nptv6: T2518: Initial support for nat66 (NPT)

1 files changed, 221 insertions, 0 deletions

diff --git a/src/conf_mode/nat66.py b/src/conf_mode/nat66.py
new file mode 100755
index 000000000..fdfffe335
--- /dev/null
+++ b/src/conf_mode/nat66.py
@@ -0,0 +1,221 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2020 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 jmespath
+import json
+import os
+
+from sys import exit
+from netifaces import interfaces
+
+from vyos.config import Config
+from vyos.configdict import dict_merge
+from vyos.template import render
+from vyos.util import cmd
+from vyos.util import check_kmod
+from vyos.util import dict_search
+from vyos.template import is_ipv6
+from vyos.xml import defaults
+from vyos import ConfigError
+import platform
+from vyos import airbag
+airbag.enable()
+
+k_mod = ['nft_nat', 'nft_chain_nat']
+
+iptables_nat_config = '/tmp/vyos-nat66-rules.nft'
+ndppd_config = '/run/ndppd/ndppd.conf'
+
+def get_handler(json, chain, target):
+    """ Get nftable rule handler number of given chain/target combination.
+    Handler is required when adding NAT66/Conntrack helper targets """
+    for x in json:
+        if x['chain'] != chain:
+            continue
+        if x['target'] != target:
+            continue
+        return x['handle']
+
+    return None
+
+def get_config(config=None):
+    if config:
+        conf = config
+    else:
+        conf = Config()
+    
+    base = ['nat66']
+    nat = conf.get_config_dict(base, key_mangling=('-', '_'), get_first_key=True)
+
+    # T2665: we must add the tagNode defaults individually until this is
+    # moved to the base class
+    for direction in ['source', 'destination']:
+        if direction in nat:
+            default_values = defaults(base + [direction, 'rule'])
+            for rule in nat[direction]['rule']:
+                nat[direction]['rule'][rule] = dict_merge(default_values,
+                    nat[direction]['rule'][rule])
+
+    # read in current nftable (once) for further processing
+    tmp = cmd('nft -j list table ip6 raw')
+    nftable_json = json.loads(tmp)
+
+    # condense the full JSON table into a list with only relevand informations
+    pattern = 'nftables[?rule].rule[?expr[].jump].{chain: chain, handle: handle, target: expr[].jump.target | [0]}'
+    condensed_json = jmespath.search(pattern, nftable_json)
+
+    if not conf.exists(base):
+        nat['helper_functions'] = 'remove'
+
+        nat['pre_ct_conntrack'] = get_handler(condensed_json, 'PREROUTING', 'NAT_CONNTRACK')
+        nat['out_ct_conntrack'] = get_handler(condensed_json, 'OUTPUT','NAT_CONNTRACK')
+
+        nat['deleted'] = ''
+
+        return nat
+
+    # check if NAT66 connection tracking helpers need to be set up - this has to
+    # be done only once
+    if not get_handler(condensed_json, 'PREROUTING', 'NAT_CONNTRACK'):
+        nat['helper_functions'] = 'add'
+
+        # Retrieve current table handler positions
+        nat['pre_ct_conntrack'] = get_handler(condensed_json, 'PREROUTING', 'VYATTA_CT_PREROUTING_HOOK')
+        nat['out_ct_conntrack'] = get_handler(condensed_json, 'OUTPUT','VYATTA_CT_OUTPUT_HOOK')
+    else:
+        nat['helper_functions'] = 'has'
+
+    return nat
+
+def verify(nat):
+    if not nat or 'deleted' in nat:
+        # no need to verify the CLI as NAT66 is going to be deactivated
+        return None
+
+    if 'helper_functions' in nat and nat['helper_functions'] != 'has':
+        if not (nat['pre_ct_conntrack'] or nat['out_ct_conntrack']):
+            raise Exception('could not determine nftable ruleset handlers')
+    
+    if dict_search('source.rule', nat):
+        for rule, config in dict_search('source.rule', nat).items():
+            err_msg = f'Source NAT66 configuration error in rule {rule}:'
+            if 'outbound_interface' not in config:
+                raise ConfigError(f'{err_msg}\n' \
+                                  'outbound-interface not specified')
+            else:
+                if config['outbound_interface'] not in 'any' and config['outbound_interface'] not in interfaces():
+                    print(f'WARNING: rule "{rule}" interface "{config["outbound_interface"]}" does not exist on this system')
+
+
