radvd: T6118: add nat64prefix support RFC8781

Add support for pref64 option, as defined in RFC8781. The prefix valid lifetime
must not be smaller than the "interface interval max" definition which defaults
to 600.

  set service router-advert interface eth1 nat64prefix 64:ff9b::/96

1 files changed, 15 insertions, 3 deletions

diff --git a/src/conf_mode/service_router-advert.py b/src/conf_mode/service_router-advert.py
index dbb47de4e..88d767bb8 100755
--- a/src/conf_mode/service_router-advert.py
+++ b/src/conf_mode/service_router-advert.py
@@ -1,6 +1,6 @@
 #!/usr/bin/env python3
 #
-# Copyright (C) 2018-2022 VyOS maintainers and contributors
+# Copyright (C) 2018-2024 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
@@ -17,6 +17,8 @@
 import os
 
 from sys import exit
+from ipaddress import IPv6Network
+
 from vyos.base import Warning
 from vyos.config import Config
 from vyos.template import render
@@ -47,7 +49,9 @@ def verify(rtradv):
         return None
 
     for interface, interface_config in rtradv['interface'].items():
-        if 'prefix' in interface:
+        interval_max = int(interface_config['interval']['max'])
+
+        if 'prefix' in interface_config:
             for prefix, prefix_config in interface_config['prefix'].items():
                 valid_lifetime = prefix_config['valid_lifetime']
                 if valid_lifetime == 'infinity':
@@ -60,6 +64,15 @@ def verify(rtradv):
                 if not (int(valid_lifetime) >= int(preferred_lifetime)):
                     raise ConfigError('Prefix valid-lifetime must be greater then or equal to preferred-lifetime')
 
+        if 'nat64prefix' in interface_config:
+            nat64_supported_lengths = [32, 40, 48, 56, 64, 96]
+            for prefix, prefix_config in interface_config['nat64prefix'].items():
+                if IPv6Network(prefix).prefixlen not in nat64_supported_lengths:
+                    raise ConfigError(f'Invalid NAT64 prefix length for "{prefix}", can only be one of: /' + ', /'.join(nat64_supported_lengths))
+
+                if int(prefix_config['valid_lifetime']) < interval_max:
+                    raise ConfigError(f'NAT64 valid-lifetime must not be smaller then "interval max" which is "{interval_max}"!')
+
         if 'name_server' in interface_config:
             if len(interface_config['name_server']) > 3:
                 raise ConfigError('No more then 3 IPv6 name-servers supported!')
@@ -72,7 +85,6 @@ def verify(rtradv):
             # ensure stale RDNSS info gets removed in a timely fashion, this
             # should not be greater than 2*MaxRtrAdvInterval.
             lifetime = int(interface_config['name_server_lifetime'])
-            interval_max = int(interface_config['interval']['max'])
             if lifetime > 0:
                 if lifetime < int(interval_max):
                     raise ConfigError(f'RDNSS lifetime must be at least "{interval_max}" seconds!')