T7283: VPP add static NAT support (#24)

* T7283: VPP add static NAT support

Add static mapping NAT implementation

```
set vpp nat44 static rule 10 outbound-interface 'eth0'
set vpp nat44 static rule 10 inbound-interface 'eth1'
set vpp nat44 static rule 10 destination address 192.168.122.10    # optional, if not set outbound interface ip address is used
set vpp nat44 static rule 10 destination port 6545                 # optional
set vpp nat44 static rule 10 protocol tcp|udp|icmp|all             # optional, defaults to "all"
set vpp nat44 static rule 10 translation address 100.64.0.10
set vpp nat44 static rule 10 translation port 64010                # optional
```

* Improve help strings (Daniil Baturin)

---------

Co-authored-by: Daniil Baturin <daniil@baturin.org>

2 files changed, 211 insertions, 0 deletions

diff --git a/src/conf_mode/vpp.py b/src/conf_mode/vpp.py
index 1f4c6c0f0..ca7d19160 100755
--- a/src/conf_mode/vpp.py
+++ b/src/conf_mode/vpp.py
@@ -138,6 +138,8 @@ def get_config(config=None):
     # NAT dependency
     if conf.exists(['vpp', 'nat44', 'source']):
         set_dependents('vpp_nat_source', conf)
+    if conf.exists(['vpp', 'nat44', 'static']):
+        set_dependents('vpp_nat_static', conf)
 
