path: root/python/vyos/ifconfig/interface.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
import json
import glob
import time
from copy import deepcopy

import vyos.interfaces

from vyos.validate import *     # should not * include
from vyos.config import Config  # not used anymore
from vyos import ConfigError

from ipaddress import IPv4Network, IPv6Address
from netifaces import ifaddresses, AF_INET, AF_INET6
from time import sleep
from os.path import isfile
from tabulate import tabulate
from hurry.filesize import size,alternative
from datetime import timedelta

from vyos.ifconfig.control import Control

dhclient_base = r'/var/lib/dhcp/dhclient_'
dhcp_cfg = """
# generated by ifconfig.py
option rfc3442-classless-static-routes code 121 = array of unsigned integer 8;
timeout 60;
retry 300;

interface "{{ intf }}" {
    send host-name "{{ hostname }}";
    {% if client_id -%}
    send dhcp-client-identifier "{{ client_id }}";
    {% endif -%}
    {% if vendor_class_id -%}
    send vendor-class-identifier "{{ vendor_class_id }}";
    {% endif -%}
    request subnet-mask, broadcast-address, routers, domain-name-servers,
        rfc3442-classless-static-routes, domain-name, interface-mtu;
    require subnet-mask;
}

"""

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

"""



class Interface(Control):
    options = []
    required = []
    default = {
        'type': '',
    }

    _command_set = {
        'state': {
            'validate': lambda v: assert_list(v, ['up', 'down']),
            'shellcmd': 'ip link set dev {ifname} {value}',
        },
        'mac': {
            'validate': assert_mac,
            'shellcmd': 'ip link set dev {ifname} address {value}',
        },
        'add_vrf': {
            'shellcmd': 'ip link set dev {ifname} master {value}',
        },
        'del_vrf': {
            'shellcmd': 'ip link set dev {ifname} nomaster',
        },
        'vrf': {
            'force': True,
            'convert': lambda v: f'master {v}' if v else 'nomaster',
            'shellcmd': 'ip link set dev {ifname} {value}',
        },
    }

    _sysfs_get = {
        'mtu': {
            'location': '/sys/class/net/{ifname}/mtu',
        },
    }

    _sysfs_set = {
        'alias': {
            'convert': lambda name: name if name else '\0',
            'location': '/sys/class/net/{ifname}/ifalias',
        },
        'mtu': {
            'validate': assert_mtu,
            'location': '/sys/class/net/{ifname}/mtu',
        },
        'arp_cache_tmo': {
            'convert': lambda tmo: (int(tmo) * 1000),
            'location': '/proc/sys/net/ipv4/neigh/{ifname}/base_reachable_time_ms',
        },
        'arp_filter': {
            'validate': assert_boolean,
            'location': '/proc/sys/net/ipv4/conf/{ifname}/arp_filter',
        },
        'arp_accept': {
            'validate': lambda arp: assert_range(arp,0,2),
            'location': '/proc/sys/net/ipv4/conf/{ifname}/arp_accept',
        },
        'arp_announce': {
            'validate': assert_boolean,
            'location': '/proc/sys/net/ipv4/conf/{ifname}/arp_announce',
        },
        'arp_ignore': {
            'validate': assert_boolean,
            'location': '/proc/sys/net/ipv4/conf/{ifname}/arp_ignore',
        },
        'proxy_arp': {
            'validate': assert_boolean,
            'location': '/proc/sys/net/ipv4/conf/{ifname}/proxy_arp',
        },
        'proxy_arp_pvlan': {
            'validate': assert_boolean,
            'location': '/proc/sys/net/ipv4/conf/{ifname}/proxy_arp_pvlan',
        },
        # link_detect vs link_filter name weirdness
        'link_detect': {
            'validate': lambda link: assert_range(link,0,3),
            'location': '/proc/sys/net/ipv4/conf/{ifname}/link_filter',
        },
    }

    def __init__(self, ifname, **kargs):
        """
        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.

