Re: How to configure a AX25 interface ?

[Jean-Christian de Rivaz <jc eclis ch>]

Le 09. 09. 15 13:43, Thomas Haller a écrit :
> On Wed, 2015-09-09 at 13:06 +0200, Jean-Christian de Rivaz wrote:
> > Le 09. 09. 15 10:19, Thomas Haller a écrit :
> > > On Wed, 2015-09-09 at 07:28 +0200, Jean-Christian de Rivaz wrote:
> > > > Hello,
> > > >
> > > > I have successfully setup a AX25 interface and NM see it this
> > > > way:
> > > > nmcli d
> > > > DEVICE   TYPE      STATE        CONNECTION
> > > > ax0      unknown   connected    ax0
> > > > eth2     ethernet  unavailable  --
> > > > ttyACM0  gsm       unavailable  --
> > > > lo       loopback  unmanaged    --
> > > > sit0     sit       unmanaged    --
> > > > wlan2    wifi      unmanaged    --
> > > >
> > > > How can I configure NM to add a static default gateway and a
> > > > static
> > > > DNS
> > > > server when, and only when, NM have to use the ax0 interface ?
> > > Basically, adjust the generic connection to have the settings you
> > > want.
> > > See `man nm-settings` for possible options. Especially the "ipv4"
> > > section.
> > The solution I used was:
> > nmcli con mod ax0 ipv4.addresses "192.168.222.16/24 192.168.222.15"
> > nmcli con mod ax0 ipv4.dns "192.168.222.15"
> > nmcli connection reload
> The originally created connection "ax0" was in memory only. By
> modifying it, it got persisted to disk. So this is expected.
>
> > But even after a reboot, NM don't set the gateway, nor the default
> > route, nor the DNS:
> >
> > route -n
> > Kernel IP routing table
> > Destination     Gateway         Genmask         Flags Metric Ref Use
> > Iface
> > 192.168.132.0   0.0.0.0         255.255.255.0   U     0 0        0
> > wlan2
> > 192.168.222.0   0.0.0.0         255.255.255.0   U     0 0        0
> > ax0
> >
> > cat /etc/resolv.conf
> > # Generated by NetworkManager
> >
> > Then the nmcli con show ax0 command return two 'ax0' settings:
> After reboot, NM sees again that an external device ax0 was activated.
> Again it will create a temporary, in-memory connection to reflect those
> changes.
>
> After doing that, it will look if you have a compatible persistent
> connection that might be the one that got activated. Basically, it
> compares the newly created one, with what to saved previously.
>
> If it would determine, that you have a similar-enough connection, it
> would delete the temporary connection and use the one that matched.
>
> In your case, NM thinks they are different and hence keeps the second
> connection.
>
>
> But regardless of whether NM would match your persistent connection or
> not, it would not modify your externally configured device
> automatically.
> You must manually activate the connection you want:
>    `nmcli connection up uuid 048db18b-0d5d-4f40-8ba1-ca492f888b1c`,
> This will delete the just generated connection.

Thank you Thomas for this explanation, without your help It's a kind of 
black magic. I still don't understand how NM think an ax0 is similar 
enough (or not) to an ax0... Very disturbing for a user.

After some long testing (the actual only link on that device is a 57.6kb 
AX.25 radio) I have found that the following line work after the 
kissattach command:
while true; do
    nmcli dev show ax0 >/dev/null 2>&1
    if [ $? -eq 0 ]; then
        break
    fi
    sleep 10
done
nmcli con mod ax0 ipv4.addresses "192.168.222.16/24 192.168.222.15"
nmcli con mod ax0 ipv4.dns "192.168.222.15"
nmcli con up ax0

The loop wait until NM notice that the ax0 interface exists, otherwise I 
got the 'two ax0' issue. I wonder if the NM dispatcher could be used 
instead of that waiting loop.

Best Regards,
Jean-Christian