#30825

They are invalid based on my knowledge, aren't they?

Please make sure what's valid and what's invalid from what point of view.

take 10.97.0.0/12 as example:
CIDR bases on dotted decimal, 12 mean it uses 12 bits, the first num uses whole 8 bits and the second num should use first 4 bit of whole 8 bits, 97 is invalid since it is 01100001 while 96 is valid since it is 01100000.

there is a check way using bash: https://stackoverflow.com/questions/50084229/bash-check-if-cidr-address-is-valid.

For some case, the invalidation make network not communicate.

CIDR bases on dotted decimal

Oh, please don't forget Pv6 addresses.

12 mean it uses 12 bits

It's the length of the address prefix, no more no less.

10.97.0.0/12

We usually think that "okay, the attached address is 10.97.0.0/32, the address prefix is 10.96.0.0/12; presumably, the subnet address is 10.96.0.0/32 and the directed broadcast address is 10.111.255.255/32; what a big subnet! which RIR (Regional Internet Registry) allocates this for which organization?"

take k8s network as example:
kubeadm and CNI like calico use CIDR to setup cluster network, specify 10.96.0.0/12 as pod ip range is common. If specify 10.97.0.0/12, network not works as expected.

CIDR format as ip/mask, now ParseCIDR() only check the validation of ip part not mask, so if use invalid CIDR, in this range, must have many subnets can not communicate.

kubeadm and and CNI like ... network not works as expected.

Sounds like that is not an issue of ParseCIDR. If your issue is that ParseCIDR accepts a valid CIDR notation and the behavior is not what you want, changing the behavior of ParseCIDR for your application is not an ideal solution (moreover the change will break Kubernetes and Docker).

Instead, you may use ParseCIDR more appropriately like https://play.golang.org/p/z3cYDbR21ws Closing.

Change https://golang.org/cl/168860 mentions this issue: net: update examples for ParseCIDR