Merge pull request #3274 from sever-sever/T5169

T5169: Add PoC for generating CGNAT rules rfc6888

1 files changed, 288 insertions, 0 deletions

diff --git a/src/conf_mode/nat_cgnat.py b/src/conf_mode/nat_cgnat.py
new file mode 100755
index 000000000..f41d66c66
--- /dev/null
+++ b/src/conf_mode/nat_cgnat.py
@@ -0,0 +1,288 @@
+#!/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/>.
+
+import ipaddress
+import jmespath
+import os
+
+from sys import exit
+
+from vyos.config import Config
+from vyos.template import render
+from vyos.utils.process import cmd
+from vyos.utils.process import run
+from vyos import ConfigError
+from vyos import airbag
+
+airbag.enable()
+
+
+nftables_cgnat_config = '/run/nftables-cgnat.nft'
+
+
+class IPOperations:
+    def __init__(self, ip_prefix: str):
+        self.ip_prefix = ip_prefix
+        self.ip_network = ipaddress.ip_network(ip_prefix) if '/' in ip_prefix else None
+
+    def get_ips_count(self) -> int:
+        """Returns the number of IPs in a prefix or range.
+
+        Example:
+        % ip = IPOperations('192.0.2.0/30')
+        % ip.get_ips_count()
+        4
+        % ip = IPOperations('192.0.2.0-192.0.2.2')
+        % ip.get_ips_count()
+        3
+        """
+        if '-' in self.ip_prefix:
+            start_ip, end_ip = self.ip_prefix.split('-')
+            start_ip = ipaddress.ip_address(start_ip)
+            end_ip = ipaddress.ip_address(end_ip)
+            return int(end_ip) - int(start_ip) + 1
+        elif '/31' in self.ip_prefix:
+            return 2
+        elif '/32' in self.ip_prefix:
+            return 1
+        else:
+            return sum(
+                1
+                for _ in [self.ip_network.network_address]
+                + list(self.ip_network.hosts())
+                + [self.ip_network.broadcast_address]
+            )
+
+    def convert_prefix_to_list_ips(self) -> list:
+        """Converts a prefix or IP range to a list of IPs including the network and broadcast addresses.
+
+        Example:
+        % ip = IPOperations('192.0.2.0/30')
+        % ip.convert_prefix_to_list_ips()
+        ['192.0.2.0', '192.0.2.1', '192.0.2.2', '192.0.2.3']
+        %
+        % ip = IPOperations('192.0.0.1-192.0.2.5')
+        % ip.convert_prefix_to_list_ips()
+        ['192.0.2.1', '192.0.2.2', '192.0.2.3', '192.0.2.4', '192.0.2.5']
+        """
+        if '-' in self.ip_prefix:
+            start_ip, end_ip = self.ip_prefix.split('-')
+            start_ip = ipaddress.ip_address(start_ip)
+            end_ip = ipaddress.ip_address(end_ip)
+            return [
+                str(ipaddress.ip_address(ip))
+                for ip in range(int(start_ip), int(end_ip) + 1)
+            ]
+        elif '/31' in self.ip_prefix:
+            return [
+                str(ip)
+                for ip in [
+                    self.ip_network.network_address,
+                    self.ip_network.broadcast_address,
+                ]
+            ]
+        elif '/32' in self.ip_prefix:
+            return [str(self.ip_network.network_address)]
+        else:
+            return [
+                str(ip)
+                for ip in [self.ip_network.network_address]
+                + list(self.ip_network.hosts())
+                + [self.ip_network.broadcast_address]
+            ]
+
+
+def generate_port_rules(
+    external_hosts: list,
+    internal_hosts: list,
+    port_count: int,
+    global_port_range: str = '1024-65535',
+) -> list:
+    """Generates list of nftables rules for the batch file."""
+    rules = []
+    proto_map_elements = []
+    other_map_elements = []
+    start_port, end_port = map(int, global_port_range.split('-'))
+    total_possible_ports = (end_port - start_port) + 1
+
+    # Calculate the required number of ports per host
+    required_ports_per_host = port_count
+
+    # Check if there are enough external addresses for all internal hosts
+    if required_ports_per_host * len(internal_hosts) > total_possible_ports * len(
+        external_hosts
+    ):
+        raise ConfigError("Not enough ports available for the specified parameters!")
+
+    current_port = start_port
+    current_external_index = 0
+
+    for internal_host in internal_hosts:
+        external_host = external_hosts[current_external_index]
+        next_end_port = current_port + required_ports_per_host - 1
+
+        # If the port range exceeds the end_port, move to the next external host
+        while next_end_port > end_port:
+            current_external_index = (current_external_index + 1) % len(external_hosts)
+            external_host = external_hosts[current_external_index]
+            current_port = start_port
+            next_end_port = current_port + required_ports_per_host - 1
+
+        # Ensure the same port is not assigned to the same external host
+        if any(
+            rule.endswith(f'{external_host}:{current_port}-{next_end_port}')
