Synnefo

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from django.conf import settings

from django.db import transaction

from datetime import datetime, timedelta

from synnefo.db.models import (Backend, VirtualMachine, Network,

                               BackendNetwork, BACKEND_STATUSES,

                               pooled_rapi_client, VirtualMachineDiagnostic,

                               Flavor, IPAddressLog)

from synnefo.logic import utils

from synnefo import quotas

from synnefo.api.util import release_resource, allocate_ip

from synnefo.util.mac2eui64 import mac2eui64

from synnefo.logic.rapi import GanetiApiError

from logging import getLogger

log = getLogger(__name__)

_firewall_tags = {

    'ENABLED': settings.GANETI_FIREWALL_ENABLED_TAG,

    'DISABLED': settings.GANETI_FIREWALL_DISABLED_TAG,

    'PROTECTED': settings.GANETI_FIREWALL_PROTECTED_TAG}

_reverse_tags = dict((v.split(':')[3], k) for k, v in _firewall_tags.items())

# Timeout in seconds for building NICs. After this period the NICs considered

# stale and removed from DB.

BUILDING_NIC_TIMEOUT = timedelta(seconds=180)

SIMPLE_NIC_FIELDS = ["state", "mac", "network", "firewall_profile", "index"]

COMPLEX_NIC_FIELDS = ["ipv4_address", "ipv6_address"]

NIC_FIELDS = SIMPLE_NIC_FIELDS + COMPLEX_NIC_FIELDS

UNKNOWN_NIC_PREFIX = "unknown-"

def handle_vm_quotas(vm, job_id, job_opcode, job_status, job_fields):

    """Handle quotas for updated VirtualMachine.

    Update quotas for the updated VirtualMachine based on the job that run on

    the Ganeti backend. If a commission has been already issued for this job,

    then this commission is just accepted or rejected based on the job status.

    Otherwise, a new commission for the given change is issued, that is also in

    force and auto-accept mode. In this case, previous commissions are

    rejected, since they reflect a previous state of the VM.

    """

    if job_status not in ["success", "error", "canceled"]:

        return vm

    # Check successful completion of a job will trigger any quotable change in

    # the VM state.

    action = utils.get_action_from_opcode(job_opcode, job_fields)

    if action == "BUILD":

        # Quotas for new VMs are automatically accepted by the API

        return vm

    commission_info = quotas.get_commission_info(vm, action=action,

                                                 action_fields=job_fields)

    if vm.task_job_id == job_id and vm.serial is not None:

        # Commission for this change has already been issued. So just

        # accept/reject it. Special case is OP_INSTANCE_CREATE, which even

        # if fails, must be accepted, as the user must manually remove the

        # failed server

        serial = vm.serial

        if job_status == "success":

            quotas.accept_serial(serial)

        elif job_status in ["error", "canceled"]:

            log.debug("Job %s failed. Rejecting related serial %s", job_id,

                      serial)

            quotas.reject_serial(serial)

        vm.serial = None

    elif job_status == "success" and commission_info is not None:

        log.debug("Expected job was %s. Processing job %s. Commission for"

                  " this job: %s", vm.task_job_id, job_id, commission_info)

        # Commission for this change has not been issued, or the issued

        # commission was unaware of the current change. Reject all previous

        # commissions and create a new one in forced mode!

        commission_name = ("client: dispatcher, resource: %s, ganeti_job: %s"

                           % (vm, job_id))

        quotas.handle_resource_commission(vm, action,

                                          commission_info=commission_info,

                                          commission_name=commission_name,

                                          force=True,

                                          auto_accept=True)

        log.debug("Issued new commission: %s", vm.serial)

    return vm

@transaction.commit_on_success

def process_op_status(vm, etime, jobid, opcode, status, logmsg, nics=None,

                      job_fields=None):

    """Process a job progress notification from the backend

    Process an incoming message from the backend (currently Ganeti).

    Job notifications with a terminating status (sucess, error, or canceled),

    also update the operating state of the VM.

