    #     * set connection close/fail handler
                    try:
                        self.connection.setKeepAlive(connection_manager.keepalive_interval, connection_manager.keepalive_count)
                        try:
                            self.connection.registerCloseCallback(self.__connection_close_callback, None)
                        except:
                            # Temporary fix for libvirt > libvirt-0.10.2-41
                            pass
                    except libvirtError as e:
                        # hypervisor driver does not seem to support persistent connections
                        self.last_error = str(e)
        finally:
            self.connection_state_lock.release()

    @property
    def connected(self):
        try:
            return self.connection is not None and self.connection.isAlive()
        except libvirtError:
            # isAlive failed for some reason
            return False

    def __libvirt_auth_credentials_callback(self, credentials, user_data):
        for credential in credentials:
            if credential[0] == libvirt.VIR_CRED_AUTHNAME:
                credential[4] = self.login
                if len(credential[4]) == 0:
                    credential[4] = credential[3]
            elif credential[0] == libvirt.VIR_CRED_PASSPHRASE:
                credential[4] = self.passwd
            else:
                return -1
        return 0

    def __connection_close_callback(self, connection, reason, opaque=None):
        self.connection_state_lock.acquire()
        try:
            # on server shutdown libvirt module gets freed before the close callbacks are called
            # so we just check here if it is still present
            if libvirt is not None:
                self.last_error = reason

            # prevent other threads from using the connection (in the future)
            self.connection = None
        finally:
            self.connection_state_lock.release()

    def __connect_tcp(self):
        flags = [libvirt.VIR_CRED_AUTHNAME, libvirt.VIR_CRED_PASSPHRASE]
        auth = [flags, self.__libvirt_auth_credentials_callback, None]
        uri = f'qemu+tcp://{self.host}/system'

        try:
            self.connection = libvirt.openAuth(uri, auth, 0)
            self.last_error = None

        except libvirtError as e:
            self.last_error = f'Connection Failed: {str(e)}'
            self.connection = None

    def __connect_ssh(self):
        uri = 'qemu+ssh://%s@%s/system' % (self.login, self.host)

        try:
            self.connection = libvirt.open(uri)
            self.last_error = None

        except libvirtError as e:
            self.last_error = f'Connection Failed: {str(e)} --- ' + repr(libvirt.virGetLastError())
            self.connection = None

    def __connect_tls(self):
        flags = [libvirt.VIR_CRED_AUTHNAME, libvirt.VIR_CRED_PASSPHRASE]
        auth = [flags, self.__libvirt_auth_credentials_callback, None]
        uri = 'qemu+tls://%s@%s/system' % (self.login, self.host)

        try:
            self.connection = libvirt.openAuth(uri, auth, 0)
            self.last_error = None

        except libvirtError as e:
            self.last_error = f'Connection Failed: {str(e)}'
            self.connection = None

    def __connect_socket(self):
        uri = 'qemu:///system'

        try:
            self.connection = libvirt.open(uri)
            self.last_error = None

        except libvirtError as e:
            self.last_error = f'Connection Failed: {str(e)}'
            self.connection = None

    def close(self):
        """
        closes the connection (if it is active)
        """
        self.connection_state_lock.acquire()
        try:
            if self.connected:
                try:
                    # to-do: handle errors?
                    self.connection.close()
                except libvirtError:
                    pass

            self.connection = None
            self.last_error = None
        finally:
            self.connection_state_lock.release()

    def __del__(self):
        if self.connection is not None:
            # unregister callback (as it is no longer valid if this instance gets deleted)
            try:
                self.connection.unregisterCloseCallback()
            except:
                pass

    def __str__(self):
        if self.type == CONN_TCP:
            type_str = 'tcp'
        elif self.type == CONN_SSH:
            type_str = 'ssh'
        elif self.type == CONN_TLS:
            type_str = 'tls'
        else:
            type_str = 'invalid_type'

        return f'qemu+{type_str}://{self.login}@{self.host}/system'

    def __repr__(self):
        return f'<wvmConnection {str(self)}>'


class wvmConnectionManager(object):
    def __init__(self, keepalive_interval=5, keepalive_count=5):
        self.keepalive_interval = keepalive_interval
        self.keepalive_count = keepalive_count

