Adds Service Discovery module

Resolves issue https://github.com/freedombox/Plinth/issues/231
"Option to disable avahi-daemon"

actions/avahi

@@ -0,0 +1,61 @@
+#!/usr/bin/python3
+#
+# This file is part of Plinth.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
+"""
+Configuration helper for service discovery
+"""
+
+import argparse
+
+from plinth import action_utils
+
+
+def parse_arguments():
+    """Return parsed command line arguments as dictionary."""
+    parser = argparse.ArgumentParser()
+    subparsers = parser.add_subparsers(dest='subcommand', help='Sub command')
+
+    subparsers.add_parser('enable', help='Enable avahi-daemon service')
+    subparsers.add_parser('disable', help='Disable avahi-daemon service')
+
+    return parser.parse_args()
+
+
+def subcommand_enable(_):
+    """Start service."""
+    action_utils.service_enable('avahi-daemon.socket')
+    action_utils.service_enable('avahi-daemon.service')
+
+
+def subcommand_disable(_):
+    """Stop service."""
+    action_utils.service_disable('avahi-daemon.service')
+    action_utils.service_disable('avahi-daemon.socket')
+
+
+def main():
+    """Parse arguments and perform all duties."""
+    arguments = parse_arguments()
+
+    subcommand = arguments.subcommand.replace('-', '_')
+    subcommand_method = globals()['subcommand_' + subcommand]
+    subcommand_method(arguments)
+
+
+if __name__ == '__main__':
+    main()

data/etc/plinth/modules-enabled/avahi

@@ -0,0 +1 @@
+plinth.modules.avahi

plinth/modules/avahi/__init__.py

@@ -0,0 +1,56 @@
+#
+# This file is part of Plinth.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+"""
+Plinth module for service discovery
+"""
+
+from gettext import gettext as _
+import subprocess
+
+from plinth import actions
+from plinth import action_utils
+from plinth import cfg
+from plinth import service as service_module
+
+# pylint: disable=C0103
+
+depends = ['plinth.modules.system']
+
+service = None
+
+
+def init():
+    """Intialize the service discovery module."""
+    menu = cfg.main_menu.get('system:index')
+    menu.add_urlname(_('Service Discovery'), 'glyphicon-lamp',
+                     'avahi:index', 950)
+
+    global service # pylint: disable=W0603
+    service = service_module.Service(
+        'avahi', _('Service Discovery'), ['mdns'],
+        is_external=False, enabled=is_enabled())
+
+
+def is_enabled():
+    """Return whether the module is enabled."""
+    return action_utils.service_is_enabled('avahi-daemon')
+
+
+def is_running():
+    """Return whether the service is running."""
+    return action_utils.service_is_running('avahi-daemon')

plinth/modules/avahi/forms.py

@@ -0,0 +1,30 @@
+#
+# This file is part of Plinth.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+
+"""
+Plinth module for service discovery forms
+"""
+
+from django import forms
+from gettext import gettext as _
+
+
+class ServiceDiscoveryForm(forms.Form):
+    """Service discovery form."""
+    enabled = forms.BooleanField(
+        label=_('Enable service discovery'),
+        required=False)

plinth/modules/avahi/templates/avahi.html

@@ -0,0 +1,54 @@
+{% extends "base.html" %}
+{% comment %}
+#
+# This file is part of Plinth.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+{% endcomment %}
+
+{% load bootstrap %}
+
+{% block content %}
+
+<h2>Service Discovery</h2>
+
+<p>Service discovery is a program that can discover other machines and services
+running on your local network. It can also helps those other machines find your
+FreedomBox, and the services running on it. Service discovery is not required,
+though. Some users decide to disable it to minimize the 
+<a href="https://en.wikipedia.org/wiki/Attack_surface">attack surface</a>
+of their FreedomBox.
+
+<h3>Status</h3>
+
+<p class="running-status-parent">
+  {% if status.is_running %}
+  <span class="running-status active"></span> Service discovery server is running
+  {% else %}
+  <span class="running-status inactive"></span> Service discovery server is not running
+  {% endif %}
+</p>
+
+<h3>Configuration</h3>
+
+<form class="form" method="post">
+  {% csrf_token %}
+
+  {{ form|bootstrap }}
+
+  <input type="submit" class="btn btn-primary" value="Update setup"/>
+</form>
+
+{% endblock %}

plinth/modules/avahi/urls.py

@@ -0,0 +1,27 @@
+#
+# This file is part of Plinth.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+"""
+URLs for the service discovery module
+"""
+
+from django.conf.urls import patterns, url
+
+urlpatterns = patterns( # pylint: disable=C0103
+    'plinth.modules.avahi.views',
+    url(r'^sys/avahi/$', 'index', name='index'),
+    )

plinth/modules/avahi/views.py

@@ -0,0 +1,76 @@
+#
+# This file is part of Plinth.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+
+"""
+Plinth module for service discovery views
+"""
+
+from django.contrib import messages
+from django.template.response import TemplateResponse
+from gettext import gettext as _
+import logging
+
+from .forms import ServiceDiscoveryForm
+from plinth import actions
+from plinth import package
+from plinth.modules import avahi
+
+
+logger = logging.getLogger(__name__) # pylint: disable=C0103
+
+
+@package.required(['avahi-daemon'])
+def index(request):
+    """Serve configuration page."""
+    status = get_status()
+
+    form = None
+
+    if request.method == 'POST':
+        form = ServiceDiscoveryForm(request.POST)
+        if form.is_valid():
+            _apply_changes(request, status, form.cleaned_data)
+            status = get_status()
+            form = ServiceDiscoveryForm(initial=status)
+    else:
+        form = ServiceDiscoveryForm(initial=status)
+
+    return TemplateResponse(request, 'avahi.html',
+                            {'title': _('Service Discovery'),
+                             'status': status,
+                             'form': form})
+
+
+def get_status():
+    """Get the current settings from server."""
+    return {'enabled': avahi.is_enabled(),
+            'is_running': avahi.is_running()}
+
+
+def _apply_changes(request, old_status, new_status):
+    """Apply the changes."""
+    modified = False
+
+    if old_status['enabled'] != new_status['enabled']:
+        sub_command = 'enable' if new_status['enabled'] else 'disable'
+        modified = True
+        actions.superuser_run('avahi', [sub_command])
+        avahi.service.notify_enabled(None, new_status['enabled'])
+        messages.success(request, _('Configuration updated'))
+
+    if not modified:
+        messages.info(request, _('Setting unchanged'))