I've been trying out some failure scenarios with Eth vs. GSM modem (under
ModemManager) - e.g. Eth link getting disconnected/reconnected.
eth0 was present in my /etc/network/interfaces:
auto eth0
iface eth0 inet dhcp
therefore I used the "managed=true" setting in NetworkManager.conf, with the
ifupdown plugin.
Board is booted with the eth cable connected. I'm not using systemd.
=>
root@wg:~# nmcli conn
NAME UUID TYPE DEVICE
eth0 100f5a79-f573-44ca-b746-04727dab4a7d 802-3-ethernet eth0
Ifupdown (eth0) 681b428f-beaf-8932-dce4-687ed5bae28e 802-3-ethernet --
O2 42bf3c07-9dd7-45f6-ba08-37dfc8a7a537 gsm --
I bring up the MM GSM connection.
Nameservers for both appear in resolv.conf, and 'route' shows both eth0 and
ppp0.
I can [busybox] ping a site by name on ppp0 (using the -I option).
I then unplug the eth cable, and the ping then fails [eventually!] with "bad
address". (It works if I specify IP addr instead).
It works (by name) when I reconnect the the cable.
root@wg:~# nmcli
ttyMux1: connected to O2
gsm (linmux), hw, iface ppp
ip4 default
inet4 10.65.57.212/32
eth0: unavailable
ethernet (fec), 00:0C:C6:7F:E5:51, hw, mtu 1500
lo: unmanaged
loopback (unknown), 00:00:00:00:00:00, sw, mtu 65536
DNS configuration:
servers: 82.132.254.2 82.132.254.3
interface: ppp0
servers: 192.168.10.254
interface: eth0
root@wg:~# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 192.168.10.254 0.0.0.0 UG 0 0 0 eth0
0.0.0.0 10.65.57.212 0.0.0.0 UG 700 0 0 ppp0
10.65.57.212 0.0.0.0 255.255.255.255 UH 700 0 0 ppp0
192.168.10.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
root@wg:~# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 82.132.254.2
nameserver 82.132.254.3
nameserver 192.168.10.254
On disconnect of the cable, NM logs:
May 11 15:47:45 wg2xx-tx6s user.info kernel: fec 2188000.ethernet eth0: Link is
Down
May 11 15:47:49 wg2xx-tx6s daemon.info NetworkManager[850]: <info>
[1494514069.2116] device (eth0): state change: activated -> unavailable (reason
'carrier-changed') [100 20 40]
May 11 15:47:49 wg2xx-tx6s daemon.info NetworkManager[850]: <info>
[1494514069.2324] policy: set 'O2' (ppp0) as default for IPv4 routing and DNS
May 11 15:47:49 wg2xx-tx6s daemon.notice dbus[824]: [system] Activating service
name='org.freedesktop.nm_dispatcher' (using servicehelper)
May 11 15:47:49 wg2xx-tx6s daemon.notice dbus[824]: [system] Successfully
activated service 'org.freedesktop.nm_dispatcher'
May 11 15:47:49 wg2xx-tx6s daemon.info nm-dispatcher: req:1 'down' [eth0]: new
request (1 scripts)
May 11 15:47:49 wg2xx-tx6s daemon.info nm-dispatcher: req:1 'down' [eth0]:
start running ordered scripts...
In contrast however, if I comment eth0 out of /etc/network/interfaces and
reboot (with eth cable reconnected) and repeat, then the ppp0 ping works fine
after disconnecting the eth cable.
root@wg:~# nmcli
ttyMux1: connected to O2
gsm (linmux), hw, iface ppp
ip4 default
inet4 10.67.91.236/32
eth0: unavailable
ethernet (fec), 00:0C:C6:7F:E5:51, hw, mtu 1500
lo: unmanaged
loopback (unknown), 00:00:00:00:00:00, sw, mtu 65536
DNS configuration:
servers: 82.132.254.2 82.132.254.3
interface: ppp0
root@wg:~# route -n
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
0.0.0.0 10.67.91.236 0.0.0.0 UG 700 0 0 ppp0
10.67.91.236 0.0.0.0 255.255.255.255 UH 700 0 0 ppp0
root@wg:~# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 82.132.254.2
nameserver 82.132.254.3
It seems the dns lookup is being tried on eth0 instead of ppp0 - as if the
'managed=true' isn't altering all the behaviour that it should be? (e.g. in
the failing case, eth0 is still showing in resolv.conf & in the routing
table...?).
I have no pre/post up/down scripts in /etc/network/
eth0 is in /etc/network/interfaces for not conscious reason - just the way by
image is building at present. I could chop it out if necessary, but as I'm
sticking my on NetworkManager.conf into the rootfs anyway, that would be an
easier way to flick the behaviour, if I can get it to work equivalently.
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