        # connection dict
        # maps hostnames to a list of connection objects for this hostname
        # atm it is possible to create more than one connection per hostname
        # with different logins or auth methods
        # connections are shared between all threads, see:
        #     http://wiki.libvirt.org/page/FAQ#Is_libvirt_thread_safe.3F
        self._connections = dict()
        self._connections_lock = ReadWriteLock()

        # start event loop to handle keepalive requests and other events
        self._event_loop = wvmEventLoop()
        self._event_loop.start()

    def _search_connection(self, host, login, passwd, conn):
        """
        search the connection dict for a connection with the given credentials
        if it does not exist return None
        """
        self._connections_lock.acquireRead()
        try:
            if host in self._connections:
                connections = self._connections[host]

                for connection in connections:
                    if connection.login == login and connection.passwd == passwd and connection.type == conn:
                        return connection
        finally:
            self._connections_lock.release()

        return None

    def get_connection(self, host, login, passwd, conn):
        """
        returns a connection object (as returned by the libvirt.open* methods) for the given host and credentials
        raises libvirtError if (re)connecting fails
        """
        # force all string values to unicode
        host = str(host)
        login = str(login)
        passwd = str(passwd) if passwd is not None else None

        connection = self._search_connection(host, login, passwd, conn)

        if connection is None:
            self._connections_lock.acquireWrite()
            try:
                # we have to search for the connection again after acquiring the write lock
                # as the thread previously holding the write lock may have already added our connection
                connection = self._search_connection(host, login, passwd, conn)
                if connection is None:
                    # create a new connection if a matching connection does not already exist
                    connection = wvmConnection(host, login, passwd, conn)

                    # add new connection to connection dict
                    if host in self._connections:
                        self._connections[host].append(connection)
                    else:
                        self._connections[host] = [connection]
            finally:
                self._connections_lock.release()

        elif not connection.connected:
            # try to (re-)connect if connection is closed
            connection.connect()

        if connection.connected:
            # return libvirt connection object
            return connection.connection
        else:
            # raise libvirt error
            raise libvirtError(connection.last_error)

    def host_is_up(self, conn_type, hostname):
        """
        returns True if the given host is up and we are able to establish
        a connection using the given credentials.
        """
        try:
            socket_host = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            socket_host.settimeout(1)
            if conn_type == CONN_SSH:
                if ':' in hostname:
                    libvirt_host, PORT = hostname.split(":")
                    PORT = int(PORT)
                else:
                    PORT = SSH_PORT
                    libvirt_host = hostname
                socket_host.connect((libvirt_host, PORT))
            if conn_type == CONN_TCP:
                socket_host.connect((hostname, TCP_PORT))
            if conn_type == CONN_TLS:
                socket_host.connect((hostname, TLS_PORT))
            if conn_type == CONN_SOCKET:
                socket_host = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
                socket_host.connect('/var/run/libvirt/libvirt-sock')
            socket_host.close()
            return True
        except Exception as err:
            return err


connection_manager = wvmConnectionManager(
    settings.LIBVIRT_KEEPALIVE_INTERVAL if hasattr(settings, 'LIBVIRT_KEEPALIVE_INTERVAL') else 5,
    settings.LIBVIRT_KEEPALIVE_COUNT if hasattr(settings, 'LIBVIRT_KEEPALIVE_COUNT') else 5,
)


class wvmConnect(object):
    def __init__(self, host, login, passwd, conn):
        self.login = login
        self.host = host
        self.passwd = passwd
        self.conn = conn

