#!/usr/bin/env python3
#
# Copyright (C) 2019 VyOS maintainers and contributors
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 or later as
# published by the Free Software Foundation.
#
# This program 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 General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.

import os

from sys import exit
from copy import deepcopy
from jinja2 import Template
from subprocess import Popen, PIPE
from time import sleep
from pwd import getpwnam
from grp import getgrnam
from stat import S_IRUSR, S_IWUSR, S_IXUSR, S_IRGRP, S_IXGRP, S_IROTH, S_IXOTH

from vyos.config import Config
from vyos.ifconfig import Interface
from vyos import ConfigError
from netifaces import interfaces

# Please be careful if you edit the template.
config_pppoe_tmpl = """### Autogenerated by interfaces-pppoe.py ###
{% if description %}
# {{ description }}
{% endif %}

# Require peer to provide the local IP address if it is not
# specified explicitly in the config file.
noipdefault

# Don't show the password in logfiles:
hide-password

# Standard Link Control Protocol (LCP) parameters:
lcp-echo-interval 20
lcp-echo-failure 3

# RFC 2516, paragraph 7 mandates that the following options MUST NOT be
# requested and MUST be rejected if requested by the peer:
# Address-and-Control-Field-Compression (ACFC)
noaccomp

# Asynchronous-Control-Character-Map (ACCM)
default-asyncmap

# Override any connect script that may have been set in /etc/ppp/options.
connect /bin/true

# Don't try to authenticate the remote node
noauth

# Don't try to proxy ARP for the remote endpoint. User can set proxy
# arp entries up manually if they wish.  More importantly, having
# the "proxyarp" parameter set disables the "defaultroute" option.
noproxyarp

# Unlimited connection attempts
maxfail 0

plugin rp-pppoe.so
{{ source_interface }}
persist
ifname {{ intf }}
ipparam {{ intf }}
debug
logfile {{ logfile }}
{% if 'auto' in default_route -%}
defaultroute
{% elif 'force' in default_route -%}
defaultroute
replacedefaultroute
{% endif %}
mtu {{ mtu }}
mru {{ mtu }}
user "{{ auth_username }}"
password "{{ auth_password }}"
{% if name_server -%}
usepeerdns
{% endif %}
{% if ipv6_enable -%}
+ipv6
ipv6cp-use-ipaddr
{% endif %}
{% if service_name -%}
rp_pppoe_service "{{ service_name }}"
{% endif %}

"""

# Please be careful if you edit the template.
# There must be no blank line at the top pf the script file
config_pppoe_ipv6_up_tmpl = """#!/bin/sh

# As PPPoE is an "on demand" interface we need to re-configure it when it
# becomes up

if [ "$6" != "{{ intf }}" ]; then
    exit
fi

# add some info to syslog
DIALER_PID=$(cat /var/run/{{ intf }}.pid)
logger -t pppd[$DIALER_PID] "executing $0"
logger -t pppd[$DIALER_PID] "configuring dialer interface $6 via $2"

echo "{{ description }}" > /sys/class/net/{{ intf }}/ifalias

{% if ipv6_autoconf -%}


# Configure interface-specific Host/Router behaviour.
# Note: It is recommended to have the same setting on all interfaces; mixed
# router/host scenarios are rather uncommon. Possible values are:
#
# 0  Forwarding disabled
# 1  Forwarding enabled
#
echo 1 > /proc/sys/net/ipv6/conf/{{ intf }}/forwarding

# Accept Router Advertisements; autoconfigure using them.
#
# It also determines whether or not to transmit Router
# Solicitations. If and only if the functional setting is to
# accept Router Advertisements, Router Solicitations will be
# transmitted. Possible values are:
#
# 0  Do not accept Router Advertisements.
# 1  Accept Router Advertisements if forwarding is disabled.
# 2  Overrule forwarding behaviour. Accept Router Advertisements
#    even if forwarding is enabled.
#
echo 2 > /proc/sys/net/ipv6/conf/{{ intf }}/accept_ra

# Autoconfigure addresses using Prefix Information in Router Advertisements.
echo 1 > /proc/sys/net/ipv6/conf/{{ intf }}/autoconfigure
{% endif %}
"""

PPP_LOGFILE = '/var/log/vyatta/ppp_{}.log'

default_config_data = {
    'access_concentrator': '',
    'auth_username': '',
    'auth_password': '',
    'on_demand': False,
    'default_route': 'auto',
    'deleted': False,
    'description': '\0',
    'disable': False,
    'intf': '',
    'idle_timeout': '',
    'ipv6_autoconf': False,
    'ipv6_enable': False,
    'local_address': '',
    'logfile': '',
    'mtu': '1492',
    'name_server': True,
    'remote_address': '',
    'service_name': '',
    'source_interface': ''
}

def subprocess_cmd(command):
    p = Popen(command, stdout=PIPE, shell=True)
    p.communicate()

def get_config():
    pppoe = deepcopy(default_config_data)
    conf = Config()
    base_path = ['interfaces', 'pppoe']

    # determine tagNode instance
    if 'VYOS_TAGNODE_VALUE' not in os.environ:
        raise ConfigError('Interface (VYOS_TAGNODE_VALUE) not specified')

    pppoe['intf'] = os.environ['VYOS_TAGNODE_VALUE']
    pppoe['logfile'] = PPP_LOGFILE.format(pppoe['intf'])

