path: root/python/vyos/ifconfig.py

# Copyright 2019 VyOS maintainers and contributors <maintainers@vyos.io>
#
# This library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.
#
# This library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public
# License along with this library.  If not, see <http://www.gnu.org/licenses/>.

import os
import re
import jinja2

from vyos.validate import *
from ipaddress import IPv4Network, IPv6Address
from netifaces import ifaddresses, AF_INET, AF_INET6
from subprocess import Popen, PIPE, STDOUT
from time import sleep

dhcp_cfg = """
# generated by ifconfig.py
option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;
interface "{{ intf }}" {
    send host-name "{{ hostname }}";
    request subnet-mask, broadcast-address, routers, domain-name-servers, rfc3442-classless-static-routes, domain-name, interface-mtu;
}
"""

dhcpv6_cfg = """
# generated by ifconfig.py
interface "{{ intf }}" {
    request routers, domain-name-servers, domain-name;
}
"""

dhclient_base = r'/var/lib/dhcp/dhclient_'


class Interface:
    def __init__(self, ifname, type=None):
        """
        This is the base interface class which supports basic IP/MAC address
        operations as well as DHCP(v6). Other interface which represent e.g.
        and ethernet bridge are implemented as derived classes adding all
        additional functionality.

        DEBUG:
        This class has embedded debugging (print) which can be enabled by
        creating the following file:
        vyos@vyos# touch /tmp/vyos.ifconfig.debug

        Example:
        >>> from vyos.ifconfig import Interface
        >>> i = Interface('eth0')
        """
        self._ifname = str(ifname)
        self._state = 'down'

        if not os.path.exists('/sys/class/net/{}'.format(ifname)) and not type:
            raise Exception('interface "{}" not found'.format(self._ifname))

        if not os.path.exists('/sys/class/net/{}'.format(self._ifname)):
            cmd = 'ip link add dev {} type {}'.format(self._ifname, type)
            self._cmd(cmd)

        # per interface DHCP config files
        self._dhcp_cfg_file = dhclient_base + self._ifname + '.conf'
        self._dhcp_pid_file = dhclient_base + self._ifname + '.pid'
        self._dhcp_lease_file = dhclient_base + self._ifname + '.leases'

        # per interface DHCPv6 config files
        self._dhcpv6_cfg_file = dhclient_base + self._ifname + '.v6conf'
        self._dhcpv6_pid_file = dhclient_base + self._ifname + '.v6pid'
        self._dhcpv6_lease_file = dhclient_base + self._ifname + '.v6leases'

    def _debug_msg(self, msg):
        if os.path.isfile('/tmp/vyos.ifconfig.debug'):
            print('DEBUG/{:<6} {}'.format(self._ifname, msg))

    def _cmd(self, command):
        p = Popen(command, stdout=PIPE, stderr=STDOUT, shell=True)
        tmp = p.communicate()[0].strip()
        self._debug_msg("cmd '{}'".format(command))
        if tmp.decode():
            self._debug_msg("returned:\n{}".format(tmp.decode()))

        # do we need some error checking code here?
        return tmp

    def _read_sysfs(self, filename):
        """
        Provide a single primitive w/ error checking for reading from sysfs.
        """
        value = None
        with open(filename, 'r') as f:
            value = f.read().rstrip('\n')

        self._debug_msg("read '{}' < '{}'".format(value, filename))
        return value

    def _write_sysfs(self, filename, value):
        """
        Provide a single primitive w/ error checking for writing to sysfs.
        """
        self._debug_msg("write '{}' > '{}'".format(value, filename))
        with open(filename, 'w') as f:
            f.write(str(value))

        return None

    def remove(self):
        """
        Remove interface from operating system. Removing the interface
        deconfigures all assigned IP addresses and clear possible DHCP(v6)
        client processes.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> i = Interface('eth0')
        >>> i.remove()
        """

        # do we have sub interfaces (VLANs)?
        # we apply a regex matching subinterfaces (indicated by a .) of a
        # parent interface. 'bond0(?:\.\d+){1,2}' will match vif and vif-s/vif-c
        # subinterfaces
        vlan_ifs = [f for f in os.listdir(r'/sys/class/net') \
                       if re.match(self._ifname + r'(?:\.\d+){1,2}', f)]

        for vlan in vlan_ifs:
            Interface(vlan).remove()

        # All subinterfaces are now removed, continue on the physical interface

        # stop DHCP(v6) if running
        self._del_dhcp()
        self._del_dhcpv6()

        # NOTE (Improvement):
        # after interface removal no other commands should be allowed
        # to be called and instead should raise an Exception:
        cmd = 'ip link del dev {}'.format(self._ifname)
        self._cmd(cmd)

    @property
    def mtu(self):
        """
        Get/set interface mtu in bytes.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').mtu
        '1500'
        """
        return self._read_sysfs('/sys/class/net/{0}/mtu'
                                .format(self._ifname))

    @mtu.setter
    def mtu(self, mtu):
        """
        Get/set interface mtu in bytes.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').mtu = 1400
        >>> Interface('eth0').mtu
        '1400'
        """
        if mtu < 68 or mtu > 9000:
            raise ValueError('Invalid MTU size: "{}"'.format(mru))

        return self._write_sysfs('/sys/class/net/{0}/mtu'
                                 .format(self._ifname), mtu)

    @property
    def mac(self):
        """
        Get/set interface mac address

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').mac
        '00:0c:29:11:aa:cc'
        """
        return self._read_sysfs('/sys/class/net/{0}/address'
                                .format(self._ifname))

    @mac.setter
    def mac(self, mac):
        """
        Get/set interface mac address

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').mac = '00:90:43:fe:fe:1b'
        >>> Interface('eth0').mac
        '00:90:43:fe:fe:1b'
        """
        # on interface removal (ethernet) an empty string is passed - ignore it
        if not mac:
            return None

        # a mac address consits out of 6 octets
        octets = len(mac.split(':'))
        if octets != 6:
            raise ValueError('wrong number of MAC octets: {} '.format(octets))