        # get connection from connection manager
        self.wvm = connection_manager.get_connection(host, login, passwd, conn)

    def is_qemu(self):
        return self.wvm.getURI().startswith("qemu")

    def get_cap_xml(self):
        """Return xml capabilities"""
        return self.wvm.getCapabilities()

    def get_dom_cap_xml(self, arch, machine):
        """ Return domain capabilities xml"""
        emulatorbin = self.get_emulator(arch)
        virttype = 'kvm' if 'kvm' in self.get_hypervisors_domain_types()[arch] else 'qemu'

        machine_types = self.get_machine_types(arch)
        if not machine or machine not in machine_types:
            machine = 'pc' if 'pc' in machine_types else machine_types[0]
        return self.wvm.getDomainCapabilities(emulatorbin, arch, machine, virttype)

    def get_capabilities(self, arch):
        """ Host Capabilities for specified architecture """
        def guests(ctx):
            result = dict()
            for arch_el in ctx.xpath("/capabilities/guest/arch[@name='{}']".format(arch)):
                result["wordsize"] = arch_el.find("wordsize").text
                result["emulator"] = arch_el.find("emulator").text
                result["domain"] = [v for v in arch_el.xpath("domain/@type")]

                result["machines"] = []
                for m in arch_el.xpath("machine"):
                    result["machines"].append({
                        "machine": m.text,
                        "max_cpu": m.get("maxCpus"),
                        "canonical": m.get("canonical")
                    })

                guest_el = arch_el.getparent()
                for f in guest_el.xpath("features"):
                    result["features"] = [t.tag for t in f.getchildren()]

                result["os_type"] = guest_el.find("os_type").text

            return result

        return util.get_xml_path(self.get_cap_xml(), func=guests)

    def get_dom_capabilities(self, arch, machine):
        """Return domain capabilities"""
        result = dict()

        xml = self.get_dom_cap_xml(arch, machine)
        result["path"] = util.get_xml_path(xml, "/domainCapabilities/path")
        result["domain"] = util.get_xml_path(xml, "/domainCapabilities/domain")
        result["machine"] = util.get_xml_path(xml, "/domainCapabilities/machine")
        result["vcpu_max"] = util.get_xml_path(xml, "/domainCapabilities/vcpu/@max")
        result["iothreads_support"] = util.get_xml_path(xml, "/domainCapabilities/iothreads/@supported")
        result["os_support"] = util.get_xml_path(xml, "/domainCapabilities/os/@supported")

        result["loader_support"] = util.get_xml_path(xml, "/domainCapabilities/os/loader/@supported")
        if result["loader_support"] == 'yes':
            result["loaders"] = self.get_os_loaders(arch, machine)
            result["loader_enums"] = self.get_os_loader_enums(arch, machine)

        result["cpu_modes"] = self.get_cpu_modes(arch, machine)
        if "custom" in result["cpu_modes"]:
            # supported and unknown cpu models
            result["cpu_custom_models"] = self.get_cpu_custom_types(arch, machine)

        result["disk_support"] = util.get_xml_path(xml, "/domainCapabilities/devices/disk/@supported")
        if result["disk_support"] == 'yes':
            result["disk_devices"] = self.get_disk_device_types(arch, machine)
            result["disk_bus"] = self.get_disk_bus_types(arch, machine)

        result["graphics_support"] = util.get_xml_path(xml, "/domainCapabilities/devices/graphics/@supported")
        if result["graphics_support"] == 'yes':
            result["graphics_types"] = self.get_graphics_types(arch, machine)

        result["video_support"] = util.get_xml_path(xml, "/domainCapabilities/devices/video/@supported")
        if result["video_support"] == 'yes':
            result["video_types"] = self.get_video_models(arch, machine)

        result["hostdev_support"] = util.get_xml_path(xml, "/domainCapabilities/devices/hostdev/@supported")
        if result["hostdev_support"] == 'yes':
            result["hostdev_types"] = self.get_hostdev_modes(arch, machine)
            result["hostdev_startup_policies"] = self.get_hostdev_startup_policies(arch, machine)
            result["hostdev_subsys_types"] = self.get_hostdev_subsys_types(arch, machine)

