Re: Disconnect a WiFi accespoint using cNetworkManager Python library

[Dan Williams <dcbw redhat com>]

On Fri, 2012-01-20 at 12:52 +0100, Olivier Deckmyn wrote:
> Hi,
> 
> 
> I’m building an Python application that has to connect and disconnect
> from Wifi on linux box. It's my very first experience with d-bus and
> gobject.
> 
> 
> I’m using NetworkManager layer, through the nice networkmanager lib
> found in cnetworkmanager
> (http://vidner.net/martin/software/cnetworkmanager/ thanx to Martin
> Vidner), in my daemon (named stationd).

I think the issue here is that you're trying to register two User
Settings services.  There should be only one and it should be global to
your python program.  ie in /home/biopredictive/station/lib/network.py
at line 88 is the problem; that object should only be created once (it
should really be a global object) but it looks like the call to connect
creates one each time. Since the object didn't get destroyed when the
first connect completed (and it shouldn't really be) you get the
dbus-python error.

Dan

> 
> This daemon runs a gobject.MainLoop. Once a timeout_add_seconds awake
> (triggers by an action of user in GUI), I have to disconnect current
> running Wifi and connect to a new one:
> 
> 
>     from dbus.mainloop.glib import DBusGMainLoop
>     DBusGMainLoop(set_as_default=True)
> 
> 
>     from networkmanager import NetworkManager
>     import networkmanager.applet.settings as settings
>     from networkmanager.applet import USER_SERVICE 
>     from networkmanager.applet.service import
> NetworkManagerUserSettings, NetworkManagerSettings
>     import time
>     import memcache
> 
> 
>     import gobject
>     loop = gobject.MainLoop()
> 
> 
>     nm = NetworkManager()
> 
> 
>     dummy_handler = lambda *args: None
> 
> 
>     cache = memcache.Client(['127.0.0.1:11211',] )
> 
> 
> 
> 
>     def get_device(dev_spec, hint):
>         candidates = []
>         devs = NetworkManager().GetDevices()
>         for dev in devs:
>             if dev._settings_type() == hint:
>                 candidates.append(dev)
>         if len(candidates) == 1:
>             return candidates[0]
>         for dev in devs:
>             if dev["Interface"] == dev_spec:
>                 return dev
>         print "Device '%s' not found" % dev_spec
>         return None
> 
> 
>     def kill_allconnections():
>         connections=nm['ActiveConnections']
>         for c in connections:
>             print c.object_path
>             nm.DeactivateConnection(c.object_path)
> 
> 
>     class Wifi(object):
>         
>         def connect(self, ssid, security="open", password=None):
>             "Connects to given Wifi network"
>             c=None # connection settings
>             us = NetworkManagerUserSettings([])
>             if security=="open":
>                 c = settings.WiFi(ssid)
>             elif security=="wep":
>                 c = settings.Wep(ssid, password)
>             elif security=="wpa":
>                 c = settings.WpaPsk(ssid, password)
>             else:
>                 raise AttributeError("invalid security model '%s'"%
> security)
>             svc = USER_SERVICE
>             svc_conn = us.addCon(c.conmap)
>             hint = svc_conn.settings["connection"]["type"]
>             dev = get_device("", hint)
>             appath = "/"
>             nm.ActivateConnection(svc, svc_conn, dev, appath,
> reply_handler=dummy_handler, error_handler=dummy_handler)
> 
> 
> 
> 
>     def change_network_settings():
>         key="station:network:change"
>         change=cache.get(key)
>         if change is not None:
>             print "DISCONNECT"
>             kill_allconnections()
>             print "CHANGE SETTINGS"
>             wifi=cache.get(key+':wifi')
>             if wifi is not None:
>                 ssid=cache.get(key+':wifi:ssid')
>                 security=cache.get(key+':wifi:security')
>                 password=cache.get(key+':wifi:password')
>                 print "SWITCHING TO %s"%ssid
>                 Wifi().connect(ssid, security, password)
>             cache.delete(key)
>         return True    
> 
> 
>     def mainloop():
>        gobject.timeout_add_seconds(1, change_network_settings)
>        try:
>           loop.run()
>        except KeyboardInterrupt:
>           loop.quit()
> 
> 
>     if __name__=="__main__":
>         mainloop()
> 
> 
> This runs perfectly for a first connection (read : the box is not
> connected, daemon is ran and box connects flawlessly to Wifi). Issue
> is when I try to connect to another Wifi : kill_allconnections() is
> ran silently, and connect method raises an exception on
> nm.ActivateConnection:
> 
> 
>     Traceback (most recent call last):
>       File "stationd.py", line 40, in change_network_settings
>         Wifi().connect(ssid, security, password)
>       File "/home/biopredictive/station/lib/network.py", line 88, in
> connect
>         us = NetworkManagerUserSettings([])
>       File
> "/home/biopredictive/station/lib/networkmanager/applet/service/__init__.py", line 71, in __init__
>         super(NetworkManagerUserSettings, self).__init__(conmaps,
> USER_SERVICE)
>       File
> "/home/biopredictive/station/lib/networkmanager/applet/service/__init__.py", line 33, in __init__
>         dbus.service.Object.__init__(self, bus, opath, bus_name)
>       File "/usr/lib/pymodules/python2.6/dbus/service.py", line 480,
> in __init__
>         self.add_to_connection(conn, object_path)
>       File "/usr/lib/pymodules/python2.6/dbus/service.py", line 571,
> in add_to_connection
>         self._fallback)
>     KeyError: "Can't register the object-path handler for
> '/org/freedesktop/NetworkManagerSettings': there is already a handler"
> 
> 
> It looks like my former connection didn’t release all its resources ? 
> 
> 
> Would you please help ?
> 
> 
> (I've asked this question on StackOverflow,
> too : http://stackoverflow.com/q/8938509/532219 )
> -- 
> 
> Olivier Deckmyn | olivier deckmyn org | 06 73 40 89 88
> 
> 
> 
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