        # validate against the first mac address byte if it's a multicast
        # address
        if int(mac.split(':')[0]) & 1:
            raise ValueError('{} is a multicast MAC address'.format(mac))

        # overall mac address is not allowed to be 00:00:00:00:00:00
        if sum(int(i, 16) for i in mac.split(':')) == 0:
            raise ValueError('00:00:00:00:00:00 is not a valid MAC address')

        # check for VRRP mac address
        if mac.split(':')[0] == '0' and addr.split(':')[1] == '0' and mac.split(':')[2] == '94' and mac.split(':')[3] == '0' and mac.split(':')[4] == '1':
            raise ValueError('{} is a VRRP MAC address'.format(mac))

        # Assemble command executed on system. Unfortunately there is no way
        # of altering the MAC address via sysfs
        cmd = 'ip link set dev {} address {}'.format(self._ifname, mac)
        self._cmd(cmd)

    @property
    def arp_cache_tmo(self):
        """
        Get configured ARP cache timeout value from interface in seconds.
        Internal Kernel representation is in milliseconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').arp_cache_tmo
        '30'
        """
        return (self._read_sysfs('/proc/sys/net/ipv4/neigh/{0}/base_reachable_time_ms'
                                 .format(self._ifname)) / 1000)

    @arp_cache_tmo.setter
    def arp_cache_tmo(self, tmo):
        """
        Set ARP cache timeout value in seconds. Internal Kernel representation
        is in milliseconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').arp_cache_tmo = '40'
        """
        return self._write_sysfs('/proc/sys/net/ipv4/neigh/{0}/base_reachable_time_ms'
                                 .format(self._ifname), (int(tmo) * 1000))

    @property
    def link_detect(self):
        """
        How does the kernel act when receiving packets on 'down' interfaces

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').link_detect
        '0'
        """
        return self._read_sysfs('/proc/sys/net/ipv4/conf/{0}/link_filter'
                                .format(self._ifname))

    @link_detect.setter
    def link_detect(self, link_filter):
        """
        Konfigure kernel response in packets received on interfaces that are 'down'

        0 - Allow packets to be received for the address on this interface
            even if interface is disabled or no carrier.

        1 - Ignore packets received if interface associated with the incoming
            address is down.

        2 - Ignore packets received if interface associated with the incoming
            address is down or has no carrier.

        Default value is 0. Note that some distributions enable it in startup
        scripts.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').link_detect = '1'
        """
        if link_filter >= 0 and link_filter <= 2:
            return self._write_sysfs('/proc/sys/net/ipv4/conf/{0}/link_filter'
                                     .format(self._ifname), link_filter)
        else:
            raise ValueError("Value out of range")

    @property
    def ifalias(self):
        """
        Get/set interface alias name

        Example:

        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').ifalias
        ''
        """
        return self._read_sysfs('/sys/class/net/{0}/ifalias'
                                .format(self._ifname))

    @ifalias.setter
    def ifalias(self, ifalias=None):
        """
        Get/set interface alias name

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').ifalias = 'VyOS upstream interface'
        >>> Interface('eth0').ifalias
        'VyOS upstream interface'

        to clear interface alias e.g. delete it use:

        >>> Interface('eth0').ifalias = ''
        >>> Interface('eth0').ifalias
        ''
        """
        if not ifalias:
            # clear interface alias
            ifalias = '\0'

        self._write_sysfs('/sys/class/net/{0}/ifalias'
                          .format(self._ifname), ifalias)

    @property
    def state(self):
        """
        Enable (up) / Disable (down) an interface

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').state
        'up'
        """
        return self._read_sysfs('/sys/class/net/{0}/operstate'
                                .format(self._ifname))

    @state.setter
    def state(self, state):
        """
        Enable (up) / Disable (down) an interface

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').state = 'down'
        >>> Interface('eth0').state
        'down'
        """
        if state not in ['up', 'down']:
            raise ValueError('state must be "up" or "down"')

        self._state = state

        # Assemble command executed on system. Unfortunately there is no way
        # to up/down an interface via sysfs
        cmd = 'ip link set dev {} {}'.format(self._ifname, state)
        self._cmd(cmd)

    @property
    def proxy_arp(self):
        """
        Get current proxy ARP configuration from sysfs. Default: 0

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').proxy_arp
        '0'
        """
        return self._read_sysfs('/proc/sys/net/ipv4/conf/{}/proxy_arp'
                                .format(self._ifname))

    @proxy_arp.setter
    def proxy_arp(self, enable):
        """
        Set per interface proxy ARP configuration

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').proxy_arp = 1
        >>> Interface('eth0').proxy_arp
        '1'
        """
        if int(enable) >= 0 and int(enable) <= 1:
            return self._write_sysfs('/proc/sys/net/ipv4/conf/{}/proxy_arp'
                                     .format(self._ifname), enable)
        else:
            raise ValueError("Value out of range")

    @property
    def proxy_arp_pvlan(self):
        """
        Private VLAN proxy arp.
        Basically allow proxy arp replies back to the same interface
        (from which the ARP request/solicitation was received).

        This is done to support (ethernet) switch features, like RFC
        3069, where the individual ports are NOT allowed to
        communicate with each other, but they are allowed to talk to
        the upstream router.  As described in RFC 3069, it is possible
        to allow these hosts to communicate through the upstream
        router by proxy_arp'ing. Don't need to be used together with
        proxy_arp.

        This technology is known by different names:
        In RFC 3069 it is called VLAN Aggregation.
        Cisco and Allied Telesyn call it Private VLAN.
        Hewlett-Packard call it Source-Port filtering or port-isolation.
        Ericsson call it MAC-Forced Forwarding (RFC Draft).

