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IP lifecycle

An IP is a namespaced handle to a claimed IP address. All namespaced resources wanting an IP have to claim the corresponding IP object in order to use it.

IP management

When creating an IP, a vacant IP address has to be allocated. This allocation is done via cluster-scoped IPAddress objects. An IPAddresses name is the IP it represents. As such, detecting whether an IPAddress is taken can be easily done by Getting the IPAddress with the IP to check and inspecting the result: If the IPAddress is present, it means it's taken. Otherwise, at least during the time of inspection, the IPAddress is vacant and ready to be claimed.

The IPAddress and IP are tied together in the IP's store BeforeCreate hook using the ipaddressallocator.

The Allocator tries to create IPAddresses with the claimRef pointing to the IP about to be created. It continues to do so until it either finds a vacant IPAddress (creation succeeds) or it times out after too many attempts fail (AlreadyExists errors).

The valid public IPAddress prefixes can be configured using the apiservers public-prefix flag.

When deleting an IP, the corresponding IPAddress is cleaned up alongside the claiming IP.

Claiming the IP

To claim an IP, claimer has to set the spec.claimRef of the IP. Once set, if the claimer wants to release it while it is present, the claimer has to actively delete the spec.claimRef.

If a claimer does not exist anymore, the IPGarbageCollector will take care of releasing the IP.

Claiming an IP for apinet objects

For apinet objects (NetworkInterface, NATGateway, LoadBalancer), claiming IPs is simple: When creating the object, there usually are two 'modes' for acquiring an IP: Either only the IPFamily (if applicable) is specified, causing a dynamic IP object to be created and claimed, or the desired IP is specified, causing the IPs in the namespace to be searched for the IP in question and to be claimed if possible.

For the apinet objects, this whole process is done directly during Create / Update. There is no eventual reconciliation of the IPs. This also means that if an Update causes an IP not to be used anymore, it will be released.

Example network interface claiming a dynamic public IP:

apiVersion: core.apinet.ironcore.dev/v1alpha1
kind: NetworkInterface
metadata:
  namespace: default
  name: my-public-nic
spec:
  networkRef:
    name: my-network
  nodeRef:
    name: my-node
  ips:
  - 192.168.178.3
  publicIPs:
    - name: public-ip-1
      ipFamily: IPv4