[Bug 1624320] Re: systemd-resolved appends 127.0.0.53 to resolv.conf alongside existing entries

[Adrian Wilkins]

My problem with systemd-resolved :

* My router hands out a nameserver (itself) via DNS
* When I'm inside my network, I want my router to resolve IP addresses for my domain
* When I'm outside my network, I want the public DNS to resolve them

First lookup works fine! Then systemd-resolved (I guess) caches the
secondary lookup it's doing via public DNS servers and returns the
public IP address for the server. This is not what is desired, and
breaks a bunch of stuff (like SSH to my servers using names from inside
my network).

Never had this problem with dnsmasq, because it apparently respected my
network config and didn't do an end-run around the DNS servers it was
handed by DHCP.

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https://bugs.launchpad.net/bugs/1624320

Title:
  systemd-resolved appends 127.0.0.53 to resolv.conf alongside existing
  entries

Status in systemd package in Ubuntu:
  Confirmed

Bug description:
  systemd-resolved, or more precisely the hook script
  /lib/systemd/system/systemd-resolved.service.d/resolvconf.conf, causes
  resolvconf to add 127.0.0.53 to the set of nameservers in
  /etc/resolv.conf alongside the other nameservers.  That makes no sense
  because systemd-resolved sets up 127.0.0.53 as a proxy for those other
  nameservers.  The effect is similar to bug 1624071 but for
  applications doing their own DNS lookups.  It breaks any DNSSEC
  validation that systemd-resolved tries to do; applications will
  failover to the other nameservers, bypassing validation failures.  And
  it makes failing queries take twice as long.

  /etc/resolv.conf should have only 127.0.0.53 when systemd-resolved is
  active.

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