        For creation you will need to provide the interface type, otherwise
        the existing interface is used

        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.config = deepcopy(self.default)
        self.config['ifname'] = ifname

        for k in self.options:
            if k in kargs:
                self.config[k] = kargs[k]

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

            for k in self.required:
                if k not in kargs:
                    name = self.default['type']
                    raise ConfigError(f'missing required option {k} for {name} {ifname} creation')

            self._create()

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

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

        # DHCP options
        self._dhcp_options = {
            'intf' : self.config['ifname'],
            'hostname' : '',
            'client_id' : '',
            'vendor_class_id' : ''
        }

        # DHCPv6 options
        self._dhcpv6_options = {
            'intf' : self.config['ifname'],
            'dhcpv6_prm_only' : False,
            'dhcpv6_temporary' : False
        }

        # list of assigned IP addresses
        self._addr = []

    def _create(self):
        cmd = 'ip link add dev {ifname} type {type}'.format(**self.config)
        self._cmd(cmd)

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

        # remove all assigned IP addresses from interface - this is a bit redundant
        # as the kernel will remove all addresses on interface deletion, but we
        # can not delete ALL interfaces, see below
        for addr in self.get_addr():
            self.del_addr(addr)

        # ---------------------------------------------------------------------
        # A code refactoring is required as this type check is present as
        # Interface implement behaviour for one of it's sub-class.

        # It is required as the current pattern for vlan is:
        # Interface('name').remove() to delete an interface
        # The code should be modified to have a class method called connect and
        # have Interface.connect('name').remove()

        # each subclass should register within Interface the pattern for that
        # interface ie: (ethX, etc.) and use this to create an instance of
        # the right class (EthernetIf, ...)

        # Ethernet interfaces can not be removed

        # Commented out as nowhere in the code do we call Interface()
        # This would also cause an import loop
        # if self.__class__ == EthernetIf:
        #     return

        # ---------------------------------------------------------------------

        self._delete()

    def _delete(self):
        # 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.config['ifname'])
        return self._cmd(cmd)

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

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').get_mtu()
        '1500'
        """
        return self.get_interface('mtu')

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

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').set_mtu(1400)
        >>> Interface('eth0').get_mtu()
        '1400'
        """
        return self.set_interface('mtu', mtu)

    def set_mac(self, mac):
        """
        Set interface MAC (Media Access Contrl) address to given value.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').set_mac('00:50:ab:cd:ef:01')
        """
        self.set_interface('mac', mac)

    def add_vrf(self, vrf):
        """
        Add interface to given VRF instance.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').add_vrf('foo')
        """
        self.set_interface('add_vrf', vrf)

    def del_vrf(self, vrf=''):
        """
        Remove interface from given VRF instance.

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').del_vrf('foo')
        """
        self.set_interface('del_vrf', vrf)

    def set_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').set_arp_cache_tmo(40)
        """
        return self.set_interface('arp_cache_tmo', tmo)

    def set_arp_filter(self, arp_filter):
        """
        Filter ARP requests

        1 - Allows you to have multiple network interfaces on the same
            subnet, and have the ARPs for each interface be answered
            based on whether or not the kernel would route a packet from
            the ARP'd IP out that interface (therefore you must use source
            based routing for this to work). In other words it allows control
            of which cards (usually 1) will respond to an arp request.

        0 - (default) The kernel can respond to arp requests with addresses
            from other interfaces. This may seem wrong but it usually makes
            sense, because it increases the chance of successful communication.
            IP addresses are owned by the complete host on Linux, not by
            particular interfaces. Only for more complex setups like load-
            balancing, does this behaviour cause problems.
        """
        return self.set_interface('arp_filter', arp_filter)

    def set_arp_accept(self, arp_accept):
        """
        Define behavior for gratuitous ARP frames who's IP is not
        already present in the ARP table:
        0 - don't create new entries in the ARP table
        1 - create new entries in the ARP table

        Both replies and requests type gratuitous arp will trigger the
        ARP table to be updated, if this setting is on.

