[Networkmanager] R: pppoe connection gets a secondary wrong IP address

[nmgr053 at iotti.biz]

> -----Messaggio originale-----
> Da: Beniamino Galvani <bgalvani at redhat.com>
> Inviato: mercoledì 18 ottobre 2023 08:54
> A: nmgr053 at iotti.biz
> Cc: networkmanager at lists.freedesktop.org
> Oggetto: Re: [Networkmanager] pppoe connection gets a secondary wrong IP
> address
> 
> On Tue, Oct 17, 2023 at 04:15:36PM +0200, nmgr053 at iotti.biz wrote:
> > Hi all
> >
> > I'm trying for the first time to configure a pppoe NM connection via a
> > DSL bridge. The OS is a new Alma Linux 9 install. A similar
> > connection, but made in the older network-scripts way, did work until I
> reinstalled the box.
> >
> > I simply added the connection with
> > nmcli connection add con-name dsl-pppoe type pppoe ifname ens1
> > username xxxxx password xxxxx connection.autoconnect yes
> >
> > The connection is negotiated well, PPP/IPCP works, I get my static
> > public IP address. The problem is that strangely to me, NM configures
> > the 1.0.0.0 on the interface too. This becomes the preferred source
> > address, so I can not make connections from my machine to the outside.
i.e.:
> >
> > # ip a l dev ppp0
> > 23: ppp0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1492
> qdisc
> > fq_codel state UNKNOWN group default qlen 3
> >     link/ppp
> >     inet 82.6.7.8 peer 192.168.100.1/32 scope global ppp0
> >        valid_lft forever preferred_lft forever
> >     inet 1.0.0.0 peer 82.6.7.8/32 scope global noprefixroute ppp0
> >        valid_lft forever preferred_lft forever
> >
> > I don't understand where that inet 1.0.0.0 comes from.
> >
> > I took a tcpdump of the IPCP config requests/ack and I obviously found
> > my real 82.6.7.8 IP address, but nothing about 1.0.0.0 .
> >
> > I tried to debug NetworkManger activity. The trace is long, but the
> > first time 1.0.0.0 is encountered is in these lines:
> 
> > Any hint where this 1.0.0.0 address could come from?
> 
> Hi,
> 
> I don't know. Can you please provide the full log from when you add the
> connection to when it goes up, including logs from pppd?

It turned out to be my fault, sorry. I was using a patched version of pppd
with some facilities I've been using for about twenty years, when we used
the old dial-up PSTN lines. There was something triggering this spurious
address addition. I did not even remember about this and was misled by the
fact that all the log lines talking about this 1.0.0.0 address were from
NetworkManager and not pppd. When I can reach this machine without passing
by the dsl line itself, I'll make more tests to understand wht was actually
inserting that address. But at the moment, I believe it was not
NetworkManager.  

Thank you for your attention, best regards, Luigi