lvm.py

# vim: tabstop=4 shiftwidth=4 softtabstop=4

# Copyright 2010 United States Government as represented by the
# Administrator of the National Aeronautics and Space Administration.
# All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.
"""
Driver for Linux servers running LVM.

"""

import os
import re
import socket

from oslo.config import cfg

from cinder.brick import exception as brick_exception
from cinder.brick.iscsi import iscsi
from cinder.brick.local_dev import lvm as lvm
from cinder import exception
from cinder.image import image_utils
from cinder.openstack.common import fileutils
from cinder.openstack.common import log as logging
from cinder.openstack.common import processutils
from cinder import utils
from cinder.volume import driver
from cinder.volume import utils as volutils

LOG = logging.getLogger(__name__)

volume_opts = [
    cfg.StrOpt('volume_group',
               default='cinder-volumes',
               help='Name for the VG that will contain exported volumes'),
    cfg.IntOpt('lvm_mirrors',
               default=0,
               help='If set, create lvms with multiple mirrors. Note that '
                    'this requires lvm_mirrors + 2 pvs with available space'),
    cfg.StrOpt('lvm_type',
               default='default',
               help='Type of LVM volumes to deploy; (default or thin)'),
]

CONF = cfg.CONF
CONF.register_opts(volume_opts)


class LVMVolumeDriver(driver.VolumeDriver):
    """Executes commands relating to Volumes."""

    VERSION = '2.0.0'

    def __init__(self, vg_obj=None, *args, **kwargs):
        super(LVMVolumeDriver, self).__init__(*args, **kwargs)
        self.configuration.append_config_values(volume_opts)
        self.hostname = socket.gethostname()
        self.vg = vg_obj
        self.backend_name =\
            self.configuration.safe_get('volume_backend_name') or 'LVM'
        self.protocol = 'local'

    def set_execute(self, execute):
        self._execute = execute

    def check_for_setup_error(self):
        """Verify that requirements are in place to use LVM driver."""
        if self.vg is None:
            root_helper = utils.get_root_helper()
            try:
                self.vg = lvm.LVM(self.configuration.volume_group,
                                  root_helper,
                                  lvm_type=self.configuration.lvm_type,
                                  executor=self._execute)
            except brick_exception.VolumeGroupNotFound:
                message = ("Volume Group %s does not exist" %
                           self.configuration.volume_group)
                raise exception.VolumeBackendAPIException(data=message)

        vg_list = volutils.get_all_volume_groups(
            self.configuration.volume_group)
        vg_dict = \
            (vg for vg in vg_list if vg['name'] == self.vg.vg_name).next()
        if vg_dict is None:
            message = ("Volume Group %s does not exist" %
                       self.configuration.volume_group)
            raise exception.VolumeBackendAPIException(data=message)

        if self.configuration.lvm_type == 'thin':
            # Specific checks for using Thin provisioned LV's
            if not volutils.supports_thin_provisioning():
                message = ("Thin provisioning not supported "
                           "on this version of LVM.")
                raise exception.VolumeBackendAPIException(data=message)

            pool_name = "%s-pool" % self.configuration.volume_group
            if self.vg.get_volume(pool_name) is None:
                try:
                    self.vg.create_thin_pool(pool_name)
                except processutils.ProcessExecutionError as exc:
                    exception_message = ("Failed to create thin pool, "
                                         "error message was: %s"
                                         % exc.stderr)
                    raise exception.VolumeBackendAPIException(
                        data=exception_message)

    def _sizestr(self, size_in_g):
        if int(size_in_g) == 0:
            return '100m'
        return '%sg' % size_in_g

    def _volume_not_present(self, volume_name):
        return self.vg.get_volume(volume_name) is None

    def _delete_volume(self, volume, is_snapshot=False):
        """Deletes a logical volume."""

