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  1. OpenShift Bugs
  2. OCPBUGS-44732

DNS from nmstate configuration is not set when using DHCP

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      Description of problem:

          I want to configure master nodes in OCP to get IP by DHCP but to have a specific set of DNS nameservers. I deploy with GitOps ZTP via ACM and configure siteconfig with nmstate configuration there
      
      -   name: "ens3"
          type: ethernet
          state: up
          ipv4:
            dhcp: true
            auto-dns: false
            enabled: true
          ipv6:
            enabled: false
          dns-resolver:
            config:
              server:
                  - 10.1.104.3
                  - 10.11.5.160
                  - 10.2.70.215
      
      auto-dns: false - the flag that should not allow DNS from DHCP to overwrite ones I specified in dns-resolver section.
      When I deploy the cluster, the specified DNS servers are overwritten with DHCP provided ones. I see that in masters when br-ex is being configured. 
      More context in Slack: https://redhat-internal.slack.com/archives/CUPJTHQ5P/p1731927772660789 

      Version-Release number of selected component (if applicable):

          

      How reproducible:

          Always

      Steps to Reproduce:

          1. Configure `aut-dns: false` in nmstate section of siteconfig and DHCP IP, configure specific DNS servers in dns-resolver section.
          2. Run the deployment.
          3. See that DNS servers set from nmstate config are overwritten with provided by DHCP
          

      Actual results:

          DNS servers set from nmstate config are overwritten with provided by DHCP

      Expected results:

          DNS servers are set exactly as they are configured in nmstate section of siteconfig

      Additional info:

      A few logs:
      
      $ cat /etc/resolv.conf 
      # Generated by KNI resolv prepender NM dispatcher script
      search cnfdr17.telco5g.eng.rdu2.redhat.com telco5g.eng.rdu2.redhat.com
      nameserver 10.1.105.20
      nameserver 10.11.5.19
      nameserver 10.2.32.1
      
      I see in /var/run/NetworkManager/resolv.conf it's DNS servers from DHCP, not from NMstate.
      
      Nov 18 07:40:20 cnfdr17-master-2.telco5g.eng.rdu2.redhat.com bash[3075]: NM resolv-prepender: Prepending 'nameserver 10.1.105.171' to /etc/resolv.conf (other nameservers from /var/run/NetworkManager/resolv.conf)
      Nov 18 07:40:20 cnfdr17-master-2.telco5g.eng.rdu2.redhat.com NetworkManager[2579]: <info>  [1731915620.4818] audit: op="reload" arg="2" pid=8245 uid=0 result="success"
      
      Here the first nameserver is host itself
      
      $ cat /etc/resolv.conf 
      # Generated by KNI resolv prepender NM dispatcher script
      search cnfdr17.telco5g.eng.rdu2.redhat.com telco5g.eng.rdu2.redhat.com
      nameserver 10.1.105.171  <-- this is IP of host itself
      nameserver 10.11.5.19
      nameserver 10.2.32.1
      
      another master:
      
      $ cat /var/run/NetworkManager/resolv.conf
      # Generated by NetworkManager
      search telco5g.eng.rdu2.redhat.com
      nameserver 10.11.5.19
      nameserver 10.2.32.1

              mkowalsk@redhat.com Mat Kowalski
              sshnaidm@redhat.com Sagi Shnaidman
              None
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              Ross Brattain Ross Brattain
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                Created:
                Updated:
                Resolved: