dbus: Add new module for D-Bus services

- Implement listening for CacheUpdated notification.

- Configuration to allow only root to trigger the notification.

- Trigger the notification from an apt update hook.

- Retrieve the list of packages available for upgrade and print them to log.

- Add dependency on libglib2.0-bin for the gdbus command line tool.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

data/etc/apt/apt.conf.d/20freedombox

@@ -0,0 +1,8 @@
+// This configuration is installed by FreedomBox.
+//
+// When Apt's cache is updated (i.e. apt-cache update) notify FreedomBox service
+// via it's D-Bus API. FreedomBox may then handle upgrade of some packages.
+//
+APT::Update::Post-Invoke-Success {
+    "/usr/bin/test -S /var/run/dbus/system_bus_socket && /usr/bin/gdbus call --system --dest org.freedombox.Service --object-path /org/freedombox/Service/PackageHandler --timeout 10 --method org.freedombox.Service.PackageHandler.CacheUpdated 2> /dev/null > /dev/null; /bin/echo > /dev/null";
+};

data/usr/share/dbus-1/system.d/org.freedombox.Service.conf

@@ -0,0 +1,19 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-Bus Bus Configuration 1.0//EN"
+  "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
+
+<!--
+This file is part of FreedomBox.
+
+Allow only root user to send any notifications to FreedomBox.
+-->
+
+<busconfig>
+
+  <policy user="root">
+    <allow own="org.freedombox.Service"/>
+    <allow send_destination="org.freedombox.Service"
+           send_path="/org/freedombox/Service/PackageHandler"/>
+  </policy>
+
+</busconfig>

debian/control

@@ -70,6 +70,8 @@ Depends:
  gir1.2-nm-1.0,
  javascript-common,
  ldapscripts,
+# For gdbus used to call hooks into service
+ libglib2.0-bin,
  libjs-bootstrap,
  libjs-jquery,
  libjs-modernizr,

plinth/__main__.py

@@ -23,7 +23,7 @@ import sys
 
 import axes
 
-from . import (cfg, frontpage, log, menu, module_loader, service, setup,
+from . import (cfg, dbus, frontpage, log, menu, module_loader, service, setup,
                web_framework, web_server)
 
 axes.default_app_config = "plinth.axes_app_config.AppConfig"
@@ -129,6 +129,7 @@ def adapt_config(arguments):
 def on_web_server_stop():
     """Stop all other threads since web server is trying to exit."""
     setup.stop()
+    dbus.stop()
 
 
 def main():
@@ -177,6 +178,8 @@ def main():
 
     setup.run_setup_in_background()
 
+    dbus.run()
+
     web_server.init()
     web_server.run(on_web_server_stop)
 

plinth/dbus.py

@@ -0,0 +1,154 @@
+#
+# This file is part of FreedomBox.
+#
+# 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/>.
+#
+"""
+Expose some API over D-Bus.
+"""
+
+import logging
+import threading
+
+from plinth.utils import import_from_gi
+
+from . import setup
+
+glib = import_from_gi('GLib', '2.0')
+gio = import_from_gi('Gio', '2.0')
+
+logger = logging.getLogger(__name__)
+
+_thread = None
+_server = None
+_main_loop = None
+
+
+class PackageHandler():
+    """D-Bus service to listen for messages when apt cache is updated."""
+
+    introspection_xml = '''
+<?xml version="1.0" encoding="utf-8"?>
+<!DOCTYPE node PUBLIC "-//freedesktop//DTD D-BUS Object Introspection 1.0//EN"
+  "http://www.freedesktop.org/standards/dbus/1.0/introspect.dtd">
+<node name="/org/freedombox/Service/PackageHandler">
+  <interface name="org.freedombox.Service.PackageHandler">
+    <method name="CacheUpdated"/>
+  </interface>
+</node>
+'''
+
+    def register(self, connection):
+        """Register the object in D-Bus connection."""
+        introspection_data = gio.DBusNodeInfo.new_for_xml(
+            self.introspection_xml)
+        interface_info = gio.DBusNodeInfo.lookup_interface(
+            introspection_data, 'org.freedombox.Service.PackageHandler')
+        connection.register_object('/org/freedombox/Service/PackageHandler',
+                                   interface_info, self.on_method_call, None,
+                                   None)
+
+    def on_method_call(self, _connection, _sender, _object_path,
+                       _interface_name, method_name, _parameters, invocation):
+        """Handle method being called.
+
+        No need to check all the incoming parameters as D-Bus will validate all
+        the incoming parameters using introspection data.
+
+        """
+        if method_name == 'CacheUpdated':
+            self.on_cache_updated()
+            invocation.return_value()
+
+    @staticmethod
+    def on_cache_updated():
+        """Called when system package cache is updated."""
+        logger.info('Apt package cache updated.')
+
+        # Run in a new thread because we don't want to block the thread running
+        # Glib main loop.
+        threading.Thread(target=setup.on_package_cache_updated).start()
+
+
+class DBusServer():
+    """Abstraction over a connection to D-Bus."""
+
+    def __init__(self):
+        """Initialize the server object."""
+        self.package_handler = None
+
+    def connect(self):
+        """Connect to bus with well-known name."""
+        gio.bus_own_name(gio.BusType.SYSTEM, 'org.freedombox.Service',
+                         gio.BusNameOwnerFlags.NONE, self.on_bus_acquired,
+                         self.on_name_acquired, self.on_name_lost)
+
+    def on_bus_acquired(self, connection, name):
+        """Callback when connection to D-Bus has been acquired."""
+        logger.info('D-Bus connection acquired: %s', name)
+        self.package_handler = PackageHandler()
+        self.package_handler.register(connection)
+
+    @staticmethod
+    def on_name_acquired(_connection, name):
+        """Callback when service name on D-Bus has been acquired."""
+        logger.info('D-Bus name acquired: %s', name)
+
+    @staticmethod
+    def on_name_lost(_connection, name):
+        """Callback when service name or DBus connection is closed."""
+        logger.info('D-Bus connection lost: %s', name)
+
+        # XXX: Reconnect after a while
+        #
+        # Such as by doing:
+        # connection.set_exit_on_close(False)
+        # gio.timeout_add(10000, self.connect)
+        #
+        # However, perhaps due to some cleanup issues, reconnection is not
+        # happening if it is does after an incoming method call.
+        #
+        # If D-Bus connection is lost due to daemon restart, FreedomBox service
+        # will receive a SIGTERM and exit. systemd should then restart the
+        # service again.
+
+
+def run():
+    """Run a glib main loop forever in a thread."""
+    global _thread
+    _thread = threading.Thread(target=_run)
+    _thread.start()
+
+
+def stop():
+    """Exit glib main loop and end the thread."""
+    if _main_loop:
+        logger.info('Exiting main loop for D-Bus services')
+        _main_loop.quit()
+
+
+def _run():
+    """Connect to D-Bus and run main loop."""
+    logger.info('Started new thread for D-Bus services')
+
+    global _server
+    _server = DBusServer()
+    _server.connect()
+
+    global _main_loop
+    _main_loop = glib.MainLoop()
+    _main_loop.run()
+    _main_loop = None
+
+    logger.info('D-Bus services thread exited.')

