dhcp: T2265: refactor DHCP class

Break the code between v4 and v6, remove need for getter/setter
as they are just exposing the underlying dict.

Move FixedDict from tunnel code and expose it to other part so
it can be used to prevent accidental change to the dhcp option if
no default exists already.

1 files changed, 50 insertions, 0 deletions

diff --git a/python/vyos/dicts.py b/python/vyos/dicts.py
new file mode 100644
index 000000000..79cab4a08
--- /dev/null
+++ b/python/vyos/dicts.py
@@ -0,0 +1,50 @@
+#!/usr/bin/env python3
+#
+# Copyright (C) 2019 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/>.
+
+
+class FixedDict(dict):
+    """
+    FixedDict: A dictionnary not allowing new keys to be created after initialisation.
+
+    >>> f = FixedDict(**{'count':1})
+    >>> f['count'] = 2
+    >>> f['king'] = 3
+      File "...", line ..., in __setitem__
+    raise ConfigError(f'Option "{k}" has no defined default')
+    """
+
+    def __init__(self, **options):
+        self._allowed = options.keys()
+        super().__init__(**options)
+
+    def __setitem__(self, k, v):
+        """
+        __setitem__ is a builtin which is called by python when setting dict values:
+        >>> d = dict()
+        >>> d['key'] = 'value'
+        >>> d
+        {'key': 'value'}
+
+        is syntaxic sugar for
+
+        >>> d = dict()
+        >>> d.__setitem__('key','value')
+        >>> d
+        {'key': 'value'}
+        """
+        if k not in self._allowed:
+            raise ConfigError(f'Option "{k}" has no defined default')
+        super().__setitem__(k, v)