added tests for service sessionAffinity

[yzaccc]

Commits:

• added tests for service sessionAffinity
• refactored code structures for extendibility
• enabled validator to check if the connection reached target pod, instead of only check if connection to service is successful.

Goal:

• Verify session affinity functions, that same client send request to the service via same port, will reach to same destination pod
• Verify that same client send request to the service via different port, will reach to same destination pod

Executed test plan: (setup)

1. add label app=test-session-affinity to pod-3 and pod-4
2. create service with same label, and sessionAffinity=ClientIP (memorize affinity)
3. create from/to peer map to store from/to pods
4. let all four pods to reach session affinity service via port 80
5. save the destination pod for each into the from/to peer map (verify via port 80)
6. create expected matrix based on from/to peer map
7. 4x4 matrix validation via clusterIP (verify via port81)
8. do step 6 and 7
9. remove session affinity label from pod-3 and pod-4

result: Session affinity service, from/to peers: map[pod-1:pod-3 pod-2:pod-4 pod-3:pod-3 pod-4:pod-3]

[yzaccc]

Well as discussed in issue https://github.com/kubernetes/kubernetes/issues/103000, this test encountered same problem for iptable mode kube-proxy.

Expected to use same client reach to the session affinity service via different port, the expected from/to pods peer should be same for port 80 and 81. But the reality is the destination pods are different, as below: Testing connections to different ports of sesson affinity service, should use same from/to peers: map[pod-1:pod-4 pod-2:pod-4 pod-3:pod-4 pod-4:pod-4] For port 80:

for port 81:

[yzaccc]

red pipelines are expected as iptables behavior in issue kubernetes/kubernetes#103000. Merging this PR.