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').proxy_arp_pvlan
        '0'
        """
        return self._read_sysfs('/proc/sys/net/ipv4/conf/{}/proxy_arp_pvlan'
                                .format(self._ifname))

    @proxy_arp_pvlan.setter
    def proxy_arp_pvlan(self, enable):
        """
        Private VLAN proxy arp.
        Basically allow proxy arp replies back to the same interface
        (from which the ARP request/solicitation was received).

        This is done to support (ethernet) switch features, like RFC
        3069, where the individual ports are NOT allowed to
        communicate with each other, but they are allowed to talk to
        the upstream router.  As described in RFC 3069, it is possible
        to allow these hosts to communicate through the upstream
        router by proxy_arp'ing. Don't need to be used together with
        proxy_arp.

        This technology is known by different names:
        In RFC 3069 it is called VLAN Aggregation.
        Cisco and Allied Telesyn call it Private VLAN.
        Hewlett-Packard call it Source-Port filtering or port-isolation.
        Ericsson call it MAC-Forced Forwarding (RFC Draft).

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').proxy_arp_pvlan = 1
        >>> Interface('eth0').proxy_arp_pvlan
        '1'
        """
        if int(enable) >= 0 and int(enable) <= 1:
            return self._write_sysfs('/proc/sys/net/ipv4/conf/{}/proxy_arp_pvlan'
                                     .format(self._ifname), enable)
        else:
            raise ValueError("Value out of range")

    def get_addr(self):
        """
        Retrieve assigned IPv4 and IPv6 addresses from given interface.
        This is done using the netifaces and ipaddress python modules.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').get_addrs()
        ['172.16.33.30/24', 'fe80::20c:29ff:fe11:a174/64']
        """

        ipv4 = []
        ipv6 = []

        if AF_INET in ifaddresses(self._ifname).keys():
            for v4_addr in ifaddresses(self._ifname)[AF_INET]:
                # we need to manually assemble a list of IPv4 address/prefix
                prefix = '/' + \
                    str(IPv4Network('0.0.0.0/' + v4_addr['netmask']).prefixlen)
                ipv4.append(v4_addr['addr'] + prefix)

        if AF_INET6 in ifaddresses(self._ifname).keys():
            for v6_addr in ifaddresses(self._ifname)[AF_INET6]:
                # Note that currently expanded netmasks are not supported. That means
                # 2001:db00::0/24 is a valid argument while 2001:db00::0/ffff:ff00:: not.
                # see https://docs.python.org/3/library/ipaddress.html
                bits = bin(
                    int(v6_addr['netmask'].replace(':', ''), 16)).count('1')
                prefix = '/' + str(bits)

                # we alsoneed to remove the interface suffix on link local
                # addresses
                v6_addr['addr'] = v6_addr['addr'].split('%')[0]
                ipv6.append(v6_addr['addr'] + prefix)

        return ipv4 + ipv6

    def add_addr(self, addr):
        """
        Add IP(v6) address to interface. Address is only added if it is not
        already assigned to that interface.

        addr: can be an IPv4 address, IPv6 address, dhcp or dhcpv6!
              IPv4: add IPv4 address to interface
              IPv6: add IPv6 address to interface
              dhcp: start dhclient (IPv4) on interface
              dhcpv6: start dhclient (IPv6) on interface

        Example:
        >>> from vyos.ifconfig import Interface
        >>> j = Interface('eth0')
        >>> j.add_addr('192.0.2.1/24')
        >>> j.add_addr('2001:db8::ffff/64')
        >>> j.get_addr()
        ['192.0.2.1/24', '2001:db8::ffff/64']
        """
        if addr == 'dhcp':
            self._set_dhcp()
        elif addr == 'dhcpv6':
            self._set_dhcpv6()
        else:
            if not is_intf_addr_assigned(self._ifname, addr):
                cmd = 'ip addr add "{}" dev "{}"'.format(addr, self._ifname)
                self._cmd(cmd)

    def del_addr(self, addr):
        """
        Delete IP(v6) address to interface. Address is only added if it is
        assigned to that interface.

        addr: can be an IPv4 address, IPv6 address, dhcp or dhcpv6!
              IPv4: delete IPv4 address from interface
              IPv6: delete IPv6 address from interface
              dhcp: stop dhclient (IPv4) on interface
              dhcpv6: stop dhclient (IPv6) on interface

        Example:
        >>> from vyos.ifconfig import Interface
        >>> j = Interface('eth0')
        >>> j.add_addr('2001:db8::ffff/64')
        >>> j.add_addr('192.0.2.1/24')
        >>> j.get_addr()
        ['192.0.2.1/24', '2001:db8::ffff/64']
        >>> j.del_addr('192.0.2.1/24')
        >>> j.get_addr()
        ['2001:db8::ffff/64']
        """
        if addr == 'dhcp':
            self._del_dhcp()
        elif addr == 'dhcpv6':
            self._del_dhcpv6()
        else:
            if is_intf_addr_assigned(self._ifname, addr):
                cmd = 'ip addr del "{}" dev "{}"'.format(addr, self._ifname)
                self._cmd(cmd)

    # replace dhcpv4/v6 with systemd.networkd?
    def _set_dhcp(self):
        """
        Configure interface as DHCP client. The dhclient binary is automatically
        started in background!

        Example:

        >>> from vyos.ifconfig import Interface
        >>> j = Interface('eth0')
        >>> j.set_dhcp()
        """
        dhcp = {
            'hostname': 'vyos',
            'intf': self._ifname
        }

        # read configured system hostname.
        # maybe change to vyos hostd client ???
        with open('/etc/hostname', 'r') as f:
            dhcp['hostname'] = f.read().rstrip('\n')

        # render DHCP configuration
        tmpl = jinja2.Template(dhcp_cfg)
        dhcp_text = tmpl.render(dhcp)
        with open(self._dhcp_cfg_file, 'w') as f:
            f.write(dhcp_text)

        if self._state == 'up':
            cmd  = 'start-stop-daemon --start --quiet --pidfile ' + \
                self._dhcp_pid_file
            cmd += ' --exec /sbin/dhclient --'
            # now pass arguments to dhclient binary
            cmd += ' -4 -nw -cf {} -pf {} -lf {} {}'.format(
                self._dhcp_cfg_file, self._dhcp_pid_file, self._dhcp_lease_file, self._ifname)
            self._cmd(cmd)


    def _del_dhcp(self):
        """
        De-configure interface as DHCP clinet. All auto generated files like
        pid, config and lease will be removed.