        If the ARP table already contains the IP address of the
        gratuitous arp frame, the arp table will be updated regardless
        if this setting is on or off.
        """
        return self.set_interface('arp_accept', arp_accept)

    def set_arp_announce(self, arp_announce):
        """
        Define different restriction levels for announcing the local
        source IP address from IP packets in ARP requests sent on
        interface:
        0 - (default) Use any local address, configured on any interface
        1 - Try to avoid local addresses that are not in the target's
            subnet for this interface. This mode is useful when target
            hosts reachable via this interface require the source IP
            address in ARP requests to be part of their logical network
            configured on the receiving interface. When we generate the
            request we will check all our subnets that include the
            target IP and will preserve the source address if it is from
            such subnet.

        Increasing the restriction level gives more chance for
        receiving answer from the resolved target while decreasing
        the level announces more valid sender's information.
        """
        return self.set_interface('arp_announce', arp_announce)

    def set_arp_ignore(self, arp_ignore):
        """
        Define different modes for sending replies in response to received ARP
        requests that resolve local target IP addresses:

        0 - (default): reply for any local target IP address, configured
            on any interface
        1 - reply only if the target IP address is local address
            configured on the incoming interface
        """
        return self.set_interface('arp_ignore', arp_ignore)

    def set_link_detect(self, link_filter):
        """
        Configure 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').set_link_detect(1)
        """
        return self.set_interface('link_detect', link_filter)

    def set_alias(self, ifalias=''):
        """
        Set interface alias name used by e.g. SNMP

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

        to clear alias e.g. delete it use:

        >>> Interface('eth0').set_ifalias('')
        """
        self.set_interface('alias', ifalias)

    def get_state(self):
        """
        Enable (up) / Disable (down) an interface

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').get_state()
        'up'
        """
        cmd = 'ip -json link show dev {}'.format(self.config['ifname'])
        tmp = self._cmd(cmd)
        out = json.loads(tmp)
        return out[0]['operstate'].lower()

    def set_state(self, state):
        """
        Enable (up) / Disable (down) an interface

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').set_state('down')
        >>> Interface('eth0').get_state()
        'down'
        """
        return self.set_interface('state', state)

    def set_proxy_arp(self, enable):
        """
        Set per interface proxy ARP configuration

        Example:
        >>> from vyos.ifconfig import Interface
        >>> Interface('eth0').set_proxy_arp(1)
        """
        self.set_interface('proxy_arp', enable)

    def set_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').set_proxy_arp_pvlan(1)
        """
        self.set_interface('proxy_arp_pvlan', enable)

    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.config['ifname']).keys():
            for v4_addr in ifaddresses(self.config['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.config['ifname']).keys():
            for v6_addr in ifaddresses(self.config['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']
        """

        # cache new IP address which is assigned to interface
        self._addr.append(addr)

        # we can not have both DHCP and static IPv4 addresses assigned to an interface
        if 'dhcp' in self._addr:
            for addr in self._addr:
                # do not change below 'if' ordering esle you will get an exception as:
                #   ValueError: 'dhcp' does not appear to be an IPv4 or IPv6 address
                if addr != 'dhcp' and is_ipv4(addr):
                    raise ConfigError("Can't configure both static IPv4 and DHCP address on the same interface")

        if addr == 'dhcp':
            self._set_dhcp()
        elif addr == 'dhcpv6':
            self._set_dhcpv6()
        else:
            if not is_intf_addr_assigned(self.config['ifname'], addr):
                cmd = 'ip addr add "{}" dev "{}"'.format(addr, self.config['ifname'])
                return 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.config['ifname'], addr):
                cmd = 'ip addr del "{}" dev "{}"'.format(addr, self.config['ifname'])
                return self._cmd(cmd)


    def get_dhcp_options(self):
        """
        Return dictionary with supported DHCP options.

        Dictionary should be altered and send back via set_dhcp_options()
        so those options are applied when DHCP is run.
        """
        return self._dhcp_options

    def set_dhcp_options(self, options):
        """
        Store new DHCP options used by next run of DHCP client.
        """
        self._dhcp_options = options

    def get_dhcpv6_options(self):
        """
        Return dictionary with supported DHCPv6 options.