        result["features_gic_support"] = util.get_xml_path(xml, "/domainCapabilities/features/gic/@supported")
        result["features_genid_support"] = util.get_xml_path(xml, "/domainCapabilities/features/genid/@supported")
        result["features_vmcoreinfo_support"] = util.get_xml_path(xml, "/domainCapabilities/features/vmcoreinfo/@supported")
        result["features_sev_support"] = util.get_xml_path(xml, "/domainCapabilities/features/sev/@supported")

        return result

    def get_version(self):
        """
        :return: libvirt version
        """
        ver = self.wvm.getVersion()
        major = ver // 1000000
        ver = ver % 1000000
        minor = ver // 1000
        ver = ver % 1000
        release = ver
        return f"{major}.{minor}.{release}"

    def get_lib_version(self):
        ver = self.wvm.getLibVersion()
        major = ver // 1000000
        ver %= 1000000
        minor = ver // 1000
        ver %= 1000
        release = ver
        return f"{major}.{minor}.{release}"

    def is_kvm_supported(self):
        """
        :return: kvm support or not
        """
        return util.is_kvm_available(self.get_cap_xml())

    def get_storages(self, only_actives=False):
        """
        :return: list of active or all storages
        """
        storages = []
        for pool in self.wvm.listStoragePools():
            storages.append(pool)
        if not only_actives:
            for pool in self.wvm.listDefinedStoragePools():
                storages.append(pool)
        return storages

    def get_networks(self):
        """
        :return: list of networks
        """
        virtnet = []
        for net in self.wvm.listNetworks():
            virtnet.append(net)
        for net in self.wvm.listDefinedNetworks():
            virtnet.append(net)
        return virtnet

    def get_ifaces(self):
        """
        :return: list of network interfaces
        """
        interface = []
        for inface in self.wvm.listInterfaces():
            interface.append(inface)
        for inface in self.wvm.listDefinedInterfaces():
            interface.append(inface)
        return interface

    def get_nwfilters(self):
        """
        :return: list of network filters
        """
        nwfilters = []
        for nwfilter in self.wvm.listNWFilters():
            nwfilters.append(nwfilter)
        return nwfilters

    def get_cache_modes(self):
        """
        :return: Get cache available modes
        """
        return {
            'default': 'Default',
            'none': 'Disabled',
            'writethrough': 'Write through',
            'writeback': 'Write back',
            'directsync': 'Direct sync',  # since libvirt 0.9.5
            'unsafe': 'Unsafe',  # since libvirt 0.9.7
        }

    def get_io_modes(self):
        """
        :return: available io modes
        """
        return {
            'default': 'Default',
            'native': 'Native',
            'threads': 'Threads',
        }

    def get_discard_modes(self):
        """
        :return: available discard modes
        """
        return {
            'default': 'Default',
            'ignore': 'Ignore',
            'unmap': 'Unmap',
        }

    def get_detect_zeroes_modes(self):
        """
        :return: available detect zeroes modes
        """
        return {
            'default': 'Default',
            'on': 'On',
            'off': 'Off',
            'unmap': 'Unmap',
        }

    def get_hypervisors_domain_types(self):
        """
        :return: hypervisor domain types
        """
        def hypervisors(ctx):
            result = {}
            for arch in ctx.xpath('/capabilities/guest/arch'):
                domain_types = arch.xpath('domain/@type')
                arch_name = arch.xpath('@name')[0]
                result[arch_name] = domain_types
            return result

        return util.get_xml_path(self.get_cap_xml(), func=hypervisors)

    def get_hypervisors_machines(self):
        """
        :return: hypervisor and its machine types
        """
        def machines(ctx):
            result = dict()
            for arche in ctx.xpath('/capabilities/guest/arch'):
                arch = arche.get("name")

                result[arch] = self.get_machine_types(arch)
            return result

        return util.get_xml_path(self.get_cap_xml(), func=machines)

