Custom subnet causes DNS service to not be created

[rocketraman]

Is this a request for help?: NO

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Is this an ISSUE or FEATURE REQUEST? (choose one): ISSUE

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What version of acs-engine?: latest master

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Orchestrator and version (e.g. Kubernetes, DC/OS, Swarm) Kubernetes

What happened: When using a custom service subnet and DNS service IP, acs-engine does not update the default 10.0.0.10 IP address in the DNS addon yaml. This means that the addon manager attempts to deploy the DNS service to a cluster IP which does not fall into the service subnet, which in turn fails with the error:

The Service "kube-dns" is invalid: spec.clusterIP: Invalid value: "10.0.0.10": provided IP is not in the valid range

The DNS service is therefore never created, and DNS in the cluster does not work.

This has been an issue since pull #546.

What you expected to happen:

When creating the cluster, the DNS service should be created.

How to reproduce it (as minimally and precisely as possible):

Define a custom subnet e.g. a config similar to the following:

      "kubernetesConfig": {
        "clusterSubnet": "10.2.0.0/17",
        "serviceCidr": "10.2.128.0/18",
        "dnsServiceIP": "10.2.128.10"
      }

Generate the template. Deploy the cluster. The DNS service will not be created. The file on master /etc/kubernetes/addons/kube-dns-deployment.yaml while still reference 10.0.0.10 as the DNS service clusterIP.

Anything else we need to know:

Sorry for breaking this :-) I will submit a pull request to fix it.