        Dictionary should be altered and send back via set_dhcp_options()
        so those options are applied when DHCP is run.
        """
        return self._dhcpv6_options

    def set_dhcpv6_options(self, options):
        """
        Store new DHCP options used by next run of DHCP client.
        """
        self._dhcpv6_options = options

    # 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 = self.get_dhcp_options()
        if not dhcp['hostname']:
            # 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)

        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.config['ifname'])
        return 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, we need to call dhclient and tell it should release the
        # aquired IP address. tcpdump tells me:
        # 172.16.35.103.68 > 172.16.35.254.67: [bad udp cksum 0xa0cb -> 0xb943!] BOOTP/DHCP, Request from 00:50:56:9d:11:df, length 300, xid 0x620e6946, Flags [none] (0x0000)
        #  Client-IP 172.16.35.103
        #  Client-Ethernet-Address 00:50:56:9d:11:df
        #  Vendor-rfc1048 Extensions
        #    Magic Cookie 0x63825363
        #    DHCP-Message Option 53, length 1: Release
        #    Server-ID Option 54, length 4: 172.16.35.254
        #    Hostname Option 12, length 10: "vyos"
        #
        cmd = '/sbin/dhclient -cf {} -pf {} -lf {} -r {}'.format(
                self._dhcp_cfg_file, self._dhcp_pid_file, self._dhcp_lease_file, self.config['ifname'])
        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 = self.get_dhcpv6_options()

        # better save then sorry .. should be checked in interface script
        # but if you missed it we are safe!
        if dhcpv6['dhcpv6_prm_only'] and dhcpv6['dhcpv6_temporary']:
            raise Exception('DHCPv6 temporary and parameters-only options are mutually exclusive!')

        # 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)

        # no longer accept router announcements on this interface
        self._write_sysfs('/proc/sys/net/ipv6/conf/{}/accept_ra'
              .format(self.config['ifname']), 0)

        # 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)

        # add optional arguments
        if dhcpv6['dhcpv6_prm_only']:
            cmd += ' -S'
        if dhcpv6['dhcpv6_temporary']:
            cmd += ' -T'

        cmd += ' {}'.format(self.config['ifname'])
        return 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
        self._write_sysfs('/proc/sys/net/ipv6/conf/{}/accept_ra'
              .format(self.config['ifname']), 1)

        # 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)

    def op_show_interface_stats(self):
        stats = self.get_interface_stats()
        rx = [['bytes','packets','errors','dropped','overrun','mcast'],[stats['rx_bytes'],stats['rx_packets'],stats['rx_errors'],stats['rx_dropped'],stats['rx_over_errors'],stats['multicast']]]
        tx = [['bytes','packets','errors','dropped','carrier','collisions'],[stats['tx_bytes'],stats['tx_packets'],stats['tx_errors'],stats['tx_dropped'],stats['tx_carrier_errors'],stats['collisions']]]
        output = "RX: \n"
        output += tabulate(rx,headers="firstrow",numalign="right",tablefmt="plain")
        output += "\n\nTX: \n"
        output += tabulate(tx,headers="firstrow",numalign="right",tablefmt="plain")
        print('  '.join(('\n'+output.lstrip()).splitlines(True)))

    def get_interface_stats(self):
        interface_stats = dict()
        devices = [f for f in glob.glob("/sys/class/net/**/statistics")]
        for dev_path in devices:
            metrics = [f for f in glob.glob(dev_path +"/**")]
            dev = re.findall(r"/sys/class/net/(.*)/statistics",dev_path)[0]
            dev_dict = dict()
            for metric_path in metrics:
                metric = metric_path.replace(dev_path+"/","")
                if isfile(metric_path):
                    data = open(metric_path, 'r').read()[:-1]
                    dev_dict[metric] = int(data)
            interface_stats[dev] = dev_dict

        return interface_stats[self.config['ifname']]