    def get_emulator(self, arch):
        """
        :return: emulator list
        """
        return util.get_xml_path(self.get_cap_xml(), "/capabilities/guest/arch[@name='{}']/emulator".format(arch))

    def get_machine_types(self, arch):
        """
        :return: canonical(if exist) name of machine types
        """
        def machines(ctx):
            result = list()
            canonical_name = ctx.xpath("/capabilities/guest/arch[@name='{}']/machine[@canonical]".format(arch))
            if not canonical_name:
                canonical_name = ctx.xpath("/capabilities/guest/arch[@name='{}']/machine".format(arch))
            for archi in canonical_name:
                result.append(archi.text)
            return result

        return util.get_xml_path(self.get_cap_xml(), func=machines)

    def get_emulators(self):
        """
        :return: host emulators list
        """
        def emulators(ctx):
            result = {}
            for arch in ctx.xpath('/capabilities/guest/arch'):
                emulator = arch.xpath('emulator')
                arch_name = arch.xpath('@name')[0]
                result[arch_name] = emulator
            return result

        return util.get_xml_path(self.get_cap_xml(), func=emulators)

    def get_os_loaders(self, arch='x86_64', machine='pc'):
        """
        :param arch: architecture
        :param machine:
        :return: available os loaders list
        """
        def get_os_loaders(ctx):
            return [v.text for v in ctx.xpath("/domainCapabilities/os/loader[@supported='yes']/value")]

        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_os_loaders)

    def get_os_loader_enums(self, arch, machine):
        """
        :param arch: architecture
        :param machine:
        :return: available os loaders list
        """
        def get_os_loader_enums(ctx):
            result = dict()
            enums = [v for v in ctx.xpath("/domainCapabilities/os/loader[@supported='yes']/enum/@name")]
            for enum in enums:
                path = "/domainCapabilities/os/loader[@supported='yes']/enum[@name='{}']/value".format(enum)
                result[enum] = [v.text for v in ctx.xpath(path)]
            return result

        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_os_loader_enums)

    def get_disk_bus_types(self, arch, machine):
        """
        :param machine:
        :param arch:
        :return: available disk bus types list
        """
        def get_bus_list(ctx):
            return [v.text for v in ctx.xpath("/domainCapabilities/devices/disk/enum[@name='bus']/value")]

        # return [ 'ide', 'scsi', 'usb', 'virtio' ]
        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_bus_list)

    def get_disk_device_types(self, arch, machine):
        """
        :param arch: architecture
        :param machine:
        :return: available disk device type list
        """
        def get_device_list(ctx):
            return [v.text for v in ctx.xpath("/domainCapabilities/devices/disk/enum[@name='diskDevice']/value")]

        # return [ 'disk', 'cdrom', 'floppy', 'lun' ]
        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_device_list)

    def get_graphics_types(self, arch, machine):
        """
        :param arch: architecture
        :param machine:
        :return: available graphics types
        """
        def get_graphics_list(ctx):
            return [v.text for v in ctx.xpath("/domainCapabilities/devices/graphics/enum[@name='type']/value")]

        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_graphics_list)

    def get_cpu_modes(self, arch, machine):
        """
        :param arch: architecture
        :param machine:
        :return: available cpu modes
        """
        def get_cpu_modes(ctx):
            return [v for v in ctx.xpath("/domainCapabilities/cpu/mode[@supported='yes']/@name")]

        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_cpu_modes)

    def get_cpu_custom_types(self, arch, machine):
        """
        :param arch: architecture
        :param machine:
        :return: available graphics types
        """
        def get_custom_list(ctx):
            usable_yes = "/domainCapabilities/cpu/mode[@name='custom'][@supported='yes']/model[@usable='yes']"
            usable_unknown = "/domainCapabilities/cpu/mode[@name='custom'][@supported='yes']/model[@usable='unknown']"
            result = [v.text for v in ctx.xpath(usable_yes)]
            result += [v.text for v in ctx.xpath(usable_unknown)]
            return result

