After an Ubuntu upgrade the network stopped working

Hello, after an Ubuntu upgrade my containers don’t get an IP and the name resolution don’t work either (ping containername.lxd).

I’m running LXD 4.10, here’s the result of lxc network list:

+--------+----------+---------+-----------------+---------------------------+-------------+---------+
|  NAME  |   TYPE   | MANAGED |      IPV4       |           IPV6            | DESCRIPTION | USED BY |
+--------+----------+---------+-----------------+---------------------------+-------------+---------+
| enp1s0 | physical | NO      |                 |                           |             | 0       |
+--------+----------+---------+-----------------+---------------------------+-------------+---------+
| enp2s0 | physical | NO      |                 |                           |             | 0       |
+--------+----------+---------+-----------------+---------------------------+-------------+---------+
| lxdbr0 | bridge   | YES     | 10.206.203.1/24 | fd42:5588:e06d:ebd0::1/64 |             | 6       |
+--------+----------+---------+-----------------+---------------------------+-------------+---------+

I don’t know where to look up :confused:.

The usual steps to resolve issues like this are as follows:

  1. Confirm LXD’s dnsmasq is running and listening on your bridge’s IP (using sudo ps aux | grep dnsmasq and sudo ss -ulpn | grep dnsmasq and that nothing else is preventing LXD’s dnsmasq from listening.
  2. If you have docker running on the host check its firewall rules aren’t blocking DHCP requests to lxdbr0. See Lxd and Docker Firewall Redux - How to deal with FORWARD policy set to drop
  3. Check that you haven’t got anything else that could be adding firewall rules (using sudo iptables-save and/or sudo nft list ruleset) that could be blocking LXD’s dnsmasq from getting DHCP requests.
2 Likes
  1. dsnmasq isn’t running, ps aux | grep dnsmasq gives only the grep line.
  2. Docker isn’t installed on the host.
  3. I don’t know what to look for in iptables rules, there’s still the ones commented as “generated for LXD network lxdbr0”.

You’ll most likely have something else listening on port 53 or DHCP ports that is preventing dnsmasq from starting.

Please show full output of sudo ss -ulpn

Indeed, lsof -i :53 show systemd-resolve and bind.