        Example:

        >>> from vyos.ifconfig import Interface
        >>> j = Interface('eth0')
        >>> j.del_dhcp()
        """
        pid = 0
        if os.path.isfile(self._dhcp_pid_file):
            with open(self._dhcp_pid_file, 'r') as f:
                pid = int(f.read())
        else:
            self._debug_msg('No DHCP client PID found')
            return None

        # stop dhclient
        cmd = 'start-stop-daemon --stop --quiet --pidfile {}'.format(
            self._dhcp_pid_file)
        self._cmd(cmd)

        # cleanup old config file
        if os.path.isfile(self._dhcp_cfg_file):
            os.remove(self._dhcp_cfg_file)

        # cleanup old pid file
        if os.path.isfile(self._dhcp_pid_file):
            os.remove(self._dhcp_pid_file)

        # cleanup old lease file
        if os.path.isfile(self._dhcp_lease_file):
            os.remove(self._dhcp_lease_file)


    def _set_dhcpv6(self):
        """
        Configure interface as DHCPv6 client. The dhclient binary is automatically
        started in background!

        Example:

        >>> from vyos.ifconfig import Interface
        >>> j = Interface('eth0')
        >>> j.set_dhcpv6()
        """
        dhcpv6 = {
            'intf': self._ifname
        }

        # render DHCP configuration
        tmpl = jinja2.Template(dhcpv6_cfg)
        dhcpv6_text = tmpl.render(dhcpv6)
        with open(self._dhcpv6_cfg_file, 'w') as f:
            f.write(dhcpv6_text)

        if self._state == 'up':
            # https://bugs.launchpad.net/ubuntu/+source/ifupdown/+bug/1447715
            #
            # wee need to wait for IPv6 DAD to finish once and interface is added
            # this suxx :-(
            sleep(5)

            # no longer accept router announcements on this interface
            cmd = 'sysctl -q -w net.ipv6.conf.{}.accept_ra=0'.format(self._ifname)
            self._cmd(cmd)

            # assemble command-line to start DHCPv6 client (dhclient)
            cmd  = 'start-stop-daemon --start --quiet --pidfile ' + \
                self._dhcpv6_pid_file
            cmd += ' --exec /sbin/dhclient --'
            # now pass arguments to dhclient binary
            cmd += ' -6 -nw -cf {} -pf {} -lf {} {}'.format(
                self._dhcpv6_cfg_file, self._dhcpv6_pid_file, self._dhcpv6_lease_file, self._ifname)
            self._cmd(cmd)


    def _del_dhcpv6(self):
        """
        De-configure interface as DHCPv6 clinet. All auto generated files like
        pid, config and lease will be removed.

        Example:

        >>> from vyos.ifconfig import Interface
        >>> j = Interface('eth0')
        >>> j.del_dhcpv6()
        """
        pid = 0
        if os.path.isfile(self._dhcpv6_pid_file):
            with open(self._dhcpv6_pid_file, 'r') as f:
                pid = int(f.read())
        else:
            self._debug_msg('No DHCPv6 client PID found')
            return None

        # stop dhclient
        cmd = 'start-stop-daemon --stop --quiet --pidfile {}'.format(
            self._dhcpv6_pid_file)
        self._cmd(cmd)

        # accept router announcements on this interface
        cmd = 'sysctl -q -w net.ipv6.conf.{}.accept_ra=1'.format(self._ifname)
        self._cmd(cmd)

        # cleanup old config file
        if os.path.isfile(self._dhcpv6_cfg_file):
            os.remove(self._dhcpv6_cfg_file)

        # cleanup old pid file
        if os.path.isfile(self._dhcpv6_pid_file):
            os.remove(self._dhcpv6_pid_file)

        # cleanup old lease file
        if os.path.isfile(self._dhcpv6_lease_file):
            os.remove(self._dhcpv6_lease_file)


class LoopbackIf(Interface):

    """
    The loopback device is a special, virtual network interface that your router
    uses to communicate with itself.
    """

    def __init__(self, ifname):
        super().__init__(ifname, type='loopback')


class DummyIf(Interface):

    """
    A dummy interface is entirely virtual like, for example, the loopback
    interface. The purpose of a dummy interface is to provide a device to route
    packets through without actually transmitting them.
    """

    def __init__(self, ifname):
        super().__init__(ifname, type='dummy')


class BridgeIf(Interface):

    """
    A bridge is a way to connect two Ethernet segments together in a protocol
    independent way. Packets are forwarded based on Ethernet address, rather
    than IP address (like a router). Since forwarding is done at Layer 2, all
    protocols can go transparently through a bridge.

    The Linux bridge code implements a subset of the ANSI/IEEE 802.1d standard.
    """

    def __init__(self, ifname):
        super().__init__(ifname, type='bridge')

    @property
    def ageing_time(self):
        """
        Return configured bridge interface MAC address aging time in seconds.
        Internal kernel representation is in centiseconds, thus its converted
        in the end. Kernel default is 300 seconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').aging_time
        '300'
        """
        return (self._read_sysfs('/sys/class/net/{0}/bridge/ageing_time'
                                 .format(self._ifname)) / 100)

    @ageing_time.setter
    def ageing_time(self, time):
        """
        Set bridge interface MAC address aging time in seconds. Internal kernel
        representation is in centiseconds. Kernel default is 300 seconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').ageing_time = 2
        """
        time = int(time) * 100
        return self._write_sysfs('/sys/class/net/{0}/bridge/ageing_time'
                                 .format(self._ifname), time)

