Re: ppp and "offline state"

[Dan Williams <dcbw redhat com>]

On Mon, 2009-09-07 at 12:53 +0200, Pietro Battiston wrote:
> By looking at bugs filed and words spent in several different bug
> trackers and mailing lists, I fear NM developers may be quite allergic
> to the words forming the subject of this email, but though indeed the
> problem gathered a big attention, I didn't find any (reasonably recent)
> documented answer to the three questions I'm asking, so here ends the
> prologue:
> 
> 
> 1) the most clear answer I found to the claim:
> 
> "NM doesn't support generic ppp, so I must connect with
> $APP_TO_HANDLE_PPP_CONNECTION and NM doesn't notice it, so
> $APP_USING_NETWORK doesn't connect, thinking I'm disconnected"
> 
> is at [0] and basically says:
> 
> "nobody is working on it, if somebody would like to, please step in".
> 
> This was obviously an admissible position; is it still true, or did the
> creation of MobileManager change future hopes of generic (or at least
> bluetooth) ppp support in NM? I ask it because the name of the project
> seems to suggest it, though in presenting it at [1], Dan only talks
> about "All mobile broadbands", and the same does the README.
> 
> 
> 2) supposing that answer to 1) is "no, people connecting via a
> traditional modem or a mobile via bluetooth shouldn't just hope NM
> supporting them soon", then wouldn't it make sense to allow _setting_,
> instead than just _querying_, online/offline status via DBUS?
> 
> This would allow, with few lines of code, tools like Gnome-PPP to say
> "hey, NM, we _are_ online"[2]
> 
> Then, in the network connections menu, an item "externally managed
> connection" could also possibly show up and activate...
> 
> I perfectly understand this is not something NM developers dream of,
> being not part of the standard infrastructure, but it would be of huge
> help to those who - like me and many people I know of (BTW, from
> personal experience I frankly doubt about the 98% Alexander's estimate
> in [0]) - need to connect via bluetooth/standard modems (it may be OT,
> but let me mention that this is one of the few things Windows/OS X
> softwares do nicely since many years and Linux Desktop doesn't).
> 
> I (don't know NM internals and) suppose some things may not work as
> usually: for instance, I can imagine sharing a connection would be a
> problem, if NM doesn't control it... but _this_ is really a minor
> problem.

Please read:

http://mail.gnome.org/archives/networkmanager-list/2009-May/msg00004.html

> 3) Why was PPP generic support dropped? Because it was broken/lacking
> manpower or just because mobile broadband support covered many of the
> use cases of it?

Dropped precisely because it was a complete non-integrated hack which is
not what we want, as described by the above mail.

To repeat: NM tries to manage your network connectivity.  And if it
doesn't have enough information to do that (because it's not managing
your default internet connection) then it's pretty hard to do a good job
of that, and you'll find that NM and whatever other method you're using
(gnomeppp or whatever) are stepping on each other's toes.  Want to use
one of the NetworkManager VPN plugins with your externally-managed
connection?  You can't, precisely because it's externally managed and
there's not *one* entity that has all the necessary information to make
intelligent decisions about the network.

Ok, so what if we have whatever else is managing the connection push a
bunch of information to NM and send all sorts of signals around to keep
connection state updated?  That's just about as much work as just adding
the support to NM, and we'd need to add stuff to NM to handle lifecycle
management of that external program anyway to clean up if it crashes,
etc.  If gnomeppp dies unexpectedly, what's left around to tell NM that
you're longer online?

These sorts of things are stuff that many people don't think about: the
*whole* picture, not just one partial use-case.

The solution: fix NM so it's able to handle your device natively.  It's
not that hard, it simply requires some time.  It's on the list, but the
more people that have time to help out, the faster it gets done.

Dan