No IPv4 address for hostnetwork pod in IPv6-primary dual stack

4.13.0-0.nightly-2023-04-01-062001 

Always

1. Create a hostnetwork pod and then check the pod address

Only IPv6 address is there for this pod. If create a service which having IPv6 and IPv4 and this pod as endpoint, then if curl the service IPv4 address, will not work. 

oc get pods -n e2e-test-networking-services-xfpxc -o yaml       
apiVersion: v1
items:
- apiVersion: v1
  kind: Pod
  metadata:
    annotations:
      kubectl.kubernetes.io/last-applied-configuration: |
        {"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"labels":{"name":"hello-pod"},"name":"hello-pod1","namespace":"e2e-test-networking-services-xfpxc"},"spec":{"containers":[{"image":"quay.io/openshifttest/hello-sdn@sha256:c89445416459e7adea9a5a416b3365ed3d74f2491beb904d61dc8d1eb89a72a4","name":"hello-pod","securityContext":{"allowPrivilegeEscalation":false,"capabilities":{"drop":["ALL"]}}}],"hostNetwork":true,"nodeName":"worker-0.zzhaov6p.qe.devcluster.openshift.com","securityContext":{"runAsNonRoot":false,"seccompProfile":{"type":"RuntimeDefault"}}}}
      openshift.io/scc: privileged
      seccomp.security.alpha.kubernetes.io/pod: runtime/default
    creationTimestamp: "2023-04-06T08:41:45Z"
    labels:
      name: hello-pod
    name: hello-pod1
    namespace: e2e-test-networking-services-xfpxc
    resourceVersion: "195007"
    uid: 6466f031-00ea-46e9-b099-b7384274cd15
  spec:
    containers:
    - image: quay.io/openshifttest/hello-sdn@sha256:c89445416459e7adea9a5a416b3365ed3d74f2491beb904d61dc8d1eb89a72a4
      imagePullPolicy: IfNotPresent
      name: hello-pod
      resources: {}
      securityContext:
        allowPrivilegeEscalation: false
        capabilities:
          drop:
          - ALL
      terminationMessagePath: /dev/termination-log
      terminationMessagePolicy: File
      volumeMounts:
      - mountPath: /var/run/secrets/kubernetes.io/serviceaccount
        name: kube-api-access-9xzl2
        readOnly: true
    dnsPolicy: ClusterFirst
    enableServiceLinks: true
    hostNetwork: true
    imagePullSecrets:
    - name: default-dockercfg-vf4lj
    nodeName: worker-0.zzhaov6p.qe.devcluster.openshift.com
    preemptionPolicy: PreemptLowerPriority
    priority: 0
    restartPolicy: Always
    schedulerName: default-scheduler
    securityContext:
      runAsNonRoot: false
      seccompProfile:
        type: RuntimeDefault
    serviceAccount: default
    serviceAccountName: default
    terminationGracePeriodSeconds: 30
    tolerations:
    - effect: NoExecute
      key: node.kubernetes.io/not-ready
      operator: Exists
      tolerationSeconds: 300
    - effect: NoExecute
      key: node.kubernetes.io/unreachable
      operator: Exists
      tolerationSeconds: 300
    volumes:
    - name: kube-api-access-9xzl2
      projected:
        defaultMode: 420
        sources:
        - serviceAccountToken:
            expirationSeconds: 3607
            path: token
        - configMap:
            items:
            - key: ca.crt
              path: ca.crt
            name: kube-root-ca.crt
        - downwardAPI:
            items:
            - fieldRef:
                apiVersion: v1
                fieldPath: metadata.namespace
              path: namespace
        - configMap:
            items:
            - key: service-ca.crt
              path: service-ca.crt
            name: openshift-service-ca.crt
  status:
    conditions:
    - lastProbeTime: null
      lastTransitionTime: "2023-04-06T08:41:45Z"
      status: "True"
      type: Initialized
    - lastProbeTime: null
      lastTransitionTime: "2023-04-06T08:41:46Z"
      status: "True"
      type: Ready
    - lastProbeTime: null
      lastTransitionTime: "2023-04-06T08:41:46Z"
      status: "True"
      type: ContainersReady
    - lastProbeTime: null
      lastTransitionTime: "2023-04-06T08:41:45Z"
      status: "True"
      type: PodScheduled
    containerStatuses:
    - containerID: cri-o://af520e1913a780be0b960d25bd91d4c383f305a96319fa4465e40e623958a0ab
      image: quay.io/openshifttest/hello-sdn@sha256:c89445416459e7adea9a5a416b3365ed3d74f2491beb904d61dc8d1eb89a72a4
      imageID: quay.io/openshifttest/hello-sdn@sha256:aa4e5b6448e5b38c66505216324ce247fbd14e0a4e8ab3b8c1746c0e49e70234
      lastState: {}
      name: hello-pod
      ready: true
      restartCount: 0
      started: true
      state:
        running:
          startedAt: "2023-04-06T08:41:45Z"
    hostIP: fd2e:6f44:5dd8:c956::17
    phase: Running
    podIP: fd2e:6f44:5dd8:c956::17
    podIPs:
    - ip: fd2e:6f44:5dd8:c956::17
    qosClass: BestEffort
    startTime: "2023-04-06T08:41:45Z"
kind: List
metadata:
  resourceVersion: ""