        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_custom_list)

    def get_hostdev_modes(self, arch, machine):
        """
        :param arch: architecture
        :param machine:
        :return. available nodedev modes
        """
        def get_hostdev_list(ctx):
            return [v.text for v in ctx.xpath("/domainCapabilities/devices/hostdev/enum[@name='mode']/value")]

        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_hostdev_list)

    def get_hostdev_startup_policies(self, arch, machine):
        """
        :param arch: architecture
        :param machine:
        :return: available hostdev modes
        """
        def get_hostdev_list(ctx):
            return [v.text for v in ctx.xpath("/domainCapabilities/devices/hostdev/enum[@name='startupPolicy']/value")]

        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_hostdev_list)

    def get_hostdev_subsys_types(self, arch, machine):
        """
        :param arch: architecture
        :param machine:
        :return: available nodedev sub system types
        """
        def get_hostdev_list(ctx):
            return [v.text for v in ctx.xpath("/domainCapabilities/devices/hostdev/enum[@name='subsysType']/value")]

        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_hostdev_list)

    def get_network_models(self):
        """
        :return: network card models
        """
        return ['default', 'e1000', 'virtio']

    def get_image_formats(self):
        """
        :return: available image formats
        """
        return ['raw', 'qcow', 'qcow2']

    def get_file_extensions(self):
        """
        :return: available image filename extensions
        """
        return ['img', 'qcow', 'qcow2']

    def get_video_models(self, arch, machine):
        """
        :param arch: architecture
        :param machine:
        :return: available graphics video types
        """
        def get_video_list(ctx):
            result = []
            for video_enum in ctx.xpath('/domainCapabilities/devices/video/enum'):
                if video_enum.xpath("@name")[0] == "modelType":
                    for values in video_enum:
                        result.append(values.text)
            return result

        return util.get_xml_path(self.get_dom_cap_xml(arch, machine), func=get_video_list)

    def get_iface(self, name):
        return self.wvm.interfaceLookupByName(name)

    def get_secrets(self):
        return self.wvm.listSecrets()

    def get_secret(self, uuid):
        return self.wvm.secretLookupByUUIDString(uuid)

    def get_storage(self, name):
        return self.wvm.storagePoolLookupByName(name)

    def get_volume_by_path(self, path):
        return self.wvm.storageVolLookupByPath(path)

    def get_network(self, net):
        return self.wvm.networkLookupByName(net)

    def get_network_forward(self, net_name):
        def get_forward(doc):
            forward_mode = util.get_xpath(doc, '/network/forward/@mode')
            return forward_mode or 'isolated'

        net = self.get_network(net_name)
        xml = net.XMLDesc(0)
        return util.get_xml_path(xml, func=get_forward)

    def get_nwfilter(self, name):
        return self.wvm.nwfilterLookupByName(name)

    def get_instance(self, name):
        return self.wvm.lookupByName(name)

    def get_instances(self):
        instances = []
        for inst_id in self.wvm.listDomainsID():
            dom = self.wvm.lookupByID(int(inst_id))
            instances.append(dom.name())
        for name in self.wvm.listDefinedDomains():
            instances.append(name)
        return instances

    def get_snapshots(self):
        instance = []
        for snap_id in self.wvm.listDomainsID():
            dom = self.wvm.lookupByID(int(snap_id))
            if dom.snapshotNum(0) != 0:
                instance.append(dom.name())
        for name in self.wvm.listDefinedDomains():
            dom = self.wvm.lookupByName(name)
            if dom.snapshotNum(0) != 0:
                instance.append(dom.name())
        return instance

    def get_net_devices(self):
        netdevice = []

        def get_info(doc):
            dev_type = util.get_xpath(doc, '/device/capability/@type')
            interface = util.get_xpath(doc, '/device/capability/interface')
            return dev_type, interface

        for dev in self.wvm.listAllDevices(0):
            xml = dev.XMLDesc(0)
            (dev_type, interface) = util.get_xml_path(xml, func=get_info)
            if dev_type == 'net':
                netdevice.append(interface)
        return netdevice

