GNOME.org
 

Re: Turing the NM UI into an agent

Hi Dan,


since you are re-working most of the D-Bus APIs based around
Network
Manager, I like to propose a radical change on how you handle the
UI
part. Personally I think that the current UI inside Network Manager 
(even with 0.7) has too much tasks to fulfill. I prefer having a
"stupid" UI.

So my main concern is that replacing the current UI is too
complicated. One reason is that you need a well known bus name for 
the
UI on the system bus. This makes it impossible to install two UI
components or split tasks between two applications. We did the same 
in
the early days of BlueZ and I think it is not a good design to
hard-
code a well known bus name into the daemon and have the UI use the same one. So for BlueZ we came up with the D-Bus agent concept. So 
let
me try to explain it.

So the UI only gets a unique name (no need for a D-Bus security
file).
Then it registers itself a object path (the actual path value is
unimportant). After that it calls a RegisterAgent(object path)
method
inside the daemon. Now the daemon knows where to find an agent
(object
path and the unique name from the message sender value) and can
call
into this object for additional information. It really serves as a callback interface and the only things to agree on is the interface 
description. The bus name and object path are kept random.

This concept allows an easy way of monitoring agents. So you know
the
case when you have no agent (meaning no UI is running) or when an
agent dies. No unneeded D-Bus calls that might fails etc. The other 
advantage is that in theory you can stack agents and call them in
order. This is useful if you have a wizard or some small cases
where
the UI should look different from the general case. Or unregister
and
then re-register agents. For example for multi user scenarios.


There's already a split between the UI bits and the configuration
bits;
I think what you'd like to see is the User Settings service grab
unique
bus names so that each user could provide their own user settings at 
the
same time to NetworkManager.  I'd like to go there in the future,
but
then we need to figure out things that ConsoleKit will help with,
but
which are still very much undefined, stuff like:
- If user A has activated a connection on eth0, is user B allowed to 
control eth0 and potentially tear down user A's connection?

- If user A has activated eth0, is user B allowed to start a VPN
connection on eth0?

Stuff like that.  There might be uses for this sort of thing in
virtualization actually, but it's kind of hard to see networking as 
the
same sort of thing as Multi-User X, for example, where different
users
get exclusive access to individual mice, keyboards, displays, and
USB
flash drives.
I wasn't talking on these kind of things. They are totally different.
Right now the only thing that acquires a well-known bus name is the settings service, which doesn't have to have an UI at all. Up until 
NM
0.5 it actually was a completely separate process from the applet.
If
your user has permissions to do so at the D-Bus level (ie,
at_console or
whatever), then any process can call
ActivateConnection/DeactivateConnection right now.  But only 1
process
can provide the configuration data, which limits the set of what
ActivateConnection can actually connect to.


I meant the settings service. Still need to get deeper into the
Network Manager terminology. So having a "static" settings service is a bad design (from my perspective). Turning the settings service into agent would be a good thing. From the logical point of view it is not really different, but from a technical point of view it makes all the 
difference.
Well, the point of having only one settings service was security. You 
don't want any service providing connections to NM, because then
anything can send "allowed" networks to NM.  This is made somewhat
less
of an issue by PolicyKit, but still an issue.
Some trojan could start providing bogus networks to NetworkManager via 
the settings service, which NM would then happily connect to.  With
one
user settings service claiming the bus name, only one program can
provide those settings to NM, so the user is a lot more likely to
notice
that something is wrong (unless the trojan duplicates the look &
feel of
the user's expected applet).


actually having the applet/setting service use RegisterAgent method
call to actually register an agent with the core daemon is more
secure. You can block this method call via a D-Bus security policy or
via PolicyKit. It is much simpler to integrate since it not simple
starts up, it has to tell the core daemon it is there. Also the
unregister can be protected by matching the unique name and so on. It
has a bunch of advantages than simply assuming some other service
claims a well known name.


This is true.


I guess I simply don't see a case for more than one settings service
_per_user_ providing network connection information to NetworkManager. 
There's a case for more than one in a fast-user-switching system
though.