+            for rule in rules
+        ):
+            raise ConfigError("Not enough ports available for the specified parameters")
+
+        proto_map_elements.append(
+            f'{internal_host} : {external_host} . {current_port}-{next_end_port}'
+        )
+        other_map_elements.append(f'{internal_host} : {external_host}')
+
+        current_port = next_end_port + 1
+        if current_port > end_port:
+            current_port = start_port
+            current_external_index += 1  # Move to the next external host
+
+    return [proto_map_elements, other_map_elements]
+
+
+def get_config(config=None):
+    if config:
+        conf = config
+    else:
+        conf = Config()
+
+    base = ['nat', 'cgnat']
+    config = conf.get_config_dict(
+        base,
+        get_first_key=True,
+        key_mangling=('-', '_'),
+        no_tag_node_value_mangle=True,
+        with_recursive_defaults=True,
+    )
+
+    return config
+
+
+def verify(config):
+    # bail out early - looks like removal from running config
+    if not config:
+        return None
+
+    if 'pool' not in config:
+        raise ConfigError(f'Pool must be defined!')
+    if 'rule' not in config:
+        raise ConfigError(f'Rule must be defined!')
+
+    # As PoC allow only one rule for CGNAT translations
+    # one internal pool and one external pool
+    if len(config['rule']) > 1:
+        raise ConfigError(f'Only one rule is allowed for translations!')
+
+    for pool in ('external', 'internal'):
+        if pool not in config['pool']:
+            raise ConfigError(f'{pool} pool must be defined!')
+        for pool_name, pool_config in config['pool'][pool].items():
+            if 'range' not in pool_config:
+                raise ConfigError(
+                    f'Range for "{pool} pool {pool_name}" must be defined!'
+                )
+
+    for rule, rule_config in config['rule'].items():
+        if 'source' not in rule_config:
+            raise ConfigError(f'Rule "{rule}" source pool must be defined!')
+        if 'pool' not in rule_config['source']:
+            raise ConfigError(f'Rule "{rule}" source pool must be defined!')
+
+        if 'translation' not in rule_config:
+            raise ConfigError(f'Rule "{rule}" translation pool must be defined!')
+
+
+def generate(config):
+    if not config:
+        return None
+    # first external pool as we allow only one as PoC
+    ext_pool_name = jmespath.search("rule.*.translation | [0]", config).get('pool')
+    int_pool_name = jmespath.search("rule.*.source | [0]", config).get('pool')
+    ext_query = f"pool.external.{ext_pool_name}.range | keys(@)"
+    int_query = f"pool.internal.{int_pool_name}.range"
+    external_ranges = jmespath.search(ext_query, config)
+    internal_ranges = [jmespath.search(int_query, config)]
+
+    external_list_count = []
+    external_list_hosts = []
+    internal_list_count = []
+    internal_list_hosts = []
+    for ext_range in external_ranges:
+        # External hosts count
+        e_count = IPOperations(ext_range).get_ips_count()
+        external_list_count.append(e_count)
+        # External hosts list
+        e_hosts = IPOperations(ext_range).convert_prefix_to_list_ips()
+        external_list_hosts.extend(e_hosts)
+    for int_range in internal_ranges:
+        # Internal hosts count
+        i_count = IPOperations(int_range).get_ips_count()
+        internal_list_count.append(i_count)
+        # Internal hosts list
+        i_hosts = IPOperations(int_range).convert_prefix_to_list_ips()
+        internal_list_hosts.extend(i_hosts)
+
+    external_host_count = sum(external_list_count)
+    internal_host_count = sum(internal_list_count)
+    ports_per_user = int(
+        jmespath.search(f'pool.external.{ext_pool_name}.per_user_limit.port', config)
+    )
+    external_port_range: str = jmespath.search(
+        f'pool.external.{ext_pool_name}.external_port_range', config
+    )
+
+    proto_maps, other_maps = generate_port_rules(
+        external_list_hosts, internal_list_hosts, ports_per_user, external_port_range
+    )
+
+    config['proto_map_elements'] = ', '.join(proto_maps)
+    config['other_map_elements'] = ', '.join(other_maps)
+
+    render(nftables_cgnat_config, 'firewall/nftables-cgnat.j2', config)
+
+    # dry-run newly generated configuration
+    tmp = run(f'nft --check --file {nftables_cgnat_config}')
+    if tmp > 0:
+        raise ConfigError('Configuration file errors encountered!')
+
+
+def apply(config):
+    if not config:
+        # Cleanup cgnat
+        cmd('nft delete table ip cgnat')
+        if os.path.isfile(nftables_cgnat_config):
+            os.unlink(nftables_cgnat_config)
+        return None
+    cmd(f'nft --file {nftables_cgnat_config}')
+
+
+if __name__ == '__main__':
+    try:
+        c = get_config()
+        verify(c)
+        generate(c)
+        apply(c)
+    except ConfigError as e:
+        print(e)
+        exit(1)