    """

    # See #1492, #1031, #1111 why this line has been removed

    #if (opcode not in [x[0] for x in VirtualMachine.BACKEND_OPCODES] or

    if status not in [x[0] for x in BACKEND_STATUSES]:

        raise VirtualMachine.InvalidBackendMsgError(opcode, status)

    vm.backendjobid = jobid

    vm.backendjobstatus = status

    vm.backendopcode = opcode

    vm.backendlogmsg = logmsg

    if status in ["queued", "waiting", "running"]:

        vm.save()

        return

    if job_fields is None:

        job_fields = {}

    state_for_success = VirtualMachine.OPER_STATE_FROM_OPCODE.get(opcode)

    # Notifications of success change the operating state

    if status == "success":

        if state_for_success is not None:

            vm.operstate = state_for_success

        beparams = job_fields.get("beparams", None)

        if beparams:

            # Change the flavor of the VM

            _process_resize(vm, beparams)

        # Update backendtime only for jobs that have been successfully

        # completed, since only these jobs update the state of the VM. Else a

        # "race condition" may occur when a successful job (e.g.

        # OP_INSTANCE_REMOVE) completes before an error job and messages arrive

        # in reversed order.

        vm.backendtime = etime

    if status in ["success", "error", "canceled"] and nics is not None:

        # Update the NICs of the VM

        _process_net_status(vm, etime, nics)

    # Special case: if OP_INSTANCE_CREATE fails --> ERROR

    if opcode == 'OP_INSTANCE_CREATE' and status in ('canceled', 'error'):

        vm.operstate = 'ERROR'

        vm.backendtime = etime

        # Update state of associated NICs

        vm.nics.all().update(state="ERROR")

    elif opcode == 'OP_INSTANCE_REMOVE':

        # Special case: OP_INSTANCE_REMOVE fails for machines in ERROR,

        # when no instance exists at the Ganeti backend.

        # See ticket #799 for all the details.

        if status == 'success' or (status == 'error' and

                                   not vm_exists_in_backend(vm)):

            # VM has been deleted

            for nic in vm.nics.all():

                # Release the IP

                remove_nic_ips(nic)

                # And delete the NIC.

                nic.delete()

            vm.deleted = True

            vm.operstate = state_for_success

            vm.backendtime = etime

            status = "success"

    if status in ["success", "error", "canceled"]:

        # Job is finalized: Handle quotas/commissioning

        vm = handle_vm_quotas(vm, job_id=jobid, job_opcode=opcode,

                              job_status=status, job_fields=job_fields)

        # and clear task fields

        if vm.task_job_id == jobid:

            vm.task = None

            vm.task_job_id = None

    vm.save()

def _process_resize(vm, beparams):

    """Change flavor of a VirtualMachine based on new beparams."""

    old_flavor = vm.flavor

    vcpus = beparams.get("vcpus", old_flavor.cpu)

    ram = beparams.get("maxmem", old_flavor.ram)

    if vcpus == old_flavor.cpu and ram == old_flavor.ram:

        return

    try:

        new_flavor = Flavor.objects.get(cpu=vcpus, ram=ram,

                                        disk=old_flavor.disk,

                                        disk_template=old_flavor.disk_template)

    except Flavor.DoesNotExist:

        raise Exception("Can not find flavor for VM")

    vm.flavor = new_flavor

    vm.save()

@transaction.commit_on_success

def process_net_status(vm, etime, nics):

    """Wrap _process_net_status inside transaction."""

    _process_net_status(vm, etime, nics)

def _process_net_status(vm, etime, nics):

    """Process a net status notification from the backend

    Process an incoming message from the Ganeti backend,

    detailing the NIC configuration of a VM instance.

    Update the state of the VM in the DB accordingly.

    """

    ganeti_nics = process_ganeti_nics(nics)

    db_nics = dict([(nic.id, nic)

                    for nic in vm.nics.prefetch_related("ips__subnet")])

    # Get X-Lock on backend before getting X-Lock on network IP pools, to

    # guarantee that no deadlock will occur with Backend allocator.

    Backend.objects.select_for_update().get(id=vm.backend_id)

    for nic_name in set(db_nics.keys()) | set(ganeti_nics.keys()):

        db_nic = db_nics.get(nic_name)

        ganeti_nic = ganeti_nics.get(nic_name)

        if ganeti_nic is None:

            # NIC exists in DB but not in Ganeti. If the NIC is in 'building'

            # state for more than 5 minutes, then we remove the NIC.

            # TODO: This is dangerous as the job may be stack in the queue, and

            # releasing the IP may lead to duplicate IP use.

            if db_nic.state != "BUILD" or\

                (db_nic.state == "BUILD" and

                 etime > db_nic.created + BUILDING_NIC_TIMEOUT):

                remove_nic_ips(db_nic)

                db_nic.delete()

            else:

                log.warning("Ignoring recent building NIC: %s", db_nic)

        elif db_nic is None:

            msg = ("NIC/%s of VM %s does not exist in DB! Cannot automatically"