    # Check if interface has been removed
    if not conf.exists(base_path + [pppoe['intf']]):
        pppoe['deleted'] = True
        return pppoe

    # set new configuration level
    conf.set_level(base_path + [pppoe['intf']])

    # Access concentrator name (only connect to this concentrator)
    if conf.exists(['access-concentrator']):
        pppoe['access_concentrator'] = conf.return_values(['access-concentrator'])

    # Authentication name supplied to PPPoE server
    if conf.exists(['authentication', 'user']):
        pppoe['auth_username'] = conf.return_value(['authentication', 'user'])

    # Password for authenticating local machine to PPPoE server
    if conf.exists(['authentication', 'password']):
        pppoe['auth_password'] = conf.return_value(['authentication', 'password'])

    # Access concentrator name (only connect to this concentrator)
    if conf.exists(['connect-on-demand']):
        pppoe['on_demand'] = True

    # Enable/Disable default route to peer when link comes up
    if conf.exists(['default-route']):
        pppoe['default_route'] = conf.return_value(['default-route'])

    # Retrieve interface description
    if conf.exists(['description']):
        pppoe['description'] = conf.return_value(['description'])

    # Disable this interface
    if conf.exists(['disable']):
        pppoe['disable'] = True

    # Delay before disconnecting idle session (in seconds)
    if conf.exists(['idle-timeout']):
        pppoe['idle_timeout'] = conf.return_value(['idle-timeout'])

    # Enable Stateless Address Autoconfiguration (SLAAC)
    if conf.exists(['ipv6', 'address', 'autoconf']):
        pppoe['ipv6_autoconf'] = True

    # Activate IPv6 support on this connection
    if conf.exists(['ipv6', 'enable']):
        pppoe['ipv6_enable'] = True

    # IPv4 address of local end of PPPoE link
    if conf.exists(['local-address']):
        pppoe['local_address'] = conf.return_value(['local-address'])

    # Physical Interface used for this PPPoE session
    if conf.exists(['source-interface']):
        pppoe['source_interface'] = conf.return_value('source-interface')

    # Maximum Transmission Unit (MTU)
    if conf.exists(['mtu']):
        pppoe['mtu'] = conf.return_value(['mtu'])

    # Do not use DNS servers provided by the peer
    if conf.exists(['no-peer-dns']):
        pppoe['name_server'] = False

    # IPv4 address for remote end of PPPoE session
    if conf.exists(['remote-address']):
        pppoe['remote_address'] = conf.return_value(['remote-address'])

    # Service name, only connect to access concentrators advertising this
    if conf.exists(['service-name']):
        pppoe['service_name'] = conf.return_value(['service-name'])

    return pppoe

def verify(pppoe):
    if pppoe['deleted']:
        # bail out early
        return None

    if not pppoe['source_interface']:
        raise ConfigError('PPPoE source interface missing')

    if not pppoe['source_interface'] in interfaces():
        raise ConfigError('PPPoE source interface does not exist')

    return None

def generate(pppoe):
    config_file_pppoe = '/etc/ppp/peers/{}'.format(pppoe['intf'])
    ipv6_if_up_script_file = '/etc/ppp/ipv6-up.d/50-vyos-{}-autoconf'.format(pppoe['intf'])

    # Always hang-up PPPoE connection prior generating new configuration file
    cmd = 'systemctl stop ppp@{}.service'.format(pppoe['intf'])
    subprocess_cmd(cmd)

    if pppoe['deleted']:
        # Delete PPP configuration files
        if os.path.exists(config_file_pppoe):
            os.unlink(config_file_pppoe)

        if os.path.exists(ipv6_if_up_script_file):
            os.unlink(ipv6_if_up_script_file)

    else:
        # Create PPP configuration files
        tmpl = Template(config_pppoe_tmpl)
        config_text = tmpl.render(pppoe)
        with open(config_file_pppoe, 'w') as f:
            f.write(config_text)

        tmpl = Template(config_pppoe_ipv6_up_tmpl)
        config_text = tmpl.render(pppoe)
        with open(ipv6_if_up_script_file, 'w') as f:
            f.write(config_text)

        bitmask = S_IRUSR | S_IWUSR | S_IXUSR | S_IRGRP | S_IXGRP | \
                  S_IROTH | S_IXOTH
        os.chmod(ipv6_if_up_script_file, bitmask)

    return None

def apply(pppoe):
    if pppoe['deleted']:
        # bail out early
        return None

    if not pppoe['disable']:
        # dial PPPoE connection
        cmd = 'systemctl start ppp@{}.service'.format(pppoe['intf'])
        subprocess_cmd(cmd)

        # make logfile owned by root / vyattacfg
        if os.path.isfile(pppoe['logfile']):
            uid = getpwnam('root').pw_uid
            gid = getgrnam('vyattacfg').gr_gid
            os.chown(pppoe['logfile'], uid, gid)

    return None

if __name__ == '__main__':
    try:
        c = get_config()
        verify(c)
        generate(c)
        apply(c)
    except ConfigError as e:
        print(e)
        exit(1)