[release-4.11] OVNK: NAT issue for packets exceeding check_pkt_larger() for NodePort services that route to hostNetworked pods

Create Loadbalancer type service within the OCP 4.11.x OVNKubernetes cluster to expose the api server endpoint, the service does not response for normal oc request. 
But some of them are working, like "oc whoami", "oc get --raw /api"

4.11.8 with OVNKubernetes

always

1. Setup openshift cluster 4.11 on AWS with OVNKubernetes as the default network
2. Create the following service under openshift-kube-apiserver namespace to expose the api
----
apiVersion: v1
kind: Service
metadata:
  annotations:
    service.beta.kubernetes.io/aws-load-balancer-connection-idle-timeout: "1800"
  finalizers:
  - service.kubernetes.io/load-balancer-cleanup
  name: test-api
  namespace: openshift-kube-apiserver
spec:
  allocateLoadBalancerNodePorts: true
  externalTrafficPolicy: Cluster
  internalTrafficPolicy: Cluster
  ipFamilies:
  - IPv4
  ipFamilyPolicy: SingleStack
  loadBalancerSourceRanges:
  - <my_ip>/32
  ports:
  - nodePort: 31248
    port: 6443
    protocol: TCP
    targetPort: 6443
  selector:
    apiserver: "true"
    app: openshift-kube-apiserver
  sessionAffinity: None
  type: LoadBalancer

3. Setup the DNS resolution for the access
xxx.mydomain.com ---> <elb-auto-generated-dns>

4. Try to access the cluster api via the service above by updating the kubeconfig to use the custom dns name

No response from the server side.

$ time oc get node -v8
I1025 08:29:10.284069  103974 loader.go:375] Config loaded from file:  bmeng.kubeconfig
I1025 08:29:10.294017  103974 round_trippers.go:420] GET https://rh-api.bmeng-ccs-ovn.3o13.s1.devshift.org:6443/api/v1/nodes?limit=500
I1025 08:29:10.294035  103974 round_trippers.go:427] Request Headers:
I1025 08:29:10.294043  103974 round_trippers.go:431]     Accept: application/json;as=Table;v=v1;g=meta.k8s.io,application/json;as=Table;v=v1beta1;g=meta.k8s.io,application/json
I1025 08:29:10.294052  103974 round_trippers.go:431]     User-Agent: oc/openshift (linux/amd64) kubernetes/e40bd2d
I1025 08:29:10.365119  103974 round_trippers.go:446] Response Status: 200 OK in 71 milliseconds
I1025 08:29:10.365142  103974 round_trippers.go:449] Response Headers:
I1025 08:29:10.365148  103974 round_trippers.go:452]     Audit-Id: 83b9d8ae-05a4-4036-bff6-de371d5bec12
I1025 08:29:10.365155  103974 round_trippers.go:452]     Cache-Control: no-cache, private
I1025 08:29:10.365161  103974 round_trippers.go:452]     Content-Type: application/json
I1025 08:29:10.365167  103974 round_trippers.go:452]     X-Kubernetes-Pf-Flowschema-Uid: 2abc2e2d-ada3-4cb8-a86f-235df3a4e214
I1025 08:29:10.365173  103974 round_trippers.go:452]     X-Kubernetes-Pf-Prioritylevel-Uid: 02f7a188-43c7-4827-af58-5ebe861a1891
I1025 08:29:10.365179  103974 round_trippers.go:452]     Date: Tue, 25 Oct 2022 08:29:10 GMT
^C
real    17m4.840s
user    0m0.567s
sys    0m0.163s


