IP/CIDR validation improvements

[danwinship]

Enhancement Description

• One-line enhancement description (can be used as a release note): Improvements to validation of IP addresses and CIDR values.
• Kubernetes Enhancement Proposal: https://github.com/kubernetes/enhancements/pull/4899
• Discussion Link: https://github.com/kubernetes/kubernetes/pull/122550 has background; I am belatedly writing a KEP to centralize further discussion and because it will just be easier to track this work with a KEP.
• Primary contact (assignee): @danwinship
• Responsible SIGs: sig-network
• Enhancement target (which target equals to which milestone):
  • Alpha release target (x.y):
  • Beta release target (x.y):
  • Stable release target (x.y):
• [ ] Alpha
  • [ ] KEP (k/enhancements) update PR(s): https://github.com/kubernetes/enhancements/pull/4899
  • [ ] Code (k/k) update PR(s): https://github.com/kubernetes/kubernetes/pull/122550
  • [ ] Docs (k/website) update PR(s):

Please keep this description up to date. This will help the Enhancement Team to track the evolution of the enhancement efficiently.

[danwinship]

/sig network /assign