    @property
    def forward_delay(self):
        """
        Get bridge forwarding delay in seconds. Internal Kernel representation
        is in centiseconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').ageing_time
        '3'
        """
        return (self._read_sysfs('/sys/class/net/{0}/bridge/forward_delay'
                                 .format(self._ifname)) / 100)

    @forward_delay.setter
    def forward_delay(self, time):
        """
        Set bridge forwarding delay in seconds. Internal Kernel representation
        is in centiseconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').forward_delay = 15
        """
        return self._write_sysfs('/sys/class/net/{0}/bridge/forward_delay'
                                 .format(self._ifname), (int(time) * 100))

    @property
    def hello_time(self):
        """
        Get bridge hello time in seconds. Internal Kernel representation
        is in centiseconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').hello_time
        '2'
        """
        return (self._read_sysfs('/sys/class/net/{0}/bridge/hello_time'
                                 .format(self._ifname)) / 100)

    @hello_time.setter
    def hello_time(self, time):
        """
        Set bridge hello time in seconds. Internal Kernel representation
        is in centiseconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').hello_time = 2
        """
        return self._write_sysfs('/sys/class/net/{0}/bridge/hello_time'
                                 .format(self._ifname), (int(time) * 100))

    @property
    def max_age(self):
        """
        Get bridge max max message age in seconds. Internal Kernel representation
        is in centiseconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').max_age
        '20'
        """

        return (self._read_sysfs('/sys/class/net/{0}/bridge/max_age'
                                 .format(self._ifname)) / 100)

    @max_age.setter
    def max_age(self, time):
        """
        Set bridge max message age in seconds. Internal Kernel representation
        is in centiseconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').max_age = 30
        """
        return self._write_sysfs('/sys/class/net/{0}/bridge/max_age'
                                 .format(self._ifname), (int(time) * 100))

    @property
    def priority(self):
        """
        Get bridge max aging time in seconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').priority
        '32768'
        """
        return self._read_sysfs('/sys/class/net/{0}/bridge/priority'
                                .format(self._ifname))

    @priority.setter
    def priority(self, priority):
        """
        Set bridge max aging time in seconds.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').priority = 8192
        """
        return self._write_sysfs('/sys/class/net/{0}/bridge/priority'
                                 .format(self._ifname), priority)

    @property
    def stp_state(self):
        """
        Get current bridge STP (Spanning Tree) state.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').stp_state
        '0'
        """

        state = 0
        with open('/sys/class/net/{0}/bridge/stp_state'.format(self._ifname), 'r') as f:
            state = int(f.read().rstrip('\n'))

        return state

    @stp_state.setter
    def stp_state(self, state):
        """
        Set bridge STP (Spannign Tree) state. 0 -> STP disabled, 1 -> STP enabled

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').stp_state = 1
        """

        if int(state) >= 0 and int(state) <= 1:
            return self._write_sysfs('/sys/class/net/{0}/bridge/stp_state'
                                     .format(self._ifname), state)
        else:
            raise ValueError("Value out of range")

    @property
    def multicast_querier(self):
        """
        Get bridge multicast querier membership state.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').multicast_querier
        '0'
        """
        return self._read_sysfs('/sys/class/net/{0}/bridge/multicast_querier'
                                .format(self._ifname))

    @multicast_querier.setter
    def multicast_querier(self, enable):
        """
        Sets whether the bridge actively runs a multicast querier or not. When a
        bridge receives a 'multicast host membership' query from another network
        host, that host is tracked based on the time that the query was received
        plus the multicast query interval time.

        Use enable=1 to enable or enable=0 to disable

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').multicast_querier = 1
        """
        if int(enable) >= 0 and int(enable) <= 1:
            return self._write_sysfs('/sys/class/net/{0}/bridge/multicast_querier'
                                     .format(self._ifname), enable)
        else:
            raise ValueError("Value out of range")

    def add_port(self, interface):
        """
        Add physical interface to bridge (member port)

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').add_port('eth0')
        >>> BridgeIf('br0').add_port('eth1')
        """
        cmd = 'ip link set dev {} master {}'.format(interface, self._ifname)
        self._cmd(cmd)

    def del_port(self, interface):
        """
        Remove member port from bridge instance.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> BridgeIf('br0').del_port('eth1')
        """
        cmd = 'ip link set dev {} nomaster'.format(interface)
        self._cmd(cmd)

    def set_cost(self, interface, cost):
        """
        Set interface path cost, only relevant for STP enabled interfaces

        Example:

        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').path_cost(4)
        """
        return self._write_sysfs('/sys/class/net/{}/brif/{}/path_cost'
                                 .format(self._ifname, interface), cost)

    def set_priority(self, interface, priority):
        """
        Set interface path priority, only relevant for STP enabled interfaces

        Example:

        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').priority(4)
        """
        return self._write_sysfs('/sys/class/net/{}/brif/{}/priority'
                                 .format(self._ifname, interface), priority)


class VLANIf(Interface):
    """
    This class handels the creation and removal of a VLAN interface. It serves
    as base class for BondIf and EthernetIf.
    """
    def __init__(self, ifname, type=None):
        super().__init__(ifname, type)

    def add_vlan(self, vlan_id, ethertype='', ingress_qos='', egress_qos=''):
        """
        A virtual LAN (VLAN) is any broadcast domain that is partitioned and
        isolated in a computer network at the data link layer (OSI layer 2).
        Use this function to create a new VLAN interface on a given physical
        interface.

        This function creates both 802.1q and 802.1ad (Q-in-Q) interfaces. Proto
        parameter is used to indicate VLAN type.

        A new object of type VLANIf is returned once the interface has been
        created.

