[Bug 1951701] Re: systemd-resolved doesn't play well with dnsmasq cname entries

[Nick Rosbrook]

Please open a new bug if this is still observed on newer releases.

** Changed in: systemd (Ubuntu)
       Status: New => Won't Fix

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Title:
  systemd-resolved doesn't play well with dnsmasq cname entries

Status in systemd package in Ubuntu:
  Won't Fix

Bug description:
  See also https://community.ui.com/questions/USG-dnsmasq-cname-options-
  not-playing-well-with-systemd-
  resolved/11592045-d530-4f55-9cd2-9d45fc637e1d

  I've set up my UniFi Security Gateway with dnsmasq so that I can
  resolve local hostnames on my network. I can resolve most hostnames,
  except for one: unifi.

  $ nslookup unifi
  Server:		127.0.0.53
  Address:	127.0.0.53#53

  ** server can't find unifi.lan: SERVFAIL
  $ nslookup unifi.lan
  Server:		127.0.0.53
  Address:	127.0.0.53#53

  ** server can't find unifi.lan: SERVFAIL

  However, it works if I specifically query my router:

  $ nslookup unifi 192.168.1.1
  Server:		192.168.1.1
  Address:	192.168.1.1#53

  unifi.lan	canonical name = unifi.
  Name:	unifi
  Address: 192.168.1.6
  $ nslookup unifi.lan 192.168.1.1
  Server:		192.168.1.1
  Address:	192.168.1.1#53

  unifi.lan	canonical name = unifi.
  Name:	unifi
  Address: 192.168.1.6

  So this seems specifically like a problem with systemd-resolved.
  Asking systemd-resolved to resolve these hosts is interesting:

  $ systemd-resolve unifi unifi.lan
  unifi: 192.168.1.6                             -- link: wlp2s0

  -- Information acquired via protocol DNS in 6.4ms.
  -- Data is authenticated: no
  unifi.lan: resolve call failed: No appropriate name servers or networks for name found

  Following the steps
  [here](https://wiki.ubuntu.com/DebuggingSystemd#systemd-
  resolved_:_DNS_resolution_issues) I captured some systemd-resolved
  logs:

   - unifi.lan error: https://pastebin.com/pjzUvQfi
   - unifi success: https://pastebin.com/QN8hD9a1

  And I found a setting in the router that seemed to be causing the
  problem. Removing that setting in my router resulted in this log:

   - unifi.lan success after deleting option cname:
  https://pastebin.com/4csYdW5B

  But ultimately this seems like a bug in systemd-resolved since things
  seem to be working correctly if I take systemd-resolved out of the
  loop

  $ lsb_release -rd
  Description:	Ubuntu 20.04.3 LTS
  Release:	20.04
  $ apt-cache policy systemd
  systemd:
    Installed: 245.4-4ubuntu3.13
    Candidate: 245.4-4ubuntu3.13
    Version table:
   *** 245.4-4ubuntu3.13 500
          500 http://us.archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
          100 /var/lib/dpkg/status
       245.4-4ubuntu3.11 500
          500 http://security.ubuntu.com/ubuntu focal-security/main amd64 Packages
       245.4-4ubuntu3 500
          500 http://us.archive.ubuntu.com/ubuntu focal/main amd64 Packages

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