+            prefix = dict_search('translation.prefix', config)
+            if prefix != None:
+                if not is_ipv6(prefix):
+                    raise ConfigError(f'Warning: IPv6 prefix {prefix} is not a valid address prefix')
+            
+            prefix = dict_search('source.prefix', config)
+            if prefix != None:
+                if not is_ipv6(prefix):
+                    raise ConfigError(f'{err_msg} source-prefix not specified')
+
+
+    if dict_search('destination.rule', nat):
+        for rule, config in dict_search('destination.rule', nat).items():
+            err_msg = f'Destination NAT66 configuration error in rule {rule}:'
+
+            if 'inbound_interface' not in config:
+                raise ConfigError(f'{err_msg}\n' \
+                                  'inbound-interface not specified')
+            else:
+                if config['inbound_interface'] not in 'any' and config['inbound_interface'] not in interfaces():
+                    print(f'WARNING: rule "{rule}" interface "{config["inbound_interface"]}" does not exist on this system')
+
+    return None
+
+def nat66_conf_to_ndp_proxy_conf(nat):
+    ndpproxy = {
+        'interface': {}
+    }
+    if  not nat or 'deleted' in nat:
+        # no need to verify the CLI as NAT66 is going to be deactivated
+        return None
+    # Detect and convert the default configuration of the configured interface
+    source_rule = dict_search('source.rule', nat)
+    if source_rule:
+        for rule,config in source_rule.items():
+            interface_ndp = {
+                'router': 'yes',
+                'timeout': 500,
+                'ttl': 30000,
+                'prefix': {}
+            }
+            if config['outbound_interface'] not in ndpproxy['interface']:
+                ndpproxy['interface'].update({config['outbound_interface']: interface_ndp})
+        for rule,config in source_rule.items():
+            if config['outbound_interface'] in ndpproxy['interface']:
+                prefix = dict_search('translation.prefix', config)
+                if prefix:
+                    nat66_prefix = config['translation']['prefix']
+                    if nat66_prefix not in ndpproxy['interface'][config['outbound_interface']]['prefix']:
+                        ndpproxy['interface'][config['outbound_interface']]['prefix'].update({nat66_prefix: {'mode':'auto'}})
+    
+    # Detect and convert the default configuration of the configured interface
+    destination_rule = dict_search('destination.rule', nat)
+    if destination_rule:
+        for rule,config in destination_rule.items():
+            interface_ndp = {
+                'router': 'yes',
+                'timeout': 500,
+                'ttl': 30000,
+                'prefix': {}
+            }
+            if config['inbound_interface'] not in ndpproxy['interface']:
+                ndpproxy['interface'].update({config['inbound_interface']: interface_ndp})
+        for rule,config in destination_rule.items():
+            if rule['interface'] in ndpproxy['interface']:
+                prefix = dict_search('destination.address', config)
+                if prefix:
+                    nat66_address = config['destination']['address']
+                    if nat66_prefix not in ndpproxy['interface'][config['inbound_interface']]['prefix']:
+                        ndpproxy['interface'][config['inbound_interface']]['prefix'].update({nat66_prefix: {'mode':'auto'}})
+    
+    return ndpproxy
+
+def generate(nat,ndp_proxy):
+    render(iptables_nat_config, 'firewall/nftables-nat66.tmpl', nat, permission=0o755)
+    if ndp_proxy == None:
+        return None
+    render(ndppd_config, 'proxy-ndp/ndppd.conf.tmpl', ndp_proxy, permission=0o755)
+    return None
+
+def apply(nat):
+    cmd(f'{iptables_nat_config}')
+    cmd('systemctl restart ndppd')
+    if os.path.isfile(iptables_nat_config):
+        os.unlink(iptables_nat_config)
+
+    return None
+
+if __name__ == '__main__':
+    try:
+        check_kmod(k_mod)
+        c = get_config()
+        verify(c)
+        ndp_proxy = nat66_conf_to_ndp_proxy_conf(c)
+        generate(c,ndp_proxy)
+        apply(c)
+    except ConfigError as e:
+        print(e)
+        exit(1)