Search domains missing from resolv.conf stub

[Peter Ludikovsky]

System is Mint 20.2, with the relevant packages taken from Ubuntu Focal.

This is the output of `systemd-resolv --status vpn0`:
    Link 7 (vpn0)
          Current Scopes: DNS
    DefaultRoute setting: yes
           LLMNR setting: yes
    MulticastDNS setting: no
      DNSOverTLS setting: no
          DNSSEC setting: no
        DNSSEC supported: no
      Current DNS Server: 10.0.0.53
             DNS Servers: 10.0.0.53
              DNS Domain: example.com
                          example.com.rpz
                          privatelink.blob.core.windows.net
                          node.prd.lan.example.com
                          node.stg.lan.example.com
                          node.dev.lan.example.com

However that last domain is missing from `/etc/resolv.conf` (symlink to `/run/systemd/resolve/stub-resolv.conf`), instead there is a line
    # Too many search domains configured, remaining ones ignored.

According to resolv.conf(5) since glibc 2.26 the number of search domains should be unlimited, and installed is 2.31-0ubuntu9.3

VPN is PaloAlto GlobalProtect through the OpenConnect plugin on NetworkManager.

Exact same setup and behaviour for a colleague using Pop!_OS 20.04

--
systemd:
  Installed: 245.4-4ubuntu3.13
  Candidate: 245.4-4ubuntu3.13
  Version table:
 *** 245.4-4ubuntu3.13 500
        500 http://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://archive.ubuntu.com/ubuntu focal/main amd64 Packages

libc-bin:
  Installed: 2.31-0ubuntu9.3
  Candidate: 2.31-0ubuntu9.3
  Version table:
 *** 2.31-0ubuntu9.3 100
        100 /var/lib/dpkg/status
     2.31-0ubuntu9.2 500
        500 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 Packages
     2.31-0ubuntu9 500
        500 http://archive.ubuntu.com/ubuntu focal/main amd64 Packages

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Marko (bl3nto)]

Happens as well on Ubuntu 20.04, very annoying because it works fine if those domains are manually added to /run/systemd/resolve/stub-resolv.conf file so there's not real limit since glibc is not the issue anymore.

This of course gets overwritten on any network change, and in case of VPN connections this happens a lot.

[Nick Rosbrook (enr0n)]

This restriction was dropped upstream by https://github.com/systemd/systemd/commit/1c7466aa2e5663b5595f9cef5cbece9ec63bcc14, which is included in 22.04 and later releases.