                   " fix this issue!" % (nic_name, vm))

            log.error(msg)

            continue

        elif not nics_are_equal(db_nic, ganeti_nic):

            for f in SIMPLE_NIC_FIELDS:

                # Update the NIC in DB with the values from Ganeti NIC

                setattr(db_nic, f, ganeti_nic[f])

                db_nic.save()

            # Special case where the IPv4 address has changed, because you

            # need to release the old IPv4 address and reserve the new one

            ipv4_address = ganeti_nic["ipv4_address"]

            if db_nic.ipv4_address != ipv4_address:

                remove_nic_ips(db_nic)

                if ipv4_address:

                    network = ganeti_nic["network"]

                    ipaddress = allocate_ip(network, vm.userid,

                                            address=ipv4_address)

                    ipaddress.nic = nic

                    ipaddress.save()

    vm.backendtime = etime

    vm.save()

def nics_are_equal(db_nic, gnt_nic):

    for field in NIC_FIELDS:

        if getattr(db_nic, field) != gnt_nic[field]:

            return False

    return True

def process_ganeti_nics(ganeti_nics):

    """Process NIC dict from ganeti"""

    new_nics = []

    for index, gnic in enumerate(ganeti_nics):

        nic_name = gnic.get("name", None)

        if nic_name is not None:

            nic_id = utils.id_from_nic_name(nic_name)

        else:

            # Put as default value the index. If it is an unknown NIC to

            # synnefo it will be created automaticaly.

            nic_id = UNKNOWN_NIC_PREFIX + str(index)

        network_name = gnic.get('network', '')

        network_id = utils.id_from_network_name(network_name)

        network = Network.objects.get(id=network_id)

        # Get the new nic info

        mac = gnic.get('mac')

        ipv4 = gnic.get('ip')

        subnet6 = network.subnet6

        ipv6 = mac2eui64(mac, subnet6) if subnet6 else None

        firewall = gnic.get('firewall')

        firewall_profile = _reverse_tags.get(firewall)

        if not firewall_profile and network.public:

            firewall_profile = settings.DEFAULT_FIREWALL_PROFILE

        nic_info = {

            'index': index,

            'network': network,

            'mac': mac,

            'ipv4_address': ipv4,

            'ipv6_address': ipv6,

            'firewall_profile': firewall_profile,

            'state': 'ACTIVE'}

        new_nics.append((nic_id, nic_info))

    return dict(new_nics)

def remove_nic_ips(nic):

    """Remove IP addresses associated with a NetworkInterface.

    Remove all IP addresses that are associated with the NetworkInterface

    object, by returning them to the pool and deleting the IPAddress object. If

    the IP is a floating IP, then it is just disassociated from the NIC.

    """

    for ip in nic.ips.all():

        # Update the DB table holding the logging of all IP addresses

        update_ip_address_log(nic, ip)

        if ip.ipversion == 4:

            if ip.floating_ip:

                ip.nic = None

                ip.save()

            else:

                ip.release_address()

        if not ip.floating_ip:

            ip.delete()

def update_ip_address_log(nic, ip):

    """Update DB logging entry for this IP address."""

    if not ip.network.public or nic.machine is None:

        return

    try:

        ip_log, created = \

            IPAddressLog.objects.get_or_create(server_id=nic.machine_id,

                                               network_id=ip.network_id,

                                               address=ip.address,

                                               active=True)

    except IPAddressLog.MultipleObjectsReturned:

        logmsg = ("Multiple active log entries for IP %s, Network %s,"

                  "Server %s. Can not proceed!"

                  % (ip.address, ip.network, nic.machine))

        log.error(logmsg)

        raise

    if created:

        logmsg = ("No log entry for IP %s, Network %s, Server %s. Created new"

                  " but with wrong creation timestamp."