        # zero out old volumes to prevent data leaking between users
        # TODO(ja): reclaiming space should be done lazy and low priority
        self.clear_volume(volume, is_snapshot)
        name = volume['name']
        if is_snapshot:
            name = self._escape_snapshot(volume['name'])
        self.vg.delete(name)

    def _escape_snapshot(self, snapshot_name):
        # Linux LVM reserves name that starts with snapshot, so that
        # such volume name can't be created. Mangle it.
        if not snapshot_name.startswith('snapshot'):
            return snapshot_name
        return '_' + snapshot_name

    def _create_volume(self, name, size, lvm_type, mirror_count, vg=None):
        vg_ref = self.vg
        if vg is not None:
            vg_ref = vg

        vg_ref.create_volume(name, size, lvm_type, mirror_count)

    def create_volume(self, volume):
        """Creates a logical volume."""
        mirror_count = 0
        if self.configuration.lvm_mirrors:
            mirror_count = self.configuration.lvm_mirrors

        self._create_volume(volume['name'],
                            self._sizestr(volume['size']),
                            self.configuration.lvm_type,
                            mirror_count)

    def create_volume_from_snapshot(self, volume, snapshot):
        """Creates a volume from a snapshot."""
        self._create_volume(volume['name'],
                            self._sizestr(volume['size']),
                            self.configuration.lvm_type,
                            self.configuration.lvm_mirrors)

        # Some configurations of LVM do not automatically activate
        # ThinLVM snapshot LVs.
        self.vg.activate_lv(snapshot['name'], is_snapshot=True)

        volutils.copy_volume(self.local_path(snapshot),
                             self.local_path(volume),
                             snapshot['volume_size'] * 1024,
                             execute=self._execute)

    def delete_volume(self, volume):
        """Deletes a logical volume."""

        # NOTE(jdg):  We don't need to explicitly call
        # remove export here because we already did it
        # in the manager before we got here.

        if self._volume_not_present(volume['name']):
            # If the volume isn't present, then don't attempt to delete
            return True

        if self.vg.lv_has_snapshot(volume['name']):
            LOG.error(_('Unabled to delete due to existing snapshot '
                        'for volume: %s') % volume['name'])
            raise exception.VolumeIsBusy(volume_name=volume['name'])

        self._delete_volume(volume)

    def clear_volume(self, volume, is_snapshot=False):
        """unprovision old volumes to prevent data leaking between users."""

        # NOTE(jdg): Don't write the blocks of thin provisioned
        # volumes
        if self.configuration.volume_clear == 'none' or \
                self.configuration.lvm_type == 'thin':
            return

        if is_snapshot:
            # if the volume to be cleared is a snapshot of another volume
            # we need to clear out the volume using the -cow instead of the
            # directly volume path.  We need to skip this if we are using
            # thin provisioned LVs.
            # bug# lp1191812
            dev_path = self.local_path(volume) + "-cow"
        else:
            dev_path = self.local_path(volume)

        if not os.path.exists(dev_path):
            msg = (_('Volume device file path %s does not exist.') % dev_path)
            LOG.error(msg)
            raise exception.VolumeBackendAPIException(data=msg)

        size_in_g = volume.get('size', volume.get('volume_size', None))
        if size_in_g is None:
            msg = (_("Size for volume: %s not found, "
                     "cannot secure delete.") % volume['id'])
            LOG.error(msg)
            raise exception.InvalidParameterValue(msg)
        size_in_m = self.configuration.volume_clear_size

        LOG.info(_("Performing secure delete on volume: %s") % volume['id'])

        if self.configuration.volume_clear == 'zero':
            if size_in_m == 0:
                return volutils.copy_volume('/dev/zero',
                                            dev_path, size_in_g * 1024,
                                            sync=True,
                                            execute=self._execute)
            else:
                clear_cmd = ['shred', '-n0', '-z', '-s%dMiB' % size_in_m]
        elif self.configuration.volume_clear == 'shred':
            clear_cmd = ['shred', '-n3']
            if size_in_m:
                clear_cmd.append('-s%dMiB' % size_in_m)
        else:
            raise exception.InvalidConfigurationValue(
                option='volume_clear',
                value=self.configuration.volume_clear)

        clear_cmd.append(dev_path)
        self._execute(*clear_cmd, run_as_root=True)

    def create_snapshot(self, snapshot):
        """Creates a snapshot."""

        self.vg.create_lv_snapshot(self._escape_snapshot(snapshot['name']),
                                   snapshot['volume_name'],
                                   self.configuration.lvm_type)

    def delete_snapshot(self, snapshot):
        """Deletes a snapshot."""
        if self._volume_not_present(self._escape_snapshot(snapshot['name'])):
            # If the snapshot isn't present, then don't attempt to delete
            LOG.warning(_("snapshot: %s not found, "
                          "skipping delete operations") % snapshot['name'])
            return True

