Comment 0 for bug 1721223

Hi there,
we found a replicable issue that involves the Ubuntu Core networking and causes complete loss of connectivity.
We run a custom board with ubuntu core: the architecure is amrhf.
We replicated this issue with an official Ubuntu Core image on a Raspberry Pi: other platform was been tested.
It shows that it is a snap core problem which interests networkd: we use the default network stack based on networkd + netplan.

Below steps to replicate the issue.

    1)Setup a dhcp server for lease of about some minutes (i.e 10 minutes).
    2)Boot the board and wait for get an ip from dhcp server
    3)Before the lease expires, set a reservation for a different ip address

Depending on lease duration before the lease expires( for 10 minute we have 2 minutes before ), networkd configure the new address in addition to the previous one.
When the lease expire both ip address ( the prevoius and the new one ) disappear from the interested network interface.
Depending on lease duration before the second lease expires ( for 10 minure we have 2 minutes before ) networkd configure only the new ip address on the network interface and the ping toward an outside host work properly.

During the test the dhcp server records correctly leases and their duration.

We check directly from console the network interface setting with the tool ip, checking continuously the value for ip address and valid_lft fields for the interested network interface.

Please note that if the ip address setting are the same between leases the problem doesn’t jump out.

Please note that if the ip address setting are different between lease the problem jumps out and it is very bad:

Typically the lease time on consumer router are about some day, then a board that change ip between lease loses the network connectivity for some day without a direct action.

Please, after a confirmation from your side of the issue, could you fix the problem or escalate the issue at the upstream project?

We are available for further testing.

Below syslog annotated with ip address state:

Oct 4 09:48:06 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 09:49:36 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 09:49:25 localhost systemd-timesyncd[996]: Network configuration changed, trying to establish connection.
Oct 4 09:49:26 localhost systemd-timesyncd[996]: Synchronized to time server 91.189.89.199:123 (ntp.ubuntu.com).
Oct 4 09:49:26 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
Oct 4 09:49:26 localhost systemd[1]: Started Update resolvconf for networkd DNS.
Oct 4 09:49:37 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 09:51:07 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 09:51:09 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 09:52:39 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 09:52:40 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 09:54:10 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 09:54:11 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 09:55:41 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 09:54:23 localhost systemd-timesyncd[996]: Network configuration changed, trying to establish connection.
Oct 4 09:54:23 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
Oct 4 09:54:23 localhost systemd-timesyncd[996]: Synchronized to time server 91.189.89.199:123 (ntp.ubuntu.com).
Oct 4 09:54:23 localhost systemd[1]: Started Update resolvconf for networkd DNS.
Oct 4 09:55:43 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 09:57:13 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 09:57:14 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 09:58:44 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 09:58:46 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 10:00:16 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 10:00:17 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 10:01:47 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 10:01:48 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 10:03:18 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]

Oct 4 10:03:05 localhost systemd-networkd[623]: eth0: DHCPv4 address 192.168.5.124/24 via 192.168.5.1 -----> here begin two ip address state

Oct 4 10:03:05 localhost systemd-timesyncd[996]: Network configuration changed, trying to establish connection.
Oct 4 10:03:05 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
Oct 4 10:03:05 localhost systemd[1]: Started Update resolvconf for networkd DNS.
Oct 4 10:03:15 localhost systemd-timesyncd[996]: Timed out waiting for reply from 91.189.89.199:123 (ntp.ubuntu.com).
Oct 4 10:03:16 localhost systemd-timesyncd[996]: Synchronized to time server 91.189.89.198:123 (ntp.ubuntu.com).
Oct 4 10:03:20 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 10:04:50 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]

Oct 4 10:04:23 localhost systemd-timesyncd[996]: Network configuration changed, trying to establish connection. ----> disappear any address

Oct 4 10:04:23 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
Oct 4 10:04:23 localhost systemd[1]: Started Update resolvconf for networkd DNS.
Oct 4 10:04:51 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 10:06:21 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 10:06:23 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 10:07:53 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 10:07:54 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 10:09:24 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 10:09:24 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 10:10:54 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 10:10:55 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4

10:12:25 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ] ------> before this line interface eth0 don't have address, after this line the interfaces get 192.168.5.124/24( the second lise adddress)

Oct 4 10:11:49 localhost systemd[1]: Starting Update resolvconf for networkd DNS...
Oct 4 10:11:49 localhost systemd[1]: Started Update resolvconf for networkd DNS.
Oct 4 10:12:25 localhost rsyslogd-2007: action 'action 11' suspended, next retry is Wed Oct 4 10:13:55 2017 [v8.16.0 try http://www.rsyslog.com/e/2007 ]
Oct 4 10:13:18 localhost systemd[1]: Started Session 23 of user domotz.

Cheers,
Nicolino