                  % (ip.address, ip.network, nic.machine))

        log.error(logmsg)

    ip_log.released_at = datetime.now()

    ip_log.active = False

    ip_log.save()

@transaction.commit_on_success

def process_network_status(back_network, etime, jobid, opcode, status, logmsg):

    if status not in [x[0] for x in BACKEND_STATUSES]:

        raise Network.InvalidBackendMsgError(opcode, status)

    back_network.backendjobid = jobid

    back_network.backendjobstatus = status

    back_network.backendopcode = opcode

    back_network.backendlogmsg = logmsg

    # Note: Network is already locked!

    network = back_network.network

    # Notifications of success change the operating state

    state_for_success = BackendNetwork.OPER_STATE_FROM_OPCODE.get(opcode, None)

    if status == 'success' and state_for_success is not None:

        back_network.operstate = state_for_success

    if status in ('canceled', 'error') and opcode == 'OP_NETWORK_ADD':

        back_network.operstate = 'ERROR'

        back_network.backendtime = etime

    if opcode == 'OP_NETWORK_REMOVE':

        network_is_deleted = (status == "success")

        if network_is_deleted or (status == "error" and not

                                  network_exists_in_backend(back_network)):

            back_network.operstate = state_for_success

            back_network.deleted = True

            back_network.backendtime = etime

    if status == 'success':

        back_network.backendtime = etime

    back_network.save()

    # Also you must update the state of the Network!!

    update_network_state(network)

def update_network_state(network):

    """Update the state of a Network based on BackendNetwork states.

    Update the state of a Network based on the operstate of the networks in the

    backends that network exists.

    The state of the network is:

    * ACTIVE: If it is 'ACTIVE' in at least one backend.

    * DELETED: If it is is 'DELETED' in all backends that have been created.

    This function also releases the resources (MAC prefix or Bridge) and the

    quotas for the network.

    """

    if network.deleted:

        # Network has already been deleted. Just assert that state is also

        # DELETED

        if not network.state == "DELETED":

            network.state = "DELETED"

            network.save()

        return

    backend_states = [s.operstate for s in network.backend_networks.all()]

    if not backend_states and network.action != "DESTROY":

        if network.state != "ACTIVE":

            network.state = "ACTIVE"

            network.save()

            return

    # Network is deleted when all BackendNetworks go to "DELETED" operstate

    deleted = reduce(lambda x, y: x == y and "DELETED", backend_states,

                     "DELETED")

    # Release the resources on the deletion of the Network

    if deleted:

        if network.ips.filter(deleted=False, floating_ip=True).exists():

            msg = "Can not delete network %s! Floating IPs still in use!"

            log.error(msg % network)

            raise Exception(msg % network)

        log.info("Network %r deleted. Releasing link %r mac_prefix %r",

                 network.id, network.mac_prefix, network.link)

        network.deleted = True

        network.state = "DELETED"

        if network.mac_prefix:

            if network.FLAVORS[network.flavor]["mac_prefix"] == "pool":

                release_resource(res_type="mac_prefix",

                                 value=network.mac_prefix)

        if network.link:

            if network.FLAVORS[network.flavor]["link"] == "pool":

                release_resource(res_type="bridge", value=network.link)

        # Set all subnets as deleted

        network.subnets.update(deleted=True)

        # And delete the IP pools

        for subnet in network.subnets.all():

            if subnet.ipversion == 4:

                subnet.ip_pools.all().delete()

        # And all the backend networks since there are useless

        network.backend_networks.all().delete()

        # Issue commission

        if network.userid:

            quotas.issue_and_accept_commission(network, delete=True)

            # the above has already saved the object and committed;

            # a second save would override others' changes, since the

            # object is now unlocked

            return

        elif not network.public:

            log.warning("Network %s does not have an owner!", network.id)

    network.save()

@transaction.commit_on_success

def process_network_modify(back_network, etime, jobid, opcode, status,

                           job_fields):

    assert (opcode == "OP_NETWORK_SET_PARAMS")

    if status not in [x[0] for x in BACKEND_STATUSES]:

        raise Network.InvalidBackendMsgError(opcode, status)

    back_network.backendjobid = jobid

    back_network.backendjobstatus = status

    back_network.opcode = opcode

    add_reserved_ips = job_fields.get("add_reserved_ips")

    if add_reserved_ips:

        network = back_network.network

        for ip in add_reserved_ips:

            network.reserve_address(ip, external=True)

    if status == 'success':

        back_network.backendtime = etime

    back_network.save()

@transaction.commit_on_success

def process_create_progress(vm, etime, progress):

    percentage = int(progress)