plinth/setup.py

@@ -37,6 +37,8 @@ _is_first_setup = False
 is_first_setup_running = False
 _is_shutting_down = False
 
+_force_upgrader = None
+
 
 class Helper(object):
     """Helper routines for modules to show progress."""
@@ -335,3 +337,31 @@ def run_setup_on_modules(module_list, allow_install=True):
     except Exception as exception:
         logger.error('Error running setup - %s', exception)
         raise
+
+
+class ForceUpgrader():
+    """Find and upgrade packages by force when conffile prompt is needed."""
+
+    def on_package_cache_updated(self):
+        """Find an upgrade packages."""
+        packages = self.get_list_of_upgradeable_packages()
+        if packages:
+            logger.info('Packages available for upgrade: %s',
+                        ', '.join([package.name for package in packages]))
+
+        # XXX: Implement force upgrading of selected packages
+
+    @staticmethod
+    def get_list_of_upgradeable_packages():
+        """Return list of packages that can be upgraded."""
+        cache = apt.cache.Cache()
+        return [package for package in cache if package.is_upgradable]
+
+
+def on_package_cache_updated():
+    """Called by D-Bus service when apt package cache is updated."""
+    global _force_upgrader
+    if not _force_upgrader:
+        _force_upgrader = ForceUpgrader()
+
+    _force_upgrader.on_package_cache_updated()

setup.py

@@ -236,10 +236,11 @@ setuptools.setup(
          glob.glob('data/etc/apache2/sites-available/*.conf')),
         ('/etc/apache2/includes',
          glob.glob('data/etc/apache2/includes/*.conf')),
-        ('/etc/apt/apt.conf.d',
-         glob.glob('data/etc/apt/apt.conf.d/60unattended-upgrades')),
-        ('/etc/avahi/services/',
-         glob.glob('data/etc/avahi/services/*.service')),
+        ('/etc/apt/apt.conf.d', [
+            'data/etc/apt/apt.conf.d/60unattended-upgrades',
+            'data/etc/apt/apt.conf.d/20freedombox'
+        ]), ('/etc/avahi/services/',
+             glob.glob('data/etc/avahi/services/*.service')),
         ('/etc/ikiwiki', glob.glob('data/etc/ikiwiki/*.setup')),
         ('/etc/NetworkManager/dispatcher.d/', [
             'data/etc/NetworkManager/dispatcher.d/10-freedombox-batman'
@@ -247,9 +248,10 @@ setuptools.setup(
             'data/etc/sudoers.d/plinth'
         ]), ('/lib/systemd/system',
              glob.glob('data/lib/systemd/system/*.service')),
-        ('/lib/systemd/system/mldonkey-server.service.d',
-         ['data/lib/systemd/system/mldonkey-server.service.d/freedombox.conf']),
-        ('/lib/systemd/system', glob.glob('data/lib/systemd/system/*.timer')),
+        ('/lib/systemd/system/mldonkey-server.service.d', [
+            'data/lib/systemd/system/mldonkey-server.service.d/freedombox.conf'
+        ]), ('/lib/systemd/system',
+             glob.glob('data/lib/systemd/system/*.timer')),
         ('/etc/mediawiki',
          glob.glob('data/etc/mediawiki/*.php')), ('/etc/update-motd.d/', [
              'data/etc/update-motd.d/50-freedombox'
@@ -265,6 +267,8 @@ setuptools.setup(
                             glob.glob('data/usr/share/augeas/lenses/*.aug')),
         ('/usr/share/augeas/lenses/tests',
          glob.glob('data/usr/share/augeas/lenses/tests/test_*.aug')),
+        ('/usr/share/dbus-1/system.d',
+         glob.glob('data/usr/share/dbus-1/system.d/*.conf')),
         ('/usr/share/pam-configs/',
          glob.glob('data/usr/share/pam-configs/*-freedombox')),
         ('/etc/fail2ban/jail.d', glob.glob('data/etc/fail2ban/jail.d/*.conf')),