T2898: add ndp-proxy service

VyOS CLI command
  set service ndp-proxy interface eth0 prefix 2001:db8::/64 mode 'static'

Will generate the following NDP proxy configuration

  $ cat /run/ndppd/ndppd.conf
  # autogenerated by service_ndp-proxy.py

  # This tells 'ndppd' how often to reload the route file /proc/net/ipv6_route
  route-ttl 30000

  # This sets up a listener, that will listen for any Neighbor Solicitation
  # messages, and respond to them according to a set of rules
  proxy eth0 {
      # Turn on or off the router flag for Neighbor Advertisements
      router no
      # Control how long to wait for a Neighbor Advertisment message before invalidating the entry (milliseconds)
      timeout 500
      # Control how long a valid or invalid entry remains in the cache (milliseconds)
      ttl 30000

      # This is a rule that the target address is to match against. If no netmask
      # is provided, /128 is assumed. You may have several rule sections, and the
      # addresses may or may not overlap.
      rule 2001:db8::/64 {
          static
      }
  }

1 files changed, 61 insertions, 0 deletions

diff --git a/src/migration-scripts/nat66/2-to-3 b/src/migration-scripts/nat66/2-to-3
new file mode 100755
index 000000000..f34f170b3
--- /dev/null
+++ b/src/migration-scripts/nat66/2-to-3
@@ -0,0 +1,61 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2023 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/>.
+
+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()
+
+base = ['nat66', 'source']
+new_base = ['service', 'ndp-proxy', 'interface']
+
+config = ConfigTree(config_file)
+if not config.exists(base):
+    # Nothing to do
+    exit(0)
+
+for rule in config.list_nodes(base + ['rule']):
+    base_rule = base + ['rule', rule]
+
+    interface = None
+    if config.exists(base_rule + ['outbound-interface', 'name']):
+        interface = config.return_value(base_rule + ['outbound-interface', 'name'])
+    else:
+        continue
+
+    prefix_base = base_rule + ['source', 'prefix']
+    if config.exists(prefix_base):
+        prefix = config.return_value(prefix_base)
+        config.set(new_base + [interface, 'prefix', prefix, 'mode'], value='static')
+        config.set_tag(new_base)
+        config.set_tag(new_base + [interface, 'prefix'])
+
+        if config.exists(base_rule + ['disable']):
+            config.set(new_base + [interface, 'prefix', prefix, 'disable'])
+
+try:
+    with open(file_name, 'w') as f:
+        f.write(config.to_string())
+except OSError as e:
+    print("Failed to save the modified config: {}".format(e))
+    exit(1)