    def get_host_instances(self, raw_mem_size=False):
        vname = {}

        def get_info(doc):
            mem = util.get_xpath(doc, "/domain/currentMemory")
            mem = int(mem) // 1024
            if raw_mem_size:
                mem = int(mem) * (1024 * 1024)
            cur_vcpu = util.get_xpath(doc, "/domain/vcpu/@current")
            if cur_vcpu:
                vcpu = cur_vcpu
            else:
                vcpu = util.get_xpath(doc, "/domain/vcpu")
            title = util.get_xpath(doc, "/domain/title")
            title = title if title else ''
            description = util.get_xpath(doc, "/domain/description")
            description = description if description else ''
            return mem, vcpu, title, description

        for name in self.get_instances():
            dom = self.get_instance(name)
            xml = dom.XMLDesc(0)
            (mem, vcpu, title, description) = util.get_xml_path(xml, func=get_info)
            vname[dom.name()] = {
                'status': dom.info()[0],
                'uuid': dom.UUIDString(),
                'vcpu': vcpu,
                'memory': mem,
                'title': title,
                'description': description,
            }
        return vname

    def get_user_instances(self, name):
        dom = self.get_instance(name)
        xml = dom.XMLDesc(0)

        def get_info(ctx):
            mem = util.get_xpath(ctx, "/domain/currentMemory")
            mem = int(mem) // 1024
            cur_vcpu = util.get_xpath(ctx, "/domain/vcpu/@current")
            if cur_vcpu:
                vcpu = cur_vcpu
            else:
                vcpu = util.get_xpath(ctx, "/domain/vcpu")
            title = util.get_xpath(ctx, "/domain/title")
            title = title if title else ''
            description = util.get_xpath(ctx, "/domain/description")
            description = description if description else ''
            return mem, vcpu, title, description

        (mem, vcpu, title, description) = util.get_xml_path(xml, func=get_info)
        return {
            'name': dom.name(),
            'status': dom.info()[0],
            'uuid': dom.UUIDString(),
            'vcpu': vcpu,
            'memory': mem,
            'title': title,
            'description': description,
        }

    def close(self):
        """Close connection"""
        # to-do: do not close connection ;)
        # self.wvm.close()
        pass

    def find_uefi_path_for_arch(self, arch, machine):
        """
        Search the loader paths for one that matches the passed arch
        """
        if not self.arch_can_uefi(arch):
            return

        loaders = self.get_os_loaders(arch, machine)
        patterns = util.UEFI_ARCH_PATTERNS.get(arch)
        for pattern in patterns:
            for path in loaders:
                if re.match(pattern, path):
                    return path

    def label_for_firmware_path(self, arch, path):
        """
        Return a pretty label for passed path, based on if we know
        about it or not
        """
        if not path:
            if arch in ["i686", "x86_64"]:
                return "BIOS"
            return

        for arch, patterns in util.UEFI_ARCH_PATTERNS.items():
            for pattern in patterns:
                if re.match(pattern, path):
                    return ("UEFI %(arch)s: %(path)s" % {"arch": arch, "path": path})

        return "Custom: %(path)s" % {"path": path}

    def arch_can_uefi(self, arch):
        """
        Return True if we know how to setup UEFI for the passed arch
        """
        return arch in list(util.UEFI_ARCH_PATTERNS.keys())

    def supports_uefi_xml(self, loader_enums):
        """
        Return True if libvirt advertises support for proper UEFI setup
        """
        return ("readonly" in loader_enums and "yes" in loader_enums.get("readonly"))

    def is_supports_virtio(self, arch, machine):
        if not self.is_qemu():
            return False

        # These _only_ support virtio so don't check the OS
        if arch in ["aarch64", "armv7l", "ppc64", "ppc64le", "s390x", "riscv64", "riscv32"] and \
                machine in ["virt", "pseries"]:
            return True

        if arch in ["x86_64", "i686"]:
            return True

        return False