Re: system-connection for WWAN not working

[Dan Williams <dcbw redhat com>]

On Fri, 2009-11-20 at 20:43 +0100, Hans-Gerd van Schelve wrote:
> Hi!
> 
> Now we talked about the problem. Can someone confirm this is a bug or do I
> have a
> wrong configuration? What else can I do?

Basically we get to confirm that the username and password were
correctly sent to pppd in the CHAP hook in nm-pppd-plugin.so.  That will
take a bit of debugging, but I can try to verify that today.  I thought
I'd get to it yesterday but did not.

Just because the *modem* say that the CHAP exchange was successful
doesn't mean the GSM PDP context creation was successful.

Remember, 3G modems only do PPP between the host and the card, not over
the air.  So it may be the case that the PPP exchange is just sucking
the auth credentials into the card and saving them for a bit later when
the card actually makes a request to the network for a data session (ie,
activates the PDP context).  At that point perhaps the connection is
failing because the network rejects a wrong username & password.  It's
not necessarily the case that the card authenticates to the network with
the given username & password at the same time as the PPP exchange
indicates that the *PPP* authentication is complete.

PPP with 3G modems is really just a horrible hack to allow them to still
be used with legacy operating systems.  The Option and Sony Ericsson
model of presenting an AT-compatible control port, but a real network
device for data transfer (instead of PPP) is the right way to go but not
everyone is there yet.

Dan

> -- Hans-Gerd
> 
> On Thu, 19 Nov 2009 13:17:46 +0100, van Schelve <public van-schelve de>
> wrote:
> >> Well, I am not Dan, and I am not *sure*, but this part of the log of
> > failed
> >> session does not seem to support this theory:
> >> 
> >> ====
> >> rcvd [CHAP Challenge id=0x1 <ae19e43f460f5298ca0a6933246e4335>, name =
> >> "UMTS_CHAP_SRVR"]
> >> ** Message: nm-ppp-plugin: (get_credentials): passwd-hook, requesting
> >> credentials...
> >> ** Message: nm-ppp-plugin: (get_credentials): got credentials from
> >> NetworkManager
> >> sent [CHAP Response id=0x1 <d29bfa4e9cab3171192695c3c3d62cf6>, name =
> >> "username"]
> >> rcvd [CHAP Success id=0x1 ""]
> >> CHAP authentication succeeded
> >> ====
> >> 
> >> Could the radius log be from another session, that failed for a
> > different
> >> reason?
> > 
> > This is possible but during the time from the Logfiles I really did some
> > tests.
> > If you think it can be helpful, I will try to capture the logs from a
> > complete
> > session again NM and Radius.
> > 
> > But let me put it together again:
> > 
> > - T-Mobile Internet connection is OK when configured as User connection
> > as well as system-connection
> > 
> > - MyWWAN works only when configured as User connection. When using this
> > as system-connection connection don't come up.
> > 
> > I compared T-Mobile and MyWWAN system-connection files from
> > /etc/NetworkManager/system-connections
> > and they are different only in password, username and apn (as well as
> uuid
> > and id)
> > 
> > -- Hans-Gerd
> >> 
> >> Looking closer at the logs, side by side, shows that the difference
> > starts
> >> *after* successful authentication, here:
> >> 
> >> BAD:
> >> sent [IPCP ConfReq id=0x1 <compress VJ 0f 01> <addr 0.0.0.0> <ms-dns1
> >> 0.0.0.0>
> >> <ms-dns2 0.0.0.0>]
> >> 
> >> GOOD:
> >> sent [IPCP ConfReq id=0x1 <addr 0.0.0.0> <ms-dns1 0.0.0.0> <ms-dns2
> >> 0.0.0.0>]
> >> 
> >> I cannot tell what exactly goes on here, though... Don't know the PPP
> >> protocol
> >> well enough.
> >> 
> >> Eugene
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