Bug 1662253

Summary: Cannot set '--cluster-dns' value by dnsIP
Product: OpenShift Container Platform Reporter: Min Woo Park <mpark>
Component: NetworkingAssignee: Dan Mace <dmace>
Networking sub component: router QA Contact: Hongan Li <hongli>
Status: CLOSED WONTFIX Docs Contact:
Severity: unspecified    
Priority: unspecified CC: aos-bugs, dkaylor
Version: 3.11.0   
Target Milestone: ---   
Target Release: 3.11.z   
Hardware: Unspecified   
OS: Unspecified   
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Last Closed: 2019-10-11 00:39:31 UTC Type: Bug
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description Min Woo Park 2018-12-27 08:13:11 UTC 
Description of problem:

By default, dnsIP is 0.0.0.0 and the --cluster-dns flag is set to that of the host by looking for the first up, non-loopback interface and getting the first IPv4 address from it. 

When OCP was installed in mutiple NICs environment, '--cluster-dns' can be configured as a unwanted IP address.

We can set '--clsuter-dns' value by setting dnsIP in /etc/origing/node/node-config.yaml.
But we cannot use dnsIP from ocp 3.10, because if I configure dnsIP in config map then the IP was set to all nodes.

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


How reproducible:


Steps to Reproduce:
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Actual results:


Expected results:
Want to set '--cluster-dns' to the specific IP address.

Additional info:
Comment 1 Min Woo Park 2018-12-28 05:58:40 UTC 
Hello,

I explain the issue more details.

When openshift was installed in mutiple NICs environment, I set one NIC which used by openshift as the default GW in the node host.
Because the nameserver IP in "/etc/resolv.conf" of node host will be configured with default GW NIC's IP address by "99-origin-dns.sh" script.

I could see correct nameserver IP in "/etc/resolv.conf" of node host.

But nameserver IP in "/etc/resolv.conf" of POD was different with that in "/etc/resolv.conf" of node host.

dnsIP : Configures an IP address to be prepended to a pod’s /etc/resolv.conf by adding the address here.

"dnsIP" is 0.0.0.0 by default.
I could see nodeConfig.DNSIP was set from nodeConfig.NodeIP. [1]
If nodeIP was not set, dnsIP can be set to that of the host by looking for the first up, non-loopback interface and getting the first IPv4 address from it. 

BTW from ocp 3.10, node configuration is controlled via a set of configmaps maintained in the openshift-node namespace. 
Since node configuration is managed on a per-node group basis, it is now no longer possible to specify many configuration variables that may have varied on a per host basis, such as openshift_node_ip, openshift_dns_ip, etc. 

So dnsIP can be random IP in multiple NICs environment.

As a workaround, I could create a node group for each node host and set node_ip in that node group something like,
{'name': 'node-config-node1', 'labels': ['...,...']}, 'edits': [{ 'key': 'kubeletArguments.node-ip','value': ['x.x.x.x']}]}

But my customer hopes that dnsIP can be set same with nameserver IP in "/etc/resolv.conf" of node host.

Thanks,

[1] https://github.com/openshift/origin/pull/19734/files#diff-3f3631b751f92dbca795eba99e445c4fR33