    # The percentage may exceed 100%, due to the way

    # snf-image:copy-progress tracks bytes read by image handling processes

    percentage = 100 if percentage > 100 else percentage

    if percentage < 0:

        raise ValueError("Percentage cannot be negative")

    # FIXME: log a warning here, see #1033

#   if last_update > percentage:

#       raise ValueError("Build percentage should increase monotonically " \

#                        "(old = %d, new = %d)" % (last_update, percentage))

    # This assumes that no message of type 'ganeti-create-progress' is going to

    # arrive once OP_INSTANCE_CREATE has succeeded for a Ganeti instance and

    # the instance is STARTED.  What if the two messages are processed by two

    # separate dispatcher threads, and the 'ganeti-op-status' message for

    # successful creation gets processed before the 'ganeti-create-progress'

    # message? [vkoukis]

    #

    #if not vm.operstate == 'BUILD':

    #    raise VirtualMachine.IllegalState("VM is not in building state")

    vm.buildpercentage = percentage

    vm.backendtime = etime

    vm.save()

@transaction.commit_on_success

def create_instance_diagnostic(vm, message, source, level="DEBUG", etime=None,

                               details=None):

    """

    Create virtual machine instance diagnostic entry.

    :param vm: VirtualMachine instance to create diagnostic for.

    :param message: Diagnostic message.

    :param source: Diagnostic source identifier (e.g. image-helper).

    :param level: Diagnostic level (`DEBUG`, `INFO`, `WARNING`, `ERROR`).

    :param etime: The time the message occured (if available).

    :param details: Additional details or debug information.

    """

    VirtualMachineDiagnostic.objects.create_for_vm(vm, level, source=source,

                                                   source_date=etime,

                                                   message=message,

                                                   details=details)

def create_instance(vm, nics, flavor, image):

    """`image` is a dictionary which should contain the keys:

            'backend_id', 'format' and 'metadata'

        metadata value should be a dictionary.

    """

    # Handle arguments to CreateInstance() as a dictionary,

    # initialize it based on a deployment-specific value.

    # This enables the administrator to override deployment-specific

    # arguments, such as the disk template to use, name of os provider

    # and hypervisor-specific parameters at will (see Synnefo #785, #835).

    #

    kw = vm.backend.get_create_params()

    kw['mode'] = 'create'

    kw['name'] = vm.backend_vm_id

    # Defined in settings.GANETI_CREATEINSTANCE_KWARGS

    kw['disk_template'] = flavor.disk_template

    kw['disks'] = [{"size": flavor.disk * 1024}]

    provider = flavor.disk_provider

    if provider:

        kw['disks'][0]['provider'] = provider

        kw['disks'][0]['origin'] = flavor.disk_origin

    kw['nics'] = [{"name": nic.backend_uuid,

                   "network": nic.network.backend_id,

                   "ip": nic.ipv4_address}

                  for nic in nics]

    backend = vm.backend

    depend_jobs = []

    for nic in nics:

        network = Network.objects.select_for_update().get(id=nic.network_id)

        bnet, created = BackendNetwork.objects.get_or_create(backend=backend,

                                                             network=network)

        if bnet.operstate != "ACTIVE":

            depend_jobs = create_network(network, backend, connect=True)

    kw["depends"] = [[job, ["success", "error", "canceled"]]

                     for job in depend_jobs]

    # Defined in settings.GANETI_CREATEINSTANCE_KWARGS

    # kw['os'] = settings.GANETI_OS_PROVIDER

    kw['ip_check'] = False

    kw['name_check'] = False

    # Do not specific a node explicitly, have

    # Ganeti use an iallocator instead

    #kw['pnode'] = rapi.GetNodes()[0]

    kw['dry_run'] = settings.TEST

    kw['beparams'] = {

        'auto_balance': True,

        'vcpus': flavor.cpu,

        'memory': flavor.ram}

    kw['osparams'] = {

        'config_url': vm.config_url,

        # Store image id and format to Ganeti

        'img_id': image['backend_id'],

        'img_format': image['format']}

    # Use opportunistic locking

    kw['opportunistic_locking'] = True

    # Defined in settings.GANETI_CREATEINSTANCE_KWARGS

    # kw['hvparams'] = dict(serial_console=False)

    log.debug("Creating instance %s", utils.hide_pass(kw))

