bind: Use django's form validation

CHANGELOG.md

@@ -8,6 +8,7 @@ All notable changes to this project will be documented in this file.
   list those modules.
 - Added JS license web labels for LibreJS.
 - Added basic configuration form for Minetest server.
+- Added Domain Name Server (BIND) module.
 
 ### Changed
 - frontpage: Show app logos instead of generic icons.

plinth/modules/bind/__init__.py

@@ -22,8 +22,6 @@ Plinth module to configure BIND server
 import re
 
 from django.utils.translation import ugettext_lazy as _
-from django.core.exceptions import ValidationError
-from django.core.validators import validate_ipv46_address
 
 from plinth import actions
 from plinth import action_utils
@@ -141,13 +139,3 @@ def get_default():
         'forwarders': forwarders
     }
     return conf
-
-
-def validate(ips):
-    """Validate that ips is a list of IP addresses, separated by space."""
-    for ip_addr in ips.split():
-        try:
-            validate_ipv46_address(ip_addr)
-        except ValidationError:
-            return False
-    return True

plinth/modules/bind/forms.py

@@ -20,11 +20,18 @@ Forms for BIND module.
 """
 
 from django import forms
+from django.core.validators import validate_ipv46_address
 from django.utils.translation import ugettext_lazy as _
 
 from plinth.forms import ServiceForm
 
 
+def validate_ips(ips):
+    """Validate that ips is a list of IP addresses, separated by space."""
+    for ip_addr in ips.split():
+        validate_ipv46_address(ip_addr)
+
+
 class BindForm(ServiceForm):
     """BIND configuration form"""
     set_forwarding = forms.BooleanField(
@@ -39,4 +46,5 @@ class BindForm(ServiceForm):
 
     forwarders = forms.CharField(
         required=False,
+        validators=[validate_ips],
         help_text=_('A list of IP addresses, separated by space'))

plinth/modules/bind/views.py

@@ -26,7 +26,7 @@ from plinth import actions
 from plinth.views import ServiceView
 
 
-from . import description, managed_services, get_default, validate
+from . import description, managed_services, get_default
 from .forms import BindForm
 
 
@@ -67,15 +67,11 @@ class BindServiceView(ServiceView): # pylint: disable=too-many-ancestors
 
         if old_config['forwarders'] != data['forwarders'] \
            and old_config['forwarders'] is not '':
-            if validate(data['forwarders']) is True:
-                actions.superuser_run(
-                    'bind',
-                    ['dns', '--set', data['forwarders']])
-                messages.success(self.request,
-                                 _('DNS server configuration updated'))
-            else:
-                messages.error(self.request,
-                               _('Enter a valid IPv4 or IPv6 address.'))
+            actions.superuser_run(
+                'bind',
+                ['dns', '--set', data['forwarders']])
+            messages.success(self.request,
+                             _('DNS server configuration updated'))
         elif old_config['forwarders'] is '' \
              and old_config['forwarders'] != data['forwarders']:
             messages.error(