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#
#    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.

"""Serial consoles module."""

import socket

from oslo.config import cfg
import six.moves

from nova import exception
from nova.i18n import _LW
from nova.openstack.common import log as logging
from nova import utils

LOG = logging.getLogger(__name__)

ALLOCATED_PORTS = set()  # in-memory set of already allocated ports
SERIAL_LOCK = 'serial-lock'
DEFAULT_PORT_RANGE = '10000:20000'

serial_opts = [
    cfg.BoolOpt('enabled',
                default=False,
                help='Enable serial console related features'),
    cfg.StrOpt('port_range',
                default=DEFAULT_PORT_RANGE,
                help='Range of TCP ports to use for serial ports '
                     'on compute hosts'),
    cfg.StrOpt('base_url',
               default='ws://127.0.0.1:6083/',
               help='Location of serial console proxy.'),
    cfg.StrOpt('listen',
               default='127.0.0.1',
               help=('IP address on which instance serial console '
                     'should listen')),
    cfg.StrOpt('proxyclient_address',
               default='127.0.0.1',
               help=('The address to which proxy clients '
                     '(like nova-serialproxy) should connect')),
    ]

CONF = cfg.CONF
CONF.register_opts(serial_opts, group='serial_console')

# TODO(sahid): Add a method to initialize ALOCATED_PORTS with the
# already binded TPC port(s). (cf from danpb: list all running guests and
# query the XML in libvirt driver to find out the TCP port(s) it uses).


@utils.synchronized(SERIAL_LOCK)
def acquire_port(host):
    """Returns a free TCP port on host.

    Find and returns a free TCP port on 'host' in the range
    of 'CONF.serial_console.port_range'.
    """

    start, stop = _get_port_range()

    for port in six.moves.range(start, stop):
        if (host, port) in ALLOCATED_PORTS:
            continue
        try:
            _verify_port(host, port)
            ALLOCATED_PORTS.add((host, port))
            return port
        except exception.SocketPortInUseException as e:
            LOG.warn(e)

    raise exception.SocketPortRangeExhaustedException(host=host)


@utils.synchronized(SERIAL_LOCK)
def release_port(host, port):
    """Release TCP port to be used next time."""
    ALLOCATED_PORTS.discard((host, port))


def _get_port_range():
    config_range = CONF.serial_console.port_range
    try:
        start, stop = map(int, config_range.split(':'))
        if start >= stop:
            raise ValueError
    except ValueError:
        LOG.warn(_LW("serial_console.port_range should be <num>:<num>. "
                     "Given value %(port_range)s could not be parsed. "
                     "Taking the default port range %(default)s."),
                 {'port_range': config_range,
                  'default': DEFAULT_PORT_RANGE})
        start, stop = map(int, DEFAULT_PORT_RANGE.split(':'))
    return start, stop


def _verify_port(host, port):
    s = socket.socket()
    try:
        s.bind((host, port))
    except socket.error as e:
        raise exception.SocketPortInUseException(
            host=host, port=port, error=e)
    finally:
        s.close()