# Copyright 2015 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""This module provides some utilities used by LXC and its tools.
"""

import netifaces

import common
from autotest_lib.client.bin import utils
from autotest_lib.client.common_lib import error


def path_exists(path):
    """Check if path exists.

    If the process is not running with root user, os.path.exists may fail to
    check if a path owned by root user exists. This function uses command
    `test -e` to check if path exists.

    @param path: Path to check if it exists.

    @return: True if path exists, otherwise False.
    """
    try:
        utils.run('sudo test -e "%s"' % path)
        return True
    except error.CmdError:
        return False


def get_host_ip():
    """Get the IP address of the host running containers on lxcbr*.

    This function gets the IP address on network interface lxcbr*. The
    assumption is that lxc uses the network interface started with "lxcbr".

    @return: IP address of the host running containers.
    """
    lxc_network = None
    for name in netifaces.interfaces():
        if name.startswith('lxcbr'):
            lxc_network = name
            break
    if not lxc_network:
        raise error.ContainerError('Failed to find network interface used by '
                                   'lxc. All existing interfaces are: %s' %
                                   netifaces.interfaces())
    return netifaces.ifaddresses(lxc_network)[netifaces.AF_INET][0]['addr']