    with pooled_rapi_client(vm) as client:

        return client.CreateInstance(**kw)

def delete_instance(vm):

    with pooled_rapi_client(vm) as client:

        return client.DeleteInstance(vm.backend_vm_id, dry_run=settings.TEST)

def reboot_instance(vm, reboot_type):

    assert reboot_type in ('soft', 'hard')

    kwargs = {"instance": vm.backend_vm_id,

              "reboot_type": "hard"}

    # XXX: Currently shutdown_timeout parameter is not supported from the

    # Ganeti RAPI. Until supported, we will fallback for both reboot types

    # to the default shutdown timeout of Ganeti (120s). Note that reboot

    # type of Ganeti job must be always hard. The 'soft' and 'hard' type

    # of OS API is different from the one in Ganeti, and maps to

    # 'shutdown_timeout'.

    #if reboot_type == "hard":

    #    kwargs["shutdown_timeout"] = 0

    if settings.TEST:

        kwargs["dry_run"] = True

    with pooled_rapi_client(vm) as client:

        return client.RebootInstance(**kwargs)

def startup_instance(vm):

    with pooled_rapi_client(vm) as client:

        return client.StartupInstance(vm.backend_vm_id, dry_run=settings.TEST)

def shutdown_instance(vm):

    with pooled_rapi_client(vm) as client:

        return client.ShutdownInstance(vm.backend_vm_id, dry_run=settings.TEST)

def resize_instance(vm, vcpus, memory):

    beparams = {"vcpus": int(vcpus),

                "minmem": int(memory),

                "maxmem": int(memory)}

    with pooled_rapi_client(vm) as client:

        return client.ModifyInstance(vm.backend_vm_id, beparams=beparams)

def get_instance_console(vm):

    # RAPI GetInstanceConsole() returns endpoints to the vnc_bind_address,

    # which is a cluster-wide setting, either 0.0.0.0 or 127.0.0.1, and pretty

    # useless (see #783).

    #

    # Until this is fixed on the Ganeti side, construct a console info reply

    # directly.

    #

    # WARNING: This assumes that VNC runs on port network_port on

    #          the instance's primary node, and is probably

    #          hypervisor-specific.

    #

    log.debug("Getting console for vm %s", vm)

    console = {}

    console['kind'] = 'vnc'

    with pooled_rapi_client(vm) as client:

        i = client.GetInstance(vm.backend_vm_id)

    if vm.backend.hypervisor == "kvm" and i['hvparams']['serial_console']:

        raise Exception("hv parameter serial_console cannot be true")

    console['host'] = i['pnode']

    console['port'] = i['network_port']

    return console

def get_instance_info(vm):

    with pooled_rapi_client(vm) as client:

        return client.GetInstance(vm.backend_vm_id)

def vm_exists_in_backend(vm):

    try:

        get_instance_info(vm)

        return True

    except GanetiApiError as e:

        if e.code == 404:

            return False

        raise e

def get_network_info(backend_network):

    with pooled_rapi_client(backend_network) as client:

        return client.GetNetwork(backend_network.network.backend_id)

def network_exists_in_backend(backend_network):

    try:

        get_network_info(backend_network)

        return True

    except GanetiApiError as e:

        if e.code == 404:

            return False

def create_network(network, backend, connect=True):

    """Create a network in a Ganeti backend"""

    log.debug("Creating network %s in backend %s", network, backend)

    job_id = _create_network(network, backend)

    if connect:

        job_ids = connect_network(network, backend, depends=[job_id])

        return job_ids

    else:

        return [job_id]

def _create_network(network, backend):

    """Create a network."""

    tags = network.backend_tag

    subnet = None

    subnet6 = None

    gateway = None

    gateway6 = None

    for _subnet in network.subnets.all():

        if _subnet.ipversion == 4:

            if _subnet.dhcp:

                tags.append('nfdhcpd')

            subnet = _subnet.cidr

            gateway = _subnet.gateway

        elif _subnet.ipversion == 6:

            subnet6 = _subnet.cidr

            gateway6 = _subnet.gateway

    if network.public:

        conflicts_check = True

        tags.append('public')

    else:

        conflicts_check = False

        tags.append('private')

    # Use a dummy network subnet for IPv6 only networks. Currently Ganeti does

    # not support IPv6 only networks. To bypass this limitation, we create the