Personally I don't see the need for having separate settings services
at all. I understand why you have them, but for me all of this belongs 
into the core daemon and then the daemon would ask the applet/UI for
information. And the requested information should be limited to
passphrases, actions etc. Storing passphrases system wide or in the
user keyring becomes then only an option.
Since the connections/settings must be stored in the user's session, I'm 
not sure how moving it back to the core daemon would work well.  We
don't want NM to have to poke around the user's home directory for
things (it should be well-confined with SELinux policy for example), and we don't want NM itself to have to store each user's settings somewhere 
either.  There's also the DE issue, on Gnome we use GConf, on KDE they
use something else, and people have talked about writing a CLI
client/settings service.
you call a method in the agent interface (running in user session) and let it return the needed information. Preferably in form of a dictionary. 


For the per-user settings, this can then done behind the scenes
without an extra process or code running as user. With D-Bus you can
identify the unix user of a method call. With an agent concept it is
even simpler since on the register call you can retrieve the unix user 
of the agent and store it.

My point here is really to move as much intelligence from the user
session. If we keep that simple, we can replace the UI and keep a
generic network daemon across platforms.


That's a goal, though I'm not sure how that would be implemented in
practice.  I don't really want NM itself storing all the configuration
information somewhere, I feel like it should be part of the _user's_
preferences since much of it is user data, not system data.
This really depends on. I can argue for or against it. It really depends on what the user wants. In some cases I would say, yes, it is user specific. In other cases I would say that the user acts as a system administrator. I have no clean answer for this, but my goal is to keep the UI as lightweight as possible.
Then of course you have these single user embedded system where you have no real difference between system storage or user storage. 


So I see the UI as something totally "stupid" that the daemon tells
it
what to do and the user can use it to influence settings inside the
daemon. Besides that both are loosely coupled.
The UI bits are somewhat decoupled already, it just happens that it's convenient to have them in the same process right now. When they were 
split into nm-applet and NetworkManagerInfo, it wasn't very useful
abstraction.


As mentioned above, I still think too much stuff happens inside the
user session.
An example would be that the daemon needs a passphrase for a network. 
So it calls a callback inside the UI agent. This call should always
go
to the logged in user and thus to the applet run by that user. Any
other callback into the UI (or settings service) should be like this. 

Well, that assumes only one user is logged in :)  Fast user
switching is
a bit different here.  We need integration with ConsoleKit to figure
out
where this stuff should go.  Besides, the password information is
provided by the settings service, which needs to grab that password
from
the keyring.  No service _other_ than the settings service should be
providing information to NetworkManager, and NM should only be
accepting
passwords and such from the settings service that provided the
connection which is now being activated.


I think this will become really tricky if you can only have one
settings service. So I would question the need of the settings service 
here. Is that a really good separation or should we better integrate
it back into the core daemon and make use of what D-Bus provides us to 
implement per-user settings.

A small agent running in user session can handle keyring integration
and UI.
So big technical advantage here is that the daemon always knows if an 
agent is present or not. And if not, it can do a proper fallback.
Calling a D-Bus method that fails is a bad thing. Also the fact that 
you don't have to agree on a well known name and object path makes
this a lot cleaner. The D-Bus interface for the agent should be the
only contract between the UI and the daemon. The rest a variable
details.


I don't disagree in principle here.  Right now the UI and settings
service (which in the gnome applet are implemented in the nm-applet
process) are tied together for practical reasons, though it's not
extremely hard to split them.
Could you describe some of the scenarios that would involve stacking 
UI
agents?  I'm not sure I follow the use-cases here.


So you have the applet handling all security request (passphrase
etc.), but then you wanna do a wizard to setup a new network
connection. In that case you could re-direct the passphrase request
to
the wizard (which is a different application from the applet). While 
for WiFi this might be still limited in its usefulness. For all the
other wireless technologies like Bluetooth, WiMAX, UWB etc. it is
different.


