#!/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 psutil import pid_exists
from stat import S_IRUSR, S_IWUSR, S_IXUSR, S_IRGRP, S_IXGRP, S_IROTH, S_IXOTH
from subprocess import Popen, PIPE

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

# Please be careful if you edit the template.
config_pppoe_tmpl = """
### Autogenerated by interfaces-pppoe.py ###

# Configuration file for PPP, using PPP over Ethernet (PPPOE)
# to connect to a DSL provider.

# Default parameters not set by Vyatta templates:
#
# 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

plugin rp-pppoe.so
{{ link }}
persist
ifname {{ intf }}
ipparam {{ intf }}
debug
logfile /var/log/vyatta/ppp_{{ intf }}.log
{% if 'auto' in default_route -%}
defaultroute
{% elif 'force' in default_route -%}
defaultroute
replacedefaultroute
{% endif %}
mtu {{ mtu }}
mru {{ mtu }}
user "{{ user_id }}"
password "{{ password }}"
{% if 'auto' in name_server -%}
usepeerdns
{% endif %}
{% if ipv6_enable -%}
+ipv6
{% endif %}

"""

config_pppoe_autoconf_tmpl = """
#!/bin/sh

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

echo 0 > /proc/sys/net/ipv6/conf/$1/forwarding
echo 2 > /proc/sys/net/ipv6/conf/$1/accept_ra
echo 1 > /proc/sys/net/ipv6/conf/$1/autoconf
"""

default_config_data = {
    'access_concentrator': '',
    'on_demand': False,
    'default_route': 'auto',
    'deleted': False,
    'disable': False,
    'intf': '',
    'idle_timeout': '',
    'ipv6_autoconf': False,
    'ipv6_enable': False,
    'link': '',
    'local_address': '',
    'mtu': '1492',
    'name_server': 'auto',
    'password': '',
    'remote_address': '',
    'service_name': '',
    'user_id': ''
}

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

def get_config():
    pppoe = deepcopy(default_config_data)
    conf = Config()

    # determine tagNode instance
    try:
        pppoe['intf'] = os.environ['VYOS_TAGNODE_VALUE']
    except KeyError as E:
        print("Interface not specified")

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

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

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

    # 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')

    # 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 the 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('link'):
        pppoe['link'] = conf.return_value('link')

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

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

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

    # IPv4 address of local end of the PPPoE link
    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')

    # Authentication name supplied to PPPoE server
    if conf.exists('user-id'):
        pppoe['user_id'] = conf.return_value('user-id')

    return pppoe

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

    if not pppoe['link']:
        raise ConfigError('Physical link interface for PPPoE missing')

    return None

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

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

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

    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_autoconf_tmpl)
        config_text = tmpl.render(pppoe)
        with open(config_file_ifup, 'w') as f:
            f.write(config_text)

        os.chmod(config_file_ifup,
                S_IRUSR|S_IWUSR|S_IXUSR|S_IRGRP|S_IXGRP|S_IROTH|S_IXOTH)

    return None

def apply(pppoe):
    pid = 0
    pidfile = '/var/run/{}.pid'.format(pppoe['intf'])
    if os.path.isfile(pidfile):
        pid = 0
        with open(pidfile, 'r') as f:
            pid = int(f.read())

    # Always stop PPPoE dialer first
    if pid_exists(pid):
        cmd  = 'start-stop-daemon --stop --quiet'
        cmd += ' --pidfile ' + pidfile
        subprocess_cmd(cmd)

    if not pppoe['disable']:
        # No matching PPP process running - spawn a new one
        # NOTE: PID file is only created after dial-in is complete. This is bad
        # as you could have zombie dialers.
        cmd  = 'start-stop-daemon --start --quiet'
        cmd += ' --pidfile ' + pidfile
        cmd += ' --background'
        cmd += ' --exec /usr/sbin/pppd'
        # now pass arguments to pppd binary
        cmd += ' -- '
        cmd += ' call {}'.format(pppoe['intf'])

        # execute assembled command
        subprocess_cmd(cmd)

    return None

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