     if not conf.exists(base):
         return {
diff --git a/src/conf_mode/vpp_nat_static.py b/src/conf_mode/vpp_nat_static.py
new file mode 100644
index 000000000..50384a00b
--- /dev/null
+++ b/src/conf_mode/vpp_nat_static.py
@@ -0,0 +1,209 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2025 VyOS Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# 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, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+from vyos.configdiff import Diff
+from vyos.configdiff import get_config_diff
+from vyos.configdict import node_changed
+from vyos.config import Config
+from vyos import ConfigError
+from vyos.vpp.nat.nat44 import Nat44Static
+
+
+protocol_map = {
+    'all': 0,
+    'icmp': 1,
+    'tcp': 6,
+    'udp': 17,
+}
+
+
+def get_config(config=None) -> dict:
+    if config:
+        conf = config
+    else:
+        conf = Config()
+
+    base = ['vpp', 'nat44', 'static']
+
+    # Get config_dict with default values
+    config = conf.get_config_dict(
+        base,
+        key_mangling=('-', '_'),
+        get_first_key=True,
+        no_tag_node_value_mangle=True,
+        with_defaults=True,
+        with_recursive_defaults=True,
+    )
+
+    # Get effective config as we need full dictionary per interface delete
+    effective_config = conf.get_config_dict(
+        base,
+        key_mangling=('-', '_'),
+        effective=True,
+        get_first_key=True,
+        no_tag_node_value_mangle=True,
+    )
+
+    if not config:
+        config['remove'] = True
+
+    in_iface_add = []
+    in_iface_del = []
+    out_iface_add = []
+    out_iface_del = []
+
+    changed_rules = node_changed(
+        conf,
+        base + ['rule'],
+        key_mangling=('-', '_'),
+        recursive=True,
+        expand_nodes=Diff.DELETE | Diff.ADD,
+    )
+    diff = get_config_diff(conf)
+
+    for rule in changed_rules:
+        base_rule = base + ['rule', rule]
+        tmp = node_changed(
+            conf,
+            base_rule,
+            key_mangling=('-', '_'),
+            recursive=True,
+            expand_nodes=Diff.DELETE | Diff.ADD,
+        )
+
+        if 'inbound_interface' in tmp:
+            new, old = diff.get_value_diff(base_rule + ['inbound-interface'])
+            in_iface_add.append(new) if new else None
+            in_iface_del.append(old) if old else None
+        if 'outbound_interface' in tmp:
+            new, old = diff.get_value_diff(base_rule + ['outbound-interface'])
+            out_iface_add.append(new) if new else None
+            out_iface_del.append(old) if old else None
+
+    final_in_iface_add = list(set(in_iface_add) - set(in_iface_del))
+    final_in_iface_del = list(set(in_iface_del) - set(in_iface_add))
+    final_out_iface_add = list(set(out_iface_add) - set(out_iface_del))
+    final_out_iface_del = list(set(out_iface_del) - set(out_iface_add))
+
+    config.update(
+        {
+            'in_iface_add': final_in_iface_add,
+            'in_iface_del': final_in_iface_del,
+            'out_iface_add': final_out_iface_add,
+            'out_iface_del': final_out_iface_del,
+            'changed_rules': changed_rules,
+        }
+    )
+
+    if effective_config:
+        config.update({'effective': effective_config})
+
+    return config
+
+
+def verify(config):
+    if 'remove' in config:
+        return None
+
+    required_keys = {'inbound_interface', 'outbound_interface'}
+    for rule, rule_config in config['rule'].items():
+        missing_keys = required_keys - rule_config.keys()
+        if missing_keys:
+            raise ConfigError(
+                f"Required options are missing: {', '.join(missing_keys).replace('_', '-')} in rule {rule}"
+            )
+
+        if not rule_config.get('translation', {}).get('address'):
+            raise ConfigError(f'Translation requires address in rule {rule}')
+
+        has_dest_port = 'port' in rule_config.get('destination', {})
+        has_trans_port = 'port' in rule_config.get('translation', {})
+
+        if not has_trans_port == has_dest_port:
+            raise ConfigError(
+                'Source and destination ports must either both be specified, or neither must be specified'
+            )
+
+
+def generate(config):
+    pass
+
+
+def apply(config):
+    n = Nat44Static()
+
+    # Delete inbound interfaces
+    for interface in config['in_iface_del']:
+        n.delete_inbound_interface(interface)
+    # Delete outbound interfaces
+    for interface in config['out_iface_del']:
+        n.delete_outbound_interface(interface)
+    # Delete NAT static mapping rules
+    for rule in config['changed_rules']:
+        if rule in config.get('effective', {}).get('rule', {}):
+            rule_config = config['effective']['rule'][rule]
+            n.delete_nat44_static_mapping(
+                iface_out=rule_config.get('outbound_interface'),
+                local_ip=rule_config.get('translation').get('address'),
+                external_ip=rule_config.get('destination', {}).get('address', ''),
+                local_port=int(rule_config.get('translation', {}).get('port', 0)),
+                external_port=int(rule_config.get('destination', {}).get('port', 0)),
+                protocol=protocol_map[rule_config.get('protocol', 'all')],
+                use_iface=(
+                    True
+                    if not rule_config.get('destination', {}).get('address')
+                    else False
+                ),
+            )
+
+    if 'remove' in config:
+        return None
+
+    # Add NAT44 static mapping rules
+    n.enable_nat44_ed()
+    for interface in config['in_iface_add']:
+        n.add_inbound_interface(interface)
+    for interface in config['out_iface_add']:
+        n.add_outbound_interface(interface)
+    for rule in config['changed_rules']:
+        if rule in config.get('rule', {}):
+            rule_config = config['rule'][rule]
+            n.add_nat44_static_mapping(
+                iface_out=rule_config.get('outbound_interface'),
+                local_ip=rule_config.get('translation').get('address'),
+                external_ip=rule_config.get('destination', {}).get('address', ''),
+                local_port=int(rule_config.get('translation', {}).get('port', 0)),
+                external_port=int(rule_config.get('destination', {}).get('port', 0)),
+                protocol=protocol_map[rule_config.get('protocol', 'all')],
+                use_iface=(
+                    True
+                    if not rule_config.get('destination', {}).get('address')
+                    else False
+                ),
+            )
+
+
+if __name__ == '__main__':
+    try:
+        c = get_config()
+        verify(c)
+        generate(c)
+        apply(c)
+    except ConfigError as e:
+        print(e)
+        exit(1)