ss -ulpn
State          Recv-Q          Send-Q                                       Local Address:Port                   Peer Address:Port         Process                                            
UNCONN         0               0                                             10.206.203.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=144))                  
UNCONN         0               0                                             10.206.203.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=148))                  
UNCONN         0               0                                             10.206.203.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=147))                  
UNCONN         0               0                                             10.206.203.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=146))                  
UNCONN         0               0                                             10.206.203.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=143))                  
UNCONN         0               0                                             10.206.203.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=145))                  
UNCONN         0               0                                             10.206.203.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=142))                  
UNCONN         0               0                                             10.206.203.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=141))                  
UNCONN         0               0                                            91.121.165.12:53                          0.0.0.0:*             users:(("named",pid=909,fd=110))                  
UNCONN         0               0                                            91.121.165.12:53                          0.0.0.0:*             users:(("named",pid=909,fd=108))                  
UNCONN         0               0                                            91.121.165.12:53                          0.0.0.0:*             users:(("named",pid=909,fd=115))                  
UNCONN         0               0                                            91.121.165.12:53                          0.0.0.0:*             users:(("named",pid=909,fd=114))                  
UNCONN         0               0                                            91.121.165.12:53                          0.0.0.0:*             users:(("named",pid=909,fd=113))                  
UNCONN         0               0                                            91.121.165.12:53                          0.0.0.0:*             users:(("named",pid=909,fd=112))                  
UNCONN         0               0                                            91.121.165.12:53                          0.0.0.0:*             users:(("named",pid=909,fd=111))                  
UNCONN         0               0                                            91.121.165.12:53                          0.0.0.0:*             users:(("named",pid=909,fd=109))                  
UNCONN         0               0                                                127.0.0.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=68))                   
UNCONN         0               0                                                127.0.0.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=69))                   
UNCONN         0               0                                                127.0.0.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=70))                   
UNCONN         0               0                                                127.0.0.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=72))                   
UNCONN         0               0                                                127.0.0.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=71))                   
UNCONN         0               0                                                127.0.0.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=66))                   
UNCONN         0               0                                                127.0.0.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=67))                   
UNCONN         0               0                                                127.0.0.1:53                          0.0.0.0:*             users:(("named",pid=909,fd=65))                   
UNCONN         0               0                                            127.0.0.53%lo:53                          0.0.0.0:*             users:(("systemd-resolve",pid=868,fd=12))         
UNCONN         0               0                                                    [::1]:53                             [::]:*             users:(("named",pid=909,fd=83))                   
UNCONN         0               0                                                    [::1]:53                             [::]:*             users:(("named",pid=909,fd=84))                   
UNCONN         0               0                                                    [::1]:53                             [::]:*             users:(("named",pid=909,fd=88))                   
UNCONN         0               0                                                    [::1]:53                             [::]:*             users:(("named",pid=909,fd=89))                   
UNCONN         0               0                                                    [::1]:53                             [::]:*             users:(("named",pid=909,fd=85))                   
UNCONN         0               0                                                    [::1]:53                             [::]:*             users:(("named",pid=909,fd=90))                   
UNCONN         0               0                                                    [::1]:53                             [::]:*             users:(("named",pid=909,fd=87))                   
UNCONN         0               0                                                    [::1]:53                             [::]:*             users:(("named",pid=909,fd=86))                   
UNCONN         0               0                                 [fd42:5588:e06d:ebd0::1]:53                             [::]:*             users:(("named",pid=909,fd=159))                  
UNCONN         0               0                                 [fd42:5588:e06d:ebd0::1]:53                             [::]:*             users:(("named",pid=909,fd=160))                  
UNCONN         0               0                                 [fd42:5588:e06d:ebd0::1]:53                             [::]:*             users:(("named",pid=909,fd=158))                  
UNCONN         0               0                                 [fd42:5588:e06d:ebd0::1]:53                             [::]:*             users:(("named",pid=909,fd=161))                  
UNCONN         0               0                                 [fd42:5588:e06d:ebd0::1]:53                             [::]:*             users:(("named",pid=909,fd=162))                  
UNCONN         0               0                                 [fd42:5588:e06d:ebd0::1]:53                             [::]:*             users:(("named",pid=909,fd=163))                  
UNCONN         0               0                                 [fd42:5588:e06d:ebd0::1]:53                             [::]:*             users:(("named",pid=909,fd=164))                  
UNCONN         0               0                                 [fd42:5588:e06d:ebd0::1]:53                             [::]:*             users:(("named",pid=909,fd=165))                  
UNCONN         0               0                        [fe80::216:3eff:fe24:437f]%lxdbr0:53                             [::]:*             users:(("named",pid=909,fd=177))                  
UNCONN         0               0                        [fe80::216:3eff:fe24:437f]%lxdbr0:53                             [::]:*             users:(("named",pid=909,fd=178))                  
UNCONN         0               0                        [fe80::216:3eff:fe24:437f]%lxdbr0:53                             [::]:*             users:(("named",pid=909,fd=181))                  
UNCONN         0               0                        [fe80::216:3eff:fe24:437f]%lxdbr0:53                             [::]:*             users:(("named",pid=909,fd=180))                  
UNCONN         0               0                        [fe80::216:3eff:fe24:437f]%lxdbr0:53                             [::]:*             users:(("named",pid=909,fd=176))                  
UNCONN         0               0                        [fe80::216:3eff:fe24:437f]%lxdbr0:53                             [::]:*             users:(("named",pid=909,fd=175))                  
UNCONN         0               0                        [fe80::216:3eff:fe24:437f]%lxdbr0:53                             [::]:*             users:(("named",pid=909,fd=179))                  
UNCONN         0               0                        [fe80::216:3eff:fe24:437f]%lxdbr0:53                             [::]:*             users:(("named",pid=909,fd=182))

Yes, you’re only worried about the processes listening on 10.206.203.1 and fd42:5588:e06d:ebd0::1 though as those are what LXD’s dnsmasq will listen on.

You need to reconfigure named to not listen on all IPs.

1 Like

Thanks!

I even had the old config in /etc/bind/named.conf.options.dpkg-old since it was overwritten during the upgrade.