        # TODO(yamahata): zeroing out the whole snapshot triggers COW.
        # it's quite slow.
        self._delete_volume(snapshot, is_snapshot=True)

    def local_path(self, volume, vg=None):
        if vg is None:
            vg = self.configuration.volume_group
        # NOTE(vish): stops deprecation warning
        escaped_group = vg.replace('-', '--')
        escaped_name = self._escape_snapshot(volume['name']).replace('-', '--')
        return "/dev/mapper/%s-%s" % (escaped_group, escaped_name)

    def copy_image_to_volume(self, context, volume, image_service, image_id):
        """Fetch the image from image_service and write it to the volume."""
        image_utils.fetch_to_raw(context,
                                 image_service,
                                 image_id,
                                 self.local_path(volume), size=volume['size'])

    def copy_volume_to_image(self, context, volume, image_service, image_meta):
        """Copy the volume to the specified image."""
        image_utils.upload_volume(context,
                                  image_service,
                                  image_meta,
                                  self.local_path(volume))

    def create_cloned_volume(self, volume, src_vref):
        """Creates a clone of the specified volume."""

        mirror_count = 0
        if self.configuration.lvm_mirrors:
            mirror_count = self.configuration.lvm_mirrors
        LOG.info(_('Creating clone of volume: %s') % src_vref['id'])
        volume_name = src_vref['name']
        temp_id = 'tmp-snap-%s' % volume['id']
        temp_snapshot = {'volume_name': volume_name,
                         'size': src_vref['size'],
                         'volume_size': src_vref['size'],
                         'name': 'clone-snap-%s' % volume['id'],
                         'id': temp_id}

        self.create_snapshot(temp_snapshot)
        self._create_volume(volume['name'],
                            self._sizestr(volume['size']),
                            self.configuration.lvm_type,
                            mirror_count)

        try:
            volutils.copy_volume(self.local_path(temp_snapshot),
                                 self.local_path(volume),
                                 src_vref['size'] * 1024,
                                 execute=self._execute)
        finally:
            self.delete_snapshot(temp_snapshot)

    def clone_image(self, volume, image_location, image_id):
        return None, False

    def backup_volume(self, context, backup, backup_service):
        """Create a new backup from an existing volume."""
        volume = self.db.volume_get(context, backup['volume_id'])
        volume_path = self.local_path(volume)
        with utils.temporary_chown(volume_path):
            with fileutils.file_open(volume_path) as volume_file:
                backup_service.backup(backup, volume_file)

    def restore_backup(self, context, backup, volume, backup_service):
        """Restore an existing backup to a new or existing volume."""
        volume_path = self.local_path(volume)
        with utils.temporary_chown(volume_path):
            with fileutils.file_open(volume_path, 'wb') as volume_file:
                backup_service.restore(backup, volume['id'], volume_file)

    def get_volume_stats(self, refresh=False):
        """Get volume status.

        If 'refresh' is True, run update the stats first.
        """

        if refresh:
            self._update_volume_stats()

        return self._stats

    def _update_volume_stats(self):
        """Retrieve stats info from volume group."""

        LOG.debug(_("Updating volume stats"))
        if self.vg is None:
            LOG.warning(_('Unable to update stats on non-intialized '
                          'Volume Group: %s'), self.configuration.volume_group)
            return

        self.vg.update_volume_group_info()
        data = {}

        # Note(zhiteng): These information are driver/backend specific,
        # each driver may define these values in its own config options
        # or fetch from driver specific configuration file.
        data["volume_backend_name"] = self.backend_name
        data["vendor_name"] = 'Open Source'
        data["driver_version"] = self.VERSION
        data["storage_protocol"] = self.protocol

        data['total_capacity_gb'] = float(self.vg.vg_size)
        data['free_capacity_gb'] = float(self.vg.vg_free_space)
        data['reserved_percentage'] = self.configuration.reserved_percentage
        data['QoS_support'] = False
        data['location_info'] =\
            ('LVMVolumeDriver:%(hostname)s:%(vg)s'
             ':%(lvm_type)s:%(lvm_mirrors)s' %
             {'hostname': self.hostname,
              'vg': self.configuration.volume_group,
              'lvm_type': self.configuration.lvm_type,
              'lvm_mirrors': self.configuration.lvm_mirrors})

        self._stats = data

    def extend_volume(self, volume, new_size):
        """Extend an existing voumes size."""
        self.vg.extend_volume(volume['name'],
                              self._sizestr(new_size))


class LVMISCSIDriver(LVMVolumeDriver, driver.ISCSIDriver):
    """Executes commands relating to ISCSI volumes.

