#!/usr/bin/env python3
#
# Copyright (C) 2019-2023 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 netifaces import interfaces

from vyos.base import Warning
from vyos.config import Config
from vyos.configdict import get_interface_dict
from vyos.configdict import leaf_node_changed
from vyos.configdict import is_node_changed
from vyos.configdict import node_changed
from vyos.configverify import verify_address
from vyos.configverify import verify_bridge_delete
from vyos.configverify import verify_mtu_ipv6
from vyos.configverify import verify_mirror_redirect
from vyos.configverify import verify_source_interface
from vyos.configverify import verify_bond_bridge_member
from vyos.ifconfig import Interface
from vyos.ifconfig import VXLANIf
from vyos.template import is_ipv6
from vyos.utils.dict import dict_search
from vyos import ConfigError
from vyos import airbag
airbag.enable()

def get_config(config=None):
    """
    Retrive CLI config as dictionary. Dictionary can never be empty, as at least
    the interface name will be added or a deleted flag
    """
    if config:
        conf = config
    else:
        conf = Config()
    base = ['interfaces', 'vxlan']
    ifname, vxlan = get_interface_dict(conf, base)

    # VXLAN interfaces are picky and require recreation if certain parameters
    # change. But a VXLAN interface should - of course - not be re-created if
    # it's description or IP address is adjusted. Feels somehow logic doesn't it?
    for cli_option in ['parameters', 'gpe', 'group', 'port', 'remote',
                       'source-address', 'source-interface', 'vni']:
        if is_node_changed(conf, base + [ifname, cli_option]):
            vxlan.update({'rebuild_required': {}})
            break

    # When dealing with VNI filtering we need to know what VNI was actually removed,
    # so build up a dict matching the vlan_to_vni structure but with removed values.
    tmp = node_changed(conf, base + [ifname, 'vlan-to-vni'], recursive=True)
    if tmp:
        vxlan.update({'vlan_to_vni_removed': {}})
        for vlan in tmp:
            vni = leaf_node_changed(conf, base + [ifname, 'vlan-to-vni', vlan, 'vni'])
            vxlan['vlan_to_vni_removed'].update({vlan : {'vni' : vni[0]}})

    # We need to verify that no other VXLAN tunnel is configured when external
    # mode is in use - Linux Kernel limitation
    conf.set_level(base)
    vxlan['other_tunnels'] = conf.get_config_dict([], key_mangling=('-', '_'),
                                                  get_first_key=True,
                                                  no_tag_node_value_mangle=True)

    # This if-clause is just to be sure - it will always evaluate to true
    ifname = vxlan['ifname']
    if ifname in vxlan['other_tunnels']:
        del vxlan['other_tunnels'][ifname]
    if len(vxlan['other_tunnels']) == 0:
        del vxlan['other_tunnels']

    return vxlan

def verify(vxlan):
    if 'deleted' in vxlan:
        verify_bridge_delete(vxlan)
        return None

    if int(vxlan['mtu']) < 1500:
        Warning('RFC7348 recommends VXLAN tunnels preserve a 1500 byte MTU')

    if 'group' in vxlan:
        if 'source_interface' not in vxlan:
            raise ConfigError('Multicast VXLAN requires an underlaying interface')
        verify_source_interface(vxlan)

    if not any(tmp in ['group', 'remote', 'source_address', 'source_interface'] for tmp in vxlan):
        raise ConfigError('Group, remote, source-address or source-interface must be configured')

    if 'vni' not in vxlan and dict_search('parameters.external', vxlan) == None:
        raise ConfigError('Must either configure VXLAN "vni" or use "external" CLI option!')

    if dict_search('parameters.external', vxlan) != None:
        if 'vni' in vxlan:
            raise ConfigError('Can not specify both "external" and "VNI"!')

        if 'other_tunnels' in vxlan:
            # When multiple VXLAN interfaces are defined and "external" is used,
            # all VXLAN interfaces need to have vni-filter enabled!
            # See Linux Kernel commit f9c4bb0b245cee35ef66f75bf409c9573d934cf9
            other_vni_filter = False
            for tunnel, tunnel_config in vxlan['other_tunnels'].items():
                if dict_search('parameters.vni_filter', tunnel_config) != None:
                    other_vni_filter = True
                    break
            # eqivalent of the C foo ? 'a' : 'b' statement
            vni_filter = True and (dict_search('parameters.vni_filter', vxlan) != None) or False
            # If either one is enabled, so must be the other. Both can be off and both can be on
            if (vni_filter and not other_vni_filter) or (not vni_filter and other_vni_filter):
                raise ConfigError(f'Using multiple VXLAN interfaces with "external" '\
                    'requires all VXLAN interfaces to have "vni-filter" configured!')

