fix: support ptp networks with ipv4 /31 netmask and ipv6 /127 netmask

[cnvergence]

Pull Request

• Make sure you have followed Kube-OVN Code Style.

What type of this PR

Examples of user facing changes:

• Bug fixes

It would be valuable for kube-ovn to support ptp networks, to create external subnets between kube-ovn and the router, following RFC 3021 and RFC 6164.

Which issue(s) this PR fixes

Fixes

• [BUG] panic when creating subnet with /31 netmask #4426

[zhangzujian]

Subnet checks fail for /32 subnets:

status:
  activateGateway: ""
  conditions:
  - lastTransitionTime: "2024-08-29T01:52:46Z"
    lastUpdateTime: "2024-08-29T01:52:46Z"
    message: 'validate gateway 1.1.1.0 for cidr 1.1.1.0/31 failed: 1.1.1.0 is the
      network number ip in cidr 1.1.1.0/31'
    reason: ValidateLogicalSwitchFailed
    status: "True"
    type: Error

We need to fix it.

[cnvergence]

Thanks for the review, I have added validation test cases @zhangzujian

[zhangzujian]

We need update IPAM to support p2p networks.

[cnvergence]

hi @zhangzujian, I have added test cases for IPAM in the pkg/ipam
could you verify where we should add the support for ptp in ipam?

[zhangzujian]

hi @zhangzujian, I have added test cases for IPAM in the pkg/ipam could you verify where we should add the support for ptp in ipam?

I tried the following subnet and deployment but the kube-ovn could not handle the pod creation:

apiVersion: kubeovn.io/v1
kind: ProviderNetwork
metadata:
  name: ethx
spec:
  defaultInterface: ethx
---
apiVersion: kubeovn.io/v1
kind: Vlan
metadata:
  name: vlan0
spec:
  id: 0
  provider: ethx
---
apiVersion: kubeovn.io/v1
kind: Subnet
metadata:
  name: s1
spec:
  protocol: IPv4
  cidrBlock: 1.1.1.0/31
  vlan: vlan0
  disableGatewayCheck: true
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: kubeovn
  namespace: default
spec:
  selector:
    matchLabels:
      app: kubeovn
  replicas: 2
  template:
    metadata:
      labels:
        app: kubeovn
      annotations:
        ovn.kubernetes.io/logical_switch: s1
        ovn.kubernetes.io/ip_address: 1.1.1.0,1.1.1.1
    spec:
      containers:
      - name: pod
        imagePullPolicy: Never
        # image: kubeovn/kube-ovn:v1.13.0
        image: kubeovn/kube-ovn:dev
        securityContext:
          privileged: true
        command:
        - sleep
        - infinity

If this kind of usage is wrong, please tell me how to use /31 subnets correctly.

[cnvergence]

  I tried the following subnet and deployment but the kube-ovn could not handle the pod creation:

I see, this could cause a problem with trying to assign 1.1.1.0 to a Pod, which might be a problem.
For the Point-to-point network you would use this external subnet you have created with 1.1.1.0/31, excluding 1.1.1.0, as this will be configured as a gateway and have one available IP for your pod 1.1.1.1