    We make use of model provider properties as follows:

    ``provider_location``
      if present, contains the iSCSI target information in the same
      format as an ietadm discovery
      i.e. '<ip>:<port>,<portal> <target IQN>'

    ``provider_auth``
      if present, contains a space-separated triple:
      '<auth method> <auth username> <auth password>'.
      `CHAP` is the only auth_method in use at the moment.
    """

    def __init__(self, *args, **kwargs):
        self.tgtadm = self.get_target_admin()
        super(LVMISCSIDriver, self).__init__(*args, **kwargs)
        self.backend_name =\
            self.configuration.safe_get('volume_backend_name') or 'LVM_iSCSI'
        self.protocol = 'iSCSI'

    def set_execute(self, execute):
        super(LVMISCSIDriver, self).set_execute(execute)
        self.tgtadm.set_execute(execute)

    def _create_tgtadm_target(self, iscsi_name, iscsi_target,
                              volume_path, chap_auth, lun=0,
                              check_exit_code=False, old_name=None):
        # NOTE(jdg): tgt driver has an issue where with a lot of activity
        # (or sometimes just randomly) it will get *confused* and attempt
        # to reuse a target ID, resulting in a target already exists error
        # Typically a simple retry will address this

        # For now we have this while loop, might be useful in the
        # future to throw a retry decorator in common or utils
        attempts = 2
        while attempts > 0:
            attempts -= 1
            try:
                # NOTE(jdg): For TgtAdm case iscsi_name is all we need
                # should clean this all up at some point in the future
                tid = self.tgtadm.create_iscsi_target(
                    iscsi_name,
                    iscsi_target,
                    0,
                    volume_path,
                    chap_auth,
                    check_exit_code=check_exit_code,
                    old_name=old_name)
                break

            except brick_exception.ISCSITargetCreateFailed:
                if attempts == 0:
                    raise
                else:
                    LOG.warning(_('Error creating iSCSI target, retrying '
                                  'creation for target: %s') % iscsi_name)
        return tid

    def ensure_export(self, context, volume):
        """Synchronously recreates an export for a logical volume."""
        # NOTE(jdg): tgtadm doesn't use the iscsi_targets table
        # TODO(jdg): In the future move all of the dependent stuff into the
        # cooresponding target admin class

        if isinstance(self.tgtadm, iscsi.LioAdm):
            try:
                volume_info = self.db.volume_get(context, volume['id'])
                (auth_method,
                 auth_user,
                 auth_pass) = volume_info['provider_auth'].split(' ', 3)
                chap_auth = self._iscsi_authentication(auth_method,
                                                       auth_user,
                                                       auth_pass)
            except exception.NotFound:
                LOG.debug(_("volume_info:%s"), volume_info)
                LOG.info(_("Skipping ensure_export. No iscsi_target "
                           "provision for volume: %s"), volume['id'])
                return

            iscsi_name = "%s%s" % (self.configuration.iscsi_target_prefix,
                                   volume['name'])
            volume_path = "/dev/%s/%s" % (self.configuration.volume_group,
                                          volume['name'])
            iscsi_target = 1

            self._create_tgtadm_target(iscsi_name, iscsi_target,
                                       volume_path, chap_auth)

            return

        if not isinstance(self.tgtadm, iscsi.TgtAdm):
            try:
                iscsi_target = self.db.volume_get_iscsi_target_num(
                    context,
                    volume['id'])
            except exception.NotFound:
                LOG.info(_("Skipping ensure_export. No iscsi_target "
                           "provisioned for volume: %s"), volume['id'])
                return
        else:
            iscsi_target = 1  # dummy value when using TgtAdm

        chap_auth = None

        # Check for https://bugs.launchpad.net/cinder/+bug/1065702
        old_name = None
        volume_name = volume['name']
        if (volume['provider_location'] is not None and
                volume['name'] not in volume['provider_location']):

            msg = _('Detected inconsistency in provider_location id')
            LOG.debug(_('%s'), msg)
            old_name = self._fix_id_migration(context, volume)
            if 'in-use' in volume['status']:
                volume_name = old_name
                old_name = None

        iscsi_name = "%s%s" % (self.configuration.iscsi_target_prefix,
                               volume_name)
        volume_path = "/dev/%s/%s" % (self.configuration.volume_group,
                                      volume_name)

        # NOTE(jdg): For TgtAdm case iscsi_name is the ONLY param we need
        # should clean this all up at some point in the future
        self._create_tgtadm_target(iscsi_name, iscsi_target,
                                   volume_path, chap_auth,
                                   lun=0,
                                   check_exit_code=False,
                                   old_name=old_name)

        return

    def _fix_id_migration(self, context, volume):
        """Fix provider_location and dev files to address bug 1065702.