        @param ethertype: If specified, create 802.1ad or 802.1q Q-in-Q VLAN
                          interface
        @param ingress_qos: Defines a mapping of VLAN header prio field to the
                            Linux internal packet priority on incoming frames.
        @param ingress_qos: Defines a mapping of Linux internal packet priority
                            to VLAN header prio field but for outgoing frames.
        """
        vlan_ifname = self._ifname + '.' + str(vlan_id)
        if not os.path.exists('/sys/class/net/{}'.format(vlan_ifname)):
            self._vlan_id = int(vlan_id)

            if ethertype:
                self._ethertype = ethertype
                ethertype = 'proto {}'.format(ethertype)

            # Optional ingress QOS mapping
            opt_i = ''
            if ingress_qos:
                opt_i = 'ingress-qos-map ' + ingress_qos
            # Optional egress QOS mapping
            opt_e = ''
            if egress_qos:
                opt_e = 'egress-qos-map ' + egress_qos

            # create interface in the system
            cmd = 'ip link add link {intf} name {intf}.{vlan} type vlan {proto} id {vlan} {opt_e} {opt_i}' \
                   .format(intf=self._ifname, vlan=self._vlan_id, proto=ethertype, opt_e=opt_e, opt_i=opt_i)
            self._cmd(cmd)

        # return new object mapping to the newly created interface
        # we can now work on this object for e.g. IP address setting
        # or interface description and so on
        return VLANIf(vlan_ifname)

    def del_vlan(self, vlan_id):
        """
        Remove VLAN interface from operating system. Removing the interface
        deconfigures all assigned IP addresses and clear possible DHCP(v6)
        client processes.
        """
        vlan_ifname = self._ifname + '.' + str(vlan_id)
        tmp = VLANIf(vlan_ifname)
        tmp.remove()


class EthernetIf(VLANIf):
    """
    Abstraction of a Linux Ethernet Interface
    """
    def __init__(self, ifname):
        super().__init__(ifname)

    def remove(self):
        raise OSError('Ethernet interfaces can not be removed')

    def get_driver_name(self):
        """
        Return the driver name used by NIC. Some NICs don't support all
        features e.g. changing link-speed, duplex
        """
        link = os.readlink('/sys/class/net/{}/device/driver/module'.format(self._ifname))
        return os.path.basename(link)

    def set_flow_control(self, enable):
        """
        Changes the pause parameters of the specified Ethernet device.

        @param enable: true -> enable pause frames, false -> disable pause frames
        """
        if enable not in ['on', 'off']:
            raise ValueError("Value out of range")

        # Assemble command executed on system. Unfortunately there is no way
        # to change this setting via sysfs
        cmd = 'ethtool --pause {0} autoneg {1} tx {1} rx {1}'.format(
              self._ifname, enable)
        try:
            # An exception will be thrown if the settings are not changed
            self._cmd(cmd)
        except CalledProcessError:
            pass

    def set_speed_duplex(self, speed, duplex):
        """
        Set link speed in Mbit/s and duplex.

        @speed can be any link speed in MBit/s, e.g. 10, 100, 1000 auto
        @duplex can be half, full, auto
        """

        if speed not in ['auto', '10', '100', '1000', '2500', '5000', '10000', '25000', '40000', '50000', '100000', '400000']:
            raise ValueError("Value out of range (speed)")

        if duplex not in ['auto', 'full', 'half']:
            raise ValueError("Value out of range (duplex)")

        cmd = 'ethtool -s {}'.format(self._ifname)
        if speed == 'auto' or duplex == 'auto':
            cmd += ' autoneg on'
        else:
            cmd += ' speed {} duplex {} autoneg off'.format(speed, duplex)

        return self._cmd(cmd)


class BondIf(VLANIf):
    """
    The Linux bonding driver provides a method for aggregating multiple network
    interfaces into a single logical "bonded" interface. The behavior of the
    bonded interfaces depends upon the mode; generally speaking, modes provide
    either hot standby or load balancing services. Additionally, link integrity
    monitoring may be performed.
    """
    def __init__(self, ifname):
        super().__init__(ifname, type='bond')

    def remove(self):
        """
        Remove interface from operating system. Removing the interface
        deconfigures all assigned IP addresses and clear possible DHCP(v6)
        client processes.
        Example:
        >>> from vyos.ifconfig import Interface
        >>> i = Interface('eth0')
        >>> i.remove()
        """
        # when a bond member gets deleted, all members are placed in A/D state
        # even when they are enabled inside CLI. This will make the config
        # and system look async.
        slave_list = []
        for s in self.get_slaves():
            slave = {
                'ifname' : s,
                'state': Interface(s).state
            }
            slave_list.append(slave)

        # remove bond master which places members in disabled state
        super().remove()

        # replicate previous interface state before bond destruction back to
        # physical interface
        for slave in slave_list:
             i = Interface(slave['ifname'])
             i.state = slave['state']

    @property
    def xmit_hash_policy(self):
        """
        Selects the transmit hash policy to use for slave selection in
        balance-xor, 802.3ad, and tlb modes. Possible values are: layer2,
        layer2+3, layer3+4, encap2+3, encap3+4.

        The default value is layer2

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').xmit_hash_policy
        'layer3+4'
        """
        # Linux Kernel appends has policy value to string, e.g. 'layer3+4 1',
        # so remove the later part and only return the mode as string.
        return self._read_sysfs('/sys/class/net/{}/bonding/xmit_hash_policy'
                                .format(self._ifname)).split()[0]

    @xmit_hash_policy.setter
    def xmit_hash_policy(self, mode):
        """
        Selects the transmit hash policy to use for slave selection in
        balance-xor, 802.3ad, and tlb modes. Possible values are: layer2,
        layer2+3, layer3+4, encap2+3, encap3+4.

        The default value is layer2

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').xmit_hash_policy = 'layer2+3'
        >>> BondIf('bond0').proxy_arp
        '1'
        """
        if not mode in ['layer2', 'layer2+3', 'layer3+4', 'encap2+3', 'encap3+4']:
            raise ValueError("Value out of range")
        return self._write_sysfs('/sys/class/net/{}/bonding/xmit_hash_policy'
                                 .format(self._ifname), mode)

    @property
    def arp_interval(self):
        """
        Specifies the ARP link monitoring frequency in milliseconds.