I'm not sure I see the case for an external wizard; NM will be
controlling the network device itself and will be proxying the secrets 
where necessary (for WiMAX, NM would be pushing the certificates to
the
OMA-DM client or to the driver for example, and for BT NM would be
pushing the necessary bits to Bluez).  I'm not quite sure about UWB
yet,
and I know you've done a ton of work there, so maybe that's what
you're
thinking about.


The WiMAX part is a little bit trickier and to be quite honest, I
don't have a full plan for it. I know for sure that we either need a
username/password combination or a client certificate to authenticate
the user. And of course the master CA and network certificates, but
these come from somewhere else.


At least EAP-TLS is used for the authentication, though some providers
will be using EAP-TTLS after the initial provisioning is done.  We're
going to have to get an OMA-DM client up and running for at least one
provider here in the US.  We'll also need to expose the certificates
that are stored on the EEPROM of some implementations to the OMA-DM
client and possibly to userspace as well.
I honestly hope that we can write an OMA-DM client that hides all of this for us. Re-using an existing OMA-DM client seems not a good idea at the moment. However I might be wrong on this part. WiMAX is still changing a lot. 


I don't have any setups that would use straight username/password,
though I'd be interested in learning about them so I can go buy one.


Don't look at me. I have non either ;)


However the WiMAX case is really similar to the Bluetooth case. You
have a cold setup and need to scan for your network and input your
credentials. So you might need some kind of wizard to make this work.
In case for the actual credentials you wanna have an input field
inside the wizard and not having an extra dialog popup somewhere.


Right, I'm treating WiMAX more like cellular mostly because the setup
times are longer, and it's mostly licensed spectrum and therefore you
have to deal with service providers.  There are a lot fewer variables
than WiFi, and users also don't expect it to act the same way as WiFi.
Actually the number of variables is hugh. However OMA-DM suppose to automate this for us. We will see how good that works out once this hits the real market. 


And forget about global scanning in the background for WiMAX. That is
not gonna work out at all. The overall band is too big and would take
you hours to fully scan it. So the only way to setup WiMAX is a wizard 
(or somekind of pre-configuration).


Yeah, scanning on-the-fly is definitely not going to happen for WiMAX,
just like it doesn't happen for cellular.  They are quite similar in
that way.


The Bluetooth part is pretty easy since we already have stacked
agents. So if Network Manager wants to present an integrated UI, it
can do that already.


I looked into the BT stuff in detail late last year; I put most of my
comments in the gnome.org bug report in which you also replied. Unless something has changed with Bluez there, I think the general architecture 
I advocated there is still the right way to go.
We are moving towards BlueZ 4.0 with a lot simplified D-Bus API. However in the end you have to trust that BlueZ is doing the right thing. For Network Manager 0.7 is should be quite easy to read the configured access points from BlueZ and then add them to the applet list. In a month or so, we should finally have the Bluetooth wizard in place that allows you to setup Bluetooth access points (new 4.0 API makes this finally possible). 


UWB/Wireless USB is another story. We still have to figure out bits
and pieces, but the most common thing will be that you have a cable
connection first and then authorize this. Like the PS3 does with their 
controller.


Yeah, I don't know enough about UWB yet.  Need to learn more before I
can say _anything_ about it.
The good thing is that IOGear and D-Link are now finally selling products and the Inaky and the guys from INdT got the IOGear working.
For Bluetooth, I had planned on having whatever configuration would be 
required for DUN & PAN to be implemented in the applet, since the
configuration UI can be shared between the applet, the connection
editor, and any password request dialogs.  I think it's fairly
important
to have a consistent UI for configuring these things, and I haven't
yet
seen the need for loadable modules on the applet/connection editor
side,
since any new device types will certainly need support added in both
NM
and the UI agents.  I'm not sure there's a big win by keeping the UI
bits for each device type separate at this time.


Integrating PAN should be fairly simple. We do have a network service
for Bluetooth that does this all for you. You only have to mirror its
information. It will give you a list of connections/access points and
you can connect/disconnect them. All nicely over D-Bus.


Great.  Thanks for making it all D-Bus accessible :)
If you wanna have fun, then find my comment about D-Bus from 3 or 4 years ago. I did change my mind about D-Bus :) 

Regards

Marcel
[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]