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

[Steve Langasek]

This bug, as described, is about 127.0.0.53 being configured in
/etc/resolv.conf /alongside/ other entries.  In recent releases this is
no longer the behavior; instead, /etc/resolv.conf is entirely managed by
systemd and points exclusively to the 127.0.0.53 local resolver, which
in turn will use the upstream resolvers that have been configured via
dhcp or via static netplan or network-manager config.

Concerns about the behavior of the local resolver should be filed as
separate issues.

** Changed in: systemd (Ubuntu)
       Status: Confirmed => Fix Released

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

Status in systemd package in Ubuntu:
  Fix Released
Status in Ubuntu RTM:
  New

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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