Change Validation of interface name

[adrianchiris]

interface name should not be limited to DNS-1123 label format. instead validate interface name if provided in pod network annotation in a similar manner as iproute2[1].

this will allow to request interface names such as: "uplink_p0"

[1]https://github.com/iproute2/iproute2/blob/11740815bfe69d6ee2cad7c608a8edc70147209a/lib/utils.c#L832

[coveralls]

coverage: 62.829% (+0.05%) from 62.778%
when pulling d625d48 on adrianchiris:allow_undersocre_in_ifname
into 0fd3fa7 on k8snetworkplumbingwg:master.

[dougbtv]

Hey Adrian -- this one is bigger than a breadbox :) Would you mind joining the NPWG or Multus maintainer's call to chat us about it?

I think there's some subtlety here between "attachment name" and "interface name" and the nuance there in the spec as well, we should chat it out. Thanks!

[adrianchiris]

sure, will raise it in one of the meetings. ATM on PTO (paternity leave) so will bring it up once im back. (~3 weeks )

[dougbtv]

I think my readthrough was wrong, and that this is totally reasonable given teh spec:

4.1.2.1.5 "interface"
This optional key with value of type string requires the implementation to use the given name for the pod interface resulting from this network attachment. This key’s value must be a valid Linux kernel interface name.

[killianmuldoon]

@Eoghan1232 - wondering if I could get your eyes on this one

[Eoghan1232]

lgtm - apologies I have been away for some time and only back now.

[killianmuldoon]

@adrianchiris @dougbtv WDYT about merging this one?

[dougbtv]

thanks for the submission, after considerable discussion: we couldn't find a reason why underscores would be invalid