#!/usr/bin/env python3
#
# Copyright (C) 2024 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/>.

# T6345: random - In kernel 5.0 and newer this is the same as fully-random.
#        In earlier kernels the port mapping will be randomized using a seeded
#        MD5 hash mix using source and destination address and destination port.
#        drop fully-random from CLI

from sys import argv,exit
from vyos.configtree import ConfigTree

if len(argv) < 2:
    print("Must specify file name!")
    exit(1)

file_name = argv[1]

with open(file_name, 'r') as f:
    config_file = f.read()

config = ConfigTree(config_file)

if not config.exists(['nat']):
    # Nothing to do
    exit(0)

for direction in ['source', 'destination']:
    # If a node doesn't exist, we obviously have nothing to do.
    if not config.exists(['nat', direction]):
        continue

    # However, we also need to handle the case when a 'source' or 'destination' sub-node does exist,
    # but there are no rules under it.
    if not config.list_nodes(['nat', direction]):
        continue

    for rule in config.list_nodes(['nat', direction, 'rule']):
        port_mapping = ['nat', direction, 'rule', rule, 'translation', 'options', 'port-mapping']
        if config.exists(port_mapping):
            tmp = config.return_value(port_mapping)
            if tmp == 'fully-random':
                config.set(port_mapping, value='random')

try:
    with open(file_name, 'w') as f:
        f.write(config.to_string())
except OSError as e:
    print(f'Failed to save the modified config: {e}')
    exit(1)