        The ARP monitor works by periodically checking the slave devices to
        determine whether they have sent or received traffic recently (the
        precise criteria depends upon the bonding mode, and the state of the
        slave). Regular traffic is generated via ARP probes issued for the
        addresses specified by the arp_ip_target option.

        The default value is 0.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').arp_interval
        '0'
        """
        return self._read_sysfs('/sys/class/net/{}/bonding/arp_interval'
                                .format(self._ifname))

    @arp_interval.setter
    def arp_interval(self, time):
        """
        Specifies the IP addresses to use as ARP monitoring peers when
        arp_interval is > 0. These are the targets of the ARP request sent to
        determine the health of the link to the targets. Specify these values
        in ddd.ddd.ddd.ddd format. Multiple IP addresses must be separated by
        a comma. At least one IP address must be given for ARP monitoring to
        function. The maximum number of targets that can be specified is 16.

        The default value is no IP addresses.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').arp_interval = '100'
        >>> BondIf('bond0').arp_interval
        '100'
        """
        return self._write_sysfs('/sys/class/net/{}/bonding/arp_interval'
                                 .format(self._ifname), time)

    @property
    def arp_ip_target(self):
        """
        Specifies the IP addresses to use as ARP monitoring peers when
        arp_interval is > 0. These are the targets of the ARP request sent to
        determine the health of the link to the targets. Specify these values
        in ddd.ddd.ddd.ddd format. Multiple IP addresses must be separated by
        a comma. At least one IP address must be given for ARP monitoring to
        function. The maximum number of targets that can be specified is 16.

        The default value is no IP addresses.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').arp_ip_target
        '192.0.2.1'
        """
        return self._read_sysfs('/sys/class/net/{}/bonding/arp_ip_target'
                                .format(self._ifname))

    @arp_ip_target.setter
    def arp_ip_target(self, target):
        """
        Specifies the IP addresses to use as ARP monitoring peers when
        arp_interval is > 0. These are the targets of the ARP request sent to
        determine the health of the link to the targets. Specify these values
        in ddd.ddd.ddd.ddd format. Multiple IP addresses must be separated by
        a comma. At least one IP address must be given for ARP monitoring to
        function. The maximum number of targets that can be specified is 16.

        The default value is no IP addresses.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').arp_ip_target = '192.0.2.1'
        >>> BondIf('bond0').arp_ip_target
        '192.0.2.1'
        """
        return self._write_sysfs('/sys/class/net/{}/bonding/arp_ip_target'
                                 .format(self._ifname), target)

    @property
    def miimon(self):
        """
        Specifies the MII link monitoring frequency in milliseconds.
        This determines how often the link state of each slave is
        inspected for link failures. A value of zero disables MII
        link monitoring. A value of 100 is a good starting point.

        The default value is 0.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').miimon
        '250'
        """
        return self._read_sysfs('/sys/class/net/{}/bonding/miimon'
                                .format(self._ifname))


    @miimon.setter
    def miimon(self, time):
        """
        Specifies the MII link monitoring frequency in milliseconds.
        This determines how often the link state of each slave is
        inspected for link failures. A value of zero disables MII
        link monitoring. A value of 100 is a good starting point.

        The default value is 0.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').miimon = 250
        >>> BondIf('bond0').miimon
        '250'
        """
        return self._write_sysfs('/sys/class/net/{}/bonding/miimon'
                                 .format(self._ifname), time)


    def add_port(self, interface):
        """
        Enslave physical interface to bond.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').add_port('eth0')
        >>> BondIf('bond0').add_port('eth1')
        """
        # An interface can only be added to a bond if it is in 'down' state. If
        # interface is in 'up' state, the following Kernel error will  be thrown:
        # bond0: eth1 is up - this may be due to an out of date ifenslave.
        Interface(interface).state = 'down'

        return self._write_sysfs('/sys/class/net/{}/bonding/slaves'
                                 .format(self._ifname), '+' + interface)

    def del_port(self, interface):
        """
        Remove physical port from bond

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').del_port('eth1')
        """
        return self._write_sysfs('/sys/class/net/{}/bonding/slaves'
                                 .format(self._ifname), '-' + interface)

    def get_slaves(self):
        """
        Return a list with all configured slave interfaces on this bond.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').get_slaves()
        ['eth1', 'eth2']
        """
        slaves = self._read_sysfs('/sys/class/net/{}/bonding/slaves'
                                  .format(self._ifname))
        return list(map(str, slaves.split()))

    @property
    def primary(self):
        """
        A string (eth0, eth2, etc) specifying which slave is the primary
        device. The specified device will always be the active slave while it
        is available. Only when the primary is off-line will alternate devices
        be used. This is useful when one slave is preferred over another, e.g.,
        when one slave has higher throughput than another.

        The primary option is only valid for active-backup, balance-tlb and
        balance-alb mode.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').primary
        'eth1'
        """
        return self._read_sysfs('/sys/class/net/{}/bonding/primary'
                                .format(self._ifname))

    @primary.setter
    def primary(self, interface):
        """
        A string (eth0, eth2, etc) specifying which slave is the primary
        device. The specified device will always be the active slave while it
        is available. Only when the primary is off-line will alternate devices
        be used. This is useful when one slave is preferred over another, e.g.,
        when one slave has higher throughput than another.

        The primary option is only valid for active-backup, balance-tlb and
        balance-alb mode.

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').primary = 'eth2'
        >>> BondIf('bond0').primary
        'eth2'
        """
        if not interface:
            # reset primary interface
            interface = '\0'

        return self._write_sysfs('/sys/class/net/{}/bonding/primary'
                                 .format(self._ifname), interface)

    @property
    def mode(self):
        """
        Specifies one of the bonding policies. The default is balance-rr
        (round robin).