However, it has the correct response if using --raw to request, eg:
$ oc get --raw /api/v1  --kubeconfig bmeng.kubeconfig 
{"kind":"APIResourceList","groupVersion":"v1","resources":[{"name":"bindings","singularName":"","namespaced":true,"kind":"Binding","verbs":["create"]},{"name":"componentstatuses","singularName":"","namespaced":false,"kind":"ComponentStatus","verbs":["get","list"],"shortNames":["cs"]},{"name":"configmaps","singularName":"","namespaced":true,"kind":"ConfigMap","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["cm"],"storageVersionHash":"qFsyl6wFWjQ="},{"name":"endpoints","singularName":"","namespaced":true,"kind":"Endpoints","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["ep"],"storageVersionHash":"fWeeMqaN/OA="},{"name":"events","singularName":"","namespaced":true,"kind":"Event","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["ev"],"storageVersionHash":"r2yiGXH7wu8="},{"name":"limitranges","singularName":"","namespaced":true,"kind":"LimitRange","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["limits"],"storageVersionHash":"EBKMFVe6cwo="},{"name":"namespaces","singularName":"","namespaced":false,"kind":"Namespace","verbs":["create","delete","get","list","patch","update","watch"],"shortNames":["ns"],"storageVersionHash":"Q3oi5N2YM8M="},{"name":"namespaces/finalize","singularName":"","namespaced":false,"kind":"Namespace","verbs":["update"]},{"name":"namespaces/status","singularName":"","namespaced":false,"kind":"Namespace","verbs":["get","patch","update"]},{"name":"nodes","singularName":"","namespaced":false,"kind":"Node","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["no"],"storageVersionHash":"XwShjMxG9Fs="},{"name":"nodes/proxy","singularName":"","namespaced":false,"kind":"NodeProxyOptions","verbs":["create","delete","get","patch","update"]},{"name":"nodes/status","singularName":"","namespaced":false,"kind":"Node","verbs":["get","patch","update"]},{"name":"persistentvolumeclaims","singularName":"","namespaced":true,"kind":"PersistentVolumeClaim","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["pvc"],"storageVersionHash":"QWTyNDq0dC4="},{"name":"persistentvolumeclaims/status","singularName":"","namespaced":true,"kind":"PersistentVolumeClaim","verbs":["get","patch","update"]},{"name":"persistentvolumes","singularName":"","namespaced":false,"kind":"PersistentVolume","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["pv"],"storageVersionHash":"HN/zwEC+JgM="},{"name":"persistentvolumes/status","singularName":"","namespaced":false,"kind":"PersistentVolume","verbs":["get","patch","update"]},{"name":"pods","singularName":"","namespaced":true,"kind":"Pod","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["po"],"categories":["all"],"storageVersionHash":"xPOwRZ+Yhw8="},{"name":"pods/attach","singularName":"","namespaced":true,"kind":"PodAttachOptions","verbs":["create","get"]},{"name":"pods/binding","singularName":"","namespaced":true,"kind":"Binding","verbs":["create"]},{"name":"pods/ephemeralcontainers","singularName":"","namespaced":true,"kind":"Pod","verbs":["get","patch","update"]},{"name":"pods/eviction","singularName":"","namespaced":true,"group":"policy","version":"v1","kind":"Eviction","verbs":["create"]},{"name":"pods/exec","singularName":"","namespaced":true,"kind":"PodExecOptions","verbs":["create","get"]},{"name":"pods/log","singularName":"","namespaced":true,"kind":"Pod","verbs":["get"]},{"name":"pods/portforward","singularName":"","namespaced":true,"kind":"PodPortForwardOptions","verbs":["create","get"]},{"name":"pods/proxy","singularName":"","namespaced":true,"kind":"PodProxyOptions","verbs":["create","delete","get","patch","update"]},{"name":"pods/status","singularName":"","namespaced":true,"kind":"Pod","verbs":["get","patch","update"]},{"name":"podtemplates","singularName":"","namespaced":true,"kind":"PodTemplate","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"storageVersionHash":"LIXB2x4IFpk="},{"name":"replicationcontrollers","singularName":"","namespaced":true,"kind":"ReplicationController","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["rc"],"categories":["all"],"storageVersionHash":"Jond2If31h0="},{"name":"replicationcontrollers/scale","singularName":"","namespaced":true,"group":"autoscaling","version":"v1","kind":"Scale","verbs":["get","patch","update"]},{"name":"replicationcontrollers/status","singularName":"","namespaced":true,"kind":"ReplicationController","verbs":["get","patch","update"]},{"name":"resourcequotas","singularName":"","namespaced":true,"kind":"ResourceQuota","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["quota"],"storageVersionHash":"8uhSgffRX6w="},{"name":"resourcequotas/status","singularName":"","namespaced":true,"kind":"ResourceQuota","verbs":["get","patch","update"]},{"name":"secrets","singularName":"","namespaced":true,"kind":"Secret","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"storageVersionHash":"S6u1pOWzb84="},{"name":"serviceaccounts","singularName":"","namespaced":true,"kind":"ServiceAccount","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["sa"],"storageVersionHash":"pbx9ZvyFpBE="},{"name":"serviceaccounts/token","singularName":"","namespaced":true,"group":"authentication.k8s.io","version":"v1","kind":"TokenRequest","verbs":["create"]},{"name":"services","singularName":"","namespaced":true,"kind":"Service","verbs":["create","delete","deletecollection","get","list","patch","update","watch"],"shortNames":["svc"],"categories":["all"],"storageVersionHash":"0/CO1lhkEBI="},{"name":"services/proxy","singularName":"","namespaced":true,"kind":"ServiceProxyOptions","verbs":["create","delete","get","patch","update"]},{"name":"services/status","singularName":"","namespaced":true,"kind":"Service","verbs":["get","patch","update"]}]}
 

The normal oc request should be working.

There is no such issue for clusters with openshift-sdn with the same OpenShift version and same LoadBalancer service.

We suspected that it might be related to the MTU setting, but this cannot explain why OpenShiftSDN works well.

Another thing might be related is that the OpenShiftSDN is using iptables for service loadbalancing and OVN is dealing that within the OVN services.