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zurround

hummingbird 1.1.1 does not restore DNS properly

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On Ubuntu 18.04.5 LTS, with humminbird version 1.1.1, after ending the VPN session, my DNS is shot, and I don't know how to restore it other than rebooting.
I had no problem with an earlier version of hummingbird. I tried the AirVPN Suite. Same problem.
The attached file contains the output of hummingbird. The assertion at the end "Successfully restored DNS settings" is not correct.
I would be happy enough if you could tell me where to look for the DNS settings, or how to restore them manually.

hummingbird.log

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@zurround

Hello!

If the problem persists, can you please send us the output of the following commands
  • before you run the suite (when everything works)
  • during the connection (while the system is connected successfully to the VPN)
  • after the connection (while the problem is ongoing)
cat /etc/resolv.conf
resolvectl
Open a terminal, and enter the above commands (in each of the above situations), then select and copy everything, finally paste into your message.

Kind regards
 

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BEFORE

$ cat /etc/resolv.conf
# Generated by NetworkManager
search home
nameserver 127.0.0.53

$ systemd-resolve --status
Global
          DNS Domain: home
          DNSSEC NTA: 10.in-addr.arpa
                      16.172.in-addr.arpa
                      168.192.in-addr.arpa
                      17.172.in-addr.arpa
                      18.172.in-addr.arpa
                      19.172.in-addr.arpa
                      20.172.in-addr.arpa
                      21.172.in-addr.arpa
                      22.172.in-addr.arpa
                      23.172.in-addr.arpa
                      24.172.in-addr.arpa
                      25.172.in-addr.arpa
                      26.172.in-addr.arpa
                      27.172.in-addr.arpa
                      28.172.in-addr.arpa
                      29.172.in-addr.arpa
                      30.172.in-addr.arpa
                      31.172.in-addr.arpa
                      corp
                      d.f.ip6.arpa
                      home
                      internal
                      intranet
                      lan
                      local
                      private
                      test

Link 2 (enp2s0)
      Current Scopes: DNS
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no
         DNS Servers: 192.168.0.1
                      2a02:908:2:a::1
                      2a02:908:2:b::1
          DNS Domain: ~.
                      home

 DURING
 
$ cat /etc/resolv.conf
#
# Created by AirVPN. Do not edit.
#
# Your resolv.conf file is temporarily backed up in /etc/airvpn/resolv.conf.airvpnbackup
# To restore your resolv.conf file you need to log in as root
# and execute the below command from the shell:
#
# mv /etc/airvpn/resolv.conf.airvpnbackup /etc/resolv.conf
#

nameserver 10.30.249.1
nameserver fde6:7a:7d20:1af9::1

$ systemd-resolve --status
Global
         DNS Servers: 10.30.249.1
                      fde6:7a:7d20:1af9::1
          DNSSEC NTA: 10.in-addr.arpa
                      16.172.in-addr.arpa
                      168.192.in-addr.arpa
                      17.172.in-addr.arpa
                      18.172.in-addr.arpa
                      19.172.in-addr.arpa
                      20.172.in-addr.arpa
                      21.172.in-addr.arpa
                      22.172.in-addr.arpa
                      23.172.in-addr.arpa
                      24.172.in-addr.arpa
                      25.172.in-addr.arpa
                      26.172.in-addr.arpa
                      27.172.in-addr.arpa
                      28.172.in-addr.arpa
                      29.172.in-addr.arpa
                      30.172.in-addr.arpa
                      31.172.in-addr.arpa
                      corp
                      d.f.ip6.arpa
                      home
                      internal
                      intranet
                      lan
                      local
                      private
                      test

Link 3 (tun0)
      Current Scopes: none
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no

Link 2 (enp2s0)
      Current Scopes: DNS
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no
         DNS Servers: fde6:7a:7d20:1af9::1
          DNS Domain: ~.
                      home

AFTER
 
$ cat /etc/resolv.conf
# Generated by NetworkManager
search home
nameserver 127.0.0.53

$ systemd-resolve --status
Global
          DNS Domain: home
          DNSSEC NTA: 10.in-addr.arpa
                      16.172.in-addr.arpa
                      168.192.in-addr.arpa
                      17.172.in-addr.arpa
                      18.172.in-addr.arpa
                      19.172.in-addr.arpa
                      20.172.in-addr.arpa
                      21.172.in-addr.arpa
                      22.172.in-addr.arpa
                      23.172.in-addr.arpa
                      24.172.in-addr.arpa
                      25.172.in-addr.arpa
                      26.172.in-addr.arpa
                      27.172.in-addr.arpa
                      28.172.in-addr.arpa
                      29.172.in-addr.arpa
                      30.172.in-addr.arpa
                      31.172.in-addr.arpa
                      corp
                      d.f.ip6.arpa
                      home
                      internal
                      intranet
                      lan
                      local
                      private
                      test

Link 2 (enp2s0)
      Current Scopes: none
       LLMNR setting: yes
MulticastDNS setting: no
      DNSSEC setting: no
    DNSSEC supported: no

Interesting: the link #2 after does not look like before!

Also tried the recovery, without success (as expected, since /etc/airvpn was already empty):
 
$ sudo hummingbird --recover-network
Hummingbird - AirVPN OpenVPN 3 Client 1.1.1 - 7 January 2020

It seems this program has properly exited in its last run and it has already
restored network settings on exit.
Network recovery is not needed.

 

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@zurround

Thank you! Problem detected and reproduced. Hummingbird and Bluetit rely on the ability of the system to change on the fly the global DNS settings. This is possible in most systems, Linux included. However, resolved seems unable to do that. It appears that every and each time someone needs to change global DNS on Linux when systemd-resolved works in any mode bypassing resolv.conf, she must stop and start systemd-resolved, forcing it to re-read the configuration.

A workaround fixing the problem will be included in the next, imminent AirVPN Suite release.

In the meantime you can quickly fix the problem, you don't need to reboot. You can save time by re-starting systemd-resolved when you are done using AirVPN Suite:
sudo systemctl restart systemd-resolved

Alternatively, you can consider to not use systemd-resolved.

Kind regards
 

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to my great regret, the suggested solution (sudo systemctl restart systemd-resolved) did not restore my DNS.

As for not using systemd-resolved... I am using the default settings of Ubuntu 18.04.5 LTS, and don't understand well enough (at all?) DNS resolution mechanisms to solve my problem, let alone use something else.

Thanks anyway. Do you have any other debugging suggestion I might apply?

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