        Possible values are: balance-rr (0), active-backup (1), balance-xor (2),
        broadcast (3), 802.3ad (4), balance-tlb (5), balance-alb (6)

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').mode
        'balance-rr'
        """
        return self._read_sysfs('/sys/class/net/{}/bonding/mode'
                                .format(self._ifname)).split()[0]

    @mode.setter
    def mode(self, mode):
        """
        Specifies one of the bonding policies. The default is balance-rr
        (round robin).

        Possible values are: balance-rr, active-backup, balance-xor,
        broadcast, 802.3ad, balance-tlb, balance-alb

        NOTE: the bonding mode can not be changed when the bond itself has
        slaves

        Example:
        >>> from vyos.ifconfig import BondIf
        >>> BondIf('bond0').mode = '802.3ad'
        >>> BondIf('bond0').mode
        '802.3ad'
        """
        if not mode in [
            'balance-rr', 'active-backup', 'balance-xor', 'broadcast',
                        '802.3ad', 'balance-tlb', 'balance-alb']:
            raise ValueError("Value out of range")

        return self._write_sysfs('/sys/class/net/{}/bonding/mode'
                                 .format(self._ifname), mode)


class WireGuardIf(Interface):
    """
    Wireguard interface class, contains a comnfig dictionary since
    wireguard VPN is being comnfigured via the wg command rather than
    writing the config into a file. Otherwise if a pre-shared key is used
    (symetric enryption key), it would we exposed within multiple files.
    Currently it's only within the config.boot if the config was saved.

    Example:
    >>> from vyos.ifconfig import WireGuardIf as wg_if
    >>> wg_intfc = wg_if("wg01")
    >>> print (wg_intfc.wg_config)
    {'private-key': None, 'keepalive': 0, 'endpoint': None, 'port': 0,
    'allowed-ips': [], 'pubkey': None, 'fwmark': 0, 'psk': '/dev/null'}
    >>> wg_intfc.wg_config['keepalive'] = 100
    >>> print (wg_intfc.wg_config)
    {'private-key': None, 'keepalive': 100, 'endpoint': None, 'port': 0,
    'allowed-ips': [], 'pubkey': None, 'fwmark': 0, 'psk': '/dev/null'}
    """

    def __init__(self, ifname):
        super().__init__(ifname, type='wireguard')
        self.config = {
            'port': 0,
          'private-key': None,
          'pubkey': None,
          'psk': '/dev/null',
          'allowed-ips': [],
          'fwmark': 0x00,
          'endpoint': None,
          'keepalive': 0
        }

    def update(self):
        if not self.config['private-key']:
            raise ValueError("private key required")
        else:
            # fmask permission check?
            pass

        cmd = "wg set {} ".format(self._ifname)
        cmd += "listen-port {} ".format(self.config['port'])
        cmd += "fwmark {} ".format(str(self.config['fwmark']))
        cmd += "private-key {} ".format(self.config['private-key'])
        cmd += "peer {} ".format(self.config['pubkey'])
        cmd += " preshared-key {} ".format(self.config['psk'])
        cmd += " allowed-ips "
        for aip in self.config['allowed-ips']:
            if aip != self.config['allowed-ips'][-1]:
                cmd += aip + ","
            else:
                cmd += aip
        if self.config['endpoint']:
            cmd += " endpoint {}".format(self.config['endpoint'])
        cmd += " persistent-keepalive {}".format(self.config['keepalive'])

        self._cmd(cmd)

        # remove psk since it isn't required anymore and is saved in the cli
        # config only !!
        if self.config['psk'] != '/dev/null':
            if os.path.exists(self.config['psk']):
                os.remove(self.config['psk'])


    def remove_peer(self, peerkey):
        """
        Remove a peer of an interface, peers are identified by their public key.
        Giving it a readable name is a vyos feature, to remove a peer the pubkey
        and the interface is needed, to remove the entry.
        """
        cmd = "wg set {0} peer {1} remove".format(
            self._ifname, str(peerkey))
        self._cmd(cmd)


class VXLANIf(Interface, ):
    """
    The VXLAN protocol is a tunnelling protocol designed to solve the
    problem of limited VLAN IDs (4096) in IEEE 802.1q.  With VXLAN the
    size of the identifier is expanded to 24 bits (16777216).

    VXLAN is described by IETF RFC 7348, and has been implemented by a
    number of vendors.  The protocol runs over UDP using a single
    destination port.  This document describes the Linux kernel tunnel
    device, there is also a separate implementation of VXLAN for
    Openvswitch.

    Unlike most tunnels, a VXLAN is a 1 to N network, not just point to
    point. A VXLAN device can learn the IP address of the other endpoint
    either dynamically in a manner similar to a learning bridge, or make
    use of statically-configured forwarding entries.

    For more information please refer to:
    https://www.kernel.org/doc/Documentation/networking/vxlan.txt
    """
    def __init__(self, ifname, config=''):
        if config:
            self._ifname = ifname

            if not os.path.exists('/sys/class/net/{}'.format(self._ifname)):
                # we assume that by default a multicast interface is created
                group = 'group {}'.format(config['group'])

                # if remote host is specified we ignore the multicast address
                if config['remote']:
                    group = 'remote {}'.format(config['remote'])

                # an underlay device is not always specified
                dev = ''
                if config['dev']:
                    dev = 'dev {}'.format(config['dev'])

                cmd = 'ip link add {intf} type vxlan id {vni} {grp_rem} {dev} dstport {port}' \
                       .format(intf=self._ifname, vni=config['vni'], grp_rem=group, dev=dev, port=config['port'])
                self._cmd(cmd)

        super().__init__(ifname, type='vxlan')

    @staticmethod
    def get_config():
        """
        VXLAN interfaces require a configuration when they are added using
        iproute2. This static method will provide the configuration dictionary
        used by this class.

        Example:
        >> dict = VXLANIf().get_config()
        """
        config = {
            'vni': 0,
            'dev': '',
            'group': '',
            'port': 8472, # The Linux implementation of VXLAN pre-dates
                          # the IANA's selection of a standard destination port
            'remote': ''
        }
        return config