% oc get svc -n e2e-test-networking-services-xfpxc -o yaml
apiVersion: v1
items:
- apiVersion: v1
  kind: Service
  metadata:
    annotations:
      kubectl.kubernetes.io/last-applied-configuration: |
        {"apiVersion":"v1","kind":"Service","metadata":{"annotations":{},"labels":{"name":"test-service"},"name":"test-service","namespace":"e2e-test-networking-services-xfpxc"},"spec":{"externalTrafficPolicy":"","internalTrafficPolicy":"Local","ipFamilyPolicy":"PreferDualStack","ports":[{"name":"http","port":27017,"protocol":"TCP","targetPort":8080}],"selector":{"name":"hello-pod"},"type":"ClusterIP"}}
    creationTimestamp: "2023-04-06T08:43:31Z"
    labels:
      name: test-service
    name: test-service
    namespace: e2e-test-networking-services-xfpxc
    resourceVersion: "195811"
    uid: 2ffb6cfc-66a6-4cb7-ad65-ab5c91ecec52
  spec:
    clusterIP: fd02::a708
    clusterIPs:
    - fd02::a708
    - 172.30.252.101
    internalTrafficPolicy: Local
    ipFamilies:
    - IPv6
    - IPv4
    ipFamilyPolicy: PreferDualStack
    ports:
    - name: http
      port: 27017
      protocol: TCP
      targetPort: 8080
    selector:
      name: hello-pod
    sessionAffinity: None
    type: ClusterIP
  status:
    loadBalancer: {}
kind: List
metadata:
  resourceVersion: ""

From another pod on the same node as above pod to curl service
% oc get pods -n e2e-test-networking-services-xfpxc  -o wide
NAME         READY   STATUS    RESTARTS   AGE   IP                        NODE                                            NOMINATED NODE   READINESS GATES
hello-pod1   1/1     Running   0          33m   fd2e:6f44:5dd8:c956::17   worker-0.zzhaov6p.qe.devcluster.openshift.com   <none>           <none>
%  oc get svc -n e2e-test-networking-services-xfpxc       
NAME           TYPE        CLUSTER-IP   EXTERNAL-IP   PORT(S)     AGE
test-service   ClusterIP   fd02::a708   <none>        27017/TCP   33m      
 % oc get pods -n e2e-test-networking-services-mwfw9 -o wide       
NAME         READY   STATUS    RESTARTS   AGE   IP               NODE                                            NOMINATED NODE   READINESS GATES
hello-pod2   1/1     Running   0          32m   fd01:0:0:5::37   worker-0.zzhaov6p.qe.devcluster.openshift.com   <none>           <none>
hello-pod3   1/1     Running   0          32m   fd01:0:0:6::25   worker-1.zzhaov6p.qe.devcluster.openshift.com   <none>           <none>

% oc rsh -n e2e-test-networking-services-mwfw9 hello-pod2
~ $ curl --connect-timeout 5 172.30.252.101:27017
curl: (7) Failed to connect to 172.30.252.101 port 27017 after 0 ms: Connection refused
~ $ 
~ $ 
~ $ curl --connect-timeout 5 [fd02::a708]:27017
Hello OpenShift!

Only IPv6 can be accessed as no IPv4 for the backend pod.

Both IPv4 and IPv6 are there for the pod in dualstack cluster.