        For volumes that the provider_location has NOT been updated
        and are not currently in-use we'll create a new iscsi target
        and remove the persist file.

        If the volume is in-use, we'll just stick with the old name
        and when detach is called we'll feed back into ensure_export
        again if necessary and fix things up then.

        Details at: https://bugs.launchpad.net/cinder/+bug/1065702
        """

        model_update = {}
        pattern = re.compile(r":|\s")
        fields = pattern.split(volume['provider_location'])
        old_name = fields[3]

        volume['provider_location'] = \
            volume['provider_location'].replace(old_name, volume['name'])
        model_update['provider_location'] = volume['provider_location']

        self.db.volume_update(context, volume['id'], model_update)

        start = os.getcwd()
        os.chdir('/dev/%s' % self.configuration.volume_group)

        try:
            (out, err) = self._execute('readlink', old_name)
        except processutils.ProcessExecutionError:
            link_path = '/dev/%s/%s' % (self.configuration.volume_group,
                                        old_name)
            LOG.debug(_('Symbolic link %s not found') % link_path)
            os.chdir(start)
            return

        rel_path = out.rstrip()
        self._execute('ln',
                      '-s',
                      rel_path, volume['name'],
                      run_as_root=True)
        os.chdir(start)
        return old_name

    def _ensure_iscsi_targets(self, context, host):
        """Ensure that target ids have been created in datastore."""
        # NOTE(jdg): tgtadm doesn't use the iscsi_targets table
        # TODO(jdg): In the future move all of the dependent stuff into the
        # cooresponding target admin class
        if not isinstance(self.tgtadm, iscsi.TgtAdm):
            host_iscsi_targets = self.db.iscsi_target_count_by_host(context,
                                                                    host)
            if host_iscsi_targets >= self.configuration.iscsi_num_targets:
                return

            # NOTE(vish): Target ids start at 1, not 0.
            target_end = self.configuration.iscsi_num_targets + 1
            for target_num in xrange(1, target_end):
                target = {'host': host, 'target_num': target_num}
                self.db.iscsi_target_create_safe(context, target)

    def create_export(self, context, volume):
        return self._create_export(context, volume)

    def _create_export(self, context, volume, vg=None):
        """Creates an export for a logical volume."""
        if vg is None:
            vg = self.configuration.volume_group

        iscsi_name = "%s%s" % (self.configuration.iscsi_target_prefix,
                               volume['name'])
        volume_path = "/dev/%s/%s" % (vg, volume['name'])
        model_update = {}

        # TODO(jdg): In the future move all of the dependent stuff into the
        # cooresponding target admin class
        if not isinstance(self.tgtadm, iscsi.TgtAdm):
            lun = 0
            self._ensure_iscsi_targets(context, volume['host'])
            iscsi_target = self.db.volume_allocate_iscsi_target(context,
                                                                volume['id'],
                                                                volume['host'])
        else:
            lun = 1  # For tgtadm the controller is lun 0, dev starts at lun 1
            iscsi_target = 0  # NOTE(jdg): Not used by tgtadm

        # Use the same method to generate the username and the password.
        chap_username = utils.generate_username()
        chap_password = utils.generate_password()
        chap_auth = self._iscsi_authentication('IncomingUser', chap_username,
                                               chap_password)

        tid = self._create_tgtadm_target(iscsi_name, iscsi_target,
                                         volume_path, chap_auth)

        model_update['provider_location'] = self._iscsi_location(
            self.configuration.iscsi_ip_address, tid, iscsi_name, lun)
        model_update['provider_auth'] = self._iscsi_authentication(
            'CHAP', chap_username, chap_password)
        return model_update

    def remove_export(self, context, volume):
        """Removes an export for a logical volume."""
        # NOTE(jdg): tgtadm doesn't use the iscsi_targets table
        # TODO(jdg): In the future move all of the dependent stuff into the
        # cooresponding target admin class

        if isinstance(self.tgtadm, iscsi.LioAdm):
            try:
                iscsi_target = self.db.volume_get_iscsi_target_num(
                    context,
                    volume['id'])
            except exception.NotFound:
                LOG.info(_("Skipping remove_export. No iscsi_target "
                           "provisioned for volume: %s"), volume['id'])
                return

            self.tgtadm.remove_iscsi_target(iscsi_target, 0, volume['id'],
                                            volume['name'])

            return

        elif not isinstance(self.tgtadm, iscsi.TgtAdm):
            try:
                iscsi_target = self.db.volume_get_iscsi_target_num(
                    context,
                    volume['id'])
            except exception.NotFound:
                LOG.info(_("Skipping remove_export. No iscsi_target "
                           "provisioned for volume: %s"), volume['id'])
                return
        else:
            iscsi_target = 0

        try:

            # NOTE: provider_location may be unset if the volume hasn't
            # been exported
            location = volume['provider_location'].split(' ')
            iqn = location[1]

            # ietadm show will exit with an error
            # this export has already been removed
            self.tgtadm.show_target(iscsi_target, iqn=iqn)

        except Exception:
            LOG.info(_("Skipping remove_export. No iscsi_target "
                       "is presently exported for volume: %s"), volume['id'])
            return

        self.tgtadm.remove_iscsi_target(iscsi_target, 0, volume['name_id'],
                                        volume['name'])

    def migrate_volume(self, ctxt, volume, host, thin=False, mirror_count=0):
        """Optimize the migration if the destination is on the same server.

        If the specified host is another back-end on the same server, and
        the volume is not attached, we can do the migration locally without
        going through iSCSI.
        """

        false_ret = (False, None)
        if volume['status'] != 'available':
            return false_ret
        if 'location_info' not in host['capabilities']:
            return false_ret
        info = host['capabilities']['location_info']
        try:
            (dest_type, dest_hostname, dest_vg, lvm_type, lvm_mirrors) =\
                info.split(':')
        except ValueError:
            return false_ret
        if (dest_type != 'LVMVolumeDriver' or dest_hostname != self.hostname):
            return false_ret

        if dest_vg != self.vg.vg_name:
            vg_list = volutils.get_all_volume_groups()
            vg_dict = \
                (vg for vg in vg_list if vg['name'] == self.vg.vg_name).next()
            if vg_dict is None:
                message = ("Destination Volume Group %s does not exist" %
                           dest_vg)
                LOG.error(_('%s'), message)
                return false_ret

            helper = utils.get_root_helper()
            dest_vg_ref = lvm.LVM(dest_vg, helper,
                                  lvm_type=lvm_type,
                                  executor=self._execute)
            self.remove_export(ctxt, volume)
            self._create_volume(volume['name'],
                                self._sizestr(volume['size']),
                                lvm_type,
                                lvm_mirrors,
                                dest_vg_ref)

        volutils.copy_volume(self.local_path(volume),
                             self.local_path(volume, vg=dest_vg),
                             volume['size'],
                             execute=self._execute)
        self._delete_volume(volume)
        model_update = self._create_export(ctxt, volume, vg=dest_vg)

        return (True, model_update)

    def _iscsi_location(self, ip, target, iqn, lun=None):
        return "%s:%s,%s %s %s" % (ip, self.configuration.iscsi_port,
                                   target, iqn, lun)

    def _iscsi_authentication(self, chap, name, password):
        return "%s %s %s" % (chap, name, password)


class LVMISERDriver(LVMISCSIDriver, driver.ISERDriver):
    """Executes commands relating to ISER volumes.

    We make use of model provider properties as follows:

    ``provider_location``
      if present, contains the iSER target information in the same
      format as an ietadm discovery
      i.e. '<ip>:<port>,<portal> <target IQN>'

    ``provider_auth``
      if present, contains a space-separated triple:
      '<auth method> <auth username> <auth password>'.
      `CHAP` is the only auth_method in use at the moment.
    """

    def __init__(self, *args, **kwargs):
        self.tgtadm = self.get_target_admin()
        LVMVolumeDriver.__init__(self, *args, **kwargs)
        self.backend_name =\
            self.configuration.safe_get('volume_backend_name') or 'LVM_iSER'
        self.protocol = 'iSER'