            if not vni_filter and not other_vni_filter:
                other_tunnels = ', '.join(vxlan['other_tunnels'])
                raise ConfigError(f'Only one VXLAN tunnel is supported when "external" '\
                                f'CLI option is used and "vni-filter" is unset. '\
                                f'Additional tunnels: {other_tunnels}')

    if 'gpe' in vxlan and 'external' not in vxlan:
        raise ConfigError(f'VXLAN-GPE is only supported when "external" '\
                          f'CLI option is used.')

    if 'source_interface' in vxlan:
        # VXLAN adds at least an overhead of 50 byte - we need to check the
        # underlaying device if our VXLAN package is not going to be fragmented!
        vxlan_overhead = 50
        if 'source_address' in vxlan and is_ipv6(vxlan['source_address']):
            # IPv6 adds an extra 20 bytes overhead because the IPv6 header is 20
            # bytes larger than the IPv4 header - assuming no extra options are
            # in use.
            vxlan_overhead += 20

        # If source_address is not used - check IPv6 'remote' list
        elif 'remote' in vxlan:
            if any(is_ipv6(a) for a in vxlan['remote']):
                vxlan_overhead += 20

        lower_mtu = Interface(vxlan['source_interface']).get_mtu()
        if lower_mtu < (int(vxlan['mtu']) + vxlan_overhead):
            raise ConfigError(f'Underlaying device MTU is to small ({lower_mtu} '\
                              f'bytes) for VXLAN overhead ({vxlan_overhead} bytes!)')

    # Check for mixed IPv4 and IPv6 addresses
    protocol = None
    if 'source_address' in vxlan:
        if is_ipv6(vxlan['source_address']):
            protocol = 'ipv6'
        else:
            protocol = 'ipv4'

    if 'remote' in vxlan:
        error_msg = 'Can not mix both IPv4 and IPv6 for VXLAN underlay'
        for remote in vxlan['remote']:
            if is_ipv6(remote):
                if protocol == 'ipv4':
                    raise ConfigError(error_msg)
                protocol = 'ipv6'
            else:
                if protocol == 'ipv6':
                    raise ConfigError(error_msg)
                protocol = 'ipv4'

    if 'vlan_to_vni' in vxlan:
        if 'is_bridge_member' not in vxlan:
            raise ConfigError('VLAN to VNI mapping requires that VXLAN interface '\
                              'is member of a bridge interface!')

        vnis_used = []
        for vif, vif_config in vxlan['vlan_to_vni'].items():
            if 'vni' not in vif_config:
                raise ConfigError(f'Must define VNI for VLAN "{vif}"!')
            vni = vif_config['vni']
            if vni in vnis_used:
                raise ConfigError(f'VNI "{vni}" is already assigned to a different VLAN!')
            vnis_used.append(vni)

    if dict_search('parameters.neighbor_suppress', vxlan) != None:
        if 'is_bridge_member' not in vxlan:
            raise ConfigError('Neighbor suppression requires that VXLAN interface '\
                              'is member of a bridge interface!')

    verify_mtu_ipv6(vxlan)
    verify_address(vxlan)
    verify_bond_bridge_member(vxlan)
    verify_mirror_redirect(vxlan)

    # We use a defaultValue for port, thus it's always safe to use
    if vxlan['port'] == '8472':
        Warning('Starting from VyOS 1.4, the default port for VXLAN '\
                'has been changed to 4789. This matches the IANA assigned '\
                'standard port number!')

    return None

def generate(vxlan):
    return None

def apply(vxlan):
    # Check if the VXLAN interface already exists
    if 'rebuild_required' in vxlan or 'delete' in vxlan:
        if vxlan['ifname'] in interfaces():
            v = VXLANIf(vxlan['ifname'])
            # VXLAN is super picky and the tunnel always needs to be recreated,
            # thus we can simply always delete it first.
            v.remove()

    if 'deleted' not in vxlan:
        # Finally create the new interface
        v = VXLANIf(**vxlan)
        v.update(vxlan)

    return None

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