kubernetes: ServicePort -> DNS SRV does not allow services with same name but different protocol

What happened:

Creating a service with two ports that have the same name, but different protocol, fails:

$ cat service-test.yaml 
apiVersion: v1
kind: Service
metadata:
  name: service-test
  labels:
    app: service-test
spec:
  selector:
    app: service-test
  clusterIP: None
  ports:
  - name: ldap
    protocol: TCP
    port: 389
  - name: kerberos
    protocol: TCP
    port: 88
  - name: kerberos
    protocol: UDP
    port: 88

$ oc replace -f service-test.yaml 
The Service "service-test" is invalid:
spec.ports[2].name: Duplicate value: "kerberos"

This is an important use case for some applications, and the limitation is surprising. More information in my blog post: https://frasertweedale.github.io/blog-redhat/posts/2020-12-08-k8s-srv-limitation.html#kubernetes-srv-limitation

What you expected to happen:

Such Service objects should be accepted, and should result in the creation of the corresponding DNS SRV records that have the same service name, but different protocol ID, e.g., from the object above:

_ldap._tcp.<service>.<ns>.svc.<zone>.     ...
_kerberos._tcp.<service>.<ns>.svc.<zone>. ...
_kerberos._udp.<service>.<ns>.svc.<zone>. ...

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

As shown above.

Anything else we need to know?:

I’m happy to file a KEP if it is deemed necessary. However, all that is required conceptually is to relax the uniqueness check to the name/protocol pairs instead of service name only. I hope it could be addressed without adding new fields, i.e. aligning the ServicePort semantics with the established semantics of SRV records.

Environment:

• Kubernetes version (use kubectl version):

Server Version: version.Info{Major:"1", Minor:"19", GitVersion:"v1.19.2+ad738ba", GitCommit:"ad738ba548b6d6b5cd2e83351951ccd7019afa4c", GitTreeState:"clean", BuildDate:"2020-11-25T00:18:44Z", GoVersion:"go1.15.2", Compiler:"gc", Platform:"linux/amd64"}

• Cloud provider or hardware configuration:

• OS (e.g: cat /etc/os-release):

sh-4.4# cat /etc/os-release
NAME="Red Hat Enterprise Linux CoreOS"
VERSION="47.83.202011252347-0"
VERSION_ID="4.7"
OPENSHIFT_VERSION="4.7"
RHEL_VERSION="8.3"
PRETTY_NAME="Red Hat Enterprise Linux CoreOS 47.83.202011252347-0 (Ootpa)"
ID="rhcos"
ID_LIKE="rhel fedora"
ANSI_COLOR="0;31"
CPE_NAME="cpe:/o:redhat:enterprise_linux:8::coreos"
HOME_URL="https://www.redhat.com/"
BUG_REPORT_URL="https://bugzilla.redhat.com/"
REDHAT_BUGZILLA_PRODUCT="OpenShift Container Platform"
REDHAT_BUGZILLA_PRODUCT_VERSION="4.7"
REDHAT_SUPPORT_PRODUCT="OpenShift Container Platform"
REDHAT_SUPPORT_PRODUCT_VERSION="4.7"
OSTREE_VERSION='47.83.202011252347-0'

• Kernel (e.g. uname -a):

• Install tools:

• Network plugin and version (if this is a network-related bug):

• Others: